JP4075136B2 - Single crystal growth equipment - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a single crystal growing apparatus used for manufacturing a silicon wafer or the like used for a semiconductor device, and more particularly to a single crystal growing apparatus by crystal pulling using a CZ method.
[0002]
[Prior art]
In the growth of a silicon single crystal by the CZ method, as shown in FIG. 4, a crucible 12 is arranged in the center of the chamber 11, and massive polycrystalline silicon loaded in the crucible 12 is arranged around the crucible 12. The raw material melt 40 is formed in the crucible 12 by melting under reduced pressure by the heater 14. Then, the seed crystal attached to the lower end of the pulling shaft is immersed in the raw material melt 40, and the single crystal is grown under the seed crystal by pulling it up while rotating.
[0003]
In the growth of a silicon single crystal by such a CZ method, in order to increase the pulling rate of the single crystal, it is a recent trend that an inverted conical cylindrical heat shielding member 20 called a cone is disposed above the crucible 12. is there. The heat shielding member 20 surrounds the single crystal pulled up from the raw material melt 40 in the crucible 12 and shields the radiant heat from the raw material melt 40 and the radiant heat from the heater 14 to promote cooling of the single crystal. It is possible to increase the pulling rate of the single crystal.
[0004]
In the growth of a silicon single crystal, various dopants (dopants) are used to adjust the specific resistance of the single crystal. Typical dopants are phosphorus, boron, antimony and the like. Among these dopants, phosphorus and boron are introduced into the crucible together with the bulk polycrystalline silicon before the raw material melt is formed in the crucible, that is, before the raw material is melted by the heater, and the polycrystalline silicon is heated by the heater. Dissolved together. Thereby, a raw material melt containing a predetermined amount of the dopant is formed in the crucible.
[0005]
On the other hand, antimony has a lower melting point than phosphorus and boron, and the evaporation rate becomes very high under reduced pressure. Therefore, when simultaneous dissolution with polycrystalline silicon is performed in the same manner as phosphorus and boron, a large amount of antimony is evaporated. For this reason, the procedure of adding a dopant to the melt after melting polycrystalline silicon in the crucible is followed. In the single crystal growth apparatus provided with the heat shielding member 20, the antimony is melted in the crucible 12 through the outside of the heat shielding member 20 by the dope supply pipe 30 provided outside the heat shielding member 20. The introduction into the liquid 40 is described in, for example, JP-A-4-21585.
[0006]
[Problems to be solved by the invention]
However, when antimony is added to the raw material melt 40 in the crucible 12 through the outside of the heat shielding member 20, the raw material melt 40 is formed in the crucible 12 in advance. There is a problem that antimony is heated to a high temperature during charging due to radiant heat and further radiant heat from the silicon raw material melt 40 formed in the crucible 12, and much of the antimony evaporates before reaching the raw material melt 40. Because of this problem, the concentration of antimony in the melt is lower than the amount charged, and it is necessary to add a large amount of antimony in an attempt to secure a predetermined concentration.
[0007]
Therefore, the inventors conducted an experiment in which antimony was added to the raw material melt 40 in the crucible 12 through the inside of the heat shielding member 20, as shown in FIG. As a result, it has been found that the antimony being charged is effectively shielded from the surrounding radiant heat by the heat shielding member 20, and its evaporation is suppressed. On the other hand, from the raw material melt 40 after the addition of antimony It has been clarified that the single crystal pulling frequently causes dislocations in the single crystal.
[0008]
The reason why dislocations frequently occur when antimony is introduced through the inside of the heat shielding member 20 will be described in detail later. The splash of the raw material melt 40 accompanying the introduction is granular on the inner surface of the heat shielding member 20. It adheres and this falls into the raw material melt 40 later and is taken in by the single crystal.
[0009]
The object of the present invention is to effectively suppress evaporation of the dopant when adding a highly evaporated dopant such as antimony to the raw material melt, and to reduce dislocation caused by the addition of the dopant. An object of the present invention is to provide an apparatus for growing a single crystal that can be prevented.
[0010]
[Means for Solving the Problems]
In order to achieve the above-mentioned object, the present inventors have detailed the merit in the case of adding antimony to the raw material melt in the crucible through the inside of the single crystal growing apparatus provided with the heat shielding member. We conducted a survey. As a result, the following was found and confirmed.
[0011]
In the case where a dopant such as antimony that is highly evaporated is added to the raw material melt in the crucible, the evaporation becomes remarkable when it passes through the outside of the heat shielding member. In order to suppress this evaporation, it is effective and indispensable to pass the inside of the heat shielding member. However, when passing through the inside of the heat shielding member, dislocation occurs frequently. As shown in FIG. 5, the cause is that the honey 41 of the raw material melt 40 resulting from the introduction of the dopant adheres to the inner surface of the heat shielding member 20 and solidifies in the form of particles, and the grains grow thereafter as a single crystal. It falls into the liquid surface of the raw material melt and is taken into the single crystal.
[0012]
Naturally, this splash also occurs when the dopant is introduced through the outside of the heat shielding member. However, in this case, the honey adheres to the outer surface of the heat shielding member. Since the ambient temperature on the outer surface side is higher than that on the inner surface side, the honey adhering to the outer surface spreads thinly on the outer surface and solidifies in a state where it adheres firmly. The honey solidified in such a state is difficult to peel off from the outer surface. For this reason, no fall occurs during subsequent single crystal growth, and even if dropped, it does not cause dislocation because it is liquid.
[0013]
On the other hand, since the adhering to the inner surface of the heat shielding member has a low atmospheric temperature on the inner surface side, it solidifies in a granular form after adhering. For this reason, it becomes easy to peel from the inner surface of the heat shielding member, and the material that has peeled and dropped onto the surface of the raw material melt is taken into the single crystal as a solid and causes dislocation. This is a cause of frequent occurrence of dislocation when the dopant is added through the inside of the heat shielding member. In fact, the dislocations caused by honey tend to occur frequently at the initial stage of pulling up shortly after the addition of the dopant.
[0014]
Based on these examination results, the present inventors dropped the dope agent halfway through the inside of the heat shielding member, led the dope agent to the outside of the heat shield member from the middle, and put it into the raw material melt Tried to do. As a result, it was found that even with antimony, evaporation is effectively suppressed, and dislocations caused by honey are prevented.
[0015]
The single crystal growing apparatus of the present invention has been developed based on such knowledge. A raw material melt is formed in the crucible by a heater arranged outside the crucible, and the single crystal is formed from the raw material melt by the CZ method. A heating apparatus body for pulling up, a cylindrical heat shield member disposed so as to surround the single crystal above the crucible to shield the radiant heat from the heater and the raw material melt, and the raw material melt in the crucible disposed inside the heat shielding member to the addition of antimony or arsenic as a dopant, and the raw material melt in the crucible the dopant in below the middle position is derived to the outside of the heat shield member of the heat shield member And a dope supply pipe disposed with at least the lower end facing the outside of the heat shielding member.
[0016]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a longitudinal sectional view of a single crystal growing apparatus according to an embodiment of the present invention.
[0017]
This single crystal growth apparatus is a growth apparatus main body 10 for pulling up a single crystal by the CZ method, a heat shielding member 20 provided in the growth apparatus main body 10 for increasing the pulling speed, and a growth for adding a dopant. And a dope supply pipe 30 provided inside the apparatus main body 10.
[0018]
The growth apparatus main body 10 includes a cylindrical main chamber 11. The main chamber 11 has a structure in which a cylindrical portion 11a, a bottom plate portion 11b (see FIG. 5) on which the cylindrical portion 11a is placed, and a top plate portion 11c placed on the cylindrical portion 11a are combined. A pull chamber (not shown) is placed on the top plate portion 11c. The pull chamber has a pulling shaft, a rotating lift mechanism and the like.
[0019]
In the main chamber 11, a crucible 12 is disposed at the center thereof. The crucible 12 has a double structure in which an inner quartz crucible 12a and an outer graphite crucible 12b are combined. The crucible 12 is supported on a pedestal 13 that penetrates the bottom plate portion 11 b of the main chamber 11. The pedestal 13 is driven in the circumferential direction and the axial direction in order to rotate and lift the crucible 12.
[0020]
A heater 14 is disposed outside the crucible 12, and a heat insulating material 15 is disposed outside the heater 14 along the inner surface of the cylindrical portion 11 a of the main chamber 11. A similar heat insulating material 16 is also disposed on the bottom plate portion 11 b of the main chamber 11.
[0021]
The heat shielding member 20 is a cylindrical body called a cone disposed concentrically above the crucible 12. The cylindrical body has an inverted trapezoidal shape with a diameter gradually reduced downward, and is attached to the top plate portion 11 c of the main chamber 11.
[0022]
The dope supply pipe 30 is a funnel pipe attached to the inner surface of the heat shielding member 20 along its inclination. The lower end portion passes through the lower part of the heat shielding member 20 and faces the outside of the heat shielding member 20. The upper end portion of the dope supply pipe 30 is connected to a dope additive addition jig 31 provided outside the main chamber 11. As the jig 31, for example, a dopant adding device described in JP-A-9-227275 can be used.
[0023]
Next, a procedure for manufacturing a silicon single crystal doped with antimony using the present single crystal growing apparatus will be described.
[0024]
The crucible 12 is filled with massive polycrystalline silicon. The main chamber 11 is evacuated to a predetermined degree of vacuum. Polycrystalline silicon in the crucible 12 is melted by the heater 13 to form a silicon melt 40 in the crucible 12.
[0025]
When the silicon melt 40 is formed in the crucible 12, a predetermined amount of antimony is introduced into the dope supply pipe 30 by a dopant addition device provided outside the main chamber 11. Here, the dope supply pipe 30 is basically disposed inside the heat shielding member 20, and only the lower end thereof penetrates the lower part of the heat shielding member 20 and faces the outside of the heat shielding member 20. For this reason, the antimony introduced into the dope supply pipe 30 passes through the inside of the heat shielding member 20 until reaching the lower level of the heat shielding member 20, and thereafter, is led out to the outside of the heat shielding member 20 and on the outside thereof. The silicon melt 40 in the crucible 12 is charged.
[0026]
Since the inner side of the heat shielding member 20 is cooler than the outer side, evaporation of antimony passing through the dope supply pipe 30 is suppressed. Eventually, since antimony is charged into the silicon melt 40 outside the heat shielding member 20, the splash accompanying the charging adheres to the outer surface of the heat shielding member 20. However, since the flakes are thinly spread on the outer surface of the heat shielding member 20 and solidify in a tightly attached state, they do not fall easily and do not cause dislocation.
[0027]
By introducing antimony in this way, a silicon melt 40 doped with antimony at a predetermined concentration is formed in the crucible 12.
[0028]
When the formation of the silicon melt 40 is completed, the seed crystal attached to the lower end of the pulling shaft is immersed in the silicon melt 40, and the pulling shaft is pulled up from this state while rotating the pulling shaft. Thereby, a silicon single crystal doped with antimony is grown below the seed crystal. The grown crystal passes through the inside of the heat shielding member 20 and is drawn into the pull chamber. At this time, the crucible 12 rotates in the reverse direction. Moreover, it rises to offset the liquid level drop in the crucible 12 accompanying the pulling of the single crystal.
[0029]
In the growth of the single crystal after the addition of antimony, there is no drop of honey from the heat shielding member 20, and dislocation formation is prevented.
[0030]
【Example】
Next, examples of the present invention will be shown, and the effects of the present invention will be clarified by comparing with comparative examples.
[0031]
As an example of the present invention, a silicon single crystal doped with antimony was grown using the single crystal growth apparatus shown in FIG. The inner diameter of the crucible was 16 inches with the inner diameter of the quartz crucible. The filling amount of polycrystalline silicon was 35 kg, and the input amount of antimony was 300 g. The diameter of the grown crystal is 5 inches and the crystal orientation is <100>.
[0032]
As Comparative Example 1, when the single crystal growing apparatus shown in FIG. 4 was used and antimony was charged into the silicon melt in the crucible, the charging was performed outside the heat shielding member. The rest is the same as the embodiment.
[0033]
As Comparative Example 2, the single crystal growing apparatus shown in FIG. 5 was used, and when antimony was charged into the silicon melt in the crucible, the charging was performed inside the heat shielding member. The rest is the same as the embodiment.
[0034]
For each case, 40 pulls were performed. The pulling yield was investigated in the case of Example and Comparative Example 2. The result is shown in FIG. In addition, the specific resistance of the single crystal that could be pulled up was investigated in the case of Example and Comparative Example 1. The result is shown in FIG.
[0035]
As can be seen from FIGS. 2 and 3, in the embodiment of the present invention, the number of operations capable of raising the total length exceeds 50% of the total number of operations, and reaches nearly 70% when an operation close to full length is added. The specific resistance of the grown crystal was about 0.014 Ω · cm when 300 g of antimony was used.
[0036]
On the other hand, when introducing antimony into the silicon melt in the crucible, in Comparative Example 1 in which the introduction was performed outside the heat shielding member, the pulling yield was similar to that of the example of the present invention, The specific resistance of the grown crystal decreased only to about 0.0155 Ω · cm when 300 g of antimony was used. This means that most of the antimony used was evaporated before being introduced into the melt, and did not contribute effectively to the increase in the concentration of the dopant in the melt.
[0037]
Incidentally, in order to reduce the specific resistance to the same 0.014 Ω · cm level as in the embodiment of the present invention, about 360 g of antimony is required, and the amount used is 1.2 times that of the embodiment of the present invention.
[0038]
On the other hand, in Comparative Example 2 in which antimony was introduced inside the heat shielding member, the specific resistance, that is, the required amount of antimony, was the same as that of the example of the present invention. However, dislocations frequently occurred at the initial stage of pulling up, and operations that allowed the full length to be raised were only 20% of the total number of operations. This is because honey accompanying the introduction of antimony has led to the cause of dislocation.
[0039]
Thus, in the Example of this invention, the used dopant is utilized effectively and the dislocation | rearrangement accompanying the addition of a dopant is prevented.
[0040]
In the above example, antimony is used as a dopant, but the present invention is also effective for the addition of a dopant other than antimony, such as arsenic (As).
[0041]
In the above example, the dope agent dropping path in the present invention, that is, the dope supply pipe disposition path is led out from the inside to the outside of the heat shielding member at the lower part of the heat shielding member. Depending on the kind of the dopant, the ambient temperature, and the like, this derivation may be performed at the middle stage of the heat shielding member, and it is also possible to bypass the lower portion of the heat shielding member.
[0042]
【The invention's effect】
As is clear from the above description, the single crystal growing apparatus of the present invention is configured to pass the inside of the heat shielding member halfway when the dope is introduced into the raw material melt formed in the crucible. Therefore, evaporation of the dopant during the charging can be suppressed and the amount of use can be reduced. In addition, since it is configured to be charged into the raw material melt outside the heat shielding member in the end, it is possible to prevent dislocation due to the charging, and together with the saving of the dopant, The cost for growing a single crystal can be greatly reduced.
[Brief description of the drawings]
FIG. 1 is a longitudinal sectional view of a single crystal growing apparatus according to an embodiment of the present invention.
FIG. 2 is a graph showing the effect of the present invention by raising yield.
FIG. 3 is a graph showing the effect of the present invention by the specific resistance of a single crystal.
FIG. 4 is a longitudinal sectional view of a conventional single crystal growth apparatus.
FIG. 5 is a vertical cross-sectional view of a single crystal growing apparatus cited as a comparative example.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 Growing apparatus main body 11 Main chamber 12 Crucible 13 Pedestal 14 Heater 15, 16 Heat insulating material 20 Heat shielding member 30 Dope supply pipe 40 Silicon melt (raw material melt)

Claims (1)

A growth apparatus body for forming a raw material melt in the crucible by a heater arranged outside the crucible, and pulling the single crystal from the raw material melt by the CZ method, and a crucible to shield the radiation heat from the heater and the raw material melt A cylindrical heat shielding member disposed so as to surround the single crystal above, and disposed inside the heat shielding member for adding antimony or arsenic as a dopant to the raw material melt in the crucible, and as the dopant in below the middle position of the heat shield member is inserted in the raw material melt in the outer to be derived crucible of the heat shield member, distribution and at least the lower end portion to face the outside of the heat shield member A single crystal growth apparatus comprising a dope supply pipe provided.

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