JPS5932437B2 - Band-shaped silicon crystal production equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field of the Invention The present invention relates to an improvement in an apparatus for manufacturing band-shaped silicon crystals.

Technical background of the invention and its problems Recently, a method for growing band-shaped silicon crystals has been attracting attention as one of the crystal growth techniques, but since the band-shaped silicon crystals are thin plate-like, they cannot be obtained by the Czochralski method. Unlike ingot-shaped silicon crystals, it can be used as a substrate for semiconductor devices in its original shape.

Therefore, the semiconductor device is characterized by being cheaper than using a silicon crystal obtained by the Czochralski method as a substrate.

FIG. 1 is a schematic diagram showing a conventional apparatus for growing such a band-shaped silicon crystal.

One ends of a pair of capillary dies 2a and 2b having slits made of graphite are inserted into a crucible 1 made of quartz glass, and heaters 3a and 3b are arranged around the crucible 1.

Then, polycrystalline silicon was placed in the crucible 1 and placed in a heating furnace (not shown), and the temperature inside the furnace was raised to 1500.
When the temperature is raised to about [° C.], the polycrystalline silicon becomes a silicon melt 4.

This silicon melt 4 flows through the dies 2a and 2 due to capillary action.
It rises to the tip of b.

Then, by bringing a seed crystal into contact with this rising silicon melt 4 and then pulling the seed crystal, a band-shaped silicon crystal 5 is grown.

However, when band-shaped silicon crystals were manufactured using such conventional equipment, the following problems occurred.

That is, when the surface of the grown band-shaped silicon crystal was observed, it was found that many SiC grains were fixed to the crystal surface.

It has also been found that the adhesion of these SiC grains deteriorates the crystallinity of the band-shaped silicon crystal, and also has an adverse effect on the electrical characteristics.

This is because the carbon of graphite, which is the material of the die, reacts with the silicon melt to generate SiC.

And since graphite is used as the die material,
It has been difficult to prevent the generation of SiC.

OBJECTS OF THE INVENTION An object of the present invention is to provide a method for growing band-shaped silicon crystals, which can prevent SiC grains from being generated and fixed to the crystal surface when growing band-shaped silicon crystals, and which can contribute to improving crystallinity and electrical characteristics. Our goal is to provide manufacturing equipment.

Summary of the Invention The present inventors have focused on the fact that the generation of SiC grains is used for carbon in the die material, and have developed silicon nitride or silicon as a material that has strong resistance to silicon melt, is less deformed at high temperatures, and does not contain carbon. Sialon (5iAlON:
A material consisting of silicon, aluminum, oxygen, and nitrogen was selected to form the die.

However, when such a die was used, the silicon melt did not rise through the slit of the die, making it impossible to grow a band-shaped silicon crystal.

Therefore, when we observed and analyzed the slit surface of the die, we found that
It was found that silicon oxide was formed on the slit surface, and this oxide was the cause of deteriorating the wettability of the silicon melt.

Taking this point into consideration, the inventors of the present invention have conducted extensive research, and as a result,
It has been found that the wettability problem can be solved by depositing a metal film on the inner surface of the slit of a die made of silicon nitride or sialon.

That is, by placing a metal film on the inner surface of the slit of a die made of silicon nitride or sialon, and placing this die in a heating furnace and raising the temperature in an oxygen-free atmosphere,
Mainly silicon oxide formed on the inner surface of the slit is reduced and removed.

In other words, the wettability of the silicon melt to the die is improved.

Thereafter, by bringing the die into contact with the silicon melt without taking it out of the furnace, it becomes possible to grow a band-shaped silicon crystal.

The present invention focuses on such points, and one end of a pair of capillary dies having a slit is immersed in a silicon melt contained in a crucible, and seeds are poured into the silicon melt rising through the slit of the die. In an apparatus for producing band-shaped silicon crystals that grows band-shaped silicon crystals by bringing crystals into contact with each other and pulling up this seed crystal, the capillary die is formed of silicon nitride or sialon, and a metal film is coated on the inner surface of the slit of this die. It is something to be covered with.

Effects of the Invention According to the present invention, since carbon-free silicon nitride or sialon is used as the material for the capillary die, it is possible to prevent the generation of SiC grains when growing band-shaped silicon crystals. I can do it.

Furthermore, since a metal film is coated on the inner surface of the die slit, the oxide film that deteriorates the wettability of the silicon melt can be removed by reduction, thereby improving the wettability of the silicon melt on the inner surface of the die slit. This makes it possible to improve the growth of band-shaped silicon crystals.

Therefore, high quality band-shaped silicon crystals with good crystal properties and electrical properties can be manufactured.

Embodiment of the Invention FIGS. 2 to 4 each show the configuration of essential parts of an embodiment of the present invention. FIG. 2 is a plan view of the capillary and die seen from above, and FIG. 4 is a sectional view taken along arrow AA, and FIG. 4 is a sectional view taken along arrow BB in FIG.

This embodiment differs from the conventional device shown in FIG. 1 in the structure of the capillary die and the material of its construction.

i.e. capillary. Dies 1ia and 1ib are made of silicon nitride and are attached with spacers 12a and 12b of desired thickness in between.

Then, the die 11a, llb and the spacer '12
An aluminum film 13 is deposited on the inner surface of the slit formed by a and 12b.

Note that the spacers 12a and 12b are the die 11a.

The die 11 is made of silicon nitride like the die 11b.
Of course, it may be formed integrally with one of a and 11b.

Further, the aluminum film 13 is deposited on the dies 11a and 11b.
was applied before installation.

Further, the spacing between the slits was set to D=200 Cμm.

Furthermore, the configurations of the crucible 1, heaters 2a, 2b, heating furnace, etc. were the same as those of the conventional apparatus.

Next, the operation of this device configured as described above will be explained.

First, the die 11a is attached as described above. 11b was placed in a heating furnace and heated in a rare gas atmosphere.

Next, when one end of the dies 11a and 11b was brought into contact with the silicon melt 4 in the crucible 1, the silicon melt 4, which would not have risen up the slit when the aluminum film 13 had not been deposited, moved up to the upper end of the slit. Rose.

Then, a seed crystal was brought into contact with the silicon melt 4 that had risen to the upper end of the slit, and when the seed crystal was gradually pulled up, growth of a band-shaped silicon crystal was confirmed.

S adhered to the surface of the band-shaped silicon crystal thus obtained.
The amount of iC grains was about 0.02 pieces per 1 d.

This number is extremely small compared to about 0.3 per d for conventional graphite dies.

In addition, it has been confirmed that the reason why SiC grains are not completely eliminated in the case of silicon nitride die is due to carbon contamination from the graphite heat insulating material used in the heating furnace. It is considered that there is almost no adverse effect on the characteristics of

In this way, according to this device, it is possible to almost completely eliminate SiC grains that adhere to the surface of the band-shaped silicon crystal, and it is also possible to improve the wettability between the silicon melt and the silicon nitride die. - High quality band-shaped silicon crystals with good crystal and electrical properties can be manufactured.

Furthermore, since the fixation of SiC grains is one of the causes of twin crystal formation, it can contribute to single crystallization of band-shaped silicon crystals.

Furthermore, band-shaped silicon crystals were mainly developed for use in solar cells, and solar cells made of crystals to which SiC grains are fixed have the problem that leakage current occurs and solar energy conversion efficiency decreases.

Therefore, by reducing or eliminating SiC grains as in this embodiment, the energy conversion efficiency can be greatly improved.

In addition, although band-shaped silicon crystals with twins were insufficient to be used as substrates for other semiconductor devices, by creating crystals without twins, single crystal substrates obtained by the conventional Czochralski method could be used. There is a possibility that this will change.

Therefore, it becomes possible to obtain extremely long substrates, which was previously impossible, and a wide range of applications can be expected in addition to the benefits of resource and energy savings.

Note that the present invention is not limited to the embodiments described above.

For example, instead of silicon nitride, the capillary die may be made of a material that does not contain carbon, has strong resistance to silicon melt, and is less deformed at high temperatures, that is, Sialon.

Further, the metal film deposited on the inner surface of the slit of the capillary and die is not limited to aluminum, and may be made of magnesium, calcium, titanium, barium, or the like.

The reason why aluminum was selected in the example is that the band-shaped silicon crystal is P type and its performance as a semiconductor substrate is less likely to deteriorate with respect to the amount of impurities.

Further, the slit width, slit interval, etc. of the capillary die may be appropriately determined according to specifications.

In addition, various modifications can be made without departing from the gist of the present invention.

[Brief explanation of the drawing]

FIG. 1 is a schematic configuration diagram showing a conventional manufacturing apparatus for band-shaped silicon crystals, and FIGS. 2 to 4 each show the configuration of essential parts of an embodiment of the present invention. 3 is a plan view seen from above, and FIG.
A sectional view and FIG. 4 are sectional views taken along arrow B-B in FIG. 1... Crucible, 3a, 3b... Heater, 4... Silicon melt, 5... Band-shaped silicon crystal, 11a. Ilb... Capillary, die, 12a, 12b
...Spacer, 13... Aluminum film (metal film).

Claims (1)

[Claims] 1. A crucible containing a silicon melt, a capillary and a die each having a slit with one end immersed in the silicon melt in the crucible, and heating the silicon melt and the capillary/die. In the apparatus for manufacturing a band-shaped silicon crystal, the device comprises a heat source and grows a band-shaped silicon crystal by bringing a seed crystal into contact with the silicon melt rising through the capillary and the slit of the die and pulling up the seed crystal. - An apparatus for manufacturing a band-shaped silicon crystal, characterized in that the die is made of silicon nitride or Sialon, and a metal film is coated on the inner surface of the capillary and the slit of the die. 2. The apparatus for manufacturing a band-shaped silicon crystal according to claim 1, wherein the metal film is made of aluminum.