JP2016060667A - Resistivity control method, additional dopant feed device, and n-type silicon single crystal - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a resistivity control method capable of suppressing a decrease in yield and also precisely controlling resistivity when silicon single-crystal raising by a CZ method is interrupted, and a silicon single crystal having been raised is molten again to be raised again.SOLUTION: A resistivity control method of controlling resistivity of a silicon single crystal raised by a CZ method with a dopant includes the processes of: performing initial doping with a main dopant so that the silicon single crystal has a predetermined conductivity type; and performing continuous or intermittent additional doping with a sub-dopant having the opposite conductivity type from the main dopant according to a solidification rate while raising the silicon single crystal, in which the raising of the silicon single crystal interrupted and the silicon single crystal having been raised is molten again to be raised again, the silicon single crystal is raised again after being doped with the main dopant by such an amount that top-side resistivity of a product part is within a standard if additional dopant with the sub-dopant is performed before the interruption.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a resistivity control method for a silicon single crystal grown by the CZ method, an additional dopant injection device used in this resistivity control method, and an n-type whose resistivity is controlled using this resistivity control method. It relates to a silicon single crystal.

  In a switching device used for power, such as an IGBT (insulated gate bipolar transistor), an n-type single crystal is mainly used. Conventionally, EPW (epitaxial wafer) and FZ-PW (wafer manufactured by FZ method) whose resistivity control is relatively easy have been used. However, EPW is an expensive wafer because it includes an extra step (epitaxial growth step) compared to CZ-PW (wafer manufactured by CZ method), and it is not easy to increase the crystal diameter in FZ method. Therefore, CZ-PW which is used as it is without stacking an epitaxial layer on CZ-PW is attracting attention. However, a silicon single crystal manufactured by the CZ method has a segregation phenomenon, and it is difficult to make the resistivity distribution in the axial direction (the pulling-up axis direction) uniform.

  As methods for solving this, Patent Documents 1 and 2 disclose a method of adding a main dopant and a subdopant having a polarity opposite to that of the main dopant and a small segregation coefficient (that is, counter-doping). By using this method, it is possible to improve the axial resistivity distribution of the CZ single crystal. However, the dopant most frequently used in the manufacture of n-type single crystals is phosphorus (P), and its segregation coefficient is about 0.35. On the other hand, elements having opposite polarity and having a segregation coefficient smaller than that of phosphorus (P) are Ga, In, Al and the like. These elements are heavy metals. For example, there is a report that the electrical characteristics of the oxide film deteriorate when contained in the oxide film, and it is not well understood how it affects the device characteristics. For this reason, B (boron) is the mainstream p-type dopant and is an element that is widely used in fabricating devices, so it is widely used in fabricating devices as elements of opposite polarity if possible. It is preferable to use boron (B). However, the segregation coefficient of boron (B) is about 0.78, which is larger than that of phosphorus (P), and the above technique cannot be used.

  As means for solving this problem, Patent Document 3 discloses a method of continuously adding boron (B) to phosphorus (P) as a main dopant. By using this method, an n-type single crystal with improved axial resistivity distribution can be produced by counterdoping with phosphorus (P) as the main dopant and boron (B) as the sub-dopant.

JP 2002-128591 A Japanese Patent Laid-Open No. 2004-307305 JP-A-3-247585 Japanese Patent Laid-Open No. 10-029894 Japanese Patent Application Laid-Open No. 6-234592

  However, the method disclosed in Patent Document 3 has a problem in that it cannot be remelted when the single crystal is dislocated. In the production of a single crystal in the normal CZ method (including the MCZ method), it often occurs that the single crystallization is inhibited for some reason and dislocations are generated. When dislocation occurs, a phenomenon called slip-back occurs in which dislocations generated in the dislocation portion are already single-crystallized but slip to a portion still in a high temperature state. For this reason, a single crystal can be obtained only by the length obtained by subtracting the slip-back length from the length at which dislocations have occurred. Furthermore, since the top portion of the single crystal has a portion other than the resistivity, such as the oxygen concentration and the grown-in defect characteristics, does not fall within the standard value, the portion having a certain length or more from the top portion is generally a product. Is set for. Therefore, when dislocations occur in a single crystal having a relatively short length, the product cannot be obtained at all due to the portion not suitable for the top portion and slip back. For this reason, dislocation crystals are submerged in a raw material melt (silicon melt) and remelted, and single crystal production is performed again. When the method of Patent Document 3 is used, since the dopant having the opposite polarity is already contained in the single crystal and the raw material melt at the time when the dislocation is generated, if this is remelted, the main dopant Will be in a state where there is a shortage, and it will not be possible to obtain a product. Accordingly, there is a problem in that the yield is greatly reduced since the dislocation portion is separated from the raw material melt and removed.

  In addition, Patent Document 4 discloses a method in which dopants having opposite polarities are accommodated in the bottom of the crucible, and these are eluted before the resistivity decreases. However, this method does not control the solidification rate or single crystal length but controls the amount of crucible dissolved. Since melting of the crucible proceeds even during remelting, if remelted, the dopant to be added will be dissolved earlier than the target position, and the resistivity will increase. Therefore, it cannot be remelted even in this method.

  The present invention has been made in view of the above-described problems, and it is possible to interrupt the growth of a silicon single crystal by the CZ method, remelt the grown silicon single crystal, and re-grow the silicon single crystal. It is an object of the present invention to provide a resistivity control method that can suppress the decrease in resistance and can accurately control the resistivity of a silicon single crystal.

  In order to achieve the above object, the present invention provides a method for controlling the resistivity of a grown silicon single crystal with a dopant when growing the silicon single crystal by a CZ method, wherein the silicon single crystal is a predetermined one. The step of initially doping the main dopant so as to have a conductivity type, and growing the silicon single crystal according to the solidification rate represented by (weight of crystallization) / (weight of initial silicon raw material) In a resistivity control method having a step of continuously or intermittently additionally doping a sub-dopant having a conductivity type opposite to that of the dopant, the growth of the silicon single crystal is interrupted, and the grown silicon single crystal is remelted. When the silicon single crystal is regrown, the resistivity on the top side of the product part is added if the secondary dopant is additionally doped before the growth of the silicon single crystal is interrupted. After adding the main dopant in an amount falling within the standard, to provide a resistivity control method characterized by performing re-growth of a silicon single crystal.

  In this way, when re-melting, if the secondary dopant is additionally doped before the growth of the silicon single crystal is interrupted, the main dopant is added, so that the resistivity falls within the standard from the top part of the product part, and silicon A portion to be a product can be obtained from the single crystal according to a specified length in the pulling axial direction. Moreover, since the amount of dissolution of the sub-dopant is controlled while being controlled according to the solidification rate, the resistivity of the silicon single crystal to be grown can be accurately controlled.

At this time, it is preferable that the segregation coefficient of the sub-dopant is larger than the segregation coefficient of the main dopant.
The present invention can be suitably applied when the segregation coefficients of the main dopant and the sub-dopant are in the above relationship.

  In this case, after the first silicon single crystal is grown, the method further includes a multi-pooling step in which the raw material is additionally charged and the second and subsequent silicon single crystals are repeatedly grown, and the second and subsequent silicon single crystals are grown. In consideration of the amount of the sub-dopant additionally doped in the growth of the silicon single crystal so far, the step of repeating the step of adding the main dopant, while growing the silicon single crystal, depending on the solidification rate, A step of additionally doping the sub-dopant continuously or intermittently. In such a resistivity control method, the growth of the second and subsequent silicon single crystals is interrupted, and the grown silicon single crystal When the silicon single crystal is regrowth by remelting, the silicon single crystal is grown in the second and subsequent silicon single crystals. If a subdopant is added before cutting, the second and subsequent silicon single crystals may be regrown after adding the main dopant in an amount that the resistivity on the top side of the product part falls within the specifications. it can.

  Thus, the present invention can also be applied to a multi-pooling method for growing a plurality of silicon single crystals from one crucible.

At this time, the silicon thin rod containing the sub-dopant or the dopant obtained by pulverizing the silicon single crystal containing the sub-dopant into a granular form into the silicon melt in the region between the growing silicon single crystal and the crucible wall. By inserting or introducing, the sub-dopant can be additionally doped.
Such a method can be suitably used as a method of additionally doping the subdopant continuously or intermittently.

At this time, the silicon single crystal containing the main dopant or the silicon single crystal containing the main dopant is crushed into a granular material by inserting or introducing into the silicon melt, thereby interrupting the growth of the silicon single crystal. The main dopant can be added when the grown silicon single crystal is remelted and regrown.
Such a method can be suitably used as a method of adding the main dopant when remelted.

  Further, the present invention is an additional dopant injection device used in the resistivity control method described above, wherein a silicon thin rod containing the sub-dopant or the main dopant, or a silicon single crystal containing the sub-dopant or the main dopant There is provided an additional dopant charging device characterized in that one or more devices for inserting or charging a crushed dopant into a silicon melt are provided for each of the main dopant and the sub-dopant.

  When the above resistivity control method is carried out, such an additional dopant injection device can be suitably used.

Further, according to the present invention, the resistivity is controlled using the above-described resistivity control method, the main dopant is P (phosphorus), the sub-dopant is B (boron), and the phosphorus concentration in the silicon single crystal N _P and the difference _N P -N _B with boron concentration _{N B} of the silicon single crystal ^{is, 1.4 × 10 12 atoms / cm} 3 or more and 1.4 × ¹⁰ 15 atoms / cm ³ or less, the resistivity An n-type silicon single crystal is provided in which is 3 Ω · cm or more and 3000 Ω · cm or less.

  Such an n-type silicon single crystal can be manufactured with high quality and good yield.

  As described above, according to the present invention, for example, when the grown single crystal has undergone dislocation and needs to be remelted, when the secondary dopant is additionally doped before the growth of the silicon single crystal is interrupted, By adding the main dopant in such an amount that the resistivity on the top side of the product part falls within the standard, the resistivity of the grown silicon single crystal becomes as originally aimed, and the part that becomes the product from the silicon single crystal is pulled up. It can be obtained according to the prescribed length of the direction, and the amount of dissolution of the sub-dopant is controlled while being controlled according to the solidification rate, so that the resistivity of the silicon single crystal to be grown can be accurately controlled.

It is a flowchart which shows an example of the embodiment of the resistivity control method of this invention. It is a figure which shows an example of the CZ single-crystal growth apparatus used when implementing the resistivity control method of this invention. 2 is a graph showing the relationship between the resistivity and solidification rate of a silicon single crystal grown in Example 1. FIG. 4 is a graph showing the relationship between resistivity and solidification rate of a silicon single crystal grown in Example 2.

  Hereinafter, the present invention will be described in detail as an example of an embodiment with reference to the drawings, but the present invention is not limited thereto.

  As described above, CZ-PW, which is used as it is without depositing an epitaxial layer on CZ-PW, has been attracting attention, but silicon single crystals manufactured by the CZ method have segregation phenomenon and have resistance in the axial direction (pull-up axis direction). It is difficult to make the rate distribution uniform. On the other hand, Patent Document 3 discloses a method in which B (boron) is continuously added to the main dopant P (phosphorus). If this method is used, the main dopant is P (phosphorus) and the sub-dopant is B. An n-type crystal with improved axial resistivity distribution can be produced by counterdoping with (boron). However, the method disclosed in Patent Document 3 has a problem in that it cannot be remelted when the single crystal is dislocated. That is, when the method of Patent Document 3 is used, at the time when dislocations are generated, a sub-dopant having an opposite polarity is already contained in the single crystal and the raw material melt, so that it is remelted. The main dopant becomes insufficient, and a product having a desired resistivity cannot be obtained. Therefore, the part up to the dislocation is separated from the raw material melt, taken out and disposed of, and there is a problem that the yield is greatly reduced.

  Therefore, the inventors have been able to suppress a decrease in yield when the silicon single crystal growth by the CZ method is interrupted, the grown silicon single crystal is remelted, and the silicon single crystal is regrown, and the silicon single crystal is suppressed. We have intensively studied a resistivity control method that can control the resistivity of crystals with high accuracy. As a result, if the secondary dopant is additionally doped before the growth of the silicon single crystal is interrupted before the silicon single crystal is regrown, an amount of the main dopant within which the resistivity on the top side of the product part falls within the specifications is added. By adding, the resistivity of the grown silicon single crystal becomes the original aim, the product part from the silicon single crystal can be obtained according to the specified length in the pulling axis direction, and the dissolution amount of the sub-dopant Therefore, the present inventors have found that the resistivity of the silicon single crystal to be grown can be accurately controlled, and the present invention has been made.

Here, the segregation phenomenon and the solidification rate will be briefly described. When silicon solidifies (crystallizes), impurities in the melt are difficult to be taken into the crystal. The ratio of the impurity concentration taken into the crystal to the impurity concentration in the melt at this time, that is, (impurity concentration taken into the crystal) / (impurity concentration in the melt) is called a segregation coefficient k. Therefore, the impurity concentration C _{S in} the crystal at a certain moment has a relationship of the impurity concentration C _{L in} the melt at that time and C _S = k × C _L. In general, k is a value smaller than 1, so that the impurity concentration taken into the crystal is lower than the impurity concentration in the melt. Since crystal growth is performed continuously, a large amount of impurities are left in the melt, and the impurity concentration in the melt gradually increases. Impurity concentration in the crystal due to this also increases, the concentration C _S, solidification rate represents the weight crystallized relative to the weight of the initial material at a ratio x, the use of initial melt in the impurity concentration C _L0 C _S (x) = C _L0 × k × (1−x) ^(k−1) . Therefore, as the length of the straight body portion of the crystal becomes longer and the solidification rate x increases, the impurity concentration in the crystal increases and the resistivity decreases. In order to prevent the resistivity from decreasing and falling below the standard, it is necessary to perform additional doping while adjusting the doping amount of the sub-dopant to an appropriate amount with respect to the solidification rate continuously or intermittently. . However, if the silicon single crystal grown at the time of dislocation is remelted, the subdopant additionally doped so far is contained in the raw material melt and the silicon single crystal. For this reason, if the silicon single crystal is regrowth without doing anything as it is, the resistivity is increased by the amount of the additional doped subdopant, which may not satisfy the standard. Therefore, it was decided to grow the silicon single crystal after adding the main dopant in such an amount that the resistivity on the top side of the product part falls within the standard before starting the growth of the silicon single crystal. At this time, if re-melting of the silicon single crystal is repeated multiple times, in the case of the growth of the silicon single crystal before the latest re-melting, if a sub-dopant is added before the growth of the silicon single crystal is interrupted, the product After adding the main dopant in such an amount that the resistivity on the top side of the portion falls within the specification, the silicon single crystal is regrown.

  In addition, it is more suitable to apply the method which adds a subdopant continuously or intermittently during such single crystal growth when the segregation coefficient of a subdopant is larger than the segregation coefficient of a main dopant. Of course, the present invention can be applied even when the segregation coefficient of the sub-dopant having the opposite polarity to the main dopant is smaller than the segregation coefficient of the main dopant. However, additional doping with a sub-dopant during the growth of a single crystal also has the risk of causing dislocations by that action. Patent Documents 1 and 2 disclose that when the segregation coefficient of the sub-dopant is smaller than the segregation coefficient of the main dopant, the uniformity in the axial direction can be improved even if the sub-dopant is added only at the initial stage. Therefore, a case where the segregation coefficient of the sub-dopant is larger than the segregation coefficient of the main dopant, which is more difficult to control the resistivity, is more suitable as an object to which the present invention is applied. Further, when phosphorus (P) is used as the main dopant, the segregation coefficient is larger than that of phosphorus (P), and boron (B) that is not a heavy metal can be used as a sub-dopant. For example, the case where the segregation coefficient of the sub-dopant is larger than the segregation coefficient of the main dopant is more suitable.

  Hereinafter, an example of a CZ single crystal growth apparatus used when the resistivity control method of the present invention is implemented will be described with reference to FIG.

  As shown in FIG. 2, the CZ single crystal growing apparatus 100 has a member for containing and melting the raw material polycrystalline silicon, a heat insulating member for shutting off heat, and the like. 1 is accommodated. A pulling chamber 2 extending upward is connected to a ceiling portion (top chamber 11) of the main chamber 1, and a mechanism (not shown) for pulling up a single crystal rod (silicon single crystal) 3 with a wire is provided on the upper portion. Is provided.

  In the main chamber 1, there are provided a quartz crucible 5 for containing a melted raw material melt (silicon melt) 4 and a graphite crucible 6 for supporting the quartz crucible 5, and these crucibles 5, 6 have a drive mechanism ( (Not shown) is supported by the crucible shaft so as to be rotatable up and down. And the heater 7 for melting a raw material is arrange | positioned so that the crucibles 5 and 6 may be surrounded. A heat insulating member 8 is provided outside the heater 7 so as to surround the periphery thereof.

  A gas inlet 10 is provided at the upper part of the pulling chamber 2, and an inert gas such as argon gas is introduced and discharged from the gas outlet 9 at the lower part of the main chamber 1. Further, a heat shield member 13 is provided so as to face the raw material melt 4, so that radiation from the surface of the raw material melt 4 is cut and the surface of the raw material melt 4 is kept warm.

  Further, a gas purge cylinder 12 is provided above the raw material melt 4 so that the periphery of the single crystal rod 3 can be purged by the inert gas introduced from the gas inlet 10.

The top chamber 11 is provided with a first thin rod insertion machine 14, and when the secondary dopant is additionally doped, the first thin rod crystal (first silicon thin rod) 15 containing the secondary dopant is introduced into the raw material melt 4. It can be inserted into
The top chamber 11 is provided with a second thin rod insertion machine 16, and when adding the main dopant, the second thin rod crystal (second silicon thin rod) 17 containing the main dopant is used as the raw material melt 4. It can be inserted inside.

Next, the resistivity control method of the present invention will be described with reference to FIGS.
First, the main dopant is initially doped so that the silicon single crystal to be grown has a predetermined conductivity type (see S11 in FIG. 1).

  Specifically, before starting the growth of the silicon single crystal 3, the main dopant is introduced into the raw material melt 4 so that the silicon single crystal 3 has a predetermined conductivity type. For example, phosphorus (P) can be used as the main dopant when growing an n-type silicon single crystal. The main dopant may be charged in advance in the quartz crucible 5 together with the raw material polycrystalline silicon, or the main dopant may be input into the raw material melt 4.

  Next, depending on the solidification rate represented by (crystallized weight) / (weight of initial silicon raw material), additional dopants having a conductivity type opposite to that of the main dopant are added continuously or intermittently. Then, a silicon single crystal is grown (see S12 in FIG. 1).

Specifically, the silicon single crystal 3 is grown while additional doping is continuously or intermittently added with the sub-dopant according to the solidification rate (for example, the length of the straight body portion A). For example, boron (B) can be used as the sub-dopant when phosphorus (P) is used as the main dopant. As described above, the resistivity decreases as the length of the silicon single crystal increases and the solidification rate increases, so the solidification rate is continuously or intermittently used to prevent the resistivity from falling below the standard. In contrast, additional doping is performed while adjusting the doping amount of the sub-dopant to an appropriate amount.
The silicon single crystal 3 is grown using the CZ method. Here, the CZ method includes a so-called MCZ method in which a magnetic field is applied.

Next, when the length of the straight body portion A is dislocated within a predetermined range, the process proceeds to S13, the growth of the silicon single crystal is interrupted, the grown silicon single crystal is remelted, and the silicon single crystal When the secondary dopant is additionally doped before the growth of is stopped, the main dopant is added in such an amount that the resistivity on the top side of the product part falls within the specification (see S13 in FIG. 1).
If dislocation occurs after the length of the straight body portion A is longer than the predetermined range, and if dislocation does not occur, the process proceeds to S14, where the silicon single crystal growth is completed, A single crystal is taken out (see S14 in FIG. 1).
Here, the predetermined range of the length of the straight body portion A is a range in which the length of the product portion is shortened by slipback or the like and it is determined that remelting is appropriate.

Specifically, when dislocations occur during the growth of the silicon single crystal 3, a phenomenon called slip-back occurs, resulting in a decrease in yield (that is, the length of the straight body portion that can be taken as a product is reduced). Therefore, the growth of the silicon single crystal may be interrupted and the grown silicon single crystal may be remelted. At this time, if the silicon single crystal 3 is regrowth without doing anything as it is, the resistivity becomes higher by the amount of the sub-dopant additionally doped so far, and the standard may not be satisfied. Therefore, when the secondary dopant is additionally doped before the growth of the silicon single crystal 3 is interrupted, the main dopant is added in such an amount that the resistivity on the top side of the product portion falls within the standard.
The addition of the main dopant may be performed at any timing before the re-growth of the silicon single crystal 3 is started, but if it is any timing before remelting, during remelting, or after remelting, Since it is not necessary to introduce the main dopant in the vicinity of growing the silicon crystal, it is possible to prevent dislocations resulting from the addition of the main dopant.

  Next, the process returns to S12, and a silicon single crystal is grown while additional doping is continuously or intermittently added according to the solidification rate (see S12 in FIG. 1).

  Specifically, the re-growth of the silicon single crystal 3 is started, and the silicon single crystal is added while continuously or intermittently adding the sub-dopant according to the solidification rate (for example, the length of the straight body portion A). Foster 3

  In this case, it is preferable that the segregation coefficient of the sub-dopant is larger than the segregation coefficient of the main dopant. The present invention can be suitably applied when the segregation coefficient has the above relationship.

  After the first silicon single crystal is grown, the method further includes a multi-pooling step of repeatedly charging the raw material and repeating the growth of the second and subsequent silicon single crystals, and the step of repeating the growth of the second and subsequent silicon single crystals, Considering the amount of the additional dopant added in the previous growth of the silicon single crystal, the step of adding the main dopant and the growth of the silicon single crystal while the secondary dopant is continuously or intermittently depending on the solidification rate In such a resistivity control method, the growth of the second and subsequent silicon single crystals is interrupted, and the grown silicon single crystals are remelted to form silicon single crystals. In the case of re-growing the crystal, in the growth of the second and subsequent silicon single crystals, the sub-dopant until the growth of the silicon single crystal is interrupted. If you add doped, can be performed after the top side of the resistivity of the product portion has added the main dopant in an amount falling within the standard, re-training of the second or subsequent of the silicon single crystal.

In this way, when applying the present invention in the multi-pooling method for growing a plurality of silicon single crystals by additionally charging the raw material from one crucible, at the time of starting the growth of the second and subsequent silicon single crystals, Since the sub-dopant is contained in the raw material melt 4, a sub-dopant having a conductivity type opposite to that of the main dopant is included in the single crystal to be grown from the top of the single crystal. Therefore, the concentration of the sub-dopant contained in the top of the single crystal, that is, the concentration of the sub-dopant in the raw material melt 4 multiplied by the segregation coefficient of the sub-dopant is added, and the main dopant should be added. It is necessary to adjust the amount of the main dopant corresponding to the resistivity.
Even when the silicon single crystal 3 is grown from the raw material melt 4 in which the concentration of the main dopant is adjusted in this way, an appropriate amount of a sub-dopant corresponding to the solidification rate is additionally doped continuously or intermittently. Even in such a resistivity control method, when the growth of the silicon single crystal is interrupted and the grown crystal is re-melted to re-grow the silicon single crystal, the doping is performed until the growth of the silicon single crystal is interrupted. It is preferable that a single crystal is manufactured again after adding a main dopant for offsetting the subdopant.
In this way, in the multi-pooling method in which the sub-dopant is added in the growth of the silicon single crystal before that, when the second and subsequent silicon single crystals are remelted, the second and subsequent ones are grown. The resistivity of the silicon single crystal can be accurately controlled.
At this time, if re-melting of the silicon single crystal is repeated a plurality of times, in the growth of the silicon single crystal before the latest re-melting, if a subdopant is added before the growth of the silicon single crystal is interrupted, After adding the main dopant in such an amount that the resistivity on the top side of the product part falls within the specification, the silicon single crystal is regrown.

In this case, as a method of additionally doping an appropriate amount of the subdopant according to the solidification rate, a silicon thin rod containing the subdopant is inserted into the raw material melt 4 between the growing silicon single crystal 3 and the crucible wall. Or a method of charging a raw material melt 4 between a growing silicon single crystal 3 and a crucible wall with a dopant obtained by pulverizing a silicon crystal containing a sub-dopant in a granular form can be used.
If such a method is used, an appropriate amount can be additionally doped according to the solidification rate. For example, when inserting the silicon thin rod 15 into the raw material melt 4 between the growing silicon single crystal 3 and the crucible wall, the crystal is sealed and attached to the top chamber 11 so as to maintain the furnace pressure. A movable device (the first thin rod insertion machine 14 in FIG. 2) that can move the thin rod approximately vertically can be used. For this, the technique disclosed in Patent Document 5 can be applied.
Alternatively, the top is sealed so as to maintain the furnace pressure so that a dopant obtained by pulverizing the silicon crystal containing the sub-dopant into a granular form is introduced into the raw material melt 4 between the growing silicon single crystal 3 and the crucible wall. A tube attached to the chamber 11 and guiding the crushed dopant into the raw material melt 4 between the growing single crystal and the crucible wall can be used.
As a mechanism for additionally doping the sub-dopant, the pipe for guiding the crushed dopant to the raw material melt 4 is structurally simple. However, since the granular dopant is introduced beside the growing single crystal, The dopant is scattered or floated, which increases the possibility of dislocation of the grown single crystal. On the other hand, although the installation of the movable device (first thin rod insertion machine 14) capable of moving the first crystal rod 15 in the vertical direction is higher than the above-mentioned guide tube in terms of cost, the silicon unit that is being grown is united. Even if the first crystal rod 15 is inserted in the vicinity of the crystal 3, there is an advantage that the silicon single crystal 3 being grown is difficult to dislocation.

When the growth of the silicon single crystal 3 is interrupted, the grown silicon single crystal 3 is remelted, and when the silicon single crystal 3 is regrown, the doped sub-dopant is canceled until the growth of the silicon single crystal 3 is interrupted. As a method for adding the main dopant, the second thin rod crystal (second silicon thin rod) 17 containing the main dopant or a dopant obtained by pulverizing the silicon crystal containing the main dopant in a granular form is melted as a raw material. It can be carried out by inserting or charging into the liquid 4.
When such a method is used, it is possible to additionally dope the main dopant with an appropriate amount to offset the sub-dopant. Since the addition of the main dopant is performed before the start of the regrowth of the silicon single crystal 3, it is not necessary to introduce the main dopant near the portion where the silicon single crystal 3 is actually grown. Dislocation due to the introduction of the main dopant can be prevented.

  According to the resistivity control method of the present invention described above, even if the growth of the single crystal is interrupted and remelted for reasons such as dislocation, the resistivity of the grown silicon single crystal is the original As intended, the product portion from the silicon single crystal can be obtained according to the specified length of the pulling axis, and the resistivity of the silicon single crystal to be grown can be accurately controlled.

Next, the additional dopant injection device of the present invention will be described with reference to FIG.
The additional dopant injection device of the present invention is used in the above-described resistivity control method, and pulverizes a silicon rod containing a sub-dopant or a main dopant or a silicon single crystal containing a sub-dopant or a main dopant into particles. One or more devices for inserting or introducing the dopant into the silicon melt 4 are provided for the main dopant and the sub-dopant, respectively.
The additional dopant injection device of the present invention can be configured, for example, as an additional dopant injection device 18 having the first thin rod inserter 14 and the second thin rod inserter 16 of FIG.
When a silicon rod containing a desired dopant or a dopant obtained by pulverizing a silicon crystal containing a desired dopant is inserted or charged into the silicon melt 4, the main dopant and the sub-dopant can be used together in one inlet. It is possible to do. However, as described above, when a granular dopant is introduced in the vicinity of the growing silicon single crystal, the possibility of dislocations increases. Therefore, the additional doping of the side dopant is preferably performed by inserting a silicon thin rod. However, in the method of inserting the silicon thin rod, since the silicon thin rod is attached in the chamber in advance, it is difficult to share one charging machine for the main dopant and the sub-dopant. Therefore, an additional dopant introduction device provided with at least one introduction mechanism for each of the main dopant and the sub-dopant is preferable.
As described above, since dislocations caused by the introduction of the main dopant do not occur, for example, the sub-dopant is introduced by inserting a thin silicon rod, and the main dopant is introduced by doping the silicon crystal into particles. It is good also as a method of throwing into the raw material melt 4. Of course, both may be a system in which a silicon rod is inserted, or both may be a system in which a dopant obtained by pulverizing silicon crystals in a granular form is introduced into the raw material melt 4.

Next, the n-type silicon single crystal of the present invention will be described.
The n-type silicon single crystal of the present invention is manufactured using the resistivity control method as described above, using phosphorus (P) as a main dopant, boron (B) as a sub-dopant, and a phosphorus concentration in the single crystal. N _P and the difference _N P -N _B with boron concentration _{N B} is 1.4 × ¹⁰ 12 atoms / cm ³ or more and 1.4 × ¹⁰ 15 atoms / cm ³ or less, a resistivity of 3 [Omega] · cm or more, 3000 Ω · cm or less.
In this way, if the n-type silicon single crystal with phosphorus (P) as the main dopant and boron (B) as the sub-dopant, both elements are widely used elements for device manufacturing, which is an unexpected problem. Is less likely to occur. In particular, in a vertical device for high withstand voltage power, since a current flows in the single crystal and a reverse bias is applied in the single crystal, a single crystal having a relatively high resistivity and high resistance uniformity is desired. Therefore, an n-type silicon single crystal in which the phosphorus concentration in the single crystal is higher than the boron concentration, the difference in the concentration is in the above range, and the resistivity is in the above range is suitable. Further, by using the resistivity control method of the present invention, it is possible to control the single crystal from the top part to the bottom part in the CZ method almost uniformly to a desired concentration difference and resistivity within these ranges. It is. Accordingly, a silicon single crystal that uses the resistivity control method of the present invention and is controlled so that the resistivity falls within a narrow standard within the above range is a silicon single crystal that is optimal for the latest devices such as power devices. .

  EXAMPLES Hereinafter, although an Example and a comparative example are shown and this invention is demonstrated more concretely, this invention is not limited to these.

Example 1
Using the CZ single crystal growth apparatus 100 shown in FIG. 2, an n-type silicon single crystal having a resistivity standard of 55-75 Ω · cm and a diameter of 200 mm was grown. The initial charge amount of raw material silicon was 200 kg, and about 160 kg of silicon single crystal was grown. A dopant prepared by pulverizing a silicon single crystal having a P (phosphorus) concentration of 4 × 10 ¹⁹ atoms / cm ^{3 in} order to aim at 65 Ω · cm, which is the center of the resistivity standard, from the top of the single crystal is 0.00. 97 g initial dope.

The additional doping of the sub-dopant was performed by attaching the first silicon thin rod 15 containing the sub-dopant to the tip of the thin rod insertion machine 14 in FIG. 2 and inserting it into the raw material melt (silicon melt) 4. This first silicon rod 15 is formed from a silicon single crystal block having a resistivity of 0.15 Ω · cm cut out from a silicon single crystal grown by doping B (boron) with a diameter of about 300 mm and a length of about 300 mm. What was cut out as a prism in the vertical direction of 2 cm × 2 cm × 30 cm was used. The manufacturing method of the silicon thin rod is not limited to this. For example, if the horizontal direction is cut out from the block, the resistivity control with higher accuracy can be performed.
Further, the additional doping of the sub-dopant started with the start of the growth of the straight body portion A of the silicon single crystal 3, and thereafter boron (B) was additionally doped continuously. The doping amount is {(1−x) ^(kp−1) −1+ [1 + kp × (1−x) ^(kp−1 )] / kb} (where kp is the segregation of phosphorus with reference to Patent Document 3) The amount proportional to the coefficient, kb is the segregation coefficient of boron, and x is the solidification rate).

However, when the silicon single crystal 3 was grown up to a length of 55 cm in the straight body portion A, dislocation occurred. Without doing anything, it was predicted that when the grown silicon single crystal was remelted to grow the silicon single crystal, the resistivity at the top of the single crystal would be about 77 Ω · cm. Therefore, the second silicon thin rod 17 containing the main dopant attached to the tip of the second thin rod inserting machine 16 in FIG. 2 was inserted into the raw material melt 4 and melted. This second silicon rod 17 is made of a silicon single crystal block having a resistivity of 0.10 Ω · cm cut out from a silicon single crystal grown by doping P (phosphorus) with a diameter of about 300 mm and a length of about 300 mm. What was cut out as a prism in the vertical direction of 2 cm × 2 cm × 30 cm was used. 71 g of the second silicon thin rod 17 is inserted into the raw material melt 4 next to the remelted silicon single crystal to prepare a raw material melt 4 with an adjusted dopant concentration. Started growing single crystals.
Here, the continuous dope amount of the sub-dopant was increased by about 10% compared with the initially planned amount. This is because the main dopant P (phosphorus) was additionally doped with remelting of the silicon single crystal.

  FIG. 3 shows the axial profile of the resistivity (that is, the relationship between the resistivity and the solidification rate of the grown silicon single crystal) obtained as a result of such additional doping of the main dopant and continuous doping of the subdopant. As can be seen from FIG. 3, it was possible to obtain a single crystal having a resistivity that is approximately the center value of the resistivity standard from the top side to the bottom side of the single crystal.

(Example 2)
After the silicon single crystal of Example 1 was grown, about 160 kg of silicon raw material was additionally charged to make the total raw material 200 kg. The second crystal was grown as an n-type single crystal having a size of 55-75 Ω · cm and a diameter of 200 mm, as in the first sample. The P (phosphorus) concentration in the raw material melt 4 remaining at the end of the first run was calculated to be 6.4 × 10 ¹⁴ atoms / cm ³ , and the B (boron) concentration was calculated to be 2.2 × 10 ¹⁴ atoms / cm ³ . . Therefore, in consideration of this, the P (phosphorus) concentration is set so that the resistivity falls within the standard where the length of the straight body portion A where the crystal quality such as oxygen concentration and crystal defects is within the standard is about 20 cm. A raw material melt 4 for growing a second silicon single crystal was prepared by doping 0.66 g of a dopant prepared by crushing a silicon single crystal of 4 × 10 ¹⁹ atoms / cm ³ into granules.

  The addition of the sub-dopant is the same as in Example 1 except that the first thin rod inserter 14 shown in FIG. 2 includes B (boron) having a resistivity of 0.15 Ω · cm, 2 cm × 2 cm × 30 cm. A silicon thin rod 15 was attached and inserted into the raw material melt 4. However, unlike Example 1, B (boron) was intermittently doped. The intermittent dope has a weight of about 7 g, 10 g, 12 g, 13 g, 10 g and 8 g of the first silicon rod 15 when the length of the straight body portion A is 40 cm, 70 cm, 100 cm, 130 cm, 150 cm and 165 cm, respectively. It was scheduled to be inserted into the raw material melt 4 and dissolved.

However, immediately after the introduction of the first sub-dopant, dislocation occurred at a position where the length of the straight body portion A was 40 cm. Since a slipback of about 20 cm is expected, even if crystal growth is stopped at this length and a silicon single crystal is taken out, a product part cannot be obtained. Therefore, it was judged that it was appropriate to re-melt it.
If it is remelted without doing anything, the resistivity at the top of the single crystal will be 87 Ω · cm, and the resistivity at the length 20 cm of the straight body part A on the top side of the product will be 80 Ω · cm. Was expected. Therefore, the second silicon thin rod 17 containing the main dopant attached to the tip of the second thin rod feeder 16 in FIG.
This second silicon rod 17 is a prism having a resistivity of 0.10 Ω · cm, 2 cm × 2 cm × 30 cm, as in the first embodiment. 29 g of this was dissolved so that the resistivity when the length of the straight body portion A was 20 cm was 74 Ω · cm, and the silicon single crystal was regrown.
In the regrowth, the amount of the sub-dopant to be intermittently doped was increased by 4% from the initial schedule by adding the main dopant.
As a result of the regrowth, when the silicon single crystal was grown to a position where the length of the straight body portion A was 160 cm, dislocation occurred again. At this position, even if slipback occurs 20 cm, the product portion is obtained when the length of the straight body portion A is 20 cm to 140 cm, so that the silicon single crystal was taken out without being remelted.

  An axial profile of the resistivity obtained with the silicon single crystal grown in this manner (where the portion where the slipback is generated is removed) (that is, the resistivity and solidification rate of the grown silicon single crystal The relationship is shown in FIG. As can be seen from FIG. 4, it is possible to obtain a silicon single crystal whose resistivity falls within the standard in the region where the crystal quality such as oxygen concentration and crystal defects is within the standard from the top side to the bottom side of the single crystal. did it.

(Comparative example)
A silicon single crystal was grown in the same manner as in Example 1. However, when the silicon single crystal was dislocated at a length of 55 cm in the straight body portion A of the silicon single crystal, the grown silicon single crystal was remelted and regrowth of the silicon single crystal was performed. Prior to growth, no main dopant was added. As a result, the resistivity of the grown silicon single crystal was 77 Ω · cm on the top side of the single crystal, and the resistivity did not satisfy the standard over the entire length of the single crystal.

  As described above, in the comparative example, when the grown crystal is remelted and the single crystal is grown again, the main dopant is added to offset the sub-dopant doped until the single crystal is grown again. As a result, the resistivity within the standard could not be obtained.

  The present invention is not limited to the above embodiment. The above-described embodiment is an exemplification, and the present invention has substantially the same configuration as the technical idea described in the claims of the present invention, and any device that exhibits the same function and effect is the present invention. It is included in the technical scope of the invention.

1 ... main chamber, 2 ... pulling chamber,
3 ... Single crystal rod (silicon single crystal), 4 ... Raw material melt (silicon melt),
5 ... quartz crucible, 6 ... graphite crucible, 7 ... heater, 8 ... heat insulation member,
9 ... Gas outlet, 10 ... Gas inlet, 11 ... Top chamber,
12 ... Gas purge cylinder, 13 ... Heat shield member, 14 ... First thin rod insertion machine,
15 ... 1st thin rod crystal (1st silicon thin rod), 16 ... 2nd thin rod insertion machine,
17 ... 2nd thin rod crystal (2nd silicon thin rod), 18 ... Additional dopant injection | throwing-in apparatus,
100: CZ single crystal growing apparatus, A: Straight body part.

Claims (7)

When a silicon single crystal is grown by the CZ method, the resistivity of the grown silicon single crystal is controlled by the dopant, and the main dopant is initially doped so that the silicon single crystal has a predetermined conductivity type. While growing the silicon single crystal, a sub-dopant having a conductivity type opposite to that of the main dopant is continuously applied according to the solidification ratio represented by (weight of crystallization) / (weight of initial silicon raw material). And a method of controlling resistivity having a step of additionally doping intermittently or intermittently,
If the growth of the silicon single crystal is interrupted and the grown silicon single crystal is remelted to re-grow the silicon single crystal, the product will be added if a subdopant is added before the growth of the silicon single crystal is interrupted. A silicon single crystal is regrown after adding the main dopant in an amount that the resistivity on the top side of the portion falls within the standard.   The resistivity control method according to claim 1, wherein a segregation coefficient of the sub-dopant is larger than a segregation coefficient of the main dopant. After the first silicon single crystal is grown, the method further includes a multi-pooling step in which the raw material is additionally charged and the growth of the second and subsequent silicon single crystals is repeated.
The process of repeating the growth of the second and subsequent silicon single crystals is as follows:
Adding the main dopant in consideration of the amount of the sub-dopant additionally doped in the growth of the silicon single crystal so far;
In the resistivity control method according to claim 1, further comprising the step of additionally doping the sub-dopant continuously or intermittently according to the solidification rate while growing a silicon single crystal.
When the growth of the second and subsequent silicon single crystals is interrupted and the grown silicon single crystal is re-melted and re-grown, the silicon single crystals are grown in the second and subsequent silicon single crystals. If the sub-dopant is additionally doped before the growth of the crystal is interrupted, after adding the main dopant in such an amount that the resistivity on the top side of the product part falls within the specifications, the second and subsequent silicon single crystals are added. A resistivity control method characterized by performing regrowth.   Inserting or throwing into the silicon melt in the region between the growing silicon single crystal and the crucible wall, a silicon fine rod containing the sub-dopant or a dopant obtained by pulverizing the silicon single crystal containing the sub-dopant in a granular form 4. The resistivity control method according to claim 1, wherein the sub-dopant is additionally doped. 5.   The silicon single crystal containing the main dopant, or the silicon single crystal containing the main dopant was crushed into a granular material by inserting or introducing into the silicon melt, the growth of the silicon single crystal was interrupted and grown. The resistivity control method according to any one of claims 1 to 4, wherein the main dopant is added when the silicon single crystal is re-melted to re-grow the silicon single crystal. An additional dopant injection device used in the resistivity control method according to claim 4 or 5,
A device for inserting or throwing into the silicon melt a silicon fine rod containing the sub-dopant or the main dopant or a silicon crushed silicon single crystal containing the sub-dopant or the main dopant is added to the silicon melt. And one or more additional dopants for the sub-dopant, respectively. Resistivity is controlled using the resistivity control method according to any one of claims 1 to 5,
The main dopant is P (phosphorus), the sub-dopant is B (boron),
Difference _N P -N _B with boron concentration _{N B} of the silicon phosphorus concentration _{N P} and the silicon crystal in the ^{crystal, 1.4 × 10 12 atoms / cm} 3 or ^{more, 1.4 × 10 15 atoms / cm} 3 or less And
An n-type silicon single crystal having a resistivity of 3 Ω · cm to 3000 Ω · cm.

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