Compositional characterization of SiC-SiO2 interfaces in MOSFETs

Composi ional cha ac e iza ion o SiC-SiO2 in e aces in MOSFETs AM Bel án1,2,3, S Schamm-Cha don1, V Mo e 3, E Bedel-Pe ei a3, F C is iano3, C S enge 4 and AJ Baue 4 1. CEMES-CNRS, Uni . de Toulouse, BP 94347, 31055 Toulouse Cedex 4, F ance 2. CNRS, LAAS, 7 a enue du colonel Roche, F-31400 Toulouse, F ance 3. Uni de Toulouse, LAAS, F-31400 Toulouse, F ance 4. F aunho e IISB, Scho kys asse 10, 91058 E langen, Ge many Email o co esponding au ho : bel an@cemes. Keywo ds: 4H-SiC MOSFETs, STEM-EELS, SiC/SiO2 in e ace Silicon ca bide (SiC) is ex endedly s udied o i s use in powe elec onic de ices wo king a pa icula condi ions hanks o i s ad an ageous physical p ope ies. Among he di e en poly ypes, 4H-SiC is he mos a ac i e due o i s la ges bandgap, high elec on bulk mobili y and a ailabili y. Ne e heless, he de elopmen o me al oxide semiconduc o ield e ec ansis o s (MOSFETs) based on his ma e ial is limi ed because o he mobili y deg ada ion such as he low ca ie mobili y in he in e sion laye [1,2]. La ely, i has been p oposed ha bulk aps in SiC educe elec on mobili y and hey a e ela ed o ca bon (C) clus e s (0.10-0.15 nm) a he SiC-SiO2 in e ace [3] o C-en ichmen o e ew o ew ens nm ac oss he SiC-SiO2 in e ace, as i has been obse ed by Elec on Ene gy Loss Spec oscopy (EELS) [4]. In he con ex o he MobiSiC p ojec (Mobili y enginee ing o SiC de ices) [5], we s udy 4H-SiC MOSFETs wi h he aim o ge mo e insigh in he C dis ibu ion and na u e ac oss he SiC-SiO2 in e ace and o co ela e he esul s wi h elec on mobili y measu emen s. In es iga ions a e based on he combina ion o s uc u al and composi ional analyses ca ied ou by high esolu ion ansmission elec on mic oscopy (HRTEM) and spa ially esol ed EELS. Two se s o samples wi h n-channel plana MOSFETs a e s udied. The i s se (p- epi) and he second (p-imp) we e ab ica ed on p- and n- ype 4°-o 4H-SiC (0001) Si- ace epilaye s, espec i ely. The subs a es we e p o ided by CREE Inc. The ga e oxides we e g own by oxida ion in N2O a mosphe e a 1553 K and subsequen ly annealed a he same empe a u e o 30 min unde N2 ambien . Fu he de ails abou he sample ab ica ion p ocess and he mobili y esul s can be ound in e e ences [6,7]. TEM in es iga ions ha e been pe o med on a ield emission FEI Tecnai™ F20 mic oscope ope a ing a 200 kV. This mic oscope is equipped wi h a co ec o o sphe ical abe a ion dedica ed o he di ec obse a ion o a omic s uc u es a in e aces wi h subs an ially educed con as delocaliza ion in he images. I allows us he analysis o de ec s in he SiC side and e en ual C clus e s in he amo phous SiO2. Local EELS s udies we e conduc ed wi h a scanning s age (STEM) allowing a ocused one nanome e-sized p obe o be scanned o e he sample a ea o in e es and an imaging il e (Ga an GIF TRIDIEM) used as a spec ome e . F om his, elemen al p o iles ac oss he SiC/SiO2 in e ace ha e been acqui ed. TEM-lamellas ha e been p epa ed by ocused ion beam (FIB). Addi ionally o he common di icul ies o p epa e TEM-lamellas, especially by FIB, hese samples a e e en mo e di icul since he SiC is ha de han SiO2, so a g adien o hickness a ound 30% is obse ed a he in e ace wha e e he p ocess used o he ab ica ion o he sample (p-epi and p-imp). S uc u al in es iga ions by HRTEM bu also by weak beam elec on di ac ion e eals no de ec s in he SiC excep hose ela ed o he dopan implan a ion and also no ex ended C clus e in he SiO2. F om elemen al p o iles, we do no see C o e -s oichiome y ac oss he in e ace bu a he an a ea o smoo hly composi ional a ia ion ha we de ined as ansi ion laye (TL). The only di e ence be ween bo h s udied samples is he wid h o he TL, being la ge o he p-epi han o he p-imp. This esul can be ela ed o he be e mobili y o he p- imp sample han he p-epi [6, 7]. To comple e hese s udies, addi ional chemical and s uc u al in es iga ions a e pe o ming such as a om p obe omog aphy and s ain s udies. The de ailed analyses o he composi ional dis ibu ion a he in e ace help us o unde s and he mobili y esul s and wo k on i s imp o emen in o de o achie e he bes design o MOSFETs wi h su icien ly high mobili y o build mo e ene gy e iciency de ices. Re e ences [1] A Aga wal, S Haney, J. Elec. Ma e 37 (2008), 646. [2] S Po bha e e al, J. Appl. Phys. 100 (2006), 044515. [3] KC Chang e al, Appl. Phys. Le . 77 (2000), 2186. [4] TL Bigge s a e al, Appl. Phys. Le . 95 (2009), 032108. [5] www.iisb. aunho e .de/mobisic [6] AM Bel án e al, Ma . Sci. Fo um 711 (2012), 134. [7] C S enge e al, P oceeding o he ICSCRM 2011 (2012), accep ed. [8] This wo k has been pe o med by he F ench-Ge man Conso ium MobiSiC and suppo ed by he P og amme In e Ca no F aunho e (PICF) om BMBF (G an 01SF0804) and ANR. Au ho s hank P Salles and R Cou s (bo h a CEMES-CNRS) o he sample p epa a ion by FIB and M Hÿ ch and P Benzo (bo h a CEMES-CNRS) o he ui ul discussions abou da k ield elec on holog aphy. The suppo om Robe Bosch GmbH is highly app ecia ed.