CN108770174B - Microwave plasma generating device with double-coupling resonator with microporous micro-nano structure - Google Patents

Abstract

A microwave plasma generating device with a micro-hole/micro-nano structure double-coupling resonant cavity, comprising an outer cavity and a plurality of micro-hole/micro-nano structure double-coupling resonators arranged in the outer cavity, wherein the resonance The cavity includes a cylindrical cavity, a micropore array formed by a plurality of micropores is uniformly distributed on the peripheral wall of the cylindrical cavity, the diameter of the micropores is an odd multiple of the wavelength, and the inner wall of the cavity has an array of micropores. Metal micro-nano structure, the period size of the metal micro-nano structure is λ/n, λ is the incident wavelength, and n is the refractive index of the resonant cavity material. The invention reduces the loss of the guided mode and the leaky mode by optimizing the design of the double-coupling resonance mode, achieves the purpose of maximizing the resonance in the fixed area, improves the uniformity of the plasma, and ensures the optical coupling and field space local enhancement characteristics Under the premise of , the absorption loss problem can be improved, and multiple resonators are independently controlled, which can effectively control the temperature of the plasma.

Description

Microwave plasma generating device with double-coupling resonator with microporous micro-nano structure

technical field

The invention belongs to the field of plasma, and in particular relates to a microwave plasma generating device with a double-coupling resonant cavity of a micro-hole/micro-nano structure.

Background technique

Microwave plasma generators are widely used in the semiconductor industry. The resonant cavity and the coupling device are the key components of the microwave plasma generating device. The plasma required for the gas resonance generation under the electromagnetic field requires strict matching of the resonator cavity and the coupling device, and these two devices require strict size requirements.

Ordinary microwave plasma excitation mainly relies on high electric field strength, and it is difficult to completely rely on manual design of the reaction cavity that meets the requirements for generating a large-area uniform electric field. The existing microwave plasma generators have problems such as low efficiency and poor uniformity. And the use of a single discharge unit is likely to cause the risk of excessively high or low operating temperature.

SUMMARY OF THE INVENTION

In order to solve the problems existing in the prior art, the present invention proposes a microwave plasma generating device with a micro-hole/micro-nano structure double-coupling resonant cavity, which can generate uniform plasma.

In order to achieve the above object, the present invention adopts the following technical solutions:

A microwave plasma generating device with a micro-hole/micro-nano structure double-coupling resonant cavity, comprising an outer cavity and a plurality of micro-hole/micro-nano structure double-coupling resonators arranged in the outer cavity, wherein the resonance The cavity includes a cylindrical cavity, a micropore array formed by a plurality of micropores is uniformly distributed on the peripheral wall of the cylindrical cavity, the diameter of the micropores is an odd multiple of the wavelength, and the inner wall of the cavity has an array of micropores. Metal micro-nano structure, the micro-hole array and metal micro-nano structure form a double coupling structure to achieve resonance enhancement and adjustment, the period size of the metal micro-nano structure is λ/n, λ is the incident wavelength, and n is the resonant cavity The refractive index of the material.

Preferably, the circumference of the cylindrical cavity is an integer multiple of 3/4 of the working wavelength, and the resonance occurs on the first odd mode.

Preferably, the metal micro-nano structures are periodically arranged protrusions, depressions or gratings.

Preferably, the metal micro-nano structure is a grating, including parallel slits of equal width and equal spacing.

Preferably, the cylindrical cavity is made of mica or ceramic material, and the metal coating is gold or brass

Preferably, the resonant cavities are arranged in a straight line and are respectively connected to a microwave generator through double-layer coaxial cables.

Preferably, the double-layer coaxial cable wraps a coupling probe, one end of the double-layer coaxial cable is connected to the microwave generator, and the other end is inserted into the micro-hole/micro-nano structure double-coupling resonant cavity.

Preferably, the outer cavity is a quartz tube.

Preferably, the microwave plasma generating device further comprises a stage arranged in the outer cavity, and the stage is arranged below the micro-hole/micro-nano structure double-coupling resonant cavity.

Preferably, the stage is rotatable and can be raised and lowered.

Preferably, a visual observation hole and a pyrometer are provided on the outer cavity close to the stage.

Compared with the prior art, the present invention has the following advantages:

(1) The present invention reduces the loss of the guided mode and the leaky mode by optimizing the design of the double-coupling resonance mode, so as to achieve the purpose of maximum enhancement and adjustment of the resonance in the fixed area, and can improve the uniformity of the plasma, which can make the plasma temperature The oxidation temperature is as high as 1000℃, and the plasma discharge time is adjustable, which can better realize the step-by-step plasma oxidation process;

(2) The metal plate micro-hole of the present invention adopts a double-coupling structure, which can improve the absorption loss problem under the premise of ensuring optical coupling and field space local enhancement characteristics;

(3) Multiple resonator cavities are independently controlled, which can effectively control the temperature of the plasma.

Description of drawings

Figure 1 is a graph showing the relationship between the energy distribution in the resonator cavity and the emission enhancement factor;

FIG. 2 is a micro-hole/micro-nano structure double-coupling resonator according to an embodiment of the present invention;

Fig. 3 is the microwave plasma generating device of the present invention.

Detailed ways

In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention will be further described in detail below in conjunction with specific embodiments and with reference to the accompanying drawings.

The energy in the resonator is divided into F-P output mode, guided mode, leakage mode, and absorption mode. Among them, only the F-P mode can be extracted, and the other three parts are lost to varying degrees, which is a great waste of energy. . Therefore, the design of the resonant cavity must reduce the energy loss of the non-exit modes in the cavity. At the same time, to achieve resonance enhancement in a specified area, the design of the resonant cavity is particularly important. The invention reduces the loss of the guided mode and the leaky mode by optimizing the design of the double-coupling resonance mode, so as to achieve the purpose of maximizing the resonance in the fixed area.

The relationship between the mode distribution in the cavity and the emission enhancement factor is shown in Fig. 1. According to the coupled resonance mechanism, the outgoing wave in the cavity is directly used as the incoming wave of gas plasma.

The invention reduces the energy loss of the outgoing mode in the resonant cavity by adjusting various parameters, so as to achieve the purpose of enhancing the overall radiation energy in a fixed area, that is, not only the F-P outgoing mode has high light intensity near kx, but also the guiding mode and the leakage mode. There is also an energy spike at the corresponding k; the metal plate micro-hole adopts a double-coupling structure, which can improve the absorption loss problem under the premise of ensuring the optical coupling and the local enhancement of the field space.

As shown in FIG. 2, the present invention provides a micro-hole/micro-nano structure double-coupling resonant cavity for a microwave plasma generating device, including a cylindrical cavity, and the peripheral wall of the cylindrical cavity is uniformly distributed by a plurality of The micro-hole array is formed by micro-holes, and the inner wall of the cylindrical cavity has metal micro-nano structures.

The material of the resonant cavity is mica or ceramic material, the dielectric constant is 9-10, and the refractive index is 1.5-2.0. In order to prevent oxidation of the inner layer, the metal micro-nano structure material is Au or brass. The metal micro-nano structure is a periodically arranged microstructure, which can be protrusions, depressions or gratings, etc. In the embodiment of the present invention, the metal micro-nano structure adopts a grating structure, which is composed of parallel slit periods of equal width and equal spacing. The period size of the metal micro-nano structure is λ/n, where λ is the incident wavelength and n is the refractive index of the resonator material, which can prevent microwave energy from being penetrated into the metal and dielectric surfaces or absorbed. The metal micro-nano structure can be formed by conventional semiconductor processes, for example, after the metal plating layer is formed, photolithography is performed.

A plurality of micropores are evenly distributed on the peripheral wall of the resonant cavity, and the size of the micropores is an odd multiple of the wavelength, corresponding to the nodes of the standing wave of the wave microwave, so that as much microwave energy as possible can be radiated into the reaction cavity through the micropores.

The greater the energy density in the resonant cavity, the greater the intensity of the microwave electric field generated. Therefore, a metal plate with holes on both sides is used to isolate the microwave. The formed micro-porous resonator can isolate the microwave, but does not isolate the gas. The area increases, and the enhanced microwave leaks out through the pores, plasmonizing the gas.

The size design of the micro-hole/micro-nano-structure double-coupling resonator strictly requires that its perimeter be an integer multiple of 3/4 of the working wavelength, and the resonance is on the first odd mode, which is beneficial to the microwave plasma excitation process.

The metal coating can make the internal leakage mode interact with the surface mode of the metal film fabricated on the surface of the device, and generate a coupled resonance at the cavity material and the metal micro-nano structure, so that the incident wave in the leakage mode and the free electrons on the metal surface oscillate at the same frequency The generated SP wave (non-radiative mode) is converted into a coupled SP wave (radiative mode), even if the incident wave of the leaky mode is converted into a coupled SP wave of the coupled SP mode, through this mode and energy conversion, the SP wave in the SP coupled resonance mode is converted. Only then can the light tunnel through and obtain an enhancement effect at the resonant wavelength. This radiation enhancement can be increased by at least 2-3 times.

As shown in FIG. 3 , the present invention provides a microwave plasma generating device, which includes a plurality of micro-hole/micro-nano structure double-coupling resonators 1 , and the micro-hole/micro-nano structure double-coupling resonator 1 is arranged in an outer cavity 2 . The outer cavity 2 can be a quartz tube, which is used for sealing and isolation of the working space (reaction cavity). The inner diameter of the outer cavity 2 may be 100-150 mm. A plurality of micro-hole/micro-nano-structure double-coupling resonators 1 are arranged in a straight line, and are respectively connected to a microwave generator 4 through double-layer coaxial cables 3 . The double-layer coaxial cable 3 wraps a coupling probe, one end of the double-layer coaxial cable 3 is connected to the microwave generator 4 , and the other end is inserted into the micro-hole/micro-nano-structure double-coupling resonator 1 . The double-layer coaxial cable 3 is inserted into one end of the micro-hole/micro-nano-structure double-coupling resonant cavity 1 , and the coupling probe extends out of the double-layer coaxial cable 3 . The microwave generator 4 is placed in the middle of a plurality of micro-hole/micro-nano-structure double-coupling resonator cavities 1 in a disk manner, and can be used to adjust the length and resonant frequency of the reaction cavity.

The reaction chamber system is a key component of the device operation. In order to ensure the uniformity and symmetry of microwave feeding into the reaction chamber and the convenience of processing, the reaction chamber is designed to be cylindrical to excite the plasma.

The microwave input power can be continuously adjusted in the range of 800w-2000w, the microwave frequency of the excited microwave plasma can be adjusted in the range of 2.4-2.5GHz, and the frequency sweep step is set to 0.1MHz.

Each double-layer coaxial cable 3 can be a 10cm coaxial cable.

A stage 5 is arranged in the outer cavity 2, and the stage 5 is arranged below the micro-hole/micro-nano structure double-coupling resonant cavity 1. The stage 5 can be rotated and lifted, and the diameter can be 4-6 inches. A pyrometer 6 and a visual observation hole 7 are provided on the outer wall of the outer cavity 2 close to the stage 5, so that the reaction state in the cavity can be monitored at any time. A plurality of pyrometers 6 may be arranged on the outer wall of the outer cavity 2 .

One end of the outer cavity 2 is provided with an air inlet 8 , and the other end is provided with an air outlet 9 and an equipment door 10 .

When the microwave plasma is generated, the substrate 11 to be processed can be placed on the stage 5 , gas is introduced from the gas inlet 8 , and then the microwave plasma generator is activated to generate the reaction zone 12 above the substrate 11 . Plasma is used to perform plasma processing on the substrate 11 .

The working temperature of the microwave plasma generating device can be 400-1000°C, the corresponding plasma discharge time is 400s-1000s, and the pressure of the cavity is 400mTorr-1000mTorr.

In an embodiment of the present invention, a microwave plasma generating device is used to realize two-step low-temperature oxidation of SiC, and the corresponding plasma discharge time is tunable. The present invention adopts the independent arrangement of 2-10 independent resonant cavities 1, and the resonant cavities 1 near the top of the stage are more than other positions, so as to ensure that the whole cavity can achieve the purpose of low temperature oxidation.

In this embodiment, the microwave plasma generating device plasmons oxygen molecules to form oxygen radicals or oxygen plasma, so as to replace the oxygen molecules to react with the silicon carbide surface, so as to reduce the corresponding temperature and surface oxygen concentration, thereby inhibiting the corrosion of the SiC surface The formation of pits reduces surface damage and obtains a relatively flat surface, thereby improving the carrier mobility of the MOSFET device under high temperature and high field.

In this embodiment, the specific operation steps are as follows: the microwave input power of 800w-1000w is selected, and the adjustable range of the microwave frequency for exciting the microwave plasma is 2.4-2.5GHz. Under the environment of air pressure 100mTorr and H ₂ : O ₂ =1:1, set the initial temperature of the sample stage to 100°C, and the plasma is heated at a rate of 1°C/s. After reaching 350°C, low-temperature oxidation and plasma discharge are performed. The time was 400s; then, the heating rate was changed to 0.5°C/s until the set microwave plasma oxidation temperature was 800°C, the gas was changed to pure oxygen, the air pressure was changed to 800mTorr, the plasma discharge time was 800s, and the high temperature (low temperature) was carried out. It is oxidized at 1300 ℃ of furnace tube oxidation, and the thickness of the oxide layer is about 30nm. After the oxidation is completed, the pure oxygen is changed to pure nitrogen, and the temperature is cooled in a nitrogen atmosphere.

The specific embodiments described above further describe the purpose, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above-mentioned specific embodiments are only specific embodiments of the present invention, and are not intended to limit the present invention. Within the spirit and principle of the present invention, any modifications, equivalent replacements, improvements, etc. made should be included within the protection scope of the present invention.

Claims (10)

1. a microwave plasma generating device with a micro-porous micro-nano structure double-coupling resonant cavity, is characterized in that, comprises an outer cavity and a plurality of micro-porous micro-nano structure double-coupling resonators arranged in the outer cavity, The resonant cavity includes a cylindrical cavity, and a micro-hole array formed by a plurality of micro-holes is uniformly distributed on the peripheral wall of the cylindrical cavity, and the diameter of the micro-hole is an odd multiple of the incident wavelength. There is a metal micro-nano structure on the inner wall of the shaped cavity, the micro-hole array and the metal micro-nano structure form a double-coupling structure to achieve resonance enhancement and adjustment, the period size of the metal micro-nano structure is λ/n, and λ is Incident wavelength, n is the refractive index of the resonant cavity material; wherein, the perimeter of the cylindrical cavity is an integer multiple of 3/4 of the incident wavelength, and resonance occurs on the first odd mode. 2 . The microwave plasma generating device according to claim 1 , wherein the metal micro-nano structures are periodically arranged protrusions, depressions or gratings. 3 . 3 . The microwave plasma generating device according to claim 1 , wherein the metal micro-nano structure is a grating comprising parallel slits of equal width and equal spacing. 4 . 4. The microwave plasma generating device according to claim 1, wherein the cylindrical cavity is made of mica or ceramic material, and the metal micro-nano structure is gold or brass. 5 . The microwave plasma generating device according to claim 1 , wherein the resonant cavities are arranged in a straight line and are respectively connected to a microwave generator through double-layer coaxial cables. 6 . 6. The microwave plasma generating device according to claim 5, wherein the double-layer coaxial cable wraps a coupling probe, one end of the double-layer coaxial cable is connected to the microwave generator, and the other end is inserted into the microwave generator. in the double-coupling resonator of the micro-porous micro-nano structure. 7. The microwave plasma generating device according to claim 1, wherein the outer cavity is a quartz tube. 8 . The microwave plasma generating device according to claim 1 , wherein the microwave plasma generating device further comprises a stage arranged in the outer cavity, and the stage is arranged on the microporous micronano structure double below the coupling cavity. 9. The microwave plasma generating apparatus of claim 8, wherein the stage is rotatable and liftable. 10 . The microwave plasma generating device according to claim 8 , wherein a visual observation hole and a pyrometer are arranged on the outer cavity close to the object stage. 11 .