JPH055370B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a plasma processing apparatus.

[Conventional technology]

In recent years, the degree of integration of semiconductor devices has improved dramatically, and plasma processing equipment such as etching equipment used in the manufacturing process is increasingly required to improve its processing accuracy and low damage performance. In order to meet this demand, microwave plasma processing equipment with better processing performance is being used instead of the conventional plasma processing equipment using 13.56 MHz RF.

For example, as described in Japanese Patent Publication No. 58-13627, plasma is generated by electron cyclotron resonance (hereinafter referred to as "ECR") using a magnetic field, or RF or DC bias is applied to the sample stage. As described in Japanese Unexamined Patent Application Publication No. 16424/1984, there are some methods that perform etching with high dimensional accuracy, high speed, and low damage. Plasma is shielded by making a hole or by providing a wire mesh in the waveguide wall hole, and the photoresist is etched only with active species, allowing resist ashing processing to be performed without damaging the semiconductor element. There is something.

[Problem that the invention seeks to solve]

Among the above conventional technologies, the former generates plasma in a magnetic field microwave discharge tube that satisfies the ECR conditions, so it is possible to generate high-density plasma even at relatively low pressure. When applied, it has the advantage that high-speed ashing can be easily achieved, but on the other hand, in order to achieve uniform processing, the size of the discharge chamber must be made larger than the wafer diameter.
The size of magnetic field generating coils has also increased, and with the recent trend toward larger wafer diameters such as 200 mm and 250 mm, there is an unavoidable increase in equipment costs. Furthermore, since the wafer is exposed to plasma, there is a problem in that the elements are susceptible to electrostatic damage, especially in the ashing process after etching.

In addition, in the latter example, only the electric field of microwaves is used as a means of generating plasma, so the plasma generation efficiency is low, there is a limit to improving the ashing speed, and it is difficult to improve the uniformity of the process. A problem arose that made it difficult.

An object of the present invention is to provide a plasma processing apparatus that promotes chemical reactions in the periphery of a sample and can uniformize the ashing process with the center of the sample, which has a high radical density and a high processing speed.

[Means for solving problems]

The above purpose is to provide a discharge chamber with the minimum necessary size to which microwaves can be introduced, a plasma generation means for converting the processing gas introduced into the discharge chamber into plasma by ECR discharge, and separation of radicals in the plasma generated in the discharge chamber. a sample processing chamber for ashesing a sample with radicals separated by the separation means; a sample stage disposed on the center line of the discharge chamber; and a sample mounting surface temperature distribution of the sample stage. This is achieved by providing means for heating from the periphery of the sample stage so that the temperature is higher at the periphery, and by providing a heat insulating material to limit the temperature increase in the center of the sample stage.

[Effect]

A processing gas is introduced into the discharge chamber, and an electric field generated by microwaves and a magnetic field perpendicular to the electric field are applied.
Causes ECR discharge to efficiently transform processing gas into plasma. At this time, the strength of the magnetic field in the discharge chamber is given a gradient that decreases from the sample to be processed toward the discharge chamber. This causes electrons and ions in the plasma to move in the opposite direction to the sample to be processed. The remaining neutral radicals are exhausted toward the sample, reach the sample, and chemically etch the film to be processed on the sample.

At this time, the radical density near the center of the opening of the discharge tube is highest, but in order to promote the chemical reaction, the temperature distribution on the sample mounting surface of the sample stand is set to be high at the periphery. Since a means for heating from the periphery is provided and a heat insulating material is provided to limit the temperature increase in the center of the sample stage, the film to be processed on the sample can be processed uniformly.

〔Example〕

An embodiment of the present invention will be described below with reference to FIGS. 1 to 5.

In FIG. 1, a sample stage 2 on which a sample, for example, a wafer 14 is placed, is installed in a sample processing chamber 1. A discharge chamber 3 which also serves as a circular waveguide is provided in communication with the upper part of the sample processing chamber 1 . 4 is a vacuum sealing material. A conversion waveguide 6 is provided in the upper part of the discharge chamber 3 via an insulating window 5 made of an insulating material such as quartz or alumina that transmits microwaves, in this case quartz. 18 is a vacuum sealing material. A rectangular waveguide 7 is attached to the other side of the conversion waveguide 6,
A magnetron 8 is provided at the end of the rectangular waveguide 7.

A reflective end 15 for reflecting microwaves is attached within the discharge chamber 3. A cylindrical electromagnetic coil 9 is provided outside the discharge chamber 3 to generate a magnetic field orthogonal to the electric field generated by the microwave. Electromagnetic coil 9
A shield tube 10 and a shield cover 11 made of a high air permeability material are provided on the outside. A gas inlet 12 is provided in the discharge chamber 3 between the insulating window 5 and the reflective end 15. On the side opposite to the discharge chamber 3 of the processing chamber 1, there is an exhaust port 13 connected to an exhaust device (not shown).
is provided. 16 is a heating device that heats the sample stage 2; 17 is an isolator that prevents microwaves from returning.

A discharge chamber 3 that also serves as a circular waveguide in the component parts
For example, the oscillation frequency of magnetron 8 is
2.45GHz and the resonance mode is TE112 mode, the oscillation wavelength is 12.245cm and the cutoff wavelength is
Since it is 18.58 cm, microwave power can be introduced into the discharge chamber 3 by making the inner diameter 10.9 cm and the length 16.2 cm.

In addition, a reflective end 15 attached to one end of the discharge chamber 3
For example, the cutoff wavelength is 12.245 cm or less.
In the TE11 mode, by setting the hole diameter D to 7.18 cm or less, the microwave is reflected at the reflecting end 15 and passed through the discharge chamber 3 again. In this case, the hole diameter D of the reflective end 15 is 1 cm, and the pitch is 2.
They are set at cm intervals.

Further, as shown in FIG. 2, the end of the shield tube 10 provided surrounding the electromagnetic coil 9 is
It is installed by wrapping around the inside of the. As a result, the magnetic field generated in the electromagnetic coil 9 by a DC power supply (not shown) is concentrated between the inner end of the shield tube 10 and the inner end surface of the shield cover 11. The maximum position of the concentrated magnetic field strength is located below the reflective end 15, and the magnetic flux density B(z) decreases in the Z-axis direction, that is, in the direction away from the wafer 14.

Here, the plasma generation means in this case includes the magnetron 8, the rectangular waveguide 7, the conversion waveguide 6, the discharge chamber 3, the insulating window 5, the reflective end 15, the electromagnetic coil 9, the shield tube 10, and the shield cover 11. Consists of. The microwaves generated by the magnetron 8 are transmitted from the rectangular waveguide 7 to the discharge chamber 3 via the conversion waveguide 6. The microwaves entering the discharge chamber 3 convert the processing gas introduced into the discharge chamber 3 into plasma and are consumed. Further, some of the microwaves that are not consumed at this time are reflected at the reflection end 15 and further pass through the plasma, so that the absorption efficiency of the microwaves is improved and the rate of plasma conversion is increased.

In addition, a destructive field is generated by the magnetic coil 9, and the magnetic field strength near the maximum of the microwave electric field E ₍₂₎ shown in FIG. against GHz
ECR conditions are met. Now, if the angular velocity of the microwave is ω and the angular velocity of the cyclotron motion of the electron in the static magnetic field B is ω _c = eB/m, then when ω = ω _c is satisfied, electron cyclotron resonance (ECR) occurs, and the microwave Power is efficiently absorbed for electron movement.

The plasma generated in the discharge chamber 3 is then separated into only radicals by a separating means, and then exits to the sample processing chamber 1.

Here, the means for separating radicals in this case is the electromagnetic coil 9, the shield tube 9, and the shield cover 10.
and a DC power supply (not shown). Generally, electrons in plasma are subjected to a force in the Z-axis direction, and if the magnitude of the force is F ₍₂₎ , then F ₍₂₎ = -1/4・e ² /mω ²・∂/∂Z{E _{(2 )} /1-
(ω _c /ω) ² } is known to be given by (1). Here, e is the charge of the electron, and m is the mass of the electron. According to the above equation (1), since the magnetic flux density B ₍₂₎ of the plasma generation part is decreasing in the Z-axis direction, the electrons in the plasma are subjected to a force in the direction of moving away from the wafer 14 in the Z-axis. As a result, electrons in the plasma move to the upper part of the discharge chamber 3, and the electrons and ions are temporarily separated in the plasma to generate an electric field. Thereby, the ions are also attracted by the electrons and transported to the upper part of the discharge chamber 3. In other words, electrons and ions in the plasma are transferred to the wafer 14.
Only radicals that are accelerated in the opposite direction and are not affected electrically or magnetically exit through the hole in the reflective end 15 to the sample processing chamber 1 side.

Radicals entering the sample processing chamber 1 flow toward the exhaust port 13. At this time, the radicals come into contact with the surface of the wafer 14, causing a chemical reaction and etching the wafer 14. In this way, since etching is only a chemical reaction caused by radicals, in order to promote the chemical reaction and further increase the etching rate, in this case, the sample stage 2 is heated and controlled to 50°C to 200°C by the heating device 16. . Further, the exhaust port 13 should be arranged so that the radicals coming out of the discharge chamber 3 flow so that they easily come into contact with the wafer 14.

In addition, the sample stage 2 may include a support part 22, a heat insulating part 23, and a heating part 24 as shown in FIG. 3, or a support part 22 and a heating part 2 as shown in FIG.
4 is connected to the upper surface of the heat insulating part by a connection part 26 having a small cross-sectional area, so as to have electrical uniformity on the sample mounting surface and to limit heat conduction from the heating part to the support part 22. The sample stage surface temperature and wafer temperature have the distribution shown in FIG.

The temperature of the heater is controlled by heating section 2.
This is done by omitting the illustration of the sensor attached to 4.

In this example, a means for heating from the periphery of the sample stand is provided so that the temperature distribution on the sample mounting surface of the sample stand is higher at the periphery, and a heat insulating material is provided to limit the temperature rise in the center of the sample stand. Therefore, the chemical reaction at the periphery of the sample is promoted, and the ashing process can be made uniform with respect to the center of the sample where the radical density is high and the processing speed is high. In addition, by causing ECR discharge in a minimum discharge chamber that can introduce microwaves and reducing the magnetic flux density in the direction away from the sample, it is possible to increase the amount of radicals generated and treat the sample with only radicals. Therefore, there is an effect that a high processing rate can be obtained without causing any element damage.

〔Effect of the invention〕

According to the present invention, the chemical reaction at the periphery of the sample is promoted, and the ashing process can be made uniform with respect to the central area of the sample where the radical density is high and the processing speed is high.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal cross-sectional view showing a microwave plasma processing apparatus which is an embodiment of the present invention, FIG. 2 is a diagram showing the microwave electric field and magnetic flux density by the apparatus of FIG. 1, FIGS. 3 and 4. is a detailed cross-sectional view of the sample stage in Figure 1, Figure 5 is a diagram showing the sample stage surface and wafer temperature distribution by this device, Figure 6 is a diagram showing the radical density distribution on the wafer by this device, FIG. 7 is a diagram showing a comparison of the ashing rate of the present apparatus and the ashing rate when no heating is performed by the heater. 1... Sample processing chamber, 2... Sample stage, 3... Discharge chamber, 5... Insulating window, 8... Magnetron, 9...
Electromagnetic coil, 10...shield wall, 11...shield cover, 14...wafer, 15...reflection end,
16... Heating device, 22... Support part, 23... Heat insulation part, 24... Heating part, 25... Heater, 26
...connection section.

Claims (1)

[Scope of Claims] 1. A plasma processing apparatus having a processing chamber in which a processing gas introduced into the discharge chamber is turned into plasma by electric discharge, and a sample is ashed by a chemical reaction, and a sample stage on which the sample is placed. , providing a means for heating from the periphery of the sample stand so that the temperature distribution of the sample mounting surface of the sample stand is higher at the periphery, and limiting the temperature increase in the center of the sample where the radical density is high and the ashes processing speed is high; A plasma processing apparatus characterized in that the sample stage is provided with a heat insulating material for controlling an ashes rate. 2. On the sample mounting surface side of the heat insulating material attachment part, the peripheral part and the central part are connected by a small cross-sectional area of the same member, so that electrical uniformity is achieved on the sample mounting surface, and the peripheral part 2. The plasma processing apparatus according to claim 1, wherein heat conduction from the central portion to the central portion is restricted.