US4702941A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Gold metallization process
Assignee: NXP USA Inc
•
Filing: 1984-03-27
•
Granted: 1987-10-27
•
Expires: 2004-03-27
Abstract
Abstract A one step metallization is disclosed for applying a layer of gold or gold alloy to the back of a silicon substrate to facilitate bonding that substrate to a metallized package member. The gold is applied to the substrate, for example by evaporation, while the substrate is maintained at a temperature between about 200° C. and about 360° C. Following the deposition the substrate is quickly cooled to room temperature. The thickness of the gold layer and the deposition temperature are adjusted to insure that the silicon diffusion profile is contained within the gold film during deposition. This insures good adhesion of the gold to the silicon substrate and provides a pure gold surface layer necessary for optimum bonding of the semiconductor substrate to a metallized package portion.
Inventors
- 👤 Curtis W. Mitchell
- 👤 Barry C. Johnson
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-02 04:59
CPC Classifications
C; C23; C23C; C23C14/00; C23C14/06; C23C14/14; C23C14/16; B; B23; B23K; B23K20/00; B23K20/22; B23K20/233; B23K35/00; B23K35/001; C23C14/58; C23C14/5806; C23C14/5893; C23C26/00; B23K2035/008; H; H10; H10W; H10W72/00; H10W72/071; H10W72/073; H10W72/07331; H10W72/07336; H10W72/30; H10W72/351; H10W72/352; H10W72/353; H10W72/354; H10W90/00; H10W90/701; H10W90/731; H10W90/736
Claims Analysis
Total Claims: 17
Claim 1
Independent Claim
96 words
A one step method for applying a layer of metal comprising gold to a silicon substrate surface which comprises the steps of: cleaning said surface; heating said substrate to a first temperature of between about 200° C. and about 360° C. in a reduced pressure ambient; evaporating said metal at a reduced pressure onto said surface at said first temperature, allowing silicon to diffuse into but not through said metal; and cooling said substrate to a second temperature lower than said first temperature to limit the continued diffusion of silicon into but not through said metal.
Claim 2
Dependent Claim
96 words
A one step method for applying a layer of metal comprising gold to a silicon substrate surface which comprises the steps of: cleaning said surface; heating said substrate to a first temperature of between about 200° C. and about 360° C. in a reduced pressure ambient; evaporating said metal at a reduced pressure onto said surface at said first temperature, allowing silicon to diffuse into but not through said metal; and cooling said substrate to a second temperature lower than said first temperature to limit the continued diffusion of silicon into but not through said metal.
Claim 3
Dependent Claim
11 words
The method of claim 1 wherein said metal comprises pure gold.
Claim 4
Dependent Claim
17 words
The method of claim 1 wherein said metal comprises gold admixed with small amounts of other materials.
Claim 5
Dependent Claim
12 words
The method of claim 1 wherein said second temperature is room temperature.
Claim 6
Dependent Claim
16 words
The method of claim 1 wherein said step of cooling comprises venting said vacuum with nitrogen.
Claim 7
Dependent Claim
17 words
The method of claim 5 wherein said pure nitrogen is obtained from boiling a liquid nitrogen source.
Claim 8
Dependent Claim
16 words
The method of claim 1 wherein said step of cooling comprises venting said vacuum with air.
Claim 9
Dependent Claim
99 words
An improved method for attaching a silicon die to a metallic package substrate wherein the improvement comprises the steps of: applying a single layer of gold metallization to a surface of said die by evaporation at a reduced pressure while heating said die to a temperature of 200°-360° C.; and rapidly cooling said die to about room temperature to limit the diffusion of silicon from said silicon die into said gold, allowing silicon to diffuse into but not through said gold; and eutectic bonding said die to said substrate using said single layer of gold metallization as a solder.
Claim 10
Dependent Claim
99 words
An improved method for attaching a silicon die to a metallic package substrate wherein the improvement comprises the steps of: applying a single layer of gold metallization to a surface of said die by evaporation at a reduced pressure while heating said die to a temperature of 200°-360° C.; and rapidly cooling said die to about room temperature to limit the diffusion of silicon from said silicon die into said gold, allowing silicon to diffuse into but not through said gold; and eutectic bonding said die to said substrate using said single layer of gold metallization as a solder.
Claim 11
Independent Claim
76 words
A method for applying a layer of gold metallization to a silicon substrate which comprises the steps of: evaporating gold onto an unheated silicon substrate, said substrate maintained in a reduced pressure during said evaporating; subsequently heating said substrate to a temperature between about 200° C. and about 360° C. to diffuse silicon into but not through said gold; and rapidly cooling said substrate to limit diffusion of said silicon into but not through said gold.
Claim 12
Independent Claim
76 words
A method for applying a layer of gold metallization to a silicon substrate which comprises the steps of: evaporating gold onto an unheated silicon substrate, said substrate maintained in a reduced pressure during said evaporating; subsequently heating said substrate to a temperature between about 200° C. and about 360° C. to diffuse silicon into but not through said gold; and rapidly cooling said substrate to limit diffusion of said silicon into but not through said gold.
Claim 13
Dependent Claim
18 words
The method of claim 9 wherein said substrate is heated to about 300° C. for about 10 minutes.
Claim 14
Independent Claim
55 words
A method for applying a layer of gold metallization to a silicon substrate which comprises the steps of: sputtering gold onto an unheated silicon substrate; subsequently heating said substrate to a temperature between about 200° C. and about 360° C.; and cooling said substrate to limit diffusion of silicon into but not through said gold.
Claim 15
Independent Claim
55 words
A method for applying a layer of gold metallization to a silicon substrate which comprises the steps of: sputtering gold onto an unheated silicon substrate; subsequently heating said substrate to a temperature between about 200° C. and about 360° C.; and cooling said substrate to limit diffusion of silicon into but not through said gold.
Claim 16
Dependent Claim
84 words
A one step method for applying a layer of metal comprising gold to a silicon substrate surface which comprises the steps of: cleaning said surface; heating said substrate to a first temperature of between about 200° C. and about 360° C. in a reduced pressure ambient; sputtering said metal onto said surface at said first temperature; and cooling said substrate to a second temperature lower than said first temperature to limit diffusion of silicon from said silicon substrate into but not through said metal.
Claim 17
Dependent Claim
84 words
A one step method for applying a layer of metal comprising gold to a silicon substrate surface which comprises the steps of: cleaning said surface; heating said substrate to a first temperature of between about 200° C. and about 360° C. in a reduced pressure ambient; sputtering said metal onto said surface at said first temperature; and cooling said substrate to a second temperature lower than said first temperature to limit diffusion of silicon from said silicon substrate into but not through said metal.
References Cited (Backward Citations)
US3028663A
Cited
US3063867A
Cited
US3158504A
Cited
US3393091A
Cited
US3440113A
Cited
US3729807A
Cited
US3775157A
Cited
US3969545A
Cited
US4065588A
Cited
US4309460A
Cited
JPS5517104A
Cited
JPS56103432A
Cited
US4408561A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1990-10-26 | 1991-04-27 | 1991-10-27 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1994-10-26 | 1995-04-27 | 1995-10-27 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1998-10-26 | 1999-04-27 | 1999-10-27 | $7700.00 | Window Closed / Lapsed |