Silicon wafer oxidation device and silicon wafer oxidation method
By using ozone and ultraviolet light to generate free oxygen atoms in the silicon wafer oxidation device, the defect problem caused by high temperature when the silicon wafer is grown in the silicon wafer is solved, and the dense silicon dioxide oxide layer is generated under low temperature conditions is achieved, which improves the performance of photovoltaic cells.
Patent Information
- Application Number
- CN202411791622.0
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-12-06
- Publication Date
- 2025-03-14
AI Technical Summary
In the prior art, the high temperature environment when the silicon wafer is grown in the silicon wafer with thermal oxygen, leads to a variety of defects in the internal crystals of the silicon wafer, affecting the electrical performance of the photovoltaic cells.
A silicon wafer oxidation device is adopted, which includes an oxidation chamber, an ultraviolet light assembly and an oxidation temperature control assembly. By passing ozone and protective gas into the oxidation chamber, and irradiating the free oxygen atoms with ultraviolet light, it reacts with the silicon wafer to form a silicon dioxide oxide layer.
The dense silica oxide layer is rapidly generated at a lower temperature (150℃-200℃), reducing defect generation, improving the generation quality of the oxide layer and alkali resistance, and improving the photoelectric performance of photovoltaic cells.
Smart Images
Figure CN119630104A_ABST
Abstract
Description
Technical Field
[0001] The invention relates to the technical field of silicon wafer processing for photovoltaic cells, and in particular to a silicon wafer oxidation device and a silicon wafer oxidation method. Background Art
[0002] Planar silicon oxidation refers to the chemical reaction between silicon and gas containing oxidizing substances, such as water vapor and oxygen, at a high temperature of more than 700°C, to produce a layer of silicon dioxide film on the surface of the silicon wafer. The method of silicon thermal oxidation process in the prior art is to place the silicon wafer in a reaction tube made of quartz glass, heat the reaction tube to 900°C-1200°C with a resistance wire heating furnace, and then introduce oxygen into the reaction tube. When the oxygen passes through the reaction tube, a chemical reaction occurs on the surface of the silicon wafer to form a silicon dioxide oxide layer.
[0003] However, in the process of growing a silicon dioxide layer on a silicon wafer through a quartz reaction tube thermal oxidation process, it is necessary to wait for the temperature to rise and wait for the temperature to cool down. The process generally takes more than one hour, and the equipment utilization rate is low. More importantly, due to the high temperature of more than 600°C during the growth of the silicon dioxide layer, the silicon wafer is prone to introduce oxygen vacancy defects in the silicon crystal to form oxygen rings in a high temperature environment, causing the reactive silicon wafer to be prepared to form a photovoltaic cell. After that, the electrical performance is affected, such as the concentric circle phenomenon in the electroluminescence test. At the same time, if the surface cleanliness of the silicon wafer is low during high-temperature thermal oxidation, it is also easy to form many other defects inside the silicon wafer, such as oxygen vacancies, interstitial atoms, dislocations, impurity-induced defects, etc., which further affect the electrical performance of the photovoltaic cell.
[0004] It can be seen that the effect of silicon wafer oxidation directly affects the electrical performance of subsequent photovoltaic cells. How to improve the silicon wafer oxidation effect has become a technical problem that needs to be solved urgently. Summary of the invention
[0005] Therefore, the technical problem to be solved by the present invention is to overcome the defect in the prior art that the high temperature environment during the thermal oxidation growth of the silicon dioxide layer on the silicon wafer will cause multiple defects in the crystals inside the silicon wafer, affecting the electrical performance of the subsequently prepared photovoltaic cells, thereby providing a silicon wafer oxidation device and a silicon wafer oxidation method.
[0006] In order to solve the above technical problems, the present invention provides a silicon wafer oxidation device, comprising:
[0007] The oxidation chamber is a closed chamber, the inner cavity of the oxidation chamber is connected to an ozone source and a protective gas source, and an oxidation loading assembly is provided in the oxidation chamber, and the oxidation loading assembly is used to install the parts to be oxidized;
[0008] An ultraviolet light component is installed in the oxidation chamber, and is used to irradiate ultraviolet light to the oxidation loading component;
[0009] An oxidation temperature control component is installed in the oxidation chamber and is arranged corresponding to the oxidation loading component;
[0010] It also includes: a cleaning chamber arranged upstream of the oxidation chamber, and a texturing chamber arranged downstream of the oxidation chamber, and both the cleaning chamber and the texturing chamber are sealed and connected to the oxidation chamber.
[0011] Optionally, a plurality of air inlets are provided in the oxidation chamber, the plurality of air inlets are connected to a mixing pipeline, and the ozone source and the protective gas source are both connected to the mixing pipeline.
[0012] Optionally, the oxidation temperature control component is arranged between the oxidation loading component and the air inlet. The oxidation loading component includes: a conveying part and a loading part. The loading part is installed on the conveying part so that the conveying part drives the loading part to move along the conveying direction of the conveying part. The loading part is used to install the part to be oxidized.
[0013] Optionally, it also includes a vacuum chamber, in which a vacuum loading assembly is installed. The vacuum chamber is arranged upstream of the oxidation chamber. The vacuum chamber is connected to a vacuum pumping component. A vacuum temperature control component is installed in the vacuum chamber. The vacuum temperature control component is arranged between the vacuum port of the vacuum pumping component and the vacuum loading assembly.
[0014] Optionally, it also includes a buffer chamber, in which a buffer loading assembly is installed, the buffer chamber is arranged downstream of the oxidation chamber, the buffer chamber is connected to a buffer gas source, and the buffer chamber is connected to a cooling assembly.
[0015] Optionally, the cooling assembly includes a coolant storage component, a cooling pipeline and a driving component, the inlet end of the cooling pipeline is connected to the coolant storage component, the driving component is installed on the cooling pipeline to drive the coolant body to flow in the cooling pipeline, and the cooling pipeline extends into the buffer chamber and the oxidation chamber.
[0016] The present invention also provides a silicon wafer oxidation method, using the silicon wafer oxidation device of the present invention, the silicon wafer oxidation method comprises:
[0017] The oxidation chamber is evacuated, and a silicon wafer is mounted on an oxidation loading assembly as a part to be oxidized;
[0018] Ozone and protective gas are introduced into the oxidation chamber at the same time, so that an ozone environment under the protective gas background is formed in the oxidation chamber, and the ultraviolet light component irradiates ultraviolet light toward the oxidation loading component;
[0019] The oxidation temperature control component controls the temperature in the oxidation chamber to 150°C-200°C.
[0020] Optionally, the gas pressure in the oxidation chamber is adjusted to 700 mbar-1000 mbar by controlling the amount of protective gas introduced.
[0021] Optionally, the wavelength of the ultraviolet light emitted by the ultraviolet light component is controlled to be 210nm-300nm.
[0022] Optionally, the protective gas is nitrogen, helium or other stable gases that do not react with silicon and ozone under ultraviolet light, and the molecular mass of the protective gas molecules is smaller than the molecular mass of the ozone molecules.
[0023] The technical solution of the present invention has the following advantages:
[0024] 1. The silicon wafer oxidation device provided by the present invention is used for cleaning, oxidizing and texturing the surface of the workpiece to be oxidized, so as to form an oxide layer texture surface on the surface of the workpiece to be oxidized. Since the oxidation chamber is a closed chamber, and the cleaning chamber and the texturing chamber are both sealed and connected to the oxidation chamber, the cleaning chamber, the oxidation chamber and the texturing chamber are closed and continuous, which can effectively avoid the oxidation of the silicon wafer in the oxidation chamber, and ensure the density and generation position of the silicon dioxide oxide layer. Taking the oxidation of one side of the silicon wafer to form a silicon dioxide oxide layer as an example, the oxidation chamber is first evacuated, and the clean silicon wafer is installed on the oxidation loading assembly as the oxidized part. Then, ozone and protective gas are introduced into the oxidation chamber at the same time to form an ozone environment under the protective gas background in the oxidation chamber. The ultraviolet light component irradiates ultraviolet light on the oxidation loading assembly, and the oxidation temperature control component controls the temperature to 150℃-200℃, so that ozone absorbs energy and decomposes into oxygen and free oxygen atoms. Free oxygen atoms have extremely strong oxidizing properties, and silicon has strong reducing properties. Under ultraviolet light irradiation, the silicon wafer installed on the oxidation loading assembly can quickly react with free oxygen atoms to form a silicon dioxide oxide layer. The silicon wafer oxidation device can complete the formation of the silicon dioxide oxide layer on the surface of the silicon wafer at a temperature not exceeding 200℃. Due to the small size of free oxygen atoms, they can smoothly move between the gaps of silicon dioxide oxide crystals, while the impurities remaining on the surface of the silicon wafer do not have enough energy to pass through the silicon dioxide oxide layer at the current temperature, which can greatly reduce the generation of defects in the oxidation process of the silicon wafer, improve the quality of the silicon dioxide oxide layer, effectively enhance the alkali resistance of the silicon dioxide oxide layer as a protective layer in the subsequent texturing step, improve the quality of the velvet surface obtained in the texturing step, and then improve the photoelectric performance of the prepared photovoltaic cell. Moreover, due to the small size, the movement speed of free oxygen atoms in the silicon dioxide oxide layer is much greater than that of oxygen molecules, so that the generated silicon dioxide oxide layer can be quickly thickened, and a silicon dioxide oxide layer of a specific thickness can be generated on the surface of the silicon wafer in a shorter time, shortening the time of the oxidation step in the silicon wafer processing process, and improving the silicon wafer processing efficiency.
[0025] 2. The silicon wafer oxidation device provided by the present invention connects both the ozone source and the protective gas source to the mixing pipeline, so that the ozone and the protective gas are pre-mixed and then introduced into the oxidation chamber, and the ratio of ozone to protective gas in the mixed gas of ozone and protective gas in the chamber is controlled to be 3:2-5:3, and the flow rate of the mixed gas is controlled to be maintained at 2000sccm-3000sccm. Since the molecular weight of the protective gas molecule is smaller than the molecular weight of the ozone molecule, and the protective gas can exist stably under ultraviolet light irradiation, by using the protective gas as the background gas of ozone, the ozone can be quickly driven to evenly fill the entire oxidation chamber, so that the ozone near the side of the oxidized piece irradiated by ultraviolet light is evenly distributed, ensuring the uniformity of the thickness of the generated silicon dioxide oxide layer. Moreover, the protective gas can also be used to adjust the gas pressure in the oxidation chamber so that ozone can react at an appropriate pressure of 700mbar-1000mbar. When the gas pressure exceeds 1000mbar, the silicon wafer is easily crushed due to its thin thickness and high brittleness. After the subsequent oxidation is completed, the ambient pressure of the silicon wafer in the silicon wafer oxidation device needs to be slowly increased to normal pressure and then taken out of the device. When the gas pressure is lower than 700mbar, the removal time of the silicon wafer after oxidation will be greatly prolonged, affecting the oxidation efficiency.
[0026] 3. The silicon wafer oxidation device provided by the present invention sets the oxidation temperature control component between the air inlet and the oxidation loading component, so that the gas entering the oxidation chamber from the air inlet can be heated up in time under the action of the oxidation temperature control component and then expand into the oxidation chamber, so that the temperature of the oxidation chamber can quickly reach the set temperature of the oxidation temperature control component. At the same time, when setting the oxidation temperature control component, the oxidation temperature control component should be set as close to the oxidation loading component as possible, so that the heat generated by the oxidation temperature control component can be absorbed by the silicon wafer on the oxidation loading component as much as possible to improve the oxidation efficiency.
[0027] 4. The silicon wafer oxidation device provided by the present invention cooperates with the loading part and the conveying part, so that when the part to be oxidized is installed on the loading part, it can automatically move forward under the drive of the conveying part, thereby realizing the automatic loading and unloading process of the silicon wafer oxidation device, simplifying the operating steps of the silicon wafer oxidation device and improving the oxidation efficiency.
[0028] 5. In the silicon wafer oxidation device provided by the present invention, the buffer chamber is used to cool the workpiece to be oxidized after the oxidation is completed and to serve as a pressure buffer for the workpiece to be oxidized from the rough vacuum environment of the oxidation chamber to the atmospheric environment. By arranging a cooling component in the buffer chamber, in the oxidation process, it takes 4-5 minutes for the silicon wafer to naturally cool to room temperature after oxidation. By cooling in the buffer chamber, the cooling time can be shortened to less than 2 minutes, which can speed up the cooling efficiency of the workpiece to be oxidized after the oxidation is completed and shorten the processing time of the workpiece to be oxidized.
[0029] 6. In the silicon wafer oxidation device provided by the present invention, a cooling pipeline extends into the oxidation chamber to cool down and protect the electrical components in the oxidation chamber, thereby preventing the main functional components in the oxidation chamber from being damaged by overheating.
[0030] 7. The silicon wafer oxidation device provided by the present invention generates a silicon dioxide layer through ultraviolet light-assisted ozone, which is denser than the silicon dioxide layer generated by traditional thermal oxidation technology. Under the conditions of 200°C temperature and 150W ultraviolet light, a 3nm-4nm dense silicon dioxide layer can be grown in 4min-6min, which can greatly shorten the process time of growing a silicon dioxide layer of fixed thickness, meeting the large-scale mass production requirements of the photovoltaic industry. BRIEF DESCRIPTION OF THE DRAWINGS
[0031] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.
[0032] Figure 1 This is a schematic structural diagram of a silicon wafer oxidation device provided in a first embodiment of the present invention.
[0033] Figure 2 This is a schematic diagram of the detailed structure of a silicon wafer oxidation device provided in the first embodiment of the present invention.
[0034] Explanation of the reference numerals: 1. Loading chamber; 2. Vacuum chamber; 3. Oxidation chamber; 4. Buffer chamber; 5. Unloading chamber; 6. Ozone source; 7. Protective gas source; 8. Buffer gas source; 9. Mixing pipeline; 10. Air inlet; 11. Vacuum pump; 12. Air pump outlet; 13. Coolant storage component; 14. Cooling pipeline; 15. Conveying roller; 16. Loading plate; 17. Oxidation temperature control component; 18. Vacuum temperature control component; 19. Sealed isolation door; 20. Electrical control component; 21. Ultraviolet light component. DETAILED DESCRIPTION
[0035] The technical solution of the present invention will be described clearly and completely below in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.
[0036] In the description of the present invention, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc., indicating the orientation or positional relationship, are based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first", "second", and "third" are used for descriptive purposes only, and cannot be understood as indicating or implying relative importance.
[0037] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.
[0038] In addition, the technical features involved in the different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.
[0039] Example 1
[0040] Figure 1 The figure shows a silicon wafer oxidation device provided in this embodiment, which includes an oxidation chamber 3 and an ultraviolet light component and an oxidation temperature control component 17 installed in the oxidation chamber 3.
[0041] A cleaning chamber is provided upstream of the oxidation chamber, and a texturing chamber is provided downstream of the oxidation chamber, and both the cleaning chamber and the texturing chamber are sealed and connected to the oxidation chamber. Since the oxidation chamber is a closed chamber, and both the cleaning chamber and the texturing chamber are sealed and connected to the oxidation chamber, the cleaning chamber, the oxidation chamber and the texturing chamber are sealed and continuous, which can effectively prevent the oxidation of the silicon wafer in the oxidation chamber, and ensure the density and generation position of the silicon dioxide oxide layer.
[0042] The inner cavity of the oxidation chamber 3 is connected to an ozone source 6 and a nitrogen source as a protective gas source 7. An oxidation loading assembly is provided in the oxidation chamber 3, and a silicon wafer as a part to be oxidized is mounted on the oxidation loading assembly. An ultraviolet light assembly 21 is installed in the oxidation chamber 3, and the ultraviolet light assembly 21 is suitable for irradiating ultraviolet light toward the oxidation loading assembly. The oxidation loading assembly is arranged corresponding to the oxidation temperature control assembly 17, and the oxidation temperature control assembly 17 is used to control the oxidation reaction temperature of the silicon wafer on the oxidation loading assembly.
[0043] The silicon wafer oxidation device is used to oxidize the surface of the part to be oxidized to form an oxide layer on the surface of the part to be oxidized. Taking the oxidation treatment of silicon wafers as an example, first, the oxidation chamber 3 is vacuumed, and the clean silicon wafer after cleaning is installed on the oxidation loading component as the part to be oxidized, and then ozone and nitrogen are introduced into the oxidation chamber 3 at the same time, so that an ozone environment under a nitrogen background is formed in the oxidation chamber 3, and the ultraviolet light component 21 irradiates ultraviolet light toward the oxidation loading component, and at the same time, the oxidation temperature control component 17 controls the temperature to 150℃-200℃, so that ozone absorbs energy and decomposes into oxygen and free oxygen atoms. Free oxygen atoms have extremely strong oxidizing properties, and silicon element has strong reducing properties. Under ultraviolet light irradiation, the silicon wafer installed on the oxidation loading component can quickly react with free oxygen atoms to form a silicon dioxide oxide layer. The silicon wafer oxidation device can complete the formation of a silicon dioxide oxide layer on the surface of the silicon wafer at a temperature not greater than 200℃. Due to the small size of free oxygen atoms, they can smoothly move between the gaps of silicon dioxide oxide crystals, while the impurities remaining on the surface of the silicon wafer do not have enough energy to pass through the silicon dioxide oxide layer at the current temperature, which can greatly reduce the generation of defects in the oxidation process of the silicon wafer, improve the quality of the silicon dioxide oxide layer, effectively enhance the alkali resistance of the silicon dioxide oxide layer as a protective layer in the subsequent texturing step, improve the quality of the velvet surface obtained in the texturing step, and then improve the photoelectric performance of the prepared photovoltaic cell. Moreover, due to the small size, the movement speed of free oxygen atoms in the silicon dioxide oxide layer is much greater than that of oxygen molecules, so that the generated silicon dioxide oxide layer can be quickly thickened, and a silicon dioxide oxide layer of a specific thickness can be generated on the surface of the silicon wafer in a shorter time, shortening the time of the oxidation step in the silicon wafer processing process, and improving the silicon wafer processing efficiency.
[0044] Refer to the following Figure 2 The structure and working process of the silicon wafer oxidation device are introduced in detail, and an example of using the silicon wafer oxidation device to oxidize a single side surface of a silicon wafer to form a silicon dioxide oxide layer is used for explanation.
[0045] The inner cavity of the oxidation chamber 3 is connected with an ozone source 6 and a nitrogen source as a protective gas source 7. An oxidation loading assembly is provided in the oxidation chamber 3, and the oxidation loading assembly is suitable for installing silicon wafers to be oxidized. Specifically, multiple air inlets 10 are arranged at intervals in the oxidation chamber 3, and the multiple air inlets 10 are connected in parallel through a mixing pipeline 9. The ozone source 6 and the protective gas source 7 are both connected to the mixing pipeline 9. The oxidation loading assembly in this embodiment includes a conveying roller 15 as a conveying member and a loading plate 16 movably arranged on the conveying roller 15 as a loading member. The conveying roller 15 drives the loading plate 16 to move along the conveying direction of the conveying roller 15. A plurality of slot-shaped stations for installing silicon wafers are provided on the front of the loading plate 16. The size of the slot-shaped stations matches the size of the silicon wafers, and the silicon wafers are placed in the slot-shaped stations. The loading plate 16 is made of SUS304 stainless steel and is used to carry silicon wafers that need to be oxidized on one side to prevent the occurrence of plating during the oxidation process. The silicon wafer bearing part adopts an embedded groove station with an embedded depth of 2mm-3mm. The embedded shape is consistent with the specifications of the specific oxidized silicon wafer, and the size is slightly larger by 0.5mm-1mm, ensuring that the groove station has good contact and fit with the silicon wafer of specific specifications. The sandblasting roughness of the outer surface of the loading plate 16 in this embodiment is 6.3, and the sandblasting roughness of the silicon wafer mating surface in the groove station is 0.8. In some other embodiments, the conveyor can also be a conveyor belt. The oxidation loading assembly can also be a loading plate 16 placed separately in the oxidation chamber 3, or a loading plate 16 driven by a mechanical arm in the oxidation chamber 3.
[0046] In some other embodiments, the shielding gas source may also be a helium gas source or other stable gases that do not react with silicon or ozone under ultraviolet light, and the molecular mass of shielding gas molecules is smaller than that of ozone molecules.
[0047] The ultraviolet light assembly 21 is installed in the oxidation chamber 3, and the ultraviolet light assembly 21 is suitable for irradiating ultraviolet light toward the oxidation loading assembly. In this embodiment, the ultraviolet light assembly 21 is evenly distributed on the top of the oxidation chamber 3, and irradiates ultraviolet light toward the silicon wafer on the loading plate 16 below. The ultraviolet light assembly 21 includes a quartz glass shell and a mercury lamp source disposed in the quartz glass shell. The mercury lamp source emits light after being powered on, and the light is filtered by the quartz glass shell to obtain ultraviolet light with uniform wavelength.
[0048] The oxidation loading component is arranged corresponding to the oxidation temperature control component 17, and the oxidation temperature control component 17 is used to control the oxidation reaction temperature of the silicon wafer on the oxidation loading component. The oxidation temperature control component 17 in this embodiment uses a plurality of vacuum infrared heating tubes arranged in parallel, and the plurality of vacuum infrared heating tubes are arranged horizontally side by side. In order to allow the temperature in the oxidation chamber 3 to quickly reach the set temperature of the oxidation temperature control component 17 and to ensure that the temperature in the oxidation chamber 3 is evenly distributed, the oxidation temperature control component 17 is arranged between the oxidation loading component and the air inlet 10. In some other embodiments, the oxidation temperature control component 17 can also use other heating structures such as resistance wire heaters, and the position of the oxidation temperature control component 17 can also select other settings according to the actual operation needs of the device.
[0049] During the oxidation process of the silicon wafer, the temperature of the silicon wafer is controlled to be 150°C-200°C, for example, 150°C, 160°C, 170°C, 180°C, 190°C or 200°C. The wavelength of the ultraviolet light emitted by the ultraviolet light component 21 is controlled to be 210nm-300nm, for example, 210nm, 230nm, 250nm, 270nm, 290nm or 300nm. The power of the ultraviolet light emitted by the ultraviolet light component 21 is controlled to be 150W-250W, for example, 150W, 170W, 190W, 210W, 230W or 250W. The ultraviolet light component 21 is controlled to emit ultraviolet light to irradiate the silicon wafer for 4min-10min, for example, 4min, 5min, 6min, 7min, 8min, 9min or 10min. The irradiation time in the specific process can be adjusted experimentally according to the required thickness of the silicon dioxide oxide layer. At the same time, nitrogen is used to control the pressure in the oxidation chamber 3 to be maintained at 700 mbar-1000 mbar, for example, 700 mbar, 800 mbar, 900 mbar or 1000 mbar. The ratio of ozone to nitrogen in the mixed gas of ozone and nitrogen in the chamber is 3:2-5:3, for example, 3:2, 19:12 or 5:3. When nitrogen is used to adjust the pressure in the oxidation chamber 3, it is important to prioritize the ratio of the two.
[0050] The upstream of the oxidation chamber 3 is also connected to the vacuum chamber 2, and the upstream of the vacuum chamber 2 is provided with a loading chamber 1; the downstream of the oxidation chamber 3 is connected to the buffer chamber 4, and the downstream of the buffer chamber 4 is provided with a unloading chamber 5. The silicon wafer oxidation device is also provided with an electric control component 20, which is used to provide rated power to each electric component in the silicon wafer oxidation device. The electric control component 20 in this embodiment uses a DC pulse power supply.
[0051] The vacuum chamber 2 is used to evacuate the loading chamber 1, vacuum chamber 2, oxidation chamber 3 and buffer chamber 4 before the oxidation device is operated to eliminate the impurity gas inside the oxidation device. In some other embodiments, the unloading chamber 5 can also be evacuated at the same time. A sealed isolation door 19 is provided between each of the loading chamber 1, vacuum chamber 2, oxidation chamber 3, buffer chamber 4 and unloading chamber 5 so that each chamber is isolated during operation.
[0052] A loading assembly is installed in the loading chamber 1. The loading assembly in this embodiment has the same structure as the oxidation loading assembly. When the conveying roller 15 in the loading chamber 1 drives the loading plate 16 to move to the tail of the loading chamber 1, the sealed isolation door between the loading chamber 1 and the vacuum chamber 2 is opened, so that the loading plate 16 can smoothly enter the vacuum chamber 2. After loading and unloading from the previous process equipment, the silicon wafer enters the loading plate 16 of the loading chamber 1 to complete the automatic loading.
[0053] A vacuum loading assembly is installed inside the vacuum chamber 2. The vacuum chamber 2 is located upstream of the oxidation chamber 3. A vacuum pump as a vacuum pump 11 is connected to the vacuum chamber 2. A vacuum temperature control assembly 18 is installed inside the vacuum chamber 2. The vacuum temperature control assembly 18 is located between the vacuum pump's air suction port 12 and the vacuum loading assembly. The vacuum loading assembly and the oxidation loading assembly in this embodiment use the same structure, and the vacuum temperature control assembly 18 and the oxidation temperature control assembly 17 use the same structure. Before the oxidation chamber 3 works, the vacuum pump performs vacuum treatment on all chambers of the silicon wafer oxidation device, and the silicon wafer oxidation device is evacuated to 10 5 ~10 2 Pa rough vacuum state. When the loading plate 16 drives the silicon wafer to move in the vacuum chamber 2 under the action of the conveying roller 15, the vacuum pump does not work. When the conveying roller 15 in the vacuum chamber 2 drives the silicon wafer on the loading plate 16 to move to the tail of the vacuum chamber 2, the sealed isolation door between the vacuum chamber 2 and the oxidation chamber 3 is opened, so that the loading plate 16 can smoothly drive the silicon wafer into the oxidation chamber 3. The vacuum chamber 2 receives the loading plate 16 with the silicon wafer in the loading chamber 1 and preheats the silicon wafer.
[0054] A buffer loading assembly is installed in the buffer chamber 4, and another nitrogen gas source as a buffer gas source 8 is connected to the buffer chamber 4. Nitrogen is filled into the buffer chamber 4 through the nitrogen gas source to provide a constant air pressure in the buffer chamber 4, which is used as a pressure buffer for the silicon wafer from the rough vacuum environment of the oxidation chamber 3 to the atmospheric environment. The buffer loading assembly and the oxidation loading assembly in this embodiment are of the same structure. A cooling assembly is also connected to the buffer chamber 4, which is used to cool the oxidized silicon wafer. Specifically, the cooling assembly includes a water tank as a coolant storage member 13, a cooling pipeline 14 and a driving water pump as a driving member, the inlet end of the cooling pipeline 14 is connected to the coolant storage member 13, and the driving member is installed on the cooling pipeline 14 to drive the water as the coolant body to flow in the cooling pipeline 14, and the cooling pipeline 14 extends into the buffer chamber 4. In this embodiment, in order to avoid damage to the electrical parts in the oxidation chamber 3 and the vacuum chamber 2 under a high temperature environment, the cooling pipeline 14 of the cooling assembly also extends into the vacuum chamber 2 and the oxidation chamber 3 to provide a low temperature working environment for the electrical parts in the vacuum chamber 2 and the oxidation chamber 3, and ensure that the vacuum chamber 2 and the oxidation chamber 3 can operate stably. When the conveying roller 15 in the oxidation chamber 3 drives the silicon wafer on the loading plate 16 to move to the tail of the oxidation chamber 3, the sealed isolation door between the oxidation chamber 3 and the buffer chamber 4 is opened, so that the loading plate 16 can smoothly drive the silicon wafer into the buffer chamber 4. After the buffer chamber 4 receives the silicon wafer with the silicon dioxide oxide layer grown from the oxidation chamber 3, the buffer chamber 4 is inflated from the rough vacuum to the atmospheric pressure, and the silicon wafer and the loading plate 16 are cooled down at the same time. When the conveying roller 15 in the buffer chamber 4 drives the silicon wafer on the loading plate 16 to move to the tail of the buffer chamber 4, the sealed isolation door between the buffer chamber 4 and the unloading chamber 5 is opened, so that the loading plate 16 can smoothly drive the silicon wafer into the unloading chamber 5. The conveying roller 15 in the unloading chamber 5 drives the loading plate 16 to move, and then the loading plate 16 drives the silicon wafer to move from the silicon wafer oxidation device to the processing device of the next process, completing the automatic unloading of the silicon wafer in the silicon wafer oxidation device.
[0055] The silicon wafer oxidation device provided in this embodiment uses the principle of ultraviolet light exciting ozone to generate a silicon dioxide layer on the surface of the silicon wafer when performing single-sided oxidation treatment on the silicon wafer. The ultra-high concentration ozone gas is used to irradiate the surface of the silicon wafer with ultraviolet light of a wavelength of 210nm-300nm under relatively low temperature conditions of 150℃-200℃ to generate excited oxygen atoms that react with the silicon wafer to prepare a silicon dioxide oxide layer. After rough polishing and industrial standard wet method (RCA) surface cleaning of the single crystal silicon wafer, ultraviolet light-assisted ozone single-sided oxidation is performed. The silicon dioxide oxide layer generated by ultraviolet light-assisted ozone is denser than the silicon dioxide oxide layer generated by traditional thermal oxidation technology. Generally, under the conditions of 200℃ temperature and 150W ultraviolet light, a dense silicon dioxide oxide layer of 3nm-4nm can be grown in 4min-6min, which can greatly shorten the process time of growing a silicon dioxide oxide layer of fixed thickness, matching the large-scale mass production requirements of the photovoltaic industry.
[0056] This embodiment also provides a silicon wafer oxidation method. Using the silicon wafer oxidation device provided in this embodiment, the silicon wafer oxidation method includes the following steps: first, the oxidation chamber is evacuated, and the clean silicon wafer after cleaning is installed as the oxidized part on the oxidation loading assembly; then ozone and nitrogen are introduced into the oxidation chamber 3 at the same time, so that an ozone environment under a nitrogen background is formed in the oxidation chamber 3, and the ultraviolet light component 21 irradiates ultraviolet light toward the oxidation loading assembly; the oxidation temperature control component controls the temperature in the oxidation chamber 3 to 150°C-200°C. During the oxidation process, the gas pressure in the oxidation chamber is adjusted to 700mbar-1000mbar by controlling the amount of nitrogen introduced, and the wavelength of the ultraviolet light emitted by the ultraviolet light component 21 is controlled to be 210nm-300nm.
[0057] When the silicon wafer is oxidized before texturing, the above-mentioned silicon wafer oxidation method is used. When free oxygen atoms react with the silicon wafer to form a silicon dioxide oxide layer on the surface of the silicon wafer, the silicon dioxide oxide layer is formed quickly and a thicker silicon dioxide oxide layer can be formed in a short time. The silicon dioxide layer is grown on the silicon wafer using the existing British tube thermal oxidation process. The growth of the silicon dioxide anti-alkali protective layer requires about one and a half hours. When the silicon wafer is processed by the silicon wafer processing equipment provided in this embodiment, the step of growing the silicon dioxide layer only takes about ten minutes, which can greatly shorten the process time of growing a fixed thickness silicon dioxide anti-alkali protective layer, shorten the overall silicon wafer processing time, improve the silicon wafer processing efficiency, and improve the equipment utilization rate.
[0058] In order to make ozone excited by ultraviolet light to generate excited oxygen atoms, a high-pressure mercury lamp must be used to generate ultraviolet light of a specific wavelength (wavelength 200-300nm) to directly irradiate the single crystal silicon substrate sample. The UV lamp has a wide and continuous light emission interval within a wavelength range longer than 210nm. Only ultraviolet light with a wavelength of 200-300nm contributes to ozone photodecomposition. In actual tests, wavelengths above 300nm are considered to have no contribution to the ozone excitation reaction.
[0059] The ozone generator is used to generate the process gas source. During the process of preparing the silicon dioxide oxide layer on the single side of the silicon wafer, the main reaction is that the strongly oxidizing ozone molecules excited by ultraviolet light react with silicon to generate silicon dioxide and ozone hexacyclic rings. This includes the ozone-oxygen-ozone cyclic chain reaction. The specific reaction process is as follows: a part of the ozone that has not reacted with silicon decomposes under ultraviolet light to generate oxygen and free oxygen atoms, and the obtained free oxygen atoms react with silicon elements to generate silicon dioxide; oxygen decomposes and oxidizes under ultraviolet light to generate ozone with stronger oxidizing properties, and then the above cycle is repeated. Through the above reactions, free oxygen atoms and ozone are continuously generated. In addition, the ozone source introduced by the ozone generator makes the single-crystal silicon substrate exposed to a relatively high-pressure and high-concentration oxidizing atmosphere on one side, thereby obtaining a fast and efficient oxidation reaction, so that a sufficiently thick and dense silicon dioxide layer can be generated in a short time.
[0060] By increasing the flow rate of ozone gas introduced through the ozone generator and controlling the temperature of the silicon wafer substrate, a higher oxidation rate can be obtained. Compared with the thermal oxidation process which only relies on a single oxidation reaction in a high temperature environment of more than 800°C by introducing oxygen, it is obvious that the oxidation method provided in this embodiment is more diverse and efficient and controllable.
[0061] After the silicon dioxide oxide layer is formed, the silicon wafer with the silicon dioxide oxide layer is cleaned by texturing. In terms of the technical route selection for preparing the silicon oxide layer, compared with the tubular thermal oxygen double-sided oxidation: by using ultraviolet lamps in an ozone atmosphere, large-area one-time single-sided rapid processing of single-crystal planar silicon can be performed to meet the requirements of all specifications of single-crystal silicon wafers in the current photovoltaic market. Compared with the existing tubular thermal oxygen double-sided oxidation process, it has significant advantages in convenience, especially in production cycle, production efficiency and production cost.
[0062] In the tubular hot oxygen texturing process, long-term heating at over 800°C is required. Long-term high-temperature heating will inevitably cause thermal damage and defects inside the single-crystal silicon wafer. In this embodiment, ozone is excited by ultraviolet light to generate excited oxygen atoms to oxidize the silicon wafer. The process temperature does not exceed 200°C, and the ultraviolet light energy during the oxidation process is less than the chemical bond energy between silicon atoms, so it will not cause any damage to the inside of the single-crystal silicon wafer, and will not increase the number of defects inside the single-crystal silicon wafer.
[0063] Since the oxidation rate of silicon wafers in the tubular hot oxygen texturing process is affected by the crystal orientation during oxidation, the oxidation rate is slow during the process time and the thickness distribution of the generated oxide layer film will be uneven. The method of ultraviolet-assisted ozone irradiation of single-crystal silicon wafers provided in this embodiment is used for oxidation texturing. Due to the dual effects of the strong oxidizing property of ozone itself and the auxiliary decomposition of ultraviolet light of a specific wavelength, it is sufficient to overcome the influence of the difference in the crystal orientation of silicon oxide, so that the reaction of generating the silicon dioxide oxide layer is rapid and uniform. The silicon dioxide oxide layer prepared under this process condition performs better in uniformity and thickness, and has better compactness. The corresponding silicon dioxide mask protective layer obtained in the subsequent single-sided texturing process is more effective in the tolerance limit of alkali in the texturing solution.
[0064] Obviously, the above embodiments are merely examples for the purpose of clear explanation, and are not intended to limit the implementation methods. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation methods here. The obvious changes or modifications derived therefrom are still within the scope of protection of the invention.
Claims
1. A silicon wafer oxidation device, characterized in that: include: The oxidation chamber (3) is a closed chamber, the inner cavity of the oxidation chamber (3) is connected to an ozone source (6) and a protective gas source (7), and an oxidation loading assembly is provided in the oxidation chamber (3), and the oxidation loading assembly is used to install the workpiece to be oxidized; An ultraviolet light component (21) is installed in the oxidation chamber (3), and the ultraviolet light component (21) is used to irradiate ultraviolet light to the oxidation loading component; An oxidation temperature control component (17) is installed in the oxidation chamber (3) and is arranged corresponding to the oxidation loading component; It also includes: a cleaning chamber arranged upstream of the oxidation chamber (3), and a texturing chamber arranged downstream of the oxidation chamber (3), wherein the cleaning chamber and the texturing chamber are both sealed and connected to the oxidation chamber (3).
2. The silicon wafer oxidation device according to claim 1, characterized in that: A plurality of air inlets (10) are arranged in the oxidation chamber (3), the plurality of air inlets (10) are connected to a mixing pipeline (9), and the ozone source (6) and the protective gas source (7) are both connected to the mixing pipeline (9).
3. The silicon wafer oxidation device according to claim 2, characterized in that: The oxidation temperature control component (17) is arranged between the oxidation loading component and the air inlet (10), and the oxidation loading component comprises: a conveying member and a loading member, and the loading member is installed on the conveying member so that the conveying member drives the loading member to move along the conveying direction of the conveying member, and the loading member is used to install the part to be oxidized.
4. The silicon wafer oxidation device according to any one of claims 1 to 3, characterized in that: It also includes a vacuum chamber (2) in which a vacuum loading assembly is installed. The vacuum chamber (2) is arranged upstream of the oxidation chamber (3). The vacuum chamber (2) is connected to a vacuum pumping component (11). A vacuum temperature control component (18) is installed in the vacuum chamber (2). The vacuum temperature control component (18) is arranged between the vacuum port (12) of the vacuum pumping component and the vacuum loading assembly.
5. The silicon wafer oxidation device according to any one of claims 1 to 3, characterized in that: It also includes a buffer chamber (4) in which a buffer loading assembly is installed. The buffer chamber (4) is arranged downstream of the oxidation chamber (3). The buffer chamber (4) is connected to a buffer gas source (8). The buffer chamber (4) is connected to a cooling assembly.
6. The silicon wafer oxidation device according to claim 5, characterized in that: The cooling assembly comprises a cooling liquid storage component (13), a cooling pipeline (14) and a driving component. The inlet end of the cooling pipeline (14) is connected to the cooling liquid storage component (13). The driving component is installed on the cooling pipeline (14) to drive the cooling liquid body to flow in the cooling pipeline (14). The cooling pipeline (14) extends into the buffer chamber (4) and the oxidation chamber (3).
7. A method for oxidizing a silicon wafer, characterized in that: Using the silicon wafer oxidation device according to any one of claims 1 to 6, the silicon wafer oxidation method comprises: The oxidation chamber (3) is evacuated to a vacuum state, and a silicon wafer is mounted on an oxidation loading assembly as a part to be oxidized; Ozone and protective gas are introduced into the oxidation chamber (3) at the same time, so that an ozone environment under the protective gas background is formed in the oxidation chamber (3), and the ultraviolet light component (21) irradiates ultraviolet light toward the oxidation loading component; The oxidation temperature control component controls the temperature in the oxidation chamber (3) to be 150°C-200°C.
8. The silicon wafer oxidation method according to claim 7, characterized in that: The protective gas is nitrogen, helium or a stable gas that does not react with silicon and ozone under ultraviolet light, and the molecular mass of the protective gas molecules is smaller than the molecular mass of the ozone molecules.
9. The silicon wafer oxidation method according to claim 7, characterized in that: The gas pressure in the oxidation chamber is adjusted to 700 mbar-1000 mbar by controlling the amount of nitrogen introduced.
10. The silicon wafer oxidation method according to claim 7, characterized in that: The wavelength of the ultraviolet light emitted by the ultraviolet light component (21) is controlled to be 210nm-300nm.