Lower electrode assembly and plasma processing device

Abstract

The invention provides a lower electrode assembly and plasma processing equipment, belongs to the field of semiconductor processing equipment, and aims to solve the problem of part damage caused by partial discharge of a lower electrode. The dielectric ring surrounds the base, and a gap is formed between the inner side of the dielectric ring and the base; the focusing ring is located above the dielectric ring, and the focusing ring comprises an inner ring area close to the substrate and an outer ring area away from the substrate; the insertion ring is located above the dielectric ring and located between the inner ring area and the base, and the insertion ring is made of a dielectric material; and the upper surface of the inner ring area is lower than the upper surface of the insertion ring, and the inner ring area is used for performing plasma treatment on the surface of the substrate.

Description

Technical Field

[0001] The present invention relates to the technical field of plasma etching, and particularly to a plasma processing technology field for preventing the lower electrode assembly from generating arcs under high radio frequency power. Background Art

[0002] Microfabrication of semiconductor substrates or wafers is a well-known technology and can be used to manufacture, for example, semiconductors, flat panel displays, light emitting diodes (LEDs), solar cells, etc. An important step in microfabrication manufacturing is the plasma processing step, which is carried out inside a reaction chamber into which process gases are introduced. A radio frequency source is inductively and / or capacitively coupled to the inside of the reaction chamber to excite the process gases to form and maintain a plasma. Inside the reaction chamber, the exposed substrate is supported by a lower electrode assembly and fixed in a fixed position by a certain clamping force to ensure the safety of the substrate during the process and a high qualification rate of processing.

[0003] The lower electrode assembly not only includes an electrostatic chuck for fixing the substrate and a base for supporting the electrostatic chuck, but also includes an edge ring assembly disposed around the base. During the process of processing the substrate, the lower electrode assembly is not only used to support and fix the substrate, but also used to control the temperature, electric field distribution, etc. of the substrate.

[0004] In the prior art, the commonly used material for the base is aluminum, and the material of the dielectric ring surrounding the periphery of the base is usually a ceramic material. Since the thermal expansion coefficients of the two are quite different, in order to ensure that the base works within a large temperature range, a certain space needs to be provided between the dielectric ring and the base to accommodate the thermal expansion and contraction of the base.

[0005] As the processing accuracy of the substrate becomes higher and higher, the radio frequency power applied to the reaction chamber becomes larger. High radio frequency power is very likely to generate arc discharges in the narrow space inside the reaction chamber, damaging the base and its peripheral components, and seriously threatening the stability and safety of the operation of the lower electrode assembly. Therefore, a solution is urgently needed to meet the requirements of continuously increasing radio frequency applied power and substrate processing uniformity. Summary of the Invention

[0006] In order to solve the technical problem that the lower electrode assembly is prone to generate undesired discharges and damage the substrate, the present invention provides a lower electrode assembly for carrying a substrate, including:

[0007] A base;

[0008] A dielectric ring surrounding the base, with a gap between the inner side of the dielectric ring and the base;

[0009] A focusing ring located above the dielectric ring, the focusing ring including an inner ring region close to the substrate and an outer ring region far from the substrate;

[0010] An insertion ring, which is located above the dielectric ring and between the inner ring region and the base, and the insertion ring is made of dielectric material; and

[0011] The upper surface of the inner ring region is lower than the upper surface of the insertion ring.

[0012] Optionally, at least a part of the upper surface of the insertion ring is located below the substrate.

[0013] Optionally, the range of the vertical distance between the upper surface of the insertion ring and the lower surface of the substrate is: 0.1 mm - 0.3 mm.

[0014] Optionally, the inner ring region is located below the outside of the edge of the substrate.

[0015] Optionally, the vertical distance between the upper surface of the inner ring region and the lower surface of the substrate is greater than 0.4 mm.

[0016] Optionally, at least a part of the upper surface of the inner ring region is located below the substrate.

[0017] Optionally, the vertical distance between the inner ring region and the lower surface of the substrate is greater than 0.8 mm.

[0018] Optionally, the upper surface of the outer ring region is higher than the upper surface of the inner ring region.

[0019] Optionally, the vertical distance between the upper surface of the inner ring region and the upper surface of the insertion ring is greater than 0.1 mm.

[0020] Optionally, the inner side of the insertion ring and the base are integrally processed and provided.

[0021] Optionally, the materials of the dielectric ring and the insertion ring include one or two of aluminum nitride and aluminum oxide.

[0022] Optionally, the material of the focusing ring includes one or two of silicon and silicon nitride.

[0023] Optionally, there is a gap between the inner side of the insertion ring and the base.

[0024] Optionally, the range of the radial width ratio between the inner ring region and the outer ring region is: 1 / 11 - 1 / 5.

[0025] Furthermore, the present invention also provides a plasma processing device, including:

[0026] A reaction chamber;

[0027] A gas shower head located on the upper side inside the reaction chamber for introducing reaction gas;

[0028] A lower electrode assembly as described in any one of claims 1-14 located on the lower side inside the reaction cavity;

[0029] A high-frequency RF power supply, electrically connected to the lower electrode assembly, for exciting reaction gas to form plasma for processing the substrate.

[0030] Optionally, the power range of the high-frequency RF power supply is: 5kW - 50kW, and the frequency range is: 16MHz - 120MHz.

[0031] At least one of the above technical solutions has the following advantages or beneficial effects: The present invention provides a lower electrode assembly and a plasma processing device. By setting the insertion ring, the dielectric constant between the focusing ring and the adjacent area of the base is increased, preventing discharge between the focusing ring and the upper part of the base. The distance between the insertion ring and the lower surface of the substrate is reduced, making it more difficult for the products in the reaction space to enter the space between the dielectric ring and the base through the gap between the insertion ring and the back surface of the substrate, thereby preventing discharge caused by polymer accumulation. At the same time, the inner ring area of the focusing ring is lower than the upper surface of the insertion ring, increasing the distance between the focusing ring and the adjacent area of the substrate, further reducing the discharge risk between the focusing ring and the edge of the substrate, comprehensively and effectively ensuring the safe use of the lower electrode assembly. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or in the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the following drawings are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0033] Figure 1 A partial structural schematic diagram of a lower electrode assembly showing one embodiment;

[0034] Figure 2 A partial structural schematic diagram of a lower electrode assembly showing another embodiment;

[0035] Figure 3 A partial structural schematic diagram of a lower electrode assembly showing another embodiment;

[0036] Figure 4 A structural schematic diagram of a capacitively coupled plasma processing device is shown. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0037] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Apparently, the described embodiments are some, but not all, of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0038] Figure 1 FIG. shows a partial structural schematic diagram of a lower electrode assembly according to an embodiment, including a vacuum-pumpable reaction chamber 100 surrounded by an outer wall 10. The reaction chamber 100 is used to process a substrate 103. Inside the reaction chamber, there is a lower electrode assembly for supporting the substrate and controlling factors affecting substrate processing such as the temperature and electric field of the substrate. The lower electrode assembly includes a base 101 for carrying an electrostatic chuck 102. A temperature control device is provided inside the base 101 to control the temperature of the upper substrate. The electrostatic chuck 102 is used to carry the substrate 103. A DC electrode is provided inside the electrostatic chuck, and a DC adsorption is generated between the back surface of the substrate and the carrying surface of the electrostatic chuck through this DC electrode to fix the substrate. An edge ring assembly 20 is provided around the periphery of the base and the electrostatic chuck to adjust the temperature and electric field distribution in the edge region of the substrate. A plasma confinement ring 108 is provided around the edge ring assembly 20, located between the edge ring assembly 20 and the side wall of the reaction chamber, for confining the plasma in the reaction area while allowing gas to pass through; a ground ring 109 is located below the plasma confinement ring, and its function is to provide electric field shielding to prevent plasma leakage. A bias RF power supply is usually used to apply a bias RF signal to the lower electrode assembly to control the bombardment direction of the plasma. The lower electrode assembly disclosed in the present invention can be used in, for example Figure 1 the capacitive-coupled plasma processing apparatus as shown.

[0039] In a plasma processing apparatus, a substrate is processed by applying a radio frequency (RF) to excite a reactive gas above the substrate to generate a plasma, thereby achieving a processing result with a specific surface structure. However, the RF power acts on components inside the entire reaction chamber, posing a risk of discharge between some components made of conductive or semiconductor materials. During substrate processing, discharge between the pedestal that holds the substrate and components adjacent to the substrate can have a negative impact on the processing result of the substrate. The scope of discharge includes, for example, excessive accumulation of polymers in the gap between the edge ring assembly and the pedestal, reducing the dielectric level between the back surface of the substrate edge and the metal pedestal and causing discharge; the focusing ring in the edge ring assembly is made of semiconductor material, and the distance between it and the back surface of the substrate edge is relatively close. When excessive polymers are deposited on the upper surface of the focusing ring, the dielectric level between the substrate and the focusing ring in this area is reduced and discharge occurs. In the prior art, the distance between the upper surface of the focusing ring and the back surface of the substrate affects both the amount of polymers entering the gap between the edge ring assembly and the pedestal, which causes discharge, and the discharge of the focusing ring itself to the back surface of the substrate. Moreover, these two discharge phenomena lead to contradictions in the improvement direction of the focusing ring. That is, if the distance between the upper surface of the focusing ring and the back surface of the substrate is increased, the discharge risk between the focusing ring itself and the substrate can be reduced, but the amount of polymers entering the gap between the edge ring and the pedestal is increased, raising the discharge risk between the pedestal and the back surface of the substrate; conversely, if the distance between the upper surface of the focusing ring and the back surface of the substrate is decreased, the discharge risks in the two cases are correspondingly swapped.

[0040] As Figure 1 shown, it is a partial side cross-sectional view of the lower electrode for holding a substrate according to the present invention, which only shows the cross-sectional view along one side of the axis. Specifically, it includes a pedestal 101, which can be a columnar structure. In some embodiments, the upper surface of the outer edge of the pedestal 101 is lower than the upper surface of the central region, forming an annular step for installing some edge ring assemblies to optimize the process result. A dielectric ring 40 is disposed around the pedestal 101. The dielectric ring 40 surrounds the central region of the pedestal 101, and there is a gap between the inner side of the dielectric ring 40 and the outer side of the central region of the pedestal 101. In the lower electrode assembly of the present invention, the pedestal 101 is mainly made of metal to facilitate RF coupling to the lower electrode assembly for plasma etching of the substrate, while the dielectric ring 40 is mainly composed of a dielectric material, resulting in different thermal expansion coefficients of the pedestal 101 and the dielectric ring 40. To prevent component damage caused by inconsistent thermal expansion of the two during the process, a gap needs to be left between them.

[0041] Above the dielectric ring 40, a focusing ring 20 surrounding the central area of the base 101 is provided. The focusing ring 20 can extend the plasma boundary through radio frequency coupling or change the plasma processing rate at the edge of the substrate through thermal coupling effect, ultimately improving the processing uniformity of the substrate surface. The focusing ring 20 includes an inner ring area 201 close to the substrate 103 and an outer ring area 202 far from the substrate 103. In some embodiments, the upper surface height of the outer ring area 202 is higher than that of the inner ring area 201, which can adjust the movement direction of the plasma towards the substrate along the radial direction. In other embodiments, the outer ring area 202 can also have the same height as the inner ring area 201. In some embodiments, the ratio range of the radial width of the inner ring area 201 to the outer ring area 202 is: 1 / 11 - 1 / 5. The main function of the focusing ring 20 is to adjust the plasma sheath thickness at the edge of the substrate and the bombardment direction of charged particles. The inner ring area 201 mainly compensates for the lack of the electrode below the edge of the substrate, and the outer ring area 202 is mainly to extend the radial width of the upper plasma sheath. Optionally, the focusing ring can be made of silicon or silicon carbide.

[0042] Above the dielectric ring 40 and between the inner ring area 201 and the base 101, an insertion ring 401 is provided. The insertion ring 401 is a dielectric material and can also surround the central area of the base 101. On the one hand, the insertion ring 401 is located horizontally between the base 101 and the focusing ring 20, which can increase the dielectric constant between the base 101 and the focusing ring 20 and prevent discharge between them. On the other hand, since the insertion ring 401 is a dielectric material, its upper surface can be closer to the back of the edge of the substrate 103 without increasing the discharge probability from the insertion ring 401 to the substrate 103, and it can also prevent the polymer after the reaction from accumulating through the back of the substrate 103 to the gap. At the same time, in order for the insertion ring 401 to bear the effect of blocking the polymer, the upper surface of the inner ring area 201 of the corresponding focusing ring 20 can be lower than the upper surface of the insertion ring 401, thereby increasing the vertical distance between the inner ring area 201 and the back of the substrate 103, and further reducing the discharge risk between the inner ring area 201 surface deposited with polymer and the substrate 103. In some embodiments, the vertical distance between the upper surface of the inner ring area 201 and the upper surface of the insertion ring 401 can be made greater than 0.1 mm to obtain a sufficient degree of difference to balance the discharge risks from different aspects.

[0043] In some embodiments, different from the above embodiments, the upper surface of the insertion ring 401 is at least partially located below the substrate 103. The difficulty of the polymer entering the vertical gap inside the dielectric ring 40 is adjusted by the relative area between the upper surface of the insertion ring 401 and the back surface of the edge of the substrate 103, that is, the radial width of the insertion ring 401 located below the substrate 103. When the outer diameter of the insertion ring 401 and the outer edge of the substrate 103 are in the same vertical curved surface, or the outer diameter of the insertion ring 401 exceeds the outer edge of the substrate 103, the horizontal gap between the insertion ring 401 and the substrate 103 is the longest. Under the condition of a certain spacing, the blocking ability of the polymer is the strongest. At the same time, under the condition of a certain gap length, the blocking ability of the horizontal gap to the polymer can be controlled by adjusting the spacing, that is, the size of the vertical distance H1 between the upper surface of the insertion ring 401 and the lower surface of the substrate 103. In some embodiments, the range of the vertical distance H1 is 0.1 mm - 0.3 mm. When it is less than 0.1 mm, the processing tolerance will cause the upper surface of the insertion ring 401 to touch the lower surface of the substrate, or even be higher than the upper surface of the electrostatic chuck 102, both of which are more likely to cause damage to the substrate. When it is greater than 0.3 mm, as the process proceeds, the vertical gap on the inner side of the dielectric ring 40 is filled with the polymer faster and it is easy to generate discharge.

[0044] In some embodiments, different from the above embodiments, as Figure 1 shown, the inner ring region 201 is at least partially located below the substrate 103, and the adjustment of the electrical and thermal processing effects on the edge of the substrate is achieved through the overlapping area in the vertical direction between the inner ring region 201 and the substrate 103. In this embodiment, the vertical distance H2 between the inner ring region 201 and the lower surface of the substrate 103 is greater than 0.8 mm to achieve sufficient discharge blocking effect. When the distance is less than 0.8 mm, because the tolerance of the deposition thickness of the polymer is reduced, the processing time of the substrate will be reduced. In some other embodiments, as Figure 2 shown, the inner ring region 201 is located below the outside of the edge of the substrate 103, that is, there is no overlapping area in the vertical direction between the inner ring region 201 and the substrate 103. Specifically, as Figure 2 shown, the inner diameter of the inner ring region 201 is basically in the same vertical curved surface as the outer diameter of the substrate 103, or the inner diameter of the inner ring region 201 can be far from the vertical curved surface where the outer diameter of the substrate 103 is located. In this embodiment, the vertical distance H3 between the upper surface of the inner ring region 201 and the lower surface of the substrate 103 is greater than 0.4 mm. Because in this embodiment, the inner ring region 201 and the lower surface of the substrate are no longer relatively arranged, the corresponding vertical distance can be reduced. A closer distance can make the focusing ring 20 have a stronger modulation effect on the edge of the substrate. At the same time, the insertion ring 401 can extend radially outward to extend the length of the gap between it and the lower surface of the substrate.

[0045] In other embodiments, the difference from the above embodiments is that, as Figure 3 shown, the insertion ring 401 is integrally processed with the dielectric ring 40, that is, a part of the inner edge of the dielectric ring 40 extends upward to form the insertion ring 401. In this embodiment, the material of the dielectric ring 40 and the insertion ring 401 may include one or both of aluminum nitride and alumina, and the material used may be a ceramic composed of a mixture or a ceramic made of one material.

[0046] Furthermore, the present invention also provides a plasma processing device. In Figure 4 the capacitive coupled plasma processing device 100 shown, it includes a reaction chamber 10 surrounded by side walls. In addition to the lower electrode assembly as described above, an upper electrode assembly is also included in the reaction chamber 10. The upper electrode assembly includes a gas shower head 30, which is connected to a gas supply device for introducing process gas into the reaction chamber 10. A high-frequency radio frequency power supply applies a high-frequency radio frequency signal to at least one of the lower electrode assembly or the upper electrode assembly through a high-frequency radio frequency matching, so as to form a radio frequency electric field between the upper electrode assembly and the lower electrode assembly, and excite the process gas in the reaction chamber into plasma, realizing the processing of the substrate to be processed by the plasma. The power range of the high-frequency radio frequency power supply is: 5 kW - 50 kW, and the frequency range is: 16 MHz - 120 MHz. In Figure 4 the plasma processing device shown, a plasma confinement ring 108 surrounding the lower electrode assembly is further included, and there are channels for gas to pass through on it. A grounding ring 109 is in electrical contact below the plasma confinement ring 108 to maintain the overall radio frequency circuit of the chamber. A suction pump is connected to the bottom wall of the reaction chamber 10 below the grounding ring 109 to pump away the unreacted gas and reaction products between the upper and lower electrodes through the plasma confinement ring 108. When charged particles pass through the channels of the plasma confinement ring 108, collisions will occur to decharge, thereby preventing the charged particles from reaching the suction pump and damaging its components. In order to control the bombardment direction of the charged particles in the plasma, a bias radio frequency power supply can also be electrically connected to the lower electrode assembly. After the bias radio frequency power supply is matched to the lower electrode assembly through a bias radio frequency, the total electric power on the lower electrode assembly will be further increased, and by using the lower electrode assembly of the present invention, the discharge risk between components and between the substrate and components during high-power processes can be significantly reduced.

[0047] The lower electrode assembly disclosed in the present invention is not limited to being applied to the capacitive coupled plasma processing device in the above embodiments, and can also be applicable to other plasma processing devices, such as inductively coupled plasma processing devices, which will not be elaborated here.

[0048] Although the content of the present invention has been described in detail through the above preferred embodiments, it should be recognized that the above description should not be considered as a limitation of the present invention. After those skilled in the art have read the above content, various modifications and alternatives to the present invention will be obvious. Therefore, the protection scope of the present invention should be defined by the appended claims.

Claims

1. A lower electrode assembly for carrying a substrate, characterized in that, Comprising: A base; A dielectric ring that surrounds the base, with a gap between the inner side of the dielectric ring and the base; A focusing ring that is located above the dielectric ring, and the focusing ring includes an inner ring region close to the substrate and an outer ring region far from the substrate; An insertion ring that is located above the dielectric ring and between the inner ring region and the base, and the insertion ring is made of dielectric material; and The upper surface of the inner ring region is lower than the upper surface of the insertion ring.

2. The lower electrode assembly according to claim 1, characterized in that, The upper surface of the insertion ring is at least partially located below the substrate.

3. The lower electrode assembly according to claim 2, wherein The vertical distance between the upper surface of the insertion ring and the lower surface of the substrate ranges from 0.1 mm to 0.3 mm.

4. The lower electrode assembly according to claim 1, wherein The inner ring region is located below the outside of the substrate edge.

5. The lower electrode assembly according to claim 4, wherein The vertical distance between the upper surface of the inner ring region and the lower surface of the substrate is greater than 0.4 mm.

6. The lower electrode assembly according to claim 1, wherein, The upper surface of the inner ring region is at least partially located below the substrate.

7. The lower electrode assembly according to claim 6, characterized in that The vertical distance between the inner ring region and the lower surface of the substrate is greater than 0.8 mm.

8. The lower electrode assembly according to claim 1, characterized in that, The upper surface of the outer ring region is higher than the upper surface of the inner ring region.

9. The lower electrode assembly according to claim 2, wherein The vertical distance between the upper surface of the inner ring region and the upper surface of the insertion ring is greater than 0.1 mm.

10. The lower electrode assembly according to claim 1, characterized in that, The upper surface of the inner side of the insertion ring and the dielectric ring are integrally processed.

11. The lower electrode assembly according to claim 10, characterized in that, The materials of the dielectric ring and the insertion ring include one or both of aluminum nitride and aluminum oxide.

12. The lower electrode assembly according to claim 1, characterized in that, The material of the focusing ring includes one or both of silicon and silicon nitride.

13. The lower electrode assembly according to claim 10, wherein There is a gap between the inner side of the insertion ring and the base.

14. The lower electrode assembly according to claim 1, wherein The radial width ratio range of the inner ring region to the outer ring region is: 1 / 11 - 1 / 5.

15. A plasma processing apparatus, characterized in that, Comprising: A reaction chamber; A gas shower head located on the upper side inside the reaction chamber for introducing reaction gases; A lower electrode assembly as described in any one of claims 1 - 14 located on the lower side inside the reaction chamber; A high-frequency RF power supply that is electrically connected to the lower electrode assembly for exciting reaction gases to form a plasma for processing the substrate.

16. The plasma processing apparatus according to claim 15, characterized in that, The power range of the high-frequency RF power supply is: 5 kW - 50 kW, and the frequency range is: 16 MHz - 120 MHz.

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