Single crystal growth susceptor assembly with sacrificial ring

Abstract

A susceptor assembly for supporting a crucible during a crystal growth process includes a susceptor base, a tubular sidewall connected to the susceptor base, and a removable sacrificial ring disposed between the susceptor base and the sidewall. The susceptor base and sidewall are each formed of a carbon-containing material. The susceptor base has an annular wall and a shoulder extending radially outward from the outer surface of the annular wall. The sidewall has a first end that receives the annular wall and connects the sidewall to the susceptor base. The sacrificial ring has a first surface facing the outer surface of the annular wall, a second surface facing the inner surface of the sidewall, and a ledge extending outward from the second surface to engage the first end of the sidewall.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority to U.S. Non-Provisional Patent Application No. 17 / 939,192, filed September 7, 2022, the entire disclosure of which is incorporated herein by reference. [Technical Field]

[0002] The present invention relates generally to a susceptor assembly for supporting a crucible during a single crystal growth process, and more particularly to a single crystal growth susceptor assembly with a removable sacrifice ring. [Background technology]

[0003] Single crystal silicon, the starting material for most manufacturing processes for many electronic components, such as semiconductor devices and solar cells, is typically produced by the batch Czochralski (CZ) or continuous Czochralski (CCZ) processes, in which a polycrystalline feedstock, such as polycrystalline silicon ("polysilicon") in the form of a solid feedstock, is loaded into a quartz crucible and melted, and a single seed crystal is brought into contact with the molten silicon or melt and slowly extracted to grow a single crystal silicon ingot.

[0004] In these methods, the quartz crucible is dimensionally unstable at the high temperatures required to melt the solid feedstock. To prevent warping and deformation of the crucible during the crystal growth process, the crucible is supported by a susceptor assembly suitably formed of a carbon-containing material, such as graphite or carbon fiber, that is dimensionally stable at the temperatures required to melt the silicon feedstock. Some methods use so-called "hybrid" susceptor assemblies that include a susceptor base and a cylindrical sidewall removably connected to the susceptor base, each of which is formed of a carbon-containing material. Together, the susceptor base and sidewall form an interior space that receives the crucible.

[0005] During the crystal growth process, silicon oxide (SiO X Silicon-containing gases, such as SiO2 and SiO2 species, are vaporized. The silicon-containing gases may come into contact with carbon-containing materials in the susceptor assembly. The carbon-containing materials and silicon-containing gases may react with each other to produce gaseous carbon oxide and silicon products, as well as silicon carbide (SiC) deposits on the susceptor assembly. In multi-component susceptors, SiC deposits can build up along the mating surfaces of susceptor components. The accumulated SiC deposits can adversely affect the compatibility of the components and reduce the structural integrity of the susceptor.

[0006] For example, in methods where hybrid susceptor assemblies are used, SiC precipitates can form and accumulate along the ledge of the susceptor base, which forms the contact interface with the sidewall. For example, during continuous crystal growth processes, SiC continues to accumulate on the base ledge, adversely affecting the connection between the susceptor base and the sidewall along the contact interface. SiC deposits have a hardness close to that of diamond, and removing them from the base ledge is costly and time-consuming, increasing downtime and associated costs. Consequently, susceptor bases are frequently replaced due to the accumulation of SiC deposits along the ledge, long before they reach the end of their operational life, increasing material costs.

[0007] Furthermore, accumulated SiC deposits can bond the susceptor base and sidewalls together with sufficient strength that separating the susceptor base and sidewall can damage one or both components. Therefore, if the sidewall is damaged during operation, it is not possible to salvage the intact susceptor base that is bonded to the damaged sidewall. Similarly, if the susceptor base is damaged during operation, it is not possible to salvage the intact sidewall that is bonded to the damaged base.

[0008] There is a need for a susceptor assembly that solves the above-mentioned problems related to the buildup of SiC deposits along the contact interface between the susceptor base and the sidewalls and / or adhesion between the susceptor base and the sidewalls as a result of the buildup of SiC deposits, thereby extending the useful life of the susceptor base and sidewalls of the susceptor assembly and reducing material costs associated with premature disposal of susceptor assembly components.

[0009] This section is intended to introduce the reader to 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 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. Moreover, this section is not intended to describe the scope of the various aspects of the disclosure, and is not intended to limit the scope of the disclosure. Overview

[0010] In one embodiment, a susceptor assembly for supporting a crucible during a crystal growth process includes a susceptor base, a tubular sidewall connected to the susceptor base, and a removable sacrificial ring disposed between the susceptor base and the sidewall. The susceptor base and sidewall are each formed of a carbon-containing material. The susceptor base has a concave surface extending radially inward from its upper end and an annular wall extending from its upper end to a shoulder. The shoulder extends radially outward from the outer surface of the annular wall opposite the concave surface. The sidewall has a first end that receives the annular wall and connects the sidewall to the susceptor base. The inner surface of the sidewall and the concave surface of the susceptor base define an interior of the susceptor assembly sized and shaped to accommodate the crucible. The sacrificial ring has a first surface facing the outer surface of the annular wall, a second surface facing the inner surface of the sidewall, and a ledge extending outward from the second surface to engage the first end of the sidewall.

[0011] In another aspect, a method for assembling a susceptor for supporting a crucible during a crystal growth process includes providing a susceptor base, installing a sacrificial ring on the susceptor base, and connecting a tubular sidewall to the susceptor base so that the sacrificial ring is interposed between the susceptor base and the sidewall. The susceptor base and the sidewall are each formed of a carbon-containing material. The susceptor base has a concave surface extending radially inward from an upper end and an annular wall extending from the upper end to a shoulder. The shoulder extends radially outward from an outer surface of the annular wall opposite the concave surface. The sacrificial ring has a first surface surrounding the outer surface of the annular wall, a second surface opposite the first surface, a ledge extending outward from the second surface, and a third surface opposite the ledge and overlapping the shoulder of the susceptor base. The sidewall is connected to the susceptor base by inserting the annular wall into the first end of the sidewall such that the first end engages with the shelf portion of the sacrificial ring and the sacrificial ring is interposed between the sidewall and each of the outer surface and shoulder portion of the annular wall.

[0012] In yet another aspect, a method for producing a single-crystal silicon ingot from a silicon melt includes providing a susceptor assembly including a susceptor base, a tubular sidewall connected to the susceptor base, and a removable sacrificial ring disposed between the susceptor base and the sidewall. The susceptor base and the sidewall are each formed of a carbon-containing material. The method includes placing a crucible inside the susceptor assembly defined by the susceptor base and the sidewall, adding polycrystalline silicon to the crucible, heating the polycrystalline silicon to form a silicon melt in the crucible, and withdrawing a single-crystal silicon ingot from the melt. As the single-crystal silicon ingot is pulled from the melt, silicon carbide (SiC) deposits accumulate on the sacrificial ring. The method also includes removing the sacrificial ring with the accumulated SiC deposits from the susceptor base after the single-crystal silicon ingot is pulled from the melt. [Brief explanation of the drawings]

[0013] [Figure 1]FIG. 1 is a schematic cross-sectional view of a pulling apparatus for forming a single crystal silicon ingot. [Figure 2] FIG. 2 is a perspective view of a susceptor assembly used in the pulling apparatus shown in FIG. [Figure 3] FIG. 3 is an exploded view of the susceptor assembly shown in FIG. [Figure 4] FIG. 4 is a partial cross-sectional view of the susceptor assembly shown in FIGS. [Figure 5] FIG. 5 is an enlarged view of a portion of the cross section of the susceptor assembly shown in FIG. [Figure 6] FIG. 6 is a top view of an arcuate segment forming the sacrificial ring used in the susceptor assembly shown in FIGS. [Figure 7] FIG. 7 is a cross-sectional view of the sacrificial ring taken along line AA shown in FIG. [Figure 8] FIG. 8 is a cross-sectional view of the sacrificial ring taken along line BB shown in FIG. [Figure 9] FIG. 9 shows a method for assembling the susceptor assembly shown in FIGS. [Figure 10] FIG. 10 illustrates a method for producing a single crystal silicon ingot from a silicon melt contained in a crucible supported by the susceptor assembly shown in FIGS.

[0014] Corresponding reference characters indicate corresponding parts throughout the drawings.

[0015] Referring to FIG. 1 , an ingot pulling apparatus or ingot puller is shown schematically and generally designated 100. The ingot puller 100 is used to produce monocrystalline (i.e., single crystal) ingots of semiconductor or solar-grade material, such as monocrystalline silicon ingots. In some embodiments, the ingots are grown by the so-called Czochralski (CZ) method, in which the ingots are pulled from a silicon melt 102 held in a crucible 104 of the crystal puller 100. In some embodiments, the ingots are grown by a batch CZ process, in which the crucible 104 is filled with an amount of polycrystalline silicon sufficient to grow one ingot, such that the crucible 104 is substantially depleted of silicon melt 102 after the growth of one ingot. In other embodiments, the ingots are grown by a continuous CZ (CCZ) process, in which polycrystalline silicon is continuously or periodically added to the crucible 104 to replenish the silicon melt 102 during the growth process. The CCZ process facilitates the growth of multiple ingots drawn from a single melt 102. Embodiments of the present disclosure are not limited to any particular crystal growth process.

[0016] The ingot puller 100 includes a housing 106 that defines a crystal growth chamber 108 and a pulling chamber 110 that has smaller lateral dimensions than the growth chamber 108. The growth chamber 108 includes a generally dome-shaped top wall 112 that transitions from the growth chamber 108 to the narrowed pulling chamber 110. The ingot puller 100 includes an inlet port 114 and an outlet port 116 that can be used to introduce process gases into and remove process gases from the ingot puller 100 during crystal growth.

[0017] A crucible 104 within the ingot puller 100 contains a silicon melt 102 from which a silicon ingot is pulled. The crucible 104 is suitably made of quartz or fused silica, both of which have high melting points and thermal stability and generally do not react with the molten silicon in the melt 102. The crucible 104 may contain other materials in addition to quartz; for example, the quartz crucible 104 may be a composite material including silica, silicon nitride, or silicon carbide.

[0018] The silicon melt 102 is obtained by melting polycrystalline silicon charged in a crucible 104. In a continuous system, a feed system (not shown) is used to supply solid raw material to the crucible 104 and / or the melt 102. The crucible 104 is disposed within and supported by a susceptor 118, which is supported by a rotating shaft 120. The susceptor 118 and rotating shaft 120 facilitate rotation of the crucible 104 about a central longitudinal axis X of the ingot puller 100. During operation, the temperatures required to melt the silicon charge and / or maintain the melt 102 may also soften the quartz crucible 104. The susceptor 118 is suitably made from graphite or other graphene- or carbon-containing materials having high thermal stability, providing a rigid outer structure to support the softened crucible 104.

[0019] A heating system 122 (e.g., one or more electrical resistance heaters or a radio frequency heating system) surrounds the susceptor 118 and the crucible 104 and supplies heat by conduction through the susceptor 118 and the crucible 104 to melt the silicon charge to form the melt 102 and / or maintain the melt 102 in a molten state. The heater 122 may extend beneath the susceptor 118 and the crucible 104. The heating system 122 is controlled by a control system (not shown) to precisely control the temperature of the melt 102 throughout the pulling process. For example, a controller may control the current supplied to the heating system 122 to control the amount of thermal energy supplied by the heating system 122. The controller may control the heating system 122 to maintain the temperature of the melt 102 at or above the melting point of silicon (e.g., approximately 1412°C). For example, the melt 102 may be heated to a temperature of at least about 1425° C., at least about 1450° C., or at least about 1500° C. Insulation (not shown) surrounding the heating system 122 may reduce the amount of heat lost through the housing 106. The ingot puller 100 may also include a heat shield assembly (not shown) above the surface of the melt 102 to protect the ingot from the heat of the crucible 104 and increase the axial temperature gradient at the solid-melt interface.

[0020] The pulling mechanism is attached to a pull wire 124 extending from the pulling mechanism, and can raise, rotate, and lower the pull wire 124. Depending on the type of puller, the ingot puller 100 may have a pull shaft instead of a wire. The pull wire 124 terminates in a pull assembly 126 that includes a seed chuck 128 that holds a seed crystal 130 used to grow a silicon ingot. During ingot growth, the pulling mechanism lowers the seed crystal 130 until it contacts the surface of the silicon melt 102. Once the seed crystal 130 begins to melt, the pulling mechanism slowly pulls the seed crystal through the growth chamber 108 and the pulling chamber 110 to grow a single crystal ingot. A control system controls the speed at which the pulling mechanism rotates the seed crystal 130 and the speed at which the pulling mechanism pulls the seed crystal (i.e., the pull rate v). As the seed crystal 130 is slowly pulled from the melt 102, silicon atoms in the melt 102 align along and adhere to the seed crystal 130 to form an ingot.

[0021] A process gas (e.g., argon) is introduced into the growth chamber 108 and puller 110 through an inlet port 114 and exhausted through an outlet port 116. The process gas creates an atmosphere within the housing, and the melt and the atmosphere form a melt-gas interface. The outlet port 116 is in fluid communication with the exhaust system (not shown) of the ingot puller 100.

[0022] 2-5, an exemplary susceptor assembly is generally designated 200. The susceptor assembly 200 is suitable for use as a susceptor 118 for supporting a crucible 104 in an ingot puller 100 (shown in FIG. 1). The susceptor assembly 200 includes a susceptor base 202, a tubular sidewall 204 connected to the susceptor base 202, and a sacrificial ring 206 disposed between the base 202 and the sidewall 204. Each of the base 202, the sidewall 204, and the sacrificial ring 206 is suitably made of a carbon-containing material having high thermal stability. The susceptor base 202 and the sacrificial ring 206 may be formed, for example, from graphite. The tubular sidewall 204 is suitably formed from a carbon fiber reinforced polymer (also referred to herein as "carbon fiber" or "carbon fiber composite"). Alternatively, the tubular sidewall 204 may be formed from graphite. 3, the tubular sidewall 204 is a unitary structure. In other examples, the tubular sidewall 204 may be formed from two or more connected segments (e.g., two or more connected carbon fiber segments or two or more connected graphite segments).

[0023] The susceptor base 202 has a concave surface 208 that extends radially inward from an upper edge 210 and defines a recess 214 within the susceptor base 202. An annular wall 212 surrounds the recess 214 and extends downward from the upper edge 210 to a shoulder 216. The recess 214 is generally shaped to complement the shape of the bottom of the crucible 104 (shown in FIG. 1 ) that is received by the susceptor assembly 200. In an exemplary embodiment, the recess 214 is hemispherical and is defined by the shape of the annular wall 212 and the concave surface 208. The recess 214 can have other shapes depending on the application and configuration of the crucible 104. For example, the recess 214 may be square or rectangular in shape. In these examples, the surface 208 may be recessed from the square or rectangular upper edge 210 and be a flat surface 208 surrounded by the square or rectangular wall 212.

[0024] The shoulder 216 extends radially outward from the outer surface 218 of the annular wall 212. The shoulder 216 connects the annular wall 212 to a peripheral edge 220 of the susceptor base 202. Generally, the peripheral edge 220 defines the outermost periphery of the susceptor base 202, and the shoulder 216 has a radial length L between the peripheral edge 220 and the outer surface 218. The radial length L of the shoulder 216 is a distance suitable for supporting components of the susceptor assembly 200 stacked on the susceptor base 202 (e.g., the sidewall 204 and the sacrificial ring 206). In the exemplary embodiment, the shoulder 216 defines a flat surface perpendicular to the outer surface 218 of the annular wall 212, such that the shoulder 216 and the outer surface define an L-shape. In other examples, the outer surface 218 and / or the shoulder 216 may have another orientation. Additionally, the transition between the outer surface 218 and the shoulder 216 may be sharp or angular, or may be rounded to provide a smooth transition between adjacent surfaces.

[0025] The bottom 222 of the susceptor base 202 extends downward from the periphery 220. The bottom 222 is coupled to the periphery 220 by a bottom surface 224. The bottom 222 provides a bulk region within the susceptor base 202 below the concave surface 208. The bulk region allows features (not shown) to be formed in the bottom 222. The features formed in the bottom 222 facilitate securing the susceptor base 202 to the rotating shaft 120 of the ingot puller 100 (shown in FIG. 1 ). The bottom surface 224 includes one or more notches 290. The notches 290 allow the bottom surface 224 to form a “drip edge” from which molten silicon dripping from the periphery 220 during operation falls before reaching the bottom 222. The drip edge formed by bottom surface 224 prevents molten silicon from flowing down bottom 222 onto rotating shaft 120 and potentially damaging the seals on these components.

[0026] The tubular sidewall 204 is connected to the susceptor base 202 at a first end 226 and extends to a second end 228. In this example, the sidewall 204 is cylindrically shaped to complement the shape of the side of the crucible 104 (shown in FIG. 1 ) and has a circular cross-section that complements the shape of the annular wall 212. The sidewall 204 can have other shapes (e.g., a rectangular shape with a square cross-section) depending on the application and configuration of the crucible 104. The tubular sidewall 204 and the concave surface 208 of the base 202 together define an interior 238 of the susceptor assembly 200 sized and shaped to accommodate the crucible 104. The sidewall 204 includes an inner surface 230 facing the interior 238 and an opposing outer surface 232. The inner surface 230 and the outer surface 232 each extend between the first end 226 and the second end 228. The inner surface 230 and the outer surface 232 are joined by a first edge 234 at the first end 226 and a second edge 236 at the second end 228 .

[0027] The sidewall 204 is connected to the susceptor base 202 by receiving the annular wall 212 at a first end 226. When the sidewall 204 is connected to the base 202, an inner surface 230 of the sidewall 204 faces an outer surface 218 of the annular wall 212, and a first edge 234 is supported by the shoulder 216. When the sidewall 204 is connected to the base 202, the outer surface 232 is approximately flush with the periphery 220. A thickness T1 of the sidewall 204 measured between the inner surface 230 and the outer surface 232 is appropriately smaller than a radial length L of the shoulder 216 to ensure space for a sacrificial ring 206 interposed between the base 202 and the sidewall 204, as described below.

[0028] The carbon fiber material that can be used to form the sidewall 204 allows for a reduced thickness T1 of the sidewall 204 compared to the thickness of sidewalls formed from other carbon-containing materials (e.g., graphite). Specifically, carbon fiber material has high thermal stability, high thermal conductivity and low thermal expansion behavior resulting in high thermal shock resistance, and high toughness, strength, and rigidity in high-temperature applications. By reducing the thickness T1 of the sidewall 204, the volume of the interior 238 of the susceptor assembly 200 can be increased, thereby increasing the size of the crucible 104 that the susceptor assembly 200 can support and the volume of the melt 102 contained therein.

[0029] The sacrifice ring 206 has an inner surface 240, an opposing outer surface 242, and a ledge 244 extending radially outward from the outer surface 242. The ledge 244 joins the outer surface 242 to an outer edge 246. The sacrifice ring also includes a bottom surface 248 joining the outer edge 246 to the inner surface 240, and an upper edge 250 opposite the bottom surface 248. The upper edge 250 joins the inner surface 240 to the outer surface 242.

[0030] Sacrifice ring 206 may be a unitary, one-piece structure, or sacrifice ring 206 may be divided into two or more arcuate segments 206a. FIG. 6 shows a top view of an individual arcuate segment 206a used to form sacrifice ring 206. Each arcuate segment 206a includes the same elements and features as arcuate segment 206a shown in FIG. 6, forming the elements and features of sacrifice ring 206 (e.g., inner surface 240, outer surface 242, shelf 244, bottom surface 248, and top edge 250). Accordingly, sacrifice ring 206 and arcuate segments 206a are indicated and described with like reference characters, and descriptions of elements and features of sacrifice ring 206 equally apply to elements and features of arcuate segments 206a, unless expressly stated otherwise.

[0031] The sacrifice ring 206 in this embodiment includes six arcuate segments 206a. Each arcuate segment 206a is equally sized and has an arc dimension θ of 60 degrees, such that the segments 206a collectively form a 360-degree circumferential extent of the sacrifice ring 206. In other examples, the sacrifice ring 206 may include more or fewer arcuate segments 206a, such as 2, 3, 4, 5, 7, 8, 9, or 10 arcuate segments 206a. The arc dimension θ of the arcuate segments 206a varies depending on the number of arcuate segments 206a used, and the arcuate segments 206a may be equally sized or unequal in size. In examples where the arcuate segments 206a are equally sized, the arcuate dimension θ of each arcuate segment 206a may be 360 ​​degrees / n, where n is the number of arcuate segments 206a forming the sacrifice ring 206. For example, two equal-sized segments 206a each have an arc dimension θ of 180 degrees, three equal-sized segments each have an arc dimension θ of 120 degrees, and so on. In some examples, a small gap may be formed between adjacent arcuate segments 206a in a segmented sacrificial ring 206. In these examples, for equal-sized arcuate segments 206a, the arc dimension θ of each arcuate segment 206a is less than 360 degrees / n. Any one of the segments 206a can be attached to or detached from the susceptor base 202 independently of the other segments. Thus, references herein to attachment and detachment of the sacrificial ring 206 can refer to the independent attachment and detachment of one, more than one, and less than all, or all, of the segments 206a of the sacrificial ring 206. The sacrificial ring 206 can also be formed as a unitary, one-piece structure, in which case the arcuate segments 206a completely form the sacrificial ring 206.

[0032] Each arcuate segment 206a extends an arcuate length D between a first periphery 266 and a second periphery 268. The first periphery 266 of each arcuate segment 206a abuts the second periphery 268 of an adjacent arcuate segment 206a. The first and second peripheries 266 and 268 may form flat surfaces such that no interlocking is provided between adjacent arcuate segments 206a. The absence of interlocking features between adjacent arcuate segments 206a may facilitate installation and removal of the individual arcuate segments 206a. A segmented sacrificial ring 206 without interlocking features between adjacent segments 206a may be held in place when mounted on the susceptor base 202 by the force exerted by the sidewalls 204. Alternatively, the first and second peripheries 266 and 268 may include a connecting mechanism for connecting adjacent segments 206a to facilitate retaining the segmented sacrificial ring 206 in place of the susceptor base 202. In instances where a one-piece sacrificial ring 206 is used, no connecting mechanism is required because only one segment 206a forms the sacrificial ring 206.

[0033] Figure 7 shows a cross section of sacrificial ring 206 formed of arcuate segments 206a taken along line AA shown in Figure 6. Figure 8 shows a cross section of sacrificial ring 206 formed of arcuate segments 206a taken along line BB shown in Figure 6. The cross sections of sacrificial ring 206 shown in Figures 7 and 8 are not limited to segmented ring structures; a unitary sacrificial ring 206 or a sacrificial ring 206 segmented into any number of segments 206a may have the cross sections shown in Figures 7 and 8 and described below.

[0034] As shown in FIGS. 7 and 8 , the outer surface 242 extends from a first end 260 adjacent the upper edge 250 to a second end 262 adjacent the shelf 244, with the outer surface 242 having a height H1 measured between the first end 260 and the second end 262. The upper portion 252 of the sacrifice ring 206 extends between the shelf 244 and the upper edge 250, with the upper portion 252 having a height H1 of the outer surface 242. The inner surface 240 has a first end 254 adjacent the upper edge 250 and extends downward from the first end 254, past the upper portion 252, to a second end 256 adjacent the bottom surface 248. Thus, the height H2 of the inner surface 240 between the first end 254 and the second end 256 is greater than the height H1 of the outer surface 242 and the upper portion 252. The height H2 may be substantially equal to the sum of the height H1 and the height H3 of the outer edge 246. Height H3 is measured as the distance that outer edge 246 extends between a first end 258 adjacent bottom surface 248 of outer edge 246 and a second end 264 of outer edge 246 adjacent shelf 244.

[0035] The thickness T2 of the bottom surface 248 is measured as the distance extending between the second end 256 of the inner surface 240 and the first end 258 of the outer edge 246. The upper edge 250 has a thickness T3 measured as the distance extending between the first end 254 of the inner surface 240 and the first end 260 of the outer surface 242. The shelf 244 has a thickness T4 measured as the distance the shelf 244 extends between the second end 264 of the outer edge 246 and the second end 262 of the outer surface 242. The thickness T2 of the bottom surface 248 is greater than each of the thickness T3 of the upper edge 250 and the thickness T4 of the shelf 244, and the thickness T2 may be substantially equal to the sum of the thicknesses T3 and T4.

[0036] 4 and 5 , when the sacrifice ring 206 is mounted on the base 202, the inner surface 240 faces the outer surface 218 of the annular wall 212, and the bottom surface 248 faces the shoulder 216. The height H2 of the inner surface 240 is substantially equal to the height of the outer surface 218 of the annular wall 212, and the inner surface 240 extends substantially across and around the outer surface 218. The thickness T2 of the bottom surface 248 is substantially equal to the radial length L of the shoulder 216, and the bottom surface 248 substantially crosses and covers the shoulder 316, and the outer edge 246 is substantially flush with the periphery 220 of the susceptor base 202.

[0037] When the sacrifice ring 206 is installed and the sidewall 204 is connected to the susceptor base 202, the first edge 234 of the sidewall 204 engages the ledge 244. The thickness T4 of the ledge 244 is appropriately sized to allow engagement between the ledge 244 and the first edge 234 of the sidewall 204. The upper portion 252 of the sacrifice ring 206 is received by the first end 226 of the sidewall 204 when the sidewall 204 is connected to the base 202, with the outer surface 242 facing the inner surface 230 of the sidewall 204. The thickness T4 of the ledge 244 is slightly greater than the thickness T1 of the sidewall 204, and a space (not shown) may be provided between the outer surface 242 and the inner surface 230. This space allows a strip 270 of flexible graphite material (e.g., GraFoil® flexible graphite material) to be placed between the outer surface 242 and the inner surface 230.

[0038] 4 and 5, when the susceptor assembly 200 is assembled, the sacrificial ring 206 forms a layer between the surfaces of the susceptor base 202 and the sidewall 204 that are exposed during operation of the ingot puller 100 along areas at risk of accumulating SiC deposits that could adversely affect the connection between the susceptor base 202 and the sidewall 204. In particular, the sacrificial ring 206 is interposed between the outer surface 218 and shoulder 216 of the susceptor base 202 and the inner surface 230 of the sidewall 204.

[0039] Preferably, the shape defined by shelf 244 and outer surface 242 may complement (or match) the shape defined by outer surface 218 of annular wall 212 and shoulder 216 of base 202. In an exemplary embodiment, shelf 244 is perpendicular to outer surface 242, such that shelf 244 and outer surface 242 define an L-shape. In other examples, outer surface 242 and / or shelf 244 may have alternative configurations or orientations to complement the shape defined by outer surface 218 and shoulder 216. Furthermore, the transition between outer surface 242 and shelf 244 may be sharp or angular, or may be rounded to provide a smooth transition between adjacent surfaces. By complementing the shape defined by the outer surface 218 of the annular wall 212 and the shoulder 216 of the base 202, the susceptor assembly 200 can be modified with a sacrificial ring 206 interposed between the susceptor base 202 and the sidewall 204 without significantly altering the design of the susceptor base 202 and the sidewall 204. For example, the susceptor base 202 and the sidewall 204 can be configured such that the susceptor assembly 200 can function with the first edge 234 of the sidewall 204 directly engaged with the shoulder 216 without the sacrificial ring 206 interposed therebetween, and the sacrificial ring 206 can be included without substantially altering the size, shape, dimensions, or other configuration of the susceptor base 202 and the sidewall 204.

[0040] 7 and 8, the inner surface 240 and / or the bottom surface 248 are designed to minimize contact between the sacrifice ring 206 and the susceptor base 202. The inner surface 240 includes a recess 272 having a concave surface 274, and the bottom surface 248 includes a recess 276 having a concave surface 278. When the sacrifice ring 206 is mounted on the susceptor base 202, the concave surface 274 of the inner surface 240 is spaced from the outer surface 218 of the annular wall 212, and the concave surface 278 of the bottom surface 248 is spaced from the shoulder 216. The inner surface 240 and the bottom surface 248 only partially contact the outer surface 218 and the shoulder 216 in areas where the recesses 272 and 276 are not formed. As shown in FIGS. 7 and 8, the recesses 272 and 276 can be formed along central portions of the respective surfaces 240 and 248. Thus, the inner surface 240 only contacts the outer surface 218 near the first end 254 and the second end 256 of the inner surface 240, and the bottom surface 248 only contacts the shoulder 216 near the second end 256 of the inner surface and the first end 258 of the outer edge 246. The recesses 272 and 276 may be formed along a majority of the respective surfaces 240 and 248 to minimize contact between the sacrifice ring 206 and the susceptor base 202. For example, the recesses 272 and 276 can extend along at least 20%, at least 30%, at least 40%, at least 50%, at least 60%, at least 70%, or at least 75% of the height H1 of the inner surface 240 and the thickness T2 of the bottom surface 248, respectively.

[0041] The sacrifice ring 206 also includes a protrusion 280 or series of protrusions 280 integrally formed on and extending outward from the outer surface 242, which helps minimize contact between the sacrifice ring 206 and the inner surface 230 of the sidewall 204 (or the flexible graphite material strip 270 disposed between the outer surface 242 and the inner surface 230). In embodiments including a series of protrusions 280 on the sacrifice ring 206, the protrusions 280 can be spaced apart from one another and circumferentially disposed along the outer surface 242. For example, FIGS. 7 and 8 show cross sections of the sacrifice ring 206 at a location where one of the series of protrusions 280 is formed ( FIG. 7 ) and at a portion where no protrusions 280 are formed ( FIG. 8 ). The protrusions 280 space the outer surface 242 from the inner wall 230 (or the flexible graphite material strip 270). As shown in FIG. 7 , the protrusions can be formed near the first end 260 of the outer surface 242.

[0042] 3 and 4, the susceptor assembly 200 also includes a ceiling ramp 282 and one or more flexible graphite material strips 270. The ceiling ramp 282 is disposed on and extends across the upper edge 210 of the susceptor base 202 and the upper edge 250 of the sacrificial ring 206, respectively. The ceiling ramp 282 is suitably formed of graphite. The ceiling ramp 282 includes a curved surface 284 that provides a smooth transition between the concave surface 208 of the susceptor base 202 and the inner surface 230 of the sidewall 204. The ceiling ramp 282 also includes a back surface 286 opposite the curved surface 284, which may be linear and substantially flush with the outer surface 242 of the sacrificial ring 206. The ramps 282 are provided to complete the shape of the interior 238 so that when the crucible 104 is received, the interior walls 230, the curved surface 284, and the concave surface 208 provide a complete and rigid support surface that contacts and supports the crucible 104 during operation of the ingot puller 100, during which the quartz crucible 104 may soften due to the temperatures required to melt the silicon charge and / or maintain the melt 102.

[0043] As shown in FIG. 3 , the ceiling lamp 282 is divided into six segments. In other examples, the ceiling lamp 282 may be divided into more or fewer segments, such as 2, 3, 4, 5, 7, 8, 9, or 10 segments. The flexible graphite material strip 270 forms a sacrificial layer between the quartz crucible 104 and the inner surface 230, helping to prevent and / or minimize direct contact between the silica generated from the quartz crucible and the carbon within the sidewall 204, which could otherwise result in undesirable deposits and unwanted gaseous by-products during operation of the ingot puller 100.

[0044] During the operation of the ingot puller 100 (see FIG. 1), silicon oxide (SiO XA silicon-containing gas, such as a SiO 2 species, evaporates from the melt 102 and contacts the carbon-containing material of the susceptor assembly 200 used to support the crucible 104. The region of the susceptor assembly 200 where the susceptor base 202, the sacrificial ring 206, and the first end 226 of the sidewall 204 meet is located near the heating system 122. This region is therefore exposed to a relatively higher temperature than other regions of the susceptor assembly 200. The higher temperature increases the reaction rate between the contacting carbon-containing material and the silicon-containing gas. This reaction produces gaseous carbon oxide and silicon products and silicon carbide (SiC) deposits. The SiC deposits accumulate along the sacrificial ring 206, which is interposed between the base 202 and the sidewall 204. When SiC deposits accumulate and prevent the sacrificial ring 206 from properly connecting with the base 202 and / or sidewall 204, the sacrificial ring 206 can be removed and replaced, salvaging the susceptor base 202 and sidewall 204 for the next operation. The sacrificial ring 206 can also be segmented, allowing a segment with more SiC deposits to be removed and replaced without replacing the entire sacrificial ring 206. Additionally, the sacrificial ring 206 includes a recess 272 on the inner surface 240 and a recess 276 on the bottom surface 248 that minimize contact between the sacrificial ring 206 and the susceptor base 202, and a protrusion 280 or series of protrusions 280 that minimize contact between the sacrificial ring 206 and the inner surface 230 of the sidewall 204 (or the flexible graphite material strip 270). Minimizing contact between the sacrificial ring 206 and adjacent carbon-containing components reduces bonding between the sacrificial ring 206 and these components due to accumulated SiC deposits, allowing the sacrificial ring 206 to be easily removed and replaced.

[0045] Referring to Figure 9, an example method 300 for assembling the susceptor assembly 200 (shown in Figures 2-5) is shown. The method includes step 302 of providing a susceptor base 202. The susceptor base 202 includes a concave surface 208 extending radially inward from an upper edge 210. The susceptor base 202 also includes an annular wall 212 extending from the upper edge 210 to a shoulder 216. The shoulder 216 extends radially outward from an outer surface 218 of the annular wall 212 opposite the concave surface 208. The susceptor base 202 is formed from a carbon-containing material, such as graphite.

[0046] The method 300 also includes a step 304 of installing the sacrifice ring 206 on the susceptor base 202. The sacrifice ring 206 can be installed (304) on the susceptor base 202 by mounting the sacrifice ring 206 around the annular wall 212 and supporting the sacrifice ring 206 on the shoulder 216. Additionally, the sacrifice ring 206 can be formed from two or more segments 206a, and the segmented sacrifice ring 206 is installed (304) on the base 202 by placing each segment 206a on a shoulder and forming the sacrifice ring 206 around the annular wall 212. When installed (304), the sacrifice ring 206 has a first surface 240 that surrounds the outer surface 218 of the annular wall 212, a second surface 242 opposite the first surface 240, a ledge 244 that extends outward from the second surface 242, and a third surface 248 opposite the ledge 244 that overlies the shoulder 216 of the susceptor base 202. The sacrifice ring 206 may be formed from a carbon-containing material, such as, for example, graphite.

[0047] The method 300 also includes connecting 306 the tubular sidewall 204 to the susceptor base 202 by inserting the annular wall 212 into the first end 226 of the sidewall 204. The sidewall 204 has a first edge 234 at the first end 226 that engages with a ledge 244 of the sacrificial ring 206, thereby interposing the sacrificial ring 206 between the sidewall 204 and the outer surface 218 and shoulder 216 of the annular wall 212, respectively. The sidewall 204 is formed from a carbon-containing material, such as, for example, carbon fiber.

[0048] The method 300 may also include the step 308 of placing the crucible 104 in an interior 238 of the susceptor assembly 200. The interior 238 is defined by the inner surface 230 of the sidewall 204 and the concave surface 208 of the susceptor base 202. The susceptor assembly 200 is installed within the housing 106 of the ingot puller 100 and supported on the rotating shaft 120 prior to placing 308 the crucible within the interior 238.

[0049] The method 300 may also include disassembling the susceptor assembly 200. For example, the method 300 may include removing 312 the sidewall 204 from the susceptor base 202. If placing 308 the crucible 104 within the interior 238 is performed, the method 300 may include removing 312 the crucible 104 from the interior 238 before removing 312 the sidewall 204 from the susceptor base 202. After the sidewall 204 is removed (312), the method 300 may include removing 314 the sacrificial ring 206 from the susceptor base 202.

[0050] 10, an example method 400 for producing a single crystal silicon ingot from a silicon melt 102 contained within a crucible 104 supported by a susceptor assembly 200 (shown in FIGS. 2-5) is shown. The method 400 can be performed using the ingot puller 100 (shown in FIG. 1), in which case the susceptor assembly 200 is used as the susceptor 118.

[0051] The method 400 includes step 402 of providing a susceptor assembly 200. The susceptor assembly 200 includes a susceptor base 202, a tubular sidewall 204 connected to the susceptor base 202, and a removable sacrificial ring 206 disposed between the sidewall 204 and the susceptor base 202. The susceptor assembly 200 can be assembled according to method 300 (shown in FIG. 9 ). The susceptor base 202 and the sidewall 204 are each formed from a carbon-containing material. For example, the susceptor base 202 may be formed from graphite, and the sidewall 204 may be formed from carbon fiber. The sacrificial ring 206 may be formed from a carbon-containing material, such as graphite.

[0052] The method 400 also includes placing (404) a quartz crucible 104 in the interior 238 of the susceptor assembly 202 defined by the susceptor base 202 and the sidewall 204, adding (406) polycrystalline silicon to the crucible 104, heating (408) the polycrystalline silicon to form a silicon melt 102 in the crucible 104, and withdrawing (410) a single crystal silicon ingot from the melt 102. While withdrawing (410) the single crystal silicon ingot from the melt 102, silicon carbide (SiC) deposits accumulate on the sacrificial ring 206. After withdrawing (410) the single crystal silicon ingot from the melt 102, the sacrificial ring 206 with the accumulated SiC deposits is removed (412) from the susceptor base 202. The sacrificial ring 206 can be divided into two or more segments 206a, and the step of removing (412) the segmented sacrificial ring 206 having the accumulated SiC deposits from the susceptor base 202 can include independently removing one or more segments 206a. After producing the plurality of single crystal silicon ingots, the sacrificial ring 206 having the accumulated SiC deposits can be removed (412) from the susceptor base. The method 400 can further include, after removing the sacrificial ring 206 having the accumulated SiC deposits from the susceptor base 202, installing a second sacrificial ring 206 on the susceptor base 202.

[0053] An advantage of the above example is that providing a removable sacrificial ring facilitates extending the operational life of susceptor assembly components. Hybrid susceptor assemblies, each of which includes a susceptor base and sidewalls formed from a carbon-containing material, can accumulate silicon carbide (SiC) deposits along the base-sidewall contact interface over time. Removing the SiC deposits, which have a hardness approaching that of diamond, is costly and time-consuming, resulting in the susceptor base being frequently discarded and replaced with a new one. The accumulated SiC deposits can cause adhesion between the susceptor base and sidewall, and if either the base or sidewall is damaged, the bonded structure must be discarded. In either case, material costs increase. The present disclosure provides a sacrificial ring that can accumulate SiC deposits and is easily removable and replaceable. The use of the sacrificial ring can extend the operational life of the sidewall and susceptor base. Additionally, the sacrifice ring can be configured to be retrofitted to a susceptor assembly without requiring significant design changes to the susceptor base and sidewalls.

[0054] 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 intended to cover variations that may exist at the upper and / or lower limits of the range of the property or characteristic, such as, for example, variations resulting from rounding, measurement methods, or other statistical variations.

[0055] When introducing elements of the present disclosure or embodiments thereof, the articles "a," "an," "the," and "said" are intended to mean that there are one or more elements. The terms "comprise," "include," "contain," and "have" are inclusive and mean that there may be additional elements other than the listed elements. The use of specific directional terms (such as "top," "bottom," "side," etc.) is for convenience of description and does not require a particular orientation of the items being described.

[0056] Because the above-described structures and methods are susceptible to various modifications without departing from the scope of the invention, all matter contained in the above description and shown in the accompanying drawings is intended to be interpreted as illustrative and not in a limiting sense.

Claims

1. 1. A susceptor assembly for supporting a crucible during a crystal growth process, comprising: a susceptor base formed from a carbon-containing material, the susceptor base having a concave surface extending radially inward from an upper edge and an annular wall extending from the upper edge to a shoulder, the shoulder extending radially outward from an outer surface of the annular wall opposite the concave surface; a tubular sidewall formed from a carbon-containing material, the tubular sidewall connected at a first end to the susceptor base, the first end of the sidewall receiving the annular wall to connect the sidewall to the susceptor base, the inner surface of the sidewall and the concave surface of the susceptor base defining an interior of the susceptor assembly sized and shaped to accommodate the crucible; and a removable sacrificial ring disposed between the side wall and each of the outer surface of the annular wall and the shoulder, the sacrificial ring having a first surface facing the outer surface of the annular wall, a second surface facing the inner surface of the side wall, and a ledge extending outward from the second surface to engage the first end of the side wall. Susceptor assembly.

2. The sacrifice ring is divided into two or more segments. The susceptor assembly of claim 1 .

3. the sacrifice ring is divided into six equally sized segments; The susceptor assembly of claim 2 .

4. the sacrificial ring is formed from a carbon-containing material; The susceptor assembly of claim 1 .

5. the second surface and the shelf of the sacrificial ring define a shape of the sacrificial ring that complements a shape defined by the outer surface and the shoulder of the annular wall; The susceptor assembly of claim 1 .

6. the second surface of the sacrificial ring and the shelf define an L-shape; The susceptor assembly of claim 5 .

7. the first surface of the sacrificial ring partially contacts the outer surface of the annular wall, and the first surface is recessed to define a recessed surface spaced a fixed distance from the outer surface of the annular wall. The susceptor assembly of claim 1 .

8. the first surface of the sacrificial ring contacts the outer surface of the annular wall near an opposite end of the first surface, and the recess is formed in a central portion of the first surface. The susceptor assembly of claim 7 .

9. the sacrifice ring has at least one protrusion extending outwardly from the second surface, the at least one protrusion contacting the inner surface of the sidewall, and the second surface being spaced a distance from the inner surface; The susceptor assembly of claim 1 .

10. the at least one projection comprises a series of spaced apart projections disposed circumferentially along the second surface of the sacrificial ring; The susceptor assembly of claim 9 .

11. the sacrifice ring has a third surface facing the shoulder of the susceptor base, the third surface being in partial contact with the shoulder, and a recess formed in the third surface to define a recessed surface spaced a predetermined distance from the shoulder; The susceptor assembly of claim 1 .

12. the third surface of the sacrificial ring contacts the shoulder near an opposite end of the third surface, and the recess is formed in a central portion of the third surface; The susceptor assembly of claim 11 .

13. 1. A method of assembling a susceptor for supporting a crucible during a crystal growth process, comprising: providing a susceptor base formed from a carbon-containing material, the susceptor base having a concave surface extending radially inward from an upper edge and an annular wall extending from the upper edge to a shoulder, the shoulder extending radially outward from an outer surface of the annular wall opposite the concave surface; placing a sacrificial ring on the susceptor base, the sacrificial ring having a first surface surrounding an outer surface of the annular wall, a second surface opposite the first surface, a ledge extending outward from the second surface, and a third surface opposite the ledge and covering the shoulder of the susceptor base; connecting a tubular side wall formed from a carbon-containing material to the susceptor base, wherein the annular wall is inserted into a first end of the side wall such that the first end engages the shelf of the sacrificial ring and the sacrificial ring is interposed between the side wall and each of the outer surface and shoulder of the annular wall. method.

14. further comprising placing a crucible within a susceptor interior defined by the inner surface of the sidewall and the concave surface of the susceptor base. The method of claim 13.

15. further comprising removing the sidewall from the susceptor base, and subsequently removing the sacrificial ring from the susceptor base. The method of claim 13.

16. the sacrificial ring is divided into two or more segments, and removing the sacrificial ring from the susceptor base includes independently removing one or more of the segments.

16. The method of claim 15.

17. 1. A method for producing a single crystal silicon ingot from a silicon melt, comprising: a susceptor assembly including a susceptor base, a tubular sidewall connected to the susceptor base, and a removable sacrificial ring interposed between the susceptor base and the sidewall, wherein each of the susceptor base and the sidewall is formed of a carbon-containing material; placing a crucible within the susceptor assembly defined by the susceptor base and the sidewall; adding polycrystalline silicon to said crucible; heating the polycrystalline silicon to form a silicon melt in the crucible; Pulling a single crystal silicon ingot from the melt, wherein silicon carbide (SiC) deposits accumulate on the sacrificial ring while the single crystal silicon ingot is being pulled from the melt; and removing the sacrificial ring having accumulated SiC deposits from the susceptor base after the single crystal silicon ingot is pulled from the melt. method.

18. and after removing the sacrificial ring having the accumulated SiC deposits from the susceptor base, placing a second sacrificial ring on the susceptor base.

18. The method of claim 17.

19. the sacrificial ring is divided into two or more segments, and removing the sacrificial ring having the accumulated SiC deposits from the susceptor base includes independently removing one or more segments.

18. The method of claim 17.

20. The step of removing the sacrificial ring having the accumulated SiC deposits from the susceptor base is performed after producing a plurality of single crystal silicon ingots.

18. The method of claim 17.

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