JPH07118844A - Formation of oxidized film - Google Patents

Abstract

PURPOSE:To always stably form good oxidized films while preventing an abnormal discharge by controlling the phase of a high-frequency power source on a substrate side so as to have a specific delay with the phase of a high-frequency power source on a target side. CONSTITUTION:The target 2 and substrate 3 connected respectively to the high-frequency power sources 5, 7 are arranged to face each other in a sputtering chamber 1 and a sputtering gas is introduced into this chamber. As a result, the target 2 is sputtered and the components thereof are deposited by evaporation on the substrate 3, by which the oxidized film is formed. The phase of the high-frequency power source 7 is controlled by using an automatic phase shifter 9 so as to have the delay of about 40 to 120 deg. at all times with the phase of the high-frequency power source 5 on the target side. As a result, the film forming speed is approximately constantly stabilized and a low film thickness distribution is maintained regardless of the differences in the sputtering devices and batches.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is mainly applied to manufacturing and processing of semiconductor elements and thin film forming technology, by sputtering using high frequency, for example, insulators and oxides such as Al ₂ O ₃ and SiO _2. And a method for forming an oxide film made of.

[0002]

2. Description of the Related Art Conventionally, a high frequency sputtering technique has been widely used for forming an insulating film by sputtering. In order to form a good oxide film, the film formation rate, film thickness distribution, step coverage, etc. are important factors. Therefore, the high frequency sputtering is usually performed by controlling the film forming conditions such as the flow rate / pressure of the sputtering gas, the incident power on the target side, the voltage on the substrate side, and the mixed gas may be used as the sputtering gas.

[0003]

However, in the above-described conventional method for forming an oxide film by high-frequency sputtering, the film forming rate changes from batch to batch despite the film forming conditions being controlled. There is a problem in that the film thickness distribution varies depending on the sputtering apparatus or batch used, or when the film forming operation is performed for a long time, an abnormal discharge may occur due to the phase shift or change of the high frequency power source. For example, even when the same sputtering gas is used under the same film forming conditions, if the phase difference between the high frequency power source on the target side and the high frequency power source on the substrate changes by about 10 °, the film forming rate changes by about 10 Å, and The film quality changes as the film thickness distribution changes to about 2 to 5%.

Therefore, it is important to optimally control the phase of the high frequency power source, but conventionally, in order to secure the stability of the sputtering apparatus, the cable length of the high frequency power source on the target side and the substrate side is changed. Only measures were taken to control it.

Therefore, the method for forming an oxide film according to claim 1 has been made in view of the above-mentioned conventional problems, and an object thereof is to form an oxide film by sputtering. Another object of the present invention is to provide a method capable of always forming a stable and good oxide film while preventing the occurrence of abnormal discharge regardless of the apparatus or batch used.

[0006]

The present invention is to achieve the above-mentioned object, and the contents thereof will be described below with reference to the embodiments shown in the drawings.

That is, the present invention has been made paying attention to the influence of the phase difference between the high frequency power source on the substrate side and the high frequency power source on the target side on the formation of an oxide film by sputtering, for example, the film formation rate and the film thickness distribution. In the method of forming an oxide film according to claim 1, when the oxide film is formed by sputtering an oxide, the high frequency power source on the substrate side is always about 40 ° with respect to the high frequency power source on the target side. ~
It is characterized in that the film is formed while optimally controlling so as to have a phase delay within a range of 120 °.

[0008]

As described in detail below, the inventor of the present application makes the film forming rate and the film thickness distribution substantially constant when the phase difference of the substrate side high frequency power source with respect to the target side high frequency power source is within a certain specific range. I found it to be stable. Therefore, claim 1
According to the method for forming an oxide film described above, the film formation rate can always be stabilized at a substantially constant level and the film thickness distribution can be kept low regardless of the sputtering apparatus and batch used.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT FIG. 1 shows the overall construction of a high frequency sputtering apparatus suitable for carrying out the method of the present invention. In the sputtering chamber 1, a substrate 3 is held in parallel by a substrate holder above a target 2 placed horizontally on an electrode. The target 2 is connected to the high frequency power source 5 on the target side via the matching hox 4 on the target side, and the substrate 3 is connected to the high frequency power source 7 on the substrate side via the matching hox 6 on the substrate side. . Both power supplies 5 and 7 have a common oscillator 8, but an auto phase shifter 9 for automatically shifting the phase is inserted between the high frequency power supply 5 on the target side and the oscillator 8. Further, between the target 2 and the target-side matching hox 4 and between the substrate 3 and the substrate-side matching hox 6, high-frequency waves for detecting the phases of high-frequency waves actually applied to the target 2 and the substrate 3, respectively. Phase detectors 10 and 11 are provided and connected to the auto phase shifter 9.

By using the high-frequency sputtering apparatus having the above-mentioned structure, the phase difference between the substrate-side high-frequency power source 7 and the target-side high-frequency power source 5 is changed so that the relationship between the phase difference and the oxide film deposition rate and film thickness distribution. I studied about. The output of the board side power supply 7 is 2 kW and the output of the target side power supply 5 is 15 kW
W, using Al ₂ O ₃ with a purity of 99.9% as a target, input power of 7.5 kW, and sputtering gas of A
Flow rate of r gas is 140 cm ³ / min, gas pressure is 20 × 10 ^-3
An Al ₂ O ₃ film was formed on the substrate 3 under the film forming conditions of Torr and the substrate-side negative bias voltage of −130V. When the phase difference was changed using the auto phase shifter 9,
The results shown in FIGS. 2 and 3 were obtained.

2 and 3, the horizontal axis represents the phase difference, that is, the phase delay, of the substrate-side high-frequency power source with respect to the target-side high-frequency power source, and the vertical axes represent the deposition rate of the Al ₂ O ₃ film and the phase difference, respectively. It is a film thickness distribution. As is clear from FIG. 2, the film forming rate is 390 ± 300 when the phase difference is in the range of about 40 ° to 120 °.
A stable and high value of 10 angstroms / min is shown, but the values sharply decrease on both sides. In particular, when the phase difference was 40 ° or less, the film forming rate decreased by 20 Å / min or more, and when the phase difference was 120 ° or more, not only the film forming rate became slow, but also abnormal discharge occurred. According to FIG. 3, in the phase difference of about 40 ° to 160 °, the film thickness distribution is stable at a substantially constant low value of 2% or less, but at 40 ° or less, it rapidly rises and deteriorates. I understand. Further, in this embodiment, the incident power on the target side is set to ² to 4 W / cm ^2, and the negative bias voltage on the substrate side is set to -5.
It was found that good results were obtained when the voltage was set to 0 to -200V.

Therefore, according to the present invention, it is preferable that the phase delay of the high frequency power source on the substrate side with respect to the high frequency power source on the target side is always controlled to a value in the range of about 40 ° to 120 °. It is easily understood that the velocity can be maintained at a substantially constant high value and the film thickness distribution can be suppressed at a substantially constant low value.

When an oxide film is formed on the surface of the substrate 3 using the high frequency sputtering apparatus shown in FIG. 1, a predetermined high frequency is applied to the substrate side high frequency power source 7 from a common oscillator 8. On the other hand, the high frequency power of the oscillator 8 is applied to the target side high frequency power source 5 via the auto phase shifter 9 so as to cause a phase shift such that the substrate side is delayed within a preset range of 40 ° to 120 °. To be done. A high-frequency voltage is applied to the target 2 from the target-side power supply 5 via the matching box 4. On the substrate 3,
As described above, the high frequency voltage having the phase delayed from the target side is applied from the power supply 7 through the matching box 6. The phases of the high frequencies applied to the target 2 and the substrate 3 are detected by the high frequency phase detectors 10 and 11, respectively, and fed back to the auto phase shifter 9. Then, when the phase difference of the actually applied high frequency and the preset phase difference are different from each other, the auto phase shifter 9 causes the target side power source 5 to eliminate the difference.
Adjust the phase of high frequency applied to. Thereby, the phase difference between the board-side high-frequency power supply and the target-side high-frequency power supply,
It is automatically controlled to the optimum conditions for always forming an oxide film.

[0014]

Since the present invention is constituted as described above, it has the following effects.

According to the oxide film forming method of the first aspect, by positively controlling the phase difference between the high frequency power source on the substrate side and the high frequency power source on the target side, even when the apparatus or batch used is changed, The film formation rate is stably maintained at a substantially constant high value, whereby abnormal discharge is effectively prevented, and the film thickness distribution can be suppressed to a low value of 2% or less, so that it is always stable and good. An oxide film can be formed.

[Brief description of drawings]

FIG. 1 is a diagram showing an example of the overall configuration of a high-frequency sputtering apparatus suitable for carrying out the method according to the present invention.

FIG. 2 is a diagram showing a deposition rate of an Al ₂ O ₃ film with respect to a phase difference between a substrate side high frequency power source and a target side high frequency power source.

FIG. 3 is a diagram showing a film thickness distribution of an Al ₂ O ₃ film with respect to a phase difference between a substrate side high frequency power source and a target side high frequency power source.

[Explanation of symbols]

 1 Sputter Chamber 2 Target 3 Substrate 4 Target Side Matching Hox 5 Target Side High Frequency Power Supply 6 Substrate Side Matching Hox 7 Substrate Side High Frequency Power Supply 8 Oscillator 9 Auto Phase Shifter 10, 11 High Frequency Phase Detector

Claims (1)

[Claims] 1. A method of forming an oxide film by sputtering an oxide, wherein the high frequency power source on the substrate side is always delayed by about 40 ° to 120 ° with respect to the phase of the high frequency power source on the target side. A method for forming an oxide film, which is characterized by controlling to have.