Wafer boat

Abstract

To provide a wafer boat which can accommodate a large number of wafers while minimizing local stress on a wafer.SOLUTION: A wafer boat for holding substrates in a spaced vertical arrangement is disclosed. The boat comprises: a first end plate and a second end plate spaced apart in a boat axis direction; and first and second side rods and a back rod, the rods extending between the first end plate and the second end plate. The back rod comprises a plurality of back rod supports for at least partially supporting a wafer, the back rod supports being substantially semicircular in shape and spaced apart in the boat axis direction. The first and second side rods comprise a plurality of first and second side rod supports respectively, spaced apart in the boat axis direction, where the first and second side rod supports each comprise a wafer contact portion being substantially arc shaped.SELECTED DRAWING: None

Description

[Technical Field]

[0001] FIELD OF THE INVENTION This application relates generally to substrate processing, and more particularly to an apparatus for supporting a substrate. [Background technology]

[0002] Batch manufacturing equipment such as vertical furnaces allows many substrates to be processed simultaneously in the same reaction chamber, thereby increasing substrate processing throughput. To support a large number of substrates in the reaction chamber, a wafer boat having a series of vertically spaced wafer supports is commonly used. Substrates can be loaded onto and removed from the wafer boat in a wafer transfer chamber. The boat can be moved into the reaction chamber for wafer processing and removed after processing is complete.

[0003] A wafer held by a wafer support experiences localized stress at the contact point with the wafer support due to the wafer's weight. If the localized stress exceeds the yield strength of the wafer material, undesirable plastic deformation or slippage of the wafer can occur. This effect can be more pronounced at high process temperatures because such temperatures can lead to a decrease in yield strength. Slippage can cause multiple problems, including wafer breakage, defects, and difficulty in depositing a uniform overlay.

[0004] So-called "long-finger boats" provide wafer support through elongated, straight finger supports. The supports must be thick enough to prevent significant bending when a wafer is placed on them. Sufficient space must be provided between vertically adjacent finger supports so that any bending will prevent a support from contacting a wafer held by another support directly below it. This reduces the number of supports that can be provided, thereby reducing wafer capacity. Summary of the Invention [Problem to be solved by the invention]

[0005] Therefore, there is a need for a wafer boat that minimizes localized stress on the wafers supported therein. There is also a need for a wafer boat that is capable of accommodating a large number of wafers while minimizing localized stress on the wafers supported therein. [Means for solving the problem]

[0006] According to a first embodiment of the present invention, there is provided a wafer boat for holding substrates in a spaced-apart vertical arrangement, the wafer boat comprising: a first end plate and a second end plate spaced apart in a boat axial direction; and first and second side rods and a back rod extending between the first and second end plates, the back rod comprising a plurality of back rod supports for at least partially supporting wafers, the plurality of back rod supports being generally semicircular in shape and spaced apart in the boat axial direction, the first and second side rods comprising a plurality of first and second side rod supports, respectively, spaced apart in the boat axial direction, the first and second side rod supports each comprising a wafer contact portion having a generally arc-shaped wafer.

[0007] One advantage of embodiments of the present invention is that a boat can be provided that minimizes localized stresses on wafers supported therein. One advantage of embodiments of the present invention is that a boat can be provided that accommodates a large number of slots for supporting wafers, e.g., 150 slots or more, while minimizing localized stresses. One advantage of embodiments of the present invention is that a boat can be provided that minimizes localized stresses while allowing for slight misalignment between the side rod supports and the back rod supports, so that tolerances for manufacturing such a boat do not need to be as tight as, for example, a long-finger boat.

[0008] The first and second side rods may be slightly offset from the front surface of the wafer boat but positioned approximately opposite each other in the diameter direction via the central axis of the wafer boat, allowing wafers to be inserted into the wafer boat from the front surface, and the back rod may be positioned approximately equidistant from the first and second side rods.

[0009] Each of the generally arc-shaped wafer contact portions may be below an angle of 10 to 30 degrees with respect to the central axis of the boat, and the expansion angle may be 15 to 25 degrees.

[0010] Each of the first and second side rods may have a first side surface facing the central boat axis and a second side surface facing away from the central boat axis, and the second side surfaces may each have two generally planar surfaces extending between the first end plate and the second end plate, and at least one of the first and second generally planar surfaces may not have a slot formed therein. The angle between the two generally planar surfaces may be 15 to 30 degrees.

[0011] One advantage of embodiments of the present invention is that by providing two flat surfaces on the side rods, the boat manufacturing process can be facilitated.

[0012] For each side rod, the second plane may be closer to the back rod than the first plane, and the second plane may not have a slot formed therein. For each side rod, the second plane may be closer to the back rod than the first plane, and the slot may be formed in the second plane. The first plane may have a width in the wafer insertion plane that is at least twice the width of the second plane in the wafer insertion plane.

[0013] The first and second side rods may extend between first and second ends within the wafer insertion plane, the second ends being located closer to the back rod than the first ends, and the width of the side rods at the first ends may be different from the width of the side rod support at the second ends.

[0014] The first and second side rods may extend between first and second ends within the wafer insertion plane, the second end being located closer to the back rod than the first end, and the width of the side rod at the first end may be approximately equal to the width of the side rod at the second end.

[0015] The boat may include at least 160 back rod supports and at least 160 corresponding sets of first and second side rod supports, thereby providing space within the boat to support at least 160 wafers, thereby allowing for more substrates to be processed simultaneously.

[0016] The first end plate and the second end plate may each include a cutout portion centered about the central boat axis.

[0017] According to a second aspect of the present invention, there is provided a furnace apparatus for substrate processing, the furnace apparatus comprising: a reaction chamber configured to receive one or more substrates supported on a wafer boat, one or more heating elements for heating the reaction chamber, a gas flow source for providing a flow of gas into the reaction chamber, a gas outlet for removing gas from the reaction chamber, and a wafer boat according to the first embodiment. The wafer boat may be configured to support at least 150 substrates, at least 160 substrates, or at least 165 substrates.

[0018] This summary is provided to introduce some concepts in a simplified form that are described in more detail below in the detailed description of exemplary embodiments of this disclosure. This summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used to limit the scope of the claimed subject matter.

[0019] Specific embodiments of the present invention will now be described, by way of example, with reference to the accompanying drawings, in which: [Brief explanation of the drawings]

[0020] [Figure 1a] 1 is a schematic perspective view of a wafer boat according to an embodiment of the present invention; [Figure 1b] 1 is a schematic perspective view of a wafer boat according to an embodiment of the present invention, shown with wafers that may be inserted into the wafer boat. [Figure 2] 2a and 2b are cross-sectional views of a wafer insertion plane of a first back rod and a second back rod, respectively, that may be included in a wafer boat according to an embodiment of the present invention. [Figure 3] 3a and 3b are cross-sectional views of a wafer insertion plane of a side rod that may be included in a wafer boat according to an embodiment of the present invention, and FIG. 3c is a cross-sectional view of a wafer insertion plane of a wafer boat according to an embodiment of the present invention. [Figure 4] FIG. 2 is a schematic perspective view of a first side rod that may be included in a wafer boat according to an embodiment of the present invention. [Figure 5] 5a and 5b are top views of wafer supports in a long-finger boat and a standard boat, respectively. [Figure 6]Figure 6a shows simulated stresses on a wafer supported on supports such as those shown in Figure 5a, Figure 6b shows simulated stresses on a wafer supported on supports such as those shown in Figure 5b, and Figure 6c shows simulated stresses on a wafer supported on supports such as those shown in Figure 3c. [Figure 7] 1 is a schematic cross-sectional view along the central axis of a vertical furnace apparatus including a boat according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0021] It will be understood that elements in the figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale. For example, the dimensions of some of the elements in the figures may be exaggerated relative to other elements to help to improve understanding of the illustrated embodiments of the present disclosure.

[0022] While certain specific embodiments and examples are disclosed below, it will be understood by those skilled in the art that the invention extends beyond the specifically disclosed embodiments and / or uses of the invention, and obvious variations and equivalents thereof. It is therefore not intended that the scope of the disclosed invention should be limited by the specific disclosed embodiments described below.

[0023] As used in this disclosure, the term "substrate" may refer to any single or multiple underlying materials, such as any single or multiple underlying materials that may be modified or upon which a device, circuit, or film may be formed. A "substrate" may be continuous or discontinuous, rigid or flexible, solid or porous, and combinations thereof. A substrate may be in any form, such as a powder, a plate, or a workpiece. Substrates in plate form may include wafers of various shapes and sizes. Substrates may be made from semiconductor materials, including, for example, silicon, silicon germanium, silicon oxide, gallium arsenide, gallium nitride, and silicon carbide.

[0024] The continuous substrate may extend beyond the boundaries of the process chamber in which the deposition process occurs. In some processes, the continuous substrate may move through the process chamber so that the process continues until the edge of the substrate is reached. The continuous substrate may be supplied from a continuous substrate supply system to enable the production and output of the continuous substrate in any suitable form.

[0025] The illustrations presented herein are not meant to be actual representations of any particular materials, structures, or devices, but merely idealized representations used to describe embodiments of the present disclosure.

[0026] The specific examples shown and described are illustrative of the present invention and its best mode and are not intended to limit the scope of the present aspects or implementations in any way. Also, for the sake of brevity, conventional manufacturing, association, preparation, and other functional aspects of the present system may not be described in detail. Furthermore, connecting lines shown in the various figures are intended to represent example functional relationships and / or physical couplings between the various elements. Many alternative or additional functional relationships or physical connections may be present in an actual system and / or may not be present in some embodiments.

[0027] It will be understood that the configurations and / or approaches described in this disclosure are exemplary in nature, and that these specific embodiments or examples are not to be construed in a limiting sense, as numerous variations are possible. The specific routines or methods described in this disclosure may represent one or more of several processing strategies. As such, various illustrated operations may be performed in the order illustrated, in other orders, or omitted in some cases.

[0028] The subject matter of this disclosure includes all novel and non-obvious combinations and subcombinations of the various processes, systems, and configurations, as well as other configurations, functions, operations and / or properties disclosed in this disclosure, as well as any and all equivalents thereof.

[0029] 1a and 1b, a wafer boat 1 according to an embodiment of the present invention includes a first end plate 2 and a second end plate 3. The first end plate 2 and the second end plate 3 are spaced apart in a boat axial direction z. The first end plate 2 and the second end plate 3 may be generally circular in shape and may be aligned with their centers along the same axis, referred to herein as the central boat axis A. The first end plate 2 and the second end plate 3 may have respective cutout central circular sections 4 and 5, which may help reduce thermal stress in the end plates 2 and 3. In some embodiments, the first end plate 2 and the second end plate 3 may have a non-circular shape, and the central boat axis may be defined as a line connecting the centers of the first and second end plates 2 and 3 along the boat axial direction. Support legs (not shown) may extend from the underside of the second end plate 3.

[0030] The wafer boat 1 includes a first side rod 6, a second side rod 7, and a back rod 8. The side rods 6, 7, and back rod 8 each extend between a first end plate 2 and a second end plate 3. The rods 6, 7, and 8 may be removably attached to the first end plate 2 and the second end plate 3, for example, using screws (not shown). In the event of damage, this may allow the rods 6, 7, and 8 to be individually removed and replaced without having to replace the entire boat 1. The rods 6, 7, and 8 may be attached to the first end plate 2 and the second end plate 3 by welded joints. This may allow for more uniform thermal behavior of the boat 1.

[0031] The rods 6, 7, and 8 may be arranged circumferentially to define an opening through which wafers 9 may be loaded into the boat 1 in a wafer introduction direction D, for example, by a wafer transfer robot (not shown). For example, the first and second side rods 6 and 7 may be arranged slightly offset from the back rod 8 rather than being substantially diametrically opposed, and the back rod 8 may be arranged substantially equidistant from the first side rod 6 and the second side rod 7. The back rod 8 may be positioned such that the back rod 8 and the center C of a wafer loaded into the boat 1 are collinear in the wafer loading direction D. The wafers 9 may be, for example, silicon wafers.

[0032] The back rod 8 includes a plurality of back rod supports 10 for at least partially supporting the wafers 9 in the boat 1. The plurality of back rod supports 10 are spaced apart in the boat axial direction. The plurality of back rod supports 10 may be evenly spaced apart in the boat axial direction, as shown in FIG. 1 . In some embodiments, the back rod supports 10 may be unevenly spaced apart in the boat axial direction. The back rod supports 10 are generally semicircular in shape, with a diameter defined by the back rod 8. The back rod supports 10 protrude toward the central boat axis A.

[0033] Referring also to FIG. 2a, the backrod 8 may be generally cylindrical with a series of slots cut into one side of the cylinder in a plane perpendicular to the axis of the cylinder to form semicircular backrod supports 10. The backrod 8 may also have a non-cylindrical shape to which multiple backrod supports 10 are attached. Referring to FIG. 2b, the backrod 8 may have a semi-cylindrical shape with a series of slots cut into a plane perpendicular to the axis of the semi-cylindrical cylinder to form semicircular backrod supports 10. The diameter d1 of the semicircular backrod supports 10 may be 5 mm to 50 mm, 10 mm to 45 mm, 15 mm to 40 mm, or 20 mm to 35 mm. The diameter of the semicircular backrod supports 10 may be 20 mm to 25 mm, 25 mm to 30 mm, or 30 mm to 35 mm.

[0034] Because the first side rod 6 and the second side rod 7 have the same shape, it will be understood that the following description of the first side rod 6 applies equally to the second side rod 7. Referring to FIGS. 3a and 3b, the first side rod 6 includes a plurality of first side rod supports 11. Each first side rod support 11 includes a generally arc-shaped wafer contact portion 12. The wafer contact portion 12 is a portion of the first side rod support 11 that contacts the wafer 9 when the wafer 9 is supported in the boat 1. By providing the arc-shaped contact portion 12, the wafer 9 can be supported over a greater perimeter of its circumference compared to, for example, a long-finger boat, which can help reduce stress on the wafer material and, accordingly, can help reduce slippage, especially at high temperatures. Furthermore, distributing the contact points with the wafers over the arc-shaped contact portions 12 can result in reduced bending of the supports 11 compared to, for example, a long-finger boat, which means that a relatively large number of wafers can be supported in the boat 1 without the need to make the thickness of the supports 11 in the z-direction as large as that of a long-finger boat. For example, in the boat 1 according to an embodiment of the present invention, the wafers may be supported by a set of substantially coplanar first side rod supports, a second side rod support, and a back rod support. The boat 1 may be configured to include at least 150 such support sets, at least 160 support sets, or at least 165 support sets.

[0035] The contact portion 12 may extend between a first end 13 and a second end 14. The first end 13 and the second end 14 form an angle α with the central axis A of the boat 1. The angle α may be between 10 and 40 degrees, between 10 and 30 degrees, between 15 and 35 degrees, between 20 and 30 degrees, or between 15 and 25 degrees. The angle α may be between 20 and 25 degrees, or between 25 and 30 degrees. The first side rod support 11 may be configured with an intermediate portion 15 extending radially away from the central boat axis A, which may or may not be arc-shaped. The intermediate portion 15 may be at least partially terminated by one or more linear edges E, each spaced generally radially from the contact portion 12.

[0036] The first side rod 6 may comprise a first side rod body 16 to which a plurality of first side rod supports 11 are attached or form a continuous piece with a plurality of first side rod supports 11 that are spaced apart longitudinally along the first side rod body. An intermediate portion 15 of the first side rod support 11 may be attached to or adjacent to the first side rod body 16 at one or more edges E. The first side rod body 16 extends axially between the first end plate 2 and the second end plate 3.

[0037] In this disclosure, when an element is described as being attached to another element, it is understood that this can encompass an arrangement in which two elements are manufactured or machined as separate parts and then fastened together. When an element is described as being attached to another element, it is understood that this can encompass a configuration in which the parts are machined so that the first and second elements are part of a single body, without the need to physically fasten one element to the other. For example, the first side rod 6 may be formed by first machining a solid part having the shape shown in FIG. 3a and a constant cross-section extending along its axis, and then forming a series of slots in the solid part in a plane having the axis of the solid part as its normal. The remaining material of the solid part forms the support 11 and the side rod body 16.

[0038] The first side rod 6 may have a first side facing toward the central boat axis A and a second side 17 facing away from the central boat axis A. The second side 17 may include first and second generally flat planes 18, 19, respectively. The first and second generally flat planes 18, 19 extend between the first end plate 2 and the second end plate 3. The second plane 19 is closer to the back rod 8 than the first plane. A slot may be formed in one, both, or neither of the first and second planes 18, 19. For example, in some embodiments, a slot may be formed in the first plane 18 to at least partially provide support 11. The angle β between the planes 18, 19 measured on the second side 17 may be between 185 and 220 degrees. The angle β may be between 195 and 210 degrees. The angle β may be between 200 and 205 degrees. Forming the second side 17 in two flat surfaces 18, 19 may help provide a side rod 6 that is easy to manufacture.

[0039] The first plane 18 and the second plane 19 have respective widths w1 and w2 within the wafer insertion plane. The wafer insertion plane is a plane having the boat axis direction z as its normal. The width w1 of the first plane 18 may be at least twice the width w2 of the second plane 19. The width w1 of the first plane 18 may be at least 1.5 times the width w2 of the second plane 19. The width w1 of the first plane 18 may be at least 2.5 times or at least 3 times the width w2 of the second plane 19. The width w1 of the first plane 18 may be 1 to 5 times the width w2 of the second plane 19.

[0040] 3a, the side rods 6 extend between a first end 20 and a second end 21 at the wafer insertion plane, with the second end 21 being closer to the back rod 8 than the first end 20. The side rods 6 have a width w3 at the first end 20 and a width w4 at the second end 21, measured at the wafer insertion plane and in a generally radial direction. The width w3 of the first end 20 may be different from the width w4 of the second end 21. The width w3 of the first end 20 may be generally equal to the width w4 of the second end 21.

[0041] By providing back rod supports 10 having a semicircular shape in combination with first and second side rod supports 11, 22 having arc-shaped wafer contact portions 12, boat 1 can be provided with greater tolerance for alignment of corresponding supports in the boat axial direction while still providing the required wafer support, thereby providing easier manufacture and transportation of boat 1.

[0042] Finite element simulations were performed to evaluate stresses on wafers supported in a boat according to an embodiment of the present invention, as well as on wafers supported in a long-finger boat and a standard boat for comparison. In the simulations, the wafers had a diameter of 300 mm, and the wafers and boat had material properties identical to those of silicon. The simulated long-finger boat wafer support is shown in Figure 5a. The simulated standard boat wafer support is shown in Figure 5b. In both figures, the back rod support is labeled B, and the side rod support is labeled S. For boat 1 according to an embodiment of the present invention, the wafer support shown in Figure 3c was used in the simulations.

[0043] Referring to Figure 6a, a wafer yield stress map is shown for the long-finger boat support. Referring to Figure 6b, a wafer yield stress map is shown for the standard boat support. Referring to Figure 6c, a wafer yield stress map is shown for the boat according to the embodiment of the present invention shown in Figure 3c. The highest stress value for the boat according to the embodiment of the present invention was found to be comparable to that of the long-finger boat and 67% less than that of the standard boat. The boat according to the embodiment of the present invention accommodates more wafers than the long-finger boat while allowing for comparable yield stress for the wafers compared to the long-finger boat.

[0044] Referring to FIG. 7 , an embodiment of the present invention may provide a vertical furnace apparatus 100 including the wafer boat 1 described above. The vertical furnace apparatus 100 includes a reaction tube 101, which is generally bell-jar shaped and defines a reaction chamber 102 therein. The reaction tube 101 is surrounded by a heating means, such as one or more thermo-resistive heating coils 103 powered by a power supply (not shown). The heating means 103 is configured to provide heat to the reaction tube 101, which heats the reaction chamber 102. The heating means 103 may be configured to heat the reaction chamber 102 to a temperature of 500° C. or higher, e.g., 800° C., 900° C., or 1000° C. The reaction tube 101 may be supported at its lower end on a flange 104, which may partially close the open end of the reaction tube 101. The wafer boat 1 may enter and exit the reaction chamber 102 through a central furnace opening 105 provided in the flange 104. A vertically movable door 106 may be configured to close the opening 105 and support the wafer boat 1. The wafer boat 1 may be inserted into the chamber empty, i.e., while not supporting any wafers 9. In some cases, the wafers 9 may be dummy wafers not intended for further manufacturing. The door 106 may be provided with a pedestal 107. The pedestal 107 may be configured to rotate to rotate the wafer boat 1 within the reaction chamber 102. The flange 104 may include a gas inlet 108 for providing gas into the reaction chamber 102 and a gas outlet 109 for removing gas from the reaction chamber 102. The gas may include, for example, argon, hydrogen, nitrogen, oxygen, water vapor, oxygen with a trace amount of HCl, and / or any mixture of the foregoing.

[0045] The apparatus 100 may be configured with a purge gas inlet 110 on the flange 104 to supply a purge gas to the reaction chamber 102. In some embodiments, the purge gas inlet 110 is not provided, and the gas inlet 108 is configured to provide both a process gas flow source for flowing process gas into the reaction tube 101 and a purge gas flow source for flowing purge gas into the reaction tube 101. For example, the gas inlet 108 may be connected to a valve (not shown) coupled to a process gas source and a purge gas source, the valve being configured to accommodate at least one configuration in which only process gas can flow through the gas inlet 108 and one in which only purge gas can flow through the gas inlet 108.

[0046] The boat 1 may be made of silicon. The boat may be made of silicon carbide. The boat may be made of quartz.

[0047] While illustrative embodiments of the invention have been described above, in part with reference to the accompanying drawings, it should be understood that the invention is not limited to these embodiments. Variations to the disclosed embodiments can be understood and effected by those skilled in the art in practicing the claimed invention, from a study of the drawings, the disclosure, and the appended claims.

[0048] Throughout this specification, a reference to "one embodiment" or "an embodiment" means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the present invention. Thus, the appearances of the phrases "in one embodiment" or "in an embodiment" in various places throughout this specification do not necessarily refer to the same embodiment. Furthermore, it is noted that particular features, structures, or characteristics of one or more embodiments may be combined in any suitable manner to form new embodiments not expressly described. The subject matter of this disclosure includes all novel and non-obvious combinations and subcombinations of the various processes, systems, and configurations, as well as other features, functions, operations, and / or characteristics, disclosed in this disclosure, and any and all equivalents thereof. [Explanation of symbols]

[0049] 1 wafer boat 2 First End Plate 3 Second End Plate 4 Central circular section 5 Central circular section 6. First Side Rod 6 Side Rod 7 Side Rod 8 Back Rod 10 Back rod support 11 First side rod support 12 Wafer contact area 13 First Edge 14 Second End 15 Middle part 16 First side rod body 17 Second Side 18 First Plane 19 Second Plane 20 First End 21 Second End 22 Second side rod support 100 vertical furnace equipment 101 reaction tubes 102 Reaction Chamber 103 Heating means 104 flange 105 Central furnace opening 106 Doors 107 Pedestal 108 Gas inlet 109 Gas outlet 110 Purge gas inlet

Claims

1. A wafer boat for holding substrates in a spaced apart vertical arrangement, comprising: a first end plate and a second end plate spaced apart in an axial direction of the boat; first and second side rods and a back rod extending between the first end plate and the second end plate; Equipped with the back rod includes a plurality of back rod supports for at least partially supporting the wafers, the plurality of back rod supports being generally semicircular and spaced apart in an axial direction of the boat; the first and second side rods each include a plurality of first and second side rod supports spaced apart in the boat axial direction; The wafer boat, wherein the first and second side rod supports each include a wafer contacting portion that is generally arc-shaped.

2. 2. The wafer boat of claim 1, wherein the first and second side rods are slightly offset from a front surface of the wafer boat but are positioned substantially opposite each other in a diametrical direction via a central axis of the wafer boat, so that wafers can be inserted into the wafer boat from the front surface, and the back rod is positioned substantially equidistant from the first and second side rods.

3. 3. The wafer boat according to claim 1, wherein each of the substantially arc-shaped wafer contact portions forms an angle of 10 to 30 degrees with the central axis of the wafer boat.

4. 3. The wafer boat according to claim 1, wherein each of the substantially arc-shaped wafer contact portions forms an angle of 15 to 25 degrees with the central axis of the wafer boat.

5. 5. The wafer boat of claim 1, wherein the first and second side rods each have a first side surface facing a central boat axis and a second side surface facing an opposite side from the central boat axis, the second side surfaces each having two substantially planar surfaces extending between the first end plate and the second end plate, and at least one of the first and second substantially planar surfaces is free of slots.

6. 6. The wafer boat according to claim 5, wherein the angle between the two substantially flat planes is between 15 degrees and 30 degrees.

7. 7. The wafer boat according to claim 5, wherein for each side rod, the second plane is closer to the back rod than the first plane, and no slots are formed in the second plane.

8. 8. The wafer boat of claim 7, wherein a slot is formed in the second plane.

9. 9. The wafer boat according to claim 5, wherein the first plane has a width of the wafer insertion plane that is at least twice the width of the second plane in the wafer insertion plane.

10. 10. The wafer boat of claim 1, wherein the first and second side rods extend between first and second ends within a wafer insertion plane, the second ends being positioned closer to the back rod than the first ends, and a width of the side rods at the first ends differs from a width of the side rod supports at the second ends.

11. 10. The wafer boat of claim 1, wherein the first and second side rods extend between first and second ends within a wafer insertion surface, the second ends are positioned closer to the back rod than the first ends, and the width of the side rods at the first ends is approximately equal to the width of the side rods at the second ends.

12. 12. The wafer boat of claim 1, comprising at least 160 back rod supports and at least 160 corresponding sets of first and second side rod supports.

13. The wafer boat of any one of claims 1 to 12, wherein the first end plate and the second end plate each include a cutout portion centered about a central boat axis.

14. 1. A furnace apparatus for processing substrates, comprising: a reaction chamber configured to receive one or more substrates supported on a wafer boat; one or more heating elements for heating the reaction chamber; a gas flow source for providing a flow of gas into the reaction chamber; a gas outlet for removing gas from the reaction chamber; The wafer boat according to any one of claims 1 to 13, A furnace apparatus comprising:

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