JPH09209179A - Dry etching device and its cleaning method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To stably detect the end point of etching without degrading a working rate even if the number of treating sheets increases and without creating the cause for particles with a dry etching device having a window for an optical type end point detector. SOLUTION: The window 6 for detecting the end point of the side wall of the treating chamber 1 of the dry etching device is formed to a projecting shape and means (14, 15) for forming plasma for cleaning separately from plasma for etching are disposed, by which the deposits 11 sticking to the window 6 are removed. Then, even if the number of the treating sheets increases, the degradation in the working rate as in the conventional wet cleaning does not arise and the cause for the particles like the conventional dry cleaning is not created.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dry etching apparatus used as a semiconductor manufacturing apparatus, and more particularly to a detection window structure of an optical etching end point detector and a cleaning method thereof.

[0002]

2. Description of the Related Art In recent years, in the manufacturing process of semiconductor devices,
For example, a plasma etching method using a reaction component in gas plasma is used as an etching method capable of forming a fine pattern with high accuracy. In a dry etching apparatus using a plasma etching method, a window is provided in a processing chamber, and a change in emission intensity in plasma is monitored through this window to detect the end point of etching processing. This type of dry etching apparatus is known, for example, in "Introduction to Ultrafine Machining", pages 62 to 69 (published by Ohmsha in 1989).

Here, as an example, a sectional view of a processing chamber of the RIE dry etching apparatus is shown in FIG. An upper electrode 2 and a lower electrode 3 are provided in the processing chamber 1, and a high frequency voltage is applied to the lower electrode 3. The upper electrode 2 is provided with a gas hole 4 for supplying a process gas, and the inside of the processing chamber 1 is evacuated from an exhaust port 5 connected to a vacuum pump and a pressure control mechanism (not shown). A window 6 fixed by a window frame 7 is provided on the side wall of the processing chamber 1, and an end point detector 8 is provided at a position where the emission intensity of plasma inside the processing chamber 1 can be monitored through the window 6. Window 6 in FIG.
The sectional view which expanded the part is shown. The window 6 is screwed together with the window frame 7
And the processing chamber 1 side is kept in vacuum by an O-ring 10.

Next, the operation of the conventional RIE dry etching apparatus will be described. The wafer 12 to be etched is placed on the lower electrode 3. A process gas having an arbitrary flow rate is supplied from the gas hole 4, and the processing chamber 1 is adjusted to an arbitrary pressure between 0.1 and 100 Pa by a vacuum pump and a pressure control mechanism. By applying a high frequency voltage to the lower electrode 3, an etching plasma 13 is generated in the processing chamber 1. CF is a commonly used process gas.
4, Cl2, etc. The etching target thin film on the wafer 12 is etched with high precision by the ions and neutral active species generated in the etching plasma 13.

At this time, the end point detector 8 monitors the change in the emission intensity at a specific wavelength in the etching plasma 13 through the window 7, for example, a wavelength of 308 nm in the case of aluminum etching. Plasma for etching 1
Since the light emission color differs depending on the atoms and molecules present in 3, the etching end point can be detected by monitoring the change in the emission intensity of the wavelength matching the film to be etched.

[0006]

As the number of processed wafers increases, the deposition (deposition) component in the etching plasma adheres to the side wall of the processing chamber 1 as a deposit 11. .. This depot 11 naturally adheres to the window 6, and as it adheres thicker, the light from the plasma becomes less likely to pass through the window, and the level of the emission intensity of the light received by the end point detector 8 decreases. . As a result, the change in emission intensity cannot be monitored, the end point of etching cannot be determined, the etching time is exceeded, and there is a problem that etching abnormality occurs.

As a method of removing the deposit attached to the window, there is a method of performing wet cleaning or dry cleaning. However, in the former, there is a problem in that the operation rate of the apparatus is lowered because it takes time to open the processing chamber 1 to the atmosphere, and to clean each component and perform a vacuuming work.

The latter is a method of removing the deposit formed in the window 6 by the gas plasma of O2, SF6 or the like. This dry cleaning is performed by a dry etching device or CVD.
It is well known for devices. However, the plasma V generated on the anode side as in the RIE dry etching apparatus
When an etching method with a small dc is used, there is a problem that ions are less incident on the anode side and deposits that cannot be completely removed by cleaning remain on the upper electrode and side walls, and these deposits are peeled off to cause generation of particles. Furthermore, since the atmosphere in the processing chamber changes after dry cleaning, it becomes necessary to introduce seasoning for the purpose of stabilizing the atmosphere in the chamber for several tens of minutes under the same conditions as etching.

Further, as a method of preventing the deposit 11 from adhering to the window 6, a dry etching apparatus in which a heating mechanism such as a heater is attached to the window is disclosed in Japanese Patent Laid-Open No. 3-75389. However, as fine processing of etching progresses in recent years, particularly in etching in which a deposition gas is supplied as a process gas, the amount of depot attached to the side wall of the processing chamber increases, so that temperature control of the side wall of the processing chamber becomes important. Is coming. In the method of attaching the heating mechanism to the processing chamber window in this publication, it is not possible to heat only the window portion, and there occurs a portion where the temperature of the sidewall of the processing chamber becomes uneven.
Deposition also becomes non-uniform, which causes particles due to desorption from the thick deposition area.

As described above, when the wet cleaning method is used as a method for removing the window deposit that affects the etching end point determination, the operating rate of the apparatus is lowered.
Further, there is a problem that dry cleaning in the RIE dry etching device causes generation of particles.

The object of the present invention is to solve these problems,
It is an object of the present invention to provide a dry etching apparatus and a cleaning method thereof capable of removing the deposit attached to the end point detection window.

[0012]

According to the structure of the present invention, a detection window is provided in an etching processing chamber, and a detector is used to monitor the emission intensity during etching in the processing chamber through the detection window. The window is provided so as to project in a convex shape outside the processing, and a plasma generating means for generating a cleaning plasma is provided inside the convex shape.

In the present invention, cleaning plasma is generated in the convex window. For example, by providing a coil around the window and applying a high frequency to this coil,
Separately from the etching plasma, cleaning plasma is generated only on the convex portion of the EPD window, and the cleaning plasma can remove the deposits formed on the surface of the window.

Further, the structure of the present invention is a method for cleaning a detection window of a dry etching apparatus in which a detection window is provided in the etching processing chamber, and the emission intensity during etching in the processing chamber is monitored by the detector from the detection window. It is characterized in that plasma is generated and cleaning is performed inside the detection window at a timing other than during the etching process.

According to the present invention, since the deposit attached to the side wall of the processing chamber remains as it is and the amount of the deposit that is peeled off by cleaning is small, it is possible to suppress the generation of particles and the cleaning plasma is used only in the convex portion of the window. Can be minimized and the effect on the atmosphere of the processing chamber can be minimized, so the seasoning time can be shortened,
Further, since the deposits attached to the side wall of the processing chamber are constantly and uniformly attached, only a part of the deposits is thickly attached and easily peeled off, which does not cause particles.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, the present invention will be described with reference to the drawings. As an embodiment of the present invention, a configuration using an inductive coupling for a method of generating cleaning plasma will be described with reference to a partial sectional view of FIG. Also in this embodiment, the apparatus configuration uses the RIE dry etching apparatus of FIG. The upper electrode 2 and the lower electrode 3 in the processing chamber 1 are provided, and the high frequency voltage of the lower electrode 3 is applied. The upper electrode 2 is provided with a gas hole 4 for supplying a process gas, and the inside of the processing chamber 1 is evacuated from an exhaust port 5 connected to a vacuum pump and a pressure control mechanism (not shown). A window 6 fixed by a window frame 7 is provided on the side wall of the processing chamber 1, and the window 6 has a convex shape. An end point detector 8 is provided at a position where the emission intensity of the etching plasma 13 inside the processing chamber 1 can be monitored through the window 6.

FIG. 1 shows an enlarged sectional view of a portion of the window 6. The window 6 is fixed together with the window frame 7 by screws 9, and the inside of the processing chamber 1 is held in vacuum by an O-ring 10. The window frame 7 has a shape that covers the periphery of the window 6, and a gap is provided between the windows 6 of the window frame 7, and a coil 15 having a structure capable of applying a high frequency is provided. Further, a conductive seal 14 is provided between the window frame 7 and the window 6 and plays a role of preventing leakage of high frequencies.

The wafer 12 to be etched is placed on the lower electrode 3. A process gas having an arbitrary flow rate is supplied from the gas holes 4, and the processing chamber 1 has a pressure of 0.1 to 100 Pa.
The plasma 13 is generated in the processing chamber 1 by applying a high-frequency voltage to the lower electrode 3 by adjusting the pressure to an arbitrary pressure between. CF4, Cl2, etc. are used for the supplied process gas. The thin film to be etched on the wafer 12 is etched by the ions and neutral active species generated in the etching plasma 13. At this time, the end point of the etching is detected by monitoring the change in the emission intensity of a certain wavelength in the etching plasma 13 by the end point detector 8 through the window 7.

Next, the operation of cleaning the window for the optical end point detector of this embodiment will be described. As the number of processed wafers 12 to be etched increases, wafer 1
Aluminum or a resist which is an object to be etched on 2 reacts with active species in the etching plasma 13 and adheres to the side wall of the processing chamber 1 and the window 6 as a chloride of aluminum or a resist-based deposit 11.

In order to remove the deposit 11 attached to the window 6, a cleaning gas such as O 2 or SF 6 is supplied from the gas hole 4 at a time other than the etching process, for example, immediately after the etching step is completed or between lots. When the pressure in the processing chamber 1 is adjusted to an arbitrary pressure of several 1 to 100 Pa and a high frequency, for example, 13.56 MHz is applied to the coil 15, the cleaning plasma 16 is generated only inside the window 6, and the convex window 4 is generated. The deposited depot 11 is hit by the ions and radicals in the plasma, gasified, exhausted to the outside of the processing chamber 1, and removed to perform cleaning.
At this time, a high frequency power of about several hundred W is applied although it depends on the pressure of the processing chamber and the volume of the convex window. The cleaning plasma 16 removes the deposit 11 attached to the window 6.

Further, the deposit 11 such as aluminum chloride deposited on the side wall of the processing chamber 1 is likely to be peeled off by the cleaning plasma 16, and after the cleaning, the seasoning is performed by plasma using etching gas such as Cl 2 and BCl 3. However, a very short time is sufficient as compared with the seasoning time described in the prior art. Therefore, when the next wafer 12 is subjected to the etching process, the window 6 has already been cleaned, and the emission intensity of the light passing through the window 6 does not decrease, so that the etching end point can be surely detected.

In the present embodiment, the cleaning plasma 16 is generated by the inductive coupling system provided with the coil 15 for applying a high frequency around the window 6, but the means for generating the plasma has a different structure. But it doesn't matter.

[0023]

As described above, according to the present invention, in the dry etching apparatus having the window for the optical end point detector, the structure of the window is made convex, and the plasma is generated around the convex window. Since the cleaning plasma can be generated only in the window portion, the deposit attached to the window can be removed, and thus stable etching end point detection can be performed. Further, even if the number of processed wafers is increased, the window surface wet cleaning time and seasoning time are not required, and the operation rate of the apparatus is not lowered.

[Brief description of the drawings]

FIG. 1 is a sectional view of a window portion for an end point detector of a dry etching apparatus of the present invention.

FIG. 2 is a sectional view of a processing chamber of a conventional RIE dry etching apparatus.

FIG. 3 is a cross-sectional view of an end point detector window portion of a conventional dry etching apparatus.

[Explanation of symbols]

 1 Processing Chamber 2 Upper Electrode 3 Lower Electrode 4 Gas Hole 5 Exhaust Port 6 Window 7 Window Frame 8 End Point Detector 9 Screw 10 O-ring 11 Depot 12 Wafer 13 Etching Plasma 14 Conductive Seal 15 Coil 16 Cleaning Plasma

Claims (4)

[Claims] 1. A dry etching apparatus in which a detection window is provided in the etching processing chamber, and the emission intensity during etching in the processing chamber is monitored by a detector from the detection window,
A dry etching apparatus characterized in that the detection window is provided so as to project out of the process in a convex shape, and a plasma generating means for generating cleaning plasma is disposed inside the convex shape. 2. The dry etching apparatus according to claim 1, wherein the plasma generating means portion comprises a coil for applying high frequency power in the convex portion. 3. The dry etching apparatus according to claim 2, further comprising a conductive seal disposed between the detection window and the convex window frame to prevent leakage of frequency power. 4. A method for cleaning a detection window of a dry etching apparatus, wherein a detection window is provided in the etching processing chamber, and the emission intensity during etching in the processing chamber is monitored by a detector from the detection window, in a timing other than the etching processing. Then, a cleaning method for an etching apparatus, characterized in that plasma is generated inside the detection window to perform cleaning.