JPS6292443A - Plasma apparatus - Google Patents

Abstract

PURPOSE:To raise the efficiency by producing a magnetic field intensity near a high frequency input unit less than the magnetic field intensity B0 of ECR condition, producing a magnetic field intensity near a substrate less than B0 and forming a magnetic field distribution having at least one magnetic field being higher than the magnetic field intensity B0 of ECR condition from the input unit to the substrate, thereby preventing an impurity from being mixed. CONSTITUTION:A TE01 mode square waveguide (WJR-2) is used as a high frequency input unit 1, and the end of the unit 1 is used as a high frequency input unit terminal 8 by a quartz plate 2 having 10mm in thickness to interrupt the atmosphere from vacuum. Argon-diluted silane gas (SiH4 containing 20% of silane) and nitrogen gas are fed at 4:3 of flow rate under total pressure of 0.08Pa. A magnetic field 3 is disposed on the outer periphery of a plasma chamber 5, a Helmholtz's coil (0.093wb/m<2> of maximum magnetic flux density) is used, and the unit 1 is secured to a substrate supporting base 7 opposed to the unit 1. The magnetic field intensity is 0.08wb/m<2> at the terminal 8, 0.093wb/m<2> of the maximum magnetic flux density 70cm from said terminal 8 and 0.06wb/m<2> near the substrate.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to improvement of a plasma device using RGR plasma using high frequency waves and a magnetic field, and particularly relates to the intensity distribution of the magnetic field.

Conventional technology Plasma CVD and plasma dry etching are important core technologies in H9 film processes such as semiconductor processes. Research is being actively conducted to lower the incident energy of ions. Regarding this field, for example, the basic technology is described ([3. - Electronic Materials] Editorial Department [Plasma Chemistry in the VLSI Era] Industrial Research Group, Published in 1988, P11-P119). In order to lower the incident energy of ions to the substrate and maintain plasma discharge,
The frequency of the radio frequency and the strength and distribution of the magnetic field play important roles.

For example, in the case of a 245 GHz microwave, the magnetic field strength should be 0.0875 Th/Im2 if the high frequency is set to a high frequency and the magnetic field strength is set to the electron cyclotron resonance (KCR) condition determined by the high frequency. It is known that plasma discharge can be easily maintained and, by providing an appropriate magnetic field distribution, the incident energy of ions to the substrate can be lowered to about several tens of eV. Further, research is being carried out on using such plasma to perform CvD and etching.

The strength distribution of the conventional magnetic field is shown in Figures 2(a) and (b).

In the following, the high frequency frequency f will be simplified as 2.45 GH2. In the magnetic field distribution in Figure 2 (&),
The magnetic field strength Bo is set near the high frequency introduction part to satisfy the FOR condition determined by the frequency of the high frequency.

(Bo = 0.087 when f: 2.45 GHz
5 Wb, i2. ) Thereafter, the intensity of the magnetic field is gradually monotonically decreased in the direction of propagation of the high frequency wave, thereby accelerating and diffusing the ions generated by the KCR discharge.

Next, in the magnetic field distribution in Fig. 2(b), the magnetic field strength near the high frequency introduction part is set to be higher than the ECR condition magnetic field strength Bo, and the magnetic field strength is monotonically decreased as in the magnetic field distribution in Fig. 2(a). , magnetic field strength B under ECR conditions.

The magnetic field strength was lowered to below, and then increased again to the magnetic field strength of ECR conditions or higher.

By changing the magnetic field temperature distribution as described above, the incident energy of ions to the substrate is lowered, thereby reducing damage to the substrate.

Problems to be Solved by the Invention However, the above distribution of magnetic field strength causes the following problems.

The high frequency introduction part is usually the end face of the antenna or waveguide, or a material that transmits high frequencies (conventionally quartz plate or Teflon).
It consists of an O-ring and other devices to isolate the atmosphere on the waveguide side from the vacuum of the plasma chamber, but since it is directly exposed to KCR discharge near the high-frequency introduction section, there is a risk of damage to the components of the high-frequency introduction section. This can cause contaminants to enter the plasma or, in the worst case, cause leaks. Further, when ECR discharge occurs, the electron density increases and the reflected power of high frequency increases.

Next, when the magnetic field strength near the high-frequency introduction part is set to 80 or higher under the ECR conditions, high-frequency discharge occurs and the high-frequency waves are absorbed even in the plasma, but [ion generation in OR discharge does not yield any number of electrons.

The present invention has been made in view of this point, and provides an efficient plasma device that prevents impurity contamination through the distribution of magnetic field strength.

Measures to solve the problem: Change the magnetic field strength near the high frequency introduction part to 8 under ECR conditions.
0, and the magnetic field strength near the substrate is below BO,
Magnetic field strength 80 under ECR conditions from the high frequency introduction part to the board
The magnetic field is at least 16 be.

Create a magnetic field distribution with a force field.

Magnetic field strength B near the working high frequency introduction part under 1EcR condition
By directly exposing the high frequency introduction part to ECR discharge at a temperature below 0, high frequency power can be effectively absorbed and damage to the high frequency introduction part can be reduced. By having a discharge region, high frequency power could be effectively absorbed.

Example The present invention will be explained below along with examples.

FIG. 1(a) is a schematic diagram of a plasma device according to an embodiment of the present invention, and FIG. 2(b) shows the relationship between the distance from the end of the high frequency introduction part of the plasma device and the magnetic field strength.

Here, the formation of a silicon nitride film using a plasma CVD apparatus will be explained as a temporary process.

Microwaves (2.45 GHz) were used as the high frequency.

Microwaves were generated with a magnetron (not shown).

1 is a high frequency introduction section, which is a TEn1 mode rectangular waveguide (WJ
R-2)'jz was used, and the end 7' of the high frequency introduction part 1 was made into the high frequency introduction part end 8 by using a quartz plate 2 with a thickness of 10πm to block the atmosphere and vacuum. From gas inlet 4,
Argon-diluted silane gas (SiH2, containing 20% silane) and nitrogen gas were introduced at a flow rate ratio of 4:3 and a total pressure of 0.08 Pa. The magnetic field 3 is placed around the outer periphery of the plasma chamber 5, and is a Helmholtz coil (maximum magnetic flux density 0.093 wbβ).
was used. The substrate 6 was fixed to a substrate support stand 7 provided opposite the high frequency introduction section 1. Microwave power lI'j:
It was set to 200W. The microwave power here is the difference between incident power and reflected power.

As shown in Figure 1, the magnetic field strength distribution is 0.08 W b /n? at the end 8 of the high frequency introduction section. The maximum magnetic flux density is 0.70 CILL from the high frequency introduction end.
093wb/n? and 0.06 Vrbl near the board
It was set as d. A silicon substrate and a quartz plate were used as the substrate 6.

Note that the substrate was not heated.

When a silicon nitride film was formed on the silicon substrate 6 with the above configuration, the refractive index of the silicon nitride film was 2. o1
Buffered hydrofluoric acid (50% HF:50%NH4F=3:1
The etching speed according to 7) is 7 min for two people, which means that it is very precise. Next, a silicon nitride film was formed on the quartz plate in the same manner. The optical band gap of this silicon nitride film was measured to be 6e.
v or more, which is a value equivalent to that of a thermal nitride film. The temperature of the substrate surface was measured to be 60° C. or less without heating the substrate. ! , the incident power is 206W,
Since the reflected power is 6 W, only 3% of the incident power is reflected.

Figure 3 shows a comparison of the characteristics of the conventional example when the magnetic field strength distribution is set to the magnetic field intensity distribution shown in Figure 2 (a) and the present invention, with the incident power on the horizontal axis and the reflected power on the vertical axis. In the case of , the violation was 10%, but in the case of the present invention, it was 3% or less.

No damage was observed on the quartz plate of the high-frequency introduction part, the O-ring, or the high-frequency introduction part side of the plasma chamber.

Furthermore, no oxygen or contamination from components around the plasma chamber was observed in Auger electron spectroscopy or X-ray photoelectron spectroscopy.

9.-- As described above, according to the magnetic field strength distribution in the present invention, no impurities are found in the nitriding process, and high frequency power can also be used effectively.

Note that here, a 2.45 GHz microwave was used as the high frequency, but any high frequency of several kHz or more is sufficient, and the magnetic field strength near the high frequency introduction part and the substrate may be less than that satisfying the ECR conditions. , and the magnetic field strength near the substrate may satisfy the EOR condition. Although the plasma apparatus is described here as plasma CVD, plasma etching may be performed using chlorine gas, fluoride gas, Freon gas, or the like as the introduced gas. In addition, in plasma CVD, the silicon nitride film was formed here using silane gas and nitrogen gas, but one or more gases constituting the molecules of the desired thin film and, for example, helium gas, which maintains or promotes plasma discharge, are also used. It may also be formed by gas. Furthermore, the magnetic field strength may be greater than or equal to the magnetic field strength that satisfies the ECR condition in areas other than the vicinity of the high-frequency introduction part and the vicinity of the substrate, and the magnetic field strength that satisfies the %RCR condition in the area from the high-frequency introduction part to the substrate is 10'. ＼.

The following magnetic field strengths may be included at one or more locations.

In addition, although the magnetic field is a mirror magnetic field using a Helmholtz coil, an electromagnet or a permanent magnet may be used, or a cusp magnetic field may be used. Regardless of the polarity of the magnetic field, the intensity distribution of the absolute value of the magnetic field is Any magnetic field strength distribution according to the present invention may be used.

Effects of the Invention As described above regarding the embodiment of the plasma device of the present invention as an all-plasma CVD system, by making the magnetic field intensity distribution the distribution of the present invention, high frequency power can be effectively absorbed,
It is also effective in preventing plasma contamination in the components of the high frequency introduction section, and is particularly effective in industrial fields where impurity contamination is extremely disliked, such as film formation and etching in semiconductor integrated circuits. The effect is extremely large.

[Brief explanation of drawings]

Figures 1 (a) and (b) are schematic diagrams of a plasma device according to an embodiment of the present invention, and magnetic field strength distribution diagrams from the end of the high-frequency introduction section; Figures 2 (a) and (b) are diagrams of the high-frequency introduction of a conventional example. FIG. 3 is a diagram showing the relationship between incident power and reflected power in the conventional example shown in FIG. 2(a) and the present invention 11 l·−. 1... High frequency introduction section, 2... Quartz plate,
3... Magnetic field, 6... Substrate. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
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Claims (4)

[Claims] (1) A vacuum device that uses plasma induced by applying high-frequency power and a magnetic field in a vacuum chamber, which is parallel to the direction from the high-frequency power introduction section to the substrate between the high-frequency power introduction section and the substrate. The intensity distribution of the magnetic field is set to be less than the magnetic field density that satisfies the electron cyclotron resonance condition determined by the frequency of the high-frequency power near the high-frequency power introduction part, and below the magnetic field density that satisfies the resonance condition near the substrate, and A plasma device characterized in that it has at least one region between the high frequency introduction part and the substrate where the magnetic field density is stronger than the magnetic field density that satisfies the resonance condition. (2) The plasma apparatus according to claim 1, wherein the direction from the high-frequency power introduction part to the substrate is made to coincide with the propagation direction of the high-frequency power. (3) The plasma apparatus according to claim 1 or 2, characterized in that an etching gas is introduced into the vacuum chamber to induce plasma to etch the substrate surface. (4) The plasma apparatus according to claim 1 or 2, wherein at least one type of gas is introduced into the vacuum chamber to induce plasma to form a film on the surface of the substrate.