KR920006897B1 - Dry etching apparatus using electron cyclotron resonance - Google Patents

Abstract

A grid having ground level is deposited between a plasma discharging cavity and an etching process cavity to form a RF bias applied ECR etching apparatus and the grid is moved up and down to change the mode of microwave. The apparatus includes a plasma discharging cavity (2) in which a gas discharge is occured, a wave guide (5) for guiding microwave having frequency of 2.45 GHz to the top of the cavity (2), a microwave generator having a structure to prevent damage of a magnetron due to reverse microwave, a solenoid magnetic coil (8) for providing magnetic flux density of 875 Gauss to generate divergent magnetic field, and a process cavity (1) for etching a semiconductor plate.

Description

Dry etching apparatus using ELECTRON CYCLOTRON RESONANCE plasma

1 is a block diagram of a dry etching apparatus of an electronic cyclotron resonance method of the present invention.

2 is a schematic configuration diagram of a microwave generator.

3 is a perspective view of a metal grid for reflection and microwave acceleration of the present invention.

4a, 4b and 4c show the magnetic field distribution according to the arrangement of the magnetic coil, 4a is a mirror magnetic field, 4b is a distorted magnetic field, and 4c is a diverging magnetic field.

5 is a perspective view of the alumina ceramic plate of the present invention.

* Explanation of symbols for main parts of the drawings

1: process reaction chamber 2: plasma discharge chamber

3: microwave generator 4: impedance adjusting screw

5: waveguide 6: quartz plate

7: metal grid 8: magnetic coil

9 coolant inlet 10 coolant outlet

11: oxygen (O ₂ ) gas 12: sulfur hexafluoride (SF) gas

13: C ₃ F ₈ gas 14: CCl ₂ F ₂ gas

15: chlorine (Cl ₂ ) gas

16-20: Each regulator of 11-15 gas

21 to 25: each manual shut-off valve of 11 to 15 gases

26: Mass Flow Controller of Oxygen Gas

27: Common flow regulator for SF ₆ , C ₃ F ₈ , CCl ₂ F ₂ gas

28: chlorine gas flow regulator

29: power supply and flow indicator for gas flow controller

30: Pneumatic Valve

31: Gas Manifold 32: Gas inlet

33 Plasma Stream 34 Semiconductor Specimen

35 aluminum electrode 36 alumina ceramic plate

37: RF matching controller 38: RF power

39: spectrometer 40: silicon light detector

41 optical fiber 42 multi-spectral spectrometer

43: Vacuum Manifold

44: Throttle valve 45: O-ring

46: throttle valve controller 47: vacuum piping

48: nitrogen inlet 49: manual throttle valve

50: oil diffusion pump 51: cold Trap

The present invention uses microwaves, generators, and electromagnets as gas discharge means to accurately etch wafers into desired shapes in various dielectric materials, such as oxide films, nitride films, and semiconductors, which are used as essential materials for the manufacture of various high-performance semiconductor devices. The present invention relates to a dry etching apparatus using gas discharge by electron cyclotron resonance by arranging according to an appropriate design and designing and manufacturing a plasma resonator based on theoretical calculations.

Many types of dry etching devices have been developed in the United States and Japan and used in semiconductor manufacturing processes.

Currently, the most widely used method is a reactive ion or plasma etching device having two parallel plate electrodes and an ion beam acceleration etching device using an RF power source, all of which have high resolution anisotropy ( Since a very large energy is used to achieve the anisotropy shape, the etch selectivity between the materials to be etched is low and the characteristics of the fabricated semiconductor device may be degraded due to lattice defects.

On the other hand, as the demand for high speed, high integration, and high reliability for various semiconductor devices is gradually increased, high etching selectivity and especially low damage processing are further desired with the progress of miniaturization, and with high progress, high etching selectivity and especially low damage As processing became more and more demanded, the development of a new concept of equipment rather than the existing standardized dry etching equipment was urgently needed.

In response to this trend, a dry etching apparatus using gas discharge by cyclotron resonance of electrons has begun to be researched and developed at Hitachi, Japan.

As an inherent method of generating gas plasmas, ion sources using electron cyclotron resonance (ECR) can form high-current plasmas in large areas. Although developed, practical research in semiconductor processing has been led by Japanese scientists.

In particular, ECR plasma has low etching damage to semiconductor substrate due to relatively low distribution of ion energy (several tens of electron volts or less), high-speed etching and high vacuum due to generation of high density plasma (10 ¹⁰ to 10 ¹² / cm 2). ^-3 to 10 ^-5 Torr), there are various advantages such as high etching resolution due to long mean free path ions due to plasma generation.

Therefore, it is considered to be very promising for the semiconductor etching process, and several patent applications (Japanese Patent Registration No. 60198728, 61204936, etc.) have been filed by Adelbas, Hitachi, etc. in Japan, and began to manufacture and sell commercialized equipment.

However, most equipments do not fully meet the requirements of equipment users, such as fixed magnet arrangements and improper design of process reaction chambers in RF additional ECR equipment.

In other words, it does not completely solve the detailed problems of the etching process for manufacturing mega-bit devices, so the share of the dry etching equipment market in the world is very small.

In order to supply the magnetic flux density of 875 gauss, which is the basic requirement of ECR discharge, the present invention can arrange four electromagnet disks that surround a circular plasma generating chamber which acts as a resonator. It is possible to control the distribution of magnetic flux density in the discharge chamber according to the user's process requirements by supplying DC power variably. This is the case of the permanent magnet type or electromagnet of the existing device. Its position is fixed so that only a magnetic flux density of a certain size is formed within a certain section of the discharge chamber, and its application is limited. However, the present invention has been devised to improve such a disadvantage.

On the other hand, the ECR etching apparatus also has a disadvantage: in an ECR plasma having a divergent magnetic field, the wafer is far from the aperture between the plasma discharge chamber and the process reaction chamber or the size of the wafer compared to the direct space of the discharge chamber. Is much larger, the plasma stream is obliquely contacted near the edge of the wafer by the diffusion of the plasma toward the outer wall of the process chamber so that the effective non-proliferative etching characteristics are achieved only by the plasma stream, which is induced by the conventional diverging magnetic field. It is difficult.

Therefore, in recent years, ECR etching equipment manufacturers are trying to achieve anisotropic anisotropy by applying RF power to the electrode on which the wafer is placed to compensate the plasma wires from being perpendicular to the wafer. Since the reaction chamber, which has a center hole as an anode relative to a powered cathode, acts as an upper wall, a disadvantage of substantially inefficient efficiency of the auxiliary function of RF bias is derived.

Accordingly, in the present invention, a metal grid in a ground state is installed between the plasma discharge chamber and the reaction chamber in order to solve this disadvantage, and the grid serves as a reflector for microwaves to suppress secondary discharge in the reaction chamber. In addition, the height can be changed up and down along the thread of the inner wall of the discharge chamber, it is possible to convert the micro mode (mode) and also to act as a perfect upper anode when applying an RF bias.

Hereinafter, the technical configuration and the preferred embodiment of the present invention will be described in detail.

As shown in the drawing, an electron cyclotron resonance plasma apparatus includes a microwave generator 3, an etching reaction chamber 1, a plasma discharge chamber 2, a magnetic coil 8, a gas supply system and a vacuum exhaust system, a power supply system, and the like. It can be divided into measurement control system.

First, the microwave generator 3 uses a magnetron 58 having a frequency of 2.45 kHz and an output of 800 watts connected to the power source 57 as an oscillation source, and then installs an isolator 59 to supply microwaves. The magnetron was prevented from being damaged by the reverse flow of.

In addition, by using a directional coupler (60) directly above to improve the directionality of the microwave to reduce the error of the monitoring power, then applied microwave power and re-reflected power to the power meter (Power Meter) 61).

In the middle of the L-type waveguide system 5 for transmitting the generated microwaves to the plasma discharge chamber 2, a matching adjusting screw 4 is provided for matching the microwave impedance.

The plasma chamber 2 of FIG. 1 is a kind of cylindrical waveguide, and the upper side thereof is connected to the L-type waveguide system 5 by a vacuum-sealed circular quartz plate 6 which can pass microwave energy better. The side is also connected to a grid 7 in a ground state of a metallic component such as a third degree to which a ground or direct current voltage is applied, which reflects microwaves and can pass a plasma stream 33.

This grid is movable up and down about 3 cm along the screw line of the inner wall of the plasma discharge chamber 2.

The plasma discharge chamber 2 was made of aluminum, and the inner wall of the discharge chamber was anodized to protect the surface from chemical erosion by reactive ions and neutral groups. In addition, the gas distribution system includes five gas cylinders 11 to 15, respective gas pressure regulators, manual gas shutoff valves 21 to 25, and gas flow controllers 26 and 27. ), (28) and the final pneumatic gas shutoff valve 30 on the integrated gas supply pipe 31 is to cut off the gas supply.

The five gases used in the present invention are, firstly, carbon using the discharge of oxygen (O ₂ ) 11 for selective etching of photoresist or ashing of the front surface of the wafer, which is basically used in semiconductor processes. The photoresist composed of a polymer compound of hydrogen and hydrogen is decomposed into a reaction product of CO ₂ and H ₂ O to be etched.

Second, chlorine (C ₁₂ ) (15) and sulfur hexafluoride for etching of the silicon substrate itself for the formation of polycrystalline silicon, or trench isolation and trench capacitor structures, used as gates of silicon transistors. (SF ₆ ) (12) can be used to decompose the silicon into silicide tetrafluoride (SiF ₄ ) or silicon tetrachloride (SiCl ₄ ).

Third, silicon tetrafluoride using only C ₃ F ₈ (13) instead of the mixed gas of CHF ₃ and C ₂ F ₆ (Freon-116), which is usually used for etching silicon oxide film (SiO ₂ ), which is mainly used as an insulating film. And decomposition into carbon monoxide and carbon dioxide.

Finally, the volatility of the aluminum trichloride (AlCl ₃ ) product is extremely reduced by the use of CCl ₂ F ₂ (Freon-12) gas (14) for selective etching of gallium arsenide (GaAs) of aluminum gallium arsenide (AlGaAs). A small one was used.

The three gas flow regulators 26, 27, and 28 used in the present invention are connected to a power supply and flow indicator 29 for one flow regulator, and the gas distribution relationship for chlorine is melted by using a VCR connection material. Careful handling of toxic gases was observed.

In addition, the plasma discharge chamber 2 is surrounded by four independent magnetic coils 8 and the process gas introduced into the plasma discharge chamber 2 by interaction with the microwaves generated by the microwave generator 3. Is discharged by electron cyclotron resonance to generate plasma.

In general, magnetic flux density B for electron cyclotron resonance conditions is

Where m is the mass of the electron, e is the absolute charge, and f is the frequency of the microwave.

That is, it can be seen that the magnetic flux density for the electron cyclotron resonance condition is 875 gauss (Gauss: 10-4T) at a microwave frequency of 2.45 GHz.

Each of the four magnetic coils 8 is composed of a solenoid coil of 100 revolutions each, and the inlet 9 and the outlet 10 are formed by cooling water in order to efficiently dissipate heat generated by a large current flow. It is intended to be water cooled through.

In the plasma system of electron cyclotron resonance, three types of magnetic fields are formed as shown in FIGS. 4A, 4B, and 4C according to the arrangement of the magnetic coil 8.

FIG. 4A is a mirror magnetic field, FIG. 4B is a distortion magnetic field, and FIG. 4C is a divergent magnetic field.

Here, the magnetic coil 8 is arranged to take the distribution of the diverging machine.

It is difficult to achieve perfect anisotropy only by the plasma streamline 33, which is usually led by the configuration of the diverging magnetic field.

This is because the semiconductor is separated from the aperture connecting the plasma discharge chamber 2 and the process reaction chamber 1 by a predetermined distance of the semiconductor specimen 34 so that the semiconductor is spread by the plasma to the reaction chamber 1 outer wall. This is because the plasma streamline 33 does not vertically contact the edge portion as compared with the central portion of the specimen 34.

Therefore, in order to compensate for this, the RF power source 38 is connected to an anodized aluminum electrode plate 35 on which the semiconductor specimen 34 is placed, through a regulator (RF Matching Network) 37 for matching impedance by adjusting a vacuum capacitor. By applying this, the direct current component of the ions can be further increased to improve the anisotropic etching characteristic of the semiconductor specimen 34.

In addition, the RF power supply 38 is electrically insulated from the process reaction chamber 1 by the alumina ceramic plate 36 specially processed for symmetrical vacuum exhaust as shown in FIG.

The holes 36a at the edges are for evacuation and the inner holes 36b are for connection with the RF power source 38.

On the other hand, the spectrometer 39 (Spectrograph) and the silicon photodetector 40 (detecting the change of the product using the optical spectroscopy of the reaction material generated by the plasma discharge for the end point detection of the etching process according to the properties of the material) Photodetector) was installed in connection with the multispectral analyzer main body 42 through the optical fiber 41. In addition, a Langmuir Plobe for measuring the characteristics of the plasma and a device for measuring the intensity of the magnetic field were attached.

In addition, the vacuum exhaust system is a combination of the oil diffusion pump 50 and the rotary pump 55 so that the pressure in the process reaction chamber 1 can be lowered to a minimum of 10 ^-6 Torr when no reaction gas is introduced. Pump oil was used to minimize the chemical reaction with the reaction gas is exhausted (Fomblin) oil.

During the etching process, an appropriate range of pressure control is about 10 ^-2 -10 ^-5 Torr. The pressure diffusion between the vacuum pipe connected to the opening in the vacuum reserve chamber 43 and the alumina ceramic plate 36 and the oil diffusion pump 50 is shown. The throttle valve 45 of the stepping motor type | system | group which is comprised automatically by an electrical signal according to the pressure value set in the throttle valve controller 46 is provided.

The throttle valve controller 46 is connected to a thermocouple pressure gauge 57 (10 to 10 ^-3 Torr) and an ion pressure gauge 58 (10 _2r to 10 ^-7 Torr) to form a mutually closed circuit. It is designed to achieve a constant process pressure at all times regardless of the change of gas flow rate into the reaction chamber (1).

In order to prevent the back flow of the pump oil, a certain amount of nitrogen flows through the nitrogen inlet 48 in the vacuum pipe 47 connected to the throttle valve 44, and also the cold chub 51 and the cooling water washing tank (Water Baffle) ( 52) was further installed to filter the reaction product during etching, and then exhaust gas was discharged through the exhaust port 56 of the rotary pump 55.

As described above, the present invention provides four pairs of highly variable magnetic coil disks enclosing a microwave generator and a plasma discharge chamber, an RF power system, a gas supply system, and a vacuum drain applied to the cathode of the etching reaction chamber and the wafer. It is composed of organic components such as a system, and its main feature is a perfect RF bias-applied ECR etcher which has not been realized in conventional etching equipment by installing a grounded metal grid between the plasma discharge chamber and the etching process reaction chamber. The lattice plate can be moved up and down along the inner wall of the discharge chamber to enable microwave mode conversion.

In addition, the distribution of magnetic flux density in the discharge chamber can be arbitrarily controlled by individually controlling the placement of electromagnets and the amount of current outside the discharge chamber. The process conditions required at the time of manufacture can be mentioned.

Claims (3)

In a device using a gas discharge by electron cyclotron resonance by appropriate application of microwaves and magnetic fields, a cylindrical plasma discharge chamber 2 in which high vacuum in which gas discharge occurs is maintained, and 2.45 kPa fastened to an upper side of the plasma discharge chamber. A waveguide (5) for inductively transmitting microwaves, a microwave generator installed at a lower portion of the waveguide to prevent damage to the magnetron due to backflow of microwaves, and a microwave introduced from the upper portion surrounding the plasma discharge chamber (2); Arranged and powered variable solenoid magnetic coils 8, which are capable of supplying a magnetic flux density of 875 gauss to form a diverging magnetic field to work together to satisfy the electron cyclotron resonance conditions, and are installed at the bottom of the plasma discharge chamber 2 And the process reaction chamber 1 in which the etching reaction of the semiconductor substrate occurs. Dry etching apparatus using an electron cyclotron resonance plasma. The cyclotron resonance plasma according to claim 1, wherein the magnetic coil 8 surrounding the plasma discharge chamber 2 can be changed up and down, but has four pairs of disks capable of controlling current flow. Dry etching apparatus using. 2. The separator according to claim 1, wherein the micro-generator is coupled to the magnetron 58 having a frequency of 2.45 GHz output, 1 kilowatt, a power source 57 connected thereto, and a magnetron 58 to prevent damage to the magnetron. And a direct directional coupler 60 for improving the directionality of the microwave toward one side of the separator, and an electric cyclotron resonance plasma for measuring the applied microwave power and the power reflected back. Dry etching apparatus using.

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