Low-K wafer cutting protection liquid, preparation method, use and cutting protection method

Abstract

The present invention provides a water-based cutting protection liquid for Low-K wafers, a preparation method, a purpose, a Low-K wafer cutting protection method using the protection liquid, etc. The protection liquid includes a water-soluble polymer, a wetting agent, a solubilizer, a defoaming agent and ultrapure water, wherein a mixture of relatively low molecular weight PEO / PEG and low molecular weight PVP is adopted to form a dense network molecular arrangement, thereby forming a dense film layer on the wafer, blocking the heat and slag generated during the laser cutting process of the Low-K wafer. At the same time, in the subsequent cutter wheel cutting, the silicon chips generated by the cutting can be wrapped, playing the role of suspending and dispersing particles and cleaning the wafer. Therefore, the water-based cutting protection liquid can be simultaneously applied to the laser cutting protection and cutter wheel cutting protection of Low-K wafers without the need to switch the protection liquid, which can greatly improve production efficiency and reduce production costs, and facilitate automatic control and yield control.

Description

Technical Field

[0001] The present invention relates to a composition used in semiconductor processing, a preparation method, its use, and a cutting protection method using the same. More specifically, it relates to a cutting protection liquid for Low-K wafers, its preparation method, its use, and other specific aspects, belonging to the field of precision semiconductor processing technology and applications. Background Art

[0002] With the advancement of science and technology, and in particular the rapid development of ultra-large-scale integrated circuits (VLSI), the integration density of chips continues to increase while feature sizes continue to decrease. However, this is accompanied by increases in the resistance, inter-line capacitance, and inter-layer capacitance of metal interconnects, leading to increases in resistance-capacitance (RC) delay time, crosstalk noise, and power consumption. These issues have become significant and critical factors limiting the further development of integrated circuits.

[0003] Inside an integrated circuit, interconnects on different layers require ILD (Inter Layer Dielectrics) to isolate and support each other. Due to the presence of ILD, parasitic capacitance is inevitably present between the wires.

[0004] In order to solve the above problems, especially to improve the computing speed of the chip, on the one hand, Cu metal interconnects can be used instead of Al metal to reduce parasitic resistance. On the other hand, low-k dielectric materials (k<3) can be used instead of SiO2 (where k=3.9-4.2) as ILD, which can effectively reduce the parasitic capacitance between metal interconnects, thereby improving the stability and operating frequency of the chip.

[0005] Low-K materials are primarily used in process technologies at 0.13μm and below. By combining Low-K materials with copper metal interconnect technology, they can significantly reduce circuit parasitic capacitance (Cu has a much lower resistivity than Al, significantly reducing parasitic resistance). This approach can improve chip stability and operating frequency. Precisely because of these advantages, Low-K processes are currently a key focus of integrated circuit development, particularly in areas such as logic operations and storage, where they are the mainstream approach.

[0006] On the other hand, diamond cutting wheels are difficult to cut Low-K materials because the direct impact of diamond cutting wheels can cause splashing, chipping, cracking, passivation, metal layer lifting and other undesirable appearance phenomena. Therefore, in the field of wafer processing, laser cutting is first used to remove the Low-K layer on the surface of the silicon wafer, and then the cutting wheel is used to cut the silicon and other substrate materials.

[0007] Before laser cutting, the wafer surface needs to be covered with a temporary protective coating to prevent the silicon vapor vaporized by heat during laser cutting from condensing and depositing on the wafer. During the wheel cutting process, fine contamination residues or particles such as silicon chips are generated, which can adhere to the wafer surface and accumulate in the welding area and slot positions, which can cause abnormalities in subsequent packaging operations. At the same time, the exposure of the welding area can lead to metal corrosion and cause device failure. To solve these problems, the sawing area and the rotating wheel are usually immersed in a certain proportion of the wheel cutting protection liquid at a high flow rate during wheel cutting.

[0008] The prior art discloses a variety of laser cutting protection fluids and cutter wheel cutting protection fluids for separate use, but there are still few public reports on new multifunctional cutting protection fluids that can be used for both cutting methods.

[0009] Therefore, it is necessary to develop a universal composition that can be used for both laser cutting and cutter wheel cutting of wafers with Low-K materials to prevent silicon vapor condensation and deposition during laser cutting and to prevent contamination by pollutants during cutter wheel cutting. This is one of the current research hotspots and difficulties in the field of Low-K wafers, which has very important industrial significance for improving cutting efficiency, reducing production costs, and improving product yield. Summary of the Invention

[0010] The present invention is a creative result of in-depth research and design to avoid and solve many problems such as silicon vapor deposition and tiny particle contamination of Low-K wafers caused by laser cutting and wheel cutting.

[0011] More specifically, the present invention aims to provide a water-based cutting protection fluid for Low-K wafers and its associated technical solutions (including its preparation method, its use, and a cutting protection method using the same). This cutting protection fluid has excellent film-forming properties, capable of forming a smooth and flat protective film. It can also form a water-soluble protective film during laser cutting to isolate silicon slag contamination. It can also prevent defects such as silicon chip residue during wheel cutting. These remarkable advantages can significantly improve the processing yield of precision semiconductor components, greatly enhance processing efficiency, and significantly reduce production costs.

[0012] It should be noted that, in the present invention, unless otherwise specified, the specific meaning of "including" in relation to composition limitations and descriptions includes both open-ended "including", "comprising", etc. and similar meanings, as well as closed-ended "consisting of..." etc. and similar meanings.

[0013] The present invention mainly relates to the following specific technical solutions.

[0014] [The first technical solution]

[0015] The first technical solution, one purpose of the present invention is to provide a water-based cutting protection liquid for Low-K wafers (hereinafter sometimes also referred to as "water-based cutting protection liquid" or "cutting protection liquid" or "protective liquid" or "wafer cutting protection liquid" or "water-based protection liquid", all of which have the same meaning).

[0016] The water-based cutting protection fluid comprises a water-soluble polymer, a wetting agent, a solubilizer, a defoaming agent and ultrapure water.

[0017] More specifically, the water-based cutting protection liquid comprises the following components in parts by mass:

[0018]

[0019] In the water-based cutting protection fluid of the present invention, the mass fraction of the water-soluble polymer is 1-20 parts, for example, 1 part, 2 parts, 5 parts, 10 parts, 15 parts or 20 parts.

[0020] The water-soluble polymer is selected from any one or more of polyethylene glycols (PEG), polyvinyl alcohols, polyacrylic acids, polyethylene oxides (PEO), polyacrylamides, polyvinyl pyrrolidones, carboxymethyl cellulose and polyether esters.

[0021] Among them, preferably, the polyethylene glycol polymer is an oligomer with an average molecular weight of 200-600, for example, 200, 300, 400, 500 or 600; the average molecular weight of the polyethylene oxide is 100,000-400,000, for example, 100,000, 150,000, 200,000, 250,000, 300,000, 350,000 or 400,000; the average molecular weight of the polyvinyl pyrrolidone polymer is K30 (i.e., the number average molecular weight is 40,000) or K60 (i.e., the number average molecular weight is 160,000), and K30 is most preferred.

[0022] More preferably, the water-soluble polymer is any one or more of the above-mentioned polyethylene glycol polymer (PEG), polyethylene oxide (PEO) and the above-mentioned polyvinyl pyrrolidone polymer (PVP).

[0023] Still further preferably, the water-soluble polymer is most preferably a mixture of three substances of the above-mentioned polyethylene glycol polymer (PEG), polyethylene oxide (PEO) and the above-mentioned polyvinyl pyrrolidone polymer (PVP), wherein the mass ratio of the three, i.e., the mass ratio of PEG:PEO:PVP is 1-2:0.5-1:3-10, and further preferably 1-2:0.5-0.8:5-8, wherein 1-2 involving PEG includes 1, 1.5 or 2 thereof, 0.5-0.8 involving PEO includes 0.5, 0.6, 0.7 or 0.8 thereof, and 5-8 involving PVP includes 5, 6, 7 or 8 thereof. Any combination of these specific point values ​​is included in the range of 1-2:0.5-0.8:5-8, and they are not listed one by one here.

[0024] In the water-based cutting protection fluid of the present invention, the mass proportion of the wetting agent is 1-3 parts, for example, 1 part, 1.5 parts, 2 parts, 2.5 parts or 3 parts.

[0025] Wherein, the wetting agent is alkylphenol polyoxyethylene ether, C 12 -C 16 One or more of sodium secondary alkyl sulfonate, fatty alcohol sulfate, and sodium secondary alkylbenzene sulfonate.

[0026] For example, the wetting agent can be nonylphenol polyoxyethylene ether, octylphenol polyoxyethylene ether, sodium lauryl sulfonate, fatty alcohol polyoxyethylene sodium sulfate, disodium benzenesulfonate, etc.

[0027] Most preferably, the wetting agent is disodium benzenesulfonate, for example, disodium decyl(sulfophenoxy)benzenesulfonate.

[0028] In the water-based cutting protection fluid of the present invention, the mass fraction of the solubilizer is 5-20 parts, for example, 5 parts, 7.5 parts, 10 parts, 12.5 parts, 15 parts, 17.5 parts or 20 parts.

[0029] Wherein, the solubilizer is any one or more of 1,2-propylene glycol, isopropyl alcohol, glycerol, pentaerythritol, ethylene glycol butyl ether, diethylene glycol butyl ether, propylene glycol methyl ether, dipropylene glycol methyl ether, diethylene glycol ethyl ether or diethylene glycol hexyl ether.

[0030] Most preferably, the solubilizer is propylene glycol methyl ether or a mixture of isopropyl alcohol and propylene glycol methyl ether. When it is a mixture of isopropyl alcohol and propylene glycol methyl ether, the mass ratio between the two is 1:1-2, for example, 1:1, 1:1.5 or 1:2.

[0031] In the water-based cutting protection fluid of the present invention, the mass fraction of the defoaming agent is 0.01-1 part, for example, it can be 0.01 part, 0.05 part, 0.1 part, 0.2 part, 0.3 part, 0.4 part, 0.5 part, 0.6 part, 0.7 part, 0.8 part, 0.9 part or 1.0 part.

[0032] Wherein, the defoaming agent is a polyether defoaming agent, such as a GP-type polyether defoaming agent, a GPE-type polyether defoaming agent or a GPES-type polyether defoaming agent.

[0033] Preferably, the defoaming agent is a GP-type polyether defoaming agent polymerized from propylene oxide and ethylene oxide or propylene oxide and glycerol.

[0034] Among them, the GP type polyether defoamer, GPE type polyether defoamer or GPES type polyether defoamer are all well-known defoamers and can be purchased through various commercial channels, and will not be described in detail here.

[0035] In the water-based cutting protection fluid of the present invention, the mass fraction of the pure water is 60-90 parts, for example, 60 parts, 65 parts, 70 parts, 75 parts, 80 parts, 85 parts or 90 parts.

[0036] The ultrapure water is deionized water with a resistance of ≥18 MΩ.

[0037] As described above, the present invention provides a water-based cutting protection liquid for Low-K wafers. The inventors have found that in the water-based cutting protection liquid of the present invention, by selecting a specific, most preferred mixture of three water-soluble polymers with a specific low molecular weight range, and the most preferred solubilizer, etc., the best technical effect can be achieved (see the subsequent performance test section for details), especially the laser cutting protection performance, the cutter wheel cutting protection performance and the film forming performance, etc., thereby having many advantages such as no silicon slag, no slag particle contamination, and uniform and smooth film formation. It can be simultaneously applicable to the laser cutting protection and cutter wheel cutting protection of Low-K wafers, thereby improving the simplicity of the process flow and significantly improving the cutting protection performance of Low-K wafers.

[0038] In the water-based cutting protection liquid for Low-K wafers of the present invention, especially in the water-soluble polymer, by mixing PEO / PEG with low molecular weight PVP, the CH in the PEO and PEG structures can generate intramolecular hydrogen bonds with the highly electronegative group -C=O on PVP, thereby causing the two structures to entangle with each other and form a dense network molecular arrangement. After spin coating and solvent volatilization, a dense film layer can be formed, thereby blocking the heat and slag generated during the laser cutting process of Low-K wafers. At the same time, after the entangled network structure is mixed with deionized water, the degree of entanglement is reduced, forming an enclosed space, so that in the subsequent wheel cutting process of the Low-K wafer, when the diluent is sprayed between the wheel and the wafer, the enclosed space can wrap the silicon chips generated by the cutting, thereby achieving a cleaning effect such as suspending and dispersing the particles and preventing them from adhering and re-sticking.

[0039] The mechanism is as follows:

[0040]

[0041] [Second technical solution]

[0042] The second technical solution is to provide a method for preparing the water-based cutting protection liquid.

[0043] The preparation method comprises the following steps:

[0044] A1: Weigh the required amounts of water-soluble polymer, wetting agent, solubilizer, defoaming agent, and ultrapure water respectively;

[0045] A2: Add PVP to 1 / 2 part by mass of ultrapure water and stir until completely dissolved to obtain a PVP solution.

[0046] A3: adding a wetting agent, a solubilizer and a defoaming agent to the PVP solution and stirring thoroughly to obtain a mixed solution A;

[0047] A4: Add PEO to the remaining 1 / 2 of ultrapure water and stir until completely dissolved to obtain PEO solution. Then add PEG and stir thoroughly to obtain mixed solution B.

[0048] A5: Add the mixed solution B to the mixed solution A and stir thoroughly to obtain the water-based cutting protection liquid.

[0049] In the preparation method of the present invention, the stirring speed in steps A2-A5 is not particularly limited, as long as the components can be mixed evenly. Those skilled in the art can make appropriate selections and determinations based on actual conditions. Typically, it can be, for example, 150-300 rpm, and there is no particular strict limitation.

[0050] [The third technical solution]

[0051] The third technical solution, one object of the present invention is to provide the use of the above-mentioned water-based cutting protection liquid in Low-K wafer cutting protection.

[0052] Wherein, the cutting is laser cutting and cutter wheel cutting.

[0053] As mentioned above, the water-based cutting protection liquid of the present invention can be used for both laser cutting protection and cutter wheel cutting protection of Low-K wafers, whereas the laser cutting protection liquid and cutter wheel cutting protection liquid in the prior art are two different cutting protection liquids that need to be prepared separately and the protection liquid needs to be replaced after the laser cutting is completed, thereby significantly reducing the process production efficiency and increasing the process complexity.

[0054] The water-based cutting protection liquid has many properties such as excellent film-forming performance, laser cutting protection performance, knife wheel cutting protection performance, and a narrow film thickness range. Therefore, it has many advantages such as few residual particles, uniform and transparent film formation, and a narrow film thickness range. It can be used for laser cutting protection and knife wheel cutting protection of Low-K wafers at the same time, and thus has excellent process simplicity and significantly improves the cutting protection performance of Low-K wafers.

[0055] [The fourth technical solution]

[0056] A fourth technical solution of the present invention is to provide a method for protecting a Low-K wafer from cutting using the water-based cutting protection liquid. The method comprises the following steps:

[0057] Step 1: Spin-coat the water-based cutting protection liquid on the surface of a Low-K wafer to obtain a coating layer.

[0058] Step 2: drying the coating layer to form a film to obtain a protective film;

[0059] Step 3: Perform laser cutting to form grooves on the Low-K wafer;

[0060] Step 4: premixing the water-based cutting protection liquid with ultrapure water at a mass ratio of 1:5-50 to obtain a premixed liquid;

[0061] Step 5: Use a cutting wheel to perform subsequent through-cutting operations, cutting from the groove to form a single chip, and completing the cutting operation. During the cutting process, use the premixed liquid to rinse the contact area between the cutting wheel and the wafer. After cutting, use ultrapure water to wash and dry thoroughly, and the cutting protection treatment is completed.

[0062] Wherein, in step 1, the spin coating speed may be 500-1500 rpm, for example, 500 rpm, 750 rpm, 1000 rpm, 1250 rpm or 1500 rpm. Those skilled in the art may make appropriate selections according to actual conditions, which will not be described in detail here.

[0063] In step 1, the amount of the cutting protection liquid used is not particularly strictly limited, and is usually the conventional amount used in the semiconductor processing field. For example, for 6-12 inch wafers, the amount used can be 10-80 ml, for example, 10 ml, 30 ml, 50 ml, 70 ml or 80 ml.

[0064] In step 2, a variety of drying methods can be used to dry and form the film, such as vacuum drying, radiation drying, etc. These are conventional drying methods in the semiconductor field and will not be described in detail here.

[0065] Wherein, in step 3, the power of the laser cutting may be 2-8 watts, for example, 2 watts, 3 watts, 4 watts, 5 watts, 6 watts, 7 watts or 8 watts.

[0066] Wherein, in step 4, the ultrapure water is deionized water with a resistance of ≥18 MΩ. The mass ratio of the water-based cutting protection fluid to the ultrapure water is 1:5-50, for example, 1:5, 1:10, 1:20, 1:30, 1:40 or 1:50.

[0067] Wherein, in step 5, the ultrapure water is deionized water with a resistance ≥ 18 MΩ.

[0068] In summary, the present invention provides a water-based cutting protection liquid for Low-K wafers, a preparation method, uses, a Low-K wafer cutting protection method using the protection liquid, and other technical solutions. All of the above technical solutions have many advantages, such as:

[0069] 1. The protective fluid, composed of PEO, PEG, and PVP within a specific molecular weight range, synergistically forms intramolecular hydrogen bonds, creating a dense protective film on the surface of low-K wafers before laser cutting, thereby preventing thermal melting and slag contamination. During subsequent wheel cutting, the entangled network structure of these three substances in the protective fluid creates a space that encloses cutting debris, preventing contamination of the wafer. This makes it particularly suitable for protecting low-K wafers during cutting.

[0070] 2. It is precisely because of the above advantages that the water-based cutting protection fluid can be used for both laser cutting protection and cutter wheel cutting protection of Low-K wafers without switching the protection fluid, which greatly improves production efficiency and reduces production costs, and facilitates automated control and yield control. BRIEF DESCRIPTION OF THE DRAWINGS

[0071] Attachment Figure 1 This is a 100x magnification of the groove after laser cutting of a Low-K wafer using water-based cutting protection liquid L1.

[0072] Attachment Figure 2 This is a 100x magnification of the groove after laser cutting of a Low-K wafer using water-based cutting protection liquid L17.

[0073] Attachment Figure 3 This is a 100x magnification of the groove after laser cutting of a Low-K wafer using water-based cutting protection liquid L8.

[0074] Attachment Figure 4 This is a 100x magnification of the groove after laser cutting of a Low-K wafer using water-based cutting protection liquid L4.

[0075] Attachment Figure 5 This is a 100x magnification of the groove after laser cutting of a Low-K wafer using water-based cutting protection liquid L11.

[0076] Attachment Figure 6 This is a 50x magnified image of the wafer after the Low-K wafer is cut with a knife wheel using water-based cutting protection liquid L1.

[0077] Attachment Figure 7 This is a 50x magnified image of the wafer after the Low-K wafer was cut with a knife wheel using water-based cutting protection liquid L17.

[0078] Attachment Figure 8 This is a 50x magnified image of the wafer after the Low-K wafer is cut with a knife wheel using water-based cutting protection liquid L4.

[0079] Attachment Figure 9 This is a 50x magnified image of the wafer after the Low-K wafer was cut with a knife wheel using water-based cutting protection liquid L8.

[0080] Attachment Figure 10 This is a 50x magnified image of the wafer after the Low-K wafer was cut with a knife wheel using water-based cutting protection liquid L11.

[0081] Attachment Figure 11 (a)-11(b) are photos of the appearance of the protective film obtained after coating with water-based cutting protection liquid L1.

[0082] Attachment Figure 12(a)-12(b) are photos of the appearance of the protective film obtained after coating with water-based cutting protection liquid L23.

[0083] Attachment Figure 13 This is a schematic diagram of the yield test after laser cutting and wheel cutting using water-based cutting protection liquid L1, where white chips mean unqualified.

[0084] Attachment Figure 14 This is a schematic diagram of the yield test after laser cutting and wheel cutting using water-based cutting protection liquid L1, where white chips mean unqualified. DETAILED DESCRIPTION

[0085] The present invention is described in detail below through specific examples, but the use and purpose of these exemplary embodiments are only used to illustrate the present invention and do not constitute any form of limitation on the actual protection scope of the present invention, nor do they limit the protection scope of the present invention to them.

[0086] Unless otherwise specified, the ultrapure water used in any step of the following examples and performance tests is deionized water with a resistance of ≥18 MΩ, and therefore will not be listed one by one.

[0087] The components used below can be purchased through commercial channels and will not be described in detail here.

[0088] Example 1: Preparation of Low-K Wafer Water-Based Cutting Protection Fluid

[0089] A1: Weigh 13 parts by mass of a water-soluble polymer (a mixture of PEG, PEO, and PVP in a mass ratio of 1:0.5:5; PEG is PEG-400, i.e., polyethylene glycol with an average molecular weight of 400, PEO has an average molecular weight of 250,000, and PVP has a molecular weight of K30), 3 parts by mass of a wetting agent (decyl(sulfophenoxy)benzenesulfonic acid disodium salt), 12.5 parts by mass of a solubilizer (a mixture of isopropyl alcohol and propylene glycol methyl ether in a mass ratio of 1:1.5), 0.5 parts by mass of a defoamer (GP-type polyether defoamer), and 75 parts by mass of ultrapure water;

[0090] A2: Add the above PVP to 1 / 2 part by mass of the above ultrapure water and stir until completely dissolved to obtain a PVP solution;

[0091] A3: adding the above-mentioned wetting agent, the above-mentioned solubilizer and the above-mentioned defoaming agent to the PVP solution and stirring thoroughly to obtain a mixed solution A;

[0092] A4: Add the above-mentioned PEO to the remaining 1 / 2 of the above-mentioned ultrapure water and stir until completely dissolved to obtain a PEO solution. Then add the above-mentioned PEG and stir thoroughly to obtain a mixed solution B.

[0093] A5: Add mixed solution B to mixed solution A and stir thoroughly to obtain a water-based cutting protection liquid, which is named L1.

[0094] The stirring speed in steps A2-A5 is 250 rpm, and the mixture is stirred until completely mixed.

[0095] Example 2: Preparation of Low-K Wafer Water-Based Cutting Protection Fluid

[0096] A1: Weigh 5 parts by mass of a water-soluble polymer (a mixture of PEG, PEO, and PVP in a mass ratio of 1.5:0.8:7.7; PEG is PEG-200, i.e., polyethylene glycol with an average molecular weight of 200, PEO has an average molecular weight of 400,000, and PVP has a molecular weight of K30), 1 part by mass of a wetting agent, decyl (sulfophenoxy) benzenesulfonic acid disodium salt, 20 parts by mass of a solubilizer (a mixture of isopropyl alcohol and propylene glycol methyl ether in a mass ratio of 1:1), 0.05 parts by mass of a defoamer (a GPE-type polyether defoamer), and 90 parts by mass of ultrapure water;

[0097] A2: Add the above PVP to 1 / 2 part by mass of the above ultrapure water and stir until completely dissolved to obtain a PVP solution;

[0098] A3: adding the above-mentioned wetting agent, the above-mentioned solubilizer and the above-mentioned defoaming agent to the PVP solution and stirring thoroughly to obtain a mixed solution A;

[0099] A4: Add the above-mentioned PEO to the remaining 1 / 2 of the above-mentioned ultrapure water and stir until completely dissolved to obtain a PEO solution. Then add the above-mentioned PEG and stir thoroughly to obtain a mixed solution B.

[0100] A5: Add mixed solution B to mixed solution A and stir thoroughly to obtain a water-based cutting protection liquid, which is named L2.

[0101] The stirring speed in steps A2-A5 is 150 rpm, and the mixture is stirred until completely mixed.

[0102] Example 3: Preparation of Low-K Wafer Water-Based Cutting Protection Fluid

[0103] A1: Weigh 20 parts by mass of a water-soluble polymer (a mixture of PEG, PEO, and PVP in a mass ratio of 2:0.8:7.2; PEG is PEG-600, i.e., polyethylene glycol with an average molecular weight of 600, PEO has an average molecular weight of 100,000, and PVP has a molecular weight of K30), 5 parts by mass of a wetting agent (decyl(sulfophenoxy)benzenesulfonic acid disodium salt), 5.1 parts by mass of a solubilizer (a mixture of isopropyl alcohol and propylene glycol methyl ether in a mass ratio of 1:2), 1 part by mass of a defoamer (a GPES-type polyether defoamer), and 60 parts by mass of ultrapure water;

[0104] A2: Add the above PVP to 1 / 2 part by mass of the above ultrapure water and stir until completely dissolved to obtain a PVP solution;

[0105] A3: adding the above-mentioned wetting agent, the above-mentioned solubilizer and the above-mentioned defoaming agent to the PVP solution and stirring thoroughly to obtain a mixed solution A;

[0106] A4: Add the above-mentioned PEO to the remaining 1 / 2 of the above-mentioned ultrapure water and stir until completely dissolved to obtain a PEO solution. Then add the above-mentioned PEG and stir thoroughly to obtain a mixed solution B.

[0107] A5: Add mixed solution B to mixed solution A and stir thoroughly to obtain a water-based cutting protection liquid, which is named L3.

[0108] The stirring speed in steps A2-A5 is 300 rpm, and the mixture is stirred until completely mixed.

[0109] Example 4-7: Preparation of Low-K Wafer Water-Based Cutting Protection Fluid

[0110] Except that PEG-400 in Example 1 was replaced by triethylene glycol, PEG-200 in Example 2 was replaced by diethylene glycol, PEG-600 in Example 3 was replaced by PEG-800, and PEG-400 in Example 1 was replaced by PEG-1000, other operations / parameters remained unchanged, and the corresponding examples were repeated in sequence to obtain Examples 4-7. The obtained protective solutions were named L4, L5, L6 and L7, respectively.

[0111] Examples 8-10: Preparation of Low-K Wafer Water-Based Cutting Protection Fluid

[0112] Except that the PVP with a molecular weight of K30 in Examples 1-3 was replaced by PVP with a molecular weight of K60, other operations / parameters remained unchanged, and Examples 1-3 were repeated in sequence to obtain Examples 8-10 accordingly. The obtained protective solutions were named L8, L9 and L10, respectively.

[0113] Example 11-19: Preparation of Low-K Wafer Water-Based Cutting Protection Fluid

[0114] A. Except for deleting PEG in Examples 1-3, other operations / parameters remained unchanged, and thus Examples 1-3 were repeated in sequence to obtain Examples 11-13. The obtained protective solutions were named L11, L12 and L13 respectively.

[0115] B. Except for deleting PEO in Examples 1-3, other operations / parameters remained unchanged, and thus Examples 1-3 were repeated in sequence to obtain Examples 14-16 respectively. The obtained protective solutions were named L14, L15 and L16 respectively.

[0116] C. Except for deleting PVP in Examples 1-3, other operations / parameters remained unchanged, and thus Examples 1-3 were repeated in sequence to obtain Examples 17-19 respectively. The obtained protective solutions were named L17, L18 and L19 respectively.

[0117] Examples 20-25: Preparation of Low-K Wafer Water-Based Cutting Protection Fluid

[0118] A. Except for replacing the solubilizer in Examples 1-3 with a single component propylene glycol monomethyl ether having a mass equal to the total mass of the original solubilizer and the original solubilizer, all other operations / parameters remained unchanged. Examples 1-3 were repeated in sequence to obtain Examples 20-22, and the resulting protective solutions were named L20, L21, and L22, respectively.

[0119] B. Except for replacing the solubilizer in Examples 1-3 with a single component of isopropyl alcohol having a mass equal to the total mass of the original solubilizer and the original isopropyl alcohol, all other operations / parameters remained unchanged. Examples 1-3 were repeated in sequence to obtain Examples 23-25, and the resulting protective solutions were named L23, L24, and L25, respectively.

[0120] After obtaining the above-mentioned multiple water-based cutting protection liquids, the following performance tests were performed respectively, as follows.

[0121] Laser cutting protection test of Low-K wafer

[0122] The laser cutting protection test of the Low-K wafer includes the following cutting steps:

[0123] Step 1: Spin-coat 50 ml of a water-based cutting protection liquid on a 12-inch Low-K wafer surface to obtain a coating layer; the spin-coating speed is 1000 rpm;

[0124] Step 2: drying the coating layer to form a film to obtain a protective film;

[0125] Step 3: Perform laser cutting to form grooves on the Low-K wafer, where the laser cutting power is 5 watts.

[0126] The obtained cutting protection performance after using different cutting protection fluids is shown in the following figures.

[0127] 1. Attachment Figure 1 This is a 100x magnified image of the groove (i.e., the cutting path) after laser cutting using L1 according to the above steps 1-3. It can be seen from the figure that there is no silicon slag on the inner side of the cutting path boundary (i.e., the inner side of the two upper and lower black boundaries in the figure, the same below), and the outer surface of the cutting path (i.e., the two wider white parts above and below in the figure, the same below) is very clean and there is no silicon slag particle contamination.

[0128] When using water-based cutting protection fluid L2-L3, the groove enlarged diagram is the same as the attached Figure 1 Exactly the same, similarly there is no silicon slag inside the boundary of the cutting path, and there is no silicon slag particle contamination on the outer surface of the cutting path, so they are not listed one by one.

[0129] 2. Attachment Figure 2 This is a 100x magnified image of the groove (i.e., the cutting path) after laser cutting using L17 according to the above steps 1-3. It can be seen from the figure that a large amount of irregularly shaped silicon slag is deposited on the inner side of the cutting path boundary (see the white oval in the figure, which may be unclear after submission to the system. If necessary, the applicant can provide a clearer electronic drawing), and there are a large number of silicon slag particles on the outer surface of the cutting path (i.e., the many black dots shown in the figure).

[0130] When using water-based cutting protection fluid L18-L19, the groove enlarged diagram is the same as the attached Figure 2 The results are highly similar. Similarly, a large amount of irregularly shaped silicon slag is deposited on the inner side of the cutting path boundary, and a large amount of silicon slag particles are also contaminated on the outer surface of the cutting path, so they are not listed one by one.

[0131] This is because when polyvinyl pyrrolidone polymers (PVP) are omitted, polyethylene glycol polymers (PEG) and polyethylene oxide (PEO) cannot form the above-mentioned intramolecular hydrogen bonds (due to the absence of PVP substance), and thus will not form a dense network molecular arrangement structure. The film layer formed after the solvent evaporates is too thin and not dense, resulting in the inability to block the formation and deposition of slag and slag particles during the laser cutting process.

[0132] 3. Attachment Figure 3 This is a 100x magnified image of the groove (i.e., the cutting path) after laser cutting using L8 according to the above steps 1-3. It can be seen from the figure that although there is no silicon slag on the inner side of the cutting path boundary, there are a large number of silicon slag particles on the outer surface of the cutting path (i.e., the many black dots shown in the figure).

[0133] When using water-based cutting protection fluid L9-L10, the groove enlarged diagram is the same as the attached Figure 3 The results are highly similar. Similarly, there is no silicon slag inside the cutting path boundary, but there are a lot of silicon slag particles on the outer surface of the cutting path, so they are not listed one by one.

[0134] This is because when the molecular weight of polyvinylpyrrolidone (PVP) is increased, the length of the PVP molecular chain increases significantly, and the viscosity of the composition increases significantly, resulting in a significant increase in the thickness of the formed film compared to low molecular weight PVP. When laser cutting is performed, the film layer is too thick, which causes the film layer on both sides of the groove to lift up to a certain extent, resulting in the following problems: Figure 3 The outer surface of the scribe line is shown to be contaminated with a large amount of silicon slag particles.

[0135] 4. Attachment Figure 4 This is a 100x magnified image of the groove (i.e., the cutting path) after laser cutting using L4 according to the above steps 1-3. It can be seen from the figure that although there are a small amount of silicon slag particle contamination on the outer surface of the cutting path (i.e., a few black dots in the upper and lower white areas), a large amount of silicon slag is deposited on the inner side of the cutting path boundary (as shown in multiple white ovals).

[0136] When using water-based cutting protection fluid L5-L7, the groove enlarged diagram is the same as the attached Figure 4 The results are highly similar. Similarly, there are relatively few silicon slag particles on the outer surface of the cutting street, but a large amount of silicon slag is deposited on the inner side of the cutting street boundary, so they are not listed one by one.

[0137] This is because when the molecular weight of polyethylene glycol polymer (PEG) is changed, the degree of entanglement of the molecular chain is reduced due to the decrease in the molecular weight of PEG, which reduces the density of the film layer after film formation. After laser ablation, the film layer at the edge of the cutting path that is more heated is more likely to denature, causing slag to adhere to the inner side of the groove and a small amount of silicon slag particles to adhere to the outer surface of the cutting path. When the molecular weight of PEG is increased (for example, increased to PEG-800 or PEG-1000), the original state of PEG changes from a viscous liquid to a milky white paste, which is extremely difficult to dry during the spin coating process. Although the surface layer is dried, it is difficult for the interior to dry thoroughly, resulting in a reduction in the barrier ability of the film layer during laser cutting, making it easy for slag to adhere to the inner side of the cutting path and a small amount of silicon slag particles to adhere to the outer surface of the cutting path after laser cutting.

[0138] 5. Attachment Figure 5This is a 100x magnified image of the groove (i.e., cutting street) after laser cutting using L11 according to the above steps 1-3. It can be seen from the figure that a small amount of silicon slag is deposited on the inner side of the cutting street boundary (as shown in multiple white ovals), and the deposition amount is small (extending to a smaller height inside the cutting street). There is an even smaller amount of silicon slag particle contamination on the outer surface of the cutting street (i.e., a few black dots in the upper and lower white areas), but it is still significantly inferior to the effect of L1-L3 (see attached). Figure 1 ).

[0139] When using water-based cutting protection fluid L12-L16, the groove enlarged diagram is the same as the attached Figure 5 The two methods are highly similar. Similarly, a small amount of silicon slag is deposited on the inner side of the cutting line boundary, and the deposition amount is relatively small. There is also an even smaller amount of silicon slag particle contamination on the outer surface of the cutting line, so they are not listed one by one.

[0140] This is because when polyethylene glycol polymers (PEG) or polyethylene oxide (PEO) are deleted, the film-forming ability of the water-based cutting protection fluid is significantly reduced, which in turn causes the film to become thinner. The larger slag and larger slag particles generated during the cutting process will directly penetrate the film layer and adhere to the inner side of the cutting path boundary and the outer surface of the cutting path due to the high heat they carry, while the smaller slag and smaller slag particles can still be blocked outside the film layer, thus producing the protection state shown in the figure.

[0141] Knife wheel cutting protection test for Low-K wafers

[0142] The specific steps of the cutter wheel cutting protection test are as follows: First, use the most excellent water-based cutting protection liquid L1 to perform the front process, namely laser cutting protection, according to steps 1-3 in the above "Laser cutting protection test of Low-K wafer". Figure 1 The wafer is in a clean state, and then the following cutting steps (step numbers continue from the previous step), namely steps 4-5, are performed. Different water-based cutting protection fluids are used to test the protection performance of the cutting wheel, thereby examining the advantages and disadvantages of each cutting protection fluid for the protection of the cutting wheel. Steps 4-5 are as follows:

[0143] Step 4: Premix the water-based cutting protection fluid with ultrapure water at a mass ratio of 1:30 to obtain a premixed solution;

[0144] Step 5: Use a cutting wheel to perform subsequent through-cutting operations, cutting from the groove to form a single chip, and completing the cutting operation. During the cutting process, use the premixed liquid to rinse the contact area between the cutting wheel and the wafer. After cutting, use ultrapure water to wash and dry thoroughly, and the cutting protection treatment is completed.

[0145] It should be noted that after the through-cutting operation, the chip particles are still fixed on the blue film (the blue film is used to fix the chips and prevent the water flow during the cutting process from washing away the separated individual chips), so they are still tightly arranged. Figure 6-10 The grooves can still be clearly seen.

[0146] After using different cutting protection liquids in the above steps 4-5, the obtained cutting protection performance is shown in the following figures.

[0147] 1. Attachment Figure 6 This is a 50x magnified image of the wafer after using L1 to cut the wafer according to steps 4-5 above. As can be seen from the image, the wafer surface is very clean and there are no silicon powder particles.

[0148] When using water-based cutting protection liquid L2-L3, the wafer magnification and the attached Figure 6 Exactly the same, the wafer surface is also clean and free of any silicon powder particles, so they are not listed one by one.

[0149] 2. Attachment Figure 7 This is a 50x magnified image of the wafer after using L17 to cut the wafer with a cutter wheel according to steps 4-5 above. As can be seen from the image, there are a large number of silicon powder particles around the groove surface of the wafer.

[0150] When using water-based cutting protection liquid L18-L19, the wafer magnification and the attached Figure 7 The figures are highly similar. Similarly, there are a large number of silicon powder particles around the groove surface of the wafer, so they are not listed one by one.

[0151] 3. Attachment Figure 8 This is a 50x magnified image of the wafer after using L4 to cut the wafer according to steps 4-5 above. It can be seen from the image that there are more silicon powder particles around the groove surface of the wafer, but less than the surrounding silicon powder particles. Figure 7 .

[0152] When using water-based cutting protection liquid L5-L7, the wafer magnification and the attached Figure 8 The two wafers are highly similar. Similarly, there are many silicon powder particles around the groove surface of the wafer, so they are not listed one by one.

[0153] 4. Attachment Figure 9 This is a 50x magnified image of the wafer after the L8 was used to cut the wafer according to the above steps 4-5. It can be seen from the figure that there are fewer silicon powder particles around the groove surface of the wafer, which is clearly less than the silicon powder particles attached to the wafer. Figure 8 .

[0154] When using water-based cutting protection liquid L9-L10, the wafer magnification and the attached Figure 9The wafers are highly similar, and similarly, there are fewer silicon powder particles around the groove surface of the wafer, so they are not listed one by one.

[0155] 5. Attachment Figure 10 This is a 50x magnified image of the wafer after using L11 to cut the wafer according to steps 4-5 above. It can be seen from the image that there are a few silicon powder particles around the groove surface of the wafer, but they are less than the surrounding Figure 9 .

[0156] When using water-based cutting protection liquid L12-L16, the wafer magnification and the attached Figure 10 The wafer is highly similar, and similarly, there are a few silicon powder particles around the groove surface of the wafer, so they are not listed one by one.

[0157] The inventors believe that the reason is as follows: the three water-soluble polymers in the water-based cutting protection liquid can exert a unique synergistic effect. The molecular chains of PEG and PEO have no side groups and are linear regular helical structures. When PEO or PEG is not added, the degree of spatial entanglement is low, resulting in a poor effect (see attached). Figure 10 ). When PVP is introduced, in addition to forming a tighter entanglement space with PEO or PEG, it itself also has the function of improving the lubricity of the diluent, so that when the cutting protection liquid is diluted, the mutually entangled molecular chains formed gradually open, and some carbonyl groups that fail to form hydrogen bonds with PEO or PEG can be exposed, thereby interacting with water molecules to form hydrogen bonds. A PVP molecular chain can interact with multiple water molecules to form a hydrated molecular shell. At the same time, the hydrated molecular shells are intertwined with each other with the help of hydrogen bonds and molecular interaction forces to form a complex hydrated molecular layer. Combining these results, due to the presence of PVP, a complex hydrated PVP lubricating layer can be formed in the system, which plays a lubricating effect and reduces the back-sticking and adhesion of slag particle contaminants, thereby achieving the most excellent protection effect (see Appendix). Figure 6 When PVP is not added, the failure to form a hydrated molecular layer and a hydrated PVP lubricating layer results in severe particle adhesion and back-sticking (see Appendix Figure 7 When the molecular weight of PEG or PVP is changed, as mentioned above, this will lead to a decrease in the degree of molecular entanglement, and then the lubrication performance of the hydrated molecular layer and the hydrated PVP lubricating layer will be reduced, thereby reducing the effect of preventing particle adhesion and back-sticking (see Appendix Figure 8-9 ).

[0158] Film forming performance research

[0159] The inventors have discovered that in the water-based cutting protection fluid of the present invention, the type of solubilizer has a significant impact on the film-forming performance. Therefore, the film-forming process is performed according to the following steps:

[0160] Step 1: Spin-coat 50 ml of a water-based cutting protection liquid on a 12-inch Low-K wafer surface to obtain a coating layer; the spin-coating speed is 1000 rpm;

[0161] Step 2: Drying the coating layer to form a film to obtain a protective film.

[0162] After using different cutting protection liquids in the above step 1, the appearance of the resulting protective film is shown in the following figure.

[0163] Among them, it should be noted that due to reflection, the attached Figure 11 The black boxes in (b) and 12(b) are the emitted ceiling grids, and the white light blocks are the reflected ceiling lights.

[0164] 1. Attachment Figure 11 This is the protective film obtained by using L1 according to the above steps 1-2. It can be seen that a smooth and flat protective film is obtained.

[0165] When using water-based cutting protection liquid L2-L22, the resulting protective film is Figure 11 They are exactly the same and also have a smooth and flat protective film, so I will not list them one by one.

[0166] 2. Attachment Figure 12 This is a protective film obtained by using L23 according to the above steps 1-2, where Figure (a) is an overall view and Figure (b) is a local enlarged view. It can be clearly seen from Figures (a) and (b) that the obtained protective film has poor flatness and produces many wrinkles, which makes it impossible to perform subsequent laser cutting protection.

[0167] When using water-based cutting protection liquid L24-L25, the resulting protective film is Figure 12 (a)-(b) are exactly the same, and the flatness is also very poor, with many wrinkles, so they will not be listed one by one.

[0168] It can be seen that the change of solubilizer can significantly affect the film-forming properties of the protective liquid. In the water-based cutting protective liquid system of the present invention, the use of isopropyl alcohol alone may lead to a faster exchange rate of the membrane-water interface after coating due to its volatilization rate, which is prone to instantaneous phase separation and leads to the formation of larger pores, resulting in poor flatness of the obtained film after drying, which is manifested as Figure 12 There are obvious wrinkles in the.

[0169] Wafer yield test

[0170] Use different water-based cutting protection fluids to perform steps 1-5 below:

[0171] Step 1: Spin-coat 50 ml of a water-based cutting protection liquid on a 12-inch Low-K wafer surface to obtain a coating layer; the spin-coating speed is 1000 rpm;

[0172] Step 2: drying the coating layer to form a film to obtain a protective film;

[0173] Step 3: Perform laser cutting to form grooves on the Low-K wafer, where the laser cutting power is 5 watts;

[0174] Step 4: Premix the water-based cutting protection fluid with ultrapure water at a mass ratio of 1:30 to obtain a premixed solution;

[0175] Step 5: Use a cutting wheel to perform subsequent through-cutting operations, cutting from the groove to form a single chip, and completing the cutting operation. During the cutting process, use the premixed liquid to rinse the contact area between the cutting wheel and the wafer. After cutting, use ultrapure water to wash and dry thoroughly, and the cutting protection treatment is completed.

[0176] The water-based cutting protection liquid used in step 1 and step 4 is the same cutting protection liquid, so as to examine the advantages and disadvantages of the comprehensive protection performance of different water-based cutting protection liquids when used for laser cutting protection and cutter wheel cutting protection at the same time.

[0177] After completing steps 1-5 above, the yield rate is tested using optical automatic inspection equipment, and the number of qualified wafers that can proceed to subsequent processes is counted. The results are as follows:

[0178] 1. As attached Figure 13 As shown, it is a schematic diagram of yield detection after protection using water-based cutting protection liquid L1, where a white chip means unqualified.

[0179] After cutting and protecting five 12-inch wafers and counting the qualified wafers, it was found that an average wafer yield of up to 99.52% could be achieved using L1.

[0180] When water-based cutting protection liquid L2-L3 was used, average wafer yields of 99.37% and 99.55% were obtained respectively, and their detection schematics are not listed one by one.

[0181] 2. As attached Figure 14 As shown, it is a schematic diagram of yield detection after laser cutting and cutter wheel cutting using water-based cutting protection liquid L17, where white chips mean unqualified.

[0182] Similarly, after cutting and protecting 5 12-inch wafers and counting the qualified wafers, it was found that using L17 could ultimately achieve an average wafer yield of 56.44%.

[0183] When water-based cutting protection liquids L18-L19 were used, average wafer yields of 55.83% and 56.01% were obtained, respectively. The detection schematic diagrams are not listed one by one.

[0184] 3. Carry out the same test on other water-based cutting protection fluids. Figure 13-14 The only difference is the number of qualified wafers, so the test diagrams are not listed one by one. After calculation, the results are shown in Table 1 below. For easy comparison, the results of L1-L3 and L17-L19 are listed together.

[0185] Table 1

[0186]

[0187] Among them, the yield (%) is expressed in the form of maximum and minimum values, which means that among the cutting protection liquids used, one protection liquid has the highest yield, and the other protection liquid has the lowest yield, while the chip yields of other protection liquids are between the highest and lowest values, so they are no longer listed in detail.

[0188] This demonstrates that the water-based cut protection fluids L1-L3 of the present invention can be used for full-process protection, namely, for both laser cutting protection in the upstream process and wheel cutting protection in the downstream process. However, L4-L19 exhibit significant, even dramatic, degradation compared to L1-L3, demonstrating a significant or significant degradation in their protective performance. This further demonstrates the unexpected synergistic effect of the multiple specific components of the water-based cut protection fluids of the present invention.

[0189] In summary, the present invention provides a water-based cutting protection liquid for Low-K wafers. The inventors found that in the water-based cutting protection liquid of the present invention, by selecting a specific, most preferred mixture of three water-soluble polymers with a specific low molecular weight range, and the most preferred solubilizer, etc., the best technical effect can be achieved (see the multiple performance test sections above for details), especially the laser cutting protection performance, the cutter wheel cutting protection performance, and the film forming performance, etc., thereby having many advantages such as no silicon slag, no slag particle contamination, and uniform and smooth film formation. It can be simultaneously applied to the laser cutting protection and cutter wheel cutting protection of Low-K wafers, thereby improving the simplicity of the process flow, and can significantly improve the cutting protection performance of Low-K wafers, thereby significantly improving the product yield of precision semiconductor components.

[0190] It should be understood that the purpose of these embodiments is only to illustrate the present invention and is not intended to limit the scope of protection of the present invention. In addition, it should also be understood that after reading the technical content of the present invention, those skilled in the art may make various changes, modifications and / or variations to the present invention, and all of these equivalent forms also fall within the scope of protection defined by the claims appended hereto.

Claims

1. A water-based cutting protection liquid for Low-K wafers, the water-based cutting protection liquid comprising the following components in parts by mass: Water-soluble polymer 1-20 Wetting agent 1-5 Solubilizer 5-20 Defoaming agent 0.01-1 Ultrapure water 60-90 The water-soluble polymer is a mixture of three substances: polyethylene glycol polymer, polyethylene oxide and polyvinyl pyrrolidone polymer, wherein the mass ratio of the three is 1-2:0.5-1:3-10; The average molecular weight of the polyethylene glycol polymer is 200-600; the average molecular weight of the polyethylene oxide is 100,000-400,000; the number average molecular weight of the polyvinyl pyrrolidone polymer is 40,000; The solubilizer is a mixture of isopropyl alcohol and propylene glycol methyl ether, and the mass ratio of the two is 1:1-2.

2. The water-based cutting protection fluid according to claim 1, wherein: The mass fraction of the water-soluble polymer is 5-20 parts.

3. The water-based cutting protection fluid according to claim 1 or 2, characterized in that: The mass fraction of the wetting agent is 1-3 parts.

4. The method for preparing the water-based cutting protection fluid according to any one of claims 1 to 3, comprising the following steps: A1: Weigh the required amounts of water-soluble polymer, wetting agent, solubilizer, defoaming agent, and ultrapure water respectively; A2: Add a polyvinyl pyrrolidone polymer to 1 / 2 ultrapure water and stir until completely dissolved to obtain a polyvinyl pyrrolidone polymer solution; A3: adding a wetting agent, a solubilizer, and a defoaming agent to the polyvinyl pyrrolidone polymer solution and stirring thoroughly to obtain a mixed solution A; A4: Add polyethylene oxide to the remaining 1 / 2 of ultrapure water and stir until completely dissolved to obtain a polyethylene oxide solution. Then, add a polyethylene glycol polymer and stir thoroughly to obtain a mixed solution B. A5: Add the mixed solution B to the mixed solution A and stir thoroughly to obtain the water-based cutting protection liquid.

5. Use of the water-based cutting protection liquid according to any one of claims 1 to 3 in Low-K wafer cutting protection.

6. The use according to claim 5, characterized in that: The cutting is laser cutting and cutter wheel cutting.

7. A method for protecting Low-K wafers from cutting using the water-based cutting protection liquid according to any one of claims 1 to 3, the method comprising the following steps: Step 1: Spin-coating the water-based cutting protection liquid on the surface of the Low-K wafer to obtain a coating layer; Step 2: drying the coating layer to form a film to obtain a protective film; Step 3: Perform laser cutting to form grooves on the Low-K wafer; Step 4: premixing the water-based cutting protection liquid with ultrapure water at a mass ratio of 1:5-50 to obtain a premixed liquid; Step 5: Use a cutting wheel to perform subsequent through-cutting operations, cutting from the groove to form a single chip, and completing the cutting operation. During the cutting process, use the premixed liquid to rinse the contact area between the cutting wheel and the wafer. After cutting, use ultrapure water to wash and dry thoroughly, and the cutting protection treatment is completed.

8. The cutting protection method according to claim 7, wherein: In the step 1, the spin coating speed is 500-1500 rpm.

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