Method for growing single crystal silicon ingot using continuous czochralski method

Abstract

To provide a method for growing a single crystal silicon ingot by the continuous Czochralski method.SOLUTION: The critical v / G is determined by the hot zone configuration, and the continuous replenishment of silicon to the melt during growth enables growth of the ingot at a constant pull rate consistent with the critical v / G during growth of a substantial portion of the main body of the ingot. The melt depth and thermal conditions are constant during growth because the silicon melt is continuously replenished as it is consumed, and the crucible location is fixed.SELECTED DRAWING: None

Description

[Technical Field]

[0001] (CROSS-REFERENCE TO RELATED APPLICATIONS) This application claims priority to U.S. Provisional Application No. 62 / 835,735, filed April 18, 2019, the disclosure of which is incorporated herein by reference as if set forth in its entirety.

[0002] FIELD OF THE DISCLOSURE The field of the disclosure relates to methods for growing crystalline silicon ingots using the continuous Czochralski method. [Background technology]

[0003] (background) Single-crystal silicon, the starting material for most processes in the fabrication of semiconductor electronic components, is commonly produced by the Czochralski ("Cz") process. In this process, polycrystalline silicon ("polysilicon") is introduced into a crucible and melted. A seed crystal is brought into contact with the molten silicon, and the single crystal is grown by slow extraction. After neck formation is complete, the crystal diameter is expanded, for example, by decreasing the pulling rate and / or melt temperature until the desired or target diameter is reached. The cylindrical body of the crystal, having an approximately constant diameter, is then grown by controlling the pulling rate and melt temperature while compensating for the decrease in melt level. Near the end of the growth process, but before the crucible is emptied of molten silicon, the crystal diameter is typically gradually reduced to form a tail end in the form of an end-cone. The end-cone is usually formed by increasing the crystal pulling rate and the amount of heat supplied to the crucible. The crystals are then separated from the melt when their diameter is small enough.

[0004] Czochralski growth techniques include batch Czochralski and continuous Czochralski. In batch Czochralski, a single polycrystalline charge is loaded into a crucible; the single charge should be sufficient to grow a single crystalline silicon ingot, after which the crucible is substantially depleted of silicon melt. In continuous Czochralski (CCZ) growth, polycrystalline silicon is continuously or periodically added to the molten silicon to replenish the melt during the growth process; thus, multiple ingots can be pulled from a single crucible during the growth process.

[0005] To implement the CCZ process, conventional batch Czochralski growth chambers and equipment are modified to include a means for supplying additional polycrystalline silicon to the melt in a continuous or semi-continuous manner without adversely affecting the properties of the growing ingot. As seed crystals are continuously grown from the melt, solid polycrystalline silicon, such as granular polycrystalline silicon, is added to the melt to replenish the melt. The rate at which the additional solid polycrystalline silicon is added to the melt is typically controlled to maintain process parameters. To reduce the adverse effects of this replenishment activity on the concurrent crystal growth, conventional quartz crucibles are often modified to provide an outer, or annular, melting zone, into which additional material is delivered, in addition to the inner growth zone from which the silicon ingot is pulled. These zones are in fluid communication with each other.

[0006] The continuously shrinking size of modern microelectronic devices imposes challenging restrictions on the quality of silicon substrates, which is substantially determined by the size and distribution of grown-in microdefects. Most microdefects formed in silicon crystals grown by the Czochralski (CZ) and Float Zone (FZ) processes are agglomerates of intrinsic point defects: silicon vacancies and self-interstitials (or simply interstitials).

[0007] A series of studies established that interstitial aggregates exist in two forms: spherical interstitial clusters, named B-swirl defects (or B defects), and dislocation loops, named A-swirl defects (or A defects). Later, the later-discovered vacancy agglomerates, known as D defects, were identified as octahedral spaces (or voids). Voronkov provided a widely accepted explanation for the microdefect distribution observed in silicon crystals based on the crystal growth conditions. According to Voronkov's model or theory, the temperature field near the melt / crystal interface drives the recombination of point defects and provides the driving force for their diffusion from the melt / crystal interface (where point defects exist at their respective equilibrium concentrations) into the crystal bulk. The interplay between point defect transport by both diffusion and convection and their recombination establishes a point defect concentration over a short distance from the interface, named the recombination length. Typically, the difference between the vacancy and interstitial concentrations beyond the recombination length, termed the excess point defect concentration, remains substantially constant away from the sides of the crystal. In rapidly pulled crystals, spatial redistribution of point defects due to their diffusion beyond the recombination length is generally insignificant—with the exception of regions near the sides of the crystal, which act as sinks or sources of point defects. Thus, if the excess point defect concentration beyond the recombination length is positive, vacancies remain in excess and agglomerate to form D defects at lower temperatures. If the excess point defect concentration is negative, interstitials remain the predominant point defect and agglomerate to form A and B defects. If the excess point defect concentration is below some detection threshold, no detectable microdefects are formed. Thus, typically, the type of grown microdefect is simply determined by the excess point defect concentration established beyond the recombination length. The process of establishing excess point defect concentration is termed initial incorporation, and the predominant point defect species is termed incorporated predominant point defect.The type of incorporated point defect is determined by the ratio of the crystal pull rate (v) to the magnitude of the axial temperature gradient (G) near the interface. At higher v / G, the vacancy concentration at the interface is higher than the interstitial concentration, so point defect convection dominates their diffusion, and vacancies remain the dominant incorporated point defect. At lower v / G, diffusion dominates convection, allowing fast-diffusing interstitials to become incorporated as dominant point defects. At v / G near its critical value, both types of point defects are incorporated at very low and comparable concentrations, mutually annihilating each other, thus suppressing the potential formation of any microdefects at lower temperatures. The observed spatial microdefect distribution can typically be explained by the radial nonuniformity of G and the change in v / G caused by the axial change in v. A striking feature of the radial microdefect distribution are oxide particles, which form through oxygen interaction with vacancies in a small range of v / G slightly above the critical v / G in regions of relatively lower incorporated vacancy concentration. These particles form narrow spatial bands that can be revealed by thermal oxidation as OSF (oxidation-induced stacking fault) rings. Quite often, OSF rings mark the boundaries between adjacent vacancy- and interstitial-dominated crystalline regions, known as V / I boundaries.

[0008] However, the microdefect distribution in CZ crystals grown at slower rates in many modern processes is influenced by the diffusion of point defects in the crystal bulk, including diffusion induced by the crystal's lateral surfaces. Therefore, accurate quantification of microdefect distribution in CZ crystals preferably incorporates two-dimensional point defect diffusion in both the axial and radial directions. Quantifying only the point defect concentration field can qualitatively capture the microdefect distribution in CZ crystals, since the type of microdefect formed is thereby directly determined. However, for more accurate quantification of microdefect distribution, it is necessary to capture point defect agglomeration. Traditionally, microdefect distribution is quantified by separating the initial incorporation of point defects and the subsequent formation of microdefects. This approach ignores the diffusion of dominant point defects near the nucleation region from higher temperature regions (where microdefect density is negligible) to lower temperature regions (where microdefects are present in higher densities and consume point defects). Alternatively, accurate numerical simulations based on prediction of the size distribution of the microdefect population at each location in the crystal are numerically expensive.

[0009] The transition between vacancy and interstitial dominated material occurs at a critical value of v / G, which is currently about 2.5×10 -5 cm 2 / sK. If the value of v / G exceeds a critical value, vacancies are the predominant intrinsic point defect, and the concentration of vacancies increases with increasing v / G. If the value of v / G is below the critical value, silicon self-interstitials are the predominant intrinsic point defect, and their concentration increases with decreasing v / G. Therefore, process conditions such as growth rate (which affects v) and hot zone configuration (which affects G) can be controlled to determine whether the intrinsic point defects in single crystal silicon will be predominantly vacancies (v / G is generally greater than the critical value) or self-interstitials (v / G is generally less than the critical value).

[0010] Generally, agglomerated defect formation occurs in two steps. First, defects called "nucleation" occur, which are the result of intrinsic point defects being supersaturated at a given temperature; above this "nucleation threshold" temperature, the intrinsic point defects remain soluble in the silicon lattice. The nucleation temperature for agglomerated intrinsic point defects is greater than about 1000°C.

[0011] Once this "nucleation threshold" temperature is reached, the intrinsic point defects agglomerate; that is, precipitation of these point defects from the "solid solution" of the silicon lattice occurs. The native point defects will continue to diffuse through the silicon lattice as long as the temperature of the portion of the ingot in which they reside is maintained above a second threshold temperature (i.e., the "diffusion threshold"), below which the native point defects are no longer mobile within a commercially practical time period.

[0012] As long as the ingot remains above the "diffusion threshold" temperature, native point defects, either vacancies or interstitials, diffuse through the silicon lattice to existing sites of agglomerated vacancies or interstitials, respectively, causing a given agglomerated defect to increase in size. Growth occurs as these agglomerated defect sites essentially act as "sinks," attracting and collecting native point defects due to their more favorable energy state for agglomeration.

[0013] Vacancy-type defects are recognized as the origin of such crystalline defects observable as D defects, flow pattern defects (FPDs), gate oxide integrity (GOI) defects, and crystal-origin particle (COP) defects, as well as a class of bulk defects observed by infrared light scattering techniques such as scanning infrared microscopy and laser scanning tomography. Also present in regions of excess vacancies are clusters of oxygen or silicon dioxide. Some of these clusters are small, remain relatively strain-free, and pose virtually no harm to the majority of devices prepared from such silicon. Some of these clusters are large enough to act as nuclei for ring oxidation-induced stacking faults (OISFs). This particular defect is speculated to be promoted by previously nucleated oxygen aggregates catalyzed by the presence of excess vacancies. Oxide clusters form primarily during CZ growth below 1000°C in the presence of moderate vacancy concentrations.

[0014] Self-interstitial related defects have been less studied. They are generally considered to be low densities of interstitial-type dislocation loops or networks. While such defects are not the cause of gate oxide integrity failure, which is a critical wafer performance criterion, they are widely recognized as the cause of other types of device failures, typically related to leakage current problems.

[0015] In this regard, it should be noted that, generally speaking, oxygen in the interstitial form in the silicon lattice is typically considered to be a point defect in silicon rather than an intrinsic point defect, while silicon lattice vacancies and silicon self-interstitials (or simply interstitials) are typically considered to be intrinsic point defects. Thus, substantially all microdefects can be generally considered to be agglomerated point defects, while D defects (or voids), as well as A and B defects (i.e., interstitial defects), can be more specifically considered to be agglomerated intrinsic point defects. Oxygen clusters are formed by the absorption of vacancies; thus, oxygen clusters can be considered to be aggregates of both vacancies and oxygen.

[0016] Furthermore, the density of such vacancies and self-interstitial agglomerated point defects in Czochralski silicon has historically been about 1×10 3 / cm 3 ~Approx. 1×10 7 / cm 3 , while the density of oxygen clusters is approximately 1×10 8 / cm 3 ~1×10 10 / cm 3 It should be noted that agglomerated intrinsic point defects are therefore of rapidly increasing importance to device manufacturers because such defects can significantly impact the yield potential of single crystal silicon materials in the production of complex, advanced integrated circuits.

[0017] In light of the above, in many applications, it is preferable that some or all of the silicon crystals subsequently sliced ​​into silicon wafers be substantially free of these agglomerated intrinsic point defects. To date, several approaches for growing substantially defect-free silicon crystals have been reported. Generally speaking, all of these approaches involve controlling the v / G ratio to determine the initial type and concentration of intrinsic point defects present in the growing CZ single crystal silicon crystal. However, such approaches may additionally involve controlling the crystal's subsequent thermal history to allow extended diffusion times to suppress the concentration of intrinsic point defects therein, thus limiting or avoiding the formation of agglomerated intrinsic point defects in some or all of the crystal. (See, e.g., U.S. Patent Nos. 5,627,131; 5,627,137; 5,627,137; and 5,627,137; the entire contents of which are incorporated herein by reference.) Alternatively, however, such approaches may involve a rapidly cooled silicon (RCS) growth process, in which the crystal's subsequent thermal history is then controlled to rapidly cool at least a portion of the crystal through a target nucleation temperature to control the formation of agglomerated intrinsic point defects in that portion. Alternatively, one or both of these approaches may allow at least a portion of the grown crystal to be maintained above the nucleation temperature for an extended period of time, reducing the concentration of intrinsic point defects prior to rapidly cooling this portion of the crystal through the target nucleation temperature, thus substantially limiting or avoiding the formation of agglomerated intrinsic point defects therein. (See, e.g., U.S. Patent No. 6,223,999, the entire disclosure of which is incorporated herein by reference.) Still further, methods have been developed to reduce or eliminate agglomeration of point defects from the center to the edge of the ingot by simultaneous control of the cooling rate of the solidified ingot and the radial variation of the axial temperature gradient near the interface (G). (See, e.g., U.S. Patent No. 6,223,999, the entire disclosure of which is incorporated herein by reference.)

[0018] Polished silicon wafers that meet manufacturers' requirements for the absence of agglomerated point defects, such as crystal-origin pits (COPs), may be referred to as neutral silicon or perfect silicon. Perfect silicon wafers are preferred for many semiconductor applications, for example, as a low-cost polished alternative to wafers with higher epitaxial deposition. Over the past two decades, many silicon wafer suppliers have developed defect-free and COP-free wafer products in both 200 mm and 300 mm diameters, primarily for sale to the memory (DRAM / NAND / FLASH) market, which has traditionally been more sensitive to cost pressures within the market. As customer-application device nodes have shrunk, industry standards for tolerable defectivity have evolved over this timeframe in terms of acceptable levels of light point scatter (LLS) and gate oxide integrity (GOI). For example, the industry COP-free specification could once be less than a few hundred at sizes below 0.12 μm. More current standards require a COP of less than 20 at sizes below 0.026 μm to qualify as full silicon. As another example, the past standard for GOI in MOS transistors was 95% at ≤8 MV (B-mode). Currently, the specification has shifted to 99% at 10-12 MV (D-mode). On top of this requirement, the need for improved radial oxygen precipitation across the wafer, traditionally measured by BMD density (bulk microdefects) and BMD size distribution, is required as device nodes shrink to avoid substrate slip during processing or warp, which can impact patterned overlays during device lithography. As these specifications (LLS, GOI, BMD uniformity, etc.) have tightened, the control window for defect- and COP-free silicon growth has shrunk significantly, significantly reducing the crystal throughput of the process because the allowable band structure (which can be directly translated into the process window of operation) has changed over time in the specifications.

[0019] This section is intended to inform the reader of various aspects of art that may be related to various aspects of the 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 disclosure. As such, these statements should not be read as admissions of prior art in this light. [Prior art documents] [Patent documents]

[0020] [Patent Document 1] U.S. Patent No. 6,287,380 [Patent Document 2] U.S. Patent No. 6,287,380 [Patent Document 3] U.S. Patent No. 6,254,672 [Patent Document 4] U.S. Patent No. 5,919,302 [Patent Document 5] U.S. Patent No. 6,312,516 [Patent Document 6] U.S. Patent No. 6,328,795 [Patent Document 7] U.S. Patent Application Publication No. 2003 / 0196587 [Patent Document 8] U.S. Patent No. 8,673,248 Summary of the Invention [Means for solving the problem]

[0021] (summary) One embodiment of the present disclosure is directed to a method for producing a single crystal silicon ingot by a continuous Czochralski process. The method includes adding an initial charge of polycrystalline silicon to a crucible; heating the crucible containing the initial charge of polycrystalline silicon to form a silicon melt in the crucible, wherein the silicon melt comprises an initial volume of molten silicon and has an initial melt elevation level; contacting a silicon seed crystal with the silicon melt; withdrawing the silicon seed crystal to grow a neck, wherein the silicon seed crystal is withdrawn at a neck pull-up rate during the neck growth; and withdrawing the silicon seed crystal to flare outward adjacent the neck. growing a flaring seed-cone, wherein the silicon seed is pulled at a seed-cone pull-up rate during growth of the flaring seed-cone; and pulling the silicon seed to form a main body (or main body) of the single crystal silicon ingot adjacent to the flaring seed-cone. growing a single crystal silicon ingot body, wherein the silicon melt comprises a volume of molten silicon and a melt height level during growth of the single crystal silicon ingot body, wherein the single crystal silicon ingot body is grown at an initial variable body pull-rate and a constant body pull-rate, and the single crystal silicon ingot body is grown at the initial variable body pull-rate for less than about 20% of the single crystal silicon ingot body length and at the constant body pull-rate for growth of at least about 30% of the single crystal silicon ingot body length; and further continuously supplying polycrystalline silicon to a crucible, thereby replenishing the volume of molten silicon and the melt height level in the crucible during growth of the single crystal silicon ingot body.

[0022] Various refinements exist for the features noted in connection with the above embodiments of the present disclosure. Additionally, additional features may be incorporated into the above embodiments of the present disclosure as well. These refinements and additional features may exist individually or in any combination. For example, the various features discussed below in connection with any of the illustrated embodiments of the present disclosure may be incorporated, alone or in any combination, into any of the above embodiments of the present disclosure. [Brief explanation of the drawings]

[0023] [Figure 1] Figures 1A (early body growth), 1B (mid-body growth), and 1C (late body growth) show the melt volume or depth and crucible position as a function of crystal length during a typical batch Czochralski process. [Figure 2] FIG. 2 is a graph showing the constant variation in pull rate required to achieve adequate defectivity control in ingots grown by a typical batch Cz process. [Figure 3] FIG. 3 is a graph showing the pull rate profile required to achieve sufficient defectivity control in ingots grown by a typical batch Cz process that includes the application of a magnetic field. [Figure 4] FIG. 4 is a graph illustrating the pull rate profile required to achieve adequate defectivity control in an ingot grown by a typical continuous Cz process according to the method of the present invention. [Figure 5] FIG. 5 shows a typical crucible configuration suitable for a typical continuous Cz process according to the method of the present invention. [Figure 6] 6A, 6B and 6C show the melt level and ingot growth of a typical continuous Cz process according to the method of the present invention. [Figure 7] 7A and 7B show the magnetic field applied to a silicon melt during ingot growth by a typical continuous Cz process according to the method of the present invention.

[0024] Corresponding reference characters indicate corresponding parts throughout the drawings. DETAILED DESCRIPTION OF THE INVENTION

[0025] (Detailed explanation) In the context of this invention, "perfect silicon" refers to a single crystal silicon wafer sliced ​​from a Czochralski-grown single crystal silicon ingot grown under conditions that meet or exceed the criteria of Perfect Silicon® (SunEdison Semiconductor, Ltd.). These criteria include ingots that meet or exceed industry specifications for agglomerated defects, DSOD (direct surface oxide defects), COP (crystal-origin pits or particles), D-defects, and I-defects. For example, a "perfect silicon" wafer may be characterized by no detectable FPD (flow pattern defects by Secco etching technique) and DSOD (direct surface oxide defect particle count after electrical breakdown), and zero I-defects (A-defects) by Secco etching technique. Secco etch (or etch) involves the application of a dilute aqueous solution of alkali dichromate and hydrofluoric acid to adequately reveal dislocations and other lattice defects in the various crystallographic (100), (111), and (110) planes of silicon. The etch introduces both lines (low angle grain boundaries) and slip lines. The method of the present invention enables the growth of single crystal silicon ingots comprising full silicon over at least about 70% of the body length of the single crystal silicon ingot, e.g., over at least about 80% of the body length of the single crystal silicon ingot, or even over at least about 90% of the body length of the single crystal silicon ingot. In some embodiments, wafers sliced ​​from ingots grown over at least about 70% of the body length of the single crystal silicon ingot, e.g., over at least about 80% of the body length of the single crystal silicon ingot, or even over at least about 90% of the body length of the single crystal silicon ingot, are characterized by no detectable FPD (flow pattern defects by Secco etching technique) and DSOD (direct surface oxide defect particle count after electrical breakdown) and zero I defects (A defects) by Secco etching technique.In some embodiments, wafers sliced ​​from ingots grown over at least about 70% of the body length of the monocrystalline silicon ingot, e.g., over at least about 80% of the body length of the monocrystalline silicon ingot, or even over at least about 90% of the body length of the monocrystalline silicon ingot, are characterized by a GOI in MOS transistors of 95% at ≦8 MV (B-mode), preferably 99% at 10-12 MV (D-mode).

[0026] In the conventional batch Czochralski method for growing single-crystal silicon ingots, both the crystal melt / interface and thermal conditions change continuously as a function of increasing ingot length due to the variability of silicon melt consumption and crucible position during ingot growth. A depiction of melt depletion and crucible movement can be found in Figure 1. Figures 1A (early body growth), 1B (middle body growth), and 1C (late body growth) show the melt level and crucible height as a function of crystal length during the batch Cz process. Because melt conditions, such as mass, height level, and crucible position, are continuously changing during the batch process, the v / G ratio (growth rate V / axial temperature gradient G) required to minimize defectivity continuously changes the crystal length and alters crystal quality. To maintain the desired quality within specifications within the process window, continuous control adjustment of several parameters is required depending on the position. These parameters include crucible rotation rate (C / R), seed rotation rate (S / R), seed lift rate (S / L), heater power, reflector height, etc. See Figure 2, which is a graph showing the constant variation in pull-rate required to achieve sufficient defectivity control in ingots grown by a typical batch Cz process. The lines defined by the triangles (---▲---) are the ever-changing critical pull-rates for achieving critical v / G values. The pull-rate can be varied within the upper critical pull-rate ("UCL"), indicated by squares (---■---), and the lower critical pull-rate ("LCL"), indicated by diamonds (---◆---), and still achieve acceptable defectivity control. These three lines represent pull-rates capable of producing perfect silicon. Within the upper and lower pull-rate boundaries, perfect silicon with predominant intrinsic point defects can be produced. For example, when the applied pulling rate is controlled between the lines labeled with triangles and squares in Figure 2 (and Figures 3 and 4), vacancy-dominated ("Pv") silicon is produced, and when the applied pulling rate is controlled between the lines labeled with triangles and diamonds in Figure 2 (and Figures 3 and 4), interstitial-dominated ("Pi") silicon is produced.In the example depicted in FIG. 2 (as well as FIGS. 3 and 4), in the early and middle portions of ingot growth, perfect silicon with vacancy-dominated point defects can be grown, as shown by the representation of the ingot cross-section labeled "Pv." FIG. 2 shows that the ingot is vacancy-dominated from the center to the edge. In the example shown in FIG. 2, in later growth, the ingot is characterized by regions of vacancy-dominated point defects and interstitial-dominated point defects, as shown in the cross-sectional area region labeled "Pi." For example, an ingot can be grown that is interstitial-dominated from the center to a radial length less than the entire ingot radius, surrounded by a band of vacancy-dominated material to the ingot's edge. Still, in the later region, the ingot cross-section shows vacancy-dominated material in the center, surrounded by another band of vacancy-dominated material at the edge. These depictions are merely illustrative and are not intended to be limiting on the method of the present invention. Perfect silicon, i.e., ingots and their rice wafers free of detectable agglomerated point defects, is due in part to the proper control of excess point defects (vacancies and interstitials) due to the ingot pull rate. Intrinsic point defects, such as vacancies and interstitials, occur in ingots grown by the Czochralski method. The presence of such defects has no impact on whether the silicon is perfect. Rather, perfect silicon is characterized as being free of agglomerated point defects, such as COP, DSOD, and I defects.

[0027] FIG. 2 (as well as FIGS. 3 and 4) also shows the agglomerated defects that can occur in ingots as a function of pull-rate outside the upper and lower critical v / G limits at any crystal length. If the upper critical pull-rate is exceeded (v / G is higher than the critical v / G), defects that can occur include DSOD (direct surface oxide defects) or COP (crystal-origin pits or particles). If the pull-rate is below the lower critical pull-rate (v / G is lower than the critical v / G), defects that can occur include I-defects. The bands in which these defects occur are also shown in the ingot cross-section. In regions where the predominant excess point defects are vacancies, agglomeration of vacancy defects forms bulk defects such as COPs and DSOD due to vacancy agglomeration and precipitation during Cz silicon crystal growth and cooling. In regions where the predominant excess point defects are interstitial silicon atoms, they agglomerate to form bulk defects such as I defects due to the agglomeration / precipitation of interstitial silicon atoms, punching out dislocations. Any small deviation in v / G will form defects due to the agglomeration of either vacancies or interstitial silicon atoms.

[0028] magnetic place , e.g., horizontal or Cusp (or tip: cusp) magnetic place Applying a magnetic field can be used to alter the melt flow pattern within the crucible and allow for increased control of the shape and height of the crystal / melt interface, thereby enhancing quality control. However, as illustrated in Figure 3, pulling speed and other parameters must still be modified to achieve acceptable defectivity control. Figure 3 shows the effect of an applied magnetic field on the melt flow pattern within the crucible. place2 is a graph showing the pull-rate profile required to achieve sufficient defectivity control in an ingot grown by a typical batch Cz process at 1000 K. The line defined by the triangles (---▲---) is the critical pull-rate for achieving a critical v / G value, which is continuously varied, if necessary, during the growth of the single crystal silicon ingot. The pull-rate can be varied within the upper critical pull-rate ("UCL") indicated by the squares (---■---) and the lower critical pull-rate ("LCL") indicated by the diamonds (---◆---) and still achieve acceptable defectivity control. The regions of native point defects and agglomerated point defects in the cross-sectional area of ​​the single crystal silicon ingot are substantially the same as those described above in the description of FIG. 2.

[0029] According to the method of the present invention, single crystal silicon ingots are grown by the continuous Czochralski (CCZ) method under conditions that allow the melt depth (i.e., the height level of the molten silicon) and thermal conditions to remain substantially constant during growth, as the melt is continuously replenished as it is consumed. In some embodiments, maintaining the molten silicon at a substantially constant height level allows the crucible to be maintained in a fixed position. Once v / G is fixed with the appropriate hot zone configuration, the process window will be fixed (i.e., no control adjustments) over a substantial portion of the crystal length. Once the process conditions (S / R, power, gas flow and / or pressure, magnetic flux density, Cusp Once the HMCZ MGP position is set, gas flow, chamber pressure, and C / R are used to control the oxygen content. Thus, the method of the present invention allows for the growth of single crystal silicon ingots by the continuous Czochralski (CCZ) method, where the pull rate is constant throughout the growth of a substantial length of the ingot, and ingots grown by this method have consistent and acceptable defectivity control, O, throughout a substantial portion of the ingot's axial length. i It has uniformity and BMD uniformity.

[0030] After all conditions are set to steady state, the pull rate to produce a single crystal silicon ingot with the desired defectivity control across the entire crystal length will be consistent with significantly reduced quality loss in production due to process control compared to conventional Cz processes. Figure 4 is a graph of pull rate as a function of axial length of a single crystal silicon ingot during a typical continuous Czochralski growth method according to the present invention. As shown in Figure 4, a constant pull rate is maintained throughout a substantial portion of the growth of the main body portion of the single crystal silicon ingot. The line defined by the triangles (---▲---) is the critical pull rate for achieving a critical v / G value, which has an initial varying region followed by a region of constant pull rate throughout a substantial portion of the growth of the main body portion of the single crystal silicon ingot. The pull rate can vary within an upper critical pull rate ("UCL") indicated by squares (---■---) and a lower critical pull rate ("LCL") indicated by diamonds (---◆---) and still achieve acceptable defectivity control. The regions of intrinsic point defects and agglomerated point defects in the cross-sectional area of ​​the single crystal silicon ingot are substantially the same as those described above in the description of Figure 2.

[0031] In the CCZ process according to the present invention, the polycrystalline silicon feed is continuous with the growing crystal, so that the melt volume remains substantially the same as the initial melt depth regardless of the crystal length. Because the melt elevation is controlled by the mass balance between the growing crystal weight and the continuously fed polycrystalline silicon, the thermal conditions in the melt and the growing crystal remain constant throughout the axial growth. Thereafter, once the desired crystal / melt interface is reached, the melt volume remains substantially the same as the initial melt depth regardless of the crystal length. place If the parameters such as C / R and S / R, pulling speed, heater power, etc. are determined and fixed, the defect quality and O iControl will be maintained constant throughout the growth of the crystal axis. Furthermore, a constant pull rate for a given HZ and crystal / melt interface will be quasi-steady ( q It can be used over the entire crystal length for steady-state control.

[0032] According to the method of the present invention, the thermal conditions suitable for achieving the growth of a single-crystalline silicon ingot that meets the requirements for defect control are established by a hot-zone configuration. This growth method is a continuous Czochralski process. Accordingly, the furnace chamber includes a means for continuous supply of polycrystalline silicon, e.g., a feed tube. While chunk polysilicon can be used, the solid polysilicon added to the crucible is typically granular polysilicon, which is fed to the crucible using a polysilicon feeder optimized for granular polysilicon applications. Chunk polysilicon typically has a size of 3 to 45 millimeters (e.g., maximum dimension), while granular polysilicon typically has a size of 400 to 1400 microns. Granular polysilicon has several advantages, including easier and more precise control of the feed rate due to its smaller size. However, the cost of granular polysilicon is typically higher than that of chunk polysilicon due to the chemical vapor deposition process or other manufacturing methods used to produce it. Chunk polysilicon has the advantage of being cheaper and allowing for higher feed rates given its larger size. Adapt the polysilicon feeder by adjusting the position of the heating unit, the operation of the cooling jacket and the power controls.

[0033] A depiction of a crucible 10 having multiple weirs (20, 30, 40) or fluid barriers that separate the melt into different melt zones is shown in FIG. 5. In the illustrated embodiment, the crucible assembly 10 includes a first weir 20 (broadly, a fluid barrier) that defines an inner melt zone 22 of the silicon melt. The inner melt zone 22 is a growth region in which a single crystal silicon ingot 50 is grown. A second weir 30 defines an intermediate melt zone 32 of the silicon melt. Finally, a third weir 40 defines an outer melt zone 42 of the silicon melt. A feed pipe (not shown) delivers polycrystalline silicon, which may be grains, chunks, or a combination of grains and chunks, to the outer melt zone 42 at a rate sufficient to maintain a substantially constant melt height level and volume during ingot growth. Each of the first weir 20, second weir 30, and third weir 40 has a generally annular shape and at least one opening defined therein to allow molten silicon to flow radially inward toward the growth region of the inner melt zone 22. The crucible configuration shown in FIG. 5 is exemplary and suitable for carrying out the process of the present invention. Other configurations suitable for CCZ may be used without departing from the scope of the present invention. For example, the crucible 10 may lack the second weir 30 and / or may lack the third weir 40.

[0034] Typically, the melt from which the ingot is extracted is formed by loading polycrystalline silicon into a crucible to form an initial silicon charge. Typically, the initial charge is about 100 to 200 kilograms of polycrystalline silicon, which can be granules, chunks, or a combination of granules and chunks. The mass of the initial charge depends on the desired crystal diameter and HZ design. Because polycrystalline silicon is continuously fed during crystal growth, the initial charge does not reflect the crystal length. For example, if polycrystalline silicon is continuously fed and the chamber height is sufficiently high, the crystal length can extend to 2000 mm, 3000 mm, or even 4000 mm. The crucible can have the configuration shown in Figure 5 or another configuration suitable for CCZ growth. Various sources of polycrystalline silicon can be used, including granular polycrystalline silicon produced by the pyrolysis of silane or halosilane in a fluidized-bed reactor or polycrystalline silicon produced in a Siemens reactor. Once polycrystalline silicon is added to the crucible to form a charge, the charge is heated to a temperature above about the melting temperature of silicon (e.g., about 1412°C) to melt the charge, thereby forming a silicon melt comprising molten silicon. The silicon melt has an initial volume of molten silicon and an initial melt height level, these parameters being determined by the size of the initial charge. In some embodiments, the crucible containing the silicon melt is heated to a temperature of at least about 1425°C, at least about 1450°C, or even at least about 1500°C.

[0035] Once the charge is liquefied to form a silicon melt containing molten silicon, the silicon seed crystal is lowered into contact with the melt. The silicon seed crystal is then removed from the melt attached thereto (i.e., with reference to FIG. 5 , the seed crystal portion and neck 52), thereby forming a melt / solid interface near or at the surface of the melt. Generally, the initial pulling speed to form the neck is high. In some embodiments, the silicon seed crystal and neck are pulled at a neck pulling speed of at least about 1.0 mm / min, e.g., about 1.5 mm / min to about 6 mm / min, e.g., about 3 mm / min to about 5 mm / min. In some embodiments, the silicon seed crystal and crucible are rotated in opposite directions (i.e., counter-rotation). Counter-rotation achieves convection in the silicon melt. Crystal rotation is primarily used to provide a symmetrical temperature profile, suppress angular variations in impurities, and control the crystal-melt interface shape. In some embodiments, the silicon seed crystal is rotated at a speed of about 5 rpm to about 30 rpm, or about 5 rpm to about 20 rpm, or about 8 rpm to about 20 rpm, or about 10 rpm to about 20 rpm. In some embodiments, the crucible is rotated at a speed of about 0.5 rpm to about 10 rpm, or about 1 rpm to about 10 rpm, or about 4 rpm to about 10 rpm, or about 5 rpm to about 10 rpm. In some embodiments, the seed crystal is rotated at a faster speed than the crucible. In some embodiments, the seed crystal is rotated at a speed at least 1 rpm higher than the rotation speed of the crucible, e.g., at least 3 rpm higher, or at least 5 rpm higher. Typically, the neck portion 52 has a length of about 300 millimeters to about 700 millimeters, e.g., about 450 millimeters to about 550 millimeters. However, the length of the neck portion 52 can vary outside these ranges.

[0036] After the formation of the neck 52, with reference to FIG. 5 , an outwardly flaring seed cone portion 54 adjacent the neck 52 is grown. Generally, the pulling rate is reduced from the neck pulling rate to a rate appropriate for growing the outwardly flaring seed cone portion 54. For example, the seed cone pulling rate during growth of the outwardly flaring seed cone is about 0.5 mm / min to about 2.0 mm / min, e.g., about 1.0 mm / min. In some embodiments, the outwardly flaring seed cone 54 has a length of about 100 mm to about 400 mm, e.g., about 150 mm to about 250 mm. The length of the outwardly flaring seed cone 54 can vary outside these ranges. In some embodiments, the outwardly flaring seed cone 54 is grown to a terminal diameter of about 150 mm, at least about 150 mm, about 200 mm, at least about 200 mm, about 300 mm, at least about 300 mm, about 450 mm, or even at least about 450 mm. The end diameter of the outwardly flaring seed cone 54 is generally equivalent to the diameter of the constant diameter body of the single crystal silicon ingot.

[0037] Then, the neck 52 and adjacent to the neckAfter the formation of the outwardly flaring seed cone 54, a main ingot body 56 having a constant diameter is grown adjacent to the cone portion. The constant diameter portion of the main ingot body 56 has a peripheral edge, a central axis parallel to the peripheral edge, and a radius extending from the central axis to the peripheral edge. The central axis also passes through the outwardly flaring seed cone 54 and the neck 52. The diameter of the main ingot body 56 can vary, and in some embodiments, the diameter can be about 150 mm, at least about 150 mm, about 200 mm, at least about 200 mm, about 300 mm, at least about 300 mm, about 450 mm, or even at least about 450 mm. The main ingot body 52 of the single crystal silicon ingot is eventually grown to be at least about 1000 millimeters long, e.g., at least 1400 millimeters long, e.g., at least 1500 millimeters long, or at least 2000 millimeters long, or at least 2200 millimeters long, e.g., 2200 millimeters long, or at least about 3000 millimeters long, or at least about 4000 millimeters long.

[0038] 4 shows a typical, non-limiting pull rate protocol for pulling the body of a single crystal silicon ingot according to some embodiments of the method of the present invention. As is evident from the typical illustration, the pull rate decreases from a relatively high pull rate to a minimum pull rate and then increases to a constant pull rate for a significant portion of the growth of the body of the single crystal silicon ingot. According to the process of the present invention, the pull rate is selected to achieve perfect silicon, i.e., silicon characterized by a lack of detectable agglomerated defects selected from agglomerated defects, DSOD (direct surface oxidation defects), COP (crystal origin pits), D-defects, and I-defects, etc. The initial high pull rate can be about 0.5 mm / min to about 2.0 mm / min, for example, about 1.0 mm / min, then reduced to a pull rate that can be as low as about 0.4 mm / min or as low as about 0.3 mm / min, and then increased to a constant pull rate of about 0.4 mm / min to about 0.8 mm / min, about 0.4 mm / min to about 0.7 mm / min, or about 0.4 mm / min to about 0.65 mm / min.

[0039] Typical, non-limiting examples of hot zone configurations within a furnace chamber 100 suitable for practicing the method of the present invention are shown in Figures 6A, 6B, and 6C. Other hot zone configurations are suitable for practicing the method of the present invention. The hot zone configuration includes a cooling jacket 102, a reflector 104, a side heater 106, and a bottom heater 108. The growing crystal diameter and meniscus shape and height are monitored by a camera (not depicted) located in the top window. Data obtained from the camera provides feedback to the side heater 106 and bottom heater 108. During crystal growth, the power distribution can be adjusted between the heaters to enable uniformity of the melt / solid interface, i.e., to maintain the desired meniscus shape and height. The reflector 104 will reflect heat flow from the hot parts of the furnace, including the heaters and crucible, to the melt. The reflector 104 reduces heat transfer from the hot section of the furnace to the cooler section (maintained by the cooling jacket 102), thereby maintaining separation between these two regions of the furnace. The reflector helps control the axial and radial temperature gradients that drive the solidification and crystallization of the molten silicon into the growing ingot.

[0040] 6A, 6B, and 6C show the first, second, and third steps, respectively, which correspond to the regions of the pulling rate shown in FIG. 4. That is, the first step shown in FIG. 6A corresponds to the region in FIG. 4 where the pulling rate is high and decreases to a minimum. The second step shown in FIG. 6B corresponds to the region in FIG. 4 where the pulling rate is minimum and increases to a constant pulling rate. The third step shown in FIG. 6C corresponds to the region of constant pulling rate in FIG. 4. During each step, polycrystalline silicon is continuously supplied to the melt during growth of the ingot 112 (see FIG. 5), so that the melt 110 maintains a constant melt volume and melt height level in accordance with an embodiment of the present invention.

[0041] The initial region for growing the single crystal silicon ingot body characterized by a variable pull rate may encompass less than about 20% of the total length of the single crystal silicon ingot body. In some embodiments, the variable pull rate regime may encompass about 5% to about 20% of the single crystal silicon ingot body length, e.g., about 5% to about 15% of the single crystal silicon ingot body length, or about 10% to about 15% of the single crystal silicon ingot body length. The percentage of the single crystal silicon ingot body length grown under variable pull rate conditions depends in part on the total length of the ingot body. For example, the body length of an ingot pulled under variable rate conditions may vary from about 50 mm to about 200 mm, from about 100 mm to about 200 mm, e.g., from about 150 mm to about 200 mm. If 200 mm is grown under variable rate conditions and the total body length of the ingot is 1400 mm, then about 14% of the body is grown under variable rate conditions, while only about 9% of the body is grown under variable rate conditions for a total body length of 2200 mm.

[0042] After an initial region of the body is grown under variable pull-rate conditions, the remainder of the body is grown under a constant pull-rate. In some embodiments, the ingot body is grown at a constant body pull-rate during growth of at least about 30% of the length of the single crystal silicon ingot, e.g., at least about 50% of the length of the single crystal silicon ingot, at least about 70% of the length of the single crystal silicon ingot, at least about 80% of the length of the single crystal silicon ingot, or even at least about 90% of the length of the single crystal silicon ingot. In some embodiments, the constant body pull-rate is between about 0.4 mm / min and about 0.8 mm / min, between about 0.4 mm / min and about 0.7 mm / min, or between about 0.4 mm / min and about 0.65 mm / min.

[0043] During growth of the main body of the single crystal silicon ingot, polycrystalline silicon, i.e., grains, chunks, or a combination of grains and chunks, is added to the molten silicon to achieve a constant volume of molten silicon and a constant melt height level. According to the method of the present invention, maintaining a substantially constant melt volume during growth of a substantial portion of the axial length of the main body of the single crystal silicon ingot allows for the achievement of high ingot quality over a substantial portion of the axial length of the main body of the single crystal silicon ingot at a constant pulling rate. A constant melt volume, regardless of crystal length, allows for a constant crystal / melt interface, thus allowing for uniform crystal quality over a substantial portion of the main body of the ingot. Thus, in some embodiments, the volume of molten silicon varies by no more than about 1.0% by volume during growth of at least 90% of the main body of the single crystal silicon ingot, or by no more than about 0.5% by volume during growth of at least 90% of the main body of the single crystal silicon ingot, or by no more than about 0.1% by volume during growth of at least 90% of the main body of the single crystal silicon ingot. Stated another way, in some embodiments, the melt height level varies by less than about + / - 0.5 millimeters during the growth of at least 90% of the body of the single crystal silicon ingot.

[0044] In addition, the process of the present invention place may be applied to a crucible containing silicon melt. Cusp or horizontal of magnetic place (or magnetic world A magnet field can be applied to set the appropriate crystal / melt interface, i.e., meniscus, shape and height. place The desired crystal / melt interface shape and height are first fixed using the oxygen content O i Control of the is a subordinate objective.

[0045] Control of the melt flow and the shape of the melt / solid interface, and therefore the quality of the ingot, depends on the magnetic field exerted on the silicon melt during the growth of the main body of the monocrystalline silicon ingot. place In some embodiments, the applied magnetic field place maintains a substantially constant melt / solid interface profile for at least about 70% of the growth of the body of the single crystal silicon ingot, or between about 70% and about 90% of the growth of the body of the single crystal silicon ingot. place applies electromagnetic forces that affect the silicon melt flow and therefore the heat transfer in the melt, which changes the crystal / melt interface profile and the temperature at which the crystal grows, which are key control parameters for perfect silicon.

[0046] magnetic place The oxygen source of the ingot is determined by the melting of the quartz crucible wall, evaporation of the melt-free surface (controlled by the melt flow dynamics), and the oxygen content and uniformity of the ingot. i O x (g) and from incorporation into the growing crystal surface. place can strongly affect the convective melt flow during growth, which in turn can strongly affect oxygen evaporation and incorporation. The change in oxygen incorporation into a single crystal silicon ingot with time increment can be calculated using the following equation:

[0047]

number

[0048] C is the oxygen concentration of the solidifying silicon, t is time, v is the convection velocity (melt flow velocity), ρ (rho) is the density of the silicon melt, and ∇ is the gradient (d / dx). place influences the melting rate (v) and the gradient of the oxygen concentration in the melt (dC / dx=∇C). place As a result, a steady state melt flow occurs, and oxygen O i The uptake of oxygen is a time constant, which enhances the radial and axial oxygen concentration uniformity. The term SOURCE refers to the relationship between two parameters: oxygen production (S i (l)+S i O2(s)→S i Ox (g)) is quartz (S i O2) melting of the crucible and oxygen (S i O x (g)) is due to evaporation, which is the removal (disappearance) of oxygen (O2). In the batch Cz process, this term SOURCE is not constant. Instead, the SOURCE depends on the crystal length, since the melt mass decreases as the crystal grows. When the ingot grows a substantial portion of its body length, the remaining melt volume is low, and as a result, the amount of silicon melt in contact with the crucible decreases, thus leading to a decrease in the oxygen concentration taken up by the melt from the crucible. Therefore, if other terms (diffusion, convection, evaporation) are constant, the oxygen incorporated into the solidifying silicon crystal decreases. The melt-free surface area (the contact surface between the melt and the gas) is S i O x (g). The small melt mass in the batch Cz process has a relatively smaller surface area due to the crucible geometry shown in Figure 1C. S i O x Less evaporation of (g) means more oxygen incorporation into the solidifying silicon crystal. According to the method of the present invention, as polysilicon is added as the crystal ingot grows, the melt mass remains constant. Therefore, all source terms (S into the melt) i Oxygen generation by crucible melting and S through the melt-free surface i O x (g) Evaporation of gases is constant. Therefore, the diffusion and convection terms affect the oxygen in the solidifying silicon crystal. placeThis makes the melt flow more stable because oxygen incorporation is uniform and stable axially and radially throughout the growth of the ingot (i.e., the melt flow is constant, similar to a time-independent steady-state condition). In some embodiments, interstitial oxygen may be incorporated into the ingot at a concentration of about 4 PPMA to about 18 PPMA. In some embodiments, interstitial oxygen may be incorporated into the ingot at a concentration of about 10 PPMA to about 35 PPMA. In some embodiments, the ingot contains oxygen at a concentration of about 15 PPMA or less, or about 10 PPMA or less. Interstitial oxygen may be measured according to SEMI MF 1188-1105.

[0049] In some embodiments, a horizontal magnetic place is applied to the silicon melt during the growth of the body of a single crystal silicon ingot. Such a horizontal field is shown in Figure 7A, which can be seen in Figure 5 as a horizontal magnetic field placed over the crucible and growing ingot. place This is a depiction of the horizontal magnetic field. place Crystal growth in the presence of a horizontal magnet is achieved by placing a crucible that holds the silicon melt between the poles of a conventional electromagnet 200. In some embodiments, a horizontal magnet place The magnetic flux density in the melt region may be about 0.2 Tesla to about 0.4 Tesla. place The variation is less than + / - about 0.03 Tesla of a given strength. place The application of the force generates a Lorentz force along the axial direction, opposite the direction of the fluid motion and countering the force driving melt convection. Thus, convection in the melt is suppressed, and the axial temperature gradient in the crystal near the interface increases. The melt-crystal interface then shifts upward toward the crystal, accommodating the increased axial temperature gradient in the crystal near the interface, and the contribution from melt convection in the crucible decreases.

[0050] In some embodiments, Cusp magnetic place is applied to the silicon melt during growth of the body of the single crystal silicon ingot. Cusp The field is shown in FIG. 7B, which is placed over the crucible and growing ingot, as shown in FIG. Cusp magnetic place This is a depiction of the following. Cusp magnetic place is controlled by two control parameters: magnetic flux density and magnetic place It has a shape. Cusp magnetic place is the perpendicular (axial) magnetic field in the melt near the axis of the ingot. place and a horizontal (radial) magnetic field at the nearest surface of the melt combined with place The components are applied. Cusp magnetic place is generated using a pair of Helmholtz coils carrying currents in opposite directions. As a result, two magnetic place At the midpoint of the ingot, a magnetic place cancel each other out, and perpendicular magnetic fields are formed at or near zero. place Create a component, for example: Cusp The magnetic flux density in the axial direction is typically about 0 to about 0.2 Tesla. The magnetic flux density in the radial direction is generally higher than the magnetic flux density in the perpendicular direction. For example, Cusp The magnetic flux density is typically about 0 to about 0.6 T at a radial position, depending on the radial position, for example, about 0.2 to about 0.5 T. Cusp magnetic place The radial direction of the melt is suppressed, thereby stabilizing the melt. Cusp magnetic place The application of heat acts as an effective method to induce convection adjacent to the solid-liquid interface where crystal growth occurs and suppress convection in the remaining part of the melt, thereby achieving a uniform oxygen distribution. The melt convection of heat occurs simultaneously at the melt-free surface and at the melt-crucible interface. Cusp magnetic place This allows for control of the oxygen concentration in the growing crystal solely by the magnetic flux density, regardless of the crystal rotation speed. place In the presence of oxygen, control of the oxygen concentration is achieved through control of the crystal rotation rate. Cusp magnetic placeThe application of the magnetic field is preferably about 15 PPMA or less, or about 10 PPMA or less. place This may allow growth on an ingot containing a lower oxygen content than an ingot grown without interstitial oxygen. Interstitial oxygen may be measured by SEMI MF 1188-1105.

[0051] The method of the present invention enables the growth of single crystal silicon ingots by the continuous Czochralski process that meet or exceed industry specifications for perfect silicon. Factors that contribute to the growth of perfect silicon crystals include determining the critical pull rate for growing perfect silicon, maintaining a constant pull rate at the critical rate throughout a substantial portion of the growth of the body of the single crystal silicon ingot, and magnetically controlling the melt / solid interface to maintain its shape and height. place Once the pulling speed and magnetic place Once the configuration is determined, the pull rate can be maintained at a constant rate by continuously adding polycrystalline silicon to maintain a constant melt volume and melt height level. Thus, unlike conventional methods of growing ingots, the pull rate is constant over a substantial portion of the ingot's growth. In light of the process control enabled by the methods disclosed herein, the inventive methods enable the growth of single crystal silicon ingots that contain full silicon over at least about 70% of the single crystal silicon ingot's body length, e.g., over at least about 80% of the single crystal silicon ingot's body length, or even over at least about 90% of the single crystal silicon ingot's body length.

[0052] 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 cover variations that may exist at the upper and / or lower limits of the range of the property or characteristic, including, for example, variations due to rounding, measurement method, or other statistical variations.

[0053] When introducing elements of the disclosure or embodiments thereof, the terms "a," "an," "the," and "the" are intended to mean that there are one or more 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 terms indicating a particular orientation (e.g., "top," "bottom," "side," etc.) is for convenience of description and does not require a particular orientation of any of the described items.

[0054] Because various changes can be made in the above-described structures and methods without departing from the scope of the disclosure, it is intended that all matter contained in the above specification and shown in the accompanying drawings be interpreted as illustrative and not in a limiting sense. The present invention includes the following aspects. (Aspect 1) (Document title) Claims (Aspect 1) A method for producing a single crystal silicon ingot by a continuous Czochralski method, comprising: adding an initial charge of polycrystalline silicon to the crucible; heating a crucible containing an initial charge of polycrystalline silicon to form a silicon melt in the crucible, wherein the silicon melt includes an initial volume of molten silicon and has an initial melt height level; contacting a silicon seed crystal with a silicon melt; pulling the silicon seed crystal to grow a neck, wherein the silicon seed crystal is pulled at a neck pull rate during the growth of the neck; pulling the silicon seed crystal to grow an outwardly extending seed cone adjacent the neck portion, wherein the silicon seed crystal is pulled at a seed cone pull-up rate during growth of the outwardly extending seed cone; and pulling the silicon seed crystal to grow a body of the single crystal silicon ingot adjacent an outwardly extending seed cone, wherein the silicon melt comprises a volume of molten silicon and a melt height level during growth of the body of the single crystal silicon ingot; Including, The single crystal silicon ingot body is grown at an initial variable body pull rate and a constant body pull rate, wherein the single crystal silicon ingot body is grown at the initial variable body pull rate for less than about 20% of the single crystal silicon ingot body length and at the constant body pull rate for growth of at least about 30% of the single crystal silicon ingot body length; and The method further comprises continuously feeding polycrystalline silicon into the crucible, thereby replenishing the volume of molten silicon and melt height level in the crucible during growth of the main body of the single crystal silicon ingot. (Aspect 2) 2. The method of claim 1, wherein a magnetic field is applied to the silicon melt during growth of the main body of the single crystal silicon ingot. (Aspect 3) 3. The method of claim 2, wherein a horizontal magnetic field is applied to the silicon melt during growth of the main body of the single crystal silicon ingot. (Aspect 4) 3. The method of claim 2, wherein a cusp magnetic field is applied to the silicon melt during growth of the main body of the single crystal silicon ingot. (Aspect 5) 3. The method of claim 2, wherein the applied magnetic field maintains a substantially constant melt / solid interface profile during at least about 70% of the growth of the body of the single crystal silicon ingot. (Aspect 6) 3. The method of claim 2, wherein the applied magnetic field maintains a substantially constant melt / solid interface profile during about 70% to about 90% of the growth of the main body of the single crystal silicon ingot. (Aspect 7) Aspect 7. The method of any one of aspects 1-6, wherein the body of the single crystal silicon ingot is at least about 1000 millimeters long, at least 1400 millimeters long, or at least 1500 millimeters long. (Aspect 8) Aspect 7. The method of any one of aspects 1-6, wherein the body of the single crystal silicon ingot is at least 2000 millimeters long, at least 2200 millimeters long, at least about 3000 millimeters long, or at least about 4000 millimeters long. (Aspect 9) Aspect 9. The method of any one of aspects 1-8, wherein the diameter of the body of the single crystal silicon ingot is at least about 150 millimeters, or at least about 200 millimeters. (Aspect 10) 9. The method of any one of aspects 1-8, wherein the diameter of the body of the single crystal silicon ingot is at least about 300 millimeters, or at least about 450 millimeters. (Aspect 11) 11. The manufacturing method according to any one of aspects 1 to 10, wherein the constant body lifting speed is about 0.4 mm / min to about 0.8 mm / min, about 0.4 mm / min to about 0.7 mm / min, or about 0.4 mm / min to about 0.65 mm / min. (Aspect 12) 12. The method of any one of aspects 1 to 11, wherein the single crystal silicon ingot body is grown at an initial variable body pull rate for about 5% to about 20% of the single crystal silicon ingot body length. (Aspect 13) 13. The method of any one of aspects 1 to 12, wherein the single crystal silicon ingot body is grown at a constant body pull rate during growth of at least about 50% of the single crystal silicon ingot body length. (Aspect 14) 13. The method of any one of aspects 1 to 12, wherein the single crystal silicon ingot body is grown at a constant body pull rate during growth of at least about 70% of the single crystal silicon ingot body length. (Aspect 15) 13. The method of any one of aspects 1 to 12, wherein the single crystal silicon ingot body is grown at a constant body pull rate during growth of at least about 80% of the single crystal silicon ingot body length. (Aspect 16) 13. The method of any one of aspects 1 to 12, wherein the single crystal silicon ingot body is grown at a constant body pull rate during growth of at least about 90% of the single crystal silicon ingot body length. (Aspect 17) 17. The manufacturing method of any one of aspects 1 to 16, wherein the body pull-up rate is a constant critical pull-up rate sufficient to avoid agglomerated point defects over at least 70% of the body length of the single crystal silicon ingot. (Aspect 18) 17. The manufacturing method of any one of aspects 1-16, wherein the body pull rate is a constant critical pull rate sufficient to avoid agglomerated point defects over at least 90% of the body length of the single crystal silicon ingot. (Aspect 19) 19. The method of any one of embodiments 1-18, wherein the volume of the molten silicon changes by no more than about 1.0 vol.% during growth of at least about 90% of the body of the single crystal silicon ingot. (Aspect 20) 19. The method of any one of embodiments 1-18, wherein the volume of the molten silicon changes by no more than about 0.5% by volume during growth of at least about 90% of the body of the single crystal silicon ingot. (Aspect 21) 19. The method of any one of aspects 1-18, wherein the volume of the molten silicon changes by no more than about 0.1 vol.% during growth of at least about 90% of the body of the single crystal silicon ingot. (Aspect 22) 19. The method of any one of embodiments 1-18, wherein the melt height level varies by less than about + / - 0.5 millimeters during growth of at least about 90% of the body of the single crystal silicon ingot. (Aspect 23) 23. The method of any one of aspects 1 to 22, wherein the body of the single crystal silicon ingot comprises full silicon across at least about 70% of the length of the body of the single crystal silicon ingot. (Aspect 24) 23. The method of any one of aspects 1 to 22, wherein the body of the single crystal silicon ingot comprises full silicon across at least about 80% of the length of the body of the single crystal silicon ingot. (Aspect 25) 23. The method of any one of aspects 1 to 22, wherein the body of the single crystal silicon ingot comprises full silicon across at least about 90% of the length of the body of the single crystal silicon ingot.

Claims

1. A method for producing a single crystal silicon ingot by a continuous Czochralski method, comprising: adding an initial charge of polycrystalline silicon to a crucible; heating a crucible containing an initial charge of polycrystalline silicon to form a silicon melt in the crucible, wherein the silicon melt includes an initial volume of molten silicon and has an initial melt height level; contacting a silicon seed crystal with a silicon melt; pulling the silicon seed crystal to grow a neck, wherein the silicon seed crystal is pulled at a neck pull rate during the growth of the neck; pulling the silicon seed crystal to grow an outwardly extending seed cone adjacent the neck, wherein the silicon seed crystal is pulled at a seed cone pull-up rate during growth of the outwardly extending seed cone; and pulling the silicon seed crystal to grow a body of the single crystal silicon ingot adjacent an outwardly extending seed cone, wherein the silicon melt comprises a volume of molten silicon and a melt height level during growth of the body of the single crystal silicon ingot; Including, The single crystal silicon ingot body is grown at an initial variable body pull rate and a constant body pull rate, wherein the single crystal silicon ingot body is grown at the initial variable body pull rate for less than about 20% of the single crystal silicon ingot body length and at the constant body pull rate for growth of at least about 30% of the single crystal silicon ingot body length; and The method further comprises continuously feeding polycrystalline silicon into the crucible, thereby replenishing the volume of molten silicon and melt height level in the crucible during growth of the main body of the single crystal silicon ingot.

2. The method of claim 1 , wherein a magnetic field is applied to the silicon melt during growth of the main body of the single crystal silicon ingot.

3. The method of claim 2 , wherein a horizontal magnetic field is applied to the silicon melt during growth of the main body of the single crystal silicon ingot.

4. The method of claim 2 , wherein a tip magnetic field is applied to the silicon melt during growth of the main body of the single crystal silicon ingot.

5. The method of claim 2 , wherein the applied magnetic field maintains a substantially constant melt / solid interface profile during at least about 70% of the growth of the body of the single crystal silicon ingot.

6. The method of claim 2 , wherein the applied magnetic field maintains a substantially constant melt / solid interface profile during about 70% to about 90% of the growth of the body of the single crystal silicon ingot.

7. The method of any one of claims 1 to 6, wherein the body of the single crystal silicon ingot is at least about 1000 millimeters long, at least 1400 millimeters long, or at least 1500 millimeters long.

8. The method of any one of claims 1 to 6, wherein the body of the single crystal silicon ingot is at least 2000 millimeters long, at least 2200 millimeters long, at least about 3000 millimeters long, or at least about 4000 millimeters long.

9. The method of any one of claims 1 to 8, wherein the diameter of the body of the single crystal silicon ingot is at least about 150 millimeters, or at least about 200 millimeters.

10. The method of any one of claims 1 to 8, wherein the diameter of the body of the single crystal silicon ingot is at least about 300 millimeters, or at least about 450 millimeters.

11. The method of any one of claims 1 to 10, wherein the constant body pull-up rate is between about 0.4 mm / min and about 0.8 mm / min, between about 0.4 mm / min and about 0.7 mm / min, or between about 0.4 mm / min and about 0.65 mm / min.

12. The method of any one of claims 1 to 11, wherein the single crystal silicon ingot body is grown at an initial variable body pull rate for about 5% to about 20% of the single crystal silicon ingot body length.

13. The method of any one of claims 1 to 12, wherein the body of the single crystal silicon ingot is grown at a constant body pull rate during growth of at least about 50% of the length of the body of the single crystal silicon ingot.

14. The method of any one of claims 1 to 12, wherein the body of the single crystal silicon ingot is grown at a constant body pull rate during growth of at least about 70% of the length of the body of the single crystal silicon ingot.

15. The method of any one of claims 1 to 12, wherein the body of the single crystal silicon ingot is grown at a constant body pull rate during growth of at least about 80% of the length of the body of the single crystal silicon ingot.

16. The method of any one of claims 1 to 12, wherein the body of the single crystal silicon ingot is grown at a constant body pull rate during growth of at least about 90% of the length of the body of the single crystal silicon ingot.

17. The method of any one of claims 1 to 16, wherein the body pull rate is a constant critical pull rate sufficient to avoid agglomerated point defects over at least 70% of the body length of the single crystal silicon ingot.

18. The method of any one of claims 1 to 16, wherein the body pull rate is a constant critical pull rate sufficient to avoid agglomerated point defects over at least 90% of the body length of the single crystal silicon ingot.

19. The method of any one of claims 1 to 18, wherein the volume of molten silicon changes by no more than about 1.0 vol% during growth of at least about 90% of the body of the single crystal silicon ingot.

20. The method of any one of claims 1 to 18, wherein the volume of molten silicon changes by no more than about 0.5% by volume during growth of at least about 90% of the body of the single crystal silicon ingot.

21. The method of any one of claims 1 to 18, wherein the volume of molten silicon changes by no more than about 0.1% by volume during growth of at least about 90% of the body of the single crystal silicon ingot.

22. The method of any one of claims 1 to 18, wherein the melt height level varies by less than about + / - 0.5 millimeters during growth of at least about 90% of the body of the single crystal silicon ingot.

23. The method of any one of claims 1 to 22, wherein the body of the single crystal silicon ingot comprises full silicon across at least about 70% of the length of the body of the single crystal silicon ingot.

24. The method of any one of claims 1 to 22, wherein the body of the single crystal silicon ingot comprises full silicon across at least about 80% of the length of the body of the single crystal silicon ingot.

25. The method of any one of claims 1 to 22, wherein the body of the single crystal silicon ingot comprises full silicon across at least about 90% of the length of the body of the single crystal silicon ingot.

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