JPH09219390A - Monitoring method for etching - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent production of defects by detecting the effective power of a plasma etching system during the etching operation and the time that will elapse before the end of the etching, detecting variation in the etching rate according to the result of the detection of effective power and time, and stopping the operation of the system based on the result of the detection of variation in etch rate. SOLUTION: The monitoring method for etching involves a means 2 for detecting effective power during etching operation and a means for detecting the etching time for an etching film. Arithmetic operation is performed to calculate a time integration value of effective power and a deviation of etching time from that of normal etching to obtain variation in etch rate. Thus variation in the etching rate is detected and compared in each etching operation to simply inspect the condition of the etching equipment 1. Etching operation is continued or discontinued depending on the result of the inspection.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an etching monitor method suitable for preventing occurrence of defects due to fluctuations in etching rate in plasma etching and the like.

[0002]

2. Description of the Related Art With the increase in integration of LSIs, high precision is required for processing. In order to perform high-precision processing, it is of course to improve the performance of each processing device,
In order to improve productivity, it is important to maintain the performance of each processing device stably for a long time and to prevent defects.

Looking at an etching apparatus which forms a pattern on a wafer surface by plasmaizing a processing gas in a vacuum container in a processing apparatus, a resist which is a mask of the pattern is decomposed during the etching processing to generate an organic substance. Metals (aluminum, molybdenum, or tungsten) that are materials to be etched, silicon as a substrate material, and reaction products thereof adhere to the inner wall of the processing chamber as a film.

When these deposits come into contact with plasma, gas is generated due to the action of ions in the plasma and the temperature rise on the wall surface of the processing chamber, and the supply state (matching state) of the plasma-generated power to the processing chamber changes. As a result, the state of plasma in the processing chamber changes. Since the etching process is performed by plasma, the etching characteristics represented by the etching rate also change due to the change of the plasma state. Further, the O-ring for vacuum sealing may be deteriorated by the etching gas to cause a minute leak and change the plasma state.

As described above, when the etching apparatus is continuously operated for a long period of time, the etching characteristics gradually change, that is, a so-called change with time occurs, and eventually the inspection pass condition is not satisfied, leading to the occurrence of defects. Further, the adhered matter on the inner wall of the processing chamber is peeled off and becomes a foreign matter when it reaches a certain thickness. This is also the case with other plasma processing apparatuses (CVD apparatus, sputtering apparatus, etc.), which is an obstacle to keeping the performance stable for a long time.

Up to now, for example, as in the plasma etching apparatus disclosed in Japanese Patent Laid-Open No. 63-42124, the state of plasma is monitored by the light emission during the etching process. It is used only to detect the end of. In other words, during etching, the material to be etched (aluminum, polysilicon, etc.) appears in the plasma due to the etching reaction. Is being detected. There is also an application to prevent erroneous detection of the etching end point due to device abnormality or noise, such as the dry etching device disclosed in Japanese Patent Laid-Open No. 5-251398.

[0007]

In the above-mentioned prior art, the purpose is to detect the end of the etching process, not the change in the etching process characteristics. Therefore, although the etching time for one wafer can be obtained, no consideration is given to the change in the etching characteristics with time (particularly to the suppression of the fluctuation of the etching rate), and therefore the occurrence of defects can be prevented. No preventive measures were taken.

It is an object of the present invention to detect fluctuations in the etching rate during the etching process and prevent defects from occurring.

[0009]

A change in processing characteristics (especially, a change in etching rate) is closely related to a plasma state, and there are mainly two causes of the change in the etching rate. (1) The gas is newly released from the film of the reaction product adhering to the inner wall of the processing chamber, whereby the composition of the discharge gas changes, and the pressure changes during the processing. (2) The film of the reaction product adheres to the inner wall of the processing chamber, and part of the electric power is reflected and is not absorbed by the plasma, so that the effective electric power changes.

Of these, the amount of gas released from the reaction product is smaller than that of the feed material gas, and therefore the change in power has a greater effect than the change in pressure. In particular, when etching a metal wiring film of aluminum or the like, a thin metal film as a reaction product film adheres to the inner wall of the processing chamber, and part of the electric power is reflected and is not absorbed by the plasma, resulting in fluctuations in effective power. It directly corresponds to the fluctuation of the etching rate. Further, the time integral value of the effective power corresponds to the etching amount.

Therefore, in each etching process, there is provided a means for detecting the effective power and a means for detecting the etching time of the etching film, and a fluctuation detection for detecting the etching rate from the time integral value of the effective power and the etching time. Equipped with a device. Then, a simple inspection of the etching rate fluctuation is performed by detecting and comparing the fluctuation in each etching process, and depending on the result, the subsequent etching process is stopped by the method of solving the above problem, that is, preventing the occurrence of defects in advance. To achieve. As the means for detecting the etching time, the end point detecting means in the prior art may be used. Further, as will be described later in detail, since there is a variable factor in the film thickness of the etching film even if the effective power does not change, a means for detecting the etching time of the etching film is required.

With the above structure, the effective power detecting means sequentially monitors the power supplied to the plasma during the etching process,
It acts to integrate with respect to the etching time. This is an amount proportional to the etching amount. On the other hand, the etching time detection means (end point detection means) outputs the etching processing time. Then, with respect to the integrated value of the effective power and the etching time, the fluctuation detecting device calculates the difference (fluctuation) between the integrated value of the average effective power and the average etching time during normal etching processing, and calculates the fluctuation of the etching rate.

[0013]

Embodiments of the present invention will be described below. FIG. 1 shows a block diagram of an etching monitor of the present invention, and FIG. 2 shows an etching sectional view. Further, FIG. 3 shows a light emission spectrum during etching and a monitor waveform of effective power, and FIG. 4 is a characteristic comparison diagram of etching results. Although not shown in FIG. 1, the etching apparatus 1 includes a processing chamber having a structure for holding a vacuum, a gas supply system for introducing an etching gas into the processing chamber, and controlling the processing chamber to a predetermined pressure. Equipped with a vacuum exhaust system. An etching power source 3 generates and maintains plasma in the etching apparatus 1, and is connected to the etching apparatus 1 via the effective power detecting means 2. Further, the end point detecting means 4 detects the etching time and the etching amount in combination with the effective power detecting means 2. Reference numeral 5 is a fluctuation detecting device.

The etching rate is obtained from the etching amount and the etching time.
This will be described with reference to FIG.

In FIG. 2, the portion of the etching target film 11 without the mask pattern 12 is etched. The etching amount w at this time is expressed by Expression 1 where the etching rate is r and the etching time is t, and the variation thereof is expressed by Expression 2. Also, the effective power is p and the time to the etching end point is
It was found experimentally that the time integration value P of the effective power was an amount proportional to the etching amount when the tend was used. That is, it is expressed by Equation 3 using k as a proportional constant. Therefore, the variation of the etching rate is given by equation 4. The etching end point can be detected by the end point detecting means 4 from the emission spectrum in plasma (21 in FIG. 3), and if the end point can be detected, the effective power (22 in FIG. 3) can be integrated (23 in FIG. 3).

Therefore, the fluctuation detecting device 5 in FIG. 1 can obtain the data of the fluctuations in the etching time and the etching amount for the processed wafer, and the fluctuations in the etching rate can be obtained by the equation 4. Further, when the fluctuation of the etching rate is an abnormal value, it is possible to output a stop command to the etching power source to stop the etching and suppress the occurrence of defects.

[0017]

[Equation 1]

[0018]

[Equation 2]

[0019]

(Equation 3)

[0020]

(Equation 4)

In the above equations 1 to 4, w is the etching amount, r is the etching rate, t is the etching time,
tend is the time to the etching end point, p is the effective power, and P is the time integrated value of the effective power.

FIG. 4 shows the results of this processing, where A, B, C, D and E indicate the wafers. The end point detection function suppresses the amount of overetching within a certain range and detects the fluctuation of the etching rate, and detects the decrease in the speed as in the wafer E as an abnormality.

As described above, by detecting the fluctuation of the etching rate by the method shown in the present invention, the fluctuation (abnormality) of the apparatus in the etching process can be found.

[0024]

According to the present invention, since it is possible to detect the fluctuation of the etching rate in each etching process, depending on the result, the subsequent etching process is stopped to prevent the occurrence of defects. be able to.

[Brief description of drawings]

FIG. 1 is a block diagram of an etching monitor according to an embodiment of the present invention.

FIG. 2 is an explanatory view of etching processing.

FIG. 3 is an explanatory diagram of a monitor waveform of an emission spectrum and an effective power during etching.

FIG. 4 is a characteristic diagram of etching results.

[Explanation of symbols]

1 ... Etching device, 2 ... Effective power detecting means, 3 ... Etching power supply, 4 ... End point detecting means, 5 ... Fluctuation detecting device.

Claims (5)

[Claims] 1. A processing chamber having a structure for holding a vacuum, a gas supply system for introducing an etching gas into the processing chamber and controlling the processing chamber to a predetermined pressure and a vacuum exhaust system, and a plasma for the processing chamber. In a plasma etching apparatus having a means for generating and maintaining, the etching rate of the target etching target film is monitored from the film thickness information of the target etching target film and the time until the etching of the etching target film is completed. Etching monitoring method characterized by the above. 2. A processing chamber having a structure for holding a vacuum, a gas supply system for introducing an etching gas into the processing chamber and controlling the processing chamber to a predetermined pressure, a vacuum exhaust system, and a plasma in the processing chamber. In a plasma etching apparatus having a means for generating and maintaining the etching rate, the variation in the etching rate of the target etching film is calculated from the variation in the film thickness of the target etching film and the variation in the time until the etching of the etching target film is completed. An etching monitoring method comprising: 3. The etching monitoring method according to claim 2, wherein the variation in the film thickness of the target film to be etched is detected from the variation in the effective power supplied to the plasma during etching. 4. The etching monitoring method according to claim 1, wherein the method for detecting the time until the etching of the object to be etched is detected by the spectrum change of plasma emission during etching. 5. The etching monitoring method according to claim 1, wherein an abnormality of the plasma etching apparatus is detected based on the etching rate or its variation.