A helium-based plasma etching method and a specialized ICP system

Abstract

This invention discloses a helium-based plasma etching method and a specialized ICP system, belonging to the field of semiconductor plasma etching technology. It includes an inductively coupled plasma cavity; a substrate; an RF coil; a matching network; a shielded temperature-controlled shell with multiple temperature sensors and multiple cooling fans installed in sections, each temperature sensor linked to its corresponding cooling fan; and a top cover plate positioned on top of the inductively coupled plasma cavity. The top cover plate has cooling water channels inside and temperature sensors are installed on it. Cooling water pneumatic valves are installed on the cooling water channels, and the temperature sensors are linked to the cooling water pneumatic valves. This invention utilizes the extremely small mass of He+ ions, resulting in a very low physical sputtering rate and high thermal conductivity that rapidly dissipates bombardment energy. The wafer surface temperature remains consistently below the photoresist denaturation threshold, completely eliminating paste and lattice damage.

Description

Technical Field

[0001] This invention relates to the field of semiconductor plasma etching technology, specifically to a helium-based plasma etching method and a specialized ICP system. Background Technology

[0002] In the plasma etching process of inductively coupled cavity (ICP), a variety of process gases are used, and different process gases are adapted according to different etching materials. Among them, Ar is an extremely important inert process gas, which needs to be added in appropriate amounts in most processes. Its role spans chemical etching and physical etching. It provides ions for physical bombardment and assists chemical etching. At the same time, due to its easy ionization properties, it is also the core of maintaining plasma stability.

[0003] However, in some specialized etching processes, Ar, due to its inherent properties, may fall short: Etching of temperature-sensitive materials: These materials exhibit a defined temperature response range. Temperature changes trigger significant alterations in their physical or chemical properties. These abrupt changes can be reversible or irreversible. Ar+ bombardment can lead to supercritical temperatures, causing material failure. For example, the critical temperature at which photoresist materials undergo irreversible physical or chemical property changes due to temperature increases is called the photoresist denaturation threshold. For UV positive photoresists, this threshold is 100°C. For other types of photoresists, those skilled in the art can determine their denaturation threshold based on the photoresist's glass transition temperature (Tg) and thermal decomposition temperature.

[0004] Ar+ bombardment causes more physical damage and destruction; excessive damage to the structure can lead to device failure and introduce risks.

[0005] In etching processes, endpoint detection systems determine the reaction endpoint by capturing the different wavelengths of different substances, thus determining the moment to stop etching. This is crucial within the system. However, argon gas in plasma forms various polyatomic ions, which can disrupt the mass spectrometry background. For example, ArO2... + Ar2 + ArC + Interference peaks are close to the material being captured, which severely limits the sensitivity and accuracy of endpoint detection systems in detecting certain key elements.

[0006] In the etching of some high aspect ratio structures, Ar+ cannot maintain the bottom structure angle well. This is determined by the size and mass of Ar+ ions, which can also introduce the risk of failure and performance degradation.

[0007] Helium (He) can theoretically overcome the aforementioned shortcomings of Ar, and helium-based plasma has the following advantages: 1. High stability: Extremely high ionization energy: Helium's ionization energy (24.6 eV) is higher than argon's (15.8 eV), requiring higher energy for excitation. This means that more energy (higher source power) needs to be injected into the system to ionize helium. This directly leads to changes in plasma properties and increases electron temperature, which is crucial for processes requiring high chemical reactivity but low reaction temperatures.

[0008] 2. Heat sensitive: extremely high thermal conductivity: helium is the gas with the highest thermal conductivity besides hydrogen.

[0009] In plasma, helium can efficiently transfer energy from high-temperature regions (such as the plasma core) to low-temperature regions (such as the reaction chamber walls and substrate). This allows: Lower process temperature: Ideal for temperature-sensitive processes, such as etching of temperature-sensitive materials.

[0010] Better thermal management: helps maintain process uniformity and stability, and prevents localized overheating.

[0011] 3. Low damage: Small atomic mass and radius: Helium molecules are the lightest gas molecules besides hydrogen molecules, and also have the smallest radius. They have a higher diffusion coefficient and can enter narrow structures (such as high aspect ratio contact holes) more effectively. This helps to etch the bottom of these structures, and the physical sputtering rate is low, reducing the damage to materials caused by physical bombardment alone.

[0012] 4. Easy to detect: Helium is an inert gas with extremely stable chemical properties. It almost never forms stable polyatomic ions (such as HeO+, He2+, etc., which are extremely difficult to form and unstable). Therefore, when using helium plasma, the mass spectrometry background for endpoint detection becomes very "clean," making it easier to determine the reaction endpoint, ensuring accurate detection, timely stopping, and better etching process results.

[0013] Technical problems existing in the current technology: However, due to the extremely high ionization energy of He, industrial etching using pure helium-based plasma requires a source power far exceeding that of conventional Ar processes. This high-power operation presents a series of new engineering challenges: The plasma heat load increases dramatically: high power input causes the temperature of the coil and cavity wall to rise sharply, exceeding the heat dissipation capacity of conventional ICP systems, which may cause thermal breakdown of components and failure of vacuum seal.

[0014] Power coupling efficiency decreases: At high power, the losses of traditional circular coils and matching networks increase, the reflected power increases, and the heat generation problem is further aggravated.

[0015] The problem of temperature uniformity control of high-power helium-based plasma remains unresolved: Traditional ICP systems lack the ability to independently monitor and dynamically control the temperature of the cavity cover and dielectric cylinder, making them unable to meet the high requirements for thermal uniformity in He etching processes.

[0016] Therefore, simply replacing Ar with He cannot be directly applied to mass production processes. A targeted and systematic redesign of the ICP system is necessary to solve the core technical bottleneck of efficient excitation and thermal management of high-power helium plasma. Summary of the Invention

[0017] To achieve the above objectives, the technical solution of the present invention includes a helium-based plasma etching system, the system comprising: Inductively coupled plasma cavity; The substrate is a temperature-sensitive material, which is either a UV positive photoresist or a material with a temperature response range. The substrate has an etched structure with an aspect ratio greater than 2. An RF coil is disposed outside the inductively coupled plasma cavity. The RF coil is a hollow, flat rectangular copper tube with a silver-plated outer surface. Cooling water is circulated inside the hollow, flat rectangular copper tube. A matching network, wherein the topology of the matching network is π-type, and the capacitors in the matching network are vacuum capacitors driven by a high-torque motor; A shielded temperature control shell is arranged around the inductively coupled plasma cavity. Multiple temperature sensors and multiple cooling fans are installed in sections on the shielded temperature control shell, and each temperature sensor is linked to its corresponding cooling fan. The upper cover plate is disposed on the top of the inductively coupled plasma cavity. The upper cover plate has a cooling water channel inside. A temperature sensor is installed on the upper cover plate. A cooling water pneumatic valve is provided on the cooling water channel. The temperature sensor is linked with the cooling water pneumatic valve. The fan and its corresponding temperature sensor are linked, and the sensor polls the area temperature detected by the sensor every second. If the temperature exceeds the preset temperature, an alarm is triggered and the system crashes, waiting for manual inspection and recovery. If the temperature is below the preset temperature but exceeds a certain value, the fan is turned on to cool down. If the temperature is below the certain value, the fan is turned off. The fan and sensor combination in each area polls according to this judgment logic. After the process gas is introduced through the process inlet pipe, it is evenly distributed through the bottom air hole and then introduced into the cavity. Inside the cover plate, there is a copper cooling water pipe, which is connected to the external water supply end through a quick-connect connector. At the outlet of the cooling water pipe, there is a pneumatic water valve. When it is open, the cooling water flows, and when it is closed, the cooling water stops. The sensor on the upper part of the cover plate can measure the center temperature of the upper cover plate and control the opening and closing of the pneumatic water valve. The pneumatic valve is linked with the corresponding temperature sensor, which polls the area temperature detected by the sensor every second. If the temperature exceeds the preset temperature, an alarm is triggered and the system crashes, waiting for manual inspection and recovery. If the temperature is below the preset temperature but exceeds a specific value, the pneumatic valve is opened for water cooling. If the temperature is below the specific value, the pneumatic valve is closed to stop water cooling.

[0018] Preferably, the inductively coupled plasma cavity is provided with an alumina ceramic tube, the wall thickness of which is 8-10 mm; the RF coil is arranged around the outside of the alumina ceramic tube, and the number of turns of the RF coil is configured as 4-6 turns.

[0019] Preferably, the main body of the shielded temperature control shell is a metal aluminum plate, and the inner and outer surfaces are treated with conductive oxidation to form an electromagnetic shielding layer. The shielded temperature control shell has a double-layer air duct structure for achieving zoned temperature control.

[0020] Preferably, the substrate of the upper cover plate is aluminum, and the bottom of the upper cover plate is provided with evenly distributed air holes. The process gas enters from the top of the upper cover plate and then enters the interior of the inductively coupled plasma cavity through the evenly distributed air holes.

[0021] Preferably, the RF coil is clamped and fixed to the inductively coupled plasma cavity by an insulating fastener, the insulating fastener being made of polyetheretherketone; all fasteners connected to the RF system within the inductively coupled plasma cavity are insulating.

[0022] Preferably, the system is configured to operate in pulse power mode with a pulse frequency of 500-1000Hz and a duty cycle of 0.5-0.8.

[0023] Preferably, a helium-based plasma etching method implemented by the system includes: Helium is used as an auxiliary gas or carrier gas, which is mixed with the main etching gas and then introduced into the inductively coupled plasma cavity; Helium-based plasma is excited and formed in the inductively coupled plasma cavity to etch a substrate disposed in the inductively coupled plasma cavity; During the etching process, the temperature of the wafer surface is controlled to be below the photoresist denaturation threshold.

[0024] Preferably, the main etching gas includes at least one of SF6, CF4, Cl2, or HBr.

[0025] Preferably, during the etching process, the reaction endpoint is detected by a mass spectrometry endpoint detection system, and the mass spectrometry background of the helium-based plasma does not contain polyatomic ion peaks that interfere with the detection of target elements.

[0026] Compared with the prior art, the beneficial effects of the present invention are as follows: 1) Achieve low-damage etching of temperature-sensitive materials: Due to the extremely small mass of He+ ions and the extremely low physical sputtering rate, and the high thermal conductivity that rapidly dissipates the bombardment energy, the wafer surface temperature is always below the photoresist denaturation threshold, thus completely eliminating smearing and damage. 2) Significantly improves etching uniformity: The hollow water-cooled coil and zoned temperature control system effectively suppress thermal non-uniformity, improving the uniformity of the entire surface; 3) Provides a high signal-to-noise ratio endpoint detection environment: He hardly forms any stable polyatomic ions, resulting in a clean mass spectrometry background, which greatly improves the accuracy and reliability of endpoint determination, and is especially suitable for etching multiple material stacks; 4) Improved sidewall control in high aspect ratio structures: He has a small atomic radius and a high diffusion coefficient, which enables it to enter the bottom of narrow structures to provide etching reactants while maintaining a steep sidewall angle; 5) Strong system robustness: Through active dynamic thermal management, the system can operate continuously in high-power mode for a long time, extending component life and shortening maintenance cycle. Attached Figure Description

[0027] Figure 1 This is a schematic diagram of the overall appearance of the specialized inductively coupled plasma system of the present invention; Figure 2 This is a side cross-sectional view of the specialized inductively coupled plasma system of the present invention; Figure 3 A side view of a specialized inductively coupled plasma system after removing the shielding temperature control housing; Figure 4 This is a side view of the RF path of the present invention; Figure 5 This is a schematic diagram of the cooling water flow of the RF coil of the present invention; Figure 6 This is a cross-sectional view of the RF coil of the present invention; Figure 7 This is a schematic diagram of the structure of the alumina ceramic cylinder of the present invention; Figure 8 This is a schematic diagram of the structure of the shielded temperature control shell assembly of the present invention; Figure 9 This is a side cross-sectional view of the shielded temperature control shell assembly of the present invention; Figure 10 This is a schematic diagram of the structure of the components related to the upper cover plate of the present invention. Figure 1 ; Figure 11 This is a schematic diagram of the structure of the components related to the upper cover plate of the present invention. Figure 2 ; Figure 12 The judgment logic of this invention Figure 1 ; Figure 13 The judgment logic of this invention Figure 2 ; Figure 14 This is a schematic diagram of the π-type topology within the matcher of the present invention; Figure 15 This is a comparison image of etching in an embodiment of the present invention; Figure 16 These are comparative images of surface damage in embodiments of the present invention; Figure 17 This is a comparison diagram of the paste in the embodiments of the present invention.

[0028] List of reference numerals in the attached diagram: 1-RF inlet; 2-Grounding terminal; 3-RF coil cooling water outlet; 4-RF coil cooling water inlet; 5-Thick-walled ceramic cylinder; 6-Fan; 7-Infrared sensor; 8-Double-layer air passage; 9-Process air inlet pipe; 10-Quick-connector; 11-Pneumatic water valve; 12-Contact sensor; 13-Cooling water pipe; 14-Process air inlet; 15-Upper cover cooling water outlet; 16-Upper cover cooling water inlet; 100-Temperature-controlled upper cover assembly; 101-Shielded temperature-controlled outer shell assembly; 102-Cavity body; 103-RF matching unit; 104-Specialized RF coil assembly. Detailed Implementation

[0029] The present invention will be further illustrated below with reference to the accompanying drawings and specific embodiments. It should be understood that the following specific embodiments are for illustrative purposes only and are not intended to limit the scope of the present invention. Example

[0030] This embodiment provides a helium-based plasma etching method suitable for temperature-sensitive materials and high aspect ratio structures (>2), as well as a specialized ICP system. Figure 1 , Figure 2 , Figure 3 ). Figure 1 The overall appearance of the specialized cavity is as follows: the bottom is made of aluminum with hard anodizing on both the inner and outer surfaces, which is the main body of the upper cavity; the upper part is a shielded temperature control shell, the main body of which is a metal aluminum plate with conductive anodizing on both the inner and outer surfaces, which serves as electromagnetic shielding; fans and temperature sensors are installed in sections for zoned temperature control; the top part is the top cover plate, made of aluminum, through which process gas is introduced from the upper gas pipe, and after being uniformly distributed through the gas holes, it is introduced into the cavity; the rear of the cavity is a matching device, which matches the impedance of the cavity to ensure that RF can be fed into the plasma in the cavity normally without reflection. Figure 2 The side cross-section of the specialized cavity shows the RF copper coil inside the shielded temperature control shell, as well as the thick-walled alumina ceramic cylinder further inside. The top cover shows evenly distributed air holes to improve airflow uniformity. Figure 3The side view of the specialized cavity without the shielded temperature control shell shows a 5-turn RF coil with a hollow cooling water chamber. The entire coil is fixed to the cavity using a PEEK (polyether ether ketone) insulating material fastener.

[0031] The ICP (Inductively Coupled) system transfers energy through a coil to a process gas with helium as an auxiliary gas, forming a plasma. This plasma is then used to etch temperature-sensitive materials and structures with a depth / width greater than 2, according to the process requirements.

[0032] This invention completely replaces argon as the auxiliary / carrier gas, mixing it with the main etching gas (such as SF6, CF4, Cl2, HBr, etc.) for etching temperature-sensitive materials or high aspect ratio structures. To address the thermal management challenges posed by the high power input required by helium-based plasmas, the ICP system underwent a systematic reconfiguration, including: RF system enhanced design: Matcher optimization: Select vacuum capacitors with sufficient margin in rated capacitance, and use models with high withstand voltage and high current carrying capacity; optimize the design of the matching network, use better topologies such as π type, and equip it with high torque and fast automatic matching to reduce matching and path losses; and enable pulse power mode to reduce overall energy consumption and heat generation.

[0033] Schematic diagram of the π-type topology inside the matching unit: The capacitor is equipped with a high-torque motor, and all components and circuits use specifications that support pulse function.

[0034] RF coil optimization: The coil was changed from a circular shape to a hollow, flat rectangular copper tube with a silver-plated outer surface and cooling water flowing through the center. This allows for a higher cooling water flow rate under high power output conditions, significantly improving heat dissipation efficiency. The number of coil turns was increased by 20% compared to a conventional Ar system to improve plasma density and power coupling efficiency, which improves power utilization and the etching rate within the cavity. Figure 4 , Figure 5 , Figure 6 ) Figure 4 Side view of the RF path: On the right is a 5-turn RF coil, which is fixed by four clamps made of insulating PEEK material. On the left is the matching unit. The RF enters the coil's RF input terminal through the matching unit via a copper busbar, and then follows the coil to the ground terminal at the bottom, where it is grounded via the grounding copper busbar. Figure 5 The RF coil is a hollow copper tube with a constant supply of cooling water, which enters from the lower interface and flows out from the upper opening to ensure a stable and full water flow inside the tube. Figure 6 : Cross-sectional view of RF coil. The coil is a hollow, flat rectangular copper tube with silver plating on the outer surface and water flowing through the middle.

[0035] Vacuum components for cavity thermal management: Optimized ceramic dielectric cylinder design (zoned air cooling): Uses a thick-walled, well-cooled ceramic cylinder to prevent thermal breakdown. Figure 7 ); Figure 7 The interior consists of a 10mm thick-walled alumina ceramic cylinder, surrounded by an RF coil. Independent non-contact infrared temperature sensors monitor the temperature of the upper and lower ceramic cylinders. If the temperature exceeds a preset value, the corresponding cooling fans in each cylinder activate for air cooling; if the temperature falls below the preset value, the fans automatically shut off. The entire process is dynamically monitored and automatically adjusted. Figure 8 , Figure 9 Logic 1) Figure 8 The shielded temperature control housing is made entirely of aluminum plate with conductive oxidation on both the inner and outer surfaces to provide electromagnetic shielding and prevent RF leakage and interference. Four fans and four corresponding temperature sensors are installed in separate zones, and the fans are switched on and off based on sensor feedback. Figure 9 : Side cross-sectional view of the shielded temperature control housing assembly. The specialized double-layer air duct design enables zoned temperature control and real-time adjustment. Judgment Logic 1: One fan and one corresponding temperature sensor are linked, polling the area temperature detected by the sensor every second. If the temperature is ≥100℃, an alarm is triggered and the system shuts down, awaiting manual recovery after inspection. If the temperature is <100℃ but ≥65℃, the fan is activated for cooling. If the temperature is <60℃, the fan is deactivated. This judgment logic is used for all four fan and sensor combinations.

[0036] Optimized upper cavity design: All fasteners connected to the RF system use higher-grade insulation to prevent breakdown and arcing under high power; the upper cavity metal cover has an internal cooling water channel and uses an insertion contact temperature sensor linked to a cooling water pneumatic valve. If the sensor detects that the internal temperature of the upper cavity cover exceeds the preset temperature value, the cooling water pneumatic valve opens to cool down; once the temperature falls below the preset value, the cooling water pneumatic valve automatically closes, with dynamic monitoring and automatic adjustment throughout the process. Figure 10 , Figure 11 Logic 2) Figure 10 , Figure 11 The components of the upper cover plate are made of aluminum. Process gas enters through the process inlet pipe, is evenly distributed through the bottom vent, and then enters the cavity. Inside the cover plate, there is a copper cooling water pipe connected to an external water supply via a quick-connect fitting. At the outlet of the cooling water pipe, there is a pneumatic water valve. When open, the cooling water flows; when closed, the cooling water stops. A sensor on the upper part of the cover plate measures the center temperature and controls the opening and closing of the pneumatic water valve. Judgment Logic 2: The pneumatic valve and the corresponding temperature sensor are linked. The sensor polls the area temperature detected every second. If the temperature is ≥100℃, an alarm is triggered and the system crashes, requiring manual recovery after inspection. If the temperature is <100℃ but ≥65℃, the pneumatic valve is opened for water cooling. If the temperature is <60℃, the pneumatic valve is closed to stop water cooling.

[0037] Through the above design, the present invention achieves stable operation of pure helium or helium-based mixed plasma at high source power, while controlling the wafer surface temperature below 100°C, meeting the process requirements of UV positive photoresist. The denaturation threshold of other temperature-sensitive materials is determined based on the glass transition temperature (Tg) and thermal decomposition temperature of the photoresist.

[0038] I. Detailed Implementation Methods (Process Example) Process gas: He; Process parameters: 8mT, 2000 / 200W, pulse frequency 500Hz, duty cycle 0.8, 10SF6, 120He, cavity temperature control 60℃, ESC temperature control 40℃; Table 1 - Comparison of Process Parameters

[0039] Table 2 - Comparison of Etching Effects

[0040] Under conventional Ar etching system: the photoresist etching rate is 329 nm / min (>300 nm / min), but the UV positive photoresist shows obvious sticking phenomenon (surface temperature exceeds 100℃), the selectivity is only 1.2, the uniformity is 5.6%, the mass spectrometry detection is affected by ArO+ interference and cannot accurately determine the endpoint, and the endpoint detection time of the structure sheet fluctuates within 10%.

[0041] In the unmodified system: helium-based plasma is difficult to stably ignite, and the etching rate needs to be further improved; the source power needs to be increased to more than 1500W (higher than the modified system), the coil temperature is >120 ℃, the ceramic tube contact temperature reaches more than 100℃, the temperature difference between the upper and lower cavities is large, causing the ceramic tube to crack; the unoptimized matcher and matching network consume a lot of extra energy, resulting in a slow etching rate, and the overall voltage withstand rating and current carrying capacity of the matcher are low. Long-term processes will cause the matcher to overheat and shut down, making the process unsustainable.

[0042] The He process of this invention achieves an etching rate of 214 nm / min (slightly lower but can be compensated for by increasing power), with no denaturation and complete pattern in the UV-Vis positive photoresist, completely solving the thermal damage problem of temperature-sensitive materials and meeting the requirements for etching high aspect ratio structures; the selectivity reaches 2.5 (108% improvement compared to conventional Ar processes), and the uniformity is 2.2% (61% improvement compared to conventional Ar processes); moreover, the mass spectrometry background is clean, the endpoint detection sensitivity is improved, the fluctuation range is reduced to 3% (signal-to-noise ratio is significantly improved), and the endpoint detection is more accurate.

[0043] Table 3 - Description of Examples and Comparative Figures

[0044] Figure 15 This is a schematic diagram comparing the morphology of photoresist after etching in the embodiments of the present invention and Comparative Example 1. The left side shows the photoresist outline of the present invention (He process) with clear and complete outline, while the right side shows the photoresist of Comparative Example 1 (Ar process) with thermally induced paste formation, resulting in outline distortion and thinning of the photoresist layer.

[0045] Figure 16 This is a schematic diagram comparing the surface damage of the substrate after etching in the embodiment of the present invention and Comparative Example 1. The left side shows the surface of the present invention (He process) – smooth and without bombardment damage marks, while the right side shows the surface damage caused by Ar⁺ bombardment in Comparative Example 1 (Ar process).

[0046] Figure 17 This is a schematic diagram comparing the morphology of the photoresist after long-term etching in the embodiments of the present invention and Comparative Example 1. The left side shows the present invention (He process) – the photoresist pattern remains intact after long-term etching, while the right side shows Comparative Example 1 (Ar process) – the photoresist is completely smeared after long-term etching, and the pattern is completely distorted.

[0047] It should be noted that the above content merely illustrates the technical concept of the present invention and should not be construed as limiting the scope of protection of the present invention. For those skilled in the art, various improvements and modifications can be made without departing from the principle of the present invention, and all such improvements and modifications fall within the scope of protection of the claims of the present invention.

Claims

1. A helium-based plasma etching system, characterized in that the system... include: Inductively coupled plasma cavity; substrate; The material is a temperature-sensitive material, which is a UV positive photoresist or a material with a temperature response range, and the substrate has an etched structure with an aspect ratio greater than 2; An RF coil is disposed outside the inductively coupled plasma cavity. The RF coil is a hollow, flat rectangular copper tube with a silver-plated outer surface. Cooling water is circulated inside the hollow, flat rectangular copper tube. A matching network, wherein the topology of the matching network is π-type, and the capacitors in the matching network are vacuum capacitors driven by a high-torque motor; A shielded temperature control shell is arranged around the inductively coupled plasma cavity. Multiple temperature sensors and multiple cooling fans are installed in sections on the shielded temperature control shell, and each temperature sensor is linked to its corresponding cooling fan. The upper cover plate is disposed on the top of the inductively coupled plasma cavity. The upper cover plate has a cooling water channel inside. A temperature sensor is installed on the upper cover plate. A cooling water pneumatic valve is provided on the cooling water channel. The temperature sensor is linked with the cooling water pneumatic valve. The fan is linked with the corresponding temperature sensor, which polls the temperature of the area detected by the sensor every second. If the temperature exceeds the preset temperature, an alarm is triggered and the system crashes, waiting for manual recovery after inspection. If the temperature is below the preset value but exceeds a certain value, the fan is turned on to cool down; if the temperature is below the certain value, the fan is turned off. The fan and sensor combination in each area polls according to this judgment logic. After the process gas is introduced through the process inlet pipe, it is evenly distributed through the bottom air hole and then introduced into the cavity. Inside the cover plate, there is a copper cooling water pipe, which is connected to the external water supply end through a quick-connect connector. At the outlet of the cooling water pipe, there is a pneumatic water valve. When it is open, the cooling water flows, and when it is closed, the cooling water stops. The sensor on the upper part of the cover plate can measure the center temperature of the upper cover plate and control the opening and closing of the pneumatic water valve. The pneumatic valve is linked with the corresponding temperature sensor, and polls the temperature of the area detected by the sensor every second. If the temperature exceeds the preset temperature, an alarm will be triggered and the system will shut down, waiting for manual recovery after inspection by personnel. If the temperature is below the preset temperature and exceeds a specific value, the pneumatic valve will be opened for water cooling. If the temperature is below the specific value, the pneumatic valve will be closed to stop water cooling.

2. The specialized ICP system according to claim 1, characterized in that, The inductively coupled plasma cavity is equipped with an alumina ceramic tube with a wall thickness of 8-10 mm; the RF coil is arranged around the outside of the alumina ceramic tube with 4-6 turns.

3. The specialized ICP system according to claim 1, characterized in that, The main body of the shielded temperature control shell is a metal aluminum plate, and the inner and outer surfaces are treated with conductive oxidation to form an electromagnetic shielding layer. The shielded temperature control shell has a double-layer air duct structure for achieving zoned temperature control.

4. The specialized ICP system according to claim 1, characterized in that, The base material of the upper cover plate is aluminum, and the bottom of the upper cover plate is provided with evenly distributed air holes. The process gas is introduced from the top of the upper cover plate and enters the interior of the inductively coupled plasma cavity through the evenly distributed air holes.

5. The specialized ICP system according to claim 1, characterized in that, The RF coil is clamped and fixed to the inductively coupled plasma cavity by an insulating fastener made of polyetheretherketone (PEEK); all fasteners connected to the RF system within the inductively coupled plasma cavity are insulating.

6. The specialized ICP system according to claim 1, characterized in that, The system is configured to operate in pulse power mode with a pulse frequency of 500-1000Hz and a duty cycle of 0.5-0.

8.

7. A helium-based plasma etching method implemented by the system described in any one of claims 1 to 6, characterized in that, The methods include: Helium is used as an auxiliary gas or carrier gas, which is mixed with the main etching gas and then introduced into the inductively coupled plasma cavity; Helium-based plasma is excited and formed in the inductively coupled plasma cavity to etch a substrate disposed in the inductively coupled plasma cavity; During the etching process, the temperature of the wafer surface is controlled to be below the photoresist denaturation threshold.

8. The helium-based plasma etching method according to claim 7, characterized in that, The main etching gas includes at least one of SF6, CF4, Cl2, or HBr.

9. The helium-based plasma etching method according to claim 8, characterized in that, During the etching process, the reaction endpoint is detected by a mass spectrometry endpoint detection system. The mass spectrometry background of the helium-based plasma does not contain polyatomic ion peaks that interfere with the detection of target elements.

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