JP7219140B2 - Deposition method - Google Patents

Description

TECHNICAL FIELD The present invention relates to a film formation method, and more particularly to a method for forming a predetermined metal oxide film such as an IGZO film or a SiO ₂ film on the surface of a substrate such as glass having a large area.

In the manufacturing process of a flat panel display, there is a process of forming a predetermined metal oxide film such as IGZO on the surface of a substrate such as glass having a large area, and the sputtering method is widely used for this purpose. As a sputtering apparatus, there is known one in which a plurality of targets are arranged side by side at predetermined intervals along one direction so as to face a substrate in a vacuum deposition chamber (see, for example, Patent Document 1).

In the above conventional sputtering apparatus, when plasma is formed in the vacuum deposition chamber and each target is sputtered with rare gas ions ionized by the plasma, sputtered particles are not emitted from the regions between the targets. For this reason, the film thickness distribution on the substrate surface becomes non-uniform in a wavy manner (that is, thick and thin portions are repeated at the same period). As a solution to this problem, the targets are aligned in the X-axis direction, and the substrate is reciprocated integrally with respect to each target in the direction in which the targets are aligned during film formation by sputtering. is continuously or intermittently changing the area where is not emitted.

The stroke of the reciprocating motion is usually set equal to the center-to-center distance between adjacent targets, which eliminates the undulating film thickness variation and improves the uniformity of the film thickness distribution in the substrate plane. can. However, when the film thus formed is a metal oxide film such as an IGZO film, when the characteristics of the metal oxide film are evaluated by the μ-PCD (Microwave Photo Conductivity Decay) method, the film quality remains uneven. (That is, the in-plane uniformity of film quality distribution is poor). Since such unevenness in film quality affects the performance of devices such as flat panel displays, it is necessary to suppress this as much as possible.

Japanese Patent No. 4246547 JP 2016-029709

In view of the above points, it is an object of the present invention to provide a film formation method capable of forming a predetermined metal oxide film with good in-plane uniformity of film quality distribution over the entire surface of a substrate.

In order to solve the above problem, a plurality of targets are arranged in parallel in one direction at predetermined intervals so as to face the substrate in a vacuum film formation chamber, and a sputtering gas is introduced into the vacuum film formation chamber. In the film forming method of the present invention, in which a metal oxide film is formed on a substrate surface by sputtering each target by turning on power, the direction in which the targets are arranged side by side is the X-axis direction, and during the film formation by sputtering, the target is The substrate is relatively reciprocated in the X-axis direction by a predetermined stroke, and the stroke is set to be at least twice the center-to-center distance between adjacent targets. In this case, the metal oxide film is an IGZO film.

According to the present invention, for example, during film formation by sputtering, the substrate is reciprocated with a predetermined stroke with respect to the targets arranged side by side. At this time, as a result of intensive research by the present inventors, the stroke for reciprocating the substrate is lengthened. Even if the metal oxide film thus obtained is evaluated by the μ-PCD method, it has been found that the film can be formed without unevenness in film quality, that is, with good in-plane uniformity of film quality distribution over the entire surface of the substrate. It should be noted that increasing the stroke for reciprocating the substrate inevitably increases the size of the sputtering apparatus, so the upper limit of the stroke is determined in consideration of this.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a diagram schematically showing the configuration of a sputtering apparatus capable of carrying out the film forming method of the present invention; FIG. 2 is a partially enlarged view of FIG. 1 for explaining the reciprocating motion of the substrate; (a) shows the starting position of the reciprocating motion, (b) shows one folding position, and (c) shows the other folding position.

Hereinafter, the film forming method of the embodiment of the present invention will be described with reference to the drawings, taking as an example the case where the substrate Sw is a rectangular glass substrate and a metal oxide film is formed on one surface of this substrate Sw. In the following, the direction from each target toward the substrate Sw is defined as the top, and the direction in which the targets are arranged side by side is defined as the X-axis direction (horizontal direction). shall be used.

Referring to FIG. 1, SM is a magnetron type sputtering apparatus capable of carrying out the film forming method of the present embodiment. The sputtering apparatus SM includes a vacuum chamber 1 defining a vacuum deposition chamber 10, and a vacuum exhaust means P such as a rotary pump or a turbo molecular pump is connected to the vacuum chamber 1 via an exhaust pipe P1 to create a vacuum. The film forming chamber 10 can be evacuated to a predetermined pressure. The vacuum chamber 1 is also provided with gas introduction means 2 for introducing a sputtering gas made of a rare gas such as argon (which may contain a reactive gas such as oxygen) into the vacuum film forming chamber 10 . The gas introduction means 2 has a gas pipe 21 attached to the side wall of the vacuum chamber 1 , and the gas pipe 21 communicates with a gas source 23 via a mass flow controller 22 .

A holder 3 for holding the substrate Sw with its lower surface (film-forming surface) open is provided in the upper part of the vacuum film-forming chamber 10 . A first driving shaft 41 of a first driving means 4 such as a motor or an air cylinder is connected to the holder 3. During film formation by sputtering, the holder 3 holding the substrate Sw is moved in the X-axis direction at a predetermined speed and Reciprocating movement is enabled with a predetermined stroke St. A cathode unit Cu is also provided in the lower part of the vacuum deposition chamber 10 so as to face the substrate Sw.

The cathode units Cu are arranged side by side at equal intervals in the X-axis direction. and magnet units 6 provided in the spaces below the targets 51a to 51n. A sintered body (IGZO) containing indium, gallium, and zinc is used as each of the targets 51a to 51n, and is manufactured to have the same shape (in this embodiment, a substantially rectangular parallelepiped that is rectangular in plan view). In addition to IGZO, the film forming method of the present embodiment can also be applied to targets such as SiO ₂ and ITO. Also, the number of targets arranged side by side is not limited to the above, and is appropriately set so that the area where the targets are arranged side by side is larger than the contour of the substrate Sw.

Backing plates 52a to 52n for cooling the targets 51a to 51n during film formation are bonded to the lower surfaces of the targets 51a to 51n via a bonding material (not shown) such as indium or tin. The targets 51a to 51n are supported by a single support plate 53 via backing plates 52a to 52n while being electrically insulated from each other. Each of the targets 51a to 51n is paired with two targets adjacent to each other, and the paired targets 51a to 51n are connected to the outputs Ao from the AC power sources As, respectively. Since a known AC power source can be used, detailed description is omitted here.

Each magnet unit 6 has a supporting plate (yoke) 61 made of a magnetic material provided parallel to each of the targets 51a to 51n. The supporting plate 61 is provided with a central magnet 62 linearly arranged in the central portion thereof and peripheral magnets 63 arranged along the outer periphery of the supporting plate 61 with opposite polarities on the upper side. A balanced closed-loop tunnel-like magnetic field is formed in the upper space of 51n. Each magnet unit 6 is integrally connected to a second driving shaft 71 of a second driving means 7 such as a motor or an air cylinder, and the magnet units 6 are integrally reciprocated in parallel with a predetermined stroke in the X-axis direction at a constant speed. allowing it to move.

The sputtering apparatus SM has a control means (not shown) equipped with a microcomputer, a sequencer, etc., and controls the driving means 4 and 7, as well as the operation of each AC power source As, the mass flow controller 22, and the evacuation means P. controlled. The film forming method of this embodiment using the sputtering apparatus SM will be described below with reference to FIG. 2 as well.

After setting the substrate Sw on the holder 3 in the vacuum deposition chamber 10 , the vacuum evacuation means P evacuates the inside of the vacuum deposition chamber 10 . At this time, the holder 3 is positioned so that both ends of the substrate Sw in the X-axis direction are located at starting positions (positions shown by solid lines in FIG. 1 and positions shown by solid lines in FIG. position). When the vacuum deposition chamber 10 reaches a predetermined pressure (for example, 10 ⁻⁵ Pa), a sputtering gas (including a reaction gas such as oxygen) is introduced at a predetermined flow rate through the gas introduction means 2, and each of the targets 51a to 51n. , power is supplied from each AC power source As. As a result, plasma is formed in the spaces between the substrate Sw and the targets 51a to 51n, the targets 51a to 51n are sputtered by the ions of the sputtering gas in the plasma, and the sputtered particles scattered from the targets 51a to 51n are generated. A metal oxide film is formed on the surface (lower surface) of the substrate Sw by adhering and depositing on the substrate Sw.

During film formation by sputtering, the holder 3 holding the substrate Sw is reciprocated in the X-axis direction at a predetermined speed and with a predetermined stroke St. The stroke St at this time is set to be at least twice the cathode pitch Dt. Specifically, the holder 3, and thus the substrate Sw, is moved by the first driving means 4 from the starting position shown in FIG. When it is moved by the length (that is, half the length of the stroke St) and reaches the reciprocating turn-back position shown in FIG. 2(b), the cathode It is moved by a length equivalent to twice the pitch Dt, and reaches another folding position of the reciprocating motion shown in FIG. 2(c). After that, the holder 3 is continuously reciprocated with a stroke St having a length equivalent to twice the cathode pitch Dt. The speed at which the holder 3 is reciprocated is appropriately set in consideration of the film formation time and the like so that the holder 3 reciprocates at least once during film formation by sputtering. During film formation by sputtering, each magnet unit 6 is also reciprocated at least once at a predetermined speed by the second driving means 7 .

According to the above embodiment, even if the characteristics of the surface of the substrate Sw on which the film is formed are evaluated by the μ-PCD method, there is no unevenness in the film quality, and the uniformity of the film quality distribution over the entire surface of the substrate Sw is good. material films can be deposited. In this case, the longer the stroke St in which the targets 51a to 51n are reciprocated relative to the substrate Sw, the more the in-plane uniformity of the film quality distribution is improved. It should be noted that increasing the stroke St for reciprocating the substrate Sw inevitably increases the size of the sputtering apparatus, so the upper limit of the stroke St is determined in consideration of this.

In order to confirm the above effect, the following experiment was conducted using the sputtering apparatus SM shown in FIG. In this experiment, the substrate Sw was a glass substrate, and the targets 51a to 51n arranged side by side in the vacuum deposition chamber 10 were sintered bodies containing indium, gallium, and zinc, each measuring 180 mm x 2650 mm x 10 mm in plan view. A substantially rectangular shape was used, and the cathode pitch Dt was set to 202 mm. As film formation conditions, the distance between the targets 51a to 51n and the substrate Sw is set to 150 mm, and Ar gas and O ₂ gas are introduced so that the pressure in the vacuum film formation chamber 10 is maintained at 0.5 Pa. bottom. Also, 13 kW of AC power was supplied from each AC power supply As to each of the targets 51a to 51n to sputter each of the targets 51a to 51n. At this time, the stroke St (404 mm) of the substrate Sw (holder 3) was twice the cathode pitch Dt (202 mm). The magnet unit 6 was also reciprocated with a stroke of 64 mm. Then, after forming an IGZO film with a film thickness of 40 nm on the surface of the substrate Sw, the characteristics of the surface of the substrate Sw formed with the film were evaluated by the μ-PCD method. As for the measurement conditions of the μ-PCD method, generally used conditions (see, for example, Patent Document 2) can be used, so detailed description is omitted here.

According to this, it was confirmed that the distribution of peak values measured by the μ-PCD method was 15%. As a comparative experiment, the above sputtering apparatus SM was used under the same conditions as above except that the stroke St (202 mm) of the substrate Sw was set to the same length as the cathode pitch Dt (202 mm) (that is, 1 time). , the distribution of peak values measured by the μ-PCD method was 23%. From the above results, it can be seen that the film formation method of the present invention can improve the film thickness distribution and form an IGZO film with good in-plane uniformity of the film quality distribution over the entire surface of the substrate.

Although the embodiments of the present invention have been described above, various modifications are possible without departing from the scope of the technical idea of the present invention. In the above embodiment, the substrate Sw is reciprocated with respect to the targets 51a to 51n as an example, but the present invention is not limited to this. The drive shaft of the drive means may be connected to the support plate 53 of the cathode unit Cu to reciprocate both the substrate Sw and the targets 51a to 51n or only the targets 51a to 51n. In this case, the sum of the stroke of the reciprocating motion of the substrate Sw and the stroke of the targets 51a to 51n should be set to be at least twice the cathode pitch Dt.

In the above embodiment, the targets 51a to 51n are arranged side by side, and the output Ao of each AC power source As is connected to each of the targets 51a to 51n to supply AC power to each of the targets 51a to 51n. However, the targets 51a to 51n may be sputtered by connecting the output of a DC power supply to the targets 51a to 51n and applying the DC power.

Sw... substrate, St... stroke, Dt... center-to-center distance between adjacent targets (cathode pitch), 10... vacuum deposition chamber, 51a to 51n... target,

Claims (2)

A plurality of targets are arranged side by side at predetermined intervals along one direction in a vacuum deposition chamber facing the substrate, a sputtering gas is introduced into the vacuum deposition chamber, and power is supplied to each target to sputter each target. A film forming method for forming a metal oxide film on a substrate surface by
With the direction in which the targets are arranged side by side in the X-axis direction, the substrate is reciprocated relative to the target in the X-axis direction with a predetermined stroke during film formation by sputtering,
A film forming method, wherein the stroke is set to be at least twice the center-to-center distance between adjacent targets. 2. The film forming method according to claim 1, wherein the metal oxide film is an IGZO film.

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