Back to results
US 5,851,702 AGranted
Method for producing a photomask
AssigneeSharp Kabushiki Kaisha
InventorsKunio Watanabe, Shinji Kobayashi, Masashi Inoue
Life of this patent
Estimating the term…
Loading patent…
Loading patent…
AssigneeSharp Kabushiki Kaisha
InventorsKunio Watanabe, Shinji Kobayashi, Masashi Inoue
Estimating the term…
A method for producing a photomask of the present invention includes the steps of: forming a light-blocking film on a surface of a transparent substrate; forming a resist film for an EB on the light-blocking film; patterning the resist film by EB writing and development; and selectively etching the light-blocking film using the patterned resist film to form a photomask, wherein the light-blocking film has a thickness in the range of about 60 nm to about 70 nm.
A method for producing a photomask, comprising the steps of:
Dependencies are inferred from the claim text.
Drawings are temporarily unavailable. Open the PDF at USPTO
Originals for photomechanical production of textured or patterned surfaces, e.g., masks, photo-masks, reticles; Mask blanks or pellicles…
Originals for photomechanical production of textured or patterned surfaces, e.g., masks, photo-masks, reticles; Mask blanks or pellicles…
Photomechanical production of textured or patterned surfaces
Term ended 10 Jun 2017 (estimated)
USPTO file history isn’t available for this patent, so only indexed dates are shown.
1. Field of the Invention
The present invention relates to a method for producing a photomask.
2. Description of the Related Art
FIG. 1 is a graph showing a correlation between the thickness of a chromium film and the transmittance at each light exposure wavelength.
FIG. 2 is a graph showing characteristics of a light exposure amount and a critical dimension (CD) shift amount with varying thickness of a resist film.
FIG. 3 is a graph showing a relationship between the sensitivity and the thickness of a resist film in which EB exposure amounts at a CD shift amount of zero in FIG. 2 are plotted.
Hereinafter, a method for producing a photomask according to the present invention will be described by way of an illustrative embodiment with reference to the drawings. More specifically, a method for producing a photomask will be described, which includes the steps of patterning a resist film on a light-blocking film formed on the surface of a substrate; and etching the light-blocking film using the patterned resist film as a mask to form a photomask.
According to the present invention, the decrease in thickness of the resist film caused by dry etching is minimized by making a light-blocking film as thin as possible so as to shorten a dry etching time. FIG. 1 shows a relationship between the thickness of a chromium film as a light-blocking film and the transmittance at each light exposure wavelength of a KrF excimer laser, i-line and g-line.
As shown in FIG. 1, the thickness of a chromium film which can be used becomes smallest in the case of using a KrF excimer laser for EB writing at constant transmittance. That is, the use of a beam with a shorter wavelength allows the thickness of a chromium film which can be used to be smaller. In the case where the transmittance which is a required property of the light-blocking film is set to be 0.5% or lower (which does not cause rapid optical changes), and a KrF excimer laser is used, a thin chromium film having a thickness of about 60 nm can be used.