JPH05226461A - Dry cleaning method - Google Patents

Abstract

PURPOSE:To protect the attraction surface of a stage which holds a processed object against deterioration attendant on cleaning and to ensure the processing characteristics of a device in reproducibility after and before cleaning by a method wherein the attracting surface of the stage is covered with a covering material whose attracting surface has the same two-dimensional or three-dimensional shape with the processed object while cleaning is executed. CONSTITUTION:The electrostatic attraction surface of a stage 3 is covered with a covering material 34 whose attraction surface has the same two-dimensional or three- dimensional shape with a wafer 5 while cleaning is executed. The covering material 34 is material capable of electrostatically attracting the wafer 5 and high in resistance to cleaning or electrostatically attractable material covered with other material high in resistance to cleaning. By this setup, the attracting surface of the stage 3 holding the wafer 5 can be protected against deterioration due to dry cleaning, the processing characteristics of a device can be kept high in reproducibility after and before cleaning, and the device can be enhanced in safety. Furthermore, the covering material 34 can be mounted without any additional function and process, so that the device can be kept high in processing reliability without deteriorating in operating efficiency.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dry cleaning method for an apparatus which holds an object to be processed by utilizing electrostatic attraction in a semiconductor manufacturing process or the like.

[0002]

2. Description of the Related Art A stage utilizing electrostatic attraction has a function of burying an electrode near one surface of an insulator and attracting and holding the object by an electric field generated between the object and the electrode. It has a function of improving the heat transfer effect between the stage including the electrostatic attraction surface and the object to be processed by applying an appropriate electric field.

On the other hand, in the PVD or CVD apparatus, or the etching or ashing apparatus, the increase of particles due to the deposition of the film on the inner wall of the apparatus and the variation of the processing characteristics have become problems as the operation is repeated. As one method to solve this, dry cleaning using plasma is known, and it is a general operation method to operate while maintaining the device characteristics by alternately performing processing and cleaning. There is. Dry cleaning, which utilizes a chemical reaction between a cleaning gas excited by heat, discharge, or light, and a substance to be cleaned is kinetic energy supplied to the substance to be cleaned by the interposition of ions or electrons and the electric field or magnetic field. It is known that the reaction can be promoted by such a method, and the processing time is usually made efficient by appropriately combining these methods. Also, in order to improve the effect on the position to be cleaned, such as the stage for fixing the object to be processed and the container wall, the plasma effect is controlled using a magnetic field or an assist effect by ion energy is applied by applying an electric field. Cleaning was performed by using the or changing the cleaning pressure.

[0004]

When the dry cleaning is performed by the conventional method, the state of the adsorption surface of the stage changes before and after the dry cleaning, and the heat transfer characteristics change. This causes a problem that the growth rate and its distribution are changed, and the processing reproducibility of the apparatus is lowered. This phenomenon remarkably occurs when an attempt is made to improve the cleaning effect of the stage part by utilizing the charged particle energy supplied to the stage by the electric field and the concentration of the plasma flow generated by the magnetic field, and it is also a cause of hindering the operating rate of the device. It was

An object of the present invention is to provide a dry cleaning method in which the processing characteristics after dry cleaning do not change.

[0006]

In order to solve the above-mentioned problems, the present invention provides a dry cleaning method for an apparatus having a function of holding an object to be processed by electrostatic attraction.
Cleaning is performed while the object to be treated and the object to be attracted have the same planar shape on the electrostatic attraction surface, or cleaning is performed while the object to be treated and the object to be treated are three-dimensionally identical in shape. The method of doing

Here, if the cover placed on the electrostatic attraction surface is made of an electrostatically attractable material, a cleaning resistant material, or a constituent material in which the electrostatically attractable material is coated with a cleaning resistant material. It is suitable.

[0008]

Function: The portion of the stage where the object to be treated is adsorbed is not contaminated due to the object to be treated during normal processing.
The adsorption surface is usually exposed even when the device requires cleaning. In practice of dry cleaning, re-dissociation of sublimable products due to cleaning and recombination of substances generated by re-dissociation into non-sublimable substances are also progressing at the same time. As described in the related art, when the effect of the magnetic field or the electric field is used, the energy may cause surface modification such as nitriding or oxidation, and further deterioration due to deposition. Occur. However, all of these phenomena are due to chemical-physical contact from the outer space to the surface, and by preventing this contact, the occurrence of problems can be stopped. In order to solve these problems, in the present invention, during dry cleaning, the object to be treated and the adsorption surface are covered with the same shape so as to prevent the portion to which the object to be treated is adsorbed from being directly exposed to the dry cleaning atmosphere. Is placed so that the state of the surface for adsorbing the object to be treated does not change before and after cleaning.

Since the object to be processed and the adsorption surface have the same shape, the surface to be adsorbed for the object to be treated is covered without being exposed without hindering the cleaning of the contaminated portion on the stage including the adsorption surface. Can be prevented. In addition, the cover is made of a material capable of adsorbing to improve the adhesion to the adsorbing surface and further enhance the above-mentioned effect. This effect can be used even when the structure has a structure in which the cover cannot be fixed without the action of.

Further, by forming the cover from a cleaning-resistant material, the supply of the cleaning substance by the cover is eliminated, and the above problems can be prevented without impairing the cleaning effect of the apparatus. Further, by forming the cover with a constituent material in which a suction-resistant material is covered with a cleaning-resistant material, a high suction surface protection effect can be obtained without impairing the cleaning effect.

Further, since the cover is spatially formed in the same shape as the object to be processed, the cover can be introduced in the same manner as when the object to be processed is introduced into the apparatus. Therefore, the cover is fixed to the suction surface. Since no new process or mechanism is required, the above effect can be obtained without lowering the operation rate of the device.

[0012]

EXAMPLE FIG. 1 (a) shows a cross-sectional view of one structural example of a stage utilizing electrostatic attraction. In the electrostatic chuck 100 made of an insulator attached to the stage base 200, adsorption electrodes 51 and 52 are embedded near the adsorption surface. By applying a voltage from the DC power supply 13 to this electrode, an electric field is formed between the electrode and the wafer 5, and this can be held by electrostatic force. FIG. 2 shows an example of the configuration of an apparatus according to the present invention using microwave plasma. Further, FIG. 1 (b) shows a state in which the wafer to be processed is adsorbed in this apparatus. In FIG.
A reaction chamber 1 includes a wafer stage 3 and a table for holding a wafer 5 which is an object to be processed by an electrostatic adsorption mechanism. The wafer is loaded and unloaded by a transport mechanism (not shown) from a wafer transport port 32 that can be opened and closed by a gate valve (not shown), and is held on the wafer stage 3. The gas supply ports 41 and 42 are connected to a gas supply system (not shown), and a CVD gas,
An etching gas is supplied during the etching process. The exhaust port 16 is connected to an exhaust system (not shown) so that the pressure in the reaction chamber can be kept constant while introducing gas. A magnetic field control coil 6 is provided on the outer periphery of the reaction chamber 1. At the position facing the wafer stage 3 in the reaction chamber,
The plasma chamber 2 is hermetically connected. A waveguide 7 for supplying microwave power is connected to the plasma chamber 2 through a microwave window 21. The main coil 8 is arranged such that its geometric center is on the atmosphere side of the vacuum side end surface of the microwave window.

At the time of dry cleaning, the gas supply port 4
Cleaning gas is supplied from 1, 42 to supply microwave power and main coil power for plasma generation, and the direction of the plasma flow is controlled by adjusting the magnetic field control coil current to control the respective parts of the reaction chamber. A high cleaning effect is obtained. Further, by supplying RF power from an RF power source (not shown) to the stage 3, an electric field is generated in the vicinity of the stage to improve the cleaning effect.

Using the above apparatus as a CVD apparatus, Si
After forming the O ₂ film, the inside of the apparatus is cleaned with NF ₃ gas, and the film forming characteristics after that, such as film forming speed, film thickness distribution and refractive index, are shown with the number of processed wafers as the horizontal axis. Figure 4 shows the case of cleaning without doing
FIG. 3 shows the case of covering and cleaning. When cleaning was performed without covering, the wafer processing time of about 10 sheets was required to recover the desired characteristics, whereas with covering, the desired characteristics were obtained immediately after cleaning. Has been.

In addition, an example of the cover of the present invention having the same planar shape when a wafer is used as the object to be processed is shown in FIG.
FIG. 6 shows an example of the cover of the present invention having the same three-dimensional shape. The core substrate is made of silicon wafer and the outer circumference is made of Al
It is also possible to coat with a spatter or the like to form an adsorbent. Reference numeral 33 in FIG. 5 is a knob. When the three-dimensional shape is the same, the thickness is set to a value (0.6 to 30 mm) that can be transferred by the device transfer system. In the figure, A is used as a cleaning resistant material when a fluorine-based gas is used.
l and sapphire are W and quartz as an example of the cleaning resistant material when chlorine gas is used.
It goes without saying that u and the like can be used.

[0016]

As described above, the object to be treated and the suction surface are planarly the same shape, or the object to be treated is cleaned by covering the suction surface with a cover having the same shape spatially as the object to be treated. Since the adsorption surface that holds the body can be prevented from deterioration due to cleaning, reproducibility of the device processing characteristics before and after cleaning can be ensured, stability can be improved, and the cover can be covered without any new function or process. Since it can be mounted, this effect can be obtained with high reliability and without lowering the operating efficiency of the apparatus.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration example of a stage which is an apparatus for holding an object to be processed by an electrostatic attraction force, which is a target of dry cleaning according to the present invention, and FIG. Figure, (b) is bottom view

FIG. 2 is an apparatus cross-sectional view showing a configuration example of a microwave plasma CVD apparatus that performs CVD and etching by microwave plasma using the stage shown in FIG. 1 for holding a wafer to be processed.

FIG. 3 is a diagram showing the reproducibility of the processing characteristics when performing dry cleaning with the adsorption surface of the stage covered, and FIGS. 3 (a), 3 (b), and 3 (c) are respectively FIG. The changes in the refractive index, film thickness distribution and film formation rate of the SiO ₂ film formed on the surface of the wafer by the microwave plasma CVD apparatus of
Figure obtained under different operating conditions A and B of the device

FIG. 4 is a diagram showing the reproducibility of processing characteristics when dry cleaning is performed without covering the adsorption surface of the stage, and FIGS. 4 (a) and 4 (b) are respectively the microwave plasma of FIG. The change in the refractive index and film thickness distribution of the SiO ₂ film formed on the surface of the wafer by the CVD apparatus, and the film formation rate depending on the number of wafers processed are shown in FIG.
Figure obtained under the same operating conditions as operating condition A in

FIG. 5 is a diagram showing an example of a cover having the same planar shape as that of the surface to be attracted of the object to be treated, FIG. 5A is a plan view of the cover,
The figure (b) is a side view, and the figure (c) is a diagram showing an example of a cleaning-resistant material used for the cover, separately for adsorbing substances and non-adsorbing substances.

6A and 6B are views showing an example of a cover having the same three-dimensional shape as the object to be processed, where FIG. 6A is a plan view of the cover, FIG. 6B is a side view, and FIG. The figure which shows one example of the anti-cleaning material used for the cover for the adsorptive substance and non-adsorptive substance

[Explanation of symbols]

 3 Stage 5 Wafer 51 Electrode 52 Electrode 100 Electrostatic Chuck 200 Stage Base

Claims (5)

[Claims] 1. In dry cleaning of an apparatus having a function of holding an object to be processed by electrostatic attraction, cleaning is performed while placing a cover having an identical planar shape on the electrostatic attraction surface. A dry cleaning method characterized by carrying out. 2. In dry cleaning of an apparatus having a function of holding an object to be processed by electrostatic attraction, cleaning is performed while a cover having a three-dimensionally same shape as the object to be treated is placed on the electrostatic attraction surface. A dry cleaning method characterized by: 3. The dry cleaning method according to claim 1, wherein the cover placed on the electrostatic adsorption surface is made of a material capable of electrostatic adsorption. 4. The dry cleaning method according to claim 1 or 2, wherein the cover placed on the electrostatic attraction surface is made of a cleaning resistant material. 5. The dry cleaning method according to claim 1, further comprising a cover placed on the electrostatic attraction surface,
A dry cleaning method, characterized in that a material capable of electrostatic adsorption is covered with a cleaning resistant material.