Pyrolytic boron nitride container and manufacture thereof

Details Pyrolytic boron nitride container and manufacture thereof Pyrolytic boron nitride container and manufacture thereof

1997-11-17

2001-03-06

Robinson, Ellis (Department: 1772)

Stock material or miscellaneous articles

Hollow or container type article

Glass, ceramic, or sintered, fused, fired, or calcined metal...

C428S034600, C428S156000, C428S170000, C428S174000, C428S212000, C428S333000, C428S337000, C428S338000, C428S446000, C428S457000, C428S698000, C428S704000, C427S255280, C427S255380, C427S590000

Reexamination Certificate

active

06197391

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a pyrolytic boron nitride container. More particularly, the present invention relates to a pyrolytic boron nitride container suitable for retaining a material serving as a source of molecular beams used in molecular beam epitaxy (hereinafter abbreviated as “MBE”).
2. Description of the Related Art
MBE is one method of manufacturing thin film, in which a thin-film growth chamber is maintained at ultra-low vacuum of 10
−9
-10
−11
Torr; a container that contains a material serving as a molecular beam source is heated to, for example, a temperature of 500-1600° C.; and molecular beams generated from the melt material are caused to impinge onto a heated substrate, so that a layer having a thickness corresponding to a few atoms is formed on the substrate in a controlled manner. Especially, the MBE method has been widely used for manufacture of epitaxial film of compound semiconductors such as GaAs, and from the viewpoints of purity, heat resistance, and strength, a pyrolytic boron nitride (PBN) container made through chemical vapor deposition (hereinafter abbreviated as “CVD”) has been widely used as a container for accommodating a material serving as the molecular beam source.
Conventionally, when an operation according to such an MBE method is carried out for a prolonged period of time, material melt rises along the inner wall surface due to the capillary phenomenon and leaks out of the container, with the result that the material melt adheres to a heater, other heating members, and members inside a furnace, resulting in corrosion, degradation, and/or breakage of these components and members; and/or short-circuit of the heater. Especially, evaporated and scattered material melt is likely to adhere to the upper portion of the inner wall surface of the, container having a low temperature. With time, such material melt adhering to the upper portion of the container may rise along the inner wall of the container and leak out of the container or drop into the material melt to splash droplets of the material melt.
When the above-described phenomena occur, the life-times (or service-lives) of the above-described components and members decrease, resulting in an increase in cost and unstable operation. In addition, splashed droplets of the material melt may adhere to the substrate, resulting in formation of defects in the epitaxial film.
In order to solve the above-described problems, there has been proposed a pyrolytic boron nitride container in which carbon film having a high absorption coefficient with respect to infrared rays (IR) is applied to the outer or inner surface of the container in order to provide a radiant light absorbing layer (see Japanese Patent Application Laid-Open (kokai) No. 2-204391 and Japanese Utility Model Publication (kokoku) No. 7-2617). When the pyrolytic boron nitride container having the radiant light absorbing layer is heated by a heater, radiant light from the heater is absorbed by the absorbing layer, so that the container is heated efficiently and uniformly. Thus, the upper portion of the container is prevented from becoming excessively cool, so that adhesion of the material metal to the upper portion is suppressed.
Graphite and high-melting-point metal are generally considered to be suitable materials of the radiant light absorbing layer. However, these materials involves a fear that they may splash within the furnace and become mixed into epitaxial film, and a fear that since these materials are electrically conductive, if they come in contact with a heater disposed to surround the container, they may cause a short-circuit.
In order to solve this problem, there has been proposed a method to cover a graphite-made light absorbing layer with pyrolytic boron nitride (see Japanese Patent Application Laid-Open (kokai) Nos. 5-105557 and 4-231459). However, since this method involves a process of forming a composite layer of two different materials, manufacture of a pyrolytic boron nitride container involves much time and high cost. In addition, such a pyrolytic boron nitride container has a drawback that the composite layer tends to peel off during use.
SUMMARY OF THE INVENTION
The present invention has been conceived in view of the foregoing drawbacks. An object of the present invention is to provide a pyrolytic boron nitride container through a simple process and at low cost, which can prevent material melt from rising along the inner wall surface and prevent splashed material melt from adhering to the upper portion of the container when an operation is carried out for a prolonged period of time, which can be used in a stable manner, and which can stabilize molecular beam epitaxial growth and improve the quality of epitaxial film.
In order to achieve the above object, the present invention provides a pyrolytic boron nitride container for accommodating a material serving as a source of molecular beams for molecular beam epitaxy, wherein the transmissivity of the pyrolytic boron nitride container with respect to light having a wave number of 2600 cm
−1
to 6500 cm
−1
has a profile such that the transmissivity changes in the height direction of the container.
As a result of imparting such a profile to the IR transmissivity of the pyrolytic boron nitride used as a container for accommodating a material serving as a source of molecular beams for molecular beam epitaxy, the temperature distribution within the container can be controlled into a desired distribution. Accordingly, it is possible to effectively prevent rising of material melt along the inner wall surface and adhesion of material melt to the upper portion of the container.
Preferably, the profile of the transmissivity is set such that the transmissivity decreases stepwise or gradually from the bottom portion to the opening portion of the container. Alternatively, the profile of the transmissivity is preferably set such that the transmissivity increases stepwise or gradually from the bottom portion to the opening portion of the container.
As described above, as a result of imparting a profile to the IR transmissivity from the bottom portion to the opening portion of the container (in the height direction of the container), the temperature of the upper portion of the container is maintained high, so that adhesion of material melt to the upper portion and rising of the material melt thereto can be suppressed. Also, since the wettability with pyrolytic boron nitride varies with the kind of material melt, there is a case where the rising phenomenon can be suppressed through reduction of the temperature of the upper portion of the container. In such a case, the transmissivity of the container at the opening portion may be set high.
In the present invention, in order to impart a profile to the transmissivity of the pyrolytic boron nitride container with respect to light having a wave number of 2600 cm
−1
to 6500 cm
−1
, the absorptivity of the pyrolytic boron nitride is preferably changed.
The present invention also provides a method of manufacturing a such a pyrolytic boron nitride container. In this method, pyrolytic boron nitride is deposited on a graphite mandrel by CVD in order to form a pyrolytic boron nitride container, and the pyrolytic boron nitride container is then separated from the mandrel, wherein the absorptivity of the deposited pyrolytic boron nitride produced by CVD is controlled through placement of the mandrel according to the pressure profile in a CVD furnace, such that the transmissivity of the pyrolytic boron nitride container with respect to light having a wave number of 2600 cm
−1
to 6500 cm
−1
varies in the height direction of the container.
As described above, if a desired profile is imparted to the transmissivity of the container through change of the physical properties of pyrolytic boron nitride, there can be solved the problem involved in the case where pyrolytic boron nitride is combined with other materials; i.e., contamination due to im

Affiliated with

Also associated with

Rating

Pyrolytic boron nitride container and manufacture thereof does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Pyrolytic boron nitride container and manufacture thereof, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Pyrolytic boron nitride container and manufacture thereof will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-2522596