JP2002275628A - Sputtering film-forming method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a sputtering film-forming method which easily provides a stable film-forming quality in a continuous process via a simple controlling method. SOLUTION: A reactive sputtering film-forming method employs a reactive sputtering apparatus which forms a thin film on a substrate by introducing a discharge gas and a reactive gas into a vacuum tank to discharge electricity, using a target containing at least a metal. Here, the discharge source of sputtering is controlled to give a constant power output to keep a constant discharge voltage.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a reactive sputtering method for forming an optical thin film, a conductive film, a gas barrier film and the like which are used in a wide range of applications such as packaging materials and electronic components. The present invention relates to a sputtering film forming method that is effectively applied to a longer continuous process such as a roll, and can easily realize stable film forming quality in a long continuous process.

[0002]

2. Description of the Related Art Sputtering is performed when forming various thin films such as an optical thin film, a conductive thin film, and a gas barrier film. In sputtering, a discharge gas is turned into plasma by glow discharge, ion particles in the gas are accelerated electrically and magnetically to collide with a target material, and thereby the particles of the target material that are beaten out (sputtered). Is applied to the substrate to form a film on the substrate. An inert gas such as an argon gas is introduced into the vacuum chamber for glow discharge, but a reactive gas such as an oxygen gas or a nitrogen gas is further introduced when performing reactive sputtering. The thin film formed by sputtering has a denser film structure and physical and physical properties as compared with a film formed by vacuum evaporation represented by a resistance heating method or an electron beam heating method.
There is an advantage that a chemically stable product can be obtained and a thin film having a strong adhesive force to a substrate can be obtained. In particular, the field in which a film having high film structure stability and high strength is required is the electronics field. Sputtering has been remarkably developed as a thin film forming means for members in this field, and liquid crystal display elements, solar cells, electromagnetic wave shields, etc. Demand for transparent substrates such as touch panels, EL substrates, and color filters is increasing. In recent years, these transparent substrates have been demanded to be lighter and larger, and have also been required to have higher requirements such as long-term reliability, freedom of shape, and curved surface display. Polymer film substrates such as transparent plastics have begun to be used in place of transparent glass substrates.

In general, when a thin film is formed on a substrate by reactive sputtering, an inert gas such as Ar is introduced into the vacuum chamber at a partial pressure of 1E-4 to 5E-3 Torr as a discharge gas, and the reaction is performed. Oxygen and nitrogen are introduced as gas at 1E-4 to 5E-3Torr. When power is applied to a metal target electrode placed in parallel with the substrate being transported here, glow discharge occurs and plasma is generated. The metal target is not particularly limited, but includes Si, Al, In, Sn, Zn, Ti, Cu,
It is preferable to use one containing at least one of Ce and the like, and an alloy obtained by combining a plurality of metals, or an oxide, nitride, or oxynitride thereof can be used. The discharge gas ions in this plasma hit the target surface, and the target material is sputtered,
The substrate reacts with the introduced reaction gas on the surface of the substrate being transported to form a target thin film. At this time, it is common to keep the deposition power constant to keep the film formation speed constant, and hence to keep the discharge power applied in order to keep the film quality constant. In addition, there are an RF, AC, DC method and the like as a method of supplying discharge power, and a DC method with a high film forming speed is generally used. DC
The method had a problem of abnormal discharge due to contamination of the surface of the material target in a long-term film forming process.
Japanese Patent Publication No. 379 and the like overcome the problem of abnormal discharge, which is a weak point of the DC method in which the film formation speed is high, by making the power application of the sputtering pulse-like. However, if the film is continuously transferred and a film is formed for a long time, a change in the vacuum chamber causes
Specifically, there are a decrease in gas and water molecules attached to the wall surface and a spout of gas from the substrate, but a change occurs in the gas partial pressure in the plasma atmosphere. In that case, for example, in the case of a film that is required to have gas barrier properties such as a SiOx film, there is a problem that the light transmittance decreases and the gas barrier performance deteriorates. In the case of a transparent conductive film such as ITO, a transparent film having a constant electric resistance is required, but similarly, a decrease in light transmittance and a variation in sheet resistance have occurred.

[0004]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a reactive sputtering film forming method which conventionally requires a large-scale control device to form a film with stable and constant quality. Accordingly, it is an object of the present invention to provide a sputtering film forming method capable of easily realizing stable film forming quality in a continuous process.

[0005]

That is, the present invention provides: (1) Using a target containing at least a metal, introducing a discharge gas and a reaction gas into a vacuum chamber and performing a discharge to form a thin film on a substrate. In a reactive sputtering apparatus, a discharge power supply for sputtering is controlled at a constant power output, and then the discharge voltage is controlled to be kept constant. (2) The reactive sputtering film forming method according to (1), wherein the method of controlling the discharge voltage to be constant is to feed back the discharge voltage to control the reaction gas introduction amount as needed. (3) The metal is Si, Al, In, Sn, Zn, Ti, Cu, Ce.
(1) and (2), wherein the reactive sputtering method comprises at least one of the following. (4) The reactive sputtering film forming method according to any one of (1) to (3), wherein the substrate is a plastic. (5) The reactive sputtering film forming method according to (4), wherein the plastic is polyether sulfone. (6) The reactive sputtering film forming method according to (4) or (5), wherein the plastic is a sheet having a thickness of 100 to 400 μm. (7) At least one surface of the substrate is coated with an organic layer, and a thin film is formed on the coating layer (1).
To (6). (8) The reactive sputtering film forming method according to (7), wherein the thickness of the organic layer is 0.1 to 10 μm. (9) The reactive sputtering film forming method according to (1) to (8), wherein the reactive gas is oxygen. (10) An SiOx thin film manufactured by the method of (1) to (9), wherein x is in the range of 1.5 <x <1.9. (11) The thickness of the thin film is in the range of 10 nm to 500 nm (1
0) SiOx thin film. (12) A SiOxNy thin film produced by the method of (1) to (9), wherein the x / y ratio is in the range of 0.6 to 4.0. (13) The thickness of the thin film is in the range of 10 nm to 200 nm (1
2) SiOxNy thin film. (14) An ITO thin film manufactured by the method of (1) to (9) and having a sheet resistance of 500Ω / □ or less. (15) The ITO thin film according to (14), wherein the variation in sheet resistance of the thin film is ± 10% or less. (16) The thickness of the thin film is in the range of 10 nm to 200 nm (1
4) and (15) ITO thin film. (17) A display element substrate manufactured by the method of (1) to (9). (18) A display element substrate having a thin film of (10) to (16) on one or both surfaces. It is.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention controls a sputtering power supply to keep a constant power when forming an oxide film or a nitride film on a substrate by using a reactive sputtering apparatus, and feeds back a sputtering voltage. This is a reactive sputtering film forming method for controlling the flow rate of a reactive gas to be introduced. The sputtering apparatus used in the present invention is not particularly limited as long as it is a reactive sputtering apparatus, but an apparatus such as a continuous pass film forming method in which a film is formed by continuous discharge for a long time is more preferable. Thus, the effects of the present invention can be sufficiently exhibited. In addition, RF, AC, DC, etc. can be used as the discharge power supply method, and if a high film formation rate is desired, there is a function to suppress abnormal discharge with the DC method. It is preferable to select a DC method that can superimpose an applied or AC component. In general, in order to perform stable film formation, a method of controlling a sputtering power source at a constant power in order to keep the input energy of sputtering constant is often used. However, when long-term continuous film formation is performed by this method, the impedance between the sputtering electrodes changes due to the change in the atmosphere in the vacuum chamber, and the sputtering voltage also changes accordingly. For example, Si used in transparent gas barrier films
In the case of an Ox film, 1.6 <x <1.9 is desirable in order to achieve both good gas barrier properties and high light transmittance. The phenomenon that the light transmittance of the film formed during the film formation changed occurred. The present inventors first monitored the light transmittance and considered feeding back this to the reactive gas introduction amount, but the light transmittance for the reactive gas introduction amount in the region where the required characteristics were obtained was slow. The change was so small that I couldn't get a signal that could be used for precise feedback control. When a film is formed on a multi-layer substrate with a primer or the like, light transmittance is dispersed so as to affect the control due to interference reflection of light due to a slight change in thickness of each layer.

It is considered that the change in the atmosphere in the vacuum chamber is mainly due to the change of the gas adhering to the inner wall surface of the vacuum chamber, jigs and the like, steam, gas ejected from the substrate, and steam over time. As the gas component decreases, the impedance between the sputtering electrodes increases, and the sputtering voltage increases. Thus, the present inventors have found that the change in the light transmittance of the thin film is related to the change in the sputtering voltage, and furthermore, the change in the sputtering voltage is steeper than the change in the light transmittance, and is ideal as a control parameter. Was found to be a target. Based on this discovery, the sputtering voltage is fed back, the flow rate of the reactive gas is controlled, and the voltage is always kept constant, thereby realizing a film with stable light transmittance, which can be used as a display element substrate. A plastic sheet having gas barrier properties and transparency was obtained.

The present invention can be applied not only to the SiOx example but also to reactive sputtering using another metal as a target. The target metal is not particularly limited. For example, Si, Al, In, Sn, Metals and alloys containing one or more of Zn, Ti, Cu, Ce and the like, and oxides, nitrides, oxynitrides, and the like thereof can also be used. Also, the reaction gas is not particularly limited, and examples thereof include oxygen, nitrogen, and halogen. As another application example of the present invention, it is possible to stably form a SiOxNy thin film having an x / y ratio in the range of 0.6 to 4.0 by using oxygen as a reaction gas with silicon nitride as a target. By setting the film thickness to 10 nm to 200 nm, excellent gas barrier properties and light transmittance that can be used as a substrate for a display element were realized. Further, by using an IT target and forming an ITO film using oxygen as a reaction gas and setting the thickness of the thin film to 10 nm to 200 nm, the variation in sheet resistance is 500Ω / □ or less and the variation is ± 10%.
% Of ITO thin film could be formed. Also,
It is possible to form a film in which the variation in the sheet resistance of the thin film is ± 10% or less and both the light transmittance and the sheet resistance are stable.

As described above, according to the reactive sputtering film forming method of the present invention, good film performance at the start of film formation,
For example, it has been found that durability, film adhesion, volume resistivity, gas barrier properties, etc., such as light transmittance, can be maintained even after a long continuous process. Note that there is no limitation on the substrate of the present invention, but glass, ceramic such as quartz, polysulfone resin, polyether sulfone resin, polycarbonate resin, polyarylate resin, polyacrylate resin, polyester resin, polyamide resin, epoxy resin, Plastics such as polyimide resin and polyolefin resin, metals such as iron, stainless steel, and copper can be used.When plastic is applied to the base material, it can respond to and follow changes in atmosphere due to gases ejected from the plastic base material. Therefore, it is particularly effective. Also, there is no particular limitation on the thickness, size, shape, and the like of the base material.
In addition, the substrate can be coated with an organic layer for the purpose of improving adhesion, and the thickness is 0.1%.
1010 μm is preferred. Hereinafter, the present invention will be described in detail based on embodiments. Here, the present embodiment can effectively carry out the method of the present invention, but the present invention is not limited to these embodiments.

[0010]

<Example 1> As shown in FIG. 1, a sputtering equipment having a DC discharge power source in a pass-through film forming method was used. This equipment forms a film by passing through a rack (3) of a substrate carrier before film formation and a film formation zone (4) in which a carrier (2) on which a substrate is set is stored as a transfer system in a vacuum chamber (1). A rack (5) for a film-formed substrate carrier for accommodating the carrier of the substrate after the film formation is provided. In the vacuum exhaust system, the interior of the vacuum chamber (1) is always exhausted from the exhaust port (6) by the vacuum pump (7). Cathode (9) connected to a DC-type discharge power supply (8) that can apply pulsed power as a film forming system
The target (10) is mounted on top. Further, the discharge power supply (8) is equipped with a voltage monitor (11) for displaying the discharge voltage during the process in real time. The introduction gas system includes a discharge gas cylinder (12) and a reaction gas cylinder (13) .The discharge gas is set by the flow controller (14), and the reaction gas is set by the flow controller (15). Is controlled to be constant. Each flow controller is provided with an adjusting mechanism, and the value of the gas introduction amount to be controlled to be constant can be varied by setting the adjusting mechanism. First, a substrate prepared by primer-coating a polyether sulfone film with an easily adhesive organic layer was prepared. The film is set on the carrier (2) so that the film is formed on the primer surface of the film, and the carrier (2) is placed in a vacuum chamber.
About 50 units were set on the rack (3) in (1). Target (1
Pure Si was set as 0). Start the vacuum pump (7),
The inside of the vacuum chamber (1) was evacuated to the order of 10 @ -6 Torr, and argon was introduced as a discharge gas at a partial pressure of 2.times.10@-3 Torr, and oxygen was introduced as a reaction gas at a partial pressure of 2.times.10@-3 Torr. When the atmospheric pressure became stable, the discharge power supply (8) was turned on, the discharge power was controlled to be constant, plasma was generated on the Si target (10), and the sputtering process was started. When the process was stabilized, the carrier (2) was started to be conveyed. The carriers (2) in the rack (3) pass one by one through the film formation zone (4), at which time an SiOx film is formed on the substrate, and then stored in the rack (5). This operation was continuously performed until there was no substrate before film formation in the rack (3). During this time, while monitoring the discharge voltage with the voltage monitor (14),
If the discharge voltage drops below the initial value at the start of film formation, decrease the oxygen flow rate.If the discharge voltage rises above the initial value at the start of film formation, feed back the discharge voltage so as to increase the oxygen flow rate. The discharge voltage was controlled to be constant by changing the setting of the reaction gas flow controller (13). After 50 films were continuously formed, the atmosphere was introduced into the vacuum chamber (1), and the substrate in the rack (5) was taken out. The substrate on which the first film was formed as the film formation starting part was
The 50th substrate was selected as the film-forming end part, and the discharge voltage, the light transmittance of the substrate on which the thin film was formed, and the oxygen gas barrier property were compared between the film-forming start part and the film-forming part. As shown in the figure, stable film formation was achieved in both the light transmittance at 400 nm and the oxygen barrier property, and the required characteristics as a display element substrate could be satisfied.

[0011]

[Table 1]

<Comparative Example 1> Sputtering was performed under the same power condition as in the example. All the conditions were the same as in the example, but 50 sheets of continuous film formation were performed without performing feedback control of the discharge voltage. In the same manner as in the embodiment, the substrate on which the first film was formed was selected as the film formation start portion, and the substrate on which the 50th film was formed was selected as the film formation end portion. When the light transmittance and oxygen gas barrier property of the formed substrate were compared, as shown in Table 2, the sputtering voltage was increased, and the light transmittance at 400 nm and the oxygen gas barrier property were both unstable, resulting in a film.
In particular, in the film formation end portion, it is no longer possible to satisfy the characteristics required for optical use, particularly for a display element substrate.

[0013]

[Table 2]

Example 2 As shown in FIG. 1, a sputtering equipment having a DC discharge power source in a pass-through film forming method was used. This equipment forms a film by passing through a rack (3) of a substrate carrier before film formation and a film formation zone (4) in which a carrier (2) on which a substrate is set is stored as a transfer system in a vacuum chamber (1). A rack (5) for a film-formed substrate carrier for accommodating the carrier of the substrate after the film formation is provided. In the vacuum exhaust system, the interior of the vacuum chamber (1) is always exhausted from the exhaust port (6) by the vacuum pump (7). Cathode connected to DC-type discharge power supply (8) that can apply pulsed power as a film forming system
The target (10) is mounted on (9). Further, the discharge power supply (8) is equipped with a voltage monitor (11) for displaying the discharge voltage during the process in real time. The introduction gas system includes a discharge gas cylinder (12) and a reaction gas cylinder (13) .The discharge gas is set by the flow controller (14), and the reaction gas is set by the flow controller (15). Is controlled to be constant. Each flow controller is provided with an adjusting mechanism, and the value of the gas introduction amount to be controlled to be constant can be varied by setting the adjusting mechanism. First, a substrate prepared by primer-coating a polyether sulfone film with an easily adhesive organic layer was prepared. The film was set on the carrier (2) so as to form a film on the primer surface, and about 50 carriers (2) were set on the rack (3) in the vacuum chamber (1). target
As (10), an indium tin target (IT target) of 90% In and 10% Sn was set. Start the vacuum pump (7), evacuate the vacuum chamber (1) to the order of 10-6 Torr, introduce argon as a discharge gas at a partial pressure of 2 × 10-3 Torr, and supply oxygen as a reaction gas at a partial pressure of 1 × 10-3 Torr. 10-3 Torr introduced. When the atmospheric pressure was stabilized, the discharge power supply (8) was turned on, the discharge power was controlled to be constant, plasma was generated on the IT target (10), and the sputtering process was started.
When the process was stabilized, the carrier (2) was started to be conveyed. The carriers (2) in the rack (3) pass one by one through the film formation zone (4), at which time an indium tin oxide film (ITO film) is formed on the substrate, and then the carrier (2) is placed in the rack (5). Is stored. This operation was continuously performed until there was no substrate before film formation in the rack (3). During this time, while monitoring the discharge voltage with the voltage monitor (14), if the discharge voltage falls below the initial value at the start of film formation, decrease the oxygen flow rate, and the discharge voltage rises from the initial value at the start of film formation. In this case, the discharge voltage was fed back so as to increase the oxygen flow rate, and the discharge gas was controlled so as to keep the discharge voltage constant by changing the setting of the flow controller (13). After performing continuous film formation of 50 sheets, the atmosphere was introduced into the vacuum chamber (1), and the substrate in the rack (5) was taken out. The substrate on which the first film was formed was selected as the film formation start part, and the substrate on which the 50th film was formed was selected as the film formation end part, and the discharge voltage and the thin film were formed at the film formation start part and the end part. When the light transmittance and the sheet resistance were compared, as shown in Table 3, stable film formation was possible at both the light transmittance and the sheet resistance at 400 nm, and the characteristics required for optical applications, particularly as substrates for display elements, were Could be fulfilled.

[0015]

[Table 3]

<Comparative Example 2> As in Example 2, sputtering was performed under the condition of constant power. All the conditions were the same as in Example 2, except that feedback control of the discharge voltage was not performed and 50 films were continuously formed. In the same manner as in the embodiment, the substrate on which the first film was formed was selected as the film formation start portion, and the substrate on which the 50th film was formed was selected as the film formation end portion. When the light transmittance and the sheet resistance of the substrate formed were compared, as shown in Table 4, the sputtering voltage was increased, and the light transmittance and the sheet resistance at 400 nm were both unstable. In the film end portion, it is no longer possible to satisfy the characteristics required for optical use, especially for a display element substrate.

[0017]

[Table 4]

[0018]

According to the present invention, in an apparatus for forming a reactive sputtering film, the discharge power is controlled at a constant power, and the amount of the reaction gas introduced is adjusted so as to keep the discharge voltage constant. Stable film formation quality can be easily realized in a continuous process over time. Further, the method of the present invention can be carried out even under automatic control by creating a calculation device for inputting the discharge voltage value and outputting the gas introduction amount setting and adding the calculation device to the calculation device. That is, it is also possible to provide a reactive sputtering apparatus which can be operated unattended even during long-time film formation.

[Brief description of the drawings]

FIG. 1 shows an example of a sputtering facility used in the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Vacuum tank 2 Carrier 3 Rack of substrate carrier before film formation 4 Film formation zone 5 Rack of substrate carrier after film formation 6 Exhaust port 7 Vacuum pump 8 Discharge power supply 9 Cathode 10 Target 11 Voltage monitor 12 Discharge gas cylinder 13 Reaction gas cylinder 14 Flow controller 15 Flow controller

 ──────────────────────────────────────────────────の Continuing on the front page F term (reference) 4F100 AA17B AA19B AA20B AA21B AA25B AA28B AA33B AK01A AK55A AT00A BA02 BA03 BA07 BA10A BA10B CC00C EH462 EH662 GB15 GB41 JA20A JA20C JD03 JG00BJA02BYYABAYYBBAYYAYBYA4A EA01 EA04 EA06 EA09 FA07

Claims (18)

[Claims] In a reactive sputtering apparatus for forming a thin film on a substrate by performing a discharge by introducing a discharge gas and a reactive gas into a vacuum chamber using a target containing at least a metal, a discharge power source for sputtering is used. A reactive sputtering film forming method, characterized in that a constant power output is controlled and a discharge voltage is controlled to be constant. 2. The reactive sputtering film forming method according to claim 1, wherein the method of controlling the discharge voltage so as to keep it constant is to feed back the discharge voltage and to control the amount of reactant gas introduced as needed. 3. The method according to claim 1, wherein the metal is Si, Al, In, Sn, Zn, T
3. The reactive sputtering film forming method according to claim 1, wherein the reactive sputtering method includes at least one of i, Cu, and Ce. 4. The method according to claim 1, wherein said base material is plastic.
The reactive sputtering film forming method according to any one of claims 1 to 3. 5. The reactive sputtering film forming method according to claim 4, wherein the plastic is polyether sulfone. 6. The reactive sputtering film forming method according to claim 4, wherein the plastic is a sheet having a thickness of 100 to 400 μm. 7. The reactive sputtering film forming method according to claim 1, wherein an organic layer is coated on at least one surface of the substrate, and a thin film is formed on the coating layer. 8. The reactive sputtering film forming method according to claim 7, wherein the thickness of the organic layer is 0.1 to 10 μm. 9. The reaction gas according to claim 1, wherein said reaction gas is oxygen.
The reactive sputtering film forming method according to any one of the above items. 10. SiOx produced by the method according to claim 1, wherein the value of x is in the range of 1.5 <x <1.9.
Thin film. 11. The SiOx thin film according to claim 10, wherein the thickness of the thin film is in a range of 10 nm to 500 nm. 12. Si produced by the method according to claim 1, wherein the x / y ratio is in the range of 0.6 to 4.0.
OxNy thin film. 13. The SiOxNy thin film according to claim 12, wherein the thickness of the thin film ranges from 10 nm to 200 nm. 14. An ITO thin film manufactured by the method according to claim 1 and having a sheet resistance of 500Ω / □ or less. 15. The ITO thin film according to claim 14, wherein the variation of the sheet resistance value of the thin film is ± 10% or less. 16. The ITO thin film according to claim 14, wherein the thin film has a thickness in a range of 10 nm to 200 nm. 17. A display element substrate manufactured by the method according to claim 1. Description: 18. The method according to claim 10, wherein one or both surfaces are provided.
A display element substrate comprising the thin film according to claim 1.