JPH04124265A - Sputtering device and production of film - Google Patents

Abstract

PURPOSE:To reduce the absolute value of the self-bias voltage of the cathode and to prevent the resputtering of a film on a substrate by negative ions emitted from the cathode by arranging magnets generating a strong magnetic field near a target electrode and using halogen-contg. gas as part of gas to be introduced. CONSTITUTION:When magnets are arranged near a target in a vacuum vessel and a thin oxide film is produced on a substrate by high-frequency sputtering of the target, halogen-contg. gas, preferably bromine or fluorine-contg. gas is used as part of gas to be introduced into the vessel. The absolute value of the self-bias voltage of the cathode can be reduced by negative halogen ions and the self-bias voltage of the cathode can be controlled by controlling the flow rate of the halogen-contg. gas. Magnets generating a strong magnetic field on the surface of the magnet are preferably arranged so that a component of the magnetic field parallel to the surface of the target becomes >=400G at a position at which a component of the magnetic field perpendicular to the surface of the target becomes zero.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a sputtering device that performs high-frequency sputtering by placing a magnet near a target, and also relates to a sputtering device that performs high-frequency sputtering by disposing a magnet near a target, and also relates to a sputtering device that performs high-frequency sputtering by placing a magnet near a target, and also relates to a sputtering device that uses this device to produce an oxide thin film. Regarding the manufacturing method.

[Conventional technology] In recent years, thin films have been created using sputtering phenomena, the basic physical properties of the thin films have been measured, and basic research and practical technology have been developed to process thin films and apply them to devices, etc. Things are actively happening.

The sputtering phenomenon is a phenomenon in which sputter particles (neutral particles) are generated from the target by injecting high-energy ions into the target, and the sputter particles are deposited on a substrate.

Oxide superconductor thin films and ITO thin films (transparent conductive films), which have recently been in the spotlight, are also produced using this sputter link phenomenon. However, it has been reported that when sputtering an oxide target when producing these thin films, the following phenomenon occurs.

(1) When high-energy ions are injected into a target and the secondary ions emitted from the target are analyzed, negative oxygen ions are detected as the main peak (50th Japan Society of Applied Physics Conference Proceedings 28a) -PB-17
, 1989).

(2) Negative ions emitted from the target are accelerated toward the substrate by the sheath electric field on the target. This negative ion has almost the same energy as the acceleration energy due to the self-bias voltage of the target (37th Applied Physics Conference Proceedings 29a-V-9,
1990).

(3) High-energy negative ions accelerated by the cathode sheath electric field impact the substrate surface, causing a phenomenon in which the sputtered particles (film) attached to the substrate surface are re-sputtered (37th Applied Physics Union Lecture Conference Proceedings 29a-■8, 1990).

Due to this re-sputtering phenomenon, the composition of the oxide superconductor thin film no longer matches that of the target, and its superconducting properties are significantly degraded. Also, ITO
The conductivity of thin films also deteriorates significantly due to similar reasons.

This re-sputtering phenomenon is caused by negative ions being given high energy by the electric field of the cathode sheath, so in order to prevent the re-sputtering phenomenon, the electric field of the cathode sheath can be reduced. That is, in high-frequency sputtering, the absolute value of the cathode self-bias voltage may be reduced. The value of this self-bias voltage depends on the following conditions.

(a) The self-bias voltage of the cathode depends on the high frequency power applied to the cathode. In other words, as the power increases, the absolute value of the self-bias voltage also increases. 6th
The figure shows the relationship between self-bias voltage and applied power.

(b) The self-bias voltage of the cathode depends on the pressure inside the vacuum vessel. In other words, as the pressure increases, the absolute value of the self-bias voltage decreases.

FIG. 7 shows the relationship between self-bias voltage and pressure.

(C) The self-bias voltage of the cathode depends on the frequency of the applied high-frequency power. In other words, the higher the frequency, the smaller the absolute value of the self-bias voltage (References: THE 5ECOND 15TECWORKSI)
OP ON 5IjPERCOND[1CTIVY,
MAY28-30゜1990, 9.21).

Therefore, by controlling the power applied to the cathode, the pressure inside the vacuum container, and the frequency of the applied power, the self-bias voltage can be controlled.

[Problems to be Solved by the Invention] However, there are the following problems in controlling these conditions.

The above power control (a) has the following problems. The absolute value of self-bias voltage tends to decrease when the power is lowered, but if the absolute value of self-bias voltage is reduced to 100
In order to make the applied power less than 30W, the applied power must be less than 30W. However, this reduces the film deposition rate. Further, when the power is changed within the range of 0 to 30 W, the self-bias voltage changes rapidly, and it is practically impossible to precisely control the self-bias voltage.

The above pressure control (b) has the following problems. As the gas pressure increases, the absolute value of the self-bias voltage tends to decrease, but if the absolute value of the self-bias voltage is reduced by 10
In order to reduce the pressure to 0V or less, the pressure must be 500mTorr or more. However, in this case, sputtered particles and gas particles collide and cause scattering, resulting in large in-plane variations in film thickness distribution and film composition distribution. Therefore, the effective membrane area becomes small. Furthermore, as in the case of "double series (a)", the film deposition rate tends to be extremely low, making it impractical.

The above frequency control (c) has the following problems.

When the frequency is increased from 13.56 MHz to 100 MHz, the absolute value of the self-bias voltage tends to decrease. However, as shown in the literature cited in "double (C)", even if the frequency is increased by 1 to 100 MH2, the absolute value of the self-bias voltage will not become less than 100 V. Further, as is clear from this document, although the uniformity of the film composition is certainly good, the target composition and the film composition do not match. This is because the absolute value of the self-bias voltage is as high as 100 cm, causing compositional fluctuations. Furthermore, changing the frequency requires changing the oscillator, power supply, and impedance matching device, which is very expensive. Furthermore, as the frequency is increased, stray capacitance is affected, and it takes a lot of effort to adjust the impedance matching.

Therefore, an object of the present invention is to provide a sputtering apparatus that can reduce the self-bias voltage by a method other than the above-mentioned method, and to provide a film manufacturing method using this apparatus.

[Means for Solving the Problems] A sputtering apparatus of the first invention is a high-frequency sputtering apparatus in which a magnet is arranged near a target, and has a gas introduction part that introduces a halogen-based gas as part of the introduced gas. It is characterized by

In addition to the features of the first invention, the sputtering apparatus of the second invention has a magnetic field component parallel to the target surface of 400 Gauss or more at a position where the magnetic field component perpendicular to the target surface becomes zero. It is characterized by

In addition to the features of the second invention, the sputtering apparatus of the third invention is characterized by having a substrate bias mechanism that applies a negative voltage to a substrate holder that holds a substrate to be processed.

A film manufacturing method according to a fourth aspect of the invention is a film manufacturing method in which a magnet is placed near a target and an oxide thin film is created on a substrate to be processed by high frequency sputtering of the target. It is characterized by introducing a halogen gas into a vacuum container.

The film manufacturing method of the fifth invention is characterized in that a bromine gas or a fluorine gas is used as the halogen gas in the fourth invention.

The film manufacturing method of the sixth invention is characterized in that the self-bias voltage of the cathode is controlled by controlling the flow rate of the halogen-based gas according to the fourth invention.

In addition to the feature of the fourth invention, the film fabrication method of the seventh invention provides a method in which the magnetic field component parallel to the target surface at a position where the magnetic field component perpendicular to the target surface becomes zero is 400 Gauss or more. It is characterized by certain things.

In addition to the features of the seventh invention, the film manufacturing method of the eighth invention is characterized in that a negative voltage is applied to a substrate holder that holds a substrate to be processed.

A film manufacturing method according to a ninth invention is characterized in that, in the eighth invention, a negative voltage having an absolute value smaller than the self-bias voltage of the cathode is applied to the substrate holder.

[Function] When a halogen-based gas is used as part of the introduced gas, negative ions of halogen (for example, Br-1F-) are generated in the plasma. These negative ions act to reduce the absolute value of the self-bias voltage of the cathode. By controlling the flow rate of the halogen-based gas, the amount of negative halogen ions in the plasma can be controlled, so the self-bias voltage of the cathode can be precisely controlled. If the self-bias voltage can be precisely controlled, the film deposition rate can be precisely controlled.

In so-called magnetron sputtering, which increases the plasma density by forming a magnetic field on the target surface, the position where the magnetic field is parallel to the target surface (i.e. target area) and the magnetic field component perpendicular to the surface (hereinafter referred to as Bv) become zero. The plasma density increases at certain positions. and,
The larger the magnetic field component parallel to the target surface (hereinafter referred to as Bh) at the position where Bv becomes zero, the higher the plasma density becomes, and the absolute value of the quad self-bias voltage becomes smaller accordingly.

Preferably, the absolute value of the self-bias voltage is 100V or less. In this invention, Bh is set to be 400 Gauss or more. To obtain such a large magnetic field, it is recommended to use rare earth magnets. Note that in a normal magnet for magnetron sputtering, Bh is about 250 Gauss.

As described above, the absolute value of the cathode self-bias voltage can be reduced by using a halogen-based gas or by using a large magnetic field. As a result, the acceleration energy of negative ions emitted from Turkella I can be reduced, and the impact of these negative ions on the substrate can be alleviated.

Further, it is possible to take measures to alleviate the above-mentioned negative ion impact on the substrate holder side as well.

That is, negative ion impact can be alleviated by applying a negative voltage to the substrate holder.

The negative voltage applied to the substrate holder is set to have a smaller absolute value than the self-bias voltage of the cathode.

[Example] Next, the present invention will be described in detail with reference to the drawings.

FIG. 1 is a front sectional view of an embodiment of a sputtering apparatus of the present invention. The vacuum vessel 1 can be evacuated by a main exhaust system installed in the direction of arrow 6 and can be maintained at a pressure of 0-7 Torr or less. The vacuum container 1 is provided with a gas introduction system 29 for supplying the gas necessary for producing a thin film, so that the gas can be introduced into the vacuum container 1 via valves 23, 24, and 25. . For example, arrow 10
Ar gas from direction, 02 gas from arrow 11 direction, arrow 1
Br2 gas is introduced from two directions, mixed and introduced into the vacuum vessel 1. The pressure inside the vacuum vessel can be set to an appropriate value by adjusting the mass flow meter (not shown) of the gas introduction system 29 and the main exhaust system installed in the direction of arrow 6.

A substrate 14 is held in the vacuum container 1 and heated to 800°C.
A substrate holder 13 that can be heated to Heating method is temperature controller 19 and thyristor unit 1
8 and a thermocouple 26 attached to the surface of the substrate holder 13.
In this method, the lamp heater 15 is controlled by the following.

The substrate holder 13 is electrically insulated from the vacuum vessel 1 by an insulating stone 17. The substrate holder 13 is connected to a bias power source 2 outside the vacuum container 1 by a lead wire 16.
Connected to 0. The bias power supply 20 is a bipolar power supply, and can select either a positive voltage or a negative voltage to apply to the substrate holder 13. Substrate holder 13
By applying a bias voltage to the target, the energy of negative ions that enter the substrate from the target can be controlled.

A target shield 2 is installed at a position facing the substrate holder 13, and a target 3 and a cathode body 30 are installed inside the target shield 2 via an insulating ring 8 (made of fluororesin). This cathode body 3
0 is cooled by flowing cooling water (arrows 9a, 9b). Further, an impedance matching device 21 and a high frequency power source 22 are connected to the cathode body 30. This high frequency power supply 22 supplies power to the cathode body 30.

The cathode body 30 houses a cylindrical high-field magnet 7 made of a rare earth magnet. FIG. 2 is a front cross-sectional view of the high-field magnet 7. This high-field magnet 7 generates a magnetic field 4, and at a position on the surface of the target 3 where the magnetic field component Bv perpendicular to the surface of the target 3 becomes zero, the magnetic field component Bh parallel to the surface of the target 3 becomes zero. It has a magnetic field strength of 1200 Gauss.

Returning to FIG. 1, a voltmeter 28 is connected to the cathode body 30 via a robust filter 27. When high frequency power is applied to the cathode body 30, a self-bias voltage is induced in the cathode body 30 when a discharge occurs within the vacuum vessel 1.

This self-bias voltage Vs is monitored by a voltmeter 28.

FIG. 3 shows the relationship between the magnetic field component Bh and the self-bias voltage Vs at the position of Bv=0 when the high frequency power is 150 W and the pressure is 25 mTorr.

Bh=O, that is, when there is no magnet, Vs--933V
It is. When the magnetic field component Bh is increased, the absolute value of the self-bias voltage Vs rapidly decreases.

When B h, = 1200 Gauss, Vs = -70
It becomes V. By increasing the magnetic field component Bh in this way, the absolute value of the self-bias voltage Vs can be reduced. However, since the high-field magnet 7 is a permanent magnet, once the magnet is installed, the self-bias voltage Vs cannot be controlled by the magnet. That is, although the magnet strength can be roughly set by selecting the magnet, other measures are required to precisely control Bh.

Therefore, in this embodiment, the self-bias voltage Vs is precisely controlled by introducing a halogen-based gas. In this embodiment, bromine gas (Br2) is introduced into the vacuum vessel 1 through a mass flow meter (not shown) and a valve 25 in a gas introduction system 29. At this time, the self-bias voltage Vs and the partial pressure ratio r of Br2 gas
Br2/(Ar+02+Br2)" is shown in FIG. By increasing the partial pressure ratio of the Br2 gas, the absolute value of the Lissertz-Biasmi pressure Vs can be lowered. Therefore, by keeping the high frequency power and the pressure in the vacuum container constant and adjusting the partial pressure ratio of the Br2 gas, the self-bias voltage Vs can be precisely controlled.

The film deposition rate by sputtering depends on the self-bias voltage, so if the self-bias voltage can be precisely controlled, the film deposition rate can be precisely controlled. In particular, when superlattice thin films are deposited several angstroms at a time by multi-cathode sputtering, it is necessary to precisely control the film deposition rate, and precise control of the self-bias voltage is effective in such cases. .

As is clear from Fig. 4, as the partial pressure ratio of Br2 gas increases, the absolute value of the self-bias voltage decreases;
Br2 gas is highly corrosive, so do not increase the partial pressure ratio too much (
This may cause the gas introduction system and the inside of the chamber to be contaminated by corrosion. Therefore, the partial pressure ratio of Br2 gas is 0.
It is preferable to suppress it to about 1.

Although it is important to reduce the absolute value of the self-bias voltage in order to alleviate negative ion impact on the substrate, if the absolute value of the self-bias voltage is made too small, the film deposition rate becomes too low to be practical. Therefore, it is preferable that the absolute value of the self-bias voltage is not less than 50V.

Next, a method for producing an oxide thin film using this sputtering apparatus will be explained.

As an example of a substance that generates negative ions from the target,
There are oxide superconductors Y and Ba2CugO. Therefore, as target 3, YIBa2C with a diameter of 4 inches was used.
u30. A sintered target is used. In the gas introduction system 29 in Fig. 1, the valves 23, 24 and the mass 70 meter (
(not shown), Ar gas is supplied from the direction of arrow 10 and 02 gas is supplied from the direction of arrow 11, and these are mixed and introduced into the vacuum vessel 1. The mixing ratio of Ar gas and 02 gas at this time is 1:1. The pressure inside vacuum container 1 is 2
Set it to 5 mTorr. Target 3 and substrate holder 13
The distance between them is 25 mm. A high magnetic field is generated near the target 3 by a high magnetic field magnet 7 . That is,
On the target surface, the magnetic field component Bh is 1200 Gauss at the position where the magnetic field component Bv becomes zero. For target 3, 13.56MHz from high frequency power supply 22
A high frequency power of 150 W is applied at a frequency of 150 W, and the reflected wave is adjusted to OW (zero watt) using an impedance matching device 2]. At this time, the self-bias voltage Vs monitored by the voltmeter 28 through the filter 27 was -70V.

To further lower the self-bias voltage Vs, use arrow 1.
Br2 gas was introduced into the vacuum container 1 from two directions via a mass flow meter (not shown).

Then, adjust the flow rates of Ar gas, 0□ gas, and Br2 gas so that the pressure inside the vacuum container becomes 25 mTorr,
Partial pressure ratio of Br2 gas rB r2 / (A r+02
+ B r 2 ) J was set to 0.1.

The self-bias voltage Vs at this time was -50V.

In order to obtain superconducting properties in an as-grown state, a thin film was deposited under the above conditions while the substrate 14 was heated to 600 to 700°C. MgO (100) was used for the substrate 14 to obtain a C-axis oriented film. After confirming that this film could be obtained with good reproducibility, the influence of the substrate bias voltage was investigated.

That is, a negative bias voltage was applied to the substrate 14 by the bias power supply 20, and the value of the bias voltage was varied to produce superconductor thin films. As a result, a film having the best characteristics when the bias voltage vb was -10V was obtained.

FIG. 5 shows the composition ratio distribution of the film on the substrate. (a) shows the case of the embodiment, and (b) shows the case of the conventional example. A comparison between the embodiment and the conventional example will be shown below.

(a) Example (1) Uniform film composition region with variation in composition ratio within ±5%: diameter within 100 mm (2) Superconducting critical temperature of film: 90K (3) Self-bias voltage: -50V (b) Conventional example (1) Uniform film composition region with variation in composition ratio within ±5% and diameter within 45 mm (2) Superconducting critical temperature of film = 82K (3) Self-bias voltage - 1B2V In the example, a high field magnet is used By doing so, the self-bias voltage was lowered, and furthermore, by controlling the flow rate of Br2 gas, the self-bias voltage was precisely controlled. As a result, when comparing the example and the conventional example, the film composition was improved in the example, and in particular, the area of the uniform film composition area was more than four times that of the conventional example. Moreover, YSBa is contained in the film.

Although a peak of Br was observed in addition to Cu10, Br does not deteriorate the superconducting properties. In the conventional example described above, the film was formed using a standard magnet, without introducing Br2 gas, and without applying a body bias.

A film similar to the above can be obtained by using a bromine gas or a fluorine gas shown below in addition to Br gas. That is, as Br-based gas, BBr3, HBr, BrF3
, BrF5, CBrF3, C2Br2 F4, C
H3Br can be used. In addition, fluorine-based gases include NF3, BF3, SF4, SF6, CF4, H
F1CIF3, C2F6, C3F8, CH3F can be used.

Although an oxide superconductor was used as the target material in this embodiment, similar effects can be obtained when using other oxides as the target that emit negative ions from the target.

[Effects of invention According to this invention, the following effects can be obtained.

(1) By installing a high-field magnet near the target electrode, the absolute value of the cathode self-bias voltage can be reduced.

(2) By using a halogen-based gas as part of the introduced gas, the absolute value of the cathode self-bias voltage can be reduced. Furthermore, by controlling the flow rate of this halogen-based gas, the self-bias voltage of the cathode can be precisely controlled.

(3) By reducing the absolute value of the self-bias voltage of the cathode as described above, it is possible to prevent the film on the substrate from being re-spudded by negative ions emitted from the cathode.

(4) By applying a negative bias voltage to the substrate to be processed, the incident energy of negative ions incident on the substrate can be controlled. As a result, the incident energy of negative ions can be lowered to an appropriate value, promoting the chemical reaction between sputtered particles and negative ions on the substrate surface, and improving the film quality and crystal structure of the oxide film. I'm coming.

[Brief explanation of the drawing]

FIG. 1 is a front sectional view of an embodiment of the sputtering apparatus of the present invention, FIG. 2 is a front sectional view of a high magnetic field magnet, FIG. 3 is a graph showing the relationship between magnetic field strength and self-bias voltage, and FIG. The figure is a graph showing the relationship between the self-bias voltage and the partial pressure ratio of bromine' gas. Figure 5 is a graph showing the composition ratio distribution of the film on the substrate. Figure 6 is the graph showing the relationship between the self-bias voltage of the cathode and the applied power. The graph shown in Figure 7 is a graph showing the relationship between the self-bias voltage of the cathode and the pressure inside the vacuum chamber. 1... Vacuum vessel 3... Target 7... High magnetic field magnet 13... Base boulder 14... Base 20... Base bias power supply 22... High frequency power supply 29... Gas introduction system 30...Cathode body

Claims (9)

[Claims] (1) A high-frequency sputtering apparatus in which a magnet is arranged near a target, the sputtering apparatus comprising a gas introduction part for introducing a halogen-based gas as part of the introduced gas. (2) The sputtering apparatus according to claim 1, wherein the magnetic field component parallel to the target surface is 400 Gauss or more at a position on the target surface where the magnetic field component perpendicular to the target surface becomes zero. (3) The sputtering apparatus according to claim 2, further comprising a substrate bias mechanism for applying a negative voltage to a substrate holder that holds a substrate to be processed. (4) In a film production method in which a magnet is placed near a target and a thin oxide film is produced on a substrate to be processed by high-frequency sputtering of the target, a halogen-based gas is introduced into a vacuum vessel as part of the introduced gas. A method for producing a film characterized by introducing the method into the method. (5) The film manufacturing method according to claim 4, wherein a bromine gas or a fluorine gas is used as the halogen gas. (6) The film manufacturing method according to claim 4, wherein the self-bias voltage of the cathode is controlled by controlling the flow rate of the halogen-based gas. (7) The film manufacturing method according to claim 4, wherein the magnetic field component parallel to the target surface is 400 Gauss or more at a position on the target surface where the magnetic field component perpendicular to the target surface becomes zero. (8) The method for producing a film according to claim 7, characterized in that a negative voltage is applied to a substrate holder that holds the substrate to be processed. (9) The film manufacturing method according to claim 8, characterized in that a negative voltage having an absolute value smaller than the self-bias voltage of the cathode is applied to the substrate holder.