Method for etching and cleaning quartz reaction furnace
By adjusting the pressure and temperature inside the quartz reactor and using a fluorine-containing gas plasma etching and cleaning method, the problems of uneven etching and shortened quartz tube lifespan were solved, achieving efficient and uniform polycrystalline silicon layer cleaning and a long quartz tube lifespan.
Patent Information
- Application Number
- CN202511072288.8
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-07-31
- Publication Date
- 2025-11-07
AI Technical Summary
In existing chemical vapor deposition equipment, the etching and cleaning of the reaction chamber has problems such as uneven etching and shortened service life of the quartz tube. Especially when using fluorine ion etching, the etching degree varies in different parts of the quartz tube, leading to stress concentration and the risk of breakage.
By adjusting the pressure and temperature inside the quartz reactor and employing a fluorine-containing gas plasma etching and cleaning method, the cleaning rate of the polycrystalline silicon layer can be selectively increased without accelerating the etching of the quartz tube, thus controlling the uniformity of etching and extending the service life of the quartz reactor.
This method achieves efficient and uniform cleaning of polycrystalline silicon layers, reduces excessive etching of quartz tubes, extends the service life of quartz reactors, and lowers maintenance costs and safety risks.
Smart Images
Figure CN120901034A_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The application belongs to the technical field of chemical vapor deposition equipment, and relates to a quartz reaction furnace etching and cleaning method. BACKGROUND
[0002] In the semiconductor and photovoltaic industries, chemical vapor deposition equipment is a commonly used film coating equipment. Taking a low pressure chemical vapor deposition (LPCVD) equipment as an example, it is used to prepare thin films such as amorphous silicon films and silicon oxide films through a low pressure chemical vapor deposition process. However, during the preparation of the thin films, a polysilicon film layer is deposited on the inner wall of the reaction cavity, and as the number of processes increases, the thickness of the film layer increases continuously, and even slagging may occur. Moreover, due to the difference between the deposited film layer and the material of the reaction cavity, cracks may occur in the quartz cavity, thereby seriously affecting the stability of the equipment and increasing the use and maintenance costs of the equipment.
[0003] Based on the problems of the low pressure chemical vapor deposition equipment during use, two sets of quartz tubes and quartz boats are usually used alternately in actual production to shorten the maintenance time. However, the disassembled quartz tube needs to be cleaned with hydrofluoric acid or nitric acid, and then a large amount of water needs to be used for rinsing, followed by drying. The process is relatively complex. Moreover, the quartz tube is operated at high temperature for a long time, and due to the difference in thermal stress between the deposited film and the quartz, the quartz tube is prone to breakage during cooling and cleaning, which poses a safety risk. In addition to the above-mentioned chemical wet cleaning method, a plasma cleaning method is also used for surface treatment or etching to clean the quartz cavity by using the reaction between the plasma and the polysilicon layer.
[0004] CN 219616295U discloses an LPCVD quartz tube cleaning device, which includes a reaction cavity and furnace mouth flanges and furnace tail flanges arranged at both ends of the reaction cavity. The furnace tail flange is provided with a gas extraction port, an electricity introduction port and a gas inlet port. The electricity introduction port is used to install an electricity introduction assembly, which is connected with a discharge device and a radio frequency assembly in the reaction cavity. The gas inlet port is used to install a gas inlet pipe for conveying fluorine compound gas into the reaction cavity. Under the excitation of the discharge device, the fluorine compound gas is decomposed into fluorine ions, which react with the amorphous silicon layer on the inner wall of the reaction cavity to remove the amorphous silicon layer. The gas extraction port is connected with a vacuum pump to extract waste gas from the reaction cavity. However, the ionized fluorine ions also have an etching effect on the quartz tube during use. The amorphous silicon layer is difficult to be completely removed by relying on the free diffusion of the fluorine ions, and the concentration of the fluorine ions at different positions is different due to the consumption during the diffusion process, so that the etching degree of the quartz tube at different positions is different, thereby causing uneven wall thickness and stress concentration problems, and posing a risk of quartz tube breakage.
[0005] CN 118904829A discloses a remote plasma cleaning equipment and a cleaning method. The cleaning equipment includes a cleaning chamber, a chamber door, a first remote plasma source, a second remote plasma source, and a vacuum unit. The first and second remote plasma sources are respectively connected with the first end and the second end of the cleaning chamber. The first end and the second end of the cleaning chamber are respectively provided with a first vacuum port and a second vacuum port, and the first vacuum port and the second vacuum port are connected with the vacuum unit. The equipment uses two remote plasma sources and two vacuum ports to realize multiple cycles of forward and reverse alternating air intake and air exhaust to improve the uniformity of cleaning. However, this will cause complex equipment structure and operation process, which is not easy to control. Moreover, the etching rate of the plating layer film on the quartz tube and the quartz tube body is not controlled, which cannot weaken the etching of the quartz tube and cannot guarantee the service life of the quartz tube.
[0006] In summary, for the etching cleaning of the reaction chamber in the chemical vapor deposition equipment, it is necessary to selectively increase the reaction rate of the etching ions and the polysilicon layer, without accelerating the etching of the chamber itself, and to ensure the uniformity of etching, so as to avoid the influence of the non-uniform wall thickness after etching on the service life. SUMMARY
[0007] In view of the problems existing in the prior art, the purpose of the present application is to provide a method for etching and cleaning a quartz reaction furnace. The method uses a plasma etching and cleaning process for the quartz reaction furnace, and selectively adjusts the pressure, temperature and other parameters during etching, so as to selectively increase the cleaning rate of the polysilicon layer without accelerating the etching of the quartz tube, improve the overall cleaning efficiency, avoid the non-uniformity of etching, reduce the over-etching of the local area, and improve the service life of the quartz reaction furnace.
[0008] To achieve this purpose, the present application adopts the following technical solutions:
[0009] The present application provides a method for etching and cleaning a quartz reaction furnace, which comprises the following steps:
[0010] The cleaning gas is introduced into the reaction furnace until the pressure in the furnace tube reaches a selective pressure for the reaction of the cleaning gas and the polysilicon, and the selective pressure is maintained for 60-300 minutes to clean the polysilicon on the inner wall of the furnace tube.
[0011] In an embodiment, the selective pressure is 100-400 mTorr.
[0012] In an embodiment, the selective pressure is 200-300 mTorr.
[0013] In an embodiment, a cleaning gas is introduced into the furnace tube from the furnace opening of the furnace tube, and before the cleaning gas is introduced into the furnace tube, the furnace tail region of the furnace tube is heated to a temperature of 160-170℃.
[0014] In an embodiment, the furnace opening region and the furnace region of the furnace tube are heated to a temperature of 20-30℃.
[0015] In an embodiment, before the step of introducing the cleaning gas into the reaction furnace tube, the furnace tube is subjected to a vacuumizing treatment.
[0016] In an embodiment, the quartz reaction furnace is provided with a remote plasma source, and the cleaning gas comprises a fluorine-containing gas, and the fluorine-containing gas ionized by the remote plasma source is introduced into the furnace tube.
[0017] In an embodiment, the cleaning gas further comprises a carrier gas.
[0018] In an embodiment, when the cleaning gas is introduced into the furnace tube, the carrier gas is introduced first, then the fluorine-containing gas is introduced, and then the carrier gas is introduced again.
[0019] In an embodiment, the flow rate of the carrier gas introduced first is 800-1200sccm;
[0020] and / or, the flow rate of the fluorine-containing gas is gradually increased from 100sccm to 2500-3500sccm;
[0021] and / or, the flow rate of the carrier gas introduced again is 400-800sccm;
[0022] and / or, after the gas is introduced into the furnace tube, the pressure in the furnace tube is maintained at the selected pressure by adjusting the valve.
[0023] Compared with the prior art, the present application has the following beneficial effects:
[0024] (1) The method of the present application sets the pressure in the quartz reaction furnace, so that the pressure in the furnace tube is adjusted to the conditions of etching cleaning by the cleaning gas under the selective pressure of the polysilicon, so as to selectively improve the cleaning rate of the polysilicon layer, but will not accelerate the etching of the quartz tube by the cleaning gas, which can improve the overall cleaning efficiency, reduce the cleaning time, and avoid excessive etching of the quartz tube.
[0025] (2) The method of the present application is simple to operate, has high cleaning efficiency, excellent cleaning effect, low operation cost, and wide application range. BRIEF DESCRIPTION OF DRAWINGS
[0026] Figure 1 is a graph of the etching rate test results of the silicon wafer provided in embodiments 1-8 of the present application.
[0027] Figure 2 These are the silicon wafer etching rate test results provided in Embodiment 1 and Comparative Examples 1-3 of the present invention.
[0028] Figure 3 These are the test results of the etching rate of silicon wafers and quartz wafers provided in Embodiments 1-8 of the present invention.
[0029] Figure 4 This is a schematic diagram of the etching and cleaning process in a quartz reactor according to an embodiment of the present invention. Detailed Implementation
[0030] To better illustrate the present invention and facilitate understanding of its technical solutions, the present invention will be further described in detail below. However, the following embodiments are merely simplified examples of the present invention and do not represent or limit the scope of protection of the present invention. The scope of protection of the present invention is determined by the claims.
[0031] The following describes the etching and cleaning method for a quartz reactor according to an embodiment of this application, with reference to the accompanying drawings.
[0032] Figure 2 This is a schematic diagram of quartz reactor etching and cleaning provided in an embodiment of this application.
[0033] Reference Figure 2 In this embodiment, the quartz reactor is a reactor made of quartz material, generally employing a cylindrical furnace tube structure for thin film preparation. During the thin film preparation process, a polycrystalline silicon film layer is deposited on the inner wall of the furnace tube. When the polycrystalline silicon film reaches a certain thickness, it can cause cracks in the quartz reactor, leading to damage to the quartz furnace tube and affecting its lifespan. Therefore, this solution employs etching cleaning to clean the quartz furnace tube, thereby improving the quartz lifespan of the quartz reactor. When cleaning the quartz reactor, the oar is first removed, and the furnace door is closed.
[0034] In one embodiment, the quartz reactor etching and cleaning method includes introducing cleaning gas into the reactor until the pressure inside the furnace tube reaches the selective pressure for the reaction between the cleaning gas and polysilicon, maintaining this selective pressure for 60 to 300 minutes, and cleaning the polysilicon on the inner wall of the furnace tube.
[0035] Since both polysilicon and quartz contain silicon, the cleaning gas used to clean polysilicon can also corrode the quartz reactor, leading to a reduction in the thickness of the quartz furnace tubes and thus shortening their lifespan. Therefore, this solution adjusts the pressure and temperature within the furnace tubes to maximize the selectivity of corrosion between the polysilicon and quartz on the furnace wall (the greater the difference in corrosion rates, the better). This ensures that the cleaning gas corrodes the polysilicon far more than the quartz, thereby extending the lifespan of the quartz tubes and reducing replacement frequency.
[0036] The time of maintaining the selective pressure is determined according to the thickness of the polysilicon film and the length of the furnace tube. If the polysilicon film is thicker or the furnace tube is longer, the time of maintaining the selective pressure is longer. If the polysilicon film is thinner or the furnace tube is shorter, the time of maintaining the selective pressure is shorter. The time of maintaining the selective pressure can be 60 min, 70 min, 80 min, 90 min, 100 min, 110 min, 120 min, 130 min, 140 min, 150 min, 160 min, 170 min, 180 min, 190 min, 200 min, 210 min, 220 min, 230 min, 240 min, 250 min, 260 min, 270 min, 280 min, 290 min, or 300 min, but is not limited to the listed values. Other values not listed in the range are also applicable.
[0037] Further, the selective pressure is 100-400 mTorr. At the selective pressure, the etching rate of the cleaning gas to the quartz tube is one-fifth of the etching rate of the cleaning gas to the polysilicon film. In general, when the thickness of the polysilicon deposited on the inner wall of the chamber is 5-40 μm, cleaning is needed. At the selective pressure, the etching thickness of the quartz tube is 1-8 μm when the quartz tube is cleaned. Thus, the etching of the quartz tube is greatly reduced, and the quartz tube can maintain its structural strength after multiple cleanings, thereby prolonging the service life. In practice, the selective pressure can be 100 mTorr, 150 mTorr, 200 mTorr, 230 mTorr, 260 mTorr, 265 mTorr, 270 mTorr, 275 mTorr, 280 mTorr, 285 mTorr, 290 mTorr, 300 mTorr, 320 mTorr, 360 mTorr, 380 mTorr, or 400 mTorr, but is not limited to the listed values. Other values not listed in the range are also applicable.
[0038] Further, the selective pressure is 200-300 mTorr. At the selective pressure, the etching rate of the cleaning gas to the quartz tube and the polysilicon film can be more accurately controlled. The selective pressure can be 200 mTorr, 230 mTorr, 260 mTorr, 265 mTorr, 270 mTorr, 275 mTorr, 280 mTorr, 285 mTorr, 290 mTorr, or 300 mTorr, but is not limited to the listed values. Other values not listed in the range are also applicable.
[0039] In an embodiment, the cleaning gas is introduced into the furnace tube from the furnace mouth of the furnace tube, before the cleaning gas is introduced into the furnace tube, the furnace tail area of the furnace tube is heated, and the temperature of the furnace tail area is 160-170°C. The length of the furnace tube is generally 3 meters. Since the cleaning gas is introduced from the furnace mouth, the cleaning gas first corrodes the polysilicon film layer at the furnace mouth, and then corrodes the furnace tail. Due to the length of the furnace tube and the first corrosion at the furnace mouth, the concentration of the cleaning gas at the furnace tail is lower than that at the furnace mouth. When the furnace tail is corroded, the furnace mouth has been basically completely corroded, and then the furnace tube is corroded. In order to reduce the corrosion of the furnace tube at the furnace mouth, heating the furnace tail can accelerate the corrosion rate at the furnace tail, that is, the corrosion rate at the furnace tail is supplemented by increasing the temperature, so that the corrosion time of the furnace tail, the furnace mouth and the furnace is basically the same, so as to shorten the corrosion difference and avoid over-etching, thereby prolonging the service life of the furnace tube.
[0040] The temperature of the furnace tube, the furnace mouth area and the furnace area is 20-30°C. The furnace mouth and the furnace are kept at room temperature and are not heated, so as to maintain the normal corrosion rate. In combination with the heating of the furnace tail described above, the corrosion rates of different parts of the furnace tube are as consistent as possible, thereby reducing the over-etching of the furnace tube at the furnace mouth.
[0041] In an embodiment, before the step of introducing the cleaning gas into the reaction furnace tube, the furnace tube is subjected to vacuumizing treatment. Before the cleaning of the furnace tube, the furnace tube is subjected to vacuumizing treatment to remove the air in the furnace tube, so as to avoid affecting the cleaning of the furnace tube by the cleaning gas. When the furnace tube is subjected to vacuumizing, the furnace tube can be vacuumized to the bottom pressure of the quartz reaction furnace, or the vacuum degree in the furnace tube can be less than 30 mTorr.
[0042] In an embodiment, the quartz reaction furnace is provided with a remote plasma source, and the cleaning gas comprises a fluorine-containing gas. The fluorine-containing gas ionized by the remote plasma source is introduced into the furnace tube. The fluorine-containing gas ionized by the remote plasma source generates fluorine ions, which can react with polysilicon, thereby achieving the cleaning of the furnace tube.
[0043] In an embodiment, the cleaning gas further comprises a carrier gas. The carrier gas is an inert gas, which plays a role in assisting ionization and promotes the dissociation of fluorides to generate fluorine ions. The carrier gas comprises any one or a combination of at least two of argon, helium or neon. Typical but non-limiting examples of the combination include a combination of argon and helium, a combination of argon and neon, a combination of argon, helium and neon, etc.
[0044] In an embodiment, when the cleaning gas is introduced into the furnace tube, the carrier gas is introduced first, then the fluorine-containing gas is introduced, and then the carrier gas is introduced again. The carrier gas is introduced first to generate plasma by starting the glow of the remote plasma source, then the fluorine-containing gas is introduced to generate fluorine ions for cleaning the furnace tube, and finally the carrier gas is introduced again to push the ionized fluorine-containing gas in the furnace tube to the tail of the furnace tube until the reaction is complete and the fluorine ions in the furnace tube are completely discharged.
[0045] Further, the first carrier gas flow is 800-1200sccm; the fluorine-containing gas flow is gradually increased from 100sccm to 2500-3500sccm; and the second carrier gas flow is 400-800sccm.
[0046] The first carrier gas flow is 800-1200sccm, for example, 800sccm, 850sccm, 900sccm, 950sccm, 1000sccm, 1050sccm, 1100sccm, 1150sccm or 1200sccm, but not limited to the listed values, and other values not listed in the range are also applicable. After the fluorine-containing gas is introduced, the carrier gas flow is reduced to 400-600sccm, for example, 400sccm, 450sccm, 500sccm, 550sccm or 600sccm, but not limited to the listed values, and other values not listed in the range are also applicable.
[0047] The fluorine-containing gas flow is gradually increased from 100sccm to 2500-3500sccm, for example, 100sccm, 300sccm, 500sccm, 800sccm, 1000sccm, 1200sccm, 1400sccm, 1600sccm, 1800sccm, 2000sccm, 2200sccm, 2500sccm, 2700sccm, 2800sccm, 3000sccm, 3200sccm, 3400sccm or 3500sccm, but not limited to the listed values, and other values not listed in the range are also applicable.
[0048] In the above scheme, the fluorine-containing gas flow is gradually increased to prevent the plasma from being blown out due to the excessively large flow rate of the directly introduced gas.
[0049] In an embodiment, after the gas is introduced into the furnace tube, the valve is opened to maintain the pressure in the furnace tube at a selected pressure. Since there is a selective pressure between the cleaning gas and the polysilicon, during cleaning, the pressure in the furnace tube is maintained within the selected pressure range, so that the cleaning gas corrodes more polysilicon and reduces the corrosion of the furnace tube.
[0050] The specific embodiment part of the present application provides a method for etching and cleaning a quartz reaction furnace, which comprises the following steps:
[0051] (1) When the polysilicon layer accumulated on the inner wall of the cavity of the quartz reaction furnace reaches a certain thickness, the furnace door is closed to start vacuumizing, and the temperature of the quartz reaction furnace is set;
[0052] (2) After the vacuumizing of step (1) is completed, clean gas is introduced into the remote plasma source, and fluorine ion-containing gas is obtained by dissociation, and the fluorine ion-containing gas enters the quartz reaction furnace cavity;
[0053] (3) The fluorine ion-containing gas obtained in step (2) reacts with the polysilicon layer during the transmission in the cavity, and the pressure in the cavity is controlled to be 100-400 mTorr during the reaction, and the reaction product is promptly extracted;
[0054] (4) The polysilicon layer on the inner wall of the cavity is completely cleaned after the reaction of step (3), and then the clean gas is stopped, the remote plasma source is closed, and the gas is purged to complete the cleaning.
[0055] The following is a typical but non-limiting embodiment of the present application:
[0056] Example 1:
[0057] The present embodiment provides a method for measuring the etching rate of each part of the quartz reaction furnace, which comprises the following steps:
[0058] (1) Put the silicon wafer and the quartz piece with measured mass and thickness into the quartz boat, and put them together into the furnace tail area of the quartz reaction furnace, close the furnace door and start vacuumizing, which includes pre-extraction and main extraction stages, the pressure in the cavity is reduced to 150 mTorr after pre-extraction, and the pressure in the cavity is reduced to 20 mTorr after main extraction, leak detection is performed after the vacuumizing is completed, the leak detection time is 60 s, the leak rate is 12 mTorr / min, the air tightness is qualified, and the temperature of the furnace mouth, furnace and furnace tail of the quartz reaction furnace is set, the temperature of the quartz reaction furnace is controlled by the temperature control system, the temperature of the furnace mouth and furnace area is set to normal temperature 20℃, and the temperature of the furnace tail area is set to 166℃;
[0059] (2) After the vacuumizing of step (1) is completed, clean gas is introduced into the remote plasma source, and fluorine ion-containing gas is obtained by dissociation, and the fluorine ion-containing gas enters the quartz reaction furnace cavity;
[0060] (3) The fluorine ion containing gas obtained in step (2) is reacted with the silicon wafer during the transmission in the cavity. After the fluorine ion containing gas is introduced, nitrogen gas is introduced as a carrier gas to adjust the pressure in the quartz reaction furnace cavity. The flow rate of the nitrogen gas is 1000 seem. The pressure in the cavity is controlled to 270 mTorr by adjusting the opening of the valve during the reaction. The reaction time is 5 min. The reaction product includes silicon tetrafluoride and volatile byproducts, which include silicon trifluoride and silicon difluoride. The reaction product is removed in real time by a vacuum pump;
[0061] (4) After the reaction in step (3) is completed, the introduction of argon gas and nitrogen trifluoride is stopped in sequence. The remote plasma source is turned off. Then, the nitrogen gas flow rate is increased to perform a purge. The flow rate of the nitrogen gas is 30000 seem. The purging time is 180 s. After the purging is completed, the pressure in the cavity is reduced to 30 mTorr. The vacuum is broken after 200 s. The furnace door is opened again. The quartz boat is removed. The mass and thickness of the etched silicon wafer and the quartz wafer are measured. The difference between the mass and thickness before and after the etching is used to obtain the difference curve of the etching rate of the fluorine ion on the quartz (which is approximately the etching rate of the quartz tube wall thickness) and the etching rate of the silicon (which is approximately the etching rate of the polycrystalline silicon layer attached to the tube wall).
[0062] Example 2:
[0063] This example provides a method for measuring the etching rate of each part of a quartz reaction furnace. The method is similar to the method in Example 1, except that the pressure in the cavity is controlled to 100 mTorr in step (3).
[0064] Example 3:
[0065] This example provides a method for measuring the etching rate of each part of a quartz reaction furnace. The method is similar to the method in Example 1, except that the pressure in the cavity is controlled to 200 mTorr in step (3).
[0066] Example 4:
[0067] This example provides a method for measuring the etching rate of each part of a quartz reaction furnace. The method is similar to the method in Example 1, except that the pressure in the cavity is controlled to 220 mTorr in step (3).
[0068] Example 5:
[0069] This example provides a method for measuring the etching rate of each part of a quartz reaction furnace. The method is similar to the method in Example 1, except that the pressure in the cavity is controlled to 300 mTorr in step (3).
[0070] Example 6: This example provides a method for determining the etching rate of each part of the quartz reaction furnace, which refers to the method in Example 1, the difference is that the pressure in the cavity is controlled to be 400 mTorr in step (3).
[0071] Example 7:
[0072] This example provides a method for determining the etching rate of each part of the quartz reaction furnace, which refers to the method in Example 1, the difference is that the silicon wafer and the quartz boat are placed together in the furnace opening area of the quartz reaction furnace in step (1).
[0073] Example 8:
[0074] This example provides a method for determining the etching rate of each part of the quartz reaction furnace, which refers to the method in Example 4, the difference is that the silicon wafer and the quartz boat are placed together in the furnace opening area of the quartz reaction furnace in step (1).
[0075] Comparative Example 1:
[0076] This comparative example provides a method for determining the etching rate of each part of the quartz reaction furnace, which refers to the method in Example 1, the difference is that the pressure in the cavity is controlled to be 450 mTorr in step (2), and the furnace tail temperature is adjusted to 20°C.
[0077] Comparative Example 2:
[0078] This comparative example provides a method for determining the etching rate of each part of the quartz reaction furnace, which refers to the method in Example 1, the difference is that the pressure in the cavity is controlled to be 495 mTorr in step (2), and the furnace tail temperature is adjusted to 100°C.
[0079] According to the mass change of the silicon wafer before and after etching in Examples 1-8 and Comparative Examples 1-2 above, the etching rate of the furnace tail area or the furnace opening area under different pressure conditions in the cavity is calculated, and the etching rate test results are shown in Figure 1 and Figure 2 According to the thickness change of the silicon wafer and the quartz wafer in Examples 1-8 and Comparative Examples 1-2 above, the etching rate of the silicon wafer and the quartz wafer under different pressure conditions in the cavity is calculated, and the etching rate test results are shown in Figure 3
[0080] from Figure 1 and Figure 2 It can be seen that in the pressure range of 100-400 mTorr, the etching rate of fluorine ions to the silicon wafer is higher in Examples 1-6, and the etching rate at the furnace tail is all above 0.46 g / min, especially at 270 mTorr, the etching rate reaches the highest, which is 0.48 g / min; when the pressure in the cavity is higher than 400 mTorr, the etching rate decreases obviously with the increase of pressure, because the gas phase molar number increases after the reaction of nitrogen trifluoride and polysilicon, and the too high pressure in the cavity is not conducive to the forward reaction. In Example 1, the etching rate at 270 mTorr is increased by 10.1% compared with the etching rate at 495 mTorr in Comparative Example 2. It can be seen that in the pressure range of 100-400 mTorr, the etching rate of fluorine ions to the silicon wafer is above 2.5 μm / min, and the etching rate of fluorine ions to the quartz wafer is below 0.5 μm / min, and the etching rate of the quartz wafer is much lower than that of the silicon wafer, so cleaning the quartz tube in the pressure range of 100-400 mTorr can greatly reduce the corrosion of the quartz tube. Figure 3 It can be seen that in the pressure range of 100-400 mTorr, the etching rate of fluorine ions to the silicon wafer is higher in Examples 1-6, and the etching rate at the furnace tail is all above 0.46 g / min, especially at 270 mTorr, the etching rate reaches the highest, which is 0.48 g / min; when the pressure in the cavity is higher than 400 mTorr, the etching rate decreases obviously with the increase of pressure, because the gas phase molar number increases after the reaction of nitrogen trifluoride and polysilicon, and the too high pressure in the cavity is not conducive to the forward reaction. In Example 1, the etching rate at 270 mTorr is increased by 10.1% compared with the etching rate at 495 mTorr in Comparative Example 2. It can be seen that in the pressure range of 100-400 mTorr, the etching rate of fluorine ions to the silicon wafer is above 2.5 μm / min, and the etching rate of fluorine ions to the quartz wafer is below 0.5 μm / min, and the etching rate of the quartz wafer is much lower than that of the silicon wafer, so cleaning the quartz tube in the pressure range of 100-400 mTorr can greatly reduce the corrosion of the quartz tube.
[0081] According to the etching rate at the furnace mouth in Examples 7 and 8, it can be seen that the etching rate at the furnace mouth can keep the same order of magnitude as the etching rate at the furnace tail, the selection of pressure in the application also has the same effect on the etching rate of the furnace mouth, and the change trend of the etching rate at the furnace mouth and the furnace tail is nearly consistent, which indicates that in the pressure range selected in the application, the change of pressure does not have a significant effect on the etching rate due to the long distance between the furnace mouth and the furnace tail.
[0082] Example 9:
[0083] The embodiment provides a method for etching and cleaning a quartz reaction furnace, and the method comprises the following steps:
[0084] (1) After the polysilicon layer on the inner wall of the cavity of the quartz reaction furnace reaches a preset value, the preset thickness of the polysilicon layer is 40 μm, the furnace door is closed to start vacuumizing, vacuumizing comprises pre-vacuumizing and main-vacuumizing stages, the pressure in the cavity is reduced to 150 mTorr after pre-vacuumizing, the pressure in the cavity is reduced to 20 mTorr after main-vacuumizing, leak detection is performed after vacuumizing is completed, the leak detection time is 60 s, the leak rate is 14 mTorr / min, the air tightness is qualified, and the temperature of the furnace mouth, the furnace middle and the furnace tail of the quartz reaction furnace is set, the temperature of the quartz reaction furnace is controlled by a temperature control system, the temperature of the furnace mouth and the furnace middle is set to normal temperature 20 ℃, and the temperature of the furnace tail is set to 165 ℃.
[0085] (2) After the vacuuming in step (1) is completed, clean gas is introduced into the remote plasma source, the clean gas comprising nitrogen trifluoride and argon, the argon being introduced first, then the nitrogen trifluoride, the argon being introduced in two stages, before and after the nitrogen trifluoride is introduced, the flow rate of the argon before the nitrogen trifluoride is introduced being 1000 sccm, the flow rate of the argon after the nitrogen trifluoride is introduced being reduced to 500 sccm, the flow rate of the nitrogen trifluoride being gradually increased to 3000 sccm, the flow rate of the nitrogen trifluoride reaching the set value causing the flow rate of the argon to be reduced, the remote plasma source being preheated for 50 s after being turned on, then being formally operated, the remote plasma source being turned on after the argon is introduced and before the nitrogen trifluoride is introduced, the power of the remote plasma source being 6000 W, the fluorine-containing gas being dissociated to obtain fluorine ion-containing gas, the fluorine ion-containing gas also comprising argon ions, the dissociated gas being introduced into the quartz reaction furnace cavity;
[0086] (3) The fluorine ion-containing gas obtained in step (2) reacts with the polysilicon layer during transmission in the cavity, after the fluorine ion-containing gas is introduced, nitrogen gas is introduced as a carrier gas to adjust the pressure in the quartz reaction furnace cavity, the flow rate of the nitrogen gas being 750 sccm, the pressure in the cavity being controlled to be 270 mTorr by adjusting the opening of the valve during the reaction, the reaction time being 300 min, the reaction product comprising silicon tetrafluoride and volatile byproducts, the volatile byproducts comprising silicon trifluoride and silicon difluoride, the reaction product being removed in real time by the vacuum pump;
[0087] (4) After the polysilicon layer on the inner wall of the cavity is completely cleaned in step (3), the introduction of the argon and the nitrogen trifluoride is stopped in sequence, the remote plasma source is turned off, then the nitrogen gas flow rate is increased for purging, the flow rate of the nitrogen gas being 30000 sccm, the purging time being 180 s, after the purging is completed, the cavity is broken after the pressure in the cavity is reduced to 30 mTorr, the breaking time being 200 s, until the normal pressure is reached, then the furnace door is opened, and the cleaning effect of the inner wall of the cavity is confirmed.
[0088] In this embodiment, the quartz tube in the quartz reaction furnace is cleaned by the above method, the cleaning rate of the polysilicon layer can reach 99%, and the inner wall of the quartz tube is flat after cleaning, without excessive etching areas.
[0089] Example 10:
[0090] The embodiment provides a quartz reaction furnace etching and cleaning method, the method comprising the following steps:
[0091] (1) After the polysilicon layer on the inner wall of the cavity of the quartz reaction furnace reaches the preset value, the preset thickness of the polysilicon layer is 20 μm, the furnace door is closed to start vacuumizing, vacuumizing includes pre-vacuumizing and main vacuumizing stages, after the pre-vacuumizing, the pressure in the cavity is reduced to 100 mTorr, after the main vacuumizing, the pressure in the cavity is reduced to 10 mTorr, after the vacuumizing is completed, leak detection is performed, the time of the leak detection is 90 s, the leak rate is 12 mTorr / min, the air tightness is qualified, and the temperature of the furnace mouth, the furnace and the furnace tail of the quartz reaction furnace is set, the temperature of the quartz reaction furnace is controlled by the temperature control system, the temperature of the furnace mouth and the furnace area is set to normal temperature 25℃, and the temperature of the furnace tail area is set to 160℃;
[0092] (2) After the vacuumizing in step (1) is completed, clean gas is introduced into the remote plasma source, the clean gas includes nitrogen trifluoride and argon, when the clean gas is introduced, argon is introduced first, and then nitrogen trifluoride is introduced, the introduction of argon is divided into two stages, before and after the introduction of nitrogen trifluoride, the flow rate of argon before the introduction of nitrogen trifluoride is 800 sccm, and the flow rate of argon after the introduction of nitrogen trifluoride is reduced to 400 sccm, the flow rate of nitrogen trifluoride is gradually increased to 2500 sccm, and then the flow rate of argon is reduced after the flow rate of nitrogen trifluoride reaches the set value; the remote plasma source is preheated for 40 s after being turned on, and then it starts to operate formally, the remote plasma source is turned on after the introduction of argon and before the introduction of nitrogen trifluoride, the power of the remote plasma source is 4000 W, the fluorine-containing gas is dissociated to obtain fluorine ion-containing gas, the fluorine ion-containing gas also includes argon ions, and the dissociated gas enters the cavity of the quartz reaction furnace;
[0093] (3) The fluorine ion-containing gas obtained in step (2) reacts with the polysilicon layer during transmission in the cavity, after the fluorine ion-containing gas is introduced, nitrogen gas is introduced as a carrier gas to adjust the pressure in the cavity of the quartz reaction furnace, the flow rate of the nitrogen gas is 900 sccm, the pressure in the cavity is controlled to be 300 mTorr by adjusting the opening degree of the valve during the reaction, the reaction time is 150 min, the reaction products include silicon tetrafluoride and volatile by-products, the volatile by-products include silicon trifluoride and silicon difluoride, and the reaction products are pumped out in real time by the vacuum pump;
[0094] (4) After the polysilicon layer on the inner wall of the cavity is completely cleaned in step (3), the introduction of argon and nitrogen trifluoride is stopped in sequence, the remote plasma source is turned off, then the nitrogen gas flow is increased for purging, the flow rate of the nitrogen gas is 25000 sccm, the purging time is 240 s, after the purging is completed, the pressure in the cavity is reduced to 20 mTorr, the vacuum breaking time is 180 s, until the normal pressure is reached, and then the furnace door is opened to confirm the cleaning effect of the inner wall of the cavity.
[0095] In this embodiment, the above method is used to clean the quartz tube in the quartz reaction furnace, and the cleaning rate of the polysilicon layer can reach 98%, and the inner wall of the quartz tube is flat after cleaning without excessive etching area.
[0096] Embodiment 11:
[0097] The embodiment provides a method for etching and cleaning a quartz reaction furnace, and the method comprises the following steps:
[0098] (1) After the polysilicon layer on the inner wall of the cavity of the quartz reaction furnace reaches a preset value, the preset thickness of the polysilicon layer is 5 μm, the furnace door is closed to start vacuumizing, vacuumizing comprises pre-vacuumizing and main-vacuumizing stages, the pressure in the cavity is reduced to 200 mTorr after pre-vacuumizing, the pressure in the cavity is reduced to 30 mTorr after main-vacuumizing, leak detection is performed after vacuumizing is completed, the time for leak detection is 30 s, the leak rate is 10 mTorr / min, the air tightness is qualified, and the temperature of the furnace mouth, the furnace and the furnace tail of the quartz reaction furnace is set, the temperature of the quartz reaction furnace is controlled by a temperature control system, the temperature of the furnace mouth and the furnace area is set to normal temperature 30 DEG C, and the temperature of the furnace tail area is set to 170 DEG C;
[0099] (2) After vacuumizing in step (1) is completed, clean gas is introduced into the remote plasma source, the clean gas comprises carbon tetrafluoride and neon, when the clean gas is introduced, neon is introduced first, and then carbon tetrafluoride is introduced, the introduction of neon is divided into two stages, before and after the introduction of carbon tetrafluoride, the flow rate of neon before the introduction of carbon tetrafluoride is 1200 sccm, and the flow rate of neon is reduced to 600 sccm after the introduction of carbon tetrafluoride, the flow rate of carbon tetrafluoride is gradually increased to 3500 sccm, and the flow rate of neon is reduced after the flow rate of carbon tetrafluoride reaches the set value; the remote plasma source is preheated for 60 s after being turned on, and then formal operation is started, the remote plasma source is turned on after the introduction of neon and before the introduction of carbon tetrafluoride, the power of the remote plasma source is 8000 W, the fluorine-containing gas is dissociated to obtain fluorine ion-containing gas, the fluorine ion-containing gas also comprises neon ions, and the dissociated gas enters the cavity of the quartz reaction furnace;
[0100] (3) The fluorine ion-containing gas obtained in step (2) reacts with the polysilicon layer during transmission in the cavity, after the fluorine ion-containing gas is introduced, nitrogen gas is introduced as a carrier gas to adjust the pressure in the cavity of the quartz reaction furnace, the flow rate of the nitrogen gas is 1000 sccm, the pressure in the cavity is controlled to be 400 mTorr by adjusting the opening degree of the valve during the reaction, the reaction time is 60 min, the reaction product comprises silicon tetrafluoride and volatile by-products, the volatile by-products comprise silicon trifluoride and silicon difluoride, and the reaction product is pumped out in real time by a vacuum pump;
[0101] (4) After the cleaning of the polysilicon layer on the inner wall of the cavity is completed, the neon gas and the carbon tetrafluoride are stopped from being introduced in sequence, the remote plasma source is closed, and then the nitrogen gas flow is increased for purging, the nitrogen gas flow is 40000sccm, the purging time is 120s, after the purging is completed, the pressure in the cavity is reduced to 30mTorr, and then the vacuum is broken, the vacuum breaking time is 240s, until the normal pressure is reached, and then the furnace door is opened to confirm the cleaning effect of the inner wall of the cavity.
[0102] In this embodiment, the quartz tube in the quartz reaction furnace is cleaned by the above method, and the cleaning rate of the polysilicon layer can reach 98%, and the inner wall of the quartz tube is flat after cleaning, and there is no area of excessive etching.
[0103] Comparative Example 3:
[0104] This comparative example provides a method for etching and cleaning a quartz reaction furnace, which refers to the method in Example 7, and the only difference is that in step (1), the temperature of the tail area of the quartz reaction furnace is also set to normal temperature 20℃.
[0105] In this comparative example, the tail area of the quartz reaction furnace is also set to normal temperature, but due to the difference in the concentration of fluorine ions at the furnace mouth, the etching and cleaning rates of the two areas are quite different, and the tail area is not completely cleaned in the same time, and the cleaning rate is only 85% at this time, and if the cleaning time is prolonged, the furnace mouth area will be over-etched, as shown in Figure 4 .
[0106] Comparative Example 4:
[0107] This comparative example provides a method for etching and cleaning a quartz reaction furnace, which refers to the method in Example 7, and the only difference is that in step (2), the pressure in the cavity is controlled to be 470mTorr.
[0108] In this comparative example, the pressure in the quartz tube is too high, which reduces the reaction rate of fluorine ions and polysilicon, and causes the etching rate to decrease, and the polysilicon layer is not completely cleaned in the same time, and the cleaning rate is only 92% at this time.
[0109] Comparative Example 5:
[0110] This comparative example provides a method for etching and cleaning a quartz reaction furnace, which refers to the method in Example 7, and the only difference is that in step (2), the pressure in the cavity is controlled to be 60mTorr.
[0111] In this comparative example, the pressure in the quartz tube is too low, which limits the gas concentration of fluorine ions, resulting in a significant decrease in the etching rate, and also causing the polysilicon layer to be not completely cleaned in the same time, and the cleaning rate is only 91% at this time.
[0112] From the above examples and comparative examples, it can be seen that the method of the present application performs plasma etching cleaning on the quartz reaction furnace, and by controlling and adjusting the etching pressure and other parameters, the cleaning rate of the polysilicon layer is selectively increased, but the etching of the quartz tube is not accelerated, so that the overall cleaning efficiency is improved, the cleaning time is reduced, and the quartz tube is not excessively etched; the method accurately controls the temperature of different regions of the quartz tube, especially increases the temperature at the furnace tail, increases the reaction rate of the furnace tail region, shortens the difference between the reaction rates of the furnace tail region and the furnace mouth region, avoids the problem of uneven wall thickness of the quartz tube, and improves the service life; the method is simple to operate, has high cleaning efficiency, excellent cleaning effect, low operation cost, and wide application range.
[0113] The applicant declares that the detailed devices and methods of the present application are illustrated by the above examples, but the present application is not limited to the above detailed devices and methods, that is, it does not mean that the present application must rely on the above detailed devices and methods to be implemented. It should be understood by those skilled in the art that any improvement of the present application, equivalent replacement of the devices of the present application, addition of auxiliary devices, selection of specific modes, etc. fall within the protection scope and disclosure scope of the present application.
Claims
1. A method for etch cleaning of a quartz reaction furnace, characterized by, The method comprises introducing a cleaning gas into the reaction furnace to reach a selective pressure of the cleaning gas reacting with the polysilicon in the tube, maintaining the selective pressure for 60-300 minutes to clean the polysilicon on the inner wall of the tube.
2. The method of claim 1, wherein, The selective pressure is 100-400 mTorr.
3. The method of claim 2, wherein, The selective pressure is 200-300 mTorr.
4. The method of claim 1, wherein, The cleaning gas is introduced into the tube from the furnace opening of the tube, and before the cleaning gas is introduced into the tube, the end region of the tube is heated to a temperature of 160-170°C.
5. The method of claim 4, wherein, The temperature of the furnace opening region and the middle region of the tube is 20-30°C.
6. The method of claim 4, wherein, The tube is vacuumized before the step of introducing the cleaning gas into the tube.
7. The method according to any one of claims 1 to 6, characterized in that, The quartz reaction furnace is provided with a remote plasma source, and the cleaning gas comprises a fluorine-containing gas, and the fluorine-containing gas ionized by the remote plasma source is introduced into the tube.
8. The method of claim 7, wherein, The cleaning gas further comprises a carrier gas.
9. The method of claim 8, wherein, The carrier gas is introduced into the tube first, then the fluorine-containing gas is introduced, and then the carrier gas is introduced again.
10. The method of claim 9, wherein, The flow rate of the first introduced carrier gas is 800-1200 sccm. The flow rate of the fluorine-containing gas is gradually increased from 100 sccm to 2500-3500 sccm. The flow rate of the second introduced carrier gas is 400-800 sccm. After the gas is introduced into the tube, the pressure in the tube is maintained at the selective pressure by adjusting the valve.