JP2833015B2 - Wiring formation method - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wiring forming method in a semiconductor device manufacturing process.

[Summary of the Invention]

The present invention relates to a method of forming a wiring in a manufacturing process of a semiconductor device, and more particularly, to a method of forming a wiring in which a wiring material made of aluminum (Al) or an alloy mainly composed of Al is embedded in a connection hole having an aspect ratio of 1 or more on a substrate. , The wiring is thinly deposited while the base is kept at a low temperature, and then the wiring is thickly deposited by raising the base to a high temperature to form wiring having excellent step coverage without leaving voids in the connection holes. It is something to do.

[Conventional technology]

In semiconductor devices such as LSIs, the aspect ratio of the connection hole, that is, the ratio of the depth to the diameter of the hole is being adopted as a large value of 1 or more with the miniaturization, high density, and multi-layer of the element. It is becoming difficult to make the wiring material buried flat.

Conventionally, as a method of forming a wiring material made of Al or an alloy mainly composed of Al on a substrate in the form of a thin film, a sputtering method such as a parallel plate type has been mainly used. However, in the conventional sputter link method, when a connection hole having a large aspect ratio is formed, the wiring material cannot enter into the connection hole due to a so-called shadowing effect, and the step coverage at the bottom and the side wall of the connection hole is insufficient. Then, the reliability of the wiring is reduced. As a way to improve this,
There is a bias sputtering method in which a film is formed while applying a negative DC bias voltage or an RF bias voltage to a substrate, a high temperature sputtering method in which a film is formed while heating a substrate at a high temperature, or a high temperature bias sputtering method in which both methods are used (for example, Monthly Semiconductor World Magazine, February 1988, p. 77). All of these methods achieve re-sputtering of wiring material such as Al or Al-based alloy deposited on the substrate, or surface migration by thermal energy to improve the filling characteristics and achieve flattening. It is to try.

[Problems to be solved by the invention]

On the other hand, the present inventors have previously proposed a high-temperature deposition method in which a wiring material is vacuum-deposited while heating the substrate to a high temperature not lower than the melting point of the wiring material at 450 ° C. or higher as a method for achieving more reliable embedding. did. This method has a higher degree of vacuum than the sputtering method, so that the mean free path of the particles from the evaporation source is large, and the angle of incidence of the particles with respect to the direction perpendicular to the substrate surface is small. And a wiring material can be easily deposited inside the connection hole.
Further, since the substrate is heated at a high temperature, the surface migration of the deposited wiring material is performed at the same time, and the step coverage of the deposited film is further improved.

However, in this high-temperature deposition method, for example, a silicon substrate (1) on which a SiO ₂ film (2) having a connection hole (3) on the surface shown in FIG. In the initial state of film formation (for example, Al film formation), island-like growth of Al (4) occurs as shown in the figure, and voids are formed in the connection holes (3). There is a problem that (5) tends to remain.

The present invention has been made in view of the above-described circumstances, and provides a wiring forming method in which a wiring material is buried without leaving a void in a connection hole and a wiring having excellent step coverage to the connection hole can be formed. .

[Means for solving the problem]

In the wiring forming method according to the present invention, a wiring material made of Al or an alloy mainly composed of Al is vacuum-deposited on a substrate such as a semiconductor having a connection hole, but the substrate is first kept at a low temperature of less than 450 ° C. Then, the substrate is vacuum-deposited thickly while heating the substrate to a high temperature of 450 ° C. or higher and lower than the melting point of the wiring material.

If the heating temperature of the latter substrate is less than 450 ° C., the step coverage of the deposited film of the wiring material at the connection hole portion is not sufficient. On the other hand, if it exceeds the melting point of the wiring material, the surface tension of the liquid wiring material becomes liquid. And the viscous flow deteriorates the flatness, and cannot exert the effects of the present invention.

The method of heating the substrate is not particularly limited,
For example, a method using a resistance heater, a method using irradiation with a halogen lamp or an arc lamp, or the like is used.

The vacuum evaporation apparatus is not particularly limited, and an apparatus that evaporates a wiring material made of Al or an alloy mainly containing Al by means of, for example, resistance heating, electron beam heating, high-frequency heating, or the like is used. The pressure in the chamber at the time of vacuum deposition is sufficient to be the degree of vacuum used in ordinary vacuum deposition, and may be, for example, 10 ⁻⁵ Torr. In short, it is only necessary that the degree of vacuum is such that the mean free path of the evaporating particles of the wiring material is large and the perpendicular incidence component to the substrate occupies a sufficiently large ratio as compared with the sputtering method, so long as the effects of the present invention are not impaired. , Can be arbitrarily selected.

[Action]

In the vacuum evaporation method, the area of the evaporation source is smaller than the area of the substrate. Also, the degree of vacuum in the chamber at the time of forming the deposited film is, for example,
Since the degree of vacuum is much higher than that of the sputtering method at 10 ^-5 Torr, the mean free path of the particles from the evaporation source is large, and the incident angle of the particles with respect to the direction perpendicular to the substrate surface is small. That is, there are many perpendicular incident components of the particles on the substrate surface. Therefore, particles of the wiring material can easily enter the bottom of the deep connection hole formed perpendicular to the substrate surface, and the wiring material can be deposited inside the connection hole.

Then, by first depositing the substrate at a low temperature of less than 450 ° C. and thinly depositing it, island-like growth of the deposited film does not occur, and a uniform deposited film is formed along the steps. Next, when the substrate is subsequently heated to a temperature not lower than the melting point of the wiring material made of Al or an alloy mainly composed of Al at a temperature of 450 ° C. or higher and deposited to a required thickness, a uniform deposited film is present in the lower layer. Because
Island growth does not occur, a uniform deposited film is continuously formed,
As a result, embedding of the wiring material is achieved without leaving voids in the connection holes. In addition, by vapor-depositing the latter substrate at a high temperature, the surface migration of the deposited wiring material is performed at the same time, and the step coverage of the deposited film is further improved.

By the above operation, a deep connection hole on a substrate such as a semiconductor is formed.
In a wiring forming method of embedding with a wiring material made of Al or an alloy mainly composed of Al, a wiring having an excellent embedding property in a connection hole and a good flatness of a wiring material deposition film surface in a connection hole portion and an excellent step coverage. Formation is possible.

〔Example〕

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

Examples e.g., CVD substrate (1) such as a first silicon to form a silicon oxide insulating film made of (SiO ₂₎ (2), wherein the opening of the aspect ratio of about 1.2 of the connecting hole (3). Next, as shown in FIG. 1, a single-wafer vacuum evaporation apparatus (14) having two evaporation chambers (11) and (12), a transfer chamber (13), and a charging / unloading chamber (not shown) is prepared. .

The substrate (1) is sent from the charging chamber to the first vapor deposition chamber (11) via the transfer chamber (13), and is set on the holder (15). The pressure in the first vapor deposition chamber (11) is, for example, controlled by a vacuum pump (16).
Reduce pressure to 10 ^-6 Torr. High purity Al of high purity Five Nine is dissolved in the hearth (17) and used as an evaporation source (18). In addition,
The expected angle α facing the substrate (1) from the evaporation source (18) is approximately 10
Within ゜. Then, the substrate (1) is vacuum-deposited at room temperature (or may be heated to less than 450 ° C.) without heating, and as shown in FIG. 2A, a thin Al deposit of about 500 ° is formed along the step. A film (21A) is formed. In this vapor deposition, since the film is formed at a low temperature, Al island growth is suppressed and a uniform Al deposited film (21A) is formed. Next, the substrate (1) is sent to the second vapor deposition chamber (12) via the transfer chamber (13),
Installed in close contact with the heater block (19). Conditions such as the internal pressure of the second vapor deposition chamber (12) and the evaporation source (18) are as follows.
Same as 1). Then, the substrate (1) is vacuum-deposited while being heated to 450 ° C. to 600 ° C. via the heater block (19), and a thicker Al deposited film (about 7500 °) (about 7500 °) is further formed on the thinner Al deposited film (21A). 21B). At this time, unlike the case where heating is performed from the beginning of the film formation, since the uniform Al deposited film (12A) exists in the lower layer, the upper Al deposited film (21B)
No island growth occurs, and a uniform film is continuously formed. Further, since the substrate (1) is deposited at a high temperature of 450 ° C. to 600 ° C., the surface diffusion of the Al deposited film (21B) is active, so that Al uniformly flows into the connection hole (3) without voids. The burying is achieved, and the surface of the Al deposition film (21) is flattened well.
Excellent step coverage.

Example 2 In Example 1, a vacuum evaporation apparatus (14) having two evaporation chambers (11) and (12) for low temperature and high temperature was used.
As shown in the figure, it is also possible to use a vacuum evaporation apparatus (32) having one evaporation chamber (31). That is, in the vapor deposition chamber (31) of the vacuum vapor deposition device (32), first, FIG.
As shown in (1), the base (1) is held at the lower portion of the heater block (19) via the claw (33) so as not to be in contact with the lower part, and the temperature of the base (1) is kept below 450 ° C. In this state, the evaporation source (1
8) Al is vapor-deposited to a thickness of about 5 as shown in FIG.
A thin Al deposition film (21A) of about 00 ° is formed. Then the fourth
As shown in FIG. B, the substrate (1) is brought into close contact with a heater block (19) heated to 450 ° C. to 600 ° C. to form a thin Al deposited film (21A).
A thick Al deposition film (21B) of about 7500 約 is formed thereon.
As a result, as in the first embodiment, void-free filling of the connection hole (3) is achieved, and an Al deposition film (21) having good step coverage is formed.

〔The invention's effect〕

According to the present invention, in a wiring forming method in which a connection hole having an aspect ratio of 1 or more formed on a substrate made of a semiconductor or the like is filled with a wiring material made of Al or an alloy containing Al as a main component, After holding and vapor-depositing the wiring material thinly along the step, subsequently heating the substrate to 450 ° C. or higher and lower than the melting point of the wiring material, and vacuum-depositing the wiring material to leave voids inside the connection holes. Wiring material can be buried without any problems, and excellent wiring characteristics (including wiring in each layer) with excellent filling characteristics in connection holes and good step coverage with good flatness of wiring material deposition surface in connection hole portions can do.

Therefore, let alone the conventional ordinary sputtering method,
Connection holes with an aspect ratio of more than 1 that were difficult even with methods that were considered excellent in step coverage, such as bath as sputtering, can be buried well, and highly reliable wiring can be formed. It is what becomes.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view showing a wiring forming method according to a first embodiment of the present invention, FIGS. 2A and 2B are wiring forming process drawings according to the present invention, and FIG. 3 is a second embodiment of the present invention. FIGS. 4A and 4B are schematic cross-sectional views showing a wiring forming method according to an example, FIGS. 4A and 4B are side views showing a method of holding a base on the heater block, and FIG. 5 is a cross-sectional view for explaining the present invention. (1) is a substrate such as silicon, (2) is an insulating film, (3) is a connection hole, (4) is Al, (5) is a void, (21A) and (21B).
Is an Al deposited film.

Claims (1)

(57) [Claims] 1. A wiring forming method for embedding a wiring material made of aluminum or an alloy mainly composed of aluminum into a connection hole having an aspect ratio of 1 or more formed on a substrate, wherein the substrate is kept at a temperature of less than 450 ° C. Then, the wiring material is vacuum-deposited to form a thin first deposited film formed along a step, and then the substrate is heated to 450 ° C. or higher and the melting point of the wiring material, and A method for forming a wiring, comprising: vacuum depositing a material to form a second deposited film thicker than the first deposited film on the first deposited film.