JPH0294629A - Plasma treatment - Google Patents

Abstract

PURPOSE:To detect a fine change in a plasma luminance value and to detect an and point highly accurately by a method wherein a mean value of pieces of plasma luminance information in a plasma treatment region is found in advance and an end point of an operation is found by a fluctuation in a measured value by making use of this means value as a reference point of a measuring operation. CONSTITUTION:Plasma luminance values are measured at prescribed time intervals in a stable region T2; a mean value Vav of these measured values is found; this value is stored in an CPU 25. Then, in order to amplify the computed mean value Vav to a desired voltage Vav', the CPU 25 computes a setting gain; a gain is set by a gain adjustment mechanism 22 on the basis of this gain-setting signal. The means value Vav of pieces of plasma luminance information in a treatment region is found in advance in this manner; this mean value is amplified at a prescribed amplification factor; after that, an end point of an operation is found by a fluctuation in a measured value by making use of this amplified mean value Vav' as a reference point of a measuring operation. Thereby, a fine change in a plasma luminance value is detected, and the end point can be detected with high accuracy.

Description

[Detailed description of the invention] [Purpose of the invention] (Industrial application field) The present invention relates to a plasma processing method.

(Prior Art) Semiconductor processing apparatuses that utilize plasma, such as plasma CVD apparatuses, plasma etching apparatuses, and sputtering apparatuses, have been widely used as semiconductor processing apparatuses.

As such a plasma processing apparatus, for example, an etching apparatus uses a reaction gas such as CCβ4, CF, etc. in a reaction vessel.
This device introduces a gas to excite the reaction gas into a plasma state, and uses the generated plasma to etch a substrate to be processed, such as a liquid crystal display substrate (hereinafter referred to as an "LCD substrate"), a semiconductor wafer, etc., in a reaction vessel.

By the way, such plasma processing equipment is provided with an end point detection mechanism (for example, a special (See JP-A-51-35639 and JP-A-53-34641).

Another end point detection mechanism is a mechanism that determines the processing state based on changes in the brightness of plasma generated in the reaction vessel, which extracts plasma light from a monitoring window installed on the wall of the reaction vessel and controls the plasma light to a specified level. There is a mechanism that photoelectrically converts only a single wavelength of the signal to create an electrical signal, such as a voltage signal, and detects an end point based on this electrical signal (see, for example, Japanese Patent Laid-Open No. 55-6407).

Figure 4 is a diagram showing the relationship between plasma brightness obtained by a conventional end point detection mechanism and processing time. In the figure, the horizontal axis shows the processing time, and the vertical axis shows the measured change in plasma light brightness. The figure shows the value converted to voltage value.

Up to 11 hours from the start of processing, there is a so-called unstable region where the processing gas introduced into the reaction vessel is gradually excited to a plasma state, and after this, a region T2 where the plasma brightness, that is, the voltage value is almost constant, becomes stable. In this stable region T2, an object to be processed, such as an LCD substrate, is etched.

When the etching of the substrate to be processed is completed, T3 in the figure
The voltage value gradually changes as shown by the area.

The change in the voltage value between ITpj and ITpj differs depending on the wavelength of the plasma light that is determined. For example, when the wavelength of the light emitted from the active component in the plasma component (λ1 in the figure) is determined, Since there is no object to be etched on the substrate at the same time that etching is completed, the active components in the plasma are not consumed, the amount of active components increases, and the brightness increases.

In addition, when measuring the wavelength (λ2 in the figure) of the light emitted from the reaction product generated by the reaction between the plasma active component in the reaction vessel and the object to be etched, the reaction product can be detected as soon as etching is completed. The brightness decreases because the amount of .

The method of calculating the end point using such an end point detection mechanism is to first calculate the average value Va of the voltage values in the stable region T2.
v is determined, and a rate of change S is set in advance to determine how much the voltage value should change from this average value Vaν to determine the end point.

Then, when the δ-j constant value changes by this change rate of 5 minutes, this is set as the end point a.

In this way, the work is automatically terminated when the measured voltage value becomes equal to end point 3.

(Problem to be Solved by the Invention) However, with the conventional end point detection mechanism described above, if the substrate to be processed has a large opening, such as a large LCD board, the luminance changes greatly at the end of the work. Detection of the end point is a good thing, but in etching processing with a small aperture ratio, such as contact holes, etc., there is little change in brightness when the work is completed because the surface to be processed is small. There was a problem in that it was difficult to detect an accurate work end point.

The present invention has been made to solve the above-mentioned problems, and even if the change in plasma brightness at the end of the work is small,
It is an object of the present invention to provide a plasma processing method that can detect changes in plasma brightness with high precision and greatly improves the detection sensitivity of end point detection.

[Structure of the Invention] (Means for Solving the Problems) The plasma processing method of the present invention accommodates a workpiece in a reaction vessel, generates the workpiece in the reaction vessel, and generates a predetermined amount of plasma. In a method of performing plasma processing while referring to changes in brightness of wavelength, the method includes a step of calculating in advance an average value of plasma brightness of the plasma light in a plasma treatment area, and a step of calculating the average value of plasma brightness of the plasma light in the plasma treatment area, and calculating the average value of the calculated plasma brightness as plasma brightness lpI.
The present invention is characterized by the step of converting the DJ fixed point at the fixed point, and the step of detecting the end point of the plasma processing work based on the fluctuation range of the measured plasma brightness with respect to the measurement origin.

(Function) In the method of the present invention, the average value Vav of plasma brightness information in the plasma processing area is determined in advance, and the work end point is determined by the fluctuation of the measured value using the average value VaV as the measurement reference point. It is also possible to detect minute changes in the temperature, making it possible to detect the end point with high precision.

In addition, after amplifying the above average value Vav with a predetermined amplification factor, this amplified VaV- is used as the measurement reference point and is 1.111J.
If the fixed value is also amplified by a similar amplification factor and the work end point is determined by variation with respect to the measurement reference point, the range of change in the measured value becomes larger, so it becomes possible to detect the end point with higher sensitivity.

(Example) Hereinafter, an example in which the method of the present invention is applied to a plasma etching apparatus will be described with reference to the drawings.

FIG. 1 is a diagram showing the configuration of a plasma etching apparatus according to an embodiment. In a reaction vessel 1 kept airtight, a workpiece 2 such as an LCD substrate or a semiconductor wafer is placed on a mounting table 3 serving as a ground electrode. It is set up.

A high frequency electrode 4 is arranged above the mounting table 3 and facing the mounting table 3, and the high frequency electrode 4 is connected to a high frequency power source 5 for applying a predetermined high frequency power, for example, 13.56 MIIz. It is connected.

A gas introduction pipe 6 for introducing a processing gas is provided on the upper wall of the reaction vessel 1, and a processing gas such as CC4 or C
The processing gas from the processing gas source 7 that supplies the gas is introduced into the reaction vessel 1 through the gas introduction pipe 6 with its flow rate controlled by the flow rate adjustment mechanism 8 .

On the other hand, a gas exhaust port 9 for exhausting the gas in the reaction container 1 is provided on the lower wall of the reaction container 1, and a vacuum mechanism 10 connected to the gas exhaust port 9 keeps the inside of the reaction container 1 at a predetermined level. Gas exhaust control is performed to maintain the degree of vacuum.

Further, a monitoring window 11 for monitoring the brightness of the plasma g during processing is provided at a position corresponding to the approximate center between the mounting table 3 and the high-frequency electrode 4 on the side wall of the reaction vessel 1. The end point is automatically determined based on the change in the brightness of the plasma light that has passed through the plasma light source 11.

Processing using such a plasma etching apparatus is performed by keeping the inside of the reaction vessel 1 at a predetermined degree of vacuum, for example, 10 to 10-1 Torr.
After that, a predetermined high frequency power, for example, 13.58 M1lz, is applied to the high frequency electrode 4 to turn the introduced processing gas into plasma, and the generated plasma g causes the object to be processed 2 to etching.

The end of the etching work is automatically detected by the work status monitoring mechanism 114, which includes a photoelectric conversion mechanism 12 for converting changes in the brightness of the plasma light into electrical signals, and an end point detection mechanism 13 based on the information of this electrical signal. Ru.

The automatic end point detection operation by the working state monitoring mechanism 14 will be described below with reference to FIGS. 2 and 3.

When the processing gas introduced into the reaction vessel 1 is turned into plasma, the plasma light emitted from the plasma g passes through the monitoring window 11 and enters the wavelength selection filter, for example, the interference filter 15 of the photoelectric conversion mechanism 12. .

This interference filter 15 selects a predetermined single wavelength from the plasma light used for monitoring the working state, for example, the wavelength λ1 of light from an active component in the plasma (hereinafter referred to as etchant), or a reaction product generated by etching. The wavelength λ2 of the light from the source is selected.

In this way, the wavelength selected by the interference filter 15, for example, λ1
is converted into an electrical signal by the light receiving element 16 and output to the end point detection mechanism 16.

The luminance information signal input to the end point detection mechanism 16 is first
After being amplified by the first stage amplifier 21 etc., it is output to the gain adjustment mechanism 22 for setting the gain.

The brightness information signal input to the gain:A adjustment mechanism 22 is amplified based on a predetermined amplification factor, and then output to the A/D converter 24 via the mode switching mechanism 23, where it is converted into a digital signal. After being converted into , it is output to the CPU 25 which controls the entire device.

The CPU 25 outputs gain setting information of the gain adjustment mechanism 22 via the Do unit 26 and the like, and performs desired gain settings.

As shown in FIG. 3, the brightness change at wavelength λ1 during the processing operation is caused by the voltage value changing from the start of the processing until time T1 because the processing gas introduced into the reaction vessel 1 is gradually excited to a plasma state. (brightness) gradually increases. After this,
A region where the voltage value is approximately constant is a stable region T2, and an etching process for the object 2, such as an LCD substrate, is performed in this stable region T2.

When the etching of the object to be processed 2 is completed, T3 in the figure
The voltage value gradually changes as shown by the area, for example, the wavelength λ
With the light of 1, the object to be etched disappears on the substrate at the same time as the etching of the object to be processed is completed, so that the etchant increases and the voltage value increases. Furthermore, with light having a wavelength of λ2, the reaction product decreases at the same time as etching is completed, so the voltage value decreases.

Here, in the stable region T2, the plasma brightness is constant at a predetermined time interval, and the average value Va of all these constant values is
v is determined and stored in the CPU 25.

Next, the CPU 25 calculates a setting gain in order to amplify the calculated average value Vav to a desired voltage Vav'', for example, 5V, and the gain is set by the gain adjustment mechanism 22 based on this gain setting signal (b in Fig. 3). ).That is, the set gain is given by:

After setting the gain in this way, the mode switching mechanism 23 of the end point detection mechanism is switched to the end point measurement side 23a, and the plasma brightness measurement value of the work end area T3 is transmitted to the CPU 25. At this time, in order to use the set average value Vav'' as the OV reference, the reference voltage V rel' is added to the average value Vav. In this example, the gain was set so that the average value Vav was 5V, so The reference voltage to be added to the measured value is -5
v. Then, the reference voltage V rer is added to all the measured values in the work completion area T3.

By doing so, fluctuations in the measured value in the work completion region T3 are amplified in a manner corresponding to the set gain, and become fluctuations based on 0■.

On the other hand, the CPU 25 calculates the end point value a based on the calculated average value VaV.

The end point value a is defined by the rate of change S with respect to the average value Vav- set by the desired gain, and since the average value Vav- is set to 5v in this embodiment, it is given by:

After calculating the end point a in this way, this end point value is compared with the measured value in the work completion area T3 measured at a predetermined time interval, and the measured value satisfying the condition of measured value ≦ end point value is found a predetermined number of times. CPU25 continuously
Considering this as an endpoint if entered in
finish the work.

As described above, in the method of this embodiment, the average value Vav of the plasma brightness information in the processing region is determined in advance, and this average value Vav is calculated in advance.
After aV is amplified by a predetermined amplification factor, the work end point is determined by fluctuations in the measured value using this amplified average value VaV- as the al constant reference point, so even minute changes in plasma brightness can be detected. This enables highly accurate end point detection.

In the above embodiment, the gain was set so that the average measured value Aav was 5V, but of course this may be any value, and in that case, the reference voltage is set so that the set average value Aav- becomes 0V. All you have to do is change V rer.

Furthermore, the method of the present invention can be applied to processing apparatuses other than plasma etching apparatuses, such as ashing apparatuses, plasma etching apparatuses, dundancy apparatuses, and the like.

[Effects of the Invention] As explained above, according to the plasma processing method of the present invention, even if the change in plasma brightness at the end of the work is small, the change in plasma brightness can be detected with high accuracy, and the end point detection can be easily detected. Sensitivity is greatly improved.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the configuration of a plasma etching apparatus according to an embodiment to which the method of the present invention is applied, FIG. 2 is a diagram showing the configuration of the end point detection mechanism of FIG. 1, and FIG. 3 is a diagram showing the end point detection method of the embodiment. FIG. 4 is a diagram showing the relationship between plasma brightness and working time to explain the conventional end point detection method. 1...Reaction container, 2...Product to be treated, 4
...High frequency branch electrode, 12...Photoelectric conversion mechanism, 13...End point detection mechanism, 14...
Working condition monitoring mechanism, 15...Interference filter, 1
6... Light receiving element, 22... Gain adjustment mechanism, 23... Mode switching mechanism, 25...
・CU0

Claims (1)

[Scope of Claim] A method for storing a workpiece in a reaction vessel and subjecting the workpiece to plasma treatment while referring to a change in brightness of a predetermined wavelength of plasma generated in the reaction vessel, comprising: a step of calculating the average value of the plasma brightness of the plasma light in , a step of converting the calculated average value of plasma brightness to a measurement origin in plasma brightness measurement, and a step of calculating the plasma brightness according to the fluctuation range of the measured plasma brightness with respect to the measurement origin. A plasma processing method characterized by comprising the step of detecting the end point of a processing operation.