JP2018006269A - Ceramic heater - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a ceramic heater capable of soaking a substrate. A ceramic heater 100 is made of ceramics, and has a base material 10 on which an object to be heated is placed on the upper surface, a heat generating resistor 20 embedded in the base material 10, and both ends of the heat generating resistor 20. It includes a terminal 30 to be connected. The heat generation resistor 20 is composed of two spiral heat generation resistance elements 21A and 21B, which are connected to the terminal 30 at the outer end and arranged so as not to overlap each other. The two spiral heat generation resistance elements 21A and 21B are connected in a ring shape at the center. [Selection diagram] Fig. 2

Description

  The present invention relates to a ceramic heater for heating an object to be heated such as a semiconductor wafer.

  In ceramic heaters for heating an object to be heated such as a semiconductor wafer, there are terminals in which terminals for supplying current to a heating resistor arranged inside a substrate are respectively connected to both ends of the heating resistor. (For example, refer to Patent Document 1).

JP 2001-068255 A

  However, in the conventional ceramic heater, since the heating resistor has a shape that can be drawn with a single stroke, the heating resistor is not symmetrically located in the center of the heating resistor, and the heating resistor is symmetrical to the center. It was difficult to place. Further, in a general ceramic heater, a gas supply hole to be supplied to the back surface of the wafer is often disposed at the center of the base material and thus the heating resistor. Therefore, it was difficult to heat symmetrically with respect to the center of a base material.

  This invention is made | formed in view of this situation, and it aims at providing the ceramic heater which can aim at symmetrical heating with respect to the center of a base material.

  The first aspect of the present invention is a ceramic substrate made of ceramics, on which an object to be heated is placed, a heating resistor embedded in the ceramic substrate, and connected to both ends of the heating resistor. Each of the heating resistors is connected to the power supply terminal at an outer end, and is arranged from two spiral heating resistor elements arranged without overlapping each other. Thus, the two spiral heating resistance elements are connected in an annular shape at the center.

  The second aspect of the present invention is a ceramic substrate made of ceramics, on which an object to be heated is placed, a heating resistor embedded in the ceramic substrate, and a linear symmetry and point symmetry in the heating resistor. A ceramic heater comprising a pair of power supply terminals arranged at a position that is neither in the direction of rotational property nor rotational symmetry, wherein the heating resistor comprises a circular heating resistance element located on the outermost periphery, an outermost periphery The virtual terminal located at a position inverted by 180 ° around the center of the ceramic substrate with respect to the power supply terminal adjacent to the power supply terminal and the other power supply terminal are connected and arranged without overlapping. The two spiral heating resistance elements are connected in a ring shape at the center.

  According to the first and second aspects of the present invention, the two spiral heating resistance elements are connected in an annular shape at the center. Accordingly, the heating resistor element can be arranged in line symmetry with respect to the center without the heating resistor element existing at the center of the heating resistor. Therefore, it becomes possible to aim at symmetrical heating with respect to the center of a base material.

The schematic cross section of the ceramic heater which concerns on embodiment of this invention. The II-II line | wire schematic cross section of FIG. The schematic horizontal sectional view of the ceramic heater which concerns on the deformation | transformation of embodiment of this invention. The schematic horizontal sectional view of the ceramic heater which concerns on the comparative example 1. FIG. The model horizontal sectional view of the ceramic heater which concerns on the comparative example 2. FIG.

  First, a ceramic heater 100 according to an embodiment of the present invention will be described with reference to the drawings.

  As shown in FIG. 1, the ceramic heater 100 is based on a substrate 10 made of a substantially disk-like insulator for adsorbing and holding a wafer (substrate), which is not shown, to be heated. And a heating resistor 20 embedded in the material 10.

  In addition to the heating resistor 20, the substrate 10 includes an electrostatic chuck electrode for attracting the wafer to the mounting surface 11 by a Johnsen-Rahbek force and a plasma electrode for generating plasma above the substrate 10. At least one of them may be embedded.

  However, the ceramic heater 100 may also serve as an electrostatic chuck that attracts the substrate to the surface of the base material 10 by a Coulomb force generated when a voltage is applied to the electrode from the power supply rod.

  Further, the ceramic heater 100 includes a pair of power supply terminals (power supply terminals) 30 for supplying power to the heating resistor 20.

  Each terminal 30 is connected to a current supply member (not shown) embedded in the base material 10.

  The terminal 30 and the current supply member are brazed or welded. The terminal 30 is mainly made of foil, plate, massive nickel (Ni), Kovar (registered trademark) (Fe-Ni-Co), molybdenum (Mo), tungsten (W), or molybdenum (Mo) and tungsten (W). It is composed of a heat-resistant metal such as a heat-resistant alloy as a component. The current supply member is made of molybdenum (Mo) or tungsten (W).

  The base material 10 is a ceramic base material made of a ceramic sintered body such as alumina, aluminum nitride, or silicon nitride. The base material 10 may be formed into a disk shape by hot press firing or the like, for example, in order to form and densify the above material in a mold having a predetermined shape.

  In this embodiment, the heating resistor 20 is made of a foil such as a heat-resistant metal such as molybdenum (Mo) or tungsten (W) and has a planar shape. However, the heating resistor 20 may have a configuration such as a film, a plate, a wire, a mesh, a fiber, a coil, or a ribbon made of a heat-resistant metal. In the present embodiment, the thickness of the heating resistor 20 is constant.

  The base material 10 is baked in a state where the heating resistor 20 is sandwiched between the base materials 10.

  An example of the pattern of the heating resistor 20 will be described with reference to FIG.

  The heating resistor 20 is connected at the outer end located in the vicinity of the terminal 30 and the outermost arc-shaped heating resistor elements 22Aa, 22Ba, respectively, and two spiral heating resistor elements 21A arranged without overlapping each other. , 21B. These two spiral heating resistance elements 21A and 21B are connected in an annular shape at the center.

  Here, the first spiral heating resistor element 21 </ b> A is connected to the terminal 30, and is arranged in a plurality of arc-shaped heating resistor elements 22 </ b> Aa to 22 </ b> Ad arranged in concentric annular regions and adjacent annular regions. The arc-shaped heat generating resistance elements 22Aa to 22Ad are linearly connected to the heat generating resistance elements 23Aa to 23Ac.

  On the other hand, the second spiral heating resistor element 21B has an end connected to the terminal 30, and is arranged in a plurality of arc-shaped heating resistor elements 22Ba to 22Bd arranged in concentric annular regions and in an adjacent annular region. It is comprised from linear heating resistance element 23Ba-23Bc which connects the edge part of arc-shaped heating resistance element 22Ba-22Bd linearly.

  The arc-shaped heating resistor element 22Aa is an arc-shaped heating resistor element 22Ba, the arc-shaped heating resistor element 22Ab is an arc-shaped heating resistor element 22Bb, the arc-shaped heating resistor element 22Ac is an arc-shaped heating resistor element 22Bc, and an arc-shaped heating element. The resistance element 22Ad is disposed in the same annular area as the arc-shaped heat generation resistance element 22Bd.

  Furthermore, the arc-shaped heating resistor element 22Ad, the linear heating resistor element 23Ac, the arc-shaped heating resistor element 22Bd, and the linear heating resistor element 23Bc are annularly connected in this order to form an annular portion.

  Note that the annular region may be a substantially annular region, and although not shown, it interferes with various parts such as a through-hole penetrating in the thickness direction of the base material 10 and a temperature detecting means disposed in the base material 10. In order to avoid this, a partially serpentine region may be provided.

  Also. Here, the thickness and width of the arc-shaped heat generating resistor elements 22Aa to 22Ad, 22Ba to 22Bd and the linear heat generating resistor elements 23Aa to 23Ac and 23Ba to 23Bc are the same, but are not limited thereto.

  The heating resistor 20 configured as described above is point-symmetric about the center O. Thereby, it becomes possible to bring symmetry to the heating of the upper surface of the substrate 10.

  In the conventional ceramic heater, the heating resistor does not have a branch, and the heating resistor passes through the center O when it is arranged symmetrically with respect to the center O. However, in many cases, the center O of the ceramic heater 100 is provided with a supply hole for a gas supplied to the back surface of the wafer, and it is difficult to arrange the heating resistor in this way.

  In addition, it is preferable that the widths of the arc-shaped heating resistor elements 22Ad and 22Bd and the linear heating resistor elements 23Ac and 23Bc forming the annular portion are about half of the width of the heating resistor 20 other than the annular portion. Accordingly, the total resistance per unit length of the heating resistor 20 branched into two corresponds to the resistance per unit length of the heating resistor 20 not branched, and the heating resistor 20 branched into two. It is possible to suppress the local increase in heating in the portion where the slag exists.

  The spiral heating resistance elements 21A and 21B are not limited to those composed of arcuate and linear heating resistance elements. The spiral heating resistance elements 21A and 21B may be generally spiral as a whole, and even if they are composed of only curved heating resistance elements, linear heating resistance elements are connected to each other. Also good.

  In the present invention, the feeding resistor 30 is symmetrical when the power feeding terminal 30 is located at the outermost periphery of the arc-shaped heating resistor elements 22Aa to 22Ad at a position inverted by 180 ° with respect to the center O of the base material 10. The purpose is to improve the temperature uniformity of the substrate 10 as a result.

  However, the power supply terminal 30 is determined by the positional relationship with the semiconductor process apparatus on which the ceramic heater 100 is mounted, and may not necessarily be disposed on the outermost periphery, or may not be disposed with good symmetry.

  In that case, as shown in FIG. 3, a certain degree of symmetry can be maintained by providing a circular heating resistor element 24 outside the arc-shaped heating resistor elements 22Aa to 22Ad. At this time, the two spiral heating resistance elements 21A and 21B are arranged such that the virtual terminal 31 and other terminals are located at a position that is inverted by 180 ° around the center O of the substrate 10 with respect to the terminal 32 close to the outermost periphery. 30 may be connected and arranged without overlapping.

  Hereinafter, the present invention will be described with specific examples of the present invention.

Example 1
In Example 1, the ceramic heater 100 was obtained from the base material 10 made of aluminum nitride added with yttrium oxide in which a heating resistor 20 made of metal was embedded.

[Production of ceramic heater]
A powder mixture composed of 97% by mass of aluminum nitride powder and 3% by mass of yttrium oxide powder was obtained, filled in a mold, and subjected to uniaxial pressure treatment. Thereby, a first layer having a diameter of 340 mm and a thickness of 10 mm was formed.

  Next, a molybdenum mesh (wire diameter: 0.1 mm, opening: 50 mesh) having a diameter of 290 mm to be the heating resistor 20 having the shape shown in FIG. 2 was placed on the first layer. Subsequently, the previously formed powder mixture was filled on the heating resistor 20 to a predetermined thickness to form a second layer. Then, hot press firing was performed at a pressure of 10 MPa at a firing temperature of 1800 ° C. and a firing time of 2 hours, to obtain a ceramic sintered body having a diameter of 340 mm and a thickness of 20 mm.

  Thereafter, the entire surface was ground and polished, and the surface roughness was Ra 0.4 μm and the flatness was 0.9 μm.

  The terminal 30 was formed by drilling a hole having a diameter of 8 mm from the back surface to the heating resistor 20 and silver brazing a cylindrical nickel metal terminal having a diameter of 8 mm on the exposed heating resistor 20.

[Evaluation results]
A black dummy wafer was placed on the wafer mounting surface of the ceramic heater 100, electric power was supplied to the terminals 30 to raise the temperature of the ceramic heater 100, and the temperature of the dummy wafer surface was measured with an IR camera. The power supplied to the terminals 30 was made the same for 15 minutes from the time when the surface temperature of the dummy wafer reached 500 ° C. Thereafter, the temperature distribution of the dummy wafer was measured.

  The temperature difference between the maximum temperature and the minimum temperature was as small as 5 ° C., and it was found that the thermal uniformity of the ceramic heater 100 was good. It was also found that the poor symmetry of the position of the terminal 30 can be alleviated by making the heating resistor 20 the shape shown in FIG.

(Example 2)
Except that the shape of the heating resistor 20 and the arrangement of the terminals 30 and 32 were as shown in FIG.

[Evaluation results]
The temperature difference between the maximum temperature and the minimum temperature was as small as 6 ° C., and it was found that the thermal uniformity of the ceramic heater 100 was good. It has also been found that the poor symmetry of the position of the terminal 30 can be alleviated by making the heating resistor 20 the shape shown in FIG.

(Comparative Example 1)
Except that the shape of the heating resistor 120 and the arrangement of the terminals 30 are as shown in FIG. Specifically, the heating resistor 120 is, as compared with the heating resistor 20 shown in FIG. 2, the arc-shaped heating resistor element 22Ad and the linear heating resistor element 23Ac that connects the arc-shaped heating resistor elements 22Ad and 22Bd. This part was deleted, and the annular part at the center was made semi-annular.

[Evaluation results]
The temperature difference between the maximum temperature and the minimum temperature was 10 ° C., which was larger than that in Example 1.

(Comparative Example 2)
Except that the shape of the heating resistor 220 and the arrangement of the terminals 30 and 32 are as shown in FIG. Specifically, the heating resistor 220 is, as compared with the heating resistor 20 shown in FIG. 3, an arc-shaped heating resistor element 22Bd and a linear heating resistor element 23Bc that connects the arc-shaped heating resistor elements 22Ad and 22Bd. This part was deleted, and the annular part at the center was made semi-annular. Furthermore, the heating resistor 220 is a straight line connecting the arc-shaped heating resistor elements 22Aa, 22Ab, 22Ac and the arc-shaped heating resistor elements 22Ba, 22Bb, 22Bc, 22Bd in order, as compared with the heating resistor 20 shown in FIG. The arc-shaped heating resistor elements 23Aa, 23Bb, 23Bc are deleted and the arc-shaped heating resistor elements 25A, 25B and the arc-shaped heating resistor elements 22Bb, 23Ab are connected in order. In addition, arc-shaped heating resistor elements 25C and 25D for connecting the linear heating resistor element 23Bc in order, and an arc-shaped heating resistor element 25E for connecting the linear heating resistor element 23Ba and the circular heating resistor element 24 are added.

[Evaluation results]
The temperature difference between the maximum temperature and the minimum temperature was 12 ° C., which was larger than that in Example 2.

  DESCRIPTION OF SYMBOLS 10 ... Base material (ceramics base material), 20 ... Heat generating resistor, 21A, 21B ... Spiral heat generating resistive element, 22Aa-22Ad, 22Ba-22Bd ... Arc-shaped heat generating resistive element, 23Aa-23Ac, 23Ba-23Bc ... Linear Heat generation resistance element, 24 ... Circular heat generation resistance element, 30, 32 ... Terminal (power supply terminal), 31 ... Virtual terminal, 100 ... Ceramic heater.

Claims (2)

A ceramic substrate made of ceramics, on which an object to be heated is placed, and
A heating resistor embedded in the ceramic substrate;
A ceramic heater provided with power supply terminals respectively connected to both ends of the heating resistor,
Each of the heating resistors comprises two spiral heating resistance elements that are connected to the power feeding terminal at the outer end and are arranged without overlapping, and the two spiral heating resistance elements are at the center. A ceramic heater characterized by being connected in an annular shape. A ceramic substrate made of ceramics, on which an object to be heated is placed, and
A heating resistor embedded in the ceramic substrate;
A ceramic heater comprising a pair of power feeding terminals arranged at a position that is not line-symmetric, point-symmetric, or rotationally symmetric to the heating resistor,
The heating resistor is a circular heating resistor element located at the outermost periphery, and a virtual terminal located at a position 180 ° inverted with respect to the power supply terminal adjacent to the outermost periphery around the center of the ceramic substrate. It is composed of two spiral heating resistance elements that are connected to other power supply terminals and arranged without overlapping, and the two spiral heating resistance elements are connected in a ring shape at the center. Ceramic heater characterized by