JPS6231491B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for accurately manufacturing an electron beam mask having a pattern of fine transmitting parts, haze shielding parts, etc.

Recently, lithography technology using an electron beam as an irradiation source is being developed as a microfabrication technology for VLSI, magnetic valve elements, etc. Lithography technology that uses an electron beam as an irradiation source includes a scanning method that scans and draws images while turning the beam on and off.
There is a projection method in which an electron beam mask having a pattern is provided in the path of the electron beam, and the electron beam passing through the opening of the mask is reduced by a lens system or projected at the same magnification for exposure. The scanning method has the function of generating a pattern, so it has the advantage of not requiring an electron beam mask, but it has the disadvantage that drawing takes time. On the other hand, the projection method has a short exposure time, but it is difficult to micro-process thin metal foils to create precise patterns.
This is a problem in practical application. This electron beam mask consists of a part that transmits the electron beam and a part that blocks the electron beam, and it has been proposed to use a fine mesh to hold the blocking part in the air. When projection exposure is performed using an electron beam using this mask, the electron beam is scattered in various ways and spreads out beyond the holes through which it passes, eliminating fine meshes and projecting only the necessary pattern. For example, when projected to a tenth of a scale, it spreads by about 0.05 μm on both sides on the projection plane, so by making the line width of the support mesh on the mask about 1 μm, the mesh can be eliminated.

Such an electron beam mask can be used at conventional wavelengths of 3500
The case of manufacturing by photolithography using near-ultraviolet light to visible light of ~4500 Å, such as photoelectroforming method, will be explained with reference to FIG. First, a photoresist is applied onto the conductive substrate 1. The thickness of the photoresist must be approximately 0.5 μm in order to increase resolution. This photoresist is exposed and developed to form a resist pattern 2. (Figure 1a). Next, electroforming is performed in a plating bath to form a metal layer 3 (Fig. 1b)
However, the thickness of the metal layer needs to be approximately 2 μm or more in terms of strength, and the metal layer 3 is similar to the resist pattern 2.
It will form a raised shape on top. Next, the resist pattern 2 and the substrate 1 are removed to create a metal foil (FIG. 1c). This metal foil is fixed to a support frame.
(not shown) to obtain an electron beam mask. The opening of this metal foil becomes narrower than the photoresist pattern because the metal rises above the resist pattern 2, and the cross-sectional shape becomes complicated as shown in FIG. 1c, making it difficult to control the size and shape. . Furthermore, even if the opening 2' on the back side is square, the corners of the opening 4 are flattened and the shape is close to a circle as shown in the plan view of Figure 1d, making it difficult to manufacture an electron beam mask with high precision. Can not. moreover,
It is impossible to produce a fine mesh with a line width of about 1 μm because the lines become thick due to the swell of the mesh. There is also a method of applying photoresist to a thickness of about 3 μm, exposing it to light, developing it, and plating it within the thickness of the photoresist, but in this case, the resolution of the photoresist is 2 to 3 μm.
As a result, both the edge shape and dimensional accuracy deteriorate, making it impossible to obtain a metal foil with a better pattern than the method described above, and thus an electron beam mask.

The present inventors utilized the long depth resolution of electromagnetic waves with a wavelength of 3000 Å or less, such as deep ultraviolet rays, to form a resin image with sharp edges using a thick photosensitive resin, and used this as a resist for plating, etc. The present invention was completed based on the discovery that by using this method, it is possible to manufacture an electron beam mask having a fine mesh with a line width of about 1 μm.

That is, the present invention provides a substrate with a layer 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.
After forming a resin layer with a thickness of μm, a pattern is printed using the electromagnetic waves described above, and then developed, the thickness is equal to or less than the thickness of the patterned resin layer on the substrate exposed by the patterning. grow a metal layer with a thickness of 100 mL and sufficient strength to support itself, then remove the patterned resin layer, peel the metal layer from the substrate, and fix it to a support frame. Alternatively, the gist of the present invention is a method for manufacturing an electron beam mask characterized by etching the substrate to leave only a portion that will serve as a support frame.

In the present invention, the sensitive wavelength range is mainly 3500
In contrast to the conventional photoelectroforming method that uses ~4500 Å photoresist, we use a photoresist with a sensitive wavelength range of 3000 Å or less, reducing diffraction effects due to the short wavelength and the high gamma property of the photoresist (exposure By taking advantage of both effects (the ratio of solubility change to quantity change being large), it is possible to form a resin image with minute dimensions and sufficient thickness, and to create a highly accurate electron beam mask. . The resin used as the resist is an acrylic resin such as PMMA (polymethyl methacrylate), PBMA (polybutyl methacrylate), poly α-cyanocarbamic acid acrylate, etc.; or a polysulfonic acid resin such as poly 1-butenesulfon; or Polyketone resins, such as PMIPK (polymethyl isopropenyl ketone). All of these are positive type, that is, photodegradable, but the difference from conventional positive type photoresists is that they do not contain special compounds such as quinone diazide as photosensitive groups (sensitizers), and the light energy directly absorbed by the polymer is absorbed by the polymer. This is the point where the main chain of the polymer is cut.
This is considered to be the cause of the high resolution and high gamma characteristics. For example, it is possible to form a resin image with a line width of 0.5 μm and a height of 3 μm by closely baking PMMA with a thickness of 3 μm and developing it with MIBK (methyl isobutyl ketone). Metal layers of equal or less thickness can be grown to produce electron beam masks with high precision and sufficient strength to be self-supporting.

The manufacturing method of the present invention will be explained below using the drawings. In FIG. 2, a substrate 5 is coated with a resin that is sensitive to electromagnetic waves having a wavelength of 3000 Å or less. The thickness of the resin layer is approximately several μm to 10 μm depending on the required thickness of the metal foil. Next, the pattern is printed using electromagnetic waves such as far ultraviolet rays with a wavelength of 3000 Å or less, and then developed with an appropriate solvent to create a resin image 6.
The remaining portion of the substrate surface is exposed (FIG. 2a). The resulting resin image 6 has approximately vertical edges. Next, the resin image 6 is
(FIG. 2b). Thereafter, the resin image 6 is dissolved and removed using an appropriate solvent, peeled off from the substrate, and fixed to a support frame, or unnecessary parts of the substrate are etched away, leaving the support frame to obtain an electron beam mask (see Fig. 2). c). FIG. 2d shows a cut end view of the metal foil portion of the electron beam mask, and the opening 8 has substantially vertical edges and has good dimensional accuracy. FIG. 2e shows a plan view. Since the metal does not bulge on the resist, the corners of the opening 8 are not rounded, and a highly accurate electron beam mask can be manufactured. Note that if a low-temperature sputtering method is used to form the metal layer 7, the metal layer will also grow on the resin image 6, but it can be removed at the same time as the resin image is removed. Second
Reference numeral 9 in Figure c is a support frame, but this can be removed by etching only the center part of the board as described above and using the remaining part, or you can use another ring-shaped support frame with epoxy. It can also be used by adhering with an adhesive such as resin, or by fixing it by soldering, brazing, welding, joining by growing a plating layer, or the like.

Next, specific examples of the present invention will be described.
The manufacturing method according to the present invention is not limited to the following examples.

Example 1 This will be explained using FIG. 3. mirror polished diameter
The surface of a 50 mm silicon wafer 10 was etched with buffered hydrofluoric acid, and deep ultraviolet photosensitive resin polymethyl methacrylate (manufactured by DuPont, USA,
8% of Elvacite (trade name: Elvacite 2041) was dissolved in ethyl cellosolve acetate and coated with a spinner to a thickness of 3 μm (Figure 3a). Using a 500W xenon-mercury lamp as a light source, the light was transmitted through a patterned mask on pure quartz glass for 20 minutes.
Close exposure was carried out for 1 minute. Next, a resin image 12 was formed by developing with methyl isobutyl ketone for 2 minutes (FIG. 3b). Although this resin image had a thickness of 3 .mu.m, it had nearly vertical edges even at a line width of 1 .mu.m in the exposed and removed portion, and its dimensional accuracy was good. Next, nickel plating was applied to a thickness of 3 μm in a sulfamic acid bath (Figure 3c). Since the plated metal layer did not rise above the resin image, the accuracy of the resin image was maintained. Next, the resin image 12 was dissolved and removed with ethyl acetate to form an opening 15, and then the central part of the silicon wafer as the substrate was etched away with a 20% potassium hydroxide solution to complete an electron beam mask ( Third
Figure d). The remaining portion of the silicon wafer was used as the support frame 14 as is. FIG. 3e is a plan view of the completed electron beam mask, in which 17 is an electron beam blocking portion, 16 is a support mesh with a line width of 1 μm, and 15 is an opening with a size of 4 μm×4 μm. The thickness of each metal foil is 3 μm.

Example 2 Another example will be explained using FIG. 4. An indium layer 19 is deposited on a mirror-polished glass substrate 18 to make the surface electrically conductive (FIG. 4a). Next, 20% of deep ultraviolet photosensitive resin polybutyl methacrylate (manufactured by DuPont, USA, Elvacite 2046) was dissolved in ethyl cellosolve acetate and coated with a spinner to a thickness of 4 μm. Hereinafter, the exposure method is the same as in Example 1. Next, the resin image 20 is developed using isopropyl alcohol.
was formed (Fig. 4b). The thickness of the resin image is 4μ
It was m. Next, copper plating was applied to a thickness of 4 μm in a bright copper plating bath to form a metal layer 21 (FIG. 4c). After the resin image was dissolved and removed with toluene, indium 19 was dissolved in an oil bath to peel off the metal layer 21, and the resultant was washed with a solvent to create a metal foil. The obtained copper foil has an outer diameter of 40 mm and an inner diameter of 30 mm.
A copper ring 22 with a thickness of 1 mm and 1 mm was crimped and bonded by growing a plating layer on the contact portion in a nickel plating bath, thereby producing an electron beam mask (FIG. 4d). Opening of copper foil 21 1μm×5μ
It was possible to manufacture a highly accurate electron beam mask with a supporting copper wire of 1 μm x 4 μm and a thickness of 4 μm.

Example 3 An example of manufacturing an electron beam mask using the lift-off method will be described with reference to FIG. Far-UV photosensitive resin polymethyl isopropenyl ketone is deposited to a thickness of 3 μm on a mirror-polished silicon wafer 25 with an outer diameter of 40 mm.
Coated to a thickness of . A 200W deuterium lamp was used as a light source, and contact exposure was performed for 20 minutes through a quartz glass mask. Next, it was developed with methyl cellosolve for 2 minutes to form a resin image 26 (FIG. 5a). Thereafter, copper was deposited to a thickness of 2 μm using a flat plate magnetron-type low-temperature, high-speed sputtering device to form a metal layer 27 (FIG. 5b). A metal layer 27a is also deposited on the resin image, which is then removed at the same time as the resin image 26 is removed with ethyl acetate, forming an opening (FIG. 5c). Next, support frame 2 was added with 15% sodium hydroxide solution.
The central portion of the silicon wafer was etched away, leaving the area 8, to produce an electron beam mask (FIG. 5d). Opening dimensions 4μm x 4μm, support line width 1
It was possible to manufacture a highly accurate electron beam mask with a thickness of 2 μm.

[Brief explanation of the drawing]

1a to 1c are enlarged cutaway end views schematically showing the main parts of the manufacturing process of the conventional method; FIG. 1d is an enlarged plan view schematically showing the main parts of the electron beam mask obtained by the conventional method; Figures 2 a to c are enlarged cross-sectional views schematically showing the main parts of the manufacturing process according to the method of the present invention, and Figure 2 d schematically shows the main parts of the electron beam mask obtained by the method of the present invention. The enlarged cutaway end view, Fig. 2e, is the same enlarged plan view, Fig. 3a~
d, FIGS. 4a to 4d, and 5a to 5d are enlarged cutaway end views showing the manufacturing process of the embodiment of the present invention, and FIG. 3e is a schematic diagram of an electron beam mask obtained by the embodiment of the present invention. FIG. 5...Substrate, 6...Resin image, 7...Metal layer,
8...Opening, 9...Support frame.

Claims (1)

[Claims] 1. After forming a 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, on a substrate, a pattern is printed using the electromagnetic waves, and then, after development treatment, the patterning is performed. A metal layer having a thickness equal to or less than the thickness of the patterned resin layer and having sufficient strength to support itself is grown on the exposed substrate, and then the patterned resin layer is grown. A method for manufacturing an electron beam mask, which comprises removing the metal layer from the substrate and fixing it to a support frame by peeling the metal layer from the substrate, or etching the substrate to leave only a portion that will become the support frame.