JP3976993B2 - Ceramic substrate bonding method, ceramic substrate bonded body, and ceramic heater - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for bonding ceramic substrates and a ceramic heater.
[0002]
[Prior art]
A ceramic heater in which a resistance heating element is embedded inside a susceptor made of ceramics such as silicon nitride is used for heating a semiconductor wafer in a semiconductor manufacturing apparatus.
[0003]
[Problems to be solved by the invention]
The inventor has attempted to form a passage for flowing a cooling medium inside the ceramic heater. After embedding a resistance heating element in the ceramic bulk, it is impossible to form an elongated passage by machining. For this reason, this inventor tried to form a channel | path inside a ceramic susceptor by the green sheet lamination | stacking method. In order to form a passage with a predetermined depth in the susceptor by the green sheet lamination method, it is necessary to form a groove with a predetermined depth in the green sheet in advance, and then laminate a plurality of green sheets and integrally sinter them. There is. However, in such a method, the sheet is deformed in the vicinity of the groove in the green sheet sintering stage, and a groove having a predetermined depth cannot be formed accurately. In particular, at the bonding interface of a plurality of green sheets, gas leakage at the bonding interface after sintering is likely to occur, and it is difficult to maintain airtightness. Although the green sheet laminating method has a track record in laminating and sintering green sheets with a relatively small area, a ceramic flat plate having a large area that can accommodate an 8-inch wafer is laminated and fired integrally. It is considered that it means that it is difficult to form a good bonding interface when bonding.
[0004]
In addition, the inventor installs and heats a semiconductor wafer on a ceramic heater, and when performing a predetermined process using a film forming gas, a corrosive gas, etc., corrosive gas is present on the back side of the ceramic heater. It was found that a slight amount of sneaking around occurred, causing deposits and corrosion on the back side. For this reason, the technique which prevents the deposit and corrosion in the terminal junction part comprised from the back side of a ceramic heater and metal parts is required.
[0006]
Another object of the present invention is to provide a ceramic heater including a ceramic susceptor having an installation surface for installing a wafer and a resistance heating element embedded in the susceptor. And to suppress the occurrence of deposits and corrosion at the terminal joint composed of metal parts.
[0007]
[Means for Solving the Problems]
The present invention is a method for producing a ceramic heater having a joined body obtained by joining the first joined surface of the first ceramic substrate and the second joined surface of the second ceramic substrate,
Center line average surface roughness Ra of the first joint surface and the second joint surface before joining is 1.0 μm or less, and the first joint surface and the second joint surface before joining are planes. The degree is 50 μm or less, and the contact area when the first bonding surface and the second bonding surface are in contact is 200 cm ² or more,
The first ceramic substrate and the second ceramic substrate are heated and re-sintered while applying pressure in a direction substantially perpendicular to the first bonding surface, thereby re-sintering the first ceramic substrate and the second ceramic substrate. By obtaining a joined body of the ceramic base material and the second ceramic base material, and forming a groove on the joint surface side of the second ceramic base material before joining, a side surface of the joined body is obtained. A passage having an opening is formed in the joined body .
[0008]
The present invention also relates to a ceramic heater obtained by the joining method.
[0009]
In the present invention, particularly when two ceramic base materials are joined along a joining surface having a cross-sectional area of 200 cm ² or more, pressure is applied in a direction substantially perpendicular to the first joining surface. It has been found that it is effective to heat and re-sinter the first ceramic substrate and the second ceramic substrate, whereby the structure of the joint interface is continuous and high airtightness can be obtained.
[0010]
At this time, the center line average surface roughness Ra of the first and second bonding surfaces is set to 1.0 μm or less, and the flatness of the first bonding surface and the second bonding surface before bonding is set to 50 μm or less. It is necessary that the first bonding surface and the second bonding surface are almost in close contact with each other and are not clearly separated spatially.
[0011]
The center line average roughness (Ra) is a value obtained by dividing the roughness profile curve from the center line and dividing the area (including the folded portion) obtained by the roughness curve and the center line by the length L. is there. Flatness is the magnitude of the deviation of the plane part from the geometric plane. In JIS, when the plane part is sandwiched between two parallel geometric planes, the distance between these two planes is minimized. It is expressed by the distance between the two geometric planes. The centerline average roughness and flatness can be measured with a surface roughness meter and a laser interferometer.
[0012]
Ra of the first and second bonding surfaces before bonding is more preferably 0.9 μm or less, and the flatness is more preferably 30 μm or less. There is no particular lower limit to these values.
[0013]
In order to bring the flatness and centerline average roughness of each joint surface of the first and second ceramic base materials into the range of the above values, the joint surface is preferably processed with a surface grinder and a high-speed lapping machine. .
[0014]
Re-sintering the first and second ceramic base materials means that heat treatment is performed at a temperature equal to or higher than the temperature at which the existing ceramic particles in each ceramic base material grow. This grain growth occurs to some extent even at relatively low temperatures. However, when the sintering temperature of each ceramic substrate is T, heat treatment is preferably performed at a temperature of (T-50) ° C. or more and (T + 50) ° C. or less, and at a temperature of T ° C. or more and (T + 10) ° C. or less. More preferably, heat treatment is performed. Thereby, a joined body having substantially the same strength as a sintered body manufactured by integral sintering can be manufactured.
[0015]
When the temperature of the heat treatment is the sintering temperature T ° C .− (T + 10) ° C., the strength of the joined body can be maximized. If this is higher than the sintering temperature, the microstructure and composition change at the joint during the grain growth at the joint interface, depletion layer defects occur in that part, and the strength at the joint interface is increased. This is because it will decrease.
[0016]
In the present invention, it has been found that it is essential to pressurize in a direction substantially perpendicular to the joint surface together with re-sintering of each ceramic substrate. This seems to be related to the fact that the bonding surface is very large as a method for bonding ceramic substrates. In a normal bonding method in which the bonding surface of the ceramic base material is small, the weight from the ceramic base material is likely to be effectively applied to the entire bonding surface, and the ceramic base material is likely to adhere. However, when the joint surface has a large area as in the present invention, it is considered that such self-weight is not effectively added to the entire joint surface. For this reason, it is thought that it is necessary to apply pressure from the outside in order to control the adhesion state in which stress is effectively applied to the entire bonding surface of the ceramic base material so that the entire surface is closely adhered.
[0017]
Although this pressure is not particularly limited, it has been found that generally 3 kg / cm ² or more is preferable.
[0018]
Moreover, when the contact area was xcm ^2, by the pressure (x / 100) kg / cm 2 or more, especially the adhesion and airtightness at the joint interface was found to be higher. Such a relationship was also discovered for the first time. According to the usual way of thinking, even if the area of the joint surface is large, the joint surface should be just a collection of many small joint surfaces. Since the pressure is an applied stress per unit area, the pressure necessary to obtain a predetermined performance should not change theoretically even if the area of the joint surface increases.
[0019]
However, in reality, it has been discovered that when the contact area of the joint surface increases, it is necessary to increase the pressure, that is, it is desirable to increase the stress per unit area. The reason for this is not clear. Probably, when the contact area increases, the pressure applied from the pressing means such as a press to the ceramic substrate is considerably reduced at the contact surface between the pressing means and the ceramic substrate, and the contact portion between the two joining surfaces It seems that it will not be transmitted effectively. In order to compensate for this pressure reduction, it is necessary to increase the pressure on the ceramic substrate as the contact area increases.
[0020]
The upper limit of the pressure is not particularly limited. However, when the pressure is 15 kg / cm ² or less, it is possible to prevent a decrease in yield due to the ceramic substrate being damaged.
[0021]
The upper limit of the contact area is not particularly limited, but the bonding method of the present invention is effective even when the contact area is 2000 cm ² , for example.
[0022]
The type of ceramic is not particularly limited, but aluminum nitride, silicon nitride, silicon carbide, and alumina are particularly suitable.
[0023]
In a preferred embodiment of the present invention, effective sintering is performed between at least one of the first ceramic substrate and the second ceramic substrate between the first bonding surface and the second bonding surface. Heat treatment is performed after interposing a solution containing the auxiliary agent. For example, when the ceramic substrate is made of aluminum nitride or silicon nitride, one or more joining aids selected from the group consisting of yttrium compounds, ytterbium compounds and alkaline earth element compounds are preferred, and yttrium compounds are particularly preferred. .
[0024]
The sintering aid is easy to get wet with, for example, chloride, sulfate, phosphate, nitrate and carbonate, and has good handling properties. For example, it is preferable to use an aqueous solution of yttrium chloride, yttrium chloride hydrate, yttrium sulfate, or yttrium acetate, or an aqueous solution of yttrium chloride, yttrium chloride hydrate, or yttrium acetate.
[0025]
In particular, when the present invention is applied to a heating device used in a semiconductor manufacturing apparatus, alkali metals such as K, Na, and Ca, alkaline earth metals, and the like that are particularly disliked as impurities that can become a contamination source are used as bonding aids. One or more joining aids selected from the group consisting of yttrium compounds and ytterbium compounds are preferred, and yttrium compounds are particularly preferred because they are inappropriate as agents.
[0026]
As a heating method at the time of joining, there are a heat treatment at normal pressure, a hot press method, plasma activated sintering, a local heating method using a racer, and the like. As a result of joining, the sintering aid contains more sintering aid at the joining interface than the other parts of the substrate.
[0027]
The present invention also relates to a ceramic heater comprising a ceramic susceptor having an installation surface for installing a wafer, and a resistance heating element embedded in the susceptor, and formed inside the susceptor. And a passage opening on the side surface of the susceptor, and purge gas is jetted from the passage through the opening on the side surface of the susceptor.
[0028]
According to such a ceramic heater, by ejecting a purge gas from the side surface of the susceptor, a corrosive gas, a film forming gas, a cleaning gas, etc., wrap around the back side of the ceramic heater and the terminal joint composed of metal parts. It can be effectively prevented.
[0029]
Hereinafter, the present invention will be described in more detail with reference to the drawings.
[0030]
FIG. 1A is a plan view showing the first ceramic substrate 1, FIG. 1B is a plan view showing the second ceramic substrate 3, and FIG. It is the front view which illustrated the state before joining and 3 after joining. This example shows a manufacturing process of the ceramic heater 6.
[0031]
The substrate 1 has a disk shape having two main surfaces 1 a and 1 c and a side surface 1 b, and a through hole 2 is formed in the central portion of the substrate 1. The main surface 1c is a bonding surface. The base material 3 has a disk shape having two main surfaces 3a and 3c and a side surface 3b, and the main surface 3a is a bonding surface. A groove 4 is formed on the joint surface 3a, and the groove 4 includes three radially elongated grooves 4a, 4b, and 4c. The resistance heating element is embedded in one or both of the base materials 1 and 3.
[0032]
The bonded body 6 is manufactured by bringing the bonding surface 1c of the base material 1 into contact with the bonding surface 3a of the base material 3 and processing as described above. In the joined body 6, the through hole 2 of the base material 1 and the groove 4 of the base material 3 communicate with each other. And each groove | channel 4a, 4b, 4c is provided with the opening 7 exposed to the side surface 3b. 1a is a back surface of the ceramic heater, and 3c is an installation surface of the semiconductor wafer.
[0033]
When a corrosive gas, a film forming gas, a cleaning gas, or the like is used in the semiconductor manufacturing process, a purge gas is supplied from the through hole 2, and this purge gas is ejected from each opening 7 through each groove 4a-4c.
[0034]
In the example of FIGS. 1 and 2, the manufacturing process of the ceramic heater provided with the opening for ejecting the purge gas on the side surface has been described. However, the bonding method of the present invention is not limited to the formation of such a purge gas supply groove. For example, it is also effective in forming a passage for flowing a cooling medium (inert gas such as nitrogen gas or argon gas or fluid such as water or oil). In any case, according to the bonding method of the present invention, the passage inside the ceramic heater can be easily formed by forming grooves on the surface of the ceramic substrate in advance. At this time, for example, a groove having a depth of 0.2 mm or more can be easily formed.
[0035]
【Example】
A ceramic heater 6 was manufactured according to the embodiment shown in FIGS. However, each of the ceramic substrates 1 and 3 was formed of an aluminum nitride sintered body having a relative density of 99.9%. This aluminum nitride sintered body has a sintering temperature of 1800-2000 ° C. and contains 5 mol% of yttrium as a sintering aid. The four-point bending strength at room temperature of the aluminum nitride sample itself was about 400 MPa. The four-point bending strength was measured in accordance with JIS R 1601 so that the joint surface was positioned vertically at the approximate center between the inner spans.
[0036]
Each joining surface 1c, 3a is a circle having a diameter of 240 mm (the area of each joining surface is 450 cm ² and the contact area is the same). The thickness of each base material 1 and 3 is 18 mm. The depth of the groove 4 of the substrate 3 is 1 mm, and the width is 5 mm. Each joint surface 1c, 3a is machined by a surface grinding machine and a high-speed lapping machine, respectively . The thickness was 0 μm and the flatness was 30 μm.
[0037]
An yttrium nitrate solution hydrate having a yttrium concentration of 2.61 × 10 ⁻⁴ mol / cc: Y (NO ₃ ) ₂ .6H ₂ O aqueous solution was applied to each joint surface. The joining surfaces 1c and 3a were brought into contact, accommodated in a hot press apparatus, applied with a pressure of ² kg / cm ² , and heat-treated at 1900 ° C. for 3 hours. The atmosphere during the heat treatment was nitrogen gas.
[0038]
When the test sample was cut out from the obtained joined body 6 so as to extend perpendicularly to the joining interface and the four-point bending strength was measured (20 tests), it was 300 to 450 MPa.
[0039]
Further, when the bonded body was cut out and the bonded interface was observed with an optical microscope (1000 times), no peeling, deformation, or crack was observed.
[0040]
In addition, an ultrasonic flaw detection test of the joined body was performed. That is, the measurement was performed on the bonded surface under the conditions of the size of the bonded body 20 mm × 40 mm × 20 mm, the probe frequency 25 MHz, the probe diameter 0.25 seconds, and the focal length 4 seconds. As a result, no peeling was observed on the joint surface.
[0041]
The amount of leak was measured using a helium leak detector manufactured by ULVAC. As a result, the amount of helium leak was less than 10 ⁻⁸ sccm.
[0042]
【The invention's effect】
As described above, according to the present invention, it is possible to provide a novel method for producing a bonded body having a large-area bonded surface such as a ceramic heater, the bonded state at the bonded interface is good, and peeling and cracks are observed. It is not airtight.
[0043]
Moreover, the ceramic heater of this invention can suppress generation | occurrence | production of the deposit and corrosion in the terminal junction part comprised from the back side of a ceramic heater, and a metal component.
[Brief description of the drawings]
1A is a plan view showing a first ceramic substrate 1, and FIG. 1B is a plan view showing a second ceramic substrate 3;
FIG. 2 is a front view showing a state before and after joining ceramic substrates 1 and 3;
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 1st ceramic base material 1a Main surface of the base material 1 (back surface of a ceramic heater) 1c 1st joint surface 2 Through-hole 3 2nd ceramic base material 3a 2nd joint surface 3c Main surface of the base material 3 ( Wafer mounting surface of ceramic heater) 4, 4a, 4b, 4c Purge gas passage (groove) 6 Joint (ceramic heater)
7 Opening to the side of passage 4

Claims (10)

A method for producing a ceramic heater having a joined body obtained by joining a first joining surface of a first ceramic substrate and a second joining surface of a second ceramic substrate,
Center line average surface roughness Ra of the first joint surface and the second joint surface before joining is 1.0 μm or less, and the first joint surface and the second joint surface before joining are planes. The degree is 50 μm or less, the contact area when the first joint surface and the second joint surface are contacted is 200 cm ² or more,
The first ceramic substrate and the second ceramic substrate are heated and re-sintered while applying pressure in a direction substantially perpendicular to the first bonding surface, thereby re-sintering the first ceramic substrate and the second ceramic substrate. By obtaining a joined body of the ceramic base material and the second ceramic base material, and forming a groove on the joint surface side of the second ceramic base material before joining, a side surface of the joined body is obtained. A method of manufacturing a ceramic heater, wherein a passage having an opening is formed in the joined body. A solution containing a sintering aid effective for sintering at least one of the first ceramic substrate and the second ceramic substrate between the first bonding surface and the second bonding surface. 2. The method for manufacturing a ceramic heater according to claim 1, wherein the heat treatment is performed after the interposition. The method for manufacturing a ceramic heater according to claim 1 or 2, wherein the pressure is 1 kg / cm ² or more. When the contact area and xcm ^2, wherein said pressure is (x / 100) kg / cm 2 or more, a manufacturing method of a ceramic heater according to claim 3, wherein. The sintering aid is present in a greater amount along the bonding interface between the first ceramic substrate and the second ceramic substrate than in a portion other than the bonding interface of the bonded body. The manufacturing method of the ceramic heater as described in any one of Claims 2-4. A ceramic heater obtained by the joining method according to claim 1. The ceramic heater according to claim 6, wherein the passage is for circulating a corrosive gas or a cooling medium. The ceramic heater according to claim 6 , wherein the passage is for circulating a purge gas. A ceramic heater comprising a ceramic susceptor having an installation surface for installing a wafer, and a resistance heating element embedded in the susceptor,
The susceptor has a joined body obtained by joining the first joining surface of the first ceramic substrate and the second joining surface of the second ceramic substrate, and the first joining surface before joining and the The center line average surface roughness Ra of the second bonding surface is 1.0 μm or less, the flatness of the first bonding surface and the second bonding surface before bonding is 50 μm or less, and the first bonding surface is The contact area when the joining surface and the second joining surface are brought into contact is 200 cm ² or more, and the first ceramic is applied while applying pressure in a direction substantially perpendicular to the first joining surface. By heating and re-sintering the base material and the second ceramic base material, the first ceramic base material and the second ceramic base material are joined,
The ceramic heater has a passage formed inside the susceptor and opened to a side surface of the susceptor, and is configured to eject a purge gas from the passage through the opening on the side surface of the susceptor. A ceramic heater. The sintering aid is present along the bonding interface between the first ceramic substrate and the second ceramic substrate more than the portion other than the bonding interface of the bonded body. The ceramic heater according to claim 9.

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