JPH09289201A - Plasma treating apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the uniformity of the temp. of a heat transferring gas by providing a softer support member than ceramics for an electrostatic chuck, for only its portion contacting the back side periphery of a substrate to be treated. SOLUTION: An electrostatic chuck 11 has an upper ceramic face 13 with a support member composed of polyimide tape 14 peelably adhered to the marginal edge of the ceramic face 13 so as to form the outline of a wafer. He gas flowing out in a space between the back side of the wafer and the chuck 11 leaks from the contact face of the chuck 11 with the back side of the wafer, and the polyimide tape 14 at the marginal edge of the chuck 11 makes the flow of the leaking He gas approximately uniform over the periphery, thus forming a uniform flow of the gas over the back side of the wafer. This improves the uniformity of the temp. in a substrate being treated.

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 configured to perform processing such as etching, film formation and sputtering on a substrate to be processed in a plasma atmosphere.

[0002]

2. Description of the Related Art Conventionally, in a semiconductor device manufacturing process, a plasma for performing a plasma process such as etching or film formation on a substrate to be processed such as a semiconductor wafer (hereinafter referred to as “wafer”) in a plasma atmosphere. Although a processing apparatus is used, it is necessary to hold the substrate to be processed at a predetermined position such as a susceptor during the processing.
In a conventional plasma processing apparatus, an electrostatic chuck that attracts and holds a substrate to be processed by a Coulomb force or the like is provided inside a processing container on a susceptor.

By the way, since the treatment is performed in a plasma atmosphere, the dielectric layer of the electrostatic chuck is made of, for example, Al for the purpose of preventing the sputtering of the electrostatic chuck itself during treatment and extending its life. _It may be composed of ceramics such as ₂ O ₃ . It has also been proposed to use ceramics for the outer peripheral edge of the side surface of the electrostatic chuck, as in the technique disclosed in Japanese Patent Laid-Open No. 61-33833.

[0004]

By the way, in this type of plasma processing apparatus, a heat transfer gas such as helium gas is made to flow out to the back surface of the substrate to be processed from the outflow hole provided in the holding surface of the electrostatic chuck. This heat transfer gas is circulated between the back surface of the substrate to be processed and the surface of the electrostatic chuck to improve the uniformity of the in-plane temperature of the substrate to be processed so that the uniformity of the process can be achieved. There is. In that case, it is also seen that the grooves are appropriately formed concentrically so that the heat transfer gas flows to the back surface of the substrate to be processed.

However, in the above-mentioned conventional technique, even if the heat transfer gas is caused to flow out in this manner, the nonuniform temperature distribution in the substrate to be processed is still outstanding. This is because in the conventional technology, the leak of heat transfer gas is partially biased,
As a result, it is thought that the main cause is that the back surface of the substrate to be processed is not evenly distributed. Therefore, some improvement has been desired in this respect.

The present invention has been made in view of the above point, and further improves the temperature uniformity due to the heat transfer gas in a plasma processing apparatus employing a ceramic electrostatic chuck having good durability. It is an object of the present invention to provide a new plasma processing apparatus capable of solving the above-mentioned problems.

[0007]

According to a first aspect of the present invention, there is provided a decompressible processing container and an electrostatic chuck provided in the processing container. A processing gas is introduced and plasma is generated in the processing container, and the substrate to be processed held on the electrostatic chuck is subjected to a predetermined processing under the plasma atmosphere. In the chuck, in the plasma processing apparatus, at least the holding surface of the substrate to be processed is made of ceramics, and the holding surface has an outflow hole for letting out a heat transfer gas to the back surface of the substrate to be processed. A support member made of a material softer than the ceramic used in the electrostatic chuck is provided only in a portion of the electrostatic chuck that comes into contact with the peripheral portion of the back surface of the substrate to be processed. To plasma processing apparatus is provided.

As described above, the heat transfer gas is an inert gas such as helium for flowing out to the back surface of the substrate to be processed and controlling the temperature of the substrate to be processed, and transfers cold heat. In some cases, it is also called back cooling gas. A material softer than the ceramic used as the material of the electrostatic chuck means a material having a hardness lower than that of the ceramic. Further, it is easier to process the supporting member in a substantially annular shape over the entire circumference of the holding surface of the electrostatic chuck.

According to the plasma processing apparatus of the first aspect, since the supporting member is provided at the portion which comes into contact with the peripheral portion of the back surface of the substrate to be processed, the load of the substrate to be processed is eventually evenly applied to this supporting member. become. Therefore, when the electrostatic chuck is operated to adsorb and hold the substrate to be processed by the Coulomb force, the substrate to be processed is evenly adsorbed on the support member. Since this supporting member is made of a material softer than the ceramic used for the electrostatic chuck, the inventors of the present invention have found that the heat transfer gas from the outflow holes is coupled with the uniform adsorption. Is evenly leaked from the contact surface between the support member and the substrate to be processed. Therefore, as shown in the embodiments described later, the temperature uniformity of the substrate to be processed by the heat transfer gas is improved.

According to a second aspect of the present invention, there is provided a processing container whose pressure can be freely reduced and an electrostatic chuck provided in the processing container.
A processing gas is introduced into the processing container, plasma is generated in the processing container, and a predetermined processing is performed on the substrate to be processed held on the electrostatic chuck under the plasma atmosphere. Further, the electrostatic chuck is
At least the holding surface on the side of the substrate to be processed is made of ceramics, and a groove for allowing the heat transfer gas to flow from the outflow hole in the holding surface to the back surface of the substrate to be processed is formed on the holding surface. In the plasma processing apparatus, a supporting member made of a material softer than the ceramic is provided on a portion of the holding surface of the electrostatic chuck except the groove substantially, and the plasma processing apparatus is provided. To be done.

In the case of the plasma processing apparatus of claim 2,
The support member is provided in a portion excluding the gas flow groove, but in this case also, when the electrostatic chuck is operated, the gas in the groove leaks evenly from these support members. As in claim 1, the uniformity of the in-plane temperature of the substrate to be processed is improved. It should be noted that what is substantially removed from the groove means that a member protruding from the electrostatic chuck holding surface such as a lifter pin in an embodiment to be described later and a storage hole thereof are also removed. Further, it is not always necessary to provide the supporting member on the entire surface except the entire part.

A plasma processing apparatus according to a third aspect is characterized in that the supporting member in the plasma processing apparatus according to the first and second aspects is configured such that it can be attached / detached to / from an electrostatic chuck. Therefore, replacement of the support member becomes easy.

Since at least the holding surface and the side surface of the electrostatic chuck used in the plasma processing apparatus according to the above claims 1 to 3 are made of ceramics, they have good durability against sputtering by plasma and the like. is there. Further, as a material of the supporting member which is softer than the ceramics used in this electrostatic chuck, it is desirable that the material has elasticity, heat resistance and plasma resistance and does not emit gas and does not become a pollution source. Practicality,
Considering availability, polyimide, for example, is suitable. Therefore, as the support member that can be adhered and peeled off as in claim 3, for example, a polyimide tape can be cited.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a cross section of an etching apparatus 1 which is a plasma processing apparatus according to the present embodiment. A processing chamber 2 in the etching apparatus 1 includes a cylindrical processing container 3 made of aluminum which has been subjected to anodized alumite treatment. The processing chamber 2 is airtightly closed. The processing vessel 3 itself is grounded, for example, by being connected to a ground wire 4.

An insulating support plate 5 such as ceramics is provided at the bottom of the processing chamber 2, and the insulating support plate 5 is provided.
A substantially columnar susceptor 6 for mounting the wafer W is housed in the upper part of the. The susceptor 6 is made of, for example, anodized aluminum and constitutes a lower electrode.

A refrigerant circulation path 7 through which a refrigerant flows is formed in the susceptor 6, and the refrigerant introduced from the refrigerant introduction pipe 8 circulates in the refrigerant circulation path 7 and a refrigerant discharge pipe 9 is formed.
From the processing container 3. With this configuration, the susceptor 6 and the wafer W can be cooled to a predetermined temperature. At the same time, a heating means such as a ceramic heater is separately provided in the susceptor 6, and the heating means is controlled by the control of an appropriate temperature sensor, and the wafer W is controlled to a predetermined temperature together with the action of the coolant circulation path 7 described above. It may be configured to. In this case, finer temperature adjustment is possible.

An electrostatic chuck 11 for attracting and holding the wafer W is provided on the susceptor 6 as shown in FIGS. The electrostatic chuck 11 has a structure in which a conductive thin film 12 is sandwiched between ceramics 13 from above and below, and a predetermined DC voltage from a high-voltage DC power supply 14 installed outside the processing container 3, for example, 1.5.
When a voltage of kV to 4 kV is applied to the thin film 12, the Coulomb force based on the charges generated on the ceramics 13 causes the wafer W placed on the electrostatic chuck 11.
Are adsorbed and held on the upper surface of the electrostatic chuck 11.

The planar shape of the electrostatic chuck 11 is similar to the outer shape of the wafer W and has a size slightly smaller than the wafer W. A polyimide tape 14 as a support member that can be adhered and peeled off is formed on the peripheral edge of the ceramics 13 on the upper surface of the electrostatic chuck 11 so as to have a shape similar to the outer shape of the wafer W, as shown in FIG. It is attached to. The polyimide tape 14 has a thickness of 50 μm and a width d of 3 as shown in FIG.
mm (the shaded area in FIG. 4 is the polyimide tape 14)
Is shown).

Further, inside the susceptor 6, there is provided a heat transfer gas introducing pipe 21 penetrating the bottom portion of the processing container 3 and the insulating support plate 5, and the heat transfer gas introducing pipe 21 is the static gas shown in FIG. It is connected to a gas flow path 24 communicating with the outflow holes 22 and 23 formed in the ceramics 13 which is the upper surface of the electric chuck 11. In this embodiment, the outflow holes 22 and 23 are
Are formed on concentric circles, and the outflow holes 22 and 23 are also formed at a total of four locations at every 90 ° center angle when viewed from the plane as shown in FIG. Further, the outflow hole 22 located on the outer side and the outflow hole 23 located on the inner side are formed at the bottoms of the corresponding narrow annular grooves 25, 26, respectively.

Therefore, when an appropriate heat transfer gas, for example, He (helium) gas is flown into the heat transfer gas introducing pipe 21, this He gas is blown out from the outflow holes 22 and 23 through the gas flow path 24, and each groove. While circulating around 25 and 26, it flows out to the back surface of the wafer W held on the electrostatic chuck 11, and the heat transfer efficiency between the wafer W and the electrostatic chuck 11 (ceramics 13) is improved. There is. The outflow pressures from the outflow holes 22 and 23 may be different from each other, for example, the pressure may be higher from the inner outflow holes 23. Further, regarding the groove, a groove having no outflow hole may be separately added concentrically.

A lifter pin 27 for lifting the wafer W as shown in FIG. 2 from above the electrostatic chuck 11 is built in the susceptor 6, and the lifter pin 27 includes the susceptor 6 and the electrostatic chuck. It is housed in a housing hole 28 penetrating 11 and can project from the surface of the ceramic 13 on the upper surface of the electrostatic chuck 11. The He gas also flows out from the storage hole 28 to the back surface of the wafer W. In the present embodiment, as shown in FIGS. 3 and 4, the storage holes 28 for storing the four lifter pins 27 are provided at a total of four locations at a central angle of 90 ° when viewed from the plane.

A focus ring 29 is provided around the electrostatic chuck 11 on the outer peripheral edge of the upper surface of the susceptor 6 so as to surround the electrostatic chuck 11 and improve the efficiency of incidence of ions in plasma onto the wafer W. Is provided.

A baffle plate 31 having a large number of through holes is arranged around the susceptor 6 described above, and an exhaust port 32 is provided below the baffle plate 31 near the bottom of the processing container 3. The exhaust port 32 is provided, and is connected to an exhaust pipe 34 that communicates with a vacuuming unit 33 such as a turbo molecular pump. Therefore, the evacuation means 33
By the operation of, the inside of the processing container 3 can be evacuated to a desired degree of reduced pressure, for example, an arbitrary degree of reduced pressure up to 10 mTorr. Moreover, in that case, since the gas in the processing container 3 is exhausted through the baffle plate 18, it is possible to uniformly exhaust the gas.

The evacuation of the inside of the processing container 3 and the maintenance of the reduced pressure inside the processing container 3 by the operation of the vacuuming means 33 are detected by a detection signal from a pressure sensor (not shown) provided in the processing container 3. It is designed to be controlled automatically based on this.

An upper electrode 42 is provided above the processing chamber 2 via an insulating material 41 made of alumina, for example. The upper electrode 42 is made of a conductive material, for example, aluminum which has been subjected to alumite oxide treatment, but at least the surface 42a facing the wafer W is made of another material having high frequency conductivity, for example, a single material. It may be formed of crystalline silicon. The upper electrode 42 has a hollow structure having a hollow portion 42b therein, and a gas inlet 43 is formed in the upper center of the upper electrode 42. The gas inlet 43 communicates with the hollow portion 42b. There is. Then, on the surface 42a facing the wafer W, the wafer W
In order to supply the processing gas uniformly over the entire surface to be processed,
A large number of discharge ports 42c are formed. In the present embodiment, the surface 42 of the upper electrode 42 facing the wafer W.
a and the ceramics 13 on the upper surface of the electrostatic chuck 11.
The distance to the surface, that is, the gap, is set to 10 mm.

A gas introduction pipe 44 is provided at the gas introduction port 43.
Is connected to the gas introduction pipe 44, and the valve 4 is connected to the gas introduction pipe 44.
5, 45, 45 and a plurality of process gas supply sources 47, 47, 47 are connected via mass flow controllers 46, 46, 46 for flow rate adjustment. In the present embodiment, an etching gas such as CHF ₃ gas, CF ₄ gas, and A as a processing gas is supplied from these processing gas supply sources 47.
r gas is supplied, the flow rate of this etching gas is adjusted by the mass flow controller 46, and the etching gas is uniformly ejected to the wafer W from the ejection port 42c of the upper electrode 42. ing.

Next, the high frequency power supply system of the etching apparatus 1 will be described. For the susceptor 6 serving as the lower electrode and the upper electrode 42, for example, 380 kHz.
The high-frequency power source 51 for oscillating the high-frequency power is supplied from the high-frequency power source 51. However, in the present embodiment, as shown in FIG. It uses a so-called power split configuration that is separated.

That is, the high frequency power supply 51 is installed on the primary side of the transformer section 52 composed of an induction coil or the like through a matching unit 53 for matching, and further on the secondary side of the transformer section 52. A slide controller 54 is provided. The secondary sides of the transformer 52 are connected to the susceptor 6 and the upper electrode 42, respectively, and are configured to apply high-frequency power with a phase difference of 180 ° to the susceptor 6 and the upper electrode 42. There is.

The etching apparatus 1 according to the present embodiment is
It is configured as described above, and the oxide film (Si
When etching O ₂ ), first, the lifter pin 27 receives the wafer W transferred into the processing container 3 from a separately provided load lock chamber (not shown), and the lifter pin 27 receives the wafer W. By descending inward, the wafer W is placed on the upper surface of the electrostatic chuck 11, that is, on the upper ceramics 13. In this state, as shown in FIG. 2, the wafer W is supported only by the polyimide tape 14 provided on the peripheral portion of the ceramics 13 at the peripheral portion thereof.

Next, a predetermined voltage from the high voltage DC power supply 14
For example, 1.5 kV is applied to the conductive thin film 12 in the electrostatic chuck 11, and the wafer W is adsorbed and held on the electrostatic chuck 11, but at this time, Coulomb force also acts on the ceramics 13. , Wafer W is polyimide tape 1
In addition to the adsorption and holding of only the peripheral portion by 4, the central portion of the ceramic 13 is also adsorbed and retained.

Thereafter, the inside of the processing container 3 is evacuated by a vacuuming means 33.
After being evacuated to a predetermined degree of decompression by the processing gas supply source 47, CHF ₃ gas, CF ₄ gas,
The Ar gas and the gas required for the etching process are supplied at a predetermined flow rate. Then, when the high-frequency power from the high-frequency power source 51 is applied to the susceptor 6 and the upper electrode 42 at the time when the pressure in the processing chamber 2 is set and maintained at the degree of pressure reduction during processing, plasma is generated in the processing container 3. The etching gas in the processing container 3 is dissociated, and etchant ions generated at that time are generated as silicon oxide film (SiO 2) on the surface of the wafer W.
₂ ) Etching.

During the etching, the temperature of the wafer W tends to rise due to the plasma, but He supplied to the back surface of the wafer W from the outflow holes 22 and 23 and the storage hole 28.
The wafer W is maintained at a predetermined process temperature by the cold heat from the gas.

In this case, the He gas flowing into the space between the back surface of the wafer W and the electrostatic chuck 11 leaks from the peripheral portion, that is, the contact portion between the electrostatic chuck 11 and the back surface of the wafer W. The electrostatic chuck 11 according to the present embodiment
Since the polyimide tape 14 is provided on the peripheral edge portion of He, the He gas leaks from the peripheral portion substantially evenly. Therefore, the distribution of He gas on the back surface of the wafer W is made uniform, and as a result, the uniformity of the in-plane temperature of the wafer W is good.

In order to verify this, the results of the in-plane temperature distribution when an 8-inch wafer W is actually etched by using the etching apparatus 1 according to the embodiment are compared with the results of the conventional ceramic electrostatic chuck. The comparison is shown in the table of FIG. This is a summary of the results of measuring the temperatures at nine points on the wafer W as shown in FIG. 6 when the wafer W was actually etched. Regarding each of the measurement points P _{1 to} P ₉ , the measurement point P ₁ is the center of the wafer W, and the measurement points P _{2 to} P ₅ are the measurement points P ₁
And the edges of the wafer W are located on concentric circles and are set at central angles of 90 ° when viewed from the plane. The measurement points P ₂ and P ₄ are located on the diameter passing through the midpoint of the orientation flat. Further, the measurement points P _{6 to} P ₉ are located closer to the center side by 3 mm from the edge, and the measurement points P ₆ and P ₈ are
It is located on the diameter connecting the measurement points P ₂ , P ₁ and P ₄ , and the measurement point P ₇
And P ₉ are set on the diameter connecting the measurement points P ₃ , P ₁ , and P ₅ .

The process conditions are as follows: the pressure in the processing container 3 is 150 mTorr, the gap is 10 mm, the etching gas is a mixed gas of CHF ₃ gas, CF ₄ gas, and Ar gas, and the high frequency power from the high frequency power source 51 (380 kHz).
The output of z) was applied at 1300 W for 2 minutes. At that time, the temperature of the refrigerant in the susceptor 6 was 0 ° C., and the pressure of the heat transfer gas was 25 Torr. The temperature at the bottom of the processing container 3 is 0
℃, the temperature of the side part is 40 ℃, the temperature of the upper electrode 42 is 20 ℃
Met. The DC voltage applied to the electrostatic chuck 11 is 4 kV.

In the table of FIG. 5, a conventional ceramic electrostatic chuck (the dielectric layer is made of ceramics) is shown in the upper stage.
The result of the electrostatic chuck 11 in the embodiment in which the polyimide tape 14 having a width of 3 mm is attached to the peripheral portion of the ceramic electrostatic chuck is shown in the lower part. The experiment was performed three times each, and the measurement results were obtained each time by measuring the temperature (2 minutes after the high frequency from the high frequency power source was applied to the positions corresponding to the respective measurement points P _{1 to} P ₉ in the wafer pattern. (° C) is indicated by a number. At the same time, the leak rate of He gas is shown in the lower column.

As can be seen from the results of this experiment, the conventional ceramic electrostatic chuck has a problem of in-plane temperature uniformity, and the maximum temperature difference between the edge and the center is 17 at the first time.
The second temperature was 11 ° C, and the third temperature was 18 ° C. On the other hand, in the electrostatic chuck 11 in the embodiment, the in-plane temperature uniformity of the wafer W was better, and the maximum temperature difference between the edge and the center was 7 ° C. in each time. Therefore, it can be confirmed that the temperature uniformity of the wafer during the process is better when the electrostatic chuck 11 according to the present embodiment is used.

The electrostatic chuck 11 according to the present embodiment.
In general, the wafer temperature is higher, but this can be easily solved by lowering the temperature of the susceptor 6 itself or raising the pressure of He (helium) gas used as heat transfer gas. There is no problem in the process of.

Moreover, the dielectric on the upper surface of the electrostatic chuck 11 is
Since it is a ceramic, it is strong against plasma sputtering and has a long life. Further, since the polyimide tape 14 can be attached and detached freely, even if the polyimide tape 14 is sputtered by plasma,
You can easily replace this.

In the above embodiment, the polyimide tape 14 is attached only to the peripheral edge of the ceramics 13 on the upper side of the electrostatic chuck 11, but instead of this, as shown in FIG. The ceramic tape 14 may be attached to the portion excluding the grooves 25 and 26 and the storage hole 28. With such a configuration, the temperature distribution of the wafer during the process is made more uniform than in the conventional ceramic electrostatic chuck.

Although the above-described embodiment is an example configured as an etching apparatus, the present invention is not limited to this, and the present invention can be embodied as another plasma processing apparatus such as an ashing apparatus, a sputtering apparatus, and a CVD apparatus. Further, the object to be processed is not limited to the wafer but may be an LCD substrate.

[0042]

According to the present invention, the leak of the heat transfer gas from between the back surface of the substrate to be processed and the holding surface of the electrostatic chuck is equalized, and the substrate to be processed is being processed. The uniformity of the in-plane temperature can be improved. Therefore, processing uniformity is improved. Further, the durability of the electrostatic chuck itself is good. According to the invention of claim 3, replacement of the support member or the like becomes easy.

[Brief description of drawings]

FIG. 1 is a cross-sectional explanatory view of an etching apparatus according to an embodiment of the present invention.

FIG. 2 is a side sectional view of an electrostatic chuck in the etching apparatus of FIG.

3 is a perspective view of an electrostatic chuck in the etching apparatus of FIG.

4 is a plan view of an electrostatic chuck in the etching apparatus of FIG.

5 is a chart showing the measurement results of the temperature distribution of the wafer when the wafer is etched using the conventional ceramic electrostatic chuck and the electrostatic chuck of the embodiment in the etching apparatus of FIG.

FIG. 6 is an explanatory diagram showing measurement points when a temperature distribution is measured.

FIG. 7 is a plan view of an electrostatic chuck in which a polyimide tape is attached to a portion of the electrostatic chuck that is substantially free of grooves.

[Explanation of symbols]

 1 Etching Device 2 Processing Chamber 3 Processing Container 6 Susceptor 11 Electrostatic Chuck 13 Ceramics 14 Polyimide Tape 22, 23 Outflow Hole 25, 26 Groove 27 Lifter Pin 28 Storage Hole 33 Vacuum Evacuation Means 42 Upper Electrode 47 Processing Gas Supply Source 51 High Frequency Power Supply W wafer

Claims (3)

[Claims] 1. A static pressure reducing processing container and an electrostatic chuck provided in the processing container, wherein a processing gas is introduced into the processing container and a plasma is generated in the processing container to generate the static gas. The substrate to be processed held on the electric chuck is configured to perform a predetermined process in the plasma atmosphere, and the electrostatic chuck has at least a holding surface of the substrate to be processed made of ceramics, On the surface, in the plasma processing apparatus in which an outflow hole for outflowing the heat transfer gas to the back surface of the substrate to be processed is formed, only a portion of the electrostatic chuck that abuts the peripheral portion of the back surface of the substrate to be processed, A plasma processing apparatus comprising a support member made of a material softer than the ceramics. 2. A processing container that can be decompressed and an electrostatic chuck provided in the processing container, wherein a processing gas is introduced into the processing container and a plasma is generated in the processing container to generate the static gas. The substrate to be processed held on the electric chuck is configured to perform a predetermined process in the plasma atmosphere, and the electrostatic chuck has at least a holding surface on the substrate to be processed side made of ceramics, In the holding surface, in the plasma processing apparatus in which a groove for circulating the heat transfer gas from the outflow hole in the holding surface with respect to the back surface of the substrate to be processed is formed, among the holding surfaces in the electrostatic chuck, A plasma processing apparatus, characterized in that a supporting member made of a material softer than the ceramic is provided substantially in a portion excluding the groove. 3. The plasma processing apparatus according to claim 1, wherein the support member is attachable / detachable to / from the electrostatic chuck.