JP3063761B2 - Plasma processing method and apparatus - Google Patents

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 etching and film-forming a sample such as a semiconductor element substrate in a processing chamber where plasma is generated. It is about.

[0002]

2. Description of the Related Art As a technique for etching a sample such as a semiconductor element substrate by using microwave plasma, for example, a technique described in Japanese Unexamined Patent Application Publication No. 56-13480, which discloses a method of applying a microwave electric field and a magnetic field. A technique in which an etching gas is converted into plasma by a synergistic action and a sample is etched using the plasma.
No. 636, etc., a technique for converting a film-forming gas into a plasma by synergistic action of a microwave electric field and a magnetic field and using the plasma to form a film on a sample. A technique for converting an etching gas into a plasma by a microwave electric field and etching a sample using a gas plasma as described in, for example, JP-A-5574, and a technique described in, for example, JP-A-62-218575. In addition, a technique is known in which a film-forming gas is turned into plasma by a microwave electric field, and a sample is formed into a film using the plasma.

Incidentally, a magnetron (magnet tube) is usually used as a microwave power supply, and a direct current or a high voltage whose commercial frequency is smoothed is used as an output of a driving device thereof.

[0004]

In the processing of a sample using microwave plasma, it is strongly desired to increase the processing speed. However, the above-mentioned conventional technique cannot sufficiently satisfy this demand. is not.

An object of the present invention is to provide a plasma processing method and apparatus capable of improving the processing speed of a sample by increasing the electron temperature of plasma.

[0006]

The object of the present invention is to provide a processing chamber in which plasma is generated, an exhaust means for evacuating the processing chamber to a reduced pressure, a means for introducing a processing gas into the processing chamber, and a processing gas plasma. A pulse discharge in which the intensity of the electromagnetic field to be generated is generated in a pulsed manner, the cycle of generating the pulse is set to 1 ms or less, the pulse width is set to 100 μs or less, and the pulse duty for generating the pulse is 1 to 50%. Means, a sample stage for holding the sample in the processing chamber, and a bias power supply connected to the sample stage and applying a bias voltage in synchronization with the pulse during the processing of the sample. Of the electromagnetic field for generating plasma in a pulse-like manner, and the period for generating the pulse is 1 m.
s or less, the pulse width of the pulse is 100 μs or less, and the pulse duty for generating the pulse is 1 to 50.
% As pulse discharge in the processing chamber,
This is achieved by applying a bias voltage to the sample in synchronization with the pulse discharge during the processing of the sample, thereby processing the sample placed in the processing chamber.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION Measures for improving the plasma processing speed of a sample are categorized into two measures of increasing the electron temperature of the plasma and increasing the plasma density. Among them, the electron temperature of the plasma can be increased by lowering the pressure of the processing gas in the processing chamber or reducing the diameter of the processing chamber. However, when the pressure of the processing gas in the processing chamber is reduced, the plasma density is reduced, and at a certain pressure or lower, the plasma processing speed is also reduced. Further, the diameter of the processing chamber is limited by the size of the sample to be processed, and therefore, the diameter of the processing chamber cannot be sufficiently reduced.

By the way, a decrease in the pressure of the processing gas in the processing chamber and a reduction in the diameter of the processing chamber correspond to an increase in the loss at the plasma wall. Therefore, if a pulse discharge is generated to forcibly increase the loss at the wall during the discharge suspension period, an increase in the electron temperature of the plasma can be expected.

An embodiment of the present invention will be described below with reference to FIGS. FIG. 1 is a configuration diagram of a so-called magnetic field type microwave plasma etching apparatus.
Microwave source driving device 2, waveguides 3 to 5, quartz chamber 6 for vacuum sealing, magnetic field generating coil 7, coil driving device 8, sample table 9, bias power source 10, sample 11, vacuum vessel 12, gas introduction pipe 13, a gas introduction valve 14, an exhaust pipe 15, and the like.

In FIG. 1, when a magnetron tube (magnetic tube) is used as the microwave generating source 1, the output high voltage current I and high voltage E of the microwave driving device 2, the output voltage P _B of the bias power source 10, the coil driving Figure 2 the output current _{I C} of the device 8
Shown in

[0011] The SiO ₂ used as a sample 11, CnFm or CnHlFm as a gas (l, n, m is an integer)
When the etching is performed by using the magnetron, the frequency of the magnetron tube is 2.45 GHz, the frequency of the bias power supply 10 is 2 MHz, and the current of the coil 7 causes electron cyclotron resonance near the sample 11 placed on the sample stage 9. Set as follows. The gas pressure is 0.01 Pa to
A relatively low pressure range of 10 Pa is preferred.

The etching period of the sample 11 is, for example, 2
In the first half (several + seconds), etching at high electron temperature using pulse discharge (mode 1) is performed, and in the second half (several seconds-
20 seconds), normal low damage etching (mode 2) is performed.

In mode 1, the half width T of the pulse current
Current pulse control is performed at _W = 10 μs and pulse period T _R = 30 μs. Current I _L of the period between pulses of the current pulse
Is effective when the value is 0. On the other hand, the discharge may be unstable. In this case, the discharge can be stabilized by flowing a small current of (I _L / I _H ) ≦ 0.1 or less. The voltage E applied to the magnetron tube at this time is
Does not change much (E _H / E _L ≧ 0.7). The output of the bias power supply 10 is set high in mode 1 and low in mode 2.

[0014] current applied to the coil 7, may be constant during the entire processing period, but as shown in I _C in Figure 2, to increase substantially corresponding to the period current is large applied to the magnetron tube in mode 1, the magnetron By reducing the current applied to the tube substantially corresponding to the period during which the current is small, the etching processing speed can be improved.

According to the present embodiment, by using pulse discharge, the etching process speed can be improved by raising the electron temperature, and by using the process of the steady discharge, high speed and low damage can be achieved. Etching can be performed.

That is, when a strong discharge is started in the state of a weak discharge or no discharge, a large amount of energy is supplied to the discharge at the start of the discharge, and the electron temperature of the discharge increases. After a predetermined time, when the discharge is returned to a weak state or a non-discharge state, electrons, charged particles, and the like generated by the strong discharge are attenuated by recombination at the container wall. For this reason,
When a strong discharge is started, a large energy is supplied to start the discharge, and the electron temperature of the discharge increases. As described above, by increasing the electron temperature of the discharge by the pulse discharge, much energy is given to the electrons and the charged particles, so that the etching processing speed can be improved.
When pulse discharge is used, damage to the sample tends to increase. Therefore, first, after performing a high-speed etching process by pulse discharge, a low-speed, low-damage etching process by a normal steady-state discharge is performed for a short time, thereby performing a high-speed, low-damage etching process. .

[0017] as a half-width _{T W} of the pulse current, 100
The effect is large when μs or less, and the above effect by pulse discharge is recognized up to about 1 ms. The smaller pulse width is considered to be effective up to about several tens of ns. However, since a filter is provided in the magnetron tube of the continuous wave used, in this case, the driving of T _W = 1 μs or less is performed. Was difficult. Further, the pulse duty (T _W / T _R)
× 100) (%) is preferably 1% to 50%. Further, in the above-described embodiment, the case of two modes has been described. However, it is needless to say that the number of modes can be increased and the mode can be smoothly changed by gradually changing the pulse duty.

Further, if the electron cyclotron resonance magnetic field is reduced during the discharge pause period, the binding force on the electrons by the magnetic field is reduced, and the loss during this period can be increased. It is convenient for you.

Further, if a bias power supply applied to the sample stage is applied so as to accelerate only ions during a pulse discharge period or within a predetermined time after the discharge is stopped, only ions having high energy reach the sample. Therefore, the etching processing speed can be improved.

Further, in the apparatus configuration of the above embodiment, for example, a mixed gas of Ar, SiH ₄ and O ₂ is used as a gas,
By processing at a gas pressure of 0.001 Pa to 10 Pa, it is possible to deposit a high-speed, low-damage SiO ₂ film.

FIG. 3 shows an application example in which no magnetic field coil is used. A metal plate 17 with a hole is placed between the quartz chamber 6 for vacuum sealing and the sample mounting table 9, and a discharge occurs in a space between the quartz chamber 6 for vacuum sealing and the metal plate 17 with hole, so The particles can move into the space of the sample, but the charged particles are blocked by the perforated metal plate 17. Therefore, the sample 11
Plasma treatment with uncharged particles. O ₂ as gas
+ CF ₄ mixed gas, gas pressure 1 Pa-100
By setting the pressure to Pa and using the method of FIG. 2, ashing processing with low damage and high speed can be performed.

When plasma treatment with ions is required as in the etching of SiO ₂ , the metal plate 1 with holes is required.
It is preferable that 7 is not provided.

In order to improve the uniformity of the plasma treatment in the sample, a stirrer 21 for rotating or changing a metallic, high dielectric or high magnetic material is provided with a microwave electromagnetic field. It is effective when used for parts.

FIG. 4 shows an embodiment of a configuration for shifting from mode 1 to mode 2 in FIG. The wire mesh which does not transmit the microwave electromagnetic field but transmits the light is also provided with the window 18, the photoelectric conversion is performed by the light detection unit 19 having a spectral function, and the end of the processing is determined by the signal processing unit 20. 2, a mode switching signal 22 for switching from mode 1 to mode 2 and an end signal 2 for terminating mode 2
3 is output. During the signal processing section 20 is a portion for smoothing a signal that varies the pulse period T _R and internal organs. As a method for extracting light via a microwave electromagnetic field, in addition to the above-described method using a wire mesh window, an optical fiber made of a material (for example, quartz) with low loss due to microwaves can be used.

The mode switching and termination can be performed not only by changing the light but also by the time from the start of discharge.

FIG. 5 shows an embodiment of a microwave source driving device for generating a pulse current. High pressure (3-4.
High voltage DC power supply unit 2-1 that controls slow changes at 5 KV)
And a cascade connection of a pulse power supply section 2-2 for generating a pulse. The output current of the high-voltage DC power supply 2-1 is stored in the high-voltage capacitor 2-15,
The pulse of the pulse power supply unit 2-2 is superimposed on the voltage of.
The high frequency blocking coil 2-1 so that the output of the pulse power supply 2-2 does not affect the output of the high voltage DC power supply 2-1.
2, 2-13 and 2-14 are provided. Pulse power supply 2
-2, the high-voltage capacitor 2-5, and the high-frequency blocking coils 2-12, 2-13, and 2-14 are preferably installed near the microwave source 1.

The signal from the current detection resistor 2-3 is amplified by the error amplifier 2-5 through the low current section / average current detection circuit 2-4, and the difference between the low current section / average current setting value is amplified. , High-voltage current power supply 2-1.

On the other hand, the difference between the signal from the current detection resistor 2-3 and the peak current set value is amplified by the error amplifier 2-7 via the peak detector 2-6, and the pulse source 2-
8 is input to the pulse power supply section 2-2 via the mode switch 2-10. In the pulse power supply unit 2-2, a current pulse is generated by a transistor, boosted by a high-frequency boosting transformer, and output. The low current section / average current detection circuit 2-4 operates in a pulse discharge mode (FIG. 2).
In the mode 1), the operation of detecting and holding the current of the IL portion in FIG. 2 is performed, and in the steady discharge mode (mode 2 in FIG. 2), the operation of the low-pass filter is performed. In the steady discharge mode, the mode switch 2-10 is switched to the earth side. When the end signal is input, the switch 2-
16, 2-17 are switched to the ground side. The heater power supply 2-11 is a power supply for supplying a heater current of the microwave generation source 1.

FIG. 6 shows another embodiment of a microwave source driving device for generating a pulsed current, and FIG. 7 shows waveforms of main parts thereof. Pulse repetition of about 10 KHz or more 2
On the basis of the two pulse signal sources 2-28 and 2-29, a high voltage is supplied by a variable low-voltage DC power supply 2-20, a coil 2-21, a pulse driving transistor 2-23, a capacitor 2-24, and a step-up transformer 2-22. The voltage pulse is applied to the microwave source 1 after voltage doubling and rectification by the high voltage capacitor 2-25 and the high voltage diodes 2-26 and 2-27. The voltage E and the current I between the anode heaters of the microwave source 1 are shown in FIG. In mode 1, the pulse duty T
The _W1 / _{T R1} is small pulse source 2-29, to generate a narrow pulse current width, added to the microwave source 1. In the mode 2 for low damage, the pulse duty T _W2 / T
A wide pulse current is generated using the pulse source 2-28 having a large _R2 and applied to the microwave source 1.

In mode 1, the signal from the current detection resistor 2-3 is amplified via a peak detector, and the difference from the peak current set value is amplified by an error amplifier 2-7. Control.

In mode 2, a signal from the current detection signal is amplified by an error amplifier 2-5 through an average current detector 2-30 via an average current detector 2-30, and the voltage of a variable low voltage DC power supply 2-20 is amplified. Control.

Although several embodiments have been described above, the present invention is not limited to these embodiments. The present invention is also applicable to any apparatus that performs plasma processing on a sample using microwaves.

The present invention has a portion for generating plasma having a high electron temperature by periodically generating pulsed microwave power and generating plasma in addition to various gases. The cycle of the wave power is limited to 1 ms or less, and the duty of the pulse is limited to 50% or less.

[0034]

According to the present invention, there is an effect that the electron temperature is increased by using the pulse discharge, and the plasma processing can be performed at a high speed.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a magnetic field type microwave plasma etching apparatus according to an embodiment of the present invention.

FIG. 2 is a schematic waveform diagram of an output high-voltage current, a high-voltage, an output power of a bias power supply, and an output current of a coil driving device of the microwave source driving device in the device of FIG.

FIG. 3 is a configuration diagram of a non-magnetic field type microwave plasma device according to another embodiment of the present invention.

FIG. 4 is a configuration diagram of an embodiment of a mode transition configuration in FIG. 2;

FIG. 5 is a circuit configuration diagram of an embodiment of a microwave source driving device.

FIG. 6 is a circuit configuration diagram of another embodiment.

FIG. 7 is a schematic waveform diagram of a main part of the microwave source driving device of FIG. 6;

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Microwave source, 2 ... Microwave source drive, 8 ... Coil drive, 10 ... Bias power supply.

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification code FI H01L 21/3065 H01L 21/31 C 21/31 21/302 AB (56) References JP-A-64-184299 (JP, A JP-A-63-80539 (JP, A) JP-A-1-236629 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H05H 1/46 C23C 16/517 C23F 4 / 00 H01L 21/205 H01L 21/3065 H01L 21/31

Claims (6)

(57) [Claims] The method includes the steps of: generating a plasma and applying a bias voltage to a sample; generating an intensity of an electromagnetic field for generating a plasma in a pulse form; and setting a cycle for generating the pulse to 1 ms or less. 100μs pulse width
The pulse duty for generating the pulse is 1
A pulse discharge is generated in the processing chamber at about 50%, and a bias voltage is applied to the sample in synchronization with the pulse discharge during the processing of the sample to process the sample placed in the processing chamber. Plasma processing method. 2. The plasma processing method according to claim 1, wherein said plasma is ECR plasma. 3. The plasma processing method according to claim 2, wherein the magnetic field for generating the ECR plasma is set to the ECR plasma.
A plasma processing method synchronized with an electromagnetic field for plasma generation. 4. The plasma processing method according to claim 1, wherein the bias voltage is applied during a period of a pulse discharge or within a predetermined time after a pause in the discharge. 5. A processing chamber in which plasma is generated, exhaust means for reducing and evacuating the processing chamber, means for introducing a processing gas into the processing chamber, and an electromagnetic field for generating plasma of the processing gas. The intensity is generated in a pulse form, the period for generating the pulse is set to 1 ms or less, and the pulse width is set to 1
A pulse discharge generating means having a pulse duty of 1 to 50% for generating the pulse, a sample stage for holding the sample in the processing chamber, and a pulse generator connected to the sample stage for processing the sample. A bias power supply for applying a bias voltage in synchronization with the bias power supply. 6. A plasma processing apparatus according to claim 5, wherein said pulse discharge generating means uses ECR plasma discharge.