JP2675000B2 - Plasma processing equipment - Google Patents

Description

The present invention relates to the manufacture of semiconductor devices using low-temperature plasma, and particularly to a plasma processing apparatus suitable for high-speed processing of various technologies such as CVD, etching, sputtering, and ashing. Regarding [Prior art] An apparatus using low-temperature plasma is roughly classified into an apparatus using a technique of generating a plasma by applying a high frequency voltage of about 10 KHz to 30 MHz to one of parallel plate electrodes in a vacuum (Semiconductor Research) 18; P121-P170, Semiconductor Research 19; P225-P267)
And a technique using a technique of introducing a 2.45 GHz microwave into a vacuum chamber to generate plasma. Conventionally, the technique using parallel plate electrodes has been mainly used among them. On the other hand, with the miniaturization of semiconductor devices, there has been a problem that the device characteristics are affected by the impact of ions generated during plasma processing. Further, it is required to increase the processing speed in order to improve the processing capacity. When increasing the processing speed, simply increasing the density of plasma or the concentration of radicals (active particles immediately before ionization) is not sufficient. In dry etching by plasma treatment and plasma CVD, ion energy plays an important role. In the case of dry etching, if the energy of the ions is too large, the underlying film is shaved or affects the crystal structure, and the device characteristics are degraded. On the other hand, if it is too small, the polymer formed on the etched surface is not sufficiently removed, and the etching rate decreases, or conversely, the polymer protective film is not formed and the side surface of the pattern is etched, resulting in poor pattern dimensional accuracy. The problem occurs. In plasma CVD, too, the ion energy affects the film formation such that the film composition becomes coarse when the energy of the ions is weak, and becomes dense when the energy is strong. Therefore, increasing the density of the plasma and appropriately controlling the ion energy are indispensable for future plasma processing. When plasma is generated by microwave,
Even if the microwave generated by the magnetron is radiated to the low-pressure plasma generation chamber, the electric field strength of the microwave is not sufficient, so sufficient energy is not supplied to the electrons,
It is difficult to generate plasma. Therefore, in order to generate plasma by microwaves, there is a method of supplying energy to electrons by matching the frequency of the microwave with the cyclotron frequency at which the electrons rotate on a plane perpendicular to the magnetic field and supplying energy to the electrons in a resonant state, and There are two methods of supplying the energy to the electrons by radiating the microwaves to the resonator to increase the amplitude of the microwave and increasing the electric field strength. The former is called a magnetic field microwave or Electron Cyclotron Resonance (hereinafter referred to as ECR) method as described in JP-A-56-13480, and the latter is, for example, a special method. It is described in Kaisho 56-96841. [Problems to be Solved by the Invention] As mentioned earlier, the energy of ions plays an important role in plasma processing. In the prior art, in the ECR method, as shown in JP-A-56-13480, when a high-frequency voltage is applied to an electrode on which a substrate is mounted, there is no ground electrode on the opposite side of this electrode,
The high-frequency current flows between the surrounding processing chambers, and the effect of ion energy on the substrate is strong around the substrate and weak at the central portion, so that the entire substrate cannot be processed under uniform conditions. In the method using a cavity resonator, plasma is generated in the resonator, so when plasma is generated,
Since the wavelength of the microwave changes depending on the density of the plasma, there is a problem that the resonance condition is not satisfied and the plasma becomes unstable. That is, since the resonance condition is satisfied until the plasma is generated, the electric field strength of the microwave is increased and the plasma is generated. However, when plasma is generated and the plasma density is increased, the wavelength of the microwave changes and the resonance condition is no longer satisfied, and the electric field intensity decreases. Then, the supply of energy to the electrons decreases, and the plasma density decreases. When the plasma density decreases, the resonance condition is satisfied, and the plasma density increases again. Due to such a phenomenon, it is difficult to stably generate plasma. In addition, if a high-frequency voltage application electrode is provided in the cavity resonator to control the energy of ions entering the substrate from these plasmas, microwave reflection occurs and the plasma becomes more unstable. was there. The object of the present invention is to solve the above-mentioned problems of the prior art, to generate stable and high-density plasma, to control the energy of the ions incident on the substrate, and to make the ions of uniform energy incident on the entire substrate. It is to provide a plasma processing apparatus that enables the above. [Means for Solving Problems] The above-described object is to provide a plasma processing apparatus with a processing chamber means that is provided with a mounting portion for mounting a substrate to be processed therein, and is evacuated to a vacuum and maintained at a predetermined pressure. A first high frequency power supply means for generating a first high frequency power, a plasma generating means connected to the first high frequency power supply means for generating a discharge by the first high frequency power inside the processing chamber means, A second high frequency power having a frequency lower than the first high frequency power
High frequency power supply means, power applying means connected to the second high frequency power supply means for applying the second high frequency power to at least a part of the plasma generating means, the first high frequency power means and the second high frequency power. First electrically separated from the means
This is achieved by including the high-frequency power and the second high-frequency power, and insulating and separating means for preventing the high-frequency power and the second high-frequency power from affecting each other when they occur. [Operation] In the conventional ECR method, microwaves are directly radiated from the opening of the waveguide to the plasma generation chamber. Therefore, if a high frequency electrode is installed between the plasma generation chamber and the opening of the waveguide, the microwave is reflected by the high frequency electrode and cannot be supplied to the plasma generation chamber. In the present invention, the end face of the waveguide is closed, a conductor having a slit for radiating a microwave is provided on the end face, and a choke flange and an electrically insulating member are provided between the conductor and the waveguide. An object is inserted and a high frequency voltage is applied to the conductor. Therefore, the microwave does not leak from the waveguide to the outside due to the choke flange, and the high frequency voltage does not adversely affect the magnetron that is the source of the microwave due to the insulator, so that the high frequency voltage is stabilized in the conductor. Can be applied. Further, since the opening area of the slit can be formed to be about 1/3 of the surface area of the conductor, when a high-frequency voltage is applied to the conductor, a high-frequency current flows evenly between the conductor and the substrate, so that the ion The effect of can be generated uniformly over the entire surface of the substrate. Further, since a sufficient amount of microwave can be supplied between the conductor and the substrate through the slit, high density plasma can be generated between the conductor and the substrate. On the other hand, when a cavity resonator formed of a conductor having a slit is connected to the waveguide, microwaves whose amplitude is increased by resonance in the cavity resonator are radiated to the plasma generation chamber through the slit. It is possible to generate high-density plasma without using a cavity resonator structure in the plasma generation chamber as in the prior art. Even in this case, a choke flange is inserted between the cavity resonator and the conductor, and the inserted portion is electrically insulated so that a high frequency voltage can be stably applied to the slit surface facing the substrate. it can. Therefore, the electrode structure using the conductive plate according to the present invention is not restricted by the relationship with the cavity resonator as in the conventional case. Further, since no plasma is generated in the cavity resonator, there is no change in the resonance state, and the plasma can be generated stably. In addition, since a choke flange and an electrically insulating insulator are inserted between the cavity resonator and the waveguide or conductor and a high frequency voltage is applied to the conductor, it is possible to configure a high frequency electrode parallel to the substrate. The effect of ions can be evenly generated on the entire surface of the substrate. [Embodiment] Hereinafter, FIG. 1 and FIG. 2 which are one embodiment of the present invention will be described. As shown in FIG. 1, the cavity resonator 1 is an E ₀₁ mode cavity resonator, and a microwave is supplied from a magnetron 3 through a waveguide 2. A choke flange 4 and an insulator 9 are inserted in the middle of the waveguide 2. In addition, the waveguide 2 improves the coupling with the E ₀₁ mode, so the cavity resonator 1
It is attached to the eccentric position. The cavity resonator 1 has a ceramic plate 6 on the opposite side of the waveguide 2.
And a conducting plate 7 having a slit 7a is fixed, and a plasma generating chamber 8 is connected below the conducting plate 7 via an insulator 9. The ceramic plate 6 is installed to seal the inside of the cavity resonator 1 in a vacuum. The cavity resonator 1 is electrically connected to the high frequency power supply 10. The conductive plate 7 having the slits 7a has a plurality of slits 7a which are opened in a ring shape at right angles to the electric field of the E ₀₁ mode as shown in FIG. The length of each slit 7a, when using a microwave of 2.45GHz, in order to improve the radiation of the microwave from the slit 7a, it is formed with a dimension of 60mm or more corresponding to 1/2 wavelength of the microwave. There is. The plasma generation chamber 8 (FIG. 1) is provided with a substrate mounting table 11, a gas supply pipe 12, and a gas exhaust pipe 13, and the substrate mounting table 1
A substrate 14 is placed on top of 1. A gas for plasma processing can be supplied to the gas supply pipe 12 from a gas source (not shown) at a set flow rate. A vacuum exhaust pump (not shown) is connected to the gas exhaust pipe 13 so that the inside of the plasma generation chamber 8 can be controlled to a pressure of 1 to 10 ^-3 Torr. The magnetron 3 is operated to oscillate a microwave, which is supplied to the cavity resonator 1 by the waveguide 2. The energy of the microwave whose amplitude is increased in the cavity resonator 1 is radiated to the plasma generation chamber from the slit 7a of the conductive plate 7. The amplitude of the microwave radiated to the plasma generation chamber 8 is the cavity resonator 1
Therefore, the plasma is turned on and maintained even if the plasma generation chamber 8 does not have the cavity resonator structure. Further, when a voltage is applied to the cavity resonator 1 from the high frequency power supply 10, the high frequency energy is injected into the plasma in the plasma generation chamber 8 to increase the plasma potential. As a result, the sheath potential between the plasma and the substrate 14 is increased, and the energy of ions entering the substrate 14 is increased,
By setting the applied high frequency voltage to an appropriate value,
The substrate 14 can be plasma treated with the desired ion energy. Further, since the choke flange 4 is inserted on the cavity resonator 1 side of the waveguide 2, even if the inserted portion is electrically insulated, the microwave does not leak outside. In addition to this, since the insulator 9 is inserted in the inserted portion, even if a high frequency voltage is applied to the cavity resonator 1, the magnetron 3 is not adversely affected. Since the plasma processing apparatus according to the present invention is configured as described above, application to etching and plasma CVD will be described next. First, the case of etching will be described. The etching gas is supplied from the gas supply pipe 12 and exhausted from the gas exhaust pipe 13 to maintain the inside of the plasma generation chamber 8 at a constant pressure. A microwave plasma is generated between the substrate and the substrate. In this case, since the microwave directly acts on the electrons in the plasma, the potential difference between the plasma and the conducting plate 7 is 20.
It is a level of ~ 30V. Then, the substrate 14 to be processed is placed on the substrate platform 11,
When a high-frequency voltage is applied from the high-frequency power source 10 to the cavity resonator 1, the high-frequency current flows evenly between the conducting plate 7 and the substrate 14 because the substrates 7 and 14 are installed in parallel. Therefore, the electric field generated between the conductive plate 7 and the plasma becomes uniform, and the ions of the etching gas of uniform energy are incident on the entire surface of the substrate 14 under the control of the high frequency voltage. The ions of the etching gas and the active species (radicals) of the etching gas excited in the plasma react with the film to be processed on the substrate 14 to advance the etching. At this time, since the energy of the incident ions is uniform, uniform etching can be performed on the entire surface of the wafer. Next, application of this apparatus to plasma CVD will be described. A mixed gas of SiH ₄ and N ₂ , N ₂ O is supplied from the gas supply pipe 12, N ₂ O and SiH ₄ are decomposed by plasma to generate SiO, and a film is formed on the substrate 14. Further, the film quality is controlled by the incidence of ions from the plasma. At this time, since the incident energy of ions can be equalized, a uniform film can be formed on the entire surface of the wafer. As described above, according to the present invention, the effect of ions essential for plasma processing can be equalized, and stable plasma can be generated. Next, FIG. 3 showing another embodiment of the present invention will be explained. As shown in FIG. 3, the conducting plate 7'has a slit 7a 'formed at a position facing the substrate 14, and a minute gap 7b' is formed at the outer peripheral portion of the slit 7a 'at the tip and the facing surface of the cavity resonator 1. Forming an inner convex portion 7c 'and an outer convex portion 7e' with a space 7d 'on the outer periphery of the inner convex portion 7c', and connecting the minute gap 7'b and the void 7'b. A choke flange 4'is formed by the space 7'd, and a ring-shaped insulator 5 is inserted between the tip of the outer convex portion 7e 'and the cavity resonator 1. Further, the high frequency power supply 10 applies a high frequency to the substrate mounting table 11 or the conductive plate 7 ′ by the changeover switch 15. Therefore, since the plasma processing apparatus in the present embodiment is configured as described above, in addition to the plasma processing according to the above-described embodiments, plasma can be used to clean the conducting plate 7'and the substrate mounting table 11. That is,
CF ₄ as the processing gas is introduced from the gas inlet into the plasma generation chamber 8
It is introduced inside to generate CF ₄ . In this case, when a high frequency is applied to the conductive plate 7'from the high frequency power source 10 by the change-over switch 15, high density plasma is generated by the microwaves and at the same time the ion energy is increased, so that the conductive plate 7'can be cleaned at high speed. . When a high frequency is applied to the substrate mounting table 11, the substrate mounting table 11 can be plasma cleaned at a high speed for the same reason as above. [Advantages of the Invention] According to the present invention, since plasma is not generated in the cavity resonator, there is an effect that the resonance state does not change and the plasma can be stably generated. Further, according to the present invention, since a high frequency voltage can be applied between the substrate and the plasma, there is an effect that the sheath potential between the substrate and the plasma can be controlled and the energy of the ions incident on the substrate can be controlled to an appropriate value. Further, since the substrate and the conductive plate are parallel to each other, it is possible to make the ions evenly incident on the substrate and to perform uniform plasma treatment.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a sectional view of a plasma processing apparatus which is an embodiment of the present invention, FIG. 2 is an enlarged plan view of a conductive plate shown in FIG. 1, and FIG. It is sectional drawing of the plasma processing apparatus which is another Example. 1 ... Cavity resonator 2 ... Waveguide 3 ... Magnetron 4 ... Choke flange 5,9 ... Insulator 6 ... Ceramics plate 7,7 '... Substrate 8 ... Plasma generation chamber 10 ... High-frequency power source 11 …… Substrate mounting table 12 …… Gas supply pipe 13 …… Gas exhaust pipe 14 …… Substrate 15 …… Changeover switch

Continuation of front page    (56) References JP-A-62-31112 (JP, A)                 JP 59-41838 (JP, A)                 JP-A-62-97328 (JP, A)

Claims (1)

(57) [Claims] A processing chamber means that has a mounting portion for mounting a substrate to be processed therein, is evacuated to a vacuum, and is maintained at a predetermined pressure; a first high-frequency power supply means that generates a first high-frequency power;
Plasma generation means connected to the high frequency power supply means to generate discharge by the first high frequency power inside the processing chamber means, and second high frequency power having a frequency lower than the first high frequency power. Second high frequency power supply means, power application means connected to the second high frequency power supply means for applying the second high frequency power to at least a part of the plasma generation means, and the first high frequency power means Insulating isolation means for electrically separating the second high frequency power means from each other and preventing the first high frequency power and the second high frequency power from affecting each other when they are generated. A plasma processing apparatus characterized by the above. 2. The first high frequency power supply means is a microwave power supply for generating microwave power, the plasma generation means includes a conductive plate having a slit portion, and the plasma generation means is supplied from the first high frequency power supply means. The plasma processing according to claim 1, wherein a plasma is generated inside the processing chamber means by radiating microwave power to the inside of the processing chamber means from the slit portion of the conducting plate. apparatus. 3. The plasma processing apparatus according to claim 2, wherein the power applying means applies high frequency power to the conductive plate.