Heaters for wafer processing apparatus and methods for manufacturing thereof, and plasma processing apparatus

Abstract

This invention discloses a heater structure and a heater manufacturing method. The heater of this invention utilizes a cyclical process of heating layer formation and heating layer polishing steps during manufacturing, repeating this process multiple times until a heating layer of the target thickness is formed. During the repeated polishing and formation steps, the pores on the upper surface of the heating layer are filled. Ultimately, the heating layer manufactured by this method has significant advantages such as high surface flatness and fewer internal pores and cracks. This results in uniform heating of the final heater, and the upwardly conducted heat is also evenly distributed across the entire heater plane. Finally, this leads to a controllable and uniform temperature on the focusing ring above the heater, improving the uniformity of wafer processing.

Description

[Technical Field]

[0001] This invention relates to the field of semiconductor fabrication technology, and in particular to a heater structure for a wafer processing apparatus and its manufacturing method, which achieves uniform temperature control of the annular component surrounding the wafer to be processed. [Previous Technology]

[0002] The integrated circuit manufacturing field requires a large number of wafer processing equipment to perform various processes on wafers. Some of these processes require precise temperature control, especially the temperature of the focusing ring surrounding the wafer, which is one of the key factors affecting the process effect. As shown in Figure 1, a plasma processing device includes a cavity 1, a support base 4 at the bottom of the cavity 1, an assembly plate 5 on the support base 4, and a wafer base 6 fixed above the assembly plate 5. The base 6 typically includes a coolant channel and an electrostatic chuck located at the top of the base 6 for electrostatic adsorption of the wafer to be processed and for temperature control of the wafer. The space 40 in the central area of ​​the support base 4 allows the pipelines for RF cables, coolant, and auxiliary gas to be connected upwards to the assembly plate 5. The base 6 and the assembly plate 5 are surrounded by an insulating ring 10 and a conductive shielding ring 9 to isolate the RF electric field. The outer periphery of the base 6 includes a shoulder, on which a coupling ring 82 is disposed. Above the coupling ring 82 is a heater 8, and above the heater 8 is a focusing ring 7, wherein the focusing ring 7 surrounds the wafer to be processed disposed above the base 6. Inside the reaction chamber 1, opposite to the base 6, there is also a reaction gas supply plate 2, which is connected to an external gas source through at least one gas supply pipe 3.

[0003] In order to control the temperature of the focusing ring 7, a heater needs to be set below the focusing ring 7. Chinese patent CN218783000U, filed by the same applicant, discloses the structure of the heater. It sets thermal pads with different thermal conductivity above and below the heater to improve the distribution of heat conduction in the vertical direction of the heater. However, this structure cannot improve the uneven heat distribution in the horizontal direction of the plane where the heater is located.

[0004] During plasma processing of the wafer on the substrate 6, the horizontal temperature distribution on the focusing ring 7 has a significant impact on the wafer processing effect. Areas with lower temperatures on the focusing ring 7 will result in a large amount of polymer deposition, while areas with higher temperatures will result in less surrounding polymer. Therefore, uneven temperature distribution will affect the electric field distribution of the focusing ring 7, thus affecting the surrounding plasma distribution. In addition, uneven polymer distribution around the focusing ring will also lead to uneven gas composition and gas flow distribution in the wafer edge area. The combination of these factors will result in the plasma processing result being significantly affected by the temperature distribution on the focusing ring 7. However, the heater 8 in the prior art is usually made by screen printing. First, the fluid material is printed onto the substrate, and then cured at high temperature to form a heating wire with a corresponding pattern. This manufacturing process will result in a very uneven film thickness after the heating wire is cured, and the heating wire will also contain a large number of unevenly distributed bubbles and microcracks. Plasma processing operates in a near-vacuum environment, where heat transfer is solely through contact conduction. Uneven heating wire thickness and the presence of bubbles or cracks result in highly uneven heat conduction pathways between the upper surface of the heating wire and the lower surface of the focusing ring 7. Furthermore, the heating wire itself exhibits uneven heating. Areas with thicker heating wires experience greater heat conduction, leading to higher temperatures in the focusing ring 7, while areas with thinner heating wires show weaker heat conduction and lower temperatures. The temperature difference between these two regions can typically reach tens of degrees Celsius or even higher, an unacceptable gap for the uniformity requirements of wafer processing. Therefore, the industry urgently needs a thin-film heater capable of uniformly heating the focusing ring to improve wafer processing uniformity. [Summary of the Invention]

[0005] The purpose of this invention is to provide a heater for a wafer processing apparatus, comprising: a substrate, a first insulating layer disposed on the substrate, and a heating layer thereon; the heating layer comprising a plurality of sub-heating layers defined by a plurality of interface layers parallel to the upper surface of the substrate, the plurality of sub-heating layers being stacked vertically to form the heating layer, wherein the porosity at the interface layers is less than that in the remaining areas. The heating layer has a flat lower surface and an upper surface, the roughness Ra of the upper surface and the lower surface being less than 0.8, thereby ensuring that the heat transferred upward by the heater of this invention is stable and uniformly distributed.

[0006] Optionally, a second insulating layer is further provided above the heater, wherein the thickness of the first insulating layer and the second insulating layer is less than the thickness of the heating layer.

[0007] Optionally, the thickness of each sub-heating layer is less than or equal to 12 micrometers and greater than 6 micrometers.

[0008] The heating layer of the heater includes one of lead oxide, ruthenium oxide, silicon oxide, and aluminum oxide.

[0009] The present invention also provides a plasma processing apparatus, comprising a base for supporting a wafer to be processed, the outer periphery of the base including a shoulder, a coupling ring having a coupling ring having a focusing ring having a focusing ring surrounding the wafer to be processed, wherein a groove is provided between the coupling ring and the focusing ring for mounting the aforementioned heater, the upper and lower surfaces of the heater being in close contact with the lower surface of the focusing ring and the upper surface of the coupling ring through respective thermally conductive pads, the thermally conductive pads having gaps between the groove sidewalls of the coupling ring and the focusing ring to form an expansion space for the thermally conductive pads. The groove extends upward from the bottom surface of the focusing ring into the focusing ring, such that the heater and at least one thermally conductive pad are located above the bottom surface of the focusing ring.

[0010] The present invention also provides a method for manufacturing a heater, comprising: providing a substrate having an insulating layer thereon, and further comprising the steps of: a heating layer forming step, printing a heating layer paste onto the insulating layer, and heating and curing the heating layer paste to form a solid heating layer having a first thickness; a heating layer polishing step, polishing a portion of the material layer on the upper surface of the heating layer, retaining a heating layer having a second thickness; repeatedly alternating between the heating layer forming step and the heating layer polishing step until a heating layer having a target thickness is formed; forming an interface layer on the upper surface of the heating layer with the second thickness retained in the repeated heating layer polishing steps, wherein the porosity at the interface layer is less than that in the remaining areas.

[0011] Optionally, the second thickness is less than 12 micrometers.

[0012] Wherein the above manufacturing method, the number of alternating cycles is greater than 3, so that the heater has a thickness of 50 micrometers or more. Optionally, in the multiple alternating cycles, the second thickness in the polishing step of the last alternating cycle is less than 20% of the first thickness, and in the intermediate multiple alternating cycles, the second thickness is greater than 30% but less than 60% of the first thickness, so that the pore density of the topmost of the multiple sub-heating layers is less than the pore density of the intermediate multiple sub-heating layers.

Implementation Method

[0014] The following describes in further detail a heater for a wafer processing apparatus, its manufacturing method, and a plasma processing apparatus proposed in this invention, in conjunction with the accompanying drawings and specific embodiments. The advantages and features of this invention will become clearer from the following description. It should be noted that the drawings are in a very simplified form and use non-precise proportions, used only to facilitate and clearly illustrate the embodiments of this invention. Please refer to the drawings to make the objectives, features, and advantages of this invention more apparent and understandable. It should be understood that the structures, proportions, sizes, etc., depicted in the accompanying drawings are only for the purpose of assisting those skilled in the art in understanding and reading the content disclosed in the specification, and are not intended to limit the implementation conditions of this invention. Therefore, they have no substantial technical significance. Any modifications to the structure, changes in the proportional relationships, or adjustments to the size, without affecting the effects and objectives achieved by this invention, should still fall within the scope of the technical content disclosed in this invention.

[0015] Figure 2 shows a partial enlarged view of the plasma processing device of the present invention. Its basic structure is similar to the plasma processor shown in Figure 1. A thermally conductive pad 81 is included above the coupling ring 82, and the heater 8 is placed on the thermally conductive pad 81. The heater 8 is in close contact with part of the lower surface of the focusing ring 7 through another thermally conductive pad. The thermally conductive pads above and below the heater 8 effectively heat the focusing ring or conduct the heat on the focusing ring downward to the coupling ring 82 and the base 6. An upper insulating ring 84 and a cover ring 83 covering the upper insulating ring 84 are also provided around the coupling ring 82. The cover ring is usually made of quartz to resist the corrosion of the plasma above. In the present invention, the lower surface of the focusing ring 7 has a groove, so that the heater 8 and the upper thermally conductive pad are located in the groove of the focusing ring 7, reducing the heat conduction distance from the heater 8 to the upper surface of the focusing ring 7 and reducing the thermal resistance. Furthermore, the thermal pads are typically made of silicone. During heating, the thermal pads expand. At room temperature, the thermal pads of this invention can have gaps between themselves and the inner and outer side walls of the groove on the upper surface of the coupling ring 82. Similarly, the thermal pad above the heater 8 also has gaps between itself and the inner and outer side walls of the groove below the focusing ring 7. During the plasma processing, the thermal pads expand to fill the grooves, preventing the heater 8 from being squeezed, deformed, or displaced. The aforementioned gaps also prevent the focusing ring 7 from misaligning with the coupling ring 82 due to compression. Any deformation or misalignment would cause a rapid change in the temperature of the upper surface of the focusing ring.

[0016] Figures 3a to 3e show schematic diagrams of the material layers on the heater during the manufacturing process of the heater of the present invention. Firstly, a flat annular substrate 80 is provided. To improve thermal conductivity, the substrate 80 can be made of materials with high thermal and electrical conductivity, such as aluminum nitride, which are also resistant to high temperatures and corrosion. An insulating layer 80D1 is first coated on the substrate 80. The coating method can be to first coat a slurry, then cure it at high temperature to form a glass glaze, and then polish it to make the upper surface of the insulating layer 80D1 flat (Ra < 0.6). Then, multiple layer-by-layer screen printing is performed on the upper surface of the insulating layer 80D1 to form a heating wire layer with sufficient thickness and sufficient uniformity. The method for forming a multi-layer heating wire is described in detail below:

[0017] First, the paste used to form the heating wire layer is printed on the insulating layer 80D1, and then cured at high temperature to form a material layer structure as shown in Figure 3a. The material layer C1 has an initial average thickness of D1 (e.g., 0.02 mm). During the high-temperature curing process, the material layer shrinks and deforms, resulting in uneven undulations on the upper surface. At the same time, the material layer C1 includes a large number of unevenly distributed pores and cracks (not shown in the figure). Some pores Pu are located near the top surface of the material layer, some pores Pm are located at the middle height of the material layer C1, and some pores Pb are located near the bottom of the material layer C1. The paste can be made by dissolving and stirring conductive metal particles (gold, silver) and resistive material particles (lead oxide, ruthenium oxide, silicon oxide, aluminum oxide, etc.) with liquid. Then, the paste is coated onto the flat surface of the insulating layer according to the required heating wire pattern.

[0018] Then, the material layer C1 is smoothed by grinding, removing a certain thickness of the surface material layer, so that the heater forms a material layer structure as shown in Figure 3b, where the thickness of the remaining effective material layer after the upper material layer is ground off is D2 (approximately 0.01 mm). The upper pores Pu are removed as the material layer is ground, most of the middle pores Pm have through holes exposed on the upper surface, and the bottom pores Pb remain in the material layer C1'. The surface roughness of the material layer C1' after grinding is significantly reduced, and the Ra profile arithmetic mean deviation is approximately 0.4. As long as the Ra value is less than 0.8, it can basically meet the temperature uniformity requirements of this invention.

[0019] Then, the above cycle of screen printing-heat curing-smoothing is repeated to form the material layer structures shown in Figures 3c to 3e. As shown in Figure 3c, after the heater material layer is coated again to form a new heating layer C2, the slurry flowing during the screen printing stage fills the pores Pm with exposed surface pores, thus eliminating these pores. As shown in Figure 3d, after the heating layer C2 is polished, layer C2' is formed. Layer C2' is then covered by a new coating layer to form the effective material layer L2 (the top pores are filled). As shown in Figure 3e, a new material layer C3 is formed on the effective material layer L2. After polishing and a new coating layer, the material layer C3 can form the effective material layer L3. Therefore, in the material layer structure diagram shown in Figure 3e, only 2 and 1 remaining pores remain in the last effective material layers L1 and L2. Compared with the two material layers C1 and heating layer C2 when they were just heated and cured before polishing, the number of pores is greatly reduced. At the same time, the cracks in the material layers are also filled and disappear. Therefore, the heater resistance wire has a more uniform resistance distribution.

[0020] The pores in Figures 3a to 3e above are only examples. In actual manufacturing, the pores have different sizes. For smaller pores, the effect on the resistance distribution is very small and can be ignored. For larger pores, since the present invention is more likely to open a through hole in the large pore during the polishing process, it is unlikely that large pores will exist after the polishing-coating cycle of the present invention.

[0021] After multiple cycles of screen printing, heating and curing, and sanding, the heating layer 80H shown in Figure 4 is formed. The heating layer 80H includes multiple effective material layers L1 to L4 stacked together. The total thickness of the heating layer 80H can be selected according to the design requirements of the heating wire resistivity. When a large heating power is required, a thicker heating wire is needed, and vice versa. Therefore, the number of stacked layers in this invention is related to the design thickness. Thus, the number of stacked layers in this invention is not limited to the above-mentioned 4 layers, but can also be 5 layers or more. As long as there are 3 or more layers, the purpose of this invention can be achieved. In addition, an insulating layer 80D2 can be further provided above the heating layer 80H. The insulating layer 80D2 can be formed by the same processing method as the insulating layer 80D1. The multiple effective material layers L1 to L4 in this invention have at least three processing interfaces formed during the processing. At the interface height, especially below the interface, there are basically no pores, forming a pore-free or sparsely pored area. There are residual pores in other depth areas, but these pores are usually very small and do not affect the overall resistance distribution of the heating wire. Since both the material layer C1 and the heating layer C2 of this invention require multiple coating and polishing processes, the smaller the remaining thickness D2 of the material layer after each polishing, the more pores are eliminated, and the smaller the volume of the remaining pores. However, manufacturing the same thickness heating layer 80H requires more cycles of processing, resulting in excessively high costs. Therefore, it is preferable to select a remaining thickness D2 that is 30-60% of the original thickness D1.

[0022] In another embodiment of the present invention, as shown in FIG5, during the first coating of the heating layer, the material layer thickness D2 retained after the first grinding is less than 20%, which can further eliminate the pores of the bottom heating layer. Then, in subsequent cycles, grinding is performed to retain a larger thickness (30-60%), which can quickly form a heating layer of sufficient thickness. In the grinding step of the last cycle, only the thickness D2 is retained to be less than 20%. The number of pores in the top sub-heating layer L40 and the bottom sub-heating layer L10 of the heater produced by this method is much smaller than that in the multi-layer sub-heating layers in the middle region. This further reduces the non-uniformity of heat conduction upward and downward by the heater. In particular, the uniformity of the top sub-heating layer has a more direct impact on the heating effect of the upper focusing ring 7.

[0023] Through the heater processing described in this invention, a heating layer 80H with flat upper and lower surfaces is obtained. At the same time, the upper and lower insulating layers 80D1 and 80D2 also have flat surfaces, and the thickness of the insulating layers 80D1 and 80D2 is much smaller than the thickness of the heating layer 80H, so that the insulating layers 80D1 and 80D2 will not block the upward and downward heat conduction of the heater.

[0024] This invention discloses a cycle of heating layer formation and heating layer polishing steps, repeated multiple times until a heating layer with a target thickness is formed. Ultimately, the heating layer manufactured by the method of this invention has obvious advantages such as high surface flatness and fewer internal pores and cracks. This makes the final heater 8 itself heat up evenly, and the heat conducted upward is also evenly distributed on the entire heater plane. Ultimately, the focusing ring 7 above the heater has a controllable and uniform temperature, improving the uniformity of the wafer processing effect.

[0025] Although the present invention has been described in detail through the above preferred embodiments, it should be understood that the above description should not be considered as a limitation of the present invention. Various modifications and substitutions to the present invention will be apparent to those skilled in the art after reading the above content. Therefore, the scope of protection of the present invention should be defined by the appended claims. [Simplified Explanation of the Diagram]

[0013] Figure 1 is a schematic diagram of a plasma processor structure in the prior art; Figure 2 is a partially enlarged schematic diagram of a plasma processor of the present invention; Figures 3a to 3e are schematic diagrams of the material layer on the heater during the heater processing of the present invention; Figure 4 is a schematic diagram of the material layer after the heater processing of the present invention is completed; Figure 5 is a schematic diagram of the material layer after the heater processing of another embodiment of the present invention is completed.

Claims

1. A heater for a wafer processing apparatus, comprising: A substrate, wherein a first insulating layer is disposed on the substrate, and a heating layer is disposed on the first insulating layer; the heating layer includes a plurality of sub-heating layers divided by a plurality of interface layers parallel to the upper surface of the substrate, the plurality of sub-heating layers being stacked one on top of the other to form the heating layer, wherein the porosity at the interface layer is less than that in the other areas; the heating layer has a flat lower surface and an upper surface, wherein the roughness Ra of the upper surface and the lower surface is less than 0.

8.

2. The heater for a wafer processing apparatus as described in claim 1, wherein, The heater also includes a second insulating layer above it, and the thickness of the first insulating layer and the second insulating layer is less than the thickness of the heating layer.

3. The heater for a wafer processing apparatus as described in claim 1, wherein, The heating layer includes one of lead oxide, ruthenium oxide, silicon oxide, and aluminum oxide.

4. The heater for a wafer processing apparatus as described in claim 1, wherein, The thickness of each sub-heating layer is less than or equal to 12 micrometers and greater than 6 micrometers.

5. A plasma treatment apparatus, comprising: A base for supporting a wafer to be processed, the base having a shoulder on its outer periphery, a coupling ring having a focusing ring on the coupling ring, the focusing ring surrounding the wafer to be processed, a groove between the coupling ring and the focusing ring for mounting a heater for a wafer processing apparatus as described in any one of claims 1 to 4, the upper and lower surfaces of the heater being in close contact with the lower surface of the focusing ring and the upper surface of the coupling ring via respective thermally conductive pads, the thermally conductive pads having gaps between the sidewalls of the groove between the coupling ring and the focusing ring to form an expansion space for the thermally conductive pads.

6. The plasma treatment apparatus as claimed in claim 5, wherein, The groove extends upward from the bottom surface of the focusing ring into the focusing ring, such that the heater and at least one of the thermal pads are located above the bottom surface of the focusing ring.

7. A method for manufacturing a heater, comprising: A substrate is provided, the substrate having an insulating layer, and the method further includes the steps of: a heating layer forming step, wherein a heating layer paste is printed onto the insulating layer, and the heating layer paste is heated and cured to form a solid heating layer having a first thickness; a heating layer polishing step, wherein a portion of the material layer on the upper surface of the solid heating layer is polished, leaving a heating layer having a second thickness; the heating layer forming step and the heating layer polishing step are performed alternately multiple times until a heating layer having a target thickness is formed; an interface layer is formed on the upper surface of the heating layer with the second thickness remaining in the multiple heating layer polishing steps, the porosity at the interface layer being lower than that of the remaining areas.

8. The method for manufacturing a heater as described in claim 7, wherein, The second thickness is less than 12 micrometers.

9. The method for manufacturing a heater as described in claim 7, wherein, The alternating cycles are repeated more than three times, resulting in a heater with a thickness of 50 micrometers or more.

10. The method for manufacturing a heater as described in claim 7, wherein, The interface layer is parallel to the upper surface of the substrate.

11. The method for manufacturing a heater as described in claim 7, wherein, In the multiple alternating cycles, the second thickness is less than 20% of the first thickness in the polishing step of the last alternating cycle, and the second thickness is greater than 30% but less than 60% of the first thickness in the middle multiple alternating cycles, so that the pore density of the topmost of the multiple sub-heating layers is less than the pore density of the middle multiple sub-heating layers.

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