TWI686489B - Stress adjustment method - Google Patents

Abstract

Provided is a method for adjusting the stress of the aluminum oxide film to within ±500 MPa when forming an aluminum oxide film on the surface of the film-forming object by sputtering.

In the present invention, the film-forming object S and the aluminum-made targets 2 ₁ and 2 _{2 are} arranged in the vacuum chamber 1, and a rare gas and oxygen are introduced into the vacuum chamber in the vacuum atmosphere, and the target The target material is sputtered with specific power, and the reaction product between aluminum atoms and oxygen is adhered and deposited on the surface of the film-forming object to form an aluminum oxide film. At this time, water vapor is introduced into the vacuum chamber. Set the partial pressure of water vapor to the range of 1×10 ^-3 Pa~0.1Pa.

Description

Stress adjustment method

The present invention relates to a method of adjusting stress, and more specifically, to forming an aluminum oxide film on the surface of a film-forming object by sputtering to adjust the stress of the aluminum oxide film to Within ±500MPa.

The aluminum oxide film has been used as a protective film (passivation film) or an insulating film for elements such as thin film transistors in display devices or semiconductor devices from the prior art. In the formation of such an aluminum oxide film, the sputtering method is generally known (for example, refer to Patent Documents 1 and 2). Among them, the so-called reactive sputtering method is used. General use. In this case, a person who uses aluminum as a target material, arranges the target material and the film-forming object in a vacuum chamber to perform vacuum evacuation, and if a certain pressure is reached, rare gas and oxygen for discharge are used The reaction gas is introduced, and a specific power having a negative potential is input to the target, and the target is sputtered. As a result, the reaction product between the aluminum atoms and oxygen scattered from the target is attached to and deposited on the film-forming object, and an aluminum oxide film is formed on the surface thereof.

The aluminum oxide film formed as described above usually has It has stress in the compressive direction. However, if the compressive stress becomes larger, it will cause problems such as increased curvature of the substrate. In this case, if the power input to the target is gradually increased, the compressive stress will increase accordingly, and if the flow rate of the rare gas used for discharge is reduced during the film formation caused by sputtering and Gradually reduce the pressure in the vacuum chamber, the same compressive stress will increase. Therefore, if the power input to the target material is reduced or the pressure of the vacuum chamber during film formation is increased, an aluminum oxide film with a film stress within a certain value (for example, ±500 MPa) can be formed. However, such a In the future, the film formation rate will decrease.

[Prior Technical Literature] [Patent Literature]

[Patent Document 1] Japanese Patent Laid-Open No. 2003-3259

[Patent Document 2] Japanese Patent Application Publication No. 2010-114413

In view of the above problems, the present invention aims to provide a stress adjustment method for adjusting the stress of this aluminum oxide film to within ±500 MPa while maintaining a specific film formation rate.

In order to solve the above-mentioned problems, the present invention is a stress-adjusting film-forming method, which is characterized in that the film-forming object and the target made of aluminum or aluminum oxide are arranged in a vacuum chamber, and the vacuum atmosphere Into the vacuum chamber, introduce rare gas and oxygen-containing reaction gas, or only introduce rare gas, and input specific power to the target material to sputter the target material, thereby on the surface of the film to be formed When forming an aluminum oxide film, it is used to adjust the stress of the aluminum oxide film to within ±500MPa. For the vacuum chamber, hydrogen or water vapor is introduced. When the film is formed by sputtering, the water Steam exists at a partial pressure in the range of 2×10 ^-3 Pa to 0.1 Pa. In this case, it is preferable that at least two of the above-mentioned targets are installed in a vacuum chamber, and AC power of a specific frequency is input between the paired targets to perform sputtering on each target.

According to the present invention, hydrogen or water vapor is introduced by not changing the power input to the target, the partial pressure of the rare gas and the reaction gas (the amount of sputtering gas introduction) in the vacuum chamber during film formation It is an aluminum oxide film that can maintain a lower stress under a specific film formation rate than the case where hydrogen or water vapor is not introduced.

In the present invention, when water vapor is introduced into the vacuum chamber, it is desirable to set the partial pressure of the water vapor in the vacuum chamber to 1×10 ⁻ when forming a film by the sputtering ^{. 3} Pa~0.1Pa range. According to this, it is possible to reliably reduce the stress of the aluminum oxide film while maintaining a specific film formation rate. When the partial pressure of water vapor is 1×10 ^-2 Pa, it is confirmed that the The compression stress is set to about -50 MPa. In addition, if the partial pressure of water vapor becomes lower than 1×10 ^-3 Pa, the alumina film cannot be formed in a state where the stress is effectively reduced, and if the partial pressure of water vapor becomes If it is higher than 0.1 Pa, for example, an abnormal discharge may be induced and the aluminum oxide film may not be formed.

SM: Sputtering device

1: vacuum chamber

2 ₁ , 2 ₂ : target material

42a: Gas pipe (for rare gas)

43a: Mass flow controller (for rare gas)

42b: Gas tube (for reaction gas)

43b: Mass flow controller (for reaction gas)

42c: Gas tube (for steam)

43c: Mass flow controller (for steam)

S: substrate (film-formed object)

FIG. 1 is a schematic cross-sectional view of a sputtering apparatus that can implement the film formation method of the present invention.

[FIG. 2] A graph showing the results of an experimental example exhibiting the effects of the present invention.

In the following, referring to the drawings, a case where an aluminum oxide film is formed by reactive sputtering to form a glass substrate (hereinafter, referred to as a substrate S) with a target made of aluminum and a film-formed object is rectangular. As an example, a film forming method according to an embodiment of the present invention will be described.

Referring to FIG. 1, SM is a magnetron sputtering device capable of implementing the film forming method of the present invention. The sputtering device SM is provided with a vacuum chamber 1 that defines a film forming chamber 11. In the following, the terms representing the directions such as up and down are based on the posture of the sputtering apparatus SM shown in FIG. 1. At the side wall of the vacuum chamber 1, an exhaust port 12 is opened, and at the exhaust port 12, a vacuum exhaust formed by a rotary pump, a dry pump, a turbo molecular pump, etc. is connected The exhaust pipe 13 comes from the means P, and is configured to be able to evacuate the inside of the film forming chamber 11 and maintain it at a specific pressure (for example, 1×10 ⁻⁵ Pa).

In the lower part of the vacuum chamber 1, two cathode units Cu composed of targets 2 ₁ , 2 ₂ made of aluminum (for example, purity 99.999%) and magnet units 3 ₁ , 3 ₂ are provided. Each of the targets 2 ₁ and 2 ₂ is formed into a substantially rectangular parallelepiped shape, and underneath it is bonded by a sputtered material such as indium (not shown). During the film formation, the copper back plate 22 that cools the targets 2 ₁ and 2 ₂ . Then, in a state of being bonded to the back plate 22, the respective targets 2 ₁ and 2 ₂ are provided on the inner surface of the lower portion of the vacuum chamber 1 via an insulator 23 which also serves as a vacuum seal. In this case, each target 2 ₁ , 2 ₂ is vacated with a specific interval in the left-right direction of the film forming chamber 11 and the upper surface of the target 2 ₁ , 2 ₂ when not in use will be positioned as described below The substrate S is parallel to the same plane. At each target 2 ₁ and 2 ₂ , the output Pk from the AC power source Ps is respectively connected, and a specific frequency is input between each target 2 ₁ and 2 ₂ by the AC power source Ps (for example , 1kHz~100kHz) AC power.

The magnet units 3 ₁ and 3 ₂ , which are arranged below the back plates 22 (outside of the vacuum chamber 1 ), respectively, have the same shape, and the magnet units 3 ₁ , 3 ₂ have the same The back plate 22 is provided parallel to the support plate 31 (yoke) made of a flat plate made of magnetic material. On the support plate 31, a central magnet 32 arranged on the center line of the support plate 31, and a circle along the upper periphery of the upper surface of the support plate 31 so as to surround the center magnet 32 The peripheral magnet 33 in the shape of a target is provided by changing the polarity of the targets 2 ₁ and 2 ₂ sides. In this case, for example, it is the sum of the volume when the central magnet 32 is converted to the same magnetization and the peripheral magnet 33 surrounding it is converted to the same magnetized volume (peripheral magnet: central magnet: peripheral magnet =1:2:1, (refer to FIG. 1)) to design. As a result, a tunnel-shaped leakage magnetic field (not shown) that is balanced with each other is formed above each of the targets 2 ₁ and 2 ₂ . The central magnet 32 and the peripheral magnet 33 are well-known objects such as neodymium magnets. The central magnet 32 and the peripheral magnet 33 may be integrated, or may be a plurality of magnet pieces of a specific volume as a plurality of rows Set up what constitutes. In addition, for example, in order to improve the utilization efficiency of the target materials 2 ₁ and 2 ₂ , it may be configured to connect driving means (not shown) to the magnet units 3 ₁ and 3 ₂ and form a film by sputtering In the middle, at least one of the up-down direction or the left-right direction, with a specific stroke for reciprocating movement.

In addition, gas supply ports 41a and 41b are opened at the side wall of the vacuum chamber 1, and gas pipes 42a and 42b are connected to the gas supply ports 41a and 41b, respectively. The gas pipes 42a and 42b are connected to the gas source of the rare gas such as argon and the gaseous source of oxygen-containing reaction gas such as oxygen or ozone through the mass flow controllers 43a and 43b. In addition, it is possible to introduce rare gas and reaction gas whose flow rate is controlled into the film forming chamber 11.

In the case of sputtering each target 2 ₁ and 2 ₂ by the sputtering device SM described above and forming an aluminum oxide film by reactive sputtering on the surface of the substrate S, Vacuum transfer robot to place the substrate S at a specific position on the upper part of the film forming chamber 11 opposite to the targets 2 ₁ and 2 ₂ arranged side by side, and vacuum evacuate the film forming chamber 11 to a specific pressure until. If the film forming chamber 11 reaches a specific pressure, the mass flow controllers 43a and 43b are controlled to introduce rare gas and reaction gas, and AC power is supplied between the targets 2 ₁ and 2 ₂ by the AC power supply Ps . With this, a high-density plasma is generated in a racetrack shape above each target 2 ₁ , 2 ₂ . However, with the rare gas ions in the plasma, the targets 2 ₁ and 2 ₂ are respectively sputter-plated. As a result, the reaction product between the aluminum atoms scattered from the targets 2 ₁ and 2 ₂ and oxygen is attached and deposited on the surface of the substrate S to form an aluminum oxide film.

Here, the aluminum oxide film formed as described above generally has a stress in the compressive direction. However, if the compressive stress becomes larger, it will cause a problem such as a greater curvature of the substrate. Therefore, it is necessary to be an aluminum oxide film capable of efficiently forming a film forming stress within a specific value (for example, ±500 MPa) while maintaining a specific film forming rate. In this embodiment, a gas supply port 41c is further opened at the side wall of the vacuum chamber 1, and a gas pipe 42c interposed with a mass flow controller 43c is connected to the gas supply port 41c, so that it can be configured for film formation. The water vapor whose flow rate is controlled is supplied into the chamber 11. In addition, for example, when forming a film by sputtering, the mass flow controller 43c is controlled to introduce steam into the film forming chamber 11. In this case, it is desirable to use the mass flow controller 43c so that the partial pressure of the water vapor in the film forming chamber 11 during film formation will be in the range of 1×10 ^-3 Pa to 0.1 Pa. Control the flow of water vapor.

When the configuration described above, by the target does not change for _{21, 22} of the input power, the deposition of the noble gas and the partial pressure of the reaction gases (i.e., the mass flow controller by the 43a, 43b of the Controlling the amount of rare gas and reaction gas introduced) and introducing water vapor can maintain a lower film formation stress at a specific film formation rate, compared with the case where water vapor is not introduced. Aluminum oxide film. At this time, if the partial pressure of water vapor is in the range of 1×10 ⁻³ Pa to 0.1 Pa, the stress of the aluminum oxide film can be reliably reduced. For example, when the partial pressure of water vapor is 1×10 ^{− At 2} Pa, it was confirmed that the compression stress can be set to about -50 MPa. In addition, if the partial pressure of water vapor becomes lower than 1×10 ^-3 Pa, the alumina film cannot be formed in a state where the stress is effectively reduced, and if the partial pressure of water vapor becomes If it is higher than 0.1 Pa, for example, an abnormal discharge may be induced and the aluminum oxide film may not be formed.

In order to confirm the above effects, an experiment of forming an aluminum oxide film on the surface of the substrate S was performed using the sputtering device SM shown in FIG. 1. First, as a comparative experiment, the distance between each target 2 ₁ , 2 ₂ and the substrate S is set to 180 mm, and the input power (AC power) between the targets 2 ₁ , 2 ₂ due to the AC power source Ps It is set to 40kW, and the sputtering time is set to 271 seconds. In addition, the mass flow controllers 43a and 43b are operated in such a manner that the pressure in the film forming chamber 11 being evacuated is maintained at 0.5 Pa. Argon and oxygen as rare gases were introduced at a flow rate of 8:2 under control. Furthermore, when the film formation rate and stress of the aluminum oxide film formed on the surface of the substrate S were measured at the center of the substrate S, the result was that the film formation rate was 10.56 nm/min and the stress was About -1000MPa (compressive stress). In addition, the film thickness was measured using an ellipsometer, and the stress was measured using a thin-film stress measuring device.

Next, as an experiment demonstrating the effect of the present invention, the sputtering conditions were set to the same as described above, and during film formation, the mass flow controller 43c was controlled to introduce water vapor at a specific flow rate. In this case, the partial pressure of water vapor is changed in the range of 5×10 ^-4 Pa~1Pa, and the change of the stress (MPa) of the aluminum oxide film at this time is shown in FIG. 2. According to this, if the introduction of water vapor, the stress of the aluminum oxide film is reduced. When the partial pressure of water vapor is 1×10 ^-3 Pa, it can be known that the stress of the aluminum oxide film can be reduced to about- Near 500MPa. The film formation rate at this time was 10.48 nm/min, and it was confirmed that there was almost no change in the film formation rate. Furthermore, it was confirmed that until the partial pressure of water vapor becomes 1×10 ⁻² Pa, the stress of the aluminum oxide film is further reduced inversely proportional to the partial pressure of water vapor, when the partial pressure of water vapor becomes 1× At 10 ^-2 Pa, the stress of the aluminum oxide film can be set to about -50 MPa. The film formation rate at this time was 11.00 nm/min. Furthermore, it was confirmed that if the partial pressure of water vapor is further increased, the stress of the aluminum oxide film becomes a stress in the tensile direction (tensile stress), even when the partial pressure of water vapor is 0.1 Pa, The stress of the aluminum oxide film can also be set to about +100 MPa. The film formation rate at this time was 11.20 nm/min. However, if the partial pressure of water vapor becomes higher than 0.1 Pa, abnormal discharge is induced, and the aluminum oxide film cannot be formed normally.

Although the embodiment of the film forming method of the present invention has been described above, the present invention is not limited to the above-mentioned embodiment. In the above-mentioned embodiment, although the case of introducing water vapor at a specific partial pressure into the film formed by sputtering is described as an example, it is confirmed that even if it is When hydrogen is introduced at a specific partial pressure, the stress of the aluminum oxide film can also be reduced. In addition, in the above-mentioned embodiment, although the gas supply ports 41a, 41b, and 41c provided in the side wall of the vacuum chamber 1 are used as an example to introduce rare gas, oxygen, and water vapor as examples, , Department is not limited to this. Although not specifically illustrated, for example, it may be configured such that a gas tube is installed through the bottom wall of the vacuum chamber 1 and is ejected from the front end of the gas tube positioned around the targets 2 ₁ and 2 ₂ Rare gas, oxygen or water vapor.

Moreover, in the above embodiment, the case where the target materials 2 ₁ and 2 _{2 are} made of aluminum has been described as an example. However, even if the target materials 2 ₁ and 2 _{2 are} made of alumina In the case where only rare gas is introduced or oxygen is introduced together with the rare gas and high-frequency power is input while sputtering is performed on the target materials 2 ₁ and 2 ₂ , the present invention can be applied. Furthermore, although a plurality of targets 2 ₁ and 2 _{2 are} provided side by side, and a pair of targets is supplied with AC power through the AC power supply Ps as an example, the system is not limited to Therefore, the present invention can be applied even when a single target material is used and DC power is generally input by a DC power source. Furthermore, in the above embodiment, the case where the film-forming object is a glass substrate has been described as an example. However, for example, the film-forming object may be a resin-made substrate. In this case, even if the sheet-like substrate moves between the driving roller and the winding roller at a certain speed and an aluminum oxide film is formed by sputtering on a single surface of the substrate , The invention can also be applied.

SM: Sputtering device

1: vacuum chamber

11: Film-forming room

12: Exhaust

13: Exhaust pipe

2 ₁ , 2 ₂ : target material

3 ₁ , 3 ₂ : magnet unit

22: backplane

23: insulator

31: Support board

32: Central magnet

33: Peripheral magnet

41a, 41b, 41c: gas supply port

42a: Gas pipe (for rare gas)

43a: Mass flow controller (for rare gas)

42b: Gas tube (for reaction gas)

43b: Mass flow controller (for reaction gas)

42c: Gas tube (for steam)

43c: Mass flow controller (for steam)

S: substrate (film-formed object)

Cu: cathode unit

P: Vacuum exhaust method

Pk: output from AC power

Ps: AC power

Claims (2)

A method of stress adjustment, characterized in that it is configured as a film-forming object and a target made of aluminum or aluminum oxide in a vacuum chamber, and a rare gas and oxygen are introduced into the vacuum chamber in a vacuum atmosphere The reaction gas, or the introduction of rare gas only, and the specific power is input to the target and the target is sputtered to form an aluminum oxide film on the surface of the film to be used to oxidize the target The stress adjustment of the aluminum film is within ±500MPa. For the vacuum chamber, hydrogen or water vapor is introduced. When the film is formed by sputtering, the water vapor should be 2×10 ^-3 Pa~0.1Pa There exists a partial pressure within the range. The stress adjustment method as described in item 1 of the patent application scope, wherein at least two of the aforementioned targets are provided in a vacuum chamber, and AC power of a specific frequency is input between the paired targets to each target Perform sputtering.

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