Method for producing single crystal silicon ingot using boric acid as dopant and ingot pulling device using solid phase dopant

Abstract

To provide a method for doping a silicon melt (e.g., counter doping) that involves boric acid.SOLUTION: An ingot is doped with boron using solid-phase boric acid as the source of boron. Boric acid may be used to counter-dope the ingot during ingot growth. Ingot puller apparatuses that use a solid-phase dopant are also disclosed. The solid-phase dopant may be disposed in a receptacle that is moved closer to the surface of the melt or a vaporization unit may be used to produce a dopant gas from the solid-phase dopant.SELECTED DRAWING: Figure 2

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of U.S. Provisional Patent Application No. 62 / 868,573, filed June 28, 2019, which is incorporated by reference in its entirety. [Technical field]

[0002] The field of the disclosure relates to methods of producing single crystal silicon ingots, where the ingots are doped with boron using solid phase boric acid as a source of boron, and to ingot pulling apparatus using solid phase dopants. [Background technology]

[0003] In high resistivity silicon wafer applications, the resistivity of the monocrystalline silicon ingot from which the wafers are sliced ​​is controlled by adding various dopants to the melt. The dopants may be used to compensate for various impurities (e.g., boron or phosphorus) in the source of polycrystalline silicon used to form the melt from which the silicon ingot is pulled.

[0004] When one or more dopants are added to achieve a target resistivity in an ingot, certain dopants and / or impurities may accumulate in the melt due to differences in the segregation coefficients of the compounds. For example, boron has a segregation coefficient of about 0.8, meaning that it is easily incorporated into the growing ingot. On the other hand, phosphorus has a segregation coefficient of about 0.35, meaning that while boron is easily incorporated, phosphorus is easily accumulated in the melt. Thus, as the ingot grows and the melt is depleted, phosphorus accumulates in the melt, changing the resistivity of the growing ingot. This results in a lower resistivity, outside of customer specifications, or a change in ingot type.

[0005] A need exists for a method of counterdoping a silicon melt during ingot growth to increase the length of the ingot while remaining within customer specifications. A need exists for a doping method that allows for the use of readily available and / or relatively inexpensive dopant source materials and allows for a relatively easy doping of the melt. A need exists for an ingot pulling apparatus that allows for the use of solid phase dopants as a dopant source.

[0006] This section is intended to introduce the reader to various aspects of art that may be related to various aspects of the present disclosure, which are described and / or claimed below. This discussion is believed to be helpful in providing the reader with background information to facilitate a better understanding of the various aspects of the present disclosure. As such, it should be understood that these statements are to be read in this light, and not as admissions of prior art. Summary of the Invention

[0007] One aspect of the present disclosure relates to a method for producing a single crystal silicon ingot from a silicon melt held in a crucible. Polycrystalline silicon is added to the crucible. The crucible is placed in an inner chamber of an ingot puller. The polycrystalline silicon is heated to form a silicon melt in the crucible. An ingot of single crystal silicon is pulled from the silicon melt. A source of solid phase boric acid is provided. A boron-containing gas is formed from the solid phase boric acid. The boron-containing gas is contacted with a surface of the melt to introduce boron into the melt as a dopant while the single crystal silicon ingot is pulled from the melt.

[0008] Another aspect of the disclosure relates to an ingot pulling apparatus for producing doped single crystal silicon ingots. The ingot pulling apparatus includes an ingot pulling outer housing and an ingot pulling inner chamber formed within the ingot pulling outer housing. A crucible is disposed within the ingot pulling inner chamber. An outer feed tube is disposed at least partially outside the ingot pulling outer housing. The outer feed tube defines an outer feed tube chamber. The outer feed tube has a distal end, a proximal end, and an outer feed tube axis extending through the distal end and the proximal end. An elongated member is movable within the outer feed tube chamber along the outer feed tube axis. A dopant container is coupled to the elongated member. The dopant container is movable between a fill position, where the dopant container is disposed outside the ingot pulling outer housing, and a feed position, where the dopant container is disposed within the ingot pulling inner chamber.

[0009] Yet another aspect of the present disclosure relates to an ingot pulling apparatus for producing doped single crystal silicon ingots. The ingot pulling apparatus includes an ingot pulling outer housing and an ingot pulling inner chamber formed in the ingot pulling outer housing. A crucible is disposed within the ingot pulling inner chamber. A dopant conduit having a gas inlet is disposed outside the ingot pulling inner chamber and a gas outlet is disposed within the ingot pulling inner chamber. A dopant vaporization unit is disposed outside the ingot pulling chamber. The dopant vaporization unit includes a dopant chamber for holding a dopant in a solid phase. The dopant vaporization unit includes a heating device for heating the solid phase dopant and for forming a dopant gas. The dopant vaporization unit includes an outlet through which the dopant gas passes. The outlet is in fluid communication with the dopant conduit.

[0010] There are various refinements to the features noted in relation to the above-mentioned aspects of the disclosure. Further features may also be incorporated into the above-mentioned aspects of the disclosure as well. These refinements and additional features may exist individually or in any combination. For example, the various features described below in relation to any of the illustrated embodiments of the disclosure may be incorporated alone or in any combination into any of the above-mentioned aspects of the disclosure. [Brief description of the drawings]

[0011] [Figure 1] FIG. 1 is a schematic diagram of an example of a method for growing a silicon ingot using boric acid as a source of dopant. [Diagram 2] 1 is a partial cross-sectional side view of an embodiment of an ingot pulling apparatus having a dopant reservoir in a dopant fill position. [Diagram 3] FIG. 2 is a partial cross-sectional side view of an ingot pulling apparatus with a dopant container in a dopant supply position. [Figure 4] FIG. 2 is a detailed cross-sectional side view of the ingot pulling apparatus with the dopant reservoir in the dopant supply position. [Diagram 5] FIG. 2 is a side view of an elongated member including a dopant container for holding a solid phase dopant and a movement unit for moving the elongated member. [Figure 6] FIG. [Figure 7] FIG. 13 is a cross-sectional side view of a joint between an elongated member and a moving unit. [Figure 8] FIG. 2 is a perspective cross-sectional view of an elongated member within an outer tube with the container in a dopant filling position. [Figure 9] FIG. 2 is a cross-sectional side view of the container. [Figure 10] FIG. 13 is a cross-sectional side view of another embodiment of an ingot pulling apparatus. [Figure 11] FIG. 2 is a cross-sectional side view of a vaporization unit of an ingot pulling apparatus. [Figure 12] FIG. [Figure 13]FIG. 2 is a detailed cross-sectional side view of the vaporization unit.

[0012] Corresponding reference characters indicate corresponding parts throughout the drawings. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] The present disclosure provides for a method for doping (e.g., counterdoping) a silicon melt with boric acid. Additional provisions relate to an ingot puller configured to dope a silicon melt, particularly an ingot puller configured to dope with a solid phase dopant such as boric acid.

[0014] Doping method using boric acid An example of the method of the present disclosure is shown in Figure 1. The method may be practiced by use of an ingot pulling apparatus configured to form a boron-containing gas from solid phase boric acid. Exemplary ingot pulling apparatuses for use in accordance with the method of doping with boric acid are shown in Figures 2-13. For purposes of illustrating the method, it may be described with reference to the ingot pulling apparatus 100 shown in Figures 2-9 or the ingot pulling apparatus 400 shown in Figures 10-13, but unless otherwise indicated, the method should not be limited to the ingot pulling apparatus 100, 400.

[0015] 2, in accordance with an embodiment of a method for preparing a silicon ingot, a silicon melt is prepared in a crucible 104 disposed in an inner chamber 102 of an ingot pulling apparatus 100. The crucible 104 may be supported by a susceptor (not shown). The ingot pulling apparatus 100 may be configured to rotate the crucible 104 and / or move the crucible 104 vertically within the ingot pulling apparatus 100.

[0016] To prepare the silicon melt, polycrystalline silicon is added to the crucible 104. The polycrystalline silicon is heated above the melting temperature of silicon (approximately 1414° C.) to liquefy the polycrystalline silicon into silicon melt 108. A heating system is operated to melt the polycrystalline silicon. For example, one or more heaters below or to the side of the crucible 104 are operated to melt the silicon.

[0017] Before or after the melt 108 is produced, the melt may be doped with a dopant, typically an n-type dopant, to compensate for p-type impurities (e.g., boron) in the melt. The n-type dopant may be added before growth of the ingot 112 is initiated. Compensating the melt may increase the resistivity of the resulting ingot 112. For example, the seed end of the ingot (i.e., the portion of the ingot closest to the ingot crown) may have a resistivity of at least about 1,500 Ω·cm, or in other embodiments, at least about 2,000 Ω·cm, at least about 4,000 Ω·cm, at least about 6,000 Ω·cm, at least about 8,000 Ω·cm, at least about 10,000 Ω·cm, or in a range from about 1,500 Ω·cm to about 50,000 Ω·cm, or from about 8,000 Ω·cm to about 50,000 Ω·cm. Suitable n-type dopants include phosphorus and arsenic.

[0018] Once the melt 108 is prepared, a single crystal silicon ingot 112 is pulled from the melt 108. A seed crystal 118 is secured to a seed chuck 114. The seed chuck 114 and crystal 118 are lowered until the seed crystal 118 contacts the surface of the silicon melt 108. Once the seed crystal 118 begins to melt, a pulling mechanism slowly pulls the seed crystal 118 up, causing the single crystal ingot 112 to grow.

[0019] A process gas (e.g., argon) is circulated through the inner chamber 102 of the ingot pulling apparatus 100. The process gas creates an atmosphere within the chamber 102.

[0020] As shown in FIG. 1, an embodiment of the disclosed method includes providing a source of solid-phase boric acid (H3BO3). The boric acid may be relatively pure, such as about 99% or greater purity, 99.9% or greater purity, or 99.99% or greater purity. In some embodiments, the boric acid may be relatively isotopically pure (i.e., boron-11). For example, the boric acid may be provided within the inner chamber 102 (i.e., within the housing 116) of the ingot pulling apparatus 100, such as the vessel 156 (FIG. 4) of the ingot pulling apparatus 100 of FIGS. 2-9. Alternatively, the solid-phase boric acid may be located outside the ingot pulling outer housing 416, such as within the dopant chamber 424 of the vaporization unit 414 of the ingot pulling apparatus 400 of FIGS. 10-13.

[0021] Boron-containing gases are formed from solid boric acid. The gases formed are generally boric acid (H3BO3) or its derivatives (B x O y H z + complex) and not other compounds (e.g., diborane (B2H6) or boron dihydrogen (BH2). However, it should be understood that other boron compounds may be added to the boron-containing gas.

[0022] The solid phase boric acid may be heated above its melting point (about 171° C.) to liquefy the solid phase boric acid and form a boric acid liquid. The boric acid liquid may then be heated above its vaporization temperature (about 300° C.) to form a boron-containing gas. For example, the solid phase boric acid may be heated by heat radiated from the silicon melt 108 of the ingot pulling apparatus of FIGS. 2-9 or by the heating device 428 (FIG. 12) of the vaporization unit 414 of the ingot pulling apparatus of FIGS. 10-13.

[0023] Once the boron-containing gas is formed, it can contact the surface of the melt 108 and diffuse boron into the melt. For example, the flow path of the boron-containing gas in the outlet tube 168 (FIG. 4) can be restricted so that the boron-containing gas travels only through the tube outlet 170 as in the ingot pulling apparatus 100 of FIGS. 2-9, or the boron-containing gas can be carried by the process gas as in the ingot pulling apparatus 400 of FIGS. 10-13.

[0024] As boron enters the melt, due to phosphorus' relatively low segregation coefficient, the boron compensates for the phosphorus enrichment in the melt, thereby increasing the resistivity of the remainder of the ingot 112 being formed in the ingot puller.

[0025] Ingot pulling apparatus for doping with solid dopants. An exemplary ingot pulling apparatus 100 is shown generally in Figures 2-9, and another exemplary ingot pulling apparatus 400 is shown in Figures 10-13. The apparatus 100 of Figures 2-9 and the apparatus 400 of Figures 10-13 may be used to dope an ingot with boron using solid phase boric acid as in the method described above, or may use other solid phase dopants (e.g., doped glass with a relatively high concentration of B2O3 mixed with SiO2, or a highly doped Si-B alloy) that may be vaporized below the melting point of silicon (about 1414°C) in its natural form, or in a hydrated form, or a compound that is non-contaminating to the crystal growth process.

[0026] 2, the ingot pulling apparatus 100 includes an ingot pulling outer housing 116 that defines an ingot pulling inner chamber 102 within the housing 116. Disposed within the ingot pulling inner chamber 102 is a crucible 104. The crucible 104 contains a silicon melt 108 from which a silicon ingot 112 is pulled. The ingot 112 is covered by a heat shield 120.

[0027] The ingot pulling apparatus 100 includes a dopant supply system 126. The dopant supply system 126 includes an outer supply tube 130 disposed at least partially outside the ingot pulling housing 116. The outer supply tube 130 defines an outer supply tube chamber 136 therein. The outer supply tube 130 has a distal end 140 furthest from the outer housing 116 and a proximal end 144 closest to the housing 116. An outer supply tube axis A 130 extends through the distal end 140 and the proximal end 144 of the outer supply tube 130. The outer supply tube 130 may be made of stainless steel or other suitable material.

[0028] The elongated member 150 is aligned with the outer supply pipe axis A. 130 4. The elongated member 150 may be lowered into the ingot pulling inner chamber 102, as shown in FIG. 4. In the illustrated embodiment, the elongated member 150 is a tube. In other embodiments, a rod or shaft may be used. The elongated member 150 may be made of any material that will withstand the environment within the ingot pulling chamber 102, such as quartz.

[0029] The dopant reservoir 156 is coupled to (e.g., nested within) the elongated member 150 (FIG. 4). As shown in FIG. 8, the reservoir 156 may abut a ledge 160 of the elongated member 150. The reservoir 156 may include a shoulder 162 (FIG. 9) that seats on the ledge 160. By moving the elongated member 150, the dopant reservoir 156 moves between a raised position (FIG. 2, also referred to as the "dopant loading position") in which the dopant reservoir 156 is disposed outside the ingot pulling outer housing 116 and a lowered position (FIGS. 3 and 4, also referred to as the "dopant supply position") in which the reservoir 156 is disposed within the ingot pulling inner chamber 102 near the surface of the melt 108. The heat shield 120 may include a channel 124 (FIG. 2) formed therein to provide a path for the elongated member 150 and the dopant reservoir 156 coupled thereto to access the melt 108.

[0030] The container 156 may be separable from the elongated member 150. The elongated member 150 includes a notch 164 (FIG. 5) that allows access to the container 156. In the filling position (FIG. 2), the container 156 may be removed from the elongated member 150 for filling with dopant. The notch 164 aligns with an access port 166 that allows access to the container 156 when the container 156 is in the filling position. The container 156 may be grasped by a connecting loop 172 of the container 156 to pull the container 156 through the notch 164 and the access port 166. In other configurations, the dopant may be added to the container 156 when the container 156 is disposed in the elongated member 150.

[0031] A dopant gas is formed from the solid phase dopant at the feed position of the vessel (FIGS. 3 and 4) The dopant gas passes through an outlet tube 168 and is directed through an outlet 170 to the surface of the melt 108.

[0032] In the illustrated embodiment, the container 156 is a capsule 158 (FIG. 9) that holds a solid-phase dopant. The capsule 158 includes an outer capsule housing 180. A weir 182 is disposed within the outer capsule housing 180. The weir 182 forms a channel 184 therein. The weir 182 has an upper end 188 and a lower end 190 that are each open to allow gas to pass through the channel 184. An annular chamber 194 is disposed between the weir 182 and the outer capsule housing 180. A solid dopant 174 (e.g., boric acid) is disposed within the annular chamber 194 and rests on a capsule floor 198. When the container 156 is in its lowered position (FIGS. 3 and 4), the solid-phase dopant 174 is heated, causing the dopant to sublime or melt and evaporate. The dopant gas rises within the annular chamber 194 and enters the weir channel 184 through the upper end 188 of the weir 182. The gas continues through the channel 184 and exits through the open lower end 190 of the weir 182. The dopant gas proceeds through the exit tube 168 (FIG. 4) and through the tube exit 170 toward the surface of the melt.

[0033] The elongated member 150 includes a gas barrier wall 240 (FIG. 8) that prevents gas from flowing back up the elongated member 150. Alternatively, the elongated member may be a rod or shaft that does not include a path for gas to flow back up.

[0034] 4, the ingot pulling apparatus 100 includes an isolation valve 200 in the outer supply tube 130. The isolation valve 200 seals the ingot pulling inner chamber 102 when the elongated member 150 is withdrawn from the ingot pulling inner chamber 102. This allows the dopant reservoir 156 to be accessed through the access port 166 while the port 156 is isolated from the inner chamber 102. When the elongated member 150 is lowered, the access port 166 may be closed or connected to a source of process gas (e.g., argon). The isolation valve 200 is connected to a valve controller 202 which operates the valve 200.

[0035] The ingot pulling apparatus 100 includes a moving apparatus 208 (FIG. 2) for moving the dopant reservoir 156 between a dopant fill position (FIG. 2) and a dopant supply position (FIGS. 3 and 4). The moving apparatus 208 moves the elongated member 150 and the dopant reservoir 156 within the inner chamber 102 and the outer supply tube chamber 136 of the ingot pulling apparatus 100 (i.e., along the outer supply tube axis A). 130 In general, any moving device 208 capable of moving the container 156 between the dopant fill position and the dopant supply position of the container 156 can be used unless otherwise specified.

[0036] In the illustrated embodiment, the moving device 208 is a magnetically coupled through-wall moving device. The moving device 208 includes an outer tube 212 and an inner member 214 that moves within the outer tube 212. The inner member 214 is magnetically coupled to a moving device handle 216. The outer tube 212 may be made of stainless steel (non-magnetic) or other suitable material. The moving device handle 216 and the inner member 214 may have magnets embedded therein to enable magnetic coupling between the handle 216 and the inner member 214.

[0037] The inner member 214 is also connected to the elongated member 150 at a joint 220 (FIG. 7). The exemplary joint 220 includes a threaded member 224 that surrounds a lower portion of the inner member 214 and engages threads on a sleeve 218 pinned thereto. The joint 220 includes first and second O-rings 228, 232 and a bushing 236 disposed between the O-rings 228, 232. The threaded member 224 compresses the O-rings 228, 232 to move radially outward, facilitating a frictional connection between the transfer device inner member 214 and the elongated member 150.

[0038] The handle 216 of the moving device 208 is connected to the axis A. 130 (FIG. 2). As the handle 216 moves, the inner member 214 moves within the outer tube 212. The inner member 214 is coupled to the elongated member 150 such that the elongated member 150 and the vessel 256 move in and out of the inner chamber 102 of the ingot pulling apparatus 100. In some embodiments, when the vessel 156 is in a lowered position for delivering dopant, the distance between the vessel 156 and the melt 108 may be varied (e.g., by an operator) to vary the heat applied to the vessel 156 and the solid phase dopant therein to control the rate at which dopant gas is formed. In other embodiments, the vessel 156 may be moved between its fill position (FIG. 2) and its dopant delivery position (FIGS. 3 and 4) by an actuator rather than manually.

[0039] As mentioned above, the movement device 208 may have other configurations. Other example movement devices may include a bellows system or an externally operated linear movement device (e.g., a rod mounted on either an externally isolated linear rail or a pneumatic cylinder). Any external actuators should be isolated from the heat and vacuum within the inner chamber 102.

[0040] Another example ingot pulling apparatus 400 is shown in Figures 10-11. Ingot pulling apparatus 400 may operate similarly to ingot pulling apparatus 100 described above, and it is believed that the operation of apparatus 100 is applicable to apparatus 400 (in aspects not related to the use of solid phase dopants). For example, ingot pulling apparatus 400 includes an outer housing 416 forming an inner chamber 402 within housing 416. A crucible 404 is disposed within chamber 402 for holding a silicon melt 408 therein. Apparatus 400 includes a heat shield (not shown) that obscures an ingot being pulled from the melt.

[0041] The ingot pulling apparatus 400 includes a dopant evaporation unit 414 that supplies a doped gas to a dopant conduit 430. The doped gas passes through the dopant conduit 430 to contact and dope the melt 408. The dopant conduit 430 includes a gas inlet 422 ( FIG. 11 ) located outside the ingot pulling chamber 402 and a gas outlet 426 located within the ingot pulling inner chamber 402 and relatively close to the surface of the melt 408.

[0042] The dopant vaporization unit 414 is disposed outside the ingot pulling inner chamber 402. The dopant vaporization unit 414 includes a dopant chamber 424 (FIG. 13) for holding a solid phase dopant (e.g., boric acid as discussed in the above manner). A process gas (e.g., argon) may be circulated through the vaporization unit 414 through first and second process gas inlets 436, 440. A doping gas outlet 452 of the vaporization unit 414 is in fluid communication with a dopant conduit 430 (FIG. 11) for transporting the doping gas to the surface of the melt 408.

[0043] Surrounding the dopant chamber 424 is a heating chamber 472 (FIG. 13). A heating device 428 (e.g., a resistive heating element) heats the gas circulating in the vaporization unit 414. The heated gas contacts the solid phase dopant in the dopant chamber 242 and a dopant gas forms (e.g., by sublimation or by liquefying and vaporizing the solid phase dopant). The dopant gas entrains the process gas to form a doped process gas that is exhausted through the doped gas outlet 452 to the dopant conduit 430 (FIG. 11). The vaporization unit 414 includes a heat shield 476 to reduce heat lost through the walls of the heating chamber 472. The heating chamber 472 may be made of quartz to reduce contamination.

[0044] An isolation valve 460 is in the process gas path, downstream of the heater chamber 472 and the dopant chamber 424. The isolation valve 460 isolates the vaporization unit 414 from the inner chamber 402 of the ingot pulling apparatus 400 and seals the chamber 402 when dopant is not being added to the melt 408. A valve controller 464 may be used to operate the valve 460.

[0045] The vaporization unit 414 includes a temperature sensor 448 (FIG. 12) to measure the temperature of the heating chamber 472 (FIG. 13). The temperature sensor 448 may send a signal to the control unit to vary the power of the heating device 428 based on the detected temperature. The vaporization unit 414 includes a vacuum port 456 to equalize pressure with the ingot puller inner chamber 402 for pump-down, leak testing, and before opening the isolation valve 460 for doping.

[0046] Compared to conventional methods for producing single crystal silicon ingots from silicon melts, the methods of the present disclosure have several advantages. In embodiments where the melt is counterdoped by using boric acid, a larger portion of the ingot is within customer specifications (e.g., high resistivity) and / or ingot type change is prevented. The dopant gas can be produced relatively easily because solid phase boric acid has a relatively low melting point and vaporization temperature.

[0047] Compared to conventional ingot pulling apparatus, the ingot pulling apparatus of the present disclosure has several advantages. In embodiments where a dopant container is used to hold the solid dopant, the container can be placed close to the melt, where the heat of the melt can melt and vaporize the dopant. The formation of precipitates or condensation of elemental boron or boron compounds, which can result in loss of crystal structure or integrity, can also be reduced or prevented. The use of a dopant container that includes a weir allows the dopant particles to move within the container without being propelled from the container into the melt. If the dopant particles were to enter the melt directly, it could damage the zero dislocations in the ingot. The use of an isolation valve allows the ingot pulling inner chamber to be isolated from the solid dopant system, preventing contamination of the melt and allowing refilling of the solid dopant. The use of a magnetically coupled through-wall movement unit can simplify sealing and make the system more robust (e.g., without a separate seal) to maintain an airtight environment.

[0048] In embodiments where the solid phase dopant is converted to a gas by a vaporization unit external to the ingot pulling housing, a heating device may be used to heat the dopant, allowing for improved control of the rate at which the dopant is added to the melt. The rate at which the process gas is circulated through the vaporization unit may also be used to control the rate at which the melt is doped. In embodiments where the supply tube or conduit is movable within the ingot pulling apparatus, its distance from the melt may be controlled to control the rate at which the dopant is added to the melt.

[0049] As used herein, the terms "about," "substantially," "essentially," and "approximately," when used in connection with a dimension, concentration, temperature, or other physical or chemical property or range of properties, are intended to cover the variation that may exist at the upper and / or lower limits of the property or range of properties, including, for example, variations that result from rounding, measurement method, or other statistical variations.

[0050] When introducing elements of the disclosure or embodiments thereof, the articles "a," "an," "the," and "said" are intended to mean that there are one or more of the element. The terms "comprising," "including," "containing," and "having" are intended to be inclusive and mean that there may be additional elements other than the listed elements. The use of specific orientation terms (e.g., "top," "bottom," "side," etc.) is for convenience of description and does not require a particular orientation of the items being described.

[0051] Because various changes may be made in the structures and methods described above without departing from the scope of the present disclosure, it is intended that all matter contained in the above description and shown in the accompanying drawings be interpreted as illustrative and not in a limiting sense.

Claims

1. 1. A method for producing a single crystal silicon ingot from a silicon melt held in a crucible, comprising: adding polycrystalline silicon to a crucible, the crucible being disposed within an inner ingot pulling chamber; heating the polycrystalline silicon to form a silicon melt in a crucible; Pulling a single crystal silicon ingot from the silicon melt; providing a source of solid phase boric acid; forming a boron-containing gas from solid phase boric acid; and while pulling the single crystal silicon ingot out of the melt, bringing a boron-containing gas into contact with the surface of the melt to introduce boron into the melt as a dopant; The method includes:

2. 10. The method of claim 1, further comprising the step of adding an n-type dopant to the crucible prior to pulling the single crystal silicon ingot from the melt.

3. The method of claim 2, wherein the n-type dopant is phosphorus.

4. The boron-containing gas is liquefying the solid phase boric acid to form a boric acid liquid; and evaporating the boric acid liquid to form a boron-containing gas; The method of claim 1 formed by

5. 10. The method of claim 1, wherein the solid phase boric acid is disposed within an ingot pulling inner chamber.

6. The method of claim 5 , wherein the solid phase boric acid is disposed in a capsule.

7. 10. The method of claim 1, wherein the solid phase boric acid is disposed external to an ingot pulling housing of the ingot pulling apparatus.

8. The method of claim 7, wherein the solid phase boric acid is in a chamber of the vaporization unit.

9. The crucible is disposed within an ingot pulling apparatus having an ingot pulling outer housing; an outer feed tube disposed at least partially outside the ingot pulling outer housing, the outer feed tube defining an outer feed tube chamber, the outer feed tube having a distal end, a proximal end, and an outer feed tube axis extending through the distal end and the proximal end; and an elongate member movable within the outer feed tube chamber along the outer feed tube axis, the method comprising: adding a source of solid phase boric acid to a dopant reservoir coupled to an elongated member; and 6. The method of claim 5, comprising: moving the elongated member from a loading position where the dopant container is disposed outside the ingot pulling outer housing to a feed position where the dopant container is disposed within the ingot pulling inner chamber, generating a boron-containing gas from solid phase boric acid while the elongated member is in the feed position, the boron-containing gas being discharged from the dopant container to contact a surface of the melt and enter the melt as a boron dopant while pulling the single crystal silicon ingot from the melt.

10. 10. The method of claim 9, wherein the dopant container is a capsule separable from the elongated member.

11. The capsules are an outer capsule housing; and 11. The method of claim 10, including a weir disposed within the outer capsule housing, the weir forming a channel for passage of dopant gas, the weir having an upper end and a lower end, the upper end and the lower end being open, and an annular chamber disposed between the weir and the outer capsule housing for holding the dopant in a solid phase.

12. 10. The method of claim 9, wherein the ingot puller includes a tube disposed below the dopant vessel for directing the dopant gas to the surface of the melt.

13. The method of claim 9 , wherein the elongated member is a tube.

14. 10. The method of claim 9, further comprising a valve for sealing the inner ingot pulling chamber when the elongated member is withdrawn from the inner ingot pulling chamber.

15. 10. The method of claim 9, including the step of operating a translation device to move the dopant container between the loading position and the delivery position.

16. The method of claim 15, wherein the translator is a magnetically coupled through-wall translator.

17. The method of claim 15, wherein the translation device is a bellows system.

18. The crucible is disposed within an ingot pulling apparatus having an ingot pulling outer housing, a dopant conduit having a gas inlet disposed outside the ingot pulling inner chamber and a gas outlet disposed within the ingot pulling inner chamber, and a dopant evaporation unit disposed outside the ingot pulling chamber, the method comprising: adding a source of solid phase boric acid to a dopant chamber of a dopant vaporization unit; activating a heating device of the vaporization unit to heat the solid phase boric acid and generate a boron-containing gas; and 8. The method of claim 7, further comprising the step of: passing the boron-containing gas through an outlet of the vaporization unit and into a dopant conduit.

19. 20. The method of claim 18, including the step of admitting the process gas through an inlet in fluid communication with the dopant chamber, the process gas passing through the dopant chamber and passing through an outlet.

20. 1. An ingot pulling apparatus for producing a doped single crystal silicon ingot, comprising: Ingot pulling outer housing, an ingot pulling inner chamber formed within an ingot pulling outer housing; a crucible disposed within the inner ingot pulling chamber; a dopant conduit having a gas inlet located outside the inner ingot pulling chamber and a gas outlet located within the inner ingot pulling chamber; and a dopant vaporization unit located outside the ingot pulling chamber, a dopant chamber for holding a solid phase dopant; a heating device for heating the solid phase dopant to form a dopant gas; an outlet through which a dopant gas passes, the outlet being in fluid communication with the dopant conduit; and a dopant vaporization unit including an inlet for introducing a process gas, the inlet being external to the ingot pulling outer housing, the inlet being in fluid communication with the dopant chamber, the process gas passing through the dopant chamber and through an outlet; An ingot pulling apparatus comprising:

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