JPH03245528A - Pattern formation - Google Patents

Abstract

PURPOSE:To form a pattern with excellent dimensional precision without forming a thick resist for lift-off resist at all by a method wherein, in order to pattern a relatively thick thin film formed on a substrate, both etching process and lift-off process are used together. CONSTITUTION:A cleaned up substrate 5 is coated with a Cr film by vacuum deposition process so as to be formed into an electrode 6 by photolithoetching process and then a negaresist 7 having a specific opening is formed on the whole surface including the electrode 6. Next, a relatively thick Al film for wiring 8 is formed on the whole surface and then a positive resist 9 is formed only on the wiring 8 sunk by the pattern of the resist 7. Later, the wiring 8 on both sides of the resist 9 is etched away using the resist 9 as a mask and then the resist 9 is removed to expose the sunk wiring 8 only. Finally, an upper wiring 11 is formed on the whole surface including the exposed wiring 8 to complete the lower layer wiring 8 and the upper layer wiring 11.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a pattern forming method for forming a relatively thick thin film on a substrate using a combination of an etching method and a lift-off method.

[Prior Art] Conventionally, as a method for patterning a relatively thick thin film of about 2Ij, lT1 or more provided on a substrate, the method shown in FIG. 3(a) is used.
A photolithography method as shown in (b) has been carried out.

In this process, a thin film 12 is deposited on a substrate 1, and a photoresist 13 is formed thereon by photolithography (see FIG. 3(a)). Next, the thin film 12 is patterned by wet etching (see FIG. 3(b)).

In this method, if the thin film is relatively thick (approximately 2 pm or more), the thin film is side-etched to a size comparable to the thickness of the thin film, resulting in a small pattern size.

Therefore, side etching of the thin film can be prevented by using a dry etching method such as ion milling or active ion etching. However, in ion milling, the substrate 1
Therefore, selective etching of the thin film 12 is impossible, and etching damage occurs to the substrate 1. Further, although it is possible to selectively etch the substrate 1 and the thin film 12 using reactive ion etching, the etching rate is basically small and it takes a long time to process a thick thin film.

Next, FIG. 4 shows a lift-off method that does not cause side etching and can form a thin film pattern that is almost the same as the resist pattern. In the figure, reference numeral 14 denotes a photoresist pattern, which is formed on the substrate 1, on which a relatively thick thin film 15 is deposited.

Here, if the thickness of the photoresist 14 is thicker than the thin film 15, the photoresist 14 can be easily dissolved and peeled off during boat fishing, and the thin film 15 can be patterned. However, as shown in FIG. 4, if the photoresist 14 is thinner than the thin film 15, the thin film 15 will cover the stepped portion of the photoresist 14, and the stripping solution for dissolving and stripping it will not be able to touch the photoresist 14. Patterning using the lift-off method is not possible.

Also, the ease of lift-off varies depending on the thin film material.
P has the property of being extremely difficult to lift off compared to materials such as Cu.

In addition, the thickness of photoresist is generally 0.3 μm to 2 μm.
Generally, it is on the order of μm, and when the film thickness is further increased, the film thickness distribution of the resist coating becomes thicker, and pattern dimensional accuracy decreases due to resist non-uniformity phenomena, light wraparound during exposure, etc.

[Problems to be Solved by the Invention] In the conventional examples described above, when patterning a relatively thick thin film of 2 μm or more, in the etching method: (1) In the wet etching, the side etching of the thin film is large and the pattern dimension accuracy is poor. decreases.

(2) Ion milling and active ion etching cannot selectively etch the underlying substrate, and processing takes a long time.

In addition, in the lift-off method, it is necessary that the lift-off resist is thicker than the thickness of the thin film to be patterned, and there is a limit to the resist thickness due to the decrease in resist film thickness accuracy and pattern dimensional accuracy. Patterning using the thin film lift-off method is not possible.

It had some flaws.

That is, an object of the present invention is to provide a pattern forming method that can solve the above-mentioned problems.

[Means and effects for solving the problems] The present invention is characterized by forming a first resist pattern on a substrate, depositing a thin film, and depositing a negative film on the thin film with respect to the first resist pattern. - A second resist pattern with the positive inverted is provided, and the thin film is etched in the thickness direction to cause side etching at the boundary between the first resist pattern and the second resist pattern. The pattern forming method is such that after exposure, the first resist pattern and the thin film on the first resist pattern are removed.

That is, according to the present invention, by using a combination of an etching method and a lift-off method to form a thick thin film, patterning can be performed with good dimensional accuracy without the need for a thick lift-off resist.

Hereinafter, the pattern forming method of the present invention will be explained in FIGS.
The explanation will be based on e).

(2) First, a lift-off photoresist 2 is formed on the cleaned smooth substrate 1 by photolithography (
Figure 1(a)).

(2) A thin film 3 to be patterned is deposited on the lift-off photoresist 2. At this time, it is particularly effective when the thickness of the thin film 3 is thicker than the lift-off photoresist 2 (FIG. 1(b)).

01 Next, on the lift-off photoresist 2, an etching photoresist 4 whose negative and positive patterns are reversed with respect to the pattern of the lift-off photoresist 2 is formed (FIG. 1(C)).

09 Next, the thin film 3 is etched in the thickness direction to cause side etching at the pattern boundary between the lift-off photoresist 2 and the etching photoresist 4, exposing the end of the lift-off photoresist 2 (Fig. 1). (d)).

(2) Finally, at the same time as the lift-off photoresist 2 is dissolved and peeled off, the thin film 3 left in the step (2) and on the lift-off photoresist 2 is removed, and the etching photoresist 4 is also dissolved and peeled off at the same time. 3 is patterned (FIG. 1(e)).

According to the above method, even if the thickness of the thin film 3 is thicker than the lift-off photoresist 2, sufficient pattern formation is possible. Therefore, the thickness of the lift-off photoresist 2 is
No need for film thickness accuracy.

The resist thickness can be formed with good pattern dimensional accuracy.

In addition, since the thin film 3 is finally processed by the lift-off method, the pattern of the thin film 3 at the interface between the substrate 1 and the thin film 3 is small (without becoming narrower due to side etching, etc.), and the lift-off photoresist 2 It is possible to form a pattern with high precision that is approximately equal to the dimensions of .

Furthermore, the lift-off photoresist 2 and the etching photoresist 4 can be easily formed with high precision by using the same photomask and using a negative resist and a positive resist.

The etching method and lift-off method used in the process are techniques used for boat fishing, and do not require special equipment (they are easy to process. It is also easy to realize.

Hereinafter, the present invention will be specifically explained in detail with reference to Examples.

[Example] A specific example of the present invention will be described based on FIGS. 2(a) to (i).

FIG. 2(i) is a diagram showing a cross section of a multilayer electrode wiring formed according to the present invention. In this figure, 5 is a substrate made of a glass material with a smooth surface, and 6 is an electrode made of Cr with a thickness of 0.1 pm formed on the substrate 5. 8 is a 2H thick AFlo formed by the method of the present invention, 0
The wiring is made of Cr with a thickness of 1 μm, and the cross section of the wiring has a two-step side profile due to side etching that occurs during etching. IO is an insulating layer made of 5i02 with a thickness of 1.8 μm, and 11 is an upper layer wiring made of Cr with a thickness of 1.5 μm and Aj)10.01 pm.

Here, the wiring 8 and the upper layer wiring 11 intersect with each other through the insulating layer io, but even though the film thickness of the insulation layer lo and the upper layer wiring 11 is thinner than that of the wiring 8, each step portion is different from the above-mentioned The film thickness sufficiently covers the steps, making it possible to form multilayer electrode wiring without disconnections or short circuits. This is wiring 8
This is because the side surface shape is formed into two stages by the pattern forming method of the present invention. That is, when covering the wiring 8 with the laminated film, it is sufficient to step over approximately half the film thickness of the wiring 8, thereby providing a sufficient step cover.

Hereinafter, the forming method of this embodiment will be explained in order according to FIGS. 3(a) to 3(i).

■First, a vacuum evaporation method is applied to the cleaned substrate 5.
．． A 1 μm thick Cr film is formed and patterned by photolithography to form the electrode 6 (FIG. 2(a)).
.

■First step: RD200ON (manufactured by Hitachi Chemical Co., Ltd.) negative resist is spin-coated at approximately 1500r, p, m, and after baking and drying, a photomask pattern is exposed using PLA520 (manufactured by Canon), developed, and baked to dry. resist 7
The thickness is about 1.5#1. A pattern was formed using m (Fig. 3 (
b)).

09Next, 001μ is deposited on the substrate to be bent by vacuum evaporation method.
An AP film with a thickness of 2μ5 was formed by subbing a Cr film with a thickness of m and was used for the wiring 8 (Fig. Spin coat the resist and apply pu5o after drying.

(manufactured by Canon Inc.), the same photo 37 pattern was exposed, developed, and baked to form a pattern of photogist 9 (FIG. 3(d)).

(2) After that, the AI film formed in the above-mentioned step (2) (Fig. 3 (C)) was coated with H,PO4:HNO3:CH,C0OH:
Using an etching solution of H20=16:1:2:1, agitation etching was performed for about 3 minutes at a heating temperature of about 40"C to remove a dot thickness of 1 p and m.
At this time, as shown in the figure, side etching occurred due to the positive resist 9 (FIG. 3(e)).

01 Next, the positive resist 9 and the negative resist 7 are dissolved and peeled off by immersion in acetone, an organic solvent, and ultrasonic cleaning is performed.Finally, the wiring 8 made of AR/Cr is formed into a cross-sectional shape with a two-step side surface. (Fig. 3(f)).

On the electrodes 6 and wiring 8 formed in steps 00 or more,
A film of approximately 1.8 μm of SiO□ was formed by sputtering to form an insulating layer 1O (FIG. 3(g)).

■, Furthermore, 0.011zm thick Cr was deposited by vacuum evaporation method.
An upper layer wiring 11 consisting of an Al film with a thickness of 1.5 gm was formed using the film as an undercoat layer (FIG. 3(h)).

(2) The upper layer wiring 11 formed in the previous process is patterned by photolithography, and the relatively thick wiring 8. A multilayer electrode wiring consisting of an insulating layer 10 thinner than the wiring 8 and an upper layer wiring 11 was formed (see Fig. 3).
i)).

In the steps described above, the dimensional width of the formed wiring 8 facing the electrode 6 was almost the same as the dimensional width formed with the negative resist 7. Further, in this embodiment, the electrode 6 is made of Cr material, and the wiring 8 formed thereon is made of Al/Cr material, so the electrode 6 is etched by wet etching of the wiring 8.
Cr was not damaged.

Similarly, the lower electrode 6 is set to AIl, and the wiring 8 above it is set to A
j) Even when only the material was used, there was no damage to the AI of the electrode 6 due to the wet etching of the electrode 6. This is because the negative resist 7 for lift-off protects the electrode 6 from the etching solution.

[Effects of the Invention] As explained above, according to the pattern forming method of the present invention, by forming a pattern using a combination of an etching method and a lift-off method, it solves the conventional problems and at the same time has the following effects. .

(2) A thick thin film can be patterned with high dimensional accuracy without forming a thick resist for lift-off.

(2) Since the general techniques of etching and lift-off are used, no special equipment is required, and large-area substrates can be easily processed.

(2) Since the electrode patterns and the like previously formed on the base substrate are covered and protected by the lift-off resist, no damage occurs due to etching during pattern formation.

Furthermore, since the side surface of the cross-sectional shape of the patterned thin film is two-step, even if the insulating layer and upper layer wiring are thinner than the thickness of the patterned thin film, the step cover is good. A multilayer electrode wiring can be formed.

It has this effect.

[Brief explanation of drawings]

FIGS. 1(a) to 1(e) are cross-sectional views showing the pattern forming method of the present invention. FIGS. 2(a) to 2(i) are sectional views showing the manufacturing process of a multilayer electrode wiring according to an embodiment of the present invention. 3 and 4 are cross-sectional views showing a conventional forming method. 1.5... Substrate 2, 4.13.14... Photoresist 3, 12.15... Thin film 6... Electrode 7... Negative resist 8... Wiring 9... Photoresist lO...・Insulating layer 11...upper layer wiring tototo

Claims (1)

[Claims] (1) After forming the first resist pattern on the substrate,
A thin film is deposited, a second resist pattern whose negative and positive sides are reversed with respect to the first resist pattern is provided on the thin film, and the thin film is etched in the thickness direction to separate the first resist pattern and the second resist pattern. A pattern forming method comprising: causing side etching at the boundary to expose an end of the first resist pattern; and then removing the first resist pattern and the thin film on the first resist pattern.