阅读说明：本技术 一种提高微波cvd窗口耐热性的复合窗口结构 (Composite window structure for improving heat resistance of microwave CVD window ) 是由 胡常青 赵建海 于 2021-06-10 设计创作，主要内容包括：本发明公开了一种提高微波CVD窗口耐热性的复合窗口结构,包括：真空组件及固接于所述真空组件上的复合窗口组件；所述真空组件包括多个金属反射挡板及用于封盖金属反射挡板,多个所述金属反射挡板构成一密封腔室,所述密封腔室的上端通过端盖进行密封,所述金属反射挡板上一体式连接于平面板,所述平面板上开设有微波孔；所述复合窗口组件包括固定于所述平面板上的第一窗口件及固接于所述平面板远离第一窗口件一端面上的第二窗口件,所述第一窗口件与所述第二窗口件平行且间隔设置。根据本发明,自身良好的散热特点,形成一个较低温度的热屏蔽层,避免传统的微波窗口过热,可以大幅度提高微波馈入真空腔的功率值。(The invention discloses a composite window structure for improving heat resistance of a microwave CVD window, which comprises the following components: the composite window assembly is fixedly connected to the vacuum assembly; the vacuum assembly comprises a plurality of metal reflecting baffles and a metal reflecting baffle used for sealing the metal reflecting baffles, the metal reflecting baffles form a sealed cavity, the upper end of the sealed cavity is sealed through an end cover, the metal reflecting baffles are integrally connected to a plane plate, and microwave holes are formed in the plane plate; the composite window assembly comprises a first window piece fixed on the plane plate and a second window piece fixedly connected to one end face, far away from the first window piece, of the plane plate, and the first window piece and the second window piece are arranged in parallel at intervals. According to the invention, a heat shielding layer with lower temperature is formed by the good heat dissipation characteristic of the microwave oven, thereby avoiding the overheating of the traditional microwave window and greatly improving the power value of the microwave fed into the vacuum cavity.)

1. A composite window structure for improving the heat resistance of a microwave CVD window, comprising:

the composite window assembly is fixedly connected to the vacuum assembly;

the vacuum assembly comprises a plurality of metal reflecting baffles and a metal reflecting baffle used for sealing the metal reflecting baffles, the metal reflecting baffles form a sealed cavity, the upper end of the sealed cavity is sealed through an end cover, the metal reflecting baffles are integrally connected to a plane plate, and microwave holes are formed in the plane plate;

the composite window assembly comprises a first window piece fixed on the plane plate and a second window piece fixedly connected to one end face, far away from the first window piece, of the plane plate, and the first window piece and the second window piece are arranged in parallel at intervals.

2. A composite window structure for increasing heat resistance of a microwave CVD window as recited in claim 1, wherein said first window member is a silica material, and said silica material is a quartz material.

3. A composite window structure for improving heat resistance of a microwave CVD window as claimed in claim 1, wherein said second window member is a thermally conductive material, said thermally conductive material being a CVD diamond thick film.

4. The composite window structure of claim 1, wherein said first and second window members are circular in shape, and said second window member is soldered to said flat plate, and said first window member is sealed to said metal reflective baffle by a circular metal vacuum seal.

5. A composite window structure for improving heat resistance of a microwave CVD window as claimed in claim 2, wherein an opposite side of the first window member is polished flat and the first window member has a thickness of between 8.0 mm and 12.0 mm.

6. A composite window structure for improving heat resistance of a microwave CVD window as claimed in claim 3, wherein the second window 5 is polished flat on opposite sides and the second window member has a thickness of between 1.0 mm and 2.0 mm.

7. A composite window structure for improving heat resistance of a microwave CVD window according to any of claims 1-6, further comprising a vacuum pumping assembly and a gas supply assembly connected to the vacuum assembly, a plasma reaction chamber disposed in the vacuum assembly, and a microwave assembly communicated with the vacuum assembly, wherein the vacuum pumping assembly comprises a vacuum pump connected to the vacuum assembly; the gas supply assembly comprises reaction raw material gas communicated with the vacuum assembly and a gas flow controller used for controlling the flow of the reaction raw material gas; the microwave assembly comprises a microwave source, a waveguide tube communicated with the microwave source and a microwave mode converter connected with the waveguide tube; the plasma reaction chamber comprises a substrate table and a plasma sphere arranged on the substrate table.

Technical Field

The invention relates to the technical field of vacuum microelectronics, in particular to a composite window structure for improving heat resistance of a microwave CVD window.

Background

The fourth state of the plasma as a substance follows from the solid state, the liquid state and the gas state, and the plasma has wide application in many fields. To make the material in a plasma state, a certain amount of energy needs to be supplied. Microwave plasma technology is widely used in many fields because microwave, which is an electromagnetic wave, can excite a gas into a plasma state relatively easily in a vacuum environment.

The Microwave Plasma Chemical Vapor Deposition (MPCVD) device generally comprises a microwave system, a vacuum system, a gas supply system and a plasma reaction chamber, wherein the plasma reaction chamber is internally provided with a self-rotating substrate table 6, taking the preparation of a diamond film as an example, the microwave generated by the microwave system penetrates a round window material (usually silicon dioxide) prepared by a microwave-transparent material from a normal pressure area, enters a vacuum chamber, exciting gas provided by a gas supply system above the self-rotating substrate table 6 to generate a plasma ball, wherein the plasma ball is tightly attached to the surface of a film-forming substrate material, CVD diamond [ 1 ] can be deposited on the surface of the substrate table 6, and in order to improve the growth speed and the growth quality of the CVD diamond, the improvement of the input power of microwave is one of the selection schemes [ 2 ]. However, since the microwave window of the microwave vacuum chamber is directly opposite to the plasma ball generated by microwave excitation, the core temperature of the plasma ball will gradually rise with the increase of the microwave input power, and the heat radiation quantity will also increase. When the microwave input power of the input vacuum cavity reaches more than 5KW, the growth speed of the CVD diamond can be improved, but two adverse effects are caused: 1) the heat radiation generated by the plasma ball easily causes heat damage to the traditional microwave window material, and the microwave window strength is reduced or even damaged in serious cases, so that the vacuum sealing effect is lost; 2) the strong plasma spheres etch the microwave window material, creating impurities that mix into the CVD diamond, reducing the purity of the CVD diamond. Thus, the maximum tolerable microwave input power of such a microwave window (in the case of silicon dioxide) is 5.0-6.0 KW. If the maximum power of microwave input is further increased, the heat radiation resistance of the microwave window is improved.

Reference documents:

【1】 Mode study of microwave mode converter 2 in luqingao, wuchang chong, microwave plasma CVD apparatus, vacuum electronics, 1997, 5: 12-15;

【2】 Man-wei-dong, wangsuan, manshu, etc., microwave plasma chemical vapor deposition-an ideal method for preparing diamond films, vacuum and low temperature, 2003, 1: 50-56.

Disclosure of Invention

Aiming at the defects in the prior art, the invention aims to provide a composite window structure for improving the heat resistance of a microwave CVD window, which has the characteristic of good heat dissipation, forms a heat shielding layer with lower temperature, avoids the overheating of the traditional microwave window and can greatly improve the power value of microwave fed into a vacuum cavity. To achieve the above objects and other advantages in accordance with the present invention, there is provided a composite window structure for improving heat resistance of a microwave CVD window, comprising:

the composite window assembly is fixedly connected to the vacuum assembly;

the vacuum assembly comprises a plurality of metal reflecting baffles and a metal reflecting baffle used for sealing the metal reflecting baffles, the metal reflecting baffles form a sealed cavity, the upper end of the sealed cavity is sealed through an end cover, the metal reflecting baffles are integrally connected to a plane plate, and microwave holes are formed in the plane plate;

the composite window assembly comprises a first window piece fixed on the plane plate and a second window piece fixedly connected to one end face, far away from the first window piece, of the plane plate, and the first window piece and the second window piece are arranged in parallel at intervals.

Preferably, the first window member is a silica material, and the silica material is a quartz material.

Preferably, the second window member is a thermally conductive material, and the thermally conductive material is a CVD diamond thick film.

Preferably, the first window piece and the second window piece are both of circular structures, the second window piece 5 is welded on the plane plate in a brazing mode, and the first window piece is hermetically arranged on the metal reflection baffle plate through an annular metal vacuum sealing ring.

Preferably, an opposite surface of the first window member is polished flat, and the thickness of the first window member is between 8.0 and 12.0 mm.

Preferably, one opposite side of the second window member is polished flat, and the thickness of the second window member is between 1.0 and 2.0 mm.

Preferably, the plasma reactor further comprises a vacuumizing assembly and an air supply assembly connected with the vacuum assembly, a plasma reaction chamber arranged in the vacuum assembly and a microwave assembly communicated with the vacuum assembly, wherein the vacuumizing assembly comprises a vacuum pump connected with the vacuum assembly; the gas supply assembly comprises reaction raw material gas communicated with the vacuum assembly and a gas flow controller used for controlling the flow of the reaction raw material gas; the microwave assembly comprises a microwave source, a waveguide tube communicated with the microwave source and a microwave mode converter connected with the waveguide tube; the plasma reaction chamber comprises a substrate table and a plasma sphere arranged on the substrate table.

Compared with the prior art, the invention has the beneficial effects that: the window is arranged into an upper layer structure and a lower layer structure, each layer structure is circular, one layer is made of a traditional microwave window material, and the microwave window which can penetrate microwaves and can be vacuum-sealed is formed through metal vacuum sealing; the vacuum area below the microwave window is provided with a layer of window which is made of high heat conduction material and can penetrate through heat shielding medium material of microwave, the material is circular, the material is arranged in parallel with the traditional microwave window material, the outer edge of the circumference of the material is welded on a water-cooled metal vacuum cavity through brazing, and a heat shielding layer with a lower temperature is formed through the good heat dissipation characteristic of the material, so that the traditional microwave window is prevented from being overheated, and the power value of feeding the microwave into the vacuum cavity can be greatly improved.

Drawings

Fig. 1 is a schematic structural view of a composite window structure for improving heat resistance of a microwave CVD window according to the present invention.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

Referring to fig. 1, a composite window structure for improving heat resistance of a microwave CVD window, includes: the composite window assembly is fixedly connected to the vacuum assembly; the vacuum assembly comprises a plurality of metal reflecting baffles 9 and a sealing cover used for sealing the metal reflecting baffles 9, the metal reflecting baffles 9 form a sealed cavity, the upper end of the sealed cavity is sealed through an end cover, the metal reflecting baffles 9 are integrally connected to a plane plate, and microwave holes are formed in the plane plate; the composite window assembly comprises a first window piece 4 fixed on a plane plate and a second window piece 5 fixedly connected to the plane plate and far away from one end face of the first window piece 4, the first window piece 4 and the second window piece 5 are arranged in parallel and at intervals, the first window piece 4 is made of silicon dioxide, the silicon dioxide is made of quartz materials, the second window piece 5 is made of heat conducting materials, and the heat conducting materials are CVD diamond thick films.

Furthermore, first window spare 4 and second window spare 5 are circular structure, just second window spare 5 welds on the flat panel through brazed mode, first window spare 4 sets up on metal reflecting baffle 9 through ring shape metal vacuum seal ring is sealed.

Furthermore, one opposite surface of the first window piece 4 is polished to be flat, the thickness of the first window piece 4 is 8.0-12.0 mm, the other opposite surface of the second window piece 5 is polished to be flat, the thickness of the second window piece 5 is 1.0-2.0 mm, under the traditional microwave window with the vacuum sealing effect, the window made of a microwave-transparent material (a CVD diamond film is selected and used, and the thermal conductivity is 2000W/m.K) with high thermal conductivity is added, so that the etching effect of the plasma on the traditional microwave window is reduced, the direct contact of the plasma on the traditional microwave window can also be reduced, the traditional microwave window is protected, the silicon impurities are reduced, and the purity of the CVD diamond film is improved. Since the CVD diamond film window material is composed of carbon. Even if plasma etching is performed, carbon-containing substances are generated, and the carbon substances are also effective components for growing the CVD diamond and cannot generate new impurity pollution. The high thermal conductivity of the CVD diamond can transfer the heat radiated from the plasma ball to the wall of the water-cooling metal vacuum cavity through the brazing around the CVD diamond. And thus is not itself prone to thermal damage. Since the CVD diamond thick film window does not need to be vacuum sealed, the thickness of the CVD diamond thick film does not need to be large, and a thickness of 1.0 to 2.0 mm is generally sufficient to provide good thermal conduction.

In the working process, microwaves generated by the microwave system penetrate through the composite microwave window to enter the plasma reaction chamber, gas provided by the gas supply system is excited above the self-rotating substrate table 6 to generate a plasma ball, and CVD diamond grows on the surface of the substrate table 6 below the plasma ball.

In the growth of CVD diamond by using a microwave CVD method, the larger the microwave power input is, the higher the plasma activity generated by microwave excitation is, and the higher the growth speed of the CVD diamond is; meanwhile, the active components in the plasma are increased along with the increase of the microwave power density, so that the growth quality of the CVD diamond is also improved. Therefore, the plasma formed by feeding high-power microwaves into the vacuum chamber is a key factor for improving the growth speed and quality of the CVD diamond. However, in the microwave CVD vacuum chamber described in the document [ 1 ], due to the design requirement of the microwave vacuum chamber, the microwave window needs to be directly faced to the plasma generated by microwave excitation, and when the microwave power input is increased, since both the vacuum chamber wall and the substrate stage 6 are water cooled, the increase in microwave power has little effect on the vacuum chamber wall and the substrate stage 6, whereas since the microwave window material is silicon dioxide, the thermal conductivity of the material is lower by 7.6W/m.K, and the vacuum seal which needs mechanical pressing is added, therefore, a certain mechanical strength is required, and therefore the thickness of the microwave window made of silica is between 8.0 and 12.0 mm, and the silicon dioxide is in heat conduction contact with the water-cooled metal cavity wall through the metal vacuum sealing ring, therefore, the cooling effect of the water-cooling metal vacuum cavity wall on the silicon dioxide microwave window is not ideal, so that the temperature of the silicon dioxide window is increased along with the increase of the microwave input power; in addition, due to the increase of the feeding amount of the microwave power, the plasma activity is large, and part of the active plasma diffuses to the vicinity of the microwave window, so that the surface of the microwave window is etched, and impurities containing silicon are formed and mixed into the CVD diamond.

The plasma reaction chamber is arranged in the vacuum assembly, and the microwave assembly is communicated with the vacuum assembly; the gas supply assembly comprises a reaction raw material gas 8 communicated with the vacuum assembly and a gas flow controller 7 for controlling the flow of the reaction raw material gas 8; the microwave assembly comprises a microwave source 1, a waveguide 3 communicated with the microwave source 1 and a microwave mode converter 2 connected with the waveguide 3; the plasma reaction chamber comprises a substrate table 6 and a plasma sphere arranged on the substrate table 6, wherein the diameter of the self-rotating substrate table 6 is 60mm, the maximum power of the microwave source 1 is 10KW, and the microwave power is continuously adjustable. The reaction gases used to excite the plasma were H2 (99.999% pure), CH4 (99.9999% pure).

Example one

The upper microwave window is made of silicon dioxide, and the thickness is as follows: 10.0 mm; the lower microwave window is not provided.

Microwave input power is 5KW, the air pressure in the metal vacuum cavity is 21.0kPa, and the gas flow is H2: CH4 ═ 200: 4.0sccm (sccm: standard cubic centimeter per minute), the growth temperature of the CVD diamond film is 880 ℃, and the substrate material is a monocrystalline silicon wafer. After 8 hours of operation, the thickness of the CVD diamond film was measured and the growth rate was calculated to be 6.2 μm/hr: the Si content in the CVD diamond film was 1.153ppm by secondary mass spectrometry.

Example two

The upper microwave window is made of silicon dioxide, and the thickness is as follows: 10.0 mm; a lower microwave window is arranged below the microwave oven.

The lower microwave window material is two CVD diamonds, thickness: 1.5 mm; the outer edge brazing width was 3.0 mm.

Microwave input power is 10KW, the air pressure in the metal vacuum cavity is 21.0kPa, and the gas flow is H2: CH4 ═ 200: 4.0sccm (sccm: standard cubic centimeter per minute), the growth temperature of the CVD diamond film is 880 ℃, and the substrate material is a monocrystalline silicon wafer. After 8 hours of operation, the thickness of the CVD diamond film was measured and the growth rate was calculated to be 8.6 μm/hour: the Si content in the CVD diamond film was 0.218ppm by secondary mass spectrometry.

Comparing the first embodiment with the second embodiment, it can be seen that the etching effect of the plasma ball on the quartz window is greatly reduced due to the use of the composite microwave window, and the microwave feed-in power value is improved, so that the growth speed of the CVD diamond is obviously improved.

The number of devices and the scale of the processes described herein are intended to simplify the description of the invention, and applications, modifications and variations of the invention will be apparent to those skilled in the art.

While embodiments of the invention have been described above, it is not limited to the applications set forth in the description and the embodiments, which are fully applicable in various fields of endeavor to which the invention pertains, and further modifications may readily be made by those skilled in the art, it being understood that the invention is not limited to the details shown and described herein without departing from the general concept defined by the appended claims and their equivalents.