JPH0465827A - Manufacturing of semiconductor device - Google Patents

Abstract

PURPOSE:To control an increase of contact resistance and lowering of reliability of contact by forming a conductive film to be connected electrically with the surface of a conductive base substance, after making smooth the edge of a contact hole due to application of sputter etching to a protective film and an insulating film, and making the bottom of the contact hole exposed due to removal of the protective film. CONSTITUTION:APSG film 2 as an insulating film is grown on an aluminum (Al) wiring 1 as a base conductor, and a contact hole 3 is opened by using a resist film as a mask. Then, the resist film 5 is removed, and a positive-type resist 4, which is familiar with semiconductor process, is adhered. Next, sputter etching is applied, and the corner of shoulder part of the contact hole are made round. When a desired taper is obtained, the resist 4 is removed, and an aluminum wiring 6 is formed as the upper wiring to over the contact hole. The Spin- on-Glass(SOG) may be used as a protective film.

Description

DETAILED DESCRIPTION OF THE INVENTION [Summary] This invention relates to a method of forming a contact hole in an insulating film deposited on a substrate.

The object of the present invention is to provide a method that suppresses an increase in contact resistance and a decrease in contact reliability when tapering a contact hole using a sputter etching method.

1) Spinning a flowable material onto the conductive base on which an insulating film having a contact hole is coated so as to cover at least the surface of the conductive base exposed at the bottom of the contact hole; 2) Next, solidifying the flowable material to form a protective film having a thickness thinner at the edge of the contact hole than at the bottom of the contact hole, and sputter etching the protective film and the insulating film. a step of smoothing the edge of the contact hole; a step of removing the protective film to expose the bottom of the contact hole; and electrically connecting the surface of the conductive substrate exposed at the bottom of the contact. The method is configured to include a step of forming a conductive film in the contact hole.

2) The protective film is made of resin.

3) The protective film is made of spin-on glass (SOG).

[Industrial application field]

The present invention relates to a method of manufacturing a semiconductor device, and more particularly to a method of forming a contact hole in an insulating film deposited on a substrate.

In recent years, as semiconductor devices have become more highly integrated, contact holes have also become finer, and it has become necessary to form tapers attached to contact holes with good reproducibility in order to improve single-step coverage.

The present invention can be used as a method that meets this requirement.

[Prior art] Conventional techniques that are usually used to improve the shape of contact holes (Taber formation) include (1) isotropic etching followed by anisotropic etching; (2) absolute amorphous film and resist mask; A resist retreat method that creates a taber by reducing the selectivity ratio between etching and retreating the resist as etching progresses.

(3) There is a devoteber method that increases the amount of deposits formed on the etched side surface during etching to create a taper, but this technique cannot be used in mass production processes because the reproducibility of the taper shape is poor.

Therefore, recently, ordinary reactive ion etching (RIE)
) method, the shoulder of the opening of the contact hole is rounded by anisotropic processing using a resist mask and then sputter etching with an inert gas (e.g. Ar) plasma. It's starting to look like this.

In this method, the condition of the equipment performing sputter etching is thick (as long as the condition does not change, the same taper can be obtained even with contact holes of different sizes.

This technology is becoming a technology that can actually be used.

However, increasing the sputter etching to create a sufficient taper improves the one-step coverage, but this results in problems such as alteration of the contact surface, increasing contact resistance, and further reducing contact reliability. There is.

[Problem to be solved by the invention]

SUMMARY OF THE INVENTION An object of the present invention is to provide a method that suppresses an increase in contact resistance and a decrease in contact reliability when tapering a contact hole using a sputter etching method.

[Means to solve the problem]

The solution to the above problem is to apply a flowable material onto the conductive substrate on which an insulating film having a contact hole is attached, so as to cover at least the surface of the conductive substrate exposed at the bottom of the contact hole. spinning and then solidifying the flowable material to form a protective film that is thinner at the edge of the contour foot hole than at the bottom of the contact hole; A step of sputter-etching the film to smooth the edge of the contact hole, a step of removing the protective film to expose the bottom of the contact hole, and a step of forming an electrical contact with the surface of the conductive substrate exposed at the bottom of the contact. This is achieved by a method for manufacturing a semiconductor device, which comprises the step of forming a conductive film in the contact hole so as to connect to the contact hole.

The protective film is made of resin, and spin-on glass (SO
G).

[Effect]

FIGS. 1(a) to 1(d) are diagrams explaining the principle of the present invention.

In FIG. 1(a), aluminum (AI) wiring [or silicon (Si) substrate itself] 1 is used as the underlying conductor.
A phosphosilicate glass (PSG) film 2 is grown as an insulating film thereon, and a contact hole 3 is opened by anisotropic etching.

FIG. 1(b) shows a conventional example. If sputter etching is performed as is after opening, the AI (or Si) surface of the contact surface will be oxidized and lose its conductivity as the amount of sputter etching increases.

Therefore, the method shown in FIG. 1 (CL(d)) according to the present invention is adopted.

In FIG. 1C, before sputter etching, a protective film 4 made of a material that is easy to remove, such as resin, and does not alter the contact surface during removal, is filled into the contact hole.

In FIG. 1(d), sputter etching is performed to take the corners of the shoulders of the contact holes.

After the desired taper is formed, the resist 4 is removed.

In this case, since the contact surface is covered with resist, no deterioration of the contact surface due to sputter etching occurs.

In this case, care must be taken when the amount of resist covering the contact surface is too small.

Since there is a phenomenon in which the resist is implanted from the contact surface, it is necessary to adjust the thickness of the resist depending on the amount of sputter etching.

[Embodiment] FIGS. 2(a) to 2(d) are cross-sectional views illustrating an embodiment of the present invention.

In FIG. 2(a), a PSG film 2 with a thickness of 1 μm is grown as an insulating film on the AI wiring 1 as a base conductor,
Contact hole 3 is opened by RIE using resist film 5 as a mask.

Reactant gas: CHF, 100 SCC Cl
I4 100 SCCM Gas pressure crab 0.3-0.4 TorrRF frequency: 13.56 MHzRF Electric crab 80
0W time: 180 sec Then, the resist film 5 is removed.

In FIG. 2(b), a positive resist (
Tokyo Ohka Kano PR-800, viscosity 80 cp) was applied so that the thickness at the flat part was 5000 g.

Here, as the resin for the protective film, a resist, which is familiar to semiconductor processes, was used.

In FIG. 2(C), sputter etching is performed.

Take the corner of the shoulder of the contact hole.

The conditions for sputter etching are as follows.

Equipment: RIE equipment gas: Ar gas pressure crab Q, l Torr RF frequency: 13.56 Hz RF electric crab 700W lQQ SCCM Under these conditions, the corner sputtering rate was 500 sputtering/m1n (in the direction of film thickness), The time in the example is 90 to 120 seconds
ec◇ Once the desired taper is formed, the resist 4 is removed.

The conditions for resist removal are as follows.

Equipment: Barrel type ashing device Gas: Ar 101005CC
□ 100 SCCM Gas Pressure Crab l Torr μ Electric Crab 600W Time: 5 min If spin-on glass (SOG) is used as a protective film, remove the SOG film by etching with 5% liver for 1 minute.

In FIG. 2(d), an At wiring 6 is formed as an upper layer wiring so as to cover the contact hole whose opening is tapered.

As shown in the figure, due to the presence of the taper, the step coverage of the At wiring 6 is good.

〔Effect of the invention〕

As explained above, according to the present invention, a method has been obtained in which an increase in contact resistance and a decrease in contact reliability are suppressed when tapering a contact hole using a sputter etching method.

As a result, it has become possible to contribute to the miniaturization of semiconductor devices.

It is a front view.

In fig.

l is the underlying conductor and At wiring.

2 is an insulating film, which is a PSG film.

3 is a contact hole.

4 is a protective film and a resist film 5 is a resist mask.

6 is upper layer wiring and At wiring It is.

Claims (1)

[Scope of Claims] 1) A conductive substrate is coated with an insulating film having a contact hole on its surface, and a fluid material is applied to the conductive substrate so as to cover at least the surface of the conductive substrate exposed at the bottom of the contact hole. and then solidifying the flowable material to form a protective film that is thinner at the edge of the contact hole than at the bottom of the contact hole; a step of sputter etching the insulating film to smooth the edge of the contact hole; a step of removing the protective film to expose the bottom of the contact hole; and a step of removing the surface of the conductive substrate exposed at the bottom of the contact. A method of manufacturing a semiconductor device, comprising the step of forming a conductive film in the contact hole so as to be electrically connected to the contact hole. 2) The method of manufacturing a semiconductor device according to claim 1, wherein the protective film is made of resin. 3) The method of manufacturing a semiconductor device according to claim 1, wherein the protective film is made of spin-on glass (SOG).