JPH036814A - Method for forming contact hole of semiconductor device - Google Patents

Abstract

PURPOSE:To reduce an aspect ratio of a contact hole, to improve coverage of metal wirings and to prevent halation by removing only an upper half to the vicinity of the surface of a semiconductor substrate in the thicknesswise direction of an insulating film, removing its lower half simultaneously with the side along the upper half of the film, forming a contact hole of a two-stage configuration, and removing the stepwise corner in the hole. CONSTITUTION:A resist film 3 formed on an insulating film 2 covering a semiconductor substrate 1 is patterned, and a pattern 10 for a first contact hole is formed. An anisotropic dry etching is conducted through the pattern 10, and a recess 11 is formed. A second anisotropic dry etching is executed through a second contact hole pattern 12 wider than the hole 10, the side of the recess 11 is removed, a wide recess 13 is formed, the film 2 in the bottom of the recess 11 is removed to form a recess 14. Then, the recess 13 and the recess 14 are continuously formed, isotropic wet etching is conducted through the pattern 12, the stepwise corner 16 in a contact hole 15 is removed, the film 3 is then removed. Since the corner is removed, an aspect ratio is reduced, and coverage of metal wirings is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for forming contact holes in a semiconductor device.

[Conventional technology]

Conventionally, in forming contact holes in semiconductor devices, methods such as those shown in process cross-sectional views in FIGS. 2(a) to 2(d) have been adopted.

That is, in this conventional method, first, as shown in FIG. 2(a), the resist film 3 formed on the surface of the insulating wave WA2 covering the semiconductor substrate 1 is patterned to form a contact hole pattern 4. do. Then, by performing isotropic wet etching through this contact hole pattern 4, the upper half of the insulating film 2 along the thickness direction is removed, and the side surface is removed as shown in FIG. 2(b). A recessed portion 5 extending to the lower side of the resist covering wj 43 is formed.

Next, by performing anisotropic dry etching through the contact hole pattern 4, the lower half of the insulating film 2 located below the bottom surface of the recess 5 is removed, as shown in FIG.
), a recess 6 having a narrower width than the recess 5 is formed. Therefore, these two consecutively formed concave portions 5.6
As a result, a contact hole 7 having a depth extending from the surface of the insulating film 2 to the surface of the semiconductor substrate 1 is formed. Thereafter, as shown in FIG. 2(d), the resist film 3 is removed from the surface of the insulating film 2 in which the contact hole 7 is formed.

In the metal wiring forming step (not shown) following this contact hole forming step, a metal layer and a resist film are formed on the insulating film 2 from which the resist film 3 has been removed, and this resist film is After patterning to form a wiring pattern, etching is performed through this wiring pattern to form metal wiring having a predetermined line width.

(Problems to be Solved by the Invention) By the way, in the conventional method described above, since the recess 5 that becomes the contact hole 7 is formed by isotropic wet etching, the depth of the recess 5 cannot be made very deep.
As a result of the increased aspect ratio of contact hole 7,
When forming a metal layer on the insulating film 2 in the metal wiring forming process, there has been a problem in that the coverage of the side and bottom surfaces of the contact hole 7 is poor. Furthermore, since the corner portion 8 is formed between the recess 5 and the recess 6 constituting the contact hole 7, halation of the metal wiring is likely to occur, leading to disconnection.

It is an object of the present invention to provide a method for forming contact holes in a semiconductor device that can prevent such inconveniences from occurring.

[Means to solve the problem]

A method for forming a contact hole in a semiconductor device according to the present invention includes the steps of patterning a resist film formed on an insulating film covering a surface of a semiconductor substrate to form a first contact hole pattern; removing only the upper half of the insulating film along the thickness direction close to the surface of the semiconductor substrate by a first anisotropic dry etching performed through the hole pattern;
The resist film is patterned again to form a wider second contact hole pattern, and a second anisotropic dry etching is performed through the second contact hole pattern to remove the insulation. removing the side portion along the upper half of the magnetic coating and simultaneously removing the lower half thereof to form a two-stage contact hole; and isotropic processing performed through the second contact hole pattern. The method is characterized in that it includes a step of removing the step corner portion in the contact hole by wet etching.

[Effect]

According to the above method, a two-step contact hole having a step is formed near the surface of a semiconductor substrate by two times of anisotropic dry etching and etching, and a step corner in the contact hole is formed by isotropic wet etching. Since the metal wiring is removed, its aspect ratio becomes smaller, which improves the coverage of the metal wiring, and reduces the chance of halation occurring in the metal wiring.

〔Example〕

Embodiments of the present invention will be described below based on the drawings.

FIGS. 1(a) to 1(f) are process cross-sectional views showing step by step a method for forming contact holes in semiconductor IT. In addition,
In FIGS. 1(a) to <f>, parts and portions that are the same as or corresponding to those in FIGS. 2(a) to (d) showing the conventional method described above are given the same reference numerals.

In this method, first, as shown in FIG. 1(a), a resist film Wj3 formed on an insulating film 2 covering a semiconductor substrate 1 is patterned to form a first contact hole pattern 10. .

Then, by performing the first anisotropic dry etching through this first contact hole pattern 10, only the upper half along the thickness direction of the insulating film 2 is removed, as shown in FIG. ) is formed. At this time, it is desirable to control the anisotropic dry etching so that the depth of the recess 11 to be formed is about 1/2 to 2/3 of the thickness of the insulating film 2.

Next, the resist film 3 is patterned again, and as shown in FIG. 1(C), a second contact hole pattern 12 is formed which is wider than the first contact hole IO
form. Then, a second anisotropic dry etching is performed through the second contact hole pattern 12, and as shown in 111(d), the side portion along the upper half of the insulating film 2, that is, At the same time, the lower half of the insulating coating 2 exposed on the bottom surface of the recess 11 is removed to form a wider recess 13.
form 4. Then, the wide recess 13 and the narrower recess 14 are formed continuously,
A two-stage contact hole 15 is formed at a depth extending from the surface of the insulating film 2 to the surface of the semiconductor substrate l.

Furthermore, by performing isotropic wet etching through the second contact hole pattern 12, as shown in FIG. As shown in Figure (f), the resist coating II! Remove 3.

Note that the contents of the metal wiring forming process following this contact hole forming process are the same as in the conventional example.
The explanation here will be omitted.

〔Effect of the invention〕

As explained above, according to the method for forming a contact hole in a semiconductor device according to the present invention, by performing anisotropic dry etching twice, a wide recess with a step near the surface of the semiconductor substrate and a narrow recess are formed. A two-step contact hole is formed, and the stepped corner portions in the contact hole are removed by isotropic wet etching. Therefore, the aspect ratio of the contact hole is reduced, and the coverage range of the metal wiring is improved, and the excellent effects that halation of the metal wiring is less likely to occur and disconnection of the metal wiring will not occur can be obtained.

[Brief explanation of drawings]

1(a) to Cf) are step-by-step cross-sectional views showing a method for forming a contact hole in a semiconductor device according to the present invention, and FIGS. FIG. 3 is a process cross-sectional view showing a contact hole forming method. In the figure, 1 is a semiconductor substrate, 2 is an insulating film, 3 is a resist film, 10 is a first contact hole pattern, 12 is a second contact hole pattern, 15 is a contact hole, and 16 is a step corner. be. Note that the same reference numerals in the drawings indicate parts and portions that are the same or correspond to each other. 2.vA edge pourable coating resist coating (a) (c) Fig. 1 (b) 1 (c) (e) (f) Fig. 2 (, b) (d) 2111112

Claims (1)

[Claims] (1) A step of patterning a resist film formed on an insulating film covering the surface of a semiconductor substrate to form a first contact hole pattern, and a first step performed through the first contact hole pattern. a step of removing only the upper half along the thickness direction of the insulating film close to the surface of the semiconductor substrate by anisotropic dry etching; and patterning the resist film again to form a second part having a wider width. Through the step of forming a contact hole pattern and the second anisotropic dry etching performed through the second contact hole pattern, the side portion along the upper half of the insulating film is removed, and at the same time, the side portion of the insulating film is removed. a step of removing the lower half to form a two-stage contact hole; and a step of removing a step corner in the contact hole by isotropic wet etching performed through the second contact hole pattern. A method for forming a contact hole in a semiconductor device, the method comprising: