JPS6156317B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a method for accurately manufacturing metal foil having minute openings.

[Conventional technology]

In the electronics field, metal foils with precise openings are used, for example, in the field mesh of image pickup tubes and the apertures of lasers, but these are usually made by the FET electroforming method. There is.

The thickness of the metal foil is several μm as it is necessary to have strength.
A thickness of about 20 μm is used. In the general photoelectroforming method, as shown in FIG.
After that, a metal foil 3 is formed by electroforming,
This metal foil is peeled off from the substrate and used.

The thickness of the photoresist is approximately 0.5 μm to 3 μm depending on the dimensional accuracy of the image, the shape of the edges, etc.
The metal foil needs to have a thickness of 3 .mu.m or more in terms of strength, and as shown in FIG. 1C, the electroformed metal has a raised shape on the photoresist. Therefore, the dimensions of the opening are smaller than the dimensions of the photoresist image. This has been used to create pinholes with a very small diameter (about 1μ), but the cross-sectional shape of the opening becomes complex as shown in Figure 1C, and the dimensions can be precisely controlled. Further, it was completely impossible to form a minute rectangular opening of about 3 to 5 μm. Another method is to apply a thick layer of photoresist to about 3 to 5 μm so that it does not build up on top of the photoresist during electroforming, but in this case, the image accuracy of the photoresist deteriorates and openings of about 1 μm are formed. become unable to do so.

Generally, when a mask pattern is transferred to a photoresist by contact baking, if the pattern size is 1 μm or less, it will be close to the wavelength of the ultraviolet light used for baking (around 0.4 μm).
Diffraction phenomena cause blurring or deformation of images. This phenomenon becomes more noticeable as the distance between the patterned surface of the mask and the photoresist increases. Accuracy will decrease. Furthermore, since the transmittance of ultraviolet rays in the photoresist is low, the amount of exposure differs greatly between near the surface and the deep part of the photoresist, which causes a reduction in image accuracy. Furthermore, when a photoresist is applied to the surface of a conductive metal and exposed to light as in the photoelectroforming method, phenomena such as halation due to ultraviolet rays reflected back from the metal surface and standing waves due to interference between incident light and reflected light occur. This is known to cause step-like wrinkles at the edges of photoresist images, reducing shape and dimensional accuracy. For the above reasons, it is extremely difficult to transfer a pattern with dimensions of 1 μm or less onto a photoresist with a thickness of about 3 to 5 μm.

There is also a method of applying a sufficiently thin layer of photoresist to increase the precision of the image and plating it thinly, but thin foils are easily destroyed and difficult to manufacture.

[Problem that the invention seeks to solve]

Therefore, the problem to be solved by the present invention is to have sufficient thickness for self-supporting and one
It is an object of the present invention to provide a method for manufacturing a metal foil having a highly accurate opening used for a field mesh of an image pickup tube, a laser aperture, etc. having a size of approximately μ or less.

[Means for solving problems]

The inventors of the present invention conducted research to solve the above problems. After forming a polymethyl methacrylate resin layer on a substrate that is sensitive to electromagnetic waves with a wavelength of 3000 Å or less, such as far ultraviolet rays, a pattern is printed using the electromagnetic waves. Then, by carrying out a development process, even if the resin layer is formed to have a thickness of several μm to about 10 μm, a resin image having precisely formed almost vertical edges can be obtained even if the resin layer extends deep in the thickness direction. The present invention was completed based on this knowledge.

The manufacturing method of the present invention involves forming on a substrate a polymethyl methacrylate resin layer with a thickness of several μm to 10 μm that is sensitive to electromagnetic waves with a wavelength of 3000 Å or less, such as deep ultraviolet rays, and then printing a pattern using the electromagnetic waves. Next, a resin image is formed by a development process, and then a resin image is placed on the substrate exposed by the patterning, and the layer has a thickness equal to or less than the thickness of the patterned resin layer and has sufficient strength to self-hold. The method comprises growing a metal layer, then removing the resin image, and then peeling the metal layer from the substrate or removing at least a portion of the substrate by etching.

Recently, as a microfabrication technology for ultra-LSIs, magnetic valve elements, etc., lithography technology is being developed that uses electron beams, soft X-rays, and other irradiation sources and uses high-precision masks. Attempts have been made to make the projection mask used for this from a metal foil having openings, blocking portions, and supporting meshes with dimensions of approximately 1 μm or less, but conventional photoelectrophotography Production is difficult using the mining method, but production is possible using the method of the present invention.

The method according to the invention will be explained below using the drawings. In FIG. 2, a conductive substrate 4 is first coated with a polymethyl methacrylate resin that is sensitive to electromagnetic waves such as deep ultraviolet rays having a wavelength of 3000 Å or less, which is dissolved in a suitable solvent. The thickness of the resin layer varies from several μm to 10 μm depending on the thickness of the metal foil required.
degree. Next, a pattern is printed using electromagnetic waves such as deep ultraviolet rays with a wavelength of 3000 Å or less, and then developed with a suitable poor solvent such as methyl isobutyl ketone, xylene, isoamyl acetate, etc.
Expose the surface of the substrate in the exposed area. The obtained resin image 5 has sharp edges, has a size of 1 μm or less, and has high precision and high resolution. Next, a metal foil layer 6 having a thickness equal to or less than the thickness of the resin image is formed by a plating method or the like. Thereafter, the resin image is dissolved and removed using a suitable good solvent such as ethyl acetate, toluene, trichloroethylene, etc., and then peeled off from the substrate to obtain a metal foil (FIG. 2C). The opening of the obtained metal foil is
The dimensional accuracy is good even for minute patterns whose dimensions are within the thickness, and the cross-sectional shape of the edge has a sharp opening shape close to vertical. In order to use the metal foil obtained in this way, for example as a mask, it is adhered to a support frame using a suitable adhesive.

FIG. 3 shows another method according to the present invention, in which the sputtering method is used to form the metal foil 9, and the metal 9a attached to the resin image 8 in the opening is removed from the resin image 8. It is removed at the same time when it is dissolved and removed (Fig. 3C). The required portions of the metal foil can then be etched away from the substrate, and the remaining substrate can be used as a support frame (FIG. 3d).

[Effect]

By using the method of transferring the pattern on the mask using electromagnetic waves to a polymethyl methacrylate resin that is sensitive to electromagnetic waves with a wavelength of 3000 Å or less, such as far ultraviolet rays, blurring and deformation of the image due to diffraction phenomenon is reduced, and sharpness is reduced. A resist image with edges can be formed. Polymethyl methacrylate resin can be used with conventional ultraviolet rays (wavelengths of 3000 Å to 4500 Å).
Å), it selectively absorbs and decomposes far-UV light to produce sharp images without reducing image accuracy due to long-wavelength ultraviolet light simultaneously emitted from far-UV sources such as xenon mercury lamps. can be formed. Furthermore, the transmittance of deep ultraviolet light at the peak sensitivity wavelength (2200 Å) of acrylic resin is much higher than that of ultraviolet light at the peak sensitivity wavelength of general photoresists, allowing deep exposure. Furthermore, since the surface reflectance of metals is lower in the far ultraviolet region than in the ultraviolet region, effects such as halation and standing waves are less likely to appear, which is thought to contribute to the high resolution deep down. .

〔Example〕

Example 1 An example used in manufacturing a mask for electron beam exposure will be described with reference to FIG. Polymethyl methacrylate (manufactured by DuPont, USA, trade name: Elbasite) was placed on a mirror-polished silicon wafer 10.
2041) in ethyl cellosolve acetate,
It was coated to a thickness of 3 μm. The mask is patterned on pure quartz glass,
A resin image 11 was formed by contact exposure with a xenon-mercury lamp and development with methyl isobutyl ketone. This resin image had almost vertical edges and reproduced the mask pattern down to the line width of the exposed area of 0.5 μm and the line width of the residual resin of 0.3 μm. Next, plating was applied to a thickness of 3 μm in a nickel plating bath to form a nickel foil 12. Since the plating did not rise above the resin image, the shape of the opening maintained the accuracy of the resin image. Next, the central part of the silicon wafer 10 is removed by etching, and the resin 11 is removed by etching.
An electron beam mask was created by dissolving and removing.

Example 2 An example of application to the production of fine mesh will be shown.
A flat plate of stainless steel was buffed to a mirror surface, coated with polymethyl methacrylate to a thickness of 4 μm, and the same procedure as in Example 1 was carried out up to the formation of the resin image. Next, it was chromate treated by immersing it in a potassium dichromate solution and plated to a thickness of 4μ in a nickel plating bath. The resin image was dissolved and removed with trichlorethylene, and the nickel was peeled off from the substrate. By this method, a nickel mesh with a line width of 1 .mu.m pitch and a thickness of 5 .mu.m and a thickness of 4 .mu.m was obtained.

Example 3 An example in which a fine mesh was similarly manufactured using the lift-off method will be described with reference to FIG. A low melting point metal (tin) is placed on the mirror-polished glass substrate 13.
14 was deposited, and polymethyl methacrylate was coated thereon to a thickness of 5 μm.

Thereafter, the steps up to the formation of the resin image 15 were carried out in the same manner as in Example 1. Next, a 3 μm thick copper layer 16 was deposited using a low temperature, high speed sputtering device. After that, when the resin image 15 is dissolved, the copper 1 on the resin image
6a is removed together with the resin to form an opening. Next, the low melting point metal layer 14 was melted by heating, and the copper mesh 16 was peeled off from the glass substrate. By this method, a copper mesh with a line width of 1 μm, a pitch of 5 μm, and a thickness of 3 μm was obtained.

Example 4 A low melting point metal (tin) was deposited on a mirror-polished glass substrate, and polymethyl methacrylate was coated thereon to a thickness of 3 μm. Thereafter, the steps up to the formation of the resin image were carried out in the same manner as in Example 1.

Next, plating was applied to a thickness of 3 μm in a copper plating bath to form a copper foil. Next, heat is applied to melt the low-melting point metal layer, and the copper foil is peeled off from the glass substrate.
A mask for electron beam exposure was manufactured by adhering the mask to a copper ring of 500 mm with an epoxy adhesive.

〔Effect of the invention〕

As described in detail above, according to the present invention, the nearly vertical opening has sufficient thickness (3μ or more) for self-supporting, and the opening accuracy does not deteriorate even if it extends deep in the thickness direction. a field mesh of an image pickup tube having an opening having a sharp edge;
Metal foils can be manufactured that have openings used for laser apertures and the like.

[Brief explanation of the drawing]

FIG. 1 shows a method for manufacturing metal foil using a conventional method, and FIGS. 2 and 3 show a method for manufacturing metal foil according to the present invention.
FIGS. 4 and 5 are schematic cut-away end views for explaining an embodiment of the present invention. 1, 4... Conductive substrate, 2... Photoresist, 3, 6, 9, 12, 16... Metal foil, 5,
8, 11, 15... Polymethyl methacrylate resin, 7... Substrate, 10... Silicon wafer,
13...Glass substrate, 14...Low melting point metal.

Claims (1)

[Claims] 1. After forming a layer of polymethyl methacrylate resin sensitive to electromagnetic waves with a wavelength of 3000 Å or less, such as deep ultraviolet rays, to a thickness of several micrometers to 10 micrometers on a substrate, a pattern is printed using the electromagnetic waves, and then developed to form a resin. forming an image and then growing a metal layer on the substrate exposed by the patterning to a thickness equal to or less than the thickness of the resin image and having sufficient strength to be self-supporting; A method for producing a metal foil having an opening, the method comprising removing the resin image and further peeling off the metal layer from the substrate or removing at least a portion of the substrate by etching.