Large-size ultrathin ceramic uniform sintering equipment and sintering process

Abstract

The invention is suitable for the technical field of ceramic sintering, and provides uniform sintering equipment and a sintering process for large-size ultrathin ceramic. The large-size ultra-thin ceramic uniform sintering equipment comprises a heating assembly and a sintering assembly, wherein the heating assembly is used for uniformly radiating heat in the heating assembly; the at least one burning tray is arranged in the heating assembly; the upper surface of the burning tray is a plane and is used for bearing workpieces, and the center thickness of the lower surface is smaller than the edge thickness. The burning tray is thick in edge and thin in the middle, the temperature correspondence of the burning tray is improved, and the temperature difference on the horizontal plane of a workpiece is reduced.

Description

Technical Field

[0001] The invention belongs to the technical field of ceramic sintering, and in particular relates to a large-size ultra-thin ceramic uniform sintering device and a sintering process. Background Art

[0002] In the semiconductor production process, the transfer of chips requires the use of components such as wafer boats, chucks, and suction cups. These parts are usually thin-walled parts. For example, the thickness of the suction cup is about 5mm. Such parts are easily warped and deformed due to the influence of the plane temperature difference during the firing process. With the development of industrial technology, the size of wafers has grown from 6 inches and 8 inches to 12 inches, and the size of existing suction cups and other components will also become larger. The higher the plane temperature difference requirement during the sintering process, the lower the product qualification rate. For example, for a workpiece with a diameter greater than 400mm (thickness of 5mm), the horizontal temperature difference is required to be no more than 3°C.

[0003] In the past, ceramic sintering equipment was usually a vertical structure. After the tubular cage-type heating element was powered on and heated, it heated the components in the form of radiation. However, due to the small radiation area of ​​the heating element, the components could not be radiated evenly, and a temperature difference would be formed on the horizontal plane, which was not conducive to production. Summary of the invention

[0004] The purpose of the embodiment of the present invention is to provide a large-sized ultra-thin ceramic uniform sintering device, aiming to solve the problem of uneven sintering of large-sized ultra-thin ceramics.

[0005] The embodiment of the present invention is implemented as follows: a large-sized ultra-thin ceramic uniform sintering device, the large-sized ultra-thin ceramic uniform sintering device comprising:

[0006] Heat generating components, used to radiate heat evenly inside;

[0007] At least one firing tray is arranged inside the heating component; the upper surface of the firing tray is flat and used to carry the workpiece, and the center thickness of the lower surface is smaller than the edge thickness.

[0008] Furthermore, the heating component comprises:

[0009] The crucible has the sintering tray arranged inside.

[0010] A plurality of heating elements are arranged around the crucible.

[0011] Furthermore, an upper cover is provided on the top of the crucible, and a lower cover is provided on the bottom; a first air flow channel is provided in the circumferential direction of the crucible, a first air vent is provided on the lower cover, a second air vent is provided on the upper cover, and a radial second air flow channel is provided inside; the second air vent is connected to the second air flow channel, the second air flow channel is connected to the first air flow channel, and the first air flow channel is connected to the first air vent.

[0012] Furthermore, the large-size ultra-thin ceramic uniform sintering equipment also includes an insulation layer and a furnace shell, the insulation layer wraps the heat-generating component, the furnace shell wraps the insulation layer, and the first vent and the second vent pass through the insulation layer and the furnace shell.

[0013] Furthermore, the large-size ultra-thin ceramic uniform sintering equipment also includes a vacuum system for extracting air between the insulation layer and the furnace shell.

[0014] Furthermore, the crucible material is an isotropic material.

[0015] Furthermore, the profile of the lower surface of the support plate is a natural logarithmic function curve.

[0016] Furthermore, the method for determining the thickness of the outer circle of the support plate is as follows: determine the amount of heat that needs to be transferred based on maintaining the maximum temperature difference of the support plate at no more than 3°C, select a suitable temperature difference between the support plate and the crucible, and calculate the outer circumferential area of ​​the support plate required to transfer the corresponding heat based on the radiation law formula, and then determine its height.

[0017] Furthermore, the large-size ultra-thin ceramic uniform sintering equipment also includes a control system, and thermocouples are arranged on the outer surface of the crucible and the center of the workpiece; the control system is used to control the heat generation of the heating element, and control the temperature difference between the crucible surface and the center of the workpiece, the temperature difference of the crucible itself, the designed temperature difference between the crucible and the firing plate, and the temperature difference between the heating element and the outer surface of the crucible within a preset range.

[0018] Another object of the embodiment of the present invention is to provide a large-size ultra-thin ceramic uniform sintering process, which is applied to the large-size ultra-thin ceramic uniform sintering device, and the large-size ultra-thin ceramic uniform sintering process specifically includes the following steps:

[0019] Select the sintering plate according to the product to be sintered;

[0020] Air is extracted through the vacuum system so that the heating components are isolated by vacuum;

[0021] According to the characteristics of the workpiece and the sintering plate, select the heating program and keep the temperature to sinter;

[0022] After sintering is completed, the airflow is controlled so that the airflow passes through the first airflow channel of the crucible in the heating component from top to bottom or from bottom to top.

[0023] The embodiment of the present invention provides a large-size ultra-thin ceramic uniform sintering device. The workpiece is placed on a sintering plate. During the sintering process, heat is transferred from the outer diameter to the center. According to the laws of thermodynamics, the sintering plate must have a high external temperature and a low internal temperature during the heating process; during the cooling process, the internal temperature must be high and the external temperature must be low. This phenomenon will cause deviations in the uniformity of the workpiece temperature and lead to product sintering failure. Therefore, the sintering plate of the present invention is thick at the edge and thin in the middle, which improves the temperature responsiveness of the sintering plate and reduces the temperature difference on the horizontal surface of the workpiece. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 A cross-sectional view of a large-size ultra-thin ceramic uniform sintering device in the first embodiment;

[0025] Figure 2 for Figure 1 Partial view of center A;

[0026] Figure 3 A cross-sectional view of the crucible in the first embodiment;

[0027] Figure 4 A transverse cross-sectional view of the upper cover in the first embodiment;

[0028] Figure 5 A transverse cross-sectional view of the crucible in the first embodiment;

[0029] Figure 6 A structural diagram of the workpiece and the sintering plate in the first embodiment;

[0030] Figure 7 FIG. 4 is a flow chart of a uniform sintering process for large-sized ultra-thin ceramics in a second embodiment.

[0031] Reference numerals:

[0032] 100, heating component; 110, crucible; 120, heating element; 130, upper cover; 140, lower cover; 150, first air flow channel; 160, first vent; 170, second vent; 180, second air flow channel;

[0033] 200, firing tray;

[0034] 300, insulation layer;

[0035] 400, furnace shell;

[0036] 500. Vacuum system;

[0037] 600, Thermocouple;

[0038] 700. Workpiece. DETAILED DESCRIPTION

[0039] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0040] It can be understood that the terms "first", "second", etc. used in the present application can be used in this article to describe various elements, but unless otherwise specified, these elements are not limited by these terms. These terms are only used to distinguish the first element from another element.

[0041] like Figure 1 As shown, in the first embodiment, a large-sized ultra-thin ceramic uniform sintering device is provided, and the large-sized ultra-thin ceramic uniform sintering device comprises:

[0042] The heating component 100 is used to radiate heat evenly inside;

[0043] At least one receiving tray 200 is disposed inside the heating component 100 ; the upper surface of the receiving tray 200 is flat and used to carry the workpiece 700 , and the center thickness of the lower surface is smaller than the edge thickness.

[0044] In this embodiment, it should be noted that "large size" and "ultra-thin" are relative technical terms. For example, a workpiece with a diameter greater than 400 mm and a thickness of 5 mm can be called a large-size ultra-thin workpiece. This embodiment can be applied to the precision sintering of large-size ultra-thin ceramics, which are mainly used in precision ceramics in the semiconductor manufacturing process, such as electrostatic chucks, wafer chucks and other fields; it is also applicable to other fields with strict deformation requirements during the ceramic sintering process; it can also be used for the production and manufacturing of large-size ultra-thin alumina, silicon carbide, silicon nitride and their composite ceramics to obtain products with small deformation, high flatness, uniformity and density, and then used in subsequent process production processes.

[0045] In this embodiment, the number of the sintering tray 200 is not less than one; when there are multiple sintering trays 200, the sintering trays 200 are stacked in multiple layers, and a workpiece 700 can be placed on each sintering tray 200. The sintering tray 200 can be made of an isotropic high thermal conductivity material (graphite, silicon carbide, aluminum nitride, etc.), and is designed with a specific configuration to support the sintered workpiece 700 so that its heat can be quickly transferred.

[0046] The workpiece 700 of this embodiment is placed on the sintering tray 200, and heat is transferred from the outer diameter to the center. According to the laws of thermodynamics, the sintering tray 200 must have a high external temperature and a low internal temperature during the heating process; and a high internal temperature and a low external temperature during the cooling process. This phenomenon will cause the temperature uniformity of the workpiece 700 to deviate, resulting in product sintering failure. Therefore, this embodiment optimizes the thickness of different positions of the sintering tray 200, and the overall shape is thin in the middle and thick at the edge, thereby improving the temperature responsiveness of the sintering tray 200, improving the thermal conductivity of the sintering tray 200, and thereby reducing the temperature difference on the horizontal plane of the workpiece 700.

[0047] In the first embodiment, if Figure 2 and 3 As shown, the structure of the heating component 100 is specifically optimized, and the heating component 100 includes:

[0048] The crucible 110 has the sintering tray 200 disposed therein.

[0049] A plurality of heating elements 120 are disposed around the crucible 110 .

[0050] In this optimization scheme, the heating element 120 is columnar, with a diameter of not less than 30 mm, the spacing between the heating elements 120 is not more than 150 mm, and the spacing between the heating element 120 and the crucible 110 is not less than 50 mm, so that after the heat generated by the heating element 120 is radiated to the surface of the crucible 110, the temperature difference with the outer surface of the crucible 110 body is not more than 0.5°C. The heating element 120 is made of high-purity graphite and has a tubular cage structure or a cylindrical structure as a whole.

[0051] The crucible 110 is made of high thermal conductivity graphite material, with a thin-wall structure and a thickness of no more than 30 mm. In order to prevent the heating element 120 from directly radiating the surface of the workpiece 700, causing the temperature difference of the workpiece 700 to increase, a crucible 110 is added between the heating element 120 and the workpiece 700. The heat of the heating element 120 is first radiated to the crucible 110 and quickly transferred, so that the temperature of the crucible 110 is uniform. The crucible 110 with a low temperature difference wraps the entire workpiece 700, and the heat radiation can form a uniform scattering, so that the workpiece 700 can be heated evenly. In order to reduce the temperature non-uniformity caused by the transfer of heat in the crucible 110, the material of the crucible 110 should be an isotropic material, such as isostatic graphite. The thickness of the crucible 110 is determined based on the heat required to maintain a stable temperature difference (3°C) when the sintering plate 200 is heated or cooled, and the internal and external temperature difference is kept at more than 0.5°C (this temperature can be adjusted according to the control progress). The thickness of the crucible 110 needs to be reduced as much as possible while meeting the process conditions, with the maximum thickness not exceeding 30 mm, so as to reduce thermal inertia, increase the temperature response rate of heating control, and reduce the risk of temperature overshoot.

[0052] In the first embodiment, if Figure 2-5 As shown, the structure of the crucible 110 is specifically optimized. The top of the crucible 110 is provided with an upper cover 130, and the bottom is provided with a lower cover 140; the crucible 110 is provided with a first air flow channel 150 in the circumferential direction, the lower cover 140 is provided with a first vent 160, the upper cover 130 is provided with a second vent 170, and radial second air flow channels 180 are provided inside; the second vent 170 is connected to the second air flow channel 180, the second air flow channel 180 is connected to the first air flow channel 150, and the first air flow channel 150 is connected to the first vent 160.

[0053] In this optimization scheme, the crucible 110 is made of isotropic material, and the thickness is specifically designed according to the properties of the sintered workpiece 700 and the sintering tray 200. The crucible 110 is provided with a first air flow channel 150 parallel to the axis in the circumferential direction, and an upper cover 130 is provided on the top. A second vent 170 is provided at the center of the upper cover 130. The upper cover 130 is provided with a radial second air flow channel 180, and the second air flow channel 180 corresponds to the first air flow channel 150 of the crucible 110. The size of the second air flow channel 180 of the upper cover 130 is optimized according to numerical simulation so that the flow rate of each hole is consistent. The bottom of the crucible 110 is provided with a lower cover 140, and the lower cover 140 is provided with a first vent 160 corresponding to the first air flow channel 150 of the crucible 110. The first air flow channel 150 is collected at the center and discharged through the pipeline. In the fast cooling stage, the gas enters through the second vent 170 at the top, disperses into the crucible 110, and then flows out through the bottom; similarly, the gas can also enter the crucible 110 through the first vent 160 at the bottom, disperse into the crucible 110, and then flows out through the top. Through the careful design of the number of flow channels and the hole diameter, the temperature of the crucible 110 itself can be evenly cooled on the same horizontal plane, thereby avoiding the influence of the external environment of the crucible 110 on the crucible 110, and the uneven temperature distribution leads to inconsistent temperature of the internal sintering plate 200.

[0054] In the first embodiment, if Figure 1 As shown, the structure of the large-sized ultra-thin ceramic uniform sintering equipment is specifically optimized. The large-sized ultra-thin ceramic uniform sintering equipment also includes a thermal insulation layer 300 and a furnace shell 400, wherein the thermal insulation layer 300 wraps the heating component 100, and the furnace shell 400 wraps the thermal insulation layer 300, and the first vent 160 and the second vent 170 pass through the thermal insulation layer 300 and the furnace shell 400. The large-sized ultra-thin ceramic uniform sintering equipment also includes a vacuum system 500 for extracting air between the thermal insulation layer 300 and the furnace shell 400.

[0055] In this optimization scheme, the insulation layer 300 is made of high-purity, low-thermal-conductivity carbon fiber insulation material. The furnace shell 400 is made of stainless steel to construct a closed environment required for production. The vacuum system 500 consists of a mechanical pump, a booster pump, a diffusion pump, a maintenance pump (increase or decrease as needed) and corresponding pipeline valves to construct and maintain the vacuum environment of the equipment.

[0056] In the first embodiment, if Figure 6 As shown, the structure of the support plate 200 is specifically optimized. The profile of the lower surface of the support plate 200 is a natural logarithmic function curve. The method for determining the outer circle thickness of the support plate 200 is: determine the amount of heat to be transferred based on keeping the maximum temperature difference of the support plate 200 not exceeding 3°C, select a suitable temperature difference between the support plate 200 and the crucible 110, and calculate the outer circumference area of ​​the support plate 200 required to transfer the corresponding heat according to the radiation law formula, and then determine its height.

[0057] In this optimization scheme, the upper surface of the sintering tray 200 is flat for carrying the workpiece 700; the lower surface is thin in the center and thick at the edge, and its profile is related to the thermal conductivity, specific heat, and density of the fired workpiece 700 and the sintering tray 200, and is similar to the curve of the natural logarithmic function. By design, the temperature difference between the center and the outer circle of the sintering tray 200 does not exceed 3°C; the outer circle thickness of the sintering tray 200 is determined according to radiation calculation.

[0058] In the first embodiment, the structure of the large-sized ultra-thin ceramic uniform sintering equipment is specifically optimized. The large-sized ultra-thin ceramic uniform sintering equipment also includes a control system, and a thermocouple 600 is provided on the outer surface of the crucible 110 and the center of the workpiece 700; the control system is used to control the heating of the heating element 120, and control the temperature difference between the surface of the crucible 110 and the center of the workpiece 700, the temperature difference of the crucible 110 itself, the design temperature difference between the crucible 110 and the sintering plate 200, and the temperature difference between the heating element 120 and the outer surface of the crucible 110 within a preset range.

[0059] In this optimization scheme, thermocouples 600 are provided on the outer surface of the crucible 110 and at the center of the workpiece 700, and the control process needs to meet the following requirements: the temperature difference between the outer surface temperature and the center temperature of the crucible 110 does not exceed the allowable temperature difference of the workpiece 700, the design temperature difference between the crucible 110 and the sintering plate 200 (determined by material properties and radiation heat transfer) and the temperature difference of the crucible 110 itself; it is not greater than 3.5°C + the design temperature difference between the crucible 110 and the sintering plate 200; the temperature difference between the heating element 120 and the outer surface of the crucible 110 is determined; under radiation conditions, the heating rate does not exceed 0.5°C / min, and the heat transferred is equal to the heat required for the workpiece to maintain the design temperature difference.

[0060] The various optimized features of the above-mentioned first embodiment can be combined arbitrarily. In order to make the description concise, not all possible combinations of the technical features in the above-mentioned embodiment are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0061] like Figure 7 As shown, in the second embodiment, a large-size ultra-thin ceramic uniform sintering process is proposed, and the large-size ultra-thin ceramic uniform sintering process is applied to the large-size ultra-thin ceramic uniform sintering device described in the first embodiment, and the large-size ultra-thin ceramic uniform sintering process specifically includes the following steps S1 to S4:

[0062] Step S1, selecting the sintering plate 200 according to the sintered product.

[0063] In this embodiment, the thermal conductivity, specific heat, density, and bottom profile shape of the support plate 200 can be selected so that the temperature difference between the center and the outer circle of the support plate 200 does not exceed 3° C. through design.

[0064] In step S2, air is extracted through the vacuum system 500 so that the heating component 100 is isolated by vacuum.

[0065] In this embodiment, the initial vacuum environment component of the equipment is completed by the vacuum system 500, and the vacuum environment of the equipment during the process is maintained by the maintenance pump.

[0066] Step S3, according to the characteristics of the workpiece 700 and the sintering plate 200, a heating program is selected and sintering is performed at a constant temperature.

[0067] In this embodiment, the corresponding sintering process program is selected, and the heating program is started to complete the heating and heat preservation sintering. At this time, the heat is transferred from the outside to the inside. The heating program needs to be selected according to the characteristics of the workpiece 700 itself and the sintering plate 200.

[0068] Step S4, after sintering is completed, the airflow is controlled so that the airflow passes through the first air flow channel 150 of the crucible 110 in the heating component 100 from top to bottom or from bottom to top.

[0069] In this embodiment, according to the characteristics of the sintering tray 200, before 500°C, the corresponding cooling program is selected, and the system controls the cooling. After 500°C, the airflow is controlled to enter the channel of the crucible 110 evenly for rapid cooling. The airflow flows in the second vent 170, the second air flow channel 180, the first air flow channel 150 and the first vent 160 in sequence; the airflow direction can also be reversed in sequence. Therefore, this embodiment designs the structural design of the sintering tray 200 for uniform sintering of large-sized ultra-thin ceramics, the heating strategy and the uniform cooling strategy to reduce the temperature difference on the horizontal plane of the workpiece and improve the sintering quality.

[0070] The above-mentioned embodiments only express several implementation methods of the present invention, and the description thereof is relatively specific and detailed, but it cannot be understood as limiting the scope of the patent of the present invention. It should be pointed out that, for ordinary technicians in this field, several variations and improvements can be made without departing from the concept of the present invention, which all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be subject to the attached claims.

Claims

1. A large-size ultra-thin ceramic uniform sintering device, characterized in that: The large-size ultra-thin ceramic uniform sintering equipment comprises: Heat generating components, used to radiate heat evenly inside; At least one firing tray is arranged inside the heating component; the upper surface of the firing tray is flat and used to carry the workpiece, and the center thickness of the lower surface is smaller than the edge thickness.

2. The large-size ultra-thin ceramic uniform sintering equipment according to claim 1 is characterized in that: The heating component comprises: The crucible has the sintering tray arranged inside. A plurality of heating elements are arranged around the crucible.

3. The large-size ultra-thin ceramic uniform sintering equipment according to claim 2 is characterized in that: The crucible is provided with an upper cover on the top and a lower cover on the bottom; the crucible is provided with a first air flow channel in the circumferential direction, the lower cover is provided with a first air vent, the upper cover is provided with a second air vent, and radial second air flow channels are provided inside; the second air vent is connected to the second air flow channel, the second air flow channel is connected to the first air flow channel, and the first air flow channel is connected to the first air vent.

4. The large-size ultra-thin ceramic uniform sintering equipment according to claim 3 is characterized in that: The large-size ultra-thin ceramic uniform sintering equipment also includes a thermal insulation layer and a furnace shell, the thermal insulation layer wraps the heat-generating component, the furnace shell wraps the thermal insulation layer, and the first vent and the second vent pass through the thermal insulation layer and the furnace shell.

5. The large-size ultra-thin ceramic uniform sintering equipment according to claim 4 is characterized in that: The large-size ultra-thin ceramic uniform sintering equipment also includes a vacuum system for extracting air between the thermal insulation layer and the furnace shell.

6. The large-size ultra-thin ceramic uniform sintering equipment according to claim 2 is characterized in that: The crucible material is an isotropic material.

7. The large-size ultra-thin ceramic uniform sintering equipment according to claim 1 is characterized in that: The profile of the lower surface of the support plate is a natural logarithmic function curve.

8. The large-size ultra-thin ceramic uniform sintering equipment according to claim 7 is characterized in that: The method for determining the thickness of the outer circle of the support plate is as follows: determine the amount of heat that needs to be transferred based on keeping the maximum temperature difference of the support plate no more than 3°C, select a suitable temperature difference between the support plate and the crucible, and calculate the outer circumferential area of ​​the support plate required to transfer the corresponding heat based on the radiation law formula, and then determine its height.

9. The large-size ultra-thin ceramic uniform sintering equipment according to claim 1 is characterized in that: The large-size ultra-thin ceramic uniform sintering equipment also includes a control system, and thermocouples are arranged on the outer surface of the crucible and the center of the workpiece; the control system is used to control the heat generation of the heating element, and control the temperature difference between the crucible surface and the center of the workpiece, the temperature difference of the crucible itself, the designed temperature difference between the crucible and the firing plate, and the temperature difference between the heating element and the outer surface of the crucible within a preset range.

10. A large-size ultra-thin ceramic uniform sintering process, characterized in that: The large-size ultra-thin ceramic uniform sintering process is applied to the large-size ultra-thin ceramic uniform sintering device according to any one of claims 1 to 9, and the large-size ultra-thin ceramic uniform sintering process specifically comprises the following steps: Select the sintering plate according to the product to be sintered; Air is extracted through the vacuum system so that the heating components are isolated by vacuum; According to the characteristics of the workpiece and the sintering plate, select the heating program and keep the temperature to sinter; After sintering is completed, the airflow is controlled so that the airflow passes through the first airflow channel of the crucible in the heating component from top to bottom or from bottom to top.

Images