US5567638A
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Method for suppressing boron penetration in PMOS with nitridized polysilicon gate
Assignee: National Science and Technology Council
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Filing: 1995-06-14
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Granted: 1996-10-22
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Expires: 2015-06-14
Abstract
Abstract A method for suppressing boron penetration in a PMOS with a nitridized polysilicon gate includes steps of 1) growing a layer of gate oxide on a substrate, 2) forming at least one first polysilicon layer on the gate oxide layer, 3) nitridizing the first polysilicon layer, 4) forming a second polysilicon layer on the first polysilicon layer; and 5) implanting B-containing ions into the first and second polysilicon layers for constructing a PMOS structure wherein the nitridizing step suppresses a boron ion from penetration into the substrate. The present invention is characterized in nitridation on a polysilicon gate instead of a gate oxide which can effectively suppress boron penetration, avoid drawbacks resulting from nitridizing a gate oxide, and moreover, improve the reliability of the device owing to the slight nitridation effect in the polysilicon gate and the gate oxide.
Inventors
- 👤 Yung-Hao Lin
- 👤 Chao-Sung Lai
- 👤 Chung-Len Lee
- 👤 Tan-Fu Lei
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-04 08:23
CPC Classifications
H; H10; H10D; H10D64/00; H10D64/60; H10D64/66; H10D64/661; H10D64/01; H10D64/013; H10D64/01302; H10D64/01304; H10D64/01306; H10D64/01308; H10D64/01312; H10D64/662
Claims Analysis
Total Claims: 15
Claim 1
Independent Claim
117 words
A method of suppressing boron penetration in a PMOS with a nitridized polysilicon gate comprising the steps of: 1) growing a layer of gate oxide on a substrate; 2) forming at least one first polysilicon layer on said gate oxide layer; 3) nitridizing said at least one first polysilicon layer; 4) removing a layer of nitridized silicon which is generated by said nitridizing step 3) on said at least one first polysilicon layer; 5) forming a second polysilicon layer on said at least one first polysilicon layer; and 6) implanting B-containing ions into said first and second polysilicon layers for constructing a PMOS structure wherein said nitridizing step suppresses a boron ion from penetration into said substrate.
Claim 2
Independent Claim
117 words
A method of suppressing boron penetration in a PMOS with a nitridized polysilicon gate comprising the steps of: 1) growing a layer of gate oxide on a substrate; 2) forming at least one first polysilicon layer on said gate oxide layer; 3) nitridizing said at least one first polysilicon layer; 4) removing a layer of nitridized silicon which is generated by said nitridizing step 3) on said at least one first polysilicon layer; 5) forming a second polysilicon layer on said at least one first polysilicon layer; and 6) implanting B-containing ions into said first and second polysilicon layers for constructing a PMOS structure wherein said nitridizing step suppresses a boron ion from penetration into said substrate.
Claim 3
Dependent Claim
15 words
A method according to claim 1 wherein said B-containing ions are BF 2 + ions.
Claim 4
Dependent Claim
13 words
A method according to claim 1 wherein said substrate is a Si-based substrate.
Claim 5
Dependent Claim
13 words
A method according to claim 1, wherein said at least one means two.
Claim 6
Dependent Claim
34 words
A method according to claim 4, wherein said Si substrate in said step 1) is an N-type Si substrate in a direction of (1, 0, 0) with a resistivity of 5˜10 Ω/cm 2 .
Claim 7
Dependent Claim
46 words
A method according to claim 5, wherein said gate oxide layer in said step 2) is grown for 80 minutes in a condition that rates of O 2 volume over time and N 2 volume over time are in a ratio of 1:6 at 900° C.
Claim 8
Dependent Claim
20 words
A method according to claim 6, wherein a thickness of said gate oxide layer in said step 2) is 80Å.
Claim 9
Dependent Claim
30 words
A method according to claim 7, wherein said at least one first polysilicon layer is grown to a thickness of 1000Å under 625° C. in a low-pressure CVD (LPCVD) system.
Claim 10
Dependent Claim
18 words
A method according to claim 8, wherein NH 3 is used for said nitridation in said step 3).
Claim 11
Dependent Claim
25 words
A method according to claim 9, wherein step 3) is taken place under a nitridation pressure of 120 mtorr at 900° C. for 80 minutes.
Claim 12
Dependent Claim
30 words
A method according to claim 10, wherein said second polysilicon layer in said step 5) is grown at 625° C. in a LPCVD system and has a thickness of 1000Å.
Claim 13
Dependent Claim
29 words
A method according to claim 11, wherein in said step 6), an ion implantation energy is 50 kev and an ion implanting dosage is 5×10 15 number/cm 2 .
Claim 14
Dependent Claim
56 words
A method according to claim 12, wherein said step 6) is followed by steps of: annealing said substrate in O 2 at 800° C. for 30 minutes to form a polysilicon oxide layer on said second polysilicon layer; and annealing said substrate in N 2 at 900° C. for 10˜40 minutes to activate said boron-containing ions.
Claim 15
Dependent Claim
35 words
A method according to claim 13 further including after annealing said substrate in said N 2 a step of: using diluted HF to remove said polysilicon oxide layer generated in said O 2 -annealing step.
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