ENCAPSULATED SURFACE-BARRIER PARTICLE DETECTORS …

37
ANL-6526 ANL-6526 2brgonne Badonal laboratorg ENCAPSULATED SURFACE-BARRIER PARTICLE DETECTORS Some Methods and Techniques by Niels J. Hansen

Transcript of ENCAPSULATED SURFACE-BARRIER PARTICLE DETECTORS …

Page 1: ENCAPSULATED SURFACE-BARRIER PARTICLE DETECTORS …

ANL-6526 ANL-6526

2brgonne Badonal laboratorg

ENCAPSULATED SURFACE-BARRIER PARTICLE DETECTORS

Some Methods and Techniques

by

Niels J. Hansen

Page 2: ENCAPSULATED SURFACE-BARRIER PARTICLE DETECTORS …

LEGAL NOTICE

This report was prepared as an account of Government sponsored work. Neither the United States, nor the Commission, nor any person acting on behalf of the Commission:

A. Makes any warranty or representation, expressed or implied, with respect to the accuracy, completeness, or usefulness of the information contained in this report, or that the use of any information, apparatus, method, or process disclosed in this report may not infringe privately owned rights; or

B. Assumes any liabilities with respect to the use of, or for damages resulting from the use of any information, apparatus, method, or process disclosed m this report.

As used m the above, "person acting on behalf of the Commission" includes any employee or contractor of the Commission, or employee of such contractor, to the extent that such employee or contractor of the Commission, or employee of such contractor prepares, dis­seminates, or provides access to, any information pursuant to his employment or contract with the Commission, or his employment with such contractor.

Page 3: ENCAPSULATED SURFACE-BARRIER PARTICLE DETECTORS …

ANL-6526 Instruments (TID-4500, 17th Ed.) AEC Research and Development Report

ARGONNE NATIONAL LABORATORY 9700 South Cass Avenue

Argonne, Illinois

ENCAPSULATED SURFACE-BARRIER PARTICLE DETECTORS Some Methods and Techniques

by

Niels J. Hansen

Chemistry Division

March 1962

Operated by The Univer.sity of Chicago under

Contract W-31 -109-eng-3H

Page 4: ENCAPSULATED SURFACE-BARRIER PARTICLE DETECTORS …
Page 5: ENCAPSULATED SURFACE-BARRIER PARTICLE DETECTORS …

T A B L E O F CONTENTS

P a g e

I. INTRODUCTION 4

II. HISTORICAL CONSIDERATIONS AND S I M P L E THEORY . . . 4

III. PRELIMINARY T R E A T M E N T AND ENCAPSULATION . . . 7

A. P r e p a r a t i o n of the Si l icon Wafers 7

B. A s s e m b l y and E n c a p s u l a t i o n 7

IV. P R E P A R A T I O N O F THE SURFACE 8

A. Lapping 8

B. E tch ing 9

V. EDGE P R O T E C T I O N 10

1. Ciba Amine F r e e Epoxy 10 2. Shell Epoxy Pa in t 10

3. G r o d a n PI HIV AC 10

VI. GOLD EVAPORATION H

VII. T Y P I C A L P E R F O R M A N C E DATA 11

VIII. CONCLUSIONS 15

IX. ACKNOWLEDGEMENTS 15

X. A P P E N D I X 1^

REFERENCES '''

Page 6: ENCAPSULATED SURFACE-BARRIER PARTICLE DETECTORS …
Page 7: ENCAPSULATED SURFACE-BARRIER PARTICLE DETECTORS …

LIST OF FIGURES

No. Title Page

1. Energy Levels of Semiconductor Surface Barr ier Rectifier . . . 6

2. .Assembly and Details of Device Construction 8

3. Application of Edge Protection 10

4. Reverse Character is t ics of Typical Devices at Atmospheric P r e s s u r e and at 10"' mm Hg 12

5. Resolution of Typical Devices for the b.l Mcv Alpha Part icles from Curium-242 13

6. Resolution of 3000 ohm-cm Devices for Conversion Electrons from B a ' " and T e ' " 14

7. Vacuum Chamber for Cooling Devices 15

Page 8: ENCAPSULATED SURFACE-BARRIER PARTICLE DETECTORS …
Page 9: ENCAPSULATED SURFACE-BARRIER PARTICLE DETECTORS …

ENCAPSULATED SURFACE-BARRIER PARTICLE DETECTORS Some Methods .ind Techniques

by

Niels J. Hansen

I. INTRODUCTION

This report will describe in detail techniques that have been developed for the manufacture of encapsulated surface-barr ier particle detectors. There is a belief among some workers in the field that it is not possible to control the conditions of manufacture well enough to assure consistent resul t s . We have developed a method with which even inexperienced workers have been able to produce good devices with al ­most lOC o yield. The devices manufactured to date have found use as counters and spect rometers for fission fragments, alpha part icles, and low-energy electrons from radioactive nuclei. Devices, 50 mm^ in area , have a resolution for 6.1-Mev alpha particles of 26 kev at room temperature and 18 kev at 78°K. Resolution for 1.1-Mev electrons has been measured as 7.5 kev at 78°K for devices 28 mm^ in area . The silicon used has been n-type, grown with a 111 orientation, and purchased in the form of ingots about 2 cm in diameter; the resistivity has ranged from 100 to 3000 ohm-cm.

U. HISTORICAL C0.\SIDER..\T10XS AND SIMPLE THEORY

The ordinary, gas-filled ionization chamber! ' ) has been used for many years in various branches of nuclear physics as a detector of ion­izing nuclear par t ic les . Essentially, it consists of a parallel-plate ca­pacitor, the space between the plates being filled with a gas; a high voltage is applied across the capacitor to produce a high field between the plates. The part icles enter the chamber and lose their energy by collision with the gas molecules, and leave in their wake a trail of ion­ized gas atoms and free electrons. The electrons are swept up by the applied electr ic field; the charge is collected on the plates and the vol­tage thus produced is amplified for analysis. For a brief period some interest was shown in the crystal , or solid-state bulk conductivity, counter . '^ ' This device consisted of a piece of single crystal insulator, such as diamond, across which a voltage was applied: the energy lost by the ionizing particles as they were stopped in the material excited electrons into the conduction band, and they were subsequently swept up by the applied field; the voltage pulse produced was amplified for analysis . The usefulness of this device wa.s limited by the polarization of the insulator.

Page 10: ENCAPSULATED SURFACE-BARRIER PARTICLE DETECTORS …
Page 11: ENCAPSULATED SURFACE-BARRIER PARTICLE DETECTORS …

Beginning with the work of Mayer,(3) much has been done to develop the semiconductor junction detector. The bulk of the work that has been done is reported in the proceedings of two symposia that brought together most of the workers in the field.H) The junction detector is simply a r e ­verse biased semiconductor diode.(5) When ionizing particles t raverse the charge-depleted region of the diode, holes and electrons are produced and these c a r r i e r s a re swept up by the applied field. The device is linear with the energy of the ionizing particles when the lifetime of the ca r r i e r s against recombination or trapping is long with respect to the collection time of the c a r r i e r s . There a re at present two kinds of broad area p-n junctions used as diodes for the detection of charged particles: the diffused junction, and the sur face-bar r ie r junction.

The diffused junction is produced by thermal diffusion of a donor impurity into s ingle-crystal p-type silicon, or of an acceptor impurity into single-crystal n-type silicon to produce a shallow p-n junction, perhaps a micron or so below the surface of the silicon. When a reverse bias is applied ac ross such a junction, c a r r i e r s are withdrawn from the region of a junction, and a charge-depleted region is produced just beneath the suf-face. If the depth of the junction is shallow enough the charged particles will enter the depletion region with little energy loss in the dead volume, or "window," at the surface. The diffused junction has one serious draw­back: the heat treatment which is necessary to accomplish the thermal diffusion tends to degrade, or shorten, the lifetime of the ca r r i e r s against recombination, trapping, or both. Long ca r r ie r lifetime is desirable, as pointed out above, because, in order that the output of the device be linear with the energy of the part icles detected, it is essential that the ca r r i e r s be collected before they recombine or are trapped. We have confined most of our efforts to the development of the surface-barr ier junction because of its inherent simplicity.

The sur face-bar r ie r junction is the easiest to produce because nature does most of the work. Surface states on germanium were postu­lated by Bardeen'^) to explain the fact that the contact potential and the rectification charac ter is t ics of metal-semiconductor diodes did not appear to depend upon the metal that was used for the contact. The surface states are represented as a well containing electrons that are withdrawn from the interior of the semiconductor; the surface levels trap electrons until the height of the Fermi level in the surface is equal to that of the Fermi level in the inter ior . There results a thin region, just below the surface, which has been depicted of its ordinary share of electrons; the space charge due to uncompensated donors gives r ise to an electric field which distorts the energy levels and leads to the formation of an asymmetrical potential b a r r i e r . The bending of the energy levels in effect lowers the Fe rmi level at the surface, such that a p-type surface resul ts . P-type silicon will thus have formed a more strongly p-type surface, whereas in the case of n-type mater ia l , then- will .xi.st an inversion l.iyer with a

Page 12: ENCAPSULATED SURFACE-BARRIER PARTICLE DETECTORS …
Page 13: ENCAPSULATED SURFACE-BARRIER PARTICLE DETECTORS …

p-n junction just below the surface (sec Figure 1). The Bardeen theory does not specify the exact nature of these surface s ta tes , but there is a possibi l i ty that they a r i s e from the formation on the surface of a s table , or q u a s i - s t a b l e , oxide layer . The sur face -barr i er detector is made of n-type s i l i con; the meta l contact to the p-type surface is made with gold which IS evaporated over the surface .

C«*4wct>0B s a M

ftCmCOilOUCTOM CNCOOT L C V C L O.AGMAM. NO SUKFACC

H:=_

«v: a—4 l>««*a<ea LOv«

tCM.CONOUCTO* V . T H tUHFACC STATES. NO iffHtO VOLTAOt

— f»imi L«««'

MICONOUCTOII «>rM tunrACC fTATCft. RCvCRSe y0cT46C V A P P L . E D

Figure 1

Energy L e v e l s of Semicon­ductor Surface Barr ier Rect i f ier

The shape of the potential barrier and the depth of the charge depleted region can be obtained from the solution of P o i s s o n ' s equa­tion for the case of uniform conduc­tivity in the semiconductor . ( ' ) Po i s son ' s equation for the one-dimensional case is

dx

47T a

where 0 is the charge density, which, at room temperature is given by e N j , Njj the donor impurity concen­tration, e the e lectronic charge (in esu) , and K:= 12 for s i l i con. The solution is

2,-eNd (D^ - x^) ,. . V = 2-J '- (in esu)

If the potential V drops from VQ on the surface (x = 0) to zero inside the semiconductor , the depth of the s p a c e - c h a r g e , or charge-deple ted , region will be given by

27reNd (cm)

When an external r e v e r s e bias is applied, the depth of the space -charge

region will be given by

D = V ^ Vo* V)

2reNd (cm)

Page 14: ENCAPSULATED SURFACE-BARRIER PARTICLE DETECTORS …
Page 15: ENCAPSULATED SURFACE-BARRIER PARTICLE DETECTORS …

The associated capacity oi the junction will be

C = A eN,,

4-D V8-:(V„ + V)

where .A is the area of the junction in cm' .

A broad space-charge region is desirable because the associated capacity will decrease as the charge-depleted region is increased: a low capacity resul ts in a larger signal and an improved signal-to-noise ratio. From the above relations, we see that the dependence on resistivity and bias voltage is

D'.yvf 1

where the resistivity is related to the impurity concentration by

in which ^ is the mobility of the c a r r i e r .

III. PRELIMINARY TREATMENT AND ENCAPSULATION

A. Preparat ion of the Silicon Wafers

The ingot is mounted in black wax and cut into slices with a precision diamond cutoff saw. Devices smaller than 2 cm in diameter are made by cutting small wafers out of these slices with an ultrasonic boring machine by means of a hollow tool. Rectangular pieces can be cut with the diamond saw and i r regular shapes can be formed with the ultrasonic boring machine. The wafer is lapped on both sides on a glass plate in a slurry of optical finishing powder(8' in water to remove the gross damage done by the saw, rinsed in running tap water, cleaned in an ultrasonic cleaner in a strong detergent solution to remove the crushed bits of silicon and finishing powder adhering to the surface, and again rinsed in tap water. The wafer is nickel plated in an electroless nickel plating solut ionO: about 15 min in the boiling solution is long enough to permit the deposition of a suitable layer of nickel.

B. Assembly and Encapsulation

The ohmic contact is made to the wafer by soldering a #22 tinned copper wire to one side of the wafer with ordinary rosin-core solder; the flux is cleaned off with trichloroethylene. The solder connection is painted with Q-Dope (polystyrene dissolved in toluene),!'0) and when the paint is

Page 16: ENCAPSULATED SURFACE-BARRIER PARTICLE DETECTORS …
Page 17: ENCAPSULATED SURFACE-BARRIER PARTICLE DETECTORS …

dry the nickel is stripped off by immersion in CH-4(11) for a few seconds, after which it is rinsed in running tap water. After being dried in air , the back of the device is again painted with Q-Dope to protect the edge of the nickel plating under the solder joint, and the silicon is etched in CP-4 at room temperature for about 10 sec to polish the edges of the wafer, after which It IS rinsed in running tap water and then in running distilled water. The assembly is now ready for encapsulation.

The wafer is mounted on a piece of tape with adhesive on both faces which has been laid down on a thin piece of Lucite, or any other flexible mater ial . A short piece of polystyrene tubing is mounted concentrically about the wafer, and a gold contact wire is inserted beside the wafer (see Figure 2). An epoxy resin is poured into the tubing, care being taken to remove any bubbles before the resin sets . The resin we have been using is R-313,!' '-) mixed in the proportions 2 drops hardener B to one gram of resin.

f .1 S-i<co" OOtO'

O-SiJ E»o i>^ Poi,tt, . .«« V, T»b«

' ic4J o.oeo'--]r- *'8'-4

• — iV — •

Figure 2

Assembly and Details of Device Construction

IV. PREPARATION OF THE SURFACE

A. Lapping

The surface is lapped on a glass plate in a slurry of grinding powder and water, starting with any convenient grade of grindingpowder and working down by stages to #95 optical finishing powder.(8) An essential step in the lapping process is the cleaning of the surface between each grade of grind­ing powder and after the final lapping with the #95 finishing powder. The surface is rinsed in running tap water and then cleaned in an ultrasonic cleaner in a strong detergent solution to remove the crushed bits of silicon and finishing powder adhering to the surface. The ultrasonic agitation serves to shake the bits of material loose and tin- d.t.rg.-nt solution holds

Page 18: ENCAPSULATED SURFACE-BARRIER PARTICLE DETECTORS …
Page 19: ENCAPSULATED SURFACE-BARRIER PARTICLE DETECTORS …

It in suspension, and thus prevents recombination with the surface. The ultrasonic cleaning is followed by a rinse in running tap water and then in running distilled water. This is a most important step in the prepara­tion of the surface, as it is essential that the surface be free of loose matter during the etching: small particles clinging to the surface will react more rapidly with the etch than will the body of the silicon wafer, and the result will be a variation of the etch rate over the surface owing to the presence of "hot spots" caused by the rapid reaction at the sites of these small par t ic les . This variation in etch rate will result in the formation of pits or protuberances on the surface. The technique de­scribed enables one to chemically polish a silicon surface, 3 cm' in area , completely free of these unsightly blemishes.

B. Etching

The etching and all the subsequent handling of the device are carr ied out in a dust-free atmosphere. A Lucite glove box has been outfitted with a large, highly efficient filter and a stack which is vented into a hood. The surface is etched with CP-4 . ( '2 ) ^ preferential etch that we have used with great success . The etch is mixed in a large polyethylene bottle, 1.1 l i ters being mixed up at a t ime. The etch is stored in the polyethylene bottle and aging seems to have no adverse effect. It is important that all the bottles and graduates used in mixing and measuring be clean, of course. The etch is used in a polyethylene beaker, and is cooled to 0°C in an ice bath. The etch is s t i r red with a magnetic st irr ing device, and no more than four wafers of 50 mm area are etched in one 100 ml batch of etch; if larger pieces a re to be polished then the number of pieces per pot of etch will be reduced accordingly. The silicon surface is immersed in the cold etch for 3.j min, and must not be lifted out of the etch before the time is up. The piece is removed immediately into a stream of running distilled water, and rinsed until it passes the water film break test. The test is easily performed and will indicate the presence of hydrophobic contaminants. The device is removed from the s t ream of distilled water and the excess water is shaken off; it is held with its surface vertical: if the surface is free of hydrophobic contaminants the water film that remains on the surface will dry slowly and interference fringes will be seen at the edge of the film; if the surface is not free of hydrophobic contaminants the film will break and the water will run off the surface. This is a good test for cleanliness, but our ex­perience has been that there is no correlation between passing the water film break test and performance as a good detector. No attempt is made to remove organics or ions from the distilled water. The device is per­mitted to dry and is stored in the dust free atmosphere for twenty four hours, or more , to permit the growth of an oxide l.iyer. ,illrr whn li edge protection is applied.

Page 20: ENCAPSULATED SURFACE-BARRIER PARTICLE DETECTORS …
Page 21: ENCAPSULATED SURFACE-BARRIER PARTICLE DETECTORS …

10

V. EDGE PROTECTION

A c l o s e e x a m i n a t i o n of the device af ter e tching r e v e a l s that the edge of the s i l i c o n s u r f a c e is very i r r e g u l a r at the s i l i con epoxy in t e r f ace (see F i g u r e 3). Owing to th i s i r r e g u l a r i t y the su r f ace b a r r i e r junc t ion at the edge is v e r y n o n u n i f o r m . When an e l e c t r i c field is appl ied a c r o s s the junct ion b r e a k d o w n will o c c u r a round the edge. The high e l e c t r i c field can be moved away f rom the i r r e g u l a r edge of the junct ion by the app l i ca t ion , a f ter e t ch ing , of an insu la t ion of s o m e s o r t a round the edge of the s i l i con wafer . When such edge p r o t e c t i o n is app l ied , the dev ices a r e abl^ to Uke ve ry high vo l t ages and the r e v e r s e leakage c u r r e n t will be very s m a l l .

• « i C««t«ct Ed9t Pro.tc'i**

F i g u r e 3

.•\pplication of Edge P r o t e c t i o n

We have found 3 di f ferent m a t e r i a l s to be effective for edge p r o ­tec t ion :

1. Ciba Amine F r e e Epoxy: 502 A r a l d i t c with #204 Harden ing

Th i s is the m a t e r i a l r e p o r t e d by B lankcnsh ip , B o r k o w s k i . and Fox . ' ' ** ' They u s e d it with a s m a l l amount of iodine in solut ion, but we have found that it works j u s t as well without the iodine . It is a good p r o ­tec t ive m a t e r i a l , but it has a very s h o r t pot life: it h a r d e n s so quickly that it is not p o s s i b l e to apply it with a hypode rmic s y r i n g e .

2 . Shel l Epoxy Pa in t Ax 211 (Resin #1002 in a so lven t ) . ( ' 5 )

This m a t e r i a l is mixed a c c o r d i n g to the m a n u f a c t u r e r ' s s p e c i ­f ica t ions and IS p e r m i t t e d to s tand until it ge ts too thick to run when appl ied to the s e m i c o n d u c t o r s u r f a c e . It can be appl ied with a fine b r u s h or with a h y p o d e r m i c s y r i n g e .

3. G r o d a n #1 H I V A c C ^ ^

Th i s is the m a t e r i a l we have used for a l m o s t al l of our work . F o u r d r o p s of h a r d e n e r a r e m i x e d with 1 g r a m of r e s i n . It i s a l lowed to

Page 22: ENCAPSULATED SURFACE-BARRIER PARTICLE DETECTORS …
Page 23: ENCAPSULATED SURFACE-BARRIER PARTICLE DETECTORS …

u

stand until it begins to get so thick th.it it will not run when applied to the semiconductor sur face . It can be applied with either a fine brush or a hypodermic s y r i n g e . We have used a -j -ml syringe with .1 #30 needle .

VI. GOLD EVAPORATION

The dev ice is s tored overnight in the dus t - f ree a tmosphere while the edge protect ion hardens . It is then removed to a vacuum evaporator and a layer of gold, about 200 A (approximately 40 j jg /cm') thick, is evap­orated onto the surface to e s tab l i sh contact between the gold lead and the p-type sur face , at a p r e s s u r e of about 5 x 10"' mm Hg. The device is mounted about b-S in. from the source fi lament; this a s s u r e s that if many dev ices are coated at one t ime that the thickness of gold will be about the s a m e on all of them. It has been our exper ience that on some occas ions the evaporated layer does not make contact with the gold lead, or that the contact b e c o m e s noisy when voltage is applied. The front surface of the epoxy and the surface of the gold wire do not join smoothly because they are r^ough. even when lapped with a fine grade of finishing powder. The 200-A-th ick layer of gold is not heavy enough to form a bridge from the epoxy surface to the gold wire . This can be remedied in advance when the edge protect ion is being applied: s imply run a little str ing of epoxy from the edge over to just touch the gold wire such that, when gold is evaporated over the sur face , there will be a smooth, continuous layer of gold from the s i l i con surface to the gold wire ( see Figure 3). This e s tab l i shes a con­tinuity that will permit cooling the device to liquid nitrogen temperature (78"K) without caus ing the contact to open or to become noisy because of differential contract ion.

VII. TYPICAL PERFORMANCE DATA

Resu l t s with d e v i c e s prepared in this manner are shown in F igures 4, 5. and 6. As is evident from the f igures , m e a s u r e m e n t s were made at room temperature (300'*KJ and at liquid nitrogen temperature (78''K). No curve of current vs r e v e r s e bias i s presented for 78''K because the current in all c a s e s was l e s s than lO''" amp up to a bias of 350 v. In general , d e v i c e s made with mater ia l in the re s i s t i v i ty range from 100 to 850 o h m - c m have all given the s a m e r e s u l t s . Figure 5 shows the resolut ion obtained for the 6 .1 -Mev alpha par t i c l e s from c u r i u m - 2 4 2 (the two l ines arc separated by 44 kev) for 3 s i z e s of dev ice . The 3 0 0 0 - o h m - c m mater ia l that we have has not been useful for l o w - e n e r g y a lpha-part ic l e spec troscopy because the best reso lut ion for 6 .1 -Mev alphas has been about 70 kev for a device 28 m m in a r e a . It h a s , however , proven to be useful for e l ec tron spec troscopy , and F igure 6 shows the resolut ion that has been m e a s u r e d at 78''K for the b25-kev c o n v e r s i o n line from bar ium-137 and the convers ion l ines from bismuth-207 . The best r o o m - t e m p e r a t u r e f igures arc: 17 kev for the b25-kev line at 175 v, and 25 kev for the 1.1-Mcv line at a bias of 400 vol ts . Figure 7 shows the vacuum chamber which has been used for cooling the d e v i c e s .

Page 24: ENCAPSULATED SURFACE-BARRIER PARTICLE DETECTORS …
Page 25: ENCAPSULATED SURFACE-BARRIER PARTICLE DETECTORS …

12

•0

• 0

*»*»

'9

>0'* MM M|^

'

J >0*

. . . . ^.j^j. .j^^^^jj,^

• - - -

Llft>*U CU*«CMT ,m A M ^ a c t LC*K«aC CUimCMT I N AMPCMCS

^ < * MOD • • • »

LC*««OC CUUKCMT

Figure 4

Reverse Character is t ics of Typical Devices at Atmosphcru Pressure and at 10"' mm Hg

Page 26: ENCAPSULATED SURFACE-BARRIER PARTICLE DETECTORS …
Page 27: ENCAPSULATED SURFACE-BARRIER PARTICLE DETECTORS …

13

- ; — I — " — I — " — I — -

- i . 1 . 1 . I 1 1_ » 40 60 80 "00 'to

C H A N N E L N U U B C * )

- T . 1 • , . 1 . j -

• • « • • « . a l t .

J . i I L_L L • I I 0 20 40 60 eo 100 iZO

CHANNEL NUMBER

- — I — • — 1 — • — I — • — I — ' — I — • — r

• •• n -•••t

1 — I — . — , — . — , — . — , — . — I — , — J -

# • •OS' I S ««it«

C H X U M > « t

40 t o t o CHANNEL NUMBCA

40 60 e o lOC CHANNEL NUMBER

Figure 5

R e s o l u t i o n of T y p u a l D e v i c e s f o r the 6 , 1 M e v

A l p h a P a r t i < l e s f r o m C u r i u m - . i 4 i i

Page 28: ENCAPSULATED SURFACE-BARRIER PARTICLE DETECTORS …
Page 29: ENCAPSULATED SURFACE-BARRIER PARTICLE DETECTORS …

*tM MOO « • •> M M , * l%.m

Figure 6

Resolution of 3000 ohm-cm Devices for Conversion Electrons from B a ' " and Te'^*

Page 30: ENCAPSULATED SURFACE-BARRIER PARTICLE DETECTORS …
Page 31: ENCAPSULATED SURFACE-BARRIER PARTICLE DETECTORS …

15

S-gnoi Out

Figure 7

Vacuum Chamber for Cooling Dev ices

VIII. CONCLUSION

The technique descr ibed above has been used success fu l ly at this laboratory for the fabrication of detec tors that have found use as g r o s s counters and as s p e c t r o m e t e r s ; it has been found that with a little pract ice workers with no previous exper ience have been able to manufacture dev ices that connpare with those d i s c u s s e d in the present report. We feel that with a modes t investment in t ime and money any laboratory can eas i ly set up to manufacture d e v i c e s for their own use .

IX. ACKNOWLEDGEMENTS

Mention must be made of the contributions made by Donald Sparlin, who began the present program, John Dame, and Alan Sandborg, all three of whom were employed as cooperat ive or part - t ime employees while attending Northwestern Univers i ty . .Special mention must be made of the t ime spent by Dale Henderson, of the Chemistry Division, in improving the behavior of the Instrument Development Laboratory i h . irge-sens i t ive ampl i f ier that was used in making the m e a s u r e m e n t s .

Page 32: ENCAPSULATED SURFACE-BARRIER PARTICLE DETECTORS …
Page 33: ENCAPSULATED SURFACE-BARRIER PARTICLE DETECTORS …

16

X. APPENDIX

A. Chemica l Po l i sh: C P - 4

From: Trans i s tor Technology, Edited by Bridges , Scaff, and Shive, Bell Labs S e r i e s , D. Van Nostrand (1958), Vol. I, p. 354.

Hydrofluoric Acid HF (48%) 300 cc Nitric Acid HNO, (71%) 500 cc Glacial Acetic Acid CHjCOOH 300 cc Bromine (omitted in our etch) 5 cc

Mix and s tore in polyethylene container.

B. E l e c t r o l e s s Nickel Plating Solution

F r o m : Trans i s tor Technology, Edited by F. J. Biondi, Bell Labs S e r i e s , D. Van Nostrand (1958), Vol. HI, p. 173.

Nickel Chloride 30 g m / i Sodium Hypophosphate 10 g m / £ Ammonium Citrate 65 g m / i Ammonium Chloride 50 gm/1

Fi l ter

To use; Add ammonium hydroxide (NH4OH) to pH 8-10 and heat to boi l ­ing; at pH 8-10 the solution should be a bright blue color .

Page 34: ENCAPSULATED SURFACE-BARRIER PARTICLE DETECTORS …
Page 35: ENCAPSULATED SURFACE-BARRIER PARTICLE DETECTORS …

17

REFERENCES

B. B. Rossi and H. II Staub. Ioni?..itioii Chambers .ind Counters, National Nuclear Energy Series V-2, McGr.iw Hill, New York (1949).

2. R Hofstader. Crystal Counters, Proc. Inst. Radio Engrs., 38, 726 (1950).

3. J. W. Mayer. Perforniaiice of Ge and Si Surface Barr ier Diodes as •Alpha Particle Spectrometers . J. Appl. Phys., 30, 1937, (1959),

4. Semiconductor Nuclear Particle Detectors, edited by J. W. T. Dabbs and F. J Walter, NAS-NRC 871, Nuclear Science Series Report #32, (1960). Proceedings of the Meeting on Solid State Radiation Detectors, IRE T r ans , on Nuclear Science. Vol. NS-8, No. I, (1961).

5. W. Shockley, The Theory of p-n Junctions in Semiconductors and p-n Junctions Trans i s to r s , Bell System Tech. J., 28 , 335, (1949).

6. J. Bardeen. Surface States and Rectification at a Metal Semiconductor Contact. Phys. Rcv..JJ_. 717 (1947).

7. W. C. Dunlap, An Introduction to Semiconductors, John Wiley and Sons, New York (1957), Chap. 7

8. The Carborundum Company, Electro Materials Division, Niagara Fal ls , New York.

9. Trans is tor Technology, Edited by F J Biondi, Bell Labs Series , D. Van Nostrand (1958), Vol. Ill, p. 173.

JO. General Cement Manufacturing Co., Rockford, Illinois.

11. Trans is tor Technology, Edited by Bridgers, Scaff, and Shive, Bell Labs Ser ies , D. Van Nostrand (1958), Vol. I, p. 354.

12. Carl H. Biggs Co., 1547-14th Street, Santa Monica, California.

13. Ciba Products Corporation, Fairlawn, New Jersey .

14. J. L Blankenship, C J. Borkowski, and R . J . Fox, Silicon Surface Bar r ie r Nuclear Part icle Detectors, from a Conference on Nuclear Electronics (References Number NE, 136).

15. Shell Chemical Corporation, 380 Madison Avenue, New York 17, New York.

16. Grodan Manufacturing and Sales, Inc., 5815 West Jefferson Avenue, Detroit 9, Michigan.

Page 36: ENCAPSULATED SURFACE-BARRIER PARTICLE DETECTORS …
Page 37: ENCAPSULATED SURFACE-BARRIER PARTICLE DETECTORS …

AnniYMi lutnui i/w w i i