阅读说明：本技术 陶瓷加热器 (Ceramic heater ) 是由 相川贤一郎 赤塚祐司 竹林央史 安藤孝浩 于 2020-09-15 设计创作，主要内容包括：本发明的陶瓷加热器在氧化铝基板的上表面设有晶片载置面,从晶片载置面侧起依次在氧化铝基板中埋设有设置于每个区域的电阻发热体以及向电阻发热体供电的多级跳线,且具备将电阻发热体和跳线沿上下方向连结的发热体连结导通孔、以及为了向跳线供电而向外部取出的供电导通孔。发热体连结导通孔的电阻率小于电阻发热体的电阻率。发热体连结导通孔的热膨胀系数与氧化铝基板的热膨胀系数之差的绝对值小于电阻发热体的热膨胀系数与氧化铝基板的热膨胀系数之差的绝对值。(The ceramic heater of the present invention is provided with a wafer mounting surface on the upper surface of an alumina substrate, resistance heating elements provided in each region and a multi-stage jumper wire for supplying power to the resistance heating elements are embedded in the alumina substrate in this order from the side of the wafer mounting surface, and is provided with a heating element connecting via hole for connecting the resistance heating elements and the jumper wire in the up-down direction, and a power supply via hole for taking out the resistance heating elements and the jumper wire to the outside for supplying power to the jumper wire. The resistivity of the heating element connecting through hole is smaller than that of the resistance heating element. The absolute value of the difference between the thermal expansion coefficient of the heating element connecting via hole and the thermal expansion coefficient of the alumina substrate is smaller than the absolute value of the difference between the thermal expansion coefficient of the resistance heating element and the thermal expansion coefficient of the alumina substrate.)

1. A ceramic heater having a wafer mounting surface on the upper surface of an alumina substrate, resistance heating elements provided in each region and a multi-stage jumper wire for supplying power to the resistance heating elements embedded in the alumina substrate in this order from the wafer mounting surface side, and having a heating element connecting via hole for connecting the resistance heating elements and the jumper wire in the vertical direction and a power supply via hole for taking out the resistance heating elements and the jumper wire to the outside,

the resistivity of the heating element connecting through hole is smaller than that of the resistance heating element,

the absolute value of the difference between the thermal expansion coefficient of the heating element connecting via hole and the thermal expansion coefficient of the alumina substrate is smaller than the absolute value of the difference between the thermal expansion coefficient of the resistance heating element and the thermal expansion coefficient of the alumina substrate.

2. The ceramic heater according to claim 1, wherein a resistivity of the heat-generating element connecting via hole is less than 0.75 times a resistivity of the resistance heat-generating element.

3. The ceramic heater according to claim 1 or 2, wherein a thermal expansion coefficient of the resistive heating element is within ± 4ppm/K of a thermal expansion coefficient of the alumina substrate, and a thermal expansion coefficient of the heating element connecting via hole is within ± 0.6ppm/K of a thermal expansion coefficient of the alumina substrate.

4. The ceramic heater according to any one of claims 1 to 3, wherein the heat-generating body connecting via hole contains 10 wt% or more and 95 wt% or less of ruthenium metal.

5. The ceramic heater according to any one of claims 1 to 4, wherein diffusion from the heat-generating element connecting through hole to the resistance heat-generating element is larger than diffusion from the resistance heat-generating element to the heat-generating element connecting through hole.

6. The ceramic heater according to any one of claims 1 to 5, a main component of the resistance heating body is tungsten carbide or ruthenium metal,

the main component of the heating element connecting through hole is metal ruthenium.

7. The ceramic heater according to any one of claims 1 to 6, wherein the power supply via hole and the jumper wire are made of the same material as the heat-generating body connection via hole.

Technical Field

The present invention relates to a ceramic heater.

Background

Conventionally, an electrostatic chuck heater for holding a wafer by suction is used when processing a semiconductor wafer. As such an electrostatic chuck heater, as shown in patent document 1, there is known an electrostatic chuck heater including an electrostatic chuck in which an electrostatic electrode is embedded in a ceramic sintered body, and a sheet heater which is a resin sheet having a plurality of resistance heating elements and has one surface bonded to an electrostatic chuck resin. The sheet heater further includes a jumper wire for supplying power to each of the plurality of resistance heating elements, a heating element connection via hole for vertically connecting the resistance heating element and the jumper wire, a power supply via hole for externally taking out the resistance heating element and the jumper wire for supplying power to the jumper wire, and the like.

Documents of the prior art

Patent document

Patent document 1: international publication No. 2017/029876 pamphlet

Disclosure of Invention

Problems to be solved by the invention

In such an electrostatic chuck heater, since sufficient heat resistance and heat dissipation capability cannot be obtained in the case of a resin sheet, there is a demand for changing to a structure in which an electrostatic electrode is embedded in a ceramic sintered body, but in the case of using alumina as a ceramic, there is a problem that heat generation of a via hole due to current conduction is large, heat uniformity of a wafer deteriorates, and a periphery of the via hole is damaged.

The present invention has been made to solve the above problems, and a main object of the present invention is to improve the heat uniformity of a wafer and prevent damage around a via hole in a ceramic heater in which a resistance heating element, a jumper wire, and a via hole are built in an alumina substrate.

Means for solving the problems

The ceramic heater of the present invention is a ceramic heater having a wafer mounting surface on an upper surface of an alumina substrate, resistance heating elements provided in respective regions and a multi-stage jumper wire for supplying power to the resistance heating elements are embedded in the alumina substrate in this order from the wafer mounting surface side, and the ceramic heater is provided with a heating element connecting via hole for connecting the resistance heating elements and the jumper wire in the up-down direction, and a power supply via hole for taking out the resistance heating elements and the jumper wire to the outside,

the resistivity of the heating element connecting through hole is smaller than that of the resistance heating element,

the absolute value of the difference between the thermal expansion coefficient of the heating element connecting via hole and the thermal expansion coefficient of the alumina substrate is smaller than the absolute value of the difference between the thermal expansion coefficient of the resistance heating element and the thermal expansion coefficient of the alumina substrate.

In the ceramic heater, the resistivity of the heating element connecting via hole is smaller than the resistivity of the resistance heating element. Therefore, heat generation by the conduction of the resistance heating element is large, but heat generation by the conduction of the heating element connecting via hole is small. Therefore, the heat uniformity of the wafer is improved. In addition, the absolute value of the difference between the thermal expansion coefficient of the heating element connecting via hole and the thermal expansion coefficient of the alumina substrate is smaller than the absolute value of the difference between the thermal expansion coefficient of the resistance heating element and the thermal expansion coefficient of the alumina substrate. Therefore, it is possible to prevent the generation of cracks due to the thin resistance heating element, and to reduce the risk of damage during manufacturing and use even if the cross-sectional area of the heating element connecting via hole is increased to suppress heat generation due to current flow.

In the ceramic heater according to the present invention, it is preferable that the resistivity of the heating element connecting via hole is less than 0.75 times the resistivity of the resistance heating element. This further improves the heat uniformity of the wafer.

In the ceramic heater according to the present invention, it is preferable that the coefficient of thermal expansion of the resistance heating element is within ± 4ppm/K of the coefficient of thermal expansion of alumina, and the coefficient of thermal expansion of the heating element connecting through hole is within ± 0.6ppm/K of the coefficient of thermal expansion of alumina. Since the resistance heating element is thin, if the thermal expansion coefficient of the resistance heating element is within + -4 ppm/K relative to the alumina serving as the base material, the generation of cracks can be sufficiently prevented. The heating element connecting via hole preferably has a large cross-sectional area in order to suppress heat generation due to current conduction, but in this case, when the difference in thermal expansion coefficient from the alumina serving as the base material is as small as ± 0.6ppm/K, the risk of damage during production and use can be sufficiently reduced.

In the ceramic heater according to the present invention, it is preferable that the heating element connecting via hole includes ruthenium metal. The thermal expansion coefficient of the aluminum oxide is 7.9ppm/K at 40-800 ℃, and the thermal expansion coefficient of the metal ruthenium is 7.2ppm/K at 40-800 ℃. Therefore, the difference in thermal expansion between the alumina substrate and the via hole is very small. Therefore, if the via hole is connected using the heating element containing ruthenium metal, the occurrence of cracks due to the via hole connected to the heating element can be suppressed during the production and the use. The heat-generating element connecting via hole is preferably contained in an amount of 10 wt% to 95 wt%, more preferably 20 wt% to 95 wt%, and still more preferably 60 wt% to 95 wt%. The heat-generating element connecting via hole may contain a filler component in addition to ruthenium metal. As the filler component, alumina and/or zirconia is preferred. Since alumina is the same material as the base material (alumina substrate), the interface strength between the heat-generating element connecting via hole and the base material is improved. Since zirconia has a higher thermal expansion coefficient than alumina, the thermal expansion coefficient of the heat-generating-element-connecting via hole can be made to match the thermal expansion coefficient of the alumina substrate by adding a small amount of zirconia. When both alumina and zirconia are added as filler components, the effects of both can be obtained.

The thermal expansion coefficient of 40 to 800 ℃ is a value obtained by dividing the amount of expansion (unit: μm) per 1m when the temperature is changed from 40 ℃ to 800 ℃ by the temperature difference 760 ℃ (or K) (the same applies hereinafter).

In the ceramic heater according to the present invention, it is preferable that the diffusion from the heating element connecting via hole to the resistance heating element is larger than the diffusion from the resistance heating element to the heating element connecting via hole. In this way, since diffusion from the resistance heating element to the heating element connecting via hole is small, it is possible to prevent the thermal expansion coefficient of the heating element connecting via hole from deviating from the thermal expansion coefficient of alumina. Therefore, it is possible to prevent cracks from occurring from the heat generating element connecting through hole as a starting point during manufacturing and use, and cracks from occurring around the heat generating element connecting through hole. Further, the diffusion from the heating element connecting via to the resistance heating element can ensure the bonding of both.

In the ceramic heater according to the present invention, it is preferable that the main component of the resistance heating element is tungsten carbide or ruthenium metal, and the main component of the heating element connecting via hole is ruthenium metal. The term "main component" means a component accounting for 50% by volume or more, or the highest volume percentage of all the components.

In the ceramic heater according to the present invention, the power supply via hole and the jumper wire may be made of the same material as the heating element connecting via hole.

Drawings

Fig. 1 is a longitudinal sectional view of an electrostatic chuck heater 10.

Detailed Description

Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. In the present embodiment, the electrostatic chuck heater 10 is shown as an example of the ceramic heater of the present invention. Fig. 1 is a longitudinal sectional view of an electrostatic chuck heater 10.

As shown in fig. 1, the electrostatic chuck heater 10 has a wafer mounting surface 12a on the upper surface of an alumina substrate 12, and an electrostatic electrode (ESC electrode) 14, a resistance heating element 16 provided in each region, and a multi-stage (here, 2-stage) jumper wire 18 for supplying power to the resistance heating element 16 are buried in the alumina substrate 12 in this order from the wafer mounting surface 12a side. The alumina substrate 12 is provided with a heating element connecting via hole 20 for vertically connecting the resistance heating element 16 and the jumper wire 18, and a power supply via hole 22 for taking out the resistance heating element and the jumper wire 18 to the outside for supplying power.

The resistivity of the heating element connecting via hole 20 is smaller than the resistivity of the resistance heating element 16. The resistivity of the heating element connecting via hole 20 is preferably 0.75 times or less the resistivity of the resistance heating element 16. The absolute value of the difference between the thermal expansion coefficient of the heating element connecting via hole 20 and the thermal expansion coefficient of the alumina substrate 12 is smaller than the absolute value of the difference between the thermal expansion coefficient of the resistance heating element 16 and the thermal expansion coefficient of the alumina substrate 12. The coefficient of thermal expansion of the resistance heating element 16 is preferably within. + -. 4ppm/K relative to the coefficient of thermal expansion of the alumina substrate 12, and the coefficient of thermal expansion of the heating element connecting via hole 20 is preferably within. + -. 0.6ppm/K relative to the coefficient of thermal expansion of the alumina substrate 12.

The resistance heating element 16 preferably contains tungsten carbide as a main component. The resistance heating element 16 may contain alumina as a filler component in addition to tungsten carbide. The thermal expansion coefficient of tungsten carbide is 4.0ppm/K at 40-800 ℃, and the thermal expansion coefficient of aluminum oxide is 7.9ppm/K at 40-800 ℃. Therefore, the coefficient of thermal expansion of tungsten carbide is within. + -. 4ppm/K of that of alumina. The resistance heating element 16 may contain zirconia as a filler component instead of or in addition to alumina. The thermal expansion coefficient of alumina is 7.9ppm/K at 40-800 ℃, and the thermal expansion coefficient of zirconia is 10.5ppm/K at 40-800 ℃. Therefore, alumina and zirconia are useful as filler components when the thermal expansion coefficient of the resistance heating element 16 is to be increased. By adjusting the content of the filler component of the resistance heat-generating body 16, the absolute value of the difference between the thermal expansion coefficient of the heat-generating body connecting via hole 20 and the thermal expansion coefficient of the alumina substrate 12 can be made smaller than the absolute value of the difference between the thermal expansion coefficient of the resistance heat-generating body 16 and the thermal expansion coefficient of the alumina substrate 12, or the thermal expansion coefficient of the resistance heat-generating body 16 can be adjusted to within ± 4ppm/K with respect to the thermal expansion coefficient of the alumina substrate 12.

The heating element connecting via hole 20 is preferably composed mainly of ruthenium metal. The thermal expansion coefficient of the metal ruthenium is 7.2ppm/K at 40-800 ℃, and the thermal expansion coefficient of the aluminum oxide is 7.2ppm/K at 40-800 DEG C7.9 ppm/K. Therefore, the thermal expansion coefficient of the metal ruthenium is within. + -. 0.6ppm/K of that of the alumina. Further, the resistivity of metallic ruthenium was 2X 10^-5Omega cm, resistivity of tungsten carbide 3X 10^-5Omega cm. Therefore, the resistivity of ruthenium metal is 0.75 times or less the resistivity of tungsten carbide. Further, the diffusion from metallic ruthenium to tungsten carbide is larger than the diffusion from tungsten carbide to metallic ruthenium. The heating element connecting via hole 20 may contain alumina and/or zirconia as a filler component in addition to ruthenium metal. Alumina and zirconia are useful as filler components when the thermal expansion coefficient of the resistance heating element 16 is to be increased. By adjusting the content of the filler component in the heat-generating element connecting via hole 20, the absolute value of the difference between the thermal expansion coefficient of the heat-generating element connecting via hole 20 and the thermal expansion coefficient of the alumina substrate 12 can be made smaller than the absolute value of the difference between the thermal expansion coefficient of the resistance heat-generating element 16 and the thermal expansion coefficient of the alumina substrate 12, or the thermal expansion coefficient of the heat-generating element connecting via hole 20 can be adjusted to be within ± 0.6ppm/K with respect to the thermal expansion coefficient of the alumina substrate 12.

The jumper wire 18 and the power supply via hole 22 are preferably made of the same material as the heat-generating element connecting via hole 20.

In the electrostatic chuck heater 10 described in detail above, the heating element connecting via hole 20 has a lower resistivity than the resistance heating element 16. Therefore, heat generation by the current passing through the resistance heating element 16 is large, but heat generation by the current passing through the heating element connecting via hole 20 is small. Therefore, the heat uniformity of the wafer is improved. The absolute value of the difference between the thermal expansion coefficient of the heat-generating-element connecting via hole 20 and the thermal expansion coefficient of the alumina substrate 12 is smaller than the absolute value of the difference between the thermal expansion coefficient of the resistance heat-generating element 16 and the thermal expansion coefficient of the alumina substrate 12. Therefore, it is possible to prevent the occurrence of cracks due to the thin (for example, 10 to 100 μm) resistance heating element 16, and to reduce the risk of damage during manufacturing and use even if the cross-sectional area of the heating element connecting via hole 20 is increased to suppress heat generation due to energization.

The resistivity of the heating element connecting via hole 20 is preferably less than 0.75 times the resistivity of the resistance heating element 16. This further improves the heat uniformity of the wafer.

Further, it is preferable that the thermal expansion coefficient of the resistance heating element 16 is within. + -. 4ppm/K relative to the thermal expansion coefficient of the alumina substrate 12, and the thermal expansion coefficient of the heating element connecting via hole 20 is within. + -. 0.6ppm/K relative to the thermal expansion coefficient of the alumina substrate 12. Since the resistance heating element 16 is thin (for example, 10 to 100 μm), if the coefficient of thermal expansion of the base material alumina is within ± 4ppm/K, the occurrence of cracks can be sufficiently prevented. The heating element connecting via hole 20 is preferably increased in cross-sectional area to suppress heat generation due to current conduction, but in this case, when the difference in thermal expansion coefficient from alumina as the base material is as small as ± 0.6ppm/K, the risk of damage during production and use can be sufficiently reduced.

Further, the diffusion from the heating element connecting through hole 20 (mainly composed of ruthenium metal) to the resistance heating element 16 (mainly composed of tungsten carbide) is larger than the diffusion from the resistance heating element 16 to the heating element connecting through hole 20. That is, the diffusion from the resistance heating element 16 to the heating element connecting via hole 20 is small. Therefore, the thermal expansion coefficient of the heat-generating element connecting via hole 20 can be prevented from being deviated from the thermal expansion coefficient of alumina. Therefore, it is possible to prevent cracks from occurring from the heat generating element connecting via hole 20 as a starting point during manufacturing and use, and cracks from occurring around the heat generating element connecting via hole 20. Further, the heat-generating element connecting via hole 20 can be diffused into the resistance heat-generating element 16 to ensure the bonding of the two.

The present invention is not limited to the above embodiments, and it is needless to say that the present invention can be implemented in various forms as long as the technical scope of the present invention is satisfied.

For example, in the above-described embodiment, it has been described that the heating element connecting via hole 20 is preferably composed mainly of ruthenium metal, but the present invention is not particularly limited thereto. For example, the heat-generating element connecting via hole 20 may contain ruthenium metal. In this case, the heating element connecting via hole 20 preferably contains 10 wt% to 95 wt% of metallic ruthenium, more preferably 20 wt% to 95 wt% of metallic ruthenium, and still more preferably 60 wt% to 95 wt% of metallic ruthenium. The heating element connecting via hole 20 may contain a filler component in addition to ruthenium metal. As the filler component, alumina and/or zirconia is preferred.

In the above embodiment, the resistance heating element 16 may contain metallic ruthenium, or may have metallic ruthenium as a main component. The resistance heating element 16 may contain a filler component in addition to the metal ruthenium. As the filler component, alumina and/or zirconia is preferred.

Examples

The electrostatic chuck heaters 10 of fig. 1 were produced as experimental examples 1 to 7. The electrostatic chuck heater 10 is formed by embedding an electrostatic electrode 14 having a diameter of 290mm and a thickness of 0.1mm, a resistance heating element 16 on the inner and outer circumferential sides, a band-shaped jumper wire 18 having a width of 5mm, and via holes 20 and 22 having a diameter of 1.2mm and a thickness of 0.6mm in an alumina substrate 12 having a diameter of 300mm and a thickness of 4 mm. The inner resistive heating elements 16 are wired in a circular region of 200mm diameter concentric with the alumina substrate 12 in one stroke, and the outer resistive heating elements 16 are wired in an annular region outside the circular region in one stroke. The material of the electrostatic electrode 14 is tungsten carbide, the material of the resistance heating element 16 is tungsten carbide, and the material of the jumper wire 18 is ruthenium metal. The filler component used in the via holes 20 and 22 is alumina, zirconia, or both alumina and zirconia. In experimental examples 1 to 7, the electrostatic chuck heaters 10 were produced under the same conditions except that the materials shown in table 1 were used as the materials of the heat-generating-element connecting via hole 20 and the power-feeding via hole 22, respectively.

The CTE of the via holes 20 and 22 at 40 to 800 ℃ in the experimental examples 1 to 7, the difference (first CTE difference) between the CTE of the via holes 20 and 22 at 40 to 800 ℃ and the CTE of the alumina substrate 12 at 40 to 800 ℃, the difference (second CTE difference) between the CTE of the resistance heating element 16 at 40 to 800 ℃ and the CTE of the alumina substrate 12 at 40 to 800 ℃, and the ratio (ratio of the resistivity) of the resistivity of the via holes 20 and 22 to the resistivity of the resistance heating element 16 are shown in Table 1. In addition, the resistivity of the via holes 20 and 22 is also shown in table 1 for the experimental examples 4 and 5.

The electrostatic chuck heaters 10 of experimental examples 1 to 7 were each placed in a vacuum chamber, and the temperature distribution of the wafer mounting surface 12a when a predetermined reference point was 60 ℃. In addition, the presence or absence of cracks in the alumina substrate 12 was examined. Specifically, after cross-sectional polishing, the presence or absence of cracks was examined by SEM (scanning electron microscope) observation. The results are shown in table 1.

[ Table 1]

As is clear from table 1, in experimental examples 1 to 7, heat generation directly above the via holes 20 and 22 can be suppressed to 2.0[ ° c ] or less, and cracks are not generated. In particular, in experimental examples 2 to 7, the heat generation directly above the via holes 20 and 22 can be suppressed to 1.8[ ° c ] or less, and in experimental examples 4 to 7, the heat generation directly above the via holes 20 and 22 can be suppressed to 1.0[ ° c ] or less. Examples 1 to 7 correspond to the examples of the present invention. It should be noted that the present invention is not limited to these examples.

The present application takes japanese patent application No. 2019-169383, filed on 9/18 of 2019, as a basis for claiming priority, and the contents thereof are incorporated in their entirety by reference into the present specification.

Industrial applicability of the invention

The present invention can be used, for example, in a technique for processing a semiconductor wafer.

Description of the symbols

10 electrostatic chuck heater, 12 alumina substrate, 12a wafer carrying surface, 14 electrostatic electrode, 16 resistance heating element, 18 jumper, 20 heating element connecting via hole, 22 power supply via hole.