JP2002146525A - Sputter deposition system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To achieve short-term and long-term stability of film deposition rate while uniformizing film thickness. SOLUTION: A target 3 and a rotatable polygonal drum type substrate holder 2 are disposed inside a vacuum chamber 1. Substrates 9 are held on the respective sides of the substrate holder 2. A film thickness correction plate 8 for correcting the variability in the thickness of a thin film depending on the position is provided in an ungrounded state between the target 3 and the substrate holder 2.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sputter film forming apparatus in which a film thickness compensating plate is disposed between a substrate and a target in order to make a film thickness of a thin film formed on a substrate surface uniform over a wide area.

[0002]

2. Description of the Related Art Conventionally, a film forming method by sputtering has been used for forming an optical thin film on a substrate surface. Among optical thin films, for general applications such as dichroic mirrors, for example, cost reduction is the most important issue, and high throughput is also required for a sputter film forming apparatus.

When a film is formed on the surface of a substrate, the substrate needs to be disposed so as to face the target. Therefore, the number of substrates that can be formed in one process is limited, and the throughput can be improved. There is a limit. In addition, the amount of particles emitted from the target due to positive ions of plasma generated between the substrate and the target and adhered to the substrate varies between the central portion and the peripheral portion of the substrate, and as a result, the film thickness varies. I will. This variation in film thickness appears as variation in optical characteristics.

In order to improve the throughput, a film formation method called a carousel type has been devised. The carousel type film forming apparatus has a rotating polygonal drum type substrate holder (carousel), and a substrate is held on each side surface of the substrate holder. At the time of film formation, film formation is performed while rotating the substrate holder. Thus, the substrates held on each side surface of the substrate holder sequentially face the target, and a large number of substrates can be formed in one process.
In addition, by forming a film while rotating the substrate holder, variation in the film thickness in the rotation direction is reduced.
However, it is difficult to eliminate variations in film thickness in a direction perpendicular to the rotation direction only by rotating the substrate holder.

Therefore, a shielding member called a film thickness correction plate is provided between the substrate and the target, and the shape of the film thickness correction plate is optimized according to the film thickness distribution of the thin film formed on the substrate. Thus, a method has been devised in which the film thickness is made uniform also in the direction perpendicular to the rotation direction.

[0006]

However, in practice, the provision of the film thickness correction plate greatly increases short-term and long-term fluctuations in the film formation rate, film optical characteristics, and the like. This is considered to be because the plasma atmosphere itself is changed by installing the film thickness correction plate in the plasma atmosphere, and as a result, the stability at the time of film formation is affected.

Accordingly, an object of the present invention is to provide a sputter film forming apparatus which stabilizes a film forming rate in a short term and a long term while making the film thickness uniform.

[0008]

To achieve the above object, a sputter film forming apparatus according to the present invention comprises: a substrate holding means for holding a substrate on which a thin film is to be formed at a position facing a target;
Plasma generating means for generating plasma between the substrate and the target, and support between the target and the substrate holding means for correcting variations in the thickness of the thin film formed on the substrate due to position. In a sputter film forming apparatus having a film thickness correction plate provided, the film thickness correction plate is supported in a non-grounded state.

In the sputter film forming apparatus of the present invention, the positive ions of the plasma generated by the plasma generating means
The target is sputtered, and the sputtered sputtered particles are emitted toward the substrate and adhere to the substrate, whereby a thin film is formed on the substrate. At this time, since a film thickness correction plate is provided between the target and the substrate holding means, the movement of the sputtering particles from the target to the substrate is regulated by the film thickness correction plate, and a thin film having a uniform film thickness is formed. Formed on the substrate.

Here, the plasma atmosphere is affected by the film thickness correction plate provided between the target and the substrate holding means, but since the film thickness correction plate is supported in a non-grounded state, Even if a film thickness correction plate is provided between the substrate and the substrate holding means, there is almost no change in impedance of plasma during discharge. As a result, the deposition rate is stable for a short term and a long term, and a higher-quality thin film is stably formed.

In the present invention, the material constituting the film thickness correction plate is not particularly limited as long as the film thickness correction plate is supported in a non-grounded state. When the film thickness compensating plate is made of a conductive material, if the film thickness compensating plate is supported by a fixture made of an insulating material, the film thickness compensating plate is supported in an ungrounded state. Further, the thickness correction plate itself may be made of an insulating material.

The type of the sputter film forming apparatus of the present invention is not particularly limited as long as the sputtered particles are released from the target using plasma and the released sputtered particles are deposited on the substrate. In order to increase the throughput, a so-called carousel type sputtering film forming apparatus is used in which the substrate holding means is a rotatable polygonal drum type holder, and a plurality of substrates are held on each side of the holder. Preferably, there is.

[0013]

Embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a diagram showing a configuration of a sputtering film forming apparatus used for forming a multilayer optical thin film according to an embodiment of the present invention.

This sputter film forming apparatus is a carousel type film forming apparatus, and includes a decompression chamber 1 evacuated by a vacuum pump (not shown), a substrate holder 2 and a target 3 disposed inside thereof and opposed to each other. An RF power supply 4 and a DC power supply 5 for applying a high-frequency voltage and a DC voltage to the target 3; a gas introduction line 6 for introducing an Ar gas as a sputtering gas and an O ₂ gas as a reactive gas into the decompression chamber 1. And a H ₂ O introduction line 7 for introducing H ₂ O as moisture into the decompression chamber 1.

The substrate holder 2 is a polygonal drum type holder, and is rotated by a driving source (not shown) in the direction of an arrow about an axis O which is the central axis of the polygonal drum. On each side surface 2a of the substrate holder 2, a plurality of substrates 9 on which a thin film is to be formed are held along a central axis of the polygonal drum.

The high frequency voltage of the RF power supply 4 is applied to the target 3 via the matching network 4a. DC
The DC voltage of the power supply 5 is applied to the target 3 via the low-pass filter 5a.

Between the target 3 and the substrate holder 2,
By covering a specific area between the target 3 and the substrate 9, the movement of the sputtered particles from the specific area toward the substrate 9 is regulated, and a film thickness correction plate 8 for correcting a variation in the thickness of the thin film depending on the position is provided. Supported. This particular area is defined as an area between the target 3 and the substrate 9.
This is a region where the amount of sputtered particles from the target 3 toward the substrate 9 is larger than in other regions.

Here, the support structure of the film thickness correction plate 8 will be described with reference to FIG. FIG. 2 is a diagram illustrating a structure around a target of the sputtering film forming apparatus shown in FIG.
(A) is a front view seen from the substrate holder side, (b) is (a)
2 is a sectional view taken along line AA of FIG.

As shown in FIG. 2, the target 3 is fixed on a backing plate 10 made of an alloy containing copper as a main component. Also, when forming a film on the substrate 9 (see FIG. 1),
If copper, which is the main component of the backing plate 10, is sputtered, it adversely affects the quality of the thin film formed on the substrate 9. Therefore, in order to prevent this, a cover for covering the periphery of the target 3 and the backing plate 10 is provided. 11 are provided. The cover 11 is formed of aluminum or the like which does not significantly affect the quality of the thin film. The cover 11 is grounded.

The film thickness compensating plate 8 is fixed on the cover 11 by a fixture 12. As described above, the film thickness correction plate 8 covers a specific region between the target 3 and the substrate 9, thereby regulating the amount of sputtered particles reaching the substrate 9 from the specific region. The purpose is to limit the amount of the sputtered particles reaching the substrate 9 according to the region and to make the thickness of the thin film formed on the substrate 9 uniform. Therefore, the shape and number of the film thickness are determined according to the type of the target and the film forming conditions. In the present embodiment, two film thickness correction plates 8 each having a convex shape on one side are formed so as to regulate the movement of sputtered particles at both sides of the target 3 and at the center in the vertical direction. , So that the arc-shaped sides face each other,
Are installed on both sides.

The material of the film thickness compensating plate 8 is a cover 11
Similarly to the above, as long as a material that does not affect the film quality of the thin film is used, it may be a conductive substance or an insulating substance. However, as described later, the thickness compensating plate 8
It is necessary that the film thickness compensating plate 8 is made of a metal such as aluminum similar to the cover 11 because the film thickness compensating plate 8 must be at least a ground potential so as not to affect the plasma atmosphere. Fix it away from 11,
In addition, an insulating material is used for the fixture 12.

Further, at least one of the cover 11 and the film thickness compensating plate 8 may be made of an insulating material. In this case, the fixture 12 does not need to be made of an insulating material. May be used. However, when the fixture 12 made of a conductive substance is used, the fixture 12 itself may affect the plasma atmosphere instead of the film thickness correction plate 8, so that the fixture 12 is positioned so as not to be exposed to the plasma atmosphere. Preferably, or when the fixture 12 is exposed to a plasma atmosphere, the fixture 12 is preferably in a non-grounded state.

The fixture 12 has a small coefficient of thermal expansion and a material which is less likely to be degraded by heat in order to prevent a relative displacement between the target 3 and the film thickness correction plate 8 even during film formation. For example, it is preferable to use a insulator or quartz.

Next, a process of forming an oxide thin film on the substrate 9 using the above-described sputtering film forming apparatus will be described.

First, the substrate 9 is held on the substrate holder 2, the pressure in the decompression chamber 1 is reduced to a predetermined degree of vacuum, and Ar gas and O ₂ gas are introduced from the gas introduction line 6 while H ₂ O is introduced. H ₂ O is introduced from the line 7, and at least one of the high frequency voltage of the RF power supply 4 and the DC power supply 5 is applied to the target 3 to generate plasma P by so-called magnetron sputter discharge.

The target 3 is sputtered by positive ions, and the sputtered particles are partially oxidized by oxidizing active species in the vicinity of the surface of the target 3 and are deposited on the substrate 9 on the rotating substrate holder 2. It is released toward. The sputtered particles reaching the substrate 9 are oxidized by the oxidizing active species in the plasma P and near the surface of the substrate 9, whereby an oxide thin film is formed on the surface of the substrate 9.

When the sputtered particles travel from the target 3 to the substrate 9, the movement of the sputtered particles in the area covered by the film thickness correction plate 8 is hindered by the film thickness correction plate 8 provided near the target 3, The amount of sputtered particles deposited on the substrate 9 is controlled.

As described above, by providing the film thickness compensating plate 8, the substrate 9 moving with respect to the target 3 by the rotation of the substrate holder 2 can be moved not only in the moving direction but also in the direction perpendicular to the moving direction ( Also in the direction of the rotation axis of the substrate holder 2, a thin film is formed with a uniform film thickness. Of course, since the film forming apparatus of the present embodiment is a carousel type film forming apparatus, it is possible to form a film on a large number of substrates in one process, and it is possible to form a film with high throughput. In the case where the film thickness is controlled by film formation by sputtering, the film thickness may be optically controlled using a quartz oscillator or the like, but is generally controlled by time. This is based on the premise that the deposition rate is stable, but in many cases it is not. One of the causes is that the impedance of the plasma is not stable. Therefore,
As one measure for stabilizing the film formation rate, it is important to stabilize the plasma impedance.

Here, consider a case where a substance having a certain positive potential is inserted into the plasma. Then, electrons gather around it and act to cancel the electric field. Then, the ions gather around the negative charge to form a sheath for shielding the negative potential. That is, when a substance having a positive potential is inserted into the plasma, the plasma atmosphere is affected. At that time, if the substance is grounded, the electrons gathered around the substance constantly flow to the ground plane.
As a result, electrons are constantly supplied from the plasma, and a stable atmosphere cannot be maintained.

Also in the present embodiment, the film thickness correction plate 8 exists in the plasma atmosphere between the target 3 and the substrate 9. However, in this embodiment, as described above, the fixing member 12 made of an insulating material supports the cover 11 in a non-grounded state. By supporting the film thickness compensating plate 8 in a non-grounded state, electrons slightly flow into the film thickness compensating plate 8 at the initial stage of discharge, but the film thickness compensating plate 8 is electrically insulated. Immediately, a so-called saturated state is reached, an equilibrium state is reached, and the plasma atmosphere is stabilized. This appears as a variation in the impedance of the plasma.

FIG. 3 shows the results of measuring the impedance of the plasma at regular time intervals from the start of discharge when the film thickness compensating plate 8 is made of aluminum and supported by the fixture 12 made of an insulating material. Referring to FIG. 2, the impedance of the plasma slightly fluctuates immediately after the start of discharge, but it can be said that the plasma is substantially stable as a whole. When the impedance of the plasma is stabilized, the deposition rate is stabilized. Although the actual film formation rate was lower than when the film thickness correction plate was grounded, the reproducibility was good and the amount of absorption per unit film thickness was also lower.

As the discharge time increases, that is, as the thickness of the thin film formed on the substrate 9 increases, the thickness correction plate 8
The amount of the film deposited on the substrate also increases. However, since the film thickness correction plate 8 is kept insulated from the beginning, the influence on the plasma atmosphere is small. As described above, by supporting the film thickness correction plate 8 in a non-grounded state, the film formation rate, film characteristics, and the like are stable in the short term and the long term, and a higher quality thin film is stably formed. It becomes possible to film. Therefore, according to the sputter film forming apparatus of the present embodiment, even in the case of an optical thin film for general use where cost reduction is required, such as a dichroic mirror, a large amount and stable without reducing the optical characteristics. Can be made.

On the other hand, FIG. 4 shows a change in plasma impedance, similar to FIG. 3, when the film thickness correction plate is supported by a conductive substance such as metal and is grounded. Looking at FIG.
When the film thickness compensator is grounded, compared to when it is not grounded,
The amount of change in the impedance during the discharge is large, and the impedance tends to decrease even after 60 minutes from the start of the discharge. This means that the film formation rate is not stable.

Although the present invention has been described with reference to the carousel type sputter film forming apparatus as an example, the sputter film forming apparatus of the present invention is not limited to the carousel type, and the substrate is fixedly opposed to the target. In addition, the present invention can be applied to a sputtering film forming apparatus of a type in which there is no relative movement between a target and a substrate.

[0036]

As described above, according to the present invention, by providing the film thickness compensating plate in a non-grounded state, the thin film formed on the substrate can be formed with a uniform film thickness and for a short period of time. Since the film can be formed at a stable film formation rate,
Higher quality thin films can be stably formed. In particular, by using a so-called carousel type sputtering film forming apparatus as a substrate holding means, which is a polygonal drum type holder rotatably provided and holding a substrate on each side surface, a higher quality thin film as described above. Can be formed in a large amount in one process.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of a sputtering film forming apparatus used for forming a multilayer optical thin film according to an embodiment of the present invention.

2A and 2B are diagrams illustrating a structure around a target of the sputtering film forming apparatus shown in FIG. 1, wherein FIG. 2A is a front view as viewed from a substrate holder side, and FIG. FIG.

FIG. 3 is a graph showing a relationship between discharge time and plasma impedance when a film thickness correction plate is supported in a non-grounded state.

FIG. 4 is a graph showing the relationship between discharge time and plasma impedance when a film thickness correction plate is grounded.

[Explanation of symbols]

1 vacuum chamber 2 substrate holder 3 Target 4 RF Power 4a matching network 5 DC power 5a pass filter 6 gas introduction line 7 H ₂ O introducing line 8 film thickness correcting plate 9 substrate 10 the backing plate 11 cover 12 fasteners

Claims (6)

[Claims] A substrate holding means for holding a substrate on which a thin film is to be formed at a position facing the target; a plasma generating means for generating plasma between the substrate and the target; In a sputter deposition apparatus having a film thickness correction plate supported between the target and the substrate holding means for correcting a variation in a thickness position of a thin film, the film thickness correction plate is in an ungrounded state. A sputter film forming apparatus characterized by being supported by: 2. The sputter film forming apparatus according to claim 1, wherein the film thickness correction plate is made of a conductive material, and is supported in a non-ground state by a fixture made of an insulating material. 3. The target is supported on a metal backing plate, and a metal cover for covering the backing plate is provided between the film thickness correction plate and the backing plate. The sputter film forming apparatus according to claim 2, wherein the thickness correction plate is fixed to the cover separately from the cover. 4. The sputtering film forming apparatus according to claim 2, wherein said film thickness correction plate is made of aluminum. 5. The sputter film forming apparatus according to claim 1, wherein said thickness correction plate is made of an insulating material. 6. The substrate holding means is a polygonal drum-shaped holder rotatably provided, and a plurality of substrates are held on respective side surfaces of the holder.
The sputtering film forming apparatus according to any one of the above.