JP4401577B2 - Deposition method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a film forming method based on ion plating, a vacuum film forming apparatus control device, and a vacuum film forming apparatus.
[0002]
[Prior art]
In a vacuum film-forming apparatus based on ion plating, a substrate disposed in a vacuum chamber is generated by supplying high-frequency power while maintaining a predetermined gas pressure in the vacuum chamber and generating plasma discharge in the vacuum chamber. It can be formed into a film.
[0003]
When film formation is performed by such ion plating, the gas pressure and electric power during film formation are controlled so as to take a constant gas pressure value and electric power value according to the film formation conditions. That is, the gas pressure and power are controlled so as to generate a desired plasma so that it can be formed into a target film according to the raw material of the film, the type of the substrate, and the like.
[0004]
[Problems to be solved by the invention]
By the way, when performing vacuum film formation based on such ion plating, it may be desired to form a film at a relatively low gas pressure.
[0005]
That is, when the substrate to be formed is made of resin or the like, it may be desired to reduce the thermal influence on the substrate, and it is desired to form the film at a lower gas pressure.
[0006]
In addition, when the film is formed at a low pressure, the probability that the vaporized particles that have jumped out of the evaporation source will collide with the gas molecules before reaching the substrate is lower. It can be made incident. Thereby, the density of the formed film can be increased, and the refractive index of the film with respect to light can be increased.
[0007]
However, it is difficult to generate a plasma discharge stably when trying to form a film with a low gas pressure, and it is difficult to generate a plasma discharge, or it may cause instability of the generated plasma discharge and cause it to disappear. Sometimes it ends up.
[0008]
Accordingly, an object of the present invention is to control film forming conditions so as to stably maintain plasma discharge when forming a film by ion plating.
[0009]
[Means for Solving the Problems]
In order to solve the above-mentioned problems, the present invention is configured by ion plating on a substrate disposed in the vacuum chamber by setting the inside of the vacuum chamber to a predetermined gas pressure and supplying at least a predetermined high-frequency power into the vacuum chamber. A film forming method for forming a film, comprising: a main step of supplying a first high-frequency power under a first gas pressure to form a film on the substrate; and a predetermined step under a predetermined gas pressure prior to the main step. And a preliminary step of generating a plasma discharge by supplying a high frequency power of
In the preliminary step, the gas pressure at the start is larger than the first gas pressure, the high frequency power at the start is equal to or higher than the first high frequency power,
By the start of the main process, the gas pressure is reduced to the first gas pressure, and the high-frequency power is adjusted to the first high-frequency power (Claim 1).
[0010]
According to this film forming method, the preliminary step is executed prior to the main step of actually forming a film on the substrate, and the main step is executed after the plasma discharge is generated from the preliminary step to stabilize the plasma discharge. . Therefore, even if it is not easy to start the plasma discharge under the first gas pressure and the first high-frequency power, which are the film forming conditions in the main process, the plasma discharge is stably generated in advance by the preliminary process. Therefore, the plasma discharge can be stably maintained under the film forming conditions in the main process.
[0011]
Then, in the preliminary step, the adjustment of the high-frequency power can be started after the gas pressure starts decreasing (Claim 2). As a result, the gas pressure is changed before the high-frequency power is adjusted. Therefore, when the high-frequency power is supplied to the vacuum chamber, the operation can be made more stable and the plasma discharge can be made more stable.
[0012]
In starting the adjustment of the high-frequency power after starting the reduction of the gas pressure (Claim 2), the adjustment of the high-frequency power is started after reducing the gas pressure to the first gas pressure. (Claim 3). Thereby, since the high frequency power is adjusted after the gas pressure is set to the first gas pressure, the plasma discharge is more easily stabilized when the high frequency power is supplied while maintaining the plasma discharge.
[0013]
And about the above film-forming method (Claims 1 thru | or 3), it can carry out by supplying further DC power in a vacuum chamber,
Supply the DC power in the main process as the first DC power,
The DC power can be supplied from the preliminary process and increased to the first DC power by the start of the main process.
[0014]
Thereby, when supplying the DC power, the DC power is supplied from the preliminary process prior to the main process, which is the first DC power required for film formation. Instability of the plasma discharge accompanying this is not caused.
[0015]
And in supplying the DC power in the preliminary step (Claim 4), it can be started after the high-frequency power is adjusted to the first high-frequency power (Claim 5). As a result, in the preliminary process, when both the high frequency power and the direct current power are supplied into the vacuum chamber, both of them are not changed, so that the plasma discharge can be maintained more stably.
[0025]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to FIGS. 1 to 3.
[0026]
FIG. 1 is a schematic diagram showing a schematic configuration of a vacuum film forming apparatus 20 that can be used in the practice of the present invention. The vacuum film forming apparatus 20 is configured to be able to form a film based on a vacuum film forming method called ion plating.
[0027]
The interior space of the vacuum chamber 1 is evacuated by a vacuum pump. The vacuum chamber 1 is configured to be able to supply an inert gas or a film source gas from an air supply port 18 to an internal space.
[0028]
Then, by adjusting the exhaust force of the opening and closing degree and the vacuum pump valve to conduct the gas into the chamber 1 of the air supply port 18, but may be freely adjusted in the gas pressure in the chamber 1, 10 ^-3 Pa The range of 10 ⁻¹ Pa or less can be freely adjusted.
[0029]
The degree of opening and closing of the valve of the air supply port 18 and the exhaust force of the vacuum pump are controlled by a control device 12 described later, whereby the gas pressure in the chamber 1 is controlled. ing.
[0030]
A substrate holder 2 for holding a substrate 5 on which a film is formed is disposed in the upper part of the vacuum chamber 1. The substrate holder 2 is driven to rotate by a motor not specifically shown in FIG. 1, and is held rotatably.
[0031]
The substrate holder 2 is formed of a conductive material and is connected to each of the high frequency power source 15 and the DC power source 16. That is, in the example of the vacuum film forming apparatus 20, the substrate holder 2 functions as an electrode for supplying electric power for generating plasma discharge.
[0032]
The high frequency power source 15 outputs high frequency power, and the DC power source 16 outputs DC power. The high frequency power supply 15 is connected to the substrate holder 2 via a DC blocking capacitor not shown in FIG. 1 and a matching circuit (MB) 17 shown in FIG. The DC power supply 16 is connected to the substrate holder 2 via a choke coil not shown in FIG.
[0033]
In connecting the high frequency power supply 15 and the DC power supply 16 to the chamber 1 side, the vacuum chamber 1 formed of a conductive material is grounded and the output terminal of the high frequency power supply 15 is connected as shown in FIG. Among these, the other side with respect to the substrate holder 2 side is grounded. The DC power supply 16 is connected so that the substrate holder 2 side is a negative electrode.
[0034]
Although film formation is possible even when only high-frequency power is supplied without using the DC power supply 16, if DC power is also supplied, ions can be made to enter the substrate 5 more strongly, and the substrate 5 Therefore, the film can be easily attached to the film.
[0035]
The high-frequency power supply 15 and the DC power supply 16 are controlled by a control device 12 described later with respect to the output size, the output start and end timing, the characteristics of the output changing with time, and the like. Yes. The high frequency power supply 15 is controlled by the control device 12 with respect to the output frequency.
[0036]
The matching circuit 17 performs a matching operation to match the impedance on the chamber 1 side with respect to the high-frequency power supply 15. As shown in FIG. 2, the matching circuit 17 is a well-known circuit including, for example, variable capacitors C1 and C2 and a choke coil L1.
[0037]
The matching circuit 17 responds to a change in impedance on the chamber 1 side due to a change in gas pressure in the chamber 1 or a change in impedance on the power source 15 side due to a change in the operating state of the power source 15. The impedance 17 is automatically changed to match the impedance on the power source 15 side with the impedance on the chamber 1 side.
[0038]
An evaporation source 10 for evaporating the raw material material of the film into the space in the chamber 1 is disposed in the lower part of the chamber 1. The evaporation source 10 can be constituted by a crucible 7 and an electron gun 8 as shown in FIG. The crucible 7 is supplied with a film material 9. The raw material 9 of the film is evaporated into the space in the chamber 1 by irradiation of the electron beam 11 by the electron gun 8. Then, the raw material of the film evaporated from the evaporation source 10 can be turned into plasma by the high-frequency power and direct-current power supplied into the vacuum chamber 1.
[0039]
The control device 12 outputs a control signal to control the operation of each device described above included in the film forming device 20 other than the control device 12, and the signal output from these devices is input. The film forming process executed by the film forming apparatus 20 is controlled.
[0040]
Note that signal input / output between the control device 12 and each of the devices is configured via an interface mechanism, an A / D conversion mechanism, or the like not shown, which is well-known in digital control.
[0041]
The control device 12 includes a programmable controller, and can freely describe a film forming procedure in a program given to the programmable controller. Thereby, the control apparatus 12 can set freely the film-forming conditions performed with the film-forming apparatus 20, and can perform a desired film-forming process.
[0042]
An example of the programmable controller is a sequencer. According to the sequencer, it is easy to describe the contents of a process to be executed in a program, and it is easy to set a desired film forming process.
[0043]
The program given to the programmable controller of the control device 12 includes a film forming condition for executing a main process for forming a film on the substrate 5 and a preliminary process for generating plasma discharge prior to the main process. Deposition conditions are described.
[0044]
The contents set as the film forming conditions for the main process include the following contents. That is, in the main process, the gas pressure in the chamber 1 is set to the first gas pressure. This first gas pressure is relatively low and is generally in the range of 6.67 × 10 ⁻³ Pa to 6.67 × 10 ⁻² Pa. In the main process, the power output from the high frequency power supply 15 is the first high frequency power, and the power output from the DC power supply 16 is the first DC power.
[0045]
With respect to the first gas pressure, the first high-frequency power, and the first DC power, the required plasma corresponding to the type of the substrate 5 and the raw material of the film can be generated and formed on the target film. Selected.
[0046]
The contents set as the film forming conditions in the preliminary process include the following contents. That is, the gas pressure in the chamber 1 in the preliminary process is made larger than the first gas pressure at the start thereof, and is reduced to the first gas pressure by the start of the main process.
[0047]
About the initial gas pressure including the start time of the preliminary process, a range of 4 times to 100 times the first gas pressure, for example, a range of 1.33 × 10 ⁻¹ Pa to 6.67 × 10 ⁻¹ Pa. It is preferable to set with. That is, it is because the plasma discharge is stably generated at the initial stage of the preliminary process, while the pressure is not higher than necessary as compared with the first gas pressure.
[0048]
Further, the output of the high-frequency power source 15 in the preliminary process is set to be equal to or higher than the first high-frequency power at the start, and is adjusted to the first high-frequency power by the start of the main process. That is, in the preliminary process, when the high frequency power at the start is made larger than the first high frequency power, it is reduced to the first high frequency power by the start of the main process, and the high frequency power at the start is reduced. When the first high-frequency power is used, it is maintained as it is until the start of the main process.
[0049]
The initial high-frequency power including the start of the preliminary process is preferably set in a range of 5 times or less that of the first high-frequency power. That is, it is because the plasma discharge is stably generated at the initial stage of the preliminary process, while the power is not larger than necessary as compared with the first high-frequency power.
[0050]
Further, the output of the DC power supply 16 is started from the preliminary process and increased to the first DC power by the start of the main process.
[0051]
In reducing the gas pressure in the preliminary step, it is preferable to continuously change the gas pressure within a predetermined time. This is because the plasma discharge can be stabilized by continuously changing the gas pressure without changing it abruptly, and the plasma once generated can be stably maintained.
[0052]
Further, in reducing the high-frequency power in the preliminary step, it is preferable that the high-frequency power is continuously changed within a predetermined time. This is because, when changing the high-frequency power, the plasma discharge can be stabilized by continuously changing the high-frequency power without abrupt changes, and the once generated plasma discharge can be stably maintained.
[0053]
In addition, it is preferable that the DC power is continuously changed within a certain time when the DC power is increased in the preliminary step. This is because, when changing the DC power, the plasma discharge can be stabilized by continuously changing without changing the DC power, and once generated plasma can be stably maintained.
[0054]
And when changing the said gas pressure, high frequency electric power, and direct-current power continuously within a fixed time, it is more preferable to change linearly with progress of time. This is because the gas pressure and power are gradually changed in proportion to the elapsed time, so that the plasma discharge can be stabilized more reliably.
[0055]
Further, regarding the gas pressure and the output of the high-frequency power source 15 in the preliminary process, it is more preferable to start the adjustment of the high-frequency power after setting the gas pressure to the first gas pressure. That is, after the gas pressure is stabilized at the first gas pressure, the matching circuit 17 is more easily adjusted in matching the impedance on the vacuum chamber 1 side with the impedance of the high-frequency power source 15, and plasma discharge This is because it is possible to more easily achieve stability.
[0056]
Further, regarding the output of the high frequency power supply 15 and the output of the DC power supply 16 in the preliminary process, it is more preferable to start the output of the DC power after adjusting the high frequency power to the first high frequency power. This is because the plasma discharge can be more reliably stabilized as compared with the case where the supply of DC power is also started while changing the high-frequency power.
[0057]
By performing the preliminary process described above, the following significance is obtained. That is, when the first gas pressure in the main process for forming a film on the substrate 5 is the low pressure, it is not easy to start plasma discharge with the required first gas pressure and the first high-frequency power. When the preliminary process is executed, it is easy to start plasma discharge under the initial gas pressure and power conditions set here.
[0058]
And, to maintain the plasma discharge stably at the end of the preliminary process, without causing instability such as abnormal plasma discharge, and to shift to the main process executed afterwards with the plasma discharge stabilized Can do.
[0059]
A more specific example of the film forming conditions for executing the preliminary process and the main process described above will be described with reference to FIG. FIG. 3 is a diagram showing film forming conditions for gas pressure and electric power with respect to the passage of time of the film forming process.
[0060]
In FIG. 3, the horizontal axis corresponds to the elapsed time. The vertical axis corresponds to the magnitude of the voltage D related to the gas pressure G in the vacuum chamber 1, the high-frequency power P output from the high-frequency power supply 15, and the DC power output from the DC power supply 16. In FIG. 3, I is a range executed as a preliminary process, and II is a range executed as a main process.
[0061]
In the main process, the first gas pressure G1 is any pressure in the range of 6.67 × 10 ⁻³ Pa to 6.67 × 10 ⁻² Pa, and the output of the first high-frequency power P1 is about 200 W. The first DC power is supplied with the DC voltage D1 of about 500V. Further, as shown in FIG. 3, the gas pressure G1, the high-frequency power P1, and the DC power D1 in the main process are substantially constant from the start of the main process without changing over time. Be controlled.
[0062]
Next, in the preliminary step, the initial gas pressure G0 is made approximately constant at about 1.33 × 10 ⁻¹ Pa from the start to time T1. Then, the gas pressure in the preliminary process starts to decrease at time T1, and is decreased to become the first gas pressure G1 at time T2. After the time T2, the first gas pressure G1 is kept substantially constant.
[0063]
It is desirable to set the time T1 in the range of 1 second to 5 seconds. This is because, if the initial gas pressure in the preliminary process is maintained within the time range, it is sufficient to start and stabilize the plasma discharge.
[0064]
Then, when the gas pressure is decreased from time T1 to time T2, as shown in FIG. 3, it is decreased linearly with respect to time. That is, the gas pressure is decreased so that a certain proportional relationship is established between the amount of decrease in gas pressure and time.
[0065]
When the gas pressure is decreased linearly with respect to time, the proportional coefficient k _{G is set} to a range of −3.33 × 10 ⁻³ Pa / sec or more and −1.32 × 10 ⁻¹ Pa / sec or less. It is desirable to do. This is because the impedance on the chamber 1 side can be changed gently, and the plasma discharge can be maintained more stably.
[0066]
Next, in the preliminary process, the initial high-frequency power P0 is approximately constant at about 600 W from the start to time T2. Then, the high-frequency power in the preliminary process starts to decrease at time T2, and is adjusted to become the first high-frequency power P1 at time T3. After the time T3, the first high frequency power P1 is kept substantially constant.
[0067]
Then, in reducing the high-frequency power from time T2 to T3, as shown in FIG. 3, it is decreased linearly with respect to time. That is, it is reduced so that a certain proportional relationship is established between the reduction amount of the high frequency power and the time. Then, in reducing the high-frequency power linearly with respect to time, it is desirable that the proportionality coefficient k _{P be} in the range of −100 W / sec or more. This is because the supplied electric power can be gradually reduced and the plasma discharge can be maintained more stably.
[0068]
Next, in the preliminary process, the DC power is started to be supplied from time T3 and is increased to become the first DC power at time T4 (at the end of the preliminary process and at the start of the main process). . Then, when increasing the DC power, as shown in FIG. 3, it is increased linearly with respect to time. That is, the DC power is increased so that a certain proportional relationship is established between the amount of increase in DC power and time. When the direct-current power is increased linearly with respect to time, it is desirable that the proportionality coefficient k _{D be} in the range of 30 V / sec to 100 V / sec. This is because the supplied electric power can be gradually increased and the plasma discharge can be maintained more stably.
[0069]
If there is no need to provide a power difference between the first high-frequency power P1 in the main process and the initial high-frequency power P0 in the preliminary process, the initial high-frequency power P0 is maintained at about 600 W in the preliminary process. You may transfer to a main process as the 1st high frequency electric power P1 with the state adjusted so.
[0070]
【The invention's effect】
As described above, according to the present invention, when film formation is performed by ion plating, a preliminary process is performed prior to the main process of actually forming a film on a substrate, and plasma discharge is generated from the preliminary process to stabilize the film. Therefore, the plasma discharge can be stabilized and maintained even under the film forming conditions in the main process executed thereafter. Thereby, even when the film forming conditions in the main process are set to conditions that make it difficult to start plasma discharge, the plasma discharge can be stabilized and maintained in the main process.
[Brief description of the drawings]
FIG. 1 is a schematic view of a vacuum film forming apparatus that can be used in the present invention.
FIG. 2 is a schematic circuit diagram of a matching circuit of the vacuum film forming apparatus of FIG.
FIG. 3 is a diagram illustrating a specific example of film forming conditions that change with time.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Vacuum chamber 2 Substrate holder 5 Substrate 7 Crucible 8 Electron gun 9 Film raw material 10 Evaporation source 11 Electron beam 12 Control device 15 High frequency power source 16 DC power source 17 Matching circuit 18 Air supply port 20 Vacuum film-forming device C1, C2 Variable capacitor L1 choke coil

Claims (5)

A film forming method for forming a film in a vacuum chamber with a predetermined gas pressure, supplying at least a predetermined high-frequency power into the vacuum chamber, and forming a film on the substrate disposed in the vacuum chamber by ion plating,
A main step of supplying a first high-frequency power under a first gas pressure to form a film on the substrate, and a plasma discharge by supplying a predetermined high-frequency power under a predetermined gas pressure prior to the main step A preliminary step of generating
In the preliminary step, the gas pressure at the start is larger than the first gas pressure, the high frequency power at the start is equal to or higher than the first high frequency power,
By the start of the main process, the gas pressure is reduced to the first gas pressure, and the high frequency power is adjusted to the first high frequency power.   2. The film forming method according to claim 1, wherein, in the preliminary step, the adjustment of the high-frequency power is started after the reduction of the gas pressure is started.   3. The film forming method according to claim 2, wherein, in the preliminary step, the adjustment of the high-frequency power is started after the gas pressure is reduced to the first gas pressure. The film forming method further supplies DC power into the vacuum chamber,
Supply the DC power in the main process as the first DC power,
4. The film forming method according to claim 1, wherein the DC power is supplied from a preliminary process and is increased to the first DC power by the start of the main process.   5. The film forming method according to claim 4, wherein the DC power supply in the preliminary process is started after the high-frequency power is adjusted to the first high-frequency power.

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