JPS62132348A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To improve a film shape against an abrupt step of a semiconductor device by forming a metal wiring layer on the step formed on a semiconductor substrate, and melting the wiring layer. CONSTITUTION:A metal wiring layer 4 is formed on a substrate 1 having steps 2 and 3. A metal wiring layer 4 is thermally melted by heat treatment. The layer 4 is flattened by thermally melting, and the abrupt steps 2, 3 are smoothened. Even if the thickness of the layer 4 is thick, the steps can be readily flattened.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to techniques for alleviating steps in metal wiring layers and improving step coverage in a method of manufacturing a semiconductor device.

[Summary of the invention]

The present invention applies a metal wiring layer to a semiconductor substrate having a stepped portion, and by forming the metal wiring layer and melting the metal wiring layer, the steep step difference is alleviated and the covering shape is improved.

[Conventional technology]

2. Description of the Related Art As semiconductor devices become more highly integrated and miniaturized, there is an increasing need in their manufacturing technology for forming a film with good coverage in narrow recesses with steep steps.

That is, with the trend towards miniaturization of semiconductor devices, there is a growing demand for so-called multilayer wiring structures, and one of the challenges when manufacturing semiconductor devices with multilayer wiring structures is to alleviate steps and improve step coverage.

Incidentally, vapor deposition methods, sputtering methods, CVD methods, and the like are generally known as methods for forming metal films.

For example, when a metal film is formed on a semiconductor substrate having a step by vapor deposition or sputtering, as shown in FIG. The thickness of the metal film 32 is different from the thickness of the metal film 32 formed on the top surface of the convex part and is thinner on the bottom part 33 and side wall part 34 of the convex part. The ratio of the thickness of the metal film 32 and the thickness of the metal film 32 on the bottom 33 and side wall 34 of the recess may be about 10:3.

Therefore, as techniques for forming a metal wiring layer on a semiconductor substrate having a stepped portion, there are known a so-called bias sputtering method in which sputtering is performed while applying a bias to a semiconductor substrate, and a so-called selective CVD method using vapor phase growth.

[Problem that the invention seeks to solve]

However, for example, the bias sputtering method is highly dependent on the underlying shape, and flattening is not easy when the substrate has steep steps. Furthermore, since the film is formed while being scraped, damage to the semiconductor substrate is also large. Furthermore, when the so-called aspect ratio of concave portions such as contact holes is reduced due to miniaturization of semiconductor devices, by applying bias sputtering, cavities etc. are formed in the metal film formed in the four portions. There is also a possibility that

Furthermore, although the selective CVD method is an excellent method in terms of film properties, on the other hand, the configuration of the apparatus is complicated and it is difficult to control various conditions such as gas and temperature. Furthermore, it is not easy to form a thick metal film.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems and to provide a method for manufacturing a semiconductor device that provides a good coating shape for steep steps using a simple method.

[Means for solving problems]

The present invention provides a method for manufacturing a semiconductor device characterized by comprising the steps of forming a metal wiring layer on a stepped portion formed on a semiconductor substrate, and melting the metal wiring layer by heat treatment. Solve problems.

Here, the material of the metal wiring/layer is, for example, Sn, Zn, I
Metal materials and alloys such as n, Pb, Mg, AA, etc. are selected, but are not limited thereto, and metal materials with a relatively low melting point that can be melted by heat treatment are selected.

The metal wiring layer can be formed by, for example, a vapor deposition method or a sputtering method.

Further, the heat treatment is performed while holding the substrate horizontally, and can be performed using, for example, a vertical electric furnace or an infrared lamp annealing device.

[Effect]

After forming the metal wiring layer, heat treatment is performed to melt the metal wiring layer. At this time, the metal wiring layer melted by the heat fills the recessed portion of the stepped portion, and the entire surface is flattened by the metal wiring layer.

〔Example〕

Preferred embodiments of the present invention will be described with reference to the drawings.

This example is based on an experimental example conducted by the inventors of the present invention. It goes without saying that the present invention is not limited to this embodiment.

First, this example will be specifically explained according to the steps in the experimental example.

(a) In the experiment, a substrate 1 having silicon oxide stepped portions 2 and 3 as shown in FIG. 1(a) is used. The height h of the stepped portion 2 is, for example, 6000 people. The stepped portion 2 and the stepped portion 3 have different widths in cross section.

(b) Subsequently, as shown in FIG. 1(b), a metal wiring layer 4 having a thickness of t is formed. The film thickness t is, for example, 8000, and the metal wiring layer 4 is made of Sn (tin) in this experiment. Note that the metal wiring layer 4 is not limited to this, and may be made of Zn
, In, Pb, Mg, A1, or other metal materials or alloys, and a metal material with a relatively low melting point that can be melted by heat treatment is selected.

In this experiment, the metal wiring layer 4 was formed by electron beam heating evaporation.

(c) Next, the metal wiring layer 4 is heated and melted by heat treatment using an infrared lamp. The metal wiring layer 4 is flattened by heating and melting, and the steep step portion 2.3 is alleviated. In addition, since the metal wiring layer 4 is melted as will be described later, it is less dependent on the underlying layer and can reduce the level difference.Furthermore, even if the metal wiring layer 4 is thick, it can be easily flattened. It is possible to achieve this goal.

Here, in this experiment, the maximum temperature reached by heat treatment was 200°C.
, 250°C, 300°C, 350°C, and 400°C.

Table 1 shows the relationship between each of these maximum temperatures and the metal wiring layer 4 made of Sn.

(Hereinafter, blank space) Table 1 As shown in Table 1, for example, as the metal wiring layer 4, Sn
If you select , the maximum temperature of heat treatment will be 300℃.
The step coverage range is improved at ~400°C.

In addition, the actual shape measured by the surface film difference meter is shown in Figures 2(a) to 2.
Shown in Figure (C).

Figures 2(a) to 2(c) show the results obtained using a surface film difference meter.
This is data on the surface of the substrate, with the vertical axis representing the distance (μm) in one direction on the main surface of the substrate, and the horizontal axis representing the height (k people).

Fig. 2(a) shows the shape of the substrate itself; Fig. 2(a)
In the middle, point A indicates the bottom of the step, and point B indicates the top of the step. This corresponds to FIG. 1(a).

FIG. 2(b) shows that the S
This is an actual measurement of the step shape on the surface after n was vapor-deposited. At this time, there is a slight difference in level, and even after reaching Sn7, the bottom of the level difference is point A1, and the top of the level difference is point B.
It has become 1.

FIG. 2(C) shows the result of heat treatment at 300°C using the above-mentioned infrared lamp annealing equipment.As the metal wiring layer melts due to this heat treatment, the steep level difference is alleviated, and there is no dependence on the underlying layer, and the result is approximately It is shown that flattening within 1000 people has been achieved.

The above-mentioned experimental results indicate that the present example achieves good step reduction and step coverage improvement. Further, in this embodiment, after forming a metal wiring layer, a predetermined heat treatment is performed to melt the metal wiring layer and planarize it. Therefore, it is easier to reduce the level difference than in the conventional method, and moreover, it is possible to achieve reliable flattening. Furthermore, by reducing the level difference, it is possible to realize a good connection in the contact hole.

〔Effect of the invention〕

By using the method of manufacturing a semiconductor device of the present invention, it is possible to reduce a steep step difference without depending on the underlying layer and achieve flattening. In addition, good connections can be made in the contact holes of the wiring layer by planarization.

Furthermore, the manufacturing process is simple and the reliability of the device can be improved.

[Brief explanation of drawings]

FIGS. 1(a) to 1(c) are cross-sectional views showing experimental examples for explaining the method for manufacturing a semiconductor device of the present invention in the order of steps, and FIGS. C) is a diagram showing data from an experimental surface film difference meter based on the semiconductor device manufacturing method of the present invention, and FIG. 3 is a cross-sectional view for explaining the conventional semiconductor device manufacturing method. 1 ---------------・-1-・・, Motomutan 2 ・
−−−−−−−−1−−−−−−−−−One step part 3 −
−−１−・・−−−−−・・−・−・One step part 4−・−
・−・−・−−−−−−・−When metal wiring is opened Applicant Sony Corporation representative Patent attorney
Kobua Mima Tamura Sakae - Figure 1 (0) & Genus eJt! N! Figure 1 (b) Hideout 1 Figure 1 (C) Lid plate half-extracted Figure 2 (0) Snn Flo soaking day) - Figure 2 (b) Figure 2 (C) Motoze '] Figure 3

Claims (1)

[Scope of Claim] A method for manufacturing a semiconductor device, comprising the steps of: forming a metal wiring layer on a step portion formed on a semiconductor substrate; and melting the metal wiring layer by heat treatment.