JPH1197420A - Etching device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain the etching end point for dry etching when plasma light emission is weak or is not generated, and to detect a more highly accurate etching end point. SOLUTION: When dry etching is performed for an object 11 such as metal film by plasma, the gas pressure during etching in a etching chamber is detected by a gas-pressure detector 5. The etching end point is determined by the amount of fluctuation. The change of plasma light emission generated during etching is detected with a photoelectric converter 6 and utilized together. Thus, the unwanted fluctuating amount can be removed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an etching apparatus suitable for manufacturing a semiconductor device and the like.

[0002]

2. Description of the Related Art In the manufacture of liquid crystal display devices and semiconductor devices,
In the process of fabricating devices and circuits on semiconductor thin films on glass substrates and single crystal wafers, patterning of areas such as bases and wiring that are indispensable for the devices and circuits to be formed,
Along with so-called photolithography, a so-called RIE (Reactive Ion Etching) method using an active gas is generally used.

That is, a substrate to be etched is placed with a pair of electrodes facing each other in a decompression chamber to which a gas source and an exhaust pump are connected, and a plasma is generated between the electrodes. The substrate to be processed is etched. In order to stabilize the quality, the voltage applied to the electrode, the indoor gas pressure,
Plasma emission is detected and monitored, and feedback control of each parameter is performed so that constant conditions are always maintained.

In anisotropic etching such as the RIE method, it is preferable that a vertical groove is dug along a resist mask pattern to be deposited on a workpiece and no material to be etched remains on an exposed underlying surface. It is called patterning, and it is important to determine an etching end point (end point).

On the other hand, when the so-called over-etching is performed by isotropic etching in which the etching proceeds in the same direction in the vertical and horizontal directions, not only a predetermined size cannot be obtained, but also fine processing such as a super LSI is required. In a product type, highly accurate end etching, that is, an etching end point is a more important technical item.

When active gas ion etching is performed on a wiring electrically connected to a passive element or an active element built in a wafer in a reduced-pressure container, the active gas extracted from the plasma of the generated active gas becomes a wiring, for example. A unique electromagnetic wave is generated from the aluminum exposed in the plasma due to the collision with the aluminum and the chemically active etching.

In the conventional setting of the etching end point, a specific electromagnetic wave generated from a material to be etched is detected through an optical filter or the like, and an optical signal of the electromagnetic wave is input to a photoelectric conversion device including a photodiode or the like. . Here, when converted into a voltage signal having a level corresponding to the optical signal, a characteristic curve A of light emission intensity (replaced by voltage (V)) as shown in FIG. 3 is formed, and the etching end point TE is estimated from its critical value. To stop the plasma discharge
Control method was adopted.

In the characteristic curve of FIG. 3 in which time is plotted on the horizontal axis, there is a transition region R2, a stable region R3, a falling region R4, and a flat region R5 from a sharp rise (rise region R1) starting from the start of etching. The characteristic curve is obtained,
Generally, the etching is considered to be completed near the end point TE, and the discharge is finally stopped after a short time ΔT has elapsed. This slight time ΔT is called an over-etching time.

However, as described above, the control by the etching end point is an important factor for determining the quality of a semiconductor element or a circuit. In practice, however, the type of the sealing gas used, the material to be etched, Furthermore, since it depends on the patterning conditions such as the type of the underlying substrate,
It is hard to decide uniquely. Therefore, the setting of the etching end point requires the judgment of the altitude and the accumulation of experience with reference to the past data.

In addition, in order to distinguish a change in the amount of electromagnetic waves generated when aluminum or the like is peculiarly etched from a variation in the total plasma light emission generated in the depressurized vessel, signals obtained from both light emissions are arithmetically processed. A method of removing the fluctuation of the plasma is used.

By employing this method, fluctuations in light emission due to fluctuations in power supply voltage and the like not caused by etching can be removed, and more accurate detection can be performed.

[0012]

However, the materials to be etched are diversified. For example, materials having a very weak electromagnetic emission at the time of plasma etching, such as forming the gate of a thin film transistor (TFT) with tungsten or molybdenum, are also available. is increasing. In addition, a plasma apparatus that generates plasma outside the decompression vessel and introduces the plasma into the vessel is put into practical use, and it may be difficult to detect a specific change in light emission accompanying the progress of etching. In such a case, the weak light emission itself is treated as a voltage characteristic curve of the etching. However, since a variation due to factors other than the etching is included, highly reliable processing cannot be performed.

In the conventional etching process, it is difficult to distinguish between the variation of the electromagnetic wave peculiar to the etching material and the variation of the total plasma emission due to the diversification of the material to be etched and the plasma process. The setting of the etching end point that determines the end was incorrect.

The present invention provides a novel etching apparatus which solves such disadvantages.

[0015]

SUMMARY OF THE INVENTION The present invention provides an etching chamber in which an object to be etched is installed and etched by a plasma gas, a gas pressure detecting device for detecting a gas pressure in the etching chamber, and a gas pressure detecting device. A means for determining the etching end time based on the output.

Further, an etching chamber for installing an object to be etched and etching with a plasma gas, a photoelectric conversion device for detecting electromagnetic waves generated by plasma discharge, a gas pressure detection device for detecting a gas pressure in the etching chamber, Means for obtaining a signal of a characteristic curve having a rising area, a stable area, a falling area and a flat area after the start of etching of the object to be etched from the output of the photoelectric conversion device and the output of the gas pressure detecting device; Means for determining an etching end time from a signal of a curve.

The present inventor utilizes the fact that the plasma emission changes with a waveform similar to the differential waveform in response to the fluctuation of the pressure in the chamber, and applies this pressure fluctuation to the setting of the etching end point. For example, FIG. 2 axis horizontal axis represents time and the vertical axis the light emission intensity (photoelectric conversion value V) and a characteristic curve when the pressure (Pa), a MoW alloy thin film on a SiO ₂ substrate 1
10 ° C., CF ₄ : 330 SCCM, O ₂ : 370S
Etched by CCM. The plasma power is 1000 W and the initial gas pressure is 26 Pa. Gas pressure from 26Pa to 30P
a, the emission intensity changes from 0.06 V to 0.1
It shows that it changes to 2V.

Since the light emission intensity is approximately proportional to the etching amount, the etching amount can be estimated by detecting a gas pressure fluctuation corresponding to the light emission intensity. In an actual etching system, the gas pressure in the etching chamber is monitored by a gas pressure detector, and the fluctuation is fed back.
Since the gas source valve is controlled to maintain a constant gas pressure and perform stable etching, the gas pressure fluctuates slightly throughout the process, but by detecting the feedback amount, the pressure is increased. You can know the magnitude of the fluctuation.

In FIG. 3, the curve shows the change in gas pressure (curve B) and the change in plasma light emission intensity (curve A) with respect to the etching time, and is an example of the case applied to the etching of an aluminum thin film.

In the plasma etching, for example, the emission luminance changes as a metal thin film having a predetermined thickness to be dry-etched is etched, and the intensity change is represented along with the time axis, as shown in FIG. Region R1,
A characteristic curve having a transition region R2, a stable region R3, a descending region R4, and a flat region R5 is obtained.

Since the etching end point is determined on the basis of the fall of the change in the light emission intensity, the etching end point TE can be similarly determined on the basis of the pressure change. That is, in the figure, the characteristic curve B shows a change in the gas pressure (feedback amount of gas adjustment to the gas source) corresponding to the curve A, and it can be seen that the characteristic curve B largely fluctuates in the regions R1 and R4.

From this result, it is possible to apply the present invention to an etching process in which plasma light emission is weak or no light emission occurs.

When plasma light emission is generated, this light emission can be used in combination with gas pressure output to set a more accurate etching end point.

Further, the present invention mainly uses a characteristic curve based on light emission, further uses gas pressure detection, and uses a light emission phenomenon for endpoint detection during dry etching.
The detection accuracy can be improved by detecting the pressure and removing the pressure fluctuation component from the light emission characteristic curve.

That is, in the case of ordinary light emission detection, an electromagnetic wave having a wavelength that changes by etching and a change due to a parameter change such as electric power, such as total light, are captured, and only the components that change by etching are extracted by taking the ratio. According to the present invention, the accuracy can be further improved by removing the variation of the gas pressure component.

[0026]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of an etching apparatus according to the present invention will be described with reference to FIGS.

As shown in FIG. 1, an etching apparatus 1 includes an etching chamber 2 on which a substrate 11 to be etched is placed on a support 10, a plasma gas source 3 for introducing a plasma gas into the etching chamber 2, and an etching chamber 2. A gas pressure detecting device 5 is connected to the etching chamber, and photoelectric conversion for detecting plasma emission at a small distance from an optical filter window 12 formed in the wall of the etching chamber. The device 6 is arranged. The gas pressure control device 7 controls the gas source 3 and the exhaust system 4 according to the output of the gas pressure detection device 5.
Is adjusted so that the gas pressure in the etching apparatus 2 becomes constant. The etching end point detecting device 8 determines the time of the etching end point based on the output signal of the gas pressure detecting device 5 and the output signal of the photoelectric conversion device 6. The etching end point detecting device 8 corresponds to the etching condition,
The configuration is such that it is possible to select whether to use only the output signal of the gas pressure detection device 5 or to use both the output signal of the gas pressure detection device 5 and the output signal of the photoelectric conversion device 6.

Further, inside the etching chamber 2, discharge electrodes 13 and 14 for generating plasma are opposed to each other, and plasma discharge can be performed by an external high-frequency power supply 15. The photoelectric conversion device 6 is constituted by, for example, a photodiode or a phototransistor as a sensor.
Captures the emission of electromagnetic waves generated when is etched.

A description will be given of a case where a semiconductor element for forming a MoW film as a wiring is dry-etched using the apparatus 1.

First, one semiconductor element is sampled from the same lot, the characteristics of the etching are examined, and an optimum etching end point is determined.

That is, the selected semiconductor element 11 to be etched is placed on the support 10 in the etching chamber 2, and dry etching by plasma discharge is started.
Since the film to be etched on the semiconductor device is a MoW alloy, since the plasma emission is weak, it is difficult to capture the electromagnetic wave emission peculiar to MoW. Therefore, the total emission of the plasma is detected by the photoelectric conversion device 6. Etching equipment 1
In order to ensure that the various conditions required for etching, that is, the composition of the introduced gas, the gas pressure, and the discharge power, always conform to the predetermined program, feedback is made to compensate for any fluctuation in each element. ing. In the figure, when the gas pressure in the etching chamber fluctuates,
The gas pressure detecting device 5 detects the fluctuation and inputs the output to the gas pressure control device 7 to control the gas source 3 and the exhaust system 4 so as to be controlled to be constant.

At the start of the etching, the gas pressure in the etching chamber 2 is detected by the gas pressure detecting device 5 and converted into an electric signal.
On the one hand, this signal is fed back to the gas source to adjust the gas pressure so that the pressure is maintained at a predetermined level, and is input to the etching end point detecting device 8 on the other hand.

After the electromagnetic wave generated in the room is extracted through the filter 12, it is converted into an electric signal by the photoelectric conversion device 6.

The signals from the gas pressure detecting device 5 and the photoelectric conversion device 6 are amplified by the etching end point detecting device 8 and are subjected to A / D conversion.
The converter performs sampling in, for example, 0.1 second steps. In addition, after this value is converted into a 12-bit digital signal, it is electrically connected to the computer 20.

In the computer 20, a RAM 22, a CPU 23, a ROM 24, an HDD (hard disk) 25, and an FDD (floppy disk) 2 are connected via a bus line 21 to which an output signal of the etching end point detecting device 8 is input.
6. The storage 27, the display circuit 28 and the keyboard 29 are electrically connected. The storage device 27 is configured by a magnetic or optical disk storage device and stores digital data.

As described above, after being converted into a 12-bit digital signal, the signal is stored in the RAM 22 via the bus line 21. Data can be read and stored as needed, and the operation result and command can be stored. The display 28 to be displayed is
It is composed of a liquid crystal display device and the like.

Next, the operation of the computer 20 will be described. A 12-bit digital signal is stored in the RAM 22 and the storage device 27. At the same time, the result of the differentiation operation of the same signal is stored.

On the other hand, the application program stored in the FDD 26 incorporates a program for changing a certain threshold level.
Read application program from memory 2
7 and stored in the RAM 22. When this is executed by the CPU 23, the threshold level at the start point and the threshold level at the end point of the descending region R4 are displayed on the screen displayed on the display 28 by the application program, and further, these are arbitrarily moved. it can.

Accordingly, the progress of the etching in the etching chamber 2 is stored in the memory 27 and the RAM 22 via the gas pressure detecting device 5, the photoelectric conversion device 6, the etching point detecting device 8 and the bus line 21 each time. , Can be simultaneously displayed on the display 28 if necessary.

This display means drives the CPU 23 in response to an instruction input from the keyboard 29 or the like, and first reads out the control program stored in the HDD 25 and displays it on the display unit 28. Therefore, the operator operates the keyboard 29 and the like by the program means projected on the display 28,
Data and differential operation results stored in the RAM 22 and the storage device 27 can be selectively and arbitrarily extracted and displayed on the display device 28. Further, in addition to the differential operation result of the data, the threshold level can be superimposed and displayed, and the threshold level can be moved to an arbitrary level by operating the keyboard 29. By simulating the etching end point in these individual data, an optimum end point in the etching process is set.

The end time can be determined by adding a predetermined over-etching time from the end point.

In the present embodiment, both the pressure and the light emission are detected, and the (light emission / pressure) value, the (pressure / light emission) value, and the like are calculated, whereby the light emission phenomenon and the fluctuation of the pressure are mutually recognized. Has a function of compensating and removing, and a highly accurate etching end point can be obtained even when the light emission is weak.

The plasma generated by the external discharge, instead of the plasma discharge by the electrodes 13 and 14, is applied to the etching chamber 2
, It may be difficult to detect fluctuations in plasma emission in a room. In such a case,
The etching end point can be determined by the output of the gas pressure detecting device 5. Further, for a material to be etched which does not generate a specific electromagnetic wave spectrum or is difficult to detect, it is effective to determine the etching end point by detecting the gas pressure.

[0044]

According to the present invention, a change in gas pressure generated during etching by plasma discharge is detected, and an etching end time after the start of plasma etching is determined. Therefore, the time is determined independently of plasma emission. Even when the detection of plasma emission cannot be expected, the etching end can be detected. Even when the specific spectrum has weak emission and large fluctuation noise, an accurate end can be determined by the combined use. Therefore, it is possible to obtain an etching apparatus capable of stably processing an object having the same film quality and an object having a similar configuration between the same lot.

[Brief description of the drawings]

FIG. 1 is a conceptual diagram showing an etching apparatus according to an embodiment of the present invention.

FIG. 2 is a curve diagram showing a relationship between a change in pressure and plasma emission in an etching process.

FIG. 3 is a characteristic curve diagram of plasma emission and pressure change generated in the etching process.

[Explanation of symbols]

 1: Etching apparatus 2: Etching chamber 3: Gas source 4: Exhaust system 5: Gas pressure detector 6: Photoelectric converter 7: Gas pressure controller 8: Etching end point detector 10: Support body 11: Substrate to be etched 12 : Optical filter window 13, 14: Electrode 20: Computer

Claims (2)

[Claims] An etching chamber in which an object to be etched is placed and etched by a plasma gas, a gas pressure detecting device for detecting a gas pressure in the etching chamber, and an etching end point is determined by an output of the gas pressure detecting device. An etching apparatus comprising: 2. An etching chamber for installing an object to be etched and etching with a plasma gas, a photoelectric conversion device for detecting electromagnetic waves generated by plasma discharge, and a gas pressure detecting device for detecting a gas pressure in the etching chamber. Means for obtaining a signal of a characteristic curve having a rising area, a stable area, a falling area, and a flat area after the start of etching of the etching target from the output of the photoelectric conversion device and the output of the gas pressure detection device, Means for determining an etching end point from the signal of the characteristic curve.