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On-Mirror Surfaces Obtained with and without Polishing
On-Mirror Surfaces Obtained with and without Polishing* Prof. V.C. Venkatesh ( I ) , Dr. F. Fang, W.K. Chee School of Mechanical b Production Engineering, Nanyang Technological University, Singapore Received on January 9,1997
s - ~ r f s c ewere s c r e a 1 e 9 b--i t 2 r r : i n g a n d l c r 3 r L ~ d i r . c- i a r i x s na:erisls: s i l i c o ~ , g l a s s ! ; y z e x and 3 : / . 7 j , a l u m i n i u m & ?.l-Sialloy, ar.6 2l-c s e l t n i d e , s c n e c ~ F c ? ~ s : ? E ~ and o:kers golisked. :he n i r r o r s u r f a c 2 s were a s s e s s e d b y t.wc r.ov2l te=k-niTGos, or.? by m e a s i l r i n g l i g h r n e s s .,a m e a s u r e of t h e i r r e f l e c : i v l z y j , azd t h e o z h e r by s c r a t c h i n g w i t h a c s n i - c y l i z d e r i c s l diar?.ond ( f u l l y s . y x r , e t r i c a l : , a s a g a i z s t the i r a d i t i o z a l V i c k e r s diamond i n d e n z o r t h a c :?as t w o a l t e r n a t e c u t t i n g ed3es ( f a r e o r wedge!. 3 y u s i n g a n P.?X t c s e c c i c n t h z s c r a t c h , =he p i l e u z ( d o u b l - 3 r s i n g l e : was c b s e r v e d azd 5341 c c n f i r n e 2 t h e nat.;re c f t k e s c r a t c h whz-her i: was d c c r i l e o r brittle. 3esul:s show ihat po1ish;r.g :nprc,ves :he m i r r o r s u r f z c e ?xi*dover ~ o o d:he i n i c i a l s x r f a c e xay b e . YLrr2r
Keyworis:
mirror s u r f a = e s , scra:chizg,
u l t r a - p r e c i s i a n machining
1. INTRODUCTION
Mirror s u r f a c e s have r e c e n t l y been t h e f o c u s of a t z e n t i o n . Semba e t a 1 [ l ] have shown t h a t high porosity i n diamond w h e e l s i s a n e s e n c i a l f a c t o r f o r h i g h q u a l i t y mirror s u r f a c e s i n d i e m a t e r i a l s . D e C h i f f r e e t a1 [ 2 1 u s i n g AFY a n d r s u g h n e s s have shown tha: t h e g r a i n s i z e of h a r d e n e d d i e s t e e l i s a n i m p o r c a n r f a c t o r . Chmori a n d Nakagswa [ 3 ] grouzd silicor., g l a s s , azd ceramic macer-als u s i n g me:al bor.dtd g r i n d i n g w h e e l s w i t h f i x e diamcnd ? z i t s ra:.ging from C . 1 3 t a 4um a r d s n p l o y i n g t h e i r w e l l e s z a b l i s h e d E L I 2 wheel d r e s s i n g p r o c e s s . They u s e d AFM, SEM, a n d X r a y s t o assess s u r f a c e I n t e g r i t y . S u r f a c e s as good a s 2.4nm w i t h g l a s s a r d c e r a m i c s , a n d 3nrn w i t h s i l i c o n were o b c a r n e d w i t h s u r f a c e damage b a r e l y e x c e e d i r . 9 1 .urn; t h e i r wheel w i t h t h e E L I D p r o c e e s a n d ' t h e s t i f f machine t o o l were c o n t r i b u t o r y f a c t o r s . Konig e t a i [ G I have p r e c i s i o n t u r n e d v e r y h a r d s t e e l w i t n PCBX tools and o b c a i n e d m i r r o r s1Jrfaco-s; a p r e c i s i o n l s t h e of high s t i f f n e s s is a c m t r i b u t o r y f a c t o r . w i t h s i n g l e c r y s t a l CBN t D o l s and a n u l t r a - p r e c i s i o n l a t h e i t i s possible t h a t even Setter s u r f a c e s are o b t a i n e d . Yuar! e t a1 [ 5 : h a v e machined S i c whisker r e i n f o r c e d aluminium a l l o y and 6061 a l u m i n i u m , a n d o b t a i n e d R a v a l u e s of 1 0 a n d 7nm r e s p e c t i v e l y . They a t t r i b u t e d t h e i r s u c c e s s t o t h e c u t t i n g of w h i s k e r s , r a t h e r thafi t h e i r p a l l o u t o r t h e i r d i s p l a c e m e n t . 161 have shown t h a t :he Namba a n d Pbe p o l y c r y s t a 1l i n e structure of w a t e r i a 1s i n h i b i t s t h e f o r m a t i m of m i r r o r s u r f a c e s due to s t e p s a t both g r a i n boundaries axd s l i p i n a grai7.. G l a s s is a n a t e r i a l without g r a i n s , s l i p o r twinning and t h e r e f o r e w e l l s u i t e d for f i n i s h i x g . They u s e d t h e d u c t i l e mode z o n c e p t and s b z a i n e d s u r f a c e s free of s u r f a c e damagt a n d w i z h o c t t h e 7.eed f c r p o l i s h i n g [ 6 ; . The recenc keynote paper or? Fc1Lshir.g (7; i c d i c s t e s t n e need f o r more s u s t a i n e d . a r k t o wors c i z e d b e t z e r u n d e r s i a n d t h i s p r ~ c e s s The . h e r e Ci-71 c o v e r s a w;Qe v a r i e t y of m a z e r i a l s , d i f f e r e z c concepts, v a r i x s c k a l l e s g e s , azc s u c c e s s f c l r e s u i r s t?.at form t h e i n s p i r a z i a c
f o r t h e work d i s c u s s e d i n t h i s c a p e r . I n t h e present study, i n v e s t i g a t i o n s a r e or. a v a r i e t y of m a t e r i a l s - S i a n d Ge, h a r d ar.2 s o f t glass (BK7 and p y r e x ) , s o f t and b r i t t l e i n f r a r e d o p t i c s ( z i n c s e l e n i d e ) , alurninun?, and aluminum s i l i c c n a l l o y . The m a c h i n i r g p r o c e s s e s i n v o l v e 5 a r e t u r n i n g arid g r i n d i r . 5 , Experimental a n d p o l i s h i n g i n ssme r a s e s . techr'.iques s s e d a r e s i n g l e g r i t m a c h i - i n c , AFM, SZM, s t y l u s I n s E r u m e n t , and t h e Chroma Meter ( c 3 l o r i D e r ) . ?..do new methods, zoz r e p o r t e d by o t h e r s , a r ? x e d h e r e . Ore 1s ti-.? measurement 0 5 n i r r z r r e f l e c t i v i t y . The o t k e r i s t h e u s e of s i n g l e p o i n t s c r a t c h i n g w i t h a c u r v i - c o n i c a l d i a n o n d which i s s y m m e t r i c a l i n all d i r e c t i o n s , which -,he V i c k e r s i n c l e 2 t o r i s r o t . A l s o t u r n i n g of s i l i c o n , which h a s b a r e l y b e e n r e p o r t e d , is d i s c u s s e d h e r e at iength. 2 .SILICON MiI7ROR
SURFACES
WIT3
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POL1 SH IMG An u l t r a - p r e c i s i o n t u r n i n s and g r i n d i x g m a c h i n e , w i t h a f e e 5 S a c k r e s o l u t i o n of 8nm, was u s e d f o r m a c h i n i n g . T*Jrning r e s u l z s were extremely encouraging, and contrary to e x p e c t a t i o n s c o m p a r a b l e t o t h a t o b t a i n e d b.1 grinding. 2 . 1 T u r n i n g of s i l i c o n
s i n g l e crys:al diawond to31 wi:h a rake a n g l e of 0 d e g r e e v i t h a r a d i u s of 3 . 7 5 n m (waviness c o n t r o l l e d i was u s e d t o c u r ? m o n o c r y s t a l l i n e s i l i c o n . A number of c u t t i n g p a r a m e t e r s were t r i e d 3 u t t o g e t t h e b e s t s u r f a c e . A t a DOC of 1 u m , f e e d of C . 4 mm/min, a n d a s g e e d sf 4 0 3 n : / n i n . a nirror s u r f a c e of ,?a=:. 3nm was o b r a i r . e d ( F i g . 1 s ) ; i n c r e a s i n g t k i s f e e d 1 3 z i n e s tc 4nm/miz p r o d u c e s a r o u g h z e s s v a l u e s f ?a=5.9r.m (Fig.lb1. ' J a z i a t i o r . c f R a w i t h s c i r . d l e s p e d ar.d e d g e r a d i i c a n Se s e e n i r : F i 3 s 1 c j, 5 r e s p e c t i v e l y . Fig.:e shows :he wear 92 a s i n g l e c r y s t a l diamond tool. F i 3 . If sr.aws th;. A
Annals of the CIRP Vol. 46/1/1997 'Published under the privilege of the Active Member
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2 . 2 G r i n d i x g of s i l i c o n S i n i g h t v i s i o n l e n s e s a7.d m i r r o r s a r e t r s d i t i o z a l l y ma?e b y g r i n d l r . 9 and p o ! i s h i n g . EgT machine by G r i n z i n g of SL was done CII u s i n g a g r i r i d i n g attach;r.en: whiz:? h a s a n a i r s p i n d l e anci r o t a t e s a t 3 6 2 3 rFm. ?esinciic! bcr.de3 d i m c r . 3 g r i n d i n g wk.eels were ~ s e 5 . _ .
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2 . 3 C r i n c i n g 3 5 s i l i c o : . w i r h ;oi:s?.izg F s l i s h i n g o f Si a f z e r g r i n d i n s renc-ist s x r f z c e =anage. Fic:ures D € a : z y o l l s k e d g r o c d S i , Ra= l . 3 n r L , L = 5 . ? 7 , a z d b: g c l i s h e d Si, Ra= O.Znrn, L=:.95 a r c showT. i n 7 ~ 9 . 2 3 i b . Ses.~1:s dc n c c c s r i o r m t 3 t h e z - r n i-c e-..---. l,a.llm i i : .
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( C o r n i n g : a n d B K 7 (Schct:! a s a n i r r o r and t h e l a t t e r f z r p r e c i s i c n l e n s e s . The r e f l e z c i v i t y ( 5 ) v a l ~ 5 sof c h e s e two a r e 2 4 . 4 5 & 3 6 . 1 2 . I t i s p o s s i b l e t 3 o b t a i n h i g h q - ~ a l i c yr n i r r s r s u r f a c s s on g l a s s w i t h c u t 3 o l i s h i r . g a s r e c o r t o d 5:; Karnba [ G I . 4 . ALUMINI'JM AVD ALUMIK'iC'H SILICCN MIRXOR SUTZTACZS WITXOUT PCLISHING
ALLC'I
With 6 3 5 1 A1 t u r n e d s u r f a c e s Sa=5.3nm w i t h a l i g h t n e s s v a l u e ;=12; i c r c k e A l - S i alicy R a = l 3 .lnm , and L = 2 4 . However w:th lurukawa A l . t h e m i r r o r s u r f a c t . was ?.a=2.7nn h L = 1 2 . 3 5. Z I N C SXLENiDE MIRZOR SURFACES
Though ZnSe i s d i f f i c u l t t o f i n i s h machine a s t h e f i n e powdery c h i p s r e a c t wlrh t h e coola?.:, a n d i t r e q u i r e s t o x i c CMP ? o l i s h i n c , t h e surface obtained after polishing was e x c e l l e n t . R a = 5 . 5 nm, L = 2 9 . 5 €
F i g . 2 b . P o l i s h e d S i , Ra=G.2nrn, L=1.05
5 . SINGLE G R I T MACXIKING (SCPATCHING)
S i n g l e g r i t mackinir.g o f z e n Xzown a s s i n g l e p0ir.t s c r a z c h i n a o r m i . z r c c u z t i n 3 , c c n s t i ~ u c e s a a s e f c l r n e t h o d o f u n d e r s t a z d i - g t h a mechanics of m a c h i n i n g b r i t c l e m a t e r i a l s a s ws c a n 7et f Q n d a m e n t a l i n f o r m a t i o n on t h e i n t e r a c z i c n betwser. che a b r a s i v e a n d :he w ~ r km a c e r i a l . I t i s w e l l known t h a t b r i t t l e m a t e r i a l s d e f o r m p l a s t i c a l l y when t h e d e p t h of c u t i s v e r y s m a l l . T h i s d e p t h of clit i s known a s t h e c r i t i c a l d e p t h of b r i t t l e - d u c t i l e t r a n s i t i o r . d c , when t h e c u t t i n g mode c h a n g e s from b r i t t l e node t o d u c t i l e mode. V a r i o u s a p p r o a c h e s h a v e been adopted: a ) Yu e t a1 !131 u s e d a V i c k e r s h a r d n e s s i r i d e n t o r c n a grir.dir.9 machir.e w i t h a s l o p i n g w o r k p i e c e co a c t i e v e v a r i a b l e d e p t h s c f c u t and t h u s determined t h e c r i t i c a l depth d c . 5) T a n i k e l l a & S c a t t e r g o o d [ill a l s o u s e d a Vickers indentor to study subsurface f r a c t u r e darnageproducedduringgrindi=gandpolishir.g. c) Caniel & Cornfeld [ 1 2 ] s t u d i e d high speed s c r a t c h i n g w i t h t h e h e l p of a h i g h s p e e d a i r s p i c d l e t o which was a t t a c h e d a V i c k e r s i n d e n t o r whose t i p was g r o u n d t o a 1x1 urn f l a t . Ry a c o u s t i c s e n s i r g t h e y were a b l e t o detect d n c t i l e - b r i t E l e t r a n s i t i o n . d ) I n t h i s s t u d y a c u r v i - c o n i c a l diamond t i p a s shown i n F i g . 4a was used on a s t y l u s meas.Jrina machine a t a c o n s t a n t f o r c e . The a d v a n t a g e o f t h i s t i p is :hat i s s - p m e t r i c a l , w h e r e a s w i t h t h e V i c k e r s i n d e z z o r , i: c a n b e o r i e n t e d a l o z g t h e d i a g c x a l (wedge s h a p e d t o o l i c r a1sr.a i:s s i d e ( f l a t - f a c e d zocl r e s p e c t :a t h e c u t t i n g direction. S c a z t e r g c c d
*Published under the privilege of the Active Member
F i g . ? . Mirror made from Furukawa A l [l;] b a s shown :hat w i t h g l a s s t h e r e I s more damage wi:h :he l a t t e r d i r e c L i o r . , anC with s i x g l e c r y s t a l Si i t i s e x a c t l y t h e c p p o s i t e . With o u r diamond t o o l a v e r y f i n e g r o o v e i s p r o d u c e d a n d i t s C ~ G S S s e c t i o n is a n a l y s e d i n a n APM. The amount of p i l e up on e i t h e r s i d e of t h e groove i s o b s e r v e d . A d o u b l e p i l e up was o b s e r v e d f o r ZnSe a s o f t a n d b r i i z t l e m a t e r i a l . A s i n g l e o n e s i d e p i l e up f o r bozh S i a n d glass iBK7) h a v e b e e n o b s e r v e d . The r e a s o n s c o u l d be tha: s o f t m a t e r i a l s have a d o u b l e p i l e up a n d h a r d m a t e r i a l s a s i n g l e p i l e u p . R e f l e c t i v i t y toc i s b e t t e r w i t h h a r d m a t e r i a l s . A d o u b l e p i l e up when o b s e r v e d u n d e r c h e SEX a p p e a r s to be a d x c t i l e s t r e a k , fractilred anci a s i n g l e p i l e c ' j h 3 s a a p p e a r a n c e . T y r e x , w h i c h i s s o f t e r ::?a?. E X 7 but has higher sofeezing tempsratures s50ws dcuble p i l e ups; i t has t e i t e r r ~ r ' l e c t i . i i t i / and s x r f s c e r x g h n e s s . T5.e 5 : r e c t i c n 2 5 m a c h i n i n g c c u l d be a n iT*pcr:aci f a c t z r a s shcwr. " 1 ~S c a z c e r g o c d i:::.
507
(a) Curvi-conical diam0r.d indentor with f r m t and top views. Ciametr of tip is 2 um.
7.CCNCLUSIGNS Two novel techniques, not reported by others elsewhere, have been used ssccessf
REFERENCSS
(b)Sectional analysis on an AFM of the scratch on ZnSe showing double pile up.
(c! Sectional analysis on an AFM of the scratchonpolishedglass (BK7! showing single pile up.
i. Semba,T., Tani,?!., & Sac-o,II., 1996, Development of aelamine-bor.deddiamond whPe?s with high porosicy f o r saooth and mirror finishing of die materials, Annals of :he CIRP, Volume 45/1, pp.315-318. De Chiffre,L., Iiar.sen,H.N., & 2. Bronstein,A.,1996, Inves:igation on the surface topography in polishin5 using atomic force microscopy, Ibid, pp.523-528. 3 . Ohmori,X . , & Nakagawa,T., 1995 Analysis of mirror surface generation of hard a n d brittle materials by ELID grinding with superfine grain metallic bond wheels, Annals of the CIRP, Volume 44/1, pp.287-290. 4. Konig, W., Berktold, A . , & Koch,K.F.,1993, Turning vs Grinding -A comparison of surface integrity aspects and attainable accuracies, Annals of the CIXP, Vclume 42/1, pp.39-43. 5. Yuan,2 . J . ,Geng,L . , & Dong,S.,1393, Ultraprecision machir.ing of SiCw/A? composites, Annals of the CIR?, Volume 42/1, pp.107-1C3. 6. Namba,Y., & Abe, M., 1993, Ultra-precision grinding of optical glass to produce suGersmooth surfaces, Annals of the CIRP, Volume 42/1, pp . 4 17-420. 7 . Venkatlesh, V.C., Inasaki, I . , Tonshoff, H.K., Nakagawa, T . , Marinescu, I.D., 1995, Observations on polishing andultra-precision machining of semiconductor substrate materials, Annals of the CIRP, Volume 44/2, pp.611-618. 8 .Blackley,S., & Scattergood,R.N., 1991, Ductile regime model for diamond turning of brittle materials, Cournal of ?recision Engineering, V01.13/2,95-102. 9. Zhong,Z., & VenXatesh,V.C., Generation of parabolic & toroidal mirrors in Si and Si based compounds using diamond cup grinding wheels, Annals of the CIRP, Volume 43/1, pp.323-326. 10. Yu,H., Terashima,S., Morita,N., & Yoshida,Y., 1996, Cryogenic grinding of brittle materials, Proc. 11th ASPE Annual Meeting, Monterey, CA., Vol. 14, pp.606-609. 11. Tanikella,B.V.,& Scattergood,R.O.,1996, Controlled microcutting tests on single crystal silicon, Ibid, pp.524-531. 12. Daniel,J., & Cornfeld,D., 1996, Inprocess detection of the ductile-brittle transition in high speed scratching of glassTheory & Experiment, Ibid, pp.561-565.
Fig.4 a to c. Single p0ir.t scratchrng
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*Published under the privilege of the Active Member
s - ~ r f s c ewere s c r e a 1 e 9 b--i t 2 r r : i n g a n d l c r 3 r L ~ d i r . c- i a r i x s na:erisls: s i l i c o ~ , g l a s s ! ; y z e x and 3 : / . 7 j , a l u m i n i u m & ?.l-Sialloy, ar.6 2l-c s e l t n i d e , s c n e c ~ F c ? ~ s : ? E ~ and o:kers golisked. :he n i r r o r s u r f a c 2 s were a s s e s s e d b y t.wc r.ov2l te=k-niTGos, or.? by m e a s i l r i n g l i g h r n e s s .,a m e a s u r e of t h e i r r e f l e c : i v l z y j , azd t h e o z h e r by s c r a t c h i n g w i t h a c s n i - c y l i z d e r i c s l diar?.ond ( f u l l y s . y x r , e t r i c a l : , a s a g a i z s t the i r a d i t i o z a l V i c k e r s diamond i n d e n z o r t h a c :?as t w o a l t e r n a t e c u t t i n g ed3es ( f a r e o r wedge!. 3 y u s i n g a n P.?X t c s e c c i c n t h z s c r a t c h , =he p i l e u z ( d o u b l - 3 r s i n g l e : was c b s e r v e d azd 5341 c c n f i r n e 2 t h e nat.;re c f t k e s c r a t c h whz-her i: was d c c r i l e o r brittle. 3esul:s show ihat po1ish;r.g :nprc,ves :he m i r r o r s u r f z c e ?xi*dover ~ o o d:he i n i c i a l s x r f a c e xay b e . YLrr2r
Keyworis:
mirror s u r f a = e s , scra:chizg,
u l t r a - p r e c i s i a n machining
1. INTRODUCTION
Mirror s u r f a c e s have r e c e n t l y been t h e f o c u s of a t z e n t i o n . Semba e t a 1 [ l ] have shown t h a t high porosity i n diamond w h e e l s i s a n e s e n c i a l f a c t o r f o r h i g h q u a l i t y mirror s u r f a c e s i n d i e m a t e r i a l s . D e C h i f f r e e t a1 [ 2 1 u s i n g AFY a n d r s u g h n e s s have shown tha: t h e g r a i n s i z e of h a r d e n e d d i e s t e e l i s a n i m p o r c a n r f a c t o r . Chmori a n d Nakagswa [ 3 ] grouzd silicor., g l a s s , azd ceramic macer-als u s i n g me:al bor.dtd g r i n d i n g w h e e l s w i t h f i x e diamcnd ? z i t s ra:.ging from C . 1 3 t a 4um a r d s n p l o y i n g t h e i r w e l l e s z a b l i s h e d E L I 2 wheel d r e s s i n g p r o c e s s . They u s e d AFM, SEM, a n d X r a y s t o assess s u r f a c e I n t e g r i t y . S u r f a c e s as good a s 2.4nm w i t h g l a s s a r d c e r a m i c s , a n d 3nrn w i t h s i l i c o n were o b c a r n e d w i t h s u r f a c e damage b a r e l y e x c e e d i r . 9 1 .urn; t h e i r wheel w i t h t h e E L I D p r o c e e s a n d ' t h e s t i f f machine t o o l were c o n t r i b u t o r y f a c t o r s . Konig e t a i [ G I have p r e c i s i o n t u r n e d v e r y h a r d s t e e l w i t n PCBX tools and o b c a i n e d m i r r o r s1Jrfaco-s; a p r e c i s i o n l s t h e of high s t i f f n e s s is a c m t r i b u t o r y f a c t o r . w i t h s i n g l e c r y s t a l CBN t D o l s and a n u l t r a - p r e c i s i o n l a t h e i t i s possible t h a t even Setter s u r f a c e s are o b t a i n e d . Yuar! e t a1 [ 5 : h a v e machined S i c whisker r e i n f o r c e d aluminium a l l o y and 6061 a l u m i n i u m , a n d o b t a i n e d R a v a l u e s of 1 0 a n d 7nm r e s p e c t i v e l y . They a t t r i b u t e d t h e i r s u c c e s s t o t h e c u t t i n g of w h i s k e r s , r a t h e r thafi t h e i r p a l l o u t o r t h e i r d i s p l a c e m e n t . 161 have shown t h a t :he Namba a n d Pbe p o l y c r y s t a 1l i n e structure of w a t e r i a 1s i n h i b i t s t h e f o r m a t i m of m i r r o r s u r f a c e s due to s t e p s a t both g r a i n boundaries axd s l i p i n a grai7.. G l a s s is a n a t e r i a l without g r a i n s , s l i p o r twinning and t h e r e f o r e w e l l s u i t e d for f i n i s h i x g . They u s e d t h e d u c t i l e mode z o n c e p t and s b z a i n e d s u r f a c e s free of s u r f a c e damagt a n d w i z h o c t t h e 7.eed f c r p o l i s h i n g [ 6 ; . The recenc keynote paper or? Fc1Lshir.g (7; i c d i c s t e s t n e need f o r more s u s t a i n e d . a r k t o wors c i z e d b e t z e r u n d e r s i a n d t h i s p r ~ c e s s The . h e r e Ci-71 c o v e r s a w;Qe v a r i e t y of m a z e r i a l s , d i f f e r e z c concepts, v a r i x s c k a l l e s g e s , azc s u c c e s s f c l r e s u i r s t?.at form t h e i n s p i r a z i a c
f o r t h e work d i s c u s s e d i n t h i s c a p e r . I n t h e present study, i n v e s t i g a t i o n s a r e or. a v a r i e t y of m a t e r i a l s - S i a n d Ge, h a r d ar.2 s o f t glass (BK7 and p y r e x ) , s o f t and b r i t t l e i n f r a r e d o p t i c s ( z i n c s e l e n i d e ) , alurninun?, and aluminum s i l i c c n a l l o y . The m a c h i n i r g p r o c e s s e s i n v o l v e 5 a r e t u r n i n g arid g r i n d i r . 5 , Experimental a n d p o l i s h i n g i n ssme r a s e s . techr'.iques s s e d a r e s i n g l e g r i t m a c h i - i n c , AFM, SZM, s t y l u s I n s E r u m e n t , and t h e Chroma Meter ( c 3 l o r i D e r ) . ?..do new methods, zoz r e p o r t e d by o t h e r s , a r ? x e d h e r e . Ore 1s ti-.? measurement 0 5 n i r r z r r e f l e c t i v i t y . The o t k e r i s t h e u s e of s i n g l e p o i n t s c r a t c h i n g w i t h a c u r v i - c o n i c a l d i a n o n d which i s s y m m e t r i c a l i n all d i r e c t i o n s , which -,he V i c k e r s i n c l e 2 t o r i s r o t . A l s o t u r n i n g of s i l i c o n , which h a s b a r e l y b e e n r e p o r t e d , is d i s c u s s e d h e r e at iength. 2 .SILICON MiI7ROR
SURFACES
WIT3
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POL1 SH IMG An u l t r a - p r e c i s i o n t u r n i n s and g r i n d i x g m a c h i n e , w i t h a f e e 5 S a c k r e s o l u t i o n of 8nm, was u s e d f o r m a c h i n i n g . T*Jrning r e s u l z s were extremely encouraging, and contrary to e x p e c t a t i o n s c o m p a r a b l e t o t h a t o b t a i n e d b.1 grinding. 2 . 1 T u r n i n g of s i l i c o n
s i n g l e crys:al diawond to31 wi:h a rake a n g l e of 0 d e g r e e v i t h a r a d i u s of 3 . 7 5 n m (waviness c o n t r o l l e d i was u s e d t o c u r ? m o n o c r y s t a l l i n e s i l i c o n . A number of c u t t i n g p a r a m e t e r s were t r i e d 3 u t t o g e t t h e b e s t s u r f a c e . A t a DOC of 1 u m , f e e d of C . 4 mm/min, a n d a s g e e d sf 4 0 3 n : / n i n . a nirror s u r f a c e of ,?a=:. 3nm was o b r a i r . e d ( F i g . 1 s ) ; i n c r e a s i n g t k i s f e e d 1 3 z i n e s tc 4nm/miz p r o d u c e s a r o u g h z e s s v a l u e s f ?a=5.9r.m (Fig.lb1. ' J a z i a t i o r . c f R a w i t h s c i r . d l e s p e d ar.d e d g e r a d i i c a n Se s e e n i r : F i 3 s 1 c j, 5 r e s p e c t i v e l y . Fig.:e shows :he wear 92 a s i n g l e c r y s t a l diamond tool. F i 3 . If sr.aws th;. A
Annals of the CIRP Vol. 46/1/1997 'Published under the privilege of the Active Member
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2 . 2 G r i n d i x g of s i l i c o n S i n i g h t v i s i o n l e n s e s a7.d m i r r o r s a r e t r s d i t i o z a l l y ma?e b y g r i n d l r . 9 and p o ! i s h i n g . EgT machine by G r i n z i n g of SL was done CII u s i n g a g r i r i d i n g attach;r.en: whiz:? h a s a n a i r s p i n d l e anci r o t a t e s a t 3 6 2 3 rFm. ?esinciic! bcr.de3 d i m c r . 3 g r i n d i n g wk.eels were ~ s e 5 . _ .
. .
2 . 3 C r i n c i n g 3 5 s i l i c o : . w i r h ;oi:s?.izg F s l i s h i n g o f Si a f z e r g r i n d i n s renc-ist s x r f z c e =anage. Fic:ures D € a : z y o l l s k e d g r o c d S i , Ra= l . 3 n r L , L = 5 . ? 7 , a z d b: g c l i s h e d Si, Ra= O.Znrn, L=:.95 a r c showT. i n 7 ~ 9 . 2 3 i b . Ses.~1:s dc n c c c s r i o r m t 3 t h e z - r n i-c e-..---. l,a.llm i i : .
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Fig.2a.Ground S i , Ra=l.anm, L=5.37
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( C o r n i n g : a n d B K 7 (Schct:! a s a n i r r o r and t h e l a t t e r f z r p r e c i s i c n l e n s e s . The r e f l e z c i v i t y ( 5 ) v a l ~ 5 sof c h e s e two a r e 2 4 . 4 5 & 3 6 . 1 2 . I t i s p o s s i b l e t 3 o b t a i n h i g h q - ~ a l i c yr n i r r s r s u r f a c s s on g l a s s w i t h c u t 3 o l i s h i r . g a s r e c o r t o d 5:; Karnba [ G I . 4 . ALUMINI'JM AVD ALUMIK'iC'H SILICCN MIRXOR SUTZTACZS WITXOUT PCLISHING
ALLC'I
With 6 3 5 1 A1 t u r n e d s u r f a c e s Sa=5.3nm w i t h a l i g h t n e s s v a l u e ;=12; i c r c k e A l - S i alicy R a = l 3 .lnm , and L = 2 4 . However w:th lurukawa A l . t h e m i r r o r s u r f a c t . was ?.a=2.7nn h L = 1 2 . 3 5. Z I N C SXLENiDE MIRZOR SURFACES
Though ZnSe i s d i f f i c u l t t o f i n i s h machine a s t h e f i n e powdery c h i p s r e a c t wlrh t h e coola?.:, a n d i t r e q u i r e s t o x i c CMP ? o l i s h i n c , t h e surface obtained after polishing was e x c e l l e n t . R a = 5 . 5 nm, L = 2 9 . 5 €
F i g . 2 b . P o l i s h e d S i , Ra=G.2nrn, L=1.05
5 . SINGLE G R I T MACXIKING (SCPATCHING)
S i n g l e g r i t mackinir.g o f z e n Xzown a s s i n g l e p0ir.t s c r a z c h i n a o r m i . z r c c u z t i n 3 , c c n s t i ~ u c e s a a s e f c l r n e t h o d o f u n d e r s t a z d i - g t h a mechanics of m a c h i n i n g b r i t c l e m a t e r i a l s a s ws c a n 7et f Q n d a m e n t a l i n f o r m a t i o n on t h e i n t e r a c z i c n betwser. che a b r a s i v e a n d :he w ~ r km a c e r i a l . I t i s w e l l known t h a t b r i t t l e m a t e r i a l s d e f o r m p l a s t i c a l l y when t h e d e p t h of c u t i s v e r y s m a l l . T h i s d e p t h of clit i s known a s t h e c r i t i c a l d e p t h of b r i t t l e - d u c t i l e t r a n s i t i o r . d c , when t h e c u t t i n g mode c h a n g e s from b r i t t l e node t o d u c t i l e mode. V a r i o u s a p p r o a c h e s h a v e been adopted: a ) Yu e t a1 !131 u s e d a V i c k e r s h a r d n e s s i r i d e n t o r c n a grir.dir.9 machir.e w i t h a s l o p i n g w o r k p i e c e co a c t i e v e v a r i a b l e d e p t h s c f c u t and t h u s determined t h e c r i t i c a l depth d c . 5) T a n i k e l l a & S c a t t e r g o o d [ill a l s o u s e d a Vickers indentor to study subsurface f r a c t u r e darnageproducedduringgrindi=gandpolishir.g. c) Caniel & Cornfeld [ 1 2 ] s t u d i e d high speed s c r a t c h i n g w i t h t h e h e l p of a h i g h s p e e d a i r s p i c d l e t o which was a t t a c h e d a V i c k e r s i n d e n t o r whose t i p was g r o u n d t o a 1x1 urn f l a t . Ry a c o u s t i c s e n s i r g t h e y were a b l e t o detect d n c t i l e - b r i t E l e t r a n s i t i o n . d ) I n t h i s s t u d y a c u r v i - c o n i c a l diamond t i p a s shown i n F i g . 4a was used on a s t y l u s meas.Jrina machine a t a c o n s t a n t f o r c e . The a d v a n t a g e o f t h i s t i p is :hat i s s - p m e t r i c a l , w h e r e a s w i t h t h e V i c k e r s i n d e z z o r , i: c a n b e o r i e n t e d a l o z g t h e d i a g c x a l (wedge s h a p e d t o o l i c r a1sr.a i:s s i d e ( f l a t - f a c e d zocl r e s p e c t :a t h e c u t t i n g direction. S c a z t e r g c c d
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F i g . ? . Mirror made from Furukawa A l [l;] b a s shown :hat w i t h g l a s s t h e r e I s more damage wi:h :he l a t t e r d i r e c L i o r . , anC with s i x g l e c r y s t a l Si i t i s e x a c t l y t h e c p p o s i t e . With o u r diamond t o o l a v e r y f i n e g r o o v e i s p r o d u c e d a n d i t s C ~ G S S s e c t i o n is a n a l y s e d i n a n APM. The amount of p i l e up on e i t h e r s i d e of t h e groove i s o b s e r v e d . A d o u b l e p i l e up was o b s e r v e d f o r ZnSe a s o f t a n d b r i i z t l e m a t e r i a l . A s i n g l e o n e s i d e p i l e up f o r bozh S i a n d glass iBK7) h a v e b e e n o b s e r v e d . The r e a s o n s c o u l d be tha: s o f t m a t e r i a l s have a d o u b l e p i l e up a n d h a r d m a t e r i a l s a s i n g l e p i l e u p . R e f l e c t i v i t y toc i s b e t t e r w i t h h a r d m a t e r i a l s . A d o u b l e p i l e up when o b s e r v e d u n d e r c h e SEX a p p e a r s to be a d x c t i l e s t r e a k , fractilred anci a s i n g l e p i l e c ' j h 3 s a a p p e a r a n c e . T y r e x , w h i c h i s s o f t e r ::?a?. E X 7 but has higher sofeezing tempsratures s50ws dcuble p i l e ups; i t has t e i t e r r ~ r ' l e c t i . i i t i / and s x r f s c e r x g h n e s s . T5.e 5 : r e c t i c n 2 5 m a c h i n i n g c c u l d be a n iT*pcr:aci f a c t z r a s shcwr. " 1 ~S c a z c e r g o c d i:::.
507
(a) Curvi-conical diam0r.d indentor with f r m t and top views. Ciametr of tip is 2 um.
7.CCNCLUSIGNS Two novel techniques, not reported by others elsewhere, have been used ssccessf
REFERENCSS
(b)Sectional analysis on an AFM of the scratch on ZnSe showing double pile up.
(c! Sectional analysis on an AFM of the scratchonpolishedglass (BK7! showing single pile up.
i. Semba,T., Tani,?!., & Sac-o,II., 1996, Development of aelamine-bor.deddiamond whPe?s with high porosicy f o r saooth and mirror finishing of die materials, Annals of :he CIRP, Volume 45/1, pp.315-318. De Chiffre,L., Iiar.sen,H.N., & 2. Bronstein,A.,1996, Inves:igation on the surface topography in polishin5 using atomic force microscopy, Ibid, pp.523-528. 3 . Ohmori,X . , & Nakagawa,T., 1995 Analysis of mirror surface generation of hard a n d brittle materials by ELID grinding with superfine grain metallic bond wheels, Annals of the CIRP, Volume 44/1, pp.287-290. 4. Konig, W., Berktold, A . , & Koch,K.F.,1993, Turning vs Grinding -A comparison of surface integrity aspects and attainable accuracies, Annals of the CIXP, Vclume 42/1, pp.39-43. 5. Yuan,2 . J . ,Geng,L . , & Dong,S.,1393, Ultraprecision machir.ing of SiCw/A? composites, Annals of the CIR?, Volume 42/1, pp.107-1C3. 6. Namba,Y., & Abe, M., 1993, Ultra-precision grinding of optical glass to produce suGersmooth surfaces, Annals of the CIRP, Volume 42/1, pp . 4 17-420. 7 . Venkatlesh, V.C., Inasaki, I . , Tonshoff, H.K., Nakagawa, T . , Marinescu, I.D., 1995, Observations on polishing andultra-precision machining of semiconductor substrate materials, Annals of the CIRP, Volume 44/2, pp.611-618. 8 .Blackley,S., & Scattergood,R.N., 1991, Ductile regime model for diamond turning of brittle materials, Cournal of ?recision Engineering, V01.13/2,95-102. 9. Zhong,Z., & VenXatesh,V.C., Generation of parabolic & toroidal mirrors in Si and Si based compounds using diamond cup grinding wheels, Annals of the CIRP, Volume 43/1, pp.323-326. 10. Yu,H., Terashima,S., Morita,N., & Yoshida,Y., 1996, Cryogenic grinding of brittle materials, Proc. 11th ASPE Annual Meeting, Monterey, CA., Vol. 14, pp.606-609. 11. Tanikella,B.V.,& Scattergood,R.O.,1996, Controlled microcutting tests on single crystal silicon, Ibid, pp.524-531. 12. Daniel,J., & Cornfeld,D., 1996, Inprocess detection of the ductile-brittle transition in high speed scratching of glassTheory & Experiment, Ibid, pp.561-565.
Fig.4 a to c. Single p0ir.t scratchrng
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