JPS6296671A - Sputtering electrode - Google Patents

Abstract

PURPOSE:To increase the rate of film coating in a difference part in level by providing a slant on a target face generating a plasma ring and by making the adhesion quantity of a filming material on both a side wall part of the difference in level of the difference part in level and a flat part on the surface of a base material uniform. CONSTITUTION:The target faces opposite to a base plate 1 to be coated wherein the targets 2-2, 2-3 have a shape of an axis-symmetrical rotating body form are provided with the slanted faces (e.g. angles theta1 and theta2). The targets are divided into every members contg. the slanted faces and each member is electrically insulated from each target member. Voltage is impressed from the electric power sources 29, 30 to the insulated members respectively and independently. Furthermore the closed magnetic fields 19, 20 which start from each slanted face and reenter the same slanted face are formed on each slanted face.

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to a method for forming a coating on the surface of an object by sputtering, and particularly for forming a thin film on an uneven surface such as a wafer surface of an IC substrate. When doing 1. The present invention relates to a sputter electrode suitable for forming a film of uniform thickness.

[Background of the invention]

In sputtering film formation using conventional circular flat magnetron electrodes, Semiconductor World (SEMICONDUC)
TORWORLD) 1cp September 1984 issue P125-1
As described in 31, it has been pointed out that in pattern steps on the outer periphery of a wafer, which is a coated substrate, the film coverage at the outward step opposite to the wafer center direction decreases. This rate is generally referred to as step coverage, and if this step coverage is poor, the resistance of the wiring will increase and the life of the formed device will be shortened, or in extreme cases, the wiring will break and the circuit elements that can be printed on the wafer will be damaged. Yield decreases.

Therefore, in order to improve step coverage, in recent years the monthly paper [Shinku 4, 1985, Vol. 28, No. 5, P181-18
A target structure and sputter electrode as shown in No. 3 was proposed. According to this proposal, in order to increase the amount of film deposited on the outward step on the outer periphery of the wafer, a sputter deposition source (target) that is considerably larger than the wafer diameter is arranged, and this sputter deposition source is tapered in a conical shape. There is.

Furthermore, a flat target is placed facing the wafer.
A film of uniform thickness is formed by releasing film material from both the Taber target and the flat target.

However, since the contribution of the film material ejected from the flat target to the flat part of the step outside the wafer is not taken into account, a sufficient film coverage rate has not yet been achieved.

[Purpose of the invention]

SUMMARY OF THE INVENTION An object of the present invention is to provide a sputter electrode which eliminates the above-described drawbacks of the conventional sputter electrode and improves the film coverage on the outward step at the outer periphery of the wafer.

[Summary of the invention]

FIG. 1 shows a planar magnetron sputtering electrode that is currently widely used when sputtering film formation with a wafer and a target stationary facing each other. The principle is that a high-density doughnut-shaped plasma 7 is generated by an electric field between an anode 6 and a target 2, which is a cathode, and a tunnel-shaped magnetic field 4 formed on the target surface.

The annular portion 8 of the target 2 directly under the donut-shaped plasma 7 is mainly subjected to sputtering, ejecting film material and forming a film on the opposing wafer 1.

Now, the characteristics of covering steps on a wafer will be explained using FIG. 2. The target portion that contributes to forming a film on the outward step 9 of the external local part of the wafer (the step in which the normal to the side wall of the step faces in the opposite direction to the center of the wafer) is represented by an arc A shown by a solid line.
(12-1) only.

On the other hand, the target portion that contributes to forming a film on the inward step 10 (the step whose normal to the side wall of the step is directed toward the wafer center) is located along the arc A (12
-2), and the annular portion 1-2 entirely contributes to the flat portion 11. When discussing the step coverage rate and considering the amount of film deposited on the step sidewalls and flat areas, it is important to consider not only the above-mentioned contributing area, but also the solid angle from which the target area that contributes to film formation is viewed from the step sidewalls and flat areas. It should be noted that it also depends on For this reason, if a plasma ring having the same size as the wafer diameter is generated to form a film, in principle, the film coverage of the outward step at the outer periphery of the wafer is lower than that of the step at the center of the wafer.

Therefore, in order to improve the film coverage of the outward steps in the outer part of the wafer, 1) Generate a plasma ring larger than the wafer diameter and contribute to the film formation of the outward steps with respect to the target area that contributes to the flat area. It is necessary to increase the relative ratio of target areas; and 2) to increase the solid angle from which the target (solid line in Figure 2) contributing to the outward step is viewed. As shown in FIG. 3, the method for achieving this is to use a dovetail-shaped target 2-1 that is sufficiently larger than the wafer diameter and inclined toward the wafer center.
If the film is formed, however, the film thickness near the outer part of the wafer becomes thicker (see FIG. 4), and the desired film thickness uniformity cannot be obtained. (In practice, film thickness uniformity of ±5 inches is required.) Therefore, in order to obtain a uniform film thickness distribution, it is necessary to form a film to obtain a film thickness distribution as shown in Figure 4, and to form a film in the center of the wafer. It is sufficient to synthesize a film that has a thick film thickness distribution as shown in FIG. Fifth
In order to obtain the film thickness distribution shown in the figure, it is necessary to generate a plasma ring that is smaller than the wafer diameter and then deposit the film.While obtaining a uniform film thickness distribution, it is possible to improve the step coverage. The measurement was made using the sputtering electrode described in the monthly paper [Shinku J, 1985, Vol. 28, No. 5, P181-P183.

However, in this method, since the target surface on which the small plasma rings are generated is a flat plate, when the small plasma rings are generated, the film is formed on the flat part of the outer periphery of the wafer and on the inward step sidewalls, but on the outward step sidewalls. Since no film is formed on the outer surface, the film coverage of the outward steps is relatively reduced.

Therefore, in the present invention, the target surface that generates the small plasma ring is sloped toward the wafer center.
When a small plasma ring occurs, the flat part on the wafer's outer periphery and the inward step sidewall are also coated in the same manner as the outward step sidewall, and as a result, a higher film coverage rate than before can be obtained. did.

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to FIG.

Two coils 14 and 15 are wound concentrically around a center yoke 15 made of soft iron.A circular yoke 16 is located between the inner coil 15 and the outer coil 14.
(referred to as an intermediate yoke) is provided, and an annular yoke 17 (referred to as an outer peripheral yoke) is also provided on the outer periphery of the outer coil.
is provided. Each yoke is integrated by a disk yoke 1B to form a magnetic path.

Nuclear carp! 14.15, a magnetic field 19 is formed between the intermediate yoke and the outer yoke, exiting from the inclined surface of target piece A (2-2) and entering the inclined surface again, and further between the intermediate yoke and the center yoke. A magnetic field 20 is formed that exits from the inclined surface (2-3) and enters this inclined surface again. Target piece A (2-2), B (2-3)
are water-cooled backing gray) A (5-1), B (5
-2), and a voltage is applied to each target piece independently by a power source 29.30.

As a result, two donut-shaped plasmas 20, 21 (plasma ring and throat) are formed due to the action of the electromagnetic field. Each target piece has an axially symmetrical rotating body shape with the center yoke as its axis, and the surface to be sputtered is an inclined surface facing in the axial direction (angle of inclination θl).

θ2). By controlling the amount of ions that collide with the target piece surface from each plasma ring by the amount of power applied to each target heath, the amount of film forming material released from each target is controlled.
A film of uniform thickness is formed on opposing wafer surfaces (power source for supplying power to each target: 29.so).

The magnet on the back surface of each target may be a permanent magnet, but as the target wears out, the magnetic flux density increases and the discharge impedance decreases, making it impossible to supply a predetermined power. When configured with electromagnets as in this embodiment, the magnetic field can be controlled so that the discharge impedance can be set within a predetermined range, so that a predetermined amount of power can be supplied. As a result, a constant film formation rate can be maintained.

FIG. 7 shows the step coverage obtained by the present invention. The large and small plasma dimensions in Figure 7 are φ240 and φ120, respectively.
．． As a representative example, the target inclination angles are 45° and 50°, the wafer target spacing is 40 mm, and 75 mm. In the wafer and target layout diagram of FIG. 7, the step coverage ratio can be improved by using the inclined target shown by the solid line rather than by using the flat plate target shown by the broken line.

In addition, in this embodiment, the yoke portion 13.16.17°1
8 is an anode, and a positive potential can be applied to the anode (power supply 51). As a result, electrons escaping from the plasma toward the wafer are attracted to node 7, thereby preventing damage to the wafer due to the electrons. It is prevented.

FIG. 8 shows a second embodiment. A target in the form of an axially symmetrical rotating body is divided into two members 2-2.2-5, each member having a conical shape with an inclination pointing in the direction of a common axis of symmetry of the wafer and the target, and a The structure is similar in that an independent negative high voltage is applied.

The difference from the embodiment of '/fJ1 lies in the yoke and electromagnetic structure for forming a tunnel-like m field on the target surface. Four disc-shaped yokes 22.23° 24.25 and a cylindrical yoke 26.27 are integrated to form a magnetic path, and between each disc-shaped yoke, coils 14 and 15 are arranged around the axis of symmetry of the target. wrapped around. By using such an electromagnetic structure, a tunnel-shaped magnetic field 19, 20 is formed on each target surface, and two donut-shaped glasmas 21 are simultaneously formed by an externally applied electric field.

In this way, the same effect as in Example 1 with Serum 1 can be obtained.

Figure 9 shows an example of 1g5. Basically, it is an application of the second embodiment, with two simultaneous targets across an axisymmetric target.
It is designed to be able to process multiple wafers. As an effect, similar to the first embodiment, the step coverage ratio can be improved, while a unique effect of this embodiment is that two wafers can be processed at the same time, so the processing capacity is twice that of the conventional method. Also, target 2-2.2-3 and target 2-2'.

If 2-5' is made of different materials, wafer 1 and wafer 1
' can form films of different materials. It is also possible to form films with different thicknesses by changing the power input to each target.0 [Effects of the Invention] According to the present invention, it is possible to form films on the step sidewalls and flat parts of the step portion on the wafer surface. Adhesion of materials! 8 can be made uniform, so
It is possible to improve the film coverage at the stepped portion. Compared to the conventional step coverage (30 inches) due to the H1@-separation of a tapered target and a flat target, it is expected that this can be improved to 39% with the present invention, in which the flat target part is also tapered, for targets of the same size. Ruru.

As a result, the performance of each LSI chip formed on the wafer is stabilized, and the yield can be improved.

[Brief explanation of drawings]

Figure 1 is a schematic diagram of the magnetron sputtering electrode, Figure M2 is a diagram showing the cause of coverage deterioration due to outward steps, Figure 3 is a diagram showing the relationship between the cone-shaped target and the wafer, and Figure 4 is the same as Figure 3. Diagram of the film thickness distribution on the wafer according to the target shown, I! Figure 5 shows the film thickness distribution on the wafer when deposited using a small plasma ring, Figure 6 is a longitudinal cross-sectional view of the sputter electrode according to the present invention, and Figure 7 shows step coverage with the electrode according to the present invention. 8 and 9 respectively show the second embodiment of the present invention. It is a vertical cross-sectional view of a sputter electrode as a third example.n1...Wafer 2.2-1.2-2.2-5.2=2
'. 2-3'...Target 5.5-1.3-2...
・Backing plate 4, 19.20.19',
20'... Lines of magnetic force 7, 21, 21'... Plasma 8... Part of target to be spattered\~

Claims (1)

[Scope of Claims] 1. In a film forming method in which a film is formed by placing a coating substrate and a sputter electrode facing each other, and in which a sputter electrode whose target, which is a film forming material, has an axially symmetrical rotating body shape, the coating of the target is The target surface facing the substrate has a plurality of inclined surfaces facing in the direction of the symmetry axis of the target, and is divided into members including the inclined surfaces, so that a part or all of each member is electrically disconnected from each target member. It is configured such that power can be input independently to each insulated member, and furthermore, on each slope, there is a power source that comes out from each slope,
A sputter electrode characterized by forming a closed magnetic field that enters the same slope again. 2. In the sputter electrode according to claim 1,
A sputtering electrode in which a plurality of coated substrates are placed across the axis-symmetric rotating body target, and a film can be formed on the plurality of substrates simultaneously or separately for each substrate facing the target surface. 3. In the sputter electrode according to claim 2,
The target material facing the substrate is made of different substances,
A sputtering electrode that can form a film of a different material on each substrate facing the target.