Dry-type semiconductor etching process based on dual-frequency electric field control

Abstract

The invention relates to a dry-type semiconductor etching process based on dual-frequency electric field control, which is mainly realized by the following steps of: firstly, simultaneously applying a high-frequency electric field with the frequency of 13.56 MHz and a low-frequency electric field with the frequency of 400 kHz in an etching process; secondly, plasma density and ion energy are monitored in real time, and electric field power output and a phase relation thereof are dynamically adjusted so as to optimize uniform distribution of plasmas; and finally, adjusting the electric field frequency and power ratio according to the characteristics of the material layer, and controlling the plasma generation rate and the ion energy distribution. The invention aims to improve the etching uniformity, the selectivity and the etching precision of the high aspect ratio structure, and reduce the plasma damage.

Description

Technical Field

[0001] The invention relates to a dry semiconductor etching process based on dual-frequency electric field control. Background Art

[0002] In the semiconductor manufacturing process, etching technology is one of the key links that determine the precision and performance of devices. With the continuous reduction in the size of semiconductor devices and the continuous improvement in integration, more and more stringent requirements are placed on the etching process. Especially when manufacturing high aspect ratio microstructures and processing complex multilayer materials, the traditional single-frequency electric field dry etching process has been difficult to meet the requirements of high precision, high selectivity and low damage.

[0003] Traditional dry etching processes usually use a single-frequency electric field to excite plasma, but this method has the following major problems: a single-frequency electric field can only excite plasma at a fixed frequency, resulting in uneven density and energy distribution of the plasma, especially when processing complex material structures, prone to uneven etching and residues, affecting the performance of the final device; when etching multi-layer materials, the physical and chemical properties of different materials vary greatly, and a single-frequency electric field cannot effectively distinguish the etching rates and selectivity of different material layers, which can easily lead to damage to the underlying material or increase the surface roughness, thereby affecting the reliability of the device; in the high-aspect ratio microstructure etching process, due to inaccurate ion kinetic energy control, sidewall collapse or morphology distortion problems often occur, and high-precision etching requirements cannot be achieved, especially in the processing of deep trenches and narrow channels.

[0004] Therefore, a dry semiconductor etching process based on dual-frequency electric field control is needed to achieve higher etching accuracy and material selectivity through independent phase adjustment and real-time monitoring, especially in the processing of complex multilayer structures and high aspect ratio microstructures. Summary of the invention

[0005] The purpose of the present invention is to solve the above deficiencies in the prior art and provide a dry semiconductor etching process based on dual-frequency electric field control to improve etching uniformity, enhance selectivity, improve etching accuracy of high aspect ratio structures, and reduce plasma damage on the material surface. The following is a specific solution:

[0006] A dry semiconductor etching process based on dual-frequency electric field control comprises the following steps: S1: during the etching process, a first frequency electric field and a second frequency electric field are applied simultaneously, wherein the first frequency electric field is a high frequency electric field with a frequency of 13.56 MHz, the second frequency electric field is a low frequency electric field with a frequency of 400 kHz, the power of the first frequency electric field is 500-1500 watts, and the power of the second frequency electric field is 100-500 watts;

[0007] S2: Real-time monitoring of plasma density and ion energy, dynamic adjustment of the power output and phase relationship of the first frequency electric field and the second frequency electric field, the phase difference range of the first frequency electric field is between 0° and 180°, and the phase difference range of the second frequency electric field is between 0° and 360°, and the adjustment of the phase relationship is used to optimize the uniform distribution of plasma density, and the kinetic energy of the ions bombarding the target material is controlled within the range of 10-100 eV by adjusting the ion energy of the low-frequency electric field;

[0008] S3: During the etching process, according to the conductivity and dielectric constant of the material layer, the frequency and power ratio of the first frequency electric field and the second frequency electric field are adjusted to control the plasma generation rate and ion energy distribution, wherein the frequency adjustment range is ±5MHz, and the power ratio adjustment range is 1:2 to 2:1.

[0009] The first frequency electric field and the second frequency electric field are powered by independent RF power supplies, and each RF power supply has an independent phase control module, which is used to adjust the phase difference of the electric field in real time to control the energy distribution of the plasma and ensure that when etching a high aspect ratio structure, the kinetic energy of the ions is concentrated within the optimal range of 30-70eV to achieve a high-precision etching effect.

[0010] The real-time monitoring of plasma density and ion energy includes real-time monitoring of plasma electron density and ion kinetic energy distribution, and the monitoring means include optical emission spectroscopy and Langmuir probe. According to the real-time monitoring data, the power output of the first frequency electric field and the second frequency electric field is dynamically adjusted to keep the plasma electron density at 1×10 11 Up to 5×10 11 cm -3 The ion kinetic energy distribution is maintained in the range of 10-100eV to ensure efficient material removal rate and uniform etching depth.

[0011] In S3, when etching a multi-layer structure, the parameters of the dual-frequency electric field are adjusted in steps, including: when etching the upper oxide layer, the power of the first frequency electric field is set to 1000 watts, the power of the second frequency electric field is set to 200 watts, and the phase difference of the first frequency electric field is set to 90°, and the phase difference of the second frequency electric field is set to 180°, so as to achieve efficient selective etching of the oxide; when etching the lower silicon layer, the power of the first frequency electric field is adjusted to 1200 watts, the power of the second frequency electric field is adjusted to 400 watts, and the phase difference of the first frequency electric field is set to 45°, and the phase difference of the second frequency electric field is set to 270°, so as to reduce the etching damage to the silicon layer and increase the etching rate.

[0012] In the process of etching a high aspect ratio microstructure, the modulation waveform of the second frequency electric field is precisely controlled, specifically in the form of square wave modulation, the frequency is maintained at 400 kHz, and the waveform rise time is controlled within 100 nanoseconds, so as to ensure that the low-frequency electric field can effectively regulate the kinetic energy of ions in the plasma, thereby reducing the collapse of the microstructure side wall and improving the verticality and surface smoothness of the side wall.

[0013] During the etching process, according to the conductivity and dielectric constant of the material layer, the frequency and power ratio of the first frequency electric field and the second frequency electric field are adjusted, specifically: when the etching material is a high dielectric constant material, the power of the first frequency electric field is adjusted to 1300 watts, the frequency is fine-tuned to 13.60 MHz, the power of the second frequency electric field is adjusted to 300 watts, and the frequency is fine-tuned to 395 kHz to optimize the stability of the plasma; when the etching material is a low dielectric constant material, the power of the first frequency electric field is adjusted to 900 watts, the frequency is fine-tuned to 13.55 MHz, the power of the second frequency electric field is adjusted to 200 watts, and the frequency is fine-tuned to 405 kHz to ensure the uniformity of the plasma and minimal damage to the material surface.

[0014] The dual-frequency electric field also uses a synchronous control mechanism with the plasma generation system to keep the electric field modulation parameters consistent with the plasma generation rhythm. Specifically, in each plasma generation cycle, the phase of the high-frequency electric field is adjusted to be synchronized to the excitation peak of the plasma, and the modulation waveform of the low-frequency electric field is kept consistent with the plasma density peak to reduce plasma oscillations, thereby improving the fidelity and structural accuracy of the etched pattern.

[0015] Beneficial effects: By simultaneously applying a 13.56MHz high-frequency electric field and a 400kHz low-frequency electric field during the etching process, and dynamically adjusting the power output and phase relationship of the two electric fields, the present invention can achieve precise control of plasma density and ion energy distribution. Specifically, the high-frequency electric field is used to maintain high-density plasma, while the low-frequency electric field adjusts the kinetic energy of the ions to ensure that the kinetic energy of the ions bombarding the target material is controlled within the range of 10-100eV, which can significantly improve the uniformity of the etching process, reduce uneven etching and residues, and thus improve the quality of the final device;

[0016] The present invention optimizes the plasma generation rate and ion energy distribution by dynamically adjusting the power ratio and frequency setting of the first frequency electric field and the second frequency electric field according to the conductivity and dielectric constant of the material layer during the etching process. In this way, the present invention can achieve precise control of different material layers, significantly improve the etching selectivity of multilayer materials, avoid damage to the underlying material, and improve the surface smoothness after etching, thereby improving the overall performance of the device.

[0017] The present invention can effectively regulate the kinetic energy of ions by precisely controlling the modulation waveform of the second frequency electric field and controlling the waveform rise time within 100 nanoseconds, ensuring that the kinetic energy of ions is concentrated within the optimal range of 30-70 eV. This control method enables high verticality of the sidewalls to be achieved when etching high aspect ratio microstructures, avoiding the sidewall collapse problem commonly seen in traditional processes, thereby greatly improving the processing accuracy and stability of the microstructures.

[0018] The present invention adopts a synchronous control mechanism of a dual-frequency electric field and a plasma generation system to keep the electric field modulation parameters consistent with the plasma generation rhythm. Specifically, in each plasma generation cycle, the phase of the high-frequency electric field is adjusted to be synchronized to the excitation peak of the plasma, and the modulation waveform of the low-frequency electric field is kept consistent with the plasma density peak. This synchronous control mechanism ensures the stability of the plasma generation process and improves the etching accuracy. Especially in high-precision processing, it can significantly reduce the adverse effects caused by plasma fluctuations during the etching process. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is a schematic flow chart of a dry semiconductor etching process based on dual-frequency electric field control. DETAILED DESCRIPTION

[0020] In order to deepen the understanding of the present invention, the present invention will be further described in detail below in conjunction with embodiments and drawings. The embodiments are only used to explain the present invention and do not constitute a limitation on the protection scope of the present invention.

[0021] Embodiment 1:

[0022] Please see Figure 1 , a dry semiconductor etching process based on dual-frequency electric field control, comprising the following steps: S1: during the etching process, a first frequency electric field and a second frequency electric field are applied simultaneously, wherein the first frequency electric field is a high frequency electric field with a frequency of 13.56 MHz, the second frequency electric field is a low frequency electric field with a frequency of 400 kHz, the power of the first frequency electric field is 500-1500 watts, and the power of the second frequency electric field is 100-500 watts;

[0023] S2: Real-time monitoring of plasma density and ion energy, dynamic adjustment of the power output and phase relationship of the first frequency electric field and the second frequency electric field, the phase difference range of the first frequency electric field is between 0° and 180°, and the phase difference range of the second frequency electric field is between 0° and 360°. The adjustment of the phase relationship is used to optimize the uniform distribution of plasma density. By adjusting the ion energy of the low-frequency electric field, the kinetic energy of the ions bombarding the target material is controlled within the range of 10-100 eV;

[0024] S3: During the etching process, according to the conductivity and dielectric constant of the material layer, the frequency and power ratio of the first frequency electric field and the second frequency electric field are adjusted to control the plasma generation rate and ion energy distribution, wherein the frequency adjustment range is ±5MHz, and the power ratio adjustment range is 1:2 to 2:1.

[0025] The first frequency electric field and the second frequency electric field are powered by independent RF power supplies, and each RF power supply has an independent phase control module, which is used to adjust the phase difference of the electric field in real time to control the energy distribution of the plasma and ensure that when etching high aspect ratio structures, the kinetic energy of the ions is concentrated within the optimal range of 30-70eV to achieve high-precision etching effects.

[0026] Real-time monitoring of plasma density and ion energy includes real-time monitoring of plasma electron density and ion kinetic energy distribution. The monitoring methods include optical emission spectroscopy and Langmuir probe. According to the real-time monitoring data, the power output of the first frequency electric field and the second frequency electric field is dynamically adjusted to keep the plasma electron density at 1×10 11 Up to 5×10 11 cm -3 The ion kinetic energy distribution is maintained in the range of 10-100eV to ensure efficient material removal rate and uniform etching depth.

[0027] In S3, when etching a multi-layer structure, the parameters of the dual-frequency electric field are adjusted in steps, including: when etching the upper oxide layer, the power of the first frequency electric field is set to 1000 watts, the power of the second frequency electric field is set to 200 watts, and the phase difference of the first frequency electric field is set to 90°, and the phase difference of the second frequency electric field is set to 180°, so as to achieve efficient selective etching of the oxide; when etching the lower silicon layer, the power of the first frequency electric field is adjusted to 1200 watts, the power of the second frequency electric field is adjusted to 400 watts, and the phase difference of the first frequency electric field is set to 45°, and the phase difference of the second frequency electric field is set to 270°, so as to reduce the etching damage to the silicon layer and increase the etching rate.

[0028] The process optimizes the stability of the plasma; when the etching material is a low dielectric constant material, the power of the first frequency electric field is adjusted to 900 watts, the frequency is fine-tuned to 13.55 MHz, and the power of the second frequency electric field is adjusted to 200 watts, the frequency is fine-tuned to 405 kHz to ensure the uniformity of the plasma and minimal damage to the material surface.

[0029] The dual-frequency electric field also uses a synchronous control mechanism with the plasma generation system to keep the electric field modulation parameters consistent with the plasma generation rhythm. Specifically, in each plasma generation cycle, the phase of the high-frequency electric field is adjusted to be synchronized to the excitation peak of the plasma, and the modulation waveform of the low-frequency electric field is kept consistent with the plasma density peak to reduce plasma oscillations, thereby improving the fidelity and structural accuracy of the etched pattern.

[0030] Embodiment 2:

[0031] The substrate material is silicon, and a series of groove structures are formed on the surface through photolithography. The groove depth is 1μm and the width is 100nm. The etching equipment is a dual-frequency electric field controlled reactive ion etching equipment, equipped with an independent 13.56MHz high-frequency power supply and 400kHz low-frequency power supply.

[0032] During the etching process, Cl 2 A mixed gas of HBr and HBr was used, the chamber pressure was controlled at 20 mTorr, a high-frequency electric field of 13.56 MHz was applied, and the power was set to 800 watts, while a low-frequency electric field of 400 kHz was applied, and the power was set to 300 watts.

[0033] The electron density and ion kinetic energy of the plasma are monitored in real time, and data is obtained using a Langmuir probe and an OES sensor. According to the monitoring results, the phase difference of the low-frequency electric field is adjusted to 120°, and a square wave modulation form is adopted, and the waveform rise time is controlled within 80 nanoseconds to ensure that the low-frequency electric field can effectively regulate the kinetic energy of the ions in the plasma; after adjustment, the ion kinetic energy is concentrated in the range of 50-70eV, ensuring that the verticality of the side wall of the etched microstructure is close to 90°, there is no residue at the bottom of the groove, and the side wall surface is smooth without obvious roughness. The other steps and parameters are the same as those in Example 1.

[0034] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the purpose and scope of the technical solution of the present invention, which should be included in the scope of the claims of the present invention.

Claims

1. A dry semiconductor etching process based on dual-frequency electric field control, characterized in that: The following steps are involved: S1: During the etching process, a first frequency electric field and a second frequency electric field are applied simultaneously, wherein the first frequency electric field is a high frequency electric field with a frequency of 13.56 MHz, the second frequency electric field is a low frequency electric field with a frequency of 400 kHz, the power of the first frequency electric field is 500-1500 watts, and the power of the second frequency electric field is 100-500 watts; S2: Real-time monitoring of plasma density and ion energy, dynamic adjustment of the power output and phase relationship of the first frequency electric field and the second frequency electric field, the phase difference range of the first frequency electric field is between 0° and 180°, and the phase difference range of the second frequency electric field is between 0° and 360°, and the adjustment of the phase relationship is used to optimize the uniform distribution of plasma density, and the kinetic energy of the ions bombarding the target material is controlled within the range of 10-100 eV by adjusting the ion energy of the low-frequency electric field; S3: During the etching process, according to the conductivity and dielectric constant of the material layer, the frequency and power ratio of the first frequency electric field and the second frequency electric field are adjusted to control the plasma generation rate and ion energy distribution, wherein the frequency adjustment range is ±5MHz, and the power ratio adjustment range is 1:2 to 2:

1.

2. A dry semiconductor etching process based on dual-frequency electric field control according to claim 1, characterized in that The first frequency electric field and the second frequency electric field are powered by independent RF power supplies, and each RF power supply has an independent phase control module, which is used to adjust the phase difference of the electric field in real time to control the energy distribution of the plasma and ensure that the ion kinetic energy is concentrated in the optimal range of 30-70eV when etching high aspect ratio structures.

3. The dry semiconductor etching process based on dual-frequency electric field control according to claim 1, characterized in that: The real-time monitoring of plasma density and ion energy includes real-time monitoring of plasma electron density and ion kinetic energy distribution, and the monitoring means include optical emission spectroscopy and Langmuir probe. According to the real-time monitoring data, the power output of the first frequency electric field and the second frequency electric field is dynamically adjusted to keep the plasma electron density between 1×1011 and 5×1011 cm-3, and the ion kinetic energy distribution is kept within the range of 10-100 eV.

4. The dry semiconductor etching process based on dual-frequency electric field control according to claim 1, characterized in that: In S3, when etching the multilayer structure, the parameters of the dual-frequency electric field are adjusted step by step, including: when etching the upper oxide layer, the power of the first frequency electric field is set to 1000 watts, the power of the second frequency electric field is set to 200 watts, and the phase difference of the first frequency electric field is set to 90°, and the phase difference of the second frequency electric field is set to 180°; When etching the lower silicon layer, the power of the first frequency electric field is adjusted to 1200 watts, the power of the second frequency electric field is adjusted to 400 watts, and the phase difference of the first frequency electric field is set to 45°, and the phase difference of the second frequency electric field is set to 270°.

5. The dry semiconductor etching process based on dual-frequency electric field control according to claim 1, characterized in that: In the process of etching a high aspect ratio microstructure, the modulation waveform of the second frequency electric field is precisely controlled, specifically in the form of square wave modulation, the frequency is maintained at 400 kHz, and the waveform rise time is controlled within 100 nanoseconds.

6. The dry semiconductor etching process based on dual-frequency electric field control according to claim 1, characterized in that: During the etching process, according to the conductivity and dielectric constant of the material layer, the frequency and power ratio of the first frequency electric field and the second frequency electric field are adjusted, specifically: when the etching material is a high dielectric constant material, the power of the first frequency electric field is adjusted to 1300 watts, the frequency is fine-tuned to 13.60 MHz, and the power of the second frequency electric field is adjusted to 300 watts, and the frequency is fine-tuned to 395 kHz; When the etching material is a low dielectric constant material, the power of the first frequency electric field is adjusted to 900 watts, and the frequency is fine-tuned to 13.55 MHz, and the power of the second frequency electric field is adjusted to 200 watts, and the frequency is fine-tuned to 405 kHz.

7. The dry semiconductor etching process based on dual-frequency electric field control according to claim 1, characterized in that: The dual-frequency electric field also uses a synchronous control mechanism with the plasma generation system to keep the electric field modulation parameters consistent with the plasma generation rhythm. Specifically, in each plasma generation cycle, the phase of the high-frequency electric field is adjusted to be synchronized to the excitation peak of the plasma, and the modulation waveform of the low-frequency electric field is kept consistent with the plasma density peak.

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