JPS6355931A - Formation of electrode - Google Patents

Abstract

PURPOSE:To remove any chute on pattern or uneven contact part while preventing a metallic film from being disconnected by a method wherein an overhanged negative resist patterns are formed on an insulating film. CONSTITUTION:A thermal oxide film 2 is formed on a semiconductor substrate 1 to form overhanged resist patterns 6 thereon. First, the film 2 is etched to make a contact hole 4 until the substrate 1 is exposed and then Al films 5 are evaporated on the hole 4 and patterns 6 while maintaining the overhanged shape of patterns 6. Second, the patterns 6 are peeled off by ultrasonic wave cleaning process and then Al films 5 evaporated on the patterns 6 are removed to form a contact pattern with the hole 4 filled with the Al films 5. The patterns 6 are composed of naphthoquinonediazidesulphonic acid ester. Finally, an Al film 7 is formed on the buried Al films 5 and the film 2 to form a flat pattern with the hole 4 filled with a conductor.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for forming electrodes in semiconductor integrated circuits, and particularly to a method for forming flat and fine contact holes.

[Conventional technology]

The conventional method for forming electrodes in semiconductor integrated circuits is to form an insulating film on a semiconductor substrate, form a contact hole in a predetermined part of this insulating film, and form a metal film such as aluminum on top of the contact hole to connect the semiconductor substrate with the contact hole. electrical contact.

However, in the above method, as the contact hole becomes finer, a steep step occurs in the contact hole, and the upper metal film does not sufficiently cover the contact hole.
Problems such as disconnection occurred.

Further, since the device structure is not flat, problems arise such as difficulty in forming a non-turn upper layer.

In order to solve this further problem, for example,
A contact hole burying technique as shown in Japanese Patent No. 52130 has been proposed. This is shown in FIG. In this method, a thermal oxide film 2 is first deposited on a silicon substrate 1.
A resist pattern 3 is formed thereon, and a contact hole 4t is formed in the thermal oxide film 2 by etching using this resist pattern 3. This state is shown in FIG. 2 (1). Next, as shown in FIG. 2(2), a metal film, for example, an aluminum film 5, is deposited with the resist pattern 3 remaining, and then the resist pattern 3 is removed by lift-off, leaving the aluminum film 5 only in the contact hole 4. It is being removed.

[Problem that the invention seeks to solve]

However, in the method shown in FIG. 2, since the normally used positive resist pattern 3 is used, the edge angle of the resist pattern 3 is inclined at about 70 to 80 degrees, and the aluminum film is 5, as shown in II (2) K, the aluminum film 5 deposited on the resist pattern 3 and the aluminum film 5 deposited in the contact hole 4 are not separated, resulting in a connection portion 9. During the lift-off of resist pattern 3, the second
As shown in Figure (3), a residue 10 of the aluminum film was formed. For this reason, there were problems such as short-circuiting of the spear turn and failure of the contact portion to be flattened.

This invention eliminates pattern shorts and non-flat contact areas caused by metal film residues as described above, prevents pattern shorts, keeps contact areas flat, and prevents disconnection of gold (IA) film. It is an object of the present invention to provide an electrode forming method that does not cause the occurrence of

[Elaborate means to solve problems]

In an electrode forming method, the present invention includes forming a negative resist pattern having an overhang shape on an insulating film,
Using this resist pattern as a mask, a contact hole is opened, a metal film t'' is deposited inside the contact hole and on the resist pattern, and the resist pattern is removed so that the metal film remains only in the contact hole.

[Effect]

In this invention, since the resist pattern formed on the insulating film is a negative type, it has an overhang shape, and the resist pattern is formed on the insulating film. The pattern edge shape is expanded toward the insulating film side. Therefore, using this resist pattern as a mask, there is no connection between the metal film deposited in the contact hole made in the insulating film by etching and the metal film deposited on top of the resist pattern, and the resist pattern is removed. No residue is left on the metal film during the process. Furthermore, the contact portion is also flat.

〔Example〕

Embodiments of the present invention will be described below with reference to the drawings. First, as shown in FIG. 1(1), a thermal oxide film 2 having a thickness of 0.8 μm is formed on a semiconductor substrate 1, and an overbank-shaped resist pattern 6 is formed thereon. When forming this resist pattern 6, 30 wt% of naphthoquinonediazide sulfonic acid ester of Tumerac (LMR-UV) was added.
About 1 μm of the solution dissolved in metelcerone rugacetate is applied onto the thermal oxide film 2 by spin coating. Thereafter, baking was performed at 60° C. for 30 minutes, and exposure was performed at 60 mJ/c using a 1/10 reduction glozi extension aligner using N line (365 nm) as a light source.
Expose the pattern under the conditions of j. Then, at 100℃
After 0 minutes of shaking, use a mixture of 1 volume of monochlorobenzene and 0.15 volume of dichlorobenzene at 23°C.
Developing is performed for 50 seconds to form a resist pattern 6. At this time, since the negative resist has a high absorption coefficient,
The resist pattern 6 has an overhang shape expanding toward the thermal oxide film 2 side.

Next, as shown in FIG. 1(2), the thermal oxide film 2 is etched by reactive ion etching using a mixed gas of CtF* and CHFj to form a contact hole 4 and expose the silicon substrate 2. At this time, a part of the surface of the resist pattern 6 is etched and removed, but the overhang shape is maintained. Next, as shown in FIG. 1(3), an aluminum film 5 is deposited in the contact hole 4 and on the resist groove 6. At this time, since the resist pattern 6 is formed in an overhang shape, the aluminum film 5 embedded in the contact hole 4 and the aluminum film 5 deposited on the resist pattern 6 are separated. Next, as shown in Figure 1 (4),
Ultrasonic cleaning is performed using acetone, and the lettuce 9 turns 6 are peeled off. As a result, the aluminum film 5 deposited on the resist pattern 6 is also removed, and a contact pattern in which the contact hole 4 is filled with the aluminum film 5 is formed.

Next, as shown in FIG. 1(5), an aluminum film 7 is formed on the aluminum film 5 filled in the contact hole 4 and on the thermal oxide film 2. As a result, a flat pattern in which the contact holes 4 are filled with a conductor is formed.

〔Effect of the invention〕

As described above, according to the present invention, a contact hole is etched using a negative resist with a high absorption coefficient that allows an easy formation of an over-part ring shape, a metal film is deposited thereon, and the resist is removed by lift-off. After removing the pattern and the metal film deposited on it, since the resist pattern has an overhang shape, a connecting portion is created between the metal film deposited in the contact hole and the metal film deposited on the resist pattern. Since no metal film residue is generated during lift-off, /J? Short-circuiting of the turns does not occur, and a flat contact portion in which the metal film is embedded in the contact hole portion is formed.

Furthermore, since the contact portion is flattened, the shape of the metal film deposited on the contact portion is improved, and problems such as disconnection at steps are also improved. Also, because the surface is flat, there are fine particles! It becomes easier to form turns.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing the method of the present invention in order of steps, and FIG. 2 is a sectional view showing the conventional method in order of steps. DESCRIPTION OF SYMBOLS 1... Silicon substrate, 2... Thermal oxide film, 4... Contact hole, 5, 7... Aluminum film, 6...
・Resist pattern. 6: L Jinwoo L Ha 0 turn

Claims (2)

[Claims] (1) (a) Forming an insulating film on a semiconductor substrate;
(b) a step of forming a negative resist pattern having an overhang shape on the insulating film; (c) a step of etching the insulating film using this resist pattern as a mask to open a contact hole; (d) a contact An electrode forming method comprising the steps of: depositing a metal film in the hole and on the resist pattern; and (e) removing the resist pattern to leave only the metal film in the contact hole. (2) The method for forming an electrode according to claim 1, wherein a naphthoquinonediazide sulfonic acid ester of novolac is used as the negative resist pattern.