JPH05275194A - Method and device for generating plasma - Google Patents

Abstract

PURPOSE:To generate a variety of plasma conditions by applying an FM modulated wave or AM modulated wave power to a pair of electrodes facing each other, and varying the frequency in the sub-second time range while the intra- chamber pressure is held unchanged. CONSTITUTION:An etching gas is sent into a chamber 1 via a rate-of-flow limiter and the internal pressure of the chamber 1 is kept at a specified level by a turbo pump. A signal generator 2 generates a modulated power of AM waves or FM waves, and this power is applied to a cathode (specimen stage) 5 and anode (counter-electrode) 4 through an amplifier. Accordingly the frequency is varied in the sub-second time range while the gas composition and the internal pressure of chamber are kept unchang, so as to produce a variety of plasma conditions. The power and frequency are varied for Am waves and FM waves, respectively, at millisecs intervals, and fine processing of element can be done stably with good controllability.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus and method for generating plasma.

[0002]

2. Description of the Related Art Plasma using high-frequency discharge is applied to various processes such as dry etching for fine processing, sputtering for thin film formation, plasma CVD, and ion implantation machine. For example, dry etching applied to microfabrication uses a chemical or physical reaction on a gas-solid surface due to plasma, radicals, ions, etc., and removes unnecessary portions on a thin film or a substrate. Is a processing method for forming a pattern. Reactive ion etching (RIE), which is widely used as a dry etching technique, exposes a sample to a high frequency discharge plasma of an appropriate gas to cause a reaction.
The unnecessary portion of the sample is removed by etching. Necessary portions are protected by a photoresist pattern which is usually used as a mask.

An example of the above-mentioned conventional dry etching apparatus will be described below with reference to the drawings.

FIG. 4 shows a conventional high frequency power source, for example, 13.5.
It is a schematic diagram which shows the reactive ion etching apparatus which used 6 MHz. In FIG. 4, the reactive gas G is introduced into the metallic chamber 11 through a gas controller (not shown), and is controlled to have an appropriate pressure by the exhaust system. An anode (anode) 14 is provided in the upper part of the chamber, and a sample table 13 serving as a cathode (cathode) is provided in the lower part. An RF power source 12 is connected to the sample stage via an impedance matching circuit, and high frequency discharge is generated between the sample stage and the anode. 11 is a metal chamber. Reference numeral 12 is an anode, 13 is a cathode, and 14 is a high frequency power source. When etching,
By changing the composition of the etching gas, the pressure in the chamber and the RF power in steps of several tens of seconds,
A desired etching shape was obtained by changing the state of plasma and performing step etching.

[0005]

With the miniaturization of devices,
It is being demanded more strictly than the controllability and stability of fine processing. However, with the current step etching,
There is a limit in controlling adsorption, ion collision reaction, etc. by using constant plasma for several tens of seconds in each step. A method of controlling the shape by alternately performing the fine etching and the sidewall deposition has also been proposed.
However, in the configuration of the apparatus as described above, since only the power source of a constant frequency is used, the flow rate of the etching gas, the composition of the etching gas, the pressure in the chamber and the RF power are changed to change the plasma state. Inevitably,
It was very difficult to control the above elements from the viewpoint of the response of the mass flow controller and the RF matching characteristic in the time zone of less than a second. In addition, in the configuration of the apparatus as described above, even when the RF power is changed, step etching in which the RF power is changed in a unit of several tens of seconds is unavoidable from the viewpoint of the RF matching characteristics, and formation of contact holes, etc. At, when forming the taper angle,
It is very difficult to control the etching shape because unnecessary side etching may occur. In addition, a method has been devised in which a plurality of high-frequency power supplies are used and plasma is generated at different frequencies at a certain step during step etching, but the flow rate of the etching gas, the composition of the etching gas, and the pressure in the chamber are set at It was very difficult to control in the time zone from the point of view of the responsiveness of the mass flow controller and the RF matching characteristic, like the change of the RF power. In view of the above problems, the present invention provides a plasma generator capable of generating various plasma states under a high vacuum with a constant gas composition and a constant chamber internal pressure.

[0006]

In order to solve the above problems, in the plasma generator of the present invention, a modulated wave generating power source is arranged on one of a pair of parallel plate type counter electrodes, and the modulated wave power, for example, A time-varying plasma is generated in a vacuum by an amplitude modulation wave (hereinafter referred to as an AM wave) or a frequency modulation wave (hereinafter referred to as an FM wave).

[0007]

According to the present invention, the FM modulation wave power or the AM modulation wave power is applied to the pair of opposed electrodes by the above-described structure.
By applying the modulated wave power, it is possible to create various plasma states by changing the frequency in the time range of seconds or less without changing the gas composition and the chamber internal pressure. In the case of the AM wave, the power is changed in units of several milliseconds, and in the case of the FM wave, the frequency is changed in units of several milliseconds, and plasma is generated without changing the gas composition and the chamber internal pressure. As a result, the reactivity between the gas phase and the solid is controlled, and etching and sidewall deposition are possible without changing pressure or RF power.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A dry etching apparatus of an embodiment in which the plasma generator of the present invention is applied to a dry etching apparatus will be described below with reference to the drawings.

FIG. 1 shows the structure of a dry etching apparatus according to an embodiment of the present invention. In FIG. 1, 1 is a chamber, 2 is a signal generator for generating AM or FM wave modulation power, 3 is amplification, 4 is an anode electrode serving as a counter electrode, and 5 is a cathode electrode to which modulation wave power is applied. It is a sample stand. The etching gas is introduced into the chamber 1 from an inlet through a mass flow controller (not shown), and the internal pressure of the chamber 1 is controlled to about 5 Pa to 100 Pa by a turbo pump (not shown).

The dry etching apparatus configured as described above will be described below (FIG. 1), (FIG. 2), and (FIG. 3).
The operation will be described using.

First (FIG. 2) is a diagram schematically showing a change in the power of the AM wave power applied to the pair of parallel plates in an extremely short time. By using the AM wave power, it becomes possible to change the power in a unit of several milliseconds while keeping the frequency constant. By changing the power in a time of several milliseconds, various plasma states could be generated without changing the gas composition, gas flow rate, and pressure, which are major factors for plasma generation and stabilization. For example, when the gas flow rate, gas composition, and chamber pressure are constant, the ion energy in the plasma increases when the power (eg, several hundred watts) is large, and the ion energy in the plasma decreases when the power (eg, several tens of watts) is small. As the power becomes low, the plasma state changes even by changing the power by 10 watts, and various plasma states can be generated. The various plasmas generated in this way are closely related to the reactivity of the gas phase and the solid that control the etching. As described above, according to the present embodiment, by applying the AM wave power capable of changing the power in a few milliseconds to the parallel plate, the gas flow rate, the gas composition, and the pressure can be changed without changing in a few milliseconds. It is possible to generate various plasma states in such a short time. The dry etching apparatus is capable of performing RIE using the plasma thus generated.

Next, a dry etching apparatus using an FM modulated wave power source according to the second embodiment of the present invention will be described. The configuration of the device is as shown in FIG. 1 similarly to the AM modulated wave. FIG. 3 is a diagram schematically showing a change in frequency of FM wave power applied to a pair of parallel plates in an extremely short time. By using the FM wave power, the power can be kept constant and the frequency can be changed in units of several milliseconds.
By changing the frequency with time, various plasma states could be generated without changing the gas flow rate, gas composition, and pressure. For example, when the gas flow rate, gas composition, and pressure are constant, plasma with various states occurs when the frequency is low, the ion energy in the plasma is high, and when the frequency is high, the ion energy in the plasma is low. is there. It is possible to change the plasma state by this frequency in units of several milliseconds. These various plasma states change the reactivity between the solid phase and the gas phase during etching, and the reactivity can be controlled. As described above, according to this embodiment, by applying the modulated wave power such as the FM wave power capable of changing the power in a few milliseconds, the gas flow rate, the gas composition, and the pressure are not changed, and the millimeter wave is not changed. Various plasma states can be generated in a short time of seconds.
Further, more uniform plasma was obtained as compared with the plasma generated by the AM modulated wave. The dry etching apparatus is capable of performing RIE using the plasma thus generated.

A dry etching method using an AM modulated wave will be described below as a third embodiment of the plasma generator of the present invention. In order to obtain a desired etching shape in dry etching, that is, in order to improve the anisotropy of etching, unnecessary portions are removed and added to the products and etching gas at the time of etching at the portions that should not be etched. A film formed by polymerization in a plasma with a certain gas species formed has anisotropy. In the conventional device, R is set between steps of several tens of seconds.
Although the F power has been changed and etching has been performed with 2 to 4 types of plasma, AM plasma power can create various plasma states in a few milliseconds, so by changing the power in a few milliseconds. , It is possible to control whether the etching proceeds or the formation of the deposition on the portion that should not be etched. In addition, it is possible to etch an ultrafine pattern by changing the plasma state in units of several milliseconds.

FIG. 5 is a schematic diagram of an etching shape generated by depositing an Al alloy on SiO ₂ and applying it to a film having a pattern formed with a resist by the dry etching method using the AM modulated wave. .. 50 is a resist, 51
Is, for example, a silicon semiconductor substrate on which SiO ₂ is formed,
Reference numeral 52 is a material to be etched such as Al or Al alloy, 53 is an etching portion where etching is progressed by plasma generated by a modulated wave power source, and 54 is a deposition portion where deposition is progressed by plasma generated by a modulated wave power source. FIG. 6A is a schematic view of a state in which etching is progressed by plasma generated by the modulated wave power source. AM
When the power is low at the wave power, the etching progresses when the FM is low at the frequency when the power is low.
This is a 1-layer film, and side etching only occurs from a few angstroms to a few hundred angstroms. A
In the case of the M-modulated wave, when the power is small, side etching progresses and a recess 63 of several angstroms to several hundred angstroms is formed on the side wall of the Al film as shown in FIG.

FIG. 6B is a schematic diagram of a state in which the plasma state is changed by the power change by the modulated wave power source after the etching as shown in FIG. 6A and the deposition is advanced. .. With AM wave power, deposition proceeds when the power is large, but the change in power is in the unit of several milliseconds, so a deposition portion 54 of several angstroms to several hundred angstroms is deposited on the Al film sidewall. When the etching and the deposition are alternately performed for several milliseconds, the cross section becomes as shown in FIG. 6C, the side wall surface has irregularities, and the etching shape is almost vertical. As shown in the figure, a desired etching pattern can be obtained without causing a large side etch in the wiring part which is the material to be etched. It is possible to form irregularities of several angstroms on the side wall of the pattern thus etched. When this etching is applied to the capacitance formation of the VLSI, since the side wall is made uneven, it is possible to form a capacitance having a larger volume according to the same rule as the conventional one. The large deposition increases the capacitance, which is a very effective means for VLSI wiring. However, when the plasma generated by the AM modulated wave power is used for dry etching, the plasma state becomes non-uniform simply by changing only the power, and the device is often damaged when it is etched. Therefore, considering the damage to the device, the dry etching method using the FM modulated wave power is effective. Less than,
A dry etching method using an FM modulated wave according to the third embodiment of the present invention will be described. Since the frequency can be changed in the FM modulated wave power, various plasma states can be created in a unit of several milliseconds, gas composition,
By changing only the frequency without changing the gas flow rate and the pressure, it is possible to control whether the etching progresses or the formation of the deposition in the portion which should not be etched progresses. Basically, when the gas conditions and pressure are the same, the etching proceeds when the ion energy is increased, and the deposition proceeds when the ion energy is lowered. When dry etching is performed using FM modulated wave power, the etching proceeds when the frequency is low,
Deposition proceeds when the frequency is high.

Etching caused by depositing an Al alloy on SiO ₂ and applying a pattern on a resist by the dry etching method using the power of the FM modulated wave as described above is similar to that of the AM modulated wave. 5 and FIG. FIG. 6A is a schematic view of a state in which etching is progressed by plasma generated by the modulated wave power source. In FM, etching progresses when the frequency is low with electric power,
Since the frequency change is in the order of milliseconds, it is only the Al film of several angstroms to several hundred angstroms that is etched, and the side etching also occurs only from several angstroms to hundreds of angstroms.
In the case of FM modulated waves, if the frequency gradually decreases,
As the side etching progresses, as shown in FIG.
A recess 63 of several angstroms to several hundred angstroms is formed on the side wall of the film. FIG. 6B is a schematic diagram of a state in which the plasma state changes due to the frequency change by the modulated wave power source after the etching as shown in FIG. 6A and the deposition progresses. In the case of FM, the deposition progresses when the frequency is high when the power is high, but since the change in the frequency is in the unit of several milliseconds, a deposition 54 of several angstroms to several hundred angstroms is deposited on the Al film sidewall. When the etching and the deposition are alternately performed for several milliseconds, the cross section becomes as shown in FIG. 6C, the side wall surface has irregularities, and the etching shape is almost vertical. As shown in the figure, a desired etching pattern can be obtained without causing a large side etch in the wiring part which is the material to be etched. It is possible to form unevenness of several angstroms to several hundred angstroms on the side wall of the pattern etched in this way, as in the case of using AM waves. This etching is super L
When applied to the formation of the SI capacitance, the side wall has irregularities, so that it is possible to form a capacitance having a larger volume according to the same rule as the conventional one. The large deposition increases the capacitance, which is a very effective means for VLSI wiring. At the same time, plasma becomes more uniform and dry etching with less damage becomes possible as compared with the case of using AM wave power.

By changing the etching conditions, the taper angle, which is a very important condition for the etching shape, can be freely controlled. For example, when plasma is generated by an AM modulated wave and etching is performed, a small power is first applied to generate plasma and the etching is advanced. At this time, since the deposition on the side wall is small, side etching also progresses. However, if the plasma power is gradually increased with the lapse of time, deposition on the sidewall is promoted and side etching is limited. That is, the etching shape can be controlled to be tapered by changing the plasma power with time and controlling the side etching. Further, the taper angle can be controlled by appropriately combining etching and deposition. When the FM modulated wave power source is used, the same effect can be obtained by changing the frequency with time. The present invention can also be applied to a plasma CVD apparatus.

[0018]

As described above, according to the present invention, by using modulated wave power, plasma in various states can be generated without controlling the gas composition, gas flow rate, and chamber internal pressure. When this plasma generator is applied to a dry etching device and dry etching is performed, power is used when an AM modulated wave power source is used and an FM modulated wave power source is used without controlling the gas composition and chamber pressure. The frequency can be changed in a short time of a few milliseconds to control etching and deposition to obtain a desired etching shape.

[Brief description of drawings]

FIG. 1 is a schematic diagram of a dry etching apparatus according to a first embodiment of the present invention.

FIG. 2 is a schematic diagram of an AM modulated wave for explaining the operation in the same embodiment.

FIG. 3 is a schematic diagram of an FM modulated wave for explaining the operation in the same embodiment.

FIG. 4 is a schematic diagram of a conventional dry etching apparatus.

FIG. 5 is a schematic sectional view of an etching shape obtained by a dry etching method according to a second embodiment of the present invention.

FIG. 6A is a schematic cross-sectional view of a state where etching is progressing by the dry etching method according to the second embodiment of the present invention, and FIG. 6B is a schematic sectional view by the dry etching method according to the second embodiment of the present invention. (C) is a schematic cross-sectional view of a state in which the position is advanced, and FIG. 6C is a schematic cross-sectional view of a state in which etching and deposition are alternately performed by the dry etching method according to the second embodiment of the present invention.

[Explanation of symbols]

 1 Chamber 2 Signal Generator for Generating Modulated Wave Power 3 Amplifier 4 Cathode 5 Anode 11 Chamber 12 RF Wave Power Supply 13 Cathode 14 Anode 50 Resist 51 Substrate 52 Etching Material 53 Etching Section 54 Deposition Section

Claims (4)

[Claims] 1. A plasma generator in which a power source for generating a modulated wave is disposed on at least one of opposite electrodes, and the power source generates a plasma that changes with time. 2. The plasma generator according to claim 1, wherein the power supply is an amplitude modulation wave power supply or a frequency modulation wave power supply. 3. A plasma generating method characterized by applying modulated wave power to modulate ion energy. 4. The plasma generating method according to claim 3, wherein the applied modulation wave power is amplitude modulation wave generation power or frequency modulation wave generation power.