JP2012182221A - Substrate supporting member - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a substrate supporting member capable of equalizing a plasma production density in a space provided on a side where a substrate is mounted in a high-frequency electrode.SOLUTION: Holes 121 or slits 122 are provided to a high-frequency electrode 12. The high-frequency electrode 12 is sectioned into a plurality of ranges by a concentric circle C having a radius αr (0.25≤α≤0.75), that is, α times of a radius of the high-frequency electrode 12. Distributions or arrangement forms of the holes 121 or the slits 122 in the respective ranges are differentiated from each other.

Description

  The present invention relates to a substrate support member mounted on a high-frequency plasma processing apparatus.

  As a substrate support member used in a semiconductor process apparatus such as a CVD apparatus for forming a thin film on a substrate such as a wafer using high frequency plasma, a heater element and a plasma generating electrode are embedded in a ceramic substrate. A known heater plate is known (see Patent Document 1).

JP 2007-088498 A

  However, conventionally, as shown in FIG. 6, a smooth metal foil, a printed metal layer, or the like is used as a high-frequency electrode incorporated in a ceramic substrate. Further, from the viewpoint of protecting the high-frequency electrode and the power supply system for the high-frequency electrode from the plasma gas, as shown in FIG. 6, the high-frequency power is centered on the high-frequency electrode (approximately the center surrounded by a broken line). Supplied through the feeding position). As a result, high-frequency current propagates radially outward from the approximate center of the high-frequency electrode, but due to factors such as the volume resistivity or thickness of the electrode, the plasma impedance in the space above the electrode, and hence the plasma generation density, is not uniform. become. For this reason, depending on the film forming process, the film thickness tends to be different for each substrate, or the film thickness tends to be non-uniform in the radial direction of the high-frequency electrode.

  Also, when a disk-shaped metal electrode or mesh-shaped metal with a plurality of circular holes provided uniformly is used as a high-frequency electrode, the propagation of high-frequency current in the radial direction of the electrode may occur or be delayed. As a result, the plasma generation density in the space above the electrode becomes non-uniform. For this reason, the film thickness formed on the substrate tends to be non-uniform in the radial direction of the high-frequency electrode.

  Therefore, an object of the present invention is to provide a substrate support member capable of equalizing the plasma generation density in the space on the side where the substrate of the high-frequency electrode is placed.

  The present invention has a substantially disc shape comprising a ceramic base having a mounting surface on which a substrate is mounted, and a metal or intermetallic compound embedded in the ceramic base in a posture parallel to the mounting surface. The present invention relates to a substrate support member including a high-frequency electrode and a high-frequency power supply terminal connected to a central portion of the high-frequency electrode.

  In the present invention, the high-frequency electrode is provided with a hole or a slit, and the plurality of ranges of the high-frequency electrode are divided by concentric circles having a radius α times (0.25 ≦ α ≦ 0.75) of the high-frequency electrode. The hole or slit distribution or arrangement mode in each of the above is differentiated.

  The hole or the slit may be provided so as to have rotational symmetry around the center of the high-frequency electrode.

  The high-frequency electrode is divided into a circular first range and an annular second range surrounding the first range, and one of the first range and the second range is provided with a hole or a slit. On the other hand, the other of the first range and the second range may be flat without holes and slits.

  The high-frequency electrode is divided into a circular first range and an annular second range surrounding the first range, and the hole or the slit is provided in each of the first range and the second range. Also good.

The structure explanatory view of the substrate support member of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS FIG. Explanatory drawing regarding the arrangement | positioning aspects, such as a slit, in the high frequency electrode of 1st Embodiment. The structure explanatory view of the high frequency electrode of a 2nd embodiment. Explanatory drawing regarding the arrangement | positioning aspects, such as a slit, in the high frequency electrode of 2nd Embodiment. The structure explanatory drawing of the conventional high frequency electrode.

(Configuration of substrate support member)
A substrate support member 1 as an embodiment of the present invention shown in FIG. 1 includes a ceramic substrate 11 having a mounting surface 10 on which a substrate W is mounted, and a posture parallel to the mounting surface 10. The high-frequency electrode 12 embedded in the ceramic substrate 11 and the high-frequency power supply terminal 13 connected to the central portion of the high-frequency electrode 12 are provided.

The ceramic substrate 11 is a substantially disk-shaped ceramic sintered body, and is manufactured from, for example, a raw material mainly composed of aluminum nitride (AlN) having high thermal conductivity in order to suppress local unevenness in temperature distribution. ing. In addition, yttria (Y ₂ O ₃ ) may be added to the raw material in order to improve the thermal uniformity. The ceramic substrate 11 may be a ceramic sintered body using silicon carbide (SiC), Mg ₂ Al ₂ O ₄ , Al ₂ O ₃ or the like as a raw material in addition to aluminum nitride.

  The high-frequency electrode 12 as the plasma generating electrode is preferably formed by patterning from a foil or mesh sheet of heat-resistant metal such as molybdenum or tungsten. The high frequency electrode 12 may be formed by printing. A detailed configuration of the high-frequency electrode 12 will be described later.

  The terminal 13 is formed in a substantially bottomed cylindrical shape from a metal having a relatively small thermal expansion coefficient, such as Kovar, molybdenum, or nickel, and is connected and fixed to the central portion of the high-frequency electrode 12 by brazing or the like. A rod electrode 14 made of Ni or the like is inserted into the tube of the terminal 13 from the viewpoint of heat resistance and oxidation resistance, and is connected and fixed by brazing.

  For example, a resistance heating element for adjusting the temperature of the substrate W may be embedded in the ceramic substrate 11 below the high-frequency electrode 12. A pair of rod electrodes made of Ni or the like are connected to the resistance heating element, and power is supplied to the resistance heating element from the heater power source (not shown) through the rod electrode, whereby the resistance heating element generates heat.

  The substrate support member 1 shown in FIG. 1 is joined to a shaft 15 at the central portion of the surface opposite to the mounting surface 10. By being joined and used, the amount of heat is transmitted to the shaft 15 so that the end of the support member is easily cooled. Therefore, the substrate support member 1 in which the shaft 15 is joined in the vicinity of the center as shown in FIG. 1, the temperature distribution in the vicinity of the center is likely to change, and the film thickness control in the film forming process is difficult.

  Further, the cooling rate and the process temperature vary depending on the film forming conditions. Therefore, in order to make the plasma generation density uniform, it is very meaningful to use the electrode configuration as in the present invention.

(Configuration of high frequency electrode)
The high-frequency electrode 12 is provided with holes or slits (referred to as “slits” as appropriate). A plurality of high-frequency electrodes 12 divided by concentric circles having a radius αr that is α times (0.25 ≦ α ≦ 0.75) r (the distance from the center to the outermost arcuate edge) r of the high-frequency electrode 12 The distribution or distribution of holes or slits in each of the ranges is differentiated. When α is less than 0.25 or exceeds 0.75, the effect of equalizing the plasma generation density is reduced. In order to equalize the plasma generation density in the space above the mounting surface 10 of the substrate support member 1, α may be set to a value in the range of 0.40 to 0.60.

(Configuration of high-frequency electrode (first embodiment))
As shown in FIGS. 2A to 2C, the high-frequency electrode 12 used in the substrate support member 1 according to the first embodiment is formed into a circular shape by one concentric circle C having a radius αr (see the broken line). It is divided into a first range S ₁ and an annular second range S ₂ surrounding the first range S ₁ . One of the first range S ₁ and the second range S ₂ is provided with a slit or the like, while the other of the first range S ₁ and the second range S ₂ is flat without holes or slits. Yes.

  The outline of the high-frequency electrode 12 does not need to be completely circular, and may be a substantially circular shape such that 80% or more of the outline is on the same circumference.

Example 1
A disk-shaped ceramic sintered body having an outer diameter of 300 [mm] and a thickness of 25 [mm] is obtained from a raw material obtained by adding ₃ wt% yttria (Y ₂ O ₃ ) to aluminum nitride (AlN) as a main component. Manufactured as a substrate 1. From a raw material in which 5 wt% yttria (Y ₂ O ₃ ) is added to aluminum nitride (AlN), a substantially cylindrical shaft 15 having an outer diameter of 50 [mm], an inner diameter of 40 [mm], and a height of 150 [mm]. Was manufactured. The high-frequency electrode 12 is composed of a Mo sheet having a diameter of 290 [mm] and a thickness of 0.1 [mm].

As shown in FIG. 2A, in the first range S ₁ of the high-frequency electrode 12, three slits 122 arranged so as to have rotational symmetry are formed. Each slit 122 has a shape in which a straight line segment is bent by about 120 ° in the vicinity of the center thereof, and the bent portion is located near the center of the high-frequency electrode 12. On the other hand, no slit or hole is formed in the second range S ₂ of the high-frequency electrode 12. α was set to “0.50”.

  The distribution mode of slits and the like in the high-frequency electrode 12 is represented by the ratio y of the length of the portion of the circumference where the slits overlap with the length of the circumference of the concentric circle at a distance x from the center of the high-frequency electrode 12. It is. A distribution mode such as a slit means a change mode of the ratio y with respect to the distance x.

From FIG. 3A showing the distribution mode of the slits and the like of the high-frequency electrode 12 of Example 1, among the distance ranges corresponding to the first range S ₁ , the high-frequency electrode in the distance range where the concentric circles overlap the slit 122 having the same width. It can be seen that there are locations where the ratio y decreases in inverse proportion to the distance x from the center of 12.

  Depending on the process, for example, in the PECVD film forming process, (1) the source gas is decomposed by the assistance of plasma, (2) the intermediate is adsorbed on the substrate, and (3) the intermediate adsorbed on the substrate is It consists of several elementary reactions such as chemical changes to the final film product through reactions such as dehydration and dealcoholization. If there is an elementary reaction in which the uniformity of plasma is rate-limiting, it is necessary to suppress or control the fluctuation. In such a case, adjustment of the impedance in the radial direction of the electrode is necessary and highly effective.

In order to evaluate the uniformity of the plasma generation density in the space on the mounting surface 10 side of the substrate support member 1, in this embodiment, a SiO ₂ film is formed on the substrate W by the PECVD film forming process 1, and the standard of the film thickness is determined. Deviation was measured. As a result, the coefficient of variation obtained by dividing the standard deviation by the average film thickness was 1.0 [%].

(Example 2)
As shown in FIG. 2B, in the first range S ₁ of the high-frequency electrode 12, a plurality of circular holes 121 arranged so as to have rotational symmetry along each of the plurality of concentric circles. Is formed. On the other hand, no slit or hole is formed in the second range S ₂ of the high-frequency electrode 12. The other configuration is the same as that of the first embodiment.

From FIG. 3B showing the distribution mode of the slits and the like of the high frequency electrode 12 of Example 2, the ratio y with respect to the distance x from the center of the high frequency electrode 12 in the distance range corresponding to the first range S ₁ It turns out that the increase / decrease is repeated intermittently.

The variation coefficient of the film thickness of the SiO ₂ film formed on the substrate W by the PECVD film forming process 1 used in this example was 0.6 [%]. At this time, α was set to “0.50”.

(Example 3)
As shown in FIG. 2C, in the second range S ₂ of the high-frequency electrode 12, a plurality of circular holes 121 arranged so as to have rotational symmetry along each of the plurality of concentric circles. Is formed. On the other hand, no slit or hole is formed in the first range S ₁ of the high-frequency electrode 12. The other configuration is the same as that of the first embodiment.

From FIG. 3C showing the distribution mode of slits and the like of the high-frequency electrode 12 of Example 3, the ratio y with respect to the distance x from the center of the high-frequency electrode 12 in the distance range corresponding to the second range S ₂ It turns out that the increase / decrease is repeated intermittently.

The variation coefficient of the film thickness of the SiO ₂ film formed on the substrate W by the PECVD film forming process 2 used in this example was 0.9 [%]. Α at this time was set to “0.75”.

(Configuration of the high-frequency electrode of the second embodiment)
As shown in FIG. 4, the high-frequency electrode 12 used in the substrate support member 1 of the second embodiment has a circular first range S ₁ by one concentric circle C having a radius αr (see the broken line), It is divided into an annular second range S ₂ surrounding the first range S ₁ . A slit or the like is provided in each of the first range S ₁ and the second range S ₂ .

Example 4
As shown in FIG. 4, a plurality of fan-shaped slits 122 arranged so as to have rotational symmetry are formed in the first range S ₁ of the high-frequency electrode 12. In addition, a plurality of linear slits 122 arranged so as to have rotational symmetry are formed in the second range S ₂ of the high-frequency electrode 12.

FIG. 5 showing the distribution mode of the slits and the like of the high-frequency electrode 12 of the fourth embodiment. From the distance range corresponding to the first range S ₁ , from the center of the high-frequency electrode 12 in the distance range where the concentric circles overlap the fan-shaped slit 122. It can be seen that there is a portion where the ratio y gradually decreases with respect to the distance x. Similarly, from FIG. 5, in the distance range corresponding to the second range S ₂ , the ratio y gradually decreases with respect to the distance x from the center of the high-frequency electrode 12 in the distance range where the concentric circles overlap the linear slit 122. It can be seen that there is a place.

Due to the difference in the shape of the slit 122 in each of the first range S ₁ and the second range S ₂ , the reduction rate of the ratio y to the distance x in the second range S ₂ is the ratio to the distance x in the first range S ₁ . It is smaller than the rate of decrease of y.

The variation coefficient of the film thickness of the SiO ₂ film formed on the substrate W by the PECVD film forming process 1 used in this example was 0.5 [%]. At this time, α was set to “0.25”.

(Comparative example)
When the flat high-frequency electrode shown in FIG. 6 was employed, the variation coefficient of the film thickness of the SiO ₂ film formed on the substrate W by the PECVD film forming process was 3.5 [%].

Table 1 shows the variation coefficient of the film thickness of the SiO ₂ film formed on the substrate W by the PECVD film forming process of each example and comparative example.

  From Table 1, the variation coefficient of the film thickness in each of Examples 1 to 4 is smaller than the variation coefficient of the film thickness of the comparative example, so that the film formation is made uniform, and thus the plasma generation density is made uniform. It can be seen that Moreover, it turns out that (alpha) is suitable in the range of 0.25-0.75.

(Operational effect of the present invention)
According to the substrate support member of the present invention having the above-described configuration, the high-frequency electrode can be obtained by devising the distribution mode or distribution mode (see FIGS. 3 and 5) of the holes 121 or the slits 122 provided in the high-frequency electrode 12. 12, and as a result, the plasma generation density in the space on the mounting surface 10 side can be equalized. Thereby, equalization of the surface treatment of the substrate W placed on the placement surface 10 is achieved (see Table 1).

(Other embodiments of the present invention)
In the embodiment, the high-frequency electrode 12 is divided into a circular first range S ₁ and one annular second range S ₂ by one concentric circle C. However, as another embodiment, the high-frequency electrode 12 is divided. May be divided into a circular first range S ₁ and a plurality of annular second ranges S ₂ surrounding the first range S ₁ by a plurality of concentric circles C. In addition, distribution modes such as slits in each of the plurality of second ranges may be differentiated from each other.

  The slits or the like provided in the high-frequency electrode may not be arranged so as to have rotational symmetry around the center of the high-frequency electrode.

Both the hole and the slit may be provided in the high frequency electrode. For example, in the first embodiment, both the slit and the hole may be provided in _{one of} the first range S ₁ and the second range S ₂ . In the second embodiment, both the first range S ₁ and the second one of the range S ₂ or both slits and holes may be provided, of the first range S ₁ and the second range S ₂ One may be provided with a slit, while the other may be provided with a hole.

  A voltage for electrostatically adsorbing the substrate may be superimposed on the high-frequency electrode.

  DESCRIPTION OF SYMBOLS 1 ... Base support member, 10 ... Mounting surface, 11 ... Ceramic base, 12 ... High frequency electrode, 13 ... Terminal, 14 ... Rod electrode, 15 ... Shaft, 121 ... Hole, 122 ... Slit.

Claims (4)

A ceramic substrate having a mounting surface on which a substrate is mounted; a disk-shaped high-frequency electrode made of metal or an intermetallic compound embedded in the ceramic substrate in a posture parallel to the mounting surface; A substrate support member comprising a high-frequency power supply terminal connected to a central portion of the high-frequency electrode,
The high frequency electrode is provided with a hole or a slit,
The distribution or arrangement of the holes or the slits in each of the plurality of ranges of the high-frequency electrode divided by concentric circles having a radius α times that of the high-frequency electrode (0.25 ≦ α ≦ 0.75) is differentiated. A substrate support member characterized by being provided. The substrate support member according to claim 1,
The substrate support member, wherein the hole or the slit is provided so as to have rotational symmetry around the center of the high-frequency electrode. The substrate support member according to claim 1 or 2,
The high-frequency electrode is divided into a circular first range and an annular second range surrounding the first range, and one of the first range and the second range is provided with a hole or a slit. On the other hand, the other of the first range and the second range is flat without holes and slits, and is a substrate support member. The substrate support member according to claim 1 or 2,
The high-frequency electrode is divided into a circular first range and an annular second range surrounding the first range, and the hole or the slit is provided in each of the first range and the second range. A substrate support member.

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