阅读说明：本技术 一种铌酸锂单晶的变速切割方法 (Variable-speed cutting method of lithium niobate single crystal ) 是由 王雄龙 杨洪星 张伟才 杨静 李聪 陈晨 索开南 庞炳远 于 2019-11-18 设计创作，主要内容包括：本发明公开了一种铌酸锂单晶的变速切割方法。基本步骤为：1、用胶水粘接铌酸锂单晶,保证晶向在合格范围内；2、聚乙二醇和碳化硅微粉按照一定比例配置成切割砂浆；3、将粘接好的铌酸锂单晶放入多线切割机的工作台工位中,将工作台的匀速进给切割过程改为按照切割位置分段的不同速度的进给切割；4、切割后的铌酸锂晶片进行脱胶、清洗、干燥。本发明采用的切割方法操作简单；一次切割可得到数百片晶片,切割效率高；切割后的几何参数优于定速多线切割后样片的几何参数；通过公式可以快速找到合适的切割速度,进而设置较为合理的切割程序,可以避免反复试验,节省了时间和物料。(The invention discloses a variable-speed cutting method of lithium niobate single crystals. The method comprises the following basic steps: 1. bonding the lithium niobate single crystal by glue to ensure that the crystal orientation is in a qualified range; 2. preparing cutting mortar from polyethylene glycol and silicon carbide micropowder according to a certain proportion; 3. placing the bonded lithium niobate single crystal into a working table station of a multi-wire cutting machine, and changing the constant-speed feeding cutting process of the working table into feeding cutting at different speeds according to the cutting position in a segmented mode; 4. and degumming, cleaning and drying the cut lithium niobate wafer. The cutting method adopted by the invention is simple to operate; hundreds of wafers can be obtained by one-time cutting, and the cutting efficiency is high; the geometric parameters after cutting are superior to those of the sample wafer after constant-speed multi-line cutting; can find suitable cutting speed fast through the formula, and then set up comparatively reasonable cutting procedure, can avoid the repetition test, save time and material.)

1. A variable-speed cutting method of lithium niobate single crystals is characterized in that a mortar type multi-wire cutting machine is used as cutting equipment, mortar prepared from polyethylene glycol and silicon carbide micropowder is used, and a variable-speed cutting process is used for cutting the lithium niobate single crystals, and the method comprises the following steps:

determining the crystal orientation of the lithium niobate single crystal, and bonding the lithium niobate single crystal to a proper resin strip by glue;

secondly, preparing mortar by using polyethylene glycol and silicon carbide micro powder, wherein the mass ratio of the polyethylene glycol to the silicon carbide micro powder is (0.9-1.1): 1, and the mortar density is (1.6-1.65) kg/m³(ii) a Stirring and mixing polyethylene glycol and silicon carbide micro powder for more than 4 hours to be used as cutting mortar of the multi-wire cutting machine; injecting the prepared mortar into a mortar tank of the multi-wire cutting machine, automatically extracting the mortar by equipment, spraying the mortar onto a cutting wire, and then starting cutting;

(III) the variable-speed cutting process of the lithium niobate single crystal: the wire diameter of the cutting wire is 0.12-0.16 mu m, the tension of the cutting wire is 20-23N, and the feeding speed range is 0.135-0.5 mm/min;

(IV) adjusting according to the cutting position of the lithium niobate single crystal, dividing the whole cutting process into 10-20 sections, ensuring that the cutting areas of the cutting lines in unit time are basically the same, and calculating the cutting speed by the following formula:

in the formula:v: cutting speed;V: the volume of the cutting seam is lost;L: a length of the single crystal;d _w : the diameter of the cutting line;d: the slot spacing;s: the thickness of the mortar layer is increased,R: the radius of the single crystal;h: a cutting position;

and (V) after the cutting process is finished, placing the lithium niobate single crystal into a degumming machine for degumming, wherein the degumming process adopts a lactic acid solution for soaking, the temperature of the lactic acid solution is room temperature-70 ℃, and the volume ratio is lactic acid: water =1: (0-3);

and (VI), putting the wafer into a cleaning machine for cleaning, washing off residual mortar particles and metal residues on the surface, and putting the wafer into a spin dryer for spin-drying after cleaning to obtain the lithium niobate wafer.

2. The method for cutting a lithium niobate single crystal at a variable speed according to claim 1, wherein in the step (ii), the particle size of the silicon carbide fine powder is 1500 #.

Technical Field

The invention relates to a cutting method of a lithium niobate single crystal, in particular to a variable-speed multi-wire cutting method of the lithium niobate single crystal, and particularly relates to a cutting method of a lithium niobate wafer with higher requirements on geometric parameters.

Background

The processing technology of the lithium niobate wafer is similar to that of a silicon wafer, and semiconductor technologies such as photoetching, film coating and the like are applied to a single wafer to form a layer of metal, then patterning is carried out, and then cutting is carried out to obtain the chip. In the whole process, the requirement on the geometric parameters of the lithium niobate wafer is higher. In order to obtain a high-geometry lithium niobate wafer, the geometry needs to be controlled from the beginning of the dicing step.

In the past, the traditional cutting method is inner circle cutting or outer circle cutting, the efficiency is low, the loss is large, and the multi-line cutting process is adopted at present. The multi-wire cutting process is widely applied to the semiconductor industry and the photovoltaic industry, and can be applied to cutting of various materials such as silicon, germanium, gallium arsenide, indium phosphide, crystal, sapphire, lithium niobate/lithium tantalate and the like. The traditional multi-line cutting is constant-speed cutting, the feeding speed of a cutting line is fixed, the geometric parameters of a wafer obtained by cutting are poor, the bending degree is large, and the flatness is low. Researchers believe that the main reasons are: in the constant-speed cutting process, the volume of single crystals removed by the cutting line in unit time is increased and then reduced, and the heat generated by cutting is not uniform, thereby influencing the flatness of the wafer. In order to ensure the cutting effect, the current mainstream cutting mode is variable speed cutting, the cutting speed is firstly high and then low and then is high, the single crystal volume removed by the cutting line in unit time is basically the same, the generated heat is uniform, and the cutting effect is good.

At present, the semiconductor silicon material industry generally adopts a variable-speed cutting mode. It is considered that this cutting method is applied to cutting of a lithium niobate single crystal. However, no report of the variable-speed multi-wire cutting process of the lithium niobate can wafer is found at present, so the invention researches the variable-speed multi-wire cutting process of the lithium niobate can wafer.

Disclosure of Invention

In view of the state of the art, it is an object of the present invention to provide a method for variable speed multi-wire cutting of a lithium niobate single crystal. According to the difference of the interface position of the lithium niobate single crystal in the multi-wire cutting process, the corresponding cutting length is different, the cutting speed needs to be changed correspondingly, and the constant speed feeding of the worktable of the multi-wire cutting machine is changed into the variable speed feeding. The method comprises mortar preparation, cutting speed control, degumming method and the like. The method is adopted to cut the lithium niobate single crystal, and the lithium niobate wafer with better geometric parameters can be obtained. The invention uses a variable speed cutting method, a mortar type multi-wire cutting machine is used for cutting the lithium niobate single crystal, and the lithium niobate wafer can be obtained after lactic acid degumming.

The technical scheme adopted by the invention is as follows: a variable-speed cutting method of lithium niobate single crystals is characterized in that a mortar type multi-wire cutting machine is used as cutting equipment, mortar prepared from polyethylene glycol and silicon carbide micropowder is used, and a variable-speed cutting process is used for cutting the lithium niobate single crystals, and the method comprises the following steps:

and (I) determining the crystal orientation of the lithium niobate single crystal, and adhering the lithium niobate single crystal to a proper resin strip by using glue.

Secondly, preparing mortar by using polyethylene glycol and silicon carbide micro powder, wherein the mass ratio of the polyethylene glycol to the silicon carbide micro powder is (0.9-1.1): 1, and the mortar density is (1.6-1.65) kg/m³(ii) a Stirring and mixing polyethylene glycol and silicon carbide micro powder for more than 4 hours to be used as cutting mortar of the multi-wire cutting machine; and injecting the prepared mortar into a mortar tank of the multi-wire cutting machine, automatically extracting the mortar by the equipment, spraying the mortar onto a cutting wire, and then starting cutting.

(III) the variable-speed cutting process of the lithium niobate single crystal: the diameter of the cutting line is 0.12-0.16 μm, the tension of the cutting line is 20-23N, and the feeding speed is 0.135-0.5 mm/min.

(IV) adjusting according to the cutting position of the lithium niobate single crystal, dividing the whole cutting process into 10-20 sections, ensuring that the cutting areas of the cutting lines in unit time are basically the same, and calculating the cutting speed by the following formula:

in the formula:v: cutting speed;V: the volume of the cutting seam is lost;L: a length of the single crystal;d _w : the diameter of the cutting line;d: the slot spacing;s: the thickness of the mortar layer is increased,R: the radius of the single crystal;h: the cutting position.

And (V) after the cutting process is finished, placing the lithium niobate single crystal into a degumming machine for degumming, wherein the degumming process adopts a lactic acid solution for soaking, the temperature of the lactic acid solution is room temperature-70 ℃, and the volume ratio is lactic acid: water =1: (0-3).

And (VI), putting the wafer into a cleaning machine for cleaning, washing off residual mortar particles and metal residues on the surface, and putting the wafer into a spin dryer for spin-drying after cleaning to obtain the lithium niobate wafer.

In the step (II), the grain diameter of the silicon carbide micro powder is 1500 #.

At present, the semiconductor silicon material industry generally adopts a variable-speed cutting mode. Theoretically, the same area is covered by the cutting line per unit time, and the same amount of heat is generated. Since the contact area between the cutting line and the single crystal is increased and then decreased in the cutting process, the cutting speed also needs to be adjusted to be fast before slow. If the cutting speed is kept constant, the cutting wire generates the most heat when being fed to the vicinity of the diameter portion of the single crystal, and the mortar has difficulty in taking away a large amount of heat, resulting in heat accumulation. It is this accumulated heat that acts on the wafer itself, causing warping and bowing of the wafer and deterioration of the geometric parameters. It is conceivable to apply the variable-speed cutting method to cutting of the lithium niobate single crystal.

The invention has the following function principle: in the multi-wire cutting process, the contact area between the cutting wire and the single crystal is increased firstly and then reduced. To ensure that the volume removed per unit time is substantially the same, it is necessary to slow the speed of the cutting line from fast to fast. Heat is generated during the cutting process, and the larger the single volume removed per unit time, the more heat is generated. After the cutting speed is adjusted, when the cutting line reaches the position close to the diameter part of the single crystal, the contact area of the cutting line and the single crystal is the largest, and the speed needs to be reduced to the slowest; the cutting speed can be adjusted to be fastest immediately after the cutting line has come into contact with the single crystal and the cutting process is about to end.

The invention has the following beneficial effects: 1. the cutting speed is not a fixed value, so that the wire breakage probability under the condition of excessively high cutting speed can be reduced. 2. The cut lithium niobate wafer has better geometric parameters and smaller removal amount of the subsequent processing technology. 3. The cutting efficiency is high, the whole single crystal can be completely cut into wafers by cutting each time, and the efficiency is higher than that of inner circle cutting and single line cutting. 4. The cutting speed can be given according to a formula, then fine setting is carried out according to the condition in actual production, suitable cutting speed is found fast, repeated tests are avoided, and time and materials are saved.

Drawings

FIG. 1 is a schematic view of a cut from an end face of a single crystal;

FIG. 2 is a schematic view of the cut from the side of the single crystal as viewed from the main roller wire chase.

Detailed Description

The present invention will be further described with reference to the following examples.

Assuming approximately equal areas are cut per unit time, the volume of single crystal removed should also be approximate, thus allowing for the determination of the volume of single crystal removed per unit time, i.e., the kerf loss volume. As can be seen from FIG. 1, in a very short timetIn the above, the upper and lower chord lengths of the area passed by the cutting line are substantially the same, and the passed area is considered to be substantially rectangular, and the width of the rectangle isv*tThe length is the chord length. At a certain cutting positionhThe chord length can be determined by trigonometric functions. As can be seen from fig. 2, the single crystal removal volume is the portion occupied by the cutting line and the slurry layer. Thus, the volume of single crystals removed per unit time can be considered as highv* tThe length is a chord length, and the width is a cuboid with the cutting line and the thickness of the mortar layer occupying the width. The following equation is derived from the geometric relationship:

in the formula:v: cutting speed;V: the volume of the cutting seam is lost;L: a length of the single crystal;d _w : the diameter of the cutting line;d: the slot spacing;s: the thickness of the mortar layer is generally 30 μm;Rthe radius of the single crystal;h: the cutting position.