JP2002208587A - Plasma processing method and apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method and an apparatus, for a plasma treatment, wherein charging damage is suppressed, the yield of a semiconductor device is increased and a high-accuracy surface treatment can be executed. SOLUTION: A substrate electrode 115 is installed inside a treatment chamber 105. The apparatus is composed of a first high-frequency power supply which gives electromagnetic waves generating a plasma without applying electric power to the substrate electrode 115 and a second high-frequency power supply which is connected to the substrate electrode 115 and which applies a substrate bias voltage. The potential of a plasma potential in the outer circumferential part of the substrate electrode 115 is made higher than a plasma potential on a material 116 to be treated.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a plasma processing method and apparatus, and more particularly to a plasma processing method and apparatus suitable for performing surface treatment of a material to be processed such as a semiconductor using plasma.

[0002]

2. Description of the Related Art In the case of a plasma processing apparatus for performing an etching process, a process gas is efficiently ionized and activated to speed up the process, and a high-frequency bias power is supplied to a material to be processed to remove ions in the plasma. By making the light perpendicularly incident on the material to be processed, anisotropy is improved and highly accurate etching processing is realized. As a plasma processing apparatus for performing such a process, for example, an etching apparatus in a magnetic field UHF band as described in Japanese Patent Application Laid-Open No. 9-321031 is known.

In a magnetic field UHF band etching apparatus, a circular conductor plate is arranged at a position facing a sample to be processed in a vacuum vessel, an electromagnetic wave in the UHF band is supplied to the circular conductor plate, and a magnetic field is formed in the vacuum vessel. ECR plasma is generated, an electric field having a frequency different from that of the UHF band is superimposed on the circular conductor plate, the bias applied to the circular conductor plate is increased, the reactivity between the circular conductor plate and the reaction gas is increased, and the etching reaction is performed. In addition to generating a large number of active species contributing to the sample, a bias voltage is applied to the sample stage on which the sample to be processed is arranged, and the sample to be processed is plasma-processed. The apparatus includes a high-frequency power source applied to the sample stage, a UHF-band high-frequency power source applied to a circular conductor plate facing the sample stage, and a high-frequency power source different from the UHF-band high-frequency power source applied to the same circular conductor plate. Can be controlled independently.

In such a magnetic field plasma processing apparatus, "Charging Damage in Semiconductor Process" published by Realize Inc., 1996, edited by Moritaka Nakamura, pp. 9-2.
As described in 8, it has been known that the plasma impedance in the direction perpendicular to the magnetic field becomes larger than the plasma impedance in the direction parallel to the magnetic field, and there is a possibility of forming a potential distribution in the surface of the material to be processed.

[0005]

At present, as the degree of integration of a semiconductor integrated circuit is increasing, for example, a MOS (Metal Oxide Semiconductor) transistor, which is a typical example of a semiconductor device, is becoming thinner, and the gate is becoming thinner. In the processing of an oxide film, the problem of dielectric breakdown (charging damage) of a gate oxide film during plasma processing is becoming more serious. In the above-described plasma processing apparatus in the related art,
An electric field due to the high-frequency power applied to the material to be processed is formed between the sample stage and the side of the vacuum vessel at the ground potential, and the high-frequency power propagates in a direction crossing the magnetic field. For this reason, a potential distribution is formed in the surface of the material to be processed, and there is a possibility that charging damage that deteriorates the withstand voltage of the gate oxide film may occur.

An object of the present invention is to provide a plasma processing method and apparatus capable of suppressing charging damage, increasing the yield of semiconductor devices, and performing highly accurate surface treatment.

[0007]

SUMMARY OF THE INVENTION The object of the present invention is to provide a processing chamber to which a vacuum exhaust device is connected and whose inside can be depressurized, a gas supply device for supplying gas into the processing chamber, and a processing chamber provided in the processing chamber. A substrate electrode that can be mounted, a first high-frequency power supply that emits an electromagnetic wave that converts a gas supplied into the processing chamber into plasma into the processing chamber, and a second high-frequency power supply that is connected to the substrate electrode and applies a substrate bias voltage to a material to be processed. A high-frequency power supply, and an apparatus in which an auxiliary electrode that generates a positive peak voltage greater than the positive peak voltage of the high-frequency voltage applied to the substrate electrode is provided on the outer peripheral portion of the material to be processed, and the processing gas Is supplied to the inside of the processing chamber, the inside of which is evacuated to a predetermined pressure, and a bias voltage is applied to a substrate electrode provided in the processing chamber, so that ions in the plasma are exposed independently of the generation of the plasma. This is achieved by controlling the incident energy to the processing material and processing the material to be processed by setting the plasma potential at the outer peripheral portion of the substrate electrode higher than the plasma potential on the material to be processed. .

That is, by increasing the plasma potential at the outer peripheral portion of the electrode, the inside of the processing chamber having a low potential (ground potential), that is, the side wall of the inner wall of the vacuum vessel forming the processing chamber is changed from the surface of the material to be processed having a high potential. Since the formation of the circuit to be formed is inhibited, the potential difference generated in the surface of the material to be processed can be reduced. Thus, the potential distribution in the surface of the material to be processed due to the in-plane distribution of the plasma characteristics can be made uniform. Further, in the case where an antenna electrode facing the substrate electrode is provided in the processing chamber, even if a high-frequency voltage is applied to the substrate electrode, the plasma potential at the outer peripheral portion of the substrate electrode is high, so that the substrate electrode is transferred to the processing chamber wall functioning as an earth. , The current flowing between the antenna electrode and the antenna electrode functioning as the opposite ground electrode increases. That is, since the high-frequency current flows more between the electrodes facing each other than the inner wall of the processing chamber, the current in the direction crossing the magnetic field decreases, and the magnetic field is not affected by the plasma impedance in the direction perpendicular to the magnetic field. Since the plasma impedance in the horizontal direction to the magnetic field is uniform in the plane, the potential distribution in the surface of the workpiece due to the in-plane distribution of the plasma characteristics is further reduced, and the occurrence of charging damage can be suppressed. Accurate plasma processing becomes possible.

A third high-frequency power supply is connected to the antenna electrode, and the frequency of the first high-frequency power supply connected to the substrate electrode and the third high-frequency power supply connected to the antenna electrode are set to be the same frequency. By setting the phase difference of each high-frequency power supply to 180 ° ± 30 °, the positive high-frequency peak voltage of the substrate electrode can be reduced, and the plasma potential of the outer peripheral portion of the substrate electrode as viewed from the plasma potential on the workpiece is reduced. It can be even higher. This further amplifies the effect of the opposing electrode functioning efficiently as ground,
The occurrence of charging damage can be suppressed, and highly accurate plasma processing can be performed.

[0010]

[Embodiment 1] Hereinafter, the first embodiment of the present invention will be described.
The embodiment will be described with reference to FIGS. FIG. 1 is a longitudinal sectional view of an etching apparatus which is an embodiment of a plasma processing apparatus to which the present invention is applied. A processing chamber 104, a dielectric window 102 (for example, made of quartz), and an antenna electrode 103 (for example, made of Si) are installed on the upper part of a vacuum vessel 101 having an open top, and a processing chamber 105 is formed by sealing with an antenna cover 121. . A magnetic field generating coil 114 is provided on the outer peripheral portion of the processing chamber 104 and on the antenna cover 121. The antenna electrode 103 has a porous structure for flowing an etching gas, and is connected to a gas supply device 107. The vacuum container 101 has a vacuum exhaust port 106.
Is connected to a vacuum exhaust device (not shown).

The coaxial line 11 is provided above the antenna electrode 103.
1, a high-frequency power supply 108 (for example, a frequency of 450 MHz) is connected as a power supply for plasma generation via a matching unit 110 and a filter 109. Further, the antenna electrode 10
3, a coaxial line 111, a matching unit 119, and a filter 1
An antenna bias power supply 112 (for example, a frequency of 13.56 MHz) is connected via the power supply 13. The substrate electrode 115 on which the material to be processed 116 can be placed is the vacuum vessel 101.
A substrate bias power supply 117 (e.g., a frequency of 800 KHz) is provided at a lower portion and passes through a coaxial line 122 and a matching unit 118.
It is connected to the. Plasma is generated by the high-frequency power supply 108, and the plasma composition or plasma distribution is controlled by the antenna bias power supply 112.
Reference numeral 17 controls the amount of ions incident on the substrate. With such a configuration, there is an advantage that the plasma generation, the plasma composition / distribution, and the amount of ions incident on the processing target material 116 can be independently controlled. Further, in order to electrostatically attract the processing target material 116, the electrostatic chuck power supply 120 is connected to the substrate electrode 11.
5 is connected.

An auxiliary electrode 127 is provided on the outer periphery of the substrate electrode 115.
And the auxiliary electrode 127 is connected to the potential control circuit 12.
6, connected to the matching unit 118 via the coaxial line 122.

FIG. 2 shows a circuit configuration example of the potential control circuit 126. The potential control circuit 126 is a circuit that controls the waveform of the high-frequency voltage from the substrate bias power supply 117 to an arbitrary voltage waveform. A capacitor (C1) and a diode (D1) are connected in parallel between the auxiliary electrode 127 and the coaxial line 122. The diode (D1) is connected to the coaxial line 12 from the auxiliary electrode.
Connect so that the direction toward 2 is forward. When a high-frequency voltage is applied to the auxiliary electrode 127 by the substrate bias power supply 117, the circuit configuration suppresses the flow of electrons from the plasma to the auxiliary electrode 127, and the auxiliary electrode 127
To reduce the absolute value of the high frequency self-bias voltage (Vdc).

In the apparatus configured as described above, after the inside of the processing chamber 105 is depressurized by the vacuum exhaust device, the etching gas is introduced into the processing chamber 105 by the gas supply device 107 and adjusted to a desired pressure. High-frequency power having a frequency of, for example, 450 MHz, oscillated from the high-frequency power supply 108, propagates through the coaxial line 111, is introduced into the processing chamber 105 through the antenna electrode 103 and the dielectric window 102, and is provided with a magnetic field generating coil 114 (for example, The processing chamber 105 interacts with the magnetic field formed by the solenoid coil.
A high-density plasma is generated inside. In particular, when a magnetic field strength (for example, 160 G) that causes electron cyclotron resonance is formed in the processing chamber, high-density plasma can be efficiently generated. Further, high frequency power (for example, frequency of 13.56 MHz) is supplied from the antenna bias power supply 112 to the antenna electrode 103 via the coaxial line 111.
The workpiece 116 placed on the substrate electrode 115 is supplied with high-frequency power (for example, a frequency of 800 KHz) from the substrate bias power supply 117 and subjected to a surface treatment (for example, an etching process).

A high frequency power of, for example, 800 V peak-to-peak voltage (Vpp) is supplied to the substrate electrode 115 to generate a self-bias voltage (Vdc).
The 15 positive high-frequency peak voltages are fixed at about 100V to 200V. At this time, a high frequency is also applied to the auxiliary electrode 127, but since the diode (D1) is connected in the forward direction and the capacitor (C1) having a smaller capacity than the capacitor in the matching unit 118 is provided in parallel, When a positive voltage of a high-frequency voltage is applied to the auxiliary electrode, electrons attracted from the plasma by the diode (D1) cannot flow toward the matching unit 118, and
Since the capacitance of (C1) is small, the amount of electrons stored in the auxiliary electrode 127 is also small, and the absolute value of the self-bias voltage (Vdc) at the auxiliary electrode 127 is small. Since the electron current is suppressed and the absolute value of the self-bias voltage (Vdc) becomes smaller, the positive high-frequency peak voltage of the auxiliary electrode 127 becomes higher than that of the substrate electrode 115, and the plasma potential on the auxiliary electrode 127 becomes higher than the plasma potential on the substrate electrode 115. The plasma potential increases. FIG. 3 shows a plasma potential state when a high-frequency voltage is applied to the auxiliary electrode 127. By increasing the plasma potential on the auxiliary electrode 127, the potential distribution in the surface of the processing target material 116 is reduced, and the in-plane distribution of plasma characteristics can be made uniform. Furthermore, the substrate electrode 115 and the processing chamber 10
5 has a high plasma potential in the middle of the circuit formed between the processing container 104 and the processing container 104, and the current flowing through the circuit is reduced. More will be flowing.
As a result, there is an effect that the current in the direction crossing the magnetic field decreases, the occurrence of charging damage is suppressed, and a highly accurate etching process can be performed. Embodiment 2 A second embodiment of the present invention will be described with reference to FIG. In this figure, the same reference numerals as those in FIG. 1 denote the same members, and a description thereof will be omitted. The difference between this figure and FIG. 1 will be described below.
A coaxial line 111 and a matching device 1 are provided above the antenna electrode 103.
19. Antenna bias power supply 1 via filter 113
12 (for example, frequency 800 KHz) are connected. Further, a substrate electrode 115 on which the processing target material 116 can be placed
Is installed below the vacuum vessel 101, and a substrate bias power supply 117 (for example,
(Frequency 800 KHz). The antenna bias power supply 112 and the substrate bias power supply 117 are connected to the phase controller 125, and the antenna bias power supply 112
And the phase of the high frequency output from the substrate bias power supply 117 can be controlled. Here, the frequencies of the antenna bias power supply 112 and the substrate bias power supply 117 are the same.

When the phase difference between the high-frequency voltages applied to the antenna electrode 103 and the substrate electrode 115 is 180 ° ± 30 °, for example, when a positive voltage is applied to the substrate electrode 115, the antenna electrode 103 becomes negative. Is applied, ions are incident on the antenna electrode 103 but no electrons are incident on the antenna electrode 103, and a lot of electrons are present in the vicinity of the antenna electrode 103, and the opposing electrode has a function as a ground efficiently. When the phase difference is applied at 180 ° ± 30 °, the impedance from the substrate electrode 115 to the opposing grounding antenna electrode 103 is reduced. For example, a high-frequency power of 800V peak-to-peak voltage (Vpp) is applied. Then, the positive high frequency peak voltage of the substrate electrode 115 is fixed at 20 to 30V. The positive high-frequency peak voltage of the substrate electrode 115 of this embodiment is smaller than the positive high-frequency peak voltage of the substrate electrode 115 shown in the first embodiment, and the effect that the opposing electrode efficiently functions as ground is further amplified and realized. It is possible to do. By further increasing the plasma potential on the auxiliary electrode 127 from the viewpoint of the plasma potential on the substrate electrode 115, more high-frequency current flows between the electrodes facing each other than the side wall, so that the current in the direction crossing the magnetic field decreases and the charge increases. This has the effect of suppressing the occurrence of etching damage and enabling high-precision etching. [Embodiment 3] A third embodiment of the present invention will be described with reference to FIG. 2, the same reference numerals as those in FIG. 2 denote the same members, and a description thereof will be omitted. The difference between this figure and FIG. 2 will be described below.
A point that the diode (D1) of the potential control circuit 126 is connected in the opposite direction to that of FIG. 2 and the variable resistor R1 is additionally connected in series;
A point that the capacitor (C1) of the potential control circuit 126 is a variable capacitor, and a controller 128 for adjusting the resistance value of the variable resistor R1 and the capacity of the variable capacitor C1.
Is connected.

With this configuration, when a high-frequency voltage is applied to the auxiliary electrode 127 by the substrate bias power supply 117, for example, the resistance value of the resistor R1 is increased to suppress the flow of current, thereby reducing the current flow from the plasma. Auxiliary electrode 127
The flow of electrons into the auxiliary electrode 127 from the plasma can be increased by reducing the resistance value of the resistor R1 and making the current easier to flow.
Thus, the absolute value of the high-frequency self-bias voltage (Vdc) of the auxiliary electrode 127 can be controlled, so that the self-bias voltage (Vdc) is reduced, and the plasma on the auxiliary electrode 127 is actuated as in the first embodiment. The potential in the plasma is increased or the self-bias voltage (Vdc) is slightly increased so that the ions in the plasma are incident on the auxiliary electrode 127 so that the incident amount of the ions can be controlled. It is also possible to control the reaction with the active species in the plasma on the surface of the auxiliary electrode 127 by the incidence of ions on the auxiliary electrode 127. For example, in the oxide film etching using a CF-based gas, if the material of the auxiliary electrode 127 is made of high-purity silicon, the auxiliary electrode 1 is formed by a scavenging action of silicon.
By controlling the reaction of F radicals and CF radicals at 27,
In particular, it is possible to improve the etching uniformity in the outer peripheral portion of the wafer.

When a high frequency voltage is applied to the auxiliary electrode 127 by the substrate bias power supply 117, for example,
By suppressing the high frequency power to be applied by reducing the capacity of the capacitor C1, it is possible to suppress the inflow of ions from the plasma to the auxiliary electrode 127, and to increase the high frequency power to be applied by increasing the capacity of the capacitor C1. Thus, the flow of ions into the auxiliary electrode 127 from the plasma can be increased. Thus, the absolute value of the high-frequency self-bias voltage (Vdc) of the auxiliary electrode 127 can be controlled, so that the self-bias voltage (Vdc) is reduced, and the plasma on the auxiliary electrode 127 is actuated as in the first embodiment. Increase potential or self bias voltage (Vdc)
Is slightly increased so that the ions in the plasma
And the amount of ion incident can be controlled. By controlling the incidence of ions on the auxiliary electrode 127, it is also possible to control the reaction with the active species in the plasma on the surface of the auxiliary electrode 127. Thereby, the same effect as when the above-described variable resistor (R1) is controlled can be obtained.

As described above, it is effective to control the variable resistor (R1) and the variable capacitor (C1) individually, or to control the variable resistor (R1) and the variable capacitor (C1) in combination for more optimal control.

According to the third embodiment, the auxiliary electrode 127
By controlling the plasma potential above, there is an effect that the occurrence of charging damage can be suppressed and the uniformity of etching by the scavenging action can be improved.

In the above embodiments, the etching apparatus has been described. However, the present invention can be similarly applied to other plasma processing apparatuses for supplying high-frequency power to the substrate electrode, such as an ashing apparatus and a plasma CVD apparatus.

[0022]

According to the present invention, by making the plasma potential on the outer peripheral portion of the substrate electrode higher than the plasma potential on the material to be processed, the in-plane potential distribution of the material to be processed can be reduced. The function as a ground for both electrodes is improved, and more high-frequency current flows to the opposing electrode than the inner wall of the processing chamber in the processing chamber, reducing the current across the magnetic field and suppressing charging damage. Thus, a plasma processing method and apparatus capable of improving the yield of semiconductor devices and performing high-precision surface treatment can be provided.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view showing a plasma processing apparatus according to a first embodiment of the present invention.

FIG. 2 is a diagram showing a potential control circuit of the device of FIG.

FIG. 3 is a diagram showing a plasma potential when the potential control circuit of FIG. 2 is used.

FIG. 4 is a longitudinal sectional view showing a plasma processing apparatus according to a second embodiment of the present invention.

FIG. 5 is a diagram showing a potential control circuit of a plasma processing apparatus according to a third embodiment of the present invention.

[Explanation of symbols]

101: vacuum container, 102: dielectric window, 103: antenna electrode, 104: processing container, 105: processing chamber, 106:
Vacuum exhaust port, 107 gas supply device, 108 high frequency power supply, 109, 113 filter, 110 matching device, 1
11 ... coaxial line, 112 ... antenna bias power supply, 11
4: coil for generating a magnetic field, 115: substrate electrode, 116: material to be processed, 117: substrate bias power supply, 118, 119
Matching device, 120: electrostatic chuck power supply, 121: antenna cover, 122: coaxial line, 125: phase controller, 126
... potential control circuit, 127 ... auxiliary electrode, 128 ... control device.

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Seiichi Watanabe 794, Higashitoyoi, Katsumatsu-shi, Yamaguchi Prefecture F-term in Kasado Works, Hitachi, Ltd. FC11 FC15 4K030 CA04 CA12 FA02 FA04 HA16 JA16 JA17 JA18 JA19 KA15 KA19 KA20 KA30 KA41 5F004 AA01 AA06 BA14 BB07 BB11 BB14 BB23 BB32 BD01 CA03 CA06

Claims (6)

[Claims] A plasma is generated in a processing chamber in which a processing gas is supplied and the inside of the processing chamber is depressurized and evacuated to a predetermined pressure, and a bias voltage is applied to a substrate electrode provided in the processing chamber. In the plasma processing method of controlling the incident energy of ions in the plasma to the material to be processed independently and processing the material to be processed, the plasma potential at the outer peripheral portion of the substrate electrode is made higher than the plasma potential at the material to be processed. A plasma processing method, wherein the processing target material is processed. 2. A processing chamber to which a vacuum evacuation device is connected and whose inside can be decompressed, a gas supply device for supplying gas into the processing chamber, a substrate electrode provided in the processing chamber and capable of mounting a material to be processed, and A first high-frequency power supply for radiating an electromagnetic wave for converting a gas supplied into the processing chamber into plasma into the processing chamber, and a second high-frequency power supply connected to the substrate electrode and applying a substrate bias voltage to the material to be processed In the plasma processing apparatus comprising: an auxiliary electrode that generates a positive peak voltage larger than the positive peak voltage of the high-frequency voltage applied to the substrate electrode on the outer peripheral portion of the workpiece; A plasma processing apparatus characterized by the above-mentioned. 3. The plasma processing apparatus according to claim 2, wherein said first high-frequency power supply is connected to said auxiliary electrode via said substrate electrode and a potential control circuit. 4. The plasma processing apparatus according to claim 3, wherein an antenna electrode for radiating an electromagnetic wave for plasma generation is provided in the processing chamber so as to face the substrate electrode, and a third high frequency power supply is connected to the antenna electrode. A plasma processing apparatus, wherein the first high-frequency power supply connected to the substrate electrode and the third high-frequency power supply connected to the antenna electrode have the same frequency, and a means for controlling the phase of each high-frequency power supply is provided. . 5. A plasma is generated in a processing chamber in which a processing gas is supplied and the inside of the processing chamber is evacuated to a predetermined pressure, and a bias voltage is applied to a substrate electrode provided in the processing chamber. In the plasma processing method of controlling the incident energy of ions in the plasma to the material to be processed independently and processing the material to be processed, the plasma potential at the outer peripheral portion of the substrate electrode is made higher than the plasma potential at the material to be processed. A plasma processing method comprising: increasing the height of the substrate; and causing a scavenging effect at an outer peripheral portion of the substrate electrode to process the material to be processed. 6. A processing chamber to which a vacuum evacuation device is connected and whose inside can be depressurized, a gas supply device for supplying a gas into the processing chamber, a substrate electrode provided in the processing chamber and capable of mounting a material to be processed. A first high-frequency power supply for radiating an electromagnetic wave for converting a gas supplied into the processing chamber into plasma into the processing chamber, and a second high-frequency power supply connected to the substrate electrode and applying a substrate bias voltage to the material to be processed And a positive peak voltage higher than the positive peak voltage of the high-frequency voltage applied to the substrate electrode is generated, and ions in the plasma are injected to activate the plasma in the plasma. A plasma processing apparatus, wherein an auxiliary electrode made of a material that reacts with a seed is provided on an outer peripheral portion of the material to be processed.