KR20180115731A - Stress adjustment method - Google Patents

Abstract

Provided is a film forming method capable of efficiently forming an aluminum oxide film having a stress within a predetermined value while maintaining a predetermined film forming rate. In the present invention, the film-forming material S and the aluminum targets 2 ₁ and 2 ₂ are disposed in the vacuum chamber 1 so that the rare gas and oxygen gas are introduced into the vacuum chamber in the vacuum atmosphere, The target is sputtered by applying electric power to adhere and deposit the reaction product of aluminum atom and oxygen on the surface of the film to be filmed to form an aluminum oxide film. At this time, water vapor is introduced into the vacuum chamber. The partial pressure of water vapor is set in the range of 1 × 10 ^-3 Pa to 0.1 Pa.

Description

How to deposit

BACKGROUND OF THE INVENTION Field of the Invention The present invention relates to a film forming method and, more particularly, to forming an aluminum oxide film on a surface of a film to be film-formed by sputtering.

The aluminum oxide film is conventionally used as a protective film (passivation film) or an insulating film of a device such as a thin film transistor in a display device or a semiconductor device. It is generally known that the aluminum oxide film is formed by a sputtering method (see, for example, Patent Documents 1 and 2), and among them, a so-called reactive sputtering method is generally used. In this case, the target and the film-forming material are placed in a vacuum chamber by using aluminum as a target and vacuum suction is performed. When a predetermined pressure is reached, a reactive gas such as oxygen and rare gas is introduced into the target, And the target is sputtered by applying a predetermined electric power having a negative potential. As a result, the reaction product of aluminum atoms and oxygen scattered from the target adheres to and deposits on the film to be filmed, and an aluminum oxide film is formed on the surface of the film.

The aluminum oxide film thus formed usually has a stress in the compression direction, but when the compressive stress is large, the warpage of the substrate is increased. In this case, when the power applied to the target is increased, the compressive stress is increased, and when the pressure in the vacuum chamber is lowered by reducing the flow rate of the discharge rare gas at the time of film formation by sputtering, . Therefore, when the power applied to the target is lowered or the pressure of the vacuum chamber at the time of film formation is increased, an aluminum oxide film having a stress within a predetermined value (for example, ± 500 MPa) can be formed. The film formation rate is lowered.

Patent Document 1: JP-A-2003-3259 Patent Document 2: JP-A-2010-114413

In view of the above, it is an object of the present invention to provide a film forming method capable of effectively forming an aluminum oxide film having a stress within a predetermined value while maintaining a predetermined film forming rate.

In order to solve the above problems, the present invention is characterized in that a film-forming material and an aluminum or aluminum oxide target are arranged in a vacuum chamber, only a rare gas and an oxygen-containing reaction gas or rare gas are introduced into a vacuum chamber in a vacuum atmosphere, In which a target is sputtered to form an aluminum oxide film on the surface of a film to be formed, characterized in that hydrogen gas or steam is introduced into the vacuum chamber.

According to the present invention, hydrogen gas or steam is introduced without changing the applied electric power to the target, the rare gas in the vacuum chamber at the time of film formation, and the partial pressure of the reactive gas (introduction amount of the sputter gas) , An aluminum oxide film having a low stress can be formed as compared with the case where hydrogen gas or steam is not introduced.

In the present invention, when introducing steam into the vacuum chamber, it is preferable that the partial pressure of the steam in the vacuum chamber be set in the range of 1 × 10 ^-3 Pa to 0.1 Pa at the time of film formation by the sputtering. According to this, it is possible to reliably lower the stress of the aluminum oxide film while maintaining a predetermined deposition rate, and it is confirmed that the compressive stress can be set to about -50 MPa when the partial pressure of steam is 1 10 ^-2 Pa. . If the partial pressure of the water vapor is lower than 1 x 10 < ^-3 > Pa, the aluminum oxide film can not be formed in a state in which the stress is effectively reduced, and if the partial pressure of steam exceeds 0.1 Pa, So that the aluminum oxide film can not be formed.

1 is a schematic cross-sectional view of a sputtering apparatus capable of carrying out the deposition method of the present invention.
2 is a graph showing the results of an experimental example showing the effect of the present invention.

Hereinafter, with reference to the drawings, a case where an aluminum oxide film is formed by reactive sputtering with a target made of aluminum and a film to be deposited as a rectangular glass substrate (hereinafter referred to as a substrate S) Will be described.

1, SM is a magnetron type sputtering apparatus capable of carrying out the deposition method of the present invention. The sputtering apparatus SM has a vacuum chamber 1 for partitioning a deposition chamber 11. Hereinafter, the terms "direction" and "direction" refer to the orientation of the sputtering apparatus SM shown in FIG. An exhaust port 12 is formed in a side wall of the vacuum chamber 1. An exhaust pipe 13 from a vacuum exhaust means P constituted by a rotary pump, a dry pump and a turbo molecular pump is connected to the exhaust port 12 , The inside of the deposition chamber 11 can be vacuum-sucked and maintained at a predetermined pressure (for example, 1 × 10 ^-5 Pa).

A lower portion of the vacuum chamber 1, aluminum (e. G., A purity of 99.999%) of the target _{(21, 22)} and magnet unit _{(31, 32),} two cathode unit (Cu) consisting of Respectively. Each of the targets 2 ₁ and 2 ₂ is formed in substantially the same rectangular parallelepiped shape and a copper cooling plate 22 for cooling the targets 2 ₁ and 2 ₂ during film formation by sputtering (Not shown) such as indium. The targets 2 ₁ and 2 ₂ are attached to the inner surface of the lower portion of the vacuum chamber 1 through the insulator 23 serving as a vacuum seal together with the cooling plate 22. In this case, each of the targets 2 ₁ and 2 ₂ has a predetermined gap in the left-right direction of the deposition chamber 11, and the surface of the target 2 ₁ , 2 ₂ at the time of un- S in the same plane. Each target _{(21, 22),} the AC output (Pk) from the power source (Ps) are connected, respectively, between each target _{(21, 22)} by the AC power (Ps), for a predetermined frequency (for example, , 1 kHz to 100 kHz) is to be applied.

The magnet units 3 ₁ and 3 ₂ disposed at the lower side of each cooling plate 22 (outside the vacuum chamber 1) have the same shape and the magnet units 3 ₁ and 3 ₂ are cooled And a support plate 31 (yoke) provided parallel to the plate 22 and composed of a flat plate made of a magnetic material. A central magnet 32 is disposed on the support plate 31 on the center line of the support plate 31. The center magnet 32 is annularly formed along the outer periphery of the upper surface of the support plate 31 so as to surround the periphery of the center magnet 32 The disposed peripheral magnets 33 are provided so as to change the polarity of the targets 2 ₁ and 2 ₂ . In this case, for example, when the volume of the central magnet 32 converted into the magnetization of the central magnet 32 is converted into the magnetization of the surrounding magnet 33 surrounding the periphery thereof (the peripheral magnet: Center magnet: peripheral magnet = 1: 2: 1 (see Fig. 1)). As a result, a balanced magnetic field (not shown) having a tunnel shape is formed above each of the targets 2 ₁ and 2 ₂ . The central magnet 32 and the peripheral magnet 33 are known ones such as a neodymium magnet. Such a central magnet and a surrounding magnet may be integrated or may be constituted by arranging a plurality of magnet pieces of a predetermined volume. Further, for example, driving means (not shown) may be connected to the magnet units 3 ₁ , 3 ₂ to increase the utilization efficiency of the targets 2 ₁ , 2 ₂ , and during the film formation by sputtering, Or reciprocating in a predetermined stroke in at least one of the left and right directions.

Gas supply ports 41a and 41b are formed in 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 a gas source of a rare gas such as argon (not shown) and a gas source of an oxygen-containing reaction gas such as oxygen gas or ozone (not shown) via mass flow controllers 43a and 43b, So that the rare gas and the reaction gas whose flow rate is controlled can be introduced into the chamber 11.

When the aluminum oxide film is formed on the surface of the substrate S by reactive sputtering by sputtering the targets 2 ₁ and 2 ₂ by the sputtering apparatus SM, The substrate S is set at a predetermined position above the deposition chamber 11 opposed to the targets 2 ₁ and 2 ₂ and the deposition chamber 11 is evacuated to a predetermined pressure. When the film forming chamber 11 reaches a predetermined pressure, the mass flow controllers 43a and 43b are controlled to introduce the rare gas and the reactive gas, and alternating current power Ps is applied between the targets 2 ₁ and 2 ₂ , . As a result, a high-density plasma is generated in the form of a racetrack above each of the targets 2 ₁ and 2 ₂ . Then, the targets 2 ₁ and 2 ₂ are sputtered by the ions of the rare gas in the plasma. As a result, reaction products of aluminum atoms and oxygen scattered from the targets (2 ₁ , 2 ₂ ) adhere to and accumulate on the surface of the substrate (S), and an aluminum oxide film is formed.

Here, the aluminum oxide film formed as described above generally has a stress in the compression direction, but when the compressive stress is large, a problem arises that the warp of the substrate becomes large. Therefore, it is necessary to be able to form an aluminum oxide film having a stress within a predetermined value (for example, ± 500 MPa) while maintaining a predetermined deposition rate. In this embodiment, a gas supply port 41c is additionally provided on the side wall of the vacuum chamber 1, a gas pipe 42c via a mass flow controller 43c is connected to the gas supply port 41c, So that the flow rate-controlled steam can be introduced into the deposition chamber 11. Then, for example, at the time of film formation by sputtering, the mass flow controller 43c is controlled to introduce water vapor into the film formation chamber 11. In this case, it is preferable to control the flow rate of the water vapor by the mass flow controller 43c so that the partial pressure of the water vapor in the film formation chamber 11 at the time of film formation is in the range of 1 × 10 ^-3 Pa to 0.1Pa.

The input electric power to the targets 2 ₁ and 2 ₂ and the partial pressure of the rare gas and oxygen gas at the time of film formation (that is, the introduction amount of the rare gas and the reactive gas under the control of the mass flow controllers 43 a and 43 b) It is possible to form an aluminum oxide film having a lower stress as compared with the case where steam is not introduced while maintaining a predetermined deposition rate. At this time, when the partial pressure of steam is in the range of 1 × 10 ^-3 Pa to 0.1 Pa, the stress of the aluminum oxide film can be reliably lowered. For example, when the partial pressure of steam is 1 × 10 ^-2 Pa, It was confirmed that the stress can be set to about -50 MPa. If the partial pressure of the water vapor is lower than 1 x 10 < ^-3 > Pa, the aluminum oxide film can not be formed in a state in which the stress is effectively reduced, and if the partial pressure of steam exceeds 0.1 Pa, So that the aluminum oxide film can not be formed.

In order to confirm the above effect, an experiment was conducted to form an aluminum oxide film on the surface of the substrate S by using the sputtering apparatus SM shown in Fig. First, as a comparative experiment, the distance between each of the targets 2 ₁ and 2 ₂ and the substrate S is 180 mm, and the input power (AC power) between the targets 2 ₁ and 2 ₂ by the AC power source Ps is The mass flow controllers 43a and 43b were controlled so that the pressure in the deposition chamber 11 to be evacuated was maintained at 0.5 Pa so that argon and oxygen gas as rare gases were supplied at a rate of 8: . The deposition rate and the stress of the aluminum oxide film formed on the surface of the substrate S at the center of the substrate S were measured. The deposition rate was 10.56 nm / min and the stress was about -1000 MPa (compressive stress) Respectively. The film thickness was measured with an ellipsometer, and the stress was measured with a thin film stress measuring apparatus.

Next, as an experiment showing the effect of the present invention, the sputtering conditions were the same as the above, and the steam was also introduced at a predetermined flow rate by controlling the mass flow controller 43c at the time of film formation. In this case, the partial pressure of water vapor is changed in the range of 5 × 10 ^-4 Pa ~ 1Pa, also shown in the variation of the time the aluminum oxide film stress (MPa) of the. According to this, when steam is introduced, the stress of the aluminum oxide film is lowered, and when the partial pressure of steam is 1 10 ^-3 Pa, the stress of the aluminum oxide film can be lowered to about -500 MPa. The deposition rate at this time was 10.48 nm / min, and it was confirmed that the deposition rate hardly changed. And, until the partial pressure of water vapor 1 × 10 ^-2 Pa, and inversely proportional to the partial pressure of the water vapor the aluminum oxide film stress is further reduced, when the partial pressure of water vapor 1 × 10 ^-2 Pa, the aluminum oxide film stress of about - It was confirmed that the pressure was 50 MPa. The deposition rate at this time was 11.00 nm / min. Further, it was confirmed that when the partial pressure of water vapor was increased, the aluminum oxide film had a tensile stress (tensile stress) in the tensile direction, and the stress of the aluminum oxide film was about +100 MPa even when the partial pressure of steam was 0.1 Pa. The film formation rate at this time was 11.20 nm / min. However, if the partial pressure was higher than 0.1 Pa, an abnormal discharge was induced, and the aluminum oxide film could not be normally formed.

The embodiments of the film forming method of the present invention have been described above, but the present invention is not limited thereto. In the above embodiment, the case where water vapor is introduced at a predetermined partial pressure during film formation by sputtering has been described as an example. However, the present invention is not limited to this, and even when hydrogen gas is introduced at a predetermined partial pressure, It was confirmed that it could be. In the above embodiment, rare gas, oxygen gas and steam are introduced from the gas supply ports 41a, 41b and 41c provided in the side wall of the vacuum chamber 1. However, the present invention is not limited to this. Although not shown in the drawing, for example, gas pipes are passed through the bottom wall of the vacuum chamber ₁ , and rare gas, oxygen gas or steam is jetted from the tip of the gas pipe located around the targets 2 ₁ , 2 ₂ You may.

Further, in the above-mentioned embodiments, the target _{(21, 22)} a has been described that the aluminum zero example, create a target _{(21, 22)} of aluminum oxide, introducing an oxygen in addition to the rare gas only, or a noble gas The present invention can also be applied to a case where the targets 2 ₁ and 2 ₂ are sputtered by applying high-frequency power to form a film. In the above description, a plurality of targets 2 ₁ and 2 _{2 are} provided in parallel and alternating current power is supplied to the pair by an alternating current power source Ps. However, the present invention is not limited to this, And the present invention can be applied to the case where DC power is supplied from a DC power source. In the above embodiment, the case where the film-forming material is a glass substrate has been described. However, for example, the film-forming material may be made of a resin base material. In this case, the present invention can also be applied to forming an aluminum oxide film on one surface of a substrate by sputtering while moving the sheet-like base material between the driving roller and the winding 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)
S: Substrate (film forming material)

Claims (2)

A target to be formed is placed in a vacuum chamber and a target made of aluminum or aluminum oxide is introduced into a vacuum chamber of a vacuum atmosphere to introduce only a rare gas and an oxygen containing reactive gas or a rare gas, A film forming method for forming an aluminum oxide film on a surface of a film-
Wherein hydrogen gas or water vapor is introduced into the vacuum chamber.
The film forming method according to claim 1, wherein when steam is introduced into the vacuum chamber, the partial pressure of the water vapor in the vacuum chamber is set to 1 × 10 ^-3 Pa to 0.1 Pa when the film is formed by sputtering.

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