Polyimide dielectric materials were acquired for comparative and evaluative studies in double layer metal processes. Preliminary experiments were performed. Also, the literature indicates that sputtered aluminum films may be successfully patterned using the left-off technique provided the substrate temperature remains low and the argon pressure in the chamber is relatively high at the time of sputtering. Vendors associated with dry processing equipment are identified. A literature search relative to future trends in VLSI fabrication techniques is described

Wade, T. E.

English

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https://ntrs.nasa.gov/search.jsp?R=19810023782 2020-03-21T11:08:24+00:00Z
VE. Wade
nvestigator
0.
esearch Laboratory
ate University
trical Engineering
Mississippi 39762
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OQUAIRITERLY REPORT
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Contra t NASA-33448
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	 HIGH D--NSI'IY C:FC01T
TECHNOLOGY Quarterly Rp rort, 13 Jul. - 13
Oct. 1979
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QUARTERLY REPORT
July 13, 1979 - October 1-'
Contract NAS8- 33448
HIGH DENSITY
CTRCUIT TECHNOLOGY
j
Prepared for
George C. Marshall Space `light Center
Marshall Space Flight Center, Alabama 15312
by
Thomas E. Wade
Principal Investigator
1
Microelectronics Pesearch LaboraLory
Mississippi State University
Department of Electrical Engineering
Mississippi State, Mississippi 1976?
TABLE OF CONTENTS
Page
I. INTRODUCTION .
	 1
11. MULTI--LEVEL METAL TLCliNTQi1F. .
	 . .	 . .	 1
III. METAL LIFY-OFF TECHNIQUE .	 4
IV. DRY PROCESSING EQUIPMENT EVALUATION .
	 5
V. l'UTURF Ti; 1;NDS "1N VLSI FABRICATION TECHNIQUES 	 G
VI. M. S.U. MICROELEA.A'RONICS RESFARC11 LABORATORY 	 7
V11. PROPOSED WORT: FOR NEXT QUARTER . 	 7
VII T . PROBLEM AREAS.
	 8
IX. DRY PROCESSINC VENDORS
	 8
X. FINANCIAL S'lATI?A LM'S .
	 11
i
I. INTRODUCTION
Progress has been accomplished in all of the proposed areas as
listed under the Scope of Work, Exhibit A, Contract NAS8-33448.
Some delays have been experienced due to metal deposition equipment
malfunctions and start-up procedures associated with the Mississippi
State Microelectronics Research Laboratory. It is felt that many
of these problems have been eliminated to the extent that normal
progress will be rendered during the next contract quarter. This
is especially true since a full time processing technician has
recently been hired to assist in these and other endeavors.
In accordance with the contracts "Report Requirements" section
which states "quarterly reports shall be in narrative form, and
brief and informal in content", the following research areas of
emphasis will be addressed.
II. MULTI-LEVEL METAL TECHNIC
This sr.udy is a continuation of last years NASA contact effort
(J. D. Trotter, T. E. Wade, J. D. Gassaway, "Trends and Techniques
for Space Base Electronics", NASA Contract NAS8-26749, June, 1979).
In addition to heat treatment studies and the use of phosphosili--
sate glass as a dielectric (T. E. Wade, Special Report, "Post Heat
Treatment Effects on Double Layer Metal Structuree for VLSI Appli-
cations," NASA Contract NAS8-26749, November, 1979), se, ►eral wafers
having first level patterned metal were sent to the West Coast for
processing. In these semiconductor houses, the wafers had dielec-
tric materials deposited on them of C.V.D. silicon dioxide (vapox),
2silicon nitride and polyimide (GAF and Hitachi versions) after
which via's were realized as per the M.S.F.C. test pattern. These
wafers were received from the West Coast after the termination of
last years contract. Prior to depositing the second layer metal,
the wafers will have to be back-spuitered in-situ to eliminate the
Al203 present on the first layer metal in the via's. Final pro-
1
	 cessing, of these wafers is anticipated to take place at M.S.F.C.
using their new back-sputtering capability (to be installed within
the next quarters effort)'.
During the first quarter, polyimide materials have been
received from two different companies, Hitachi. and Dupont, for
experimental and comparative studies. Some Hitachi materials were
obtained from M.S.F.C. personnel (thanks to Mr.. Donald Routh) while
additional materials and information have been ordered from the
company. Dupont has forwarded their polyimide (PI-2550) and
thinner, but their adhesion promoter has been back logged. This
should be arriving soon. Attempts will also be made to acquire
some G.A.F. iolyimide material for comparative studies. Initial
studies (i.e., -endors info, literature and preliminary experi-
ments) indicate the Hitachi P. I.Q. to be superior polyimide over
the others, however, it is much too early to draw definite conclusions.
Hopefully, before the termination of this contract, Mississippi
State's Microelectronics Research Laboratory will have the capability
of depositing silicon nitride as a dielectric using the Unipak VIII
Rpitaxial Reactor. This reactor is well on its way to becoming operati.onal,
w:th anticipated completion date of December, 1979.	 As of to date,
the machine has been installed, most of the plumbing (water, vent,
a
gasen , etc.) has been complete, and some system checks have been
accomplished.
A problem experienced during the firs ,: quarter of this contract
was with the metal deposition system. 	 A short in the d.c. sputter
gun resulting; from an accumulation of aluminum on oucc side of the
gun caused the gun's power supply to fail. 	 Attempts to repair this
by local technicians were unsuccessful (due to inability to monitor
f
sequential timing of power SCRs-and poor documentation), and hence
the 2.5 Kw power supply had to be sent- to the {Jest Coast for repair.
w Other laboratory activities involved in during the past quarter
included a complete replumbing of gae lines in the laboratory. 	 For
wafer processing during our "Fundamentals of LST" course last Spring,
r
gases such as nitrogen, oxygen, air, etc. were supplied to those
locations in tbs: laboratory where required in some what of a tem-
porary arrangement.	 Beginning with this academic school year, all
temporary lines were dismantled and replaced with permanent lines
to our gas bottle closets with all stainless steel runs placed in
w:
the ceiling, etc.	 This replumbing task is essentially complete for
.,;
primary gases.	 The complete replumbing activity should be com-
pleted in the near future, depending on the receipt of parts now
III. METAL LIFT-OFF TECHIZ ULS
A review of the literature indicates that sputtered aluminuun
films may be successfully patterned using the lift-off technique
provided the vubstrate surface temperature remains low (<100'C)
and the atmospheric pressure in the chamber is relatively high at
the time of sputtering. if these conditions are met, aluminum films
which exceed the photoresist in thickness can be successfully
deposited without reductAon in pattern width. Also, the slope of
the side walls of metallized aluminum patterns is controlled by
the argon pressure during sputtering in the following manner.
As illustrated below, the aluminum films grows perpendicular Co the
sidewalls of the photoresist pattern and the substrate surface,
-
DC ;-k
Mf ilm Z§
M.Weraje.\\ \ \\ ^ ^ -3rmc^► oh
ofoty
..5c: ^s-a
C z or S'i
respectively. The films contact each other near the photoresist
pattern edges, but do not fuse together since they have different
growth directions (at low temperatures), resulting in a microcrack
formation. A suitable stripper can then penetrate through the
microcrack to dissolve the photoresist.
!!^tCIN
k0oit QU GF isALtr;
5The slope, 0, of the resulting metal pattern is a function of
^.	 (1) the metal deposition rata on the photoresist sidewalls, Vp
and (2) the deposition rate: normal to the substrate, V s , and can
be exprvnsed us
V
8 eon 1 VB
p
At low argon pressure in the chamber, Vs is large and V  is
small since most deposited atoms fall on the substrate surface
(directly f.om the target). Whereas, for higher argon pressure In
the chamber, V  increases due to an increased number of collisions
metal atoms have with argon ions. Thus, elope angle for metal
line side walls, 0 , decreases as the argon pressure increases.
At least three additional metal lift-off techniques have been
researched as reported in the literature (i.e. conventional, use
of auxiliary layer, multiple wall calf-aligned, etc.)
IV. DRY PROCESSING GgUIPt4CNT EVALUATION
With the assistance of former colleagues who are presently
located on the West Coast, a list of primary vendors for dry
processing equipment have been compiled and is attached to this
report. Letters of inquiry and/or telephone contact have been
forwarded to most companies on this list, several of which have
responded with equipment literature and/or specification sheets.
It is anticipated that after reviewal of the vendors literature,
equipment can be identified which has the potential of meeting
the needs of H.S.F.C.'s objectives, and at a later date a
W6
demonstration and evaluation of such equipment can be undertaken.
A prototype parallel plate plasma etch machine has been
identified for either purchase at a much reduced price or donated
to the Microelectronics Research Laboratory at M.S.U. If this
machine is acquired, it probably will not arrive until the first
of next year. It is hoped that delivery and installatlor ► of this
etcher is such that experimental studies may be reported during
this contract period.
A considerable amodnt of material has been collected via
personal contacts, library stud3ea, vendor's info, etc. as related
to the physics of plae;ma processing. This material will be reviewed
and essential portions presented in the final report of this contract.
V. FUTURE '!'RENDS IN 'VLSI FABRICATION TECIR'l $S
An extensive study is underway to evaluate present and future
trends. These ir.corporate the following broad areas:
A. Lithography, with emphasis on optical. (contact, projection
and proximity), electron beam, x-ray, D.S.W. (direct-step-
on-the-wafer), testing and analysis thereof.
B. Processes as related to devices, namely CMOS, VMOS, CMOS
on sapphire, fast TTL, SOS, GaAs devices, I 2L, n-MOS, etc.
C. Processes as related to fabrication, as low pressure C.V.11,
high pressure oxidation, resist materials, etc.
D. Also, proposed materials and areas as metal silicide inter-
connection technology, refractory metal gate processes,
laser annealing (of ion-implanted or lattice damage, of
amorphous or poly, etc.)
'	 1
Report of theses findings will. be
 presented in tho final report.
VI. M.S.U. MICROELECTRONICS RESEARCH LABORAT0RY
Thanks principally to NASA M.S.F.C.'s early support, the
Micro-electronics Research Laboratory at M.S.U. shows procaine of
becoming a prowinent research and teaching facility. Last Spring,
a Unipak VIII epitaxial reactor was received and is now almost
operational. It is anticipated that in addition to growing epitaxial
layers, polysilicon and silicon nitride cspabilitics will be realized.
This past summer, two Kasper 1.00 • Kev ion implantors (one will be
used for parts) were received and installation of one of these is
presently underway. As mentioned early, it is hoped that the
parallel plate plasma etcher can be acquired this year and used
for this contract effort.
A new full time laboratory fabrication technician has been
hired and reported to work this month (October, 1979). Mrs. Becky
tiamiltan has had fifteen years of processing experience in major
semiconductor companies on the West Coast. She will make a
tremendous contribution to our overall microelectronics effort.
VII. PROPOSED WORK FOR NEXT QUARTER
It is anticipated that for next quarter, a continuation of
began this quarter will be undertaken with considerable
emphasis on laboratory experimental studies as related to
le. layer metal processing and thh rletal 11-ft-off techniques. Rack
red supplies should be forthcoming in the next few weeks and
laboratory facilities should also be in working order.
8Trips to the International Electron Devices Meeting in Waahin8ton
D.C. are planned, as well as possible ., trip to the West Coast to
attend the Materials Research Corporations conference and school
on Sputtering and Plasma Etching.
VIII. PROBLEMS ARF %S
As indicated, this quarters problems have been experienced with
failures of the metallization system power supply and sputter gun.
These have been corrected. Alao, replumbing of 1nboratory San runs
and alterations in equipment location have hampered laboratory
experimentation in addition to long delay:; in rwceiving orderwd
supplies (as Shipley photo resist, Dupont pnlyimide coupler,
sputter gun holder., etc.).
IX. DRY PROCFSSiNC VENDORS
A. plasma Etch Venders
1. Tegrl, Inc.
528 Weddell Dr.
Sunnyvale, California 94086
	
(408)744-0872
	 Contact: Phil Crabtree
Barrel and "in-line" parallel plate reactors both with
end point detectors.
2. IFE
2920 San XsI,1ro Way
Santa Clara, Californin 95051
	
(408)727-2360
	 Contact: Ken Scow
Barrel and small parallel plate reactors also, an
"in-line" 5 wafer system
3. D-W Industries (part of Kasper Instruments)
844 Del Rey
Sunnyvale, California 94086
	
(408)733-9800	 Contact: Berl Bragg
Parallel Plate batch system only
4. Dionex (Formerly I.P.C.)
3115^ San Benito Street
Hayward, California 94544
	
(415)489-3030	 Contact: Wayne Landman
Parallel plate batch and barrel oquipmont
5. Applied Materials
3050 Bower. Avenue
Santa Clara, California 94051
	
(408)249-5555
	 Contact: Steve Corlett
Plasma nitride deposition and etch aystems. Also new
types of plasma oxide etchers being developed by a
group headea by Robert Anglin
6. E. 1'. Systems
23780 Walsh Avenue
Santa Clara, California 05050
	
(408)984-230G	 Contact: Clint Graves
Planar Aluminum, poly, nitride batch etchers
4
R. Reactive YON Etchers
Varian
375 nistel Circle
Los Altos, California 94022
(415)966-1110
Still, in development
C. ION Beam Milling
Contact: Louis Kunz
VEECO
599 N. Mathilda Avenue, 'Suite 140
Sunnyvale, California 94086
(608)732-2330
In production
A. Plasma Deposition Vendors
1. Tegal (see above)
2. L.F.E. (see above)
3. AMT (see above)
4. Pacific-Western Systems
855 Maude Avenue
Mountain View, California
(415)961.-8861	 Contact: Norm Lewis
Both nitride and oxide plasma deposition
10
R. Low Pressure CVD Vendors (Oxide. Nitr'.de. Poly)
1. Thermco
1465 N. Sataula Street
Orange, California 92668
(714)639-2340
2. Advance Crystal Science
2995 Copper Road
Santa Clara, California 95051
	
(40..)733-3633	 Contact: Roger McKinley
3. Tylan Corporation
4203 Spencer Street
Torrance, CA 90503
4. ASM/America .
2328A Walsh Avenue
Santa Clara, California 95050
	
(408)727-2323
	
Contact: Ing-tiurie Helmer
F. Sputter Deposition System AL ;, Al, Al/Si, Al/Si/Cu,
Silleides, etc.
1. Perkin-Elmer
361 Wallow Street
San Jose, California 95110
(408)249-5540	 Ext. 270
2. C.P.A. Inc.
725 Kifer Road
Sunnyvale. California 94086
(408)733-9823
3. Varian (see above)
4. MRC
1101 San Antonio Road
Mt. View, California 94040
(415)964-7272
Contact: David Tam
Contact: Ed Wilder
Contact: Dick Walker
11,
S1
i
i
:w
QUARTERLY
FINANCIAL REPORT
FOR
NASA Contract NAS8-334!i8
July 13, 1979 - October 13, 1979
Prepared for
George C. Marshall Space Flight Center
Marshall Space Flight Center, Alabama 35812
Submitted by
Thomas E. Wade
Principal Investigator
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High density circuit technology

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