JPH02272731A - Metallic film pattern formation method, and aligner and mask used for the method - Google Patents

Abstract

PURPOSE:To form metallic film patterns different in thickness with the exposure process of one time by forming X-ray and photo resists on a substrate, and exposing and developing the resists with the mask where specified patterns are formed by X-ray and photo absorbing substances. CONSTITUTION:A positive X-ray resist 5 and a photoresist 3 are formed on a piezoelectric substrate 1. Next, when the resists are exposed and developed using a mask wherein specified patterns are formed on an X-ray transmitting film 6 by an X-ray absorbing substance 7 and a photo absorbing substance 8, the substrate 1 is exposed only at a bonding pad part. Next, Al 11 is deposited on the whole face and the resist 3 is separated and a bonding pad is formed. Furthermore, when the resist 5 is developed again, comb-shaped electrode part is exposed. Successively, an Al film 2 for electrode is deposited, and at the same time with the separation of the resist 5 an electrode is formed by lift-off. Hereby, Al film patterns different in thickness can be formed easily by the exposure process of one time.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to metal thin film pattern forming technology applied to the manufacture of surface acoustic wave elements and semiconductor devices, etc. The present invention relates to a method for forming a thin film pattern, an exposure apparatus used in the method, and a mask used in the method.

[Prior Art] As shown in FIG. 4, a surface acoustic wave element has a piezoelectric substrate 1.
A blind-shaped metal electrode 42 is formed on the top, and the electrode 42 is connected to the lead wire 4 through a bonding pad 43. In order to use the surface acoustic wave device in the gigahertz band, the thickness of the metal film of the interdigital electrode portion must be 500 Å or less for reasons such as reducing loss. Normally, the bonding pad 43 is formed at the same time as the interdigital electrode 42 by a photolithography process, but since the metal film is very thin, it is easily damaged in the wire bonding process for connecting the lead wire 4, resulting in poor connection. Disconnection, etc. often occurs. Therefore, in many cases, a method of reinforcing the bonding pad 43 by further vapor depositing metal on the bonding pad 43 is adopted before the wire bonding process.

FIG. 5 shows an example of the manufacturing process of a general surface acoustic wave filter. First, a thin A!
The film 2 is deposited by vapor deposition (FIG. 5(a)), and then the photoresist 3 coated on the second film 2 is processed into a desired electrode shape by a photolithography process (FIG. 5(b)). The β film 2 is roughly etched into the same shape as the photoresist 3 (FIG. 5(C)), and then the photoresist is peeled off (FIG. 5(d)). In order to reinforce the bonding pad part, the β film 3 is roughly exposed only in the reinforced part by a photolithography process (FIG. 5(e)).
, 8β11 is evaporated thereon (FIG. 5(f)), the resist is peeled off (FIG. 5(q)), and finally wire bonding is performed to connect the lead wire 4 (FIG. 5(h)).
.

[Problems to be Solved by the Invention] However, the method described above has the disadvantage that the photolithography process is performed twice, making the process complicated.

An object of the present invention is to eliminate such conventional drawbacks and provide a simple method for forming a metal thin film pattern, an exposure apparatus, and a mask.

[Means for Solving the Problems] The present invention includes a step of sequentially forming a positive X-ray resist and a positive photoresist on a substrate, and a step of sequentially forming a positive X-ray resist and a positive photoresist on an X-ray transmissive film, respectively. a step of exposing and developing each of the resists using a mask with a pattern formed thereon; and a step of vapor depositing a first metal on the entire surface of the substrate;
the photoresist and the first photoresist on the photoresist;
removing the metal to expose the X-ray resist; developing the exposed portion in the exposed X-ray resist;
A metal thin film pattern forming method comprising the steps of: depositing a second metal on the entire surface of the substrate; and removing the X-ray resist and the second metal on the X-ray resist. .

Further, the exposure apparatus used in this method is provided with an X-ray generation section that irradiates X-rays onto the substrate in a vacuum container, and a light ray generation section that irradiates the substrate with light rays, and includes an The apparatus is characterized in that an irradiation switching means for switching between X-ray irradiation and light irradiation is installed.

Furthermore, the mask used in the above method is formed by forming an X-ray absorber made of a heavy metal and a light absorber made of a light metal in a predetermined pattern on an X-ray transparent film that is transparent to light and X-rays. It is characterized by

[Operation] In the present invention, each resist is exposed and developed on a substrate on which an X-ray resist and a photoresist are sequentially formed, using a mask in which a predetermined pattern is formed by an X-ray absorber and a light absorber. . Through exposure and development, the portions of the X-ray resist that correspond to the mask pattern are removed, but the portions of the X-ray resist that are exposed to X-rays but not exposed to light are removed. Even if the phenomenon occurs with a linear developer, it remains unremoved because there is unexposed photoresist on top.

Therefore, when the photoresist is removed after the first metal is vapor-deposited at this stage, the exposed portions of the X-ray resist that were covered by the photoresist are exposed, so development is performed again. Thereafter, when the second metal is deposited, the second metal is deposited on the first metal, and a new pattern is formed using only the second metal.

As described above, when the first metal and the second metal are different metals, metal thin films made of different materials can be formed in different patterns by one exposure, and the first metal and the second metal When the two metals are the same metal, metal thin film patterns having two types of film thickness can be formed by one exposure.

Further, an X-ray generation unit that irradiates X-rays onto the substrate in the vacuum container and a light ray generation unit that irradiates the substrate with light rays are provided,
If an exposure apparatus equipped with an irradiation switching means for switching between irradiation of X-rays and irradiation of light beams onto the substrate is used,
For beams and light beams, the substrate can be irradiated without moving the substrate, and the above method can be easily applied.

Furthermore, the above method uses a mask in which an X-ray absorber made of a heavy metal and a light absorber made of a light metal are formed in a predetermined pattern on an X-ray transparent film that is transparent to light and X-rays. achieved.

[Example] Next, an example of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a process diagram showing an embodiment of the metal thin film pattern forming method according to the present invention. In the figure, parts that overlap with those in FIG. 5 are given the same numbers, and their explanations will be omitted. First, a positive X-ray resist 5 is placed on the piezoelectric substrate 1 shown in FIG. 5(a).
Then, a positive photoresist 3 is applied. Next, an inverted pattern of the interdigital electrode and the bonding pad part is drawn on the X-ray transparent 119I6, which is transparent to light, using the X-ray absorber 7, and a reverse pattern of the bonding pad part is drawn with the metal thin film (light absorber) 8. The resist is exposed to X-rays and light through a patterned mask (FIG. 1(b)). Next, when the photoresist 3 and the X-ray resist 5 are developed using a dedicated developer, the piezoelectric substrate 1 is exposed only at the bonding pad portion, as shown in FIG. 1(C). Next, 8β (first metal) 11 for a bonding pad is vapor-deposited (FIG. 1(d)), and the photoresist 3 is peeled off to form a bonding pad by lift-off. When the X-ray resist 5 is roughly developed again, the interdigital electrode portions are exposed (FIG. 1(e)).

Subsequently, AINm (second metal) 2 for the interdigital electrode is vapor-deposited (FIG. 1(f)), and the electrode is formed by peeling off the X-ray resist 5 and lift-off (FIG. 1(g)).
. The subsequent wire bonding process is the same as the conventional method. In this way, you can easily create different film thicknesses with just one exposure process! A film pattern can be formed.

FIG. 2 is a schematic configuration diagram showing an embodiment of an exposure apparatus according to the present invention. This exposure apparatus has an X-ray generator 21 inside a vacuum container 29 and a mercury lamp (light generator) 23 outside the vacuum container.
6, it is possible to move the reflecting mirror (irradiation beam switching means) 24 left and right. When the anti-OA mirror 24 is directly above the mask and substrate stem 27, light 30 emitted from the mercury lamp 23 passes through the glass window 28, is reflected by the reflector 24, and is irradiated onto the mask and substrate. When the reflecting mirror 24 is retracted to the left, the mask and the substrate are irradiated with X-rays 31 emitted from the X-ray generating section 21.

FIG. 3 is a sectional view showing an embodiment of the mask according to the present invention. On the X-ray transparent membrane 6 held by the support frame 32, an inverted pattern of the interdigital electrodes and the bonding pad portion is drawn by the X-ray absorber 7. Further, an inverted pattern of the bonding pad portion is drawn by a light absorber 8 that transmits X-rays but absorbs visible light.

As the X-ray transparent membrane, silicon nitride with a thickness of about 1 to 2 μm,
Silicon carbide etc. can be used. As the X-ray absorber, gold, tungsten, tantalum, etc. with a thickness of about 0.5 to 1 mm can be used. Further, as the light absorber, a metal thin film such as beryllium or aluminum having a thickness of 0.1 mm or less can be used. This mask can be easily manufactured by forming an absorber pattern using an X-ray absorber using a conventional X-ray mask manufacturing process and then forming a light absorber.

In this example, the method of the present invention was applied to the formation of a surface acoustic wave device, but the method of forming a metal thin film of the present invention can be applied not only to surface acoustic wave devices but also to semiconductor devices in general.

Roughly speaking, in this example, both the first and second metals are A! was used, but it is also possible to use different metals in the two depositions.

[Effects of the Invention] As detailed above, according to the present invention, there is provided a metal thin film forming method capable of forming two types of metal thin films of different thicknesses or materials in one exposure process, and a method used in the method. An exposure apparatus and a mask used in the method are provided. Moreover, since this metal thin film forming method uses X-ray exposure, 0.5. It is possible to form a fine metal film pattern of crm or less.

[Brief explanation of drawings]

FIG. 1 is a process diagram showing an embodiment of the metal thin film forming method of the present invention in order of steps, FIG. 2 is a schematic configuration diagram of an embodiment of the exposure apparatus of the present invention, and FIG. 3 is an X-ray mask of the present invention. 4 is a schematic perspective view of a surface acoustic wave device, and FIG. 5 is a process diagram showing an example of a conventional method for manufacturing a surface acoustic wave device in order of steps. 1... Piezoelectric substrate 2... AI! , (aluminum) thin film 3...Positive photoresist 4...Lead wire 5...Positive X-ray resist 6...X-ray transparent film 7...X-ray absorber 8.
...Metal thin film (light absorber) 9...Light and X-rays 11...Aβ (aluminum) 21...X-ray generation part 22...Electron beam 23
...Mercury lamp 24...Reflector 25...
・Drive shaft 26...Bellows 27...
Substrate stage 28...Glass window 29...Vacuum container 30...Light 31...X-ray
32... Support frame 42... Interdigital electrode 43... Ponding pad

Claims (3)

[Claims] (1) The process of sequentially forming a positive X-ray resist and a positive photoresist on a substrate, and using a mask in which predetermined patterns are formed on an X-ray transparent film by an X-ray absorber and a light absorber, respectively. , exposing and developing each of the resists, depositing a first metal on the entire surface of the substrate, and removing the photoresist and the first metal on the photoresist to expose the X-ray resist. a step of developing the exposed portion in the exposed X-ray resist; a step of depositing a second metal on the entire surface of the substrate; and removing the X-ray resist and the second metal on the X-ray resist. A method for forming a metal thin film pattern, comprising the steps of: (2) An X-ray generation unit that irradiates X-rays onto a substrate in a vacuum container and a light ray generation unit that irradiates the substrate with light rays are provided,
An exposure apparatus comprising an irradiation switching means for switching between irradiation of X-rays and irradiation of light beams onto the substrate. (3) A mask characterized in that an X-ray absorber made of a heavy metal and a light absorber made of a light metal are formed in a predetermined pattern on an X-ray transparent film that is transparent to light and X-rays.