JP2688831B2 - Film forming equipment by sputtering method - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a film forming apparatus by a sputtering method used for forming a thin film which is one step of manufacturing a semiconductor element, and in particular, a sputtering method for improving the utilization efficiency of a target. The present invention relates to a membrane device.

[Description of Prior Art]

Conventionally, a sputtering film forming apparatus has been generally used for forming a metal thin film such as an Al wiring for a semiconductor. Typically,
A parallel plate type magnetron sputter deposition system was used. This places a thin film formation substrate on a position facing a target placed on a cathode electrode and on an anode electrode parallel to the target. At this time, the anode electrode is electrically connected to the ground. Then, high frequency power, mainly 13.56 MHz, is applied to the cathode electrode. Then, plasma discharge occurs between both electrodes. Then, the ions in the plasma sputter the target and the target material adheres to the thin film formation substrate to form a thin film. However, in order to increase the film formation speed, it is necessary to concentrate the plasma on the electrode surface on which the target is placed, and the magnetic field covers a part of the target surface.

Therefore, only the portion of the target surface where the plasma is concentrated due to the magnetic field is used for film formation. Further, since the sputtered target particles fly only from one direction, the film forming rate is deviated at the step portion of the substrate surface. Further, since the substrate on which the thin film is formed is exposed to plasma, there is a problem that it is easily damaged by plasma.

In order to solve these problems, a facing target type sputtering method has been proposed. In this method, two planar targets are opposed to each other, a thin film formation substrate is placed outside the opposed target, and the substrate surface is directed to the gap between the opposed targets. By this method, substrate plasma damage could be greatly reduced. However, since the sputtered target particles leak from the gap between the facing target and the substrate,
The problems of inefficient use of the target and contamination of the reaction chamber by target particles leaking from the gap between the counter target and the substrate remained.

Then, in order to solve this problem, a cylindrical target facing sputtering film forming apparatus has been proposed in which a cylindrical inner surface target is arranged in a diagonal direction of the substrate, plasma is confined in the vicinity of the target by an opposing magnetic field, and is separated from the substrate. (JP-A-63-100176).

FIGS. 3 (1) and 3 (2) show the above-mentioned conventional device (JP-A-63-63).
-100176) is a cross-sectional view and a side cross-sectional view for explaining the structure of a cylindrical target facing sputtering film forming apparatus.

In FIG. 3, the vacuum container 1 is evacuated from the exhaust port 3 and depressurized to about 1 × 10 ⁻⁵ torr, and then a sputtering gas such as argon (Ar) is introduced from the gas inlet port 2 to several meters to
Adjust the pressure to rr.

In the vacuum container 1, aluminum (Al), copper (Cu),
Molybdenum (Mo), tungsten (W), titanium (T
The cylindrical target 4 is placed electrically insulated from the vacuum container 1 by opening both ends of i) and silicon (Si).

An anode electrode 8 for holding the thin film formation substrate 7 is electrically connected to the ground together with the vacuum container 1 outside the target 4 and substantially perpendicular to the central axis of the cylinder.

Ions in the plasma generated by applying a negative potential (-500 to -several Kv) to the target 4 from the DC power supply 9 sputters the target to form a thin film on the substrate.

A magnet 5 is arranged on the outer periphery of the target 4 to generate lines of magnetic force in a direction parallel to the diameter of the cylinder to confine the plasma and increase the density. Since the portion of the target near the magnet has a high plasma density and is easily sputtered, the magnet 5 is
The target 4 is rotated around the axis of rotation of the cylinder to make the erosion of the target 4 uniform in the circumferential direction, thereby improving the use efficiency of the target 4.

A cooling water jacket 10 for cooling the target is provided on the outer periphery of the target 4.

In such a structure, the scattered particles sputtered from the target fly obliquely to the substrate and are deposited also on the side walls of the step, so that a film having good step coverage can be formed.

In addition, since the gap between the target and the substrate is small, it does not contribute to film formation, and the amount of target particles leaking outside the target and the substrate is very small.

Since the plasma is confined in the vicinity of the target by the lines of magnetic force, the substrate is separated from the plasma, and thus the substrate is less susceptible to plasma damage.

However, in the conventional cylindrical target facing type sputtering film forming apparatus, the magnetic force lines decrease as the distance from the center of the target increases toward the end. For this reason, the plasma is likely to concentrate at the center of the target cylinder, and the erosion of the target is large at the center of the target cylinder and decreases toward the ends. Therefore, the usage efficiency of both ends of the target is poor.

[Object of the invention]

SUMMARY OF THE INVENTION It is an object of the present invention to solve the above-mentioned problems in the conventional film forming apparatus by the sputtering method, and to provide an improved film forming apparatus by the sputtering method, which enables efficient film formation. Is.

Another object of the present invention is to provide a film forming apparatus by a sputtering method which eliminates the above-mentioned conventional problems caused by erosion of the target, improves the use efficiency of the target, and enables efficient film formation. It is in.

[Structure and effect of the invention]

The present invention solves the above-mentioned problems in the conventional sputtering apparatus and achieves the above-mentioned object of the present invention. The film forming apparatus by the sputtering method according to the present invention is "both ends open, cylindrical or A target holding cylinder having a polygonal column-shaped inner surface target, and having means for rotating the target with respect to the rotation axis of the target;
The essence is that a plurality of magnets are installed in the rotation axis direction of the target.

The film forming apparatus by the sputtering method of the present invention, which has the above points as its essence, has been completed through the experiments described below.

Experiment 1 In the conventional apparatus shown in FIG. 3, the magnet 5 is a pair. Instead of the magnet 5, five magnets that generate an equal magnetic field are arranged at equal intervals. The erosion shape of the target at this time is shown in FIG. The shaded area indicates the erosion area and the magnet. Although the problem that the erosion is deeper toward the center of the target and the erosion is shallower at the end of the target as in the conventional device, some improvements have been obtained, but they have not been solved.

Experiment 2 From the result of Experiment 1, it was found that the division of the magnet 5 was effective to some extent in order to make the erosion depth distribution of the target uniform.

From the above, it was considered to control the magnetic field of each divided magnet by the distribution of erosion velocity. That is, the laser displacement sensor was arranged on the target surface at equal intervals with the magnets divided and arranged in the rotation axis direction of the target so that the distance between the target surface and the laser displacement sensor could be measured. The distance is changed by sputtering the target surface during sputtering. The CPU calculates the erosion speed from this change and
The magnetic field of the electromagnet located at the point where the erosion velocity is smaller than the average value was strengthened by comparing with the average value at each measurement point. Moreover, the magnetic field of the electromagnet located at the point where the erosion speed is higher than the average value is made small.

As a result, the erosion distribution of the target was greatly improved as shown in FIG. The shaded area in the figure indicates the position of the erosion region of the target and the electromagnet.

Based on the facts obtained through the above experimental results, a film forming apparatus by the sputtering method of the present invention which has been completed will be described below with reference to the illustrated embodiment.

That is, FIGS. 1 (1) to 1 (3) show the contents of the film forming apparatus by the sputtering method according to the present invention.

In FIG. 1, 101 is a vacuum container, 102 is a sputtering gas introducing pipe, 103 is an exhaust port, 104 is a cylindrical target made of Al, Cu, Mo, W, Ti, Si, etc. with both ends open, and 105 is 104. A target holding cylinder and reference numeral 106 respectively denote an anode electrode which also holds the thin film growth substrate. Further, 107 is a thin film growth substrate, 108 is a motor for rotating the electrode of 106 and the substrate of 107, 109 is an electromagnet for generating a magnetic field, and 110 is a roller for holding and rotating a cylindrical target. Further, 111 is a laser displacement sensor for measuring the erosion depth of the target, 112 is a motor for rotating the target 104, 113 is a power source for the motor, 114 is a DC power source for plasma generation (a high frequency of 13.56 MHz may be used). ), 115 is a magnetic field line created by the electromagnet 109, and 116 is a power supply for the motor 108. In the figure, A indicates a power supply circuit of the electromagnet 109 shown in FIG. 1 (3). Reference numeral 117 is an A / D converter that converts the displacement amount measured by the sensor 111 into a digital amount because the displacement amount is output as a voltage. 118 is an I / F converter, D /
The signal from the A converter 117 is converted into a signal for CPU. A CPU 119 calculates the erosion speed from the rate of change in the erosion depth of the target measured by the sensor 111 per unit time, and controls the magnetic field of each electromagnet 109 according to the erosion speed. 120 is I / F
The converter transmits the signal from the CPU to the controller of each electromagnet 109. 121 is the electromagnet 109
The power supply controller 122, and the power supply 122 for the electromagnets 109, respectively.

The film forming operation by the film forming apparatus by the sputtering method of the present invention shown in FIGS. 1 (1) to 1 (3) is performed as follows, for example. That is, the inside of the vacuum container 101 is exhausted through the exhaust port 3. Next, the sputtering gas is introduced into the vacuum chamber 101 through the sputtering gas inlet 102.

When a negative potential is applied to the target 104 by the DC power supply 114 while rotating the target 104 and the thin film formation substrate 107, discharge occurs between the target 104 and the electrode 106 to generate plasma. At this time, when electric power is supplied from the power supply circuit A to the electromagnet 109 to generate magnetic force lines 115 in the target, plasma is confined inside the target 104 by the magnetic force lines 115.

Ionized sputtering gas particles in the plasma are accelerated by the sheath voltage and sputter the target surface. The target material sputtered from the target adheres to the thin film formation substrate to form a thin film.

When the sputtering is started, the target 10 is affected by the non-uniformity of the plasma density caused by the distribution of the magnetic force lines 115, etc.
Erosion non-uniformity occurs on the surface of the target 104 in the direction of the rotation axis of the target 104. At this time, sensor 1
The distance from 11 to the surface of the target 104 is measured. C
The PU 119 calculates the erosion velocity distribution of each sensor 111 measurement point from the rate of change in the distance between the sensor 111 and the target surface per unit time. Then, a signal is sent to the electromagnet power supply controller 121 in this portion so that the plasma density at the measurement point whose erosion speed is smaller than the average value of this distribution increases. At the measurement points where the erosion speed is higher than the average value, the plasma density is reduced.

In the apparatus of the present invention operated as described above, the plasma density on the surface of the target 104 in the direction of the rotation axis changes, and the erosion speed is made uniform.

In the apparatus of the present invention having the above contents, a magnet having the same shape as the magnet in FIG. 4 can be used instead of the target used in the above and the electromagnet 109 in FIG. In that case, the distribution of the erosion of the target in the rotation axis direction is as shown in FIGS. 2 and 4.

An experiment was conducted on the usage efficiency of the target according to the present invention and the usage efficiency of the target when the magnet of the conventional apparatus was used, and the relationship between them was as shown in Table 1. As is clear from the results shown in Table 1, it is understood that the device of the present invention provides a significantly superior effect as compared with the conventional device.

[Outline of Effects of the Invention] As described above, by installing a plurality of electromagnets perpendicular to the cylindrical axis of the cylindrical target, by controlling the magnetic field generated in accordance with the erosion of the target,
By adjusting the plasma density, the erosion of the target in the cylinder axis direction can be made uniform. Then, as the target rotates, the region where plasma is concentrated also rotates on the target surface.

As a result, the target has uniform erosion in the circumferential direction, and in addition to the above effects, the entire surface can be used efficiently.

[Brief description of the drawings]

FIGS. 1 (1), 1 (2) and 1 (3) are structural explanatory views of a film forming apparatus by the sputtering method according to the present invention. 1 (1) is a schematic sectional view, FIG. 1 (2) is a schematic side sectional view, and FIG. 1 (3) is a schematic block diagram of an electromagnet control system. FIG. 2 is a schematic sectional view of the target in the apparatus shown in FIG. FIGS. 3 (1) and 3 (2) are explanatory views of a conventional sputtering apparatus (Japanese Patent Laid-Open No. 63-100176).
Incidentally, FIG. 3 (1) is a schematic sectional view, and FIG. 3 (2) is a schematic sectional side view. FIG. 4 is a schematic sectional view of a target when the magnet in the conventional device shown in FIG. 3 is used in the device shown in FIG. FIG. 5 is a schematic cross-sectional view of the target in the apparatus shown in FIG. 1 when using magnets that generate magnetic fields of the same magnitude. In FIG. 1, 101 is a vacuum container, 102 is a gas inlet, 103 is an exhaust port, 104 is a target, 105 is a target holding cylinder, 106 is an anode electrode and stage, 107 is a thin film formation substrate, 108 is a motor, 109 Is an electromagnet, 110 is a target holding and rotating roller, 111 is a laser displacement sensor, 112 is a motor,
113 is a motor power source, 114 is a plasma DC power source, 115
Is a magnetic field line, 116 is a motor power supply, 117 is an A / D converter, 118 is an I / F converter, 119 is a CPU, 120 is an I / F converter, 121 is a coil power supply controller, and 122 is a coil power supply. In FIG. 3, 1 is a vacuum container, 2 is a gas inlet, 3 is an exhaust port, 4 is a target, 5 is a magnet, 6 is a line of magnetic force, 7 is a thin film forming substrate,
8 is an electrode, 9 is a DC power supply, and 10 is a target cooling water jacket.

Claims (4)

(57) [Claims] 1. A target holding cylinder having a cylindrical or polygonal column-shaped inner surface target with both ends open, and a means for rotating the target about a rotation axis of the target, and a rotation axis of the target. A plurality of magnets are installed in a predetermined direction to form a film forming apparatus by a sputtering method. 2. The film forming apparatus according to claim 1, wherein the magnet is an electromagnet capable of controlling the strength of a magnetic field. 3. A sensor for measuring the erosion depth of the target in the rotation axis direction, a circuit for calculating the erosion speed from the measured value of the sensor, and the strength of the magnetic field of the magnet according to the erosion speed. A film forming apparatus by the sputtering method according to claim 1, further comprising: 4. A means for holding the thin film forming substrate outside the inner surface target, perpendicularly to a rotation axis of the target, and further for rotating the thin film forming substrate. A film forming apparatus by the sputtering method according to (2) or (3).