A plasma reactor

Abstract

A plasma reactor comprises: a reaction chamber, a conductive base is arranged at the bottom of the reaction chamber, the conductive base is connected to a radio frequency power supply device through a radio frequency matching network, a substrate to be processed is placed above the conductive base, an upper electrode assembly is included at the top of the reaction chamber, and a plasma processing space is provided between the conductive base and the upper electrode assembly; a first conductive grounding ring is arranged around the periphery of the conductive base; a second conductive grounding ring is electrically connected between the outer side wall of the first conductive grounding ring and the inner side wall of the reaction chamber, a plurality of gas channels are provided on the second conductive grounding ring, so that the gas in the plasma processing space can be discharged through the plurality of gas channels; an insulating ring is included between the conductive base and the first conductive grounding ring, and the dielectric constant of the insulating ring is less than 3.5.

Description

Technical Field

[0001] The present invention relates to the technical field of semiconductor processing, and in particular to the technical field of a capacitively coupled plasma reactor. Background Art

[0002] Semiconductor chips are increasingly widely used in various electronic devices. In the manufacturing process of semiconductor devices, plasma etching is the key process to process wafers into designed patterns. Plasma etching processes require the use of plasma processors, which perform plasma etching, chemical vapor deposition and other processes on the substrate to be processed. In a typical plasma etching process, process gases (such as CF4, O2, etc.) form plasma under the action of radio frequency (RF) excitation in the reaction chamber. These plasmas physically bombard and chemically react with the surface of the wafer, thereby etching a wafer with a specific structure.

[0003] Capacitively coupled (CCP) plasma processors are widely used in the dielectric material layer etching step in the chip manufacturing process. With the continuous evolution of plasma etching technology, the critical dimension in semiconductor devices is getting smaller and smaller, and the current technological frontier has been pushed to the critical dimension of 7nm and 5nm or less. Under such a small critical dimension requirement, not only does the plasma processing steps increase significantly, the total number of chip processing steps can reach thousands of steps, and the uniformity requirements of the plasma processing process are also extremely high, and the uniformity requirements need to be less than 2%, or even less than 1%.

[0004] The adjustment methods of the existing technology cannot achieve the above-mentioned demanding indicators. The industry urgently needs a new capacitively coupled plasma processor with a more uniform plasma concentration distribution on the entire wafer surface. Summary of the invention

[0005] The present invention provides a plasma reactor, which can reduce the serious interference of a large number of high-frequency harmonics in the plasma reactor on the uniformity of the plasma treatment effect. The plasma reactor comprises: a reaction chamber, a conductive base is provided at the bottom of the reaction chamber, the conductive base is connected to a radio frequency power supply device through a radio frequency matching network, a substrate to be processed is placed above the conductive base, the top of the reaction chamber comprises an upper electrode assembly, and a plasma treatment space is provided between the conductive base and the upper electrode assembly; a first conductive grounding ring is arranged around the outer periphery of the conductive base; a second conductive grounding ring is electrically connected between the outer side wall of the first conductive grounding ring and the inner side wall of the reaction chamber, and a plurality of gas channels are provided on the second conductive grounding ring, so that the gas in the plasma treatment space can be discharged through the plurality of gas channels; an insulating ring is provided between the conductive base and the first conductive grounding ring, the dielectric constant of the insulating ring is less than 3.5, and a coupling ring is provided above the insulating ring, the coupling ring covers the upper surface of the insulating ring and the upper surface of the outer part of the conductive base, wherein the coupling ring is made of a first ceramic material, and the thermal conductivity of the first ceramic material is higher than the thermal conductivity of the insulating ring. The above design can not only allow a large amount of harmonic RF power to flow to the RF matching network below to avoid distribution of plasma processing, but also prevent the insulating ring from expanding significantly during plasma processing due to the selection of a low dielectric constant polymer insulating ring, thereby ensuring the long-term stability of the plasma etching process.

[0006] The present invention also proposes another embodiment, a plasma reactor comprises: a reaction chamber, a conductive base is provided at the bottom of the reaction chamber, the conductive base is connected to a radio frequency power supply device through a radio frequency matching network, a substrate to be processed is placed above the conductive base, the top of the reaction chamber comprises an upper electrode assembly, and a plasma processing space is provided between the conductive base and the upper electrode assembly; a first conductive grounding ring is arranged around the outer periphery of the conductive base; a second conductive grounding ring is electrically connected between the outer side wall of the first conductive grounding ring and the inner side wall of the reaction chamber, a plurality of gas channels are provided on the second conductive grounding ring, so that the gas in the plasma processing space can be discharged through the plurality of gas channels; an insulating ring is included between the conductive base and the first conductive grounding ring; the radio frequency matching network supplies high-frequency radio frequency power with a basic frequency to the conductive base through at least one radio frequency cable, and the basic frequency is greater than or equal to 40Mhz; the plasma in the plasma processing space generates harmonic radio frequency power of the basic frequency, and the harmonic radio frequency power flows into the radio frequency matching network through the at least one radio frequency cable, wherein the harmonic radio frequency power flowing into the radio frequency matching network is greater than 5% of the high-frequency radio frequency power. Furthermore, the RF matching network includes a first filter for passing the high-frequency RF power, and a second filter for passing the harmonic RF power and blocking the high-frequency RF power, and the dielectric constant of the insulating ring needs to be less than 3.5. Through the above comprehensive design, the harmonic RF power can be blocked by the insulating ring and can only flow to the second filter with low impedance to the harmonic RF power below, thereby consuming the harmonic RF power that seriously interferes with the plasma treatment effect in the matching network. BRIEF DESCRIPTION OF THE DRAWINGS

[0007] Figure 1 A schematic diagram of a plasma processor and a high-frequency radio frequency power flow path;

[0008] Figure 2 A schematic diagram of a plasma processor and a high-frequency harmonic radio frequency power flow path;

[0009] Figure 3 It is a schematic diagram of a plasma processor and a high-frequency harmonic radio frequency power flow path of the present invention;

[0010] Figure 4a The etching rate distribution diagram of the present invention when performing plasma treatment process A is shown compared with the prior art;

[0011] Figure 4b The etching rate distribution diagram when the present invention performs plasma treatment process B is shown compared with the prior art;

[0012] Figure 5 is a schematic diagram of another embodiment of a plasma processor of the present invention;

[0013] Figure 6 It is a schematic diagram of the structure of a radio frequency matching network in another embodiment of the plasma processor of the present invention. DETAILED DESCRIPTION

[0014] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0015] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0016] Figure 1 It is a schematic diagram of the structure of a capacitively coupled plasma reactor, including: a reaction chamber 14, the bottom of the reaction chamber includes a conductive base 5 which also serves as a lower electrode, and an electrostatic chuck 6 is arranged above the conductive base 5 for fixing the wafer to be processed and controlling the wafer temperature. A device plate 4 is also included below the conductive base, and the device plate and the conductive base can be made of aluminum or other conductive materials or the device plate is made of ceramic materials. The two are tightly fixed to each other so that the atmospheric environment gas above and below the device plate 4 is sealed. A high-frequency (HF) radio frequency power supply and a low-frequency (LF) radio frequency power supply are connected to the device plate 4 or the lower electrode 5 through an radio frequency matching network and a radio frequency cable 2, and the radio frequency power of the two frequencies is effectively applied to the plasma processor. A focusing ring 9a and an edge ring 9b are arranged on the periphery of the electrostatic chuck 6 to adjust the electric field distribution and sheath thickness of the wafer edge area to achieve a more uniform plasma etching effect. A grounded lower grounding ring 3 is also provided around the disc-shaped lower electrode 5 and the device plate 4, and the lower grounding ring includes a portion 3a surrounding the side wall of the lower electrode and a portion 3b surrounding the outer side wall and part of the bottom of the device plate 4. An insulating device is also provided between the lower electrode 5, the device plate 4 and the lower grounding ring 3 to achieve isolation between the radio frequency power radiation area (RFhot) and the lower grounding ring 3, thereby reducing the loss of the radio frequency power fed into the lower electrode 5. The insulating device may include a first insulating ring 7 and a second insulating ring 8 provided above and below, and the materials of the insulating rings 7 and 8 are usually made of ceramics such as quartz or alumina.

[0017] The top of the reaction chamber opposite to the conductive base includes a gas shower head 10, which acts as an upper electrode and a lower electrode to couple the electric field with each other, and also acts as an air intake mechanism to uniformly transport the reaction gas downward to the surface of the wafer. The gas shower head 10 is fixed to the top cover 13 of the reaction chamber through a conductive mounting plate 12. An upper grounding ring 11 can also be optionally set on the periphery of the gas shower head 10 to adjust the RF current path of the gas shower head 10. A movable ring 15 can be selectively set on the periphery of the gas shower head 10, and the movable ring 15 that can move up and down can constrain the plasma and gas flow distribution in the reaction chamber.

[0018] During the plasma etching process, both RF powers are effectively transmitted to the lower electrode 5 through the RF matching electrical network. The output frequency of the high-frequency RF power supply can be 13.56Mhz, 27Mhz or higher frequency to generate sufficient and evenly distributed plasma concentration between the upper and lower electrodes. The low-frequency RF power supply outputs RF power of lower frequencies such as 2Mhz and 400Khz to control the thickness of the plasma sheath in the wafer and the peripheral area of ​​the wafer, where the sheath thickness and morphology directly determine the energy and direction of the ions incident downward. In order to improve the uniformity of the plasma etching treatment effect on the wafer, the wafer is required to have basically consistent plasma concentration and sheath thickness (ion incident energy and direction) from the center to the edge.

[0019] like Figure 1 The transmission path of the high-frequency radio frequency power RF1 during the plasma processing process shown in the figure includes the main path RF1a: the high-frequency radio frequency power RF1 passes through the plasma (not shown in the figure) from the lower electrode 5 to the upper electrode, and then passes through the reaction chamber top cover 13, the side wall 14 and the middle grounding ring 17 in turn to reach the lower grounding ring 3 to connect to the ground. The first branch path RF1b: the high-frequency radio frequency power RF1 is directly coupled to the plasma confinement ring 18 and the middle grounding ring 17 located between the lower grounding ring 3 and the reaction chamber side wall 14 through the plasma, and finally converges to the lower grounding ring 3. The second branch path RF1c: a small amount of high-frequency radio frequency power passes directly from the lower electrode 5 through the insulating ring 7 and the insulating ring 8 to the lower grounding ring 3, and finally flows into the ground end. According to a large amount of test data, it is found that the plasma concentration in the capacitively coupled plasma processor is usually distributed in a high center and low edge, or a W-shaped distribution with gradually lower concentrations in the center, edge, and middle areas.

[0020] A method for improving the uniformity of plasma processing effects includes adjusting the impedance on the main path RF1a or the impedance on the first branch path RF1b. The impedance adjustment of the above two paths can partially improve the uniformity of plasma concentration. Researchers have used various methods such as changing the size and material combination of each component on these two paths, setting an adjustable impedance circuit, etc., but they can only improve the uniformity of plasma concentration in the edge area of ​​the wafer, and still cannot effectively solve the problem of high plasma concentration in the center area of ​​the wafer.

[0021] Another method is to set dielectric material layers with different thicknesses in different areas of the conductive base or the upper electrode to offset the plasma inhomogeneity caused by the uneven spatial distribution of high-frequency RF power. However, this method can only partially offset the original inhomogeneity, and different dielectric material layer combinations need to be redesigned when encountering different process parameters. In practical application, not only is the R&D cost high, but the adjustable range of the plasma processor is extremely small, which cannot adapt to the ever-changing process requirements.

[0022] Based on the technical problems described above, the inventors have conducted in-depth research on the various technical means used in the prior art that cannot achieve a sufficient level of plasma concentration uniformity. The industry's research based on the input high-frequency radio frequency power RF1 has not been able to find the cause of the obvious uneven plasma concentration, and attempts to use various power distribution adjustment methods to compensate for the uniformity problem can only achieve partial improvement, and cannot completely solve the problem of significantly high plasma concentration in the center of the wafer. Therefore, this problem has become a major problem that has existed for many years and cannot be effectively solved.

[0023] After research, the inventors finally found that the root cause of this long-standing unresolved problem is not the traditional belief that it is caused by the different power distribution ratios of the basic frequency (40Mhz, 60Mhz, etc.) in different paths in the reaction chamber, but is caused by the circulation and accumulation of harmonic RF power derived from the basic high-frequency RF signal in the reaction chamber.

[0024] Figure 2It is a schematic diagram of a plasma processor and the corresponding high-frequency harmonic radio frequency power flow path. After the high-frequency radio frequency power RF1 with a basic frequency (such as 60Mhz) is transmitted to the lower electrode 5, a plasma 20 is generated between the upper and lower electrodes. Since the plasma is a nonlinear impedance, the basic frequency (60Mhz) will derive a relatively high-power harmonic radio frequency power RF2 (120Mhz, 180Mhz, etc.). These harmonic radio frequency powers diffuse from the plasma 20 to various surrounding transmission paths, including the path RF2a with the maximum power ratio, passing through the upper electrode 10, the conductive mounting plate 12, the top cover 13, the reaction chamber side wall 14, and the middle grounding ring 17. After reaching the lower grounding ring 3, a large amount of harmonic radio frequency power does not flow downward to the ground end as expected, but a large amount of harmonic radio frequency power is coupled across the insulating rings 7 and 8 to reach the lower electrode 5, and continues to circulate in the above loop. For harmonic radio frequency power, the extremely high radio frequency frequency causes the equivalent capacitance Ch between the lower grounding ring 3 and the lower electrode 5 to be very large, and the corresponding equivalent impedance is very small. The lower ground ring 3 is connected to the ground end of the RF matching network from the connection with the middle ground ring 17 along the side wall of the lower ground ring. For the RF signal of the above-mentioned harmonic frequency, the impedance generated by the equivalent inductance Lh on the RF2e path will be greater than the impedance generated by the equivalent capacitance Ch on the RF2d path. Therefore, a large amount of RF power of harmonic frequency will participate in the circulation through the path RF2d, and only a small amount of RF power will flow downward into the ground end through RF2e. In addition, part of the harmonic RF power coupled from the plasma 20 to the middle ground ring 17 through the path RF2b will also circulate in the RF2a-RF2d path due to impedance distribution. For the same reason, the reverse harmonic RF current from the plasma 20 downward through RF2d-RF2a will also continue throughout the entire cycle. Part of the harmonic RF power flows downward from the plasma 20 through the lower electrode 5, the equipment board 4 and the RF cable into the RF matching network or even the RF power supply at the further end. This part of the flow path constitutes another RF propagation path RF2E. Due to the presence of filters and other inductive devices in the RF matching network, the extremely high-frequency harmonic RF power will be converted into heat and other energies in the matching network and will no longer return to the wafer processing area between the upper and lower electrodes. Due to the presence of inductive components in the RF matching network, the signal impedance to the harmonic RF frequency is relatively large, which is much larger than the equivalent impedance on the above-mentioned harmonic RF circulation path RF2a-RF2d, so only a small amount of RF current will flow downward into the RF2E path and be consumed.From the impedance ratio of each path mentioned above, it can be found that the extremely high frequency harmonic RF power RF2 generated from the plasma 20, except for a small amount of power flowing out of the reaction chamber through RF2e and RF2E, most of it is circulated and superimposed in the loop formed by the RF2a-RF2d paths. A part of the power of the RF power RF1 with the fundamental frequency continuously input into the reaction chamber will be converted into harmonic RF power. Depending on the RF frequency and process parameters, the value of the harmonic RF power RF2 is about 10-50% of the RF power RF1 with the fundamental frequency input. In the continuous circulation process, most of the harmonic RF power continues to accumulate to a considerable power and finally reaches a balance state. In contrast, the RF power RF1 with the fundamental frequency continuously input will follow. Figure 1 The lower grounding ring 3 flows downward into the grounding terminal and does not form a long-term accumulation. The high-frequency power RF1 of the basic frequency continues to flow out in the reaction chamber, and the process of continuous accumulation of harmonic RF power eventually leads to the harmonic RF power RF2, which is originally much smaller than the input basic RF power RF1, having a far greater than expected impact on the plasma concentration in the reaction chamber.

[0025] Based on the above findings, the inventors proposed a plasma processor, comprising: a reaction chamber 14, wherein a conductive base 5 is provided at the bottom of the reaction chamber 14, wherein the conductive base is connected to a radio frequency power supply device through a radio frequency matching network circuit, wherein an electrostatic chuck 6 is provided on the conductive base, wherein the upper surface of the electrostatic chuck is used to adsorb the substrate to be processed, wherein the substrate to be processed includes an upper electrode opposite to the conductive base and a reaction chamber top cover 13; an equipment plate 4, which is located below the conductive base; a lower grounding ring 3 surrounding the side and part of the bottom of the conductive base and the equipment plate, wherein one or more insulating rings 71, 81 are arranged between the conductive base, the equipment plate and the lower grounding ring 3; a middle grounding ring 17 electrically connected between the lower grounding ring 3 and the inner wall of the reaction chamber 14; and a high-frequency radio frequency power supply and a low-frequency radio frequency power supply transmit radio frequency power to the conductive base through a radio frequency matching network. The insulating rings 71, 81 are made of organic polymers, in particular, various resin materials with a dielectric constant less than 3.5, such as PTFE, polyimide, etc. Figure 3 This is a description of the power ratio of the harmonic RF power RF2 in each path after the present invention uses an insulating ring made of special materials. Since the insulating rings 71 and 81 are made of materials with low dielectric constants, their equivalent capacitance Ch is also reduced, and the impedance to the harmonic RF signal is also greatly increased. After measurement, Figure 1 The impedance of the insulating rings 7 and 8 to the harmonic RF signal is only 3 ohms. After being transformed into low-dielectric insulating rings 71 and 81, the impedance value increases to more than ten ohms. Adding the impedance of other components in the harmonic RF circulation path (RF2a-RF2d), the comprehensive impedance of the harmonic RF circulation path is close to or even greater than the impedance of the grounding circuit through the RF matching network. Figure 3 It can be seen that under such an impedance ratio, the RF power flowing through the paths RF2E and RF2e of the RF matching network will be greater than the harmonic RF power propagated through the coupling path RF2d of the insulating rings 71 and 81. In this way, the RF power participating in the harmonic RF circulation path (through the RF2d path) is greatly reduced, and the harmonic RF power consumed on the RF2E path or derived through the RF2e path accounts for the majority. Since a large amount of harmonic RF power no longer participates in the circulation accumulation, and the harmonic RF power RF2 itself only accounts for a small part of the input basic RF power, the harmonic RF power no longer has a significant impact on the plasma concentration distribution above the wafer.

[0026] like Figure 4a The figure shows the etching rate distribution diagram of the present invention when performing plasma treatment process A compared with the prior art. It can be seen from the figure that when the insulating ring of ceramic material is used, its etching rate forms a W-shaped distribution from the center of the wafer to the edge of the wafer. The center position with the highest etching rate reaches 4200A / min, and the middle area with the lowest etching rate is about 3800A / min. The difference between the etching rates of the two reaches about 10%. Such a large gap is difficult to achieve the 1-2% etching rate uniformity requirement even if various other compensation means are used. In the technical solution of the present invention, the insulating ring is made of Ultem material. At this time, the highest etching rate at the center position is 3739A / min, and the lowest etching rate on the wafer also reaches 3692A / min. The difference between the two is only about 1%, which greatly improves the etching uniformity. After adopting the technical solution of the present invention, the problem of plasma concentration uniformity is greatly improved, so various technical adjustment means can be used to improve other indicators (such as temperature uniformity, airflow distribution, etc.) in the limited space in the reaction chamber, saving a lot of R&D costs and internal space.

[0027] The technical solution of the present invention can achieve remarkable results in various plasma treatment processes. Figure 4b This is the etching rate distribution diagram when the present invention performs plasma treatment process B compared with the prior art. It can be seen from the figure that when the prior art plasma processor performs process B, the etching rate distribution shows a gradually decreasing shape from the center to the edge. The highest etching rate at the center can reach 6146A / min, and the lowest point at the edge area is only 5564A / min, and the difference between the two is also about 10%. After using the plasma processor of the present invention, the etching rate distribution curve of the device is significantly improved, and the ratio of the highest etching rate to the lowest etching rate is 4990:4945, and the difference between the two is also within 1%.

[0028] The shapes of the insulating rings 71 and 81 in the present invention can be selected in many ways, such as the insulating ring 71 can further include some parts extending inward or parts extending upward or downward, or the insulating rings 71 and 81 can be divided into a combination of more annular parts, or can be integrated into one component, as long as the insulating ring assembly can achieve electrical isolation between the lower electrode 5 and the lower grounding ring 3, so that the equivalent capacitance between the two is significantly smaller than the equivalent capacitance in the prior art. In addition to being made of solid resin material, the insulating rings 71 and 81 can also be composed of a solid ring and an annular dielectric constant adjustment cavity, wherein the dielectric constant adjustment cavity is filled with dielectric material liquid, and the overall dielectric constant in the insulating ring can be adjusted by changing the liquid level height and liquid type of the dielectric liquid. After the dielectric constant is adjustable, the equivalent capacitance Ch and the proportion of harmonic RF power flowing through the RF2d path can also be adjusted.

[0029] The middle grounding ring 17 in the present invention is electrically connected between the side wall 3a of the lower grounding ring 3 and the inner wall of the reaction chamber 14 to realize the reflux of the fundamental frequency RF power and the harmonic RF power. The middle grounding ring 17 can be a plurality of radial spokes, one end of which is connected to the side wall 3a of the grounding ring and the other end is connected to the inner wall of the reaction chamber. The middle grounding ring can also be a conductive plate, on which a large number of gas through holes are provided, so that the gas flowing downward through the upper plasma confinement ring 18 can pass through the above through holes to reach the exhaust chamber 19 below. The exhaust chamber 19 is further connected to an exhaust system including an exhaust pump and a valve plate to discharge the reaction byproduct gas and control the pressure in the reaction chamber. The inner and outer sides of the middle grounding ring 17 can be mechanically pressed against the conductive surface of the side wall 3a of the grounding ring or the conductive fixing mechanism of the inner wall of the reaction chamber to achieve good conductivity. One side of the middle ground ring 17, such as the outer side close to the inner wall of the reaction chamber, may not be in close contact with the inner wall of the reaction chamber, but may be electrically connected to the inner wall of the reaction chamber through an additional conductive component, which may be a conductive connection part with sufficient elasticity, or a specially designed impedance device or a variable impedance device such as a variable capacitor may be connected in series to the conductive component. This impedance device can not only change the distribution of harmonic RF power but also adjust the high-frequency RF power path distribution of the fundamental frequency. The plasma distribution uniformity can be better adjusted through the combined action of the insulating rings 71, 81 and the above-mentioned impedance device.

[0030] The present invention also provides another embodiment, such as Figure 5As shown, the thickness of the insulating ring 72 can surround the outer periphery of the lower electrode and the device plate, and the insulating ring 82 is arranged below the device plate and only isolates the device plate from the lower grounding ring 3b. In the present invention, since the insulating rings 72 and 82 use organic polymers, they have lower thermal conductivity and larger thermal expansion coefficient than the ceramic materials used, so under the same processing environment, the expansion of the insulating ring caused by temperature rise will be violent. A coolant pipeline is usually also provided in the conductive base 5, and the temperature of the lower electrode is basically stable through the circulation of the coolant, but a large amount of heat generated by the plasma will be transmitted downward through the focus ring 9a and the edge ring 9b above the insulating ring 72, causing the insulating ring body to expand. The large expansion will cause the focus ring 9a and the edge ring 9b around the insulating ring 72 to be broken and lifted, and the outer lower grounding ring 3a part will expand outward, which will cause many parameters of the plasma processor to shift. On the other hand, after the plasma treatment is completed, the temperature returns to the initial value, and the deformation and displacement of these components cannot guarantee the recovery to the initial state, so these deformations will cause permanent damage to the components. In order to solve this problem, the present invention sets a ceramic (Al2O3) coupling ring 21 above the insulating ring 72. The coupling ring 21 covers the upper surface of the insulating ring 72, and the bottom surface of the coupling ring 21 located on the inner side is in close contact with the conductive base 5 to achieve a large amount of heat conduction, so the heat of the upper plasma is effectively conducted to the conductive base 5 with stable temperature. The heat flowing into the insulating ring 72 from the upper plasma is also greatly reduced, avoiding the interference with the plasma treatment process caused by the excessively high thermal expansion coefficient of the resin material insulating ring. The above-mentioned coupling ring 21 can be an integral ring covering the upper surface of the outer part of the conductive base 5 and the upper surface of the insulating ring 72, or it can be a combination of multiple rings. As long as the annular structure can prevent heat from flowing downward into the insulating ring 72, it belongs to the coupling ring defined in the present invention. Among them, as long as the coupling ring 21 can cover most of the surface of the insulating ring, it can prevent it from heating up significantly, and it does not have to be completely covered to achieve the purpose of the present invention.

[0031] like Figure 6 As shown, the RF matching network in the present invention may include two matching circuits to respectively realize the matching of the above-mentioned high-frequency RF power and low-frequency RF power, and may also include at least two filtering circuits to respectively only allow the power of the high-frequency RF frequency and the low-frequency RF frequency to pass through, so as to prevent the signals of other frequencies from passing back into the RF power supply below. Furthermore, according to the cause of the uneven plasma distribution on the wafer disclosed by the present invention is that the harmonic RF power cannot be consumed quickly, but circulates and accumulates in the reaction chamber. A harmonic filter can be set in the RF matching network of the present invention, which has a lower impedance to the above-mentioned harmonic RF power RF2 (120Mhz, 180Mhz), and at the same time prevents the power (60Mhz) input into the reaction chamber from the HF RF power source from flowing out of the harmonic filter. Figure 6As shown in , the harmonic filter is connected at both ends of the high-frequency filter, or it can be connected in parallel at both ends of the low-frequency filter. The setting of the harmonic filter can further reduce the impedance of the RF matching network to the harmonic RF signal. Combined with the lower equivalent capacitance Ch, more harmonic RF power can eventually enter the RF matching network through the RF cable connected to the lower electrode and be consumed, and no longer enter the above-mentioned harmonic RF circulation path. The harmonic filter may include a variable capacitor or a variable inductor, so that the impedance ratio of the harmonic filter to the fundamental frequency and the harmonic frequency is adjustable, so that the power of the harmonic RF power flowing into the RF matching network can be adjusted, and the plasma concentration distribution on the wafer can also be adjusted. For some plasma processing processes, the plasma concentration in the center needs to be slightly higher to compensate for the imbalance of other parameters. The use of a harmonic filter with adjustable impedance can slightly adjust the concentration distribution on the basis of ensuring that the plasma concentration on the wafer is roughly uniform, thereby achieving a better plasma processing effect.

[0032] In the present invention, by changing the material selection of the insulating ring, more harmonic RF power generated in the capacitively coupled plasma processor can be consumed by flowing into the RF matching network along the frequency cable. Further, the harmonic RF power can be effectively derived by setting the above-mentioned harmonic filter at any position of the RF matching network or the RF cable. As long as the input basic frequency is high enough (40Mhz, 60Mhz, 100Mhz, etc.), a large amount of harmonic RF power will be generated in the reaction chamber. According to the frequency and specific process parameters, 10-50% of the input RF power is converted into harmonic RF power. The present invention uses the insulating ring or circuit design of the above-mentioned multiple materials to make most of the harmonic RF power (50%) generated by the input reaction chamber, that is, more than 5-25% of the input high-frequency RF power RF1, or preferably more than 10%, be introduced downward into the RF matching network through the RF cable, and no longer enter the harmonic RF circulation path, which can greatly improve the uniformity of the plasma treatment effect.

[0033] The plasma processing described in the present invention is not limited to plasma etching, but can also be plasma-assisted chemical vapor deposition (PECVD), etc. As long as high-frequency (above 40Mhz) RF power needs to be input, the plasma processing equipment that uses the plasma generated by the high-frequency RF power for processing can adopt the technical solution provided by the present invention. In the field of plasma processing such as PECVD, since downward etching is not required, low-frequency RF power is no longer required, and it is sufficient to input high-frequency RF power to the conductive base on which the substrate is installed. The present invention reveals the fundamental reason for the uneven distribution of plasma concentration when high-frequency RF power is applied to a capacitively coupled plasma processing chamber, and proposes a variety of methods such as selecting a low-dielectric constant insulating ring or changing the impedance of the RF matching network to the harmonic RF signal, so as to guide more harmonic RF power into the RF matching network and reduce the power ratio of the harmonic RF power entering the circulation path. The interference of harmonic RF power on the uniformity of plasma distribution is minimized.

[0034] Although the content of the present invention has been described in detail through the above preferred embodiments, it should be appreciated that the above description should not be considered as a limitation of the present invention. After reading the above content, it will be apparent to those skilled in the art that various modifications and substitutions of the present invention will occur. Therefore, the protection scope of the present invention should be limited by the appended claims.

Claims

1. A plasma reactor, characterized in that: include: A reaction chamber, wherein a conductive base is provided at the bottom of the reaction chamber, the conductive base is connected to a radio frequency power supply device through a radio frequency matching network, a substrate to be processed is placed above the conductive base, an upper electrode assembly is included at the top of the reaction chamber, and a plasma processing space is provided between the conductive base and the upper electrode assembly; A first conductive grounding ring is disposed around the periphery of the conductive base; a second conductive grounding ring electrically connected between the outer side wall of the first conductive grounding ring and the inner side wall of the reaction chamber, wherein the second conductive grounding ring is provided with a plurality of gas channels so that the gas in the plasma processing space can be discharged through the plurality of gas channels; A first insulating ring is included between the conductive base and the first conductive grounding ring, and the dielectric constant of the first insulating ring is less than 3.5; A coupling ring is included above the first insulating ring, the coupling ring covers the upper surface of the first insulating ring and the upper surface of the outer portion of the conductive base, wherein the coupling ring is made of a first ceramic material, and the thermal conductivity of the first ceramic material is higher than the thermal conductivity of the first insulating ring; A device board is also arranged below the conductive base, and the first conductive grounding ring surrounds the side wall and part of the bottom surface of the device board; A second insulating ring surrounds the device board and is located between the device board and the first conductive ground ring.

2. The plasma reactor according to claim 1, characterized in that The radio frequency power supply device outputs a high-frequency radio frequency power, and the frequency of the high-frequency radio frequency power is greater than 40Mhz.

3. The plasma reactor according to claim 1, characterized in that The second insulating ring covers a portion of the bottom surface of the device board, and the dielectric constant of the second insulating ring is less than 3.

2.

4. The plasma reactor according to claim 1, characterized in that The first insulating ring is disposed around the conductive base and the side wall of the device board, and a second insulating ring is located below the device board.

5. The plasma reactor according to claim 1, characterized in that A focus ring and an edge ring are arranged above the coupling ring, the focus ring and the edge ring cover the coupling ring, and the upper surfaces of the focus ring and the edge ring are exposed to the plasma processing space.

6. The plasma reactor according to claim 1, characterized in that A plasma confinement ring is disposed above the second conductive grounding ring and is arranged around the conductive base.

7. The plasma reactor according to claim 1, characterized in that The upper electrode assembly includes a mounting plate, and the mounting plate is connected to the top cover of the reaction chamber.

8. The plasma reactor according to claim 1, characterized in that One or more adjustable impedance devices are connected between the second conductive grounding ring and the inner wall of the reaction chamber.

9. A plasma reactor, characterized in that: include: A reaction chamber, wherein a conductive base is provided at the bottom of the reaction chamber, the conductive base is connected to a radio frequency power supply device through a radio frequency matching network, a substrate to be processed is placed above the conductive base, an upper electrode assembly is included at the top of the reaction chamber, and a plasma processing space is provided between the conductive base and the upper electrode assembly; A first conductive grounding ring is disposed around the periphery of the conductive base; a second conductive grounding ring electrically connected between the outer side wall of the first conductive grounding ring and the inner side wall of the reaction chamber, wherein the second conductive grounding ring is provided with a plurality of gas channels so that the gas in the plasma processing space can be discharged through the plurality of gas channels; A first insulating ring is included between the conductive base and the first conductive grounding ring; the dielectric constant of the first insulating ring is less than 3.5; A device board is also arranged below the conductive base, and the first conductive grounding ring surrounds the side wall and part of the bottom surface of the device board; a second insulating ring surrounding the device board and located between the device board and the first conductive grounding ring; The RF matching network supplies high-frequency RF power having a fundamental frequency to the conductive base through at least one RF cable, and the fundamental frequency is greater than or equal to 40Mhz; the plasma in the plasma processing space generates harmonic RF power of the fundamental frequency, and the harmonic RF power flows into the RF matching network through the at least one RF cable, wherein the harmonic RF power flowing into the RF matching network is greater than 5% of the high-frequency RF power.

10. The plasma reactor according to claim 9, characterized in that The radio frequency matching network includes a first filter for allowing the high-frequency radio frequency power to pass through, and also includes a second filter for allowing the harmonic radio frequency power to pass through and preventing the high-frequency radio frequency power from passing through.

11. The plasma reactor according to claim 9, characterized in that The radio frequency power supply device includes a high-frequency radio frequency power supply outputting radio frequency power with a basic frequency, and also includes a low-frequency radio frequency power supply outputting radio frequency power with a bias frequency, and the bias frequency is less than or equal to 2Mhz.

12. The plasma reactor according to claim 10, characterized in that The RF matching network includes a matching circuit for inputting the high-frequency RF power into the reaction chamber, the first filter and the matching circuit are connected in series between the RF cable and the RF power supply device, and also includes an impedance adjustment circuit for making the matching circuit have adjustable impedance to the high-frequency RF power and the harmonic RF power.

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