JPH08181104A - Etching monitoring method - Google Patents

Abstract

PURPOSE: To stably measure a light emitting spector by a method wherein a produced plasma state is in-process measured for monitoring the etching characteristics of an object to be etched. CONSTITUTION: A plasma production detector 102 collects the light emitting spector data from a plasma emitting light 107 of an etching device 101 to be fed to an emitted light signal processor 103 and etching state monitor 104, further to the light emitting signal processor 103 and etching state monitor 104. Besides, the light signal processor 103 corrects the emitting light spector data by a reference spectrum data. On the other hand, an etching state monitor 104 presumes the quantity, state of a reactive product in the processor of the etching device as well as the deteriorated state etc., of parts to be fed to an output displayer 105 as the data such as abnormality alarm etc., of etching processing to be displayed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a plasma etching apparatus for manufacturing a semiconductor device, and more particularly, it monitors the etching condition and maintains the etching characteristic within a predetermined range to prevent the occurrence of defects due to the fluctuation of the etching characteristic. The present invention relates to an etching monitoring method suitable for prevention.

[0002]

2. Description of the Related Art With the high integration of LSI, high precision is required for its processing. In order to perform high-precision processing, it is of course necessary to improve the performance of each processing equipment, but in order to improve productivity, it is important to maintain the performance of each processing equipment stable for a long time without causing defects. is there. In the processing equipment,
Looking at the etching device that plasmaizes the processing gas in the vacuum container to form a pattern on the wafer surface, the resist that is the mask of the pattern decomposes during the etching process to generate organic matter, which adheres to the inner wall of the processing chamber, In addition, metal (aluminum, molybdenum, or tungsten) that is the material to be etched, silicon that is the material of the substrate, and the reaction product thereof adheres 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 of the wall of the processing chamber, and the incident state (matching state) of microwaves into the processing chamber changes, 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, and a minute leak may occur to change the plasma state. As described above, when the etching apparatus is continuously operated for a long time, the etching characteristics gradually change, that is, a so-called change with time occurs, and eventually the inspection pass condition is not satisfied, which causes a defect. 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, as in the plasma etching apparatus disclosed in Japanese Patent Laid-Open No. 63-42124, for example, the state of plasma is monitored by the light emission during the etching process. It is used only to detect the end of. That is, during etching, the material to be etched (Al, Poly-Si, etc.) appears in the plasma due to the etching reaction, so the intensity of the light (wavelength peculiar to the substance) emitted by this is monitored and the intensity of that light becomes zero. It is detected that the etching is completed at the point of time. Therefore, the etching time and the etching rate for one wafer can be obtained, but no consideration is given to the change in etching characteristics over time.
Therefore, nothing has been done to prevent the occurrence of defects.

[0004]

In the above-mentioned conventional technique, the completion of the etching process is only monitored, and the result of the etching process (such as the size and shape of the cross section of the pattern and the in-plane uniformity of the processed wafer). It does not confirm that the inspection pass conditions are met. Originally, since the processing characteristics of the etching processing apparatus gradually change as the processing is repeated, it is necessary to sequentially inspect the processing results every time the processing is performed, in other words, every number of processed wafers. However, since the inspection is usually performed by an inspection device different from the processing device, the etching process is continued on the next wafer or lot at the time when it is determined as a result of inspection, that the defective product is defective. The result will be issued. However, there is a problem of throughput in the process if the etching process is performed while performing 100% inspection by the inspection device.

The change with time of the processing characteristics is related to the change with time of the plasma state. When the change of plasma is examined in detail, the cause of the change with time is considered as follows. First, the composition of the discharge gas changes due to the release of new gas from the film of the reaction product attached to the inner wall of the processing chamber.
The plasma changes. Further, the power absorbed by the plasma (effective discharge power) is changed by absorbing a part of the discharge power supplied by the reaction product film (for example, dielectric loss). Alternatively, in the case of etching a metal wiring film such as Al, a thin metal film adheres to the inner wall of the processing chamber as a reaction product film, and therefore a part of the electric power is reflected and is not absorbed by plasma. become. In this case also, the effective discharge power changes. The discharge raises the temperature of the inner wall of the processing chamber, changes the amount of gas released from the adhered film and the amount of secondary electron emitted, and changes the plasma. Such changes in plasma can be observed as changes in the emission spectrum. Therefore, in each etching process, the characteristic emission spectrum that causes the change over time in the etching characteristics is monitored, and the state of the change is detected and processed in parallel with the etching processing to perform a simple inspection of the etching characteristics. Depending on the situation, it is possible to prevent the occurrence of defects by stopping the subsequent etching process. However, the biggest problem at that time was that the amount of deposits increased as the etching process continued.
As the lighting conditions of the emission spectrum change and the lighting situation worsens,
It is how to measure the emission spectrum stably.

[0006]

As the process is repeated, the inner wall of the process chamber is hit by the plasma, and the quartz bell jar chamber becomes frosted glass. Furthermore, the reaction product adheres to the inner wall of the processing chamber, but since the method of adhesion is striped in a thin film, scattering is dominant as in the ground glass state. It was found that the light emission amount of the entire emission spectrum decreased at a certain rate. Therefore, the above problem can be solved by dividing the emission spectrum during the present processing by the emission spectrum during the wafer processing which is the reference. The standard is to take a gentle plasma state in which the original etching reaction is completed, such as discharge during overetching. In practice, an emission signal processing unit is provided, and the emission spectrum of the wafer currently being processed is divided by the emission spectrum of the reference wafer during overetching. If this is continuously monitored within the lot or over a long period such as the entire sweep period, the spectrum that truly changes can be found, and the change in power and gas composition can be clearly identified and the cause of plasma change can be identified. it can. If the cause of the change is controllable such as discharge power and pressure, the plasma can be returned to the original state by correcting this. That is, by feeding back the processing conditions (power, pressure, etc.), the plasma can be stably maintained and the etching characteristics can be stabilized. If the cause of the change is uncontrollable, such as gas release from the deposit on the inner wall, a warning can be issued and the process can be stopped to prevent the occurrence of defects. Further, it is possible to indicate the proper maintenance time of the plasma etching apparatus.

[0007]

In the plasma in which the etching reaction is completed, the spectrum does not change. Therefore, as compared with the spectrum at the end of the previous processing, only the light amount is entirely decreased due to the fogging and dirt of the bell jar chamber. On the other hand, there are many spectra that are consumed as etchants and that are generated by reactions during etching.
Changes in some of these spectra correlate with changes in etching properties. To get that change exactly,
It is necessary to eliminate the effects of fogging and dirt on the bell jar chamber, and the emission signal processing unit described above acts to calculate the emission spectrum currently being processed corrected by the reference spectrum. Therefore, a change in etching can be detected by monitoring this correction spectrum.

[0008]

Examples of the present invention will be described below. FIG. 1 shows a block diagram of a monitor device when the present invention is applied to an etching device. FIG. 2 shows a flowchart of monitor signal processing. In FIG. 1, the etching apparatus 101 has a bell jar chamber 100a and a daylighting section 100b. The etching monitor device includes a plasma emission detection unit 102, an emission signal processing unit 103,
It is composed of an etching state monitoring unit 104 and an output display unit 105. Next, the operation of each unit will be briefly described. The plasma emission detection unit 102 is the plasma emission 107 of the etching apparatus 101.
The emission spectrum data is obtained from the above and sent to the emission signal processing unit 103 and the etching state monitoring unit 104. Further, the emission signal processing unit 103 corrects the emission spectrum data with the reference emission spectrum data, and sends the corrected emission spectrum data 108 to the etching state monitoring unit 104. The method of this correction will be described later. The etching state monitoring unit 104 uses the emission spectrum data 108 to estimate the amount and state of reaction products in the processing chamber of the etching apparatus 101, the deterioration state of parts, and the like, and information such as apparatus maintenance and etching processing abnormality alarms. The output data is displayed on the output display unit 105 as. Further, setting conditions such as a processing pressure, a gas flow rate, and a plasma generation power for correcting a deviation from a predetermined etching processing characteristic are obtained, and these are sent to the etching apparatus 101 as feedback signals. The etching apparatus 101 changes the setting condition by the obtained feedback signal to correct the deviation from the predetermined etching characteristic.

Next, the above-mentioned correction of the emission spectrum data will be described with reference to FIGS. Figure 3 shows the emission spectrum during etching, 201 indicates 2 during etching.
02 indicates during over-etching. The spectral peaks 211, 212 and 213 change during etching, but hardly change during overetching. The reason for this is that the etching reaction hardly progresses in the over-etching stage.
On the other hand, many reaction products are generated during etching,
Since this adheres to the inner wall of the bell jar chamber, the intensity of the emission spectrum decreases as a whole. The deposits increase as the number of processed sheets increases, and the intensity change of the emission spectrum at that time becomes as shown by 301 in FIG. That is,
The three lines 301 in FIG. 4 show changes in the maximum value of the spectral peaks 211, 212, and 213 in FIG. 3 with respect to the number of processed wafers in terms of emission intensity (relative value). 3 in this figure
It seems that all the spectral peaks of the book decrease as the number of processed sheets increases. If the emission spectrum of each wafer during overetching is taken and the intensity of the first wafer is used as a reference to divide the spectrum intensities of the second to fourth wafers, 302 is obtained. The numbers 1 to 4 in the figure correspond to the number of processed wafers. Therefore, by correcting the emission intensity of 301 with the wavelength characteristic of 302, it is possible to eliminate the influence of the decrease in the light amount due to the adhesion of the bell jar chamber. Reference numeral 302 in FIG. 4 shows the result of correcting 301. Spectral peaks 211, 212, and 213, which appeared to have decreased at 301, were 211 as shown at 303.
Only the other two have remained unchanged.

As described above, the influence of the decrease in the light amount due to the adhesion of the bell jar chamber can be eliminated by applying the above correction in the signal processing unit of FIG. 1, and stable monitor data can be obtained.

Further, by continuously monitoring these spectral data, it is possible to know the state of plasma and perform control so as to keep the processing characteristics constant.

Although the above description has been given with respect to etching, it can be applied to a process utilizing plasma treatment in exactly the same manner.

[0013]

According to the present invention, the etching processing state of the wafer of the plasma etching apparatus can be monitored in-process and the processing characteristics can be kept constant, so that the occurrence of defects can be prevented.

[Brief description of drawings]

FIG. 1 is a block diagram of an embodiment of the present invention.

FIG. 2 is a flowchart of signal processing of the present invention.

FIG. 3 is an explanatory diagram of an emission spectrum.

FIG. 4 is an explanatory diagram of changes in emission intensity.

[Explanation of symbols]

100a ... Bell jar chamber, 100b ... Daylighting part, 10
DESCRIPTION OF SYMBOLS 1 ... Etching apparatus, 102 ... Plasma light emission detection part, 1
Reference numeral 03 ... Emission signal detection unit, 104 ... Etching state monitoring unit, 105 ... Output display unit, 107 ... Plasma emission, 10
8 ... Corrected emission spectrum data.

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 / maintaining, an etching monitoring method characterized by monitoring the etching characteristics of a target etching object by in-process measuring the state of the generated plasma. 2. The etching monitoring method according to claim 1, wherein one means for monitoring the plasma state is plasma emission spectrum change detecting means. 3. The etching monitor method according to claim 2, wherein the spectral data in which the change in the transmittance of the lighting portion is corrected is monitored. 4. The etching monitor method according to claim 2, wherein the correction method for the change in the transmittance of the daylighting section is a reference, and the discharge spectrum data of the etching is divided by the discharge spectrum data at the time of overetching of the wafer. 5. The etching monitor method according to claim 1, wherein an abnormality of the plasma etching apparatus is detected based on the result of monitoring the plasma state.