System and method for producing single crystal silicon ingots using vaporized dopants - Patents.com

Abstract

A system and method are disclosed for doping a single crystal silicon ingot pulled from a silicon melt held in an ingot puller. The ingot puller includes a housing defining a chamber, a crucible disposed in the chamber, and a dopant injector extending into the housing. The method includes heating an evaporation cup and maintaining a pressure within the housing at a first pressure. The method further includes injecting a liquid dopant into the evaporation cup. The pressure of the liquid dopant is maintained at a second pressure that is higher than the first pressure prior to injection. The method also includes vaporizing the liquid dopant by heating the liquid dopant with the evaporation cup and injecting the liquid dopant into the housing to reduce the pressure of the liquid dopant from the second pressure to the first pressure, thereby vaporizing the liquid dopant, and directing the vaporized dopant into the housing.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority to U.S. Patent Application No. 17 / 139367, filed December 31, 2020, and U.S. Patent Application No. 17 / 139352, filed December 31, 2020, the disclosures of which are incorporated by reference in their entireties herein. [Technical field]

[0002] The present invention relates to systems and methods for producing single crystal silicon ingots using vaporized dopants. [Background technology]

[0003] In high resistivity silicon wafer applications, the resistivity of the monocrystalline silicon ingot from which the wafers are sliced ​​can be controlled by adding various dopants to the melt. The dopants can 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. Summary of the Invention [Problem to be solved by the invention]

[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, which allows boron to be easily incorporated into the growing ingot. Phosphorus has a segregation coefficient of about 0.35, which causes phosphorus to accumulate in the melt relative to boron, which is more easily incorporated. Thus, as the ingot grows and the melt is depleted, phosphorus accumulates in the melt and the resistivity of the growing ingot changes. This can cause the resistivity to drop, deviate from customer specifications, and / or cause the ingot to change type.

[0005] A need exists for a method for counter-doping a silicon melt during ingot growth to increase the length of the ingot that remains within customer specifications. There is also a need for a doping method that allows for the use of dopant source materials that are readily available and / or relatively inexpensive, allowing the melt to be doped relatively easily. Additionally, a need exists for an ingot pulling apparatus that allows for liquid phase dopants to be used as the source of dopant.

[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. [Means for solving the problem]

[0007] In one aspect, an ingot pulling apparatus for producing doped single crystal silicon ingots includes a housing defining a chamber, a crucible disposed within the chamber, and a dopant injector extending into the housing. The dopant injector includes a delivery module attached to the housing and extending through the housing into the chamber. The delivery module includes a dopant injection tube disposed within the chamber, and a vaporization cup disposed within the dopant injection tube and the chamber. A second valve selectively directs liquid dopant to the vaporization cup, which vaporizes the liquid dopant into a vaporized dopant.

[0008] In another aspect, an ingot pulling apparatus for producing doped single crystal silicon ingots includes a housing defining a chamber, a crucible disposed within the chamber, and a dopant injector extending into the housing. The dopant injector includes an injection module attached to an exterior surface of the housing. The injection module includes a first reservoir for containing a liquid dopant, a second reservoir for containing a liquid dopant, a first valve for selectively directing the liquid dopant from the first reservoir to the second reservoir, and a second valve for selectively directing the liquid dopant from the second reservoir to the chamber. The dopant injector also includes a delivery module attached to the injection module and extending through the housing into the chamber. The second valve selectively directs the liquid dopant to the delivery module, which vaporizes the liquid dopant into a vaporized dopant.

[0009] In yet another aspect, an ingot pulling apparatus for producing doped single crystal silicon ingots includes a housing defining a chamber, a crucible disposed within the chamber, and a dopant injector extending into the housing. The dopant injector includes an injection module attached to an exterior surface of the housing. The injection module includes a first reservoir for containing a liquid dopant, a second reservoir for containing a liquid dopant, a first valve for selectively directing the liquid dopant from the first reservoir to the second reservoir, and a second valve for selectively directing the liquid dopant from the second reservoir to the chamber. The dopant injector also includes a delivery module attached to the injection module and extending through the housing into the chamber. The delivery module includes a dopant injection tube disposed within the chamber, and an evaporation cup disposed within the dopant injection tube and the chamber. A second valve selectively directs the liquid dopant to a vaporization cup, which vaporizes the liquid dopant into a vaporized dopant.

[0010] In another aspect, a method is provided for doping a single crystal silicon ingot pulled from a silicon melt held in a crucible disposed within an ingot puller. The ingot puller includes a housing, a dopant injector extending into the housing, and a heating system disposed with the housing. The dopant injector includes a dopant injection tube disposed within the housing, and an evaporation cup disposed within the dopant injection tube and the housing. The method includes heating the evaporation cup using the heating system. The method also includes maintaining a pressure within the housing at a first pressure. The method further includes injecting a liquid dopant into the dopant injection tube and the evaporation cup. The pressure of the liquid dopant is maintained at a second pressure that is higher than the first pressure prior to injection into the dopant injection tube and the evaporation cup. The method also includes vaporizing the liquid dopant into the housing into a vaporized dopant. The liquid dopant is vaporized by flash evaporation by heating the liquid dopant with a vaporization cup and reducing the pressure of the liquid dopant from the second pressure to the first pressure by injecting the liquid dopant into the housing, the method further including directing the vaporized dopant into the housing using a dopant injection tube.

[0011] In yet another aspect, a method is provided for producing a single crystal silicon ingot from a silicon melt held in a crucible disposed within an ingot puller. The method includes adding polycrystalline silicon to the crucible. The crucible is disposed within an ingot puller inner chamber. The method also includes heating the polycrystalline silicon to form a silicon melt in the crucible. The method further includes pulling a single crystal silicon ingot from the silicon melt. The method also includes injecting a liquid dopant into the ingot puller. The method further includes vaporizing the liquid dopant into a vaporized dopant within the ingot puller. The method also includes contacting the vaporized dopant with a surface of the melt to introduce the vaporized dopant into the melt as a dopant while pulling the single crystal silicon ingot from the melt.

[0012] In another aspect, a method is provided for doping a single crystal silicon ingot pulled from a silicon melt held in a crucible disposed within an ingot puller. The ingot puller includes a housing, a dopant injector extending into the housing, and a heating system disposed with the housing. The dopant injector includes a dopant injection tube disposed within the housing, and a vaporization cup disposed within the dopant injection tube and the housing. The method includes heating the vaporization cup using the heating system. The method also includes injecting a liquid dopant into the dopant injection tube and the vaporization cup. The method further includes vaporizing the liquid dopant into the housing into a vaporized dopant. The liquid dopant is vaporized by flash evaporation by heating the liquid dopant with the vaporization cup. The method also includes directing the vaporized dopant into the housing using the dopant injection tube.

[0013] Various refinements exist in the features noted in relation to the above-mentioned aspects of the disclosure. Additional features may 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, 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]

[0014] [Figure 1] FIG. 2 is a partial cross-sectional side view of an embodiment of an ingot pulling apparatus having a dopant injector. [Diagram 2] FIG. 2 is a perspective view of the dopant injector shown in FIG. [Diagram 3] 2 is a cross-sectional perspective view of the dopant injector shown in FIG. 1. [Figure 4A] 2 is a cross-sectional perspective view of the dopant injector shown in FIG. 1. [Figure 4B] FIG. 4B is a detailed cross-sectional perspective view of the dopant chamber shown in FIG. 4A. [Figure 5A] 2 is a cross-sectional perspective view of the dopant injector shown in FIG. 1. [Figure 5B] FIG. 5B is a detailed cross-sectional perspective view of the dopant chamber shown in FIG. 5A. [Figure 6A] 2 is a cross-sectional perspective view of the dopant injector shown in FIG. 1. [Figure 6B] FIG. 6B is a detailed cross-sectional perspective view of the delivery module shown in FIG. 6A. [Figure 7] FIG. 4 is a cross-sectional perspective view of the vaporizer cup shown in FIG. [Figure 8] 1 is a graph of ingot resistivity as a function of ingot length. [Figure 9] 1 is a schematic diagram showing an example of a method for producing a single crystal silicon ingot. [Figure 10] FIG. 1 is a schematic diagram illustrating an example of a method for doping a single crystal silicon ingot. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] Corresponding reference characters indicate corresponding parts throughout the drawings.

[0016] One example of an ingot pulling apparatus 100 is shown generally in Figures 1-8. The apparatus 100 of Figures 1-8 may be used to counterdope or dope an ingot with vaporized boron dopant, as in the methods described herein, or may be used with other liquid phase dopants that may be vaporized below the melting temperature of silicon (about 1414°C) in either their native form, hydrated form, or compounds that are non-contaminating to the crystal growth process.

[0017] 1, an ingot pulling apparatus 100 includes an ingot pulling outer housing 102 that defines an ingot pulling inner chamber 104 within the housing 102. A crucible 106 is disposed within the ingot pulling inner chamber 104. The crucible 106 contains a silicon melt 108 from which a silicon ingot 110 is pulled. The ingot 110 is covered by a heat shield 112.

[0018] The ingot puller 100 includes a dopant injector 114 for injecting liquid dopant into the ingot puller as the ingot 110 is pulled from the silicon melt 110. The dopant injector 114 allows the silicon melt 110 to be counter doped multiple times with liquid dopant as the ingot 110 is pulled from the melt, increasing the resistivity of the ingot, increasing the portion of the ingot that is within customer specifications (e.g., high resistivity), and increasing the efficiency of the ingot puller.

[0019] Dopant injector 114 includes an implant module 116, a delivery module 118, and a first flange 120. Implant module 116 and delivery module 118 are each attached to a first flange 120, which attaches the implant module and delivery module to housing 102. Specifically, housing 102 defines a dopant injector opening 122, and first flange 120 is attached to the housing such that the flange covers the dopant injector opening.

[0020] The implantation module 116 is mounted to a first side 124 of the first flange 120 such that the implantation module is disposed outside of the chamber 104. The delivery module 118 is mounted to a second side 126 of the first flange 120 such that the delivery module is disposed within the chamber 104. The implantation module 116 receives the dopant and channels the dopant to the delivery module 118, which receives the dopant from the implantation module and injects the dopant into the chamber 104 as described herein. In this embodiment, the implantation module 116 receives a liquid dopant and the delivery module 118 vaporizes the liquid dopant in the chamber 104 as described herein.

[0021] 2, the injection module 116 includes a second flange 128, a doping chamber 130 attached to the second flange 128, an actuation mechanism 132 disposed on top of the doping chamber, cooling fluid conduits 134 and 136 for directing cooling fluid to the dopant injector 114, bellows 138 attached to the first flange 120 and the second flange 128, and ports 140, 142, and 144 for directing material to and from the dopant injector 114. The doping chamber 130 is attached to a first side 146 of the second flange 128, the bellows 138 is attached to a second side 148 of the second flange 128 and the first side 124 of the first flange 120, and the ports 140, 142, and 144 are attached to and extend from the doping chamber. The bellows 138 allows the implantation module 116 to be positioned within the ingot pulling inner chamber 104 adjacent to the silicon melt 110. Specifically, the bellows 138 allows the implantation module 116 to be moved vertically relative to the silicon melt 110.

[0022] The cooling fluid conduits 134 and 136 include a cooling fluid supply 134 and a cooling fluid return 136. The cooling fluid conduits 134 and 136 extend into the doping chamber 130 through an actuation mechanism 132. The actuation mechanism 132 includes an air cylinder 150 for actuating a valve in the dopant injector 114, as described herein. The ports 140, 142, and 144 include an inert gas port 140 for supplying an inert gas to the dopant injector 114, a pressure sensor port 142 for measuring the pressure in the doping chamber 130, and a vacuum port 144 for creating a vacuum in the doping chamber.

[0023] 3, the implantation module 116 also includes a dopant addition tube 152, a first reservoir tube 154 defining a first reservoir 156, a second reservoir tube 158 partially defining a second reservoir 160, a first valve 162, a second valve 164, an actuator 166, an actuation shaft 168, and a cooling jacket 170. The dopant addition tube 152, the first reservoir tube 154, the first reservoir 156, and the first valve 162 are all disposed within the doping chamber 130. The second reservoir tube 158, the second reservoir 160, the actuation shaft 168, and the cooling jacket 170 all extend from the doping chamber 130. A second reservoir tube 158 surrounds the actuation shaft 168 to define a second reservoir 160 therebetween, and a cooling jacket 170 surrounds the second reservoir tube 158 .

[0024] The dopant addition tube 152 is coupled to a first reservoir 156, and a first valve 162 is selectively actuated by an actuation shaft 168 to maintain or release liquid dopant in the first reservoir. The dopant addition tube 152 receives liquid dopant and directs the liquid dopant to the first reservoir 156. The first valve 162 is closed, maintaining the liquid dopant in the first reservoir 156. When actuated by the actuation shaft 168, the first valve 162 is open, directing the liquid dopant to the second reservoir 160, as described herein.

[0025] The first reservoir 156 is coupled to the second reservoir 160, and a first valve 162 is selectively actuated by an actuation shaft 168 to release liquid dopant in the first reservoir to the second reservoir. The second reservoir 160 receives the liquid dopant and directs the liquid dopant to the delivery module 118. The second valve 164 is closed to maintain the liquid dopant in the second reservoir 160. When actuated by the actuation shaft 168, the second valve 164 opens to direct the liquid dopant to the delivery module 118 as described herein. The cooling jacket 170 receives cooling fluid from the cooling fluid supply 134 and returns the cooling fluid to the cooling fluid return 136. The cooling fluid cools the implant module 116 to prevent overheating of the implant module.

[0026] The ingot pulling inner chamber 104 is maintained at a first pressure and the doping chamber 130 is maintained at a second pressure higher than the first pressure. Specifically, the first pressure in the ingot pulling inner chamber 104 is maintained at a vacuum and the second pressure in the doping chamber 130 is maintained at atmospheric pressure such that the liquid dopant is also maintained at atmospheric pressure. In an alternative embodiment, the first pressure in the ingot pulling inner chamber 104 is maintained at a pressure lower than atmospheric pressure and the second pressure in the doping chamber 130 is maintained at a pressure greater than the first pressure. Thus, the liquid dopant is maintained at the second pressure (atmospheric pressure) until the liquid dopant is injected into the ingot pulling inner chamber 104 where the pressure of the liquid dopant is reduced to the first pressure (vacuum).

[0027] The actuator 164 is disposed within the doping chamber 130 and is coupled to the air cylinder 150 and the actuation shaft 168. The air cylinder 150 actuates the actuator 160, which in turn actuates the first valve 162 and the actuation shaft 168. The actuation shaft 168 actuates the second valve 164. More specifically, in the illustrated embodiment, the actuator 160 is a linear actuator that linearly translates the first valve 162 and the shaft 168 to open the first valve and linearly translates the second valve 164 to open the second valve. In alternative embodiments, the actuation shaft 168 is coupled to both the first valve 162 and the second valve 164 and actuates both the first valve and the second valve. In some embodiments, the actuation shaft 168 actuates the first valve 162 and the second valve 164 independently. In an alternative embodiment, the actuation shaft 168 simultaneously actuates the first valve 162 and the second valve 164. For example, the actuation shaft 168 can simultaneously actuate the first valve 162 and the second valve 164 such that the first valve 162 is closed when the second valve 164 is open and the first valve 162 is open when the second valve 164 is closed to maintain the first pressure in the ingot pulling inner chamber 104.

[0028] The delivery module 118 includes a supply tube 172 and a vaporizer cup 174 disposed within the supply tube. The supply tube 172 is disposed within the ingot pulling inner chamber 104 and directs vaporized dopant to the silicon melt 108. Specifically, the vaporizer tube 174 is heated by radiant heat from within the ingot pulling inner chamber 104 and receives liquid dopant from the second reservoir 160. The ingot pulling apparatus 100 includes a heating system 176 that melts the silicon melt 108 and radiates heat into the ingot pulling inner chamber 104. The liquid dopant is vaporized into vaporized dopant in the ingot pulling inner chamber 104, where the liquid dopant is vaporized by flash evaporation by heating the liquid dopant using the vaporization cup 174 and reducing the pressure of the liquid dopant from the second pressure to the first pressure by injecting the liquid dopant into the ingot pulling inner chamber 104.

[0029] The feed tube 172 has a distal end 178 furthest from the ingot pulling outer housing 102 and a proximal end 180 closest to the ingot pulling outer housing. A feed tube axis A extends through the distal end 178 and the proximal end 180 of the feed tube 172. The feed tube 172 may be made of quartz or other suitable material.

[0030] The supply tube 172 is movable within the ingot pulling inner chamber 104 along a supply tube axis A. The supply tube 172 can be lowered into the ingot pulling inner chamber 104 toward the silicon melt 108. Specifically, the supply tube 172 is attached to a cooling jacket 170, which is attached to the doping chamber 130. The bellows 138 allow the doping chamber 130, the cooling jacket 170, and the supply tube 172 to move along the supply tube axis A toward and away from the silicon melt 108. By moving the doping chamber 130, the cooling jacket 170, and the supply tube 172, a distal end 178 of the supply tube 172 moves between a raised position, in which the distal end is disposed away from the silicon melt 108, and a lowered position, in which the distal end is disposed adjacent the surface of the silicon melt 108. The heat shield 112 may include a channel 182 formed therein to provide a passageway for the supply tube 172 to access the silicon melt 108 .

[0031] In the lowered position of the feed tube 172, the vaporized dopant travels down the feed tube and is directed to the surface of the silicon melt 108. The vaporized dopant passes through a distal end 178 of the feed tube 172 and contacts the silicon melt 108 to dope and / or counter-dope the silicon melt. As the doping chamber 130, cooling jacket 170, and feed tube 172 are moved from the raised position to the lowered position, the distance between the vaporizer cup 174 and the silicon melt 108 and heating system 176 can be changed (e.g., by an operator).

[0032] Vaporizer cup 174 includes a receiver 184 and a vaporizer plug 186 disposed within the receiver, dividing the receiver into a liquid-receiving portion 188 and a vapor channel portion 190. Receiver 184 and vaporizer plug 186 define liquid-receiving portion 188, with receiver 184 defining a channel 192 that directs vaporized dopant from the liquid-receiving portion to supply tube 172. Vaporizer plug 186 has a first end 194 and a second end 196 and defines a vapor channel 198 extending from the first end to the second end that directs vaporized dopant from liquid-receiving portion 188 to vapor channel portion 190.

[0033] Excess heat from the heating system 176 heats the vaporizer plug 186, and the second valve 164 directs the liquid dopant from the second reservoir 160 to the liquid receiver 188 and onto the vaporizer plug. The vaporizer plug 186 vaporizes the liquid dopant into vaporized dopant by flash evaporation by heating the liquid dopant with the vaporizer plug 186 and lowering the pressure of the liquid dopant from the second pressure to the first pressure by injecting the liquid dopant into the liquid receiver 188. The vapor channel 198 directs the vaporized dopant to the channel 192 of the vapor channel portion 190, which directs the vaporized dopant to the supply tube 172 and into the silicon melt 108. Additionally, a process gas (eg, argon) may be circulated through the doping chamber 130 through an inert gas port 140 to direct vaporized dopant through a vaporizer cup 174 and a supply tube 172 .

[0034] A pressure sensor port 142 allows for measurement of the pressure within the ingot pulling inner chamber 104. A vacuum port 144 allows for pump down and leak testing. A cooling jacket 170 cools the implantation module 116 to prevent overheating of the implantation module.

[0035] An exemplary method of the present disclosure is illustrated in Figures 9 and 10. The method may be carried out using an ingot pulling apparatus 100 configured to produce a boron-containing gas from liquid-phase boric acid. For purposes of illustrating the method, the method may be described with reference to the ingot pulling apparatus 100 shown in Figures 1-8, but unless otherwise specified, the method should not be limited to the ingot pulling apparatus 100.

[0036] 8 , in accordance with an embodiment of a method for preparing a silicon ingot, a silicon melt is prepared in a crucible 106 disposed in an ingot pulling inner chamber 104 of an ingot pulling apparatus 100. The crucible 106 may be supported by a susceptor (not shown). The ingot pulling apparatus 100 may be configured to rotate the crucible 106 and / or move the crucible 106 vertically within the ingot pulling apparatus 100.

[0037] To prepare the silicon melt, polycrystalline silicon is added to the crucible 106. The polycrystalline silicon is heated to above the melting temperature of silicon (approximately 1414° C.) to melt the polycrystalline silicon into the silicon melt 108. The heating system 176 is activated to melt the polycrystalline silicon. For example, one or more heaters 200 below or to the side of the crucible 106 are activated to melt the silicon.

[0038] 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 the growth of the ingot 110 begins. By compensating the melt, the resistivity of the resulting ingot 110 may be increased. For example, the seed end of the ingot (i.e., the portion of the ingot closest to the top of the ingot) may have a resistivity of at least about 30 Ω·cm, or in other embodiments, at least about 35 Ω·cm, at least about 40 Ω·cm, at least about 45 Ω·cm, at least about 50 Ω·cm, at least about 55 Ω·cm, at least about 60 Ω·cm, or in the range of about 30 Ω·cm to about 60 Ω·cm. Suitable n-type dopants include phosphorous and arsenic.

[0039] Once the melt 108 is prepared, a single crystal silicon ingot 110 is pulled from the melt 108. A seed crystal 202 is secured to a seed chuck 204. The seed chuck 204 and seed crystal 202 are lowered until the seed crystal 202 contacts the surface of the silicon melt 108. Once the seed crystal 202 begins to melt, a pulling mechanism slowly pulls the seed crystal 202 up until a single crystal ingot 110 is grown. A process gas (e.g., argon) is circulated through the ingot pulling inner chamber 104 of the ingot pulling apparatus 100. The process gas creates an atmosphere within the ingot pulling inner chamber 104.

[0040] An embodiment of the disclosed method includes providing a source of liquid phase boric acid (HBO). The boric acid can 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 can be relatively isotopically pure (i.e., boron-11).

[0041] Boron-containing gases are produced from boric acid in the liquid phase. The gases produced 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 dihydride (BH2). However, it should be understood that other boron compounds may be added to the boron-containing gas.

[0042] The liquid phase boric acid can be heated above its vaporization temperature (about 300° C.) to produce a boron-containing gas. For example, the liquid phase boric acid can be heated by heat radiated from the silicon melt 108 in the ingot pulling apparatus 100 or by the heating system 176.

[0043] Once the boron-containing gas is generated, it contacts the surface of the silicon melt 108 to allow the boron to diffuse into the melt. As the boron enters the melt, it compensates for the phosphorus that has concentrated in the melt due to phosphorus' relatively low segregation coefficient, thereby increasing the resistivity of the remainder of the ingot 110 that forms within the ingot puller 100.

[0044] FIG. 8 is a graph 206 of ingot resistivity as a function of ingot length. As shown in FIG. 8, the silicon melt 108 may be counter doped multiple times as described herein when the ingot 110 is pulled from the silicon melt. Specifically, the resistivity of the ingot 110 may decrease as the ingot is pulled from the silicon melt 108 due to the concentration of phosphorus. The silicon melt 108 may be counter doped multiple times as described herein using a dopant injector 114 as described herein when the ingot 110 is pulled from the silicon melt 108 to increase the resistivity of the ingot during production so that the majority of the ingot is within customer specifications (e.g., high resistivity). More specifically, as shown in FIG. 8, the silicon melt 108 is counter doped twice as the ingot 110 is pulled from the silicon melt 108. Thus, the dopant injector 114 improves the efficiency of the ingot pulling apparatus 100 by counterdoping the silicon melt 108 multiple times during the production of the ingot 110 and maintaining the resistivity of the majority of the ingot within customer specifications (e.g., high resistivity).

[0045] FIG. 9 is a flow diagram of a method 300 for producing a single crystal silicon ingot from a silicon melt held in a crucible disposed in an ingot puller. The method 300 includes adding 302 polycrystalline silicon to a crucible, the crucible being disposed in an ingot puller inner chamber. The method 300 also includes heating 304 the polycrystalline silicon to form a silicon melt in the crucible. The method 300 further includes pulling 306 a single crystal silicon ingot from the silicon melt. The method 300 also includes injecting 308 a liquid dopant into the ingot puller. The method 300 further includes vaporizing 310 the liquid dopant into a vaporized dopant in the ingot puller. The method 300 also includes contacting 312 the vaporized dopant with a surface of the melt to introduce the vaporized dopant into the melt as a dopant while pulling the single crystal silicon ingot from the melt.

[0046] FIG. 10 is a flow diagram of a method 400 for doping a single crystal silicon ingot pulled from a silicon melt held in a crucible disposed in an ingot puller. The ingot puller includes a housing, a dopant injector extending into the housing, and a heating system disposed with the housing. The dopant injector includes a dopant injection tube disposed in the housing and an evaporation cup disposed in the dopant injection tube and the housing. The method 400 includes heating 402 the evaporation cup using the heating system. The method 400 also includes maintaining 404 a pressure within the housing at a first pressure. The method 400 further includes injecting 406 a liquid dopant into the dopant injection tube and the evaporation cup. The pressure of the liquid dopant is maintained at a second pressure, higher than the first pressure before being injected into the dopant injection tube and the evaporation cup. The method 400 also includes vaporizing 408 the liquid dopant into a vaporized dopant in the housing. The liquid dopant is vaporized by flash evaporation by heating the liquid dopant with a vaporization cup and reducing the pressure of the liquid dopant from the second pressure to the first pressure by injecting the liquid dopant into the housing. The method 400 further includes directing 410 the vaporized dopant 410 into the housing using a dopant injection tube.

[0047] Compared with conventional methods for producing single crystal silicon ingots from silicon melts, the disclosed system and method have several advantages. Specifically, the majority of the ingots can be within customer specifications (e.g., high resistivity) and / or type changes of the ingots can be prevented. More specifically, the disclosed system and method controls the doping rate so that compensating boron is incorporated into the ingot to neutralize the effects of segregation by phosphorus. Thus, the net free charge carriers can be maintained between limits over the ingot length. Depending on the target resistivity of the ingot, controlling the doping rate can prevent type changes of the ingot from n-type to p-type, or in other examples from p-type to n-type. Boric acid in liquid phase has a relatively low vaporization temperature, which allows the dopant gas to be generated relatively easily. Furthermore, a vaporization cup can be placed in the ingot pulling housing, which allows the heat of the melt and the heating system to vaporize the dopant. The supply tube is movable within the ingot puller such that the distance from the melt can be controlled, which allows the rate of dopant addition to the melt to be controlled. Thus, the systems and methods described herein improve the efficiency of the ingot puller by counterdoping the silicon melt multiple times during the production of the ingot and maintaining the resistivity of the majority of the ingot within customer specifications (e.g., high resistivity).

[0048] As used herein, when used in conjunction with a range of dimensions, concentrations, temperatures, or other physical or chemical properties or characteristics, the terms "about," "substantially," "essentially," and "approximately" are meant to cover the variation that may exist at the upper and / or lower limits of the range of the property or characteristic, including, for example, the variation that results from rounding, measurement methodology, or other statistical variations.

[0049] When introducing an element of the disclosure or embodiment(s) 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.

[0050] 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. An ingot pulling apparatus for producing a doped single crystal silicon ingot, the ingot pulling apparatus comprising: a housing defining a chamber; A crucible disposed within the chamber; and a dopant injector extending into the housing; The dopant injector is an injection module attached to an exterior surface of the housing, the injection module comprising: a first reservoir for containing a liquid dopant; a second reservoir for containing a liquid dopant; a first valve for selectively directing the liquid dopant from the first reservoir to the second reservoir; and an injection module having a second valve for selectively directing the liquid dopant from the second reservoir to the chamber; and a delivery module attached to the injection module and extending through the housing into the chamber, the second valve selectively directing the liquid dopant to the delivery module, the delivery module vaporizing the liquid dopant into a vaporized dopant; Ingot pulling equipment.

2. and a shaft coupled to the second valve, the shaft actuating the second valve.

2. An ingot pulling apparatus according to claim 1.

3. the first reservoir and the second reservoir are maintained at a pressure greater than the pressure of the chamber; 2. An ingot pulling apparatus according to claim 1.

4. 1. An ingot pulling apparatus for producing a doped single crystal silicon ingot, the ingot pulling apparatus comprising: a housing defining a chamber; A crucible disposed within the chamber; and a dopant injector extending into the housing; The dopant injector is an injection module attached to an exterior surface of the housing, the injection module comprising: a first reservoir for containing a liquid dopant; a second reservoir for containing a liquid dopant; a first valve for selectively directing the liquid dopant from the first reservoir to the second reservoir; and a second valve for selectively directing the liquid dopant from the second reservoir to the chamber; and a delivery module attached to the injection module and extending through the housing into the chamber; The delivery module is a dopant injection tube disposed within the chamber; and a vaporization cup disposed within the dopant injection tube and the chamber, the second valve selectively directing the liquid dopant to the vaporization cup, which vaporizes the liquid dopant into a vaporized dopant; Ingot pulling equipment.

5. the dopant injection tube includes a first end positioned adjacent a surface of the melt for directing vaporized dopant to the surface of the melt; 5. An ingot pulling apparatus according to claim 4.

6. and a shaft coupled to the second valve, the shaft actuating the second valve.

5. An ingot pulling apparatus according to claim 4.

7. The evaporation cup is Receiver, and a vaporization plug disposed within the receiver, the liquid dopant being injected onto the vaporization plug, the vaporization plug vaporizing the liquid dopant into a vaporized dopant; 5. An ingot pulling apparatus according to claim 4.

8. The vaporizer plug separates the receiver into a liquid receiving portion and a vapor channel portion.

8. An ingot pulling apparatus according to claim 7.

9. The receiver defines a channel for conducting vaporized dopant from the liquid receptacle to the dopant inlet tube.

9. An ingot pulling apparatus according to claim 8.

10. the vaporization plug includes a first end and a second end and defines a vapor channel extending from the first end to the second end, the liquid dopant is injected onto the vaporization plug and the vaporized dopant is directed into the channel through the vapor channel; 10. An ingot pulling apparatus according to claim 9.

11. The dopant injector includes a bellows for moving the dopant injection tube adjacent to the crucible.

5. An ingot pulling apparatus according to claim 4.

12. and a heating system for heating the evaporation cup using radiant heat from the heating system, the radiant heat from the heating system being excess heat from the heating system when the heating system melts the polycrystalline silicon in the crucible.

5. An ingot pulling apparatus according to claim 4.

13. 1. A method for doping a single crystal silicon ingot pulled from a silicon melt held in a crucible disposed within an ingot puller, the ingot puller including a housing, a dopant injector extending into the housing, and a heating system disposed with the housing, the dopant injector including a feed tube disposed within the housing and an evaporation cup disposed within the feed tube and the housing, the method comprising: heating the evaporation cup using a heating system; maintaining a pressure within the housing and the supply line at a first pressure; injecting a liquid dopant into the supply tube and vaporizer cup, the pressure of the liquid dopant being maintained at a second pressure higher than the first pressure before being injected into the supply tube and vaporizer cup; vaporizing the liquid dopant in the supply into a vaporized dopant, the liquid dopant being vaporized by flash evaporation by heating the liquid dopant with a vaporization cup and reducing the pressure of the liquid dopant from a second pressure to a first pressure by injecting the liquid dopant into the supply; and directing the vaporized dopant toward the silicon melt using a delivery tube; The method according to claim 1,

14. the step of heating the evaporation cup includes heating the evaporation cup using radiant heat from a heating system, the radiant heat from the heating system being excess heat from the heating system when the heating system melts the polycrystalline silicon in the crucible; The method of claim 13.

15. The method further includes the step of directing an inert gas to the supply tube, the inert gas directing the vaporized dopant toward the silicon melt. The method of claim 13.

16. The first pressure is a pressure below atmospheric pressure. The method of claim 13.

17. The first pressure is a vacuum and the second pressure is atmospheric pressure. The method of claim 13.

18. The method further comprises diffusing the vaporized dopant into the silicon melt. The method of claim 13.

19. the vaporizer cup includes a receiver and a vaporizer plug disposed within the receiver, and the step of heating the vaporizer cup using the heating system includes heating a vaporizer plug disposed within the receiver. The method of claim 13.

20. 1. A method for producing a single crystal silicon ingot from a silicon melt held in a crucible disposed within an ingot puller, the ingot puller including a dopant injector extending into a housing of the ingot puller, the dopant injector including a feed tube disposed within the housing and an evaporation cup disposed within the feed tube and the housing, the method comprising: adding polycrystalline silicon to a crucible; heating the polycrystalline silicon to form a silicon melt in a crucible; Pulling a single crystal silicon ingot from the silicon melt; injecting a liquid dopant into a supply tube; vaporizing the liquid dopant into a vaporized dopant in the supply tube; heating the liquid dopant using an evaporation cup; and reducing the pressure of the liquid dopant by injecting the liquid dopant into the supply tube, the housing and the supply tube being maintained at a pressure below atmospheric pressure, thereby vaporizing the liquid dopant into vaporized dopant in the supply tube; and contacting a vaporized dopant with a surface of the silicon melt to introduce the vaporized dopant into the silicon melt as a dopant while the single crystal silicon ingot is being pulled from the silicon melt; The method according to claim 1,

21. The dopant injector includes a first reservoir, a first valve, a second reservoir, and a second valve, and injecting the liquid dopant into the supply tube includes: directing the liquid dopant from the first reservoir to the second reservoir by opening a first valve; and directing the liquid dopant from the second reservoir to the supply tube by opening a second valve.

21. The method of claim 20.

22. The dopant injector includes a bellows, and the method further comprises: moving the supply tube adjacent to the silicon melt using a bellows; directing the vaporized dopant toward the silicon melt using a delivery tube adjacent to the silicon melt such that the vaporized dopant contacts a surface of the silicon melt; and diffusing the vaporized dopant into the silicon melt.

21. The method of claim 20.

23. and heating the evaporation cup using radiant heat from the heating system, the radiant heat from the heating system being excess heat from the heating system when the heating system melts the polycrystalline silicon in the crucible.

21. The method of claim 20.

24. The method further includes the step of directing an inert gas to the supply pipe, the inert gas directing the vaporized dopant toward the silicon melt such that the vaporized dopant contacts a surface of the silicon melt.

21. The method of claim 20.

25. the first reservoir and the second reservoir are maintained at a pressure that exceeds the pressure of the housing and the supply line; 22. The method of claim 21.

26. The pressure in the housing and the supply tube is a vacuum, and the first and second reservoirs are maintained at atmospheric pressure; 26. The method of claim 25.

27. The vaporizer cup includes a receiver and a vaporizer plug disposed within the receiver, and the step of heating the liquid dopant using the vaporizer cup includes: heating a vaporizer plug disposed within the receiver; heating the liquid dopant using a vaporizer plug; 21. The method of claim 20.

28. 1. A method for doping a single crystal silicon ingot pulled from a silicon melt held in a crucible disposed within an ingot puller, the ingot puller including a housing, a dopant injector extending into the housing, and a heating system disposed with the housing, the dopant injector including a feed tube disposed within the housing and an evaporation cup disposed within the feed tube and the housing, the method comprising: heating the evaporation cup using a heating system; injecting liquid dopant into a delivery tube and vaporizer cup; vaporizing the liquid dopant into a vaporized dopant in a supply tube, the liquid dopant being vaporized by flash evaporation by heating the liquid dopant with a vaporization cup at a pressure below atmospheric pressure; and directing the vaporized dopant toward the silicon melt using a delivery tube; The method according to claim 1,

29. the step of heating the evaporation cup includes heating the evaporation cup using radiant heat from a heating system, the radiant heat from the heating system being excess heat from the heating system when the heating system melts the polycrystalline silicon in the crucible; 29. The method of claim 28.

30. The dopant injector includes a first reservoir, a first valve, a second reservoir, and a second valve, and the step of injecting the liquid dopant into the supply tube includes: directing the liquid dopant from the first reservoir to the second reservoir by opening a first valve; and directing the liquid dopant from the second reservoir to the supply tube by opening a second valve.

30. The method of claim 29.

31. The vaporizer cup includes a receiver and a vaporizer plug disposed within the receiver, and the step of heating the liquid dopant using the vaporizer cup includes: heating a vaporizer plug disposed within the receiver; heating the liquid dopant using a vaporizer plug; 29. The method of claim 28.

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