JP2016108160A - Growing method of silicon single crystal - Google Patents

Abstract

There is provided a method for growing a silicon single crystal capable of controlling the carbon concentration of the silicon single crystal with high accuracy. A first calibration representing a relationship between a specific surface area of a silicon raw material and a carbon concentration of the silicon single crystal grown from a silicon melt obtained by melting the silicon raw material by previously growing a silicon single crystal. A first preliminary test step for determining a line; a first determination step for determining a silicon raw material to be used according to a target carbon concentration of a silicon single crystal to be grown using the first calibration curve; A first filling step of filling the crucible with the silicon raw material determined in one determining step; and the silicon single crystal from a silicon melt obtained by melting the silicon raw material filled in the first filling step. A method for growing a silicon single crystal, comprising a first growing step for growing. [Selection] Figure 1

Description

  The present invention relates to a method for growing a silicon single crystal, and more particularly to a method for growing a silicon single crystal by the Czochralski method.

  A silicon wafer for semiconductor devices is usually obtained by cutting out from a silicon single crystal grown by the Czochralski method (hereinafter also referred to as “CZ method”). In the CZ method, a raw material is melted in a crucible to produce a raw material melt, and after contacting the seed crystal with this raw material melt, the single crystal is pulled under the seed crystal by pulling it up while rotating the seed crystal. It is a way to grow.

  When growing a silicon single crystal, if a large amount of carbon is taken into the silicon single crystal, crystal defects are easily introduced. For this reason, normally, a silicon single crystal is grown so that carbon is not introduced as much as possible. The carbon introduced into the silicon single crystal is considered to originate from, for example, a carbon heater. More specifically, when the silicon raw material is melted in the crucible prior to pulling up the silicon single crystal, the silicon melt and the unmelted silicon raw material coexist. In this state, SiO is evaporated from the silicon melt, and this SiO reacts with a graphite member (mainly a heater) in the silicon single crystal growth apparatus (furnace) to generate CO gas, which is not melted. It is adsorbed on the surface of the silicon raw material and taken into the silicon single crystal.

  In Patent Document 1, as a method for reducing the carbon concentration of a silicon single crystal, a polycrystalline silicon raw material is melted at a furnace pressure of 5 to 60 mbar, and the silicon single crystal is pulled at a furnace pressure of 100 mbar or more. A method for pulling crystals is disclosed. According to Patent Document 1, by setting the furnace pressure during melting of the raw material to 5 to 60 mbar, mixing of CO gas generated from the graphite member into the silicon melt can be suppressed, and as a result, the carbon concentration of the crystal is reduced. It can be done.

  In Patent Document 2, a quartz crucible for containing a Si source material, a graphite crucible for holding a quartz crucible, and the entire surface of the graphite crucible are covered, and SiC, TiC, NbC, TaC, ZrC are covered. And a crystal growth apparatus for Si comprising a coating formed of any of these mixtures. According to Patent Document 2, it is said that carbon can be prevented from being mixed into Si melt from a graphite crucible through a quartz crucible by coating.

  On the other hand, in Patent Document 3, when the oxygen concentration of the grown silicon single crystal is small and the number of oxygen precipitates formed on the silicon single crystal is insufficient for effective trapping of metal impurities, It is said that a sufficient amount of oxygen precipitates can be formed by intentionally introducing carbon into the crystal during growth. In Patent Document 4, it is said that generation of vacancy clusters in which vacancies are aggregated can be suppressed by intentionally adding carbon to a silicon single crystal. Thus, for a specific purpose, carbon may be intentionally added (dope) to grow a silicon single crystal. In these cases, it is necessary to control the amount of carbon added so that the carbon concentration of the silicon single crystal is within a predetermined range.

  In Patent Document 3, the carbon concentration of the silicon melt is adjusted by controlling the flow rate of the inert gas flow that flows in the growth apparatus during the growth of the silicon single crystal. In the crystal growth method of Patent Document 4, when generating a silicon melt, carbon is introduced into the silicon single crystal by introducing carbon powder onto the bottom surface in the crucible.

Japanese Patent No. 2635456 JP 7-89789 A JP 2006-219366 A JP 2008-88056 A

  However, in the methods and apparatuses of Patent Documents 1 to 4, carbon contained in the silicon raw material is not sufficiently considered before the silicon raw material is charged into the crucible and heated. In the method of Patent Document 1, the range of the carbon concentration that can be adjusted for the silicon single crystal is narrow. For the above reasons, the carbon concentration of the silicon single crystal cannot always be sufficiently controlled both when the carbon concentration of the silicon single crystal is reduced and when carbon is intentionally added to the silicon single crystal. .

  Furthermore, the method of Patent Document 4 has a problem that the added carbon powder is not sufficiently melted in the silicon melt, so that the silicon single crystal is likely to undergo dislocation.

  The method and apparatus of Patent Documents 1 to 4 are also used when a silicon raw material is added (recharged) to the silicon melt remaining in the crucible after the growth of the silicon single crystal and melted to grow another silicon single crystal. If the above is applied, the same problem as described above occurs.

  This invention is made | formed in view of such a condition, and it aims at providing the growth method of the silicon single crystal which can control the carbon concentration of a silicon single crystal with high precision.

The gist of the present invention is the following methods (A) and (B) for growing silicon single crystals.
(A) A method for growing a silicon single crystal by a Czochralski method from a silicon melt obtained by melting a silicon raw material,
First, a silicon single crystal is grown, and a first calibration curve representing the relationship between the specific surface area of the silicon raw material and the carbon concentration of the silicon single crystal grown from the silicon melt obtained by melting the silicon raw material is obtained. 1 preliminary test process;
A first determination step of determining a silicon raw material to be used according to a target carbon concentration of a silicon single crystal to be grown using the first calibration curve;
A first filling step of filling the crucible with the silicon raw material determined in the first determination step;
And a first growth step of growing the silicon single crystal from a silicon melt obtained by melting the silicon raw material filled in the first filling step.

(B) A method for growing a silicon single crystal by a Czochralski method from a silicon melt obtained by melting a silicon raw material,
First, a silicon single crystal is grown, and a second calibration curve representing the relationship between the grain size of the silicon raw material and the carbon concentration of the silicon single crystal grown from the silicon melt obtained by melting the silicon raw material is obtained. Two preliminary test steps;
A second determination step of determining a silicon raw material to be used according to a target carbon concentration of a silicon single crystal to be grown using the second calibration curve;
A second filling step of filling the crucible with the silicon raw material determined in the second determination step;
And a second growing step of growing the silicon single crystal from a silicon melt obtained by melting the silicon raw material filled in the second filling step.

  In the growing method of (A) above, after the first growing step is completed, the first determining step, the first filling step, and the first growing step may be repeated. Similarly, in the growing method of (B) above, after the second growing step is completed, the second determining step, the second filling step, and the second growing step may be repeated.

In the second determination step, a target carbon concentration of the silicon single crystal to be grown may be 1.0 × 10 ¹⁶ atoms / cm ³ or less, and in this case, the grain size of the silicon raw material to be used Can be determined to be greater than 50 mm, for example, with the minimum length, average particle size, or maximum frequency value of the particle size distribution of the silicon source.

  The silicon raw material may be obtained by crushing polycrystalline silicon and then selecting a silicon raw material having a predetermined range size. After crushing a grown silicon single crystal, the silicon raw material having a predetermined range size is selected. It may be what you did.

  According to the method of the present invention, the carbon concentration of the silicon single crystal can be controlled with extremely high accuracy by selecting an appropriate silicon raw material using the first or second calibration curve.

FIG. 1 is a diagram showing the relationship between the surface area ratio of the silicon raw material and the carbon concentration of the silicon single crystal.

“Silicon raw material” is a raw material of silicon single crystal, which means an aggregate of silicon particles or lumps, and unless otherwise specified, individual shapes are not limited and are substantially spherical or elliptical. It may have a shape such as a plate shape or a rod shape.
The “particle diameter of silicon raw material” refers to the particle diameter of particles or lumps constituting the silicon raw material.

  The present inventors have found that there is a strong correlation between the particle size or specific surface area of a silicon raw material and the carbon concentration of a silicon single crystal grown from a silicon melt obtained by melting the silicon raw material. . Specifically, the carbon concentration of the silicon single crystal increases as the particle size of the silicon raw material decreases (as the specific surface area increases). This is because, for the following reasons, the smaller the particle size of the silicon raw material, the more carbon contained in the silicon raw material per unit volume or unit mass, and accordingly, a silicon single crystal per unit volume or unit mass. It is thought that this is because more carbon is incorporated into.

  Usually, the silicon raw material is produced by crushing larger lump silicon. The diameter of the silicon raw material after crushing is several mm to several tens mm. The carbon contained in the silicon raw material is considered to originate from, for example, the environment in which the silicon raw material is manufactured and a resin packaging material (for example, a plastic bag). Since the silicon material with a smaller particle size has a larger specific surface area, the amount of carbon attached to the surface of the silicon material per unit volume or unit mass can be increased. Will increase.

  Further, in the production stage of the silicon single crystal, the adsorption amount of the CO gas generated from the graphite member to the surface of the silicon raw material is also larger as the specific surface area of the silicon raw material per unit volume or unit mass is larger. The smaller the particle size, the larger. Accordingly, the amount of carbon taken into the silicon single crystal per unit volume or unit mass increases. Accordingly, the amount of carbon taken into the silicon single crystal per unit volume or unit mass originating from the CO gas adsorbed on the surface of the silicon raw material increases as the particle size of the silicon raw material decreases (as the specific surface area increases). Conceivable.

  The present inventors have selected the amount of carbon introduced into a silicon single crystal by selecting an appropriate silicon material using the relationship between the specific surface area or particle size of the silicon material and the carbon concentration of the silicon material. It was considered that a silicon single crystal having a desired carbon concentration can be grown by controlling

  As described above, the method for growing a silicon single crystal according to the present invention is a method for growing a silicon single crystal by a Czochralski method from a silicon melt obtained by melting a silicon raw material.

  In the growth method of the first aspect of the present invention, the silicon single crystal is grown in advance, the specific surface area of the silicon raw material, and the carbon concentration of the silicon single crystal grown from the silicon melt obtained by melting the silicon raw material The specific surface area of the silicon raw material to be used is determined according to the target carbon concentration of the silicon single crystal to be grown based on the first preliminary test step for obtaining the first calibration curve representing the relationship between the first calibration curve and the first calibration curve. A first determination step to be determined; a first filling step in which the silicon raw material determined in the first determination step is filled in a crucible; and the silicon raw material filled in the first filling step. And a first growth step of growing the silicon single crystal from the silicon melt.

  In the growth method of the second aspect of the present invention, the silicon single crystal is grown in advance, and the particle size of the silicon raw material and the carbon concentration of the silicon single crystal grown from the silicon melt obtained by melting the silicon raw material. The silicon material to be used is determined according to the target carbon concentration of the silicon single crystal to be grown using the second preliminary test step for obtaining the second calibration curve representing the relationship between the first calibration curve and the second calibration curve. Obtained by melting a second determination step, a second filling step of filling the crucible with the silicon raw material determined in the second determination step, and the silicon raw material filled in the second filling step A second growth step of growing the silicon single crystal from the silicon melt.

Embodiments of the present invention will be described below.
Consider a case where raw materials are classified into m levels with a predetermined range of sizes, and the crucibles are filled with raw materials of this m level. Here, a raw material classified into the i-th (1 ≦ i ≦ m) size is expressed as a raw material i. The crucible may be filled with all m-level raw materials, or may be filled with some of the m-level raw materials. That is, i is any or all of 1 to m. A characteristic accompanying the raw material i is expressed using a subscript i. In addition, when i is any one of 1 to m, one kind of raw material is assumed. In this case, it is determined whether or not the average carbon concentration C of the entire silicon single crystal is within the target range using the raw material. If it is determined that the average carbon concentration C is out of the range, the carbon concentration C within the target range is determined. Necessary measures will be taken so that Such treatment includes, for example, examining raw materials of different sizes or raw materials from different raw material manufacturers, and intentionally adding carbon.

Assuming that the amount of carbon contained in the silicon raw material is proportional to the surface area per unit volume (or unit mass) of the silicon raw material, that is, the specific surface area S, the average carbon concentration C of the entire silicon single crystal is as follows: It is expressed by a formula.
C = S × Kr + C ₀
= ΣC _i (value selected from i = 1 to m) + C ₀
= ΣS _i × x _i × Kr _i (value selected from i = 1 to m) + C ₀ (1)

here,
S _i : Surface area per unit volume (or unit mass) of raw material i (specific surface area)
C _i : Contribution of the raw material i to the average carbon concentration C of the silicon single crystal (from the surface)
C ₀ : Contribution to the average carbon concentration C of the silicon single crystal due to other than the surface of the raw material (including the part due to intentional carbon addition)
x _i : Ratio of input material to input material i (input ratio: mass ratio). X ₁ + ... + X _m = 1
Kr _i: contribution to the average carbon concentration C of the silicon single crystal per unit surface area of the material i (proportional constant)
It is.

Furthermore, equation (1) can be modified as follows.
C = ΣS _i × x _i × Kr _i (value selected from i = 1 to m) + C ₀
= Σ (4 × π × r _i ² / (4/3 × π × r _i ³ )) × x _i × Kr _i + C ₀
= Σ (3 / r _i ) × x _i × Kr _i + C ₀
Here, r _i can be defined as, for example, “average radius when each raw material i is formed into a spherical shape without changing the volume of the raw material i”.
Thus, the specific surface area (S _i ) and the particle size (2 × r _i ) of the raw material have an inversely proportional relationship.

The definition of the average radius r _i of the raw material is not limited to the above, but may be any definition that can be judged to have a reasonable relationship with the surface area of the raw material. Further, if appropriate, the expression (1) may be simplified by setting Kr ₁ = Kr ₂ = Kr ₃ (= constant) in the expression (1). Furthermore, as shown in FIG. 1 to be described later, the constant C _{0 in the} equation (1) is smaller than the amount of carbon brought about due to the raw material surface except when carbon is intentionally added. Also good.

As shown in the equation (1), the average carbon concentration C of the entire silicon single crystal is the sum of contributions (C _i ) of the raw material i (value selected from i = 1 to m) and contributions other than the raw material surface. It can be calculated from the minute C ₀ . Therefore, as the first calibration curve obtained in the first preliminary test step, an individual calibration curve for C _i of the raw material i or a calibration curve obtained by combining individual calibration curves can be used. The average carbon concentration C can be obtained from the sum of contributions to the average carbon concentration C of the entire silicon single crystal derived from the line.

Further, the formula (1) targets the average carbon concentration C of the entire silicon single crystal by appropriately selecting the input ratio (x _i ) of the raw material i (value selected from i = 1 to m). It shows that it can be within the range. That is, in the first determination step or the second determination step, it is determined which level of the raw material size levels 1 to m is used and what input ratio is to be used. The average carbon concentration C of the entire crystal can be set within the target range. At this time, when the target average carbon concentration C is high, in addition to carbon originating from the surface of the raw material, it is possible to intentionally add carbon to the raw material.

  The target average carbon concentration C may be a certain concentration value, or less than or less than a certain concentration value.

As a specific example, the case where the size of the silicon raw material filled in the crucible is only two levels (m = 2), “large diameter raw material A” and “small diameter raw material B” will be described. The large-diameter raw material A can have, for example, an aperture that passes through a sieve with a ₁ mm and an aperture that does not pass through a sieve with an a ₂ (a ₁ > a ₂ ) mm. For example, the aperture may pass through a sieve having a ₃ mm (a ₂ ≧ a ₃ ), and the aperture may not pass through a sieve having a ₄ mm (a ₃ > a ₄ ).

The average carbon concentration C of the entire silicon single crystal is
C = C _A + C _B + C ₀ (2)
It is expressed.

here,
C _A = 4 × π × r _A ² / (4/3 × π × r _A ³ ) × x _A × Kr _A
= 3 / r _A × x _A × Kr _A
C _B = 4 × π × r _B ² / (4/3 × π × r _B ³ ) × x _B × Kr _B
= 3 / r _B × x _B × Kr _B
r _A : average radius of large-diameter raw material A (assuming each raw material is spherical)
r _B : Average radius of small-diameter raw material B (assuming each raw material is spherical)
Kr _A : Contribution to the average carbon concentration C of the silicon single crystal per unit surface area of the large diameter raw material A (proportional constant)
Kr _B : Contribution to the average carbon concentration C of the silicon single crystal per unit surface area of the small diameter raw material B (proportional constant)
C ₀ : Contribution to the average carbon concentration C of the silicon single crystal due to other than the surface of the raw material.

For example, if the filling ratio (mass ratio) of the large diameter raw material A and the small diameter raw material B is 0.3: 0.7, x _A = 0.3, x _B = 0.7, and C _A = 3 / r _A × 0.3 × Kr _A , C _B = 3 / r _B × 0.7 × Kr _B.

By obtaining the relationship between x _A : x _B and C in advance, the values of Kr _A / r _A and Kr _B / r _B can be obtained. Therefore, in this case, even if the values of r _A and r _B are unknown, the carbon concentration C of the obtained silicon single crystal can be predicted based on the equation (2). In this case, the average carbon concentration C of the entire silicon single crystal can be controlled by the input ratio of the large diameter raw material A and the small diameter raw material B.

Also, by changing the average radius r _B of the small material B, it is possible to control the average carbon concentration C of the whole silicon single crystal. In this case, the average carbon concentration C of the entire silicon single crystal varies depending on the reciprocal of the average radius r _B of the small diameter raw material B. The carbon concentration C can also be controlled by changing the average radius r _A of the large diameter raw material A, but the small diameter raw material B contributes more to C per unit mass than the large diameter raw material A. It may be better to change the average radius r _B of the small material B, efficiently, to adjust the C.

The carbon concentration C can be controlled by both the input ratio of the large diameter raw material A and the small diameter raw material B and the average radius r _B of the small diameter raw material B. When growing a silicon single crystal having a low carbon concentration C, the ratio of the small-diameter raw material B may be reduced, and in addition to or instead of this, the average radius r _B of the small-diameter raw material _B is increased. May be.

When the contribution of the large diameter raw material A to the average carbon concentration C of the entire silicon single crystal is sufficiently smaller than that of the small diameter raw material B, it is possible to ignore the contribution of the large diameter raw material A as C≈C _B + C ₀ It is.

  As described above, the method of controlling the average carbon concentration of one silicon single crystal to be manufactured by mixing the raw materials filled in the quartz crucible with raw materials of a plurality of levels has been described. Next, the case where this method is applied to multi-pulling in which silicon raw material is added (recharged) to the silicon melt remaining in the crucible after the growth of the silicon single crystal is finished, and then further silicon single crystal is grown. explain.

When the number of recharges is n and (n + 1) single crystals are manufactured, the average carbon concentration C _{n + 1} of the entire (n + 1) th silicon single crystal is expressed by the following equation (3).
C _{n + 1} = (S × Kr + C ₀ ) + Σ ((S × Kr + C ₀ ) _j + Cp _j ) (j = 1 to n) (3)

In the above equation (3), the first term on the right side is the contribution of the initial raw material charge to the average carbon concentration C _{n + 1} of the silicon single crystal, and the second term on the right side is the average carbon concentration C _{n + 1 of the} silicon single crystal. It is a contribution by the raw material recharge. (S × Kr + C ₀ ) _{j in} the second term on the right side is a contribution to the average carbon concentration C _{n + 1} of the silicon single crystal due to carbon adhering to the raw material surface in the j-th recharge, and Cp _j is the j-th time It is the contribution to the average carbon concentration C _{n + 1} of the silicon single crystal resulting from the process in recharging. The expression (3) indicates that the carbon concentration of the silicon single crystal is determined by integrating the contribution due to recharging in addition to the contribution due to the initial raw material charge. Plural levels of raw materials having different sizes may be used as the raw material. In this case, the average carbon concentration C _{n + 1} is obtained by substituting Equation (1) into Equation (3).

  Hereinafter, controlling the carbon concentration of the silicon single crystal when performing multi-pulling will be described in detail. When performing multi-pulling, the carbon concentration of the silicon single crystal is expressed as shown in Table 1 by the specific surface area of the silicon raw material. The subscript number (≧ 1) in Table 1 corresponds to j in the expression (3), and means a recharge order number.

The meanings of symbols in Table 1 are as follows.
S: Specific surface area of silicon material in initial charge S ₁ : Specific surface area of silicon material in _first recharge S ₂ : Specific surface area of silicon material in second recharge Kr ₁ : Per specific surface area of raw material in first recharge Contribution to average carbon concentration C of silicon single crystal (proportional constant)
Kr ₂ : Contribution to the average carbon concentration C of the silicon single crystal per specific surface area of the raw material in the second recharge (proportional constant)
C _P1 : Contribution to process-induced C in the first recharge C _P2 : Process contribution to C in the second recharge
C ₁ : Contribution to C due to factors other than the raw material surface and process origin in the first recharge (including intentional carbon addition)
C ₂ : Contribution to C due to factors other than the raw material surface and process origin in the second recharge (including intentional carbon addition)

In this case as well, if the values of necessary ones of Kr ₁ , Kr ₂ , C ₁ , C ₂ , Cp ₁ , and Cp ₂ are determined by experiment, the mathematical formula in the column “Carbon concentration of silicon single crystal” in Table 1 is used. Is the calibration curve, and the average carbon concentration C of the silicon single crystal can be controlled by the average radius r of the raw material. Moreover, it can also be controlled by the input ratio of the size level of a plurality of raw materials.

The silicon raw material may be a combination of a large-diameter raw material and a small-diameter raw material, or a silicon raw material whose particle size is adjusted as a single type of raw material. Also in this case, the carbon concentration of the silicon single crystal increases as the particle size of the silicon raw material decreases (the specific surface area increases). For example, when the carbon concentration of the silicon single crystal is reduced, the initial charge is increased by setting the minimum frequency, the average particle diameter, or the maximum frequency value of the particle size distribution of the silicon raw material to be larger than 50 mm. The carbon concentration of the silicon single crystal by the recharge pulling can be reduced to 1.0 × 10 ¹⁶ atoms / cm ³ or less.

  The “minimum length” is the minimum length when the lengths of the particles or lumps constituting the silicon raw material are measured from a plurality of different directions. The “average particle diameter” may be an average value obtained by measuring an average particle diameter of each of several tens of particles or lumps randomly selected. The “particle size distribution” may be a particle size or particle size distribution of dozens of randomly selected particles or lumps.

  The calibration curve indicating the relationship between the silicon raw material particle size or specific surface area and the carbon concentration of the silicon single crystal does not necessarily need to be expressed by a linear expression of the silicon raw material particle diameter or specific surface area. When is large, for example, an nth order expression (2 ≦ n), an exponential function, a logarithmic function, or any other function expression can be employed.

  In the growth method of the present invention, when carbon is doped into a silicon single crystal, it is not necessary to use carbon powder, or even if it is necessary to use it, the amount used can be reduced. Dislocation of crystals can be suppressed. In addition, carbon powder used for doping carbon into a silicon single crystal is usually expensive because it has a special specification. In the growing method of the present invention, the incidental effect that the raw material cost can be reduced is obtained by not using carbon powder or by reducing the amount of carbon powder to be used.

  Silicon raw materials adjusted to various particle sizes (levels 1 to 6) were prepared, silicon single crystals were grown using each silicon raw material, and the relationship between the silicon raw material particle size and the carbon concentration of the silicon single crystal was examined. . For each silicon raw material, three silicon single crystals were continuously grown with a recharge interposed therebetween. Adjustment of the particle size of the silicon raw material was performed by visual selection so as to be in a predetermined raw material size range.

  Each silicon raw material was filled in the crucible (initial charge) and melted 100%, and the first silicon single crystal was pulled up from the obtained silicon melt by the CZ method. When the amount of the silicon melt became about half of the initial amount, the growth of the first silicon single crystal was completed.

  Subsequently, the silicon raw material having the same particle size as that initially filled was charged into the silicon melt remaining in the crucible (first recharge), and dissolved in the silicon melt. The second silicon single crystal was pulled up from the silicon melt in the same manner as the first silicon single crystal. When the amount of the silicon melt became about half of the initial amount, the growth of the second silicon single crystal was completed.

  Subsequently, the silicon raw material having the same particle size as that of the first filling was put into the silicon melt remaining in the crucible (second recharge) and dissolved in the silicon melt. Then, the third silicon single crystal was pulled up from this silicon melt in the same manner as the first silicon single crystal. The amount of recharge was set so that the sum of the silicon melt remaining in the crucible and the recharged silicon material was substantially equal to the filling amount of the silicon material of the initial charge.

None of the silicon single crystals produced dislocations.
For each silicon single crystal, the carbon concentration at a position where the solidification rate was 70% was measured. The carbon concentration was measured by the FTIR method.

  Table 2 shows the range of the size of the silicon raw material used, the surface area ratio of each raw material when the cylindrical raw material (level 6) having a diameter of 100 mm is 1 (hereinafter also simply referred to as “surface area ratio”), The carbon concentration of a silicon single crystal grown using each raw material (in the position where the solidification rate is 70%; hereinafter, also simply referred to as “carbon concentration”) is shown. The range of the raw material size indicates the range of the diameter of several tens of raw materials selected at random. The surface area ratio was obtained by approximating the shape of each silicon raw material to a sphere to obtain the surface area and dividing by the surface area of level 6 raw material of the same mass. Level 6 silicon raw material was a cylinder having a diameter of about 100 mm and a length of about 500 mm.

  FIG. 1 shows the relationship between the surface area ratio of the silicon raw material used and the carbon concentration of the silicon single crystal for each of the first to third silicon single crystals. In each of the first to third silicon single crystals, the surface area ratio of the silicon raw material and the carbon concentration of the silicon single crystal have a very strong correlation. For each of the first to third silicon single crystals, the regression line of the plot (shown in FIG. 1 by a solid line, a broken line, and an alternate long and short dash line, respectively) indicates the carbon concentration of the silicon single crystal relative to the surface area ratio of the silicon raw material. This is a calibration curve. Therefore, according to this calibration curve, the surface area ratio of the silicon raw material to be used is used when growing a silicon single crystal with a low carbon concentration and when growing a silicon single crystal doped with a predetermined concentration of carbon. Can be determined. Based on the calibration curve, a silicon single crystal having a substantially target carbon concentration is manufactured by using a silicon raw material having a surface area ratio (and therefore a particle size) corresponding to the target carbon concentration of the silicon single crystal. can do.

  FIG. 1 shows the results when the silicon raw material used for recharging is made to have the same particle size as the silicon raw material used for growing the first silicon single crystal in growing the second and third silicon single crystals. Show. However, the silicon raw material used for recharging in growing the second silicon single crystal may have a particle size different from that of the silicon raw material used for growing the first silicon single crystal. The silicon raw material used for recharging may have a particle size different from that of the silicon raw material used for growing the first and / or second silicon single crystal.

FIG. 1 shows a result of growing a silicon single crystal under specific conditions using a specific silicon raw material and a specific silicon single crystal growing apparatus, and silicon using a different raw material or apparatus. When a single crystal is grown, the calibration curve can be expressed by a formula different from FIG. In addition, even when the specific silicon raw material and the specific silicon single crystal growth apparatus are used, and the silicon single crystal is grown under conditions different from the specific conditions, the calibration curve is the same as FIG. It can be represented by a different formula.

Claims (8)

A method for growing a silicon single crystal by a Czochralski method from a silicon melt obtained by melting a silicon raw material,
First, a silicon single crystal is grown, and a first calibration curve representing the relationship between the specific surface area of the silicon raw material and the carbon concentration of the silicon single crystal grown from the silicon melt obtained by melting the silicon raw material is obtained. 1 preliminary test process;
A first determination step of determining a silicon raw material to be used according to a target carbon concentration of a silicon single crystal to be grown using the first calibration curve;
A first filling step of filling the crucible with the silicon raw material determined in the first determination step;
And a first growth step of growing the silicon single crystal from a silicon melt obtained by melting the silicon raw material filled in the first filling step. A method for growing a silicon single crystal according to claim 1,
A method for growing a silicon single crystal, wherein the first determining step, the first filling step, and the first growing step are repeated after finishing the first growing step. A method for growing a silicon single crystal by a Czochralski method from a silicon melt obtained by melting a silicon raw material,
First, a silicon single crystal is grown, and a second calibration curve representing the relationship between the grain size of the silicon raw material and the carbon concentration of the silicon single crystal grown from the silicon melt obtained by melting the silicon raw material is obtained. Two preliminary test steps;
A second determination step of determining a silicon raw material to be used according to a target carbon concentration of a silicon single crystal to be grown using the second calibration curve;
A second filling step of filling the crucible with the silicon raw material determined in the second determination step;
And a second growing step of growing the silicon single crystal from a silicon melt obtained by melting the silicon raw material filled in the second filling step. A method for growing a silicon single crystal according to claim 3,
A method for growing a silicon single crystal, wherein the second determining step, the second filling step, and the second growing step are repeated after finishing the second growing step. A method for growing a silicon single crystal according to claim 3,
In the second determination step, a target carbon concentration of the silicon single crystal to be grown is 1.0 × 10 ¹⁶ atoms / cm ³ or less, and the particle size of the silicon raw material to be used is set to be equal to that of the silicon raw material. A method for growing a silicon single crystal, wherein a minimum length, an average particle diameter, or a maximum frequency value of a particle size distribution is determined to be greater than 50 mm. A method for growing a silicon single crystal according to claim 4,
In at least one of the repeated second determination steps, the target carbon concentration of the silicon single crystal to be grown is 1.0 × 10 ¹⁶ atoms / cm ³ or less, and the grain size of the silicon raw material to be used Is determined to be larger than 50 mm by the minimum frequency, average particle diameter, or maximum frequency value of the particle size distribution of the silicon raw material. A method for growing a silicon single crystal according to any one of claims 1 to 6,
A method for growing a silicon single crystal, wherein the silicon raw material is obtained by crushing polycrystalline silicon and then selecting a silicon raw material having a predetermined range of sizes. A method for growing a silicon single crystal according to any one of claims 1 to 7,
A method for growing a silicon single crystal, wherein the silicon raw material is obtained by crushing a grown silicon single crystal and then selecting a silicon raw material having a predetermined range of sizes.

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