JP4684396B2 - Single crystal puller - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention includes a cable-type CZ method single crystal pulling apparatus and a method for pulling a single crystal from a raw material melt by a CZ method (Czochralski method), including a cable and other pulling members for pulling a single crystal, The present invention relates to a CZ method single crystal pulling apparatus and method to which a mechanism for suppressing the fluctuation width of a single crystal due to the resonance of a cable system that occurs during pulling of a single crystal is added.
[0002]
[Prior art]
According to the CZ method single crystal pulling apparatus, the single crystal is pulled from the raw material melt while rotating. In order to meet the strict demands for cost reduction of single crystal wafers in recent years, it has been performed to pull ingots as long as possible. In order to realize such a long ingot, a normal CZ method single crystal pulling apparatus lowers the liquid surface of the raw material melt or stores a chamber (upper stage) for storing the pulled ingot. For example, the chamber may be lengthened.
By the way, in a cable type CZ method single crystal pulling apparatus in which a single crystal is pulled by a cable (wire), resonance of the cable system occurs with the rotation of the single crystal. Then, when the swing width of the single crystal due to the resonance exceeds an allowable amount, the pulling of the crystal is not stable, and when it is severe, the pulling of the crystal cannot be performed.
[0003]
Here, when the cable system is considered as a pendulum composed of “cable”, “seed chuck and single crystal”, etc., the resonance speed n of the cable system is n = (60 / 2π) × (g / L) ^1. Determined by ^{/ 2} . In this equation, g represents the total weight (unit: g) of the seed chuck and single crystal located at the bottom of the cable system, and L represents the distance (unit: cm) from the fulcrum of the pendulum to the center of gravity. The unit of the resonance rotational speed n is rpm (rotational speed per minute)).
[0004]
As is apparent from the above equation, the resonance speed of the cable system is determined by the cable length, so the crystal will resonate and shake at a crystal speed close to the resonance speed, and the pulling will not be stable, When the position of the wire take-up mechanism is raised by modifying the device, etc., a new resonance speed is set according to the increase in the cable length, and in particular a crystal lower than the resonance point. When the crystal is pulled up at the number of revolutions, there arises a disadvantage that it is impossible to pull up at the number of revolutions that was possible until then.
[0005]
[Problems to be solved by the invention]
In this regard, in a normal cable type CZ method single crystal pulling device, the cable length, device size, and other various factors are set such that resonance does not occur in this cable system (or the fluctuation width due to resonance falls within an allowable range). Conditions are preset.
However, as described above, when the length of the raw material melt is lowered or the length of the ingot storage portion is increased in order to realize the lengthening of the pulled ingot, the cable length becomes long. In such a case, the resonance speed in the cable system decreases, and other predetermined conditions set so that resonance does not occur (or the fluctuation width due to resonance falls within an allowable range). If this is followed as it is, the resonance generated in the cable system may increase in accordance with the resonance rotational speed that has changed as the cable length becomes longer.
[0006]
The present invention has been made in view of the problems as described above. The purpose of the present invention is to satisfy various conditions in the apparatus such as the cable length in order to realize the lengthening of the ingot pulled up in the CZ method single crystal pulling apparatus. Provided is a cable-type CZ method single crystal pulling apparatus capable of suppressing the resonance of a cable system even when changed, and simultaneously realizing a longer ingot and a higher crystal rotation speed setting in a straight body portion of the ingot. There is.
[0007]
[Means for Solving the Problems]
In order to achieve the above object, as a result of intensive studies by the present inventors, it has been found that the reverse movement of the center of gravity movement of the pendulum system occurs due to the pulling up of the crystal, and all such circumstances are taken into consideration. The inventors have found that stable crystal pulling can be performed by setting various conditions relating to the apparatus, and the present invention has been completed.
In addition, the present inventors are the most effective and simplest capable of suppressing resonance and solving the problem of resonance even when various conditions in the apparatus are changed in order to realize a long ingot to be pulled up. As a method, it has been found that changing the weight of the seed chuck is appropriate, and the present invention has been completed.
[0008]
More specifically, the present invention provides the following.
[0009]
(1) A cable-type CZ method single crystal pulling apparatus that includes a cable or other pulling member for pulling a single crystal and pulls the single crystal from the raw material melt by the CZ method. When the crystal rotation speed is lower than the resonance speed of the cable system, considering that the resonance speed of the cable system decreases due to the movement of the center of gravity on the lifting member when forming the shoulder portion of the single crystal, A design method of a cable-type CZ method single crystal pulling apparatus, wherein the weight of the seed chuck and / or the length of the cable to the seed chuck are designed within a range in which the crystal swing due to resonance generated in the crystal is allowed. .
[0010]
(2) A cable-type CZ method single crystal pulling apparatus that includes a cable or other pulling member for pulling a single crystal and pulls the single crystal from the raw material melt by the CZ method. Cable-type CZ method single crystal pulling in which the weight of the seed chuck and / or the length of the cable to the seed chuck is set in preparation for a decrease in the resonance speed of the cable system when the center of gravity moves on the pulling member apparatus.
[0011]
(3) A single crystal pulling method for pulling a single crystal from a raw material melt by a cable type CZ method, wherein the resonance speed of the cable system is changed when the center of gravity moves on the pulling member when the shoulder portion of the single crystal is formed. In consideration of the decrease, the single crystal is pulled up by performing seed drawing of a length set in a range in which at least the fluctuation width of the crystal due to the resonance is suppressed in the single crystal straight body portion. Pulling method.
[0012]
(4) A seed chuck used in a cable-type CZ method single crystal pulling apparatus, wherein the constituent members of the existing seed chuck are made of an inert high-density material member. Seed chuck.
[0013]
(5) The resonance-suppressing seed chuck according to (4), wherein the inert high-density substance is tungsten.
[0014]
(6) A method for stably obtaining a straight body portion of a silicon single crystal ingot by forming a constituent member of a seed chuck used in a cable type CZ method single crystal pulling apparatus from a member made of an inert high-density material. .
[0015]
(7) The method according to (6), wherein the inert high-density substance is tungsten.
[0016]
(8) The cable type CZ method single crystal pulling apparatus according to (2), which is an apparatus for stably obtaining a straight body portion of a silicon single crystal ingot.
[0017]
(9) An apparatus for stably obtaining a straight body portion of a silicon single crystal ingot, wherein the constituent member of the seed chuck is made of an inert high-density material member to suppress the resonance of the cable system A cable-type CZ method single crystal pulling apparatus characterized by the above.
[0018]
(10) The cable type CZ method single crystal pulling method according to (8) or (9), wherein the straight body portion of the silicon single crystal ingot is stably obtained at a higher single crystal rotation speed. apparatus.
[0019]
(11) A seed chuck for pulling up a long ingot used for a single crystal pulling apparatus whose setting has been changed for pulling up the long ingot, wherein the seed chuck is made of an inert high-density material. A seed chuck for pulling up a long ingot, characterized by being made of a member.
[0020]
(12) A method for shortening the neck portion formed by the dash neck method and / or increasing the rotational speed of the single crystal by using the seed chuck according to (11).
[0021]
This “shortening of the neck portion” eliminates the necessity of adopting the dash neck method when the neck portion is zero, that is, by adding boron to the seed crystal at a predetermined concentration, and there is no neck portion at all. This includes cases where it disappears.
[0022]
Here, the “inert high-density material” means a material that does not cause a chemical reaction in the atmosphere in the CZ furnace and has a high density exceeding that of molybdenum. The inert high-density substance may be a simple substance or a compound, and preferable examples include tungsten simple substance and tungsten compound.
[0023]
Further, the conversion to the member made of inert high density material in (4) and (5), and the configuration of the member made of inert high density material in (7) may be a part of the seed chuck. Such a change or configuration is included in the scope of the present invention when a change in weight that affects the resonance speed of the cable system is applied to the seed chuck.
[0024]
In the above (8), “the setting has been changed for pulling up the long ingot” means, for example, the cable length in the cable system (more specifically, from the end of the cable take-up device, This means a case where the initial setting of the distance to the seed crystal at the time of liquid is changed.
[0025]
Here, in the single crystal pulling apparatus according to the present invention, the seed chuck includes an inert high-density material member such as a tungsten member or a tungsten compound member, thereby increasing the weight of the seed chuck.
[0026]
On the other hand, if the length of the upper chamber is increased, the cable also becomes longer, and the resonance speed of the cable system becomes smaller. This is compensated for by increasing the weight of the seed chuck at least in the straight body portion of the ingot. The And since the length of the upper chamber is set to be long, it is possible to accommodate a single crystal having a long straight body portion stably obtained by this apparatus. That is, according to this apparatus, the amount of resonance that is likely to increase as the length of the upper chamber is increased and the cable becomes longer is prevented in a state that is prevented by increasing the weight of the seed chuck. Can be stably pulled, and the length of the upper chamber is set long, so that a single crystal having a long straight body portion stably obtained by the present apparatus can be accommodated. (Above (8)).
[0027]
This also applies to the case where the neck portion is shortened and the cable is set to be longer, and the seed chuck is heavier for the portion where resonance tends to increase as the cable becomes longer. Thus, the single crystal can be stably pulled up in a state prevented by the above, and a long ingot corresponding to the shortened neck portion can be obtained ((9) above).
[0028]
According to the present invention, when the length of the upper chamber for storing the pulled silicon single crystal ingot is set longer according to the weight of the seed chuck increased by including the inert high-density material member. There is also.
[0029]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 is a diagram for explaining the present invention, and shows a cable system in a single crystal pulling apparatus as a pendulum system model composed of “cable” and “seed chuck and single crystal”. Moreover, FIG. 2 is a figure for demonstrating the movement of the gravity center at the time of pulling of a single crystal.
[0030]
As shown in FIG. 1, a cable system 10 in a single crystal pulling apparatus is attached to a cable winding drum 11, a cable (tungsten wire) 13 wound up by the cable winding drum 11, and the end of the cable 13. The seed chuck 14, a neck (seed restricting portion) 15 extending from the seed chuck 14, and a single crystal 17 pulled up from the raw material melt 16 using the neck 15. The neck (seed squeezing part) 15 is formed by seeding a seed (seed crystal) held by the seed chuck 14 (dash neck method).
[0031]
As shown in FIG. 1, the cable system 10 of such a single crystal pulling apparatus can be assumed to be a pendulum that swings with the cable winding drum 11 as a fulcrum. L in the expression “n = (60 / 2π) × (g / L) ^1/2 ” for determining the resonance speed n of the cable system is the center of gravity of the cable system from the cable unwinding position of the cable winding drum 11. It will be the distance to the place.
[0032]
Here, the “center of gravity of the cable system” moves as the single crystal is pulled up. That is, as shown in FIG. 2, the center of gravity P of the cable system is on the seed chuck 14 in the state where the neck 15 is formed (the state of FIG. 2A), but the shoulder portion 17 a of the single crystal 17. Is formed, it moves downward as the weight of the single crystal 17 increases (state shown in FIG. 2B). In the state where the single crystal 17 is pulled up, the single crystal 17 is heavier than the seed chuck 14, and most of the weight of the cable system is in the single crystal 17. Exists on the single crystal 17.
[0033]
Thus, when the shoulder portion 17a of the single crystal 17 is formed with the pulling of the single crystal, the center of gravity P of the cable system moves downward, so the cable for the crystal length measured from the seed (seed crystal) When the change in the resonance speed n of the system is examined, the change in the resonance speed n of the cable system does not increase monotonously, but draws a cubic curve as shown in FIG. In FIG. 3, parts corresponding to those shown in FIGS. 2A, 2B, and 2C are denoted by the same (a), (b), and (c). That is, when the single crystal is pulled up, the resonance rotational speed n increases monotonously until the formation of the shoulder portion 17a of the single crystal 17, but the center of gravity is increased during the formation of the shoulder portion 17a. As P moves downward, it starts to decrease, forms a minimum portion α, and starts to increase again.
[0034]
Here, when the single crystal 17 is grown while being rotated, the cable length of the single crystal pulling device and others are set with respect to the rotational speed m ₀ of the single crystal 17. For example, according to the conventional hypothesis, a monotonically increasing change as shown in (c) in FIG. 3 was assumed, but as shown in (a) and (b) in FIG. As a result, it was found that the resonance rotational speed decreased, the minimum portion α was formed, and the increase started again.
Further, (a) in FIG. 3 shows the change in the resonance speed when a conventional molybdenum seed chuck is used, and (b) shows the change in the tungsten seed chuck. This shows the change in resonance speed when used. As is apparent from this figure, when a tungsten seed chuck is used, the resonance speed of the portion of the minimum portion α increases, A resonance suppression effect can be obtained when the resonance rotational speed of the local minimum portion α is away from the rotational speed m ₀ of the single crystal 17.
[0035]
Here, in (a) and (b), at least a value of about n = 0.5 is opened at the minimum portion α (that is, the resonance speed n is opened at 1 or more at the minimum portion α). Such a setting can be realized by adjusting the weight of the seed chuck, the length of the cable to the seed chuck, and the length of the portion of the seed restrictor individually or in combination. . Among them, it is simplest and most effective to change the constituent member of the current seed chuck 14 made of molybdenum to one made of tungsten. For example, by converting about 50% of the constituent members of the current seed chuck 14 to those made of tungsten, conversion from the above (a) to (b) (n is increased by 1 or more at the minimum portion α). Can be realized. The conversion of the components of the current seed chuck 14 to those made of tungsten is preferably 50% or more, more preferably 60% or more, still more preferably 70% or more, more preferably 80% or more, and even more preferably 90%. % Or more is preferable.
The adjustment as described above for suppressing the fluctuation width of the single crystal 17 due to resonance is basically performed when the straight body portion of the single crystal 17 is formed. In other words, in the step before the formation of the shoulder portion 17a of the single crystal 17, the rotation speed of the single crystal 17 can be set so as to avoid the resonance rotation speed determined by the assembled apparatus. In other words, for example, the conversion to the tungsten seed chuck as described above is performed in order to secure a desired rotational speed at least in the straight body portion of the single crystal 17.
[0036]
FIG. 4 is a block diagram showing the overall configuration of a cable-type CZ method single crystal pulling apparatus as one embodiment of the present invention. As shown in FIG. 4, the CZ method single crystal pulling apparatus according to this embodiment includes an upper chamber 21 </ b> X, an intermediate chamber 21 </ b> Y, and chambers 21 constituting the outer shell of the apparatus being separable. The upper chamber 21 </ b> X and the middle chamber 21 </ b> Y are rotated about the rotation axis Q by the driving force of the motor 23. Then, the upper chamber 21X, the middle chamber 21Y, and the lower chamber 21Z are moved to predetermined positions when the single crystal 17 is pulled, and the upper chamber 21X and the middle chamber 21Y move to predetermined positions, respectively. The upper chamber 21X is mounted and fixed on the middle chamber 21Y and further on the middle chamber 21Y, and the chamber 21 is configured as a whole.
[0037]
Here, the single crystal after the pulling is accommodated in the upper chamber 21X. According to this apparatus, the increase in resonance associated with the increase in the length of the upper chamber 21X and the length of the cable 13 is prevented by, for example, increasing the weight of the seed chuck 14 while preventing the single crystal 17 from becoming heavy. Can be lifted stably. Along with this, the length of the upper chamber 21X is set to be long, so that a single crystal having a long straight body portion stably obtained by the present apparatus can be accommodated.
[0038]
【The invention's effect】
According to the present invention as described above, resonance of the cable system of the cable type CZ method single crystal pulling apparatus can be prevented with a simple configuration and mechanism, and stable pulling of the single crystal can be realized. Moreover, according to this apparatus, a single crystal ingot provided with a long straight body part can be obtained stably.
[0039]
In addition, as a reflective effect, in the cable type CZ method single crystal pulling apparatus, it is possible to increase the number of crystal rotations when pulling the crystal.
[Brief description of the drawings]
FIG. 1 is a diagram for explaining the present invention, and shows a cable system in a single crystal pulling apparatus as a pendulum system model including “cable” and “seed chuck and single crystal”.
FIG. 2 is a diagram for explaining the movement of the center of gravity when pulling a single crystal.
FIG. 3 is a diagram showing a change in resonance speed n of a cable system with respect to a crystal length measured from a seed (seed crystal) when a single crystal is pulled.
FIG. 4 is a block diagram showing an overall configuration of a cable-type CZ method single crystal pulling apparatus as one embodiment of the present invention.
[Explanation of symbols]
10 Cable System 11 Cable Winding Drum 13 Cable (Tungsten Wire)
14 Seed chuck 15 Neck (seeding part)
16 Raw material melt 17 Single crystal P Cable center of gravity 17a Shoulder portion m _{0 of} single crystal 17 Rotational speed of single crystal 17 21 Chamber 21X Upper chamber 21Y Middle chamber 21Z Lower chamber 23 Motor Q Rotating shaft

Claims (6)

A cable-type CZ method single crystal pulling apparatus for pulling a single crystal from a raw material melt by a CZ method, comprising a cable or other pulling member for pulling a single crystal,
In the process of pulling up the single crystal, the resonance speed of the cable system monotonously increases until the formation of the shoulder portion of the single crystal, and when the shoulder portion of the single crystal is formed, a maximum portion is formed and then decreases. Based on the fact that the minimum portion is formed and increased again when forming the straight body portion of the single crystal, the resonance frequency at the minimum portion is 1 rpm or more higher than the resonance frequency at the start of seed drawing, design method of cable-type CZ single crystal pulling apparatus characterized by designing the weight of the seed chuck. A cable-type CZ method single crystal pulling apparatus comprising a cable and other pulling members for pulling a single crystal, and pulling the single crystal from the raw material melt by the CZ method,
In the process of pulling up the single crystal, the resonance speed of the cable system monotonously increases until the formation of the shoulder portion of the single crystal, and when the shoulder portion of the single crystal is formed, a maximum portion is formed and then decreases. Based on the fact that the minimum portion is formed and increased again when forming the straight body portion of the single crystal, the resonance frequency at the minimum portion is 1 rpm or more higher than the resonance frequency at the start of seed drawing, weight is set cabled CZ single crystal puller of the seed chuck. 2. The design method of a cable type CZ method single crystal pulling apparatus according to claim 1, wherein the constituent member of the seed chuck is made of an inert high density material member. 4. The method of designing a cable type CZ method single crystal pulling apparatus according to claim 3, wherein the inert high-density material is tungsten. 3. The cable type CZ method single crystal pulling apparatus according to claim 2, wherein the constituent member of the seed chuck is made of an inert high density material member. 6. The cable type CZ single crystal pulling apparatus according to claim 5, wherein the inert high-density material is tungsten.

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