Contactless electrical thin oxide measurements
First Claim
1. In a method for measuring the thickness of an insulating layer on a semiconductor substrate, the steps comprising:
- repetitively depositing a fixed charge density on the surface of said layer,measuring the resultant changes in the surface potential of said layer relative to the bulk of said substrate,establishing a theoretical bandbending versus bias characteristic for said layer and substrate, undergoing said repetitive deposition of charge density, for an assumed value of said thickness,determining an experimental bandbending versus bias characteristic using said measured change in the insulating layer surface potential for each said deposited charge, and said assumed value of thickness,comparing said theoretical and said experimental characteristics to ascertain any difference in the accumulation region of said characteristics, anditeratively incrementing said assumed value while using said measured changes in said surface potential to determine corresponding experimental bandbending versus bias characteristics andcomparing each said corresponding characteristic with said theoretical characteristic until one of said corresponding characteristics matches said theoretical characteristic in the substrate accumulation region of said characteristics.
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Abstract
A method for measuring the thickness of very thin oxide layers on a silicon substrate. A corona discharge source repetitively deposits a calibrated fixed charge density on the surface of the oxide. The resultant change in oxide surface potential for each charge deposition is measured. By choosing a starting value for an assumed oxide thickness, the approximate change in silicon bandbending per corona discharge step is determined. The cumulative changes in bandbending versus oxide surface potential yields an experimental bandbending versus bias characteristic. A theoretical bandbending versus bias characteristic is established. The experimental and theoretical characteristics are matched at predetermined points thereof and then the assumed oxide thickness is iterated until both characteristics superimpose in the silicon accumulation region. The iterated oxide thickness that allows both characteristics to superimpose is the oxide thickness value being sought. The finally evolved experimental characteristic also is used to determine the interface states density of the oxide. Specially designed corona discharge guns are described for use with the oxide thickness and interface states density measurement techniques.
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Citations
9 Claims
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1. In a method for measuring the thickness of an insulating layer on a semiconductor substrate, the steps comprising:
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repetitively depositing a fixed charge density on the surface of said layer, measuring the resultant changes in the surface potential of said layer relative to the bulk of said substrate, establishing a theoretical bandbending versus bias characteristic for said layer and substrate, undergoing said repetitive deposition of charge density, for an assumed value of said thickness, determining an experimental bandbending versus bias characteristic using said measured change in the insulating layer surface potential for each said deposited charge, and said assumed value of thickness, comparing said theoretical and said experimental characteristics to ascertain any difference in the accumulation region of said characteristics, and iteratively incrementing said assumed value while using said measured changes in said surface potential to determine corresponding experimental bandbending versus bias characteristics and comparing each said corresponding characteristic with said theoretical characteristic until one of said corresponding characteristics matches said theoretical characteristic in the substrate accumulation region of said characteristics. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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Specification