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EE 3311 Semiconductor Devices Agendas and Homework Assignments EE 3311 Oral Exam Groups Group A: Abdelqader, Rami; Aucoin, Camille, Brogan,Roderick Group B: Holloway, John; Charania, Amaan; De Labra, Jose Group C: Dominguez, Omar; Garcia, Allison; Garcia, Graciela Group D: Gilchrist, John; Zhao, Danton; Hatcher, Laura Group E: Coday, Samantha; Jaffery, Osaid; Kezic, Tara Group F: Kleiman, Jenna; Kradin Jean-Luc; Lee, Seok Hee Group G: Matthie; Clayton; Meinecke, James; Santiago, Arianna Group H: Schmid, Olivia, Smallwood, Matthew; Stevens, Charles Group I: Templeton, William; Trinh, Vivian; Vela, Krystle Group J: Viviano, Charles; Wensowitch, John; Abdelqader, Odai list for TA's for 8 lab session and number of student in each lab. ----------------------------------------------------------------------------------------------------------------------------Group 1: Tuesday 8:00am to 10:00am TA's: Christina & Nikunj No. of Students: 4 Group 3: Tuesday 12:30pm to 2:30pm TA's: Nilay & Freddie No. of Students: 4 Group 4: Tuesday 3:30pm to 5:30pm TA's: Nilay & Freddie No. of Students: 4 Group 5: Wednesday 8:00am to 10:00am TA's: Christina & Sudip No. of Students: 4 Group 6: Wednesday 10:00am to 12:00pm TA's: Nilay & Sudip No. of Students: 4 Group 7: Wednesday 3:30pm to 5:30pm TA's: Freddie & Nikunj No. of Students: 4 Group 8: Thursday 8:00am to 10:00am TA's: Nikunj & Sudip No. of Students: 3 Group 11: Thursday 3:30pm to 5:30pm TA's: Nilay & Freddie No. of Students: 4 ------------------------------------------------------------------------------------------------------------------------------Here is the list of all students for 8 lab session. ------------------------------------------------------------------------------------------------------------------------------Group 1: Tuesday 8:00am to 10:00am Group 3: Tuesday 12:30pm to 2:30pm Group 4: Tuesday 3:30pm to 5:30pm Group 5: Wednesday 8:00am to 10:00am Group 6: Wednesday 10:00am to 12:00pm Group 7: Wednesday 3:30pm to 5:30pm Group 8: Thursday 8:00am to 10:00am Group 11: Thursday 3:30pm to 5:30pm John Wensowitch, Charles Viviano, Parker Holloway, William Templeton Danton Zhao, Camille Aucoin, Rami Abdelqader, Charles Stevens Clayton Matthie, Parker Meinecke, Arianna Santiago, Allison Garcia, Sam Coday, Matthew Smallwood, Olivia Schmid Omar Dominguez, Vivian Trinh, Graciela Garcia, Jose De Labra Amaan Charania, Tara Kezic, John Gilchrist Odai Abdelqader, Seok Hee Lee, Roderick Brogan Osaid Jaffery, Laura Hatcher, Jenna Kleiman, Krystle Vela --------------------------------------------------------------------------------------------------------------------------------- EE 3311Homework and Lab Report Schedule Abdelqader Odai Homework 1 Abdelqader Rami Lab 1 Aucoin Camille Homework 2 Brogan Roderick Lab 2 Holloway John Homework 3 Charania Amaan Lab 3 De Labra Jose Homework 4 Dominguez Omar Lab 4 Garcia Allison Homework 5 Garcia Graciela Lab 5 Gilchrist John Homework 6 Zhao Danton Lab 6 Hatcher Laura Homework 7 Coday Samantha Lab 7 Jaffery Osaid Homework 8 Kezic Tara Lab 8 Kleiman Jenna Homework 9 Kradin Jean-Luc Lab 9 Lee Seok Hee Homework 10 Matthie Clayton Lab 10 Meinecke James Homework 11 Santiago Arianna Lab 11 Schmid Olivia Homework 12 Smallwood Matthew Lab 12 Stevens Charles Homework 13 Templeton William Topic A Trinh Vivian Topic B Vela Krystle Viviano Charles Topic D Wensowitch John Topic E Zhao Danton Changed to Lab 6 (see above) Topic C Monday, August 24, 2015 Course Philosophy x1. Review Syllabus (this course may not be for you…) I have two major objectives for students taking this course: A. Make working p-channel MOSFET devices. Understand the fabrication process. Understand the concepts of photolithography, oxidation, diffusion, etching and metallization. B. Understand how basic semiconductor devices work—in particular how a p-n junction and a MOSFET transistor works. x2. Lab and Lab Safety (J. Kirk), Safety Quiz (see Blackboard) and Material Safety Data Sheets (MSDS) Our plan is to have a maximum of 4 students in each group. For safety reasons, you cannot enter the clean room without appropriate dress: long pants, covered torso and shoes that completely cover your feet (no open toes, no sandals). SAFETY QUIZ MUST BE UPLOADED TO BLACKBOARD BY FRIDAY, MIDNIGHT, AUGUST 28th, 2015. x3. Submit your first, second and third choices for lab times by email to Nilay Shah ([email protected]) before noon on Wednesday August 26th from the list below. Lab Time Possibilities (from which we will choose 8 groups) Group 1: Tuesday, 8:00 am - 10:00 am Group 2: Tuesday 10:00 am - 12:00 pm Group 3: Tuesday, 12:30 pm - 2:30 pm Group 4: Tuesday, 3:30 pm - 5:30 pm Group 5: Wednesday, 8 am - 10 am Group 6: Wednesday, 10 am to 12: pm Group 7: Wednesday, 3:30 pm - 5:30 pm Group 8: Thursday, 8:00 am - 10:00 am Group 9: Thursday, 10:00 am - 12:00 pm Group 10: Thursday, 12:00 pm – 2:00 pm Group 11: Thursday, 3:30 - 5:30 pm x4. Plagiarism: Not just an ethical question. The internet makes plagiarism easy—and the internet makes it even easier to detect. Government funding agencies routinely check proposals and reports for plagiarism. Penalties for plagiarism include banning individuals, institutions and corporations from applying for grants and contracts. x5. Teaching Baseball or Engineering? “this is the course I would have liked to have had as a student” --Old 3311 (all theory) and New 3311 (lab) --discrete college courses and Boeing 727s… --New 3311 brings together most everything you have had in all your classes: chemistry, physics, advanced math, circuits, materials, (thermodynamics, heat transfer, quantum mechanics, …) x6. x7. Historical Background (Dallas and SMU related) Jack St. Clair Kilby (November 8, 1923 - June 20, 2005) won the Nobel Prize (with Herbert Kroemer and Zhores l. Alferov for heterojunctions) in physics in 2000 for his invention of the integrated circuit during the summer of 1958 at Texas Instruments. He also is credited with the invention of the handheld calculator and thermal printer. TI Archives and the Jack St. Clair Kilby Archives are at the DeGolyer Library at Southern Methodist University. DRAM inventor Robert Denard received an honorary doctorate from SMU in 1997. He received his BSEE and MSEE from SMU in 1954 and 1956. x8. LED inventors Bob Biard and Gary Pittman--Bob Biard received an honorary doctorate from SMU at the May 2013 graduation ceremony. Gary Pittman could not attend because of poor health. Pittman received his BS in Chemistry from SMU in 1954. Gary Pittman died October, 2013. x9. Looking Backwards (mechanical logic and computers to microprocessors) and Forward (silicon photonics): History and Future of Computing (HistoryAndFutureComputingF2014.ppt on Blackboard) 10. JaegerCh01overview2013 powerpoint slides (JaegerCh01overview2013.ppt on Blackboard) (stopped at discussion of 1 T+ transistors/chip on 8/24) 11. How are we going to make a MOSFET? --Overview of Fabrication Process (MOSFETFab_Fall2014.ppt or most recent posted) 12. Basics of Materials: MaterialsBasicsAr12015.ppt (stopped on slide 27 on 8/26) 13. What do we need to know to understand how to make a MOSFET? --thermal oxidation of silicon --lithography and photoresist --etching of oxide, metals (and semiconductors) --diffusion (and ion implantation) of dopants --testing, packaging Wednesday, August 26, 2015 Agenda 1. Lab sessions (tentatively) start Tuesday, September 1 at 8:30 AM (maybe?) 2. SAFETY QUIZ MUST BE UPLOADED TO BLACKBOARD BY FRIDAY, MIDNIGHT, AUGUST 28th, 2015. Safety related articles are on Blackboard in the Safety Information folder under Course Documents. 3. Jay Kirk, Lab Instructor—Safety and Laboratory Protocol emphasis on Monday. 4. Lab Tours (maybe during first lab) --Safety, Safety Quiz and Material Safety Data Sheets (MSDS) x5. JaegerCh01overview2015 powerpoint slides (JaegerCh01overview2015.ppt on Blackboard) (completed) x6. Overview of Fabrication Process (MOSFETFab_Fall2014.ppt or most recent posted) review 3rd week of class in detail. 7. Basics of Materials: MaterialsBasicsAr12015.ppt (stopped on slide 27 on 8/26) 8. What do we need to know to understand how a MOSFET works? --electrons and holes in semiconductors, doping of semiconductors --p-n junctions --resistivity 9. What do we need to know and understand to make a MOSFET? --thermal oxidation of silicon --lithography and photoresist --etching of oxide (dielectrics), metals, and semiconductors --diffusion (and ion implantation) of dopants --testing, packaging Monday, August 31, 2015 Agenda 1. Lab sessions start Tuesday, September 1 at 8:00 AM list for TA's for 8 lab session and number of student in each lab. ----------------------------------------------------------------------------------------------------------------------------Group 1: Tuesday 8:00am to 10:00am TA's: Christina & Nikunj No. of Students: 4 Group 3: Tuesday 12:30pm to 2:30pm TA's: Nilay & Freddie No. of Students: 4 Group 4: Tuesday 3:30pm to 5:30pm TA's: Nilay & Freddie No. of Students: 4 Group 5: Wednesday 8:00am to 10:00am TA's: Christina & Sudip No. of Students: 4 Group 6: Wednesday 10:00am to 12:00pm TA's: Nilay & Sudip No. of Students: 4 Group 7: Wednesday 3:30pm to 5:30pm TA's: Freddie & Nikunj No. of Students: 4 Group 8: Thursday 8:00am to 10:00am TA's: Nikunj & Sudip No. of Students: 3 Group 11: Thursday 3:30pm to 5:30pm TA's: Nilay & Freddie No. of Students: 4 ------------------------------------------------------------------------------------------------------------------------------Here is the list of all students for 8 lab session. ------------------------------------------------------------------------------------------------------------------------------Group 1: Tuesday 8:00am to 10:00am Group 3: Tuesday 12:30pm to 2:30pm Group 4: Tuesday 3:30pm to 5:30pm Group 5: Wednesday 8:00am to 10:00am Group 6: Wednesday 10:00am to 12:00pm Group 7: Wednesday 3:30pm to 5:30pm Group 8: Thursday 8:00am to 10:00am Group 11: Thursday 3:30pm to 5:30pm John Wensowitch, Charles Viviano, Parker Holloway, William Templeton Danton Zhao, Camille Aucoin, Rami Abdelqader, Charles Stevens Clayton Matthie, Parker Meinecke, Arianna Santiago, Serdar Halac Allison Garcia, Sam Coday, Matthew Smallwood, Olivia Schmid Omar Dominguez, Vivian Trinh, Graciela Garcia, Jose De Labra Andrew Campbell, Amaan Charania, Tara Kezic, John Gilchrist Student's Name: Odai Abdelqader, Seok Hee Lee, Roderick Brogan Student's Name: Osaid Jaffery, Laura Hatcher, Jenna Kleiman, Krystle Vela --------------------------------------------------------------------------------------------------------------------------------- 2. HW#1 due Tuesday, September 1st before 11:59 PM. Review of HW #1: Odai Abdelqader REMINDER: help sessions are every Monday evening in conference room 338 in Junkins. 3. SAFETY QUIZ SHOULD HAVE BEEN UPLOADED TO BLACKBOARD BY FRIDAY, MIDNIGHT, AUGUST 28th, 2015. Safety related articles are on Blackboard in the Safety Information folder under Course Documents. 4. Jay Kirk, Lab Instructor—Safety and Laboratory Protocol emphasis (TODAY). 5. Lab Tours (maybe during first lab) --Safety, Safety Quiz and Material Safety Data Sheets (MSDS) x6. JaegerCh01overview2015 powerpoint slides (JaegerCh01overview2015.ppt on Blackboard) (stopped at discussion of 1 T+ transistors/chip on 8/24; continued to completion; completed MOSFET fab traveler; began Basic Materials) x7. Overview of MOSFET Fabrication Process (MOSFETFab_Fall2014.ppt or most recent posted) 8. Basics of Materials: MaterialsBasicsAr12015.ppt (stopped on slide 27 on 8/26) stopped at 5/40 on Ch2JaegerLithograpy 9. What do we need to know to understand how a MOSFET works? --electrons and holes in semiconductors, doping of semiconductors --p-n junctions --resistivity 10. What do we need to know and understand to make a MOSFET? --thermal oxidation of silicon --lithography and photoresist --etching of oxide (dielectrics), metals, and semiconductors --diffusion (and ion implantation) of dopants --testing, packaging 1. 2. 3. 4. Wednesday, September 2, 2015 Agenda Professor Ken Springer may (?) talk to the class on Wednesday September 9 about Writing and Lab Reports Review of HW #1: Odai Abdelqader JaegerLithographyCh2r1 powerpoint slides (completed) JaegerOxidationCh03r2 powerpoint slides (started?) Monday, September 7, 2015 No Agenda (no class) 1. 2. 3. 3. Wednesday, September 9, 2015 Agenda HW #2 discussion: Camille Aucoin; Lab 1 discussion: Rami Abdelqader JaegerLithographyCh2r1 powerpoint slides (review slide 29; look at IBM TEM photo) (completed) Diffusion Concepts2014 powerpoint slides (on blackboard) (completed) JaegerOxidationCh03r2 powerpoint slides (on blackboard) (stopped about slide 11) Monday, September 14, 2015 Agenda 0. Help session at 5:10 PM or so in Junkins 338 (conference room) On Wednesday: Brogan Roderick Lab 2 Charania Amaan Homework 3 1. JaegerOxidationCh03r2 powerpoint slides (completed) 2. Jaeger_diffusionCh04r4 powerpoint slides (on Blackboard) Wednesday, September 16, 2015 Agenda 1. HW#3 discussion: Amaan Charania (John Preston Holloway filled in); Lab 2 discussion: Roderick Brogan 2. Why are we diffusing B into Si in the laboratory sessions? 3. Continue Jaeger_diffusionCh04r4 powerpoint slides (start on slide 5) Monday, September 21, 2015 Agenda 1. HW#3 discussion last week: Amaan Charania at interview, so John Preston Holloway filled in Lab 3 discussion: Amaan Charania (would like to do this) OK with Samantha Coday? Original “modified” schedule: Coday Samantha Lab 3 De Labra Jose Homework 4 3. Completed Jaeger_diffusionCh04r4 powerpoint slides Wednesday, September 23, 2015 Agenda 1. Professor Ken Springer: On Writing Lab Reports 2. Homework #4 and Lab 3 Charania Amaan De Labra Jose 3. Begin p-n Junction Slides Lab 3 Homework 4 Monday, September 28, 2015 Agenda 1. Homework #5 but no Lab this Wednesday? Garcia Allison 2. Continue/begin p-n Junction Slides Homework 5 Wednesday, September 30, 2015 Agenda 1. Homework #5 but no Lab report today Garcia Allison 2. Continue p-n Junction Slides Homework 5 Monday, October 5, 2015 Agenda 1. Homework #6 and Lab #4 on Wednesday Dominguez Omar Lab 4 Gilchrist John Homework 6 2. “Demo” of holes and electrons 3. Continue p-n Junction Slides (start at ~ slide 27) Wednesday, October 7, 2015 Agenda 1. Homework #6 and Lab #4 Dominguez Omar Lab 4 Gilchrist John Homework 6 2. Discussion of Midterm Exam (problems 1 and 2, due MONDAY, October 19, 2015) 3. Continue p-n Junction Slides (from slide 36) Wednesday, October 14, 2015 Agenda 1. Homework #7 and Lab #5 Garcia Graciela Lab 5 Hatcher Laura Homework 7 2. EE 3311 Oral Exam Groups (Each group schedules an exam time on doodle.com) Week of October 19th or week of November 2nd? Group A: Abdelqader, Rami; Aucoin, Camille, Brogan,Roderick Group B: Holloway, John; Charania, Amaan; De Labra, Jose Group C: Dominguez, Omar; Garcia, Allison; Garcia, Graciela Group D: Gilchrist, John; Zhao, Danton; Hatcher, Laura Group E: Coday, Samantha; Jaffery, Osaid; Kezic, Tara Group F: Kleiman, Jenna; Kradin Jean-Luc; Lee, Seok Hee Group G: Matthie; Clayton; Meinecke, James; Santiago, Arianna Group H: Schmid, Olivia, Smallwood, Matthew; Stevens, Charles Group I: Templeton, William; Trinh, Vivian; Vela, Krystle Group J: Viviano, Charles; Wensowitch, John; Abdelqader, Odai Oral midterm: 1. Each group is required to come up with three questions about concepts in the course which they do not understand or do not fully understand. A question could be: How does concept A fit into the big picture of B? Each group should be prepared to present what they think they understand about their questions and what they do not fully understand. 2. Each group is required to come up with three concepts that they fully understand and should be prepared to discuss these concepts. 3. After the oral exam, each individual must submit a written report about the discussion and what concepts were clarified in the exam. 3. Continue p-n Junction Slides (from slide 55) Monday, October 19, 2015 Agenda 1. Next Wednesday Homework #8 Jaffery Osaid Homework 8 2. EE 3311 Oral Exam Groups (Each group schedules an exam time on doodle.com) Week of October 19th or week of November 2nd? Group A: Abdelqader, Rami; Aucoin, Camille, Brogan,Roderick Group B: Holloway, John; Charania, Amaan; De Labra, Jose Group C: Dominguez, Omar; Garcia, Allison; Garcia, Graciela Group D: Gilchrist, John; Zhao, Danton; Hatcher, Laura Group E: Coday, Samantha; Jaffery, Osaid; Kezic, Tara Group F: Kleiman, Jenna; Kradin Jean-Luc; Lee, Seok Hee Group G: Matthie; Clayton; Meinecke, James; Santiago, Arianna Group H: Schmid, Olivia, Smallwood, Matthew; Stevens, Charles Group I: Templeton, William; Trinh, Vivian; Vela, Krystle Group J: Viviano, Charles; Wensowitch, John; Abdelqader, Odai Oral midterm: 1. Each group is required to come up with three questions about concepts in the course which they do not understand or do not fully understand. A question could be: How does concept A fit into the big picture of B? Each group should be prepared to present what they think they understand about their questions and what they do not fully understand. 2. Each group is required to come up with three concepts that they fully understand and should be prepared to discuss these concepts. 3. After the oral exam, each individual must submit a written report about the discussion and what concepts were clarified in the exam. 3. Continue p-n Junction Slides (derive Density of States) Wednesday, October 21, 2015 Agenda 1. Problems 3 and 4 of the Midterm are due Monday, November 2, 2015 before midnight. 2. Next Wednesday Homework #8 Jaffery Osaid Homework 8 3. Briefly discuss Midterm Problem #4 4. Fermi levels, doping, ... Monday, October 26, 2015 Agenda 1. Guest Speakers: Dr. Bob Biard ([email protected]) and Dr. Ralph Johnson ([email protected]) Wednesday, October 28, 2015 Agenda 1. Problems 3 and 4 of the Midterm are due Monday, November 2, 2015 before midnight. 2. Tour of Photodigm and IntelliEPI on Saturday, November 7 3. Homework #9 and Lab #6 Kleiman Jenna Zhao Danton Homework 9 Lab 6 4. Fermi levels, doping, (later come back to the starting points of Fermi-Dirac, Bose-Einstein and Boltzman distributions AND the asymmetry of probability of occupation given by f(E) around EF), Density of States, EFFECTIVE Density of States, ... (stopped at slide 99) Monday, November 2, 2015 Agenda 1. Problems 3 and 4 of the Midterm are due today before midnight. Update on Question 3: Consider a pn junction with a cross sectional area of 10 microns x 10 microns. The doping on the p-side is a uniform NA = 7 x 1016 boron atoms/cm3 and the doping on the n-side is a uniform ND = 3 x 1015 arsenic atoms/cm3. a) Use the Einstien relation to calculate the diffusion coefficients for holes and electrons (see Fig. 3-23 on page 105 of the Streetman text or the class powerpoint slides). b) calculate the diffusion lengths for holes and electrons. Assume that the hole and electron lifetimes both equal 10-10 seconds. c) calculate the saturation (or “reverse” current before reverse breakdown). d) what applied forward voltages correspond to current densities of 10, 100, 1000, 10,000 and 100,000 A/cm2? e) draw a complete equilibrium band diagram for the pn junction. You can use Figure 4-9 of your textbook to find the acceptor and donor levels. Show EC, EV, EF, Ei, EG, EG /2, qVo, ED and EA. 2. On Wednesday November 4, Homework #10 and Lab #7 Lee Seok Hee Homework 10 Coday Samantha Lab 7 3. Complete Fermi level and band diagram discussions 4. Derive I-V relation for pn junction Wednesday, November 4, 2015 Agenda 0. Meet at 10 AM Saturday (Nov. 7th) at IntelliEPI for tour (then cross the street to Photodigm). 1. Homework #10 and Lab #7 Lee Seok Hee Homework 10 Coday Samantha Lab 7 2. Complete derivation of I-V relation for pn junction 3. reverse bias; tunneling; avalanche breakdown of pn junctions (stopped at reverse bias/tunneling) Homework Assignment #1 (due Tuesday, September 1st, 2015) 1. In your own words, state the format requirements for homework assignments. What will happen if homework is turned in that does not satisfy the format requirements? 2. What percentage of homework assignments must be completed and turned in to pass this course? What percentage of laboratory reports must be completed and turned in to pass this course? 3. Read Chapter 1 of Introduction to Microelectronic Fabrication. How many inches is a) 100 mm? b) 200 mm? c) 300 mm? d) 400 mm? How many millimeters equal 12 inches? Note: This assignment is an opportunity to show proper use of units when converting from the metric system to the Imperial (inches, feet, ...) system. You may want to use an online conversion website as a check on your own calculations. 4. How many complete 1mm x 1mm die can fit on a 100 mm wafer? How many complete 1 cm x 1 cm die can fit on a 300 mm wafer? 5. Determine the cost per good die for a wafer processing cost of $50,000 and a yield of 95% for a) a 1mm x 1 mm die size and wafer size of 100 mm? b) for a 2 cm x 2 cm die size and a wafer size of 300 mm? 6. What is the chemical make up of photoresist? What safety precautions should be used with photoresist? How and why is photoresist used? 7. Assume that you have a thousand dollars that accrues compound interest of 10%/time period over 15 time periods. (How many weeks are in this semester?) What is the accrued value of the thousand dollars after 15 time periods? How much better off will you be if you work 10% harder each week of this semester? 8. Write a summary of the article “On Physics Education in Brazil,” from the book Surely You're Joking, Mr. Feynman! (Adventures of a Curious Character), by Ralph Leighton and Edward Hutchings, 1985. This article can be found on Blackboard under Course Documents or on numerous sites online. Homework Assignment #2 (due Tuesday, September 8th, 2015) 1. Evaluate the following integrals: For problems 2 and 3 recall that the del operator is given by 2. Calculate the divergence ( 3. Calculate the curl ( ) of the following vectors: ) of the following functions: 4. Below is a list of Maxwell’s Equations in differential form: One of those equations states that the divergence of the electric displacement vector D(x,y,z,t) is equal to the charge density (x,y,z,t)—this equation is known as Gauss’s Law for the electric displacement vector. For problems in space where there is only a variation in the x direction, show that this equation reduces to the derivative of the electric field E(x) with respect to x is equal to the charge density divided by the electric permittivity: 5. The speed of light c = 1/ m oe o , where e o is the permittivity of free space and m o is the permeability of free space. Show that the units of 1/ m oe o are length/time (or meters/sec). 6. Show that the units of ∇ • 𝐷 = 𝜌 are the same on both sides of the equation. 7. (20 points) What is the oxide thickness on the Si wafer that you are processing? At what temperature was the oxide be deposited? How long is the deposition process expected to take? Was the oxide be deposited by a wet or dry process? Using the formulas in your text book (Jaeger), calculate the theoretical thickness of the first oxide layer grown in the lab. Check your calculations with the figures in the text book showing oxide thickness as a function of time for various temperatures. More about problem #1: See step 1-2 in the traveler, the initial oxidation (Offline) 1000 °C in steam, ~ 5 Hours-target 10,000Å (1 µm). This means that the <100> wafer is put in the furnace for a 1000 C (wet) for ~ 5 hours. The formula for oxide thickness as a function of time X(t) is Eq. 3.9 in Jaeger. The oxidation time t is ~ 5 hours. To use Eq. 3.9, you need to convert Centigrade to Kelvin and you need to find A and B. You can find A and B from Table 4.1 if you know the wafer orientation (100 for this class) and you know if the oxide is deposited with steam (wet) or dry. So for this problem, you will use an activation energy of 2.05 eV and a diffusion coefficient of 9.7 x 107 µm/hr to find B/A. That is, B/A = Doexp(-Ea/kT) = (9.7 x 107 µm/hr)exp(-2.05 eV/kT), where T is in Kelvin and k is Boltzman’s constant. After you calculate B/A, look at Figure 3.5 and see if your calculation agrees with the appropriate curve. Next you need to find B. From Table 3.1, B = Doexp(-Ea/kT), where the activation energy is 0.78 eV and Do is 386 µm2/hr. After you calculate B, look at Figure 3.4 and see if your calculation agrees with the curve for H20. The sentence under Eq. 3.8 in the text explains how to calculate . Explain why for this particular calculation you can assume no initial oxide thickness. (Note that a freshly cleaned Si wafer will develop a very thin (~1 to 4 nm) layer of oxide just from being exposed to air.) Check your final answer for the field oxide thickness with Fig. 3.6. 8. (20 points) In a later laboratory session, the gate oxide for the MOSFET device will be grown offline. What is the expected thickness of the gate oxide? Will the gate oxide be grown by a wet or dry process? Why? Using the time and temperature in the MOSFET traveler, calculate the gate oxide thickness. Check your calculations with the figures in the text book showing oxide thickness as a function of time for various temperatures. For best theoretical agreement with experiment, an initial oxide thickness of 25 nm should be used in the calculation—even though the initial thickness in reality is likely closer to 2.5 nm… Homework Assignment #3 (due Tuesday, September 15th, 2015) 1. (30 pts) During the processing of your wafer, there are three times that the wafer is oxidized: a) step 1.2 (in the traveler) which results in a thick field oxide of about 1 micron; b) a second oxide growth during the boron diffusion (step 2.7 in the traveler), which provides about 0.5 microns of oxide in the source and drain region; and c) a final oxide growth for the gate (step 3-17 in the traveler) which provides about 0.08 microns of oxide in the gate region. Using the time and temperatures given in the three different oxide growths, calculate the total thickness of the oxide that surrounds the source and drain regions. Note: The oxide surrounding the source and drain regions is not ever etched away—and only becomes thicker with each successive oxide growth that occurs. Check your numerical calculations with the appropriate figures in the text. Here is one way to do this problem: i) You have calculated the oxide thickness outside the source and drain after step 1.2 in the traveler in HW#2. ii) Use the (correctly calculated!) thickness (~ 1 micron) of the oxide calculated in HW #2 for the value of Xi in calculating the total thickness of the oxide that surrounds the source and drain regions after step 2.7. In other words, use Xi ~ 1.0 micron in the equation t= Xi2 Xi . Of course, you need to use the values for B and B/A that are appropriate + B ( B A) for the oxide growth of step 2.7. Once you have , then you can use 0.5 éì ù ü B Xo ( t ) = 0.5A êí1+ 4 2 ( t + t )ý -1ú to find the total thickness of the oxide outside the source and gate þ A êëî úû (after step 2.7), again using the appropriate values of B and B/A. iii) To complete this problem, you need the total thickness of the oxide after step 3-17. Now you need to calculate again, but this time you need to use the total thickness Xo that you calculated in step ii) for Xi. And of course you need to use the appropriate values of B and B/A in this second calculation. The result of this step is the answer for the total oxide thickness outside the source and drain. You will see that this answer is different from the answer you would get by (wrongly!) adding the thickness of the first, second and third oxide growths. 2. In calculating the thickness of thermal oxides, there are two different activation energies and two different diffusion terms for B and B/A, suggesting that two different physical processes are involved. In Table 3-1 (Jaeger), we see that for one of the coefficients, the activation energies and diffusion coefficients do not depend on the orientation of the wafer, while for the other coefficient, the activation energies and diffusion coefficient do depend on the wafer orientation. What are some possible mechanisms that might explain the dependence or lack of dependence on wafer orientation? (Note: the number of Si atoms/cm2 at the surface of a silicon wafer depends on the orientation.) 3. Read the article by Michael Riordan called “The Silicon Dioxide Solution, (How physicist Jean Hoerni built the bridge from the transistor to the integrated circuit),” IEEE Spectrum, December, 2007 (available online at http://spectrum.ieee.org/semiconductors/design/the-silicondioxide-solution or on Blackboard under Course Documents as SiO2_history.pdf). Write a summary of this article in WORD that includes the advantages and repercusions of Hoerni’s idea of leaving the oxide on the wafer. Homework Assignment #4 (due Tuesday, September 22nd, 2015) For Problems 1 through 4, review Chapter 4 of the (Jaeger) textbook and the slides on diffusion, which are posted on Blackboard. 1. Step 2-4 in the MOSFET process traveler is (mostly) a constant source diffusion. For this case, the solution to Eq. 4.3 in the textbook is given by Eq. 4.4. Calculate the theoretical diffusion depth of step 2-4 using formulas and graphs in the textbook. Assume that the surface concentration of this diffusion is equal to the solid solubility limit, which can be obtained from Fig. 4.6 in the text. You will need to know the background doping of your wafer. The resistivity of the n-doped substrates used this semester will be obtained in a later lab, but when we ordered the substrates, we specified that the resistivity be between 1 and 10 ohm-cm. From past measurements, the resistivity is between 5 and 6 ohm-cm. Using 5.5 ohm-cm as the resistivity, you can find the background doping from Fig. 4.8 in the text. Now you can set the constant background doping (NB) equal to the impurity concentration N(x) which is given by Eq. 4.4. The value xj that makes N(xj) = NB is the location of the metalurgical junction or the location of the p-n junction. Note that you have to calculate a diffusion coefficient D using Table 1 from the text. Equation 4.4 contains a function called the complimentary error function, which is plotted in Fig. 4.4. Fig. P1. Temperature profile for the predeposition step. 2. Step 2-7 in the MOSFET process traveler is a limited-source diffusion. For this case, the solution to Eq. 4.3 in the (Jaeger) textbook is given by Eq. 4.6. Calculate the theoretical depth of this step using formulas and graphs in the textbook. A limited-source diffusion assumes an impulse function representing the total number of boron atoms/cm2 (deposited in step 2-4 of the MOSFET process traveler) at the silicon surface. The magnitude of this impulse is related to the total dose (Q) and is given by Eq. 4.5 in the text. In problem 1 you determined the resistivity and the background doping of your wafer. Now you can set the constant background doping (NB) equal to the impurity concentration N(x) which is given by Eq. 4.6. The value xj that makes N(xj) = NB is called the metalurgical junction or the location of the p-n junction. Note that you have to calculate a diffusion coefficient D using Table 1 from the text. Equation 4.6 has a Gaussian dependence, which is also shown in Fig. 4.4. Fig. P2. Temperature profile for the drive-in step. 3. For this problem it helps to read section 4.2.3 in Jaeger. Calculate the Dt products for the diffusions in Problem 1 and Problem 2 and compare them. What can you say about the final profile after the diffusion steps have been performed according to the traveler? Fig. 4.20 of slide 20 of the Diffusion power point slides addresses this issue. Calculate the value of U = [(D1t1)/(D2t2)]0.5 According to Fig. 4.20, what is the final depth of the junction resulting from this two-step diffusion? Fig. P3. Diffusion profiles for various values of U. 4. Show that the expression on the extreme right hand side of Eq. 4.5 in the (Jaeger) text has units of atoms/cm2. Homework Assignment #5 (due Tuesday, September 29th, 2015) 1. Read the article “The Accidental Entrepreneur,” by Gordon Moore. Write a summary of this article in WORD. 2. Calculate the number of Si atoms per cubic centimeter. You can do this by considering the diamond structure (Fig. 1-8 of the "DiamondLatticeAndSilicon.pdf " notes) as the unit cell. The lattice constant of silicon is 5.43 Angstroms at room temperature (see Fig. 1-8 again). You also need to know how many Si atoms are in the diamond unit cell. With a little (or considerable) thought, you will find that each corner atom contributes 1/8th of an atom/cell (why?). And each face atom contributes (1/8th?, 1/4th? or ½?) of an atom/cell. And each interior atom contributes 1 atom/unit cell. With this information, you can now calculate the number of Si atoms per cubic centimeter. 3. Calculate the density of silicon. Hopefully you still have your first year college chemistry textbook. If so, you will find that Density = (# of atoms/cm3)*(number of grams/mole)/(number of atoms/mole) The first term is what you calculated in Problem 1. You can find the number of grams/mole from looking at Si in the periodic table. The number of atoms/mole is Avagodro's number. If you do everything right, you should get an answer of about 2 grams/cm3. 4. Find the number of Si atoms/cm2 on the (100) surface of silicon. (Read the appropriate chapters of Streetman for an understanding of the nomenclature for specifying crystal surfaces and directions.) 5. Find the number of Si atoms/cm2 on the (110) surface of silicon. (Again, read the appropriate chapters of Streetman for an understanding of the nomenclature for specifying crystal surfaces and directions.) 6. Show that the complimentary error function solution to the diffusion equation satisfies the required boundary conditions. (Note: for problems 6 and 7, see the powerpoint slides on diffusion.) 7. Show that the gaussian function solution to the diffusion equation satisfies the required boundary conditions. 8. Recall Problem 3 of HW #4: For this problem it helps to read section 4.2.3 in Jaeger and look at the Blackboard slides on Diffusion. Calculate the Dt products for the diffusions in Problem 1 and Problem 2 and compare them. What can you say about the final profile after the diffusion steps have been performed according to the traveler? Fig. 4.20 of slide 20 of the Diffusion power point slides addresses this issue. Calculate the value of U = [(D1t1)/(D2t2)]0.5 According to Fig. 4.20, what is the final depth of the junction resulting from this two-step diffusion? Fig. P3. Diffusion profiles for various values of U. Now here is the new problem: Calculate U = [(D1t1)/(D2t2)]0.5 and consider where the curve that corresponds to the value of U should fall on Fig. 4.20. From slide 20, note that the surface concentration is reduced from No, the solid solubility limit from the pre-dep step, by about 2/. (This reduction is approximate because of the (1 + U) term in the denominator of the integral and the actual value of the integral.) Note that the square root of is just the normalized depth of the diffusion that is the horizontal variable in both Figs. 4.4 and 4.20. Now the vertical axis of Fig. 4.20 begins at about 10-3 and your value of the surface concentration/NB is likely to be closer to 10-6, so you can use Fig. 4.20 to see where the curve with your calculated value of U occurs relative to the U = 0 curve (which is equivalent to a Gaussian profile) and the U = infinity curve (which is equivalent to the complimentary error function profile). Now you can use the relative placement of your value of U to sketch in a curve in Fig. 4.4 (which has values on the vertical axis down to 10-6) to find your answer. Now, how does this final answer for the junction depth compare with the answer for the junction depth obtained for the pre-deposition step? Homework Assignment #6 (due Tuesday, October 6th, 2015) 1. Calculate the total number of boron atoms that were diffused into one of the source (or drain) regions of your wafer. You can choose the dimensions of the source (or drain) of the device (#2) that you photograph during lab sessions. Recall that you first did a constant source diffusion (Eq. 4.5), which provides you with the total “dose” Q, which is the number of boron atoms/cm2. To find the total number of boron atoms diffused into either the source or drain region, you need to multiply the “dose” by the area of either the source or the drain. Problem 2. In Problem 8 of HW#5 (and Problem 3 of HW#4) you calculated the junction depth after the boron diffusion described in the MOSFET traveler. Compare your answers for the junction depth to the answer obtained from one of the online calculators for diffusions. A google search produces several, such as http://fabweb.ece.illinois.edu/utilities/difcad/ (Note: There are no guarantees that these or other online calculators are accurate…) Now that you know (within some uncertainty…) the depth of the junction, calculate the average doping concentration for the source and drain. We will use the average doping concentration of the p-region and the doping concentration of the substrate of your wafer in future calculations of the properties of the p-n junctions formed in your wafer. 3. Read the article “Changing the (Transistor) Channel,” by Richard Stevenson. This article, which appeared in the July 2013 issue of the IEEE Spectrum, is one person’s view of the future, and can be found in Course Documents on Blackboard or online at http://spectrum.ieee.org/semiconductors/design/changing-the-transistor-channel Write a summary of this article in WORD. Homework Assignment #7 (due Tuesday, October 13th, 2015 or Wednesday October 14th, 2015 before noon if Fall Break is too much of a distraction) 1. (50 pts) Figure 4.19 illustrates an npn bipolar junction transistor. Design a pnp bipolar transistor that has a reasonable chance of working. You can also look at Fig. 7-17 (a) on page 369 of “Solid State Electronic Devices,” 6th edition by Streetman and Banerjee. (For this problem, a “reasonable chance of working” means that the doping of the emitter region is greater than the doping of the base region, which in turn has a doping level greater than that of the collector. You do not have to worry (for this problem) about the dimensions of the emitter, base and collector.) You choose the substrate orientation and doping. You also choose the p and n dopants and what temperatures and times are used for the diffusions. Give reasons for your choices. Accurately plot (as opposed to sketch) N(x) for the dopant that you choose for the time and temperatures that you choose for the diffusions. Your plot should be somewhat similar to the top plot in Fig. 4.19 above. 2. Kaitlin Smith (Fall 2012) and Alex Small (Fall 2014) are responsible for these questions: a) what is the value for a constant source distribution N(x,t) if t = infinity? Why? Show that the equation for N(x,t) for a constant source distribution satisfies this boundary condition. b) what is the value for a limited source distribution N(x,t) if t = infinity? Why? Show that the equation for N(x,t) for a limited source distribution satisfies this boundary condition. Homework Assignment #8 (due Tuesday, October 20th, 2015) 1. Consider the wafer you are processing in the clean room. Although we know that the value of the p-doping in the source and drain decreases with depth, approximate the p-doping in the source and drain as a constant value. Justify (see your previous homework) the value you choose for your approximation. 2. Consider the wafer you are processing in the clean room. What is the value of the n-doping in the substrate? 3. Consider the wafer you are processing in the clean room. Calculate the total area of the depletion region associated with the source or drain. The value for ni can be obtained from Fig. 3.17 below. 4. Consider the wafer you are processing in the clean room. Calculate and plot the charge distribution in the vicinity of the junction. Assume abrupt junctions. 5. Consider the wafer you are processing in the clean room. Calculate and plot the electric field distribution in the vicinity of the junction. 6. Consider the wafer you are processing in the clean room. Calculate and plot the built in voltage across the junction. Homework Assignment #9 (due Tuesday, October 27th, 2015) The first five questions relate to the pn junctions formed by the source (or drain) regions of device #2 on your 3311 wafer: 1. What is the area of the pn junction? 2. In the equation for the I-V relationship for a pn junction (see below), what are the values of the minority carriers on either side of the junction? (In the pn junction powerpoint slides (3311pnJunctions), we show nno*pno = ni2 = npo*ppo (Eq. 29), where nno ~ ND in the n region and ppo ~ NA in the p region and ni is given in Fig. 3-17 (see HW#8). So you can use Eq. 29 to find the concentration of minority carriers in the n region from pno = ni2/ND and the concentration of the minority carriers in the p region is given by npo = ni2/NA. 3. In the equation for the I-V relationship for a pn junction (see below), what values should you use for the diffusion coefficients and diffusion lengths? (Hint: see Problem #3 a) and b) of your midterm exam.) 4. Calculate and plot the current flowing through the pn junctions of device #2 on your 3311 wafer as a function of voltage over the range of -3 volts to plus 1.5 (or so) volts. 5. (30 points) On slide 88 or so of the PN junction powerpoint slides, the following equations appear: a) For the wafer you are processing in the clean room, calculate EF for the substrate. Using this value of EF, calculate and plot n(E) = f(E)xNC(E) as a function of electron energy E in the conduction band and p(E) = [1-f(E)]xNV(E) as a function of hole energy in the valence band. Note that your plots should look like one of the plots in the fourth column below, which is Fig. 3-16 in Streetman. b) For the wafer you are processing in the clean room, calculate EF for the average value of the doping in the source (or drain). Using this value of EF, calculate and plot n(E) = f(E)xNC(E) as a function of electron energy E in the conduction band and p(E) = [1-f(E)]xNV(E) as a function of hole energy in the valence band. 6. (20 points) Explain how a pn junction works. Specifically, what happens when you bring together a block of p-type material and a block of n-type material? Why is a depletion region formed? Why do we have an electric field with no applied voltage? Why is there a built-in voltage with no applied voltage? Explain the I-V curve of a pn junction. Note that this question covers recent lectures that correspond primarily to slides 2 through 31 or so on the powerpoint slides labeled: “PNjunctions.” This is the same question you may be asked on the oral midterm and/or oral final exam. Note: a revised version of this write-up should appear as an appendix in your final MOSFET report. Homework Assignment #10 (due Tuesday, November 3rd, 2015) 1. Derive two formulas for the width W (Eq 5-21 and Eq 5-22 in the text) of the depletion region of an abrupt junction. How does W change if a forward bias is applied to the pn junction? If a reverse bias is applied? (You may want to look at Appendix 2 of the power point slides on pn junctions.) 2. Derive the formula xpo for the depletion width on the p-side (see Eq 5-23a in the text) of the depletion region of an abrupt junction. How does xpo change if a forward bias is applied to the pn junction? If a reverse bias is applied? (You may want to look at Appendix 2 of the power point slides on pn junctions.) 3. Derive the formula xno for the depletion width on the n-side (see Eq 5-23a in the text) of the depletion region of an abrupt junction. How does xno change if a forward bias is applied to the pn junction? If a reverse bias is applied? (You may want to look at Appendix 2 of the power point slides on pn junctions.) 4. Expand ex in a Taylor series. Using the first few terms in the Taylor series, calculate and plot the I-V relationship for the pn junctions of device #2 on your 3311 wafer as a function of voltage, particularly for small positive and negative values of V. How does this plot of the Taylor series solution compare to the exact plot for the same values of voltage? The following is a definition of the Taylor series (from: http://en.wikipedia.org/wiki/Taylor_series) The Taylor series of a real or complex function ƒ(x) that is infinitely differentiable in a neighborhood of a real or complex number a is the power series which can be written in the more compact sigma notation as where n! denotes the factorial of n and ƒ (n)(a) denotes the nth derivative of ƒ evaluated at the point a. The zeroth derivative of ƒ is defined to be ƒ itself and (x − a)0 and 0! are both defined to be 1. In the case that a = 0, the series is also called a Maclaurin series. 5. (70 points) Read the following articles related to blue LEDs and the 2014 Nobel prize: a PrefaceBookNakamuraALL b c d e f BlueChipScientificAmerican BlueAboutJapan Interview Nakamura BenjaminGross How America Lighted the Way for a Japanese Nobel NichiaNakamura g Nobel Prize snub: Professor Nick Holonyak questions why blue LED is worthy while his - the very first - was not After reading these articles, write down your thoughts and comments. Be prepared to discuss the articles in class. Homework Assignment #11 (due Tuesday, November 10th, 2015) 1. Show that under equilibrium conditions, the Fermi level in a semiconductor is invariant (has a constant value) throughout the semiconductor. Consider two regions of a semiconductor with one region having a density of states N1(E) and a Fermi distribution f1(E) that is adjacent to another region having a density of states N2(E) and a Fermi distribution f2(E). (You may want to look at Appendix 1 of the power point slides on pn junctins.) 2. Draw a complete band diagram for the p region (source and drain) of your class wafer. Assume an average value for the p-dopant (you have done this in previous homework assignments). You need to calculate the Fermi level for the p-region. You can use Figure 4-9 of your textbook to find the acceptor level. Show EC, EV, EF, Ei, EG, EG /2 and EA. Hints: Ei is calculated on slide 96 of the pn junction slides. You can use either equation 3-25b or 3-19 (Streetman) to find EF. 3. Draw a complete band diagram for the n region (source and drain) of your class wafer. You need to calculate the Fermi level for the n-dopant. Assume that the n-substrate is doped with Arsenic. You can use Figure 4-9 of your textbook to find the donor level. Show EC, EV, EF, Ei, EG, EG /2 and ED. Assume the n-doping is Arsenic. Hints: Ei is calculated on slide 96. You can use either equation 3-25a or equation 3-15 (Streetman) to find EF. Your sketch should look something like this: 4. Draw the band diagram for the p-n junctions that exists in the wafer you are processing in the clean room by appropriately combining the band diagrams you made in problems 2 and 3. Include this drawing of the pn junctions formed in your wafer in an Appendix of your Final Report. 5. Consider the total depletion widths and the depletion widths on the p- and nsides the p-n junctions that exists in the wafer you are processing in the clean room. Calculate these depletion widths at equilibrium (0 applied volts); in reverse bias for voltages of 5, 4, 3, 2, and 1 Volts; and in forward bias for voltages of 0.5, 1.0 and 1.5 Volts. Plot the depletion widths as a function of voltage. 6. An alternative to doping semiconductors by diffusion (the method we used in the lab) is a process called ion-implantation. Ion implantation is discussed in Chapter 5 of the Jaeger textbook and briefly in Chapters 5 (the physical process) and 6 (for adjustment of the threshold voltage of MOSFETs) of the Streetman and Bannerjee text. After reviewing these sections of the text, answer the following questions: a) what parameter determines the location of the peak concentration of the dopant in the semiconductor? b) what parameter determines the width of an implant performed at a single beam acceleration energy? c) for an implant that is fully contained within a semiconductor, what is the doping profile? 7. The same technology that is used for implanting dopants in semiconductors is the best technology (in my non-medical opinion) for treating many types of cancer. Read the following articles: “Radiation in the treatment of cancer,”Arthur L. Boyer, Michael Goitein, Antony J. Lomax, and Eros S. Pedroni; Physics Today 55(9), 34 (2002); and “Imaging particle beams for cancer treatment,”Jerimy C. Polf and Katia Parodi; Physics Today 68(10), 28 (2015). If you don’t get cancer (approximately 1 in 7 males get prostate cancer over their lifetime and about 1 in 8 females get breast cancer over their lifetime), you almost certainly will have a close friend or relative that does get cancer at some time in your life. Answer the following questions: a) give a rough/crude explanation of how radiation kills cells. b) sketch the absorption of photon (X-ray) radiation as a function of depth in water (or gelatin, or human tissue). c) On the same graph as b), sketch the distribution of protons as a function of depth in water (or gelatin, or human tissue). d) Explain how the use of a particle beam of radiation can deliver the same total dose to a cancerous tumor as a photon (X-ray) beam of radiation, but do much, much less damage to healthy tissue and organs that surrounds the tumor. NOTE 1: There are about 20 centers in the US that provide proton beams for cancer treatment. One of the most recent opened in the last year or so in the Dallas area. The oldest hospital center began treating cancer with protons in 1992 at Loma Linda University Medical Center in Loma Linda, CA. NOTE 2: Further details related to the treatment of prostate cancer by proton beams are contained in the powerpoint slides “ProstateSMUFeb28_2014rsR1,” “EvansInterview,” and “Prostate Cancer AbstractR2,” all of which are available on Blackboard.