JPH04296485A - Ceramic heater - Google Patents

Abstract

PURPOSE:To provide a ceramic heater in which the connecting part between the terminal of a resistant heating element and an electrode member is excellent in durability and reliability by using a brazing filler metal containing titanium component. CONSTITUTION:A heat resisting metal plate 5 is joined between the terminal of a resistance heating element 2 and an electrode member 4 by a titanium evaporated brazing filler metal. Thus, the heat resisting metal plate 5 and a ceramic base body 1 are firmly joined to each other by the diffusive joining of Ti in the titanium evaporated brazing filler metal. The heat resisting metal plate 5 and the terminal 3 are also firmly joined to each other by the diffusive joining of Ti. Therefore, the sealing property of the connecting part between the terminal 3 and the electrode member 4 by corrosive gas or heat is enhanced, the deterioration can be prevented, and the durability and reliability of a heater can be improved.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a ceramic heater suitable for use in plasma CVD, low pressure CVD, plasma etching, photoetching equipment, and the like.

0002

2. Description of the Related Art Corrosive gases such as chlorine-based gases and fluorine-based gases are used as deposition gases, etching gases, and cleaning gases in semiconductor manufacturing equipment that requires super-clean conditions. For this reason, if a conventional heater with a resistance heating element coated with a metal such as stainless steel or Inconel is used as a heating device to heat the wafer while it is in contact with these corrosive gases, the Exposure to these substances generates undesirable particles of chlorides, oxides, fluorides, etc. with a particle size of several μm.

Therefore, as shown in FIG. 1, an infrared lamp 47 is installed on the outside of the container 26 that is exposed to the deposition gas, an infrared transmitting window 46 is provided on the outer wall of the container, and the container is made of a material with good corrosion resistance such as graphite. A heated body 48 consisting of
An indirect heating type wafer heating device has been developed that radiates infrared rays to heat a wafer placed on the top surface of the object to be heated 48. However, with this type, the heat loss is greater than with the direct heating type, it takes time to raise the temperature, and the CVD film attached to the infrared transmitting window 46 gradually blocks the transmission of infrared rays. Transparent window 4
6, there were problems such as heat absorption and heating of the window.

0004

The coil to be embedded in the ceramic substrate is limited to heat-resistant, high-melting point metals from the viewpoint of the thermal expansion coefficient and melting point relative to the thermal expansion coefficient and sintering temperature of the ceramic substrate. Taking Si3N4 as an example of a ceramic substrate, the coefficient of thermal expansion is 2.8×10-6
℃-1 and can be used as a coil W, Mo and P
The thermal expansion coefficients of t are 4.58×10-6°C-1 and 5.
10 × 10-6 °C-1 and 10.1 × 10-6 °C-1, the sintering temperature of Si3N4 is 1850 °C, W, Mo
The melting points of Pt and Pt are 3380°C, 2610°C and 17°C, respectively.
It is 69°C. When manufacturing ceramic substrates,
Taking Si3N4 as an example, since the coil is embedded in the Si3N4 molded body and sintered at 1850°C, it is impossible if the coil melts or deteriorates at the sintering temperature. In addition, the thermal expansion of Pt is significantly different from that of Si3N4,
In addition, since the melting point is as low as 1760° C., W, Mo, and W/Mo alloys are preferable. However, insulating films other than metal films can be exposed to plasma C.
When generated by VD, thermal CVD, bias ECR plasma CVD, or sputtering, O2, N2 is used as the atmospheric gas.
Raise the temperature of the heater to a maximum of about 1200°C. In that case, with the current manufacturing method of ceramic heaters,
After hot press sintering, the surface is ground and the surface of the electrode terminal made of tungsten, etc. is carved out. Furthermore, since the thermal expansion of the W and Mo coils is different from that of Si3N4, a gap is created between the coil and the Si3N4 substrate after sintering. Therefore,
High melting point metals such as W and Mo are oxidized by O2, etc., and O2 diffuses into the electrode rod connection area on the heater surface and the gap between the coil and the Si3N4 base, producing tungsten oxide and molybdenum oxide, which deteriorates the heater. For this reason, there was a drawback that it no longer functions as a heater.

An object of the present invention is to prevent contamination within the equipment and decrease in thermal efficiency in equipment such as semiconductor manufacturing equipment that uses high temperature, oxidizing and corrosive gas, and to prevent terminals and electrode members of resistance heating elements. The aim is to provide a ceramic heater with excellent durability and reliability.

The present invention provides a ceramic substrate, a resistance heating element buried inside the ceramic substrate, a terminal provided at an end of the resistance heating element and exposed to the surface of the ceramic substrate, and the terminal. and a heat-resistant metal plate provided on the surface of the ceramic base and joined to the terminal and the ceramic base by a wax containing a titanium component, and an electrode member mechanically bonded to the heat-resistant metal plate. This is a ceramic heater featuring the following. Usually, a heat-resistant metal plate such as Kovar, which is difficult to oxidize, is used, and the terminal surface is brazed, a female thread is cut on the surface of the heat-resistant metal plate, and a male-threaded electrode rod made of stainless steel or the like is mechanically fixed.

[0007] As the heat-resistant metal plate, Kovar, 43Ni
-Fe, Pt, Cu, 26Cr-Fe, Dumet,
There are Al and Ni. The operating temperatures of these items in the atmosphere are 600℃, 600℃, 1400℃, 150℃, respectively.
1000°C, 150°C, 400°C and 600°C. The melting point of wax containing a titanium component is, for example, when applying a ceramic heater to semiconductor manufacturing equipment.
The temperature is preferably 880°C or higher. In this respect, titanium-deposited gold solder and titanium-deposited silver solder are preferred. A wax containing such a titanium component is disclosed in Japanese Patent Publication No. 2-23500 filed by the present applicant.

[0008]

[Operation] In the case of conventional stainless steel heaters, the semiconductor wafer heating surface and the terminals of the resistance heating element are far apart, and the terminals and external electrode cables are connected outside the container of the semiconductor manufacturing equipment. In contrast, in the ceramic heater of the present invention, the area around the terminals is exposed to a high temperature and corrosive atmosphere, but the melting point of the titanium-containing solder is higher than the surface temperature of the heater, and the mechanical bond is corroded. The ceramic heater is stable in a harsh atmosphere and maintains sufficient bonding strength and conductivity even after being exposed to thermal changes, making it possible to obtain a ceramic heater with excellent durability and reliability. Also,
Although general gold solder and silver solder exhibit good bonding properties between metals such as Kovar and heater terminals W, Mo, etc., they lack bonding strength with silicon nitride, which is the heater base. For this reason, not only was the bonding strength of the terminal insufficient, but also a gap was created at the interface of the heater base through which gas could pass, making it impossible to obtain sufficient atmospheric gas tightness. On the other hand, in the ceramic heater of the present invention, by mixing Ti into the brazing material, Ti diffuses into Si3N4 etc.
As noted in issue 3500, 14.7kgf/mm2
A gas-tight bonding interface with a strong bonding strength of .

[0009]

EXAMPLES The present invention will now be explained in more detail with reference to examples. FIG. 2 is a cross-sectional view showing the ceramic heater attached to a thermal CVD apparatus, and FIG. 3 is an enlarged cross-sectional view showing the joint portion between the heat-resistant metal plate 5 and the electrode member 4. Figure 2
, 26 is a container used for CVD for semiconductor manufacturing, 60 is a disk-shaped ceramic heater for heating the wafer attached to the case 6 inside the container, and the size of the wafer heating surface 30 is 4 to 8 inches. The size is set so that the wafer can be installed.

A gas for thermal CVD is supplied to the inside of the container 26 through a gas supply hole 19, and the air inside is exhausted through a suction hole 20 by a vacuum pump. The disk-shaped ceramic heater 60 has a resistance heating element 2 made of tungsten or the like embedded in a spiral shape inside a dense and gas-tight disk-shaped ceramic base 1 made of silicon nitride, and electrode members 4 at the center and ends of the disk-shaped ceramic heater 60 . Power is supplied from the outside through the disc-shaped ceramic heater 60, for example,
It can be heated to about ℃. Reference numeral 16 denotes a flange with a water cooling jacket 18 that covers the upper surface of the case 6, and is sealed with the side wall of the container 26 by an O-ring 10, thereby forming the ceiling surface of the container 26. A hollow sheath 7 is inserted into the interior of the container 26 through the wall of the flange 16 of the container 26, and is joined to the ceramic heater 60. A thermocouple 8 with a stainless steel sheath is inserted inside the hollow sheath 7. An O-ring is provided between the hollow sheath 7 and the flange 16 of the container 26 to prevent outside air from entering.

The terminal 3 of the resistance heating element 2 is connected to the back surface 36 of the heater.
A heat-resistant metal plate 5 is interposed between the terminal 3 and the electrode member 4. The heat-resistant metal plate 5 is manufactured separately in advance and is formed into a washer shape as shown in FIG. is provided and screwed into the thread 4a of the protrusion provided at the lower part of the electrode member 4. A heat-resistant metal plate 5 is hermetically bonded to the ceramic substrate 1 and the terminal 3 by titanium vapor deposition brazing.

Note that the upper surface of the terminal 3 does not necessarily have to be on the same plane as the upper surface of the ceramic base 1, but is made slightly lower than the upper surface of the ceramic base as shown in FIG. In this way, the positioning of the heat-resistant metal plate 5 becomes easy, and together with the sealing and bonding effect of the titanium-containing solder, the intrusion of outside air into the terminal 3 is more reliably prevented. Further, by providing deeper holes in the heat-resistant metal plate 5, the electrode member 4 can be firmly fixed.

According to the ceramic heater of this embodiment, it is possible to solve the problems of contamination as in the case of conventional metal heaters and deterioration of thermal efficiency as in the case of indirect heating methods. The case 6 is made of, for example, graphite, and corrosive gas inevitably enters the back side of the heater 36. Furthermore, since the ceramic base 1 is disk-shaped, the joint portion between the terminal 3 of the resistance heating element 2 and the electrode member 4 is repeatedly exposed to high temperature heating and cooling. However, on this point,
In the present invention, since the heat-resistant metal plate 5 is bonded between the terminal 3 and the electrode member 4 by titanium vapor deposition brazing, the heat-resistant metal plate 5
and the ceramic substrate 1 are firmly bonded by diffusion bonding of Ti in the titanium vapor deposition solder, and the heat-resistant metal plate 5 and the terminal 3 are also strongly bonded by diffusion bonding of Ti.
The hermeticity of the joint between the terminal 3 and the electrode member 4 due to corrosive gas or heat can be improved and deterioration can be prevented, and the durability and reliability of the heater can be improved. The material of the disc-shaped ceramic substrate 1 includes silicon nitride, sialon,
Aluminum nitride and the like are preferred, and silicon nitride and sialon are more preferred in terms of thermal shock resistance.

As the resistance heating element 2, it is appropriate to use materials such as tungsten, molybdenum, and platinum, which have a high melting point and have excellent adhesion to silicon nitride and the like. The wafer heating surface 30 is preferably a smooth surface, especially when the wafer is set directly on the wafer heating surface 30.
It is necessary to set the flatness to 500 μm or less to prevent the deposition gas from entering the back surface of the wafer. When manufacturing a disc-shaped ceramic heater, the terminal 3
The resistance heating element 2 provided with the above is embedded in a ceramic molded body, the ceramic molded body is sintered, and the back side of the thus obtained disc-shaped ceramic base 1 is ground to expose the end face of the terminal 3 to the back face 36. Next, the heat-resistant metal plate 5 is bonded to the back surface 36 of the ceramic substrate 1 by titanium vapor deposition brazing, and then the heat-resistant metal plate 5 and the electrode member 4 are mechanically bonded.

Referring to FIGS. 3 and 4, an example of mechanical connection by thread cutting is shown. For example, the terminal 3 made of tungsten has a diameter of 5 mm and a length of 10 mm.
For example, to connect the electrode member 4 made of nickel, an M3 x 6 mm female thread 5a was cut in the Kovar plate 5, and an M3 x 5 mm male thread 4a was cut in the tungsten electrode member 4, and the connection was performed with screws. . Since tungsten terminals are extremely hard and brittle and cannot be machined with a normal die, it was much easier to cut female threads in Kovar plate 5 than to cut female threads in tungsten terminals. Therefore, the electric discharge machining conventionally performed on the tungsten terminal 3 can be omitted. In the case where the mechanical connection is made in this way, the upper surface of the tungsten terminal 3 and the lower surface of the tungsten electrode member 4 are in contact with each other, and even when they are not in contact, a conductive titanium vapor-deposited solder is placed between them. Since they are interposed and joined, sufficient conductivity and airtightness are achieved. Furthermore, since a sufficient contact area is obtained, there is no possibility of current concentration at the joint. In addition, as another mechanical joining method, a hole with a diameter of 3 mm x 7 mm is made in the Kovar plate 5, a convex part with a diameter of 3 mm x 6 mm is provided on the nickel electrode member 4, and a tightening interference of 20 μm is formed.
Press-fitting was carried out at a press-fitting pressure of 1000 kgf/cm2. Room temperature and 800℃ in the range of tightening allowance 0 to 50μm
Even after 1000 cycles of cooling and heating, the bond remained strong.

In each of the above examples, the shape of the ceramic heater is preferably a disk shape in order to uniformly heat a circular wafer, but other shapes such as a square disk shape,
It may also be shaped like a hexagonal disc. The present invention is also applicable to ceramic heaters in plasma etching equipment, photoetching equipment, and the like.

[0017]

Effects of the Invention: Due to the titanium diffusion bonding effect of the solder containing a titanium component, it is possible to firmly and airtightly bond between the heat-resistant metal plate and the ceramic substrate and between the heat-resistant metal plate and the terminal. Furthermore, high bonding strength can be exhibited up to the melting point of the brazing filler metal in high-temperature oxidizing and corrosive gas. Therefore, the electrode member and the terminal can be reliably used for a long time in high-temperature oxidizing and corrosive gas. The electrical conductivity of the brazing material containing titanium ensures electrical continuity between the electrode member and the terminal. Therefore, it is not necessary to precisely match the length and end surface of the joints. Drilling holes in heat-resistant metal plates is much easier than drilling holes in terminals by electrical discharge machining.

[Brief explanation of the drawing]

FIG. 1 is a schematic cross-sectional view of a conventional indirect heating type wafer heating apparatus.

FIG. 2 is a diagrammatic cross-sectional view of a previously unpublished wafer heating device according to the applicant's invention;

FIG. 3 is a diagrammatic cross-sectional view showing an example of a coupling structure between a heat-resistant metal plate and an electrode terminal bar.

FIG. 4 is a diagrammatic cross-sectional view showing another example of a coupling structure between a heat-resistant metal plate and an electrode terminal bar.

[Explanation of symbols] 1 Ceramic base 2 Resistive heating element 3 Terminal 4 Electrode member 4a Thread 5 of electrode member 4 Heat-resistant metal plate 5a Thread groove 5b of heat-resistant metal plate 5 Projection portion 8 of heat-resistant metal plate 5 Thermocouple 16 Flange 26 Container 30 for CVD for semiconductor manufacturing Wafer heating surface 36 Back side 60 of ceramic heater 60 Ceramic heater

Claims (1)

[Claims] 1. A ceramic base, a resistance heating element buried inside the ceramic base, a terminal provided at an end of the resistance heating element and exposed to the surface of the ceramic base, and a combination of the terminal and the resistance heating element. A heat-resistant metal plate provided on the surface of a ceramic base and joined to the terminal and the ceramic base by a solder containing a titanium component, and an electrode member mechanically bonded to the heat-resistant metal plate. Ceramic heater.