Patent US5629235A successfully refreshed from Google Patents.
US5629235A
Expired / Lapsed
US
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Method for forming damage-free buried contact
Assignee: Winbond Electronics Corp
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Filing: 1995-07-05
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Granted: 1997-05-13
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Expires: 2015-07-05
Abstract
Abstract The present invention is related to a method for forming a damage-free buried contact. The method according to the present invention includes steps of a) providing a silicon substrate; b) forming an oxide layer on the silicon substrate; c) forming a first conductive layer on the oxide layer; d) defining a buried contact region on the first conductive layer on the first conductive layer; e) removing a portion of the first conductive layer according to a shape of the buried contact region; f) implanting ions in the buried contact region to form an ion-implantation region under the oxide layer; and f) removing a portion of the oxide layer to obtain the buried contact. The step f) can be executed either before or after the step f). The present invention provides a method for forming a buried contact by which trench will not be occurred on the silicon substrate during the etching process thereof, so that a damage-free buried contact can be obtained.
Inventors
- 👤 Min-Sea Liu
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-09 04:22
CPC Classifications
H; H10; H10D; H10D64/00; H10D64/01; H10D64/011; H10W; H10W20/00; H10W20/01; H10W20/031; H10W20/0698
Claims Analysis
Total Claims: 39
Claim 1
Independent Claim
161 words
A method for forming a damage-free buried contact, comprising the steps of: a) providing a silicon substrate; b) forming an oxide layer on said silicon substrate; c) forming a first conductive layer on said oxide layer; d) defining a buried contact region on said first conductive layer; e) removing a portion of said first conductive layer according to a shape of said buried contact region; f) implanting ions in said buried contact region to form an ion implantation region under said oxide layer; g) removing a portion of said oxide layer to obtain said buried contact; h) forming a second conductive layer on said buried contact and said first conductive layer; i) forming a polysilicon layer on said second conductive layer; j) defining a drain/source reserve region; and k) removing portions of said polysilicon layer and said first and second conductive layers selectively against said silicon substrate according to a shape of said drain/source reserve region to form a source/drain region.
Claim 2
Independent Claim
161 words
A method for forming a damage-free buried contact, comprising the steps of: a) providing a silicon substrate; b) forming an oxide layer on said silicon substrate; c) forming a first conductive layer on said oxide layer; d) defining a buried contact region on said first conductive layer; e) removing a portion of said first conductive layer according to a shape of said buried contact region; f) implanting ions in said buried contact region to form an ion implantation region under said oxide layer; g) removing a portion of said oxide layer to obtain said buried contact; h) forming a second conductive layer on said buried contact and said first conductive layer; i) forming a polysilicon layer on said second conductive layer; j) defining a drain/source reserve region; and k) removing portions of said polysilicon layer and said first and second conductive layers selectively against said silicon substrate according to a shape of said drain/source reserve region to form a source/drain region.
Claim 3
Dependent Claim
16 words
A method according to claim 1 wherein said step f) is executed before said step g).
Claim 4
Dependent Claim
22 words
A method according to claim 2 wherein said ions implanted in said buried contact region in said step f) are phosphoric ions.
Claim 5
Dependent Claim
36 words
A method according to claim 3 wherein an energy for ion implantation is ranged from 30 to 80 KeV and a dosage for ion implantation is ranged from 1×10 15 to 8×10 15 atom/cm 2 .
Claim 6
Dependent Claim
22 words
A method according to claim 2 wherein said ions implanted in said buried contact region in said step f) are arsenic ions.
Claim 7
Dependent Claim
36 words
A method according to claim 5 wherein an energy for ion implantation is ranged from 50 to 100 KeV and a dosage for ion implantation is ranged from 1×10 15 to 7×10 15 atom/cm 2 .
Claim 8
Dependent Claim
16 words
A method according to claim 1 wherein said step g) is executed before said step f).
Claim 9
Dependent Claim
22 words
A method according to claim 7 wherein said ions implanted in said buried contact region in said step f) are phosphoric ions.
Claim 10
Dependent Claim
36 words
A method according to claim 8 wherein an energy for ion implantation is ranged from 5 to 70 KeV and a dosage for ion implantation is ranged from 1×10 15 to 8×10 15 atom/cm 2 .
Claim 11
Dependent Claim
22 words
A method according to claim 7 wherein said ions implanted in said buried contact region in said step f) are arsenic ions.
Claim 12
Dependent Claim
36 words
A method according to claim 10 wherein an energy for ion implantation is ranged from 5 to 80 KeV and a dosage for ion implantation is ranged from 1×10 15 to 7×10 15 atom/cm 2 .
Claim 13
Dependent Claim
14 words
A method according to claim 1 wherein said silicon substrate is a p-type substrate.
Claim 14
Dependent Claim
17 words
A method according to claim 1 wherein said silicon substrate is an n-type substrate with a p-well.
Claim 15
Dependent Claim
15 words
A method according to claim 13 wherein said buried contact region is above said p-well.
Claim 16
Dependent Claim
22 words
A method according to claim 1 wherein said oxide layer is formed by thermal oxidization and a thickness thereof is about 70˜180Å.
Claim 17
Dependent Claim
24 words
A method according to claim 1 wherein said oxide layer is formed by chemical vapor deposition (CVD) and a thickness thereof is about 70˜180Å.
Claim 18
Dependent Claim
28 words
A method according to claim 1 wherein said first conductive layer is formed by a technique selected from the group consisting of sputtering deposition and chemical vapor deposition.
Claim 19
Dependent Claim
32 words
A method according to claim 1 wherein said step d) is executed by a photolithography technique which forms a photoresist mask on said first conductive layer to define said buried contact region.
Claim 20
Dependent Claim
17 words
A method according to claim 18 wherein a thickness of said photoresist mask is ranged from 7000Ř20000Å.
Claim 21
Dependent Claim
52 words
A method according to claim 19 further comprising a step h) of removing said photoresist layer by a technique selected from the group consisting of oxygen plasma etching, H 2 SO 4 and H 2 O 2 erosion, phenol-based agent stripping, and phenol-free organic agent stripping after said buried contact is obtained.
Claim 22
Dependent Claim
17 words
A method according to claim 1 wherein said step e) is executed by an anisotropic plasma-etching technique.
Claim 23
Dependent Claim
23 words
A method according to claim 21 wherein said first conductive layer is a titanium nitride layer and a thickness thereof is about 500˜1000Å.
Claim 24
Dependent Claim
24 words
A method according to claim 22 wherein an etching gas used in said step e) is a mixture of Ar and Cl 2 .
Claim 25
Dependent Claim
23 words
A method according to claim 21 wherein said first conductive layer is a titanium tungsten layer and a thickness thereof is about 500˜1000Å.
Claim 26
Dependent Claim
40 words
A method according to claim 24 wherein an etching gas used in said step e) is one selected from the group consisting of a mixture of SF 6 and Ar and a mixture of SF 6 and N 2 .
Claim 27
Dependent Claim
32 words
A method according to claim 1 further comprising after said step f) a step of performing thermal cycle annealing at a temperature equal to or greater than 800° C. at least once.
Claim 28
Dependent Claim
17 words
A method according to claim 1 wherein said step g) is executed by an anisotropic plasma-etching technique.
Claim 29
Dependent Claim
52 words
A method according to claim 23 wherein said etching gas used in said step g) is one selected from the group consisting of CCl 2 F 2 , a mixture of CHF 3 and CF 4 , a mixture of CHF 3 and O 2 , and CH 3 CHF 2 .
Claim 30
Dependent Claim
36 words
A method according to claim 1 wherein said step g) is executed by applying thereto a solution selected from the group consisting of a HF aqueous solution and an aqueous mixture of HF and buffering agent.
Claim 31
Dependent Claim
14 words
A method according to claim 29 wherein said buffering agent is NH 4 F.
Claim 32
Dependent Claim
27 words
A method according to claim 1 wherein said step i) is executed by a technique selected from the group consisting of sputtering deposition and chemical vapor deposition.
Claim 33
Dependent Claim
34 words
A method according to claim 1 wherein said second conductive layer is one selected from the group consisting of a titanium nitride layer and titanium tungsten layer, and a thickness thereof is about 5-1500Å.
Claim 34
Dependent Claim
26 words
A method according to claim 1 wherein said polysilicon layer is formed by a CVD technique at 600°-700° C., and a thickness thereof is about 1500-4000Å.
Claim 35
Dependent Claim
30 words
A method according to claim 1 further comprising after said step j) a diffusion step of POCl 3 gas at 800°-1100° C. to reduce a resistance of said polysilicon layer.
Claim 36
Dependent Claim
16 words
A method according to claim 1 wherein said step k) is executed by a photolithography technique.
Claim 37
Dependent Claim
111 words
A method according to claim 1 wherein said step l) further includes the steps of: m) using a first etching gas having a relatively high etching rate to said polysilicon layer and a relatively low etching rate to said second conductive layer to anisotropically etch off said portion in said polysilicon layer of said drain/source reserve region; and n) using a second etching gas having a relatively high etching rate to said first and said second conductive layers and a relatively low etching rate to said oxide layer and said silicon substrate to anisotropically etch off said portions of said first and said second conductive layers in said drain/source reserve region.
Claim 38
Dependent Claim
83 words
A method according to claim 36 wherein said first etching gas is one selected from the group consisting of a mixture of SiCl 3 and Cl 2 , a mixture of BCl 3 and Cl 2 , a mixture of HBr, Cl 2 and O 2 , a mixture of HBr and O 2 , a mixture of Br 2 and O 2 , a mixture of Br 2 and SF 6 and a mixture of SF 6 and 25% O 2 .
Claim 39
Dependent Claim
72 words
A method according to claim 36 wherein said second etching gas is a mixture of Ar and Cl 2 when said first and said second conductive layers are titanium nitride layers, and said second etching gas is one selected from the group consisting of a mixture of SF 6 and Ar and a mixture of SF 6 and N 2 when said first and said second conductive layers are titanium tungsten layers.
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| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
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| 3.5 Years (Year 4) | 2000-05-12 | 2000-11-11 | 2001-05-13 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 2004-05-12 | 2004-11-11 | 2005-05-13 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2008-05-12 | 2008-11-11 | 2009-05-13 | $7700.00 | Window Closed / Lapsed |