A proposal for a standard specifications listing covering requirements for silicon wafers used in solar cell manufacturing is outlined. The specific contents of the general requirements specifications include: ordering information; dimensions and permissible variations; material and manufacture; physical parameters; sampling; test methods; certification; and packaging and marking

Gallagher, B. D.

English

NASA Technical Reports Server

PRECEDlNG PAGE BLANK NOT WED 
STATUS OF SEMI'S SOLAR-GRADE SUESTRATE STANDARDS 
Brian D. Gallagher 
Jet Propulsion Laboratory 
California Institute of Technology 
Pasadena, California 
The primary purpose of the Semiconductor Equipment and Materials 
Institute, Inc. (SEMI), was to manage a local equiprent and materials trade 
s h w  that would attract Santa Clara County's semiconductor capanies. Since 
its forration in 1970, however, SEMI has grown into an international organiza- 
tion providing multiple services to its members. It is guided by industry 
caittees staffed by member-company representatives working to develop 
services beneficial to all. 
The first step of SEMI'S evolution fror a trade-shw organization into 
a full-service trade association occurred in 1973, with the forration of a 
Standards Cmittee. The cmittee explored the possibilities of an institute- 
organized industry effort to standarize specifications for materials, equiprent 
and processes used in semiconductor manufacturing. The first Book of SEMI 
Standards (BOSS) was published in 1978. 
The original Standards C-ittee evolved into seven urjor divisions: 
( 1 ) Chemical Division 
(2)  Equipment Division 
(3) Packaging Division 
(4) Photomask Division 
(5) European Liaison 
(6) Government Liaison 
(7)  Materials Division 
Because participants in the wafering workshop are interested in solar- 
grade substrate standards, a breakdown of the areas of interest to that 
aubcoaittes in the Materials Division is given: 
(1) SiliconWafer 
(2) Silicon on Sapphire 
(3) Epitaxial Substrate 
(4) Gadolinium Gallium Garnet Substrate 
( 5) Solar-Grade Substrates 
The subcommittee approved the General Requirements document on the solar- 
grade substrate standards for balloting by industry on Hay 18, 1981. It now 
stands as an addition to the BOSS. This standard specification covers require- 
ments for silicon slices (wafers) used in solar cell manufacture. Dimensional 
characteristics and crystal-structure defects are the only standardized 
https://ntrs.nasa.gov/search.jsp?R=19820015801 2020-03-21T16:59:43+00:00Z
properties set forth. Three clarrer of material are defined! polycrystallint, 
substantially monocrystalline and monocrystalline. These are defined ar: 
(1) Polycrystalline: does not meet requirements of another class. 
Minimum grain rite of El timer the slice thickness. 
(2) Subatantially Monocrystalline: not rare than X grain boundarier 
per slice or Y a total length of grain boundaries, or having no 
crystalliter amaller than 0.2 of the width of the slice.* 
(3) Honocrystallinet free of grain boundaries. 
A complete purchase spec if ication require8 that additional physical 
properties be defined. These properties are listed with test methods suit- 
able for deternining their magnitude. 
The Standards format consists of two specific documents: the first 
describes the general requirements of the specification that is applicab?e 
to all of the SEX1 Standards. The second, which will be the SEMI Sttsaard 
specification for that particular substrate, will describe the specif ic 
dimensional characteristics and crystalline structure, 
A breakdown of the specific paragraphs of the general requirements 
specification and a statement of content follows: 
Preface: contains the general information as given above. 
Applicable Documents: the applicable ASTH Standards and DIN 
Standards that are required to measure specific properties, and 
statistical documents for test sampling, are listed. 
Definitions: the required definitions are stated specifically 
(e.g., define a "lot"). 
Ordering Information. 
Dimensions and Permissible Variations. 
Materials and Manufacture: defines the structural class or 
growth method. 
Physical Parameters. 
Sampling. 
Test Methods. 
Certification. 
Packaging and Marking. 
A specific example of a proposed slice specification, in chis case for 
a square slice, is given in Table 1 and Figure 1. 
In conclusion, the general requirements for a SEMI Specification for 
solar-grade ailicon slices has been approved for balloting by industry. The 
results are expected to be publirhed at the next meeting to be held in Sep- 
tember. The definition of specif ic dimension and tolerance requireoents for 
individual slices is still in coaapittee. 
-- - -- -- - 
*19umerical Values of N, X, Y and Z are to be established in comittet. 
306 
Table 1. Example of Propored Square Cel l  Specif icat ion 
b limit for dlalocdetoa b r o n  domat Cell width. 100 0.5 m 
PD, #lip. l i m q o .  o r  s u i t 1  0.5 t o  2.0 ohm. C o l l d l a 8 o u l .  1 2 5 5 3 -  
Surf- ortomtation 00 11.1 lowth.  C14.9 r 
<loo>+ 3O Mjacsnt r ides,  90' 5 0 ~ 2 0 '  
Cryeta1 ortsntseton t o  8-h IUcknoss. .37 5 0.10 r 
l i m n  4so 2 a0 f lV. 50 p n  . u I u  
WrP. 60 r n  u x i n r  
Crone a d  b c k  wrfsces,  urn. 
L w  u r k s .  noas on one side. 
lou#hwas. 1 mIeror te r  W u x i n r  
Crecks, nono. 
Chips, coochoiC1. up t o  6 each 
with a UXIN l e q t h  or  r sd l r l  
wnotrst lon of 1.6 I. CNpa with 
bDth d i r n s i o s s  less than 0.25 r 
are o x q e .  l o  coochotdsl c h i p  
ere #nlet*d. 
Yo fracture or pointod opes chips 
of .a). 11s.. 
Lw a i t  d s f u e s  p e r n i t e d  on 
5 #rc.rit or ce l l s .  
Uo f o n i 8 n  u t t e r  visible t o  
uuldod eye p r r l t t e d .  
Fig. 1. Example of Proposed Square C e l l  Specif icat ion 
PL. 
DISCUSSION: 
GALLACHFIR: Remember t h a t  t h i s  is a s t r i c t l y  voluntary type p a r t i c i p a t i o n  and 
wt d e f i n i t e l y  need more p a r t i c i p a t i o n  than in have now. There a r e  usua l ly  
th ree  meetings a year. San Hateo, Boston, and the  t h i r d  one is usua l ly  
he ld  i n  Anaheim, i n  conjunction with the  Nepcon show. 
ILES: I should mention fo r  the  people i n  wafering, a s  a means of self-defense,  
you should keep an eye on these things.  Once these specs g e t  s l ipped  i n  
on you, you ' l l  f ind  they haven't  heard your input and they don't  know t h a t  
some things a r e  very d i f f i c u l t  t o  do a l roge ther .  
It was i n t e r e s t i n g  t h a t  many people came thinking they were going t o  
hear  a l l  s o r t s  of wonderful numbers on s l i c i n g  speeds and wafers you can 
see through and things l i k e  t ha t .  It was very i n t e r e s t i n g  t h a t  we were 
guided gradual ly  and r a t h e r  expe r t l y  i n t o  the microscopic aspec ts ,  and peo- 
p le  may be going away thinking more about what's r e a l l y  happening i n  the  
process r a t h e r  than curs ing  about the machine t h a t  rocks o r  bumps too much. 
I think we even s t rayed i n t o  philosophy l a s t  night.  I was l i s t e n i n g  
t o  Tom (Lewandowski) from STC, and he was t a lk ing  about the problem i f  you 
had 10 machines and t h e r e ' s  a noise  on one but no operator.  Sounded l i k e  
t h a t  o ld  business about the tree f a l l i n g  i n  t he  f o r e s t  and whether t he re ' s  
r e a l l y  a noise  o r  not ,  depending on whether t h e r e ' s  a human e a r  t o  hear  it. 
I guess we can be s a t i s f i e d  t h a t  we can say " i f  we see a l o t  of ch ips  on 
the  f l oo r ,  then we can t e l l  t he  philosophers something happened." I think 
the  I D  people go away f ee l i ng  t h a t  "Thank God t h a t  the  blade, saw, wire 
people have some problems" and v ice  versa ,  so  I think we've a t  l e a s t  
shared our problems and everyone f e e l s  a l i t t l e  b e t t e r  t o  know t h a t  the 
o ther  guy has a d i f f e r e n t  set of insurmountable problems, mainly based on 
low cos t .  I had a cawment from someone who'd not  been t o  any of the PIMs 
o r  any of the  JPL meetings. H e  s a id  he p a r t i c u l a r l y  appreciated the  f a c t  
t ha t  there  were so  many d i s c i p l i n e s  presented here. I think the  o r i g i n a l  
f e a r  of the  s t e e r i n g  conmittee was t h a t  we  might f ind  t ha t  some people 
would sit around bored t o  death while o the r  people ta lked about s t u f f  t h a t  
they'd been hearing a l o t  o f ,  but I think i t  is very good t o  have d i f f e r -  
e n t  viewpoints on a l l  the  questions.  I ' m  sure  JPL is  going t o  focus a l l  
t h i s  work, and upgrade a l l  t h i s  wafering thing,  and I ' l l  j u s t  f i n i s h  by 
saying the success of t h i s  conference can be t raced very accura te ly  by j u s t  
watching how well  the  ribbons do. I f  the  ribbon people take over from us,  
then we haven't  done our job i n  wafering. 


Status of SEMI's solar-grade substrate standards

Abstract

Similar works

Full text

Available Versions

NASA Technical Reports Server