3.3.3 Defects in the silicon film

1
3.3.3 Defects in the silicon film

• 3.3.3.1 Most common defect
• The most common defects in SOI layer
• COPs, dislocation, HF defects
• (1)COPs
• (crystal-originated particle or
  crystal-originated pit)
• ????Si wafer(bulk, SOI wafer???)??????
• ??????
• SOI????COPs?top?bottom?Si?????
• ?bottom??top?Si?????????pipe???
• COPs?epitaxial layer????????

2

• (2)Dislocations
• SOI????????????
• ltSIMOX???gt
• Si/buried oxide interface??Si?overlayer???????????
  ????????
• dislocation????yield?????????????????
• ??????diffuse to dislocations upon annealing
• dislocation gate oxide?weak point??????
• low breakdown voltage???
• ltEarly studygt
• SIMOX??gate oxide????integrity?Si
  bulk??oxide???integrity???
• SOI technology dislocation density
  ???????????????

3

• (3) HF defects
• Si????silicides, silicates??????????
• ???Si?????HF(?????)???
• wafer?HF????????????Si??????
• etch time??????
• ?SOI film???BOX?etch???

4

• TEM
• crystal defect?????????? technique?1?
• ?????????????????
• ltTEM cross-sectiongt
• ????????20µm
• ??0.7µm
• ?maximum observable area 10-7cm-2
• minimum measurable defect density
  107defects/cm2
• ???????????????????
• sample holder???????????
• (7mm2grid)

?????
5

• ???10,000?????dislocation??????
• ????
• ????10-5cm2
• minimum observable defect density 105
  defects/cm2
• ltTEM??gt
• lengthy, delicate sample???
• ltDefect decoration techniquegt
• optical microscopy?????????
• ?????????defects??????????
• TEM??????????

6
3.3.3.2 Chemical decoration of defects

• SOI defects decoration ?????etch mixtures
• 
  (Table3-2)

??? (CrO3, K2Cr2O7,,HNO3) ?HF???????????
7

• ltDefect decorationgt
• Si?????higher etch rate?????
• ltDecorationgt
• high-disorder defect(??????)??????
• etch rate of Si 1µm/min
• (Dash ,Secco , Stirl, Wright etch solution)
• Schimmel etch rate??????????
• SOI???decoration of dislocation?classical etch
  mixture?????????
• lt??gt
• ????Si?????decoration of defect?????????????????
• Lower etch rateetch?????????????????

8

• lt electrochemical etching gt
• ??1??decoration technique
• 5??????HF?SOI????????????????
• n-type (Nd?1015cm-3)dose?Si?overlayer???
• ohmic????????front side?back side????
• lt??gt
• 5?HF??1030??????
• 3???????
• ???Si?3V???????????()
• ?Ca/CuF2 reference??
• decoration technique? defect-free Si??etch????

9

• dislocation of defect
• metal contamination-related defect
• oxidation-induced stacking faults
• Si?????????
• optical microscopy???decoration?????? ?????????
• ltetch rategt
• Secco etch?SOI????????????
• optical microscopy???????????????????????Si???etch
  ???????
• Secco solution????etch rate???????

10

• Secco?HF etch?combination
• ?SOI????????????????
• Secco???
• ?Si layer???decorate defect??????????????
• Secco etch???????????????
• ???????????????????
• ??????HF??????
• ???Si??????????buried oxide?etch??
• ?oxide??etch?????????Si layer????????
• ??????? transferred layer etch

11
3.3.3.3 Defection of defects by light scattering

• ??wafer????laser?????????????
• ltDefect-mapping systemgt
• ??????wafer????????????
• scattering center???????????????
• Si film?????????????
• ????center??background scattering noise
• ???????????
• lt??systemgt
• bare Si wafer???

wafer?haze???????
12

• SOI wafer?Si??????????
• ltSOI wafer????gt
• BOX?Si film??????
• Si?????????????????????
• shiny dark

SOI wafer????
13

• bare Si wafer?????????
• laser scattering defect system?
• ?shiny wafer????????
• dark wafer???????????????
• ?background haze????wafer????????
• ?????????????UV laser??????
• Si??UV light?absorption depth???????
• ?????????film????????UV laser???????????

14
3.3.3.4 Other defect assessment techniques

• Impulsive Stimulated Thermal Scattering (ISTS)
• ?SOI wafer?defect density?????????
• lt??gt
• contactless
• non-destructive
• opto-acoustic(???????????)
• ??????????????laser?????
• 
  (?532nm)
• laser??????????
• ???????????

SOI layer???? ??????
15

• ???????????????acoustic wave
• ?????
• ????
• ??????????light beam????????????
• ???????????????
• SOI wafer???
• ???????????????????????????
• ???????????defect density???
• ?????
• Secco etch pit microscopic observation?????????
• 10?????????

????????? acoustic wave physics?????????????
16

• ltPhotoluminescence (PL)gt
• ??????
• ?????
• ???????????? ????
• ltPL??gt
• ??He(4.2K)???(300K)??????????
• ???laser beam???????????????????
• ????????????laser??????
• 510nm??13µm

UV laser
???
17

• ????
• ??????????????
• ???1?????????????????
• ???radiative recombination centers???????
• ??????????????
• ??????carrier?????
• ?????????non-radiatively????
• non-radiative process
• ?????????lifetime???
• ?????????????photoluminescence????????lifetime???
• ???????????????????????

18

• ltdeep-level photoemission signalgt
• ???lifetime?deep-level defect?????
• ?deep-level??????????????????????????
• ltPL systemgt
• SOI wafer?map defect???
• ltdislocation, stacking faults, metal
  precipitatesgt
• ???????lifetime???????????????????

19
3.3.3.5 Stress in the silicon film

• ltRaman microprobe techniquegt
• Si film??SOI fabrication process, device
  process???????stress???
• Ar laser(?457.9nm)????????????
• ????0.6µm ???!
• ??????????????
• virgin bulk Si??????????????
• ?????????????
• ???(FWHM)

??
Si film??stress???????????
20
3.3.4 Defect in the buried oxide

• ltburied oxidegt
• pipes??????????SIMOX???????
• ltSi filamentgt
• buried oxide????SOI layer??substrate ????????
• pipe map???Fig3-9????????????????

21

• wafer???Si film?Texwipe???
• wafer?back?Al?????
• ??????????????pipes????BOX????????
• lt????gt
• CuSO4?Cu2SO42-
• Cu22e-?Cu (s)
• ??stain?Texwipe?????

CuSO4?????SOI wafer??????????
1??pipe?????????Texwipe?????
22

• ltstain???gt
• ?pipe?????????
• ?pipe????????stain????????
• pipe?????????????d?????????
• ohms law??

d
pipe
(3.4.1)
I pipe?????? ?Si???? tBOX BOX??? V ????
23

• ltcalculationgt
• 2???????
• 1????????stain????????
• pipe????????5nm???????
• SOI wafer????????????????????
• copper stain???wafer??????????
• SOI wafer???pipe?????????

copper nitrite???????????????????
24
3.3.5 Bond quality and bonding energy

• ?wafer??bond?quality?strength???????
• Wafer bondingBESOI, Smart-Cut, Eltran
  ?preparation
• ???????
• infrared transmission imaging bouned
  wafer??void???
• ???????

ltIR-imaging?set-upgt ?????????????
25

• bond strengtherg/cm2 or J/m2??????
• 1 erg/cm2 10-3 J/m2
• bond energy???(1)crack propagation technique

bond energy ?
tbblade??? L crack???m tw ?wafer???m E
silicon Youngs modulus166GPa
???????? ??L????????????????? ?)L?10????????50
?error
26
ltYoung modulusgt ??????

• ???S,??L??????F?????????
• ??dL?????????
• ?????
• lt??gt
• sF/S
• lt?gt
• edL/L
• ltYoung?gt
• Es/e
• ?? Pa or N/m2

L
dL
F
S
27

• bond energy??(2)classical Vickers indentation
  Technique
• Vickers indenter diamond-tipped, square-based
  pyramidal

hardness of metal,???????(ceramics, glass)??????
bond interface???? crack??? ?bond energy??? Kic?

toughness of the material
P Vickers tool????? 2ccrack???
ß geometrical factor ? Poisson ratio, EYoungs
modulus