JPS5932426B2 - Semiconductor single crystal growth method and growth device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method and apparatus for pulling and growing a semiconductor single crystal.

When growing semiconductor crystals such as silicon and germanium, a quartz crucible is used, and a molten semiconductor raw material is placed in the crucible.The seed crystal is brought into contact with the liquid surface of the molten raw material and simultaneously rotated and pulled up. A commonly used method is to obtain a cylindrical single crystal by utilizing the fact that crystal growth occurs with solidification.

According to this method, quartz, which is a crucible material, chemically reacts with the molten semiconductor, so that oxygen, which is a component of quartz, mixes into the semiconductor crystal.

Therefore, a grown crystal usually contains approximately 1018 oxygen atoms/ml, and since such oxygen precipitates during the semiconductor device process and causes crystal defects, it has been conventionally difficult to add oxygen to the grown crystal. Many attempts have been made to suppress the incorporation of oxygen as much as possible, and it is becoming possible to grow crystals with low oxygen concentrations.

However, in recent years, as the effect of so-called intrinsic gettering, which attempts to capture microscopic defects on the semiconductor surface, which has an important meaning in semiconductor device formation, into crystal defects generated inside the semiconductor wafer, has become clear, The existence of oxygen mixed into the grown crystal, which is closely related to the occurrence of this phenomenon, is being reconsidered.

In other words, a semiconductor wafer containing oxygen above a certain concentration is subjected to appropriate heat treatment, crystal defects are generated inside the wafer due to the precipitation of oxygen compounds, and the surface defects or their sources are captured by internal defects, resulting in a defect-free state. The aim is to obtain a semiconductor surface.

FIG. 1 is a simplified schematic diagram of the growth of a semiconductor single crystal by a conventional pulling method.

A seed crystal 3 is brought into contact with a molten raw material 2 held in a quartz crucible 1, and a cylindrical crystal 4 is grown while giving rotation to the seed crystal (rotation may also be given to the crucible as necessary). .

At this time, the oxygen taken into the grown crystal mainly consists of oxygen eluted from the wall of the quartz crucible.

The amount of oxygen supplied from the quartz crucible wall is proportional to the contact area between the molten raw material and the quartz crucible.

In other words, oxygen mixed into the molten raw material rises along the crucible wall due to forced convection and natural convection, moves to the vicinity of the melt surface, and most of it evaporates from the melt surface, but some of it reaches the bottom of the single crystal (solid-liquid interface). It will be transported and incorporated into the growing crystal.

Therefore, the amount of oxygen taken into the grown crystal is determined by the segregation coefficient, which is a physical constant, as well as the melt-crucible area, melt surface area (
(evaporation area).

That is, when a single crystal with a constant diameter is grown, as it is pulled up, the evaporation area remains unchanged, but the contact area between the melt and the inner wall of the quartz crucible gradually decreases.

Figure 2 shows a schematic diagram of the state in which the pulling and growing has progressed.

As is clear from a comparison with FIG. 1, as the pulling growth progresses, while the melt evaporation area remains constant, the melt-quartz crucible contact area decreases.

Therefore, at -4, the upper part of the grown crystal has a high oxygen concentration, and the lower the crystal, the lower the oxygen concentration.

When considering the heat treatment applied to the semiconductor wafer for intrinsic gettering, the heat treatment conditions (temperature , time, etc.) are mainly determined by the oxygen concentration contained in the semiconductor wafer.

Therefore, if the oxygen contained in a semiconductor wafer cut out from a single grown crystal (ingot) changes as described above, the heat treatment conditions must be changed for each wafer, resulting in extremely low processing efficiency. bad.

In other words, if the oxygen concentration in the grown crystal is constant at a desired concentration from the top to the bottom of the ingot, a large amount of the webber can be extremely efficiently subjected to heat treatment effective for intrinsic gettering at once.

The present invention has been made in view of the above situation, and provides a method and apparatus for growing a semiconductor single crystal, which makes it possible to mix oxygen at a desired and constant concentration into each part of the growing crystal from the upper part to the lower part. It provides:

One feature of the present invention is that a double crucible is used, one inner wall of the crucible is covered with a silicon nitride film,
Since the outer wall of the other inner crucible is also a quartz crucible covered with a silicon nitride film, the inner crucible can be moved downward as the crystal grows, effectively
The method is to perform pulling growth while keeping the contact area between the wall surface of the quartz crucible and the raw material melt constant at an arbitrary value.

Hereinafter, details of the present invention will be specifically illustrated using the drawings.

FIG. 3 is a cross-sectional view showing an outline of the method for growing a semiconductor single crystal according to the present invention, in which the molten raw material 2 is filled in double crucibles having different constituents, which is a feature of the present invention.

The outer raw material crucible 5 is made of silicon nitride, or the crucible inner wall 6 is covered with silicon nitride.

The inner pulling crucible 7 is made of quartz, the outer wall 8 of the crucible is covered with a silicon nitride film, and the bottom of the crucible is provided with pores 9, through which the molten raw material 2 is passed from the raw material crucible 5 through the pores 9.
is supplied to the pot 7 which is pulled up.

As mentioned above, the oxygen taken into the grown crystal is mainly supplied from the quartz (Sin2) on the inner wall of the pulling crucible 7.

As the raw material melt surface is gradually lowered as described above as it is pulled and grown, the pulling crucible 7
A major feature of the present invention is to lower the .

That is, as shown in FIG. 4, as the pulling growth progresses, the contact area ratio between the raw material melt 2 and the outer raw material melt crucible 5 gradually decreases, but the contact area ratio between the inner pulling crucible 7 and the raw material melt 2 gradually decreases.
The relative positional relationship with

Since the inner wall 6 of the outer raw material crucible 5 and the outer wall 8 of the pulling crucible 7 are covered with silicon nitride, the amount of oxygen supplied is determined solely by the inner wall (quartz) of the pulling crucible 7 and the raw material melt, regardless of the oxygen supply. It is determined by the contact area with the liquid 2, and if the pulling crucible 7 is lowered in accordance with the pulling growth so as to keep this area, that is, the position of the raw material melt 2 surface with respect to the pulling crucible 7, constant. , the amount of oxygen supplied to the raw material melt 2' in the pulling crucible γ becomes constant.

It is also possible to set a desired oxygen concentration by arbitrarily adjusting the relative position of the raw material melt surface with respect to the pulling crucible 7, and furthermore, the moving speed of the pulling crucible 7 can be arbitrarily set. Accordingly, it is also possible to arbitrarily realize the oxygen concentration distribution within the growing ingot.

FIG. 5 is a sectional view showing the main parts of the semiconductor single crystal growth apparatus of the present invention, which includes a crucible 5 whose inner wall 6 is made of silicon nitride, a quartz crucible whose outer wall 8 is covered with silicon nitride, and which has pores 9 at the bottom. 7 are installed at the same position around the rotation axis 10, the quartz crucible 7 rotates around the rotation axis 10, and means (not shown) capable of moving the position of the crucible T up and down at an arbitrary speed. This is a feature not found in conventional single crystal growth equipment.

A further feature of the present invention is that a plurality of heating elements 1 are provided around the crucible 5.
2, and has a crucible heating device (not shown) having means (not shown) that can arbitrarily generate heat from the heating element.

It goes without saying that the growth apparatus of the present invention is equipped with conventional devices such as the crucible rotation mechanism 13 and the seed crystal support rotation mechanism 14.

The method of using the semiconductor single crystal growth apparatus of the present invention is as described above, but if we add the use of the heating element 12, as shown in FIG. However, adjusting the amount of heat generated by the upper heating element in accordance with the drop is a necessary operation in order to prevent the temperature inside the device from increasing unnecessarily.

As described above, by using the semiconductor single crystal growth method and growth apparatus of the present invention, it is possible to arbitrarily set the oxygen concentration in the grown crystal and to realize a uniform oxygen concentration distribution from the top to the bottom of the ingot, resulting in an extremely high The present invention makes an extremely large contribution to the semiconductor industry in that not only a high-quality single crystal can be obtained, but also an improvement in semiconductor element manufacturing yield can be achieved.

[Brief explanation of the drawing]

FIGS. 1 and 2 are diagrams schematically showing the state of single crystal growth by the conventional pulling method, and FIGS. 3 and 4 are diagrams explaining the semiconductor single crystal growth method of the present invention. 2,2'
... Raw material melt, 3... Seed crystal, 4...
...Growing crystal, 5...Raw material crucible, 6...
...Inner wall of raw material crucible made of silicon nitride, 7...
... Quartz pulling crucible, 8... Quartz crucible outer wall covered with silicon nitride, 9... Pores. FIG. 5 is a sectional view showing the main parts of the semiconductor single crystal growth apparatus of the present invention.
・・・・・・The thing to pull up is the support shaft, 12... Heat generating element, 13... Crucible rotation mechanism, 14...
... Seed crystal support rotation axis.

Claims (1)

[Claims] 1. In a semiconductor single crystal produced by a pulling method, a crucible whose inner wall is covered with a silicon nitride film or a first crucible made of silicon nitride is made of quartz whose outer wall is covered with a silicon nitride film. A second crucible with a hole in the bottom is installed, and the second crucible is
Fill a single-crystal raw material melt into a crucible, supply the raw material melt from the first crucible to the second crucible through the hole made in the bottom surface, and 7. A method for growing a semiconductor single crystal, comprising growing the single crystal while lowering the position of the second crucible in accordance with single crystal pulling growth so that the position is kept constant. 2 Inside a crucible whose inner wall is covered with a silicon nitride film or a first crucible made of silicon nitride, an outer wall centered with the second crucible is covered with a silicon nitride film and made of quartz with a hole at the bottom. a means for independently rotating each of the first and second crucibles; a means for moving the second crucible up and down at an arbitrary speed; 1. A semiconductor single crystal growth apparatus comprising a plurality of heating elements disposed around the heating element and a means for arbitrarily generating heat from the heating element.