JP6887230B2 - Film formation method - Google Patents

Description

The present invention relates to a film forming method, and more particularly to a method of forming an aluminum oxide film on the surface of a film to be formed by reactive sputtering.

The aluminum oxide film may be conventionally used as a protective film (passivation film) or an insulating film for an element such as a thin film transistor in a display device or a semiconductor device. A sputtering method is generally known for forming such an aluminum oxide film (see, for example, Patent Documents 1 and 2), and among them, a so-called reactive sputtering method is generally used. In this case, a target made of aluminum is used, and the target and the object to be deposited are placed in a vacuum chamber and evacuated. And, for example, a predetermined power having a negative potential is applied to the target to sputter the target. As a result, the reaction product of the aluminum atom and oxygen scattered from the target adheres to and accumulates on the film to be formed, and an aluminum oxide film is formed on the surface thereof.

The aluminum oxide film formed as described above usually has a stress in the compression direction, but when the stress becomes large, a problem such as a large warp of the substrate is caused. Therefore, it is an urgent task to develop a film of an aluminum oxide film having a stress within a predetermined value with high productivity by a sputtering method. Therefore, the inventors of the present application have made extensive studies and have come to find that there is a correlation between the stress of the aluminum oxide film and the refractive index.

Japanese Unexamined Patent Publication No. 2003-3259 Japanese Unexamined Patent Publication No. 2010-114413

The present invention has been made based on the above findings, and an object of the present invention is to provide a film forming method capable of forming an aluminum oxide film having a stress within a predetermined value with high productivity. ..

In order to solve the above problems, in the present invention, a film to be formed and a target made of aluminum or aluminum oxide are arranged in a vacuum chamber, and a reaction containing rare gas and oxygen is performed in the vacuum chamber in a vacuum atmosphere. In a film forming method in which an aluminum oxide film is formed on the surface of a film to be formed by introducing a gas and applying a predetermined power to the target to sputter the target, aluminum oxide formed on the surface of the object to be formed is formed. Depending on the step of measuring the refractive index of the film and the measured refractive index, the sputtering conditions are changed so that the stress of the aluminum oxide film formed on the surface of the film to be formed is within a predetermined value, and the target is changed. Including the step of forming an aluminum oxide film on the surface of the film to be formed by sputtering, a reaction gas of water vapor or hydrogen gas is further introduced into the vacuum chamber, and steam or hydrogen gas is applied to the sputtering conditions. It is characterized by further including the introduction amount. In this case, the sputtering conditions include at least one of the pressure in the vacuum chamber at the time of film formation, the power input to the target, and the distance between the target and the film to be filmed.

According to the present invention, for example, an aluminum oxide film is formed on one film to be filmed under predetermined sputtering conditions, and the refractive index of the formed aluminum oxide film is used to form the next film to be filmed. By changing the sputter conditions when forming a film, that is, when it is determined from the refractive index that the stress of the aluminum oxide film is large in the compression direction, the power applied to the target can be reduced or for discharging. By increasing the flow rate of the rare gas to increase the pressure in the vacuum chamber and / or increasing the distance between the target and the film to be filmed, the surface of the film to be filmed (already to be filmed). If the number of high-energy particles (aluminum atoms and reaction products of these and oxygen) incident on the aluminum oxide film adhering to and deposited on the surface of the object is reduced, the stress of the aluminum oxide film is increased accordingly. Can be alleviated. As a result, an aluminum oxide film having a stress within a predetermined value can be formed with high productivity.

By the way, if hydrogen gas or water vapor is introduced without changing the input power to the target and the partial pressure (introduction amount of sputter gas) of the rare gas and the reaction gas in the vacuum chamber at the time of film formation, a predetermined film formation rate can be obtained. It was found that an aluminum oxide film having a lower stress was formed as compared with the case where hydrogen gas or water vapor was not introduced while maintaining the film. Based on this finding, in the present invention, when further introducing steam or hydrogen gas into the vacuum chamber, it is preferable that the sputtering conditions further include the amount of steam or hydrogen gas introduced.

The schematic sectional view of the sputtering apparatus which can carry out the film formation method of this invention. (A) to (c) are graphs showing changes in the stress and the refractive index of the aluminum oxide film when the sputtering conditions are changed. The graph which shows the change between the stress and the refractive index of an aluminum oxide film when steam gas is introduced during film formation.

Hereinafter, the present invention will be carried out by referring to the drawings as an example in which the target is made of aluminum, the film to be filmed is a rectangular glass substrate (hereinafter referred to as substrate S), and an aluminum oxide film is formed by reactive sputtering. The film forming method of the form will be described.

With reference to FIG. 1, SM is a magnetron-type sputtering apparatus capable of carrying out the film forming method of the present invention. The sputtering apparatus SM includes a vacuum chamber 1 that defines the film forming chamber 11. In the following, the terms indicating the directions such as "up" and "down" are based on the posture of the sputtering apparatus SM shown in FIG. An exhaust port 12 is opened on the side wall of the vacuum chamber 1, and an exhaust pipe 13 from a vacuum exhaust means P composed of a rotary pump, a dry pump, a turbo molecular pump, or the like is connected to the exhaust port 12, and a film forming chamber is formed. The inside of 11 can be evacuated and held at a predetermined pressure (for example, 1 × 10 ^-5 Pa).

At the bottom of the vacuum chamber 1, aluminum (e.g., 99.999% purity) two cathode unit Cu is provided composed of the target ₂ 1, _{2 2} and the magnet units ₃ 1, _{3 2} .. Each target 2 _1, 2 ₂ has been formed respectively in the same substantially rectangular parallelepiped shape, in its lower surface, during the deposition by sputtering, the copper backing plate 22 to cool the target 2 _1, 2 ₂ They are bonded via a bonding material (not shown) such as indium. _{Then, the targets 2 1} and 2 ₂ are installed on the lower inner surface of the vacuum chamber 1 via an insulator 23 that also serves as a vacuum seal in a state of being joined to the backing plate 22. In this case, the target 2 _1, 2 _2, at predetermined intervals in the lateral direction of the film forming chamber 11, and target 2 ₁ when not in _use, 2 ₂ of the upper surface, parallel to the substrate S below It is designed to be located in the same plane. Each target ₂ 1, _{2 2,} AC power supply output Pk from Ps are respectively connected, the AC power source each target ₂ 1 by Ps, _{2 2} between the predetermined frequency (e.g., 1 kHz to 100 kHz) AC power is turned on It has become so.

_{The magnet units 3 1} and 3 ₂ arranged below each backing plate 22 (outside the vacuum chamber 1) have the same shape, and the magnet units 3 ₁ and 3 ₂ are parallel to the backing plate 22. A support plate 31 (yoke) made of a flat plate made of a magnetic material is provided. On the support plate 31, a central magnet 32 arranged so as to be located on the center line of the support plate 31, and a periphery arranged in an annular shape along the outer periphery of the upper surface of the support plate 31 so as to surround the center magnet 32. a magnet 33 is provided in place of the polarity of the target ₂ 1, _{2 2.} In this case, for example, the sum of the volumes when converted to the same magnetization of the central magnet 32 and the volume when converted to the same magnetization of the peripheral magnet 33 surrounding the central magnet 32 (peripheral magnet: central magnet: peripheral magnet = 1: 2: It is designed to be about 1 (see FIG. 1)). Thus, each target 2 _1, 2 ₂ of upward balanced tunnel-shaped leakage magnetic field (not shown) are respectively formed. The central magnet 32 and the peripheral magnet 33 are known ones such as neodymium magnets, and these central magnets and peripheral magnets may be integrated or may be configured by arranging a plurality of magnet pieces having a predetermined volume in a row. .. Incidentally, for example, in order to enhance the utilization efficiency of the target 2 _1, 2 _2, the magnet unit 3 _1, 3 ₂ to connect the drive means (not shown), during the film formation by sputtering, the vertical or horizontal direction at least a It may be reciprocated in a predetermined stroke in the direction.

Further, gas supply ports 41a and 41b are opened on 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 communicate with a gas source of a rare gas such as argon gas (not shown) and a gas source of an oxygen-containing reaction gas such as oxygen gas and ozone, respectively, via mass flow controllers 43a and 43b. The rare gas and the reaction gas whose flow rate is controlled can be introduced into the film forming chamber 11. In the present embodiment, a gas supply port 41c is further provided on the side wall of the vacuum chamber 1, and a gas pipe 42c having a mass flow controller 43c interposed is connected to the gas supply port 41c. The flow rate controlled water vapor can be introduced into the chamber 11.

The sputtering apparatus SM has a known control unit Cr including a memory, a microcomputer, a sequencer, and the like, and for example, controls the operations of the mass flow controllers 43a to 43c, the AC power supply Ps, and the vacuum exhaust means P in an integrated manner. ing. Then, when each target 2 ₁ and 2 ₂ is sputtered by the sputtering apparatus SM to form an aluminum oxide film on the surface of the substrate S by reactive sputtering, each target 2 _{1 arranged side by side by a vacuum transfer robot (not shown) is used.} , 2 ₂ sets the substrate S at a predetermined position of the opposing film formation chamber 11 to upper part, evacuating the film forming chamber 11 to a predetermined pressure. When the film forming chamber 11 reaches a predetermined pressure, the mass flow controller 43a, and controls the 43b introducing rare gas and reaction gas, to introduce the AC power between the target 2 _1, 2 ₂ by an AC power source Ps. Thus, high-density plasma is generated in each target 2 _1, 2 ₂ of the upper race track shape. Then, the target 2 ₁ of noble gas in the plasma _ion, 2 ₂ are respectively sputter. Accordingly, the target 2 _1, 2 ₂ reaction product of aluminum atoms and oxygen scattered from adhesion to the surface of the substrate S, the aluminum oxide film is formed deposited to.

Here, an experiment was conducted in which an aluminum oxide film was formed on the surface of the substrate S using the sputtering apparatus SM shown in FIG. In this case, the predetermined value the distance between each target ₂ 1, _{2 2} and the substrate S (for example, 180 mm) is set to the pressure in the film forming chamber 11 which is evacuated is held in 0.5Pa As described above, the mass flow controllers 43a and 43b are controlled to introduce argon gas and oxygen gas as rare gases at a flow rate ratio of 8: 2. Then, the AC power supply target ₂ 1 by Ps, _{2 2} input power to between the (AC power) is varied in a range of 10KW～40kW, it was measured and the stress (MPa) and the refractive index at that time, FIG results It is shown in 2 (a). The refractive index was measured using an ellipsometer, and the stress was measured using a thin film stress measuring device. According to this, when gradually increasing the power applied to the target ₂ 1, _{2 2,} which according While compressive stress in the direction of (MPa) is increased, the refractive index becomes 1.600 to 1.660 It was.

Each target ₂ 1, _{2 2} and the predetermined value the distance between the substrate S (for example, 180 mm) is set to, 40 kW AC target ₂ 1 by the power Ps, _{2 2} input power to between (AC power) Set to. Then, while increasing or decreasing the amount of argon introduced and the amount of oxygen introduced in the flow rate ratio in the range of 8: 2 to 3: 7 so that the sum of the amount of argon introduced and the amount of oxygen introduced into the film forming chamber 11 is kept constant. , The pressure of the film forming chamber 11 at the time of film formation was maintained at 0.3 Pa. The stress (MPa) and the refractive index at that time were measured, and the results are shown in FIG. 2 (b). According to this, when the amount of the rare gas for discharge is reduced and the amount of oxygen introduced in the film forming chamber 11 is increased, the stress in the compression direction increases as described above, while the refractive index is 1. It was .680 to 1.620.

Furthermore, the AC power supply target ₂ 1 by Ps, _{2 2} input power to between the (AC power) is set to 10 kW, so that the pressure in the film forming chamber 11 which is evacuated is held at 0.5 Pa, The mass flow controllers 43a and 43b were controlled to introduce argon gas and oxygen gas as rare gases at a flow rate ratio of 8: 2. Then, the substrate S and the distance between the target ₂ 1, _{2 2} of the upper surface varied from 180Mm～300mm, were measured and the stress (MPa) and the refractive index at that time, FIG. 2 (c results ). According to this, As you shorten the distance between the substrate S and the target ₂ 1, _{2 2,} while the compressive stress in the direction of (MPa) increases accordingly, the refractive index, from 1.600 to 1 It became .640.

Based on the above findings, in the present embodiment, the pressure, the target 2 _1, 2 input electric power and the target 2 ₁ to _2, 2 ₂ and the substrate S of the vacuum chamber 1 at the time of film formation (film formation chamber 11) The distance between them is set as a sputtering condition, and the relationship between the stress (MPa) of the aluminum oxide film and the refractive index when each sputtering condition is changed is stored in advance in the memory of the control unit Cr. Then, for example, an aluminum oxide film is formed on one substrate S under predetermined sputtering conditions, and the refractive index of the formed aluminum oxide film is measured. When forming a film on the next substrate S, from the measured refractive index, pressure in the vacuum chamber 1 during the deposition, the applied power and the target 2 ₁ 2 _1, 2 ₂ to the _target, 2 ₂ and the substrate S Change the sputter conditions with either or a combination of these distances. Specifically, when the refractive index, such as stress of the aluminum oxide film is determined to be larger in the compression direction, or to lower the power applied to the target 2 _1, 2 ₂ by the AC power source Ps, by the mass flow controller 43a and increasing the pressure in the vacuum chamber 1 by decreasing the flow rate of the rare gas discharge, and / or by increasing the distance between the target 2 _1, 2 ₂ and the substrate S, the substrate S surface (already If the number of high-energy particles (aluminum atoms and reaction products of this and oxygen) incident on the aluminum oxide film adhering to and deposited on the surface of the substrate S is reduced, the aluminum oxide film can be adjusted accordingly. Stress can be relieved.

According to the above embodiment, by changing the sputtering conditions according to the measured refractive index, it is possible to form an aluminum oxide film having a stress within a predetermined value with high productivity. Although not particularly illustrated and described, an auxiliary chamber is continuously provided in the vacuum chamber 1 via a gate valve, an aluminum oxide film is formed on one substrate S under predetermined sputtering conditions, and then a transfer robot is used. It is preferable to configure the sputtering apparatus SM so that the substrate S can be moved to the auxiliary chamber and the refractive index can be measured as quickly as possible. Moreover, if by attaching a drive means for reciprocating toward and away from freely substrate S relative to the target 2 _1, 2 ₂ to the holding device for holding the substrate S in the vacuum chamber 1, the substrate S and the target 2 _1, the distance between the 2 ₂ can be appropriately changed. Since known means can be used as the holding means and the driving means, detailed description thereof will be omitted here.

Next, using the sputtering apparatus SM, an experiment was conducted in which an aluminum oxide film was formed while introducing water vapor into the film forming chamber 11 at the time of film formation. In this case, set the distance between each target ₂ 1, _{2 2} and the substrate S 180 mm, the AC power supply target ₂ 1 by Ps, _{2 2} input power to between the (AC power) to 40 kW, also evacuated The mass flow controllers 43a and 43b were controlled so that the pressure in the film forming chamber 11 was maintained at 0.5 Pa, and argon gas and oxygen gas as rare gases were introduced at a flow rate ratio of 8: 2. .. Then, the mass flow controller 43c was controlled to introduce water vapor at a predetermined flow rate. In this case, the partial pressure of water vapor ^{is changed in the range of 5 × 10 -4} Pa to 1 Pa, and the change in the stress (MPa) and the refractive index of the aluminum oxide film at that time is shown in FIG. According to this, when water vapor is introduced, the stress of the aluminum oxide film is relaxed, and when the partial pressure of water vapor is 1 × 10 ^-3 Pa, the stress of the aluminum oxide film can be reduced to about -500 MPa, and the refractive index is high. , 1.630.

When the partial pressure of water vapor is 1 × 10 ^-2 Pa, the stress of the aluminum oxide film decreases in inverse proportion to the partial pressure of the water vapor, and when the partial pressure of water vapor is 1 × 10 ^-2 Pa, oxidation occurs. The stress of the aluminum film was about -50 MPa, and the refractive pressure was 1.550. Further, when the partial pressure of water vapor is increased, the aluminum oxide film has a stress in the tensile direction (tensile stress), and even when the partial pressure of water vapor is 0.1 Pa, the stress of the aluminum oxide film is increased to about +100 MPa. The refractive index was 1.500. However, when the partial pressure was higher than 0.1 Pa, an abnormal discharge was induced, and the aluminum oxide film could not be formed normally.

Based on the above findings, in the present embodiment, it is assumed that the introduction amount of water vapor is included in the sputtering conditions, and the relationship between the stress (MPa) of the aluminum oxide film and the refractive index when the introduction amount of water vapor is changed is controlled. It is stored in the memory of the unit Cr in advance. Then, at the time of film formation by sputtering, the mass flow controller 43c is controlled according to the refractive index to appropriately control the amount of water vapor introduced into the film formation chamber 11. The amount of water vapor introduced can be controlled separately from the above-mentioned changes in each sputtering condition or in combination with each sputtering condition.

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. In the above embodiment, the case where water vapor is introduced at a predetermined partial pressure during the film formation by sputtering has been described as an example, but the present invention is not limited to this, and there is also a case where hydrogen gas is introduced at a predetermined partial pressure. , It was confirmed that there is a predetermined relationship between the stress of the aluminum oxide film and the refractive index. Further, in the above embodiment, the case where the rare gas, oxygen gas and water vapor are introduced from the gas supply ports 41a, 41b and 41c provided on the side wall of the vacuum chamber 1 has been described as an example, but the present invention is not limited thereto. .. Although not shown and described, for example, fitted through the gas pipe in the bottom wall of the vacuum chamber 1, ejected from the tip of the gas pipe located around the target 2 _1, 2 _2, noble gases, oxygen gas and water vapor You may do so.

Also, in the above embodiment, the target 2 _1, 2 ₂ has been described as an example those made of aluminum, as the target 2 _1, 2 ₂ made of aluminum oxide, rare gas alone, or in addition to the rare gas oxygen while introducing a reaction gas containing, by high frequency power to the sputtering target 2 _1, 2 _2, the present invention is also applicable to the case of forming can be applied. Further, arranged in parallel a plurality of targets 2 _1, 2 _2, have been described what turning on the AC power by the AC power source Ps to those paired as an example, but the invention is not limited to one target The present invention can also be applied to a case where DC power is input from a DC power supply. Further, in the above embodiment, the case where the film to be filmed is a glass substrate has been described as an example, but for example, the film to be filmed may be a resin base material. In this case, the present invention can also be applied to a film in which an aluminum oxide film is formed on one side of the base material by sputtering while moving the sheet-shaped base material between the drive roller and the take-up roller at a constant speed. ..

SM ... Sputtering device, 1 ... Vacuum chamber, 2 ₁ , 2 ₂ ... Target, 42a ... Gas pipe (for rare gas), 43a ... Mass flow controller (for rare gas), 42b ... Gas pipe (for reaction gas), 43b ... Mass flow controller (for reaction gas), 42c ... gas pipe (for water vapor), 43c ... mass flow controller (for water vapor), Cr ... control unit, S ... substrate (film to be formed).

Claims (2)

A film to be formed and a target made of aluminum or aluminum oxide are placed in a vacuum chamber, a reaction gas containing rare gas and oxygen is introduced into the vacuum chamber in a vacuum atmosphere, and a predetermined power is applied to the target. In a film forming method in which an aluminum oxide film is formed on the surface of a film to be formed by sputtering the target.
The process of measuring the refractive index of the aluminum oxide film formed on the surface of the film to be filmed, and
Depending on the measured refractive index, the sputtering conditions are changed so that the stress of the aluminum oxide film formed on the surface of the film to be filmed is within a predetermined value, and the target is sputtered to obtain the film to be filmed. Including the step of forming an aluminum oxide film on the surface
A film forming method comprising further introducing water vapor or hydrogen gas into the vacuum chamber and further including the amount of water vapor or hydrogen gas introduced in the sputtering conditions. The film formation according to claim 1, wherein the sputtering conditions include at least one of the pressure in the vacuum chamber at the time of film formation, the power input to the target, and the distance between the target and the film to be filmed. Method.

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