JPH05275385A - Plasma processing device - Google Patents

Abstract

PURPOSE:To improve the processing efficiency and yield of the object to be processed by preventing a reaction product from sticking on the surface of a means for holding the object to be processed and a plasma concentrating means which are provided with plasma electrodes so that the means for holding the object to be processed and the plasma concentrating means can be used for a long period without frequent maintenance works such as cleaning, replacement, etc. CONSTITUTION:At least one of a means for holding the object to be processed 17 and a plasma concentrating means 14, which are provided to plasma electrodes 16 and 9, is provided with heating means H1 and H2, and the device is heated up and kept at a temperature where a reaction product generated through plasma processing will not be stuck on the means 17 and 14.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a plasma processing apparatus.

[0002]

2. Description of the Related Art In recent years, a processing apparatus using plasma is often adopted in various apparatuses such as a semiconductor manufacturing apparatus. The plasma processing apparatus includes a pair of electrodes for plasma generation that are arranged to face each other in an airtight processing chamber, and generate plasma by discharge between these electrodes,
Thereby, the object to be processed is processed.

A holding means such as a clamp ring for holding an object to be processed is provided on one side of the pair of plasma electrodes, and the object to be processed such as a semiconductor wafer is held by the holding means. After being fixed and held on the electrode on one side, a predetermined processing gas is introduced into the processing chamber to start plasma processing. At this time, the other electrode is often provided with a concentrating means for concentrating the plasma generated between the two electrodes on the object to be processed. As the concentrating means, for example, there is a focus ring formed in a ring shape having substantially the same diameter as the object to be processed, which is attached to the edge portion of the electrode.

[0004]

On the other hand, in such a plasma processing apparatus, a predetermined reaction product is generated by the plasma processing, and the reaction product is discharged from the processing chamber to the outside through the exhaust pipe path. Has been done. However, this reaction product tends to adhere to a particularly low temperature portion in the exhaust path. In particular, since the holding means and the concentrating means described above are arranged close to the plasma processing unit, the reaction products are likely to adhere to each other, and the reaction products are gradually stacked on the surfaces of the holding means and the concentrating means as the plasma processing continues. To go.

The reaction product thus deposited and laminated on the surfaces of the holding means and the concentrating means may be peeled off from the holding means and the concentrating means after adhering, and it becomes particles and adheres to the surface of the object to be treated. May occur. Therefore, conventionally, the holding means and the concentrating means are periodically removed, and cleaning such as immersion in liquid or rubbing, or replacement is performed. It is preferable not to perform such maintenance work from the viewpoint of the operating efficiency of the processing apparatus and the processing efficiency of the object to be processed, and it is preferable to make the maintenance cycle as long as possible even when performing the maintenance. ..

Therefore, an object of the present invention is to provide a plasma processing apparatus capable of satisfactorily preventing the reaction products from adhering to the holding means and the concentrating means attached to the plasma electrode.

[0007]

Means for Solving the Problems In order to achieve the above object, the means according to the present invention is such that electrodes for plasma generation are opposed to each other in a processing chamber having airtightness, and one of these electrodes is provided on either side of the electrodes. In the plasma processing apparatus, holding means for holding the object to be processed is provided, and the electrode on the other side is provided with a concentrating means for concentrating the plasma generated between the electrodes on the object to be processed, At least one of the holding means and the concentrating means is provided with a heating means for raising and maintaining a temperature at which a reaction product generated by plasma treatment does not adhere to at least one of the holding means and the concentrating means. ing.

[0008]

In the means having such a structure, even if the reaction product generated by the plasma treatment tries to adhere to the holding means and the concentrating means, the holding means and the concentrating means prevent the reaction product from adhering by the heating means. Since the temperature is raised and maintained at the avoiding temperature, the reaction products are prevented from adhering to the holding means and the concentrating means. Therefore, the shield means can be favorably used for a long period of time with almost no maintenance such as cleaning and replacement.

[0009]

Embodiments of the present invention will now be described in detail with reference to the drawings. First, the structure of an etching apparatus will be described as an example of a plasma processing apparatus. As shown in FIG. 1, the hollow box-shaped processing chamber 1 has a structure capable of holding the inside airtight, and the wall portion of the processing chamber 1 is
It is made of a conductive material, for example, aluminum whose surface is anodized. An electrode body 4 connected to an elevating mechanism 2 via a connecting rod 3 is arranged in an upper part of the processing chamber 1 so as to be vertically movable. Similar to the processing chamber 1, the electrode body 4 is made of, for example, aluminum whose surface is anodized. The elevating mechanism 2 is composed of, for example, an air cylinder, a ball screw, or the like.

A fluid flow path 5 is formed in an annular shape inside the electrode body 4, and the fluid flow path 5 has an IN side pipe 6a as shown in FIG. 3 and FIG. And the pipe 6b on the OUT side are connected. Each of the pipes 6a and the OUT-side pipe 6b is connected to a temperature controller, for example, a cooler 8a via open / close valves 7a and 7b. The heat medium whose temperature has been adjusted to a predetermined temperature by the cooler 8a, for example, a cooling liquid obtained by mixing an antifreeze liquid and water, is used as the pipes 6a and 6b.
It is configured to circulate in the electrode body 4 through the above and to enable cooling of the electrode body 4.

On the lower surface of the electrode body 4, an upper electrode 9 made of a conductive material such as amorphous carbon is used.
Are provided in a state of being electrically insulated from the electrode body 4. A space 10 is provided between the upper electrode 9 and the electrode body 4.
Is formed, and the gas supply pipe 11 is connected to the space 10 so as to open from the electrode body 4 side.
The gas supply pipe 11 is connected to a processing gas supply source (not shown), and the etching gas is supplied into the space 10 through the gas supply pipe 11. As the etching gas, halogen-based gas, for example, CF gas-based CHF ₃ and CF ₄ gas is used. On the other hand, a plurality of openings 12 are formed in the upper electrode 9, and the space 10 is formed through these openings 12.
The gas supplied to the processing chamber 1 flows into the processing chamber 1.

Further, an insulating ring 13 is fitted around the outer periphery of the electrode body 4 and the upper electrode 9, and a focus ring 14 is mounted on the lower surface of the insulating ring 13. The focus ring 14 is formed of an insulating material such as tetrafluoroethylene resin in a ring shape, and extends from the lower surface of the insulating ring 13 to the outer peripheral edge of the lower surface of the upper electrode 9. The inner diameter of the focus ring 14 is formed to have substantially the same size as the target object to be etched, for example, the semiconductor wafer 15, so that plasma having substantially the same diameter as the semiconductor wafer 15 is generated, and the generated plasma is generated. It is configured to concentrate on the object to be processed. Further, a ring-shaped heater H1 is housed inside the surface of the focus ring 14 on the lower surface side in the drawing so as to come into contact with the lower surface portions of the electrode body 4 and the upper electrode 9. The detailed structure of the heater H1 will be described later.

On the other hand, in the processing chamber 1, the upper electrode 9
A lower electrode 16 for mounting an object to be processed, for example, a semiconductor wafer 15 is disposed at a lower position facing the. The lower electrode 16 is formed of, for example, an aluminum plate whose surface is anodized, and the upper surface of the lower electrode 16 is convex toward the upper electrode 9 side and is gentle toward the peripheral portion. It is formed on a curved surface.

A clamp ring 17 is provided on the outer periphery of the lower electrode 16 to press and hold the peripheral edge of the semiconductor wafer 15 toward the lower electrode 16. The clamp ring 17 is made of, for example, aluminum, quartz, ceramics or the like whose surface is anodized to form an insulating alumina coating. In addition, inside the clamp ring 17, a ring-shaped heater H2 is provided.
Are accommodated so as to contact the upper surface of the lower electrode 16. The detailed structure of the heater H2 will also be described later.

Immediately below the clamp ring 17, a plurality of shafts 18, for example, four shafts 18 are connected so as to extend toward the outside of the processing chamber 1.
The tip of 8 has a ring 19 arranged outside the processing chamber 1.
Is connected to an elevating mechanism, for example, an air cylinder 20. As a result, the clamp ring 17 can be moved up and down.

Each heater H mounted on each of the focus ring 14 and the clamp ring 17 described above.
1 and H2 are, for example, one in which a high melting point metal heating element is embedded in a disk-shaped ceramic substrate and co-fired and integrated, or one in which a heating resistor and glass are printed and laminated on a baked ceramic substrate. For example, the focus ring 14 is formed by baking and sintering.
After being mounted in the accommodation grooves formed in the annular recesses of the clamp ring 17 and the clamp ring 17, they are fixed in place by fixing means such as bolts (not shown).

The heater of the latter structure has a ring-shaped thin plate structure as shown in FIG. 2, for example. Although the structure of the heater H1 for the focus ring 14 is shown in FIG. 2, the heater H2 has the same structure,
The same configurations regarding the heater H2 are denoted by reference numerals in parentheses. Alumina ceramics, for example, is adopted as the ceramics substrate H11 (H21). As the heating resistor H12 (H22), for example, a mixture of molybdenum silicide (MoSi ₂ ) as a main component with nickel (Ni), manganese (Mn), etc. as a sub-component is adopted. Heating resistor H12 (H22)
Is applied by screen printing in a zigzag continuous pattern shape as shown in the figure. From above the heating resistor H12 (H22), a crystallized glass coat is laminated and covered. It is being appreciated.

As the heaters H1 and H2,
A heater substrate made of electrically insulating ceramics PBN (Pyrolytic Boron Nitride) manufactured by CVD (Chemical Vapor Deposition) and an electrically conductive ceramics PG (Pyrolytic Graphite) deposited on the heater substrate are combined. What is made possible can be used. By using the heater having this structure, it is possible to prevent the heating resistor from being exposed to the processing gas atmosphere.

The heat generation temperature of each of the heaters H1 and H2 is set to a temperature equal to or higher than room temperature, and more specifically, set according to various process conditions such as the type of processing gas used and the type of reaction product. The temperature can be changed. The heating temperature of each of the heaters H1 and H2 in this embodiment is 10
The temperature is set to 0 ° C or higher, and the heating state is always maintained during the operation of the device.

Each of the heaters H1 and H2 is provided with a power feeding section and a temperature measuring section. Of these, in the power supply unit, the connection terminal H1 provided on each of the heaters H1 and H2
Rod-shaped conductors H14, H24 (see FIG. 1) are fastened and fixed to 3, H23 by fixing screws so as to extend substantially directly upward. Lead wires for power feeding are connected to the upper ends of the rod-shaped conductors H14 and H24. As a material of the fixing screw, a material having excellent gas corrosion resistance, for example, a stainless material (SUS316) is used. On the other hand, the temperature measuring unit has a structure in which rod-shaped sensors H15 and H25 are brought into pressure contact with a part of the heat generating units of the heaters H1 and H2. Note that, in FIG. 1, for convenience, a state in which the power feeding unit and the temperature measuring unit are arranged to face each other is shown, but in reality, the power feeding unit and the temperature measuring unit are arranged to face each other. That is, a pair of the power feeding unit and the temperature measuring unit are provided at diagonal positions orthogonal to each other.

A fluid passage 21 is formed in an annular shape inside the lower electrode 16, and the fluid passage 21 has an IN side pipe 2 as shown in FIGS. 2 and 3.
2a and the OUT side pipe 22b are connected. Each of the pipes 22a and the OUT-side pipe 22b is connected to a temperature controller, for example, a cooler 8b via open / close valves 23a and 23b.
Have been serialized. This cooler 8b constitutes an integral cooling device 8 together with the cooler 8a on the side of the upper electrode 9 described above. A heat medium whose temperature is adjusted to a predetermined temperature by the cooler 8b, for example, a cooling liquid obtained by mixing an antifreeze liquid and water, circulates in the lower electrode 16 through the pipes 22a and 22b, and the lower electrode 16 is cooled. It is configured to allow cooling.

Further, an exhaust ring 25 having an exhaust hole 24 is fitted in the gap between the outer peripheral surface of the lower electrode 16 and the inner wall surface of the processing chamber 1, and the exhaust of the exhaust ring 25 is exhausted. An exhaust pipe 26 is opened at a side wall of the processing chamber 1 at a lower portion of the exhaust ring 25 which is communicated with the hole 24. The exhaust pipe 26 is connected to an exhaust device (not shown) or the like, and is configured so that the gas in the processing chamber 1 is exhausted to the outside through the exhaust hole 24 and the exhaust pipe 26.

RF power sources 27a and 27b are electrically connected to the upper electrode 9 and the lower electrode 16 as described above, respectively, so that plasma discharge used in the etching process can be generated. The RF power source 27b connected to the lower electrode 16 has a high frequency output voltage of 380 KH _Z , and the RF power source 27a connected to the upper electrode 9 has a higher frequency output voltage of 13.56 MH _Z. ing.

The above-mentioned etching apparatus is provided with a heat medium discharge device 28. That is, as shown in FIGS. 2 and 3, one of the cooling liquid pipes 6a and 6b circulating in the electrode body 4 having the upper electrode 9 such as the IN side pipe 6a and the lower electrode 16 is circulated. Either one of the cooling liquid pipes 22a and 22b, for example, the IN side pipe 22a
Are connected to gas supply pipes 29a and 29b, respectively, and these gas supply pipes 29a and 29b are connected to the check valve 3
0a, 30b and open / close valves 31a, 31b are connected for communication. A pressure gauge 32 is attached to the communication joint.
Is arranged, and the regulator 33 is connected to a gas supply source (not shown). The gas supplied from the gas supply source, such as N ₂ or air, is adjusted to a predetermined pressure by the regulator 33, and then the pipe 6a. Two
It is configured to be injected into 2a.

As described above, the heat medium discharge device 28 includes the pipes 6a, 2 between the electrodes 9, 16 and the cooling device 8.
2b may be provided as an independent heat medium discharging device,
Alternatively, it may be provided as a function of the cooling device 8, and further as a function of the etching device on the side of the electrodes 9 and 16.

Next, the operation and action of the above-mentioned etching apparatus and the method for etching a semiconductor wafer will be described. First, an opening / closing mechanism (not shown) of the processing chamber 1 is opened, and the semiconductor wafer 15, which is an object to be processed, is loaded into the processing chamber 1 via the opening / closing mechanism. Then, a lifter pin (not shown) provided so as to pass through the lower electrode 16 near the center of the lower electrode 16 is lifted, and the semiconductor wafer 15 is mounted on the lifter pin. After that, the lifter pin plasma is lowered to mount the semiconductor wafer 15 on the surface of the lower electrode 16. Then, the clamp ring 17 is lowered, and the peripheral edge of the semiconductor wafer 15 is pressed toward the lower electrode 16 side by the clamp ring 17 to hold the semiconductor wafer 15 at a fixed position.

After the semiconductor wafer 15 is thus supported on the surface of the lower electrode 16, the inside of the processing chamber 1 is set airtight and the inside is set to a desired vacuum state. This vacuum operation may be performed in advance when the semiconductor wafer 15 is transferred by using a well-known preliminary vacuum chamber.

Next, the lifting and lowering mechanism 2 lowers the electrode body 4 through the connecting rod 3 to set the distance between the upper electrode 9 and the lower electrode 16 to, for example, several mm. Then, an etching gas such as CHF ₃ and CF ₄ is supplied from an etching gas supply source (not shown) through the gas supply pipe 11 to the space 1
Send to 0. The etching gas sent to the space 10 flows out to the surface of the semiconductor wafer 15 through the plurality of openings 12 provided in the upper electrode 9. At the same time, the RF power supply 27 applies high-frequency power between the upper electrode 9 and the lower electrode 16 to generate discharge. By this discharge, the etching gas is made into plasma to generate various kinds of active species, for example, CF ₂ radicals, and the semiconductor wafer 15 is etched by the radicals.

When such an etching process is performed, for example, SiF ₄ is produced in the processing chamber 1 as a reaction product. The reaction product SiF ₄ becomes a gas and is discharged to the outside through the exhaust hole 24 and the exhaust pipe 26, but tends to adhere to a low temperature portion in the exhaust path. The adhesion of the reaction product is firstly focused on the focus ring 14 and the clamp ring 1 which are closest to the etching portion.
7, the focus ring 14 and the clamp ring 17 in the present embodiment are
The heaters H1 and H2 housed inside raise and maintain the temperature at which the reaction products are prevented from adhering. Therefore, the reaction products are prevented from adhering to the surfaces of the focus ring 14 and the clamp ring 17. Therefore, the focus ring 14 and the clamp ring 17 can be used for a long period of time with almost no maintenance such as cleaning and replacement, and the focus ring 14 and the clamp ring 17 are prevented from peeling off and reacting with the semiconductor wafer 15. Product adhesion is also prevented.

Further, at this time, there is a possibility that the high temperature of the upper electrode 9 and the lower electrode 16 is caused by the application of the high frequency power, and the thermal expansion occurs. In this case, the material of the upper electrode 9 is made of, for example, amorphous carbon, and the electrode body 4 in contact with this is made of, for example, aluminum, so that the coefficient of thermal expansion is different, which causes cracking. In order to prevent the occurrence of cracks, the cooling liquid whose cooling is controlled by the cooler 8a is introduced into the fluid passage 5 formed inside the electrode body 4 having the upper electrode 9 on the IN side pipe 6a.
The upper electrode 9 is indirectly cooled by being circulated so as to be discharged from the OUT side pipe 6b.

When the temperature of the lower electrode 16 further rises, the temperature of the semiconductor wafer 15 also changes, which adversely affects the etching and may damage the resist on the surface of the semiconductor wafer 15. Therefore, the lower electrode 16 is also connected to the fluid passage 21 provided in the lower portion of the cooler 8b
The cooling liquid controlled by is circulated so as to be supplied from the IN side pipe 22a and discharged from the OUT side pipe 22b to indirectly cool the lower electrode 16.

Further, when such etching treatment is performed, it is necessary to replace the electrodes 9 and 16 when the electrodes 9 and 16 are worn or damaged, or when maintenance is performed. In this case, first, the inside of the processing chamber 1 is set to the atmospheric pressure, and the operation of the cooling device 8 is stopped. When performing maintenance of the cooling liquid piping on the electrode side to be maintained, for example, the electrode body 4 having the upper electrode 9, the opening / closing valve 7a existing in the cooling system piping 6a of the electrode body 4 is used.
Close. Then, the on-off valve 31a of the heat medium device 28 connected to the pipe 6a is opened, and N ₂ gas from a gas supply source (not shown) is regulated by the regulator 33 to a predetermined pressure, for example, 0.25 to 0.35 kg / cm ² . Adjust to the range,
The N ₂ gas is injected into the pipe 6a via the open / close valve 31a and the check valve 30a.

The presence of the check valve 30a prevents the cooling liquid in the pipe 6a from flowing back into the gas supply pipe 29a. Then, the injected N ₂ gas is
The coolant flowing inwardly of the electrode body 4 having the upper electrode 9 through the pipe 6a pushes back the cooling liquid existing in the pipe 6a and the electrode body 4 into the cooler 8a through the opening / closing valve 7a. At this time, as a means for confirming whether or not the cooling liquid is completely pushed back into the cooler 8a, for example, the above-mentioned pipe 6b is used.
A sensor for detecting the presence of the cooling liquid may be provided in the inside to confirm the presence of the cooling liquid, or the cooler 8 may be provided.
A configuration may be adopted in which the cap of a tank (not shown) provided in a is removed, and the cooling liquid pushed back into the tank is changed to N ₂ gas and bubbles are generated to confirm. After confirming that the cooling liquid has been returned to the inside of the cooler 8a by such means, the opening / closing valve 7b is immediately closed to prevent the cooling liquid from flowing backward toward the electrode body 4. When the electrode maintenance is performed and the operation is performed again, the opening / closing valve 31a is closed and the opening / closing valves 7a and 7b are opened to restart the operation of the cooling device 8. As described above, according to the present embodiment, it is possible to improve the processing efficiency of the object to be processed, eliminate the particles from adhering to the surface of the object to be processed, and improve the yield of the object to be processed and the reliability of the processing steps. Can be made

Next, in the embodiment shown in FIG. 5 in which the same components as those in the embodiment shown in FIG. 1 are designated by the same reference numerals, heaters are provided on the respective facing surfaces of the focus ring 14 and the clamp ring 17, that is, the outer surface. H3 and H4 are arranged respectively. As each of these heaters H3 and H4, as in the above-mentioned embodiment, for example, a high melting point metal heating element is embedded in a disk-shaped ceramic substrate and simultaneously fired and integrated, or on a fired ceramic substrate. In the above, the one in which a heating resistor and a printed and laminated glass are integrally baked and sintered is used, but in any case, the heating resistor is not directly exposed to the outside,
It is covered with a glass coat or the like to prevent the heating resistor from being corroded by the processing gas.

In addition, in the feeding portions of the heaters H3 and H4, rod-shaped conductors H34 and H44 are fixed so as to extend substantially directly above and directly below the connection terminals of the heaters H3 and H4, respectively, and In the warm part, the rod-shaped sensors H35, H45 are pressed against the heating parts of the heaters H3, H4. Note that, in FIG. 5, for convenience, a state in which the power feeding unit and the temperature measuring unit are arranged to face each other is shown, but in reality, the power feeding unit and the temperature measuring unit are arranged to face each other. That is, a pair of the power feeding unit and the temperature measuring unit are provided at diagonal positions orthogonal to each other.

The plasma processing apparatus to which the present invention is applied is
The present invention is not limited to the plasma etching apparatus, and can be similarly applied to all other apparatuses that perform plasma processing, such as a plasma cleaning apparatus, a plasma doping apparatus, and a plasma oxidizing apparatus.

[0037]

As described above, according to the present invention, it is possible to satisfactorily prevent the reaction product from adhering to the surface of at least one of the holding means and the concentrating means attached to the plasma electrode, and to clean and replace the same. It is possible to extend the maintenance cycle such as the above and use the holding means or the concentrating means for a long time.

[Brief description of drawings]

FIG. 1 is a vertical cross-sectional explanatory view showing an example of a plasma etching apparatus to which the present invention is applied.

FIG. 2 is an external perspective view showing the structure of a heater according to an embodiment of the present invention.

3 is an external perspective view of a heat medium discharging device provided in the device shown in FIG. 1. FIG.

4 is a system explanatory view of a heat medium discharging device provided in the device shown in FIG. 1. FIG.

FIG. 5 is a vertical cross-sectional explanatory view of a plasma etching apparatus to which another embodiment of the present invention is applied.

[Explanation of symbols]

 1 Processing Chamber 9 Upper Electrode 14 Focus Ring 15 Semiconductor Wafer 16 Lower Electrode 17 Clamp Ring H1, H2, H3, H4 Heater

Claims (2)

[Claims] 1. An electrode for plasma generation is arranged to face each other in an airtight processing chamber, and a holding means for holding an object to be processed is provided on either one of these electrodes. In the plasma processing apparatus, wherein the electrode on the other side is provided with a concentrating means for concentrating the plasma generated between the electrodes on the object to be processed, at least one of the holding means and the concentrating means is generated by the plasma processing. A plasma processing apparatus comprising a heating means for raising and maintaining a temperature at which a reaction product does not adhere to a surface. 2. The plasma processing apparatus according to claim 1, wherein the heating means is composed of a thin plate heater formed by applying a heating resistor in a pattern.