Multiple thickness of gate oxide
First Claim
1. A method of forming an integrated circuit having a first, second and third set of active areas comprising the steps of:
- preparing a silicon substrate;
oxidizing said silicon substrate to form a first oxide having a first thickness;
depositing a first blocking mask to leave said first set of active areas exposed;
implanting said first set of active areas with a dose of growth-altering ions, whereby the thermal oxide growth rate in said first set of active areas is altered;
stripping said first blocking mask;
forming a second blocking mask to leave said first set of active areas and said second set of active areas exposed;
stripping said first oxide in said first and second set of active areas;
stripping said second blocking mask;
oxidizing said substrate in a second oxidation step such that a standard oxide thickness is formed in said second set of active areas, whereby a first oxide thickness different from said standard oxide thickness is formed in said first set of active areas, and a third oxide thickness of greater than said standard oxide thickness is formed in said third set of active areas.
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Abstract
A method of forming an integrated circuit having four thicknesses of gate oxide in four sets of active areas by: oxidizing the silicon substrate to form an initial oxide having a thickness appropriate for a desired threshold voltage transistor; depositing a blocking mask to leave a first and fourth set of active areas exposed; implanting the first and fourth set of active areas with a dose of growth-altering ions, thereby making the first set of active areas more or less resistant to oxidation and simultaneously making the fourth set of active areas susceptible to accelerated oxidation; stripping the blocking mask; forming a second blocking mask to leave the first and second sets of active areas exposed; stripping the initial oxide in exposed active areas; stripping the second blocking mask; surface cleaning the wafer; and oxidizing the substrate in a second oxidation step such that a standard oxide thickness is formed in the second set of active areas, whereby an oxide thickness of more or less than the standard oxide thickness is formed in the first set of active areas, an oxide thickness of greater than the standard oxide thickness is formed in the third set of active areas, and a fourth oxide thickness greater than the third oxide thickness is formed in the fourth set of active areas.
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Citations
30 Claims
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1. A method of forming an integrated circuit having a first, second and third set of active areas comprising the steps of:
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preparing a silicon substrate;
oxidizing said silicon substrate to form a first oxide having a first thickness;
depositing a first blocking mask to leave said first set of active areas exposed;
implanting said first set of active areas with a dose of growth-altering ions, whereby the thermal oxide growth rate in said first set of active areas is altered;
stripping said first blocking mask;
forming a second blocking mask to leave said first set of active areas and said second set of active areas exposed;
stripping said first oxide in said first and second set of active areas;
stripping said second blocking mask;
oxidizing said substrate in a second oxidation step such that a standard oxide thickness is formed in said second set of active areas, whereby a first oxide thickness different from said standard oxide thickness is formed in said first set of active areas, and a third oxide thickness of greater than said standard oxide thickness is formed in said third set of active areas. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15)
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16. A method of forming an integrated circuit having first, second, third and fourth sets of active areas comprising the steps of:
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preparing a silicon substrate;
oxidizing said silicon substrate to form a first oxide having a first thickness;
depositing a first blocking mask to leave said first and said fourth sets of active areas exposed;
implanting said first and fourth sets of active areas with a dose of growth-altering ions, whereby said first and fourth sets of active areas have altered oxide growth rates;
stripping said first blocking mask;
forming a second blocking mask to leave said first set of active areas and said second set of active areas exposed;
stripping said first oxide in said first and second set of active areas;
stripping said second blocking mask;
oxidizing said substrate in a second oxidation step such that a standard oxide thickness is formed in said second set of active areas, whereby a different oxide thickness different from said standard oxide thickness is formed in said first set of active areas, an oxide thickness of greater than said standard oxide thickness is formed in said third set of active areas and an oxide thickness of greater than said third oxide thickness is formed in said fourth set of active areas. - View Dependent Claims (17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30)
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Specification