阅读说明：本技术 一种易解理半导体晶体的加工方法 (Processing method of easily-cleaved semiconductor crystal ) 是由 高尚 康仁科 董志刚 何宜伟 朱祥龙 李洪钢 于 2019-09-12 设计创作，主要内容包括：本发明公开了一种易解理半导体晶体的加工方法,该方法采用控制磨削力和工件旋转法对易解理的氧化镓晶片进行磨削加工,步骤为将氧化镓晶片固定在工作台上,其下设有力传感器；分别采用粗、细粒度的金刚石砂轮对氧化镓晶片进行粗磨削和精磨削；分别设定粗磨削和精磨削时的初始进给速度、进给量、最大磨削力F<Sub>粗</Sub>和F<Sub>细</Sub>,并且在粗、精磨削过程中分别保证磨削力在F<Sub>粗</Sub>±0.1N、F<Sub>细</Sub>±0.1N的范围内。数据处理器实时采集力传感器测得的磨削力信号,并放大处理输送给负反馈系统,负反馈系统对进给速度实时控制以实现磨削力小于氧化镓解理应力阈值。此方案解决了氧化镓机械加工中易出现的解离现象,实现了高成品率。(The invention discloses a processing method of an easily-cleaved semiconductor crystal, which adopts a method of controlling grinding force and rotating a workpiece to grind an easily-cleaved gallium oxide wafer, and comprises the steps of fixing the gallium oxide wafer on a workbench and arranging a force sensor below the gallium oxide wafer; respectively adopting diamond grinding wheels with coarse and fine particle sizes to perform coarse grinding and fine grinding on the gallium oxide wafer; initial feed speed, feed amount, and maximum grinding force F for rough grinding and finish grinding are set respectively Coarse And F Thin and thin And the grinding force is ensured to be F in the course of coarse grinding and fine grinding respectively Coarse ±0.1N、F Thin and thin In the range of ± 0.1N. The data processor collects the grinding force signal measured by the force sensor in real time, amplifies the signal and transmits the signal to the negative feedback system, and the negative feedback system controls the feeding speed in real time to realize that the grinding force is less than the gallium oxide solutionA physical stress threshold. The technical scheme solves the dissociation phenomenon easily occurring in the gallium oxide machining, and realizes high yield.)

1. A method for processing an easily-cleaved semiconductor crystal is characterized by comprising the following steps:

s1, fixing the gallium oxide wafer on a workbench, and arranging a force sensor below the gallium oxide wafer;

s2, starting the coarse-grained diamond grinding wheel and the workbench to rotate;

s3, feeding the coarse-grain diamond grinding wheel above the gallium oxide wafer until the force sensor shows a value, stopping feeding, setting the initial feeding speed of coarse grinding, and setting the maximum grinding force F_CoarseAfter the feeding amount is reached, the gallium oxide wafer is subjected to coarse grinding until the set feeding amount is reached, and the grinding force is ensured to be F in the coarse grinding process_CoarseFluctuating within a range of + -0.1N;

s4, stopping feeding, continuing to grind the roughly ground gallium oxide wafer without feeding, lifting the rough-grained diamond grinding wheel, and stopping the rough-grained diamond grinding wheel and the workbench from rotating;

s5, replacing the coarse-grained diamond grinding wheel with a fine-grained diamond grinding wheel, and starting the fine-grained diamond grinding wheel and the workbench to rotate;

s6, feeding the fine-grained diamond grinding wheel above the gallium oxide wafer after non-feed grinding, stopping feeding until the indication value appears on the force sensor, setting the initial feeding speed of the fine grinding, and setting the maximum grinding force F_{Thin and thin}And after the feed amount is reached, carrying out fine grinding on the gallium oxide wafer until the set feed amount is reached, and ensuring that the grinding force is F in the fine grinding process_{Thin and thin}Fluctuating in the range of + -0.1N.

2. The process of claim 1, wherein the gallium oxide wafer is a round wafer, which is adsorbed on a vacuum chuck of a table or fixed on the table;

or the gallium oxide wafers are a plurality of small-size gallium oxide wafers which are circumferentially and uniformly distributed on the disc, and the disc is adsorbed on a vacuum chuck of the workbench or fixed on the workbench.

3. The process of claim 1 wherein said rough grinding, said plunge grinding and said finish grinding are each cooled by a coolant at a flow rate of 4 to 6L/min, said coolant being deionized water.

4. The machining method as claimed in claim 1, wherein in the step S2, the rotation speed of the coarse-grained diamond grinding wheel is 600-1000r/min, and the rotation speed direction is clockwise;

the rotating speed of the workbench is 200-400r/min, and the rotating speed direction is anticlockwise.

5. The machining method according to claim 1, wherein in the step S3, the step of feeding the coarse-grained diamond grinding wheel above the gallium oxide wafer until the force sensor indicates that the feeding is stopped includes the following specific steps:

feeding a coarse-grain diamond grinding wheel to a position close to the upper part of the gallium oxide wafer, and then slowly feeding the gallium oxide wafer at a feeding speed of 10 mu m/min until a force sensor shows a value, and stopping feeding;

in the step S3, the initial feeding speed is 0.5-1 μm/min, and the maximum grinding force F_Coarse20-30N, and the feeding amount is 10-20 μm;

in the step S3, the grinding force during rough grinding is ensured to be F through a negative feedback system_CoarseFluctuating within a range of + -0.1N;

the data processor collects the grinding force signal measured by the force sensor in real time, amplifies the grinding force signal and transmits the signal to the negative feedback system, and the negative feedback system compares the grinding force signal with the set maximum grinding force and continuously reverses the grinding force signalThe feed control system controls the feed speed of the coarse-grained diamond grinding wheel, and the increase and decrease degree of the feed speed is related to the difference value between the real-time grinding force and the set maximum grinding force so as to ensure that the grinding force is F in the coarse grinding process_CoarseFluctuating within a range of + -0.1N;

the abrasive grain size of the coarse-grain diamond grinding wheel is W10-W14.

6. The process of claim 1 wherein said non-feed grinding parameters are consistent with said rough grinding parameters except that the feed rate is zero;

the grinding time of the non-feeding grinding is 3 min.

7. The machining method according to claim 1, wherein in the step S5, the rotation speed of the fine-grained diamond grinding wheel is 1000-2400r/min, and the rotation speed direction is clockwise;

the rotating speed of the workbench is 300-400r/min, and the rotating speed direction is anticlockwise.

8. The machining method according to claim 1, wherein in step S6, the specific steps of feeding the fine-grained diamond grinding wheel above the gallium oxide wafer after non-feed grinding until the force sensor indicates that the feeding is stopped are as follows:

feeding a fine-grained diamond grinding wheel to the position above the gallium oxide wafer which is close to the position above the gallium oxide wafer after non-feeding grinding, and then slowly feeding the gallium oxide wafer at a feeding speed of 10 mu m/min until a force sensor shows a value, and stopping feeding;

in the step S6, the initial feeding speed is 0.5-1 μm/min, and the maximum grinding force F_{Thin and thin}30-60N, and the feeding amount is 5-10 μm;

in step S6, the grinding force during the finish grinding process is ensured to be F through a negative feedback system_{Thin and thin}Fluctuating within a range of + -0.1N;

the data processor collects the grinding force signal measured by the force sensor in real time, amplifies the signal and transmits the amplified signal to the negative feedback systemThe negative feedback system compares the grinding force with the set maximum grinding force and feeds the result back to the control system to control the feeding speed of the fine-grained diamond grinding wheel, and the increase and decrease degree of the feeding speed is related to the difference value between the real-time grinding force and the set maximum grinding force so as to ensure that the grinding force is F in the fine grinding process_{Extract of Chinese medicinal materials}Fluctuating within a range of + -0.1N;

the abrasive grain size of the fine-grained diamond grinding wheel is W1-W5.

Technical Field

The invention belongs to the technical field of ultra-precision processing of hard and brittle semiconductor wafers, and particularly relates to a processing method of an easily-cleaved semiconductor crystal.

Background

Gallium oxide (. beta. -Ga)₂O₃) The ultra-wide bandgap oxide semiconductor material is a novel ultra-wide bandgap oxide semiconductor material, has very stable physical and chemical properties, high breakdown field strength and strong radiation resistance, and is more suitable for the development of high-power semiconductors. Gallium oxide (beta-Ga) as compared to the other two as new generation power semiconductor materials, such as silicon carbide (SiC) and gallium nitride (GaN)₂O₃) It is expected to produce a power semiconductor device having a high withstand voltage and a low loss at a low cost. Furthermore, beta-Ga₂O₃The ultraviolet cut-off edge of the crystal can reach 260nm, the transmittance of the ultraviolet wave band is high, the requirement of new generation photoelectric materials on the working range of short wavelength can be met, and the photoelectric detector can operate under the condition of shorter wavelength (ultraviolet ray). Thus, gallium oxide (. beta. -Ga)₂O₃) Has great application prospect in the fields of high-performance photoelectron, power electronic devices and the like.

At present, the technical difficulty of the ultraprecise processing of gallium oxide crystals lies in high hardness, large brittleness, anisotropy and easy cleavage, and belongs to a typical extremely difficult-to-process material. In conventional crystal processing, a certain amount of pressure must be applied to the wafer in order to increase the material removal rate. However, gallium oxide crystals are easily cleaved and broken under the action of stress, and the processing precision and the surface quality are unstable. In recent years, beta-Ga₂O₃The processing technology of the substrate is similar to the processing of a silicon wafer, a gallium oxide single crystal rod with good growth needs to be sliced, cutting tool marks and microcracks are left on the surface of the gallium oxide single crystal rod after the gallium oxide single crystal rod is cut, generally, a free abrasive grinding technology is adopted to quickly eliminate the tool marks, reduce the thickness of a damaged layer and improve the surface accuracy, then, a diamond grinding wheel is adopted to carry out ultra-precise grinding and mechanical polishing on the gallium oxide single crystal rod, and finally, a CMP (chemical mechanical polishing) technology is adopted to obtain the nondestructive gallium oxide single crystal rodDamaging the planarized surface. Therefore, the effect of the grinding process of gallium oxide crystal is not ideal, since gallium oxide crystal is easily cleaved and broken under stress.

In the field of ultra-precision processing of hard and brittle semiconductor wafers, the processing quality requirement is very high, the mechanical, optical and electrical properties of semiconductor materials can be obviously influenced by surface and subsurface damages caused by production or processing of gallium oxide, and the acquisition of high-quality wafers is the basis of semiconductor device manufacturing, particularly in the mechanical processing process of gallium oxide crystals which are hard and brittle and have strong cleavage property. In the ultra-precision processing, the gallium oxide wafer is often processed by grinding, although beta-Ga₂O₃The characteristic of easy cleavage causes chipping and dishing during grinding, reducing yield, but the grinding process is easier to control than the lapping process. In addition, the research on the ultraprecise processing of the easy-to-understand gallium oxide single crystal substrate at home and abroad is only in the initial exploration stage at present. Therefore, a high efficiency processing method of easily-cleaved semiconductor crystals is urgently needed to make up for the current vacancy.

Disclosure of Invention

In order to overcome the defects of the prior art, the invention provides a processing method of a semiconductor crystal easy to be cleaved, the maximum grinding force is effectively controlled based on a negative feedback system in the whole processing process, and the real-time grinding force in the whole grinding process is ensured to be smaller than the critical grinding force for the gallium oxide crystal to be cleaved; and secondly, the fine-grained diamond grinding wheel is adopted to reduce the fluctuation of the grinding force and reduce the cleavage phenomenon, the cleavage phenomenon in the traditional crystal processing technology (particularly in the grinding stage) is effectively controlled by combining the fine-grained diamond grinding wheel and the cleavage wheel, the finished product rate of the product is improved, and the surface quality of the product is improved.

The technical means adopted by the invention are as follows:

a method for processing an easily-cleaved semiconductor crystal comprises the following steps:

s1, fixing the gallium oxide wafer on a workbench, and arranging a force sensor below the gallium oxide wafer;

s2, starting the coarse-grained diamond grinding wheel and the workbench to rotate;

s3, feeding the coarse-grain diamond grinding wheel above the gallium oxide wafer until the force sensor shows a value, stopping feeding, setting the initial feeding speed of coarse grinding, and setting the maximum grinding force F_CoarseAfter the feeding amount is reached, the gallium oxide wafer is subjected to coarse grinding until the set feeding amount is reached, and the grinding force is ensured to be F in the coarse grinding process_CoarseFluctuating within a range of + -0.1N;

s4, stopping feeding, continuing to grind the roughly ground gallium oxide wafer without feeding, lifting the rough-grained diamond grinding wheel, and stopping the rough-grained diamond grinding wheel and the workbench from rotating;

s5, replacing the coarse-grained diamond grinding wheel with a fine-grained diamond grinding wheel, and starting the fine-grained diamond grinding wheel and the workbench to rotate;

s6, feeding the fine-grained diamond grinding wheel above the gallium oxide wafer after non-feed grinding, stopping feeding until the indication value appears on the force sensor, setting the initial feeding speed of the fine grinding, and setting the maximum grinding force F_{Thin and thin}And after the feed amount is reached, carrying out fine grinding on the gallium oxide wafer until the set feed amount is reached, and ensuring that the grinding force is F in the fine grinding process_{Thin and thin}Fluctuating in the range of + -0.1N.

The gallium oxide wafer is a circular wafer 7, which is adsorbed on the vacuum chuck of the table or fixed on the table, as shown in fig. 2 (b);

or, the gallium oxide wafer is a plurality of small-sized gallium oxide wafers 6 uniformly distributed on a disc in the circumferential direction, and the disc is adsorbed on a vacuum chuck of a workbench or fixed on the workbench, as shown in fig. 2 (a);

and cooling by cooling liquid in the coarse grinding process, the non-feeding grinding process and the fine grinding process, wherein the flow of the cooling liquid is 4-6L/min, and the cooling liquid is deionized water.

In the step S2, the rotation speed of the coarse-grained diamond grinding wheel is 600-;

the rotating speed of the workbench is 200-400r/min, and the rotating speed direction is anticlockwise.

In step S3, the specific steps of feeding the coarse-grained diamond grinding wheel above the gallium oxide wafer until the indication value of the force sensor appears are as follows:

feeding a coarse-grain diamond grinding wheel to a position close to the upper part of the gallium oxide wafer, and then slowly feeding the gallium oxide wafer at a feeding speed of 10 mu m/min until a force sensor shows a value, and stopping feeding;

in the step S3, the initial feeding speed is 0.5-1 μm/min, and the maximum grinding force F_Coarse20-30N, and the feeding amount is 10-20 μm;

in the step S3, the grinding force during rough grinding is ensured to be F through a negative feedback system_CoarseFluctuating within a range of + -0.1N;

the data processor collects grinding force signals measured by the force sensor in real time, amplifies the grinding force signals and transmits the signals to the negative feedback system, the negative feedback system compares the grinding force signals with the set maximum grinding force and feeds the signals back to the control system continuously to control the feeding speed of the coarse-grained diamond grinding wheel, the increase and decrease degree of the feeding speed is related to the difference value between the real-time grinding force and the set maximum grinding force, as shown in a flow chart in figure 3, m and V are_n、V_mIn a certain relationship to ensure that the grinding force is F in the course of rough grinding_CoarseFluctuating within a range of + -0.1N;

the abrasive grain size of the coarse-grain diamond grinding wheel is W10-W14.

In the course of rough grinding, utilizing data processor to analyze grinding force data, feedback-controlling feeding speed of coarse-grain diamond grinding wheel and continuously controlling its maximum grinding force to make it be in a certain fluctuation range (F)_Coarse+/-0.1N) to control the probability of the gallium oxide crystal to be cleaved.

The parameters of the non-feeding grinding are consistent with the parameters of the rough grinding except that the feeding speed is zero;

the grinding time of the non-feeding grinding is 3 min.

The purpose of the non-feeding grinding is to eliminate elastic deformation and cutter back-off amount generated during feeding, improve surface smoothness and prepare for fine grinding.

In the step S5, the rotation speed of the fine-grained diamond grinding wheel is 1000-2400r/min, and the rotation speed direction is clockwise;

the rotating speed of the workbench is 300-400r/min, and the rotating speed direction is anticlockwise.

In step S6, the specific steps of feeding the fine-grained diamond grinding wheel above the gallium oxide wafer after non-feed grinding until the force sensor shows a value, and stopping feeding, are as follows:

feeding a fine-grained diamond grinding wheel to the position above the gallium oxide wafer which is close to the position above the gallium oxide wafer after non-feeding grinding, and then slowly feeding the gallium oxide wafer at a feeding speed of 10 mu m/min until a force sensor shows a value, and stopping feeding;

in the step S6, the initial feeding speed is 0.5-1 μm/min, and the maximum grinding force F_{Thin and thin}30-60N, and the feeding amount is 5-10 μm;

in step S6, the grinding force during the finish grinding process is ensured to be F through a negative feedback system_{Thin and thin}Fluctuating within a range of + -0.1N;

the data processor collects grinding force signals measured by the force sensor in real time, amplifies the grinding force signals, and transmits the signals to the negative feedback system, the negative feedback system compares the grinding force signals with the set maximum grinding force and feeds the signals back to the control system continuously to control the feeding speed of the fine-grained diamond grinding wheel, the increase and decrease degree of the feeding speed is related to the difference value between the real-time grinding force and the set maximum grinding force, as shown in a flow chart in figure 3, and m and V are_n、V_mIn a relationship to ensure grinding forces during finish grinding at F_{Thin and thin}Fluctuating within a range of + -0.1N;

the abrasive grain size of the fine-grained diamond grinding wheel is W1-W5.

During the fine grinding process, the data processor is used to analyze the grinding force data, and the feed speed of the fine-grained diamond grinding wheel is feedback-controlled to continuously control the maximum grinding force in a certain fluctuation range (F)_{Thin and thin}+/-0.1N) to control the probability of the gallium oxide crystal to be cleaved.

Compared with the prior art, the invention has the beneficial effects that:

the invention controls the feeding speed based on the feedback of the force sensor to control the grinding force, and simultaneously adopts the ultra-precision machining method of the fine-grained diamond grinding wheel, thereby effectively solving the problem of the gallium oxide in the mechanical machining stage, particularly the grinding stage, reducing the damage degree and the damage thickness of the damaged layer by using the fine-grained abrasive particles, shortening the time of the subsequent chemical mechanical polishing process and reducing the removal amount of the subsequent chemical mechanical polishing process.

The negative feedback system receives the grinding force signal acquired and amplified by the data processor in real time and feeds the signal back to the control system to control the feeding speed in real time so as to realize that the grinding force is smaller than the gallium oxide cleavage stress threshold value, thus solving the dissociation phenomenon easily occurring in the gallium oxide machining, improving the surface quality of the gallium oxide crystal and realizing high yield.

For the above reasons, the present invention can be widely applied to the fields of ultra-precision processing of hard and brittle semiconductor wafers, and the like.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings needed to be used in the description of the embodiments or the prior art will be briefly introduced below, and it is obvious that the drawings in the following description are some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to these drawings without creative efforts.

FIG. 1 is a schematic view of the anti-cleavage of a process for producing a semiconductor crystal that is easy to cleave in accordance with an embodiment of the present invention.

FIG. 2(a) is a schematic view showing the arrangement of a small-sized gallium oxide wafer holding disk on a work table according to the present invention; fig. 2(b) is a schematic view of the arrangement of the circular wafer on the stage according to the present invention.

FIG. 3 is a flow chart of the control system of the present invention.

In the figure: 1 is a diamond grinding wheel; 2 is gallium oxide wafer; 3 is a vacuum chuck; 4 is a force sensor; 5 is a workbench; 6 is a small-sized gallium oxide wafer; 7 is a circular wafer;

Detailed Description

In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are some, but not all, embodiments of the present invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

As shown in fig. 1, a method for processing an easily-cleaved semiconductor crystal comprises the following steps:

s1, opening the ultra-precision grinding machine, adsorbing a piece of cut 2-inch gallium oxide wafer 2 on the vacuum chuck 3 on the worktable 5 of the ultra-precision grinding machine, and clamping the gallium oxide wafer 2 while the center of the worktable 5 coincides with the center of the gallium oxide wafer 2, as shown in fig. 2 (b);

s2, using a coarse-grained diamond grinding wheel 1, wherein the abrasive granularity of the coarse-grained diamond grinding wheel 1 is W10-W14, adjusting the end face of an abrasive layer of the coarse-grained diamond grinding wheel 1 to the central position of a workbench 5, and then opening cooling liquid, wherein the cooling liquid is deionized water, and the flow rate of the cooling liquid is 4-6L/min; then starting the coarse-grained diamond grinding wheel 1, wherein the rotating speed is 600-; then starting the workbench 5, wherein the rotating speed of the workbench 5 is 200-400r/min, and the rotating speed direction is anticlockwise;

s3, opening the force sensor 4, manually feeding the coarse-grain diamond grinding wheel 1 to a position 1mm above the gallium oxide wafer 2, opening automatic feeding at a feeding speed of 10 mu m/min, turning off the automatic feeding until the force sensor 4 shows a value, then opening a negative feedback system, and simultaneously setting an initial feeding speed V of coarse grinding_i0.5 μm/min, maximum grinding force F_Coarse30N, the feed rate is 20 mu m, then the gallium oxide wafer 2 is subjected to rough grinding until the set feed rate is reached, the negative feedback system receives and amplifies a grinding force signal measured by the force sensor 4 in real time in the rough grinding process, and the signal is continuously fed back to the control system to control the coarse-grained diamond grinding wheel1 feed rate to ensure grinding force at F during rough grinding_CoarseIn the range of + -0.1N, as shown in FIG. 3, to control the probability of cleavage of the gallium oxide crystal. After rough grinding, 3min non-feeding grinding is carried out to prepare for next fine grinding;

s4, lifting the coarse-grained diamond grinding wheel 1, stopping the rotation of the coarse-grained diamond grinding wheel 1 and the workbench 5, replacing the coarse-grained diamond grinding wheel 1 with a fine-grained diamond grinding wheel 1, wherein the abrasive grain size of the fine-grained diamond grinding wheel 1 is W1-W5, adjusting the end face of the abrasive layer of the fine-grained diamond grinding wheel 1 to the central position of the workbench 5, and then opening cooling liquid, wherein the cooling liquid is deionized water, and the flow rate of the cooling liquid is 4-6/min; then starting the fine-grained diamond grinding wheel 1, wherein the rotating speed is 1000-2400r/min, and the rotating speed direction is clockwise; then starting the workbench 5, wherein the rotating speed of the workbench 5 is 300-400r/min, and the rotating speed direction is anticlockwise;

s5, opening the force sensor 4, manually feeding the fine-grained diamond grinding wheel 1 to a position 1mm above the gallium oxide wafer 2 after non-feed grinding, opening automatic feeding, wherein the feeding speed is 10 mu m/min, turning off the automatic feeding after the force sensor 4 shows a value, then opening a negative feedback system, and simultaneously setting the initial feeding speed V of the fine grinding_i0.5 mu m/min, the maximum grinding force Ffine is 60N, the feed rate is 10 mu m, then the gallium oxide wafer 2 is finely ground until the set feed rate is reached, the negative feedback system receives the grinding force signal measured by the force sensor 4 collected and amplified by the data processor in real time in the fine grinding process and feeds the signal back to the control system to control the feed rate of the fine-grained diamond grinding wheel 1 so as to ensure that the grinding force in the fine grinding process is in the F fine grinding process_{Thin and thin}Fluctuating within the range of +/-0.1N, as shown in figure 3, so as to control the probability of the gallium oxide crystal to be cleaved and realize ultra-precise grinding with the grinding force lower than the cleavage grinding force;

after finishing the finish grinding, the gallium oxide wafer 2 may be removed and cleaned, and the ultra-precision grinding of the gallium oxide wafer 2 is completed. Finally, the Ra and TTV of the obtained gallium oxide wafer 2 are measured to be less than or equal to 1nm and less than or equal to 5 mu m.

Finally, it should be noted that: the above embodiments are only used to illustrate the technical solution of the present invention, and not to limit the same; while the invention has been described in detail and with reference to the foregoing embodiments, it will be understood by those skilled in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some or all of the technical features may be equivalently replaced; and the modifications or the substitutions do not make the essence of the corresponding technical solutions depart from the scope of the technical solutions of the embodiments of the present invention.