CN110579105B

CN110579105B - Oxidation furnace

Info

Publication number: CN110579105B
Application number: CN201810589310.XA
Authority: CN
Inventors: 陈志兵; 李旭刚; 刘�东
Original assignee: Beijing Naura Microelectronics Equipment Co Ltd
Current assignee: Beijing North Huachuang Semiconductor Equipment Co.,Ltd.
Priority date: 2018-06-08
Filing date: 2018-06-08
Publication date: 2021-06-08
Anticipated expiration: 2038-06-08
Also published as: CN110579105A; TW202001173A; TWI727233B; WO2019233063A1

Abstract

The present invention provides an oxidation furnace, comprising: the furnace chamber comprises a process zone, a heat insulation zone, a combustion zone and a heat preservation zone which are sequentially divided from top to bottom; the process boat is arranged in the process area and used for bearing the processed workpiece; the air inlet pipeline is used for conveying process gas, an air outlet of the air inlet pipeline is positioned in the combustion area, and an air inlet of the air inlet pipeline extends out from the bottom of the furnace chamber; the heat insulation structure is arranged in the heat insulation area, and the heat insulation structure enables the heat insulation area to form an air inlet channel so that the gas in the combustion area flows into the process area after passing through the air inlet channel; and the heat insulation structure is arranged in the heat insulation area and surrounds the periphery of the air inlet pipeline. The oxidation furnace provided by the invention can save equipment space, reduce equipment cost and improve the stability of airflow.

Description

Oxidation furnace

Technical Field

The invention relates to the field of semiconductor manufacturing, in particular to an oxidation furnace.

Background

The SiC material has the outstanding advantages of wide band gap, high saturation drift velocity, high thermal conductivity, high critical breakdown electric field and the like, belongs to the third generation semiconductor material, and is suitable for preparing high-power, high-frequency, high-voltage, high-temperature and anti-radiation electronic devices.

The SiC material is the only material capable of directly oxidizing and growing SiO₂The most common method for growing SiO by thermal oxidation of high-temperature dry oxygen or wet oxygen is to use wide-gap semiconductor of film₂Film and thermal oxidation process to obtain SiO₂The quality of the film and the interface characteristics is best.

The temperature of the SiC high-temperature oxidation process is as high as 1500 ℃, and the conventional high-temperature equipment cannot meet the process requirements. At present, the high-temperature oxidation process of the SiC wafer is carried out by utilizing a high-temperature oxidation furnace in the industry, and the high-temperature oxidation furnace is key process equipment of a SiC device integrated circuit production line.

Fig. 1 is a sectional view of a conventional oxidation furnace. Referring to fig. 1, the oxidation oven includes an explosion-proof housing 1, an ignition chamber 2, a heater 3, a hydrogen pipe 4, an oxygen pipe 5, and a temperature sensor 6. The wet oxygen oxidation process generally adopts a method that high-purity hydrogen and oxygen are ignited outside a process chamber to synthesize water vapor, specifically, the high-purity hydrogen and the high-purity oxygen enter an ignition chamber 2 through a hydrogen pipe 4 and an oxygen pipe 5 respectively, the hydrogen reaches an ignition point under the heating of a heater 3 to be combusted to generate water vapor, and the water vapor enters the process chamber (not shown in the figure) from an ignition bubble outlet 7. The explosion-proof cover body 1 is water-filled and heat-insulated so as to protect external equipment devices. The temperature sensor 6 is used to monitor the combustion temperature in the ignition chamber 2 to ensure reliable combustion when hydrogen is introduced into the ignition chamber 2.

However, the existing oxidation furnace inevitably has the following problems in practical application:

firstly, the ignition method outside the process chamber needs to occupy a large space of the equipment because the ignition chamber 2 needs to be separately arranged to ignite hydrogen.

Secondly, the ignition chamber 2 conveys the water vapor to the process chamber in a gaseous state, so that the requirements on the air tightness and the heat preservation of the water vapor conveying pipeline are high, and the equipment cost is high.

Thirdly, because the heat insulating layer of the high-temperature vacuum reaction furnace (namely, the process cavity) is thick, the water vapor conveying distance is long, and the air flow conveying process is not stable easily.

Disclosure of Invention

The invention aims to solve at least one technical problem in the prior art, and provides an oxidation furnace which can save equipment space, reduce equipment cost and improve the stability of airflow.

To achieve the object of the present invention, there is provided an oxidation furnace comprising:

the furnace chamber comprises a process zone, a heat insulation zone, a combustion zone and a heat preservation zone which are sequentially divided from top to bottom;

the process boat is arranged in the process area and used for bearing the processed workpiece;

the gas inlet pipeline is used for conveying process gas, a gas outlet of the gas inlet pipeline is positioned in the combustion area, and a gas inlet of the gas inlet pipeline extends out from the bottom of the furnace chamber;

the heat insulation structure is arranged in the heat insulation area, and the heat insulation structure enables the heat insulation area to form an air inlet channel so that the gas in the combustion area flows into the process area after passing through the air inlet channel;

and the heat insulation structure is arranged in the heat insulation area and surrounds the periphery of the air inlet pipeline.

Optionally, the air intake pipeline includes a hydrogen pipe and an oxygen pipe sleeved on the periphery of the hydrogen pipe, wherein the hydrogen pipe is used for conveying hydrogen, and the oxygen pipe is used for conveying oxygen;

the combustion zone is adapted to react the hydrogen and a portion of the oxygen to form water vapor to provide a wet oxygen stream to the process zone.

Optionally, the outlet of the oxygen pipe is lower than the outlet of the hydrogen pipe.

Optionally, a blocking part is arranged at the upper end of the hydrogen pipe, the blocking part is in a dome shape, and a first through hole serving as the air outlet is arranged in the center of the blocking part;

the diameter of the first through hole is smaller than the inner diameter of the hydrogen pipe.

Optionally, the air intake pipeline further includes a thermocouple guard tube disposed inside the oxygen tube, and a thermocouple is disposed in the thermocouple guard tube and used for detecting the temperature of the combustion area;

one end of the thermocouple protection tube positioned in the combustion area is closed, and one end of the thermocouple protection tube far away from the combustion area extends out from the bottom of the furnace chamber.

Optionally, the heat insulation structure includes a plurality of first heat insulation plates arranged at intervals in a vertical direction, and an annular channel is formed between an outer peripheral wall of the plurality of first heat insulation plates and an inner peripheral wall of the oven cavity;

the center of each first heat insulation plate is provided with a center hole, and the annular channel and the center hole are used as the air inlet channel.

Optionally, the heat insulation structure includes a plurality of second heat insulation boards arranged at intervals in the vertical direction, and a heat insulation cavity filled in the heat insulation area and located below the second heat insulation board at the lowest layer;

and the heat insulation cavity is filled with a heat insulation medium.

Optionally, the oxidation furnace further comprises: an inner layer hose and an outer layer hose sleeved on the periphery of the inner layer hose, wherein,

the air outlet of the inner hose is hermetically connected with the air inlet of the air inlet pipeline, and the air inlet of the inner hose is used for being connected with an air source;

a vacuum space is formed between the outer hose and the inner hose.

Optionally, the furnace chamber is composed of an inner furnace body, and an outer furnace body is sleeved on the periphery of the inner furnace body;

the bottom of the outer furnace body is provided with an opening, and the inner furnace body can ascend or descend relative to the outer furnace body through the opening.

Optionally, the oxidation furnace further comprises: the first flange is arranged at the lower end of the inner furnace body;

a second through hole is formed in the first flange, and an air inlet of the air inlet pipeline extends out through the second through hole; and a first sealing ring is arranged between the air inlet pipeline and the second through hole and used for sealing a gap between the air inlet pipeline and the second through hole.

Optionally, a second flange is further disposed at the lower end of the outer furnace body, and the second flange is in sealed butt joint with the first flange when the inner furnace body is located in the outer furnace body.

Optionally, the inner furnace body is provided with an upper end opening;

a gap is formed between the outer peripheral wall of the inner furnace body and the inner peripheral wall of the outer furnace body;

an exhaust port communicated with the outside is formed in the second flange;

the exhaust port, the gap and the upper end opening form an exhaust passage communicated with the interior of the inner furnace body.

The invention has the following beneficial effects:

the oxidation furnace provided by the invention adopts the ignition structure in the furnace, namely, the process zone and the combustion zone are both positioned in the furnace cavity, so that the equipment space can be saved. Meanwhile, high-temperature radiation in the process area is blocked by means of the heat insulation structure, and the heat insulation structure can enable the heat insulation area to form an air inlet channel for gas in the combustion area to pass through and flow into the process area, so that water vapor conveying in the furnace is realized, a water vapor conveying pipeline is omitted, and equipment cost is reduced. In addition, the water vapor conveying distance in the furnace is short, and stable airflow is easily formed, so that the stability of the airflow in the process area can be improved.

Drawings

FIG. 1 is a sectional view of a conventional oxidation furnace;

FIG. 2 is a sectional view of an oxidation furnace according to an embodiment of the present invention;

FIG. 3 is an enlarged view of area I of FIG. 2;

FIG. 4 is an enlarged view of area II of FIG. 2;

fig. 5 is a schematic view of a gas flow path of an oxidation furnace according to an embodiment of the present invention.

Detailed Description

In order to make those skilled in the art better understand the technical solution of the present invention, the oxidation furnace provided by the present invention will be described in detail below with reference to the accompanying drawings.

Referring to fig. 1 to 5, an oxidation furnace according to an embodiment of the present invention includes a furnace chamber 8, a process boat 9, an air inlet pipeline, a heat insulation structure 10, and a heat preservation structure 14. Wherein, the furnace chamber 8 comprises a process area A, a heat insulation area B, a combustion area C and a heat preservation area D which are divided from top to bottom in sequence.

The process boat 9 is arranged in the process area A and used for bearing the processed workpieces. For example, the workpiece to be processed is a SiC wafer. Alternatively, the process boat 9 includes a support on which fixing grooves (not shown) are formed at intervals in the vertical direction, and each fixing groove is used for supporting one workpiece to be processed. Therefore, a plurality of workpieces to be processed can be processed simultaneously by one process, and the productivity can be improved.

The air inlet pipeline is used for conveying process gas, an air outlet of the air inlet pipeline is positioned in the combustion area C, and an air inlet of the air inlet pipeline extends out from the bottom of the furnace chamber. In the embodiment, the oxidation furnace is used for carrying out a wet oxygen oxidation process, and the process is carried out by adopting a method for synthesizing water vapor by igniting high-purity hydrogen and oxygen. Specifically, the air inlet pipeline comprises a hydrogen pipe 11 and an oxygen pipe 12 sleeved on the periphery of the hydrogen pipe 11, wherein the hydrogen pipe 11 is used for conveying hydrogen; the oxygen pipe 12 is used for conveying oxygen; the combustion zone C is used to react the hydrogen and a portion of the oxygen to produce water vapor to provide a wet oxygen stream, i.e., an oxygen stream containing water vapor, to the process zone a. Optionally, the hydrogen tube 11 and the oxygen tube 12 are both quartz tubes, preferably high-purity quartz tubes, so as to improve high-temperature resistance.

The heat insulation structure 10 is disposed in the heat insulation region B for blocking high temperature radiation in the process region a. And the heat insulation structure 10 makes the heat insulation area B form an air inlet channel for the gas in the combustion area C to flow into the process area A after passing through.

The heat preservation structure 14 is arranged in the heat preservation area and surrounds the periphery of the air inlet pipeline, and is used for preserving heat and insulating heat.

The process of forming the wet oxygen stream is specifically: the hydrogen and oxygen meet in combustion zone C and react to form water vapor, and the oxygen stream containing water vapor (i.e., the wet oxygen stream) enters process zone a through the inlet passage formed in insulation zone B by insulation structure 10.

It should be noted that the ambient temperature in the furnace chamber 8 has a temperature gradient in the vertical direction, i.e., the temperature gradually decreases from top to bottom. In this case, the process gas entering the inlet line is gradually heated above the ignition point by the ambient temperature in the furnace chamber 8 during the downward and upward flow into the combustion zone C, i.e. the process gas is preheated before reaching the combustion zone C. In practical applications, the vertical distance between the combustion zone C and the furnace chamber 8 can be designed to achieve the above-mentioned effects.

The oxidation furnace provided by the embodiment of the invention adopts the ignition structure in the furnace, namely, the process area A and the combustion area C are both positioned in the furnace chamber 8, so that the equipment space can be saved. Meanwhile, high-temperature radiation in the process area A is blocked by means of the heat insulation structure 10, and the heat insulation structure 10 can enable the heat insulation area B to form an air inlet channel for gas in the combustion area C to pass through and flow into the process area A, so that water vapor conveying in the furnace is realized, a water vapor conveying pipeline is omitted, and equipment cost is reduced. In addition, the water vapor conveying distance in the furnace is short, and stable airflow is easily formed, so that the stability of the airflow in the process area A can be improved.

In the present embodiment, as shown in fig. 3, the upper end of the hydrogen pipe 11 is provided with a stopper 111, the stopper 111 has a dome shape, and the center of the stopper 111 is provided with a first through hole 112 serving as an air outlet. And, the diameter of the first through hole 112 is smaller than the inner diameter of the hydrogen pipe 11. Since the diameter of the first through hole 112 as the gas outlet of the hydrogen pipe 11 is much smaller than the diameter of the gas outlet 121 of the oxygen pipe 12, the amount of hydrogen entering the combustion area C can be much smaller than the amount of oxygen, thereby facilitating the combustion of hydrogen. In addition, by making the baffle portion 111 of the hydrogen pipe 11 dome-shaped, the smoothness of the airflow in the combustion region C can be improved, thereby facilitating the formation of a stable flow of wet oxygen.

In the present embodiment, as shown in fig. 3, the outlet 121 of the oxygen tube 12 is lower than the outlet of the hydrogen tube 11, i.e., the first through hole 112. Thus, oxygen can be made to enter the combustion zone C earlier than hydrogen, forming an oxygen atmosphere, thereby facilitating combustion of hydrogen.

In the present embodiment, the intake pipe further includes a thermocouple guard 13 disposed inside the oxygen pipe 12, and as shown in fig. 3, the thermocouple guard 13 is provided with a thermocouple 15 therein for detecting the temperature of the combustion region C. And, one end of the thermocouple guard pipe 13 located at the combustion zone C is closed, and one end of the thermocouple guard pipe 13 located away from the combustion zone C extends from the bottom of the cavity 8. The thermocouple 15 is installed in the thermocouple guard 13 from the end of the thermocouple guard 13 remote from the combustion zone C, and the detection end of the thermocouple 15 is brought into contact with the end of the thermocouple guard 13 located in the combustion zone C.

Optionally, the detection end of the thermocouple protection tube 13 is lower than the gas outlet of the hydrogen tube 11. Since the combustion zone C may have a temperature gradient in the vertical direction, i.e., the temperature gradually increases from bottom to top. In this case, since the position of the detection end of the thermocouple guard tube 13 is low, as long as the temperature of the position of the combustion region C where the detection end is located can meet the requirement, the temperature of the gas outlet of the hydrogen tube 11 is inevitably higher than the temperature at the detection end, so that it can be determined that the temperature of the gas outlet of the hydrogen tube 11 can meet the requirement.

In the present embodiment, as shown in fig. 5, the heat insulation structure 10 includes a plurality of first heat insulation boards 101 arranged at intervals in the vertical direction, and since two adjacent first heat insulation boards 101 are spaced from each other, the heat insulation effect is better. Optionally, the first heat insulation board 101 is made of a quartz material.

Optionally, the vertical distance between two adjacent first heat insulation plates ranges from 2 mm to 3 mm. Within this range, the heat insulation effect is good.

Moreover, an annular channel 103 is formed between the outer peripheral wall of the plurality of first heat insulation plates 101 and the inner peripheral wall of the furnace chamber 8, so that the gas in the combustion zone C flows into the process zone a after passing through. And, a center hole 102 is provided at the center of each first heat insulating plate 101, also for allowing the gas in the combustion zone C to flow into the process zone a after passing through. That is, the annular passage 103 and the center hole 102 serve as the gas inlet passage, so that the amount of gas flowing into the process zone a can be increased, and the uniformity of distribution of the gas in the process zone a can be improved, thereby improving the process uniformity.

In this embodiment, the insulation structure 14 includes a plurality of second insulation boards 141 arranged at intervals along the vertical direction, and an insulation cavity 142 filled in the insulation region D and located below the lowermost second insulation board 141, and the insulation cavity 142 is filled with an insulation medium. By means of the plurality of second heat insulation plates 141 and the heat insulation cavity 142, better heat insulation and heat insulation effects can be achieved. Of course, in practical application, the heat-insulating structure may also adopt any other structure as long as it can insulate heat from the outside and preheat the process gas in the air inlet pipeline.

In the present embodiment, the furnace chamber 8 is composed of an inner furnace body 81, and an outer furnace body 82 is sleeved on the outer periphery of the inner furnace body 81; the bottom of the outer furnace body 82 has an opening through which the inner furnace body 81 can be raised and lowered relative to the outer furnace body 82. When it is necessary to load and unload a workpiece to be processed or to maintain parts in the inner furnace body 81, the inner furnace body 81 is lowered to move the entire inner furnace body 81 out of the outer furnace body 82. When a process is required, the inner furnace body 81 is raised until the entire inner furnace body 81 is moved into the outer furnace body 82.

Of course, in practical applications, the outer furnace body 82 may be raised or lowered as needed. In this case, the inner furnace body 81 may be moved up and down synchronously with the outer furnace body 82, or may be fixed while the outer furnace body 82 is moved up and down.

In this embodiment, the oxidation oven further includes an inner hose 19 and an outer hose 18 sleeved on the outer periphery of the inner hose 19, wherein the air outlet of the inner hose 19 is hermetically connected to the air inlet of the air inlet pipeline, specifically, two sets of the inner hose 19 and the outer hose 18 are hermetically connected to the air inlet 112 of the hydrogen pipe 11 and the air inlet 122 of the oxygen pipe 12, respectively. In practical applications, a metal-faced sealing joint (VCR joint) may be used to achieve a sealed connection.

Wherein the air inlet of the inner hose 19 is adapted to be connected to an air source (not shown in the figures), and the process gas is fed into the air inlet line via the inner hose 19.

A vacuum space is formed between the outer hose 18 and the inner hose 19. Therefore, the leakage condition of the process gas can be monitored at the vacuum space, so that the safety protection effect can be achieved.

In the process of lifting the inner furnace body 81, the inner hose 19 and the outer hose 18 can be bent, so that the air inlet pipeline can be allowed to synchronously lift along with the inner furnace body 81. Of course, in practical applications, a bellows may be used instead of the hose.

In this embodiment, the oxidation furnace further includes a first flange 23, and the first flange 23 is disposed at the lower end of the inner furnace body 81. Specifically, the first flange 23 closes the lower end opening of the inner furnace body 81. Furthermore, a second through-hole is provided in the first flange 23, through which the air inlet of the air inlet line extends; a first sealing ring is arranged between the air inlet pipeline and the second through hole and used for sealing a gap between the air inlet pipeline and the second through hole, so that the interior of the inner furnace body 81 is kept in a vacuum state.

Specifically, as shown in fig. 4, the diameter of the upper portion of the second through hole is adapted to the outer diameter of the oxygen tube 12, and a sealing ring 20 is disposed between the oxygen tube 12 and the upper portion of the second through hole for sealing a gap therebetween. The air inlet of the hydrogen pipe 11 is lower than the air inlet of the oxygen pipe 12, the diameter of the lower part of the second through hole is matched with the outer diameter of the hydrogen pipe 11, and a sealing ring 21 is arranged between the hydrogen pipe 11 and the lower part of the second through hole and used for sealing the gap between the hydrogen pipe 11 and the second through hole. The seal rings 20 and 21 are the first seal rings described above, which are preferably made of a high temperature resistant material such as fluororubber.

In this embodiment, a second flange 84 is further provided at the lower end of the outer furnace body 82, and the second flange 84 is in sealing abutment with the first flange 23 when the inner furnace body 81 is positioned in the outer furnace body 82.

In the present embodiment, as shown in fig. 2, the inner furnace body 81 has an upper end opening. A gap 83 is provided between the outer peripheral wall of the inner furnace body 81 and the inner peripheral wall of the outer furnace body 82. The second flange 84 is provided with an exhaust port 841 communicating with the outside. The exhaust port 841, the gap 83, and the upper end opening of the inner body 81 constitute an exhaust passage communicating with the inside of the inner body 81. The exhaust passage is used to exhaust the gas in the process zone a. It will be readily appreciated that the upper end of the inner body 81 is slightly below the top of the outer body 82 so that the upper end opening of the inner body 81 can communicate with the gap 83.

In summary, the oxidation furnace provided by the invention adopts the ignition structure in the furnace, i.e. the process zone and the combustion zone are both positioned in the furnace cavity, so that the equipment space can be saved. Meanwhile, high-temperature radiation in the process area is blocked by means of the heat insulation structure, and the heat insulation structure can enable the heat insulation area to form an air inlet channel for gas in the combustion area to pass through and flow into the process area, so that water vapor conveying in the furnace is realized, a water vapor conveying pipeline is omitted, and equipment cost is reduced. In addition, the water vapor conveying distance in the furnace is short, and stable airflow is easily formed, so that the stability of the airflow in the process area can be improved.

It will be understood that the above embodiments are merely exemplary embodiments taken to illustrate the principles of the present invention, which is not limited thereto. It will be apparent to those skilled in the art that various modifications and improvements can be made without departing from the spirit and substance of the invention, and these modifications and improvements are also considered to be within the scope of the invention.

Claims

1. An oxidation furnace, comprising:

the heat insulation structure is arranged in the heat insulation area and surrounds the periphery of the air inlet pipeline, the heat insulation structure is used for insulating the outside and preheating the process gas in the air inlet pipeline, and the heat insulation structure comprises a plurality of second heat insulation plates which are arranged at intervals in the vertical direction and a heat insulation cavity which is filled in the heat insulation area and is positioned below the second heat insulation plate at the lowest layer; and the heat insulation cavity is filled with a heat insulation medium.

2. The oxidation furnace as claimed in claim 1, wherein the air inlet pipe comprises a hydrogen pipe and an oxygen pipe sleeved on the periphery of the hydrogen pipe, wherein the hydrogen pipe is used for conveying hydrogen and the oxygen pipe is used for conveying oxygen;

3. The oxidation oven as claimed in claim 2, wherein the outlet of the oxygen pipe is lower than the outlet of the hydrogen pipe.

4. The oxidation furnace as claimed in claim 2, wherein the hydrogen pipe is provided at an upper end thereof with a baffle portion having a dome shape, and a center of the baffle portion is provided with a first through hole serving as the air outlet;

5. The oxidation furnace as claimed in claim 2, wherein the air intake duct further comprises a thermocouple guard pipe disposed inside the oxygen pipe, the thermocouple guard pipe having a thermocouple disposed therein for detecting a temperature of the combustion zone;

6. The oxidation furnace as claimed in any one of claims 1 to 5, wherein the heat insulating structure includes a plurality of first heat insulating plates spaced apart in a vertical direction, an annular passage being formed between an outer circumferential wall of the plurality of first heat insulating plates and an inner circumferential wall of the furnace chamber;

7. The oxidation oven as claimed in any one of claims 1 to 5, further comprising: an inner layer hose and an outer layer hose sleeved on the periphery of the inner layer hose, wherein,

a vacuum space is formed between the outer hose and the inner hose.

8. The oxidation furnace as claimed in any one of claims 1 to 5, wherein the furnace chamber is formed by an inner furnace body, and an outer furnace body is fitted around an outer periphery of the inner furnace body;

9. The oxidation oven as claimed in claim 8, further comprising: the first flange is arranged at the lower end of the inner furnace body;

10. The oxidation furnace as claimed in claim 9, wherein a second flange is further provided at a lower end of the outer furnace body, the second flange being in sealing abutment with the first flange when the inner furnace body is positioned in the outer furnace body.

11. The oxidation furnace as claimed in claim 10, wherein the inner furnace body has an upper end opening;

an exhaust port communicated with the outside is formed in the second flange;