CN113913236A

CN113913236A - Free abrasive water-based cutting fluid for large-size silicon wafers and preparation method thereof

Info

Publication number: CN113913236A
Application number: CN202111304755.7A
Authority: CN
Inventors: 侯军; 张楠
Original assignee: Dalian Aufirst Technology Co ltd
Current assignee: Dalian Aufirst Technology Co ltd
Priority date: 2021-11-05
Filing date: 2021-11-05
Publication date: 2022-01-11
Anticipated expiration: 2041-11-05
Also published as: CN113913236B

Abstract

A large-size silicon wafer free abrasive water-based cutting fluid and a preparation method thereof belong to the technical field of semiconductor cutting. The cutting fluid comprises polyhydric alcohol and derivatives thereof, hyperdispersant, lubricant, wetting agent and ultrapure water, wherein the polyhydric alcohol is used as a main component, so that the flame retardant and cooling effects are achieved, the warping of a wafer is effectively reduced, and the quality of the wafer is improved. The hyper-dispersant is tightly adsorbed on the SiC surface by the anchoring group, and the solvation section of the hyper-dispersant can be stretched in a dispersion medium to form steric hindrance, so that the green silicon carbide abrasive is prevented from agglomerating to form a stable suspension dispersion system; by utilizing the structural characteristics of a solvent chain of the hyperdispersant, the water-based cutting fluid can be stably stretched in polyhydric alcohol and water to form the water-based cutting fluid which has high dispersibility, high suspension property, easy cleaning and environmental protection.

Description

Free abrasive water-based cutting fluid for large-size silicon wafers and preparation method thereof

Technical Field

The invention relates to a large-size silicon wafer free abrasive water-based cutting fluid and a preparation method thereof, belonging to the technical field of semiconductor cutting.

Background

The early hard and brittle material wafer wire cutting liquid is developed from metal cutting liquid of a knife saw, mainly takes mineral oil as an oily cutting liquid of a main component, is inflammable and has great pollution to the environment, is not easy to clean, needs to use a chlorine-containing alkane solvent, and has a carcinogenic effect on a human body. Therefore, the aqueous cutting fluid is developed, and the cutting fluid widely used in the early stage is prepared by taking polyethylene glycol or polypropylene glycol as a main body and adding various additives, and mainly comprises a lubricant, a penetrating agent, a chelating agent, a defoaming agent, a surfactant, organic alkali and the like. The water-based cutting fluid is a cutting fluid commonly used at home and abroad nowadays due to the characteristics of easy cleaning, no pollution, high ignition point, small corrosivity, high cutting efficiency and yield and the like. However, since a large amount of chips and silicon powder are generated in the silicon ingot cutting process, the chips and the silicon powder are easy to adhere to silicon carbide powder in mortar in cutting fluid and adhere to silicon wafers and gold wire meshes or are deposited at the bottom, so that silicon carbide suspension is layered, the surface roughness of the silicon wafers is influenced, and the cutting efficiency is reduced. And a large amount of heat is emitted during the cutting process, and the wafer is warped due to the heat effect, so that the quality of the wafer is affected.

Nowadays, silicon wafers gradually develop from 2 inches, 4 inches and 6 inches to 8 inches and 12 inches nowadays. With the continuous increase of the size of the silicon ingot, the requirements on the cutting precision and the dispersion suspension property of the used cutting fluid on the grinding material are stricter. At the same time, there is also a more urgent need for the emergence of higher performance products than the prior art.

Disclosure of Invention

The invention aims to provide a water-based free abrasive cutting fluid which has high dispersibility, high suspension property, easy cleaning and environmental protection and can be used for cutting large-size solar silicon wafers, and a preparation method thereof.

It is noted that, in the present invention, unless otherwise specified, specific meanings of "including" in relation to compositional definition and description are inclusive of both open-ended "comprising" and the like, and closed-ended "consisting of …" and the like.

The first purpose of the invention is to provide a water-based free abrasive cutting fluid, which comprises the following components in parts by mass:

the following components in parts by mass are preferred:

the polyhydric alcohol is hydrophilic polyhydric alcohol with low molecular chain such as ethylene glycol, propylene glycol, glycerol, butanediol, etc., and the polyhydric alcohol derivative preferably has the following structure:

R₁-O-R₂-OH

wherein R is₁Is straight chain alkyl radical C_qH_2q+1Q is an integer of 1 to 4; r₂Is straight chain alkyl radical C_pH_2pAnd p is an integer of 2 to 4. For example, ethylene glycol butyl ether (q-4, p-2), propylene glycol butyl ether (q-4, p-3).

The content of the polyol is not less than 40 parts, and the content of the derivative thereof is 0-20 parts. The total mass part of the polyhydric alcohol and the derivative thereof in the cutting fluid is 40 to 60 parts, and can be 40 parts, 45 parts, 50 parts, 55 parts or 60 parts, for example.

The hyper-dispersant is polyurethane anionic non-ionic hyper-dispersant, and the structural general formula (1) is as follows:

wherein the polyurethane (WPU) segment comprises a single-ended dihydroxy polyol, an aliphatic diisocyanate, a dimethylol acid, a hydroxy polyethylene glycol (PEG) carboxylic acid

Siloxane is used as an anchoring group, and hydrophilic poly-polyol or poly-polyol carboxylic acid is used as a solvating chain segment.

Among them, the mono-terminal dihydric polyol is preferably a nonionic polyester diol (A). The preferred structure of the aliphatic diisocyanate is O ═ C ═ N-R-N ═ C ═ O, R is straight chain alkyl group C_xH_2x+1(x is an integer of 6 to 12), or a cycloalkane group C_yH_2y-1(y is an integer from 8 to 16), preferably branched alkanes where x is 6 and y is 8. The dimethylol acid is preferably 2, 2-dimethylol propionic acid(B1) Or 2, 2-dimethylolbutanoic acid (B2). The average molecular weight of the hydroxyl PEG carboxylic acid is 400-1000, and the average molecular weight is preferably 400 (D).

As shown in FIG. 1, in the hyperdispersant action system, the hyperdispersant adheres closely to the particle surface with its anchor segment, and the solvating segment extends in the dispersion medium. When two particles adsorbed with hyper-dispersant molecules are brought together, the osmotic pressure will increase due to the increasing polymer concentration in the overlapping area. In this case the polymer chain links also produce entropic repulsion due to restricted motion. Both of these conditions cause the particles to spring apart by the repulsive force and return to the original state in which they do not aggregate.

The surface of silicon carbide (SiC) powder is composed of an oxide film, and the main functional group of the surface thereof is a silanol group. Aiming at the structural characteristics, siloxane capable of forming a covalent bond with the abrasive is selected as an anchoring group, the anchoring group of the hyperdispersant is hydrolyzed to form silicon hydroxyl, and the silicon hydroxyl is condensed with the silicon hydroxyl on the surface of the abrasive to form the covalent bond, so that the silicon hydroxyl is anchored on the surface of the SiC particle; the hydrophilic polymeric polyol segment acts as a solvating segment to allow stable dispersion of the SiC abrasive in water, with the anchoring mechanism shown in fig. 2.

The lubricant is fatty alcohol polyether, preferably a mixture of one or more of EO-PO random polyether which is a water-soluble copolymer of Ethylene Oxide (EO) and Propylene Oxide (PO) in any proportion, and has the following structural general formula, wherein n: m is preferably 1: 1-4: 1.

The wetting agent is polyacrylate, organosilicon, sulfosuccinate and modified alkoxy wetting agent, and fluorinated polyacrylate wetting agent is preferred.

The ultrapure water is deionized water with the resistance of at least 18M omega. The addition of the deionized water effectively improves the cooling effect of the cutting fluid, improves the cleaning capability, increases the flame retardance and greatly reduces the production cost.

Namely, the water-based free abrasive cutting fluid comprises the following components in parts by mass: 40-60 parts of the polyhydric alcohol, 10-25 parts of the hyperdispersant of the formula (1), 1-8 parts of the lubricant, 0.05-1 part of the wetting agent and 20-60 parts of the ultrapure water.

In addition, an abrasive material may be added in an amount of 0.8 to 1.0 times by mass relative to the cutting fluid, the abrasive material being selected from silicon carbide, quartz sand, black silicon carbide, green silicon carbide, and the like. Among them, green silicon carbide is preferable.

The second purpose of the invention is to provide a preparation method of the water-based cutting fluid, which comprises the following steps:

s1: adding the wetting agent, the lubricant, the polyol and the derivatives thereof into water in sequence, and stirring and mixing uniformly.

S2: slowly adding the hyperdispersant under stirring, increasing the stirring speed to 1500-2000 r/min, and stirring for 15-30 min.

The third purpose of the invention is to provide the application of the water-based cutting fluid for cutting large-size silicon wafers.

The fourth purpose of the invention is to provide a method for preparing cutting mortar by using the water-based cutting fluid, which comprises the following steps:

p1: weighing the mixed water-based cutting fluid, putting the water-based cutting fluid into a container, and weighing an abrasive material with the mass of 0.8-1.0 time of that of the cutting fluid;

p2: and keeping the rotating speed of 500 plus 800r/min, pouring the grinding material into the cutting fluid, and stirring for 1-2h to obtain the prepared cutting mortar.

As described above, the present invention provides a water-based free abrasive cutting fluid and a method for preparing the same, which have the following advantages:

1. the hyper-dispersant is tightly adsorbed on the surface of SiC by the anchoring group, and the solvation section of the hyper-dispersant can be stretched in a dispersion medium to form steric hindrance, so that green silicon carbide powder is prevented from agglomerating to form a stable suspension dispersion system.

2. The cutting fluid has the advantages that the polyhydric alcohol is introduced into the formula of the cutting fluid as a main component, so that the flame retardant and cooling effects are achieved, the warping of the wafer is effectively reduced, and the quality of the wafer is improved.

3. By utilizing the structural characteristics of a solvent chain of the hyperdispersant, the water-based cutting fluid can be stably stretched in polyhydric alcohol and water to form the water-based cutting fluid which has high dispersibility, high suspension property, easy cleaning and environmental protection.

Therefore, the water-based cutting fluid has very good application prospect and large-scale industrialized popularization potential in the field of large-size silicon wafer cutting.

Drawings

FIG. 1 is a schematic diagram of the action of a hyperdispersant.

FIG. 2 is a diagram of the mechanism of the anchoring of the hyperdispersant with SiC.

FIG. 3 shows the contact angle of the cutting fluid (without abrasive) on the silicon wafer of example 2, after the droplet is stabilized at 37.1 deg.

FIG. 4 shows the contact angle of the cutting fluid (without abrasive) on the silicon wafer of comparative example 1, which is 55.5 after the droplet is stabilized.

FIG. 5 is a particle size distribution diagram of the cutting mortar of the example.

FIG. 6 is a particle size distribution diagram of a comparative cutting mortar.

Fig. 7 is a schematic diagram of a test of cooling ability.

Detailed Description

Examples 1 to 12

A free abrasive water-based cutting fluid for large-size silicon wafers comprises the following components:

adding the wetting agent, the lubricant, the polyol and the derivatives thereof into water in sequence according to the formula, and stirring and mixing uniformly; slowly adding the hyperdispersant under stirring, increasing the stirring speed to 1500r/min, and stirring for 15 min; cutting fluids of examples 1-12 were prepared.

wherein the polyurethane (WPU) segment comprises a single-terminal dihydroxy polyol, an aliphatic diisocyanate, a dimethylol acid, a hydroxy polyethylene glycol (PEG) carboxylic acid

Wherein, the single-end dihydroxy polyalcohol is preferably nonionic polyester dihydric alcohol Ymer N120 (A); the preferred structure of the aliphatic diisocyanate is O ═ C ═ N-R-N ═ C ═ O, R is straight chain alkyl group C_xH_2x+1(x is an integer of 6 to 12), or a cycloalkane group C_yH_2y-1(y is an integer of 8 to 16).

The dimethylol acid is preferably 2, 2-dimethylol propionic acid (B1) or 2, 2-dimethylol butyric acid (B2).

The average molecular weight of the hydroxypeg carboxylic acid is 400-1000.

TABLE 1 cutting fluids of examples 1-12

Comparative examples 1 to 3

Adding the wetting agent, the lubricant, the polyol and the derivatives thereof into water in sequence according to the following table, and stirring and mixing uniformly; slowly adding the hyperdispersant under stirring, increasing the stirring speed to 1500r/min, and stirring for 15 min; the cutting fluids of comparative examples 1-3 were prepared.

TABLE 2 cutting fluids of comparative examples 1-3

EXAMPLE 13 testing of suspensibility

The suspension property test method comprises the following steps:

and (3) filling the uniformly mixed cutting mortar into a 25ml graduated test tube, and standing. The sedimentation heights after standing for 1, 3, 5, 8, 10, 15, 20 and 24 hours (the value of the 24-hour standing height is taken) are observed, and the respective suspension performances are examined according to the sedimentation heights. The test results are shown in Table 3, with smaller sedimentation heights indicating better suspension. The cutting fluids of examples 1-12 had 24h static settling heights of 10-25%, while the cutting fluids of comparative examples had 24h static settling heights of 45%, 52%, 68%, and the cutting fluids of examples had 24h static settling heights much less than those of comparative examples, indicating that the cutting fluids of examples had better suspension properties.

Example 14 testing of dispersibility

The dispersibility test method is as follows:

and testing the particle sizes of the SiC particles in different cutting fluids by adopting a laser particle size analyzer, so as to investigate the dispersion capability of the SiC particles. The results are shown in Table 3, where a smaller particle size distribution indicates better dispersibility. In the examples 1 to 12, the abrasive grains are completely distributed in the range of 3 to 12 μm and normally distributed, which shows that the abrasive grains have good dispersibility in the cutting fluid and no aggregation of the grains. In the comparative example, the particle diameters of the particles are mainly distributed between 3 and 19 mu m, and a second distribution peak appears between 30 and 60 mu m, which indicates that the abrasive has particle aggregation in the cutting fluid.

EXAMPLE 15 test of Cooling Properties

The test method of the cooling performance comprises the following steps:

the mechanism of the cooling property test is shown in fig. 7, and the surface temperature change of the hot silicon wafer before and after the liquid pouring is detected by a surface thermometer. The test results are shown in Table 3, with greater temperature change indicating better cooling. The cooling change temperatures of examples 1 to 12 were between 28 and 39, and the cooling change temperatures of comparative examples were 9, 13 and 14, and the cutting fluids of examples 1 to 12 exhibited better cooling performance.

EXAMPLE 16 testing of wettability

The test method of wettability is as follows:

and testing the dynamic contact angles of different cutting fluids on the surface of the silicon wafer by using a contact angle meter to investigate the wetting capacity of the cutting fluids on the silicon wafer. The test results are shown in Table 3, and the smaller the contact angle, the stronger the wetting ability of the cutting fluid. The contact angles of examples 1-12 are below 35.2 degrees, while the contact angles of comparative examples 1-3 are between 56-64 degrees, the contact angles in the examples are much smaller than those in the comparative examples, indicating that the cutting fluid in the application has better wetting ability.

TABLE 3 Performance test cases for examples 1-12 and comparative examples 1-3

Examples/comparative examples	Reduction of height/% of sedimentation	Particle size distribution Range/. mu.m	Cooling variation temperature/. degree.C	Contact Angle/°
					Example 1	15	3～15	28	34.5
Example 2	18	3～15	30	37.1
					Example 3	10	3～15	35	31.3
Example 4	12	3～15	33	33.7
					Example 5	20	3～15	31	35.0
Example 6	21	3～15	27	34.6
					Example 7	18	3～15	28	33.9
Example 8	15	3～15	33	34.2
					Example 9	19	3～15	32	34.1
Example 10	23	3～15	39	33.7
					Example 11	25	3～15	35	34.2
Example 12	22	3～15	36	34.4
					Comparative example 1	45	3～19	14	55.5
Comparative example 2	52	3～19	13	58.3
					Comparative example 3	68	30～60	9	63.2

As can be seen from the above table, the test results of examples 1-12 are significantly better than those of comparative examples 1-3. And examples 3 and 4 are preferred embodiments of the present application, which have superior results to other examples. The test results in table 3 show that the cutting fluid of the preferred embodiment has small sedimentation height, normal distribution of particle size and small distribution range, and the dispersibility and suspension property of the abrasive in the cutting cooling fluid are always kept in a stable state, so that the acting force of the abrasive on the crystal ingot is more uniform in the cutting process; when the contact angle is smaller, the mortar has better infiltration capacity among the wafers; the cooling capacity is improved, and the heat generated in the cutting process can be effectively reduced; and further, the problems of high warping degree, low flatness and the like caused by the problems of uneven dispersion of the abrasive in the water-based cutting fluid, poor suspension, high temperature and the like in the process of cutting the large-size wafer are obviously improved.

It should be understood that these examples are for illustrative purposes only and are not intended to limit the scope of the present invention. Further, it should also be understood that various alterations, modifications and/or variations can be made to the present invention by those skilled in the art after reading the technical content of the present invention, and all such equivalents fall within the protective scope defined by the claims of the present application.

Claims

1. A free abrasive water-based cutting fluid for large-size silicon wafers is characterized in that: the water-based cutting fluid comprises the following components in parts by mass:

the content of the polyhydric alcohol and the derivative thereof is not less than 40 parts, and the content of the derivative thereof is 0-20 parts; the hyper-dispersant is polyurethane anionic non-ionic hyper-dispersant and comprises an anchoring group, a polyurethane chain segment and a solvation chain segment, wherein the anchoring group is arranged at one end of the polyurethane chain segment, and the solvation chain segment is arranged on the polyurethane chain segment; the anchoring group adopts siloxane group, the polyurethane chain segment comprises single-ended dihydroxy polyol, aliphatic diisocyanate, dimethylol acid and hydroxy polyethylene glycol carboxylic acid, and the solvation chain segment adopts poly-polyol or poly-polyol carboxylic acid;

the lubricant is fatty alcohol polyether, and the fatty alcohol polyether is a water-soluble copolymer of ethylene oxide and propylene oxide; the wetting agent is polyacrylate, organosilicon, sulfosuccinate and modified alkoxy wetting agent.

2. The free abrasive water-based cutting fluid for large-size silicon wafers as claimed in claim 1, wherein: the water-based cutting fluid comprises the following components in parts by mass:

3. the free abrasive water-based cutting fluid for large-size silicon wafers as claimed in claim 1, wherein: the polyalcohol is hydrophilic polyalcohol with C2-4 low molecular chain, and the structural general formula of polyalcohol derivative is as follows:

R₁-O-R₂-OH

wherein R is₁Is straight chain alkyl radical C_qH_2q+1Q is an integer of 1 to 4; r₂Is straight chain alkyl radical C_pH_2pAnd p is an integer of 2 to 4.

4. The free abrasive water-based cutting fluid for large-size silicon wafers as claimed in claim 1, wherein: the single-end dihydroxy polyalcohol in the hyperdispersant is nonionic polyester dihydric alcohol;

of the aliphatic diisocyanatesThe general structural formula is O ═ C ═ N ═ C ═ O, wherein R is linear alkyl C_xH_2x+1Or cycloalkyl radical C_yH_2y-1(ii) a Wherein x is an integer of 6 to 12, and y is an integer of 8 to 16;

the dimethylol acid is 2, 2-dimethylolpropionic acid or 2, 2-dimethylolbutyric acid;

the average molecular weight of the hydroxy polyethylene glycol carboxylic acid is 400-1000.

5. The free abrasive water-based cutting fluid for large-size silicon wafers as claimed in claim 4, wherein: straight chain alkyl C_xH_2x+1Wherein x is 6, cycloalkyl C_yH_2y-1Wherein y is 8; the average molecular weight of the hydroxypolyethylene glycol carboxylic acid is 400.

6. The free abrasive water-based cutting fluid for large-size silicon wafers as claimed in claim 1, wherein: the structural general formula of the fatty alcohol polyether is as follows:

wherein n: m ranges from 1:1 to 4: 1.

7. The free abrasive water-based cutting fluid for large-size silicon wafers as claimed in claim 1, wherein: the wetting agent is polyacrylate, organosilicon, sulfosuccinate and modified alkoxy wetting agent, preferably fluorinated polyacrylate wetting agent; the ultrapure water is deionized water with the resistance of at least 18M omega.

8. The preparation method of free abrasive water-based cutting fluid for large-size silicon wafers as claimed in claim 1, characterized by comprising the following steps:

s1: adding the wetting agent, the lubricant, the polyol and the derivatives thereof into ultrapure water in sequence, and stirring and mixing uniformly;

9. The method for preparing cutting mortar by using free abrasive water-based cutting fluid for large-size silicon wafers as claimed in claim 1, comprising the following steps of:

p1: weighing the water-based cutting fluid, putting the water-based cutting fluid into a container, and weighing an abrasive material with the mass of 0.8-1.0 time that of the cutting fluid;

the abrasive is selected from carborundum, quartz sand, black silicon carbide and green silicon carbide;

p2: and keeping the rotating speed of 500-.

10. The free abrasive water-based cutting fluid for large-size silicon wafers, as claimed in claim 1, is used for cutting large-size silicon wafers.