Photolithographic dose determination by diffraction of latent image grating
AssigneeInternational Business Machines Corporation
InventorChi-Min Yuan
Life of this patent
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Abstract
A method of determining quantitatively the exposure levels for photoresists in semiconductor photolithography employs a specially designed grating pattern on a mask. The mask is first used to expose a series of LIM image gratings of different dosages. Then a normal plane wave at a longer wavelength is incident on these gratings one by one, and some nonzero order diffraction efficiency of the grating is measured to determine quantitatively the correct dosage to be used. This method can make a determination of exposure dosage, without knowledge of underlying film thickness and refractive index, and handle either resist thickness change or underlying film thickness/refractive index change or both.
Claims4
A method of determining the optimal exposure dosage required for semiconductor photolithography comprising the steps of;
- providing a photoresist to be bleached;
- constructing mask consisting of transparent and semitransparent regions, said semitransparent regions being made up of multiple opaque lines;
- placing said mask over the photoresist;
- exposing said photoresist to light through said mask;
- measuring the exposure of said photoresist to energy until said photoresist is fully bleached;
- and
- calculating an optimal exposure dosage required from measurements of exposure of said photoresist.
A method of exposing product chips to optimal exposure dosage of light comprising the steps of:
- providing a photoresist to be bleached;
- constructing a mask consisting of transparent and semitransparent regions, said semitransparent regions being made up of multiple opaque lines;
- placing said mask over the photoresist;
- exposing said photoresist to light through said mask;
- measuring the exposure of said photoresist to energy until said photoresist is fully bleached;
- calculating an optimal exposure dosage required from measurements of exposure of said photoresist;
- and
- exposing product chips to said optimal exposure dosage.
Dependencies are inferred from the claim text.