JPH08227850A - Forming method of conductive micro pattern - Google Patents

Abstract

PURPOSE: To obtain a precise conductive micro pattern by a method wherein a photoresist pattern which is large in exposure margin and of invertedly tapered shape possessed of a required tapering angle is prepared. CONSTITUTION: When a invertedly tapered photoresist pattern is formed on a substrate 1, dye-containing photoresist 2 is applied onto the substrate 1, exposed to light at a prescribed exposure, and developed into a photoresist pattern controlled in inverted tapering angle 7. Even if an applied photoresist film is varied in thickness, a photoresist pattern is capable of being controlled in tapered shape by controlling the photoresist film in exposure or in inverted tapering angle by controlling dye contained in the photoresist in amount, so that the photoresist of this constitution is capable of being very easily handled.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for forming a conductive fine pattern in which a photoresist on a substrate is patterned using a photomask and the conductive layer on the substrate is lifted off using the patterned photoresist as a mask. .

[0002]

2. Description of the Related Art Recently, when patterning on a submicron order in a photolithography process, a stepper is used to form a pattern and a conductive layer such as a gate electrode and a pad electrode is formed on a substrate, and then unnecessary. A lift-off method of removing a part is used. In order to form a fine pattern using this method, it is necessary that the stepper has an inversely tapered shape with respect to the substrate. At present, it is attempted to form an inverse taper using a positive photoresist. When a normal positive photoresist is used, as shown in FIGS. 6 and 7, the positive photoresist 3 is applied on the semiconductor substrate 1 such as Si or GaAs and pre-baked, and then, as shown in FIG. As shown in, the first exposure is performed using the photomask 4,
As shown in FIG. 6B, an exposed portion 5 having an inverse tapered shape is formed on the substrate. At this time, the exposed portion 5 (first exposed portion) having a reverse taper shape is a photoresist soluble in the alkali developing solution used. Then, the semiconductor substrate 1 is heat-treated at a temperature of 90 to 100 [deg.] C. to make the exposed portion 5 a photoresist which is insoluble in a developing solution such as alkali used. Next, as shown in FIG. 7A, the entire photoresist 3 is exposed (second exposure).

At this time, the exposed portion 5 remains as a photoresist insoluble in the developing solution, but the unexposed portion (second exposed portion) 6 in the first exposure is exposed and used as the developing solution. It is a soluble photoresist. After that, development and post-baking are performed using a developing solution such as a predetermined alkali, and the first as shown in FIG.
An inverse taper-shaped photoresist pattern is obtained for the substrate composed of the exposed portion 5. The method for forming the resist pattern is called a so-called image reverse method.
Semiconductor substrate 1 on which this photoresist pattern is formed
A conductive layer such as a metal is deposited on the entire surface including the photoresist pattern by vapor deposition or the like. Next, the photoresist pattern and the conductive layer on the photoresist pattern are removed by a lift-off method to form a conductive fine pattern having a predetermined shape on the semiconductor substrate 1.

[0004]

However, as can be seen from FIG. 5, in the conventional pattern formation using a positive photoresist, the exposure margin, which is the range of the exposure amount capable of forming the inverse taper, becomes small. However, there is a drawback in that the angle of the reverse taper shape of the photoresist can be only about 80 to 85 degrees. In the figure, a circle indicates a state where the reverse taper is formed in the photoresist pattern, and a cross (x) indicates a state where the reverse taper is not formed in the photoresist pattern. The numbers in the columns indicate the film thickness (μm) of the photoresist, and the numbers in the rows indicate the exposure amount (msec) in the exposure. For this reason, in the exposure of the photoresist for forming the reverse taper shape, the conditions regarding the exposure amount are strict, and it is difficult to form the reverse taper easily, so that the handling is troublesome. Further, since the angle of the reverse taper shape is about 80 to 85 degrees, there is a problem that it is difficult to cause step breakage of metal at the time of metal devoking to the resist side wall, and it is difficult to form a precise conductive fine pattern. The present invention has been made under such circumstances, and it is possible to obtain a reverse tapered photoresist pattern having a large exposure margin and a desired taper angle very easily. To provide a method of forming the.

[0005]

According to the present invention, in forming a reverse tapered photoresist pattern on a substrate, a dye-containing photoresist is applied and the photoresist is exposed with a predetermined exposure amount. It is characterized by developing and controlling the inverse taper angle of the photoresist pattern. The method for forming a conductive fine pattern of the present invention,
After forming a reverse tapered photoresist pattern on the substrate and forming a conductive layer on the substrate and the photoresist pattern, the lift-off method is used to remove the conductive layer on the photoresist pattern to remove the conductive layer on the substrate. In the method of forming a conductive fine pattern on a substrate, a step of applying a photoresist containing a dye onto a substrate, and exposing a predetermined portion of the photoresist to a first exposed portion having an inverse taper shape with respect to the substrate. After the step of forming, the step of heat-treating the photoresist to make the first exposed portion insoluble in the developing solution, and the step of making the first exposed portion insoluble in the developing solution, the photoresist is exposed. Forming a second exposed portion soluble in the developing solution in a region other than the first exposed portion; and removing the second exposed portion with the developing solution, the substrate Forming a reversely tapered photoresist pattern on the substrate, and forming a conductive layer on the substrate and the photoresist pattern in which a portion on the substrate and a portion on the photoresist pattern are separated from each other. And a step of removing the photoresist pattern from the substrate and removing the conductive layer on the photoresist pattern.

The photoresist may be a positive type, and the heat treatment of the photoresist may be performed in an ammonia atmosphere. An alkaline developer may be used as the developer. A metal may be used for the conductive layer.
The content of the dye is 1. of the total weight of the photoresist.
It may be 25% to 2.5%. In general, when a photoresist is exposed to light, diazonaphthoquinone in the photoresist becomes an indenecarboxylic acid by the exposure, and a decarboxylation reaction is caused by a subsequent heat treatment to make it insoluble in an alkali developing solution. When the amount of exposure is low, only the upper part of the resist is exposed and a decarboxylation reaction occurs, and most of the lower part remains the original photoresist,
Almost scraped off when performing alkali development,
The pattern may collapse. Further, when the exposure amount is large, the taper is not formed and the exposure is performed. By using the inverse tapered photoresist pattern obtained by the image reverse method of the present invention, a conductive fine pattern can be accurately formed.

In the case of the present invention, the progress of the exposure in the photoresist is delayed due to the light absorption effect of the dye in the photoresist containing the dye, so that the resist has a reverse taper shape only when a large amount of exposure is performed. Therefore, the taper will not be formed unless the amount is increased. Therefore, the reverse taper can be formed more easily than the conventional photoresist, and the above-mentioned exposure margin becomes large. And, even if the film thickness of the photoresist is changed, the shape of the taper can be controlled by adjusting the exposure amount, and by adjusting the amount of the dye in the photoresist, the angle of the reverse taper shape can be changed.
It is possible to provide a method for forming a conductive fine pattern that can be handled extremely easily.

[0008]

1 to 3 are process cross-sectional views for explaining a method for forming a conductive fine pattern on a semiconductor substrate showing an embodiment of the present invention. Hereinafter, an embodiment of the present invention will be described with reference to FIGS. 1 to 3. First, as shown in FIG. 1A, a positive photoresist 2 containing a dye is applied on a semiconductor substrate 1 to a thickness of about 1 μm to 3 μm, and heat-treated at a temperature of about 100 ° C. (bribake) in a dry atmosphere. ) Do. Then, a photomask 4 is arranged above the prebaked photoresist 2, and the photoresist 2 is exposed through this. A portion of the photomask 4 which is not shielded from light is exposed. This exposed portion (first
The exposed portion 5) has a reverse taper shape as shown in FIG. The taper angle of the first exposed portion 5 is smaller than the taper angle 7 of the reverse taper that occurs when the conventional photoresist shown in FIG. 7 is exposed. This is because the dye contained in the photoresist 2 absorbs the irradiated light, and this light is absorbed by the photoresist 2.
This is because the amount of light decreases and the taper angle increases as it travels inside. The photoresist 2 at this point is the first
And an unexposed portion 6 in the other area.

Since the dye in the photoresist 2 has a light absorbing effect, the exposure amount is 330 msec, which is larger than the conventional exposure amount.
This is all you need to do. After that, a heat treatment is performed at 90 ° C. to 100 ° C. in an ammonia gas atmosphere, so that
As shown in (c), the first exposed portion 5 changes into a photoresist 50 insoluble in the alkali developing solution. This is because by heat treatment, the indene carboxylic acid, in which the diazonaphthoquinone in the first exposed portion 5 has been changed by the exposure of the photoresist, undergoes a decarboxylation reaction with ammonia and changes into indene which is insoluble in the alkali developing solution. Because there is. The ammonia may be contained in the photoresist in advance. Further, if the first exposed portion becomes insoluble in the alkali developing solution, it is not necessary to limit it to ammonia. Next, as shown in FIG. 2A, the entire photoresist 2 is exposed. The photoresist 50 is not changed by the exposure, and the unexposed portion 6 is exposed and is changed to the second exposed portion which is soluble in the alkali developing solution. Next, FIG. 2 (b)
As shown in FIG. 3, the second exposed portion 6 is dissolved and removed by developing with an alkali developing solution. Then, the remaining photoresist 50 having the reverse taper shape and insoluble in the developer is
Heat treatment (post-baking) is performed at around 0 ° C. In this way, the resist 50 having an inverse taper shape having a predetermined taper angle and insoluble in the developing solution is easily formed by the image reverse method.

Next, as shown in FIG. 2C, the entire surface of the semiconductor substrate 1 on which the photoresist 50 insoluble in the developing solution is formed, including the photoresist 50 insoluble in the developing solution, is metal. A conductive layer 8 such as. Conductive layer 8 on semiconductor substrate 1 and photoresist 50 insoluble in developer
The upper conductive layer 8 is clearly separated by the presence of a sufficient taper of the photoresist 50 which is insoluble in the developer. Next, the photoresist 50 insoluble in the developer and the conductive layer 8 thereon are removed by a lift-off method to form a conductive fine pattern 9 having a predetermined shape to be used for wiring on the semiconductor substrate 1 (FIG. 3). Further, FIG. 4 shows whether or not an inverse taper can be formed between the photoresist film thicknesses of 1.19 and 2.40 μm in the present invention. As is clear from FIG. 4, the exposure margin, which is the range of the exposure amount capable of forming the inverse taper shape, has a photoresist film thickness of 1.76 μm.
When m is 230 msec or more. Similar to FIG. 5, the circles shown in this figure indicate that an inverse taper having a desired shape is formed, and the cross (x) marks indicate that the photoresist cannot be inversely taper. There is. The numbers in the columns indicate the film thickness (μm) of the photoresist, and the numbers in the rows indicate the exposure amount (msec) in the exposure. The case where the reverse taper cannot be performed means a phenomenon that a required taper angle cannot be obtained or the taper is advanced too much and the photoresist collapses.

On the other hand, when the conventional positive photoresist is used, the exposure margin for forming the reverse taper shape is
As shown in FIG. 5, the photoresist film thickness is 1.75 μ.
Since m is 60 msec, the reverse taper can be formed very easily by using the photoresist 2 containing the dye as in the present invention. Regarding the angle 7 of the reverse taper shape of the photoresist shown in FIG. 2B, when the conventional positive photoresist is used, the angle is 80 to 85 degrees, but the positive polarity containing the dye of the present invention is used. If a photoresist of a type is used, the temperature can be set to 80 degrees or less, and it is possible to surely cause breakage of the conductive layer when the conductive layer such as metal is deposited on the side wall of the resist. Then, the taper angle 7 of the photoresist can be controlled by changing the amount of the dye in the photoresist 2. For example, in the case of containing 2.5% of dye, the taper angle 7 is 65 degrees to 7 degrees.
It can be set in the range of 5 degrees, and in the case of containing 1.25%, it can be set in the range of 70 degrees to 80 degrees.

[0012]

As described above, when a photoresist pattern having an inverse taper shape is formed on a substrate by using a mask, a dye is added to the photoresist so that the exposure margin is large and a predetermined taper can be formed very easily. Since it is possible to obtain a photoresist pattern having an inverse taper angle, in the lift-off method using this photoresist pattern, disconnection of the conductive layer when depositing a conductive layer such as metal on the photoresist sidewall can be surely performed. It is possible to wake it up.

[Brief description of drawings]

FIG. 1 is a partial cross-sectional view showing a step of a method for forming a conductive fine pattern of the present invention.

FIG. 2 is a partial cross-sectional view showing the steps of a method for forming a conductive fine pattern of the present invention.

FIG. 3 is a partial cross-sectional view showing the steps of the method for forming a conductive fine pattern of the present invention.

FIG. 4 is a diagram showing whether or not a reverse taper of the conductive fine pattern of the present invention can be formed.

FIG. 5 is a view showing whether or not a reverse taper of a conventional conductive fine pattern can be formed.

FIG. 6 is a partial cross-sectional view showing the steps of a conventional method for forming a conductive fine pattern.

FIG. 7 is a partial cross-sectional view showing the steps of a conventional method for forming a conductive fine pattern.

[Explanation of symbols]

1 ... Semiconductor substrate, 2 ... Positive photoresist containing dye, 3 ... Positive photoresist, 4.
.. Photomask, 5 ... Photoresist exposed portion (first exposed portion), 6 ... Photoresist unexposed portion (second exposed portion), 7 ... Taper angle, ... Conductive layer, 9 ... Conductive fine pattern, 50 ... Photoresist insoluble in developer.

Continuation of the front page (51) Int.Cl. ⁶ Identification code Office reference number FI Technical display location H01L 21/306 H01L 21/30 502G 21/306 Q

Claims (5)

[Claims] 1. A reverse tapered photoresist pattern is formed on a substrate, a conductive layer is formed on the substrate and the photoresist pattern, and a conductive layer on the photoresist pattern is formed by a lift-off method. In the method of removing and forming a conductive fine pattern on the substrate, a step of applying a photoresist containing a dye on the substrate, exposing a predetermined portion of the photoresist to an inverse taper shape The step of forming the first exposed portion, the step of heat-treating the photoresist to make the first exposed portion insoluble in a developing solution, and the step of making the first insoluble portion insoluble in the developing solution; Exposing the resist to form a second exposed portion soluble in the developing solution in a region other than the first exposed portion; and forming the second exposed portion with the developing solution. A step of removing and forming the inversely tapered photoresist pattern on the substrate; and a part of the substrate on which the photoresist pattern is separated from the part of the photoresist pattern on the substrate and the photoresist pattern. A method of forming a conductive fine pattern, comprising: a step of forming a layer; and a step of removing the photoresist pattern from the substrate and removing the conductive layer on the photoresist pattern. 2. The method for forming a conductive fine pattern according to claim 1, wherein the photoresist is a positive type, and the heat treatment of the photoresist is performed in an ammonia atmosphere. 3. The method for forming a conductive fine pattern according to claim 1, wherein the developing solution is an alkaline solution. 4. The method for forming a conductive fine pattern according to claim 1, wherein the conductive layer is made of metal. 5. The conductive fine pattern as claimed in claim 1, wherein the content of the dye is 1.25% to 2.5% of the total weight of the photoresist. Forming method.