US6435398B2
Expired / Lapsed
US
⏱️ 0.0 years remaining
Method for chemically reworking metal layers on integrated circuit bond pads
Assignee: Texas Instruments Inc
•
Filing: 2001-05-24
•
Granted: 2002-08-20
•
Expires: 2021-05-24
Abstract
Abstract A method for reworking integrated circuit (IC) wafers having copper-metallized bond pads covered by deposited layers of a barrier metal and a bondable metal. After identifying the wafers with off-spec metal layers, the wafers are chemically etched using selective etchants consecutively until the metal layers over the bond pads are removed without damaging the copper metallization. Replacement metal layers are finally deposited over the bond pads. Specifically, the bondable metal, such as gold, is selectively removed by a cyclic dithio-oxamine compound, dissolved in tetra-hydro-furane or acetone. The barrier metals, such as nickel and palladium, are removed by a mixture of inorganic and organic oxidizing acids.
Inventors
- 👤 Cheryl Hartfield
- 👤 Thomas M. Moore
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-02 13:59
CPC Classifications
H; H10; H10P; H10P74/00; H10P74/23; B; B23; B23K; B23K35/00; B23K35/001; B23K35/007; H10W; H10W72/00; H10W72/01; H10W72/012; H10W72/019; H10W72/20; H10W72/251; H10W72/50; H10W72/551; H10W72/552; H10W72/5522; H10W72/5524; H10W72/5525; H10W72/90; H10W72/921; H10W72/923; H10W72/941; H10W72/9415; H10W72/951; H10W72/952
Claims Analysis
Total Claims: 15
Claim 1
Independent Claim
84 words
A method for reworking integrated circuit wafers having an active surface including copper-metallized bond pads covered by deposited layers of a barrier metal and a bondable metal, comprising the steps of: inspecting said wafers in order to identify those of said wafers which have off-spec metal layers; chemically etching said active surface of said off-spec wafers using selective etchants consecutively until said metal layers over said bond pads are removed without damaging said copper metallization; and depositing replacement metal layers over said bond pads.
Claim 2
Independent Claim
84 words
A method for reworking integrated circuit wafers having an active surface including copper-metallized bond pads covered by deposited layers of a barrier metal and a bondable metal, comprising the steps of: inspecting said wafers in order to identify those of said wafers which have off-spec metal layers; chemically etching said active surface of said off-spec wafers using selective etchants consecutively until said metal layers over said bond pads are removed without damaging said copper metallization; and depositing replacement metal layers over said bond pads.
Claim 3
Dependent Claim
16 words
The method according to claim 1 wherein said metal layers comprise at least one bondable metal.
Claim 4
Dependent Claim
48 words
The method according to claim 1 wherein said metal layers may be a single layer or a stack of two, three or four layers selected from a group consisting of platinum, rhodium, iridium, osmium, palladium, tin, nickel, cobalt, chromium, molybdenum, titanium, tungsten, gold, silver, aluminum and alloys thereof.
Claim 5
Dependent Claim
38 words
The method according to claim 3 wherein said metal layer stack provides at least one layer of barrier metal, overlaying said copper and blocking copper diffusion, and at least one layer of bondable metal, overlaying said barrier layer.
Claim 6
Dependent Claim
13 words
The method according to claim 1 wherein said layer deposition is electroless plating.
Claim 7
Dependent Claim
23 words
The method according to claim 1 wherein said off-spec layers include missing, incomplete, or defective layers, or layers otherwise not meeting specified characteristics.
Claim 8
Dependent Claim
15 words
The method according to claim 6 wherein said specified characteristics include layer thickness and uniformity.
Claim 9
Dependent Claim
25 words
The method according to claim 1 wherein said selective etchants provide a first etchant specific for etching said bondable metal, followed by a rinsing step.
Claim 10
Dependent Claim
26 words
The method according to claim 8 wherein said etchant specific for said bondable metal is based on a cyclic dithio-oxamine compound dissolved in tetra-hydro-furane or acetone.
Claim 11
Dependent Claim
17 words
The method according to claim 9 wherein said compound is epta-methyl-bis-diiodine, or the bis-diiodine adduct of N,N′-dimethylperhydrodiazepine-2,3-dithione.
Claim 12
Dependent Claim
25 words
The method according to claim 1 wherein said selective etchants provide a second etchant specific for etching said barrier metal, followed by a rinsing step.
Claim 13
Dependent Claim
22 words
The method according to claim 11 wherein said etchant specific for said barrier metal is based on oxidizing inorganic and organic acids.
Claim 14
Dependent Claim
30 words
The method according to claim 12 wherein said oxidizing acids are selected from a group consisting of hydrochloric acid, nitric acid, sulfuric acid, phosphoric acid, acetic acid, and hydrogen peroxide.
Claim 15
Dependent Claim
47 words
The method according to claim 1 further comprising the step of inspecting said wafer after said chemical etching step in order to reveal any damage to the surface of said copper metallization and to decide whether an electroless copper deposition step is needed for repairing said damage.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 2005-08-19 | 2006-02-18 | 2006-08-20 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 2009-08-19 | 2010-02-18 | 2010-08-20 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2013-08-19 | 2014-02-18 | 2014-08-20 | $7700.00 | Window Closed / Lapsed |