JPH073448A - Silicon nitride thin film and film forming method thereof - Google Patents

Abstract

PURPOSE:To prevent the occurrence of arcing at the time of film forming of silicon nitride by a reactive direct current sputtering method by specifying the ratio of a nitrogen atom-containing gas and the incorporating ratio of P of a Si target. CONSTITUTION:In the film forming method for the silicon nitride thin film by the reactive direct current sputtering method using the Si target, the reactive gas in which the ratio of the nitrogen atom-containing gaseous matter is >=0.1% is used, and the Si target incorporating P in >=10<-10>atom% is used. The nitrogen atom-containing gas is not confined particularly, but nitrogen and/or ammonia are preferable. In this way, the target having <=10<4>OMEGA.cm specific resistance is attained, and the long time and stable film forming is capable without occurrence of arcing.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a silicon nitride film formed by a reactive DC sputtering method, which does not cause arcing during discharge, and a film forming method thereof.

[0002]

2. Description of the Related Art The specific resistance of pure silicon is 10 ⁵ Ω · cm.
Because of this, the target cannot be used to form a film by the DC sputtering method. Therefore,
By mixing a conductive substance into silicon or by mixing a trace amount of impurities as a carrier generation source, the specific resistance of the Si target is lowered, and silicon nitride containing silicon containing this mixture is used as a target by the DC sputtering method. Film formation has hitherto been attempted.

When the Si target is made to have conductivity by mixing the conductive material, it is necessary to mix the conductive material up to several atomic%. Therefore, a silicon nitride film containing a large amount of impurities was obtained, and a pure silicon nitride film could not be obtained.

In the case where the Si target is made to have conductivity by mixing in a trace amount of impurities, boron has been used in many cases. This is because boron is stable and easily mixed into silicon, and therefore, as a substrate for film formation,
This is because it is often the case that silicon that is mixed with boron and is grown as a single crystal is used. However, when boron is used as an impurity, arcing often occurs during film formation, and stable discharge cannot be obtained.

Further, in the case of the DC sputtering method, attention has been paid mainly to the specific resistance of the target, and there have been few studies on the types of impurities mixed in the target. Further, phosphorus has not been used because it has a high vapor pressure and is difficult to be stably mixed into silicon.

In the high frequency sputtering method, since it is difficult to make a power source capable of outputting a large amount of power,
The maximum input power is much smaller than that of the DC sputtering method. As a result, in the high frequency sputtering method, the film forming rate is limited.

In the vapor phase growth method, a large amount of harmful gas is used when forming a silicon nitride film. Further, since the reaction temperature is high, there is a limitation on the substrate that can be used.

[0008]

In the high frequency sputtering method, it is difficult to increase the maximum power that can be applied to the power source, and thus it is difficult to improve the film forming rate. Also, it is unavoidable to use harmful gas in the vapor phase growth method. Furthermore, since the gas reaction occurs at a high temperature, the material of the substrate on which the film is formed is also limited. Therefore, in the reactive DC sputtering method using a Si target, suppressing the generation of arcing during discharge is an important issue.

In the conventional reactive DC sputtering method, the reaction product of the reactive gas and the target material is
When depositing on the target and performing film formation for a long time, the deposit gradually increases, thereby causing arcing.
Due to the occurrence of arcing, a phenomenon such as a temporary significant decrease in the film formation rate, the operation of the power supply stop function, or the inclusion of huge clusters in the film, which makes it impossible to form a stable film.

[0010]

According to the present invention, in a method for forming a silicon nitride thin film by a reactive DC sputtering method using a Si target, the gas fraction of a gas containing nitrogen atoms is 0.1% or more. It is intended to provide a method for forming a silicon nitride thin film by a reactive DC sputtering method, which is characterized by using a Si target containing a reactive gas and containing phosphorus at 10 ^-10 atomic% or more.

The present invention also uses a reactive gas in which a gas fraction containing a nitrogen atom is 0.1% or more in a silicon nitride thin film formed by a reactive DC sputtering method using a Si target, and The present invention provides a silicon nitride thin film formed by a reactive direct current sputtering method using a Si target in which phosphorus is mixed at 10 ^-10 atomic% or more.

According to the present invention, phosphorus is used as an impurity mixed in silicon, and by mixing it in an amount of 10 ^-10 atomic% or more, a target having a specific resistance of 10 ⁴ Ω · cm or less is used. This is to realize a reactive DC sputtering method in which arcing does not occur.

As the reactive gas used in the present invention, a reactive gas in which the gas fraction of the gas containing nitrogen atoms is 0.1% or more is used. In the present invention, the reactive gas may be used alone, or a mixed gas of the reactive gas and a rare gas may be used. The gas containing a nitrogen atom in the present invention is not particularly limited, but nitrogen and / or ammonia is preferably used.

In the present invention, the ratio of nitrogen to Si in the silicon nitride thin film is not particularly limited, but the atomic ratio is preferably 0.1 to 1.6.

[0015]

EXAMPLE The Si target used in this example is 1 pp.
The phosphor having a specific resistance of 1.6 Ω · cm was mixed with m of phosphorus.

A silicon nitride film was formed by reactive DC sputtering using the above Si target while keeping the applied power at 0.2 kw. The gas used at this time is N ₂
Is a mixed gas of Ar and Ar, and the total gas flow rate is 100 cc /
While maintaining at min, N ₂ gas fraction from 10% to 100
Table 1 shows the number of arcing that occurred when the percentage was changed. The measurement was performed for 5 minutes after the start of discharge. At this time, the ultimate vacuum was 1.5 × 10 ⁻⁶ Torr and the vacuum during discharge was about 7.5 × 10 ⁻³ Torr.

FIG. 1 shows the results of measuring the time variation of the applied voltage when the reactive DC sputtering shown in Table 1 was performed.

[0018]

[Table 1]

Comparative Example The Si target used in this comparative example had 1 ppm of boron mixed therein and had a specific resistance of 2.9 Ω · cm.

Using the above Si target, the number of times of arcing that occurred when reactive DC sputtering was performed and the time when the first arcing occurred were measured in the same manner as in the examples. The results are shown in Table 2. The sputtering conditions are the same as in the first embodiment.

FIG. 2 shows the results of measuring the time variation of the applied voltage when the reactive DC sputtering shown in Table 2 was performed.

[0022]

[Table 2]

As is apparent from FIGS. 1 and 2, in reactive DC sputtering using a Si target in which phosphorus is mixed as an impurity, when the applied power is kept constant, the applied voltage changes with time. Did not rise over the course of. It is considered that this is because the use of the Si target suppressed the deposition of the insulator on the target, so that the impedance did not increase and the applied voltage did not increase under the condition that the input power was kept constant. .

[0024]

According to the present invention, the specific resistance of the target can be reduced to 10 ⁴ Ω · cm or less by mixing phosphorus of 10 ^-10 atomic% or more into the Si target as an impurity. This has the effect that arcing does not occur even when reactive DC sputtering is performed for a long time in a mixed gas of a rare gas and

[Brief description of drawings]

FIG. 1 is a diagram showing a time change of an applied voltage during constant power discharge by a Si target doped with phosphorus.

FIG. 2 is a diagram showing changes in applied voltage with time during constant-power discharge by a Si target doped with boron.

Claims (5)

[Claims] 1. A method for forming a silicon nitride thin film by a reactive direct current sputtering method using a Si target, wherein a reactive gas having a gas fraction containing a nitrogen atom of 0.1% or more is used, and A method of forming a silicon nitride thin film by a reactive direct current sputtering method, which comprises using a Si target containing 10 to ¹⁰ atomic% or more of phosphorus. 2. The method for forming a silicon nitride thin film according to claim 1, wherein the gas containing nitrogen atoms is nitrogen and / or ammonia. 3. In a silicon nitride thin film formed by a reactive direct current sputtering method using a Si target, a reactive gas having a gas fraction of nitrogen atoms of 0.1% or more is used and phosphorus is 10 ^{−. A} silicon nitride thin film, which is formed by a reactive DC sputtering method using a Si target mixed with ¹⁰ atomic% or more. 4. The silicon nitride thin film according to claim 3, wherein the gas containing nitrogen atoms is nitrogen and / or ammonia. 5. The atomic ratio of nitrogen to Si is 0.1.
It is -1.6, The silicon nitride thin film of Claim 3 or 4 characterized by the above-mentioned.