A lower electrode assembly and plasma processing apparatus

Abstract

This invention provides a lower electrode assembly and a plasma processing device, belonging to the field of semiconductor processing equipment. To address component damage caused by partial discharge of the lower electrode, the assembly specifically includes a base; a dielectric ring surrounding the base, with a gap between the inner side of the dielectric ring and the base; a focusing ring located above the dielectric ring, comprising an inner ring region close to the substrate and an outer ring region away from the substrate; an insertion ring located above the dielectric ring and between the inner ring region and the base, the insertion ring being made of a dielectric material; and the upper surface of the inner ring region being lower than the upper surface of the insertion ring for plasma processing of the substrate surface.

Description

Technical Field

[0001] This invention relates to the field of plasma etching technology, and more particularly to a plasma processing technology for preventing arcing of the lower electrode assembly under high radio frequency power. Background Technology

[0002] Microfabrication of semiconductor substrates is a well-known technique used to manufacture, for example, semiconductors, flat panel displays, light-emitting diodes (LEDs), and solar cells. A crucial step in microfabrication is the plasma processing step, which takes place inside a reaction chamber where process gases are introduced. An radio frequency (RF) source, coupled to the reaction chamber via inductance and / or capacitance, excites the process gases to form and maintain plasma. Inside the reaction chamber, the exposed substrate is supported by a lower electrode assembly and held in a fixed position by a clamping force to ensure substrate safety and a high yield rate during the process.

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

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

[0005] As substrate processing precision increases, the radio frequency (RF) power applied to the reaction cavity also increases. High RF power can easily generate arcing in the confined space of the reaction cavity, damaging the substrate and its peripheral components, and seriously threatening the stability and safety of the lower electrode assembly. Therefore, a solution is urgently needed to adapt to the ever-increasing RF power applied and the uniformity requirements of substrate processing. Summary of the Invention

[0006] To address the technical problem that the lower electrode assembly is prone to generating undesirable discharges that damage the substrate, this invention provides a lower electrode assembly for supporting a substrate, comprising:

[0007] Base;

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

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

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

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

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

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

[0014] Optionally, the inner ring region is located below the outer 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, the upper surface of the inner ring region is at least partially 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 insertion ring and the inner side of the upper surface of the medium ring are integrally machined.

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

[0022] Optionally, the material of the focusing ring includes one or both 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 radial width ratio between the inner ring region and the outer ring region ranges from 1 / 11 to 1 / 5.

[0025] Furthermore, the present invention also provides a plasma processing apparatus, comprising:

[0026] Reaction chamber;

[0027] A gas spray head located on the upper side inside the reaction chamber is used to introduce reaction gas;

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

[0029] A high-frequency radio frequency power supply, which is electrically connected to the lower electrode assembly, is used to excite the reactive gas to form plasma for process treatment of the substrate.

[0030] Optionally, the power range of the high-frequency radio frequency 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 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 risk of discharge between the focusing ring and the edge of the substrate, thus comprehensively and effectively ensuring the safety of the lower electrode assembly. Attached Figure Description

[0032] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0033] Figure 1 A partial structural schematic diagram of a lower electrode assembly according to one embodiment is shown;

[0034] Figure 2 A partial structural schematic diagram of the lower electrode assembly according to another embodiment is shown;

[0035] Figure 3 A partial structural schematic diagram of the lower electrode assembly according to another embodiment is shown;

[0036] Figure 4 A schematic diagram of a capacitively coupled plasma processing device is shown. Detailed Implementation

[0037] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0038] Figure 1 A partial structural schematic diagram of a lower electrode assembly according to one embodiment is shown, including a vacuum-ejectable reaction chamber 100 enclosed by an outer wall 10. The reaction chamber 100 is used to process a substrate 103. Inside the reaction chamber is a lower electrode assembly used to support the substrate while controlling factors affecting substrate processing, such as substrate temperature and electric field. The lower electrode assembly includes a base 101 for supporting an electrostatic chuck 102. The base 101 contains a temperature control device for controlling the temperature of the substrate above. The electrostatic chuck 102 supports the substrate 103 and contains a DC electrode. This DC electrode generates DC adsorption between the back of the substrate and the supporting surface of the electrostatic chuck to fix the substrate. An edge ring assembly 20 is arranged around 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 arranged around the edge ring assembly 20, located between the edge ring assembly 20 and the sidewall of the reaction chamber, to confine the plasma within the reaction region while allowing gas to pass through; a grounding ring 109, located below the plasma confinement ring, provides electric field shielding to prevent plasma leakage. A bias radio frequency power supply, typically applying a bias radio frequency signal to the lower electrode assembly, is used to control the plasma bombardment direction. The lower electrode assembly disclosed in this invention can be used for, for example... Figure 1 The capacitively coupled plasma processing device shown.

[0039] In plasma processing equipment, plasma is generated by applying radio frequency (RF) excitation to the reactive gas above the substrate to process the substrate and achieve specific surface structure processing results. However, RF power acts on components throughout the reaction chamber, posing a risk of discharge between some conductive or semiconductor components. During substrate processing, discharges from the substrate-supporting base and adjacent components negatively impact the processing results. Examples of discharge include: excessive polymer accumulation in the gap between the edge ring assembly and the base, reducing the dielectric constant between the substrate edge and the metal base; and the focusing ring in the edge ring assembly being made of semiconductor material, which is close to the substrate edge. Excessive polymer deposition on the upper surface of the focusing ring reduces the dielectric constant between the substrate and the focusing ring in that area, causing discharge. In existing technology, the distance between the upper surface of the focusing ring and the substrate back side affects both the amount of polymer entering the gap between the edge ring assembly and the base, thus influencing the discharge from the focusing ring itself to the substrate back side. Furthermore, the two discharge phenomena contradict each other in terms of the direction of improvement of the focusing ring. Increasing the distance between the upper surface of the focusing ring and the back of the substrate can reduce the discharge risk between the focusing ring itself and the substrate, but it increases the amount of polymer entering the gap between the edge ring and the substrate, thus increasing the discharge risk between the substrate and the back of the substrate. Conversely, reducing the distance between the upper surface of the focusing ring and the back of the substrate reverses the discharge risks in the two cases.

[0040] like Figure 1 The diagram shows a partial side cross-sectional view of the lower electrode used to support the substrate according to the present invention, illustrating only one side of the cross-section along the axis. Specifically, it includes a base 101, which can be a columnar structure. In some embodiments, the upper surface of the outer edge of the base 101 forms an annular step lower than the upper surface of the central region, used to mount edge ring assemblies for optimizing process results. A dielectric ring 40 is disposed around the base 101, surrounding the central region of the base 101, and a gap exists between the inner side of the dielectric ring 40 and the outer side of the central region of the base 101. In the lower electrode assembly of the present invention, the base 101 is mainly made of metal to facilitate radio frequency coupling to the lower electrode assembly for plasma etching of the substrate, while the dielectric ring 40 is mainly composed of dielectric material. This results in a difference in the thermal expansion coefficients of the base 101 and the dielectric ring 40. To prevent component damage caused by inconsistent thermal expansion during the process, a gap is required between them.

[0041] A focusing ring 20 is disposed above the dielectric ring 40, surrounding the central region of the substrate 101. The focusing ring 20 can extend the plasma boundary through radio frequency coupling or change the plasma processing rate at the substrate edge through thermal coupling, ultimately improving the processing uniformity of the substrate surface. The focusing ring 20 includes an inner ring region 201 close to the substrate 103 and an outer ring region 202 away from the substrate 103. In some embodiments, the upper surface height of the outer ring region 202 is higher than the upper surface height of the inner ring region 201, which can achieve the effect of adjusting the movement direction of the plasma toward the substrate radially. In other embodiments, the outer ring region 202 may also be at the same height as the inner ring region 201. In some embodiments, the radial width ratio of the inner ring region 201 to the outer ring region 202 is in the range of 1 / 11 to 1 / 5. The main function of the focusing ring 20 is to adjust the thickness of the plasma sheath layer at the edge of the substrate and the bombardment direction of charged particles. The inner ring region 201 mainly compensates for the lack of electrodes below the edge of the substrate, and the outer ring region 202 is mainly to extend the radial width of the upper plasma sheath layer. Optionally, the focusing ring can be made of silicon or silicon carbide.

[0042] An insertion ring 401 is disposed above the dielectric ring 40 and between the inner ring region 201 and the base 101. The insertion ring 401 is made of dielectric material and can also surround the central region of the base 101. On the one hand, the insertion ring 401 is located between the base 101 and the focusing ring 20 laterally, 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 made of dielectric material, its upper surface can be closer to the back edge of the substrate 103 without increasing the discharge probability from the insertion ring 401 to the substrate 103. It can also prevent the polymer after the reaction from accumulating in the gaps through the back edge of the substrate 103. Meanwhile, in order for the insert ring 401 to act as a polymer blocker, the upper surface of the inner ring region 201 of the corresponding focusing ring 20 can be lower than the upper surface of the insert ring 401. This increases the vertical distance between the inner ring region 201 and the back surface of the substrate 103, thereby reducing the risk of discharge between the inner ring region 201 and the substrate 103 after polymer deposition. In some embodiments, the vertical distance between the upper surface of the inner ring region 201 and the upper surface of the insert ring 401 can be greater than 0.1 mm to obtain a sufficient difference to reduce the risk of discharge from different directions.

[0043] In some embodiments, the difference from the above embodiments is that the upper surface of the insertion ring 401 is at least partially located below the substrate 103. The difficulty of 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 edge of the substrate 103, i.e., the radial width of the insertion ring 401 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 when 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, and the barrier ability against polymer is the strongest when the spacing is constant. At the same time, when the gap length is constant, the barrier ability of the horizontal gap against polymer can be controlled by adjusting the spacing, i.e., 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 vertical distance H1 ranges from 0.1mm to 0.3mm. When it is less than 0.1mm, the processing tolerance will cause the upper surface of the insertion ring 401 to touch the lower surface of the substrate, or even higher than the upper surface of the electrostatic chuck 102. Both of these will make it easier to damage the substrate. When it is greater than 0.3mm, as the process progresses, the vertical gaps on the inner side of the dielectric ring 40 will be filled by the polymer more quickly, making it easier for discharge to occur.

[0044] In some embodiments, the difference from the above embodiments is that, as Figure 1 As shown, the inner ring region 201 is at least partially located below the substrate 103. The electrical and thermal treatment effects on the substrate edge are adjusted by the overlapping area of ​​the inner ring region 201 and the substrate 103 in the vertical direction. 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 electrical discharge isolation. When the distance is less than 0.8 mm, the processing time for the substrate is reduced because the tolerance for polymer deposition thickness decreases. In other embodiments, such as... Figure 2 As shown, the inner ring region 201 is located below the outer edge of the substrate 103, meaning that the inner ring region 201 and the substrate 103 do not overlap in the vertical direction. Specifically, it can be seen as follows... Figure 2 As shown, the inner diameter of the inner ring region 201 is basically within the same vertical curved surface as the outer diameter of the substrate 103. Alternatively, the inner diameter of the inner ring region 201 can be made to be far away 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 opposite each other, the corresponding vertical distance can be reduced. A closer distance allows the focusing ring 20 to produce 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 embodiments described above is that, for example... Figure 3 As shown, the insertion ring 401 is integrally formed with the dielectric ring 40, that is, the inner edge of the dielectric ring 40 extends upward to form the insertion ring 401. In this embodiment, the materials of the dielectric ring 40 and the insertion ring 401 may include one or both of aluminum nitride and aluminum oxide. The materials used may be ceramics composed of a mixture or ceramics made of a single material.

[0046] Furthermore, the present invention also provides a plasma processing apparatus, in Figure 4 The capacitively coupled plasma processing apparatus 100 shown includes a reaction chamber 10 surrounded by sidewalls. In addition to the lower electrode assembly described above, the reaction chamber 10 also includes an upper electrode assembly. The upper electrode assembly includes a gas spray head 30, which is connected to a gas supply device to introduce process gas into the reaction chamber 10. A high-frequency radio frequency (RF) power supply applies a high-frequency RF signal to at least one of the lower or upper electrode assemblies via RF matching to form an RF electric field between the upper and lower electrode assemblies, exciting the process gas in the reaction chamber into plasma, thereby achieving plasma processing of the substrate to be processed. The power range of the RF power supply is 5kW-50kW, and the frequency range is 16MHz-120MHz. Figure 4 The plasma processing apparatus shown also includes a plasma confinement ring 108 surrounding the lower electrode assembly, which has channels for gas passage. A grounding ring 109 is electrically connected below the plasma confinement ring 108 to maintain the overall radio frequency circuit of the chamber. A vacuum pump is connected to the bottom wall of the reaction chamber 10 below the grounding ring 109, which removes 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, they undergo collision de-charge, thereby preventing them from reaching the vacuum pump and damaging its components. To control the bombardment direction of charged particles in the plasma, a bias radio frequency power supply can be electrically connected to the lower electrode assembly. After the bias radio frequency power supply is matched to the lower electrode assembly, the total electrical power on the lower electrode assembly is further increased. Using the lower electrode assembly of this invention, the risk of discharge between components and between the substrate and components during high-power processes can be significantly reduced.

[0047] The lower electrode assembly disclosed in this invention is not limited to the capacitively coupled plasma processing apparatus described in the above embodiments. It can also be applied to other plasma processing apparatuses, such as inductively coupled plasma processing apparatuses, which will not be elaborated here.

[0048] Although the present invention has been described in detail through the preferred embodiments above, 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 description. Therefore, the scope of protection of the present invention should be defined by the appended claims.

Claims

1. A lower electrode assembly for carrying a substrate, characterized by, include: Base; A dielectric ring surrounds the base, with a gap between the inner side of the dielectric ring and the base; a focusing ring is located above the dielectric ring, the focusing ring comprising an inner ring region close to the substrate and an outer ring region away from the substrate; An insertion ring, located above the dielectric ring and between the inner ring region and the base, wherein the insertion ring is made of a 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 of claim 1, wherein, The upper surface of the insertion ring is at least partially located below the substrate.

3. The lower electrode assembly as described in claim 2, characterized in that, 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 as described in claim 1, characterized in that, The inner ring region is located below the outer edge of the substrate.

5. The lower electrode assembly as described in claim 4, characterized in that, 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 as described in claim 1, characterized in that, The upper surface of the inner ring region is at least partially located below the substrate.

7. The lower electrode assembly as described in 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 as described in 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 as described in claim 2, characterized in that, 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 as claimed in claim 1, characterized in that, The insertion ring and the inner side of the upper surface of the medium ring are integrally machined.

11. The lower electrode assembly as claimed in 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 as claimed in 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 as claimed in claim 10, characterized in that, There is a gap between the inner side of the insertion ring and the base.

14. The lower electrode assembly as claimed in claim 1, characterized in that, The radial width ratio between the inner ring region and the outer ring region ranges from 1 / 11 to 1 / 5.

15. A plasma processing apparatus, characterized in that, include: Reaction chamber; A gas spray head located on the upper side inside the reaction chamber is used to introduce reaction gas; The lower electrode assembly as described in any one of claims 1-14 is located on the lower side inside the reaction chamber; a high-frequency radio frequency power supply is electrically connected to the lower electrode assembly and is used to excite the reaction gas to form plasma to process the substrate.

16. The plasma processing apparatus as claimed in claim 15, characterized in that, The power range of the high-frequency radio frequency power supply is 5kW-50kW, and the frequency range is 16MHz-120MHz.

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