Anti-deposition furnace cover and vertical process furnace

Abstract

The present invention discloses an anti-deposition furnace cover and a vertical process furnace, wherein the anti-deposition furnace cover is used as the furnace cover of the vertical process furnace, and the anti-deposition furnace cover comprises a cover body and an electric heating element built in the cover body, and a temperature measuring device installed on the cover body, so as to control the temperature of the upper end surface of the furnace cover at the furnace mouth in a closed loop. The anti-deposition furnace cover according to the present invention is not easy to accumulate reactants on the part of the upper surface of the furnace cover exposed in the furnace chamber.

Description

Technical Field

[0001] The invention relates to a furnace cover equipped for a semiconductor vertical process furnace, and also relates to a vertical process furnace equipped with the furnace cover. Background Art

[0002] The process of making chips from wafers requires very complex techniques and numerous steps. The chip manufacturing process often involves many chemical vapor deposition (CVD) steps. In some of these low-pressure hot wall systems (the process temperature is relatively high, but the furnace chamber is generally negative pressure to accurately control the amount and partial pressure of the reaction gas), the reaction often covers the entire reaction zone in the furnace chamber, and the reactants can easily remain on the inner wall of the reaction chamber. The reactants accumulated on the inner wall need to be cleaned frequently to avoid contaminating, for example, the wafer.

[0003] It should be known that for a vertical furnace, the position of the furnace cover is prone to accumulation of reactants. After long-term research, it was found that the reaction zone of a vertical furnace is often located relatively in the middle and upper part, and the temperature of the lower part of the furnace cavity is generally relatively low, and is generally shielded by, for example, a crucible holder, a quartz boat, etc., making the temperature of the lower part of the vertical furnace cavity relatively low. In addition, due to the high temperature of the upper part and the low temperature of the lower part, heat convection is also suppressed under this condition. Therefore, accordingly, the temperature of the furnace cover is lower than the temperature of the lower part of the furnace cavity. This should be the reason why the upper end surface of the furnace cover (the end surface located in the furnace cavity) exposed in the furnace cavity is prone to accumulation of reactants. Summary of the invention

[0004] The object of the present invention is to provide an anti-deposition furnace cover which is not prone to reactant accumulation on the portion of the upper surface of the furnace cover exposed in the furnace chamber. The present invention also provides a vertical process furnace equipped with the anti-deposition furnace cover.

[0005] According to a first aspect of an embodiment of the present invention, an anti-deposition furnace cover is provided, which is used as the furnace cover of a vertical process furnace. The anti-deposition furnace cover includes a cover body and an electric heating element built into the cover body, and a temperature measuring device installed on the cover body to control the temperature of the upper end surface of the furnace cover at the furnace mouth in a closed loop.

[0006] The above anti-deposition furnace cover, optionally, the upper end surface of the cover body is formed with an upper groove, and the projection of the corresponding furnace port on the upper end surface of the cover body is located in the upper groove; The electric heating element is located in the upper groove; An upper cover is also provided which is buckled into the upper groove to shield the electric heating element and conduct heat. The upper cover is fixedly connected to the cover body.

[0007] Optionally, the connection between the upper cover and the cover body is a screw connection.

[0008] Optionally, the upper end surface of the upper cover is flush with the upper end surface of the cover body.

[0009] Optionally, a cooling chamber is provided below the electrothermal heating element so that the temperature of the portion of the cover exposed from the furnace body is lower than a preset value; The distance between the cooling cavity and the electric heating element is not less than one third of the thickness of the cover body.

[0010] Optionally, the cooling chamber is configured as: In the first configuration, the cooling chamber is constructed on the cover; In the second configuration, the cooling chamber is a cooling element fixed to the cover; or The third configuration provides a lower cover, and a water channel groove is formed on the cover body and / or the lower cover, and the lower cover is buckled on the cover body to form a water channel.

[0011] Optionally, in the third configuration, the water channel is a spiral line starting from the center of the cover body; The water inlet of the water channel is located at the center of the cover body, and the water outlet is located at the end of the spiral water channel.

[0012] Optionally, a heat insulation layer is provided between the cooling cavity and the electric heating element.

[0013] Optionally, the lower cover and the cover body are fixedly connected by welding; Correspondingly, the heat insulation layer is located in the upper groove, and an inner ring groove is formed at the bottom periphery of the upper groove, and the outer edge of the heat insulation layer extends into the inner ring groove.

[0014] According to a second aspect of an embodiment of the present invention, a vertical process furnace is provided, comprising the anti-deposition furnace cover according to the first aspect of the embodiment of the present invention.

[0015] According to the furnace cover of the embodiment of the present invention, the furnace cover is heated by a built-in electric heating element, so that the portion of the upper surface of the furnace cover exposed in the furnace cavity maintains a predetermined temperature. Under the predetermined temperature condition, the deposition of reactants on the portion of the upper surface of the furnace cover exposed in the furnace cavity can be reduced, which is a new technical route for preventing the deposition of reactants on the furnace cover. And through experiments, it is found that the temperature that needs to be maintained on the portion of the upper surface of the furnace cover exposed in the furnace cavity does not need to be very high. In most CVD processes, the temperature of the inner surface of the furnace cover is maintained at 200°C to 300°C to effectively reduce the deposition of reactants on the furnace cover, and due to the influence of the temperature field of the reaction zone, the heat required for additional heating is not high, that is, the power consumption is low, that is, the cost of reducing the deposition of reactants on the furnace cover is not high. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 Schematic diagram of the top view of the anti-deposition furnace cover in one embodiment.

[0017] Figure 2 for Figure 1 BB cross-sectional view.

[0018] Figure 3 for Figure 2 Enlarged view of part I.

[0019] Figure 4 for Figure 2 Enlarged view of Part II.

[0020] Figure 5 It is a schematic diagram of the main cross-sectional structure of an anti-deposition furnace cover in another embodiment.

[0021] In the figure: 1. cover body, 2. O-ring, 3. dovetail groove, 4. hexagon head screw, 5. upper cover, 6. thermocouple, 7. upper insulating layer, 8. electric heating element, 9. lower insulating layer, 10. lower cover, 11. water inlet, 12. water channel, 13. water outlet, 14. spring washer, 15. weld, 16. insulation layer. DETAILED DESCRIPTION

[0022] To help clearly understand the anti-deposition principle of the anti-deposition furnace cover in the embodiment of the present invention, the following first describes the relevant parts of the vertical process furnace. The typical feature of the vertical process furnace is that the axis of the furnace body is roughly vertical, and the corresponding furnace chamber is obviously vertical.

[0023] The heating method of the vertical process furnace is mainly electric heating. Generally, an electric heating wire is arranged on the inner wall or wall of the furnace body to form a heating device. The main part of the heating device on the furnace body is located in the middle and upper part of the furnace body. In more applications, the lower part of the furnace body is not provided with a heating device.

[0024] It should be understood that thermal convection is a common form of heat exchange, which relies on the property of thermal expansion and contraction of fluids, that is, the density of hot fluids is generally relatively small, while the density of the same cold fluids is relatively large. Therefore, when the hot fluid is located at the bottom of a furnace chamber, for example, it will float up due to its relatively small density, while the cold fluid will sink due to its relatively large density, thus forming thermal convection.

[0025] For vertical process furnaces, the influence of heat convection should be reduced as much as possible. Therefore, when heating, heating is often carried out in the middle and upper part instead of the bottom, which is helpful to suppress heat convection. Under this condition, the temperature at the bottom of the furnace chamber is relatively low.

[0026] At the same time, since, for example, wafers need to be carried by, for example, a quartz boat, and the quartz boat needs a supporting component to support it, and in some implementations, the supporting component that supports the quartz boat should also have the ability to rotate. Under this condition, the quartz boat and the supporting component that are involved in the furnace chamber will produce axial shielding, thereby reducing the heating of the lower space by the heat radiation (the second heat exchange method) in the middle and upper parts.

[0027] Regarding the third heat exchange method, heat conduction, firstly, the thermal conductivity of the gas itself is relatively biased, which is one of the reasons why it will produce heat convection, that is, it is difficult for heat to be transferred to the bottom of the furnace cavity through the thermal conductivity of the gas. Secondly, for the metal support shaft that supports the aforementioned supporting components, although its thermal conductivity is good, its effect on heating the lower part of the furnace cavity is relatively limited.

[0028] Based on the above manifestations of heat exchange in the vertical process furnace, the temperature of the furnace cover of the vertical process furnace is relatively low. The inventors found that reactants are more likely to deposit on relatively cold surfaces, which is also the main reason why reactants are easily deposited on the surface of the current furnace cover.

[0029] At the same time, although the three heat exchange methods have little effect on the lower part of the furnace chamber, they will still have an impact. In other words, the lower part of the furnace chamber will still have a certain temperature. Under this condition, the energy consumed by heating the furnace cover is actually not high.

[0030] The inventor believes that reducing the deposition of reactants on the furnace cover mainly considers two factors. The first factor is to reduce the deposition of reactants on the upper surface of the furnace cover exposed in the furnace cavity by heating the furnace cover itself. The second factor is to reduce the influence of heat convection when heating the furnace cover as much as possible. Combining the two factors, it is necessary to heat the furnace cover, but it is not advisable to make its temperature too high.

[0031] As mentioned above, after long-term experiments, it is found that heating the furnace cover, specifically the inner surface of the furnace cover to 200°C to 300°C can effectively inhibit the deposition of reactants on the upper surface of the furnace cover. Although the inhibition effect is better when the temperature of the inner surface is higher, more intense heat convection will be generated, which will destroy the temperature field of the reaction zone. Therefore, in the embodiment of the present invention, the heating of the furnace cover requires stricter temperature control so that the temperature of its upper surface is maintained at 200°C to 300°C.

[0032] Accordingly, it is obvious that the anti-deposition furnace cover according to the embodiment of the present invention is mainly used as the furnace cover of a vertical process furnace. By utilizing the aforementioned characteristics of the vertical process furnace and performing limited heating on the furnace cover, the impact on the temperature field of the reaction zone can be minimized while satisfying the condition of preventing the deposition of reactants.

[0033] Correspondingly, firstly, an electric heating element 8 needs to be arranged in the cover body 1 of the anti-deposition furnace cover, and at the same time, a temperature measuring device needs to be adapted and installed on the cover body 1, such as Figure 2 The thermocouple 6 shown in the figure can control the temperature of the portion of the upper end surface of the furnace cover exposed to the furnace chamber in a closed loop manner.

[0034] The covering area of ​​the cover 1 is obviously larger than the furnace mouth. Figure 2 The position where the O-ring 2 is provided is the position radially beyond the furnace mouth and combined with the lower end surface of the furnace body. Obviously, the part where the reactants can be deposited is the part exposed in the furnace cavity after the furnace cover is combined with the furnace body, which is a part of the upper surface of the furnace cover.

[0035] exist Figure 4 As can be seen, an O-ring 2 (full name: O-ring, referred to as O-ring) is provided on the upper surface of the furnace cover for sealing after the furnace cover is combined with the furnace port. The O-ring 2 is preferably a rubber sealing ring because, as mentioned above, even if the furnace cover is heated, it is mainly used to ensure that the temperature of the portion of the upper surface of the furnace cover exposed in the furnace cavity is within a predetermined range, such as 200°C to 300°C, and the temperature of its periphery is lower than this temperature.

[0036] Regarding the selection of rubber seals, high temperature resistant rubber seals should be selected, mainly silicone rubber seals with working temperatures up to 260°C and fluorinated rubber seals with working temperatures up to 250°C. If the peripheral temperature control is relatively good, you can also choose ethylene propylene rubber seals with working temperatures up to 150°C and polyurethane seals with working temperatures up to 120°C.

[0037] exist Figure 2~Figure 4 In the illustrated structure, a cooling structure is also provided on the furnace cover, which is mainly used to ensure that the outer surface temperature of the furnace cover is lower than the burning temperature of a person. Under this condition, the temperature of the furnace cover area where the O-ring 2 is set can also be relatively low, thereby increasing the material selection range of the O-ring 2.

[0038] The electrothermal element 8, also known as an electric heating element, an electric heating element, etc., is an element or device that converts electrical energy into thermal energy. Its heating power is generally adjustable. Therefore, in the embodiment of the present invention, the temperature of the upper surface of the furnace cover can be controlled by controlling its heating power.

[0039] Regarding the electric heating element 8, first of all, from the perspective of shape, it mainly includes metal tubular, quartz tubular, ceramic tubular, plate-shaped, square, round, and ceramic-coated electric heating elements. In the embodiment of the present invention, sheet or wire-shaped electric heating elements are preferably used to facilitate the layout of the distribution range of the heating wire according to the range to be heated, so that the temperature of the upper surface of the part of the furnace cover exposed in the furnace cavity can be relatively uniform.

[0040] Wire-shaped or sheet-shaped electric heating elements are mainly metal electric heating elements, such as nickel-chromium wire, iron-chromium-aluminum wire, nickel-iron wire, nickel-copper wire, etc.

[0041] In an embodiment of the present invention, a sheet-like nickel-copper electric heating element is used to form a plurality of equally spaced concentric circles or concentric regular polygon structures in a predetermined area on the upper surface of the furnace cover, so that the upper surface of the furnace cover exposed to the furnace cavity is heated relatively evenly.

[0042] It should be known that no matter how evenly the electric heating elements are distributed, it is difficult to ensure that the temperature of the area directly heated is uniform. Therefore, in an embodiment of the present invention, an upper cover 10 is constructed, and through the transition of the upper cover 10, the temperature of the portion of the upper surface of the furnace cover exposed to the furnace cavity is relatively uniform.

[0043] Furthermore, an upper groove is formed on the upper end surface of the cover body 1, and the projection of the corresponding furnace mouth on the upper end surface of the cover body 1 is located in the upper groove. Under this condition, when the furnace body is closed, the part of the cover body 1 exposed in the furnace body is all located in the area where the upper groove is located.

[0044] Furthermore, the electric heating element 6 is arranged in the upper groove; an upper cover 5 is provided which is buckled into the upper groove to shield the electric heating element 6 and conduct heat, and the upper cover 5 is fixedly connected to the cover body 1.

[0045] As is common sense, the furnace body is generally a rotating body, specifically, the main body of the furnace body is cylindrical, the upper end is sealed, specifically in the shape of a barrel, the furnace mouth faces downward, and is sealed by a furnace cover. Obviously, the seal between the furnace cover and the furnace body is a detachable connection. The basic shape of the furnace cover is also a rotating body, so that it appears in a top-down state. Figure 1 The state shown in , that is, the overall is a circular furnace cover.

[0046] Correspondingly, the upper cover 5 is located in the upper groove, and is positioned by the upper groove while also shielding the upper groove. At the same time, the diameter of the upper cover 5 is larger than the diameter of the furnace mouth. In other words, under the condition that the coaxiality between the upper cover 5 and the furnace body is relatively good, the upper cover 5 can completely seal the furnace mouth. Under this condition, part of the upper surface of the upper cover 5 is exposed in the furnace cavity.

[0047] Accordingly, under the condition that the upper cover 5 is large enough, a gap may be left between the upper cover 5 and the groove wall of the upper groove to facilitate disassembly and assembly.

[0048] In addition, Figure 2In the illustrated structure, the upper surface of the upper cover 5 is substantially flush with the upper surface of the cover body 1. In some embodiments, the lower end of the upper cover 5 may have a flange, the diameter of the flange is substantially equal to the diameter of the upper groove, and the diameter of the upper cover 5 body is substantially equal to the diameter of the furnace opening, so that the upper cover 5 can be inserted into the furnace opening, but the upper surface of the flange part is coplanar with the upper surface of the cover body 1. In this case, the part to be prevented from deposition is the upper surface of the upper cover 5. With the flange, the upper cover 5 body can protrude from the upper surface of the cover body 1, which is conducive to the assembly of the upper cover 5 on the cover body 1.

[0049] Regarding the fixing method of the upper cover 5, a detachable connection is preferred. Figure 1 and Figure 2 In the illustrated structure, the upper cover 5 is assembled on the cover body 1 by means of the hexagonal head screws 4 shown in the figure, so that the upper cover 5 can be easily disassembled and cleaned.

[0050] At the same time, considering the service life of the electric heating element 8, convenient replacement of the electric heating element 8 should be a factor to be considered, and a detachable connection between the upper cover 5 and the cover body 1 is even more necessary.

[0051] In addition, regarding the electric heating element 8, it has an insulating layer in some implementations, but some do not have an insulating layer and need to be equipped with an insulating layer, especially an electric heating wire or sheet. Figure 2 and Figure 3 In the illustrated structure, an upper insulating layer 7 is provided on the upper side of the electrothermal heating element 8, and a lower insulating layer 9 is provided on the lower side. However, the main body of the furnace cover is made of metal material in relatively many applications, and sufficient insulation needs to be considered.

[0052] In addition, regarding temperature measurement, Figure 1 In the embodiment, a measuring hole for measuring temperature is opened on the cover body 1 of the furnace cover. The side hole is a blind hole in the figure. A thermocouple 6 is provided. The measuring head of the thermocouple 6 is embedded in the measuring hole. Figure 2 It can be seen that the measuring hole is located at the periphery of the upper groove to avoid direct contact between the thermocouple 6 and the electric heating element 8. The purpose of using the blind hole is also to avoid direct contact between the measuring head and the process gas in the furnace chamber. By configuring it at the periphery of the upper groove, the measuring head is slightly above the position of the electric heating element 8, and the temperature is measured by using the good thermal conductivity of the metal material. It is an indirect temperature measurement method. It should be known that the temperature measurement result is not much different from the actual temperature value of the part of the furnace cover exposed in the furnace chamber, and is positively correlated, so it is easy to infer the temperature value of the part of the furnace cover exposed in the furnace chamber.

[0053] As mentioned above, the purpose of providing the electric heating element 8 is to make the temperature of the upper surface of the furnace cover exposed in the furnace cavity be 200°C~300°C, which is enough to burn human skin. Therefore, in a more preferred embodiment, a cooling chamber is also provided below the electric heating element 8 to make the temperature of the portion of the cover body 1 exposed from the furnace body lower than a preset value to avoid burns to the operator.

[0054] Accordingly, in order to reduce mutual interference, the distance between the cooling cavity and the electrothermal heating element 8 is not less than one third of the thickness of the cover body 1 .

[0055] In a more preferred embodiment, in order to reduce mutual interference, a heat insulation layer is further provided between the cooling cavity and the electric heating element 8, such as Figure 5 The insulation layer 16 shown in FIG.

[0056] from Figure 5 It can be seen that the coverage of the heat-insulating layer 16 used as the heat-insulating layer is larger than that of the upper cover 5, but it should be known that the heat-insulating material is generally a flexible material, such as asbestos, etc., which can be cut into a circle and its edge can be embedded into the bottom of the upper groove by utilizing its flexibility.

[0057] More specifically, a ring groove is machined at the bottom of the upper groove by a milling cutter, and the edge of the circular piece, such as an asbestos sheet, can be embedded in the ring groove to form positioning and limiting, and then the assembly consisting of the insulating layer and the electric heating element 8 is placed in the groove and then sealed with an upper cover.

[0058] Regarding the configuration of the cooling cavity, a relatively compact configuration method is to directly construct the cooling cavity on the cover body 1. This method is relatively difficult to construct. Generally, the water channel 12 is constructed by drilling. After the drilling is completed, the redundant holes need to be sealed with, for example, screw plugs, but the structure is relatively compact. This is the first configuration.

[0059] The second configuration is to directly install, for example, a heat exchange device on the furnace cover. This method has a relatively low heat exchange efficiency, but is relatively easy to process.

[0060] The third method is Figure 2 and Figure 5 In the method shown in the figure, a milling cutter can be used to process a groove structure, and then the lower cover 10 is used to cover the groove to form a water channel 12. This method has low processing difficulty and relatively good heat exchange effect, because the main body of the water channel 12 is directly constructed from the cover body 1, and does not involve the problem of heat transfer between different components.

[0061] The water channel 12 may also be partially constructed on the lower cover 10 , and a complete water channel 12 is formed by matching a partial water channel groove located on the lower cover 10 with a partial water channel groove located on the cover body 1 .

[0062] As for the connection method between the lower cover 10 and the cover body 1, welding is preferably used.

[0063] Regarding the shape of the water channel 12, it is mainly adapted to the third configuration. The other two configurations are extremely difficult to process under this water channel shape, but it is easy to achieve in the third configuration, mainly using a milling cutter for processing. The shape of the water channel 12 is a spiral line starting from the center of the cover body 1; it is similar to a coil as a whole.

[0064] Accordingly, if Figure 2 As shown, the water inlet of the water channel 12 is located at the center of the cover body 1, and the water outlet 13 is located at the end of the spiral water channel.

[0065] exist Figure 2 and Figure 5 In the structure shown, a lower groove is formed on the lower surface of the cover body 1, and the lower groove is used to accommodate the lower sealing cover 5 so that the outer contour of the furnace cover is relatively flat.

Claims

1. An anti-deposition furnace cover, used as a furnace cover of a vertical process furnace, characterized in that: The anti-deposition furnace cover comprises a cover body, an electric heating element built in the cover body, and a temperature measuring device installed on the cover body, so as to control the temperature of the upper end surface of the furnace cover at the furnace mouth in a closed loop.

2. The anti-deposition furnace cover according to claim 1, characterized in that: An upper groove is formed on the upper end surface of the cover body, and the projection of the corresponding furnace opening on the upper end surface of the cover body is located in the upper groove; The electric heating element is located in the upper groove; An upper cover is also provided which is buckled into the upper groove to shield the electric heating element and conduct heat. The upper cover is fixedly connected to the cover body.

3. The anti-deposition furnace cover according to claim 1, characterized in that: The connection between the upper cover and the cover body is a screw connection.

4. The anti-deposition furnace cover according to claim 2 or 3, characterized in that: The upper end surface of the upper cover is flush with the upper end surface of the cover body.

5. The anti-deposition furnace cover according to any one of claims 1 to 3, characterized in that: A cooling chamber is also provided below the electrothermal heating element so that the temperature of the portion of the cover body exposed from the furnace body is lower than a preset value; The distance between the cooling cavity and the electric heating element is not less than one third of the thickness of the cover body.

6. The anti-deposition furnace cover according to claim 5, characterized in that: The cooling chamber is configured as follows: In the first configuration, the cooling chamber is constructed on the cover; In the second configuration, the cooling chamber is a cooling element fixed to the cover; or The third configuration provides a lower cover, and a water channel groove is formed on the cover body and / or the lower cover, and the lower cover is buckled on the cover body to form a water channel.

7. The anti-deposition furnace cover according to claim 6, characterized in that: In the third configuration, the water channel is a spiral line starting from the center of the cover body; The water inlet of the water channel is located at the center of the cover body, and the water outlet is located at the end of the spiral water channel.

8. The anti-deposition furnace cover according to claim 6, characterized in that: A heat insulation layer is arranged between the cooling cavity and the electric heating element.

9. The anti-deposition furnace cover according to claim 8, characterized in that: The fixed connection between the lower cover and the cover body is welding; Correspondingly, the heat insulation layer is located in the upper groove, and an inner ring groove is formed at the bottom periphery of the upper groove, and the outer edge of the heat insulation layer extends into the inner ring groove.

10. A vertical process furnace, characterized in that: It comprises the anti-deposition furnace cover as described in any one of claims 1 to 9.

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