JPH0434826A - semiconductor manufacturing equipment - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention particularly relates to preventing instability such as plasma flickering in semiconductor manufacturing equipment that generates plasma using electron cyclotron resonance (ECR). It is something.

[Conventional technology]

FIG. 3(a) is a diagram showing a conventional semiconductor manufacturing apparatus. In the figure, l is a coil for generating a magnetic field, and 2 is a 2.45 GHz
a magnetron with an oscillation frequency of , 10 is a microwave,
4 is an ECR resonance point, 5 is a magnetic field line, 6 is a discharge chamber, 7 is a reactive gas inlet, 8 is a microwave inlet, and 9 is a waveguide.

Furthermore, Fig. 3 (b) shows the distribution of the magnetic field strength in the center of the discharge chamber 6, and Fig. 4 shows the dispersion relationship of microwaves when they propagate along the magnetic field in the plasma. There is.

Hereinafter, a plasma generation mechanism in a conventional semiconductor manufacturing apparatus will be explained with reference to these figures.

First, in Fig. 3(a), the magnetron 2
A 5 GHz microwave 10 is generated and introduced into the discharge chamber 6 through a microwave inlet 8 in a waveguide 9°.

At the same time, by passing a current through the coil 1, a magnetic field 5 is generated within the discharge chamber 6. At this time, ωc=eB/m.

(However, ωC is the microwave frequency (child cyclotron resonance frequency), e is the elementary charge, and m is the mass of the electron.) By adjusting the magnetic field strength B using the coil current to satisfy The microwaves resonate and plasma is generated. The magnetic field strength that satisfies the electron cyclotron resonance condition is when the microwave frequency is 2.45G.
In the case of Hz, it is 875 Gauss. Generally, the magnetic field strength generated by a coil is not uniform inside the discharge chamber (
, for example, at the center of the discharge chamber in the X direction,
) shows the distribution shown in

Further, the position of the magnetic field strength that satisfies the electron cyclotron frequency is shown at ECR resonance point 4 in FIG. 3(a).

So far, we have qualitatively explained the mechanism of plasma generation by electron cyclotron resonance, but once plasma is generated, the propagation of microwaves in the plasma must also be considered in order to maintain the plasma (discharge).

Conventional semiconductor manufacturing equipment uses 2.45G microwaves, which is unstable when considering the propagation of microwaves in plasma, resulting in plasma instability (fluctuations in plasma density, flickering), This may lead to dry etching and P-CVD using conventional semiconductor manufacturing equipment.
This will deteriorate the uniformity and reproducibility of the process.

The reason why plasma becomes unstable when 2.45 GHz microwaves are used will be explained below.

Generally, when electromagnetic waves propagate in plasma in a direction parallel to the magnetic field, the electromagnetic waves are divided into R waves and L waves, and their dispersion relationships are as shown in Figure 4.In Figure 4, ω0 is the cyclotron resonance frequency, ω1. ω1 is the cutoff frequency of the L wave and the R wave, respectively, and is defined by the formula shown below.

Here, ω9 is ωp = (ne ” / E6 m
＠) "" is the plasma frequency defined, n is the plasma density, Eo is the dielectric constant in vacuum, e is the elementary charge,
m and each indicate the mass of the electron.

Further, in FIG. 4, ω"/c"k"<0 corresponds to a microwave non-propagation region, and ω"/c"k">O corresponds to a microwave propagation region.

As is clear from FIG. 4, electron cyclotron resonance occurs only with R waves, but for plasma maintenance, absorption of microwaves propagating in the plasma must also be taken into consideration. First, in the R wave, the microwave frequency (ω) <ω. There is a propagation region in the region between the microwave inlet 8 and the ECR resonance point 4 in the discharge chamber 6 of FIG. 3(a) (in this region, as shown in FIG. 3(b) (1) C=e
B /no >2.45GHz), so R
Wave propagation is not affected by plasma density.

On the other hand, for the L wave, the cutoff frequency ω.

is affected by the plasma density as shown in equation (1).

In general, the density of plasma using electron cyclotron resonance varies depending on the conditions, but it is between lXl0'' and IX10''/
cd (References, Proceedings of the 25th Semiconductor Specialized Seminar,
SiO microwave plasma etching, Suzuki et al., P
117-147). In the region of plasma density of 2, ω is 1.87 as ωc = 2.45G7
G le〈ωt <7.86G7.

Therefore, in FIG. 3(a), from the microwave inlet 8 to the EC
Approximately ωC ~ 2.45 in the region up to R resonance point 4
GHz and the frequency ω of the microwave is 2.45G7, then ω, as shown in Figure 4, changes due to slight fluctuations in plasma density, ω〉ωL (the L wave is in the non-propagation region where it cannot enter the discharge chamber). ) or ω<ωL (a propagation region in which the L wave propagates into the discharge chamber).

At ω0〈ω, the L wave cannot penetrate into the plasma, so
Plasma density decreases. When the plasma density decreases,
According to equation (1), ω1 becomes smaller, so conversely, the state becomes ω, >ω. ω. In the state of >ω, the L wave enters the plasma and increases the plasma density, so that ωL becomes large again, resulting in the state of ω0<ωL. This repetition causes instability such as flickering in the plasma.

[Problems to be solved by the invention] As described above, since the conventional semiconductor manufacturing equipment using electron cyclotron resonance uses 2.45 GHz microwave, the propagation of the L wave in the plasma becomes unstable and the plasma There is a problem in that it causes instability (flickering), which in turn deteriorates the uniformity and reproducibility of etching and CVD using this plasma.

This invention was made to solve the above-mentioned problems, and aims to provide a semiconductor manufacturing device that can prevent plasma instability, achieve high uniformity in etching and CVD0, and have good reproducibility. shall be.

[Means to solve the problem]

A semiconductor manufacturing apparatus according to the present invention generates plasma using a magnetic field and electromagnetic waves, and the frequency of the electromagnetic waves is 1.9 GHz or less.

[Effect]

In the semiconductor manufacturing apparatus according to the present invention, the frequency of the microwave is set to 1.9 GHz or less, so that among the electromagnetic waves traveling in the plasma, the propagation of the L wave is cut, and the instability of the plasma is suppressed.

〔Example〕

Hereinafter, one embodiment of the present invention will be described with reference to the drawings.

FIG. 1 is a sectional view showing a semiconductor manufacturing apparatus according to an embodiment of the present invention. In the figure, the same reference numerals as in FIG. The configuration is similar to that in FIG. 3(a), but the difference is that the frequency of the microwave 3 is 1.9 GHz or less.

Furthermore, the dispersion relationship of microwaves propagating in the plasma parallel to the magnetic field using electron cyclotron resonance in this example is as shown in Figure 2, and the plasma density is 1×
101~1×101! /c4, ω<ω1 always holds, and the L wave does not propagate.

In this way, by using microwave 3 of 1.9 GHz or less, 1 x 10th to 1 x 10'! At a plasma density of /c4, ω<ω always holds true.

That is, if we solve this inequality, we get ω〈ω, 8 ~ 1.97G unit (plasma density; I
10"/crI) and does not propagate through the flask. Therefore, instability such as plasma flickering, which was a problem in the past, is suppressed, and the uniformity of plasma etching and CVD using electron cyclotron resonance is improved. and reproducibility are improved.

〔Effect of the invention〕

As described above, according to the present invention, by using a microwave frequency of 1.9 GHz or less, it is possible to cut the propagation of the L wave among the electromagnetic waves traveling in the plasma, thereby reducing the instability of the plasma. This has the effect that it is possible to suppress this and further improve the uniformity and reproducibility of etching and CVD using this plasma.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing a semiconductor manufacturing apparatus according to an embodiment of the present invention, and FIG. 2 is a diagram showing the dispersion relationship of microwaves (electromagnetic waves) traveling in the plasma of the semiconductor manufacturing apparatus according to the present invention and in a direction parallel to the magnetic field. , FIG. 3 is a diagram showing a conventional semiconductor manufacturing device and the magnetic field strength distribution in the discharge chamber of the semiconductor manufacturing device, and FIG. ) is a diagram showing the dispersion relationship of . In the diagram, 1 is a coil, 2 is a magnetron, and 3 is a 1.9GH
Microwave below z, 4 is ECR resonance point, 5 is magnetic field line,
6 is a discharge chamber, 7 is a reactive gas inlet, 8 is a microwave inlet, and 9 is a waveguide. Note that the same reference numerals in the figures indicate the same or equivalent parts.

Claims (1)

[Claims] (1) A semiconductor manufacturing apparatus that generates plasma using a magnetic field and electromagnetic waves, characterized in that the frequency of the electromagnetic waves is 1.9 GHz or less.