JPS6343324A - Plasma shower equipment - Google Patents

Abstract

PURPOSE:To make a plasma of a uniform energy to be incident upon a substrate by providing a magnetic field strength uniformizing means under the sample chamber when extracting a plasma, which was generated by the electron cyclotron resonance in a plasma generation chamber, into the sample chamber by means of a divergent magnetic field, in which sample chamber a thin film or the like is formed on the surface of a semiconductor substrate. CONSTITUTION:The outer periphery of a plasma chamber 11 is surrounded with a magnetic coil 17, the upper surface of which plama chamber 11 is provided with a system 12 for introducing a gas such as N2 and a waveguide 13 for introducing a microwave to generate a plasma, and the electron cyclotron resonance is utilized in the plasma chamber 11 while a plasma 16 having its magnetic field decreased is generated in the direction of an arrow H1 from a plasma extracting window 18 in the lower portion of the chamber 11 to a sample stand 14 of a sample chamber 20 provided beneath the window 18 and is radiated to a semiconductor substrate 15. At this time, an electromagnetic coil 25 is provided on the outer periphery of the sample chamber 20, and further a magnetic field strength uniformizing means consisting of an electromagnetic coil 21 is provided on the bottom opening of the sample chamber 20, and this magnetic field is directed in the direction of an arrow H2 to weaken the divergent magnetic field strength in the substrate 15 central portion, thereby uniformizing the magnetic field on the substrate 15.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a plasma shower apparatus for performing processes such as forming a thin film and etching on the surface of a semiconductor substrate.

(Prior Art) A conventional plasma shower device, as shown in Fig. 2,
Gas is introduced into the plasma generation chamber 1 from the gas introduction system 2, microwaves are introduced from the waveguide 3, and the magnetic field from the electromagnetic coil 4 generates electron cyclotron resonance (ECR).
) to generate plasma in the plasma chamber 1, and at the same time draw out the plasma from the extraction window 5 to the sample chamber 6 using the divergent magnetic field of the electromagnetic coil 4. Then, the drawn plasma is used to perform a predetermined process, for example, to form a thin film, on the surface of the substrate (wafer) 8 placed on the sample stage 7.

The plasma shower device described above has many features.

In other words, the plasma, which has become extremely active due to ECR, is taken out with appropriately adjusted energy using a divergent magnetic field and collided with the wafer 8, so that the plasma is highly active and the ions and electrons are The combined effect of the collision with the limited strength of the wafer efficiently causes a surface treatment reaction such as the formation of a film with little damage on the wafer surface.

This reaction occurs without external heating, so it can be processed at room temperature, and the various thin films produced from silicon nitride, silicon oxide, etc. have excellent acid resistance and density even when processed at room temperature. .

(Problems to be Solved by the Present Invention) However, there are some aspects in which the distribution of processing on the substrate, such as the distribution of film thickness and the distribution of film quality, is not always sufficient, and this tendency is particularly noticeable when the area of the wafer 8 becomes large. there were. The reason for this will be explained below.

The magnetic field generated by the electromagnetic coil 4 not only satisfies the ECR conditions within the plasma generation chamber 1, but also forms a useful divergent magnetic field within the sample chamber 6. (See Figure 3). Figure 3 Sunomi! B
p indicates the strength of the magnetic field at each position along the line P in the center of the plasma flow in Figure 3a, and the broken line Bq indicates the strength of the magnetic field at each position along the line Q outside the plasma flow. .

In such a diverging magnetic field, circularly moving electrons in the plasma exhibit diamagnetic properties and are therefore accelerated toward the sample stage 7, which is the direction of divergence of the magnetic field, due to the gradient of the magnetic field strength. The plasma generation chamber 1 and the sample stage 7 are electrically insulated, and the sample stage 7
The electrons accelerated in the direction generate a bipolar magnetic field that accelerates the ions so as to satisfy the neutralization condition and decelerates the electrons, resulting in an equilibrium state. In this state, electrons and ions are in the same accelerated state, so Fi/M=Fe/m where Fi, Fe: Force acting on ions and electrons,
M, m: Mass of ions and electrons.

Fi=eE E: Electric field generated in the plasma flow.

Fe=-p-(dB/dz)-eE is the magnetic moment of a circularly moving electron. Letting the circularly moving energy of the electron be ω], W=ωr/B, which is an adiabatic invariant. Z is the distance in the outflow direction.

If we calculate E from these relationships and integrate E==-dφ/dz, the potential φ becomes φ=-[(1)O/(e(1+m/M))1
(1-B/ Bv)”F (ωo /e) (1
-(B/Bo)'t, and the ion energy is eφ=-ωoil-(B/Bo))...(1)
is given by (References. SEMI TECHNOL
OGYSYMPOSIUM '85, F -4-
1) , ωo, BO are the circular kinetic energy and magnetic flux density of electrons in the plasma generation chamber l.

Further, this equation (1) indicates the collision energy of plasma on the sample stage 7. That is, the plasma extracted from the plasma generation chamber 1 collides with the wafer 8 with energy given by equation (1). This collision energy becomes the energy for processes such as film formation.

Therefore, in order to make the distribution of processing on the wafer 8 uniform, the collision energy of the plasma must be constant on the surface of the wafer 8, and for this purpose, since the charge e is a constant, the above potential φ must be constant on the surface of the sample stage 7, and in order for the potential φ on the surface of the sample stage 7 to be constant, the magnetic field strength Bo generated by the electromagnetic coil 4 is constant, and ωG in the plasma chamber 1 is Since the distribution is constant, the strength B of the magnetic field on the surface of the sample stage 7 must be constant.

However, as shown in FIG. 3, there is a difference in the magnetic field strength along the P and Q lines, and the magnetic field strength is different between the center position 0 and the end q on the wafer 8.

FIG. 4 shows an example in which the potential was measured along line P in FIG. 3 from the drawer window 5 to the sample stage 7. As is clear from FIGS. 3 and 4, the negative potential increased in response to the decrease in the magnetic field, and was about -13 V at the center position O of the sample stage 7. On the other hand, when the potential at the end q (see FIG. 3) of the sample stage 7 was measured, it was found to be -18V, which is lower than -13V since the magnetic field is weaker than at the center position O of the sample stage 7.

Conventionally, as described above, there is a difference in potential and magnetic field strength between the center position 0 and the end q of the sample stage 7, which causes a difference in the plasma incident velocity and plasma density on the surface of the wafer 8. The synergistic effect of these two differences causes a large difference in the surface treatment of the wafer 8. In other words, the film thickness distribution and film quality distribution of the thin film formed on the wafer become non-uniform, especially when the diameter of the wafer is large.
The further away from the center of the wafer, the weaker the magnetic field and the larger the potential difference, so the film thickness distribution 1f! 2
The disadvantage was that the quality distribution became even more uneven.

For this reason, with conventional equipment, the maximum diameter of the wafer 8 that can produce a practical thin film is limited to approximately 100++ m.
In order to process a wafer 8 with a larger diameter than this, the plasma generation chamber 1 and the electromagnetic coil for obtaining ECR conditions must be made larger, resulting in a problem that the entire apparatus becomes too large.

SUMMARY OF THE INVENTION An object of the present invention is to provide a plasma shower apparatus that can uniformly process large-diameter wafers by uniformizing the magnetic field of a sample stage.

(Means for Solving the Problem) In order to achieve the above object, the present invention extracts plasma generated by electron cyclotron resonance in a plasma generation chamber into a sample chamber using a divergent magnetic field, and uses the drawn plasma to generate a sample chamber. A plasma shower apparatus for treating the surface of a sample substrate placed on a sample stage is provided with a magnetic field strength equalizing means for making the magnetic field strength on the substrate uniform.

(Action of the present invention) The magnetic field strength equalizing means makes the magnetic field strength on the sample substrate uniform.

(Effects of the Invention) Since the magnetic field strength on the sample substrate becomes uniform, plasma is incident on the sample substrate with uniform energy.

Thereby, a large-diameter sample substrate can be uniformly processed without increasing the mounting size.

(Embodiment of the present invention) In FIG. 1, 11 is a plasma chamber, and a gas introduction system 12
For example, N2 gas or the like is introduced from the waveguide 13, and microwaves are introduced from the waveguide 13 to generate plasma. A magnetic coil 17 is used for electron cyclotron resonance in the plasma chamber 11, and forms a diverging magnetic field that reduces the magnetic field strength at an appropriate gradient from the plasma extraction window 18 toward the sample stage 14, for example, in the direction of arrow H1. . This divergent magnetic field causes the plasma generated in the plasma chamber 11 to flow from the plasma extraction window 8 into the sample chamber 20. The sample stage 14 holds the substrate 15 and has a diameter larger than the diameter of the plasma flow IB on the sample stage 14.

Reference numeral 21 denotes a magnetic field strength equalizing means for uniformizing the magnetic field strength of the divergent magnetic field on the surface of the sample stage 14 over a wide range, and is composed of an electromagnetic coil.

This electromagnetic coil 21 is designed to generate a magnetic field in the direction of arrow H2 when the divergent magnetic field is in the direction of arrow H1, for example. This magnetic field H2 greatly weakens the magnetic field strength of the divergent magnetic field at the center position of the sample stage 14, and gradually weakens as it moves away from the center position of -7, thereby widening the field strength of the divergent magnetic field on the surface of the sample stage 14. This is to make it uniform throughout.

Now, for example, N2 gas is introduced into the plasma chamber 11 through the gas introduction diameter 12, microwaves are roughly introduced through the waveguide 13, and a magnetic field is generated by the magnetic coil 17 to generate plasma in the plasma chamber 11. Then, the plasma in the plasma chamber 11 is drawn out from the extraction window 18 by the diverging magnetic field formed by the magnetic coil 17, flows toward the sample stage 14, and enters the sample stage 14.

On the other hand, due to the magnetic field H2 generated by the electromagnetic coil 21, the magnetic field strength of the diverging magnetic field on the surface of the sample stage 14 is formed uniformly over a wide range, and due to this uniform magnetic field, the potential on the surface of the sample stage 14 is also formed over a wide range. and become uniform. Due to these, the density of the plasma flow incident on the surface of the wafer 15 and its incident energy are also made uniform over a wide range.

Therefore, a thin film with uniform thickness and quality can be formed on a large diameter wafer.

According to experiments, the thickness distribution of the thin film formed on the wafer 15 was ±5%, but by adjusting the current value flowing through the electromagnetic coil 21 appropriately, it was improved to ±2.5%. I was able to do that. It was found that the film quality was also uniform.

In addition, the electromagnetic coil 21 may be installed, for example, at the position indicated by the broken line 25, with appropriate polarity, and if necessary, a plurality of electromagnetic coils may be installed to uniformize the magnetic field on the surface of the sample stage 14. The installation position and number of 21 are not limited to those shown in the drawings.

Although the above embodiment describes thin film formation, it is of course applicable to etching and the like using the same principle.

[Brief explanation of drawings]

Figure 1 is a configuration diagram of the plasma shower device of the embodiment, Figure 2
The figure is an explanatory diagram of a conventional plasma shower device, Figure 3 is an explanatory diagram showing the magnetic field strength at each position in the plasma generation chamber and sample chamber, and Figure 4 is an explanatory diagram showing the potential at the position between the drawer window and the sample stage. This is a measured graph. 11... Plasma chamber, 14... Sample stage, 15...
Substrate, 20...sample chamber, 21...electromagnetic coil.

Claims (1)

[Claims] In a plasma shower apparatus, plasma generated by electron cyclotron resonance in a plasma generation chamber is drawn into a sample chamber by a divergent magnetic field, and the drawn plasma is used to process the surface of a substrate placed on a sample stage in the sample chamber. A plasma shower apparatus characterized by being provided with a magnetic field strength equalizing means for uniformizing the magnetic field strength on a substrate.