TWM634330U - Pre-cleaning reactor - Google Patents

Abstract

The invention provides a pre-cleaning reactor, including: a reaction chamber, a plasma generating device at the top of the chamber, and a gas diffusion plate located below the plasma generating device, so that the plasma generated in the plasma generating device flows through the gas diffusion After the plate is turned off, it goes down to the wafer to be processed; the bottom of the reaction chamber includes a base for carrying the wafer to be processed, and the base includes a cooling liquid channel, a heater located above the cooling liquid channel, and a heater above the heater The heat conduction space; also includes a cooling liquid supply system for supplying cooling liquid to the cooling liquid channel in the base, wherein the cooling liquid supply system includes a cooling liquid source, a plurality of flow pipes and a valve group, the valve The group selectively flows the cooling liquid into the base or returns to the cooling liquid source through the at least one flow channel.

Description

Pre-cleaning the reactor

The invention relates to the technical field of semiconductors, and in particular to a pre-cleaning reactor for cleaning natural oxides and other pollutants on the surface of a wafer.

In various processes of semiconductor element manufacturing, with the evolution of technology, the critical dimension (Critical Dimension) of the semiconductor element is getting smaller and smaller, and the material layer thickness between different structural layers in the semiconductor element is also getting smaller and smaller. The critical dimension of the current high-end semiconductor processing technology is already less than 5nm, so the thickness of the material layer is only tens of layers of atoms thick. On the premise that the material layer is so thin, the crystal structure will have a great influence on the semiconductor element, so it is required that the material layer in the semiconductor element should preferably be a material layer with a regular crystal structure. However, the wafer needs to be transferred between different processing equipment, and the transfer process needs to enter the atmospheric environment, which will result in a large amount of naturally oxidized material (SiO ₂ ) on the surface of the wafer, which will cause material Layer cannot form a uniform layer of crystalline material. Therefore, before the epitaxial growth of silicon or other semiconductor materials, it is necessary to use a dedicated pre-cleaning reactor to remove such natural oxides or other pollutants.

The existing pre-cleaning reaction needs to go through two steps: the low-temperature salt-forming step (20-70 degrees), first pass through the clean reaction gas group after remote plasma start, the reaction gas group includes free components such as fluorine, nitrogen, hydrogen, etc. The substrate reacts with the silicon oxide on the surface of the wafer to produce a solid salt; then a high-temperature sublimation step is performed to increase the temperature of the wafer so that the temperature of the wafer rises to a temperature (greater than 110 degrees) for the sublimation and gasification of the solid salt, and the sublimated The gas is sucked away by the exhaust system to complete a salt-forming sublimation cycle, and the eclipse Silicon oxide on the surface is etched away. After the sublimation of solid salt is completed, enter the next silicon oxide removal cycle, lower the wafer temperature and enter the low-temperature salt formation step in the next cycle. In order to increase the processing speed of the pre-clean reactor, it is necessary to maximize the heating and cooling speed of the wafer, while maintaining the temperature uniformity in the wafer. As shown in FIG. 1 , the basic structure of the pre-cleaning reactor in the prior art includes a reaction chamber 10 . The side of the reaction chamber 10 includes a transfer port 103 for transferring wafers into/out of the reaction chamber 10 . A remote plasma source (RPS) is included above the top of the reaction chamber 10. After the remote plasma source ignites the reactive gas or inert gas, the plasma diffuses downward through the first gas diffusion plate 22 and the second gas diffusion plate 24. And the charged particles are extinguished to form free radicals and reach the wafer W to be processed downward. The outer periphery of the second gas diffusion plate 24 also includes a heater 25 for heating the second gas diffusion plate 24 . The wafer W to be processed is placed on the pedestal 14, and the pedestal 14 includes a cooling liquid pipeline 12, and the cooling liquid pipeline 12 communicates with an external cooling liquid source, so that the pedestal 14 is maintained at a low temperature for a low-temperature salt-forming step. The top surface of the base 14 includes a wafer heat conduction space 16, and the wafer heat conduction space 16 includes a plurality of upwardly protruding support parts, so that the wafer W is placed on the support parts, and the space between the support parts is connected to a heat conduction space. Gas supply system, the heat conduction gas supply system provides stable pressure to the heat conduction space 16 of the wafer. The heat transfer gas supply system can be adjusted so that the pressure of the heat transfer gas can be maintained at 2-3 Torr, which is slightly lower than the reaction pressure above the wafer W. Such heat-conducting gas pressure can not only ensure that the wafer W is stably adsorbed above the base 14, but also ensure sufficient heat-conducting air pressure, so that the heat on the wafer W can be transferred to the base 14 through the heat-conducting gas, thereby realizing the cooling of the wafer W. . A support base 11 is located below the base 14 for supporting the base 14 , and the support base 11 may be provided with heat conduction gas pipes and cooling liquid pipes. The susceptor 14 also includes a lifting device 150 , which supports the upper wafer W through several separately arranged lifting pins 151 , 152 . When performing the pre-cleaning process, the lifting device 150 is first set at a low position, the wafer W is fixed on the base 14 to achieve cooling, and the heater 25 is controlled at the same time so that the second gas diffusion plate 24 Maintain a sufficiently high temperature (above 180 degrees). After the low-bit salt formation step is completed, the wafer W is raised by the lifting device 150 so that the wafer W is close to the high-temperature second gas diffusion plate 24. Diffusion to the wafer W by radiation and a small amount of gas flow to reduce the ramp-up time.

The above-mentioned prior art can rapidly reduce the temperature of the wafer W from a high temperature state to a low temperature state, but it takes a long time to heat up due to the small power of radiation during the heating process. In addition, there are other technical problems in the prior art. When the wafer W is lifted to the gas diffusion plate, the distance between the wafer W and the second gas diffusion plate 24 needs to be very uniform. There is a very high degree of parallelism between the plane defined by the upper end of the lifting pin and the lower surface of the second gas diffusion plate 24, which is difficult to guarantee in an actual reactor. After high-temperature sublimation, the temperature of the wafer W has also reached a high temperature state, and a large increase in temperature in a short period of time will cause slight deformation and warping of the wafer W. When put back on the low-temperature base 14, the warped wafer W and the wafer heat conduction space 16 on the base 14 cannot be sealed, the wafer W cannot be effectively adsorbed on the base 14, and the reaction gas will From the gap between the edge of the wafer W and the base 14, it flows into the wafer heat conduction space W on the back of the wafer W, and the airflow flowing laterally on the back of the wafer W causes the temperature of the wafer W to be uneven, and pollutants are generated on the back of the wafer W, etc. series of questions. At the same time, due to the air leakage at the edge of the wafer W, the wafer W cannot be effectively attached to the surface of the adsorption base 14. Only a part of the wafer W area is in direct contact with the surface of the base 14 to form a high thermal conductivity area, and other areas can only The temperature uniformity of the wafer W will be further deteriorated by radiation cooling.

Therefore, although the pre-cleaning reactor of the prior art can achieve rapid cooling of the wafer, it cannot achieve rapid temperature rise, and at the same time, a series of problems affecting temperature uniformity will be brought about during the heating and cooling process of the wafer. The industry needs a new pre-clean reactor design that enables rapid wafer heating and cooling while maintaining wafer temperature uniformity.

Compared with the conventional technology, the technical solution of the embodiment of the invention has the following beneficial effects: improving the processing efficiency of the pre-cleaning reactor, reducing the generation of pollutants on the back of the wafer, and improving the stability of the pre-cleaning treatment effect.

The invention provides a pre-cleaning reactor, including: a reaction chamber, the bottom of the reaction chamber includes a base for carrying wafers to be processed, the base includes a cooling liquid channel, a heater located above the cooling liquid channel, and The heat conduction space above the heater; the top of the chamber includes a plasma generating device, and a gas diffusion plate located below the plasma generating device, the plasma generating device ignites the reactive gas and forms a plasma, and the reactive gas flows through the gas diffusion plate After the plate is extinguished, and down to the wafer to be processed; also includes a coolant supply system for supplying coolant to the coolant channel in the base, wherein the coolant supply system includes a coolant source, a plurality of flow through Pipeline and at least one valve group, the valve group selectively allows the cooling liquid to flow into the base or flow back to the cooling liquid source through the at least one circulation pipe.

The heat conduction space includes a plurality of support ribs, and a plurality of heat conduction gas passages passing through the plurality of support ribs. The plurality of supporting ribs includes a circular first supporting rib located outside the upper surface of the base, and the height of the first supporting rib is higher than that of other supporting ribs surrounded by the first supporting rib, so that the edge of the backside of the wafer and the outermost The supporting ribs are closely attached to each other to realize sealing, so as to ensure high efficiency of heat conduction.

The cooling liquid supply system includes a first flow pipe connected to the base and a second flow pipe forming a bypass, and the valve group is located between the first flow pipe and the second flow pipe. Further, a restrictor valve may be provided on the bypass pipeline, so that the flow flowing through the bypass pipeline in the sublimation step is basically consistent with the flow flowing through the base in the salt forming step. Wherein the valve group can include A first valve is connected between the first flow pipe and the cooling liquid source, and a second valve is connected between the cooling liquid source and the second flow pipe. Or the valve group can also be a three-way valve.

Further, the valve group also includes a liquid discharge valve, the liquid discharge valve is connected between the external gas source and the first circulation pipeline, which can further reduce the downward heat conduction of the heater during the heating and sublimation step, reducing Heating time to improve processing efficiency.

10,100: reaction chamber

101,11: Support seat

103: transmission port, opening

110,14: base

112,12: Coolant pipe

114,125,25: Heater

116: heat conduction space

116a: Support edge

116b: flow channel

1160: heat conduction gas flow hole

120: top cover

122,22: First gas diffuser plate

124,24: Second gas diffuser plate

150: Lifting device

151, 152: lift thimble

16: Wafer heat conduction space

200: Coolant source

201a, 201b, 201c, 202a, 202b: pipeline

203: Air supply pipeline

204: flow limiting valve

213: valve group

V1: first valve

V2: second valve

V3: third valve

W: Wafer

Fig. 1 is the structural representation of prior art pre-cleaning reactor; Fig. 2 is the structural representation of this creative pre-cleaning reactor; Fig. 3 is the base top view and partial sectional schematic diagram in this creative pre-cleaning reactor; Fig. 4 is this Schematic diagram of the cooling liquid supply system in the creative pre-cleaning reactor; and FIG. 5 is a schematic diagram of another embodiment of the cooling liquid supply system in the creative pre-cleaning reactor.

As mentioned in the background technology, the existing pre-cleaning reactor cannot be heated rapidly and there is a problem of temperature inhomogeneity during the heating and cooling process, which seriously affects the efficiency and quality of wafer processing. Therefore, this creation is dedicated to providing a new pre-cleaning The reactor will be described in detail below.

Fig. 2 is a structural schematic diagram of a pre-cleaning reactor created in the present invention.

Please refer to Fig. 2, the pre-cleaning reactor includes: a reaction chamber 100; a base 110 that can realize heating and cooling is included in the reaction chamber 100, the base 110 is made of high thermal conductivity metal materials such as aluminum, and the base 110 It includes a cooling liquid pipeline 112 located below and a heater 114 located above the cooling liquid pipeline 112 . The top surface of the base 110 above the heater 114 includes a heat conduction space 116 , and the wafer to be processed is placed above the heat conduction space 116 . The base 110 can usually be made of metal with high thermal conductivity, such as aluminum. The upper surface exposed to the reaction gas may be coated or formed with a corrosion-resistant material layer, such as anodized aluminum oxide or yttrium oxide, to prevent the surface material of the base 110 from being corroded and causing particle pollution. The base 110 also includes a support base 101 at the bottom, and the support base 101 includes a cooling liquid pipeline, a circuit for providing heating power of the heater 114 , and a gas pipeline communicating with an external heat transfer gas supply system. The sidewall of the reaction chamber 100 includes an opening (or referred to as a transfer port) 103 for wafer transfer. The top of the reaction chamber 100 includes a top cover 120, the top cover 120 provides plasma for the remote plasma source to enter the first gas diffusion plate 122 and the second gas diffusion plate 124 below the top cover 120, and make the inflow of free radicals uniform The reaction space above the wafer below. A heater 125 with a smaller power is arranged on the outer periphery of the second gas diffusion plate 124, and the heater 125 heats the second gas diffusion plate 124, so that the second gas diffusion plate 124 is always maintained at a stable temperature, such as 50-60 degrees , so that the second gas diffusion plate 124 will not be deformed due to a large change in temperature, thereby avoiding uneven distribution of the flow rate of the gas flowing through the lower surface of the second gas diffusion plate 24 . In the prior art, because the second gas diffusion plate 124 needs to be maintained at a high temperature state higher than 180 degrees, the second gas diffusion plate 124 will expand greatly from the completion of assembly at room temperature to the high temperature working state of the reactor, which is affected by the external When the reaction chamber 100 is restricted, the second gas diffusion plate 24 will be squeezed and deformed, which will cause the gas flow distribution to change with the temperature change, and a stable and uniform gas flow distribution cannot be achieved. The first gas diffusion plate 122 and the second gas diffusion plate 124 in this creation are only examples, and only one gas diffusion plate can be used to realize the uniform diffusion of gas and the effect of extinguishing plasma, which is also the gas diffusion plate in the pre-cleaning reactor of this creation An embodiment of .

The remote plasma source shown in Figure 1 is located above the chamber, directly supplying plasma to the reaction chamber, and can also be replaced by other plasma sources. For example, if the plasma source is set on the top of the reaction chamber 100, the plasma is ignited by capacitive coupling (CCP) or inductive coupling (ICP) and other excitation devices in the reaction chamber 100, and then the plasma is extinguished through the gas diffusion plate below. DOWN TO WAFER AND WAFER TABLE The silicon oxide on the surface reacts to form a salt. The various plasma sources mentioned above can be used as plasma generating devices in the reaction chamber of the present invention.

Fig. 3 is a base top view and a partial section of the base 110 of the present invention, the top view of the base above shows that the center of the top surface of the base is a heat transfer gas flow hole 1160, and the surrounding heat transfer gas flow hole 1160 includes A plurality of annular support ribs 116a are arranged concentrically from the center to the edge, and a plurality of flow grooves 116b are arranged radially to realize gas communication between each support rib 116a. The heat-conducting gas is diffused into the gaps between the support ribs 116a through the circulation grooves 116b, and the heat transfer between the wafer and the base 110 is realized through the heat-conducting gas. Wherein the support edge 116a located on the inner side of the upper surface of the base 110 may not be annular, but a plurality of small cylindrical support platforms, and a large number of support platforms are distributed on the entire upper surface of the base 110 at intervals to realize support for the wafer. The circulation of heat transfer gas is between each supporting platform. The lower picture in FIG. 3 is a partial cross-sectional view at X in the top view of the susceptor. The partial cross-sectional view shows that the wafer W is placed on the surface of the susceptor, wherein the height of the outermost support rib 116a is slightly higher than that of the inner side. The height of the other supporting ribs or supporting platforms, so that the outermost supporting ribs and the bottom surface of the outer ring of the wafer W are tightly attached to each other to form a seal, preventing the reaction gas in the reaction space above the wafer W from flowing with the heat transfer gas on the back of the wafer W . This ensures that the back of the wafer W maintains a stable thermal conductivity, and prevents the reactive gas from entering the back of the wafer W to form pollutants.

As shown in FIG. 4, the coolant pipes 112 in the base of the present invention are connected to a switchable coolant supply system. The coolant supply system includes a coolant source 200 for outputting low-temperature coolant through a pipeline 201a to a valve group 213, and the valve group 213 includes at least a first valve V1 and a second valve V2. The pipeline 201a is selectively communicated with the first end of the pipeline 201b through the first valve V1, wherein a restrictor valve 204 is connected in series with the pipeline 201b. The pipeline 201a communicates with the pipeline 202a through the second valve V2, and delivers the cooling liquid to the input end of the cooling liquid pipeline 112 in the base 110, and finally passes through the cooling liquid The output end of the cooling liquid pipe 112 communicates with the pipe 202b, and the pipe 202b communicates with the second end of the pipe 201b, and finally the cooling liquid flows back to the cooling liquid source 200 through a pipe 201c.

After adopting the pre-cleaning reactor provided by this creation, after the wafer W to be processed is transported into the base 110 in the reaction chamber, the heat conduction space 116 is maintained at a relatively low pressure (2-3torr), and the upper surface of the wafer W The air pressure in the reaction space is about 3-5 torr to realize the vacuum adsorption of the wafer W.

Enter the salt forming step and perform the following operations: the heater 114 in the base 110 stops inputting heating power, the first valve V1 in the cooling liquid supply system is closed, and the second valve V2 is opened at the same time to allow the cooling liquid to flow into the base 110, and the base 110 was rapidly cooled. The cooling liquid in the cooling liquid pipe 112 flows quickly to take away the heat in the base 110, and the heat on the wafer W is transferred to the base 110 through the heat conduction space 116, finally reducing or maintaining the temperature of the wafer W at a suitable The temperature of the salt-forming step, such as 30-80 degrees.

After the salt forming step is completed, it is necessary to enter the sublimation step so that the temperature of the wafer W reaches a temperature at which the salt generated on the wafer W can be sublimated. In the sublimation step, the input of cooling liquid to the susceptor 110 is stopped, and the heater 114 starts to input heating power to raise the temperature. Most of the heat generated in the heater 114 is used upward to heat the upper wafer W, and a small amount of heat will be downward. Diffuse down through areas of the coolant conduit 112 where there is no coolant or a small amount of coolant remains. The heaters 114 are evenly arranged on the entire susceptor 110, and can be involute or a combination of multiple annular heating wires, or a combination of multiple umbrella-shaped independent heating wires, as long as the upper wafer W can be evenly heated. apply to this work. In the sublimation step, it is necessary to close the second valve V2 so that the coolant no longer flows into the base 110, and at the same time open the first valve V1 to allow the coolant to flow back through the pipeline 201b and the restrictor valve 204, so as to prevent the coolant from being supplied due to a sharp change in the flow rate of the coolant. The device in the system is damaged, and the coolant in the coolant pipe 112 will also have a partial flow out of the base 110 and back to the coolant source 200 . Since there is only a small amount of high thermal conductivity coolant in the coolant pipeline, the thermal resistance formed by the coolant pipeline 112 minimizes the downward transfer of heat.

In order to further drain the residual coolant in the coolant pipeline 112 , the present invention proposes a modified embodiment of the coolant supply system as shown in FIG. 5 . As shown in Figure 5, the coolant supply system also includes an air supply pipeline 203, which is connected to the pipeline 202a through the third valve V3. After entering the sublimation step, after closing the second valve V2, the third valve V3 is turned on to make the high-pressure air Into the pipeline 202 a , the remaining cooling fluid in the cooling fluid pipeline 112 is discharged from the cooling fluid pipeline 112 , and returns to the cooling fluid source 200 . When entering the salt forming step, the first valve V1 and the third valve V3 are closed, and the second valve V2 is turned on, so that the cooling liquid flows into the base 110 again.

The coolant in this creation only needs to be cooled, and does not need to be kept in the high-temperature base at a high temperature, so you can choose a coolant with a lower boiling point such as water, of course, you can also choose a coolant with a higher boiling point, as long as it can quickly Refrigeration just can realize the purpose of this creation. In order to improve the temperature uniformity between the inlet and outlet of the cooling liquid in the base, microcapsules of phase change materials can be added to the cooling liquid. Due to the presence of uncapsules in the cooling liquid, the cooling liquid will not heat up after absorbing heat in the base , only the phase change of the microcapsules will occur, so the temperature of the coolant can be kept stable when it flows through the inlet and outlet of the coolant in the base, and will not gradually heat up due to heat absorption, which will lead to different heat absorption in different parts. The microcapsules are filled with materials with a lower melting point such as paraffin.

In the conventional technology, since the base needs to be kept at a low temperature all the time, and after the sublimation step is completed, the high-temperature wafer needs to be cooled quickly when it is lowered back to the upper surface of the base, so the base needs a very high heat capacity, so that the base can absorb The heat brought on the wafer can still maintain the low temperature state, so the coolant in the susceptor needs to flow continuously. The susceptor in this creation is connected to a switchable coolant supply system, which is passed through when the susceptor needs to be cooled in the salt-forming step, and quickly in the sublimation step. When the temperature rises, the base is heated at the same time, and the cooling liquid does not flow into the base through the switching of the valve group, but only flows back to the cooling liquid source through the flow-limiting bypass channel. The valve group in this creation can also be a three-way valve or a combination or integration of other multiple valve components, as long as the coolant in this creation can be selectively circulated through different pipelines, it can be applied to this creation.

Although the invention is disclosed as above, the invention is not limited thereto. Anyone with common knowledge in the technical field of this creation can make various changes and modifications without departing from the spirit and scope of this creation. Therefore, the protection scope of this creation should be based on the scope limited by the scope of the patent application.

110: Base

112: Coolant pipe

200: Coolant source

201a, 201b, 201c, 202a, 202b: pipeline

204: flow limiting valve

213: valve group

V1: first valve

V2: second valve

Claims (10)

A pre-cleaning reactor, comprising: a reaction chamber, the inner bottom of the reaction chamber includes a base for carrying wafers to be processed, the base includes a cooling liquid channel, and a heater located above the cooling liquid channel and a heat conduction space above the heater; the chamber top of the reaction chamber includes a plasma generating device, and a gas diffusion plate located below the plasma generating device, the plasma generating device ignites the reaction gas and forms plasma, The reaction gas is extinguished after flowing through the gas diffusion plate, and reaches the wafer to be processed downward; a cooling liquid supply system is also included for supplying cooling liquid to the cooling liquid channel in the susceptor, wherein the cooling liquid The supply system includes a cooling liquid source, a plurality of circulation pipes and at least one valve group, and the valve group selectively makes the cooling liquid flow into the base or flow back to the cooling liquid source through at least one of the circulation pipes. The pre-cleaning reactor as claimed in claim 1, wherein a second heater is arranged on the outer periphery of the gas diffusion plate for heating the gas diffusion plate. The pre-cleaning reactor as claimed in item 1, wherein, the base includes a support seat below, and the support seat is provided with a channel for providing heat transfer gas, a channel for delivering cooling liquid, and a channel for delivering heating power of wires. The pre-cleaning reactor as claimed in claim 1, wherein the heat conduction space includes a plurality of support ribs, and a plurality of heat conduction gas passages passing through the plurality of support ribs. The pre-cleaning reactor as claimed in item 4, wherein the plurality of supporting ribs include a circular first supporting rib located outside the upper surface of the base, and the height of the first supporting rib is higher than the Other supporting ribs surrounded by the first supporting rib. The pre-cleaning reactor as claimed in claim 1, wherein the cooling liquid supply system includes a first flow pipe connected to the base and a second flow pipe forming a bypass, the valve group is located at the first flow pipe between the pipe and the second flow pipe. The pre-cleaning reactor as claimed in item 6, wherein a restrictor valve is arranged on the second flow pipe. The pre-cleaning reactor as claimed in item 6, wherein the valve group includes a first valve connected between the first flow pipe and the cooling liquid source, and also includes a second valve connected between the cooling liquid source and the between the second flow pipes. The pre-cleaning reactor as claimed in item 6, wherein the valve group is a three-way valve. The pre-cleaning reactor as claimed in item 6, wherein the valve group further includes a drain valve, and the drain valve is connected between an external gas source and the first flow pipe.

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