Patent US5384278A successfully refreshed from Google Patents.
US5384278A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Tight control of resistor valves in a SRAM process
Assignee: Frontgrade Colorado Springs LLC
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Filing: 1994-07-07
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Granted: 1995-01-24
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Expires: 2014-07-07
Abstract
Abstract A method of forming a polycrystalline silicon resistor includes the step of forming a resistor region of poly, the region being doped per a desired resistivity of the resistor. The exposed top and side portions of the poly region are completely covered with an insulating oxide. A predetermined portion of the oxide is etched away, resulting in a portion of the oxide completely covering the resistor poly. The resistor poly region and oxide are covered (masked) with photoresist, the mask extending beyond the sides of the poly. The remaining oxide in the area outside of the mask is etched away, and the photoresist is removed.
Inventors
- 👤 Scott G. Singlevich
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-02 20:33
CPC Classifications
H; H10; H10D; H10D1/00; H10D1/40; H10D1/47
Claims Analysis
Total Claims: 22
Claim 1
Independent Claim
125 words
A method of forming a resistor having a resistivity value substantially immune to subsequent processing, said method comprising the steps of: forming a resistor region in a layer of polycrystalline silicon, said resistor region being doped to the resistivity value; forming an insulating oxide layer having a first thickness superjacent said resistor region such that said insulating oxide surrounds said resistor region; and removing an upper portion of said insulating oxide layer such that said first thickness is reduced to a second thickness; and removing a first and a second lateral portion of said insulating oxide layer such that an insulating oxide cap is formed having a top portion and a first and a second side portion, thereby protecting the resistivity value from subsequent processing.
Claim 2
Independent Claim
125 words
A method of forming a resistor having a resistivity value substantially immune to subsequent processing, said method comprising the steps of: forming a resistor region in a layer of polycrystalline silicon, said resistor region being doped to the resistivity value; forming an insulating oxide layer having a first thickness superjacent said resistor region such that said insulating oxide surrounds said resistor region; and removing an upper portion of said insulating oxide layer such that said first thickness is reduced to a second thickness; and removing a first and a second lateral portion of said insulating oxide layer such that an insulating oxide cap is formed having a top portion and a first and a second side portion, thereby protecting the resistivity value from subsequent processing.
Claim 3
Dependent Claim
35 words
The method of claim 1, wherein said step of removing an upper portion of said insulating oxide layer comprises the step of etching away said upper portion of said insulating oxide layer using an etchant.
Claim 4
Dependent Claim
12 words
The method of claim 2, wherein said etchant comprises a plasma etchant.
Claim 5
Dependent Claim
27 words
The method of claim 3, wherein said step of etching away is performed at an ambient temperature substantially within the range of 15° C. and 100° C.
Claim 6
Dependent Claim
21 words
The method of claim 1, wherein said first thickness is approximately 5000 Å and said second thickness is approximately 2000 Å.
Claim 7
Dependent Claim
13 words
The method of claim 1, wherein said insulating oxide layer comprises silicon dioxide.
Claim 8
Dependent Claim
58 words
The method of claim 1, wherein said step of removing a first and a second lateral portion of said insulating oxide layer comprises the steps of: covering said top, first and second side portions of said insulating oxide layer with a mask; removing portions of said insulating oxide layer not covered by said mask; and removing said mask.
Claim 9
Dependent Claim
11 words
The method of claim 7, wherein said mask comprises a photoresist.
Claim 10
Dependent Claim
14 words
The method of claim 9, wherein said mask is sized to reduce alignment sensitivity.
Claim 11
Dependent Claim
15 words
The method of claim 9, wherein said mask comprises an approximate thickness of 1.2 μm.
Claim 12
Dependent Claim
42 words
The method of claim 7, wherein said step of removing portions of said insulating oxide layer not covered by said mask comprises the step of etching away said first and said second lateral portions of said insulating oxide layer using an etchant.
Claim 13
Dependent Claim
11 words
The method of claim 11, wherein said etchant comprises plasma etchant.
Claim 14
Dependent Claim
24 words
The method of claim 12, wherein said step of etching away comprises a selectivity of approximately five parts oxide to one part: polycrystalline silicon.
Claim 15
Independent Claim
207 words
A method of forming a resistor, for use in a static random access memory, having a resistivity value substantially immune to subsequent processing steps, said subsequent processing steps comprising a patterning step and an etching step, said method comprising the steps of: forming a resistor region within a polycrystalline silicon layer, said resistor region being doped to the resistivity value; forming an insulating oxide layer having a first thickness superjacent said resistor region such that said insulating oxide surrounds said resistor region; and etching away an upper portion of said insulating oxide layer using a first etchant such that said first thickness is reduced to a second thickness; and etching away a first and a second lateral portion of said insulating oxide layer such that an insulating oxide cap is formed having a top portion and a first and a second side portion, thereby protecting the resistivity value from subsequent processing, said step of etching away a first and a second lateral portion comprising the steps of: covering said top, first and second side portions of said insulating oxide layer with a photoresist mask; etching away portions of said insulating oxide layer not covered by said photoresist mask using a second etchant; and removing said photoresist mask.
Claim 16
Independent Claim
207 words
A method of forming a resistor, for use in a static random access memory, having a resistivity value substantially immune to subsequent processing steps, said subsequent processing steps comprising a patterning step and an etching step, said method comprising the steps of: forming a resistor region within a polycrystalline silicon layer, said resistor region being doped to the resistivity value; forming an insulating oxide layer having a first thickness superjacent said resistor region such that said insulating oxide surrounds said resistor region; and etching away an upper portion of said insulating oxide layer using a first etchant such that said first thickness is reduced to a second thickness; and etching away a first and a second lateral portion of said insulating oxide layer such that an insulating oxide cap is formed having a top portion and a first and a second side portion, thereby protecting the resistivity value from subsequent processing, said step of etching away a first and a second lateral portion comprising the steps of: covering said top, first and second side portions of said insulating oxide layer with a photoresist mask; etching away portions of said insulating oxide layer not covered by said photoresist mask using a second etchant; and removing said photoresist mask.
Claim 17
Dependent Claim
34 words
The method of claim 14, wherein said step of etching away an upper portion comprises a plasma etching step performed at an ambient temperature substantially within the range of 15° C. and 100° C.
Claim 18
Dependent Claim
21 words
The method of claim 14, wherein said first thickness is approximately 5000 Å and said second thickness is approximately 2000 Å.
Claim 19
Dependent Claim
13 words
The method of claim 14, wherein said insulating oxide layer comprises silicon dioxide.
Claim 20
Dependent Claim
19 words
The method of claim 14, wherein at least one of said first and second etchants comprises a plasma etchant.
Claim 21
Dependent Claim
36 words
The method of claim 14, wherein said step of etching away a first and a second lateral portion of said insulating oxide layer comprises a selectivity of approximately five parts oxide to one part polycrystalline silicon.
Claim 22
Dependent Claim
14 words
The method of claim 14, wherein said mask is sized to reduce alignment sensitivity.
References Cited (Backward Citations)
US4416049A
Cited
US4178674A
Cited
US4277881A
Cited
US4408385A
Cited
JPS5645076A
Cited
WO1982002283A1
Cited
US4397077A
Cited
JPS6278853A
Cited
JPS6444671A
Cited
US4849366A
Cited
US4868135A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1998-01-23 | 1998-07-25 | 1999-01-24 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 2002-01-23 | 2002-07-25 | 2003-01-24 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2006-01-23 | 2006-07-25 | 2007-01-24 | $7700.00 | Window Closed / Lapsed |