Additive delivery system, ingot puller, and method for forming a single crystal silicon ingot using the additive delivery system

Abstract

An additive supply system is disclosed for supplying at least two different additives to silicon disposed in a crucible of an ingot puller. The additive supply system may include a first supply tray and a second supply tray that are vibrated to move a first additive and a second additive from a canister in which the additives are stored to another vessel in which the amount of the first additive or the second additive added to the vessel is sensed. The additives are discharged from the vessel into an additive supply tube through which the additives enter the crucible.

Description

[Technical Field]

[0001] [CROSS-REFERENCE TO RELATED APPLICATIONS] This application claims priority to U.S. Non-Provisional Patent Application No. 17 / 138,035, filed December 30, 2020, which is incorporated herein by reference in its entirety.

[0002] The field of the disclosure relates to an additive delivery system for delivering at least two different additives to silicon disposed in a crucible of an ingot puller. [Background technology]

[0003] During growth of single crystal silicon ingots by the Czochralski process, various additives may be added to the crucible before or after ingot growth. As customer specifications and ingot quality parameters evolve, different types of additives may be added to the crucible during the ingot cycle to improve and / or more precisely control the ingot quality parameters. For example, it may be desirable to add both dopants and quartz cullet to the crucible. The dopant changes the resistivity profile of the melt, and the cullet may act as a buffer, floating in the melt and in contact with the polysilicon added to the melt during ingot growth (e.g., as in a continuous Czochralski growth process). Summary of the Invention [Problem to be solved by the invention]

[0004] To minimize the cost and footprint of an additive delivery system, there is a need for an additive delivery system that can relatively precisely deliver two different additives from different delivery vessels with a common component. [Means for solving the problem]

[0005] This section is intended to introduce the reader to various aspects of art that may be related to various aspects of the present disclosure, as described and / or claimed below. This discussion is believed to be helpful in providing the reader with background information to better understand 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.

[0006] One aspect of the present disclosure is directed to an additive supply system for supplying at least two different additives to silicon disposed in a crucible. The additive supply system includes a first canister for holding a first additive and a second canister for holding a second additive. A vessel collects the first additive discharged from the first canister and the second additive discharged from the second canister. An additive sensor senses the amount of the first additive or the second additive in the vessel. An additive supply pipe transports the first additive or the second additive from the vessel to the crucible.

[0007] Another aspect of the present disclosure is directed to an ingot pulling apparatus for producing silicon ingots. The ingot pulling apparatus includes a crucible for holding a silicon melt and a growth chamber for pulling a silicon ingot from the melt. The crucible is disposed within the crucible. The apparatus includes an additive supply system for supplying at least two different additives to the silicon disposed within the crucible. The additive supply system includes a first canister for holding a first additive and a second canister for holding a second additive. The additive supply system includes a vessel for collecting the first additive discharged from the first canister and the second additive discharged from the second canister. The additive supply system includes an additive supply pipe for transporting the first additive or the second additive from the vessel to the crucible.

[0008] A further aspect of the present disclosure is directed to a method of forming a single crystalline silicon ingot. Solid-phase polycrystalline silicon is added to a crucible having a sidewall and a bottom. The polycrystalline silicon is heated to form a silicon melt having a surface. The silicon melt is contacted with a seed crystal. The seed crystal is pulled from the silicon melt to form a silicon ingot. A first additive is added to a vessel. An amount of the first additive is measured into the vessel. The first additive is added to the melt such that the amount of the first additive in the vessel is equal to or greater than a target amount of the first additive. A second additive is added to the vessel. An amount of the second additive is measured into the vessel. The second additive is added to the melt such that the amount of the second additive in the vessel is equal to or greater than a target amount of the second additive.

[0009] Various refinements exist for the features mentioned in connection with the above-described aspects of the present disclosure. Additionally, additional features may be incorporated into the above-described aspects of the present disclosure. These refinements and additional features may exist individually or in any combination. For example, various features described below in connection with any of the illustrated embodiments of the present disclosure may be incorporated into any of the above-described aspects of the present disclosure, either alone or in any combination. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 is a cross-sectional view of an ingot pulling apparatus prior to growth of a silicon ingot.

[0011] [Figure 2] FIG. 2 is a cross-sectional view of an ingot puller during growth of a silicon ingot.

[0012] [Figure 3] FIG. 3 is a perspective view of an additive supply system of an ingot pulling apparatus.

[0013] [Figure 4] FIG. 4 is a detailed front view of the additive delivery system with the housing removed.

[0014] [Figure 5] FIG. 5 is a front view of the reservoir of the additive delivery system with the reservoir in an open position.

[0015] [Figure 6] FIG. 6 is a perspective view of the vessel in the closed position.

[0016] [Figure 7] FIG. 7 is a rear view of the container and the actuator that opens and closes the container.

[0017] [Figure 8] FIG. 8 is a perspective view of the first canister, first tray, and first vibrator of the additive supply system.

[0018] [Figure 9] FIG. 9 is a perspective view of the second canister, second tray, and second vibrator of the additive delivery system.

[0019] [Figure 10] FIG. 10 is a schematic diagram of a control system for controlling the additive delivery system.

[0020] Corresponding reference characters indicate corresponding parts throughout the drawings. DETAILED DESCRIPTION OF THE INVENTION

[0021] The present disclosure provides an additive delivery system for supplying at least two different additives to silicon disposed in a crucible of an ingot puller, and a method of forming a crystalline silicon ingot using such an additive delivery system. Generally, the additive delivery system may be used with any ingot puller configured to pull a single crystalline silicon ingot. An example of an ingot puller (or more simply, an "ingot puller") is shown generally at "100" in FIG. 1. The ingot puller 100 includes a crucible 102 for holding a melt 104 of semiconductor or solar-grade material, such as silicon, supported by a susceptor 106. The ingot puller 100 includes a crystal pulling housing 108 defining a growth chamber 152 for pulling a silicon ingot 113 (FIG. 2) from the melt 104 along a pulling axis A.

[0022] The crucible 102 includes a floor 129 and a sidewall 131 extending upward from the floor 129. The sidewall 131 is generally vertical. Within the crucible 102 is a silicon melt 104 having a melt surface 111 (i.e., a melt-ingot interface). In some embodiments, the crucible 102 is layered. For example, the crucible 102 can be made of a quartz base layer and a synthetic quartz liner disposed on the quartz base layer.

[0023] The susceptor 106 is supported by a shaft 105. The susceptor 106, crucible 102, shaft 105, and ingot 113 (FIG. 2) have a common longitudinal axis A or "pull axis" A.

[0024] Within the ingot pulling apparatus 100 is a pulling mechanism 114 (FIG. 2) for growing and pulling an ingot 113 from the melt 104. The pulling mechanism 114 includes a pulling cable 118, a seed holder or chuck 120 coupled to one end of the pulling cable 118, and a seed crystal 122 coupled to the seed holder or chuck 120 for initiating crystal growth. One end of the pulling cable 118 is connected to a pulley (not shown) or drum (not shown), or other suitable type of lifting mechanism, such as a shaft, and the other end is connected to the chuck 120, which holds the seed crystal 122. During operation, the seed crystal 122 is lowered into contact with the melt 104. The pulling mechanism 114 is actuated to raise the seed crystal 122, thereby pulling a single crystal ingot 113 (FIG. 2) from the melt 104.

[0025] During heating and crystal pulling, a crucible drive 107 (e.g., a motor) rotates the crucible 102 and susceptor 106. A lift mechanism 112 raises and lowers the crucible 102 along the pulling axis A during the growth process. For example, the crucible 102 may be in its lowest position (near the bottom heater 126) where a charge of solid-phase polycrystalline silicon previously added to the crucible 102 is melted. Crystal growth is initiated by contacting the melt 104 with the seed crystal 122 and lifting the seed crystal 122 with the pulling mechanism 114. As the ingot 113 grows, the silicon melt 104 is consumed and the height of the melt within the crucible 102 decreases. The crucible 102 and susceptor 106 may be raised to maintain the melt surface 111 at or near the same position relative to the ingot pulling apparatus 100 (FIG. 2).

[0026] The crystal drive unit (not shown) may also rotate the pulling cable 118 and ingot 113 (FIG. 2) in a direction opposite (e.g., counter-rotation) from the direction in which the crucible drive unit 107 rotates the crucible 102. In embodiments using equal rotation, the crystal drive unit may rotate the pulling cable 118 in the same direction as the crucible drive unit 107 rotates the crucible 102.

[0027] According to the Czochralski single crystal growth process, solid-phase polycrystalline silicon or polysilicon is charged into a crucible 102. Semiconductor or solar-grade material introduced into the crucible is melted by heat provided by one or more heating elements. The ingot puller 100 includes bottom insulation 110 and side insulation 124 to retain heat within the puller 100. In the illustrated embodiment, the ingot puller 100 includes a bottom heater 126 positioned below the crucible floor 129. The crucible 102 may be moved to be relatively close to the bottom heater 126 to melt the polycrystalline material charged into the crucible 102.

[0028] To form an ingot, a seed crystal 122 is contacted with the surface 111 of the melt 104. A pulling mechanism 114 operates to pull the seed crystal 122 from the melt 104. Referring now to FIG. 2 , the ingot 113 includes a crown portion 142 where the ingot transitions outward from the seed crystal 122 and tapers to reach a target diameter. The ingot 113 includes a constant diameter portion 145 or cylindrical "body" of the crystal that is grown by increasing the pulling rate. The body 145 of the ingot 113 has a relatively constant diameter. The ingot 113 includes a tail cone or end cone (not shown) where the diameter of the ingot tapers after the body 145. Once the diameter is sufficiently small, the ingot 113 is separated from the melt 104.

[0029] The ingot pulling apparatus 100 includes a side heater 135 and a susceptor 106 surrounding the crucible 102 to maintain the temperature of the melt 104 during crystal growth. The side heater 135 is positioned radially outward relative to the crucible sidewall 131 as the crucible 102 moves up and down the pulling axis A. The side heater 135 and the bottom heater 126 may be any type of heater that enables the side heater 135 and the bottom heater 126 to operate as described herein. In some embodiments, the heaters 135, 126 are resistive heaters. The side heater 135 and the bottom heater 126 may be controlled by a control system (not shown) so that the temperature of the melt 104 is controlled throughout the pulling process.

[0030] The ingot pulling apparatus 100 may include a heat shield 151 that covers the ingot 113 and may be positioned within the crucible 102 during crystal growth (FIG. 2). The ingot pulling apparatus 100 may include an inert gas system that introduces and withdraws an inert gas, such as argon, from the growth chamber 152.

[0031] In accordance with an embodiment of the present disclosure, the ingot pulling apparatus 100 also includes an additive supply system 200 for introducing additives into the melt 104, such as via an additive supply line 214. Referring now to FIG. 3, an exemplary additive supply system 200 of the present disclosure is shown. The additive supply system 200 is configured to add two different additives to silicon disposed within the crucible 102 (FIG. 1). The additive supply system 200 may be adapted to add more than two additives (e.g., using additional additive canisters, trays, agitators, etc.).

[0032] The additive supply system 200 includes a first canister 204 for holding a first additive (not shown) and a second canister 206 for holding a second additive. The first canister 204 and the second canister 206 include removable lids 207 and 209, respectively, for sealing the canisters 204 and 206. The first canister 204 and the second canister 206 also include funnel portions 211 and 213, respectively, that direct the additive to trays 260 and 270 located below the canisters 204 and 206. The system 200 may be attached to the ingot pulling apparatus 100 by connecting the additive supply line 214 to a sight glass (not shown) on the ingot pulling apparatus 100.

[0033] System 200 includes a vessel 228 for collecting the first additive discharged from first canister 204 and the second additive discharged from second canister 206. Vessel 228 is shown in an "open" position, where the additive is discharged from the vessel. As explained further below, vessel 228 can be moved to a "closed" position (FIG. 6), where the additive collects in vessel 228. Once the amount of additive in vessel 228 is measured (i.e., when a set point is reached), actuator 230 (FIG. 7) is actuated, discharging the additive from vessel 228 into additive supply tube 214. The first additive or second additive flows through additive supply tube 214 into crucible 102 (FIG. 1). The additive supply pipe 214 may include an outer housing (not shown) that forms a seal with the first canister 204 and the second canister 206, as well as the additive supply pipe 214, to isolate the growth chamber 152 (FIG. 1) of the ingot pulling apparatus 100 from the surrounding environment.

[0034] Additive sensor 231 (FIG. 5) senses the amount of first additive or second additive added to vessel 228 (i.e., the batch of first additive or second additive added to vessel 228). In the embodiment shown, additive sensor 231 is a load cell that weighs the batch of additive added to vessel 228. In other embodiments, additive sensor 231 is a flow meter or pressure transducer.

[0035] In general, any vessel 228 and actuator 230 that allows for collecting additive in vessel 228 and discharging additive into additive supply pipe 214 may be used unless otherwise noted. The illustrated vessel 228 (FIG. 6) includes first and second pawl elements 240A and 240B that pivot about pin 242 to open and close vessel 228. A motor 245 (FIG. 7) (e.g., an electromagnetic coil) vertically moves rod 247. Rod 247 is connected to a bracket 250 that is connected to each of pawl elements 240A, 240B of vessel 228.

[0036] As bracket 250 moves vertically, pawl elements 240A, 240B pivot toward or away from each other to allow for opening and closing of vessel 228. When motor 245 is not powered, the weight of pawl elements 240A, 240B pulls rod 247 and bracket 250 down, moving pawls 240A, 240B toward each other to close vessel 228. When motor 245 is powered, motor 245 pulls rod 247 and bracket 250 up, moving pawl elements 240A, 240B away from each other to open vessel 228.

[0037] To transfer the first additive from the first canister 204 to the vessel 228, the additive supply system 200 includes a first tray 260 (FIG. 4) disposed below the first canister 204 and extending between the canister 204 and the vessel 228. A first canister outlet 265 (FIG. 8) is disposed within the first tray 260. The first tray 260 has a first tray outlet 268 disposed above the vessel 228 (FIG. 5). The first tray 260 is disposed above and connected to a first vibrator 262. When power is applied to the vibrator 262, the tray 260 vibrates, transporting the first additive from the first canister outlet 265 across the first tray 260. The first additive is discharged from the first tray outlet 268 into the vessel 228.

[0038] 9, a second tray 270 is positioned below the second canister 206. A second canister outlet 272 is disposed on the second tray 270. The second tray 270 includes a second tray outlet 274 that is disposed above the vessel 228 (FIG. 5). A second vibrator 277 is disposed below the second tray 270 and connected to the second tray 270. When power is applied to the second vibrator 277, the second tray 270 vibrates, transporting the second additive from the second canister outlet 272 across the second tray 270. The second additive is discharged from the second tray outlet 274 into the vessel 228.

[0039] 10, additive delivery system 200 includes a control system 285 for controlling additive delivery system 200. Control system 285 includes a control unit 280 for controlling the components of additive delivery system 200. For example, control unit 280 is communicatively connected to actuator 230 (FIG. 7) (e.g., connected to motor 245) to control the opening and closing of reservoir 228. The control unit is also communicatively connected to first vibrator 262 and second vibrator 277 to selectively control the addition of first and second additives to reservoir 228. Additive sensor 231 sends a signal to the control unit related to the amount of additive in reservoir 228.

[0040] Control unit 280 may implement or perform the various logic blocks, modules, and circuits described herein with a general purpose computer, a digital signal processor (DSP), an application specific integrated circuit (ASIC), a field programmable gate array (FPGA) or other programmable logic device, discrete gate or transistor logic, discrete hardware components, or any combination thereof designed to perform the functions described herein. Examples of general purpose processors include, but are not limited to, a microprocessor, a conventional processor, a controller, a microcontroller, a state machine, or a combination thereof.

[0041] The control unit 280 includes a processor, e.g., a central processing unit (CPU) of a computer, for executing instructions. The instructions may be stored, for example, in a memory area. The processor may include one or more processing units, e.g., a multi-core configuration, for executing the instructions. The instructions may be executed within a variety of different operating systems on the controller, such as UNIX, LINUX, Microsoft Windows, etc. It should also be understood that various instructions may be executed during initialization upon initiation of a computer-based method. While some operations may be required to perform one or more processes described herein, other operations may be more general and / or specific to a particular programming language, such as, but not limited to, C, C#, C++, Java, or other suitable programming language.

[0042] The processor may also be operatively coupled to a storage device. Storage device refers to any computer-operable hardware suitable for storing and / or retrieving data. In some embodiments, the storage device is integrated into the controller. In other embodiments, the storage device is external to the controller, similar to a database. For example, the control unit 280 may include one or more hard disk drives as storage devices. In other embodiments, the storage device is external to the controller. For example, the storage device may include multiple storage devices, such as hard disks or solid-state disks in a RAID configuration. The storage device may include a storage area network (SAN) and / or a network-attached storage (NAS) system.

[0043] In some embodiments, the processor is operably coupled to the storage device via a memory interface. A memory interface is any component that can provide the processor with access to the storage device. The memory interface may include, for example, an Advanced Technology Attachment (ATA) adapter, a Serial ATA (SATA) adapter, a Small Computer System Interface (SCSI) adapter, a RAID controller, a SAN adapter, a network adapter, and / or any component that provides the processor with access to the storage device.

[0044] Memory areas include, but are not limited to, random access memory (RAM), such as dynamic RAM (DRAM) or static RAM (SRAM), read-only memory (ROM), erasable programmable read-only memory (EPROM), electrically erasable programmable read-only memory (EEPROM), non-volatile RAM (NVRAM), etc. The above memory types are exemplary and do not limit the types of memory that may be used to store computer programs.

[0045] To control the addition of additive to vessel 228 and, therefore, crucible 102 ( FIG. 1 ) (and initial silicon charge or melt 104), control unit 280 selectively activates first vibrator 262 or second vibrator 277 to move a first additive or a second additive from first container 204 or second container 206, respectively. The first additive or second additive is continuously added to vessel 228 while additive sensor 231 measures the amount (e.g., mass, volume, or level) of additive in vessel 228. When a target additive amount (i.e., set point) is achieved or exceeded, vibrators 262, 277, which have been powered to move the additive, are deactivated. The control unit sends a signal to actuator 230, which activates actuator 230 to expel additive from vessel 228 into additive supply line 214.

[0046] The selection of adding the first or second additive to the vessel 228 and crucible 102 may be selected by an operator or may be automated as part of a control system for the ingot growth. The first and second additives may be added at different times during the ingot growth cycle. Some additives may be added in multiple batches (e.g., before and during ingot growth).

[0047] Generally, the first and second additives may be any solid-phase additives that can be metered by a tray and vibrator for addition to the crucible. Suitable additives include various semiconductor dopants (e.g., p-type dopants such as boron, aluminum, germanium, and / or indium and their alloys, or n-type dopants such as red phosphorus, phosphorus, arsenic, and / or antimony and their alloys). In other embodiments, one of the first and second additives is quartz cullet added to the melt as a buffer in a continuous Czochralski process. In some embodiments, one of the first and second additives is solid-phase polycrystalline silicon added to the crucible 102 (FIG. 1) during ingot growth. In other embodiments, both the first and second additives are additives other than polycrystalline silicon (e.g., dopants and cullet).

[0048] The first additive and / or the second additive may generally be added at any time during the ingot growth cycle. For example, the first additive and / or the second additive may be added before, during, or after meltdown of the initial charge of solid-phase polycrystalline silicon added to the crucible, or may be added during ingot growth. The ingot growth process may be a batch Czochralski process in which polycrystalline silicon is not added to the melt during ingot growth, or a continuous Czochralski process in which polycrystalline silicon is added to the melt (e.g., continuously or intermittently) during ingot growth.

[0049] Compared to conventional additive delivery systems, the additive delivery system of the present disclosure has several advantages. By using a common vessel into which the first and second additives may be selectively added and measured, the first and second additives can be added to the crucible with relative precision. The amount of additive added may be measured, dosed, and adjusted according to additive parameters related to ingot growth. By using a vibrating tray, each additive can be reliably transferred from a storage vessel to the vessel where it is measured. By using common components (e.g., measuring vessels, additive delivery lines, additive discharge actuators, etc.), the cost and complexity of the system are reduced.

[0050] As used herein, the terms "about," "substantially," "essentially," and "approximately," when used in conjunction with a range of dimensions, concentrations, temperatures, or other physical or chemical properties or characteristics, are meant to encompass variation that may exist at the upper and / or lower limits of the range of the property or characteristic, including, for example, variation due to rounding, measurement method, or other statistical variation.

[0051] When introducing elements of the disclosure or embodiment(s) thereof, the articles "a," "an," "the," and "said" are intended to mean there are one or more of the elements. 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 any particular orientation of the described items.

[0052] Because various changes may be made in the above structures and methods 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 additive delivery system for delivering at least two different additives to silicon disposed in a crucible, comprising: a first canister for holding a first additive; a second canister for holding a second additive; a vessel for collecting the first additive discharged from the first canister and the second additive discharged from the second canister; an additive sensor for sensing the amount of the first additive or the second additive in the vessel; an additive supply pipe for transporting the first additive or the second additive from the vessel to the crucible; An additive supply system comprising:

2. an actuator for releasing the first additive or the second additive from the container; 10. The additive delivery system of claim 1.

3. the actuator selectively opens and closes the reservoir to release the first additive or the second additive from the reservoir; 3. The additive delivery system of claim 2.

4. Further comprising a control unit; the control unit is communicatively connected to the actuator; the control unit actuates the actuator to release additive from the container into the additive supply line when the additive sensor senses that the amount of additive in the container equals or exceeds a target additive amount.

3. The additive delivery system of claim 2.

5. the control unit selectively controls the addition of a first additive to the vessel or the addition of a second additive to the vessel; 5. The additive delivery system of claim 4.

6. a first tray disposed below the first canister for transferring a first additive from the first canister to the vessel; a first vibrator for vibrating the first tray to move the first additive along the first tray toward the vessel, wherein the control unit is communicatively connected to the first vibrator; a second tray positioned below the second canister for transferring a second additive from the second canister to the vessel; a second vibrator for vibrating the second tray to move the second additive along the second tray toward the vessel, wherein the control unit is communicatively connected to the second vibrator; Equipped with 5. The additive delivery system of claim 4.

7. a first tray disposed below the first canister for transferring a first additive from the first canister to the vessel; a first vibrator for vibrating the first tray to move the first additive along the first tray toward the vessel; a second tray disposed below the second canister for transferring a second additive from the second canister to the vessel; a second vibrator for vibrating the second tray to move the second additive along the second tray to the vessel; Equipped with 10. The additive delivery system of claim 1.

8. the additive sensor senses the level, volume, or weight of the additive; 10. The additive delivery system of claim 1.

9. the additive sensor is a load cell; 10. The additive delivery system of claim 1.

10. An ingot pulling apparatus for producing a silicon ingot, comprising: a crucible for holding a silicon melt; a growth chamber for pulling a silicon ingot from the silicon melt, wherein the crucible is disposed within the growth chamber; an additive supply system for supplying at least two different additives to the silicon disposed in the crucible; It is equipped with The additive supply system comprises: a first canister for holding a first additive; a second canister for holding a second additive; a vessel for collecting the first additive discharged from the first canister and the second additive discharged from the second canister; an additive supply pipe for transporting the first additive or the second additive from the vessel to the crucible; an additive sensor for sensing the amount of the first additive or the second additive in the vessel; The ingot pulling apparatus has

11. the additive sensor is a load cell; 11. An ingot pulling apparatus according to claim 10.

12. the additive delivery system includes an actuator for releasing the first additive or the second additive from the reservoir.

11. An ingot pulling apparatus according to claim 10.

13. a first tray disposed below the first canister for transferring a first additive from the first canister to the vessel; a first vibrator for vibrating the first tray to move the first additive along the first tray toward the vessel; a second tray disposed below the second canister for transferring a second additive from the second canister to the vessel; a second vibrator for vibrating the second tray to move the second additive along the second tray toward the vessel; having 11. An ingot pulling apparatus according to claim 10.

14. 1. A method of forming a single crystal silicon ingot, comprising: adding solid phase polycrystalline silicon to a crucible having a sidewall and a bottom; heating the solid phase polycrystalline silicon to form a silicon melt having a surface; contacting a seed crystal with the silicon melt; Pulling the seed crystal from the silicon melt to form a single crystal silicon ingot; adding a first additive to the vessel; measuring an amount of a first additive into said vessel; adding the first additive to the silicon melt when the amount of the first additive in the vessel is equal to or exceeds a target first additive amount; adding a second additive to said vessel; measuring an amount of a second additive into said vessel; adding the second additive to the silicon melt when the amount of the second additive in the vessel is equal to or exceeds a target second additive amount; A method comprising:

15. the first additive is added before the silicon melt contacts the seed crystal; 15. The method of claim 14.

16. the second additive is added before the silicon melt contacts the seed crystal; 16. The method of claim 15.

17. the single crystal silicon ingot is grown in a batch Czochralski process, and no solid phase polycrystalline silicon is added to the silicon melt during growth of the single crystal silicon ingot; 15. The method of claim 14.

18. The single crystal silicon ingot is grown in a continuous Czochralski process, wherein solid phase polycrystalline silicon is added to the silicon melt during growth of the single crystal silicon ingot.

15. The method of claim 14.

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