JPH01105538A - Photoresist pattern forming method - Google Patents

Abstract

PURPOSE:To exactly etch only a part to be removed by forming a photoresist dual structure and plasma-etching a first photoresist as an etching mask of a pattern of a metal layer. CONSTITUTION:A first Al layer 2 is deposited on the surface of a substrate 1, a first photoresist layer 3 is formed thereon, a metal layer 4 acting as a mask thereon and a second photoresist layer 5 on the metal layer 4 successively. After the resist layer is exposed through a photomask in which a desired pattern is formed, it is developed and a photoresit pattern is formed. The photoresist pattern is made an etching mask and the metal layer 4 is plasma-etched to form a mask pattern. The mask pattern is made an etching mask, the resist layer 3 is plasma-etched to obtain a desired photoresist pattern. Therefore, only a part to be removed can be etched exactly.

Description

[Detailed description of the invention] B) Industrial field of application The present invention is applied to substrates in order to create electrodes and wiring conductors in the manufacturing process of 5AW (surface acoustic wave) devices, IC (integrated circuit) elements, etc. The present invention relates to a method of forming a photoresist pattern thereon.

(B) Prior Art Recent SAW devices, IC elements, etc. have come to require electrodes and wiring patterns with a pattern width of 1 μm or less. When forming such fine patterns, a photoresist is applied to the surface of a substrate on which an electrode material such as aluminum has been vapor-deposited, and this resist layer is exposed to ultraviolet light through a photomask on which an electrode pattern has been formed in advance. A so-called photolithography method is used in which a desired resist pattern corresponding to the electrode pattern is formed on the substrate by subsequent processing.

However, when the pattern width is 1 μm or less, unnecessary parts such as the side surfaces of the photoresist layer are exposed due to reflection and diffraction of ultraviolet rays from the bottom surface of the electrode material (aluminum) layer during exposure. , when the photoresist pattern phenomenon occurs, the resist pattern width becomes narrower. Therefore, when etching a metal layer on a substrate on which such a resist pattern is formed, there is a problem in that the electrodes and wiring patterns corresponding to the resist portion naturally become thinner. That is, in a SAW device having an electrode pattern or pattern as shown in Fig. 2, the abdomen of one electrode finger (T2) adjacent to the tip of one electrode finger (T1), as shown in section A in the figure, is It becomes thinner as shown in Figure 3. This is because it is thought that the above-mentioned reflection and diffraction of ultraviolet rays will be increased in such locations.

To solve this problem, for example, instead of the so-called dipping phenomenon method that uses a phenomenon liquid for the phenomenon of photoresist bars, for example, the method described in the magazine "Electronic Materials, March 1981 issue" It is conceivable to employ an anisotropic plasma dry development method as described in pages 57 to 61. However, according to this method, the photoresist in non-exposed areas is also largely etched during the phenomenon, resulting in a very thin resist layer. Therefore, if the electrode material layer is etched by plasma etching after this phenomenon, the resist will be etched and removed before the electrode material layer is etched to a predetermined thickness. There was a problem in that the layers could not be etched accurately.

4. Problems to be solved by the invention The present invention has been made in consideration of the above points, and is
In the manufacturing process of AW devices, IC elements, etc., when forming a photoresist pattern on the surface of a substrate, even if it is a fine pattern, the pattern width may become narrow or
It is an object of the present invention to enable accurate formation of a resist with a desired width and thickness without reducing the thickness of the resist.

4. Means for Solving the Problems In the present invention, a metal layer and a second photoresist layer are further formed in this order on the first photoresist layer coated on the substrate, and the second photoresist layer is coated on the substrate. Using a photoresist pattern created by exposing the layer to a desired pattern as an etching mask, the metal layer is plasma etched to form a mask pattern, and then, using this mask pattern as an etching mask, the first photoresist layer is etched with plasma. The first photoresist layer on the substrate was etched into the desired pattern.

(E) Effect According to the above method, since the photoresist has a double structure, even if the photoresist is etched by plasma etching, a sufficiently thick photoresist pattern cannot be formed on the substrate. Moreover, since the first photoresist layer is plasma etched using the pattern of the metal layer as an etching mask, only the portions to be removed are etched accurately.

(F) Example Hereinafter, as an example of the present invention, a case where an electrode pattern of a SAW device is formed on the surface of a substrate will be described with reference to FIG.

In this example, as shown in FIG. 11), first, the first
As shown in Fig. 1, the first aluminum layer (2) is deposited on the surface of the crystal substrate (1) in the form of pustules of several tenths of a micrometer, and the first photoresist layer (3) is deposited on the surface of the crystal substrate (1). .0~1.5μ
m, and then a second aluminum layer (
4) is vapor-deposited to a thickness of about several hundredths of a μm, and finally a second photoresist layer (5) is applied on top of it to a thickness of 10 to 20 μm.
Prepare a wafer coated with a coating approximately 1/2 the thickness.

Next, as shown in FIG. 1 et al., a photomask (6) having a desired electrode pattern formed thereon is placed on the second photoresist layer (5) of this wafer and exposed to ultraviolet light (7). Thereafter, this wafer is immersed in a phenomenon liquid (not shown) to perform the phenomenon of the photoresist layer (5).

As shown in FIG. 2(C), a photoresist pattern is formed on the second aluminum layer (4). At this time, the reason why the corner portion (R) of the cyst pattern is missing is that in dipping etching, the portion exposed by the above-mentioned reflected light or diffracted light is dissolved by the etching solution.

Next, the substrate after this dipping phenomenon is placed in a plasma etching apparatus (not shown), and the above-mentioned resist pattern [photoresist layer (53)] is used as an etching mask using CCl! Etching is performed perpendicularly to the first aluminum layer (2) by plasma ion particles (8) such as 4 (carbon tetrachloride) and BC1!3 (boron carbide) gas. At that time, the above-mentioned CCl4, BC1!3, etc. have a slight etching effect on the second photoresist layer (5), but this resist layer (5) is The aluminum layer (4) in the exposed area (E) is coated sufficiently thickly as shown in Figure 1.
Even when it is completely removed as shown in d), a sufficiently thick second photoresist layer (5) remains in the upper non-exposed area (N). Therefore, the aluminum layer (4) underneath is not side-etched and the width of one pattern is not narrowed.

Next, in the state shown in Figure 1 d, this time 02 (oxygen)
The aluminum layer (4) formed on the first photoresist layer (3) by the above-mentioned process (FIG. 1(C)) by injecting CF4(7) carbon) gas into the plasma etching apparatus. Using the pattern as an etching mask, the resist layer (3) is plasma etched with the ion particles (9) of the gas.

Then, the first photoresist layer (3
) and the second photoresist layer (5
1 will be etched together. At this time, the 1114 of the second photoresist layer (5) is made smaller than that of the first photoresist layer (3) as described above, and the above 02, CF4, etc. are made of aluminum. When this etching process is completed, the desired photoresist pattern is formed on the first aluminum layer (2) as shown in FIG. 1(e). (However, aluminum is deposited on the upper surface.) is obtained.

Therefore, from now on, the first photoresist layer (3)
Using the pattern of CCe4. as an etching mask, CCe4. If the first aluminum layer (2) is plasma etched using BCl3 or the like, the state shown in Fig. 1 is obtained. At this time, the first photoresist layer (3) remains with sufficient original thickness on the aluminum layer (2) in the non-exposed area (2), so the aluminum layer (2) below it remains. No side etching. therefore,
If the photoresist layer (3) remaining on the aluminum layer (21) is removed by immersing it in a resist stripping solution (not shown) as in the conventional method, a desired pattern with a specified width can be formed on the substrate (1). This is the method in which an electrode pattern is formed.

Note that, unlike the above embodiment, when the second photoresist layer (5) is made thicker than the first photoresist layer (3), the second photoresist layer (5) is Figure 1
The second aluminum layer (4) in the non-exposed area (N) shown in el
), the second photoresist layer will remain on top of the photoresist layer, but there is no problem in doing so. Furthermore, the second aluminum layer (4), which serves as an etching mask for the first photoresist layer (3), may be a layer of other metals such as copper, chromium, etc.

C) Effects of the Invention As described above, according to the present invention, when forming a fine photoresist pattern on a substrate, the pattern width becomes narrower than the desired value or the resist film thickness becomes thinner. It can be formed accurately without having to do so. Moreover, no special equipment is required, and conventional plasma etching equipment or dipping etching equipment can be used as is, and therefore, there is no significant increase in cost.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the process of forming an electrode pattern according to the present invention, FIG. 2 is a plan view showing the electrode pattern of a SAW device manufactured according to the present invention, and FIG. 3 is an enlarged view of the main part thereof. (1)...Substrate, (2)...First aluminum layer, (3)...First photoresist layer, (4)...
second aluminum layer, (5)...second photoresist layer;

Claims (1)

[Claims] (1) sequentially forming a first photoresist layer on the substrate surface, a metal layer acting as a mask for etching the resist layer thereon, and a second photoresist layer over the metal layer; a step of exposing the second photoresist layer to light through a photomask on which a desired pattern is formed and then subjecting it to a phenomenon treatment to form a photoresist pattern; using the photoresist pattern as an etching mask, etching the metal layer; A photoresist pattern forming method comprising: forming a mask pattern by plasma etching; and plasma etching a first photoresist layer using the mask pattern as an etching mask to obtain a desired photoresist pattern.