Exam1Fall2008Solution - ECE 6450 Introduction to...

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Unformatted text preview: ECE 6450 Introduction to Microelectronics Technology Exam 1 September 13, 2008 Dr. W. Alan Doolittle Print your name clearly: Solulienfi New" Solutions are on was "0m; 1'" +65%. Your 39%!" #- Instructions: exam 4 Cgrfa 'Hanj in aide . Read all the problems carefully and thoro ghly before you begin working. You are allowed to use 1 sheet of notes (1 page front and back) as well as a calculator. There are 100 total points. Observe the point value of each problem and allocate your time accordingly. SHOW ALL WORK AND CIRCLE YOUR FINAL ANSWER WITH THE PROPER UNITS INDICATED. Write legibly. If I can not read it, it will be considered to be a wrong answer. Do all work on the paper provided. Turn in all scratch paper, even if it did not lead to an answer. Report any and all ethics Violations to the instructor. Good luck! Sign your name on ONE of the two following cases: I did not observe any ethical violations during this exam: ———-—————__._._._h________ I observed an ethical violation during this exam: Problem 1. (25 points total in 5 ' point parts): TruefFalse and Multiple Choice and short answerr’calculation: ‘ a.) Based on the period table (see attached table) which of the following are true (one or more swers. possible)? a}, P BAs will have a larger bandgap than GaAs 6“ A5 InSb will have a smaller bandgap than InP . AlogGaang is not a real semiconductor since its indexes add up to 2. I V" i? 4.) All of the above 5.) None of the above 6.) I wish I had gone to Clemson instead of Ga Tech. b.) Which of the following defects can enhance diffusion of a dopant (may have more than one answer.'...or not)? Vacancies a) __ ntcrstitials I islocations 4.) Stacking faults 5.) Precipitates Grain Boundaries q H @iven the diffusion profiles obtained below ‘for the same temperature in bath-cases, which of the following are true (may have more than one answers...or not)? 1. This is a pre—deposition diffilsion. This is a drive in diffusion. @1 he diffiision coefficient is constant. @ For the 0.15 um characteristic diffusion len; h case, it was performed ’9’” 5 A“ ' a than the 0.25 um case. 5.) The diffusion coefficient is lower at high concentrations. In as 1.: :5 213 “film d.) The present (<65 node) Intel process completer replaces SiOz with Hng . True 0 (circle the correct answer) u 585 g; 0a 5 .. H F 09‘ j 0!. a w! 9 +9 1 continugd — part 6.) The equivalent oxide thickness (BOT) is the thickness of a SiOg needed to result in the same capacitance as SiOz. Using thicker “high k” (higher dielectric constant than SiOz) dielectrics can result in decreased leakage current compared to thinner SiOZ. Leakage current (in the tunnel current limited case) is proportional to: efl'thiCknessxmichess” (in words this is current is proportional to the exponential of the thickness squared). 7 q? firm where q 1: \ hm It is desired to change a 1 nm thick Si02 dielectric process into a process based on a foSl1.x02 dielectric that has a relative dielectric constant (kr or Sr) of 7.0 instead of SiOz’s value of 3.9. What reduction in leakage current (ratio of currents only NOT exact values of current) is expected? 3) “ml-‘3'? :: ~2— Inn INF if“: T. i.7afhm .‘aa W‘ “'3' Q Int at Q‘LTA); .. __ ma ‘ Q :3 rmm-ms' ,.‘,mm_. D. gov-wI‘.«H-M¢mm.mmWerJ‘5"‘5m" ' Problem 2. (15 points total): GaAs devices often use a Gold-Germanium alloy for ohmic contacts. This “alloyed contact step” must be performed at low temperature to prevent As out diffusion and other problems. A. (5 points) What is the melting points of gold (Au) and Germanium (Ge)? B. (10 points) explain how and at what lowest possible temperature the solid connection is made. For full credit, keeg our descri lion to 3 sentences or less and eel ree to draw on the hose die ram :0 urthure explain your answer. “Elfifi'! PE“ can Sfifiuflfitijfi 1:2 26' SCI ‘0 m rtxreuwnz,‘¢ U) o :1 :1. 3. 0 to 20 an m 55 7 as; Home PER can“ “$2941” a " Be Fig;- 12]. Act-Ge Harman d Aflderfw, (Tam-153‘an of Brim Alloy 1.058, p. 206 / (qt-(mews: En+ccfifc :1: 356°C sl— Lfifi 6e 8] M58 W651“? {ya Géymveal’cnr- 1‘3 37 «Mimic. Heal— +0 jmfir like“ 3552‘ (a0; 6M6! G? 35;”: “we “do a {fi-fi‘fifitf": Mum-x... '---—-. . _. M KIM \ f’ ( Problem 3;,.,..(430 points total): x.“qu “““““ Arsenic (As) is first deposited in a p—type silicon wafer uniformly boron doped at 1x1015 cm'3 _ (bulk concentratio fer using Arsine (AsH3) at 1000 degrees C where the solubility of As in C a ilicon is 1x10 cm'3. Assuming a neutral vacancy controlled diffusion with _.| cmzlsec 5 "'" a— . e '- __.. . , a— 0 points) what is the time required to achieve a dose 1: (b-10 points) If the wafer is then capped and the arsenic is then driven into degrees C, how much time is required to achieve a junction depth of 0.1 um? 6;“; , K Note:e;fc(x)=J-erf(x), erf(0)=0, 97f(°°)=1 We 2:1 re '9 _ “tr/tom) r I” .r‘" h) a? w.- : 0.0663- : use edge»,ka [000% a) __ C; e *- g’qlf’ /An(937§) up -= LEM-“1‘ sag/m @. “00°C W Problem 4. (30 points total): Problem Statement: A silicon wafer has a cylindrical hole etched into it that is 0.5 um diameter. Your university’s ! company’s cheap equipment cannot make holes smaller than this size. Because you took Dr. Doolittle’s class, you remember that oxides can “add volume" to a wafer thus you can “close up the diameter of the hole” making the oxidized hole diameter smaller than the original hole. InItlal SI Wafer with ' ' ' ‘ a h la etched Into it 5i Wafer with an (a. 10 pornts) What time 15 required to ° {top New) mama hole {up New} make a holeuofi l um diameter using W3+ @fllfié’g’oxide grown at 1200 degrees C? (b. 10 points) If the hole is fher I}, shrank by a 1200 degree quality” oxide to a diameter 0 .05 um, how much time is required? (c. 10 points) Is the new semiconductorfoxide interface (just the interface not the oxide bulk) “high quality” or “low quality” based on electrical characteristics? Justify your answer in 3 sentences or less. Assumptions: _ Assume lateral oxidation occurs at the same rate as the planar oxidations we discussed in class (LE. consider only the 1 dimensional case), the wet oxide parameters are valid for all regions, regardless of initial conditions, and the porosity and density of wet and dry oxides are the same. To answer this question you must know which oxide, wet or dry is of higher quality. 7- l" I| L,“ At 1200 degrees C: |/ Dry ' 5L 7' “a I / A=0.04 um, B=0.045 umthr and t=0.027 hr for dry oxides was. a L car a be A *7 A=0.05 urn, B=()F’7Ealiuenthr and 1:0.0 hr for wet oxides. K CQn‘ter 0 " ' " "" - ’ a'agqh q) 0. atas 0. xax :> zdg:'?_ 065,3”. I Iv A'KE (— 5: Odin-x“ You may show your work here In) Alreajy 6.654%; axfrje '. a J/ “a 7693' + A max @351) + amdoerfl '2. T; . 4'7 T "“ (9mg; ,4 Lily: % M5 I WON! " game may {Wei-"9r “'6' “ofj 3J5, +0 0.037 (a ‘09:” 45 mm! vkidrwss), I acceffla/ fé+kér 6016M, "” "‘ ._ 0.08331“ 0,5616“ -— 0.35,on 19x ral-f0f Aim \ @J'I‘GUQ + 0.0"- {0.'-l-dl) ‘: 0 .O‘HF (wt-4 3J5“) . H._ t a C) Tke new inmf‘fi‘tfié’ :fi mach“) fix'kce apgjf‘i-éflma( g} m5 canéumesf I‘m 4M2 aria 5+ef, M’. Tke. Ami fit {9(3- Me axial? We; 5+3” Le “law $MLWyH 1.“. may Amara Lean. Jammiflej Jada; >¢AQ Jr), C axiopawdh. Erf Table Table 151.1 Error Functlbn erf z." z erftz.) 2 0111-2} 2 erfiz} z erflz} 0.00 0.000000 0.50 0.520500 100 0842 201 150 0900105 0.01 0011283 0.51 0.529244 101 0.840810 1.51 0.902222 0.02 0.022565 0.52 0.532 899 102 0.850818 1.52 0.908 413 0.03 0.033 841 0.53 0.546 464 103 0.854 284 1.53 0.909 516 0.04 0.045111 0.54 0.554 939 1.04 0.858 050 1.54 0.920 580 0.05 0.050 322 0.5-5 0.503 323 1.05 0.802430 1.55 0.921023 0.06 0.002622 0.56 0.521016 106 0.800144 1.50 0.922 028 0.02 0.028 858 0.52 0.529 816 1.02 0.809 223 1.52 0.923 603 0.08 0.090 028 0.58 0.582 923 1.08 0.823320 1.58 0.924 542 0.09 0.101281 0.59 0.595 936 1.09 0.820 8.03 1.59 0.925 462 0.10 0.112 463 0.60 0.003 856 1.10 0.880 205 1.00 0.920 348 0.11 0.123023 0.61 0.611681 1.11 0.883 533 1.01 0.922 202' 0.12 0.134 258 0.02 0.019411 1.12 0.886 288 1.62 0.928 038 0.13 0.145 862 0.03 0.022046 1.13 0.889921 1.03 0.928 843 0.14 0.150 942 0.64 0.034 580 1.14 0.893 082 1.64 0.929022 0.15 0.162996 0.05 0.642 029 1.15 0.890124 1.05 0.980320 0.16 0.129012 0.00 0.049322 1.10 0.899090 1.66 0.981105 0.12 0.189992 0.02 0.050028 1.12 0.902000 1.02 0.981810 0.18 0.200930 0.08 0.063 282 1.18 0.904 832 1.68 0.982 493 0.19 0.211840 0.09 0.620840 1.19 0.902008 1.09 0.983153 0.20 0.222 203 0.20 0.022 801 1.20 0.910314 1.20 0.983 290 0.21 0.233522 0.21 0.084660 1.21 0912950 1.21 0.984402 0.22 0.244 296 0.22 0.091433 1.22 0.915 534 1.22 0.985003 0.23 0.255 023 0.2.3 0.098104 1._3 0.918050 1.23 0.985 528 0.24 0.205 200 0.24 0.204 628 1.24 0.920 505 1.24 0.980135 0.25 0.220326 0.25 0.211150 4.25-0.922900 1.25 0.980622 0.20 0.280900 0.20 0.212 532 1.20 0.925236 1.26 0.982190 0.22 0.292418 0.22 0.223 822 1.22 0.922514 1.22 0.982 091 0.28 0.302 880 0.28 13.230010 1.28 0.929 234 1.28 0.988124 0.29 0.318 283 0.29 0.230103 1.29 0.931899 1.29 0.988 641 0.30 0.328 022 0.80 0.242101 1.30 0.934 008 1.80 0.989091 0.31 0.338908 0.81 0.248003 1.31 0.930063 1.81 0.989525 0.32 0.349120 0.82 0.253 811 1.32 0.938 005 1.82 0.989 943 0.33 0.359 229 0.83 0.259524 1.33 0.940 01-5 l.83 0.990 342 0.34 0.309305 0.84 0.205143 1.34 0.941914 1.84 0.990236 0.35 0.329382 0.85 0.220008 1.35 0.943 202 1.85 0.991111 0.30 0.389330 0.86 0.220100 1.36 0.945501 1.80 0.991422 0.32 0.399 206 0.82 0.281440 1.32 0.942312 1.8-2 0.991821 0.38 0.409009 0.88 0.286 682 1.58 0.949 010 1.88 0.992150 0.39 0.418 239 0.89 0.291843 1.39 0.950 623 1.89 0.992 429 0.40 0.428 392 0.90 0.290908 1.40 0.952 285 1.90 0.992 290 0.41 0.432 909 0.91 0.801883 1.41 0.953 852 1.91 0.993090 0.42 0.442 468 0.92 0.800 208 1.42 0.955 326 1.92 0.993328 0.43 0.456 882 0.93 0.811504 1.43 0.950 852 1.93 0.993 050 0.44 0.460225 0.94 0.816 221 1.44 0.958 292 1.94 0.993923 0.45 0.425482 0.95 0.820 891 1.45 0.959095 1.95 0.994129 0.46 0.484 055 0.90 0.825424 1.40 0901054 1.96 0.994 420 0.42 0.493 245 _ 0.92 0.829 820 1.42 0.962 323 "1.92 0.994004 0.48 0.502250 0.98 0.834 232 1.48 0.903054 1.98 0.994892 0.49 0.511668 0.99 0.838508 1.49 0.904898 1.99 0.995111 Erf cont’d 2.00 0.995 322 2.50 0.999 593 3.00 0.999 92'? 91 3.50 0.999 999 25? 2.01 0.995 525 2.51 0.999 614 3.0] 0.999 929 26 3.51 0.999 999 309 2.02 0.995 219 2.52 9.999 634 3.02 0.999 980 53 3.52 0.999 999 358 2.03 0.995 906 2.53 0.999 654 3.03 0.999 981 23 3.53 0.999 999 403 2.04 0.996 086 2.54 0.999 622 3.04 0.999 982 86 3.54 0.999 999 445 2.05 0.996 258 2.55 0.999 689 3.05 0.999 983 92 3.55 0.999 999 485 2.06 0.996 423 2.56 0.999 706 3.06 0.999 984 92 3.56 0.999 999 521 2.0? 0.996 582 2.5? 0.999 222 3.07 0.999 985 86 3.57 0.999 999 555 2.08 0.996 234 2.58 0.999 736 3.08 0.999986 24 3.58 0.999 999 58? 2.09 0.996 880 2.59 0.999 251 3.09 0.999 98? 5'? 3.59 0.999 999 61? 2.10 0.997 021 2.60 0.999 764 3.10 0.999 988 35 3.60 0.999 999 644 2.11 0.997 155 2.6] 0.999 727 3.11 0.999 989 08 3.61 0.999 999 670 2.12 0.997 284- 2.62 0.999 289 3.12 0.999 989 2'? 3.62 0.999 999 694 2.13 0.997 40'? 2.63 0.999 800 3.13 0.999 990 42 3.63 0.999 999 236 2.14 0.997 525 2.64 0.999 811 3.14 0.999 991 03 3.64 0.999 999 736 2.15 0.997 639 2.65 0.999 822 3.15 0.999 991 60 3.65 0.999 999 756 2.16 0.992 247 2.66 0.999 831 3.16 0.999 992 14 3.66 0.999 999 T23 2.1? 0.997 851 2.6? 0.999 841 3.1? 0.999 992 64 3.67 0.999 999 290 2.18 0.997 951 2.68 0.999 849 3.18 0.999 993 I? 3.68 0.999 999 805 2.19 0.998 046 2.69 0.999 858 3.19 0.999 993 56 3.69 0.999 999 820 2.20 0.998 137 2.70 0.999 866 3.20 0.999 993 97 3.20 0.999 999 833 2.2! 0.998 224 " 2.21 0.999 823 3.21 0.999 994 36 3.21 0.999 999 845 2.22 0.998 308 2.22 0.999 880 3.22 0.999 994 23 3.72 0.999 999 85? 2.23 0.998 388 2.73 0.999 88? 3.23 0.999 995 07 3.73 0.999 999 867 2.24 0.998 464 2.24 0.999 893 3.24 0.999 995 40 3.24 0.999 999 87? 2.25 0.998 53‘1r 2.75 0.999 899 3.25 0.999 995 20 ' 3.75 0.999999 886 2.26 0.998 607 2.76 0.999 905 3.26 0.999 993 98 3.26 999 895 2.27 0.998 674 2.7? 0.999 910 3.2? 0.999 996 24 3.77 0.999 999 903 2.28 0.998 738 2.78 0.999 916 3.28 0.999 996 49 ' 3.?8- . 0.999 999910 2.29 0.998 799 2.29 0.999 920 3.29 0.999 996 22 3.29 0.999 999-917 2.30 0.998 857 2.80 0.999 925 3.30 0.999 996 94 3.80 0.999 999 923 2.31 0.998 912 2.81 0.999 929 3.31 0.999 992 15 3.81 0.999 999 929 2.32 0.998 966 2.82 0.999 933 3.32 0.999 997 34 3.82 0.999 999 934 2.33 0.999 016 2.83 0.999 937 3.33 0.999 997 52 3.83 0.999 999 939 2.34 0.999 065 2.84 0.999 941 3.34 0.999 997 68 3.84 0.999 999 944 2.35 0.999 11 | 2.85 0.999 944 3.35 0.999 99‘? 838 3.85 0.999 999 948 2.36 0.999 155 . 2.86 0.999 948 3.36 0.999 997 983 3.86 0.999999 952 2.37 0.999 197 2.8? 0.999 951 3.37 0.999 998 120 3.87 0.999999 956 2.38 0.999 23? 2.88 0.999 954 3.38 0.999 998 24? 3.88 0.999 999 959 2.39 0.999 275 2.89 0.999 .956 3.39 0.999 998 367 3.89 0.999 999 962 2.40 0.999 311 2.90 0.999 959 3.40 0.999 998 478 3.90 0.999 999 965 2.41 0.999 346 2.91 0.999 961 3.41 0.999 998 582 3.91 0.999 999 968 2.42 0.999 379 2.92 0.999 964 3.42 0.999 998 679 3.92 0.999 .999 970 2.43 0.999 411 2.93 0.999 966 3.43 0.999 998 270 3.93 0.999 999 973 2.44 0.999 441 2.94 0.999 968 3.44 0.999 998 855 3.94 0.999 999 975 2.45 0.999 469 2.95 0.999 970 3.45 0.999 998 934 3.95 0.999 999 9?? 2.46 0.999 497 2.96 0.999 922 3.46 0.999 999 008 3.96 0.999 999 979 2.47 0.999 523 2.9? 0.999 923 3.42 0.999 999 027 3.9? 0.999 999 980 2.48 0.999 54'? 2.98 0.999 975 3.48 0.999 999 141 3.98 0.999 999 982 2.49 0.999 521 2.99 0.999 976 3.49 0.999.999 201 3.99 0.999 999 983 M " For a more compiete table. see L. J . Comrie, Chambers Six Figure Mathematica! Tables, Vol. 2, W. & R. Chambers. Edinburgh. 1949. ...
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