JPS5919315A - Device for heating in vacuum - Google Patents

Abstract

PURPOSE:To perform a high temperature heating in a stabilized state by a method wherein a beryllium oxide sintered body is used for formation of the heat conductive material which constitutes the heating device. CONSTITUTION:A heating device 10 is constructed in such a manner that a heater 12, which is a heat generating body, is interposed between an upper flat plate 11 and a lower flat plate 13. Tungsten is used in the heater 12, and it is formed almost into a continued U-shape. Also, said flat plates 11 and 13 are formed with a beryllium oxide sintered body. A sintered body having relative density of 99.0% or above is to be used. Beryllium oxide sintered body has a high insulating property, and also it has excellet mechanical strength and heat conductivity.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a heating device, and particularly to a vacuum heating device for heating an object in a vacuum state.

[Technical background of the invention and its problems]

Conventionally, in the manufacturing process of semiconductor devices, work is performed to heat substrates, specimens, etc. (hereinafter collectively referred to as "objects" below) in order to improve crystal growth or to clean their surfaces. As is well known.

Such heating means include resistance heating, laser heating, electron beam heating, high frequency heating, and direct current heating, but it is difficult to uniformly heat a large object with any of them, and crystal technology or process technology is It is not possible to fully meet the recent technical demands, which have become possible to use large-diameter silicon wafers due to development.

Furthermore, various demands on devices in recent years have led to the complexity of devices and, in turn, the complexity of manufacturing processes, and vacuum heating equipment has become more and more complex, with the need for stable operation that can be used in high vacuum, and that can be set over a wide range of temperatures. There is an increasing demand for such things.

In particular, the materials constituting the vacuum heating device must be stable even at high temperatures and do not react with the target object or diffuse its composition into the target object, as well as high vacuum It must be made of a stable material with no unnecessary gas emissions and low vapor pressure, and must have sufficient mechanical strength to avoid damage or deterioration due to thermal cycles of heating, holding, and cooling. Fine needle thermal shock resistance, low thermal expansion, high thermal conductivity, high electrical insulation, and good thermal response characteristics are required.

In response to these technical requirements, sintered ceramics have been proposed as a material for heating devices, but they do not fully satisfy the above conditions.

[Purpose of the invention]

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a vacuum heating device capable of stably heating at a high temperature even in a high vacuum.

[Summary of the invention]

That is, in this invention, the thermally conductive material constituting the vacuum heating device is formed of a beryllium oxide sintered body, and the relative density of this sintered body is made to be as high as 99.9%. This allows for stable high temperature heating.

[Embodiments of the invention]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The vacuum heating device according to the present invention will be described in detail below according to embodiments shown in the accompanying drawings.

FIG. 1 is an exploded perspective view of a vacuum heating apparatus according to the present invention, particularly for heating a substrate such as a silicon wafer. In this FIG. 1, heating device 1
0 has a structure in which a heater 12 as a heating element is interposed between a lower flat plate 11 and a lower flat plate 13. Among these, the heater 12 is made of tungsten, for example, and has a continuous substantially U-shape as shown in the figure. Further, the upper flat plate 11 and the lower flat plate 13 are formed of a sintered body of beryllium oxide (BeO). This beryllium oxide sintered body is formed by hot pressing or pressureless sintering, and has a relative density of 99.9% or more. In addition,
This beryllium oxide sintered body and alumina CAltOs)
In order to compare the characteristics with quartz (Sin) and quartz (Sin), they are shown in the table below.

As is clear from this table, the beryllium oxide sintered body has higher insulating properties and superior mechanical frequency and thermal conductivity compared to alumina and quartz. Furthermore, especially in the case of this beryllium oxide sintered body, the maximum operating temperature in an oxidizing atmosphere is still high compared to the above-mentioned alumina and quartz (and it is suitable as a heat conductive material of a heating device, that is, the upper and lower flat plates 11 and 13). It can be said that it is an inverted slope with characteristics that do not exist.

In addition, since the above heating device is used in an ultra-high vacuum, the heat conductive material must be a material with high temperature and low vapor pressure, and the #8 beryllium sintered body is excellent in this property. . FIG. 2 shows the temperature-vapor pressure characteristics of the helium oxide sintered body and the alumina and quartz.

As is clear from FIG. 2, the K, beryllium oxide sintered body has a very low vapor pressure (even in a vacuum of 10-9'rorr or less, it can heat the object 7a'120' or more). This has been confirmed.

FIG. 3 shows an example of a vacuum evaporation apparatus for forming a thin metal film on a predetermined object using a heating apparatus using a beryllium oxide sintered body having the above characteristics. In this figure, the vacuum evaporation apparatus 20 has its Pelger 2
Gas is drawn by a bottomless vacuum pump system in the Pelger 21, so that the inside of the Pelger 21 is appropriately vacuumed.

^ On the table 22 is the heating device 1 shown in FIG.
0 is placed and fixed, and silicon ueno sheets \8A and 8B, which are objects, are further placed on top of it. Also,
The heater 12 of the heating device 10 is led out of the Pelger 21 via a suitable hermetic electrode, and is connected to a power source (not shown).

On the other hand, balls 23 and 24 are provided across the table 22, and an electrode 2 is placed between these balls 23 and 24.
A filament 27 is installed through the filament 27, and a wire-like metal 28 formed into a substantially U-shape is suspended from the filament 27. Said ball 23.24
It is also led out to the outside and connected to a power source (not shown).

Next, to explain the case of forming a film of the metal 28 on the Crycon Ueno% SA and SB with reference to FIG. 3, first, the inside of the Pel jar 21 is brought to an appropriate vacuum using a vacuum pump system (not shown). Next, before the metal 28 is vapor-deposited, the heater 21 is energized to heat the silicon wafers 8A and 8B in order to clean the surfaces of the silicon wafers 8A and 8B. Generally, it is required that the silicon wafers BA and BB be heated to 1000 t:' or more. At this time, the gas contained in the upper and lower flat plates 11.13 is released, but as mentioned above, the relative density of the beryllium oxide sintered bodies forming the upper and lower flat plates 11.13 is 99.9%. Therefore, there are almost no vacuoles inside, and the amount of gas released by this R heating is extremely small. Therefore, even in an ultra-high vacuum state of 10 Torr or less, there is almost no effect on the vacuum state (7).

Next, after cleaning the surface of the silicon wafers SA and S, the amount of electricity applied to the heater 12 is adjusted.
When the temperature of B is adjusted to a required constant temperature and electricity is applied to the filament 27 in the east, the metal 28 is melted and evaporated, and a film of the metal 28 is formed on the surfaces of the silicon wafers SA and 8B.

Finally, data from heating experiments using a prototype device of the present invention are shown below. The upper and lower flat plates 11.13' formed of beryllium oxide sintered bodies are square shaped with a Y-side length of 70 m and a thickness of ll1lI. The heater 12 has a diameter of 1 with a folding pitch of 4 mm.
Use φ tungsten wire. This device 5(), 8m
+ (2 inch) silicon wafer is placed and IQ"-'
When a current of 2 OA was passed through the heater 12 under a vacuum state of Torr, the surface temperature of this silicon wafer was approximately 10
The temperature rises to 1200C in minutes, and the vacuum level is also IQ Tor.
It was well maintained below r. Furthermore, the variation in surface temperature of the silicon (8) wafer was suppressed to within ±10 C, and the uniformity of heating was also good.

After this, the temperature was further increased and decreased 50 times, but no change was observed in the upper and lower flat plates 11 and 13, and no chemical reaction occurred with the silicon wafer. Further, there is no chemical reaction with tungsten forming the heater 12, and conversely, contamination of the silicon wafer due to evaporation of tungsten is prevented from occurring in the upper and lower flat plates 1 formed of the beryllium oxide sintered body.
1.13 could have prevented this.

In the above embodiment, the object to be heated is a silicon wafer, but other metals, insulators, etc. may be used. Further, the heating device according to the present invention may be used not only for the above-mentioned vacuum evaporation but also for manufacturing processes such as molecular beam epitaxy, and may be used for analysis and measurement equipment such as Auger spectroscopy. Furthermore, the shape of the heating device is not limited to the above-mentioned flat plate shape (it may be of various shapes,
It is also possible to embed a heater by shaping the material into a certain shape during sintering.

It is also possible to use it in combination with other beryllia porcelain.

〔Effect of the invention〕

As explained above, according to the vacuum heating device according to the present invention, the part surrounding the heating element and in contact with the object is formed of a beryllium oxide sintered body.
It is possible to heat the object uniformly and well with low heat loss without causing any damage even at high temperatures of 0C or higher, and it is also possible to create a heating device with a fairly large area, so that the size suitable for the object can be selected. In addition, the relative density of the sintered body is 99.9%, which reduces unnecessary gas emissions and prevents negative effects on the vacuum state, making it possible to stably heat objects at high temperatures in high vacuum. I blame the young fruit of being able to do it.

As an application example of the present invention, an evaporator or crucible for a low melting point metal or the like may be formed of a beryllium oxide sintered body. Further, depending on the content of the work using the vacuum equipment, extremely high temperatures may be present, but if beryllium oxide sintered bodies are used in such parts, the same effects as above can be obtained. For example, in the example of FIG. 3, the ball 23.
If it is used for the insulating members 30 and 31 of the filament 24, it is possible to maintain good insulation even if the temperature of the balls 23 and 24 rises due to the heat generation of the filament 27.

Furthermore, dielectric heating may be performed by applying an alternating electric field to the beryllium oxide sintered body. In particular, it is also possible to heat gas or liquid by providing a plurality of passages in the beryllium oxide sintered body or by forming it into a cylindrical shape and performing dielectric heating.

[Brief explanation of the drawing]

FIG. 1 is an exploded perspective view of an embodiment of a vacuum heating device according to the present invention, and FIG. 2 is a comparison of the temperature-vapor pressure characteristics of perilicum oxide sintered bodies, alumina, and quartz. 3 is a perspective view showing an example (11) of a vacuum evaporation apparatus using the heating device of FIG. 1. DESCRIPTION OF SYMBOLS 10... Vacuum heating device, 11... Upper flat plate which is a thermally conductive material 12... Heater which is a heating element, 13...
The lower flat plate is a heat conductive material. (l 2 )

Claims (2)

[Claims] (1) In a vacuum heating device that is used in a vacuum and has a heating element and a thermally conductive material that conducts heat generated from the heating element to an object, the thermally conductive material is sintered with beryllium oxide. A vacuum heating device characterized by being formed from a body. (2) Relative density of the beryllium oxide sintered body'&9
9.9% or more The vacuum heating device according to claim (1).