Method of forming optical images, mask for use in this method, method of manufacturing a device using this method, and apparatus for carrying out this method
First Claim
Patent Images
1. A method of forming a desired optical image having a give minimum feature size on a selected surface of a layer of material sensitive to optical radiation, the method comprising the steps of:
- providing a source of optical radiation having at least one predetermined wavelength λ
;
providing a layer of material, sensitive to optical radiation having the wavelength λ
, with a selected surface to receive an optical image thereon;
positioning a mask, comprising image information and being at least partly transparent to the source radiation, between the radiation source and the layer of sensitive material, so that source radiation is transmitted through the mask towards the sensitive layer, and illuminating the selected surface with source radiation received by transmission through the mask to produce the desired optical image, characterized in that use is made of a mask in the form of a diffractive element wherein the image information is encoded in a two-dimensional array of image cells having dimensions which are smaller than the minimum feature size, each image cell having one out of at least two specific transmission levels and one out of at least three phase levels.
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Abstract
The resolution achieved with a proximity printing method and apparatus can be increased considerably by using, instead of a photo mask, a diffraction mask (30) wherein the image information is encoded in a two-dimensional array (32) of image cells (37) having dimensions which are smaller than the minimum feature size to be printed, each image cell having one out of at least two amplitude levels and one out of at least three phase levels. The mask may be a multiple focus mask which has multiple focal planes within one image field.
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Citations
17 Claims
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1. A method of forming a desired optical image having a give minimum feature size on a selected surface of a layer of material sensitive to optical radiation, the method comprising the steps of:
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providing a source of optical radiation having at least one predetermined wavelength λ
;
providing a layer of material, sensitive to optical radiation having the wavelength λ
, with a selected surface to receive an optical image thereon;
positioning a mask, comprising image information and being at least partly transparent to the source radiation, between the radiation source and the layer of sensitive material, so that source radiation is transmitted through the mask towards the sensitive layer, and illuminating the selected surface with source radiation received by transmission through the mask to produce the desired optical image, characterized in that use is made of a mask in the form of a diffractive element wherein the image information is encoded in a two-dimensional array of image cells having dimensions which are smaller than the minimum feature size, each image cell having one out of at least two specific transmission levels and one out of at least three phase levels. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17)
a radiation source emitting radiation of at least one predetermined wavelength;
a mask holder for holding a mask which comprises image information and is at least partly transparent to the source radiation, and a substrate holder for holding a substrate provided with a layer of material which is sensitive to the radiation from the source, characterized in that the mask has the form of a diffractive element wherein the image information is encoded in a two-dimensional array of image cells having dimensions which are smaller than the minimum image feature size, each image cell having one out of at least two specific transmission levels and one out of at least three phase levels.
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13. An apparatus as claimed in claim 11, characterized in that source radiation of at least two discrete wavelengths is incident on the plane of the mask.
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14. An apparatus as claimed in claim 11, characterized in that the distance between the image information carrying surface of the mask and the surface of the sensitive layer is of the order of 50 μ
- m.
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15. An apparatus as claimed in claim 11, characterized in that the radiation source emits radiation composed of 40% radiation having a wavelength of 365 nm, 20% radiation having a wavelength of 405 nm and 40% radiation having a wavelength of 436 nm.
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16. A method of manufacturing a device in at least one layer on a substrate, the method comprising the steps of:
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forming an image, comprising features corresponding to device features to be configured in said layer, on a radiation sensitive layer provided on said layer, and removing material from, or adding material to, areas of said layer which are delineated by the image formed in the sensitive layer, characterized in that the image is formed in accordance with the method as claimed in claim 1.
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17. A method as claimed in claim 16, suitable for forming a device in several layers, characterized in that use is made of a mask comprising areas which differ from each other in that their image information is encoded such that, upon illumination of these areas and their surrounding areas with one illumination beam, the sub-images of these areas are formed in planes which differ from the planes wherein the sub-images of the surrounding areas are formed.
Specification