Nghiên cứu xử lý tín hiệu nhỏ phục vụ đo lường

DAI HOC QUOC GIA HA NOI TRITCING DAI HOC KHOA HOC TU^NHIEN DE TAI : NGHIEN Ciru Xir LY TIN HIEU NHO PHUC Vy DO LUCING MA SO: QT-06-45 CHU TRl DE TAI : PGS TS PHAM QLOC TRIEL CAC CAN BO THAM GIA: ThS Nguyen Anh Due HVCH N"uv6n Huu Lam JA^I HOC U U O C G l A r ^ N O ; n^ j N G TAM THONG TIN THUVIEN ^VML HA NOI - 2006 BAO CAO TOM TAT De tai; NGHIEN CUtf XL^ LY TIN HIEU NHO PHUC VU DO LUONG Ma so: QT-06-45 CHU TRI DE TAI PGS TS PHAM QUOC TRIEU CAN B O THAM GIA: ThS Nguyen Anh Due HVCH Nguyen Huu Lam Muc tieu nghicn ciiu - Nghien cuu cac phuong phap xu ly tin hieu nho, lay vf du tin hieu DLTS ling dung vao luang cac dai lugng vat ly, nhan manh phuang phap Fourier, Tach song dong bo Boxcar va Lock-in - Nghien cuu van di tang cuang tin hieu dong ihoi giiim thieu tap nhieu - Tdng hap khai quat ly thuyet va ap dung thuc te Noi dung nghien ciiu - Tong quan ly thuyet ve mot so phirang phap xu ly tin hieu DLTS - Nghien cuu cac guii phap nang cao chat luang tin hieu nho - Nghien cuii cac hieu li'ng lien quan den xu ly tin hieu - Dinh huong xay dung phep - Hudng dSn Luan van cao hoc va viet bai bao khoa hoc Cac ket qua dat diroc - Nghien cuu tinh chat ciia tin hieu nho tren ca sa moi tuang quan giua tin hieu va tap nhi^u tac dong vao he vat ly - Nghien cuu tap hop va khai quat boa mot so phuang phap xu ly tin hieu nho nhu phuang phap Fourier, phuang phap Tach song dong bo, phuang phap Boxcar, phuang phap Lock-in Tin hieu nho duac dan chung la tin hieu DLTS Tuy nhien, hoan toan c6 the su dung cac phuang phap noi tren dd dac, xu ly cac tin hieu nho khac he - Huang dSn 01 Luan van cao hoc theo huang d6 tai Ket qua ciia Luan van: Thiet ke xay dung cong bo khuech dai lock-in so hai pha bang phan mem Labview (two-phase lock-in amplifier) ung dung nghien cuu va dao tao tai Khoa Vat ly - Viet 01 bai bao khoa hoc ve cac phuong phap xu ly tin hieu nho ung dung luang DLTS Tinh hinh sii dung kinh phi - Kinh phi duac cap: 20.000.000 d - Kinh phi da quyet toan: 20.000.000 d KHOA QUAN LY (Kv va "hi rd ho ten XAC NHAN CLA NHA TRtONG S.TS.^W^/J^ CHU TRI DE TAI (Ky va ghi ro ho ten \y^/rh/(^^juci, fotui/' BRIEF REPORT Project title: STUDY ON TREATMENT WEEK SIGNAL FOR IMPROVING MEASURED SYSTEMS Project code: QT-06-45 COORDINATOR: ASSOC PROF DR PHAM QUOC TRIEU KEY IMPLEMENTORS: MSc Nguyen Anh Due Nguyen Huu Lam Project purpose - Study on signal transformation methods for applicadon in measurement the physical quantities, focusing on methods for week signal processing such as Fourier Synch Rectifier, Boxcar Lock-in - Study on problems of increase signals and decreace the noises - Summarise the theories in order to apply into measued systems Project content - Review of the theories for the week signal proccessing (for example DLTS signal) - Study of the methods for improvement of the measured quality - Study of the effects concerning the signal proccessing - Orientate to build measured systems of MSc Thesis - Full fill the contains of the scientific article Project results - 01 research paper - 01 MSc Thesis of N^uven Anh Due (2006) MUC LUC • • Trang Madau CFIUDNG L TIN HIEU DLTS TRONG By\N DAN ^ LI Tin hieu nho DLTS 1.2 Xac dinh mot so thong so \\i tin hieu nho DLTS 1.2T Xac dinh nong muc Np 1.2.2 Xac dinh tiet dicn bat 1.2.3 Xac dinh miic sau CHUDNG 2- CAC PHUONG PHy\P XU' LY TIN HIEU DLTS 2.1 Phuang phap Fourier 2.1.1 Co soTy thuyet 2.1.2 Tinh Uu viel ciia phucmg phap 2.1.3 So khoi va nguyen tac boat dong 2.2 Phuo'ng phap dich cu'a 2.2.1 C a s a l y thuyet 2.2.2 Uu nhuoc diem ciia phuong phap dich cu'a 2.3 Phuong phap tach song dong bo A - B 10 2.4 Phuo'ng phap Boxcar jI 2.4.1 C a s a l y thuyet Ij 2.4.2 Sa khoi chii'c nang ,r CHUONG 3- PFIUONG PHy\P KHUECH DAI LOCK-IN 17 3.1 Gioi thieu chung 17 3.2 Cac khai niem co" ban 17 3.3 Bo phat hien nhay pha (Phase-sensitive deicclion) 22 3.3.1 Gioi thieu 22 3.3.2 Nguyen ly boat dong 22 3.3.3 Cac khai niem lien quan den bp PSD 26 3.4 Khuech dai lock-in hai pha (fwo-phase Lock-in amplifier) 27 3.5 Cac nguon nhieu 28 Ket luan 33 MODAU Trong thuc nghiem vat ly, phep tin hieu nho la mot thach thuc thudng xuyen doi vdi ngudi nghien cuu So dT nhu vay la bai vi tin hieu nho khong phai la tin hieu CO gia tri tuyet doi nho (bien nho, dien ap nho, cuang nho, cong suat nho ) Tin hieu duac coi la nho ta xet tuang quan giua tin hieu can vai tap nhieu di kem theo no Nhu vay, tin hieu nho c6 nghla la xac dinh gia tri va quy luat ciia tin hieu tren nen tap nhieu Neu nen tap nhieu rat Ian ihi tin hieu c6 gia tri tuyet doi Ian cung tra tin hieu nho Nguac lai, neu nen tap nhieu nho thi dii tin hieu c6 gia tri tuyet doi rat nho cung dugfc goi la tin hieu Ion Tuu trung lai, nhiem vu ciia nguai lam thi nghiem dac cac tin hieu nho la phai loai bo, boc tach toi da anh huang ciia tap nhieu vao tin hieu do, phat hien ro rang nhat tin hieu vat ly c^n quan tam De tai nghien cuu ve mot so phuang phap xii' ly tin hieu nho phep dai luang dien nhu phuo'ng phap Fourier, phuong phap tach song dong bo, phuang phap Boxcar, phuang phap Lock-in Day chi la mot so phuo'ng phap thong dung, mot so cong doan qua trinh het sue da dang, phong phii cua thuc nghiem vat ly Tuy nhien chiing cung gop phan tao nhieu cong trinh khoa hoc co gia tri nhieu he gia tri cao tren the gioi cung nhu o Viet nam Nam vu'ng nguyen ly va giai phap thuc hien cac phuang phap co the giup cac nha thuc nghiem nghien cuu doi tugng quan tarn cua minh Bao cao j^om chuo'n Chuangl trinh bay ve mot loai tin hieu nho dien hinh nghien cuu vat ly ban ddn: tin hieu qua ciia cac tam sau (DLTS) Xu ly tot tin hieu ta co the' nhan duac nhieu thong tin v^ cac tam sau chat ban d5n, anh huang ciia no tai chat luang linh kien ban dan Chuong trinh bay ve cac phuo'ng phap xu ly tin hieu nho DLTS Chuong chii yeu dua cac nguyen ly va each thuc hien de co the xan dung vao cac he tin hieu nho khac Chuong trinh bay ve phuang phap Lock-in xii' ly tin hieu nho rat hieu qua cac phep thuc nghiem vdi nguyen ly va each ap dung tin hieu nho Hy vong rang, nhieu nguyen ly do, nhi(!u giai phap thuc nghiem nham nang cao chat luang phep se duac nghien cuu tiep luc irong thoi ^ian tai CHUONG TIN HIEU DLTS TRONG BAN DAN 1.1 Tin hieu nho DLTS Khi bi kich thich ( nhiet, dien hoac quang) tam sau bi lap d^y dien tu va se tra lai trang thai diing neu ngiang kich thich So dien tu tren cac lam sau bi thay doi qua trinh chuyen tiep va duac bieu diln bang phuo'ng trinh sau: dn, _ dp dn (Cp-k, ) ( N r - n , ) - ( e , + k , J n T ( I.I ) dt If dl Trong do: n, p la nong dien tii* va 16 Cp, e„ : la toe dp phat hat tai bang nhiet tuong ung vai 16 \a dien tii kp , kn la cac hang so lien quan den ban chat dan dien Nj la nong dp tam Co the thay doi dp lap day dien tii' ciia tam sau bang chuyen tiep P - N hoac bang hang rao Schottky Gia su CO mot lo'p chuyen tiep N'- P hoac diod Schottky loai P co tam sau nam a niia duoi \'ung cam Hay vo'i chuyen tiep P"^ - N hoac diod Schottky loai N co tam sau nam a nii'a tren vung cam Dien dung tren mot don vi dien tich 16p ngan la; C- (1.2) — \ 2(r, ±V) ' Trong V^^ la the khuech tan ± V tuong ung la the phan cue nguac va thuan N, la n6niz d6 ion lop ngan N,= (N^+N-,)-n-,- ^ ^ _ _ (1.3) Tir cong thiic (1.2) va (1.3) ta thay dien dung cua lop chuyen tiep the hien miic dp lap day dien tu ciia tam sau Neu e^ » e p la truang hop tam sau bat dien tu thi cong thuc (1.1) tra dn n,( e„ - n C j + Nr.n.Cn, (1.4) dl Truang hop phan cue thuan cho chuyen tiep Nong dp dien tu mii^n chuven tiep cao n ti le \(i\ N^^ \a e„ « n.Cn thi (1.4) se la: N, -n-,-(t)- jN, n^(0)) exp( -n.C,.t) Khi t — • x thi np(t)—•Nj Tat ca cac tam deu bat dien tu Truang hop phan cue nguoc lap chuyen tiep Cac hat tai dien bi diy khoi lap ngan Khi c^»x\.C^ , dien tii' duge giai phong khoi tam sau Ta CO np=N-|- e\p( -e,^.T ) S qX^'.^^'i) -exp(-c^^/) A-, + A , 2(f^.+rj Trong truc^ng hop N Y « N ^ CO dang gan diing C(t)- (1.5) C(t)= ?>(^,;+'V,y _ 2{V,+V, cho ket qua chinh xac ma don gian Doi voi qua trinh bai hat tai khong co' ban ihi phiic tap vi no phu thuoc vao co che tiem De xac dinh tiet dien bat nguoi ta co each khac la tinh tu toe dp phat xa vung ngheo e,^ MVN^expt-^'^ (1.10) kT Gia tri eiia tiet dien bat xac dinh bang phuong phap cao han mot bac so vai phuang phap quang Dieu co the cac qua trinh bat xay mot dien truang manh ciia chuyen tiep 1.2.3 Xac dinh mure sau TCr phep miic dp phat xa nhiet e^, ciia hat tai ta co the xac dinh miic sau Thiet lap thi In ( e j phu thupc I/T Dp nghieng ciia duang phu thupc chinh la nang lugng kich boat phat hat lai Tuy nhien nang lugng kich boat khong phai liic nao cung triing vai nang lugng duge Di^u co the cac nguyen nhan sau: 1/ Trong c6ng thuc (1.12) phan truac ciia ham exp phu thupc nhiet dp -Tiet dien bat a , phu thuoc vao nhiet thuanu la khoniz biel truoc -Thanh phan (r,, A; phu thupc bac ciia nhiet dp (- J-} 2/ Su phu thupc vao nhiet dp la khac co' che bat hat tai khac De hieu chinh su anh huong ciia nhiet dp tinh toan co may each sau day: - Hieu chinh theo cac phu thupc manh nhu'ng khoang nhiet dp nhat dinh -Phu thuoc '/r,,A - T" hieu chinh tir 2kT ciia thi l n ( e J \ a T 3.2.2.2 Card am 3.2.3 Ph§n mem 47 51 3.2.3.1 Tin hieu chuan (reference signal) 51 3.2.3.2 Bo nhan 53 3.2.3.3 Bo loc 55 3.2.3.4 Do bien vapha 56 CHUONG IV: KET QUA VA THAO LUAN 58 4.1 Khao sat 59 4.2 Cac ling dung 65 4.2.1 Do he so tu hoa dong 65 4.2.2 Cau can bang AC 66 4.2.3 Do tra khang AC 68 4.2.4 Xay dung bai thuc tap ve khuech dai lock-in so 70 4.3 Cac han che 71 KET LUAN 72 TAI LIEU THAM KHAO 73 PHU LUC 76 Process control and instrumentation methods of the deep-leve! transients in semiconductor devices Pham Quoc Tneu Faculn- of Physics Hanoi Diivcnin- ofSac/ict's l'.\'L.H.\' 354 Nguven Trai Thanh A'uan Hanoi-l'ietnam pliamtrieitui-vnu.edu.vn Abstract— This year marks over 30 years in the development of Deep Level Transient spectroscopy (DLTS) - the si^naJ proccssinu method for determination of characteristics of deep levels in semiconductors based on measurement of capacitance transients From its introduction in I9"4 by David Lan;^ (D.\ Lanij J .-ippL Phys 45 I9"4, p.j():3l the method has undergone many modifications: some were purely theoretical, some were n» include ^e^^ experimental iirran^emeni and technique This paper contains jimnst complete mathematical details on the DLTS me [hods, besides pn)\ idini^ inside inui (he developments \%iiich iia\e been made rL'C'jn[l\ in [he FUCUIIN of Ph\sics Hanoi L[inL'rs]r\ ni NciencL'S \ iemam in this branch of sciL-iiCL- T!ie j\;siL'r:j- ^\ "-he Jeep !e'.'e:s •> n ;rr:n()r:an[ piienomenon :n scTucomJucMr piivsics 1; ;i ueii-known ijiat :Iie;.' e:lLl^o rr.an\' eonsiaeraole '::c:^a^•;ours or" rnatcr;a;s Vr[c eharac:e.-;za:ion of ;he deep :raps laeed many dimculties 'anii! M>~- wiien Lani: has introduced a specrroscopic method ealled ihe Deen Le\'Gl Transieni Spec:roscony (DLTSi •I; This allows ;o deduce rVom :he exponennai eaoaciunce deea>s : see Fi'e.! i Cw'1 = \CL'""" :he basic pararncicrs or :ne rracs sucn as :;ie !c::'.a:;on energy, caprure cross->cc::cn an' accenied :oda; i^ 'he ^rancarc; "in., aithouLih ;[ has ^ c e r a ! !:rr:;:a::ons -Lie," a> "iie -^iou' ran and re:a::\"c:' .ou resoia;:on 10 e:;:rac: :ne :rar -"arameier- rr.mi exponeniia; jeeays Lane has ;n:roi:aee;: •; pioi ntc'.ersus lOOOT :or :lie ^e'.ermina::on n' • arame'.ers • ^ :eehniaue :s :hus '.he de:erm:na:;on w' :;',c ;emneraiure dcnenuence C~'/T L D :O nou, manv ancmpLs ha\e been made n ;h;i ;:e.u :o improve :he DLTS me'.iiod- \i"none d'e reehniques that ;ia\"c been rcponeu Z-\~] (die hst :s eertainiy not eomniete; :nere -ire :\vQ :ha[ at:rae:ed eenerai ar:en::on :nL ph\'sicai -\ X Tem peiature Fi^.l A typical capac;tanc: rransier Fi^. -anys metnod icars Si""•=C.; -'_,.•• for '.-anous /• jnd :_• -xttin'js and ara^vs :n:; lemrsraiurL' denendenc: o\ SiT) T'lc injMmum Je:em:r:e :!ie temperatures T of :ne -mission factor L-^„ -.f 'om hv ihc raie windows are both transformation methods manipulating with the whole range of measured data, usually digitally recorded 512 or 1024 points Recall that the classical S(T) uses only points and throws the rest away In general rhe Fourier and the Laplace signal forms show more sensitive peak structure of rhe gain, but since they not mvolve any rate window the exact emission factor the maximal gain can not be calculated m advance Thus the correspondence of" the peaks and the deep centers appears in these cases somehow subtle and arbitran-' L.ANG'S SIGN.AL FORM A common feature of all spectroscopic methods is the presentation of the analytic algorithm convening the set of the capacitance transients Cft) each of them has been recorded at some preset temperature T into the specific values of certain analytic Inunctions '„(Ti, shov\'ing the peak structures according to T The /,',(T) ha\e two important propenies: (I) they are spectroscopic in the context that each of the peaks m /,',(T) can be associated with one specific deep center and i2) the>' arc linear I.e rhe Arhenms plot [ln[(.'.T") versus lOOOT] transformation of the maxima of arbitrarily chosen peak is linear The t'unciions /,",(T) represent the aigorirhm and usually rhe merhod is named after /,',(TL Hereinafter rhe / , ( T ) are refered ro as the signal Jonji For short we may remove the index /; denoting the time-settings and use /fT) instead of f„(T) The different signal forms involve rhe different number of measured data and have rhe different ability in separation of rhe overlapping deep cenrers The classical Lang's signal form, for example, involves only points in rhe whole transient, whereas the Fourier and the Laplace signal forms are composed principally of rhe whole rransient There is not known any orher spectroscopic signal form rhan the above rhree unril the inrervenrion of [15] The dependence of rhe capacitance transient C(i) on time ;• is considered in general case as: C{t) = CQ^Y.^^'^' (1) where C) is C f / = ^ j , AC=Z^C, = C(r^O)-Cn and i denotes the number of present deep traps With respect to the normalized capacitance given as C„(t)=(C(iJ-C„)/AC, and denote ti=t-d t:=t~d we redefine the Lang's signal for this general case: S(T)=Cji-d)-Cji-cl) = = y_(AC.:iC)[e"'"-" -