Method of photolithographic exposure dose control as a function of resist sensitivity
AssigneeInternational Business Machines Corporation
InventorsKeith J. Machia, Matthew C. Nicholls, Charles J. Parrish, Craig E. Schneider, Charles A. Whiting
Life of this patent
Estimating the term…
Abstract
A predictive method is used to compensate for intermediate batch sensitivities which inevitably occur during resist batch changeover. The compensation is applied to historical dose levels to arrive at a new dose level estimating an optimum dose. When the system discovers that a new batch of resist is loaded to a tool, historical data is used to calculate a reference dose for each tool. A batch factor is continuously calculated and using historical data along with the batch factor, a dose adjustment is made to maintain proper image size.
Claims11
A system for controlling exposure dose in a lithographic exposure tool for exposing a photoresist material applied to semiconductor wafers, and a reticle develops images in the photoresist material applied to the semiconductor wafers, and wherein the photoresist material is subject to batch changeover and the system operates with successive lot runs, including previous lot runs that were run prior in time and a current lot run that is currently being run, comprising:
- means for adjusting said exposure dose as a function of resist sensitivity changes, further comprising;
- a) means for calculating a batch factor that is an exposure dose ratio of current exposure dose performance to previous exposure dose performance by using historical data, comprising batch factors and optimum exposure doses from at least one previous lot run that was run prior in time to the current lot run;
- b) said means for adjusting said exposure dose comprises means for calculating a value of said exposure dose based on said calculated batch factor whereby said exposure dose in said lithographic exposure tool is controlled.
A computer program product comprising:
- a computer usable medium having computer readable program code embodied therein for controlling exposure dose in a lithographic exposure tool for exposing a photoresist material applied to semiconductor wafers, and a reticle develops images in the photoresist material applied to the semiconductor wafers, and wherein the photoresist material is subject to batch changeover and the system operates with successive lot runs including previous lot runs that were run prior in time and a current lot run that is currently being run, the computer readable program code in said computer program product comprising:
- a) first computer readable program code for causing the computer to calculate a batch factor that is an exposure dose ratio of current exposure dose performance to previous exposure dose performance by using historical data, comprising batch factors and optimum exposure doses from at least one previous lot run that was run prior in time to the current lot run;
- b) second computer readable program code for causing the computer to adjust said exposure dose wherein said adjustment comprises calculating a value of said exposure dose based on said calculated batch factor whereby said exposure dose in said lithographic exposure tool is controlled.
A system for controlling a process parameter value for a material used in a process and having a batch factor which is a ratio of current material performance to previous material performance, and wherein the material is subject to batch changeover, and the system operates with successive lot runs including previous lot runs that were run prior in time and a current lot run that is currently being run, comprising:
- means for adjusting said process parameter value as a function of material performance property changes, further comprising;
- a) means for calculating a batch factor that is a ratio of current material performance to previous material performance by using historical data, comprising batch factors and an optimum of said process parameter value from at least one previous lot run that was run prior in time to the current lot run;
- b) said means for adjusting said process parameter value comprises calculating said process parameter value based on said calculated batch factor whereby said process parameter value is controlled.
Dependencies are inferred from the claim text.