JPS62210621A - Microwave plasma processing method and its device - Google Patents

Abstract

PURPOSE:To obtain a high processing rate without impairing element, by utilizing ECR to make a process gas, introduced into a discharge chamber, formed into plasma and isolating only the radicals from the plasma inside the discharge chamber and then processing the sample using the radicals being isolated. CONSTITUTION:A plasma generating means is composed of a magnetron 8, a rectangular wave guide 7, a conversion waveguide 6, a discharge chamber 3, an insulating window 5, a reflection terminal 15, an electromagnetic coil 9, a shield tube 10, and a shield cover 11. A microwave generated at the magnetron 8 is propagated from the rectangular waveguide 7 through the conversion waveguide 6 to the discharge chamber 3. By the microwave entering the discharge chamber 3, the process gas introduced inside the discharge chamber 3 is made to become plasma and consumed. A part of the microwave, which is not consumed at that time, is reflected at the reflection terminal 15, and is passed through the plasma. Therefore, the absorption efficiency of the microwave becomes improved with a plasma rate being increased. The following isolation method enables only the radicals in the plasma generated inside the discharge chamber 3 to be isolated and drawn out to a sample processing chamber 1.

Description

[Detailed Description of the Invention] [Industrial Application Field] Mr. Horomoto relates to a microwave plasma processing method and apparatus, and particularly to a microwave plasma processing method suitable for preventing electrostatic damage when a sample is subjected to plasma processing. The present invention relates to a plasma processing method and apparatus.

[Conventional technology]

The degree of integration of semiconductor integrated circuits has been increasing year by year, and we are now entering the sub-micro 7 era. Under these circumstances, plasma processing equipment such as etching equipment used in the device manufacturing process is becoming more and more There is a demand for improved performance in terms of processing accuracy and low damage resistance.In order to meet this demand, the conventional 13.56 MHz
Microwave plasma processing equipment with better processing performance is increasingly being used in place of RF plasma processing equipment.

For example, as described in Japanese Patent Publication No. 58-13627, electron cyclotron resonance (hereinafter referred to as "
ECR) is used to generate plasma, and the sample stage i
By applying this RF or DC bias, there is a method in which etching is performed with good dimensional processing accuracy, high speed, and low damage. However, in order to use this equipment for post-processing such as resist anisotropy, the GT equipment is large-scale and expensive, and the MOS type I
C has the disadvantage that charge is accumulated in the gate portion, causing electrostatic damage such as deterioration of gate characteristics and gate destruction.

Furthermore, as described in JP-A No. 60-16424, for example, plasma can be generated by making pores in the tube wall of a microwave waveguide or by providing a wire mesh in the hole in the waveguide tube wall. Some methods have been developed to perform resist ashing processing without damaging semiconductor devices by shielding and etching the photoresist using only active species.

[Problem that the invention seeks to solve]

Among the above conventional techniques, the former generates plasma in a magnetic field microwave discharge tube that satisfies the ECR conditions, so it can generate high-density plasma and easily achieve high-speed alignment of the resist. There are problems in that the cost of the device is high, and because the substrate is exposed to plasma heat, the device may suffer electrostatic damage.

The latter is also used as a means to generate plasma.
Since only the electric field generated by microwaves is used, the plasma generation efficiency is low, and there is a limit to the improvement of the assinog speed.

SUMMARY OF THE INVENTION An object of the present invention is to provide a microwave plasma processing method and apparatus that eliminates the above-mentioned drawbacks, does not cause element damage, and provides a high processing rate.

[Means to solve the problem]

The above object is to provide a plasma generating means for converting a processing gas introduced into a discharge chamber into plasma by ECR discharge, a separating means for separating radicals in the plasma generated within the discharge chamber, and a sample being separated by the radicals separated by the separating means. and a sample processing chamber for processing, converting the processing gas introduced into the discharge chamber into plasma using ECR, separating only radicals from the plasma in the discharge chamber, and processing the sample with the separated radicals. This is achieved by

[For production]

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 to cause ECR discharge, and the processing gas is efficiently turned into plasma. The intensity of heat has a decreasing gradient from the substrate to be processed to the discharge chamber.This causes the electrons and ions in the plasma to move in the direction opposite to the substrate to be processed.The remaining neutral radicals are absorbed by the substrate. The gas is evacuated in the same direction, reaches the substrate, and chemically etches the film to be processed on the substrate.

Therefore, etching can be performed without causing charge-up that causes electrostatic damage to the substrate. In addition, when a magnetic field is applied to convert the processing gas into plasma, the ionization rate of the gas is higher than when no magnetic field is applied, so that many neutral radicals generated can be processed at high speed.

〔Example〕

An embodiment of the present invention will be described below with reference to FIGS. 1, 2, and 4.

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. As shown in FIG.

A discharge chamber 3 which also serves as a circular waveguide is provided in the upper part of the sample processing chamber 1 in communication with the sample processing chamber 1 . 4 is a vacuum sealing material. A conversion waveguide 6 is provided above 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, and a magnetron 8 is provided at the end of the rectangular waveguide 7.

A reflective end 15 is attached within the discharge chamber 3 to reflect microwaves. Outside the discharge chamber 3 is a cylindrical electromagnetic coil 9 that generates a magnetic field orthogonal to the electric field generated by the microwave.
is the provision. The outside of the electromagnetic coil 9 is provided with a shield tube 10 and a shield cover 11 made of a high magnetic permeability material. The discharge chamber 3 is provided with a gas inlet between the insulating window 5 and the reflective end 15. An exhaust port 13 connected to an exhaust device (not shown) is provided on the opposite side of the processing chamber 1 to the discharge chamber 3.

16 is a heating device that heats the sample stage 2; 17 is an isolator that prevents microwaves from returning.

For example, when the oscillation frequency of the magnetron 8 is 2.45 GHz and the resonance mode is TEI 12 mode, the discharge chamber 3 that also serves as a circular waveguide in the component has a cutoff wavelength with respect to an oscillation wavelength of 12.245 cm. is 1g, 53c
rn, so inner diameter 10.9cH1, length l 6゜2cr
Microwave power can be introduced into the discharge chamber 3 by increasing the value of n by 1.

In addition, the reflection end 15 attached to one end of the discharge chamber 3 should have a cutoff wavelength of 12.245α or less. For example, in the TE11 mode, by making the hole diameter 7.18 cm or less, the microwave is transmitted to the reflection end. 15 and passes through the discharge chamber 3 again. In this case, the hole diameter of the reflective end 15 is set to lc+++, and the pitch is set at 2 crtt intervals.

Further, as shown in FIG. 2, the end of a shield tube 10 surrounding the electromagnetic coil 9 is provided so as to wrap around the inside of the electromagnetic coil 9. As a result, the magnetic field generated by 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(2) decreases in the Z-axis direction, that is, in the direction away from the wafer 14.

Here, the plasma generating means in this case includes the magnetron 8, the rectangular waveguide 7, the conversion waveguide 6, the discharge chamber 3, and the insulating window 5.
It is composed of a reflective end 15, an electromagnetic coil 9, a shield tube 10, and a shield cover 11. The microwave generated by the magnetron 8 is transferred from the rectangular waveguide 7 to the conversion waveguide 6.
It propagates to the discharge chamber 3 via. 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 magnetic field is generated by the magnetic coil 9 so that the magnetic field strength near the maximum microwave electric field Bfzl shown in FIG. 2 is approximately 875 Gauss, thereby increasing the oscillation frequency to 2.45 GHz. Contrary to that; 4ECR conditions are satisfied. Now, the angular velocity of the microwave is ω, and the static magnetic field B
The angular velocity of the cyclotron motion of the electrons inside is ω (= e
When B/m is satisfied, electron cyclotron resonance (ECR) occurs when ω=ωC, and microwave power is efficiently absorbed for electron movement.

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

Here, the radical separating means in this case is composed of the electromagnetic coil 9, the shield tube 9, the shield cover 10, and a DC power supply device (not shown). Generally, it is known that electrons in plasma are subjected to a biaxial force, and the magnitude thereof is given by Ffzl. Here, e is the charge of the electron and 2m is the mass of the electron. According to the above equation), since the magnetic flux density B(2) of the plasma generation part is decreasing in two axial directions, the electrons in the plasma are subjected to a force in the direction of moving away from the wafer 14 along 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. That is, electrons and ions in the plasma are accelerated in the direction opposite to the wafer 14, and only radicals that are not affected electrically or magnetically exit through the hole in the reflective end 15 to the sample processing chamber 1 side. Go.

The radicals that have entered 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 and cause a chemical reaction to etch the wafer 14. In this way, Since the etch knob only involves 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 to 50°C to 200°C by the heating device 16. Also, the exhaust port 13 is The arrangement should be such that the flow of radicals coming out of the discharge chamber 3 makes it easy for them to come into contact with the wafer 14.According to this example 1, only radicals that are not affected electrically or magnetically should be arranged. Since the wafer 14 can be etched by etching, there is no charge-up of electrons or ions on the processing surface of the wafer 14, and electrostatic damage to devices can be prevented.

Also, compared to conventional systems that do not use a magnetic field, the density of gas molecules is lower, for example 0. Even in the low-pressure state of OI Torr, it is possible to generate a high-density plasma due to the synergistic effect of the electron cyclotron movement of the ECR.The high-density radicals thus generated are in a low-pressure atmosphere, so they interact with other gas molecules. The collision probability of is small,
The probability that radicals will be annihilated by such collisions is also reduced, resulting in a longer lifespan of the radicals. This allows the radicals to travel over a long distance, so even if the discharge chamber 3 has a small size, it is possible to uniformly process a large diameter wafer. Since the configuration is possible, there is an effect that the mounting N can be manufactured at low cost.

Furthermore, since the amount of radicals increases due to the generation of high-density plasma, a high processing rate can be obtained.

Furthermore, by surrounding the electromagnetic coil 9 with the shield tube 10 and the shield cover 11 and concentrating the magnetic field on the ends of the shield tube 10 and the shield cover 11, the magnetic field strength can be easily changed.

Furthermore, by partitioning the front of the circular waveguide with the insulating window 5 and the reflective end 15, the circular waveguide can be used in common with the discharge chamber.

By providing a countersink and a heating device 16 on the sample stage 2, wafer processing can be speeded up.

Next, another embodiment will be described with reference to FIGS. 3 and 4.

In this figure, the same reference numerals as in FIG. 1 indicate the same members.

This figure differs from Figure 1 in that the discharge chamber 3 in Figure 1 is made of a circular waveguide partitioned by an insulating window 5 and a reflective end 15, but instead The point is that a discharge chamber 19 made of material, in this case quartz, is provided in communication with the sample processing chamber 1. Another point is that a circular waveguide n surrounding the discharge chamber 19 is provided between the conversion waveguide 6 and the sample processing chamber l. Furthermore, around the discharge tube 19, a circular waveguide n
The point is that the electromagnetic coils and the electromagnetic coils are arranged in a vertical relationship on the outside. (9) is a gas introduction port for introducing processing gas into the discharge chamber 19. B is a vacuum sealing material. 5 is a shield tube, and HAN is a shield cover, both of which are made of high magnetic permeability material.

The hole diameter of the communication hole between the discharge chamber 19, which is the terminal end of the circular waveguide 1122, and the sample processing chamber l is such that the cutoff wavelength of the microwave is 12.
．． When the diameter is 245c* or less, for example, in TBII mode, the hole diameter is set to 7.18c+n or less. This results in
The microwave is reflected on the top surface of the sample processing chamber l, and the sample processing chamber! It passes through the plasma again without entering the plasma.

The generation of magnetic field in electromagnetic coil n and Sae.

By controlling a DC power supply (not shown), as shown in FIG.
decrease. Moreover, the microwave electric field E in the discharge chamber 19
(By setting the magnetic field strength near the maximum of zl to be approximately 875 Gauss, the oscillation frequency is 2.45 GHz.
satisfies the ECR conditions for

With the above configuration and conditions, the microwaves emitted from the magnetron 8 cause the processing gas introduced into the discharge chamber 19 to undergo ECR discharge together with the magnetic field.

The plasma generated in the discharge chamber 19 by ECR discharge is
Magnetic flux density B f decreases in the direction away from the wafer 14
Due to il, only radicals in the plasma exit into the sample processing chamber 1, as in the previous embodiment. From this point on, the wafer 14 can be etched in the same manner as in the previous embodiment.

As described above, according to this embodiment, the wafer 14 can be etched only by radicals that are not affected electrically or magnetically, as in the previous embodiment, so that the processing surface of the wafer 14 is not charged up with electrons or ions. Therefore, electrostatic damage to the device can be prevented.

Furthermore, since high-density plasma can be generated in a low-pressure state as in the previous embodiment, the lifetime of radicals is extended. Thereby, the discharge chamber 19 and the electromagnetic coil 24 can be made smaller than the wafer diameter, and the device can be manufactured at low cost. Furthermore, generation of high-density plasma generates a large number of radicals, so a high processing rate can be obtained.

〔Effect of the invention〕

According to the present invention, by causing ECR discharge and decreasing the magnetic flux density in the direction away from the sample, it is possible to increase the amount of radicals generated, and it is possible to treat the sample with only radicals, without causing element damage. , it has the effect of being able to obtain a high processing rate.

[Brief explanation of drawings]

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 due to gtH of FIG. 1, and FIG. FIG. 4 is a longitudinal cross-sectional view showing a microwave plasma processing apparatus according to another embodiment, and FIG. 4 is a diagram showing the microwave electric field and magnetic flux density by the apparatus of FIG. 3. l...Sample processing room, 2...Sample stand, 3
...Discharge chamber, 5...Insulating window, 8...
...Magnetro 7%9...-1 mortar coil, lO
...shield tube, 11 ...shield cover, 14 ... wafer, 15 ... reflection end, 19 ... radiation q

Claims (1)

[Claims] 1. A step of turning a processing gas into plasma using electron cyclotron resonance (ECR), a step of separating only radicals from the plasma, and a step of treating a sample with the separated radicals. A microwave plasma processing method characterized by having the following. 2. plasma generation means for converting processing gas introduced into the discharge chamber into plasma by ECR discharge; and separation means for separating radicals in the plasma generated within the discharge chamber;
A microwave plasma processing apparatus comprising a sample processing chamber for processing a sample with radicals separated by the separation means.