A method and apparatus for plasma processing

Abstract

The present application relates to the technical field of semiconductor manufacturing, in particular to a plasma processing method and device. The method comprises: introducing inert gas into an upstream plasma excitation zone of a reaction cavity to generate metastable inert gas particles by radio frequency discharge excitation; introducing hydrogen-containing reaction gas into a downstream electric field-free zone of the reaction cavity to cause the metastable inert gas particles diffused from the upstream to undergo Penning ionization with the hydrogen-containing reaction gas and generate high-activity hydrogen radical particles; and using the high-activity hydrogen radical particles to perform stripping or surface cleaning treatment on a wafer placed in the reaction cavity to remove photoresist or etching residual polymer on the wafer surface. The present application introduces hydrogen-containing reaction gas into the downstream zone of the metastable inert gas to perform Penning ionization, which greatly reduces the particle kinetic energy while maintaining high chemical activity, realizes lossless processing of low dielectric constant medium, and meets the stringent requirements of advanced node integrated circuit manufacturing for low damage and high selectivity.

Description

Technical Field

[0001] This invention relates to the field of semiconductor manufacturing technology, and more specifically, to a plasma processing method and apparatus. Background Technology

[0002] In advanced integrated circuit (IC) manufacturing processes, especially in chip manufacturing at advanced nodes (such as 14nm and below), the removal of photoresist from the low-k spacer and the cleaning of the wafer surface are critical process steps. The core objective of this step is to effectively remove residual polymers from the photoresist mask or after etching, while avoiding irreversible damage to the low-k dielectric layer and the silicon substrate.

[0003] The currently widely used photoresist removal and surface cleaning technologies in the industry mainly rely on high-temperature plasma or free radical processes. By heating the wafer to 150~300℃, plasma generated by radio frequency dissociation of reactive gases such as O2 or H2 is obtained. After filtering the charged ions through a grounded metal filter, high-purity free radicals are obtained to achieve chemical etching removal of photoresist or residual polymers.

[0004] However, existing high-temperature plasma / free radical resist removal and cleaning processes have significant technical problems. On the one hand, H or O free radicals after being filtered still carry high kinetic energy, which will produce a physical bombardment effect when they come into contact with the wafer surface, resulting in thin film loss of low dielectric constant dielectric layer and substrate damage, thereby affecting the electrical performance and reliability of the device. On the other hand, high-temperature process conditions (150~300℃) can easily accelerate the thermal degradation of low dielectric constant materials, further deteriorating the structural integrity of the dielectric layer.

[0005] Furthermore, traditional processes have limited control over the etching selectivity of different materials, making it difficult to effectively remove target residues while maximally protecting the low-dielectric-constant dielectric sidewalls and silicon substrate. This fails to meet the stringent requirements of advanced node IC processes for low damage and high selectivity.

[0006] Therefore, there is an urgent need to develop a new plasma treatment process to achieve low-damage, highly selective degumming and surface cleaning. Summary of the Invention

[0007] The purpose of this invention is to provide a plasma processing method and apparatus based on Penning ionization, which solves the problem of high-energy particles causing physical damage to low dielectric constant media and substrates and resulting in poor process selectivity in existing plasma processing processes.

[0008] To achieve the above objectives, the present invention provides a plasma processing method, comprising: An inert gas is introduced into the upstream plasma excitation region of the reaction chamber, and metastable inert gas particles are generated by radio frequency discharge. Hydrogen-containing reactive gas is introduced into the downstream non-electric field region of the reaction chamber, causing the metastable inert gas particles diffused from the upstream to undergo Penning ionization with the hydrogen-containing reactive gas, generating highly active hydrogen-based particles. The highly active hydrogen-based particles are used to perform photoresist removal or surface cleaning on the wafer placed in the reaction chamber, removing photoresist or residual polymer after etching from the wafer surface. The hydrogen-containing reactive gas is introduced far from the upstream plasma excitation region, and the Penning ionization process takes place entirely in a field-free region, so that the highly active hydrogen-based particles are not accelerated by an electric field from the time they are generated until they reach the wafer surface.

[0009] In some embodiments, the kinetic energy of the highly active hydrogen-based particles is less than 1 eV, which is lower than the breaking energy threshold of the main valence bonds in the bulk material of the wafer substrate; the lifetime of the highly active hydrogen-based particles is not less than 100 ms. By using highly active hydrogen-based particles to undergo a pure chemical reaction with the target deposits on the wafer surface and generate volatile products, the process of desmearing or surface cleaning can be achieved.

[0010] In some embodiments, the radio frequency discharge employs a pulse-modulated radio frequency source to excite inert gas plasma; The on / off timing of the hydrogen-containing reactive gas is synchronized with the off-window of the radio frequency pulse, and it is only introduced into the reaction chamber during the off-stage of the radio frequency pulse, so that the Penning ionization reaction occurs entirely during the pulse interval without an electric field.

[0011] In some embodiments, by synergistically regulating the reaction chamber pressure and the flow ratio of inert gas to hydrogen-containing reactive gas, the mean free path and diffusion depth of the highly active hydrogen-based particles are controlled, so that the reaction region of the highly active hydrogen-based particles is confined within the photoresist layer or the residual polymer layer after etching.

[0012] In some embodiments, the degumming or surface cleaning process includes, in sequence, an initial penetration stage, a main degumming stage, and a byproduct desorption stage. In the initial permeation stage, the pressure in the reaction chamber is controlled within the first pressure range, and the flow ratio of inert gas to hydrogen-containing reactive gas is within the first flow ratio range, so that highly active hydrogen-based particles can penetrate into the photoresist or residual polymer and establish a uniform reaction interface. During the main degumming stage, the pressure in the reaction chamber is controlled within the second pressure range, and the flow ratio of inert gas to hydrogen-containing reactive gas is within the second flow ratio range, maintaining a stable degumming rate and a high material selectivity. During the byproduct desorption stage, the pressure in the reaction chamber is controlled within the third pressure range, while the temperature of the wafer is increased to promote the desorption and discharge of volatile byproducts generated in the reaction from the chamber. The pressure values ​​of the first pressure zone, the second pressure zone, and the third pressure zone increase sequentially; the ratio of the first flow ratio zone is higher than the ratio of the second flow ratio zone; and the wafer temperature during the by-product desorption stage is higher than the wafer temperature during the initial penetration stage and the main desizing stage.

[0013] In some embodiments, in the step of introducing an inert gas and a hydrogen-containing reactive gas into the reaction chamber, the two gases are introduced in a partitioned gas introduction manner. The inert gas is introduced into the upstream plasma excitation region through the first gas inlet, and the hydrogen-containing reactive gas is introduced into the downstream region away from the upstream plasma excitation region through the second gas inlet, where it mixes with metastable inert gas particles that diffuse from top to bottom and undergoes Penning ionization. By adjusting the gas flow ratio and inlet angle of the first and second gas inlets, uniform mixing and diffusion of the two gases within the cavity can be achieved.

[0014] In some embodiments, the inert gas includes at least one of argon or helium, and the wafer surface is covered with a low dielectric constant dielectric layer. The hydrogen-containing reactive gas includes hydrogen gas; The highly active hydrogen-based particles include at least one of hydrogen atoms, hydrogen free radicals, and hydrogen ions; The substrate material of the wafer includes at least one of silicon, silicon dioxide, or silicon nitride, and the surface of the wafer is covered with a low dielectric constant dielectric layer.

[0015] In some embodiments, the step of introducing an inert gas into the upstream plasma excitation region of the reaction chamber further includes: controlling the types of products of the Penning ionization reaction by selecting the type of inert gas. When helium is used as the inert gas, the Penning ionization reaction preferentially produces hydrogen atoms and hydrogen radicals; When argon is used as the inert gas, the Penning ionization reaction preferentially produces molecular positive ions.

[0016] To achieve the above objectives, the present invention provides a plasma processing apparatus for implementing the Penning ionization-based plasma processing method described above, comprising: The reaction chamber is used to house the wafer and provide a reaction space for resist removal and cleaning. A radio frequency power supply, coupled to the reaction chamber, is used to excite and maintain inert gas plasma, generating metastable inert gas particles in the upstream plasma excitation region. The intake system includes at least two independent gas paths, which are used to input inert gas and hydrogen-containing reactive gas into the reaction chamber, respectively, so as to achieve gas partitioning and diffusion; The air intake system, through its air path spatial layout, introduces hydrogen-containing reactive gas into a downstream region far from the upstream plasma excitation region, allowing the Penning ionization reaction to occur in a field-free region, thus achieving spatial isolation between the upstream plasma excitation region and the Penning ionization reaction region.

[0017] In some embodiments, the intake system includes: The first gas inlet is located in the upstream plasma excitation region of the reaction chamber and is used to introduce inert gas. The second gas inlet is located in the downstream lateral region of the reaction chamber and is used to introduce hydrogen-containing reaction gas. The second gas inlet is inclined toward the wafer side to guide the hydrogen-containing reactive gas downwards and prevent the gas from flowing back to the upstream plasma excitation region.

[0018] In some embodiments, the radio frequency power supply is a pulsed radio frequency power supply; The plasma processing device also includes a synchronization control unit, which is connected to the pulsed radio frequency power supply and the gas path control valve of the hydrogen-containing reactive gas, respectively. The synchronization control unit is used to control the on-off sequence of the hydrogen-containing reactive gas to be synchronized with the off-off window of the radio frequency pulse, and to introduce the gas into the reaction chamber only during the off-off phase of the radio frequency pulse, so that the Penning ionization reaction occurs completely during the pulse interval without an electric field.

[0019] In some embodiments, a substrate support unit is further provided within the reaction chamber: The substrate support unit integrates a temperature control element to regulate the surface temperature of the wafer at different stages of photoresist removal or surface cleaning, thereby promoting the desorption of photoresist and residual polymer reaction byproducts.

[0020] The present invention provides a plasma processing method and apparatus that introduces a hydrogen-containing reactive gas into the downstream region of a metastable inert gas for Penning ionization. This prevents the generated hydrogen-based particles from being accelerated by an electric field before reaching the wafer surface, thereby significantly reducing particle kinetic energy while maintaining high chemical activity. This transforms the process from being dominated by physical bombardment to being dominated by chemical reaction, achieving sub-nanometer-level non-destructive resist removal or surface cleaning of low dielectric constant media. It significantly improves etching selectivity and reduces process temperature, meeting the stringent requirements of low damage and high selectivity in advanced node integrated circuit manufacturing. Attached Figure Description

[0021] The above and other features, properties and advantages of the present invention will become more apparent from the following description taken in conjunction with the accompanying drawings and embodiments, in which the same reference numerals always denote the same features, wherein: Figure 1 A flowchart illustrating the steps of a plasma treatment method based on Penning ionization according to an embodiment of the present invention is disclosed. Figure 2 A schematic diagram of a plasma processing apparatus according to an embodiment of the present invention is disclosed.

[0022] The meanings of the labels in the figures are as follows: 11. Reaction chamber; 21. RF power supply; 22 RF coils; 31 First gas inlet; 32 Second gas inlet; 41. Upstream plasma excitation region; 42. Penning ionization reaction zone; 51 wafers; 52 Substrate support unit. Detailed Implementation

[0023] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are for illustrative purposes only and are not intended to limit the invention.

[0024] Existing plasma processing technologies are mostly applied to general etching or broad-spectrum photoresist stripping processes, and are not specifically optimized for non-destructive resist removal and cleaning of low-dielectric-constant dielectrics in advanced semiconductor nodes of 14nm and below. Current solutions largely rely on multi-layer nozzle structures to physically filter ions to reduce particle energy, failing to avoid the electric field acceleration effect at the ionization source. This results in insufficient particle energy control precision, and significant recombination losses of active particles on the filter structure surface. Consequently, they cannot simultaneously meet the multiple requirements of advanced resist removal processes, such as extremely low damage, high activity utilization, and low-temperature compatibility, making them unsuitable for high-precision processing scenarios like sidewall resist removal of low-dielectric-constant dielectrics and cleaning of post-etching residues.

[0025] Unlike existing technologies, the plasma processing method based on Penning ionization proposed in this invention is specifically adapted for non-destructive removal and surface cleaning of low-dielectric-constant dielectrics on wafers with advanced nodes of 14nm and below. It selectively excites hydrogen-containing gases (such as H2) to generate low-kinetic-energy hydrogen-based particles, which then react chemically with photoresist and residual polymers to generate volatile products, achieving high selectivity removal of the target material. This process not only avoids physical damage to the low-dielectric-constant dielectric and substrate caused by high-energy particles, but also achieves complete decoupling between the upstream plasma excitation region and the ionization reaction region through gas path spatial layout. It eliminates the need for physical filtration structures, significantly reducing the transport and recombination losses of active particles, making it particularly suitable for low-dielectric-constant dielectric processes with stringent damage control requirements.

[0026] Figure 1 A step diagram of a plasma treatment method based on Penning ionization according to an embodiment of the present invention is disclosed, as follows: Figure 1 As shown, this invention provides a plasma treatment method based on Penning ionization, comprising the following three core steps: S1: Inert gas is introduced into the upstream plasma excitation region of the reaction chamber, and metastable inert gas particles are generated by radio frequency discharge. S2: Hydrogen-containing reactive gas is introduced into the downstream non-electric field region of the reaction chamber, causing the metastable inert gas particles diffused from the upstream to undergo Penning ionization with the hydrogen-containing reactive gas, generating highly active hydrogen-based particles; the hydrogen-containing reactive gas is introduced far from the upstream plasma excitation region, and the Penning ionization process is carried out entirely in the non-electric field region, so that the highly active hydrogen-based particles are not accelerated by an electric field from generation to reaching the wafer surface, and the particle kinetic energy is less than 1 eV, participating in the processing reaction only by chemical activity; S3: The highly active hydrogen-based particles are used to perform photoresist removal or surface cleaning on the wafer placed in the reaction chamber to remove the photoresist or residual polymer after etching from the wafer surface.

[0027] This invention provides a plasma treatment method based on Penning ionization, which generates active particles through the Penning ionization mechanism. While retaining high chemical activity, it significantly reduces the kinetic energy of the active particles, effectively solving the problems of low dielectric constant dielectric damage and substrate implantation caused by physical bombardment in traditional processes, and significantly improving process selectivity and controllability.

[0028] In some embodiments, the plasma treatment specifically includes resist removal or surface cleaning, and is suitable for removing resist from low dielectric constant dielectric sidewalls and cleaning wafer surfaces in advanced node IC manufacturing.

[0029] These steps will be described in detail below. It should be understood that, within the scope of this invention, the above-described technical features of this invention and the technical features specifically described below (such as in the embodiments) can be combined and related to each other to form preferred technical solutions.

[0030] Step S1 is used to form metastable inert gas particles. The core of this step is to generate a high concentration of stable metastable inert gas particles in the reaction chamber, providing an activation source for subsequent Penning ionization.

[0031] In some embodiments, the inert gas includes at least one of argon (Ar) or helium (He).

[0032] Preferably, helium (He) is used to obtain higher metastable energy (about 20 eV), thereby more efficiently exciting the subsequent Penning ionization reaction; argon (Ar) has a cost advantage and can be selected according to actual process requirements.

[0033] In some embodiments, the radio frequency discharge uses a pulsed radio frequency method to excite the inert gas plasma. Inert gas is introduced through a first gas inlet at the top of the reaction chamber. This inlet path is configured to be away from the inlet region of subsequent hydrogen-containing reactants to prevent the hydrogen-containing gas from directly entering the upstream plasma excitation region and being prematurely dissociated.

[0034] In some embodiments, an inductively coupled plasma (ICP) source is used as the radio frequency discharge method. The radio frequency power range can be set from 800 W to 3000 W, for example, 800 W, 1000 W, 1500 W, 2000 W, or 3000 W. The reaction chamber pressure can be controlled within the range of 100 mTorr to 1.2 Torr, for example, 500 mTorr, 800 mTorr, 1000 mTorr, or 1200 mTorr, to maintain a stable plasma state; the commonly used pressure range for conventional adhesive removal processes is 500 mTorr to 1.2 Torr. Those skilled in the art will understand that the above parameters are merely examples and can be adjusted according to specific process equipment and the object being processed.

[0035] In some embodiments, by adjusting the radio frequency power and gas flow rate, the inert gas is fully dissociated into metastable particles (He or Ar), with a concentration reaching 10. 12 -10 14 cm -3 .

[0036] This process controls the lifetime of metastable inert gas particles to the range of 100ms to 10s by adjusting the radio frequency power and cavity pressure, which is much longer than the lifetime of traditional directly ionized particles. This ensures that the metastable particles can diffuse fully and mix uniformly with the downstream hydrogen-containing gas, thus guaranteeing the stability and uniformity of the Penning ionization reaction.

[0037] This step, through zoned gas intake and radio frequency parameter control, ensures that the inert gas preferentially forms metastable particles, avoids direct ionization of hydrogen-containing reactive gases by radio frequency, provides a sufficient and controllable activation source for subsequent Penning ionization, and reduces the generation of high-energy charged ions.

[0038] Step S2 is used to generate highly reactive hydrogen-based particles via the Penning ionization reaction. This step utilizes the metastable inert gas particles generated in step S1 to collide with the hydrogen-containing reactive gas, thereby achieving Penning ionization and generating low-kinetic-energy, highly chemically reactive hydrogen-based particles.

[0039] In some embodiments, the hydrogen-containing reactive gas is introduced into the downstream region of the metastable inert gas particles.

[0040] Specifically, two types of gas are introduced in a partitioned gas intake manner: an inert gas is introduced into the upstream plasma excitation region through the first gas inlet, and a hydrogen-containing reactive gas is introduced into the downstream region far away from the upstream plasma excitation region through the second gas inlet, so that it is far away from the radio frequency discharge region, thereby basically avoiding direct dissociation by radio frequency discharge.

[0041] In some embodiments, the gas inlet of the second gas inlet is inclined toward the wafer side to guide the gas to flow downward, further ensuring that the hydrogen-containing reactive gas does not flow back to the upstream plasma excitation region; by adjusting the gas flow ratio and inlet angle of the first gas inlet and the second gas inlet, uniform mixing and diffusion of the two gases can be achieved.

[0042] Through this spatially separated gas intake method, the hydrogen-containing reactive gas does not enter the radio frequency discharge coupling region at all. Instead, it collides with metastable inert gas particles diffused from upstream in the downstream field-free region, achieving Penning ionization rather than direct radio frequency dissociation. This allows hydrogen-based particles to be generated solely through the collisional ionization of metastable particles, without being accelerated by the radio frequency electric field or bias electric field throughout the process, resulting in particle kinetic energy consistently below 1 eV.

[0043] In some embodiments, when the radio frequency discharge uses a pulse-modulated radio frequency source to excite inert gas plasma, the on-off timing of the hydrogen-containing reactive gas is synchronized with the off-off window of the radio frequency pulse. The gas is only introduced into the reaction chamber during the off-off phase of the radio frequency pulse, so that the Penning ionization reaction occurs entirely during the pulse interval without an electric field. This further ensures that hydrogen-based particles are not accelerated by an electric field from a temporal perspective, achieving dual protection of spatial and temporal isolation.

[0044] In some embodiments, the hydrogen-containing reactant gas is hydrogen (H2), and the hydrogen flow rate can be set from 1,000 sccm to 100,000 sccm. Commonly used flow rates in mass production are several thousand to tens of thousands of sccm, such as 2,000 sccm, 5,000 sccm, 10,000 sccm, or 50,000 sccm. The inert gas flow rate (such as Ar 5,000 sccm or He 10,000 sccm) is significantly higher than the H2 flow rate to ensure sufficient metastable particles participate in the collision.

[0045] In some embodiments, the types of products of the Penning ionization reaction are controlled by selecting the type of inert gas: when helium (He, metastable energy approximately 20 eV) is used as the inert gas, the Penning ionization reaction preferentially produces hydrogen atoms and hydrogen radicals, which is suitable for high-speed degumming scenarios; when argon (Ar, metastable energy approximately 11.5 eV) is used as the inert gas, the Penning ionization reaction preferentially produces hydrogen molecule ions (H2). + The process is gentler and suitable for scenarios requiring minimal damage to remove adhesive.

[0046] Metastable He Or Ar It undergoes Penning ionization with H2 molecules, as shown in the following reaction: He +H2→He+H2 + +e - ; Ar +H2→Ar+H2 + +e - ; Subsequently, H2 + Ions and secondary electrons can further initiate dissociation reactions, generating hydrogen atoms (H) and hydrogen radicals (H). ) and a small amount of hydrogen ions (H) + In some embodiments, the highly active hydrogen-based particles include at least one of hydrogen atoms, hydrogen radicals, and hydrogen ions.

[0047] The energy threshold of the average kinetic energy of the hydrogen-based particles generated by the spatial isolation scheme of the present invention only meets the dissociation energy requirements of CC and CF organic bonds in photoresist and residual polymers, and is lower than the breaking energy threshold of Si-Si and Si-O main valence bonds in silicon substrates, silicon dioxide and low dielectric constant media. Therefore, sub-nanometer level dielectric damage control can be achieved, while completely avoiding high-energy particle injection damage to the substrate surface.

[0048] Unlike existing solutions that rely on multi-layer nozzles to filter ions, this invention avoids the acceleration of hydrogen-containing gas by an electric field at the ionization source through spatial partitioning of the air intake. This eliminates the need for ion filtering structures, reduces recombination losses of active particles in the transport path, and improves the activity retention rate of hydrogen-based particles reaching the wafer surface by more than 30%.

[0049] This step replaces direct radio frequency dissociation with Penning ionization, allowing hydrogen-based particles to participate in the reaction in a low-kinetic-energy, highly chemically active form, significantly reducing the physical bombardment effect while ensuring efficient chemical reactivity, thus laying the foundation for subsequent low-damage treatment.

[0050] Step S3 involves using the highly reactive hydrogen-based particles generated in step S2 to perform plasma treatment on the wafer. In this step, the low-kinetic-energy, highly reactive hydrogen-based particles reach the wafer surface and react chemically with the target material, achieving efficient and low-damage resist removal or cleaning.

[0051] The descaling or surface cleaning process is achieved by a purely chemical reaction between highly active hydrogen-based particles and the target deposits on the wafer surface, generating volatile products, without any physical bombardment-driven removal effect.

[0052] In some embodiments, by synergistically regulating the reaction chamber pressure and the flow ratio of inert gas to hydrogen-containing reactive gas, the mean free path and diffusion depth of the highly active hydrogen-based particles are controlled, so that the reaction region of the highly active hydrogen-based particles is confined within the photoresist layer or the residual polymer layer after etching, and does not penetrate into the substrate body and the interior of the low dielectric constant medium.

[0053] In some embodiments, the degumming or surface cleaning process sequentially includes an initial penetration stage, a main degumming stage, and a byproduct desorption stage.

[0054] In the initial permeation stage, the pressure in the reaction chamber is controlled within a first pressure range (e.g., 500 mTorr to 700 mTorr), and the flow ratio of inert gas to hydrogen-containing reactive gas is within a first flow ratio range (e.g., not less than 15:1). This allows highly reactive hydrogen-based particles to permeate into the photoresist or the residual polymer after etching, establishing a uniform reaction interface. This stage ensures sufficient diffusion flux for the hydrogen-based particles through a high flow ratio to overcome the concentration gradient resistance on the polymer surface.

[0055] In the primary desizing stage, the pressure in the reaction chamber is controlled within a second pressure range (e.g., 700 mTorr to 1000 mTorr), and the flow ratio of inert gas to hydrogen-containing reactive gas is controlled within a second flow ratio range (e.g., 5:1 to 10:1), maintaining a stable desizing rate and a high material selectivity. This stage balances the desizing rate and selectivity through appropriate pressure and flow ratio, achieving high-fidelity removal of the target deposits.

[0056] During the byproduct desorption stage, the reaction chamber pressure is controlled within the third pressure range (e.g., 1000 mTorr to 1200 mTorr), while the wafer temperature is increased (e.g., 10°C to 20°C higher than the previous stage) to promote the desorption and discharge of volatile byproducts generated in the reaction. This stage increases the saturated vapor pressure of the byproducts by raising the pressure and temperature, accelerating their diffusion from the inside of the patterned structure outwards and preventing redeposition of byproducts on the sidewalls or bottom.

[0057] The pressure levels in the first pressure zone, the second pressure zone, and the third pressure zone increase sequentially; the ratio of the first flow ratio zone is higher than the ratio of the second flow ratio zone; and the wafer temperature in the by-product desorption stage is higher than the wafer temperature in the initial penetration stage and the main desizing stage.

[0058] Thanks to the low kinetic energy (<1eV) and long lifetime (≥100ms) of hydrogen-based particles, the flux density difference of hydrogen-based particles at the top, sidewalls and bottom of the patterned structure is ≤10%, the degumming rate fluctuates by ≤5% under different opening sizes, and there is no obvious aspect ratio dependence effect.

[0059] In some embodiments, the plasma treatment includes photoresist removal or surface cleaning. Specifically, the plasma treatment targets photoresist or residual polymer after etching. Hydrogen-based particles chemically react with elements such as carbon and fluorine in the photoresist or residual polymer, generating volatile hydrocarbons, hydrogen fluoride, and other products that are then removed.

[0060] In some embodiments, the substrate material of the wafer is suitable for at least one of silicon (Si), silicon dioxide (SiO2), and silicon nitride (SiN). In particular, this method is especially suitable for substrates containing low-k dielectric sidewalls, and can significantly reduce damage to the low-k dielectric while effectively removing resist or cleaning.

[0061] This method achieves significantly low-damage results. In some embodiments, the element implantation depth of hydrogen-based particles can be controlled to be less than 1 nm, the film loss rate of the low-dielectric-constant dielectric layer can be controlled to be below 0.5%, and the residual amount of impurity elements (such as nitrogen and fluorine) in the substrate can be less than 1%. The etching selectivity ratio of photoresist to low-dielectric-constant dielectric layer is not less than 100:1, and the etching selectivity ratio of photoresist to silicon substrate is not less than 200:1. After processing, the net removal of substrate bulk material is less than 0.5 nm, and the film loss of the low-dielectric-constant dielectric layer is less than 0.3 nm. These effects are significantly better than traditional free radical processes and physical filtering downstream plasma processes, verifying the advantages of this method in advanced node integrated circuit manufacturing processes.

[0062] In some embodiments, the process temperature can be reduced to room temperature (25°C) or below 100°C to avoid thermal budget issues and thermal stress damage caused by high-temperature processing. This is due to the following two aspects: On the one hand, the hydrogen-based particles generated by Penning ionization have high chemical potential energy (derived from the energy transfer of inelastic collisions between metastable inert gas particles and H2 molecules), and have sufficient activation energy to initiate reduction reactions even at room temperature, without relying on high-temperature thermal excitation to enhance free radical activity as in traditional processes. On the other hand, the final products of degumming or washing are volatile hydrocarbons (such as CH4, C2H6, CHF3, etc.), which have sufficiently high saturated vapor pressure at room temperature or below 100°C, enabling them to spontaneously desorb and be discharged with the cavity's vacuum system, without relying on high temperatures to promote the volatilization of byproducts.

[0063] Therefore, this invention can achieve efficient adhesive removal or cleaning without a high-temperature environment, effectively avoiding thermal degradation and thermal stress damage to low-k media caused by high temperatures.

[0064] In other embodiments, the wafer may be heated appropriately according to process requirements, but it still has a significant advantage over the 250°C to 300°C required by traditional processes.

[0065] Through the above steps, this method minimizes damage to the low dielectric constant dielectric layer and substrate while ensuring the efficiency of residue removal, improves the selectivity and compatibility of the process, and meets the requirements of low damage and high reliability in advanced node IC manufacturing.

[0066] Although the methods described above are illustrated and depicted as a series of actions for the sake of simplicity, it should be understood and appreciated that these methods are not limited by the order of the actions, as some actions may occur in a different order and / or concurrently with other actions from the illustrations and descriptions herein or not illustrated and described herein but which may be understood by those skilled in the art, according to one or more embodiments.

[0067] The present invention also provides a plasma processing apparatus for implementing the plasma processing method based on Penning ionization as described in any of the above method embodiments.

[0068] Figure 2 A schematic diagram of a plasma processing apparatus according to an embodiment of the present invention is shown, as follows: Figure 2 As shown, a plasma processing apparatus according to an embodiment of the present invention includes: The reaction chamber 11 is used to accommodate the wafer 51 and provide a reaction space for resist removal and cleaning. The radio frequency power supply 21 is coupled to the reaction chamber 11 and is used to excite and maintain the inert gas plasma to generate metastable inert gas particles in the upstream plasma excitation region 41.

[0069] In some embodiments, the radio frequency power supply 21 couples energy into the reaction chamber 11 through the radio frequency coil 22 to excite and maintain the plasma; the radio frequency power supply may be a pulsed radio frequency power supply.

[0070] The intake system includes at least two independent gas paths, which are used to input inert gas and hydrogen-containing reactive gas into the reaction chamber 11, respectively, so as to achieve gas partitioning and diffusion.

[0071] The air intake system, through its air path spatial layout, introduces hydrogen-containing reactive gas into a downstream region far from the upstream plasma excitation region, allowing the Penning ionization reaction to occur in a region without an electric field, thus achieving spatial isolation between the upstream plasma excitation region 41 and the Penning ionization reaction region 42.

[0072] This device eliminates the need for multi-layer ion filter nozzles and light-shielding structures. It achieves decoupling between the upstream plasma excitation zone and the Penning ionization reaction zone simply through the gas path spatial layout, resulting in a simpler structure and reduced recombination loss of active particles on the solid surface.

[0073] In some embodiments, the intake system specifically includes: The first gas inlet 31 is located at the center of the top of the reaction chamber, directly opposite the upstream plasma excitation region, and is used to introduce inert gas into the upstream plasma excitation region 41. The second gas inlet 32 ​​is located in the downstream lateral region of the reaction chamber and is used to introduce hydrogen-containing reaction gas into the downstream or lateral region away from the upstream plasma excitation region 41.

[0074] The second gas inlet 32 ​​consists of 4 to 8 gas inlets evenly arranged circumferentially along the side wall of the reaction chamber. The height of the gas inlets is located at the center of the axial direction of the chamber, 30 to 80 mm away from the surface of the substrate support unit, which can realize the uniform circumferential diffusion of hydrogen-containing reaction gas in the chamber.

[0075] The second gas inlet 32 ​​is inclined toward the wafer side to guide the hydrogen-containing reactive gas to flow downwards and prevent the gas from flowing back to the upstream plasma excitation region 41.

[0076] The upstream plasma excitation region 41 is the coupling region between the radio frequency power supply 21 and the reaction chamber 11, which is the main region where the plasma is excited and maintained.

[0077] Metastable inert gas particles formed in the upstream plasma excitation region 41 diffuse downstream and enter the Penning ionization reaction region 42. The Penning ionization reaction region 42 is located downstream of the upstream plasma excitation region 41 and is the main region where the metastable inert gas particles undergo a Penning ionization reaction with the hydrogen-containing reactive gas introduced from the second gas inlet 32.

[0078] In some embodiments, the plasma processing apparatus further includes a synchronization control unit, which is connected to the pulsed radio frequency power supply and the gas path control valve of the hydrogen-containing reactive gas, respectively, and is used to control the on-off sequence of the hydrogen-containing reactive gas to be synchronized with the off-off window of the radio frequency pulse, so that the gas is only introduced into the reaction chamber during the off-off phase of the radio frequency pulse, so that the Penning ionization reaction occurs entirely during the pulse interval period without an electric field.

[0079] In some embodiments, the apparatus further includes a substrate support unit 52 disposed at the lower part of the reaction chamber 11 for supporting and fixing the wafer 51 to be processed. The substrate support unit 52 integrates a temperature control element for adjusting the wafer temperature at different stages of photoresist removal or surface cleaning, especially for increasing the wafer temperature during the by-product desorption stage to promote the desorption of photoresist and residual polymer reaction by-products.

[0080] Other specific structures, parameter settings, and operating conditions of this device can be found in the relevant descriptions in the foregoing method embodiments, and will not be repeated here. Those skilled in the art will understand that the above device structures are merely illustrative, and any device structure capable of implementing the method of this invention falls within the protection scope of this invention.

[0081] The present invention provides a plasma treatment method and apparatus based on Penning ionization, which has the following beneficial effects: 1) Low-kinetic-energy, highly chemically active hydrogen-based particles are generated through Penning ionization. The particles are not accelerated by the electric field from generation to reaching the wafer surface. This eliminates the physical bombardment effect of high-energy particles from the source of ionization, completely different from the existing solution that relies on physical filtration by the nozzle. This solves the problem of damage to low dielectric constant media and silicon substrates caused by traditional processes from the root. 2) By precisely controlling the particle energy threshold, hydrogen-based particles can only dissociate the chemical bonds of organic deposits and cannot break through the main valence bond energy barrier between the substrate and the dielectric material. The reaction area is strictly confined within the photoresist and residual polymer layer. The reaction automatically terminates after the deposits are completely removed, which greatly improves the material selectivity of the processing and perfectly matches the process requirements of low dielectric constant dielectric sidewalls in advanced node IC manufacturing. 3) The design of partitioned air intake and independent air path realizes the spatial decoupling of the two zones, eliminating the need for multi-layer ion filter nozzles and light shielding structures, avoiding the recombination loss of active particles on the solid surface, and improving the activity retention rate of hydrogen-based particles reaching the wafer surface by more than 30%, resulting in higher adhesive removal and cleaning efficiency at the same power. 4) By coordinating the pressure, flow rate, and temperature of the three stages of initial penetration, main degumming, and by-product desorption, it takes into account the removal of deep polymers, stable degumming rate, and by-product discharge. It can still maintain excellent processing uniformity in complex pattern structures and solve the problem of dead corner residue in pattern in traditional processes. 5) It can achieve efficient desizing or cleaning without the need for a high-temperature environment, and can operate stably from room temperature to 100°C. This avoids thermal degradation of low dielectric constant materials caused by high temperatures, resulting in stronger process stability and compatibility, which is beneficial for large-scale mass production applications.

[0082] As indicated in this application and claims, unless the context clearly indicates otherwise, the words "a," "an," "an," and / or "the" are not specifically singular and may include plural forms. Generally speaking, the terms "comprising" and "including" only indicate the inclusion of explicitly identified steps and elements, which do not constitute an exclusive list, and the method or apparatus may also include other steps or elements.

[0083] The above embodiments are provided for those skilled in the art to implement or use the present invention. Those skilled in the art can make various modifications or changes to the above embodiments without departing from the inventive concept of the present invention. Therefore, the protection scope of the present invention is not limited to the above embodiments, but should be the maximum scope that conforms to the innovative features mentioned in the claims.

Claims

1. A plasma processing method, characterized in that, include: An inert gas is introduced into the upstream plasma excitation region of the reaction chamber, and metastable inert gas particles are generated by radio frequency discharge. Hydrogen-containing reactive gas is introduced into the downstream non-electric field region of the reaction chamber, causing the metastable inert gas particles diffused from the upstream to undergo Penning ionization with the hydrogen-containing reactive gas, generating highly active hydrogen-based particles. The highly active hydrogen-based particles are used to perform photoresist removal or surface cleaning on the wafer placed in the reaction chamber, removing photoresist or residual polymer after etching from the wafer surface. The hydrogen-containing reactive gas is introduced far from the upstream plasma excitation region, and the Penning ionization process takes place entirely in a field-free region, so that the highly active hydrogen-based particles are not accelerated by an electric field from the time they are generated until they reach the wafer surface.

2. The plasma treatment method according to claim 1, characterized in that, The kinetic energy of the highly active hydrogen-based particles is below 1 eV, which is lower than the breaking energy threshold of the main valence bonds in the bulk material of the wafer substrate; the lifetime of the highly active hydrogen-based particles is not less than 100 ms. By using highly active hydrogen-based particles to undergo a pure chemical reaction with the target deposits on the wafer surface and generate volatile products, the process of desmearing or surface cleaning can be achieved.

3. The plasma treatment method according to claim 1, characterized in that, The radio frequency discharge uses a pulse-modulated radio frequency source to excite inert gas plasma; The on / off timing of the hydrogen-containing reactive gas is synchronized with the off-window of the radio frequency pulse, and it is only introduced into the reaction chamber during the off-stage of the radio frequency pulse, so that the Penning ionization reaction occurs entirely during the pulse interval without an electric field.

4. The plasma treatment method according to claim 1, characterized in that, By synergistically regulating the pressure of the reaction chamber and the flow ratio of inert gas to hydrogen-containing reactive gas, the mean free path and diffusion depth of the highly active hydrogen-based particles are controlled, so that the reaction region of the highly active hydrogen-based particles is confined within the photoresist layer or the residual polymer layer after etching.

5. The plasma treatment method according to claim 4, characterized in that, The process of degumming or surface cleaning includes, in sequence, an initial penetration stage, a main degumming stage, and a by-product desorption stage. In the initial permeation stage, the pressure in the reaction chamber is controlled within the first pressure range, and the flow ratio of inert gas to hydrogen-containing reactive gas is within the first flow ratio range, so that highly active hydrogen-based particles can penetrate into the photoresist or residual polymer and establish a uniform reaction interface. During the main degumming stage, the pressure in the reaction chamber is controlled within the second pressure range, and the flow ratio of inert gas to hydrogen-containing reactive gas is within the second flow ratio range, maintaining a stable degumming rate and a high material selectivity. During the byproduct desorption stage, the pressure in the reaction chamber is controlled within the third pressure range, while the temperature of the wafer is increased to promote the desorption and discharge of volatile byproducts generated in the reaction from the chamber. The pressure values ​​of the first pressure zone, the second pressure zone, and the third pressure zone increase sequentially; the ratio of the first flow ratio zone is higher than the ratio of the second flow ratio zone; and the wafer temperature during the by-product desorption stage is higher than the wafer temperature during the initial penetration stage and the main desizing stage.

6. The plasma treatment method according to claim 1, characterized in that, In the step of introducing inert gas and hydrogen-containing reactive gas into the reaction chamber, the two gases are introduced in a partitioned gas introduction method. The inert gas is introduced into the upstream plasma excitation region through the first gas inlet, and the hydrogen-containing reactive gas is introduced into the downstream region away from the upstream plasma excitation region through the second gas inlet, where it mixes with metastable inert gas particles that diffuse from top to bottom and undergoes Penning ionization. By adjusting the gas flow ratio and inlet angle of the first and second gas inlets, uniform mixing and diffusion of the two gases within the cavity can be achieved.

7. The plasma treatment method according to claim 1, characterized in that, The inert gas includes at least one of argon or helium, and the wafer surface is covered with a low dielectric constant dielectric layer. The hydrogen-containing reactive gas includes hydrogen gas; The highly active hydrogen-based particles include at least one of hydrogen atoms, hydrogen free radicals, and hydrogen ions; The substrate material of the wafer includes at least one of silicon, silicon dioxide, or silicon nitride, and the surface of the wafer is covered with a low dielectric constant dielectric layer.

8. The plasma treatment method according to claim 7, characterized in that, The step of introducing an inert gas into the upstream plasma excitation region of the reaction chamber further includes: controlling the types of products of the Penning ionization reaction by selecting the type of inert gas. When helium is used as the inert gas, the Penning ionization reaction preferentially produces hydrogen atoms and hydrogen radicals; When argon is used as the inert gas, the Penning ionization reaction preferentially produces molecular positive ions.

9. A plasma processing apparatus for implementing the plasma processing method as described in any one of claims 1 to 8, characterized in that, include: The reaction chamber is used to house the wafer and provide a reaction space for resist removal and cleaning. A radio frequency power supply, coupled to the reaction chamber, is used to excite and maintain inert gas plasma, generating metastable inert gas particles in the upstream plasma excitation region. The intake system includes at least two independent gas paths, which are used to input inert gas and hydrogen-containing reactive gas into the reaction chamber, respectively, so as to achieve gas partitioning and diffusion; The air intake system, through its air path spatial layout, introduces hydrogen-containing reactive gas into a downstream region far from the upstream plasma excitation region, allowing the Penning ionization reaction to occur in a field-free region, thus achieving spatial isolation between the upstream plasma excitation region and the Penning ionization reaction region.

10. The plasma processing apparatus according to claim 9, characterized in that, The intake system includes: The first gas inlet is located in the upstream plasma excitation region of the reaction chamber and is used to introduce inert gas. The second gas inlet is located in the downstream lateral region of the reaction chamber and is used to introduce hydrogen-containing reaction gas. The second gas inlet is inclined toward the wafer side to guide the hydrogen-containing reactive gas downwards and prevent the gas from flowing back to the upstream plasma excitation region.

11. The plasma processing apparatus according to claim 9, characterized in that, The radio frequency power supply is a pulse radio frequency power supply; The plasma processing device also includes a synchronization control unit, which is connected to the pulsed radio frequency power supply and the gas path control valve of the hydrogen-containing reactive gas, respectively. The synchronization control unit is used to control the on-off sequence of the hydrogen-containing reactive gas to be synchronized with the off-off window of the radio frequency pulse, and to introduce the gas into the reaction chamber only during the off-off phase of the radio frequency pulse, so that the Penning ionization reaction occurs completely during the pulse interval without an electric field.

12. The plasma processing apparatus according to claim 9, characterized in that, The reaction chamber is also equipped with a substrate support unit: The substrate support unit integrates a temperature control element to regulate the surface temperature of the wafer at different stages of photoresist removal or surface cleaning, thereby promoting the desorption of photoresist and residual polymer reaction byproducts.

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