JPH08167595A - Plasma treatment device - Google Patents

Abstract

PURPOSE: To provide a plasma treatment device which is capable of restraining abnormal discharge from occurring in the vicinity of a pad. CONSTITUTION: A plasma treatment device is equipped with a hermetically sealed treatment chamber 2 where a pad 4 equipped with an electrostatic chuck mechanism is provided, wherein a work W is placed on the electrostatic chuck mechanism of the pad 4, plasma is produced inside the treatment chamber 2 to treat the work W, and the pad 4 is provided with an insulating part 41 at the peripheral part of its surface that contacts the electrostatic chuck mechanism.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a plasma processing apparatus.

[0002]

2. Description of the Related Art Generally, in a semiconductor manufacturing process, various treatments are performed on an object to be processed, for example, a semiconductor wafer, for example, an etching process or a CVD process is performed on the object to be processed. Known plasma processing apparatus. Further, in this type of processing apparatus, a means for bringing the semiconductor wafer to be processed into close contact with the mounting table so as to be controlled at a predetermined temperature, for example, an electrostatic chuck mechanism using electrostatic force is used. There is. As a mounting table for mounting the electrostatic chuck, for example, a conductive member,
For example, a configuration is known in which a lower electrode using aluminum as a base material or an outer peripheral surface of the lower electrode is subjected to an insulating layer, for example, aluminum alumite treatment. Examples of the above-mentioned technique include Japanese Patent Laid-Open No. 62-44332 and Jpn. Pat.
It is described in many publications such as the issue.

An example of a plasma processing apparatus using such a mounting table is a plasma etching apparatus. In this etching apparatus, for example, an upper electrode and a lower electrode are provided in parallel at the upper and lower sides in an airtightly configured depressurizable processing container, and a semiconductor wafer which is an object to be processed is, for example, a lower electrode. Placed on the electrostatic chuck of the mounting table of, for example, in the case of etching treatment, an etching gas is introduced into this processing container, and high frequency power is applied to the upper electrode and / or the lower electrode, Plasma is generated between the electrodes, and the wafer is etched by dissociating the etching gas.

[0004]

However, in the conventional structure in which the insulating layer is provided on the outer peripheral portion of the mounting table, when the semiconductor wafer which is the object to be processed is treated with plasma near the upper part of the mounting table. In addition, high-frequency charge accumulation (charge-up) occurs in the processing container between the electrostatic chuck and the insulating layer. And in the part between them, due to the generation of bubbles from the adhesive due to the heat of the plasma,
The adhesive part is peeled off, the conductive member is exposed,
There is a problem that abnormal electrical discharge is caused because the electrical resistance to the conductive member is small. This abnormal discharge damages the electrostatic chuck, and there has been a problem that the operation rate of the device is lowered due to complicated maintenance work for replacement and the like. Furthermore, there is a problem that the exposed portion of the conductive material in the void is etched by active species in the plasma, such as ions, causing metal contamination and dust generation, and lowering the yield.

The present invention focuses on the above problems,
It was created to solve this effectively. An object of the present invention is to provide a plasma processing apparatus capable of suppressing abnormal discharge near the mounting table.

[0006]

According to the present invention, there is provided a mounting table provided on an airtight processing container, and an electrostatic chuck mechanism provided on the mounting table for holding an object to be processed. And a plasma processing apparatus for generating plasma in the processing container to process the object to be processed, wherein the mounting table has an insulating layer on a peripheral portion of a contact surface with the electrostatic chuck mechanism. Is characterized by.

According to a second aspect of the present invention, in the first aspect of the invention, the insulating portion is formed within a range of 10 mm or less from an outer peripheral portion of the contact surface of the mounting table.

The invention of claim 3 relates to claim 1 or claim 2.
In the invention, the contact surface has a roughness of approximately 10 μm or less.

[0009]

According to the present invention, since the insulating portion is formed on the peripheral portion of the contact surface between the mounting table and the electrostatic chuck mechanism, the conductive member is hard to be exposed, and the conductive member is not exposed to the plasma. Since the insulation resistance of is increased, abnormal discharge in the vicinity of the contact surface can be suppressed.

[0010]

EXAMPLE An example of applying a plasma etching apparatus to an example of a plasma processing apparatus according to the present invention will be described below.
Description will be given with reference to the accompanying drawings.

As shown in FIG. 1, this etching apparatus 1
Has an airtight treatment container 2 formed in a cylindrical or rectangular shape from a conductive material, for example, aluminum whose surface is anodized, and the bottom of the container 2 is made of an insulating material such as a ceramic insulating plate 3. A mounting table 4 that also functions as a substantially cylindrical lower electrode for mounting an object to be processed, for example, a semiconductor wafer W, is provided via the. The mounting table 4 is constructed by assembling a plurality of members, which will be described later, whose surfaces are formed of aluminum or the like, which is aluminum anodized, by fixing means, for example, bolts. Specifically, the mounting table 4 is mainly composed of a susceptor support base 6 formed of aluminum or the like in a cylindrical shape, and a susceptor 5 made of aluminum or the like which is detachably provided on the support base 6 with bolts 11. It is configured.

A cooling means, for example, a cooling jacket 8 is provided on the susceptor support 6, and a refrigerant such as liquid nitrogen is introduced into the jacket 8 through a refrigerant introducing pipe 10 so that the inside of the jacket 8 is cooled. And a gas discharged from the refrigerant discharge pipe 9 due to evaporation of the liquid nitrogen in the insulating portion is discharged to the outside of the container 2. The gas is cooled by a cooling means (not shown) and is circulated again in the refrigerant introduction pipe 9. It has become. Therefore, the cold heat of the liquid nitrogen is supplied to the wafer W from the cooling jacket 8 via the susceptor 5 so that the wafer W can be cooled to a desired temperature.

In the plasma etching apparatus of this embodiment, since the processing is carried out while maintaining a high vacuum, a large number of microscopic voids are generated on the physical bonding surface, and these voids become a high vacuum and are considered in heat transfer. Constitutes the thermal insulation of. Therefore, in order to improve this heat transfer, the following means are provided. That is, the susceptor support 6 and the susceptor 5 have a heat transfer gas such as He penetrating the susceptor support 6 and the back surface of the wafer W, a physical bonding surface of the support 6 and the susceptor 5, and between members forming the susceptor 5. A gas passage 15 is formed so as to supply the gas to the joints and the like. An electrostatic chuck 7 as an electrostatic chuck mechanism is provided in the wafer mounting portion at the center of the upper end of the susceptor 5. The electrostatic chuck 7 also has a large number of vent holes () through which heat transfer gas can pass. (Not shown).

A temperature adjusting heater 12 is provided below the susceptor between the electrostatic chuck 7 and the cooling jacket 8. The heater 12 is, for example, a plate-shaped ceramics heater having a thickness of about several mm.
The heater fixing base 13 fixed to the upper surface of the susceptor supporting base 6 by a bolt or the like (not shown) is made of a material having good thermal conductivity,
For example, it is made of aluminum. This heater 12
Is preferably set to be approximately the same as or larger than the wafer area, so that the cooling heat from the cooling jacket 8 located under this area controls the wafer W to a uniform temperature over the entire surface. Is configured. The temperature adjusting heater 12 and the heater fixing base 13 have pusher pins or the like for transferring the primary wafer W to / from the electrostatic chuck surface when the wafer W is loaded / unloaded by a transport means (not shown). Through-holes (not shown) and the like that penetrate are provided.

Further, the lower surface of the susceptor 5 is provided with an accommodating recess 14 for accommodating the entire heater fixing base 13, and the upper surface of the heater 12 and the accommodating recess 14 of the susceptor 5 are provided in the heater fixing base 13. He at the boundary with the bottom surface
A branch passage 16 connected to the gas passage 15 is formed for supplying a heat transfer medium such as. An electric power supply lead 22 is connected to the heater 12 and an electric power source 23 is connected to the lead 22 so that a predetermined electric power can be supplied to the heater 12.

Further, various wirings which are susceptible to high frequency for plasma generation, such as the power supply lead 22 connected to the heater and the voltage supply lead 72 connected to the electrostatic chuck 7, all supply high frequency power for plasma. It is housed in the conductive pipe lead 25 to be supplied, and is structured to have a shield effect so as not to have an influence of high frequency noise on the outside. An insulator 26 is provided at a penetrating portion of the pipe lead 25 at the bottom of the processing container,
It is intended to be electrically insulated from the container 2 side. Further, a shield 27 that is electrically grounded is provided on the outer periphery of the pipe lead 25 that extends to the outside of the container 2 so as to prevent high frequencies from leaking to the outside.

Further, above the susceptor, an upper electrode 30 which is, for example, grounded, is disposed at a distance of about 3 to 20 mm from the susceptor and acts as a counter electrode.
A gas unit 34 is connected to the upper electrode 30 via a gas supply pipe 31, and a process gas such as CF ₄ , CHF ₃ , C ₄ F ₈ ,
An etching gas such as Cl ₂ is supplied, and a processing gas is discharged in the direction of the semiconductor wafer W through a plurality of radial small holes 32 formed in the bottom wall of the upper electrode 30.
When 3 is turned on, plasma is generated between the upper electrode 30 and the semiconductor wafer W, and the upper electrode is electrically grounded via the wiring 33.

In this susceptor 5, a pipe lead 25 is connected to the susceptor support 6 by a hollow conductor, and a direct current component is limited to the pipe lead 25 via a wiring 28. Blocking capacitor 29 and high frequency, for example 380 kHz, 1
It is sequentially connected to a high frequency power source 21 for plasma generation such as 3.56 MHz and 40.68 MHz. Therefore, the susceptor 5 functions as a lower electrode.

Further, an exhaust means, for example, a vacuum pump 18 is connected to the lower side wall of the processing container 2 through an exhaust pipe 17 so that the inside of the processing container 2 can be evacuated to a desired reduced pressure atmosphere. Composed. Further, the semiconductor wafer W, which is the object to be processed, is provided on the side wall of the central portion,
An opening 20 for loading or unloading is provided inside,
On the outer wall of the opening 20, a load lock chamber (not shown) is connected to the processing container 2 via an airtight seal, for example, an O-ring, and a transfer device (not shown) is provided in the load lock chamber. Is provided, and the semiconductor wafer W is loaded into or unloaded from the processing container 2 by this transport device.

The mounting table 4 is formed in a disk shape having a convex upper end center portion, and the electrostatic chuck 7 is exposed on the wafer mounting surface to an area substantially equal to the wafer area or plasma. In order to further avoid the above, it is formed in an area slightly smaller than the area of the wafer W. This electrostatic chuck 7 is, for example, between two polymer polyimide films,
Conductive film 71 such as copper foil functioning as an electrode for electrostatic chuck
Is sandwiched in an insulating state, and the conductive film 71 is connected to a variable DC high voltage source 74 via a filter 73 for cutting high frequency, for example, a coil, on the way by a voltage supply lead 72. Therefore, by applying a high voltage to the conductive film 71, the wafer W can be sucked and held on the upper surface of the chuck 7 by the coulomber.

Further, an annular focus ring 44 is arranged on the peripheral portion of the mounting table 4 so as to surround the semiconductor wafer W which is the object to be processed. The focus ring 44 is made of an insulating material that does not attract reactive ions, and makes the plasma reactive ions incident only on the semiconductor wafer W placed inside to improve the efficiency of the etching process.

Further, as shown in FIG. 2, on the peripheral portion of the convex portion 40 formed in the central portion of the upper surface of the mounting table 4 described above, as shown in FIG.
An insulating portion, for example, an aluminum alumite layer 41 is formed to prevent abnormal discharge of plasma. The insulating portion 41 is formed in a range of a predetermined distance X ₁ from the outer peripheral edge of the convex portion 40, for example, a predetermined value of about 10 mm or less, preferably 2 to 5 mm, and more preferably 2 to 3 mm. The thickness X _{2 is} , for example, a predetermined value in the range of 50 to 100 μm, preferably about 60 μm.

The reason for forming the predetermined distance X _{1 at} a predetermined value of, for example, about 10 mm or less, preferably 2 to 5 mm, more preferably 2 to 3 mm is as follows.
_{If 1} is less than this, the insulation resistance will be small, and
This is because the conductive material 42 is more likely to be exposed and abnormal discharge is more likely to occur, and at a distance longer than this, the plasma processing effect of the semiconductor wafer W, which is the object to be processed, is reduced. Further, regarding the thickness X ₂ ,
For example, the reason why it is formed to have a thickness of about 50 to 100 μm, preferably about 60 μm is that if X ₂ is thinner than this, insulation resistance is reduced, and abnormal discharge easily occurs. This is because cracks and the like are likely to occur.

Next, a method of forming the mounting table 4 will be specifically described. As shown in FIG. 3A, the protrusion 40 is formed on the surface of the conductive member 42, for example, aluminum or aluminum alloy as a base material. For example, the height Y ₁ is 100 to 200
The convex portion 40 is formed by polishing or the like in a range of μm, for example, a height of about 60 μm. After this step, as shown in FIG. 3B, the width Y ₂
Is a predetermined value of 10 mm or less, for example, about ₃ mm, and the thickness Y ₃ is a predetermined value in the range of 50 to 100 μm, for example, about 60 μm, and the insulating portion 41, for example, aluminum alumite is formed. Then, as shown in FIG. 3C, the surface of the convex portion 40 of the conductive member 42 and the surface of the insulating portion 41 are separated from each other by the insulating portion 4.
1 has a predetermined thickness Y ₄ , for example, a predetermined value in the range of 30 to 60 μm, preferably about 40 μm, and the surface portion 44 composed of the conductive member 42 and the insulating portion 41 has a surface roughness of about 10 μm. Hereinafter, for example, it is formed by performing mirror finishing of about 5 μm or less. Further, as shown in d of FIG. 3, the mounting table 4 is formed by fixing the electrostatic chuck 7 to the mounting table 4, for example, by fixing it with an adhesive material.

The reason why the surface roughness of the surface portion 44 is about 10 μm or less, preferably about 5 μm or less in the mirror finishing step is as follows.
It is well-suited as a joint part, can prevent plasma from entering the contact surface 43 and generation of plasma in the contact surface 43, and can prevent corrosive gas such as chlorine or fluorine gas from being applied. This is to prevent the contact surface 43 from entering.

Therefore, as shown in FIG. 4, the mounting table 4 is formed such that the insulating portion 41 is arranged on the peripheral portion of the convex portion 40 of the conductive member 42. The electrostatic chuck 7 is fixed to the central surface of the upper portion of the convex portion 40 with an adhesive material.

Next, the operation of the present embodiment configured as above will be described. First, the gate valve 19 is opened, the semiconductor wafer W is loaded into the processing container 2 by the transfer device provided in a load lock chamber (not shown), and is delivered to the pusher pin. Moves into the load lock chamber, closes the gate valve 19, then pushes down the pusher pin, mounts the wafer W on a predetermined position above the mounting table 4, and moves it by the electrostatic chuck 7. It is adsorbed and held on the mounting table 4 side by a coulomb car. Then, a high frequency is applied between the upper electrode 30 and the lower electrode (susceptor) 5 through the pipe lead 25 to generate plasma. Simultaneously with or in advance of this, a processing gas is caused to flow from the upper electrode 30 side into the processing space to perform etching processing.

Further, since the wafer is excessively heated above the predetermined set temperature by the heat of the plasma, the cooling jacket 8 of the susceptor support 6 is cooled by a coolant,
For example, liquid nitrogen is circulated to maintain this portion at −196 ° C., and these cold heats are supplied to the wafer W via the susceptor 5 on the upper portion to cool the wafer W and maintain the desired low temperature state. ing. As a result, the wafer W is subjected to low temperature etching. Further, a temperature adjusting heater 1 provided between the cooling jacket 8 and the wafer W.
The temperature at which the wafer W is cooled is adjusted by adjusting the heat generation amount of 2 to maintain the wafer W at a predetermined temperature, for example, about −150 ° C. to 100 ° C. The heater 12
By controlling the amount of heat generated by and the flow rate of the coolant in the jacket 8, the wafer temperature can be raised to room temperature or higher, for example, 100 ° C.

Next, the effect of this embodiment will be described. Since the insulating portion 41 is formed on the peripheral portion of the contact surface 43 of the mounting table 4 with the electrostatic chuck 7 in the plasma processing apparatus,
Since the conductive member 42, which is the lower electrode, is less likely to be exposed and the insulating property of the conductive member 42 with respect to plasma is increased, abnormal discharge in the vicinity of the contact surface 43 can be suppressed. For this reason, it is possible to prevent damage to the electrostatic chuck 7 due to abnormal discharge, thus suppressing the generation of particles,
Further, since metal contamination or dust generation due to corrosion of the conductive member 42 is not caused, the yield of the object to be processed can be suppressed. In addition, the prevention of damage to the electrostatic chuck 7 leads to a longer life of the electrostatic chuck 7, and the complicated maintenance work for replacement thereof can be reduced, which contributes to the improvement of the operation rate of the device. can do.

Further, FIG. 5 shows that a plasma etching apparatus constructed according to the present invention and a plasma etching apparatus having a conventional configuration use a semiconductor wafer having a polysilicon film stacked as an object to be processed. Then, the relationship between the configuration of the mounting table and the etching rate is shown. As shown in this figure, the mounting table without the insulating portion formed on the upper surface of the convex portion has the highest etching rate, but there is a problem that abnormal discharge is likely to occur as described above. The etching rate distribution in the wafer is not uniform, but in the mounting table having the configuration according to the present invention, the etching rate distribution in the wafer surface is also uniform,
It is clear that the etching rate is higher than that of the mounting table having the insulating portion formed on the entire surface.

Next, the second embodiment will be described. The same parts as those of the first embodiment are designated by the same reference numerals and the description thereof will be omitted. As shown in FIG. 6, the peripheral portion of the upper portion of the mounting table 4 is formed of a convex curved surface having a predetermined curvature R, and the insulating portion 41 is formed at the peripheral portion of the convex curved surface. Has become. With this configuration, the concentration of the electric field can be suppressed, abnormal plasma discharge can be suppressed, and stable plasma can be generated, so that the object to be processed can be smoothly processed. .

In each of the above-mentioned embodiments, the case where the invention is applied to the parallel plate type plasma etching apparatus has been described, but the invention is not limited to this, and for example, a permanent magnet is rotatably installed outside the ceiling of the processing container. The present invention can be applied to an induction magnetic field type plasma device, an inductively coupled plasma device provided with an antenna for emitting microwaves instead of the upper electrode, and the like. Further, not only when the object to be processed is a semiconductor wafer and the process is etching, but it can be applied not only to a process in which an LCD substrate is a process target, but the type of process itself is not limited to etching, and sputtering, CVD, ashing, etc. It is needless to say that the present invention can also be applied to processing, and can be applied to any apparatus as long as it is an apparatus for generating plasma of those and processing the object to be processed.

[0033]

As described above, according to the present invention, since it is possible to suppress abnormal discharge with respect to plasma and generate stable plasma, the object to be processed can be smoothly and uniformly processed.
In addition, the yield can be improved.

[Brief description of drawings]

FIG. 1 is a cross-sectional configuration diagram showing an embodiment of a plasma processing apparatus according to the present invention.

FIG. 2 is an enlarged cross-sectional view showing a main part of the mounting table of FIG.

FIG. 3

FIG. 1A is a schematic sectional view showing a process of forming the mounting table of FIG.

1B is a schematic cross-sectional view showing a process of forming the mounting table of FIG.

FIG. 3C is a schematic cross-sectional view showing the process of forming the mounting table of FIG.

FIG. 3D is a schematic cross-sectional view showing the process of forming the mounting table of FIG. 1.

FIG. 4 is a schematic perspective view showing a mounting table in FIG.

5 is a table for explaining the operation of the processing of FIG.

FIG. 6 is an enlarged sectional view showing a main part of a mounting table for explaining a second embodiment.

[Explanation of symbols]

 2 Processing container 4 Mounting table 7 Electrostatic chuck 41 Insulating part 43 Contact surface W Object to be processed (semiconductor wafer)

Claims (3)

[Claims] 1. A plasma processing apparatus comprising: a mounting table provided in an airtight processing container; and an electrostatic chuck mechanism provided on the mounting table for holding an object to be processed, wherein plasma is generated in the processing container. A plasma processing apparatus for processing the object to be processed, wherein the mounting table is provided with an insulating portion on a peripheral portion of a contact surface with the electrostatic chuck mechanism. 2. The plasma processing apparatus according to claim 1, wherein the insulating portion is formed within a range of 10 mm or less from an outer peripheral portion of the contact surface of the mounting table. 3. The plasma processing apparatus according to claim 1, wherein the contact surface has a roughness of about 10 μm or less.