JPH1050673A - Apparatus and method for plasma-etching monitor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an apparatus and method for plasma etching monitor which ensure a stability of the etching process, and improve the yield. SOLUTION: To obtain the end point information in a plasma etching process, the production change rate of a gas produced for the plasma etching of a wafer 1 is detected through a synthetic bilayer 2 on the basis of the integrated quantity, i.e., the change rate of the oscillation frequency of a quartz oscillator 1 and hence the detection thereof is made on the order of ppm or ppb, according to the accuracy of the oscillator 1.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a plasma etching monitor for monitoring a process of plasma etching of a semiconductor device wafer and a method thereof.

[0002]

2. Description of the Related Art Conventionally, in a plasma etching apparatus for etching a wafer for a semiconductor device by plasma, one of end point detection methods, a probe using a probe, is used as a plasma etching monitoring method for monitoring the etching process. The plasma process and the plasma density during the etching are measured using the method, and the changes in the plasma temperature and the plasma density are detected to monitor the etching process, thereby detecting the end point of the etching and obtaining the information.

[0003] A plasma etching monitoring method using such a probe method is described in, for example, Journal Electrochemical Society, Vol. 129 (198).
2 years) pp. 2522 to 2527 (J. Elect
rochem. Soc. 129 (1982) PP252
2-PP2527).

A schematic configuration of a plasma etching apparatus using this plasma etching monitoring method will be described below. FIG. 4 shows an example of a plasma etching apparatus configured to monitor an etching process using the conventional plasma etching monitoring method disclosed in the above-mentioned literature. Here, the case where the above-described probe method is used will be described as an example. In FIG. 4, 8 is a plasma etching reaction chamber, 9 is a lower electrode, 1
Reference numeral 0 denotes an upper electrode, 11 denotes a wafer for a semiconductor element, 12 denotes a matching device, 13 denotes a high-frequency oscillator, 14 denotes a mechanical booster pump, 15a denotes a reaction gas inlet, 15b denotes a reaction gas exhaust port, and 22 denotes a probe method. This is a probe that monitors the etching process.

Here, as the wafer 11, for example, a wafer composed of silicon Si, an oxide film SiO ₂ and a nitride film Si ₃ N ₄ is used. As the probe 22, for example, a Langmuir probe or the like is used.

[0006]

However, in the conventional plasma etching monitoring method as described above, the surface area of the probe 22 must be reduced in order to accurately detect the end point of the etching, and furthermore, the plasma etching monitoring method is not required. In order to detect the end point, it is required that the plasma density on the wafer 11 is evenly distributed. However, in practice, the plasma density is not uniformly distributed, which hinders the progress of fine processing. Will come.

That is, there is a problem in that the reliability is lowered along with the accuracy of the end point detection in the plasma etching, and the yield in the production of the wafer 11 is also lowered.

SUMMARY OF THE INVENTION The present invention solves the above-mentioned conventional problems. It is possible to monitor the etching process with a simple structure, and to improve the reliability of detecting the end point of plasma etching to stabilize the etching process. Provided is a plasma etching monitor device and a method thereof, which can ensure the performance and can improve the yield in wafer manufacturing.

[0009]

In order to solve the above-mentioned problems, a plasma etching monitor apparatus and a plasma etching method according to the present invention are characterized in that a plasma etching gas generated on a wafer during plasma etching is specially coated on a quartz oscillator. The synthesized bilayer membrane is adsorbed and its weight increases, and the frequency of the crystal oscillator decreases in accordance with the increase in the weight, and the electric signal output to the outside corresponds to the decrease in the frequency. The plasma etching process is monitored by measuring the amount of adsorption of the plasma etching product gas to the synthetic bilayer film and detecting the change in the generation of the plasma etching product gas. Of the plasma etching gas generated on the wafer even when the end point is detected to obtain the end point information at Since it detected based on the integrated amount which is the amount of change of the frequency of the quartz oscillator through synthetic bilayer, to the precision of the crystal oscillator of the detection, to not ppm and performing a precision of ppb order.

As described above, it is possible to monitor the etching process with a simple structure without providing a probe that requires a small surface area as in the prior art, and to improve the reliability of detecting the end point of plasma etching. The stability of the etching process can be ensured, and the end point detection at the time of plasma etching can be automated, so that the yield in wafer manufacturing can be improved.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A plasma etching monitoring apparatus according to a first aspect of the present invention is a plasma etching apparatus for etching a wafer for a semiconductor device by using a plasma. A plasma etching monitor device for monitoring, wherein a synthetic bilayer film for adsorbing a reaction product gas generated in a reaction process of the plasma etching is specially coated and a quartz oscillator having a unique frequency is formed in a reaction chamber of the plasma etching. A frequency counter that counts the frequency of the crystal oscillator in the reaction process of the plasma etching, a converter that converts a change in the frequency counted by the frequency counter into an electric signal, Monitors the electrical signal from the converter and A monitor control device for controlling the injection of the plasma etching reaction gas into the plasma etching reaction chamber based on the monitor information, wherein the monitor control device is used in the plasma etching reaction process based on the monitor information. It is configured to detect a pre-start state and a transient state of the reaction.

According to a second aspect of the present invention, there is provided a plasma etching monitoring method, wherein a reaction product gas generated in a reaction process of the plasma etching by a plasma etching reaction gas is adsorbed in a reaction chamber for performing a plasma etching on a semiconductor element wafer. A synthetic bilayer film to be formed is provided with a crystal oscillator having a specific frequency which is specially coated, and when monitoring the reaction process of the plasma etching, a vibration for counting the frequency of the crystal oscillator in the reaction process of the plasma etching. A number counting step, a conversion step of converting a change in the frequency of the crystal resonator counted in the frequency counting step into an electric signal, and monitoring the electric signal converted in the conversion step, and monitoring information thereof. Based on the plasma etching reaction chamber of the reaction gas for plasma etching It consists of a monitor control step of controlling the injection into, in the monitor control step, based on the monitor information, a method of detecting a prestart state and transient state of reaction in the reaction process of the plasma etching.

According to the above-described structure and method, the synthetic bilayer film specially coated on the quartz oscillator adsorbs the plasma etching product gas generated on the wafer during the plasma etching, and the weight increases. The frequency of the crystal oscillator decreases as the frequency increases, and the amount of plasma etching gas adsorbed on the synthetic bilayer is measured based on the electrical signal output to the outside in response to the decrease in the frequency. Then, the process of the plasma etching is monitored by detecting the generated change amount of the plasma etching product gas.

Accordingly, even when the end point is detected in order to obtain the end point information in the plasma etching process, the amount of change in the plasma etching generated gas generated on the wafer is controlled by the vibration of the quartz oscillator through the synthetic bilayer film. Since the detection is performed based on the integral amount, which is the amount of change in the number, the detection is performed in ppm or ppb according to the accuracy of the crystal unit.
Can be performed with order accuracy.

Hereinafter, a plasma etching monitor device and a method thereof according to an embodiment of the present invention will be specifically described with reference to the drawings. FIG. 1 is an explanatory view of the configuration of a plasma etching monitor device for performing the plasma etching monitoring method of the present embodiment. FIG.
In the figure, 1 is a crystal oscillator having a special coating of a synthetic bilayer 2 which is a model substance of human nose olfactory cells, 3 is a frequency transmission cable for transmitting the frequency of the crystal oscillator 1, and 4 is
A frequency counter that counts the frequency of the crystal oscillator 1 transmitted by the frequency transmission cable 3, integrates the count, and transmits the integrated value to a post-processing device, and 5 transmits a frequency from the frequency counter 4. A converter that converts the integrated value of the frequency thus converted into an electric signal and amplifies the electric signal, for example, a voltage value at a constant amplification factor, and transmits the amplified signal to a post-processing device;
6 monitors, for example, a voltage value which is an integrated frequency decrease of the crystal unit 1 converted, amplified and transmitted by the converter 5, and transmits, for example, detection of a plasma etching end point to a post-processing apparatus. A monitor control device 7 for controlling the reaction gas for plasma etching, and 7 is a reaction gas control system for plasma etching. Here, an olfactory sensor Q1 is constituted by the crystal oscillator 1 specially coated with the synthetic bilayer film 2 and the frequency transmission cable 3. The above components constitute a plasma etching monitor.

Reference numeral 8 denotes a plasma etching reaction chamber;
Is a lower electrode, 10 is an upper electrode, 11 is a wafer for a semiconductor element to be subjected to plasma etching, 12 is a matching device for protecting a high-frequency oscillator 13 and increasing power consumed during plasma etching, and 14 is a mechanical device. A booster pump, 15a is a reaction gas inlet, and 15b is a reaction gas exhaust port. These components are the same as those shown in the conventional example of FIG.

FIG. 2 is an explanatory view of the operation principle of the plasma etching monitor of the present embodiment shown in FIG. 1, and FIG. 2 (a) is a partially enlarged view of the olfactory sensor Q1, and FIG.
(B) shows a synthetic bilayer film 2 specially coated on a quartz oscillator 1.
It is an expanded sectional view of. In FIG. 2B, reference numeral 16 denotes a plasma etching reaction gas molecule generated on the semiconductor element wafer 11 to be etched by the plasma etching, such as SiF ₄ .

FIG. 3 is an operation waveform diagram for explaining end point detection by the plasma etching monitoring method of the present embodiment. In FIG. 3, reference numeral 17 denotes a state before the start of the plasma etching reaction, 18 denotes a transition state of the plasma etching reaction, 19 denotes a state where the plasma etching reaction is completed, 20 denotes a plasma etching reaction start point, and 21 denotes a plasma etching reaction end point.

Regarding the plasma etching monitoring method using the plasma etching monitoring device configured as described above, the operation of detecting the end point of the plasma etching reaction (described as the end point of the plasma etching) and the operation of the quartz oscillator 1 are described. Will be described below.

First, as shown in FIG. 1, the wafer 11 is set by transferring it onto the lower electrode 9 installed in the plasma etching reaction chamber 8. Then, the inside of the plasma etching reaction chamber 8 is moved to the mechanical booster pump 1.
In step 4, a vacuum state is established in which the degree of vacuum is, for example, about several tens ^-7 Torr.

After the inside of the plasma etching reaction chamber 8 reaches a vacuum state in this manner, for example, carbon tetrafluoride CF _{4 is} supplied from the reaction gas inlet 15a by using the control system 7 for the reaction gas for plasma etching. Is injected, for example, about 1 Torr. After the injection of the reaction gas for plasma etching is completed, the matching device 12 and the high-frequency oscillator 1
, A high frequency voltage is applied to the plasma etching reaction chamber 8.
Is applied between the lower electrode 9 and the upper electrode 10 which are set at the same time, and plasma is generated between the electrodes.

After the plasma is generated, a chemical reaction represented by the following chemical reaction formula occurs on the wafer 11 containing, for example, silicon Si, oxide film SiO ₂ and nitride film Si ₃ N ₄ . Si + 4F _* → SiF ₄ ↑ SiO ₂ + 4F _* → SiF ₄ ↑ + O ₂ ↑ Si ₃ N ₄ + 12F _* → 3SiF ₄ ↑ + 2N ₂に お い て In this chemical reaction formula, F _* discharges the CF ₄ gas. The active fluorine radical F _* is the case. Also, S
iF ₄ is a volatile substance that evaporates immediately.

The volatile plasma etching reaction gas molecules 16 such as SiF ₄ evaporated as described above are selectively adsorbed on the synthetic bilayer film 2 above the wafer 11 as shown in FIG. Is done. According to the weight of the adsorbed plasma etching reaction gas molecules 16, the frequency of the crystal resonator 1 on which the synthetic bilayer film 2 is specially coated decreases.
This is because the weight of the synthetic bilayer 2 increases due to the plasma etching reaction gas molecules 16 adhering to the synthetic bilayer 2, and due to this weight, the quartz oscillator 1 on which the synthetic bilayer 2 is specially coated is formed. Is less likely to vibrate.

Next, the amount of change in the frequency of the crystal resonator 1 on which the synthetic bilayer film 2 is specially coated is determined by the frequency transmission cable 3.
3, and is integrated by the frequency counter 4 in the plasma etching time to the state 17 before the plasma etching reaction starts, the plasma etching reaction transient state 18 and the plasma etching reaction end state 19 shown in FIG. .

The quartz oscillator 1 integrated as described above
Is simultaneously converted into an electric signal by the converter 5, and the electric signal, for example, a voltage value is amplified at a constant amplification factor and transmitted to the monitor control device 6. The monitor control device 6 monitors, for example, a voltage value which is a change amount of the frequency of the crystal unit 1 integrated as described above, and, for example, as shown in FIG. The etching reaction end point 21 is read from the operation waveform of the frequency change amount of the crystal unit 1, and the detection of the plasma etching reaction end point 21 serving as the plasma etching end point is transmitted to the control system 7 for the reaction gas for plasma etching. .

Control system 7 for reaction gas for plasma etching
The amount of gas injected from the plasma etching reaction gas control system 7 and the matching unit 1 based on the end point detection information by the detection of the plasma etching reaction end point 21 transmitted to
2 and the high-frequency oscillator 13 and the mechanical booster pump 14 are controlled. For example, when it is determined that the plasma etching is completed, the gas injection and matching unit 12 of the reaction gas control system 7 for plasma etching, the high-frequency oscillator 13 and the mechanical booster The pump 14 and the like are stopped, the reaction gas is exhausted through the reaction gas exhaust port 15b, and the plasma etching ends.

As described above, by selectively adsorbing a small amount of plasma etching gas generated by the plasma etching reaction generated during the plasma etching, the state 17 before the start of the plasma etching reaction, the transient state 18 of the plasma etching reaction, The plasma etching reaction end state 19 can be monitored, and the end point information of the plasma etching can be obtained.

Thus, it is possible to monitor the etching process with a simple structure without providing a probe that requires a small surface area as in the prior art, and to improve the reliability of detecting the end point of plasma etching. The stability of the etching process can be ensured, and the end point detection at the time of plasma etching can be automated, so that the yield in wafer manufacturing can be improved.

In the plasma etching monitor of the above-described embodiment, the quartz resonator 1 having the special coating of the synthetic bilayer film 2 may be made into a single-wafer type or a detachable type by a simple mechanism. Is also possible, and a similar effect can be obtained.

[0030]

As described above, according to the present invention, the synthetic bilayer film specially coated on the quartz oscillator adsorbs the plasma etching product gas generated on the wafer during the plasma etching and the weight thereof increases. The frequency of the crystal oscillator decreases in accordance with the increase in the weight, and the plasma etching generated gas is applied to the synthetic bilayer film based on an electric signal output to the outside in accordance with the decrease in the frequency. The process of plasma etching is monitored by measuring the amount of adsorption and detecting the amount of change in the generated gas of the plasma etching product, thereby obtaining the end point information in the process of plasma etching. The amount of change in the plasma etching gas generated on the wafer is calculated based on the integral amount, which is the amount of change in the frequency of the quartz oscillator through the synthetic bilayer. Since detected There, it is possible to perform the detection to the precision of the crystal oscillator, to not ppm with an accuracy of ppb order.

Therefore, it is possible to monitor the etching process with a simple structure without providing a probe that requires a small surface area as in the conventional case, and to improve the reliability of detecting the end point of the plasma etching to improve the etching. The process stability can be ensured, the end point detection during plasma etching can be automated, and the yield in wafer manufacturing can be improved.

[Brief description of the drawings]

FIG. 1 is a configuration explanatory view of a plasma etching monitor device according to an embodiment of the present invention.

FIG. 2 is an explanatory diagram of an operation principle of the crystal resonator according to the embodiment.

FIG. 3 is a waveform chart for explaining the operation of the embodiment.

FIG. 4 is an explanatory view of a conventional plasma etching monitoring method.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Quartz crystal oscillator 2 Synthetic bilayer film 3 Frequency transmission cable 4 Frequency counter 5 Converter 6 Monitor control device 17 State before plasma etching reaction start 18 Plasma etching reaction transient state 19 Plasma etching reaction end state 20 Plasma etching reaction start Point 21 Plasma etching reaction end point

Claims (2)

[Claims] 1. A plasma etching apparatus for etching a wafer for a semiconductor device by plasma, wherein the plasma etching monitor monitors a reaction process of plasma etching by a reaction gas for plasma etching. A synthetic bilayer film that adsorbs the generated reaction product gas is specially coated and a quartz oscillator having a unique frequency is provided inside the reaction chamber of the plasma etching, and the quartz oscillator in the reaction process of the plasma etching is provided. A frequency counter that counts the frequency, a converter that converts a change in the frequency counted by the frequency counter into an electric signal, and monitors the electric signal from the converter, based on the monitor information, The plasma etching of the reaction gas for plasma etching A monitor control device for controlling injection into the etching reaction chamber, wherein the monitor control device is configured to detect a pre-start state and a transient state of the reaction in the plasma etching reaction process based on the monitor information. Plasma etching monitor device. 2. A synthetic bilayer film which adsorbs a reaction product gas generated in a plasma etching reaction process by a plasma etching reaction gas is specially coated inside a reaction chamber for performing plasma etching on a semiconductor element wafer. Providing a crystal resonator having a frequency of: a frequency counting step of counting the frequency of the crystal resonator in the reaction process of the plasma etching when monitoring the reaction process of the plasma etching; and the frequency counting step. A conversion step of converting the change in the frequency of the crystal unit counted in the above into an electrical signal, and monitoring the electrical signal converted in the conversion step, based on the monitor information, the reaction gas for the plasma etching. It consists of a monitor control process that controls the injection into the plasma etching reaction chamber. A plasma etching monitoring method for detecting a pre-start state and a transient state of a reaction in the plasma etching reaction process based on the monitor information in the monitor control step.