JPH038792A - Boron nitride crucible - Google Patents

Abstract

PURPOSE:To remarkably prolong life of crucible by forming boron nitride crucible for housing a raw material into a laminate structure of thin film each having different density in the above-mentioned crucible when crystal of semiconductor is grown. CONSTITUTION:A boron nitride(BN) crucible is prepared using NH3 gas and boron chloride or NH3 gas and boron fluoride according to a vapor phase growth method. In this case, a BN thin film is formed into a multi-layer thin film by integrating the thin film of BN and difference of density of adjacent each thin film is kept to about >=0.1g/cm<2>, since the structure is slightly different by preparation conditions and the difference is made in density of each part. Thereby each layer when used is uniformly released. As a result, thickness of the crucible can be uniformly kept in each part even when used for a long period and long life of crucible can be attained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a crucible, particularly a boron nitride crucible for growing compound semiconductor single crystals.

[Prior Art] Crucibles are often used as containers for melting raw materials during the production of semiconductor single crystals, and quartz (S02) crucibles are well known, but when producing compound semiconductor crystals, heat-resistant and chemical-resistant crucibles are required. Boron nitride (BN) has excellent properties and moldability.
) A crucible is used. In particular, boron nitride crucibles made by so-called vapor phase growth using ammonia gas and boron chloride or ammonia gas and boron fluoride,
P B N (Pyrotytic Boron N1
It is called a tridel crucible and is widely used as a crucible for crystal growth of compound semiconductors. This PBN crucible is also used for thin film growth by the molecular beam epitaxial (MBE) method, for example, gallium arsenide (G
aAs) Semiconductor-like so-called liquid sealed arch
When growing a single crystal using method C), a boron nitride crucible made by sintering is used.

Note that aluminum titanium crucibles, silicon carbide crucibles, and the like are being considered as alternatives to PBN crucibles, but PBN crucibles are currently used as the optimal crucibles because they are inferior in terms of purity and moldability.

[Problems to be Solved by the Invention] As mentioned above, PBN crucibles are widely used to produce single crystals of compound semiconductors because they produce high-purity single crystals, but the biggest problem is the lifespan. This is the point.

Figure 1 shows a single crystal manufacturing apparatus using the LEC method.
is a PBN crucible, 2 is a melt of GaAS, 3 is boron oxide (B203) as a liquid sealant, 4 is a GaAs crystal,
5 is a seed crystal, and 6 is a heater.

In the case of the LEC method, as the crystal growth progresses, the sealant 3 firmly adheres to the inner wall of the crucible 1, causing a so-called co-crackling phenomenon, which causes the inner wall of the crucible 1 to peel off, and in severe cases, the crucible 1 to be completely damaged. A phenomenon of damage occurs. Even if the crucible does not break immediately, the inner wall of the crucible will continue to peel off each time it is used, eventually leading to breakage.

If the degree of peeling is relatively uniform and the wall thickness does not decrease rapidly, a crucible with a relatively long life may be obtained, but since the peeling phenomenon occurs randomly, this is expected to extend the life of the crucible. I can't. In this case, it is conceivable to increase the wall thickness of the pot in advance, but this increases the cost, but is also disadvantageous because it causes a phenomenon that it is more likely to collapse during initial operation.

As mentioned above, PBN crucibles are manufactured by the vapor phase growth method, but since the vapor phase growth method has low transient properties, the manufactured crucibles are expensive, but if this expensive crucible has a short lifespan, it is economically disadvantageous. be.

It is an object of the present invention to provide a boron nitride crucible that has a significantly extended service life.

[Means for Solving the Problems] The present invention, when growing a single crystal of a compound semiconductor, uses a boron nitride crucible used for storing and melting raw materials as a multi-layered Wi layer of boron nitride thin films each having a different density. The difference in density between adjacent thin film layers is 0.10.
/Cat or higher, and the average density of the entire laminated thin film is 1.20/
The other characteristics are that the thickness of each layer is 75 μm or less, and the thickness of each layer is 75 μm or less, so that the film can be peeled off uniformly and a long-life crucible can be obtained. I am planning to achieve this.

[Function] A boron nitride crucible has a slightly different structure depending on the manufacturing conditions, and the density of each part varies. Therefore, when manufacturing a crucible using the boron nitride crucible of the present invention, thin films of boron nitride are accumulated to form a multilayer thin film. , the density difference between adjacent thin film layers is 0.10/cm3 or more, and the overall average density is 1.20/cm3 or more.
Ca+3 or more and 3.5 and less than l/cm3, thickness of each layer is 7
Since the thickness is set to 5 μm or less, and each layer is peeled off uniformly during use, it is possible to maintain the thickness of the crucible uniformly in each part even during long-term use, achieving a long life. I can do it.

[Example] Examples of the present invention will be described below.

Reference Examples, Examples, and Comparative Examples are collectively shown in Table 1. The density of each layer in the table indicates that layers of double density are layered. Also, the service life is 150mm in inner diameter, 140mm in height,
When a GaAs crystal is produced using the LEC method by placing Ga A 56 R9 and I kg of boron oxide in a crucible with a wall thickness of 1 mtn, this manufacturing process is repeated,
It is expressed as the number of times the crucible is used until it becomes unusable.

The reference examples shown in Table 1 show data for conventionally commercially available crucibles, and since this crucible is not multi-layered, the number of layers is shown as 0. The lifespan of this crucible was 9 cycles. On the other hand, in the case of the crucible according to the present invention, the life is significantly improved as shown in Examples 1 to 5, and in the case of Example 5 in particular, it is recognized that the life is significantly improved at 30 times. .

Next, as shown in Comparative Examples 1 and 2, the thickness of one layer was 75 μm.
If it is thicker, the life will not be improved, so it is necessary to keep the thickness of each layer to 75 μm or less.

Also, as shown in Comparative Example 3.4, the density difference between each layer was 0.1 g.
If it is lower than /cjI3, the life will not be improved.

Also, as shown in Comparative Example 5, the average density is 1.2 g/c! R
When lower than 3.5Q/c as shown in Comparative Examples 6 and 7
It can also be seen that when ttr is larger than 3, the life is not improved.

In this way, for this crucible, the film thickness is 75 mm for each layer.
μm or more, the density difference must be 0.10/cm” or more, and the average density must be 1.2 q/cm 2 to 3.5 Q/cm 3 .

In addition, when producing a crucible, the density of the innermost layer is 1.2Q/
cm3, and 0,110/c5 for each 1 μm thickness of each layer.
The density of the 21st layer, which is the outermost layer, is 3.
．． As a result of testing at 4Q/cm and an average density of 2.30/cm'', the life span was 20 times, and good results were obtained as in the above example.

[Effects of the Invention 1 As described above, according to this embodiment, the following effects can be obtained.

(1) Since the life of an expensive crucible can be extended and used repeatedly, the economical effect is extremely large.

Extending the RF life of the crucible allows lower costs of single crystals and therefore wafers and devices.

[Brief explanation of the drawing]

(2) FIG. 1 is an explanatory diagram of a GaAs single crystal manufacturing apparatus using the LEC method. : PBN crucible, : melt, : B2o3, : GaAS single crystal.

Claims (1)

[Claims] 1. In a boron nitride crucible for storing raw materials constituting a semiconductor during crystal growth of the semiconductor, the crucible has a structure in which thin films of boron nitride with different densities are laminated in multiple layers. A boron nitride crucible characterized by having: 2. The boron nitride crucible according to claim 1, wherein the difference in density between adjacent layers of the boron nitride thin film layer is 0.1 g/cm^3 or more. 3. The average density of the entire thin film layer of boron nitride constituting the crucible is 1.2 g/cm^3 or more and 3.5 g/cm^
The boron nitride crucible according to claim 1 or 2, wherein the boron nitride crucible is less than 3. 4. The boron nitride crucible according to claims 1 to 3, wherein each layer of the boron nitride thin film layer has a thickness of 75 μm or less.