JP3116762B2 - Plasma etching equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a plasma etching apparatus, and more particularly, to a plasma etching apparatus used for etching a semiconductor wafer or the like.

[0002]

2. Description of the Related Art FIG. 5 shows an electron cyclotron resonance (EC).
R: Electron Cycrotron Resonance (R) is a cross-sectional view schematically showing a conventional plasma etching apparatus of this type using excitation, in which 21 denotes a reaction vessel. A substantially cylindrical plasma generation chamber 22 is formed above the reaction vessel 21, and a gas introduction pipe 22 is formed on an upper wall of the plasma generation chamber 22.
d is connected. A microwave introduction hole 22a is formed at the center of the upper wall of the plasma generation chamber 22, and the microwave introduction hole 22a is sealed by a microwave introduction window 22b made of, for example, quartz glass. A flat plate electrode 22c is provided on the microwave introduction window 22b.
One end of the high-frequency oscillator 23 is connected to 2c via a matching box 23a. The high frequency oscillator 23
Is grounded, and the reaction product is unlikely to adhere to the microwave introduction window 22b when the high frequency generated by the high frequency oscillator 23 is applied to the plate electrode 22c. Further, one end of a waveguide 24a is connected to the microwave introduction window 22b and the plate electrode 22c,
The other end of the waveguide 24a is connected to the microwave oscillator 24. An excitation coil 24b is disposed concentrically around one end of the waveguide 24a and around the plasma generation chamber 22, and the excitation coil 24b is connected to a DC power supply (not shown). These plasma generation chamber 22, microwave oscillator 24, excitation coil 24b, gas introduction pipe 2
The plasma generating means 220 includes 2d and the like.

On the other hand, a sample chamber 25 is continuously provided below the plasma generation chamber 22, and the sample chamber 25 and the plasma generation chamber 22 are separated by a partition plate 25a, and a microwave introduction hole 22a at the center of the partition plate 25a. A plasma extraction window 25b is formed at a location opposite to. Further, a sample table 2 is provided at a position facing the plasma extraction window 25b at the center of the sample chamber 25.
6 are provided, and a sample 26 a is held on the sample stage 26. An electrode 27a is embedded at a predetermined position in the sample table 26, one end of a high-frequency oscillator 27c is connected to the electrode 27a via a matching box 27b, and the other end of the high-frequency oscillator 27c is grounded. . These electrodes 27a, matching box 2
7b, the high-frequency power supply means 27 includes the high-frequency oscillator 27c. A gas introduction pipe 28a is connected to one side wall of the sample chamber 25, and an exhaust pipe 28b is connected to a lower wall of the sample chamber 25. The exhaust pipe 28b is connected to a vacuum exhaust device (not shown). I have. The plasma etching apparatus 20 includes the plasma generating means 220, the sample chamber 25, the sample table 26, the high-frequency power supply means 27, and the like.

When the sample 26a is etched using the plasma etching apparatus 20 configured as described above, first, the inside of the reaction vessel 21 is depressurized to a predetermined pressure by the evacuation device, and a high frequency is applied to the electrode 27a of the sample stage 26. After that, gases such as Ar and H ₂ are introduced into the plasma generation chamber 22 through the gas introduction pipe 22 d. Further, a predetermined etching gas is introduced into the sample chamber 25 from the gas introduction pipe 28a. Then, for example, the frequency is 2.45 GHz from the microwave oscillator 24.
Of the microwave into the waveguide 24a and the microwave introduction window 22b
And the like, and a DC current is supplied to the exciting coil 24b to supply the plasma to the plasma generation chamber 22.
To form a magnetic field. Then, the gas is converted into plasma by the magnetic field and the electric field of the microwave, and the active species in the plasma are guided onto the sample 26a by the diverging magnetic field to perform etching. Target values of the supply flow rate of the gas affecting the etching rate and the like, the pressure in the reaction vessel 21, the high-frequency power supply amount to the electrode 27a, and the like are determined experimentally in advance, and are set to the target values during the processing process. Is controlled.

When a high frequency is applied to the electrode 27a, a bias voltage _Vdc is generated between the sample stage 26 and the sample 26a. It is known that there is a strong correlation between the bias voltage _Vdc and the etching rate of the sample 26a as shown in FIG.

[0006]

In the plasma etching apparatus 20 described above, even if the target value is controlled, if the sample stage 26 is changed to another one or the reaction product adheres to the sample stage 26, The electrical characteristics change.
Then, there is a problem that the bias voltage _Vdc generated between the sample stage 26 and the wafer 26a changes, and the etching rate changes.

[0007] To prevent this, the bias voltage V _dc
It is also conceivable to measure the RF power and control the high-frequency supply power so that this value becomes a predetermined value. However, in performing such control, V _dc for measuring the bias voltage V _dc
Requires a monitor and is costly. Further, in this _Vdc monitor, it is difficult to continuously measure the bias voltage _Vdc during the processing step, and it is difficult to always reliably control the etching rate.

The present invention has been made in view of such problems, and it is possible to reliably control an etching rate using parameters that can be easily measured at all times, and to reduce manufacturing costs. It is an object of the present invention to provide a plasma etching apparatus capable of performing the above.

[0009]

In order to achieve the above object, a plasma etching apparatus according to the present invention comprises means for generating plasma, a sample stage for holding a wafer, and a high frequency power for applying a high frequency to the sample stage. In the plasma etching apparatus provided with the supply means, the high-frequency power supply amount is feedback-controlled so that the measured peak-to-peak voltage value approaches a preset peak-to-peak reference voltage value. The high frequency power supply means is provided with a control means for performing the control.

[0010]

The following Table 1 shows the high-frequency power supply, the high-frequency reflected power, the etching rate, and the peak-to-peak voltage V _pp for Cases 1 and 2 in which the high-frequency matching positions supplied to the sample stage 26 are different from each other. The result of the measurement is shown.

[0011]

[Table 1]

As can be seen from Table 1, the etching rate is greatly different in both cases 1 and 2 even though the high-frequency power supply and the high-frequency reflected power are similar. The results show that it is difficult to control the etching rate by the amount of high-frequency power supplied to the substrate. Also, the peak-to-peak voltage value V _pp
Similarly, the peak-to-peak voltage value _Vpp is suitable as a control parameter for the etching rate.

As a result of an investigation by the present inventors, as shown in FIG. 4, the bias voltage V _dc and the peak-to-peak voltage V _pp have a proportional relationship, and the peak-to-peak voltage V _pp
Is measured, the bias voltage _Vdc can be obtained.

[0014] The According to the structure of a plasma etching apparatus, the feedback amount of power supplied high frequency so as to approach the peak-to-peak voltage value V _pp is peak-to-peak reference voltage value V _pp of preset 'to be measured The control means for controlling is provided in the high-frequency power supply means, and the peak-to-peak voltage V _pp having a proportional relationship with the bias voltage _Vdc can be easily and always measured in the matching box of the high-frequency power supply means. Is easily adjusted by the amount of supplied power. Peak-to-peak reference voltage value V _pp corresponding to a predetermined said bias voltage V _dc 'when setting the, the peak-to-peak reference voltage value V _pp'
And peak-to-peak voltage value V _pp is the measurements are compared with the supply power amount of the high frequency so that the difference is eliminated is adjusted, the peak-to-peak voltage value V _pp is the peak-to-peak reference voltage value V _pp ′. As a result, the sample can always be surely etched at a predetermined etching rate, and since no special measuring means is required, the manufacturing cost of the apparatus can be reduced.

[0015]

Embodiments and Comparative Examples Hereinafter, embodiments of a plasma etching apparatus according to the present invention will be described with reference to the drawings. In addition,
Components having the same functions as those of the conventional example are denoted by the same symbols. FIG. 1 is a sectional view schematically showing an embodiment of a plasma etching apparatus according to the present invention. In the drawing, reference numeral 26 denotes a sample stage. An electrode 27a is embedded at a predetermined position in the sample table 26, one end of a high-frequency oscillator 17c is connected to the electrode 27a via a matching box 17b, and the other end of the high-frequency oscillator 17c is grounded. In addition, the matching box 17b is a control unit 1
7d, and the control means 17d is connected to a high-frequency oscillator 17c
It is connected to the. Although not shown, the control means 17d
Is an operation unit for setting and inputting a peak-to-peak reference voltage value V _pp ′ (hereinafter simply referred to as a reference voltage value V _pp ′) corresponding to a predetermined bias voltage V _dc , and stores the reference voltage value V _pp ′. And a storage unit for retrieving the peak-to-peak voltage value V _pp (hereinafter simply referred to as a voltage value V _pp ) monitored by the matching box 17b and the stored reference voltage value V _pp ′, and the voltage value V _pp and the reference voltage It is configured to include an arithmetic processing unit that compares the value with the value V _pp ′, and a signal output unit that instructs the high-frequency oscillator 17c to increase or decrease the amount of supplied power or the like. These electrodes 27a, matching box 17b,
The high-frequency power supply unit 17 includes the high-frequency oscillator 17c and the control unit 17d. Other configurations are shown in FIG.
Since the configuration is the same as that described above, a detailed description of the configuration is omitted here. The plasma etching apparatus 10 includes the plasma generating means 220, the sample chamber 25, the sample table 26, the high frequency power supply means 17, and the like.

When the sample 26a is etched using the plasma etching apparatus 10 configured as described above, first, the inside of the reaction vessel 21 is depressurized to a predetermined pressure by the vacuum evacuation device, and a high frequency is applied to the electrode 27a of the sample stage 26. After that, gases such as Ar and H ₂ are introduced into the plasma generation chamber 22 through the gas introduction pipe 22 d. Further, a predetermined etching gas is introduced into the sample chamber 25 from the gas introduction pipe 28a. Then, for example, a microwave of 2.45 GHz is introduced from the microwave oscillator 24 into the plasma generation chamber 22 through the waveguide 24a, the microwave introduction window 22b, and the like, and the exciting coil 2 is introduced.
A DC current is supplied to 4b to form a magnetic field in the plasma generation chamber 22. Then, the gas is turned into plasma by the magnetic field and the electric field of the microwave, and the active species in the plasma are guided onto the wafer 26a by the diverging magnetic field to perform etching. Target values of the supply flow rate of the gas, the pressure in the reaction vessel 21, and the like are determined experimentally in advance, and are controlled to be the target values during the processing process. The etching rate is controlled by the control unit 17d.

Hereinafter, the operation of the control means 17d will be described with reference to the flowchart shown in FIG. When control is started, it is determined in S1 whether a reference voltage value V _pp ′ has been input from the operation unit. If it is determined that no reference voltage value V _pp ′ has been input, the process returns to the original state. V _pp 'is stored in the storage unit (S2). Then S
In step S3, it is determined whether or not a stop instruction has been input. If it is determined that the stop instruction has not been input, it is determined in step S4 whether or not the voltage value _Vpp has been input from the matching box 17b. When it is done, it returns to its original state.
On the other hand, if it is determined in S4 that the voltage value V _pp has been input, the arithmetic processing unit calls up the reference voltage value V _pp ′ from the storage unit (S5), and in S6, the voltage value V _pp '
_It is determined whether _{pp is} greater than reference voltage value V _pp '.
If it is determined that the power is large, a signal instructing a decrease in the supplied power is output from the signal output unit to the high-frequency oscillator 17c (S7), and thereafter, the process returns to S3. On the other hand, an increase of no greater a voltage value V _pp in the arithmetic processing unit and is judged whether or not the reference voltage value V _pp 'is smaller than is determined (S8), as small as it is determined that the supply power amount in S6 Is output from the signal output unit to the high-frequency oscillator 17c (S9), and thereafter, the process returns to S3. On the other hand, if it is determined in S8 that it is not small, a signal instructing to maintain the supplied power is output from the signal output unit to the high-frequency oscillator 17c (S10), and thereafter, the process returns to S3. Hereinafter, the above processing is repeated until it is determined in S3 that the stop instruction has been input.

A result of etching the sample 26a using the plasma etching apparatus 10 according to the embodiment will be described below. As a comparative example, an experiment was similarly performed using the device 20 shown in FIG.

FIGS. 3A and 3B are curve diagrams showing the lapse of time of etching, wherein FIG. 3A shows a voltage value V _pp , FIG.
(C) shows the etching rate. The solid line is for the example and the broken line is for the comparative example. FIG.
As is clear from the above, in the apparatus according to the comparative example, the supply power is controlled, but the voltage value _Vpp and the etching rate fluctuate. However, in the plasma etching apparatus 10 according to the embodiment, the voltage value V _pp was controlled so as to approach the reference voltage value V _pp ′ by the supplied power amount, and the etching rate was substantially constant during the operation.

As apparent from the result, in the plasma etching apparatus 10 according to the present embodiment, the bias voltage V
_The voltage value V _pp proportional to _dc is always easily measured in the matching box 17b of the high-frequency power supply means 17, and is easily adjusted by the high-frequency power supply amount. Therefore, if a reference voltage value V _pp ′ corresponding to a predetermined bias voltage V _dc is set, the reference voltage value
_pp ′ is compared with the measured voltage value V _pp , the amount of high-frequency power supply is adjusted to eliminate this difference, and the voltage value V _pp
pp can approach the reference voltage value V _pp '. As a result, the sample 26a can always be reliably etched at a predetermined etching rate, and since no special measuring means is required, the apparatus 10 can be manufactured at low cost.

[0021]

As described above in detail, in the plasma etching apparatus according to the present invention, the measured peak-to-peak voltage value V _pp is reduced to the preset peak-to-peak reference voltage value V _pp '. control means for feedback controlling the amount of power supply of the high frequency so as to approach are equipped with high-frequency power supply means, said peak-to-peak voltage value V _pp having a strong correlation with the bias voltage V _dc is the high-frequency power supply means It is always easily measured in the matching box and easily adjusted by the amount of high-frequency power supply. Therefore, if a peak-to-peak reference voltage value V _pp ′ corresponding to the predetermined bias voltage V _dc is set in advance, the peak-to-peak reference voltage value V _pp ′ and the measured peak-to-peak voltage value V _pp ′ are set. _The peak-to-peak voltage value V _pp can be made closer to the peak-to-peak voltage value V _pp ′ by comparing the peak-to-peak voltage value V _pp . As a result, the sample can always be surely etched at a predetermined etching rate, and since no special measuring means is required, the apparatus can be manufactured at low cost.

[Brief description of the drawings]

FIG. 1 is a sectional view schematically showing an embodiment of a plasma etching apparatus according to the present invention.

FIG. 2 is a flowchart schematically showing an operation of a control unit of the plasma etching apparatus according to the embodiment.

FIGS. 3A and 3B are curve diagrams showing a lapse of time when a sample is etched using the plasma etching apparatus according to the embodiment, wherein FIG. 3A shows a peak-to-peak voltage value V _pp , and FIG. The quantity, (c), shows the etching rate.

FIG. 4 shows bias voltage V _dc and peak-to-peak voltage V _pp
FIG.

FIG. 5 is a cross-sectional view schematically showing a conventional plasma etching apparatus using electron cyclotron resonance excitation.

FIG. 6 is a diagram showing a relationship between an etching rate and a bias voltage _Vdc .

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Plasma etching apparatus 17 High frequency power supply means 17d Control means 26 Sample table 26a Wafer 220 Plasma generation means

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) C23F 4/00 H01L 21/3065-21/308

Claims (1)

(57) [Claims] 1. A plasma etching apparatus comprising: a means for generating plasma; a sample stage for holding a wafer; and a high-frequency power supply unit for applying a high frequency to the sample stage. A plasma etching apparatus, characterized in that the high-frequency power supply means is provided with a control means for performing feedback control of the high-frequency power supply so as to approach a preset peak-to-peak reference voltage value.