HAL Id: jpa-00223883
https://hal.archives-ouvertes.fr/jpa-00223883
Submitted on 1 Jan 1984
HAL is a multi-disciplinary open access archive for the deposit and dissemination of sci- entific research documents, whether they are pub- lished or not. The documents may come from teaching and research institutions in France or abroad, or from public or private research centers.
L’archive ouverte pluridisciplinaire HAL, est destinée au dépôt et à la diffusion de documents scientifiques de niveau recherche, publiés ou non, émanant des établissements d’enseignement et de recherche français ou étrangers, des laboratoires publics ou privés.
X-RAY SPECTROSCOPY OF HUMAN SKIN AS A CONTAMINANT ON SEMICONDUCTORS
J. Lange
To cite this version:
J. Lange. X-RAY SPECTROSCOPY OF HUMAN SKIN AS A CONTAMINANT ON SEMICONDUCTORS. Journal de Physique Colloques, 1984, 45 (C2), pp.C2-899-C2-902.
�10.1051/jphyscol:19842206�. �jpa-00223883�
Colloque C2, supplgment au Tome 45, fgvrier 1984 page C2-899
X-RAY SPECTROSCOPY OF HUMAN S K I N A S A C O N T A M I N A N T ON SEMICONDUCTORS
J . A . Lange
Motorola, Inc., 3501 ED Bluestein BZvd., Austin, Terns 78756, U.S.A.
Resume - Le haut degre d ' i n t e g r a t i o n a provoque un accroissement de l a s e n s i b i - 1 i t 6 de c e r t a i n s composants semi-conducteurs 1 l a contamination i o n i q u e e t a f o r c e l e s i n d u s t r i e l s 1 a c c r o i t r e l e degre d ' e l i m i n a t i o n des contaminants. Ce- pendant, avant de p o u v o i r e l i m i n e r un agent contaminant, il fa u t 1 ' i d e n t i f i e r . Le personnel q u i manipule l e s p l a q u e t t e s c o n s t i t u e l a source p r i n c i p a l e du con- taminant q u i ne p r o v i e n t pas de matieres s u r l a surface de l a peau, mais de l a peau meme.
La c o n s t i t u t i o n des couches du derme e t de l ' e p i d e r m e de l a peau, t o u t en assurant l e s f o n c t i o n s physiologiques normales, chez l'homme, c o n t i e n t un grand nombre d ' i o n s n o c i f s t e l s que Nat, C1-, HCO3--, Cat+, e t c . Le melange de sub- stances chimiques rend l e probleme de 1 'i d e n t i f i c a t i o n t r e s d i f f i c i l e , m@me dans des c o n d i t i o n s optimales. Dans l e cadre de l a p r o d u c t i o n i n d u s t r i e l l e , une p e r t e de temps causee par des analyses equivaut 1 une p e r t e de p r o d u i t s causee par l a contamination, e t l e s p e r t e s de temps r e s u l t a n t d'analyses rigoureuses representent un l u x e co^uteux.
L ' a r t i c l e presente une esquisse d'une methode q u i e s t basEe s u r des r e s u l - t a t s obtenus avec des composants semi-conducteurs defectueux e t q u i permet 1 l ' o p e r a t e u r d ' i d e n t i f i e r avec un h a u t degre de f i a b i l i t e l a peau en t a n t que contaminant. La methode u t i l i s e un spectrometre X 1 d i s p e r s i o n d ' e n e r g i e monte avec l ' e c h a n t i l l o n 1 - l ' i n t e r i e u r de l a chambre du microscope e l e c t r o n i q u e 1 ba- layage, permettant a i n s i une analyse r e l a t i v e m e n t rapide, a coat o p t i m i s e .
A b s t r a c t - With s h r i n k i n g geometries making some semiconductor devices more s e n s i t i v e t o i o n i c contamination than before, manufacturers are compelled t o e l i m i n a t e t h e contaminant t o a higher degree. Before the contaminant can be e l i m i n a t e d though, i t must be i d e n t i f i e d . Evidence p o i n t s t o the people i n v o l v e d i n t h e process o f wafer handling as being t h e major source o f t h i s contamination, and n o t alone from m a t e r i a l borne on the skin, b u t from t h e s k i n i t s e l f .
The make-up o f our dermal and epidermal l a y e r s o f s k i n , i n a d d i t i o n t o t h e o t h e r normal body processes make us a c a r r i e r o f many harmful ions such as Na+, C1-, HCO --, Cat+, and others. This very mix o f chemicals makes the job o f i d e n t i f i c a Z i o n very d i f f i c u l t under t h e b e s t o f circumstances. However, i n a p r o d u c t i o n s i t u a t i o n where time l o s t i n a n a l y s i s equates t o product l o s t from contamination, the time spent i n r i g o r o u s a n a l y s i s i s a c o s t l y 1 uxury.
A method has been o u t l i n e d from the r e s u l t s o f a n a l y s i s o f f a i l e d semi- conductor devices by which an operator can, w i t h a h i g h degree o f r e l i a b i l i t y , i d e n t i f y s k i n as a contaminant. This i s done from the spectra produced by an energy d i s p e r s i y e X-Ray spectrometer which can be i n s e r t e d i n the same SEM chamber w i t h t h e specimen, thereby producing a r e l a t i v e l y f a s t , c o s t optimized a n a l y s i s .
Our body takes i n food, some o f which i s converted t o energy w i t h the b u l k being e l i m i n a t e d . Along w i t h t h i s b u l k t h e r e are e l i m i n a t e d o t h e r wastes which are t h e by-products o f energy conversion i n our c e l l s . There are t h r e e avenues o f e l i m i n a t i o n - t h e Bowel, t h e Kidneys, and t h e Sweat Glands.
The Sweat Glands,in a d d i t i o n t o t h e i r use f o r e l i m i n a t i o n , a l s o serve as a p a r t of o u r temperature regul.ation system and are a l s o l i n k e d t o our auto-
Article published online by EDP Sciences and available at http://dx.doi.org/10.1051/jphyscol:19842206
C2-900 JOURNAL DE PHYSIQUE
nomic, o r nervous system. T h e i r o u t l e t s a r e a l l o v e r o u r bodies, b u t a r e most dense i n t h e palms o f t h e hands, t h e a x i l l a e o r branches o f t h e body, t h e s o l e s o f t h e f e e t , and t h e forehead. These areas a l s o c o n t a i n t h e glands r e s p o n s i b l e f o r i n s e n s i t i v e o r "nervous" p e r s p i r a t i o n as opposed t o t h e s e n s i t i v e g l a n d s t h a t g i v e o f f sweat caused by a c t i v i t y and i n c r e a s e d energy u t i l i z a t i o n . The amount o f p e r s p i r a t i o n g i v e n o f f can v a r y f r o m about 22ml/hr t o 525 m l / h r , depending on t h e l e v e l and d u r a t i o n o f a c t i v i t y .
The i n o r g a n i c c o n s t i t u e n t s o f t h i s p e r s p i r a t i o n a r e e s s e n t i a l l y t h e same as blood, b u t i n l o w e r c o n c e n t r a t i o n s . The main e l e c t r o l y t e s a r e Na+, C1-, HC03--, s m a l l e r amounts o f K t , Ca++, HP04--, SO -- and Mg++, i n a d d i t i o n t o o r g a n i c
4 :
p r o d u c t s such as urea, u r i c a c i d , amino a c i d s , ammonia, sugar, l a c t i c a c i d and a s c o r b i c a c i d . There i s no s e t c o n c e n t r a t i o n o f e i t h e r , however s i n c e t h e r e a r e many f a c t o r s such as d i e t , d i s e a s e , o r even t i m e o f t h e l a s t meal t h a t a f f e c t t h e r e l a t i v e percentages. The sweat glands then, e x c r e t e t h e s e s elements i n an aqueous s o l u t i o n o n t o t h e s k i n where i t i s e i t h e r absorbed i n t o s k i n c e l l s o r accumulates on t h e s k i n b y c o m b i n a t i o n c e n t e r s as t h e w a t e r evaporates.
The s k i n i s made up of l a y e r s w h i c h b e g i n i n t h e Epidermis, w i t h t h e S t r a t u m Germinativum, where c e l l m u l t i p l i c a t i o n t a k e s p l a c e , t o t h e S t r a t u m Corneum where c o m b i n a t i o n s o f squamous c e l l s a r e sloughed o f f a t random. T h i s process, f r o m c e l l m u l t i p l i c a t i o n t o c o r n e a t i o n and s l o u g h i n g o f f t a k e s an average a b o u t 28 days, w i t h a t r a d i t i o n a l f i g u r e b e i n g g i v e n f o r t h e number o f p a r t i c l e s r e l e a s e d f r o m a person o f 2 m i l l i o n / m i n u t e . I n t h e l a y e r s between t h i s process, t h e c e l l s a r e undergoing a chemical c o n v e r s i o n , t a k i n g on m e l a n i n i n v a r y i n g amounts f r o m t h e melanocytes, b e i n g f l a t t e n e d and s l o w l y d y i n g . The
p r o t o p l a s m o f t h e epidermocytes, o r o r i g i n a l c e l l s , changes g r a d u a l l y t o a p r o t e i n substance c a l l e d K e r a t i n . These f l a t t e n e d k e r a t i n o c y t e s a r e overlapped, much l i k e s h i n g l e s on a house, t o serve as a h a r d c o v e r i n g f o r o u r body t o keep o u t w a t e r and b a c t e r i a and h o l d i n o u r organs and body f l u i d s . The protoplasm- k e r a t i n c o n v e r s i o n i n a d d i t i o n produces an a c i d component t h a t k i l l s many o f t h e v i r u s e s and b a c t e r i a t h a t come i n c o n t a c t w i t h o u r s k i n d a i l y , s e r v i n g t h e r e b y as a b u i l t - i n d i s i n f e c t a n t , b u t a l s o as a n o t h e r p o s s i b l e i o n i c contaminant.
These elements o f t h e body have f i r s t i o n i z a t i o n p o t e n t i a l s r a n g i n g f r o m 4 t o 7 ev w i t h second i o n i z a t i o n p o t e n t i a l s r a n g i n g a l l t h e way t o 14 ev and possess t h e c a p a b i l i t y o f p r o d u c i n g s i g n i f i c a n t t h r e s h o l d s h i f t s and subsequent leakage c u r r e n t s i f p r e s e n t between t h e g a t e o x i d e and channel areas o f an MOS t r a n s i s t o r .
An e x p e r i m e n t was performed t o i d e n t i f y t h e cause of leakage on an MOS d e v i c e . The procedure was t o measure t h e leakage on d i e on a raw w a f e r , h e a t t h e w a f e r t o a t e m p e r a t u r e s l i g h t l y l o w e r t h a n t h e maximum expected i n a normal assembly process, probe f o r leakage a g a i n , expose t h e w a f e r t o a c o n t a m i n a t i n g atmosphere, probe f o r leakage, h e a t and probe a f o u r t h t i m e f o r leakage. There was no f a l l - o u t f o r leakage u n t i l t h e f i n a l p r o b i n g a t w h i c h t i m e t h e r e were an average o f 7 d ~ e / w a f e r t h a t showed e x c e s s i v e l e v e l s o f c u r r e n t flow. I n e v e r y case a con- t a m ~ n a n t was p r e s e n t i n t h e area o f t h e f a i l i n g g a t e . I n a l l b u t two samples t h e c o n t a m i n a n t produced an e n e r g y - d i s p e r s i v e X-Ray spectrum w h i c h was i n c o n s i s t e n t w i t h known f i x e d m a t e r i a l s i n t h e area. T h i s l e a d i n g t h e n t o s u s p i c i o n o f human sources, t h e samples were s t a i n e d w i t h N i n h y d r i n w h i c h i s a common amino a c i d s t a i n used by F o r e n s i c P a t h o l o g i s t s t o c o n f i r m t h e presence o f human s k i n o r f i n g e r p r i n t s . F i g u r e s 1 and 2 a r e i n c l u d e d as examples o f t h e physico-chemical c h a r a c t e r i s t i c s o f some o f t h e s k i n samples.
There i s no one element t h a t can be used as an a b s o l u t e i n d i c a t o r o f s k i n , however i t i s suggested t h a t t h e c o m b i n a t i o n o f s e v e r a l f a c t o r s can l e a d t o a f a s t d e t e r m i n a t i o n o f s k i n o f s k i n w i t h a h i g h degree of p r o b a b i l i t y , a l o n g w i t h a good a n a l y s t s normal i n p u t s such as knowledge of t h e p r o d u c t i o n area, communication w i t h t h e r e q u e s t o r o f a n a l y s i s and s p e c i f i c f a i l u r e modes. The common f a c t o r s n o t e d i n t h i s e x e r c i s e were:
1. A general l a c k o f s p e c i f i c f e a t u r e s , such as sharp edges, d e n d r i t e s o r c o r n e r s . (An o v e r a l l " p u f f i n e s s " , l i k e c l o u d s ) 2. Presence of a t l e a s t two o f t h e elements f r o m t a b l e 1.
(More t h a n two elements, e x c l u s i v e o f any n o t i n t a b l e 1 i n c r e a s e s t h e p r o b a b i l i t y t h a t t h e contaminant i s s k i n . )
f
L
"'I
101-+ i
1
,000.~
C +
i : j
6000-:
f i
aooo-+
2000-i
i
+
0-
0.000 2.000 1.000 6 . 000 8.000
F++i 10.000 ENERG1 (KEV)
F i g u r e 2 . ( S e e t e x t )
C2-902 JOURNAL DE PHYSIQUE
P o t e n t i a l l y h a r m f u l c o n t a m i n a t i o n can o n l y be e l i m i n a t e d a t t h e source b y an e x a c t d e t e r m i n a t i o n o f t h e contaminant. Moreover, w i t h i n c r e a s i n g w a f e r c o s t s c a u s i n g an emphasis on t h r o u g h - p u t , a ' c o n t a m i n a n t w i l l have as l i t t l e impact on a p r o d u c t l i n e as t h e a n a l y s t can p r o v i d e t h r o u g h f a s t , a c c u r a t e a n a l y s i s . W i t h a few o b s e r v a t i o n s s u p p o r t e d by c o n f i r m a t i o n by more s p e c i f i c b u t t i m e consuming means ( Auger,SIMS, NAA, o r g a n i c s t a i n s , e t c . ) , an X-Ray S p e c t r o s c o p i s t can develop an eye f o r s k i n c o n t a m i n a t i o n t h a t w i l l become i n c r e a s i n g l y f a s t and r e l i a b l e .
T a b l e 1. Chemical element c o n c e n t r a t i o n s i n t h e human body and body f l u i d s w i t h i o n i z a t i o n p o t e n t i a l s .
ELEMENT CONCENTRATION ( % ) 1 s t IONIZATION POT.
Oxygen 6 5 13.618 V.
Carbon 18 11.260
Hydrogen 10 13.598
N i t r o q e n 3 14.534
~ a l c i ; m 2.2 6.113
Phosphorous .8-1.2 10.486
~ o t a s s i u m S u l f u r C h l o r i n e Sodi um Magnesium I r o n I o d i n e S i l i c o n F l u o r i n e Copper
~ a g n e s i um Cobal t N i c k e l Barium L i t h i u m
TRACE
