Back to results
US 5,629,113 AGranted
Photomask used by photolithography and a process of producing same
AssigneeMatsushita Electronics Corporation
InventorHisashi Watanabe
Life of this patent
Estimating the term…
Abstract
A photomask used by photolithography and a process for producing same which allows a single exposure to make a photomask, thereby simplifying the photomask making process, and facilitating the inspection and correction of photomasks. In addition, the phase shifter using a slanting pattern prevents a pattern from being formed outside a predetermined area. The use of a phase shifter which does not resolve under an optical projection system shields a large size area against an irradiated light, thereby allowing the formation of fine, intricate patterns suitable for use in LSIs.
Claims4
A photomask comprising:
- a transparent substrate;
- a transparent electroconductive layer formed substantially on the entire surface of the substrate;
- and
- a pattern of a transparent layer,
- wherein the photomask does not include a light shielding layer, and
- wherein the transparent layer has a thickness t defined by the following formula,
- t=(2i-1).lambda./[2(n-1)]
- where t is a thickness of the transparent layer, n is a refractive index of the transparent layer, i is an integer and .lambda. is a wavelength of an incident light to the photomask, thereby
- providing a phase difference of .pi. or .pi. multiplied by an odd number between the light transmitting the transparent substrate and the light transmitting the transparent layer;
- interfering with said two lights to reduce the intensity of the incident light;
- and
- forming resist patterns in the doubled number of that of the transparent layer pattern,
- said resist patterns having a width equal to the resolution limit R defined by the following formula,
- R=K.sub.1 .lambda./NA
- where K.sub.1 is an optical constant of the photomask, .lambda. is a wavelength of incident light and NA is a numerical aperture of the optical system.
12 more elements
Dependencies are inferred from the claim text.