JP2002030432A - System and method for sputtering - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a system and method for sputtering, by which an insulating film having high breakedown voltage can be deposited. SOLUTION: In the case where an alumina film, an aluminum nitride film, a silicon dioxide film and a silicon nitride film are deposited by the sputtering method, the sputtering system which has a substrate, a vacuum vessel having a target electrode inside, a gas feed system for feeding inert gas and oxygen or nitrogen into the vacuum vessel, and a power source for applying voltage between the vacuum vessel and the target to form a plasma region in the vacuum vessel is used. Further, a gaseous mixture containing 0.3-1.0% gaseous hydrogen is fed by the above gas feed system.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sputtering apparatus and a sputtering method, and more particularly to a sputtering apparatus and a sputtering method capable of forming a highly insulating film on a substrate.

[0002]

2. Description of the Related Art Thin film forming technology is widely used in the manufacturing process of semiconductors such as ICs, liquid crystal display elements, hard disk drives, and electronic parts for computers. Various thin film forming methods are known, and among them, the sputtering method is one of the methods that are frequently used. In the sputtering method, an inert gas is introduced into a vacuum vessel to maintain the inside of the vacuum vessel at a degree of vacuum of about 0.1 to 1 Pa, and a discharge plasma is generated by applying a voltage to a base material called a target. This is a film formation method in which ions in the plasma collide with a target to scatter the target material and deposit a thin film on a substrate. One of the features of the sputtering method is that it can form an extremely large number of types of films, for example, not only metal thin films such as aluminum and copper, but also alloy thin films such as permalloy, as well as alumina (aluminum oxide) and silicon dioxide. It is possible to form an electrically insulating thin film.

[0003] Of the above thin films, there are roughly two methods for forming an electrically insulating thin film by a sputtering method. These methods will be described by taking as an example the case of forming an alumina film. The first method is a case where sputtering is performed by high-frequency discharge using an alumina target and using argon or a mixed gas of argon and a small amount of oxygen as a discharge gas. The second method is a method in which sputtering is performed by a DC discharge or a pulse discharge using a metal target of aluminum, a mixed gas of argon and high-concentration oxygen as a discharge gas. The former method is described, for example, in "Brian N. Cha
pman, translated by Yukio Okamoto, "Basics of Plasma Processing" (published November 19, 1985) Denki Shoin. The latter method is called a reactive sputtering method. For example, "Kanahara Kan," Sputtering phenomenon "(published February 25, 1987), University of Tokyo Press,
p. 120- ".

[0004]

The withstand voltage characteristic of an insulating thin film formed on a substrate such as a semiconductor substrate is an important factor in film evaluation. The breakdown voltage of the thin film varies depending on the method of forming the film. A thin film obtained by thermally oxidizing aluminum or silicon has the highest withstand voltage, and about 10 MV / cm for a high-quality film. Next, the withstand voltage of the film obtained by the CVD method (chemical vapor deposition method) is high. However, a thin film having a sufficient withstand voltage cannot be obtained by the sputtering method.

In the sputtering method, since the inert gas is ionized and collided with the target, the inert gas remaining on the target jumps out at a high speed and is injected into the film. This is because defects are likely to occur. To reduce defects,
It is necessary to reduce the film formation rate, for example, by stacking films having a thickness equal to or less than the natural oxide film, or to heat the substrate, which causes a decrease in productivity.

The method of thermally oxidizing aluminum or silicon in an oxygen atmosphere or a water vapor atmosphere is limited to a case where the film thickness is extremely thin or a case where a high temperature treatment is possible because diffusion of oxygen in an oxide film is very slow. Also, CV
In principle, it is difficult to form an alumina film by the method D. In the formation of a silicon dioxide film, the substrate needs to be heated to about 300 ° C. That is, methods other than the sputtering method have various restrictions such as the substrate temperature, and the conditions for film formation are limited. On the other hand, since the sputtering method does not require heating of the substrate, the film formation conditions are less restricted, but the film quality, especially the withstand voltage of the formed insulating film is low as described above. The present invention has been made in view of the above problems, and provides a sputtering apparatus and a sputtering method capable of forming a highly insulating film.

[0007]

The present invention employs the following means in order to solve the above-mentioned problems.

When an aluminum oxide film or aluminum nitride is formed as an insulating film by a reactive sputtering method, a vacuum vessel containing a substrate and a target electrode made of aluminum, an inert gas, oxygen or nitrogen in the vacuum vessel. A gas supply device for supplying
In a sputtering apparatus comprising a power supply for applying a voltage between the vacuum vessel and a target to form a plasma region in the vacuum vessel, the gas supply device contains 0.3 to 1.0% of hydrogen gas. Supply mixed gas. The target electrode may use an aluminum alloy. When silicon dioxide or silicon nitride is formed as the insulating film, silicon may be used as the target electrode.

Further, when an aluminum oxide film or silicon dioxide is formed as an insulating film by a sputtering method using high-frequency discharge, a vacuum vessel containing a substrate and a target electrode made of aluminum oxide or silicon dioxide is provided. A gas supply device that supplies an inert gas and oxygen into a container, and a sputtering device including a high-frequency power supply that forms a plasma region in the vacuum container by applying a voltage between the vacuum container and a target, The gas supply device supplies hydrogen gas to 0.1 g.
A mixed gas containing 3 to 1.0% is supplied. In the case where silicon dioxide or silicon nitride is formed as the insulating film, silicon dioxide or silicon nitride may be used as the target electrode.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the present invention will be described below with reference to FIGS. FIG. 1 shows the first embodiment of the present invention.
It is a figure showing a sputtering device concerning an embodiment. In the figure, reference numeral 10 denotes an aluminum target, which is attached to the backing plate 11 by bonding. Reference numeral 11 denotes a backing plate, and an insulating seal 1
8 and insulated and airtightly attached to the vacuum vessel 20. 12 is a substrate holder for fixing and supporting the substrate 13, 1
Reference numeral 3 denotes a substrate on which a thin film is formed. Reference numeral 14 denotes a shield, on which sputter particles to be attached to other than the substrate 13 are deposited. For this reason, the shield needs to be replaced from time to time. Reference numeral 15 denotes an earth shield, and ions generated in the plasma region
The earth shield portion is maintained at the same potential as the vacuum vessel so as not to be incident on other portions. Reference numeral 16 denotes a magnet that forms a magnetic field for a magnetron, and is movable along a support shaft attached to a driving motor 17. 18 is an insulating seal, 20 is the substrate 13 and the aluminum target 10
A vacuum container 21 containing a mixed gas of 99% argon and 1% hydrogen, 22 a cylinder filled with oxygen gas, and 23 and 24 adjusting gas flow rates from the cylinders 21 and 22, respectively. A mass flow controller; 25, a turbo molecular pump for evacuating the vacuum vessel 20; 26, a threshold valve; 27, a plasma region;
8 is a DC power supply for supplying a voltage between the vacuum vessel 20 and the aluminum target 10.

In the sputtering apparatus shown in FIG. 1, the inside of the vacuum vessel 20 is evacuated by a turbo molecular pump 25 through a gate valve 26. Substrate 1 on which thin film is to be deposited
3 is fixed to the substrate holder 12 inside the vacuum vessel 20 with the film formation surface facing upward. On the other hand, the aluminum target 10
Is attached to the backing plate 11 by bonding. The backing plate 11 is an insulating seal 1
8 and is insulated and attached to the vacuum container 20. A driving motor 17 is provided on the upper atmosphere side of the backing plate 11.
The magnet 16 forms a tunnel-like magnetron magnetic field on the surface of the target 10 in a vacuum with the movable magnet 16 driven by the magnet.

There are two gas introduction systems for introducing a gas for generating electric discharge. The cylinder 21 is a gas obtained by mixing 99% of argon and 1% of hydrogen, and the cylinder 22 is an oxygen gas. The mixed gas of argon and hydrogen is introduced into the vacuum vessel 20 by adjusting the flow rate by the mass flow controller 23. Similarly, the flow rate of oxygen gas is adjusted by the mass flow controller 24 and introduced into the vacuum vessel 20. When a gas is introduced to maintain the inside of the vacuum vessel 20 at 0.4 Pa and a voltage is applied between the vacuum vessel 20 and the target 10 by the DC power supply 28, a plasma region 27 is generated, and argon ions and oxygen ions are generated. Is done. When these ions collide with the target, atoms on the surface of the target 10 fly out as sputter particles and deposit on the substrate 13. When the magnet 16 is driven by the drive motor 17 while the plasma region 27 is generated, the plasma region 27 also moves. This makes target 1
0 is sputtered, and sputter particles are deposited on the entire surface of the substrate 13. When the plasma region is fixed, an insulating film adheres to a part of the target, and a phenomenon occurs in which the insulating film causes dielectric breakdown and scatters foreign substances. However, moving the plasma region reduces such a phenomenon. Can be blocked.

Most of the generated ions are
The kinetic energy is transferred to the atoms in the target 10 and then remains in the target 10. Therefore, the oxygen remaining in the target 10 eventually receives energy from the ions and jumps out of the target 10.
In this manner, aluminum and oxygen are mixed and deposited on the substrate 13 to form an alumina thin film. Further, if hydrogen is added to the gas, the film will contain hydrogen.

As a film forming condition, a mixed gas of argon and hydrogen was flowed at 50 SCCM, oxygen gas was flowed at 50 SCCM, and a film was formed at a discharge power of 2.5 kW and a gas pressure of 0.4 Pa for 5 minutes. Was formed. When the withstand voltage of the formed film was measured, the withstand voltage was 8 to 9 MV / cm, and the variation was small. In addition, as a result of using a mixed gas of argon and hydrogen as the introduced gas and changing the mixing ratio of hydrogen in the mixed gas to form a film, the result shown in FIG. 2 was obtained.

FIG. 2 is a diagram showing a breakdown voltage characteristic.
In FIG. 2, 31 indicates the maximum value of the breakdown voltage of the obtained thin film, 32 indicates the minimum value, and 33 indicates the amount of variation. Referring to FIG. 2, the amount of hydrogen introduced to increase the withstand voltage is preferably about 0.3% to 1%, and more preferably about 0.5% to 1%.
About 1% is more preferable. Even if the hydrogen content is further increased, no decrease in withstand voltage is observed. However, one hydrogen
%, The decrease in the film formation rate becomes significant. The variation amount 33 is large when the content of hydrogen is small, and decreases as the hydrogen content increases.

The same effect can be obtained even if the target 10 is an aluminum alloy obtained by adding an additive to aluminum.

When a nitrogen gas is used for the cylinder 22 instead of the oxygen gas, a thin film of aluminum nitride is formed on the substrate 13. At this time, the film formation rate was about twice that of alumina, and a thin film of 50 nm aluminum nitride could be formed with a film formation time of two and a half minutes. When the withstand voltage of the formed film was measured, the withstand voltage was 3 to 4 MV / cm, which was lower than that of the alumina film. However, the change shape of the breakdown voltage characteristic with respect to the ratio of the hydrogen gas was similar to FIG. The amount of hydrogen introduced to increase the voltage is preferably about 0.3% to 1%, and more preferably about 0.5% to 1%, as in the case of the alumina film.

Further, when silicon is used as the target 10 and oxygen gas is used for the cylinder 22 and mixed gas of argon and hydrogen is used for the cylinder 21, a thin film of silicon dioxide is formed on the substrate 13. When the withstand voltage of the formed film was measured, the withstand voltage was 8 to 9 MV / cm, which was the same as that of the alumina film. The breakdown voltage characteristics with respect to the ratio of hydrogen in the introduced gas were almost the same as those of the alumina of FIG.
When a silicon nitride film was formed on the cylinder 22 using nitrogen gas, the withstand voltage was 7 to 8 MV / cm, and the breakdown voltage characteristic with respect to the ratio of hydrogen in the introduced gas was similar to that of the alumina of FIG. . Therefore, in any case, the ratio of hydrogen in the introduced gas is 0.3% to 1% of the whole.
Degree is preferable, and about 0.5% to 1% is more preferable.

As shown in FIG. 2, a mixed gas of 99% argon and 1% hydrogen is 50 SCCM, and oxygen gas is 50 SCCM.
When the alumina film was formed by flowing CM, the ratio of hydrogen in the introduced gas was 0.5%, and the dielectric breakdown voltage of the film at that time was 8 to 9 MV / cm. On the other hand, when the gas to be introduced is pure argon and oxygen as in the conventional case, it corresponds to the case where the proportion of hydrogen in FIG. 2 is 0%,
The breakdown voltage was as low as 3 to 6 MV / cm, and the variation was large. Therefore, according to the present invention, a dielectric breakdown voltage is improved, and a high-quality insulating film with small variation can be formed. That is, the present invention is intended to lower the defect density by bonding hydrogen to defects caused by dangling bonds in the insulating film and to improve the dielectric breakdown voltage. In addition,
The same effect can be obtained not only for the alumina film but also for the aluminum nitride film, the silicon dioxide film, and the silicon nitride film.

Next, a second embodiment of the present invention will be described with reference to FIG. FIG. 3 is a diagram showing a sputtering apparatus according to a second embodiment of the present invention. In the figure, 41
Is an alumina target, and a backing plate 40
Attach and attach to. Backing plate 4
Numeral 0 is attached to the vacuum vessel 50 insulated and airtight by an insulating seal 48. 42 is a substrate holder for fixing and supporting a substrate 43, and 43 is a substrate. Reference numerals 45 and 46 denote ground shields, which keep the ground shield portions at the same potential as the vacuum vessel so that ions generated in the plasma region do not enter the target 41 and the like. The substrate 43 is transferred from another vacuum chamber through the gate valve 49. The substrate holder 42 can set six substrates,
The substrate holder 42 can be rotated by a driving motor 47 to receive a substrate carried from another room. 48 is an insulating seal, 50 is a vacuum vessel containing the substrate 43 and the alumina target 41, etc., 51 is a gas cylinder filled with a mixed gas composed of 99% argon and 1% hydrogen, 52 is a cylinder filled with oxygen gas, 53, 54
Is a mass flow controller for adjusting gas flow rates from the cylinders 51 and 52, 55 is a turbo molecular pump for exhausting the inside of the vacuum vessel 20, 56 is a threshold valve, 58 is a frequency for supplying a voltage between the vacuum vessel 50 and the aluminum target 41. 13.56 MHz high frequency power supply, 59
Is a frequency 1 for supplying a voltage between the vacuum vessel 20 and the substrate 43.
3.56 MHz high frequency power supply.

In the sputtering apparatus shown in FIG. 3, the inside of the vacuum vessel 50 is evacuated by a turbo molecular pump 55 through a gate valve 56. Substrate 4 on which thin film is deposited
3 is fixed to the substrate holder 42 inside the vacuum vessel 50 with the film formation surface facing upward. On the other hand, the alumina target 41
It is attached to the backing plate 40 by bonding. The backing plate 40 is insulated and attached to the vacuum container 50 via an insulating seal 48.

As in the first embodiment, there are two gas introduction systems for introducing a gas for generating a discharge.
Reference numeral 1 denotes a gas obtained by mixing 99.5% of argon and 0.5% of hydrogen, and the cylinder 52 denotes an oxygen gas. The mixed gas of argon and hydrogen is introduced into the vacuum vessel 50 by adjusting the flow rate by the mass flow controller 53. Similarly, the flow rate of oxygen gas is adjusted by the mass flow controller 54 and introduced into the vacuum vessel 50. When a gas is introduced and the inside of the vacuum vessel 50 is maintained at 1.6 Pa, and a voltage is applied between the vacuum vessel 50 and the target 41 by the high frequency power supply 58, the plasma area 57 is And generate argon ions and oxygen ions. When these ions collide with the target, atoms on the surface of the target 41 fly out as sputtered particles. Furthermore, when a voltage is applied between the vacuum chamber 50 and the substrate 43 and the substrate holder 42 by the high-frequency power supply 59, the ionized sputtered particles in the plasma region 57 are attracted to the substrate 43 side. Therefore, when the high-frequency power source 59 is turned on, the film forming speed is increased as compared with the case where the high-frequency power source 59 is turned off, and the step coverage of the film on the substrate 43 is improved.

As the film forming conditions, a mixed gas of argon and hydrogen flows at 98 SCCM and an oxygen gas flows at 2 SCCM, and the target side discharge power is 10 kW and the substrate side discharge power is 3 kM.
When a film was formed at W and a gas pressure of 1.6 Pa for 40 minutes, an alumina film having a thickness of 2 μm was formed on the substrate 43. When the withstand voltage of the formed film was measured, the withstand voltage was about 1 MV / cm. FIG. 4 is a diagram showing a breakdown voltage characteristic in the present embodiment, similarly to FIG. FIG.
, The amount of hydrogen to increase the withstand voltage is preferably about 0.3% to 1%.

Even when silicon dioxide, aluminum nitride, or silicon nitride is used as the target 41, the dielectric breakdown voltages are 1 MV / cm, 0.4 MV / cm,
Although it is 0.8 MV / cm, the breakdown voltage characteristic is similar to that of FIG. 4, and the amount of hydrogen introduced to increase the withstand voltage is preferably about 0.3% to 1%.

Also in this embodiment, when the gas to be introduced is pure argon and oxygen as in the prior art, FIG.
In the case of the alumina film, the breakdown voltage was as low as 0.1 to 0.4 MV / cm, and the variation was large.

In addition, steam may be introduced into the vacuum vessel instead of hydrogen gas. Since the water vapor is decomposed by the plasma to generate hydrogen and oxygen, the result is substantially the same as when hydrogen gas and oxygen are separately introduced.

[0027]

As described above, according to the present invention, an insulating film having high insulating properties can be formed.

[Brief description of the drawings]

FIG. 1 is a view showing a sputtering apparatus according to a first embodiment of the present invention.

FIG. 2 is a diagram showing a breakdown voltage characteristic.

FIG. 3 is a diagram illustrating a sputtering apparatus according to a second embodiment of the present invention.

FIG. 4 is a diagram showing a breakdown voltage characteristic.

[Explanation of symbols]

 10, 41 Target 11, 40 Backing plate 12, 42 Substrate holder 13, 43 Substrate 14, 44 Shield 15, 45, 46 Earth shield 16 Magnet 17, 47 Driving motor 18, 48 Insulation seal 20, 50 Vacuum container 21, 22 , 51, 52 cylinders 23, 24, 53, 54 mass flow controller 25, 55 turbo-molecular pump 26, 56 gate valve 27, 57 plasma region 28 DC power supply 58, 59 high frequency power supply

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 4K029 BA44 BA46 BA58 BC05 BD01 CA06 DA04 DC03 DC05 EA05 5F058 BA01 BC03 BC04 BF12 BF29 5F103 AA08 BB22 DD27 HH03 LL14 LL20 NN06 RR05

Claims (6)

[Claims] A vacuum vessel containing a substrate and a target electrode made of aluminum; a gas supply device for supplying an inert gas, oxygen or nitrogen into the vacuum vessel; And a power supply for applying a voltage to the plasma vessel to form a plasma region in the vacuum vessel, wherein the gas supply device supplies a mixed gas containing 0.3 to 1.0% of hydrogen gas. Sputtering equipment. 2. The sputtering apparatus according to claim 1, wherein the material of the target electrode is made of silicon. 3. The sputtering apparatus according to claim 1, wherein the material of the target electrode is made of an aluminum alloy. 4. A vacuum vessel containing a substrate and a target electrode made of aluminum oxide or silicon dioxide; a gas supply device for supplying an inert gas and oxygen into the vacuum vessel; A sputtering device comprising a high frequency power supply for forming a plasma region in the vacuum vessel by applying a voltage therebetween, wherein the gas supply device supplies a mixed gas containing 0.3 to 1.0% of hydrogen gas. A sputtering apparatus characterized by the above-mentioned. 5. A vacuum vessel containing a substrate and a target electrode made of aluminum nitride or silicon nitride; a gas supply device for supplying an inert gas and nitrogen into the vacuum vessel; A sputtering device comprising a high frequency power supply for forming a plasma region in the vacuum vessel by applying a voltage therebetween, wherein the gas supply device supplies a mixed gas containing 0.3 to 1.0% of hydrogen gas. A sputtering apparatus characterized by the above-mentioned. 6. The sputtering apparatus according to claim 1, wherein the mixed gas is a mixed gas containing water vapor.