JPH08316193A - Pattern formation method - Google Patents

Abstract

PURPOSE: To provide a pattern formation method of easily forming an overhang on photosensitive resin on a substrate surface and forming a pattern with a lift-off method. CONSTITUTION: Photosensitive resin 2 is applied on the surface of a substrate 1 and is prebaked, and thereafter a thermal hardened layer 4 is formed on the surface of the photosensitive resin 2 using warm air 3 before or after exposure to light. An overhang is formed with the hardened layer 4 utilizing development to result in a configuration where lift-off is facilitated, and after Al is deposited the photosensitive resin 2 is removed to obtain a desired pattern with Al.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pattern forming method for forming a pattern on a substrate surface by a lift-off method,
In particular, the present invention relates to a method for forming a pattern on a piezoelectric substrate used for a surface acoustic wave device by a lift-off method.

[0002]

2. Description of the Related Art To form a metal pattern on a substrate,
By removing the photosensitive resin, the metal on the photosensitive resin is simultaneously removed to form a so-called lift-off. In order to facilitate this lift-off, it is necessary to form a so-called reverse taper or overhang in which the surface portion of the photosensitive resin after development is smaller than the bottom portion of the window. For this purpose, there is a method of forming a chemically changed layer on the surface by immersing it in chlorobenzene to form a layer in which a photosensitive resin is difficult to dissolve in a developing solution.

[0003]

In the above-mentioned manufacturing method, when the resin is soaked in chlorobenzene for a long time, the chemical change proceeds so much that the photosensitive resin is cracked and cannot be put to practical use, or chlorobenzene remains. Causes unevenness in development due to a chemical action with a developing solution, or the metal is adhered to the surface of the photosensitive resin so that the surface of the photosensitive resin is heated and the photosensitive resin is deformed and the overhang formed is destroyed. There was a problem.

Bi ₁₂ GeO used for surface acoustic wave devices
_For piezoelectric substrates such as ₂₀ , Li ₇ BeO ₁₂ and AlPO ₄ , which are attacked by chemicals such as acids and alkalis, the parts not covered with the photosensitive resin such as the back surface after being immersed in chlorobenzene for a long time Since the substrate is non-uniformly etched and the flatness is impaired, there is an unfavorable effect such that the jig cannot be vacuum-sucked in a later step.

The present invention provides a method for forming an overhang on a photosensitive resin by forming a layer which is hardly dissolved in a developing solution only on the surface of the photosensitive resin without immersing it in a chemical solution.

[0006]

In order to solve the above problems, in the pattern forming method of the present invention, a photosensitive resin is deposited on a substrate, prebaked and exposed to light, and then hot air is applied to the surface of the photosensitive resin. Alternatively, a light-sensitive resin other than the photosensitivity of the photosensitive resin is applied to form a thermal cured layer only on the surface of the photosensitive resin, and after development, a metal is applied to remove the photosensitive resin. By removing the above metal at the same time, a metal pattern is formed on the substrate by the lift-off method.

[0007]

According to the above manufacturing method, a dry method of heating with warm air or light is used to cure by heat that is difficult to dissolve in the developing solution only on the surface of the photosensitive resin, irrespective of wet chemical changes caused by immersion in a chemical solution. Since a layer is formed, cracks due to chemical changes are less likely to occur, making it possible to form unevenness in development due to chemical action with the developer and to form overhangs on the photosensitive resin without chemically attacking the substrate. Further, it is possible to prevent the deformation of the photosensitive resin during metal deposition, and it is possible to easily form a desired pattern by facilitating lift-off.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the pattern forming method of the present invention will be described below with reference to the drawings.

In FIG. 1, reference numeral 1 is a piezoelectric substrate, and a positive type photosensitive resin 2 which is soluble in a developing solution when irradiated with ultraviolet rays is applied to the surface of the piezoelectric substrate 1, and a hot plate at 90.degree. Prebaking is performed by heating from the back surface of the substrate for about a second. Here, the prebaking may be heated in an atmosphere of 90 ° C. such as an oven, but in any case, it is important to uniformly heat the entire piezoelectric substrate 1 and the photosensitive resin 2. Next, selective exposure is performed using a photomask. At this time, the photosensitive wavelength is determined by the photosensitive resin 2, and, for example, 436 nm g-line and 365 nm i-line are commercially available.

After that, the surface of the photosensitive resin 2 is heated to a pre-baking temperature, that is, 90 ° C. or higher, to a temperature at which the photosensitive resin 2 does not become insoluble in the developing solution and the removing solution of the photosensitive resin 2. Since this temperature has a different heat resistant temperature depending on the type of the photosensitive resin 2, it is necessary to set the temperature accordingly. As a first method for this purpose, as shown in FIG. 2, the hot air 3 of 160 ° C. is blown onto the surface of the photosensitive resin 2 so that the surface temperature of the photosensitive resin 2 becomes, for example, 130 ° C.
As a result, only the surface of the photosensitive resin 2 is thermally cured from the inside, and the cured layer 4 that is difficult to dissolve in the developing solution is formed. The degree of this hardening is determined by the temperature of the warm air 3 blown from the surface.

As a second method, a photosensitive resin 2 as shown in FIG.
In the case of a photosensitive resin for i-line, the surface of the photosensitive resin 2 is irradiated with light 5 having a wavelength of 400 nm or more, such as visible light and infrared light, as the light having a wavelength other than the photosensitive wavelength. At this time, the shorter the wavelength is, the more advantageous it is to absorb the energy as heat only on the surface. Even in this case, the photosensitive resin 2
The surface of is hardened thermally as compared with the inside, and a hardened layer 4 that is hard to dissolve in the developer is formed, and the degree of hardening is determined by the amount of light.

The surface hardening of the photosensitive resin 2 by the first and second methods has the same effect even if it is carried out after prebaking and before exposure. Further, when the warm air 3 and the light 5 are sprayed or irradiated onto the surface of the photosensitive resin 2 from an oblique direction rather than perpendicularly, the hardened layer 4 only on the surface of the photosensitive resin 2.
Can be formed and an overhang can be easily formed.

Next, a pattern of the photosensitive resin 2 is formed by removing only the area selectively exposed by the developing solution. Here, the cured layer 4 on the surface of the photosensitive resin 2
Is less likely to dissolve in the developing solution from the inside, the removal speed by development is different in the direction parallel to the surface of the piezoelectric substrate 1 at the end of the pattern that is not sufficiently exposed, and as shown in FIG. The hang 6 can be formed.

Thereafter, as shown in FIG. 5, Al7 is deposited as an electrode metal. In this case, Al7 is deposited by resistance heating deposition, electron beam deposition, etc.
A method in which the particles do not wrap around is preferable, and this makes it possible to achieve a state in which the side walls 8 of the photosensitive resin 2 are not covered with Al 7 and the photosensitive resin 2 is exposed in the overhang 6 portion of the photosensitive resin 2. When depositing this Al7,
The deformation of the photosensitive resin 2 caused by the heating of the photosensitive resin surface 2 by the heat of 7 or the radiant heat from the filament or the like causes the surface of the photosensitive resin 2 to be previously cured by thermal curing in the method according to the present invention. Since the layer 4 is formed, it can be avoided.

Thereafter, the photosensitive resin 2 is removed by immersing it in a removing solution for the photosensitive resin 2 to simultaneously remove the Al 7 on the photosensitive resin 2 and, as shown in FIG. 6, the surface of the piezoelectric substrate 1. A desired pattern of Al7 is formed by leaving only Al7 deposited on the substrate. At this time, the photosensitive resin 2 is not covered with Al 7 due to the overhang 6.
It is dissolved by the removing liquid from the side wall 8 of. In addition, the warm air 3 near the piezoelectric substrate 1 inside the photosensitive resin 2, that is, the side wall 8
Since the portion that is not cured by the light or the light 5 is exposed, it is easily dissolved in the removal liquid. That is, lift-off can be easily performed.

[0016]

As described above, according to the present invention, the surface of the photosensitive resin is dried by the dry method of heating with warm air or heating with light, regardless of the wet chemical change caused by the immersion in the chemical solution as in the prior art. Since a hardened layer is formed by heat which is difficult to dissolve in the developing solution, cracks due to chemical changes are less likely to occur, and uneven development does not occur due to the chemical action with the developing solution. Further, since it is a dry type, it is possible to form an overhang on the photosensitive resin without chemically attacking the substrate. Furthermore, since the thermally cured layer has already been formed on the surface of the photosensitive resin, it is possible to prevent the deformation of the photosensitive resin that has occurred during metal deposition. Therefore, lift-off can be facilitated, and a desired pattern can be easily formed.

[Brief description of drawings]

FIG. 1 is a sectional view when a photosensitive resin is applied to a substrate in an embodiment of a pattern forming method of the present invention.

FIG. 2 is a cross-sectional view of the photosensitive resin according to the first embodiment of the present invention when hot air is blown to the photosensitive resin.

FIG. 3 is a cross-sectional view when light is applied to the photosensitive resin in the second embodiment of the present invention.

FIG. 4 is a sectional view when developed according to the present invention.

FIG. 5 is a sectional view when the metal of the present invention is applied.

FIG. 6 is a sectional view when the photosensitive resin of the present invention is removed.

[Explanation of symbols]

 1 Piezoelectric Substrate 2 Photosensitive Resin 3 Hot Air 4 Cured Layer of Photosensitive Resin 5 Light 6 Overhang 7 Al 8 Sidewall of Photosensitive Resin

Claims (5)

[Claims] 1. A method comprising depositing a photosensitive resin on a substrate, pre-baking, and heating the photosensitive resin surface to a pre-baking temperature or higher in the steps up to development, and depositing a metal after development to remove the photosensitive resin. By doing so, the metal on the photosensitive resin is simultaneously removed to form a pattern. 2. The pattern forming method according to claim 1, wherein the heating of the surface of the photosensitive resin blows warm air onto the surface of the photosensitive resin. 3. The pattern forming method according to claim 1, wherein the heating of the surface of the photosensitive resin irradiates the surface of the photosensitive resin with light having a wavelength other than the photosensitive wavelength. 4. The method of spraying hot air or irradiating light is tilted from the vertical with respect to the surface of the photosensitive resin.
Alternatively, the pattern forming method described in 3 above. 5. The pattern forming method according to claim 1, wherein the substrate is a piezoelectric substrate.