JPH0810693B2 - Method for manufacturing semiconductor device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for manufacturing a semiconductor device, and particularly for flattening a wiring pattern formed on a contact hole or a through hole having a steep side surface. The present invention relates to a method for manufacturing a semiconductor device.

(Prior Art) In the wiring technology in the manufacture of semiconductor integrated circuits, for example, in the multi-layer wiring technology for semiconductor elements, a wiring metal such as aluminum (Al) is embedded in a contact hole or a through hole, and a stepped portion having unevenness is formed. There is a bias sputtering method as a flattening technique. This method is, for example, IEEE PROCEEDINGS OF THE INTERNATIONAL ELE
CTRON DEVICES MEETING Dec7-10 1986 p70-73.

In order to prevent the deterioration of the film quality due to the release of an impurity gas such as oxygen on the metal surface adhered before the substrate is introduced into the vacuum chamber and the damage due to the impact of argon ions on the diffusion chamber below the contact hole, As shown in FIG. 2, in the first step, a base film of aluminum or aluminum alloy is formed on the surface including a contact hole 13 which is a recess provided in an oxide film (SiO ₂ ) 12 on a semiconductor substrate, for example, a silicon substrate 11 by normal sputtering. 14 is formed in a heated state on the substrate 11 (see (b) in FIG. 2). In the second step, a film 15 of aluminum or an aluminum alloy is formed by bias sputtering in a heated state on the substrate 11 and heated by a bias. Due to the effect and ion bombardment, the contact hole is eroded by the surface tension at a temperature lower than the melting point of aluminum or aluminum alloy. The chloride or aluminum alloy is intended to be embedded by flow (see (c) of FIG. 2).

In addition to the above, as a method of filling a recess, “126
SEMICONDUCTOR INTERNATIONAL 9/1987 "and" SEMICO
N / JAPAN'86 TECHNICAL SYMPOSIUM TOKYO, JAPAN, Dec1
1-12 1986 “PLANARIZATION OF A1 ALLOY METALIZ
There is also a technology disclosed in "ATION BY SURFACE SELF-DIFFUSION".

(Problems to be Solved by the Invention) However, the above conventional methods have the following problems. First, in the former two-step method, when aluminum or aluminum alloy is used for the first layer (first step), if the film thickness is thin, the wettability is poor, and as shown in FIG. It easily grows into islands 16. In particular, since the side surface of the contact hole 13 has poor step coverage, in order to completely cover the underlayer in the above-mentioned island-shaped growth state, the first layer should be thick and at low temperature as shown in FIG. Need to be formed.

However, in a miniaturized device having a small contact hole recess, if the film thickness in the first step is increased, a bridge 42 is formed at the upper end 41 of the recess as shown in FIG. Alternatively, when the aluminum alloy film 15 is formed by via sputtering, there is a problem that a cavity 43 is likely to be formed in the contact hole as shown in FIG. As another phenomenon of FIG. 4B, the contact hole 13 as disclosed in FIGS. 5E and 5F.
There is a case where it is not adhered to the side wall of the case or a case where it is adhered to only one wall surface. Further, in the former two-step method, in the means using refractory metal in the first step, when the film thickness is thin, defects such as pinholes are generated, and the defects sufficiently occur during bias sputtering from the underlayer. It is impossible to prevent released gas such as oxygen. When aluminum or an aluminum alloy is bias-sputtered directly on the above-mentioned refractory metal film, the film is formed while growing in an island shape, so that the side surface of the contact hole tends to lack aluminum.

In addition, as a means for improving the wettability of the latter contact hole, titanium-tungsten alloy (Ti
After thinly depositing W), there is a method of forming an aluminum film by bias sputtering. When an aluminum film is formed on a titanium-tungsten alloy film,
There was a problem that the aluminum film was deposited in an island shape. Also, as a method of filling the opening, a method utilizing the resputtering effect is J, ELECTROCHEM, Soc, SOLID STATE SCIE.
NCE AND TECHNOLOGY June 1985 P1466-1472. However, in this method, it is difficult to control the process in which a film is formed to a thickness such that the opening is not blocked, and the film is formed by burying the film by sputtering and etching by a bias (etching). There is a problem that it takes a long time.

The present invention has been made in consideration of the above-mentioned conventional circumstances, and an object thereof is to provide a method for manufacturing a semiconductor device capable of quickly and easily forming a good metal layer having no defects in the concave portion of the substrate surface. And

[Structure of Invention]

(Means for Solving Problems) A method for manufacturing a semiconductor device according to the present invention is the method for manufacturing a semiconductor device in which a metal is embedded in a recess on a surface of a substrate. A first step of depositing a metal, and a second metal having a melting point lower than that of the first metal at a temperature of 150 ° C. or lower on the substrate of the first metal film, and the recess is not closed. A second step of depositing to a thickness of approximately the same, and the substrate is heated on the film of the second metal in the same state as the second metal or in the first
And a third step of causing a third metal having a melting point lower than that of the above-mentioned metal to flow while being deposited by sputtering and filling the recess into the recess.

The first metal is preferably titanium, and may be a titanium-tungsten alloy or titanium-silicide as long as it contains titanium. In addition, the second and third
As the metal, the same kind of aluminum or aluminum alloy is preferable, or different kinds of aluminum and aluminum alloy may be used. The first and second steps are usually sputtering steps, the third step is preferably a bias sputtering step, or the first step is a CVD method and the second step is a normal sputtering step. The third step may be a bias sputtering method.

(Operation) According to the method for manufacturing a semiconductor device of the present invention, first, the first metal having a high melting point is deposited on the surface of the substrate including the recess in the first step, and then the first metal is deposited in the second step. Since the second metal having a melting point lower than that of the first metal is deposited on the metal film at a temperature of 150 ° C. or lower to a thickness such that the recess is not closed, the first metal is deposited. The second metal can be made to conform uniformly over the entire surface without growing in an island shape on the film, and the wettability can be improved. Therefore, the following third
In the step of, while flowing the substrate on the second metal film while depositing a third metal, which is the same as the second metal or has a melting point lower than that of the first metal, by sputtering while heating the substrate. By doing so, it is possible to smoothly flow and embed the third metal in the recess, and it is possible to quickly and easily form a good-quality metal layer having no defects in the recess.

(Example) Hereinafter, one example of a method for manufacturing a semiconductor device according to the present invention will be described with reference to the drawings.

As shown in FIG. 1A, a contact hole 3 which is a recess is provided in an insulating layer 2 such as a silicon dioxide film formed on the surface of a semiconductor substrate, for example, a semiconductor wafer 1 made of silicon. On the surface of the semiconductor wafer 1 including the contact holes 3, as a first step, titanium (Ti) which is a refractory metal is used as a first metal without heating the semiconductor wafer 1 in advance. ~ Number 1
A first metal film 4 is formed by depositing the first metal film 4 to a thickness of about 00Å.

In this first step, the temperature of the semiconductor wafer 1 may rise due to sputtering. The semiconductor wafer 1 may be heated in advance, for example, at 300 ° C.

Next, as a second step, as shown in FIG. 2B, the semiconductor wafer 1 is deposited on the film 4 of the first metal without heating the semiconductor wafer 1 in advance. Aluminum (Al), for example, is used as the second metal which is the melting point metal to form a film 5 of the second metal by a commonly used sputtering method with a thickness such that the contact hole 3 is not closed, for example, about 1000Å. .

In this second step, the temperature of the semiconductor wafer 1 may rise due to sputtering. However, when the semiconductor wafer 1 is preheated, it is necessary to set the temperature to 150 ° C. or lower in order to uniformly deposit the second metal film 5.
This is because keeping the semiconductor wafer 1 at 150 ° C. or lower (room temperature 25 ° C. or higher) contributes to improvement of wettability.
At this time, since the first metal film 4 made of titanium previously deposited is present on the surface of the semiconductor wafer 1, the silicon of the semiconductor wafer 1 at the contact portion at the bottom of the contact hole 3 and the second metal The reaction of the metal film 5 with aluminum can be prevented. Also, as it is usually done,
Since it is not necessary to use an aluminum alloy in which excess silicon is added to aluminum in advance, it is possible to prevent the contact resistance from increasing due to the precipitation of silicon.

Next, in a third step, on the second metal film 5 made of aluminum, a third metal having the same melting point as that of the second metal or a melting point lower than that of the first metal, For example, aluminum is deposited to form the third metal film 6. The third step is performed so that the flat surface portion has a thickness of, for example, about 6000 to 9000Å. In this third step, the semiconductor wafer 1 is preheated to 300 to 600 ° C., for example, about 350 ° C., and a RE bias (self-bias voltage of 300 V) is applied to the semiconductor wafer 1 by sputtering to form a third aluminum film. A metal film 6 is formed. At this time, the third metal film 6 made of aluminum is the first metal film 5 made of aluminum deposited first
Since the entire surface of the metal film 4 and the titanium of the metal film 4 are uniformly blended with each other, the wettability of both is extremely good, and the aluminum of the third metal film 6 smoothly moves into the contact hole 13 ( Flow) and contact hole 3 above
Can be filled.

The above-mentioned first, second and third steps are continuously executed without being exposed to the atmosphere. There are various means, for example, a plurality of processes are formed in the same vacuum chamber, and the steps are moved, or three steps are sequentially performed at the same position without moving the steps.

In the method of manufacturing the semiconductor device according to the above-described embodiment, since the first metal forming the first metal film 4 is titanium, which is a high melting point material, compared with aluminum, the normal sputtering condition without bias is used. Under the conditions, the step coverage is good, and the semiconductor wafer 1 is deposited on the first metal film 4 by depositing aluminum, which is a second metal having a melting point lower than that of the first metal, at a temperature of 150 ° C. or lower. As a result, the metal of the second metal film 5 fits the entire surface of the metal of the first metal film 4 uniformly and does not grow in an island shape. Therefore, since the wettability in the contact hole 3 is improved, aluminum, which is the same as the second metal or has a melting point lower than that of the first metal, of the third metal, is formed on the second metal film 5. In the heated state, the semiconductor wafer 1 can be smoothly flowed while being deposited by the bias sputtering process, and can be quickly and easily embedded in the contact hole 3, and a good metal layer having no defect can be formed in the contact hole 3. it can.

The present invention is not limited to the above embodiments, and various modifications can be made within the scope of the present invention.
For example, the recess on the surface of the substrate may be a through hole. Further, in the above embodiment, the first step and the second step are the sputtering step, and the third step is the bias sputtering step, but the first step is the CVD (chemical vapor deposition) step. May be Furthermore, as the first metal, titanium-tungsten alloy or titanium-
It may be silicide. Further, the second and third metals may both be aluminum alloys, or may be a combination (different combination) of aluminum and aluminum alloys.

(Effects of the Invention) As described above, according to the method for manufacturing a semiconductor device of the present invention, first, a high melting point first metal is deposited on the substrate surface including the recess in the first step, and then the second In the step of, the second metal having a melting point lower than that of the first metal is deposited on the first metal film at a temperature of 150 ° C. or lower to a thickness such that the recess is not closed. Therefore, the second metal can be made to fit uniformly over the entire surface of the film of the first metal without growing in an island shape, and the wettability can be improved.
Therefore, in the next third step, on the second metal film,
While the substrate is heated, a third metal, which is the same as the second metal or has a melting point lower than that of the first metal, is flowed while being deposited by sputtering, so that the third metal is formed in the recess.
The metal can be smoothly flowed and embedded, and a good-quality metal layer having no defects can be quickly and easily formed in the recess.

[Brief description of drawings]

FIG. 1 is an explanatory diagram for explaining an embodiment of the present invention, and FIG.
FIG. 3, FIG. 4, FIG. 5 and FIG. 5 are explanatory views for explaining a conventional example. In the figure, 1 ... Semiconductor wafer (substrate), 2 ... Insulating layer, 3 ... Contact hole (recess), 4 ... First metal film, 5 ... Second metal film, 6 ... It is a film of a third metal.

Claims (6)

[Claims] 1. A method of manufacturing a semiconductor device in which a metal is embedded in a recess on a surface of a substrate, wherein a first step of depositing a high melting point first metal on the surface of the substrate including the recess, and the first step.
A second step of depositing the second metal having a melting point lower than that of the first metal on the metal film of 150 ° C. at a temperature of 150 ° C. or lower to a thickness such that the recess is not closed. On the film of the second metal, while the substrate is being heated, a third metal, which is the same as the second metal or has a melting point lower than that of the first metal, is flowed while being deposited by sputtering. And a third step of embedding in the semiconductor device. 2. The method of manufacturing a semiconductor device according to claim 1, wherein the first metal is titanium, a titanium-tungsten alloy, or titanium-silicide. 3. The method of manufacturing a semiconductor device according to claim 1, wherein the second and third metals are the same kind of aluminum or aluminum alloy. 4. The method of manufacturing a semiconductor device according to claim 1, wherein the second and third metals are different combinations of aluminum and aluminum alloy. 5. The method of manufacturing a semiconductor device according to claim 1, wherein the first and second steps are ordinary sputtering steps, and the third step is a bias sputtering step. . 6. The first step is a CVD step, the second step is a normal sputtering step, and the third step is a bias sputtering step. A method for manufacturing a semiconductor device as described above.