JP3071298B2 - Method for producing thin film by reactive DC sputtering - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a thin film, particularly an oxide thin film, by reactive DC sputtering.
In particular, the present invention relates to a method for producing a thin film by reactive direct-current sputtering that constantly exhibits the highest sputtering power.

[0002]

2. Description of the Related Art Conventionally, when a thin film is produced by reactive DC sputtering, for example, oxygen gas,
Argon gas is introduced as an inert gas to perform sputtering of a metal target by constant power control or constant current control.

For example, JP-A-64-79369 discloses a sputtering film forming method and a film forming apparatus. In reactive sputter film forming, a power supply is used to supply a target from a variable voltage power supply to a target using a power controller. It is disclosed that the sputter power is controlled to increase substantially exponentially from the start of film formation as the film is deposited on the substrate.

[0004]

In the conventional means for forming a thin film, particularly an oxide thin film, by reactive DC sputtering as described above, the reactive gas reacts with the surface of the metal target during sputtering, and thus the target surface is formed. A reaction film is formed, the film formation rate decreases with the growth of the reaction film, and the discharge becomes unstable.

For example, in the method described in JP-A-64-79369, the surface temperature of the target increases exponentially with time after application to the target,
Depending on the level of the surface temperature, the oxygen concentration of the oxide layer on the target surface changes between light and dark, and the sputter rate of the target also becomes higher and lower.As a result, the change in the composition ratio in the thickness direction of the film formed on the substrate is reduced by the sputtering power. It is intended to solve the problem by increasing the target, and it is disclosed that the sputtering rate of the target is increased and the deposition rate of the target material on the substrate is increased, but the discharge can always be stabilized, and those methods hard to say that such film can be formed to hold the highest sputtering rate at all times the best sputtering power and.

[0006]

The present invention, in order to solve the problems] is was made in view of such problems, the reactive gas and an inert gas
DC sputtering performed by introducing mixed gas of
In the method for producing a metal oxide thin film,
It is detected so that the putter discharge voltage always becomes the maximum value.
Film formation by controlling power based on fluctuation of sputter discharge voltage
By reactive DC sputtering
This is a method for producing a thin film . In addition, control of deposition power can be performed in a short time.
Be sure to reach the maximum value that can be entered at that point in the cycle
Is characterized in that the film is formed while controlling the temperature. The reactive gas
Is oxygen gas and the inert gas is argon gas
Provides a method for producing thin films by reactive DC sputtering
Is what you do.

[0008]

As described above, according to the method for producing a thin film by reactive DC sputtering of the present invention, a reactive film is formed on the surface of a metal target during sputtering, and the sputter discharge voltage is reduced.
May vary, the deposition rate is varied in association with the fluctuation of the sputtering discharge voltage, as well as most of the sputtering discharge voltage
Since such a large value corresponds to the maximum deposition rate of a reaction film on the substrate, so that sputtering discharge voltage becomes always maximum value or a value close thereto, forming a film by controlling the sputtering operation power As a result, it is possible to maintain the highest film formation rate for forming a reaction film on the substrate or a film formation rate very close to the maximum, and to stabilize the discharge in the region of the film formation rate.

Further, for example, the sputter discharge voltage is controlled.
Therefore, the deposition power is increased and the sputter discharge voltage is maximized.
When the film formation power is set to be as high as possible, a maximum film formation rate for forming a reaction film on the substrate can be obtained . The maximum time to time because change during sputtering, the need to maintain the maximum possible value of the sputtering discharge voltage at that time there Ru by adjusting the deposition power. actually
It is precisely to maintain the maximum value the method comprising hard be substantially, and be maintained at the maximum value or a value close thereto.

The problem at this time is that the sputter discharge
Pressure becomes that continues to be maintained deposition power does not reach the maximum value deposition rate decreases, scan increases the deposition power
If the film forming power is further increased after the putter discharge voltage reaches the maximum value, the sputter discharge voltage starts to decrease conversely, and after a short period of time, the sputter discharge voltage is greatly reduced and metal is formed. That is, for example, as shown in FIG. 1, FIG. After reaching the maximum value sputtering discharge voltage is increased the deposition power <br/>, reduced to greatly Suppatta discharge voltage when further increasing the deposition power FIG. 4 is a schematic data diagram showing a state of a time change of a sputter discharge voltage and a sputter discharge current when a metal film is formed. The film was formed by arbitrarily increasing the film forming power in an oxygen / argon atmosphere using a W target. At the time ,
The change in the sputter discharge voltage and the sputter discharge current is shown. The solid line is the sputter discharge voltage , and about 90 seconds after the power rise, when the film formation power is 3.8 kw, the sputter discharge voltage drops sharply from about 660 V. sputtering discharge current indicated by a broken line, approximately 90 seconds after power up, which sputtering discharge current becomes abruptly elevated metal deposited from about 5.8 a, sputtering discharge voltage is lowered becomes the metal deposition , Sputter discharge
The current will rise.

To solve these problems, first, a sputter discharge
Increase the deposition power sufficiently until the voltage reaches the maximum value, and immediately decrease the deposition power when the voltage starts to decrease to prevent metal deposition, and then re- sputter discharge power again.
Pressure increases sufficiently deposition power until it reaches a maximum value, a spa
Tsu repeated process of reducing the deposition power instantly at the motor discharge voltage began to decrease, the該際, sputtering
It is needless to say that it is preferable to control the film forming power so that the fluctuation of the discharge voltage is as small as possible because the fluctuation of the film forming rate is small.

In particular, for example, when the above-described control of the film formation power is performed manually, the control is performed to prevent a metal film from being formed.
Variation occurs in the timing of the deposition power reduction, sputtering
Variation of motor discharge voltage is increased, the thickness variation becomes large. Especially when abnormal discharge occurs frequently,
It is difficult to control the deposition power , and the variation in the film thickness is further increased. Therefore, it is needless to say that the control of the film formation power may be performed automatically by a sequencer or a computer in a short time cycle .

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be specifically described below with reference to the drawings. However, the present invention is not limited to such an embodiment.

FIG. 2 is a block diagram of a high-speed film forming control device (automatic control device) in one embodiment of the method for producing a thin film by reactive DC sputtering according to the present invention. For the high quick-film control device mainly consists sputtering power source controller and sequencer, the signal is transmitted to the sputtering power source, formed in the sputtering apparatus from the sputtering power source
Membrane power is supplied.

In the film forming method (an example based on power control), first, regarding the input of the film forming power, the analog input unit uses the sputter discharge voltage and the sputter discharge current of the sputter power controller as the film forming power of the feedback signal. /> From the detector and convert it to a digital signal.

The digital input unit receives a control signal such as a sputter discharge voltage or a parameter of a rising / falling pattern of the sputter power from a rotary switch or the like, and a film formation start signal and a stop signal for starting and stopping the apparatus.

[0017] Then, the input fetched by the analog input section and the digital input section is calculated by a program in a calculation section, converted into an analog output in an analog output section, and sputtered.
A control signal (voltage signal of 0 to 5 V; automatic) of pressure or film forming power is output. Based on the control signal, the sputtering power controller sends a control signal to the sputtering power source, sputtering power supplies film forming power to the sputtering apparatus.

The digital output unit displays input parameters, and the operation mode switching unit switches between manual and automatic operation modes for film formation control. FIG. 3 is an explanatory diagram showing a control pattern for raising and lowering the film forming power in the high-speed film forming control apparatus in one embodiment of the method for producing a thin film by reactive DC sputtering according to the present invention.

As shown in the above-mentioned explanatory diagram, the control of the rise and fall of the deposition power is performed by rapidly increasing the deposition power at Δw1,
Thereafter, the power is slowly increased at △ w2, then the maximum voltage is reached, and immediately after the voltage starts to decrease, the film forming power is reduced to a predetermined value at once at △ w3 so as not to form a metal film. The film formation power is increased until the maximum voltage is reached at Δw4, and the patterns of Δw3 and Δw4 are repeated for the time required for film formation, and the film formation power is turned off at the time of completion of the film formation.

In order to form a film with the elevation pattern, it is necessary to detect the timing at which the voltage reaches the maximum voltage and the voltage starts to drop, and ignore the abnormal discharge. Next, as for the method of detecting the timing of dropping the voltage from the maximum voltage, if the deposition power of the deposition power is excessively increased, the metal is deposited. When it starts to drop, it is necessary to reduce the film forming power, and it is necessary to detect the timing of the voltage drop (the current value rises at this time) from the maximum voltage.

[0021] That is, even if controlled by a constant power during the film formation, for example, sputtering discharge voltage rises sputtering discharge collector
Flow decreases, sputtering discharge voltage drops on the contrary sputter
Motor discharge current as rises, sputtering discharge voltage and sputter
Motor discharge current is constantly changing and the change in sputtering discharge voltage when that increasing the deposition power (sputtering discharge current), i.e. as shown in FIG. 4, sputtering discharge current also <br/> the sputtering discharge The sputter discharge voltage and sputter discharge current are captured at each sampling cycle at the microscopic signal pattern and sampling point (indicated by ●) when the voltage rises. Next, the sputter discharge voltage value at the time of a certain sampling is compared with the sputter discharge voltage value at the time of the immediately preceding sampling to detect the amount of change in the voltage. Similarly, spatter
If the discharge current is also detected amount of change current, further sputter
When the sputter discharge voltage drops and the sputter discharge current rises, it is detected as the voltage drop timing from the highest voltage.
In particular, the reason why the sputter discharge current is also detected at the same time is to distinguish it from the case of abnormal discharge.

[0022] For example, when a large width of the fluctuation of the sputtering discharge voltage, even up the whole sputtering discharge voltage, depending on the manner of sampling, since the are determined that erroneous detection down, as this countermeasure , Spatter
It is preferable to insert a capacitor (for example, about 0.1 μF each) in the signal lines of the discharge voltage and the sputter discharge current , or to use software that averages several samples instead of one.

[0023] Incidentally, the reason why the incorporation is required by the sampling, sputtering discharge voltage or sputtering
Looking microscopically at the time when the discharge current rises, the pattern rises and falls as a whole,
When data is continuously taken in, there is a portion where the voltage drops even though the voltage does not reach the maximum voltage, and this is erroneously recognized as a voltage drop from the maximum voltage. In order to prevent this, the data sampled at the rising part of the signal is taken in.

Further, as a method of ignoring abnormal discharge, if an abnormal discharge occurs during sputtering, the protection circuit of the sputter power supply operates to instantaneously turn off the power .
Both the putter discharge voltage and the sputter discharge current drop. If abnormal discharge occurs frequently, it is indistinguishable from the case where the voltage drops from the maximum voltage, so that the film formation cannot be manually controlled.

[0025] The sputter power-off time deposition power by the protection circuit is shorter than the period for taking a sputtering discharge voltage and a sputtering discharge current <br/>, sputtering discharge voltage and spa
By simply taking in the discharge current and comparing, it is not possible to distinguish between a case where the voltage drops from the maximum voltage and a case where the discharge is abnormal. Sputter discharge voltage and spa
When the timing of taking in the discharger current is different, for example,
Sputter discharge voltage takes the rising part of abnormal discharge,
In the case where no abnormal discharge is detected, that is, as shown in FIG. 5, the sputter discharge current is the sampling point of the sputter discharge voltage in the voltage diagram of an example of erroneous recognition by the control device due to the influence of the protection circuit (● When the point A is detected as a mark (mark) and then the point B when abnormal discharge occurs is detected as a sampling point (mark), it is determined that the sputter discharge voltage has dropped, and as shown in FIG. In the current diagram of an example of erroneous recognition in the control device due to the influence of the above, a point C (●) is detected as a sampling point of a sputter discharge current , and then a point D (●
Upon detection of the mark) sputtering discharge current becomes to be judged to have increased, sputtering discharge voltage is lowered, and the sputtering
Inconsistency arises in that the increase in the discharge current is detected as a metal film formation.

In order to prevent the erroneous recognition described above, first, a voltage diagram when the metal film formation is started is shown to show the difference between the voltage drop at the time of the voltage drop from the maximum voltage and the voltage drop at the time of abnormal discharge. In order to distinguish between a voltage drop when the voltage drops from the maximum voltage as shown in FIG. 7 and a voltage drop due to abnormal discharge as shown in FIG. If the voltage value dropped between each sampling (● mark is the sampling point) is less than the set value, it will be the voltage drop when the voltage drops from the maximum voltage, and if it exceeds the set value, it will be caused by abnormal discharge It is determined that there is a voltage drop. Next, in order to show the difference between the current rise at the time of the voltage drop from the maximum voltage and the current rise at the time of abnormal discharge, the current diagram when the metal film formation is started is shown in FIG. The current value is set to distinguish the current rise due to the abnormal discharge as shown in Fig. 10, which is the current diagram when the abnormal discharge occurs, to show the difference between the current rise during the voltage drop and the current rise during the abnormal discharge. If the current value that has risen between each sampling (● mark is the sampling point) is less than the set value, it is considered as the current rise when the voltage drops from the maximum voltage, and if it exceeds the set value, it is judged that the current rise due to abnormal discharge I decided to do it.

Example 1 In an in-line type (every-leaf type) continuous film forming apparatus, clear glass (Fl3) having a size of 450 mm × 450 mm and a thickness of 3 mm was used as a substrate, and sequentially washed with a neutral detergent, water rinse, and isopropyl alcohol. After being washed and dried, it is set so as to be able to reciprocate upward facing the w target set in the vacuum chamber of the magnetron sputtering apparatus. Next, after the inside of the tank was evacuated to about 5 × 10 ⁻⁶ Torr or less by a vacuum pump, O ₂ gas (however, the O ₂ gas flow rate from the target surface side discharge port and the substrate surface side discharge (The ratio of the flow rate of the O ₂ gas from the outlet is 1:17) to introduce a pressure of about 5.0 × 10 ⁻³ Torr, and further introduce Ar gas so that the total pressure becomes about 2.0 × 10 ⁻² Torr. The degree of vacuum is maintained. Further, the power applied to the w target is set to a rising / falling pattern of the film forming power as shown in FIG. 3, and the metal detection voltage of the w target is grasped from the phenomenon shown in FIG. deep. Next, in this sputtering, first, the film forming power is increased at △ w1 = about 50 w / sec, and at 80% of the metal detection power, the rate of increase of the film forming power is reduced to △ w2 = about 30 w / sec. continue to raise the deposition power until immediately before film, lowers the sputtering discharge voltage, spa
If it is determined that the discharge current rises immediately before the metal film is formed, the film forming power is reduced by about 700 w at △ w3 = about 7 kw / sec, and immediately after that, the film forming power is reduced by △ w4 = about 150 w / sec. If it is determined that the time immediately before the metal film formation is reached, the film formation power is reduced by about 700 w at about 7 kw / sec again,
Immediately thereafter, an operation of increasing the deposition power at about 150 w / sec,
Δw3 and Δw4 were repeated and performed as if patterned.

During this time, the substrate glass is flowed and sputter discharge occurs.
Fig. 11 shows an actual chart of the change in voltage and sputter discharge current .
Shown in By the above-described high-speed film forming control device, the film forming power was repeatedly controlled up to 12 to 13 times per minute up to immediately before metal film formation and then reduced. The sputter discharge voltage is always controlled to be the maximum value that can be input or a value close to the maximum value that can be input, and in addition, in a short time cycle, it is always controlled to be the maximum value that can be input at that time. Film formation was performed for a film formation time of 5 minutes to obtain a WO ₃ thin film.

If, for example, the variation width of the film forming power becomes too large, not only does the thickness of the WO ₃ thin film formed on the substrate glass decrease, but also the film thickness varies in the traveling direction. Conversely, if the width of change is small, for example, if the width of reduction or the speed of reduction is reduced, metal film formation becomes easier. In addition, even if the raising speed is increased, it becomes easy to form a metal film.

The obtained WO ₃ thin film is placed on the front side of the flow direction of the substrate glass, which is perpendicular to the flow direction of the substrate, to the side H.
The film thickness and the visible light transmittance were measured by setting the side of the substrate glass parallel to the flow direction to side H2, and the results were as follows.

(1) Measurement position a (11 cm from side H1 and 22.5 cm from side H2) Film thickness: 104 nm, visible light transmittance: 81% (2) Measurement position b (23 cm from side H1 and 22.5 cm from side H2) Film thickness: 108 nm, visible light transmittance: 82% (3) Measurement position c (side H1 to 34 cm, side H2 to 22.5 cm) Film thickness: 106 nm, visible light transmittance: 82% For example, the base pressure (back pressure), the total sputtering pressure, and the film forming time are the same, and the film forming power, which is the power applied to the Ta target, is raised and lowered as shown in FIG. That is, first, from the phenomenon shown in FIG. 1, the metal detection voltage of the Ta target is grasped, for example, by a separate preliminary sputtering test or the like. Next, in this sputtering, first,
1 = approximately 100 w / sec, and increase the film formation power at 70% of the metal detection power.
Per second, the deposition power continues to increase until just before metal deposition, the sputter discharge voltage drops, and the sputter discharge current rises.
w3 = approximately 2.8 kw film formation power is reduced at about 28 kw / sec, and immediately thereafter, △ w4 = film formation power is increased at about 500 w / sec,
If it is determined that it is immediately before the metal film formation, the
An operation of lowering the film formation power at about 2.8 kw at 8 kw / sec and immediately increasing the film formation power at about 500 w / sec.
4 was repeated and performed as patterned.

[0032] During this time in the flow of the substrate glass, a high-speed film formation control apparatus described above, which was to be controlled in the same manner as in Example 1, subjected to film forming in about 10 minutes of deposition time, Ta ₂ O
_Five thin films were obtained.

The thickness of the obtained Ta ₂ O ₅ thin film and the visible light transmittance were measured in the same manner as in Example 1, and the results were as follows. (1) Measurement position a; film thickness: 187 nm , visible light transmittance: 84% (2) Measurement position b: film thickness: 188 nm , visible light transmittance: 83% (3) Measurement position c: film thickness: 186 nm Visible light transmittance: 84% Comparative Example 1 The base pressure (back pressure), total sputtering pressure, film formation time, etc. are the same as in Example 1 above, and the input power (constant power mode) is such that the sputter discharge voltage starts sputtering. The film was set and fixed so as to be the maximum value (approximately 640 V) that can be input at the time, and a WO ₃ thin film was obtained.

The thickness and visible light transmittance of the obtained WO ₃ thin film were measured in the same manner as in Example 1, and the results were as follows. (1) Measurement position a; film thickness: 89 nm, visible light transmittance: 73
% (2) Measurement position b; film thickness: 81 nm, visible light transmittance: 73
% (3) Measurement position c; film thickness: 74 nm, visible light transmittance: 71
% As the substrate used in the present invention, various transparent glasses are preferable, not only inorganic but also organic, and may be colorless or colored. Further, the glass plate with a film obtained by the method for producing a thin film by reactive DC sputtering of the present invention is It goes without saying that it can be used not only as a single plate but also as various plate glass products such as double-glazed glass, laminated glass, and tempered glass.

[0035]

As described above, according to the present invention,
In reactive DC sputtering performed by introducing a mixed gas of a reactive gas and an inert gas, the sputter discharge voltage should always be at or near the maximum value that can be input, and at a short time The film was controlled to be the maximum value that can be input in
It is possible to prevent a decrease in the film formation rate due to the growth of the reaction film on the metal target surface and an increase in abnormal discharge, thereby maintaining a constant high-speed film formation rate at the highest level and stabilizing the discharge. And a useful reactive DC sputtering method for producing a thin film.

[Brief description of the drawings]

FIG. 1 is a diagram showing a sputter discharge when a sputter discharge voltage is increased to a maximum value that can be input after reaching a maximum value that can be input, and when the sputter discharge power is further increased, the discharge voltage is greatly reduced to form a metal film. FIG. 4 is a schematic data diagram showing how the voltage and sputter discharge current change over time.

FIG. 2 is a block diagram of a high-speed film forming control device (automatic control device) in one embodiment of the method for producing a thin film by reactive DC sputtering according to the present invention.

FIG. 3 is an explanatory view showing a control pattern for raising and lowering a film forming power in a high-speed film forming control apparatus in one embodiment of the method for producing a thin film by reactive DC sputtering according to the present invention.

FIG. 4 shows a microscopic signal pattern and a sampling point when a sputter discharge current or a sputter discharge voltage rises in one embodiment of the method for producing a thin film by reactive DC sputtering according to the present invention. FIG.

FIG. 5 is a voltage diagram showing an example of erroneous recognition in a control device due to the influence of a protection circuit in one embodiment of the method for producing a thin film by reactive DC sputtering according to the present invention.

FIG. 6 is a current diagram showing an example of erroneous recognition in a control device due to the influence of a protection circuit in one embodiment of the method for producing a thin film by reactive DC sputtering according to the present invention.

FIG. 7 is a diagram showing a method for producing a thin film by reactive DC sputtering according to the present invention, in which a metal film is formed to show the difference between the voltage drop at the time of voltage drop from the maximum voltage and the voltage drop at the time of abnormal discharge. FIG. 5 is a voltage diagram when the voltage has started to reach.

FIG. 8 shows an example of a method for producing a thin film by reactive DC sputtering according to the present invention, in which abnormal discharge was performed to show the difference between the voltage drop from the maximum voltage and the voltage drop during abnormal discharge. FIG.

FIG. 9 is a diagram showing a method for producing a thin film by reactive DC sputtering according to the present invention, in which a metal film is formed to show the difference between the current rise at the time of voltage drop from the maximum voltage and the current rise at the time of abnormal discharge. It is a current diagram when it has begun to reach.

FIG. 10 shows an example of a method for producing a thin film by reactive DC sputtering according to the present invention, in which an abnormal discharge was performed to show the difference between the current increase at the time of voltage drop from the maximum voltage and the current rise at the time of abnormal discharge. FIG.

FIG. 11 is an actual chart showing a time change state of a sputter discharge voltage and a sputter discharge current by the high-speed film forming control apparatus in one embodiment of the method for producing a thin film by reactive DC sputtering according to the present invention.

Continuing from the front page (72) Inventor Tadahiko Saito 1-6-3 Nishioi, Shinagawa-ku, Tokyo Nikon Oi Works Co., Ltd. (72) Inventor Yoshiyoshi Nakase 92-1 Ariji Meiwa-cho, Taki-gun, Mie (72) Invention Katsuyuki Hatanaka 1876 Katada-Tanakacho, Tsu-shi, Mie (72) Inventor Hiroshi Inaba 10-12 Hikaricho, Matsusaka-shi, Mie (56) References JP-A-3-223461 (JP, A) (58) Int.Cl. ⁷ , DB name) C23C 14/00-14/58 C03C 17/22 C03C 17/245

Claims (4)

(57) [Claims] A metal oxide is formed by reactive DC sputtering performed by introducing a mixed gas of a reactive gas and an inert gas .
In the method of manufacturing a thin film of the above , the sputter discharge voltage is detected so that the sputter discharge voltage always has the maximum value.
A method for producing a thin film by reactive DC sputtering, wherein the film is formed by controlling the film forming power based on the fluctuation . 2. The method according to claim 1, wherein the control of the film forming power is performed in a short time cycle.
The film is controlled so that it becomes the maximum value that can be input at the time.
The reactive DC spark plug according to claim 1,
A method of manufacturing a thin film by tarring. 3. The method according to claim 1, wherein the reactive gas is oxygen gas. 4. The method according to claim 1, wherein the inert gas is an argon gas.