Substrate supporting member and substrate processing apparatus

A substrate supporting member, and a substrate processing apparatus including the substrate supporting member are provided. The substrate supporting member for mounting and supporting a substrate on a substrate supporting surface thereof, and controlling a temperature of the substrate by thermal transfer between the substrate and the substrate supporting surface, wherein the substrate supporting surface is smaller than the substrate, and includes a central region, an intermediate region, and a peripheral region. A thermal conductivity between the substrate and the peripheral region is greater than that between the substrate and the central region which is greater than that between the substrate and the intermediate region located between the central region and the peripheral region.

FIELD OF THE INVENTION

The present invention relates to a substrate supporting member for supporting a substrate mounted thereon, and a substrate processing apparatus including the substrate supporting member.

BACKGROUND OF THE INVENTION

In a manufacturing process of semiconductor devices, e.g., an etching process or a film forming process is performed by using a plasma.

The plasma processing using the plasma is generally performed by a plasma processing apparatus. The plasma processing apparatus includes, in a processing chamber, an upper electrode to which a high frequency power for generating the plasma is applied, a susceptor for supporting a substrate, and the like. Further, an inside of the processing chamber is depressurized to a predetermined pressure, and a processing gas is supplied into the processing chamber, and then, the high frequency power for generating the plasma is applied to the upper electrode to etch a film on the substrate by the plasma generated in the processing chamber.

Even when the plasma processing is performed under a high temperature condition to generate the plasma, it is required to constantly maintain a process condition in which the substrate is processed, e.g., a temperature of the substrate. On this account, the susceptor for supporting the substrate is temperature controlled, for example, by being provided with a circulating coolant to control the temperature of the substrate.

In case a top surface of the susceptor is smaller than that of the substrate, a peripheral portion of the substrate is outwardly extended beyond the top surface of the susceptor (for example, Japanese Patent Laid-open Application No. H11-121600). Consequently, it is prevented that the top surface of the susceptor is exposed to the upper electrode side to be etched by the plasma or the like during the etching process.

However, in case the peripheral portion of the substrate is extended beyond the susceptor as described above, during the process, a large amount of heat is applied to the peripheral portion of the substrate, and the peripheral portion of the substrate is not cooled sufficiently. On this account, the temperature of the substrate mounted on the susceptor becomes higher as a position on the substrate approaches the peripheral portion of the substrate, and thus, the in-surface temperature is not maintained uniformly. In case the temperature of the substrate surface is not uniform, for example, an in-surface etching uniformity is deteriorated, and thus, for example, a size of a line width of a central portion of the substrate becomes different from that of the peripheral portion.

SUMMARY OF THE INVENTION

It is, therefore, an object of the present invention to provide a substrate supporting member such as a susceptor for supporting a substrate and controlling a temperature of the substrate, by which the in-surface temperature of the substrate is uniformly maintained.

In accordance with an aspect of the present invention, there is provided a substrate supporting member for mounting and supporting a substrate on a substrate supporting surface thereof, and controlling a temperature of the substrate by thermal transfer between the substrate and the substrate supporting surface, wherein the substrate supporting surface is smaller than the substrate, and includes a central region, an intermediate region, and a peripheral region, and wherein a thermal conductivity between the substrate and the peripheral region is greater than that between the substrate and the central region which is greater than that between the substrate and the intermediate region located between the central region and the peripheral region.

In accordance with the present invention, the in-surface temperature of the substrate supported on the substrate supporting surface is uniformly maintained.

The intermediate region of the substrate supporting surface may correspond to an area ranging from 80% to 90% of a radius of the substrate from a center of the supported substrate.

The thermal conductivity between the substrate and each region of the substrate supporting surface may be controlled by changing a contact area therebetween.

A plurality of protruded portions for supporting the substrate is formed on the substrate supporting surface, and the thermal conductivities between the substrate and the substrate supporting surface may be controlled by changing the number of the protruded portions per unit area, or a contact area between each protruded portion and the substrate.

The thermal conductivity between the substrate and the substrate supporting surface may be controlled by changing a material constituting each region of the substrate supporting surface.

The thermal conductivity between the substrate and the substrate supporting surface may be controlled by changing a surface roughness of each region of the substrate supporting surface.

In accordance with another aspect of the present invention, there is provided a substrate processing apparatus including the above-described substrate supporting member.

In accordance with the present invention, the in-surface temperature of the substrate mounted on the substrate supporting member is uniformly maintained, and accordingly, an in-surface of the substrate is uniformly processed, and a production yield is improved.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereinafter, a preferred embodiment of the present invention will be described.FIG. 1is a longitudinal cross sectional view for schematically showing a configuration of a parallel plate type plasma processing apparatus1including a substrate supporting member in accordance with the present invention.

The plasma processing apparatus1includes a processing vessel10of e.g. a substantially cylindrical shape, and a processing space S is formed in the processing vessel10. The processing vessel10is made of, for example, an aluminum alloy, and an inner wall surface thereof is coated with an alumina film or an yttrium oxide film. Further, the processing vessel10is grounded.

There is provided a cylindrical susceptor supporting table12above a central bottom portion inside the processing vessel10, with an insulating plate11being interposed between them. A susceptor13serving as the substrate supporting member for mounting and supporting a substrate W is supported on the susceptor supporting table12. The susceptor13constitutes a lower electrode.

An annular coolant chamber14is formed in the susceptor supporting table12. The coolant chamber14communicates with a chiller unit (not shown) installed outside the processing vessel10, through lines14aand14b. A coolant is circulated and supplied to the coolant chamber14through the lines14aand14b, and accordingly, a temperature of the susceptor13is controlled. Accordingly, a temperature of the substrate W mounted on the susceptor13is controlled.

The susceptor13is made of, for example, the aluminum alloy such as the alumina (Al2O3). The susceptor13is generally formed as a disk-shape in which, for example, a central portion is protruded upward. An electrostatic chuck15constitutes a central protruding portion of the susceptor13. In the electrostatic chuck15, there is provided an electrode layer17connected to a DC power supply16, and the substrate W can be adsorbed by applying DC voltage from the DC power supply16to the electrode layer17to generate a Coulomb force.

A substrate supporting surface20on which the substrate W is mounted is provided on a top surface of the electrostatic chuck15of the susceptor13. The substrate supporting surface20is formed as a circular shape having a diameter less than that of, for example, the substrate W to be mounted. Accordingly, when the substrate W is mounted on the substrate supporting surface20, a peripheral portion of the substrate W is outwardly extended beyond the periphery of the substrate supporting surface20. The substrate supporting surface20includes a peripheral ring portion21formed along its periphery and a plurality of cylindrical protruded portions22as shown in, e.g.,FIGS. 2 and 3. Top surfaces of the peripheral ring portion21and the protruded portions22have the same horizontal level, and they are formed to be flat, and contacted with the substrate W when the substrate W is mounted on the substrate supporting surface20. Accordingly, the substrate W is supported by the peripheral ring portion21and the protruded portions22of the substrate supporting surface20.

The substrate supporting surface20is formed so that a thermal conductivity between the substrate W and the substrate supporting surface20is at first constant, and then decreased, and then increased from a central portion to the peripheral portion. For example, the substrate supporting surface20is partitioned into a central region R1corresponding to an area ranging up to 80% of the radius K of the substrate W from a center of the mounted substrate W, an intermediate region R2corresponding to the area ranging from 80% to 90% of the radius K of the substrate W therefrom, and a peripheral region R3corresponding to the area ranging from 90% to 98% of the radius K of the substrate W therefrom. The thermal conductivity between the substrate W and the substrate supporting surface20is set for each of the regions R1to R3as shown inFIG. 4. Herein, the above-described thermal conductivity is an average thermal conductivity between each of the regions R1to R3and the substrate supporting surface20.

A multiple number of protruded portions22are uniformly disposed on the central region R1as shown inFIGS. 2 and 3, and an thermal conductivity corresponding to the central region R1is constant between the central region R1and the substrate W. A plural protruded portion22is formed so that its number on the intermediate region R2per unit area is less than that on the central region R1. Accordingly, because a contact ratio between the protruded portions22and the substrate W (a contact area/a total area in a region) in the intermediate region R2becomes less than that in the central region R1, the thermal conductivity between the intermediate region R2and the substrate W becomes less than that between the central region R1and the substrate W. Further, the thermal conductivity between the intermediate region R2and the substrate W is set to be about 90% of that between the central region R1and the substrate W.

A multiplicity of protruded portions22and the peripheral ring portion21are disposed on the peripheral region R3so that the contact ratio in the peripheral region R3is larger than that in the central region R1or the intermediate region R2. The contact ratio can be increased, for example, by increasing the number of the protruded portions22per unit area or a width of the peripheral ring portion21. Accordingly, the thermal conductivity between the substrate W and the peripheral region R3is larger than that between the substrate W and the central region R1or between the substrate W and the intermediate region R2.

Returning toFIG. 1, a gas supply line30passing through an inside of the susceptor13and the susceptor supporting table12is connected to the substrate supporting surface20. Accordingly, a thermally conductive gas such as a He gas can be supplied to a space between the substrate W and the electrostatic chuck15, formed when the substrate W is mounted on the substrate supporting surface20.

An annular focus ring31is installed at a periphery of the susceptor13to surround the substrate W mounted on the susceptor13. The focus ring31is made of, for example, a conductive material.

A first high frequency power supply41is electrically connected to the susceptor13via a matching unit40. The first high frequency power supply41can output a high frequency power having a frequency ranging from 2 to 20 MHz, for example, 2 MHz to apply it to the susceptor13. A self-bias potential for attracting ions in a plasma toward the substrate W can be generated by the first high frequency power supply41.

A high pass filter42for passing a high frequency from a second high frequency power supply71connected to an upper electrode50described later to ground is electrically connected to the susceptor13.

Besides, the upper electrode50is provided above the susceptor13to face the susceptor13in parallel. A plasma generation space is formed between the susceptor13and the upper electrode50.

The upper electrode50constitutes a shower head for jetting a processing gas on the substrate W mounted onto the susceptor13. The upper electrode50includes an electrode plate51facing, e.g., the susceptor13, and an electrode supporting member52for supporting the electrode plate51. The electrode supporting member52is formed substantially as, for example, a hollow cylindrical shape, and the electrode plate51is installed on its bottom. A plurality of gas injection openings51ais formed on the electrode plate51, and the processing gas introduced in the electrode supporting member52can be jetted therefrom.

One end of a gas supply line60for supplying the processing gas to the upper electrode50is connected to a central top surface of the electrode supporting member52of the upper electrode50, and the other end thereof is connected to a gas supply source61through a top surface of the processing vessel10. An insulating member62is interposed between the gas supply line60and the processing vessel10.

The second high frequency power supply71is electrically connected to the upper electrode50via a matching unit70. The second high frequency power supply71can output a high frequency power having a frequency greater than 40 MHz, for example, 60 MHz to apply it to the upper electrode50. A plasma of the processing gas can be generated in the processing vessel10by the second high frequency power supply71.

A low pass filter72for passing a high frequency from the first high frequency power supply41connected to the susceptor13to ground is electrically connected to the upper electrode50.

A gas exhaust opening80is formed at a bottom portion of the processing vessel10. The gas exhaust opening80is connected to a gas exhaust unit82including a vacuum pump or the like through a gas exhaust line81. A pressure in the processing vessel10can be reduced to a desired level by the gas exhaust unit82.

A transfer opening90for the substrate W is formed at a sidewall of the processing vessel10, and the transfer opening90is provided with a gate valve91. By opening the gate valve91, the substrate W can be loaded into or unloaded from the processing vessel10.

In an etching process performed by the plasma processing apparatus1configured as described above, the substrate W is first loaded into the processing vessel10, and adsorptively mounted on the substrate supporting surface20of the susceptor13. At this time, the temperature of the susceptor13is controlled to a predetermined level by the circulated coolant in advance. The temperature of the substrate W on the substrate supporting surface20is also controlled to a predetermined level by cooling transfer from the susceptor13. Next, a pressure in the processing space S is reduced to a predetermined level by exhausting a gas through, for example, the gas exhaust line81, and then, the processing gas is supplied into the processing space S through the upper electrode50. The high frequency power is applied to the upper electrode50by the second high frequency power supply71, and thus, the processing gas in the processing space S is turned into the plasma. Further the high frequency power is applied to the susceptor13by the first high frequency power supply41, and thus, the charged particles in the plasma are pulled to the side of the substrate W. A film on the substrate W is etched by an action of the plasma.

Hereinafter, a temperature uniformity of the substrate is verified in case of employing the susceptor13of the present preferred embodiment.FIG. 5is a graph for presenting a thermal conductivity distribution between the substrate W and the substrate supporting surface20, and a temperature distribution of the substrate W temperature controlled on the substrate supporting surface20.

A curve A shown inFIG. 5presents the temperature distribution of the substrate W in case the thermal conductivity between the substrate W on the susceptor13and the substrate supporting surface is uniform across the whole region. In this case, it can be shown that a temperature of the peripheral portion of the substrate W is notably increased. A curve B presents the thermal conductivity distribution in case the thermal conductivity between the substrate W and the substrate supporting surface is gradually increased from the central portion to the peripheral portion of the substrate supporting surface, and a curve C presents the temperature distribution of the substrate W in case of employing the thermal conductivity distribution of the curve B. In case of the curve C, although a temperature increase of the peripheral portion of the substrate W is suppressed when compared with the case of the curve A, a temperature of the substrate W is substantially decreased in a range from an intermediate portion to the peripheral portion.

A curve D presents the thermal conductivity distribution in case the thermal conductivity between the substrate W and the substrate supporting surface is increased in the order of the intermediate region R2<the central region R1<the peripheral region R3, as in the substrate supporting surface20of the susceptor13of the present preferred embodiment. A curve E presents the temperature distribution of the substrate W mounted on the substrate supporting surface20of the present preferred embodiment. In case of the curve E, the temperature decrease of the intermediate portion to the peripheral portion of the substrate W shown in the curve C is suppressed, and further, an in-surface maximum temperature difference is limited within a range of about ±1° C.

In accordance with the present preferred embodiment, because the thermal conductivity between the substrate W and the substrate supporting surface20is set so that it is increased in order of the intermediate region R2<the central region R1<the peripheral region R3by changing the number of the protruded portions22of the substrate supporting surface20of the susceptor13per unit area, the in-surface temperature of the substrate W is uniformly maintained during the etching process in the plasma processing apparatus1, and the etching process can be uniformly performed in the surface of the substrate.

Although the thermal conductivities between the substrate W and the respective regions R1to R3of the substrate supporting surface20are controlled by the number of the protruded portions22per unit area in accordance with the above-described preferred embodiment, the thermal conductivities between the substrate W and the respective regions R1to R3of the substrate supporting surface20may be controlled by changing the contact area between each of the protruded portions22and the substrate W, that is, an area of a top surfaces of each of the respective protruded portions22, on the condition that a plurality of protruded portions22is uniformly disposed on the substrate supporting surface20.

Further, the thermal conductivities between the substrate W and the respective regions R1to R3of the substrate supporting surface20may be controlled by changing materials of the respective regions R1to R3. For example, in case the substrate supporting surface20is made of a material having the alumina as a principal component, the thermal conductivities of the respective regions R1to R3may be controlled by adding a different amount of aluminum nitride (AlN) to the material of the respective regions R1to R3of the substrate supporting surface20. In this case, the amount of the added aluminum nitride is increased in order of the intermediate region R2, the central region R1, and the peripheral region R3, and thus, the thermal conductivity is set so that it is increased in order of the intermediate region R2, the central region R1, and the peripheral region R3. Further, in this case, the substrate supporting surface20may have a flat top surface without irregularity as shown inFIG. 6.

Further, the thermal conductivity of each of the regions R1to R3may be controlled by changing a surface roughness of each of the regions R1to R3of the substrate supporting surface20. In this case, the substrate supporting surface20is formed so that the surface roughness is decreased in order of the intermediate region R2, the central region R1, and the peripheral region R3, and thus, the thermal conductivity is set so that it is increased in order of the intermediate region R2, the central region R1, and the peripheral region R3. Further, in this case, the substrate supporting surface20may also have a flat top surface without irregularity.

While the preferred embodiment of the present invention have been shown and described in conjunction with the accompanying drawings, the present invention is not limited thereto. It will be understood by those skilled in the art that various changes and modifications may be made without departing from the scope of the invention as defined in the following claims, and they are embraced in the technical scope of the present invention. Accordingly, the present invention may take various forms other than the specific embodiment as illustrated herein. For example, although the preferred embodiment has described the case where the protruded portions22of the substrate supporting surface20are cylindrical, they may have various shapes, e.g., a square pillar shape. Further, on the substrate supporting surface20, an inner peripheral ring portion may be formed on an inner side of the peripheral ring portion21. Both the high frequency power supply for generating the self-bias potential and a high frequency power supply for generating the plasma may be connected to the susceptor13serving as the lower electrode. Although the above-described preferred embodiment has described the case where the susceptor13having the substrate supporting surface20is included for the plasma processing apparatus1for performing the etching process, the substrate supporting member of the present invention can be applied to a plasma processing apparatus for performing a film forming process, or other substrate processing apparatuses in which the plasma is not used.

The present invention is useful for uniformly maintaining the in-surface temperature of the substrate in the substrate supporting member for controlling a temperature of the substrate.