JPH03236216A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To improve throughput, to achieve cost reduction and to improve reliability by making it possible to perform several times of resist patternings in one resist applying step. CONSTITUTION:An ohmic electrode 2 and an oxide film 3 are formed on a semiconductor substrate 1. A positive-type photoresist layer 4 is applied. First exposure is performed at a part which does not become, e.g. a resist opening part 7 for forming wirings and pad electrodes through a mask 6. The device is heated in an ammonium atmosphere, and an alkali-insoluble layer is formed. Then, second exposure is performed at a part which is to become, e.g. a resist opening part 12 for forming a through hole through a mask 11. The layer is transformed into an alkali-developer soluble layer. After development, etching is performed, and a through hole 13 is formed. Then, the entire surface is exposed, and the part which is not exposed is transformed into an alkali-soluble layer. Development is performed, and the resist opening part 7 is formed. Then a metal layer 14 is formed on the entire surface by the vapor deposition. Lift-off is performed, and wirings and pad electrodes 14' are formed. When the image- inverting type photoresist containing amine-based compound is used, the exposed part becomes insoluble to alkali by the heating in atmosphere.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Field of Application) The present invention relates to a method for manufacturing a semiconductor device, and in particular to a method for producing a semiconductor device using a positive
This invention relates to an image reversal method that allows a negative inverted image to be obtained.

(Prior Art) Recently, patterns in lithography technology have become finer, and research and development are being conducted from various aspects.

Furthermore, as a method for forming electrodes, a lift-off method is used mainly in fields such as compound semiconductors.

This lift-off method requires an overhang or a reverse taper as the shape of the resist.

An image reversal method is sometimes used as one method for stably obtaining this reverse tapered resist shape.

Here, when forming through holes, wiring, pad electrodes, etc. on a semiconductor substrate in sequence, the conventional image reverse method is used to easily obtain a reverse tapered resist shape, especially when forming wiring and pad electrodes. The steps in this case will be explained with reference to FIGS. 2(a) to (1).

First, as shown in FIG. 2(a), after selectively forming an ohmic electrode 22 on a semiconductor substrate 21, an oxide film 23 serving as an insulating film is coated, and a BON-type photoresist layer 24 is placed on top of the oxide film 23. Apply and pre-bake. Next, Figure 2 (b
), using an aligner using ultraviolet light as a light source 25, the photoresist layer 2 is exposed through a mask 26.
A portion corresponding to the planned through hole formation position of No. 4 is selectively exposed. Next, a development process is performed to form a resist opening 27 for forming a through hole, as shown in FIG. 2(c). Next, an etching process is performed using the resist pattern as a mask, and the oxide film 23 is selectively removed to form a through hole 28 as shown in FIG. 2Cd). As shown, the photoresist layer 24 is stripped.

Next, wiring and pad electrodes are formed by an image reverse method.

That is, as shown in FIG. 2(f), a positive photoresist layer 30 is coated on the entire surface of the semiconductor substrate, and as shown in FIG. 2(g)
As shown in FIG.
using the photoresist layer 30 through the mask 31.
selectively exposes a predetermined position. As a result, in the exposed area 30a, diazonaphthoquinone, which is a photosensitizer contained in the photoresist, changes to indenecarboxylic acid which is soluble in an alkaline developer, and the photoresist layer 30 is separated from the exposed area 30a and the unexposed area. 30b.

Next, as shown in FIG. 2(h), the semiconductor substrate is heat-treated (image reversal bake) in an atmosphere 33 containing ammonia inside an oven 32 to cause a decarboxylation reaction, thereby causing a decarboxylation reaction in the exposed area 30a. Carbon dioxide 34 is released from the alkali developer to form an alkali-insoluble layer (indene) 30C that is insoluble in an alkaline developer. Next, Figure 2 (i
), the entire surface of the semiconductor substrate is exposed to light using an exposure device using ultraviolet light or the like as a light source 25.

As a result, in the unexposed area 30b, diazonaphthoquinone, which is a photosensitizer contained in the photoresist, changes to alkali-soluble indenecarboxylic acid. Next, a development process is performed to form resist openings 35 for forming wiring and pad electrodes, as shown in FIG. 2(j), and post-baking is performed. Next, as shown in Figure 2(k),
A metal layer 36 is deposited over the entire surface of the semiconductor substrate. Next, the second
As shown in FIG. 1, a lift-off is performed using an organic solvent to form wiring and pad electrodes 36'.

By the way, in the selective exposure step shown in FIG. 2(g), if misalignment of the mask 31 with respect to the through-hole 28 occurs as shown in FIG. 3(a), the second
When the lift-off shown in Figure (1) is performed, the wiring and pad electrodes 36' are formed at positions shifted from the desired positions, as shown in Figure 3 (b), and an unnecessary gap 37 is created. Put it away.

(Problem to be Solved by the Invention) However, the semiconductor device manufacturing method using the conventional image reverse method as described above requires more steps such as full-surface exposure and heat treatment than when using normal phosphorography technology. There is a problem that this increases the amount of data, which adversely affects throughput and cost.

Furthermore, when forming upper-layer wiring and pad electrodes after forming through-holes, if mask alignment with the through-holes is misaligned, the wiring and pad electrodes will be formed at positions shifted from the desired positions, resulting in unnecessary gaps. There is a problem in that the yield and reliability are lowered.

The present invention has been made in order to solve the above-mentioned problems, and its purpose is to reduce the number of resist coating steps multiple times in order to form through holes, wiring, pad electrodes, etc. on a semiconductor substrate. It is an object of the present invention to provide a method for manufacturing a semiconductor device that enables resist patterning, improves throughput, reduces costs, and improves yield and reliability.

[Structure of the Invention] (Means for Solving the Problems) A method for manufacturing a semiconductor device of the present invention includes forming a positive photoresist layer or an image reversal type photoresist layer containing an amine compound on a semiconductor substrate. a first exposure step of exposing a predetermined position of the photoresist layer, and heating the positive photoresist layer in an atmosphere containing ammonia, or reversing the image in the atmosphere. A step of heat-treating the photoresist layer of the mold to form an alkali-insoluble area in the exposed area by the first exposure process, and an exposure/development process for the unexposed area other than the exposed area are divided into multiple times. and forming a desired resist pattern by repeating the process.

(Function) The selective exposure in the image reverse method is divided into multiple times, and the second and subsequent exposure and development processes are repeated, so -
It is possible to perform resist patterning multiple times for one resist coating process. Therefore, compared to the case of adopting the conventional image reverse method, the process can be shortened, throughput can be improved, and costs can be reduced.In addition, during the first selective exposure process, resist for through-holes is placed in the unexposed area. By including both the opening and the area of the resist opening for forming wiring/pad electrodes, when forming upper layer wiring, pad electrodes, etc. after forming the through-hole, there will be no misalignment of the mask with respect to the through-hole. This eliminates the possibility that the wiring, pad electrodes, etc. formed according to the resist patterning will be displaced from desired positions, thereby improving yield and reliability.

(Example) Hereinafter, an example of the present invention will be described in detail with reference to the drawings.

FIGS. 1(a) to 1(j) show steps when an image reverse method according to an embodiment of the present invention is employed when forming through holes, wiring, and pad electrodes on a semiconductor substrate.

First, as shown in FIG. 1(a), after selectively forming an ohmic electrode 2 on a semiconductor substrate 1, an oxide film 3 serving as an insulating film is coated, and a positive photoresist (e.g. Nagashio Sangyo (trade name: NPR820DX) layer 4 is applied and prebaked. Next, as shown in Figure 1(b),
Using an aligner (for example, a stepper) that uses ultraviolet light as a light source 5, the photoresist layer 4 is exposed through a mask 6.
A predetermined position (in this example, a portion that will not ultimately become the resist opening 7 for forming wiring/pad electrodes) is selectively exposed. By this first selective exposure, the exposed portion 4a
In , diazonaphthoquinone, a photosensitizer contained in the photoresist, changes to indenecarboxylic acid soluble in an alkaline developer, and the photoresist layer 4 is divided into an exposed area 4a and an unexposed area 4b. Ru. Next, as shown in FIG. 1C, the semiconductor substrate is heat-treated (image reversal bake) in an atmosphere 9 containing ammonia inside an oven 8 to cause a decarboxylation reaction, thereby causing a decarboxylation reaction in the exposed areas 4a. Carbon dioxide 10 is released from the solution to form an alkali-insoluble layer (indene) that is insoluble in an alkaline developer.

Next, as shown in FIG. 1(d), ultraviolet rays are emitted from the light source 5.
Using an aligner, a predetermined position of the photoresist layer 4 (in this example, a portion that will become a resist opening 12 for forming a through hole) is selectively exposed through a mask 11. By this second selective exposure, a part of the unexposed area 4b is changed into indenecarboxylic acid which is soluble in an alkaline developer. Next, perform the first development process,
As shown in FIG. 1(e), resist openings 12 for forming through holes are formed. Next, an etching process is performed using the resist pattern as a mask, and as shown in FIG. 1(f), the oxide film 3 is selectively removed to form a through hole 13. Next, as shown in Figure 1(g),
The entire surface of the semiconductor substrate is exposed to light using an exposure device using a light source 5 such as ultraviolet light. As a result, in the parts of the resist that were not exposed in the first selective exposure and the second selective exposure, diazonaphthoquinone, a photosensitizer contained in the photoresist, is replaced by alkali-soluble indenecarboxylic acid. Changes to

Next, a second development process is performed, and as shown in FIG. 1(h), resist openings 7 for forming wiring and pad electrodes are formed, and post-baking is performed. Next, as shown in FIG. 1(i), a metal layer 14 is deposited over the entire surface of the semiconductor substrate.

Next, as shown in FIG. 1(j), lift-off is performed using an organic solvent to form wiring and pad electrodes 14'.

According to the manufacturing method of the above embodiment, the selective exposure in the image rinse method is divided into two, and the second and subsequent exposures are
By repeating the development process twice, it is possible to perform resist buttering twice in one resist coating process. Therefore, compared to the case of employing the conventional image reversal method, the process can be shortened, throughput can be improved, and costs can be reduced. In addition, during the first selective exposure process, the unexposed portion 4b includes both the resist opening 12 for through-hole formation and the resist opening 7 for wiring/pad electrode formation, so that after the through-hole 13 is formed, Upper layer wiring and pad electrode 14'
When forming the mask 11 for the through hole 13
There is almost no misalignment, and there is no risk that the wiring and pad electrode 14' formed according to the resist patterning will be displaced from the desired position.
Yield and reliability improve.

Note that in the above embodiment, the present invention is applied to the process of forming through holes, wiring, and pad electrodes on a semiconductor substrate, but even when the present invention is applied to the process of forming other electrodes, Similar to the embodiments described above, effects such as shortening of the process and improvement of mask alignment accuracy can be obtained. In addition, in the above embodiment, the selective exposure was divided into two times, but the selective exposure was divided into three times.
Even when the resist patterning is divided into more than one time, resist patterning can be performed multiple times for one resist coating process according to the above embodiment.

Further, as another embodiment of the present invention, when an image reversal type photoresist containing an amine compound such as imidazole (for example, product name AZ5214E of Hoechst Co., Ltd., USA) is used as the photoresist 4, an ammonia atmosphere as described above may be used. The first exposed portion 4a becomes insoluble in alkali by heat treatment in the normal atmosphere rather than heat treatment in the atmosphere, and the other steps may remain the same as in the previous embodiment.

It goes without saying that the present invention is applicable not only to the manufacture of discrete semiconductor devices but also to the manufacture of semiconductor integrated circuits.

[Effects of the Invention] As described above, according to the method for manufacturing a semiconductor device of the present invention, when forming through-holes, wiring, pad electrodes, etc. on a semiconductor substrate, it is necessary to apply the resist multiple times for -degrees of resist coating process. This is a groundbreaking method in lithography technology that enables resist patterning, and it is possible to improve throughput, reduce costs, and improve yield and reliability.

[Brief explanation of drawings]

FIGS. 1(a) to (j) are cross-sectional views showing a semiconductor substrate at each step according to an embodiment of the method for manufacturing a semiconductor device of the present invention, and FIGS. 2(a) to (1) are cross-sectional views of a semiconductor substrate of a conventional semiconductor device. FIG.
a) is a cross-sectional view showing a state in which mask misalignment with respect to the through hole has occurred in the selective exposure step of FIG. 2(g), and FIG. 3(b) is a cross-sectional view showing the wiring and wiring formed after the step of FIG. FIG. 3 is a cross-sectional view showing how a pad electrode is deviated from a desired position. 1... Semiconductor substrate, 2... Ohmic electrode, 3...
- Oxide film, 4... Photoresist, 4a... Exposed area, 4b... Unexposed area, 5... Light source, 6.11... Mask, 7... Resist for wiring/pad electrode formation Opening, 8... Oven, 9... Atmosphere containing ammonia, 10... Carbon dioxide, 12... Resist opening for through hole formation, 1 3... Through hole, metal layer, 14 ′...Wiring and ballad electrode.

Claims (2)

[Claims] (1) A step of applying a positive photoresist layer on a semiconductor substrate, a first exposure step of exposing a predetermined position of the photoresist layer, and heating the photoresist layer in an atmosphere containing ammonia. By repeating the process of forming an alkali-insoluble area in the exposed area in the first exposure process, and the exposure/developing process for the unexposed area other than the exposed area in multiple steps, the desired result is obtained. 1. A method of manufacturing a semiconductor device, comprising the step of forming a resist pattern. (2) a step of applying an image reversal type photoresist layer containing an amine compound on a semiconductor substrate; a first exposure step of exposing a predetermined position of the photoresist layer; and a step of exposing the photoresist layer to light in the atmosphere. The layer is heat treated and the first layer is heated.
A process of forming an alkali-insoluble area in the exposed area by the second exposure process, and a process of forming a desired resist pattern by repeating the exposure and development process in multiple times on the unexposed area other than the exposed area. A method for manufacturing a semiconductor device, comprising: