Double-sided scrubber and method for cleaning silicon carbide wafer surface

Abstract

The present invention relates to a double-sided scrubber, which includes a receiving structure, which is arranged below the center position between a first brush and a second brush, and is used to receive a silicon carbide wafer. The receiving structure can move up and down with the help of a lifting structure below it, and can push the cleaned silicon carbide wafer back to the cleaning area to achieve automatic repeated cleaning of the silicon carbide wafer, thereby achieving high cleanliness of the surface of the silicon carbide wafer. The present invention also relates to a cleaning method for the surface of a silicon carbide wafer, which achieves high cleanliness requirements for the surface of the wafer through two cleaning processes of ultrasonic cleaning and double-sided brush cleaning.

Description

Technical Field

[0001] The invention relates to the technical field of new silicon carbide materials, and in particular to a double-sided scrubber and a method for cleaning the surface of a silicon carbide wafer. Background Art

[0002] The third generation of wide bandgap semiconductor materials represented by SiC is the core of the development of high-power, high-frequency, high-temperature, strong radiation-resistant blue lasers and ultraviolet detectors. SiC crystals have the characteristics of large bandgap width, high thermal conductivity, large electron saturation drift rate, high critical breakdown electric field, low dielectric constant, and good chemical stability. It is the preferred substitute for Si in the field of power electronics and has broad application prospects in the fields of communications, automobiles, aviation, aerospace, oil extraction, and national defense.

[0003] The surface cleanliness requirements for silicon carbide wafers used to make application devices are very high. Polishing liquid, metal ions and other pollutants remain on the surface of the polished wafer. Therefore, the wafer is usually subjected to a series of cleaning processes before use or shipment. Currently, the industry mostly uses RCA wet chemical cleaning technology to clean wafers, and different cleaning effects are achieved by adjusting the ratio of the cleaning liquid, cleaning temperature, cleaning time and other processes. However, there are often a small amount of particles on the wafers that cannot be cleaned after cleaning using existing technologies, and the surface cleanliness standards of the wafers cannot be met before shipment, and the cleaning effect is not ideal.

[0004] Therefore, it is necessary to develop a cleaning method and a cleaning device that can achieve high cleanliness on the surface of a silicon carbide wafer. Summary of the invention

[0005] The purpose of the present invention is to overcome the shortcomings of the prior art and provide a double-sided scrubber, which includes a receiving structure, which is arranged below the center position between the first brush and the second brush, for receiving the silicon carbide wafer. The receiving structure can move up and down, and can push the cleaned silicon carbide wafer back to the cleaning area to achieve automatic repeated cleaning of the silicon carbide wafer, thereby achieving high cleanliness of the surface of the silicon carbide wafer. However, the existing double-sided scrubber cannot achieve automatic repeated cleaning, and the cleaning effect is not ideal.

[0006] The present invention also provides a method for cleaning the surface of a silicon carbide wafer. The method achieves high cleanliness requirements on the surface of the wafer through two cleaning processes of ultrasonic cleaning and double-sided brush cleaning.

[0007] To achieve the above object, the present invention provides the following technical solutions.

[0008] The present invention provides a double-sided scrubbing machine, comprising:

[0009] A first brush and a second brush, wherein the first brush and the second brush are arranged in parallel and in parallel with the surface of the silicon carbide wafer to be cleaned, the first brush can contact with and clean one surface of the silicon carbide wafer, and the second brush can contact with and clean another surface of the silicon carbide wafer;

[0010] A receiving structure, the receiving structure is arranged below the center position between the first brush and the second brush, and a slot is arranged in the middle of the receiving structure, the slot is used to receive the silicon carbide wafer;

[0011] A sensor, the sensor being disposed inside the receiving structure and used for sensing a depth of the silicon carbide wafer entering the slot;

[0012] a lifting structure, the lifting structure being arranged at the bottom of the receiving structure; and

[0013] A control system is connected to the sensor and the lifting structure respectively, and is used to receive the signal transmitted by the sensor and control the lifting of the lifting structure.

[0014] The present invention also provides a method for cleaning the surface of a silicon carbide wafer, comprising:

[0015] Ultrasonic cleaning of silicon carbide wafers; and

[0016] The double-sided brush cleaning machine is used to clean the double-sided brush.

[0017] Compared with the prior art, the present invention has the following beneficial effects:

[0018] 1. The present invention provides a double-sided scrubber, which includes a receiving structure, which is arranged below the center position between the first brush and the second brush, and is used to receive the silicon carbide wafer. The receiving structure can move up and down with the help of the lifting structure below it, and can push the cleaned silicon carbide wafer back to the cleaning area to achieve automatic repeated cleaning of the silicon carbide wafer, thereby achieving high cleanliness of the surface of the silicon carbide wafer.

[0019] 2. The present invention also provides a method for cleaning the surface of a silicon carbide wafer. The method achieves high cleanliness requirements for the wafer surface through two cleaning processes: ultrasonic cleaning and double-sided brush cleaning. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Various other advantages and benefits will become apparent to those of ordinary skill in the art by reading the detailed description of the preferred embodiments below. The accompanying drawings are only for the purpose of illustrating the preferred embodiments and are not to be considered as limiting the present invention. Moreover, the same reference symbols are used throughout the accompanying drawings to represent the same components. In the accompanying drawings:

[0021] Figure 1 Schematic diagram of the partial structure of the double-sided scrubber of the present invention (in the figure, the bristles of the first brush 100 and the second brush 200 are oriented in opposite directions).

[0022] Figure 2 It is a top view of the receiving structure of the present invention.

[0023] Description of reference numerals:

[0024] 100 is a first brush, 200 is a second brush, 300 is a silicon carbide wafer, 400 is a receiving structure, 401 is a slot, 500 is a sensor, 600 is a lifting structure, 700 is a control system, 800 is a first spraying structure, and 900 is an adsorption structure. DETAILED DESCRIPTION

[0025] Hereinafter, embodiments of the present disclosure will be described with reference to the accompanying drawings. However, it should be understood that these descriptions are exemplary only and are not intended to limit the scope of the present disclosure. In addition, in the following description, descriptions of well-known structures and technologies are omitted to avoid unnecessary confusion of the concepts of the present disclosure.

[0026] Various structural schematic diagrams according to embodiments of the present disclosure are shown in the accompanying drawings. These figures are not drawn to scale, and some details are magnified and some details may be omitted for the purpose of clear expression. The shapes of various regions and layers shown in the figures and the relative sizes and positional relationships therebetween are only exemplary, and may deviate in practice due to manufacturing tolerances or technical limitations, and those skilled in the art may further design regions / layers with different shapes, sizes, and relative positions according to actual needs.

[0027] In the context of the present disclosure, when a layer / element is referred to as being "on" another layer / element, the layer / element may be directly on the other layer / element or an intervening layer / element may exist between them. In addition, if a layer / element is "on" another layer / element in one orientation, the layer / element may be "below" the other layer / element when the orientation is reversed.

[0028] The present invention will be further described below in conjunction with specific drawings.

[0029] Figure 1 A partial structural schematic diagram of the double-sided scrubber of the present invention is given. Specifically, Figure 1As shown, the double-sided scrubber of the present invention comprises: a first brush 100 and a second brush 200, the first brush 100 and the second brush 200 are arranged in parallel and in parallel with the surface of the silicon carbide wafer 300 to be cleaned, the first brush 100 can contact with and clean one surface of the silicon carbide wafer 300, and the second brush 200 can contact and clean the other surface of the silicon carbide wafer 300; a receiving structure 400, the receiving structure 400 is arranged at a central position between the first brush 100 and the second brush 200 Below, and in the middle of the receiving structure 400, a slot 401 is provided, the slot 401 is used to receive the silicon carbide wafer 300; a sensor 500, the sensor 500 is provided inside the receiving structure 400, and is used to sense the depth of the silicon carbide wafer entering the slot; a lifting structure 600, the lifting structure 600 is provided at the bottom of the receiving structure 400; and a control system 700, the control system is respectively connected to the sensor and the lifting structure, and is used to receive the signal transmitted by the sensor and control the lifting and lowering of the lifting structure.

[0030] The first brush 100 and the second brush 200 of the present invention are arranged on opposite sides of the silicon carbide wafer to be cleaned, so that the two surfaces of the silicon carbide wafer can be cleaned simultaneously, thus saving cleaning time.

[0031] Figure 1 The directions of the bristles of the first brush 100 and the second brush 200 are opposite to each other. This is only for distinguishing the first brush 100 from the second brush 200 in the figure, and the directions of the bristles of the two are not limited thereto.

[0032] Preferably, the receiving structure is a block structure with a downwardly concave upper surface, and the design can match the outer edge shape of the silicon carbide wafer to prevent the most vulnerable part of the silicon carbide wafer from moving downward and hitting the receiving structure, causing cracking or scratching. Preferably, the upper surface is arc-shaped and concave.

[0033] Preferably, the receiving structure is made of rubber material, which will not damage the surface of the wafer.

[0034] The present invention has no particular limitation on the size of the slot 401, as long as the depth of the silicon carbide wafer entering the slot reaches a preset value. In the present invention, the depth of the silicon carbide wafer entering the slot (i.e., the preset value) can be 8-12 mm (for a 4-inch silicon carbide wafer) or 13-17 mm (for a 6-inch silicon carbide wafer).

[0035] Preferably, the lifting structure 400 is a lifting platform. When a 4-inch silicon carbide wafer is selected, the lifting structure is adjusted so that the receiving structure is 100-120 mm away from the adsorption structure; when a 6-inch silicon carbide wafer is selected, the lifting structure is adjusted so that the receiving structure is 160-170 mm away from the adsorption structure. The height setting can just make the silicon carbide wafer drop to a certain height, and the depth of entering the slot can reach a preset value, so that it can be pushed back to the original position to start a new round of cleaning.

[0036] Preferably, the first brush 100 and the second brush 200 may be made of polyvinyl alcohol, tetrafluoroethylene or nylon PA612. The brush material itself is soft and will not cause any damage during the contact and friction with the wafer surface.

[0037] Preferably, the number of the first brush 100 is at least one. Preferably, the number of the first brush 100 is more than two. More than two of the first brushes 100 are arranged in parallel along the surface of the silicon carbide wafer. Preferably, the number of the second brush 200 is at least one. Preferably, the number of the second brush 200 is more than two. More than two of the second brushes 200 are arranged in parallel along the surface of the silicon carbide wafer. In some embodiments, the number of the first brush 100 and the second brush 200 is the same, and the first brush 100 and the second brush 200 are arranged on opposite sides of the silicon carbide wafer in a one-to-one correspondence. One first brush 100 and one second brush 200 constitute a pair of cleaning brushes. In some embodiments, the first brush 100 is arranged on the left side of the silicon carbide wafer, and the second brush 200 is arranged on the right side of the silicon carbide wafer; or vice versa.

[0038] In the present invention, the first brush 100 and the second brush 200 rotate about the central axis, wherein the first brush 100 rotates clockwise and the second brush 200 rotates counterclockwise, or the first brush 100 rotates counterclockwise and the second brush 200 rotates clockwise. Preferably, the rotations are uniform and have the same rotation rate, preferably greater than 0 and less than or equal to 1600 r / min.

[0039] Preferably, the double-sided scrubber further comprises: at least two first spray structures 800 and at least two second spray structures (not shown in the figure), wherein the first spray structures and the second spray structures are respectively arranged on opposite sides of the silicon carbide wafer to be cleaned, wherein at least one of the first spray structures is used for spraying water and at least one of the first spray structures is used for spraying organic solvents; at least one of the second spray structures is used for spraying water and at least one of the second spray structures is used for spraying organic solvents. Such an arrangement can realize chemical cleaning of silicon carbide wafers and further improve the cleanliness of the wafer surface.

[0040] In some embodiments, the first spray structure and the first brush are arranged on the same side of the silicon carbide wafer to be cleaned, and the second spray structure and the second brush are arranged on the other side of the silicon carbide wafer to be cleaned. Preferably, the first spray structure is arranged above the first brush, and the second spray structure is arranged above the second brush.

[0041] Preferably, the first spray structure and the second spray structure are arranged at the middle and upper parts of opposite sides of the silicon carbide wafer.

[0042] Preferably, the first spray structure and the second spray structure are nozzles.

[0043] Preferably, the double-sided scrubber further comprises: an adsorption structure 900, which is disposed on the upper part of the surface of the silicon carbide wafer 300 and is used to adsorb the silicon carbide wafer 300 so that it can move.

[0044] Preferably, the adsorption structure 900 is a suction cup.

[0045] During the cleaning process, the silicon carbide wafer is sandwiched between the first brush 100 and the second brush 200. Through the friction between the brushes, the silicon carbide wafer moves downward at a constant speed while being brushed by the brushes until it hits the receiving structure 400. After that, the silicon carbide wafer continues to move downward and enters the slot 401. When the sensor 500 senses that the depth of the silicon carbide wafer entering the slot 401 reaches a preset value, the sensor 500 feeds back a signal to the control system 700. The control system 700 transmits a signal to the lifting structure 600 and controls the lifting structure 600 to slowly and uniformly push the receiving structure 400 upward to a certain set height. This height can just make the wafer return to the cleaning area (that is, the position where the wafer is about to start cleaning), so that its top is again adsorbed by the adsorption structure 900, thereby restarting a new round of double-sided brush cleaning process. Perform several cycles according to preset requirements.

[0046] The present invention also provides a method for cleaning the surface of a silicon carbide wafer, which specifically comprises the following steps.

[0047] First, the silicon carbide wafer is ultrasonically cleaned.

[0048] Preferably, the ultrasonic cleaning comprises: pre-cleaning the silicon carbide wafer using multi-band ultrasonic waves and a cleaning liquid.

[0049] Preferably, the cleaning solution may be a mixed solution of hydrochloric acid (33% concentration) and hydrogen peroxide (35% concentration) (mixed volume ratio 1:1), a mixed solution of hydrochloric acid (33% concentration), hydrogen peroxide (35% concentration) and dilute sulfuric acid (67% concentration) (mixed volume ratio 2:2:1), a mixed solution of hydrochloric acid, hydrogen peroxide and dilute nitric acid (mixed volume ratio 2:2:1), or a mixed solution of hydrochloric acid (33% concentration), hydrogen peroxide (35% concentration), dilute nitric acid (30% concentration) and dilute sulfuric acid (67% concentration) (mixed volume ratio 2:2:1:1). Hydrogen peroxide mainly plays an oxidizing role, and its strong oxidizing property can remove inorganic and organic contamination. The chloride ions in hydrochloric acid play a chelating role to remove metal impurities. Hydrochloric acid and other inorganic acids play a chemical corrosion role, making impurities more soluble in the solution and removed.

[0050] In addition, there will be residual cleaning liquid on the surface of the chip after ultrasonic cleaning. The chloride ions in the cleaning liquid can play a complexing role during double-sided brush cleaning, causing many metals on the surface of the chip to generate water-soluble complex ions, thereby being removed.

[0051] Preferably, the frequency of the multi-band ultrasonic wave can be 28-55KHz, 70-85KHz or 97-105KHz. The cleaning effect is sufficient within these frequencies and will not be adjusted too high to waste too much energy, thus saving process costs.

[0052] Preferably, the ultrasonic cleaning time may be 5-20 min, preferably 10-15 min.

[0053] Preferably, the ultrasonic cleaning temperature may be 70-100° C., preferably 80-95° C. For the wafer surface, impurity adsorption is an exothermic process, while desorption is an endothermic process. Increasing the temperature is beneficial to the desorption of impurity particles on the wafer surface.

[0054] Preferably, the ultrasonic cleaning time may be 5-20 minutes, preferably 10-15 minutes. Preferably, the ultrasonic cleaning temperature may be 70-100°C, preferably 80-95°C. When the cleaning time is too short or the cleaning temperature is too low, the cleaning force will be insufficient and the purpose of ultrasonic cleaning cannot be achieved; when the cleaning time is too long or the cleaning temperature is too high, on the one hand, it will cause unnecessary waste of electric energy and working time, and on the other hand, if the cleaning is too long in a high temperature environment, there is a risk of causing the silicon carbide wafer to crack and damage the surface. Within the cleaning time and temperature range of the present invention, the purpose of effectively cleaning impurities on the surface of the wafer can be achieved.

[0055] The ultrasonic cleaning of the present invention can produce sparse and dense parts inside the cleaning liquid under the action of strong ultrasonic waves. The sparse parts produce nearly vacuum holes. When the holes disappear, strong local pressure is generated near them, breaking the chemical bonds in the molecules, thereby desorbing the impurities on the surface of the chip. When the frequency of the ultrasonic wave and the vibration frequency of the holes resonate, the mechanical force reaches the maximum, and the large amount of heat energy accumulated in the bubble increases the temperature, promotes the occurrence of chemical reactions, and is conducive to removing large contamination particles attached to the surface of the chip. Ultrasonic cleaning washes away the contamination of larger metal particles on the chip through cavitation. In addition, the cleaning effect can be improved by changing the frequency band. Particles smaller than 1 micron on the chip need to be removed by double-sided brush cleaning. The double-sided brush cleaning process will be described in detail below.

[0056] Then, the double-sided brush is used to clean the double-sided brush.

[0057] Preferably, the double-sided brush cleaning includes: cleaning each surface of the silicon carbide wafer by brushing and using an organic solvent and water. Preferably, the water is ultrapure water. In some embodiments of the present invention, the organic solvent and water are sprayed on the silicon carbide wafer. The spraying can be performed by means of a spray structure in the double-sided brush cleaning machine. The brushes are the first brush and the second brush in the double-sided brush cleaning machine.

[0058] Preferably, the organic solvent may be aqueous ammonia (with a concentration of 25%), or a mixed solution of aqueous ammonia (with a concentration of 25%) and hydrogen peroxide (with a concentration of 35%) (mixing volume ratio of 1:1).

[0059] The double-sided brush cleaning is carried out with the help of a double-sided brush (i.e., the first brush and the second brush mentioned above) in combination with the organic solvent and water. On the one hand, the soft brush can quickly remove the easily soluble particles on the surface. On the other hand, ammonia water has a complexing property, and many metals generate complexing properties that are soluble in water, thereby achieving the purpose of high-cleanliness cleaning. Complexing reaction belongs to chemical adsorption. Chemical adsorption is an adsorption accompanied by charge transfer interaction or the formation of chemical bonds. The force of chemical adsorption is a strong valence bond force. Therefore, chemical adsorption has the characteristics of chemical reaction. After chemical adsorption, adsorption chemical bonds are formed between the adsorbate molecules and the adsorbent atoms to form a surface complex. Compared with the original adsorbate molecules, due to the strong influence of the adsorption bonds, its structure changes greatly, the reaction activation energy is much lower, and the reaction rate is accelerated. In physical adsorption, a molecular layer is basically formed near the surface through a weak interaction between the adsorbate and the atoms on the surface of the adsorbent; while chemical adsorption originates from the interaction between the molecular orbital of the adsorbate and the electronic orbital of the adsorbent surface. Therefore, the complexing effect of ammonia water and the oxidation effect of hydrogen peroxide can work simultaneously, so that many metal ions form stable soluble complexes and dissolve in water, thereby removing the deeper atomic impurities of the silicon carbide wafer, achieving a truly high-cleanliness cleaning. In addition, the oxidation effect of hydrogen peroxide and the dissolution effect of hydrochloric acid (residual after ultrasonic cleaning) and the complexing property of chloride ions can make many metals generate complex ions soluble in water. In the double-sided brush cleaning process, physical cleaning and chemical cleaning work together and complement each other, significantly improving the cleanliness of the wafer surface, meeting the higher cleanliness performance requirements for silicon carbide wafers in the current silicon carbide market.

[0060] The double-sided brush cleaning of the present invention is carried out in the above-mentioned double-sided brush washing machine, specifically including: contacting the two surfaces of the silicon carbide wafer with the first brush and the second brush respectively; using the first brush and the second brush as well as the organic solvent and water to clean the two surfaces of the silicon carbide wafer; during the cleaning process, the silicon carbide wafer keeps moving downward, and when the depth of entering the receiving structure reaches a preset value, the receiving structure can move upward with the help of the lifting structure connected thereto, so as to push the silicon carbide wafer back to the position where the cleaning is about to start, thus restarting a new round of double-sided brush cleaning process, and performing several cycles according to preset requirements. Preferably, double-sided brush cleaning can be repeated for 5-10 times, preferably 5-7 times.

[0061] Preferably, the cleaning method of the present invention may further include: drying after the ultrasonic cleaning and the double-sided brush cleaning are completed.

[0062] Preferably, the drying comprises: drying by blowing plasma gas on the surface of the silicon carbide.

[0063] Preferably, the plasma gas may be one or both of nitrogen and argon.

[0064] Nitrogen and argon are both stable gases, extremely inactive, and generally do not react chemically with the surface components of the wafer. Therefore, they can be used to dry the surface of silicon carbide crystals. The gas is single and pure, and does not bring additional impurities. By powerfully blowing plasma gas on the surface of the wafer, the purpose of removing the last impurities on the surface and drying can be achieved.

[0065] Preferably, the drying time may be 5-20 min, preferably 5-10 min.

[0066] The drying can be carried out at room temperature, or the drying temperature can be 80-90°C, preferably 85-90°C.

[0067] The method of the present invention is further described below in conjunction with the accompanying drawings and embodiments.

[0068] Unless otherwise specified, the raw materials and reagents used in the examples are all commercially available. Reagents, instruments or operating procedures not described herein are all routinely determined by those of ordinary skill in the art.

[0069] Example 1

[0070] First, an ultrasonic cleaning process is performed, specifically including: placing the entire material box filled with 6-inch silicon carbide wafers 300 into an ultrasonic cleaning tank, the cleaning solution (mixed solution of hydrochloric acid and hydrogen peroxide) in the tank should be large enough to completely cover the silicon carbide wafers 300, click the start button, and multi-band ultrasonic waves (frequencies of 55KHz, 85KHz and 105KHz) are used in conjunction with the cleaning solution to pre-clean the silicon carbide wafers 300 in the material box. The ultrasonic cleaning time is 5 minutes, and the ultrasonic cleaning temperature is 100°C.

[0071] Then, a double-sided brush cleaning process is performed in a double-sided brush scrubber, specifically including: placing a material box filled with silicon carbide wafers 300 in the cleaning waiting area of ​​the double-sided brush scrubber, so that the material box can be stuck in the card slot in the cleaning waiting area (the material box and card slot design in this cleaning process can meet the cleaning of silicon carbide wafers of different specifications). After that, adjust the lifting structure so that the receiving structure is 165mm away from the adsorption structure. The height setting can just make the depth of the silicon carbide wafer inserted into the slot 401 reach the preset value (15mm) when it drops to a certain height, so that it can be pushed back to the original position to start a new round of cleaning. Then, the adsorption structure 900 is moved from top to bottom to the top of the silicon carbide wafer 300 with the center line of the card slot as the axis, and the silicon carbide wafer 300 is adsorbed one by one, and then moved to the scrubbing area of ​​the double-sided scrubber, so that the silicon carbide wafer 300 is exactly in the middle of the first brush 100 and the second brush 200 and the bottom of the silicon carbide wafer 300 can just contact the first brush 100 and the second brush 200. There are four nozzles in the scrubbing area, which are respectively located on the opposite sides of the silicon carbide wafer 300 to be cleaned. The two nozzles on each side spray organic solvent (ammonia water) and ultrapure water toward the surface of the silicon carbide wafer 300, and the first brush 100 and the second brush 200 rotate respectively. The first brush 100 on the left side of the silicon carbide wafer 300 rotates clockwise at a constant speed, and the second brush 200 on the right side rotates counterclockwise at a constant speed, and the rotation speeds of the first brush 100 and the second brush 200 are the same, both 1000r / min. The silicon carbide wafer 300 is sandwiched between the first brush 100 and the second brush 200. With the friction between them, the silicon carbide wafer 300 moves downward at a constant speed while being brushed by the brush until it hits the receiving structure 400 (set below the center position between the first brush 100 and the second brush 200). After that, the silicon carbide wafer 300 continues to move downward and enters the slot 401. When the sensor 500 set in the receiving structure 400 senses that the depth of the silicon carbide wafer 300 entering the slot 401 reaches a preset value (15mm), the sensor 500 feedbacks information to the lifting structure 600 (i.e., the lifting platform), and the lifting structure 600 slowly and uniformly pushes the receiving structure 400 upward to a certain set height, which can just make the silicon carbide wafer 300 return to the cleaning area (i.e., the position where the silicon carbide wafer 300 is about to start cleaning), so that its top is re-adsorbed by the adsorption structure 900 to restart a new round of double-sided brush cleaning process. This is repeated for 5 cycles according to the preset requirements.

[0072] Finally, the adsorption structure 900 re-adsorbs the silicon carbide wafer 300 cleaned by the double-sided brush, and moves it into the material box in the drying waiting area, presses the drying (temperature is 90°C) mode button, and the air pipe in the drying waiting area blows out plasma gas (nitrogen) to completely dry the silicon carbide wafer 300 (taking 5 minutes), and the entire cleaning process is completed.

[0073] Example 2

[0074] The method described in Example 1 is followed, except that, during the ultrasonic cleaning process, the cleaning solution is a mixed solution of hydrochloric acid (concentration of 33%), hydrogen peroxide (concentration of 35%) and dilute sulfuric acid (concentration of 67%) (mixed volume ratio of 2:2:1); the multi-band ultrasonic frequencies are 28KHz, 70KHz and 97KHz; the ultrasonic cleaning time is 20 minutes, and the ultrasonic cleaning temperature is 70°C; during the double-sided brush cleaning process, the organic solvent is a mixed solution of ammonia water (concentration of 25%) and hydrogen peroxide (concentration of 35%) (mixed volume ratio of 1:1); the double-sided brush cleaning is repeated for 10 cycles; during the drying process, the plasma gas is argon; the drying time is 20 minutes, and the drying temperature is 80°C.

[0075] The conventional cleaning process that is frequently used now is to use an ultrasonic cleaning machine to wet clean the silicon carbide wafer. The ultrasonic cleaning time is 10 minutes, there is no requirement for temperature, the operating frequency is 20KHz, and the cleaning liquid composition is: 6-8% fatty alcohol polyoxyethylene ether as a surfactant, 8-12% coconut oil alkanolamide (6501) as a surfactant, 2-5% oleic acid triethanolamine as a surfactant, 6-8% monoethanolamine as a rust inhibitor, 0-1% benzotriazole as a corrosion inhibitor, 1-3% disodium as a complexing agent, 70-77% water, remove molecular impurities on the surface of the silicon carbide wafer, and then rinse the surface of the silicon carbide wafer with high-purity deionized water, and then dry to obtain a silicon carbide wafer with a clean surface. Table 1 below is a comparison of the number of impurity particles on the wafer surface after cleaning by the conventional process and the process of the present invention. It is easy to see from the table that the number of particles after cleaning by the process of the present invention is much smaller than the number of particles in the conventional cleaning process, and at the particle size level, the number of particles in each gear is also better than the conventional process.

[0076] Table 1:

[0077]

[0078]

[0079] The above is only a preferred specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed by the present invention should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention shall be based on the protection scope of the claims.

Claims

1. A double-sided scrubbing machine, characterized in that: include: A first brush and a second brush, wherein the first brush and the second brush are arranged in parallel and in parallel with the surface of the silicon carbide wafer to be cleaned, the first brush can contact with and clean one surface of the silicon carbide wafer, and the second brush can contact with and clean another surface of the silicon carbide wafer; A receiving structure, the receiving structure is arranged below the center position between the first brush and the second brush, and a slot is arranged in the middle of the receiving structure, the slot is used to receive the silicon carbide wafer; the receiving structure is made of rubber; A sensor, the sensor being disposed inside the receiving structure and used for sensing a depth of the silicon carbide wafer entering the slot; An adsorption structure for adsorbing silicon carbide wafers; A lifting structure, wherein the lifting structure is arranged at the bottom of the receiving structure; as well as A control system, the control system is connected to the sensor and the lifting structure respectively, and is used to receive the signal transmitted by the sensor and control the lifting of the lifting structure; During the cleaning process, the silicon carbide wafer is sandwiched between the first brush and the second brush. Through the friction between the first brush and the second brush, the silicon carbide wafer moves downward at a uniform speed while being brushed by the first brush and the second brush until it hits the receiving structure. After that, the silicon carbide wafer continues to move downward and enters the slot. When the sensor senses that the depth of the silicon carbide wafer entering the slot reaches a preset value, the sensor feeds back a signal to the control system. The control system transmits a signal to the lifting structure and controls the lifting structure to slowly and uniformly push the receiving structure upward to a set height. This height can just make the silicon carbide wafer return to the position when cleaning is about to begin, so that the top of the silicon carbide wafer is re-adsorbed by the adsorption structure, thereby restarting a new round of double-sided brush cleaning process.

2. The double-sided scrubbing machine according to claim 1, characterized in that: Also includes: At least two first spray structures and at least two second spray structures, wherein the first spray structures and the second spray structures are respectively arranged on opposite sides of the silicon carbide wafer to be cleaned, wherein at least one of the first spray structures is used for spraying water and at least one of the first spray structures is used for spraying an organic solvent; and at least one of the second spray structures is used for spraying water and at least one of the second spray structures is used for spraying an organic solvent.

3. A method for cleaning the surface of a silicon carbide wafer, characterized in that: include: Ultrasonic cleaning of silicon carbide wafers; as well as The double-sided brush cleaning machine according to any one of claims 1 to 2 is used for double-sided brush cleaning.

4. The cleaning method according to claim 3, characterized in that: The double-sided brush cleaning includes: cleaning each surface of the silicon carbide wafer by using a brush and an organic solvent and water; the organic solvent is ammonia water, or a mixed solution of ammonia water and hydrogen peroxide.

5. The cleaning method according to claim 3 or 4, characterized in that: The double-sided brush cleaning is repeated 5-10 times.

6. The cleaning method according to claim 3 or 4, characterized in that: The ultrasonic cleaning comprises: pre-cleaning the silicon carbide wafer using multi-band ultrasonic waves and a cleaning liquid; The cleaning solution is a mixed solution of hydrochloric acid and hydrogen peroxide, a mixed solution of hydrochloric acid, hydrogen peroxide and dilute sulfuric acid, a mixed solution of hydrochloric acid, hydrogen peroxide and dilute nitric acid, or a mixed solution of hydrochloric acid, hydrogen peroxide, dilute nitric acid and dilute sulfuric acid.

7. The cleaning method according to claim 3 or 4, characterized in that: Also includes: After the ultrasonic cleaning and the double-sided brush cleaning are completed, drying is performed.

8. The cleaning method according to claim 7, characterized in that: The drying comprises: drying by blowing plasma gas on the surface of the silicon carbide; the plasma gas is one or both of nitrogen and argon.

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