Semiconductor device manufacturing: process – Coating with electrically or thermally conductive material – To form ohmic contact to semiconductive material
Reexamination Certificate
2002-04-09
2003-05-27
Elms, Richard (Department: 2824)
Semiconductor device manufacturing: process
Coating with electrically or thermally conductive material
To form ohmic contact to semiconductive material
C438S759000
Reexamination Certificate
active
06569763
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a semiconductor fabrication process and more particularly to a process for fabricating semiconductors, such as high electron mobility transistor (HEMT) and heterojunction bipolar transistor (HBT) semiconductors, which eliminates damage to a device during lift-off of undesired metal.
2. Description of the Drawings
High electron mobility transistors (HEMTs) are well known in the art. Examples of such HEMTs are disclosed in U.S. Pat. Nos. 6,232,624; 6,177,685; 6,100,542; 6,049,097; 6,028,328 and 5,976,920 and commonly owned U.S. Pat. Nos. 5,668,387 and 5,528,769. HEMTs are also extensively covered in the literature: “Temperature-Dependent Small Signal and Noise Parameter Measurements and Modeling on InP HEMTs,” Murti et al.,
IEEE Transactions on Microwave Theory and Techniques,
Volume 48, No. 12, December 2000, pp. 2579-2587; “Pseudomorphic InP HEMT's With Dry Etched Source Vias Having 190-mW Output Power and 40% PAE at V-Band,” by Grundbacher et al.,
IEEE Electron Device Letters,
Volume 20, No. 10, October 1999, pp. 517-519; and “InP HEMT's With 39% PAE and 162-mW Output Power at V-Band,” Grundbacher et al.,
IEEE Microwave and Guided Wave Letters,
Volume 9, No. 6, June 1999.
Such HEMTs are used in various low-noise and power microwave applications where relatively high-device output power, power added efficiency and noise performance are critical. Such HEMTs have been known to be used in Q, V and W-Band microwave applications in commercial and military radar systems and communication systems.
Such HEMTs are known to be integrated into monolithic microwave integrated circuits (MMICS) for use in various applications as discussed above. Such MMICs are also well described in the literature; “An Indium Phosphide MMIC Amplifier For 180-205 GHz” by Archer et al.,
IEEE Microwave and Wireless Components Letters,
Volume 11, No. 1, January 2001, pp. 4-6; “InP REMT Amplifier Development for G-Band (140-220 GHz) Applications by Lai et al., Digest Technical International Electron Devices Meeting, San Francisco, Calif. on Dec. 10-13, 2000, pp., 175-177; “High Reliability Non-Hermetic,” and “Extremely High P1 dB MMIC Amplifiers for Ka-Band Applications” by Lai et al.,
Gallium Arsenide Integrated Circuits
(
GAAsIC
)
System
2001,
Twenty
-
Third Annual Technical Digest.
Oct. 21-24, 2001, Baltimore, Md., pp. 115-117.
Such HEMTs are formed by conventional photolithography techniques and include a T-gate structure that is susceptible to damage during conventional metal lift-off techniques, thereby lowering the yield of such devices. More particularly with reference to
FIG. 1
, an intermediate process step for a HEMT is shown which illustrates the formation of the gate structures, identified with the reference numerals
20
and
22
. These gate structures
20
and
22
are formed on top of a multi-layered structure, generally identified with the reference numeral
24
. In order to form the desired gate structure, two levels of photo-resist
26
and
28
and masking steps are used to develop the T-gate structure
20
and
22
shown. An undesired metallization layer
30
is formed during the deposition of the metal on top of the photo-resist layers
26
and
28
to form the T-gate structures
20
and
22
shown.
The undesired metallization layer
30
and photoresist layers
26
and
28
are removed by conventional metal lift-off techniques which normally involve soaking the entire structure in a solvent solution, typically acetone. The solvent solution dissolves the photoresist layers
26
and
28
underneath the undesired gate metal layer
30
. Once the photoresist layers
26
and
28
are dissolved, the undesired gate metal
30
is known to float off the wafer leaving the desired gate structures
20
and
22
. Unfortunately, when the photoresist layers
26
and
28
are dissolved, the undesired gate metal layer
30
is known to break into pieces that can scratch or damage adjacent submicron structures, such as the T-gates
20
and
22
which at the neck are on the order of 0.1-0.15 microns. Damage to the gate structures
20
and
22
can result in a lower yield for the process. Thus, there is a need to prevent metal lift-off from damaging such gate structures to improve the yield.
SUMMARY OF THE INVENTION
The present invention relates to a process or improving the yield of semiconductors, such as high electron mobility transistors (HEMTs), which are susceptible to damage during conventional metal lift-off techniques. In accordance with an important aspect of the invention, damage to relatively fragile structures, such as submicron dimensioned structures on semiconductors are minimized by utilizing an adhesive tape to peel off undesired metal in close proximity to submicron dimension structures. By using an adhesive tape to peel off undesired metal, damage to submicron dimension structures is minimized thus improving the yield.
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Grundbacher, R. et al., “InP HEMT's with 39% PAE and 162-mW Output Power at V-Band,”IEEE Microwave and Guided Wave Letters, vol. 9, No. 6, Jun. 1999.
Archer, J. et al., “An Indium Phosphide MMIC Amplifier for 180-205 GHz,”IEEE Microwave and Wireless Components Letters, vol. 11, No. 1, Jan. 2001.
Grundbacher, R. et al., “Pseudomorphic InP HEMT's with Dry-Etched Source Vias Having 190 mW Output Power and 40% PAE at V-Band,”IEEE Electron Device Lettersvol. 20, No. 10, Oct. 1999.
Murti, M. R. et al. “Temperature-Dependent Small-Signal and Noise Parameter Measurements and Modeling on InP HEMTs,”IEEE Transactions on Microwave Theory and Techniques, vol. 48, No. 12, Dec. 2000.
Lai R. et al., “InP HEMT Amplifier Development for G-Band (140-220 GHz) Applications,”International Electron Devices Meeting, San Francisco, California, Dec. 10-13, 2000, pp. 175-177.
Lai, R. et al.,“Extremely High P1dB MMIC Amplifiers for Ka-Band Applications,”2001 IEEE GaAs Digest, 2000, pp. 115-117.
Streit D. et al., “InP HBT Technology and Applications,”10th Inter. Conf. on Indium Phosphide and Related Materials, May 11-15, 1998, Tsukuba, Japan, pp. 65-67.
Streit D., “Indium Phosphide HEMT and HBT Production for Microwave and Millimeter-Wave Applications,”2001 Annual Pacific Microwave Conference, vol. 1, pp. 9-14, Dec. 3-6, 2000,.
Lai, R. et al., “0.1 &mgr; m InGaAs/InAlAs/InP HEMT Production Process for High Performance and High Volume MMW Applications,” 1999GaAs MANTECH Conference, Apr. 19-22, 1999, Vancouver, British Columbia, Canada, pp. 249-252.
Chen, Y.C., et al., “21 GHz Highly Efficient Composite-Channel InP HEMT,”2000 International Conference on Indium Phosphide and Related Materials, Conference Proceeding, Williamsburg, Virginia, May 14-18, 2000, pp. 75-78.
Grundbacher, R., et al., “InP Power HEMTs with 36% PAE at 60 GHz,”1999 Eleventh International Conference on Indium Phosphide and Related Materials, Conference Proceeding, Davos, Switzerland, May 16-20, 1999, pp. 307-310.
Streit D. et al., “High Performance Low Cost Indium Phosphide MMICs for Commercial Wireless Applications,”Digest, IEEE MTT-S Symposium on Technologies for Wireless Applications, Vancouver, B.C., Canada, Feb. 21-24, 1999, pp. 253-256.
Oki, et al., “InP HB
Dia Rosie M.
Grundbacher Ronald W.
Liu Po-Hsin
Elms Richard
Katten Muchin Zavis & Rosenman
Northrop Grumman Corporation
Owens Beth E.
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