Vertical furnace and crystal boat for a vertical furnace

Abstract

This disclosure relates to the field of semiconductor manufacturing equipment technology, providing a vertical furnace and a crystal boat for the vertical furnace. The crystal boat includes multiple support columns and a top plate disposed at the top of the support columns. The top wall of the top plate has an upwardly convex second curved surface. The vertical furnace includes a vertically arranged reaction tube and the crystal boat; the inner top wall of the reaction tube has an upwardly convex first curved surface, on which an exhaust port communicating with an exhaust pipe is opened. The curvature of the first curved surface and the second curved surface are the same; the crystal boat is erected inside the reaction tube and is coaxially spaced from the reaction tube. The top plate of the crystal boat and the top of the reaction tube form a concentric, equally spaced hemispherical air passage, allowing the rising airflow to diffuse uniformly along the annular spacing at the top and smoothly converge towards the central exhaust port. This significantly reduces flow resistance and pressure pulsation while eliminating dead zones and eddies in the airflow, ultimately achieving stable rectification of the axisymmetric flow field inside the reaction tube.

Description

Technical Field

[0001] This disclosure relates to the field of semiconductor manufacturing equipment technology, and more particularly to vertical furnaces and crystal boats used in vertical furnaces. Background Technology

[0002] In existing semiconductor vertical reactor equipment, the top plate of the crystal boat adopts a flat plate structure. In top-venting vertical reactor equipment, the top space formed between the flat top surface of the crystal boat and the inner wall of the top of the reaction tube has significant defects in terms of gas flow and particle control. First, the existing structure is prone to unstable gas flow. For equipment where the exhaust pipe is located above the reaction tube, the gas needs to be guided upwards. However, the flat top plate of the crystal boat causes the airflow to bend sharply, resulting in severe gas stagnation and the formation of eddies. This causes local pressure and concentration fluctuations, making it difficult to control the uniformity of the thin-layer resistivity (Rs) of the top wafer in high-capacity processes. Second, a horizontal dead zone is easily formed above the flat plate structure of the crystal boat. Process byproducts or fine particles can easily accumulate here and risk falling directly onto the surface of the wafer below, seriously affecting product yield. Especially in vertical furnaces using liquid sources, such as processes using POCl3 (phosphorus oxychloride) as the phosphorus diffusion source, residual POCl3 in the exhaust gas stagnates or condenses due to temperature drop during upward emission. This results in reaction byproducts (such as white powder) easily accumulating on the top of the crystal boat, causing severe particulate contamination. Furthermore, traditional designs lack effective self-cleaning mechanisms, allowing byproducts to adhere to the top of the crystal boat, increasing equipment maintenance frequency and the risk of process contamination, leading to increased equipment operating costs. Therefore, a novel reaction chamber structure that can simultaneously optimize top flow field stability and suppress particulate contamination is urgently needed. Summary of the Invention

[0003] In view of the shortcomings of the prior art described above, the purpose of this disclosure is to provide a vertical furnace and a crystal boat for the vertical furnace to solve the problems in the related art.

[0004] The first aspect of this disclosure provides a crystal boat for a vertical furnace, wherein the inner wall of the top of the vertical furnace has an upwardly convex first curved surface, and the top is provided with an exhaust port. The crystal boat includes a plurality of support columns and a top plate disposed at the top of the support columns. The top wall of the top plate has an upwardly convex second curved surface, and the curvature of the first curved surface and the curvature of the second curved surface are the same.

[0005] In an embodiment of the first aspect, the ratio of the distance between the first curved surface and the second curved surface to the inner diameter of the exhaust port is 0.8 to 1.3.

[0006] In an embodiment of the first aspect, the ratio of the distance between the first curved surface and the second curved surface to the inner diameter of the exhaust port is 1.025.

[0007] In the first aspect of the embodiment, the second curved surface is provided with a plurality of micro-dimples; and / or, the crystal boat is a split-connection structure.

[0008] In an embodiment of the first aspect, both the first and second curved surfaces are spherical cap surfaces that do not extend beyond the center of the sphere; and / or, the top plate is detachably disposed on the top of the crystal boat; and / or, the bottom surface of the top plate is a curved surface or a plane; and / or, the top plate includes a detachably connected bottom plate and a top cover.

[0009] A second aspect of this disclosure provides a vertical furnace, comprising:

[0010] A vertically arranged reaction tube has an upwardly convex first curved surface on the top inner wall of the reaction tube, and an exhaust port communicating with an exhaust pipe is opened on the first curved surface.

[0011] The crystal boat is erected inside the reaction tube and is coaxially spaced from the reaction tube.

[0012] In an embodiment of the second aspect, the vertical furnace is a phosphorus doping diffusion furnace based on a POCl3 liquid source; and / or, the material of the crystal boat and the reaction tube includes quartz.

[0013] In the second embodiment, the reaction tube is a single tube, and the vertical furnace further includes a gas supply nozzle. One end of the gas supply nozzle is connected to a gas source, and the other end is located inside the reaction tube and on the side of the crystal boat, extending along the height of the crystal boat. The gas supply nozzle is provided with multiple air jets at intervals for spraying process gases onto the wafers on the crystal boat.

[0014] In a second aspect embodiment, the exhaust pipe includes a first pipe and a second pipe, one end of the first pipe is connected to the exhaust port of the reaction tube, and the other end is connected to the second pipe, the other end of the second pipe is connected to a vacuum pump; wherein, the material of the first pipe includes quartz; the material of the second pipe includes polytetrafluoroethylene, and the first pipe is at least partially embedded in the second pipe.

[0015] In a second embodiment, a cooling unit is provided on the outer periphery of the first pipeline, and the wall thickness of the first pipeline gradually decreases in the direction away from the exhaust port.

[0016] As described above, this disclosure relates to the field of semiconductor manufacturing equipment technology, providing a vertical furnace and a crystal boat for the vertical furnace. The crystal boat includes multiple support columns and a top plate disposed at the top of the support columns, the top wall of the top plate having an upwardly convex second curved surface. The vertical furnace includes a vertically arranged reaction tube and the crystal boat; the inner top wall of the reaction tube has an upwardly convex first curved surface, the first curved surface having an exhaust port communicating with an exhaust pipe, the curvature of the first curved surface and the second curved surface being the same; the crystal boat is erected inside the reaction tube and is coaxially spaced from the reaction tube. This application constructs concentric, equally spaced hemispherical air channels on the top plate of the crystal boat and the top of the reaction tube, allowing the rising airflow to diffuse uniformly along the annular spacing at the top and smoothly converge towards the central exhaust port, thereby eliminating airflow dead zones and eddies while significantly reducing flow resistance and pressure pulsation, ultimately achieving stable rectification of the axisymmetric flow field inside the reaction tube, effectively ensuring the uniformity and batch consistency of the wafer process, and effectively reducing particulate contamination, extending equipment maintenance cycles, and reducing equipment operating costs. Attached Figure Description

[0017] Figure 1 The diagram shown is a schematic representation of a crystal boat and a vertical furnace having the crystal boat according to an embodiment of the present disclosure.

[0018] Figure 2 The diagram shown is a structural schematic of the top plate in another embodiment of this disclosure.

[0019] Figure 3 The diagram shown is a structural schematic of a crystal boat in another embodiment of this disclosure.

[0020] Figure 4 The diagram shown is a schematic diagram of the reactor structure in another embodiment of this disclosure.

[0021] Figure label:

[0022] 110. Reaction tube; 111. First curved surface; 1101. Exhaust port; 120. Crystal boat; 121. Second curved surface; 1201. Micro-dimples; 122. Support column; 123. Top plate; 124. Bottom plate; 130. Exhaust pipe; 131. First pipe; 132. Second pipe; 101. Equally spaced air passages; 140. Inner reaction tube. Detailed Implementation

[0023] The following specific examples illustrate the implementation of this disclosure. Those skilled in the art can easily understand other advantages and effects of this disclosure from the information disclosed herein. This disclosure can also be implemented or applied through other different specific embodiments, and various details in this disclosure can be modified or changed according to different viewpoints and application modules without departing from the spirit of this disclosure. It should be noted that, unless otherwise specified, the embodiments and features in the embodiments of this disclosure can be combined with each other.

[0024] The embodiments of this disclosure will now be described in detail with reference to the accompanying drawings, so that those skilled in the art to which this disclosure pertains can readily implement it. This disclosure may be embodied in many different forms and is not limited to the embodiments described herein.

[0025] In this disclosure, references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic represented in connection with that embodiment or example is included in at least one embodiment or example of this disclosure. Furthermore, the specific features, structures, materials, or characteristics represented may be combined in any suitable manner in any one or a group of embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples represented in this disclosure, as well as the features of those different embodiments or examples.

[0026] Furthermore, the terms "first" and "second" are used for illustrative purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the representation of this disclosure, "a set" means two or more, unless otherwise explicitly specified.

[0027] For the purpose of clarity, devices unrelated to the description are omitted, and the same or similar components throughout the specification are given the same reference numerals.

[0028] Throughout this specification, when it is said that a device is "connected" to another device, this includes not only "direct connection" but also "indirect connection" by placing other components in between. Furthermore, when it is said that a device "comprises" a certain constituent element, unless otherwise stated otherwise, this does not exclude other constituent elements, but rather implies that other constituent elements may be included.

[0029] While the terms first, second, etc., are used in some examples herein to refer to various elements, these elements should not be limited by these terms. These terms are used only to distinguish one element from another. For example, first interface and second interface, etc., are used. Furthermore, as used herein, the singular forms “a,” “an,” and “the” are intended to also include the plural forms unless the context indicates otherwise. It should be further understood that the terms “comprising,” “including,” indicate the presence of the stated feature, step, operation, element, module, item, kind, and / or group, but do not exclude the presence, occurrence, or addition of one or more other features, steps, operations, elements, modules, items, kinds, and / or groups. The terms “or” and “and / or” as used herein are interpreted as inclusive, or mean any one or any combination thereof. Thus, “A, B, or C” or “A, B, and / or C” means “any one of: A; B; C; A and B; A and C; B and C; A, B, and C.” Exceptions to this definition will only occur if the combination of elements, functions, steps, or operations is inherently mutually exclusive in some way.

[0030] The technical terms used herein are for reference only to specific embodiments and are not intended to limit the scope of this disclosure. The singular form used herein includes the plural form unless the statement explicitly indicates otherwise. The word "comprising" as used in this specification means to specify a particular characteristic, region, integer, step, operation, element, and / or component, and does not exclude the presence or addition of other characteristics, regions, integers, steps, operations, elements, and / or components.

[0031] Although not explicitly defined, all terms, including technical and scientific terms used herein, shall have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure pertains. Terms defined in commonly used dictionaries shall be further interpreted as having a meaning consistent with the relevant technical literature and the message of the present disclosure, and shall not be over-interpreted as having an ideal or overly formulaic meaning unless otherwise defined.

[0032] In existing semiconductor vertical reactor equipment, the top plate of the crystal boat adopts a flat plate structure. In top-venting vertical reactor equipment, the top space formed between the flat top surface of the crystal boat and the inner wall of the top of the reaction tube has significant defects in terms of gas flow and particle control. First, the existing structure is prone to unstable gas flow. For equipment where the exhaust pipe is located above the reaction tube, the gas needs to be guided upwards. However, the flat top plate of the crystal boat causes the airflow to bend sharply, resulting in severe gas stagnation and the formation of eddies. This causes local pressure and concentration fluctuations, making it difficult to control the uniformity of the thin-layer resistivity (Rs) of the top wafer in high-capacity processes. Second, a horizontal dead zone is easily formed above the flat plate structure of the crystal boat. Process byproducts or fine particles can easily accumulate here and risk falling directly onto the surface of the wafer below, seriously affecting product yield. Especially in vertical furnaces using liquid sources, such as processes using POCl3 (phosphorus oxychloride) as the phosphorus diffusion source, residual POCl3 in the exhaust gas stagnates or condenses due to temperature drop during upward discharge. This results in reaction byproducts (such as white powder) easily accumulating on the top of the crystal boat, causing severe particulate contamination. Furthermore, traditional designs lack effective self-cleaning mechanisms, allowing byproducts to adhere to the top of the crystal boat, increasing equipment maintenance frequency and the risk of process contamination. Therefore, a novel reaction chamber structure is urgently needed that can simultaneously optimize top flow field stability and suppress particulate contamination.

[0033] To address the aforementioned issues, this application constructs concentric, equally spaced hemispherical air channels on the top plate of the crystal boat and the top of the reaction tube. This allows the rising airflow to diffuse uniformly along the annular spacing at the top and smoothly converge towards the central exhaust port. This eliminates dead zones and eddies in the airflow while significantly reducing flow resistance and pressure pulsation. Ultimately, it achieves stable rectification of the axisymmetric flow field within the reaction tube, effectively ensuring the uniformity and batch consistency of the wafer process. Furthermore, it can effectively reduce particulate contamination, extend equipment maintenance cycles, and lower equipment operating costs.

[0034] The first embodiment of this disclosure provides a crystal boat for a vertical furnace. The top inner wall of the vertical furnace has an upwardly convex first curved surface, and the top is provided with an exhaust port. The crystal boat includes a plurality of support columns and a top plate disposed at the top of the support columns. The top wall of the top plate has an upwardly convex second curved surface, and the curvature of the first curved surface and the curvature of the second curved surface are the same.

[0035] Figure 1 The diagram shown is a schematic representation of a crystal boat and a vertical furnace having the crystal boat, according to an embodiment of this disclosure. Figure 1In the example, the vertical furnace includes a reaction tube 110 and a crystal boat 120. The reaction tube 110 is arranged vertically and has an upwardly convex first curved surface 111 on its inner top wall as an exhaust surface, such as a hemispherical surface. An exhaust port 1101 is provided on the first curved surface 111, preferably located at the very center of the first curved surface 111, and the opening shape of the exhaust port 1101 is adapted to the first curved surface 111.

[0036] exist Figure 1 In this example, the wafer boat 120 is implemented as a single entity. The wafer boat 120 includes a plurality of support pillars 122 and a top plate 123 disposed at the top of each support pillar 122. For example, there may be three or four support pillars 122. When there are three, the three support pillars 122 are distributed at the three vertices of an isosceles triangle; when there are four, the four support pillars 122 are distributed at the four vertices of an isosceles trapezoid. Multiple support grooves with corresponding heights are formed between the plurality of support pillars 122 along their extension direction, and the multiple support grooves at the same height on the plurality of support pillars 122 collectively support the same wafer. The top wall of the top plate 123 has an upwardly convex second curved surface 121, the second curved surface 121 having the same curvature as the first curved surface 111. In use, the crystal boat 120 is erected in the vertical furnace. The gap between the first curved surface 111 and the second curved surface 121 forms an equally spaced (the same spacing in each radial direction) exhaust channel to guide the residual gas and its by-products in the process to the exhaust port 1101.

[0037] For example, during the process, the bottom end of the support column 122 is directly connected to the support device inside the furnace. In other embodiments, the bottom end of the support column 122 may also be connected to a base plate 124, which is then connected to the support device inside the furnace.

[0038] For example, both the first surface 111 and the second surface 121 are spherical cap surfaces that do not extend beyond the center of the sphere, and the first surface 111 and the second surface 121 are arranged concentrically. That is, an equally spaced air passage 101 is formed between the first surface 111 and the second surface 121.

[0039] The advantages of this design are: the cross-sectional area of ​​the equidistant air passages 101 changes continuously without abrupt changes, resulting in lower fluid resistance; the gas flows through the equidistant air passages 101, forming a stable laminar flow that accelerates to the exhaust port 1101, without drastic pressure changes or velocity gradients during the flow; the rising airflow can diffuse evenly along the equidistant air passages 101 at the top and smoothly converge towards the central exhaust port 1101, thereby significantly reducing flow resistance and pressure pulsation while eliminating dead zones and eddies, thus improving gas replacement efficiency; as the gas replacement efficiency in the reaction tube 110 increases, the gas will not condense due to stagnation or temperature drop during the upward discharge process in the reaction tube 110, preventing process byproducts (such as white powder) from condensing or adhering to the upper end of the crystal boat 120. This improves wafer yield; with the help of the equally spaced gas channels 101, the reaction gas is uniformly converged from the periphery to the central exhaust port 1101 in a stable laminar flow, effectively eliminating top eddies and gas stagnation, and significantly improving gas replacement efficiency; under large-capacity process conditions (e.g., a 117-bay crystal boat 120), this structure can minimize the gas concentration deviation around the top wafer, suppress local overdoping or underdoping caused by uneven top flow field, thereby achieving high-precision process performance with stable control of thin-layer resistivity (Rs) uniformity at a low value.

[0040] Those skilled in the art will also understand that the hemispherical curved surface structure utilizes geometric curvature to form a continuous outward guiding slope on the top wall of the crystal boat 120, fundamentally eliminating the horizontal area where particles are trapped; even if fine particles are generated, they will move obliquely outward along the spherical surface under the combined action of gravity and airflow shear force, and will not accumulate at the top of the wafer, thereby effectively blocking the vertical falling path of particles to the wafer, reducing the wafer particle transfer rate, and significantly improving process cleanliness and product qualification rate.

[0041] For example, the spacing of the equally spaced air channels 101 is in a predetermined relationship with the inner diameter of the exhaust port 1101. For example, the ratio of the spacing (H) of the equally spaced air channels 101 to the inner diameter (D) of the exhaust port 1101. Those skilled in the art will understand that the ratio (H / D) of the distance (H) between the top wall of the top plate 123 of the crystal boat 120 and the top inner wall of the reaction tube 110 to the inner diameter (D) of the exhaust port 1101 directly determines the quality of the top flow field; if the ratio is too large, it will lead to insufficient constraint when the gas flows through the equally spaced air channels 101, which will easily form a large area of ​​eddies and dead zones at the top, causing fluctuations in process gas concentration and particle accumulation; if the ratio is too small, it will significantly increase fluid resistance, causing excessive exhaust back pressure and pressure pulsation, which will damage process stability. By controlling the ratio within a suitable range, a laminar flow channel with smooth cross-sectional shrinkage can be constructed. This ensures that the gas is discharged efficiently in a stable axisymmetric flow state, achieving a high-precision process with an Rs uniformity of <2% for the top wafer. At the same time, the self-cleaning effect of the high-speed airflow is used to quickly remove particles from above the wafer, reducing the particle transfer rate by more than 98%.

[0042] For example, the ratio (H / D) of the spacing (H) of the equally spaced air passages 101 to the inner diameter (D) of the exhaust port 1101 ranges from 0.8 to 1.3. In this embodiment, the ratio (H / D) of the spacing (H) of the equally spaced air passages 101 to the inner diameter (D) of the exhaust port 1101 is 1.025. For example, when the radius of the first curved surface 111 is 232 mm and the radius of the second curved surface 121 is 150 mm, the spacing (H) of the equally spaced air passages 101 is 232 - 150 = 82 mm. In this case, since the ratio (H / D) of the spacing (H) of the equally spaced air passages 101 to the inner diameter (D) of the exhaust port 1101 is 1.025, the inner diameter (D) of the exhaust port 1101 can be determined to be 80 mm. In other embodiments, the radii of the first surface 111 and the second surface 121 may also be other values, but it is necessary to ensure that the ratio (H / D) of the spacing (H) of the equally spaced air passages 101 to the inner diameter (D) of the exhaust port 1101 is within the range of 0.8 to 1.3.

[0043] For example, the bottom edges of the first curved surface 111 and the second curved surface 121 are flush. It is understood that if the bottom edges of the two curved surfaces are not flush (for example, the second curved surface 121 of the crystal boat 120 is slightly higher or lower than the second curved surface 121 of the reaction tube 110), a stepped structure will be formed at the junction; when the airflow passes through this point, separation flow, re-flow, or local vortices will be generated due to the abrupt change in cross-section. These vortices will act as particle traps, disrupting the self-cleaning effect in processes such as POCl3. When the edges are flush, when the airflow enters the equally spaced air passages 101 from the main body of the reaction tube 110, the flow passages are continuously and smoothly contracted; there are no geometric abrupt changes, the fluid shear layer is stable, and turbulent pulsation is significantly suppressed. The advantage of the above configuration is that, in the top-exhaust vertical furnace structure, a "full-length, equal-section axisymmetric flow channel" is constructed from the wafer reaction zone to the exhaust port 1101, eliminating local disturbances and backflow caused by abrupt changes in the flow channel, thereby achieving true "uninterrupted laminar flow" and "zero dead-angle exhaust." In this example, the first surface 111 and the second surface 121 can be hemispherical surfaces or partially spherical surfaces.

[0044] The second curved surface 121 of the top plate 123 of the crystal boat 120 can be a smooth curved surface, which has advantages such as ease of processing and less particle adhesion. Figure 2 The diagram shown is a structural schematic of the top plate according to another embodiment of this disclosure. Figure 2 In the example, the second curved surface 121 is provided with a plurality of micro-pits 1201. The plurality of micro-pits 1201 are arranged in an array on the second curved surface 121. The plurality of micro-pits 1201 are of the same size. Those skilled in the art will understand that, firstly, when the airflow flows through the second curved surface 121 covered with micro-pits 1201, tiny stagnant vortices are formed inside the micro-pits 1201. These stagnant vortices, like ball bearings, "padded" the low-velocity boundary layer that was originally tightly attached to the wall, reducing the frictional resistance between the main fluid and the second curved surface 121. This characteristic is particularly suitable for vertical furnace processes based on liquid sources. Taking the phosphorus doping process using POCl3 liquid source as the phosphorus source as an example, if the P2O5 particles generated by the decomposition of POCl3 attempt to adhere to the wall surface, they will be thrown away by the shear force of these micro-eddies, thus failing to adhere to the second curved surface 121. Secondly, the micro-pits 1201 can artificially induce small-scale turbulence in the boundary layer. This micro-turbulence generates instantaneous high shear force, periodically "slapping" the second curved surface 121, actively peeling off the submicron-sized particles that have already adhered but are not firmly bonded. Furthermore, although POCl3 is gaseous at high temperatures, it may condense into droplets when the furnace tube is cooled or in local low-temperature areas. The micro-texture structure can change the contact angle hysteresis of the surface, preventing the droplets from spreading on the surface (preventing the formation of a liquid film), and instead causing them to rapidly aggregate into spherical droplets, which roll off and are discharged under gravity or airflow, avoiding leaving hard-to-clean "white spots" on the second curved surface 121.

[0045] Similarly, it is understandable that since the size of the micro-pits 1201 is typically on the micrometer scale, while the size of the equally spaced air channels 101 is on the millimeter scale, the micro-stagnant vortices formed by the micro-pits 1201 are limited to the vicinity of the wall of the second curved surface 121 on the crystal boat 120 and inside the pits. They are localized, small-scale flow structures, and their influence is limited to the wall boundary layer, not extending to the mainstream area of ​​the equally spaced air channels 101. Therefore, the micro-stagnant vortices do not adversely affect the overall airflow uniformity, flow direction, or airflow unobstructedness of the equally spaced air channels 101, and do not disrupt the original dead-zone-free and smooth airflow effect of the equally spaced air channels 101. Simultaneously, the micro-stagnant vortices can create localized disturbances near the second curved surface 121, inhibiting particle adhesion and deposition on the second curved surface 121, achieving a wall self-cleaning function without affecting the main airflow.

[0046] It should also be noted that Figure 2 The image shown is for illustrative purposes only. Figure 2 The sizes of the various micro-pits 1201 may differ, and their illustration does not constitute a limitation on the scope of protection of this solution.

[0047] In this embodiment, the crystal boat 120 can be a one-piece structure, which has the advantage of simple structure. However, if a part of the one-piece structure is damaged, the entire structure must be replaced, resulting in extremely high costs. Especially in diffusion deposition processes based on liquid sources, it is difficult to avoid the adhesion of thin films and particles such as deposition byproducts on the surface of the crystal boat 120, making cleaning very difficult. Therefore... Figure 3 A schematic diagram of the structure of the crystal boat is shown in another embodiment of the present disclosure. Figure 3 In the example, with Figure 1 Compared to the previous embodiment, the difference is that the crystal boat 120 is implemented as multiple, or the crystal boat 120 is a detachable split structure, which is composed of several crystal boat segments (which can also be defined as sub-crystal boats) combined vertically; the multiple crystal boats 120 are arranged vertically and detachably connected, and the top wall of the top plate 123 of the uppermost crystal boat 120 forms the second curved surface 121.

[0048] The disassembly and connection method is implemented as a plug-in connection or a flange connection; for example, one of two adjacent crystal boats 120 has a plurality of grooves arranged circumferentially and extending vertically, and the other has a protrusion arranged circumferentially for insertion into the corresponding groove. The cross-sectional shapes of the grooves and protrusions are adapted to each other and are both circular or rectangular. In other embodiments, when the cross-sectional shapes of the grooves and protrusions are both rectangular, the plugged groove and protrusion are each implemented as a single unit.

[0049] In other embodiments, in addition to the plug-in connection, two adjacent crystal boats 120 can also be connected by snap-fit ​​(e.g., made of quartz) to further enhance the connection and fixation effect between the two adjacent crystal boats 120.

[0050] It should be noted that, regardless of whether the connection is plug-in or flange-connected, a small axial gap should be reserved at the connection between the two connected crystal boats 120 so that each crystal boat 120 can expand independently without restricting each other when heated; thereby effectively releasing thermal stress, preventing the overall warping of the crystal boat 120, and ensuring the dimensional stability of long-term operation.

[0051] The advantage of the above setup is that, by disassembling and connecting multiple crystal boats 120, maintenance personnel can focus on acid washing or ultrasonic cleaning of the top crystal boat 120 (the crystal boat 120 with the second curved surface 121 formed on top) which is most heavily contaminated. Furthermore, two, three, or four sub-crystal boats can be flexibly assembled as needed to adapt to the process requirements of different batches.

[0052] exist Figure 3 In the example, each of the crystal boats 120 includes a plurality of support columns 122 arranged circumferentially, and a top plate 123 and a bottom plate 124 respectively fixedly connected to the top and bottom ends of the plurality of support columns 122 (two connected crystal boats 120 are connected top to bottom). It is understood that the top wall of the top plate 123 of the uppermost crystal boat 120 forms the second curved surface 121.

[0053] Multiple support grooves with corresponding heights are formed between multiple support pillars 122 in the same crystal boat 120 along the extension direction, and the multiple support grooves at the same height on the multiple support pillars 122 jointly support the same wafer.

[0054] In a structure where multiple wafer boats 120 can be detachably assembled, wafer boats 120 at different locations can have different weights. For example, the weight of the lower wafer boat 120 can be greater than that of the upper wafer boat 120 (e.g., by increasing the thickness of the top plate 123, bottom plate 124, and / or support column 122). This lowers the overall center of gravity of the wafer boat 120, making it more stable during rotation in the process, reducing vibration risk, improving wafer stability, and reducing particle contamination. Even when the wafer boat 120 is a single structure, its center of gravity can be lowered by increasing the weight of the bottom plate 124 and / or increasing the weight of the lower part of the support column 122 to improve stability during rotation and reduce particle contamination.

[0055] It should be noted that, Figure 3 Implementation examples can be related to Figure 2 The examples are implemented in combination.

[0056] The crystal boat 120 can be a one-piece molded structure, meaning the top plate 123 and the support column 122 are fixedly connected. While convenient to use, this requires replacement of the entire structure if any part is damaged, resulting in high operating costs. In another example, the top plate 123 is detachably mounted on the top of the crystal boat 120. For example... Figure 3 In the example, the top plate 123 of the uppermost crystal boat 120 is directly and detachably connected to the top of the plurality of support columns 122. This detachable structure helps to improve the applicability of the crystal boat 120 and reduce its usage cost. For example, the top plate 123 with different curvatures can be replaced according to the curvature of the reaction tube 110, or the top plate 123 can be removed separately for cleaning when needed without cleaning the whole thing.

[0057] For example, the bottom surface of the top plate 123 is a curved surface or a flat surface. For instance, the top plate 123 is a hemispherical shell, in which case the bottom surface of the top plate 123 is an inner wall surface adapted to the curvature of the second curved surface 121.

[0058] In other embodiments, the top plate 123 includes a detachably connected bottom plate 124 and a top cover. For example, the bottom plate 124 is the top plate 123 of the uppermost crystal boat 120, and the top cover is a hemispherical shell detachably disposed on the top wall of the top plate 123 of the uppermost crystal boat 120. Alternatively, the uppermost top plate 123 of the crystal boat 120 includes a flat plate portion and a curved portion with a second curved surface 121 located above the flat plate portion, preferably detachably connected to the flat plate portion. The flat plate portion helps improve the uniformity of the thermal field in the upper region of the crystal boat 120, while the curved portion helps improve the uniformity of the exhaust flow, thereby improving production yield. The detachable structural design allows the crystal boat 120 to be used in different equipment and / or processes, such as top exhaust or bottom exhaust.

[0059] It should be noted that the crystal boat 120 disclosed herein is applicable to various types of furnace tube equipment, but its advantages are particularly prominent when used in top-vented vertical furnace equipment. Especially in diffusion / deposition processes based on liquid sources, it will effectively improve particulate contamination and thin film deposition uniformity.

[0060] A second embodiment of this disclosure provides a vertical furnace. The vertical furnace includes a reaction tube 110 and a crystal boat 120.

[0061] The material of the reaction tube 110 depends on the process, and can be, for example, quartz, silicon carbide, etc. For example, if the vertical furnace is a phosphorus doping diffusion furnace based on a POCl3 (phosphorus oxychloride) liquid source, then the reaction tube 110 is preferably made of quartz. Those skilled in the art will understand that quartz can withstand high temperatures for extended periods, has very few impurities, and will not introduce metal or particulate contamination to the wafer. It is also very stable to commonly used diffusion gases, especially exhibiting good corrosion resistance to POCl3 and its reaction byproducts. Furthermore, it can be made into large-size, thin-walled tubes, making its overall performance suitable for wafer diffusion processes.

[0062] For example, the reaction tube 110 is arranged vertically and its top inner wall forms an upwardly convex first curved surface 111, such as a hemispherical surface.

[0063] Exemplarily, the top outer wall of the reaction tube 110 is also constructed as a curved surface. Preferably, the top outer wall of the reaction tube 110 is constructed as a hemispherical surface adapted to the curvature of the first curved surface 111. That is, the top of the reaction tube 110 is a hemispherical shell. The advantage of this configuration is that it can reduce the production cost of the reaction tube 110 and improve economic efficiency. In other embodiments, the top outer wall of the reaction tube 110 may also be constructed as a plane or a curved surface of other shapes that do not adapt to the curvature of the first curved surface 111.

[0064] When the first curved surface 111 is a hemispherical surface, the reaction tube 110 is implemented as a circular tube.

[0065] Exemplarily, the reaction tube 110 includes a receiving cavity for accommodating the crystal boat 120; the exhaust port 1101 on the first curved surface 111 is connected to an exhaust pipe 130 to discharge residual gas in the receiving cavity. The exhaust pipe 130 includes a first pipe 131 and a second pipe 132. One end of the first pipe 131 is connected to the exhaust port 1101 of the reaction tube 110, and the other end is connected to the second pipe 132. The other end of the second pipe 132 is connected to an external vacuum pump. It is understood that, under the action of the vacuum pump, the residual gas in the receiving cavity is drawn to the outside through the exhaust pipe 130 for discharge treatment and / or reuse. A heater (not shown) is provided around the outside of the reaction tube 110 to heat the inside of the reaction tube 110. The heater is usually zonal and adjustable for heating, and a housing (not shown) with heat insulation function is usually provided outside the heater. Therefore, the first pipe 131 passes through the housing to communicate with the exhaust port 1101 of the reaction tube 110. In some other examples, the first conduit 131 may be fixedly connected to the reaction tube 110 and can be regarded as part of the reaction tube 110.

[0066] For example, the vertical furnace is a phosphorus doping diffusion furnace based on a POCl3 liquid source. Those skilled in the art will understand that POCl3 decomposes at high temperatures, and during the process, in addition to doping with P atoms, it also produces a large amount of white powdery byproducts such as P2O5 and POx. These byproducts easily condense in areas with lower temperatures or stagnant airflow (such as the top of the furnace tube or the upper part of the crystal boat 120). Addressing the characteristic of POCl3 easily producing white powders such as P2O5 during high-temperature decomposition, this application utilizes curved surface geometry to eliminate the top stagnation area, combined with high-speed laminar flow exhaust to form a significant "self-cleaning" effect, blocking the condensation and fall path of byproducts directly above the wafer from the source, reducing particle transfer rate by more than 98%. Secondly, under the large-capacity process conditions of 117 bays, this structure effectively suppresses the local concentration dilution or enrichment phenomenon caused by top vortexes in traditional designs, minimizing the gas concentration deviation around the top wafer.

[0067] Those skilled in the art will understand that, since the first pipe 131 is directly connected to the exhaust port 1101, the gas it comes into contact with is at a high temperature, and POCl3 and its reaction byproducts are highly corrosive, the material of the first pipe 131 includes quartz, for example, it may be made entirely of quartz; or the interior may be made of quartz, and the exterior may be made of other materials with better mechanical strength. The second pipe 132 is made of corrosion-resistant materials such as polytetrafluoroethylene. Preferably, the first pipe 131 is at least partially embedded in the second pipe 132, and the connection between the two can be secured using flanges or other connecting components.

[0068] For example, a cooling unit (not shown in the figure) is provided on the outer periphery of the first pipe 131 to reduce the temperature of the gas inside the first pipe 131, thereby extending the service life of the first pipe 131 and the second pipe 132 and reducing the adverse effects of high temperature on surrounding components. The cooling unit cools the first pipe 131 using either air cooling or liquid cooling. For example, the cooling unit may be implemented as a cooling channel spirally wrapped around the first pipe 131, or as a cooling cavity coaxially wrapped around the first pipe 131; the coolant filled in the cooling channel or cooling cavity may be a gas or a fluid.

[0069] The first pipe 131 can be non-vertically set, or the vertical section of the exhaust pipe 130 can be as short as possible to prevent impurity particles attached to the exhaust pipe 130 from falling into the reaction pipe 110.

[0070] The phosphorus doping diffusion process based on POCl3 produces exhaust gas containing a large amount of solid byproducts such as phosphorus pentoxide and phosphosilicates, which easily adhere to the interior of the exhaust pipe 130. The condensation and accumulation of these byproducts can easily lead to blockage of the exhaust pipe 130. Therefore, the first pipe 131 can be made into a funnel-shaped opening, meaning the diameter of the first pipe 131 gradually decreases along the direction away from the exhaust port 1101. On the other hand, the exhaust gas also contains the byproduct metaphosphoric acid. During the exhaust process, as the temperature decreases, metaphosphoric acid condenses and deposits on the inner wall of the quartz tube. Prolonged contact with the quartz tube under relatively high temperatures can cause corrosion, potentially leading to breakage, perforation, and leakage. Therefore, in some embodiments of this application, the thickness of the inlet end of the first pipe 131 can be increased to reduce the risk of breakage and extend the equipment's service life. Conversely, the deposition of metaphosphoric acid decreases further away from the inlet end, allowing for a correspondingly smaller thickness to facilitate compatibility with other pipes. That is, the wall thickness of the first pipe 131 can be implemented to gradually decrease in the direction away from the exhaust port 1101, thereby reducing costs.

[0071] In other embodiments, the first conduit 131 includes a quartz material layer and a plastic material layer such as polytetrafluoroethylene located outside the quartz material layer. However, it should be noted that the inner quartz material layer is directly connected to the exhaust port 1101, while the outer material layer is disposed without contacting the exhaust port 1101. That is, the inner quartz material layer and the outer material layer are nested together without complete overlap.

[0072] In other embodiments, the second conduit 132 may also be implemented as a dual-tube conduit (the inner tube is made of quartz and the outer tube is made of polytetrafluoroethylene).

[0073] Back to Figure 1In this example, the crystal boat 120 is erected inside the reaction tube 110 and is coaxially spaced from the reaction tube 110. The advantage of this arrangement is that placing the crystal boat 120, which carries the wafers, on the central axis of the reaction tube 110 ensures that the distances between each layer of wafers on the crystal boat 120 and the wall of the reaction tube 110 are essentially the same. Combined with a radially symmetrical heater (not shown in the figure), this effectively avoids localized overcooling or overheating due to proximity to the furnace wall, thereby forming a symmetrical and stable temperature and flow field in the axial direction. The annular gap between the crystal boat 120 and the wall of the reaction tube 110 provides a bottom-up (or top-down) flow channel for the reactive gases. This avoids problems such as airflow dead zones, excessive local pressure drops, or gas "short circuits" at the edges caused by excessively small gaps, ensuring that the gas can pass through the wafer surface evenly. While ensuring the airflow channel, this design avoids contact between the crystal boat 120 and the reaction tube 110 wall, providing thermal expansion space for brittle materials such as quartz during heating and cooling, which helps to reduce thermal stress and lower the risk of equipment damage due to thermal deformation.

[0074] exist Figure 1 In this example, the reaction tube 110 is a single tube. This single-tube structure simplifies the equipment structure and reduces the cost of use and maintenance. The vertical furnace can employ various gas inlet structures, but in a preferred example, it also includes a gas supply nozzle. One end of the nozzle is connected to a gas source, and the other end is located inside the reaction tube 110, on the side of the crystal boat 120, and extends along the height of the crystal boat 120. The nozzle has multiple air jets spaced apart for spraying process gases onto the wafers on the crystal boat 120, improving gas diffusion uniformity. There can be more than one gas supply nozzle; for example, two nozzles can be symmetrically arranged on opposite sides of the crystal boat 120 to further enhance gas uniformity. Furthermore, those skilled in the art will readily understand that when using liquid sources such as POCl3, a carrier gas is needed to bring the material source into the reaction tube.

[0075] Figure 4 The diagram shown is a structural schematic of a reactor in another embodiment of this disclosure. Figure 4 In the example, with Figure 1 Compared to the previous embodiment, the difference lies in that an inner reaction tube 140, coaxial with and spaced apart from the crystal boat 120, is further provided between the reaction tube 110 and the crystal boat 120. The inner reaction tube 140 is sleeved on the outside of the crystal boat 120 and is open at the top, that is, the top opening of the inner reaction tube 140 is exposed above the crystal boat 120, and the gas supply nozzle is located between the crystal boat 120 and the inner reaction tube 140.

[0076] It should be noted that, Figure 4 The embodiments can be respectively compared with Figure 2 , Figure 3The illustrated embodiments can be implemented in combination, or they can be combined with... Figure 2 , Figure 3 The illustrated embodiments are implemented.

[0077] exist Figure 1 and Figure 4 In the example, the vertical furnace also includes an outermost furnace shell. Supported by a metal plate (e.g., stainless steel), it provides mechanical support, mounting interfaces, and overall strength and protection for the equipment. Exemplarily, an insulation layer (not shown in the figure) is provided between the furnace shell and the reaction tube 110, typically composed of refractory fibers, alumina fibers, etc., for heat insulation. Exemplarily, a heating element (not shown in the figure), such as a resistance heating wire or heating coil, is provided between the furnace shell and the insulation layer to provide heat to the furnace chamber.

[0078] In other embodiments, the vertical furnace further includes an upper heater that transmits uniform thermal radiation energy along the curved surface of the concentric structure, and a heat-resistant seal and water-cooled cooling jacket that maintains the airtightness of the vacuum pipeline joint.

[0079] In summary, this disclosure relates to the field of semiconductor manufacturing equipment technology, providing a vertical furnace and a crystal boat for the vertical furnace. The crystal boat includes multiple support columns and a top plate disposed at the top of the support columns, the top wall of the top plate having an upwardly convex second curved surface. The vertical furnace includes a vertically arranged reaction tube and the crystal boat; the inner top wall of the reaction tube has an upwardly convex first curved surface, the first curved surface having an exhaust port communicating with an exhaust pipe, the curvature of the first curved surface and the second curved surface being the same; the crystal boat is erected inside the reaction tube and is coaxially spaced from the reaction tube. This application constructs concentric, equally spaced hemispherical air channels on the top plate of the crystal boat and the top of the reaction tube, allowing the rising airflow to diffuse uniformly along the annular spacing at the top and smoothly converge towards the central exhaust port, thereby eliminating airflow dead zones and eddies while significantly reducing flow resistance and pressure pulsation, ultimately achieving stable rectification of the axisymmetric flow field inside the reaction tube, effectively ensuring the uniformity and batch consistency of the wafer process.

[0080] The above embodiments are merely illustrative of the principles and effects of this disclosure and are not intended to limit this disclosure. Any person skilled in the art can modify or alter the above embodiments without departing from the spirit and scope of this disclosure. Therefore, all equivalent modifications or alterations made by those skilled in the art without departing from the spirit and technical concept disclosed in this disclosure should still be covered by the protection scope of this disclosure.

Claims

1. A crystal boat for a vertical furnace, wherein the inner wall of the top of the vertical furnace has an upwardly convex first curved surface, and the top is provided with an exhaust port, characterized in that, The crystal boat includes multiple support columns and a top plate disposed at the top of the support columns. The top wall of the top plate has an upwardly convex second curved surface, and the curvature of the first curved surface and the second curved surface are the same.

2. The crystal boat according to claim 1, characterized in that, The ratio of the distance between the first curved surface and the second curved surface to the inner diameter of the exhaust port is 0.8 to 1.

3.

3. The crystal boat according to claim 2, characterized in that, The ratio of the distance between the first curved surface and the second curved surface to the inner diameter of the exhaust port is 1.

025.

4. The crystal boat according to claim 1, characterized in that, The second curved surface has multiple micro-dimples; and / or, the crystal boat is a split-connection structure.

5. The crystal boat according to claim 1, characterized in that, The first and second curved surfaces are both spherical cap surfaces that do not extend beyond the center of the sphere; and / or, the top plate is detachably disposed on the top of the crystal boat; and / or, the bottom surface of the top plate is a curved surface or a plane; and / or, the top plate includes a detachably connected bottom plate and a top cover.

6. A vertical furnace, characterized in that, include: A vertically arranged reaction tube has an upwardly convex first curved surface on the top inner wall of the reaction tube, and an exhaust port communicating with an exhaust pipe is opened on the first curved surface. The crystal boat as described in any one of claims 1-5 is erected inside the reaction tube and arranged coaxially and at a distance from the reaction tube.

7. The vertical furnace according to claim 6, characterized in that, The vertical furnace is a phosphorus doping diffusion furnace based on a POCl3 liquid source; and / or, the crystal boat and reaction tube are made of quartz.

8. The vertical furnace according to claim 6, characterized in that, The reaction tube is a single tube, and the vertical furnace also includes a gas supply nozzle. One end of the gas supply nozzle is connected to a gas source, and the other end is located inside the reaction tube and on the side of the crystal boat, extending along the height of the crystal boat. The gas supply nozzle is provided with multiple air jets at intervals for spraying process gases onto the wafers on the crystal boat.

9. The vertical furnace according to claim 6, characterized in that, The exhaust pipeline includes a first pipeline and a second pipeline. One end of the first pipeline is connected to the exhaust port of the reaction tube, and the other end is connected to the second pipeline. The other end of the second pipeline is connected to a vacuum pump. The first pipeline is made of quartz, and the second pipeline is made of polytetrafluoroethylene. The first pipeline is at least partially embedded in the second pipeline.

10. The vertical furnace according to claim 9, characterized in that, A cooling unit is provided on the outer periphery of the first pipeline, and the wall thickness of the first pipeline gradually decreases in the direction away from the exhaust port.

Images