Methods for removing catalyst particles from nanotube films
Methods for removing a catalyst particle from a nanotube film used in a photolithographic patterning process are disclosed. The catalyst particle is identified based on its size in the nanotube film. This identification can be done using an inspection device such as a confocal microscope, which permits comparison of images taken in two or more separate focal planes to determine the size of particles. The catalyst particle is then exposed to a first absorption wavelength using a laser, which is selectively absorbed by the catalyst particle and which heats the catalyst particle to remove the catalyst particle from the nanotube film. Optionally, the catalyst particle-free nanotube film can be further exposed to a second absorption wavelength which is selectively absorbed by the film and promotes repair of the film. The resulting nanotube film can be used in a pellicle membrane.
1 . A method for patterning a circuit layout, comprising:
inspecting a pellicle membrane and identifying catalyst particles in a nanotube film of the pellicle membrane;
selectively exposing the catalyst particles in the pellicle membrane to a first absorption wavelength to remove the catalyst particles from the nanotube film;
selectively exposing areas around the removed catalyst particles to a second absorption wavelength that is different from the first absorption wavelength and which is selectively absorbed by the nanotube film and promotes repair of the nanotube film;
reflecting an exposure wavelength off a reticle and through the pellicle membrane onto a photosensitive material layer on a substrate;
developing the photosensitive material layer to form a patterned layer; and
forming the circuit layout by etching;
wherein the catalyst particles are identified by:
generating a first image in a first focal plane in a plane of the nanotube film using an inspection device;
generating a second image in a second focal plane away from the plane of the nanotube film using the inspection device;
processing the first image and the second image to identify the catalyst particle based on its presence in a given location in the first image and its absence from the given location in the second image.
2 . The method of claim 1 , wherein the difference between the first focal plane and the second focal plane is at least 0.5 micrometers.
3 . The method of claim 1 , wherein the inspection device is a confocal microscope.
4 . The method of claim 1 , wherein the second focal plane is above or below the plane of the nanotube film.
5 . The method of claim 1 , wherein the catalyst particles have an average particle size of at most 100 nanometers.
6 . The method of claim 1 , wherein the nanotube film is formed from carbon nanotubes, boron nitride nanotubes, silicon carbide nanotubes, molybdenum disulfide nanotubes, molybdenum diselenide nanotubes, tungsten disulfide nanotubes, or tungsten diselenide nanotubes.
7 . The method of claim 1 , wherein the first absorption wavelength is from about 300 nm to about 700 nm.
8 . The method of claim 1 , wherein a laser is used to expose the catalyst particles to the first absorption wavelength.
9 . The method of claim 1 , wherein the second absorption wavelength is from about 200 nm to about 300 nm.
10 . A method for preparing a pellicle assembly from a nanotube film for use in a photolithographic patterning process, comprising:
reducing a thickness of the nanotube film;
identifying locations of catalyst particles in the nanotube film;
selectively exposing the catalyst particles in the nanotube film to a first absorption wavelength to heat the catalyst particles to remove the catalyst particles from the nanotube film;
selectively exposing areas of the nanotube film around the removed catalyst particles to a second absorption wavelength that is different from the first absorption wavelength and which is selectively absorbed by the nanotube film and promotes repair of the nanotube film;
forming a pellicle membrane comprising the nanotube film; and
affixing the pellicle membrane to a mounting frame to obtain the pellicle assembly.
11 . The method of claim 10 , wherein the first absorption wavelength is from about 300 nm to about 700 nm.
12 . The method of claim 10 , further comprising removing contaminant particles from the nanotube film.
13 . The method of claim 10 , wherein a conformal coating is applied to at least an outer surface of the pellicle membrane.
14 . The method of claim 10 , wherein the second absorption wavelength is from about 200 nm to about 300 nm.
15 . The method of claim 10 , wherein the nanotube film is formed from carbon nanotubes, boron nitride nanotubes, silicon carbide nanotubes, molybdenum disulfide nanotubes, molybdenum diselenide nanotubes, tungsten disulfide nanotubes, or tungsten diselenide nanotubes.
16 . A method for patterning a circuit layout, comprising:
inspecting a pellicle membrane to produce an inspection map;
comparing the inspection map to an original map of the pellicle membrane to identify locations of catalyst particles in a nanotube film in the pellicle membrane;
selectively exposing the catalyst particles in the pellicle membrane to a first absorption wavelength to remove the catalyst particles from the nanotube film;
selectively exposing areas of the pellicle membrane around the removed catalyst particles to a second absorption wavelength that is different from the first absorption wavelength to promote repair of the nanotube film and obtain a repaired pellicle membrane; and
patterning a circuit layout using a reticle with the repaired pellicle membrane.
17 . The method of claim 16 , wherein the nanotube film is formed from nanotubes comprising carbon, boron nitride, silicon carbide, molybdenum disulfide, molybdenum diselenide, tungsten disulfide, or tungsten diselenide.
18 . The method of claim 16 , wherein the second absorption wavelength is from about 200 nm to about 300 nm.
19 . The method of claim 16 , wherein the first absorption wavelength is from about 300 nm to about 700 nm.
20 . The method of claim 16 , wherein a laser is used to expose the catalyst particles to the first absorption wavelength.