TWI638870B - Solution for forming protective layer used in picosecond laser process and method for manufacturing thereof - Google Patents

Abstract

A solution used to form a protective layer for picosecond laser processing. The solution includes a water-soluble resin and a solvent. The solvent includes water and an organic solvent, and the weight ratio of the solid content of the solution is 0.5% or more and less than 3%.

Description

Solution for forming protective layer as picosecond laser processing and manufacturing method thereof

The present invention relates to a solution, and more particularly to a solution for forming a protective layer for processing as a picosecond laser.

In the semiconductor element manufacturing step, the semiconductor wafer is divided into a plurality of regions by dicing streets arranged in a grid pattern on the surface of the semiconductor wafer, and a plurality of semiconductor wafers are cut along these divided regions. When a semiconductor wafer is cut into a semiconductor wafer by a dicing blade, flaws, scratches, or debris may be generated, and the insulating film formed on the surface of the wafer may fall off. In order to avoid the above problems, a current common practice is to apply a laser along the cutting path before cutting with a cutting blade to form a groove corresponding to the same width of the cutting blade, and then use the cutting blade to cut.

Laser development has played an important role in processing applications, such as cutting, welding and material proofing of automotive sheet metal. With semiconductor, display The development of industries such as solar cells, solar cells, and LEDs is also widely used in micro / nano processing. Nanosecond lasers can be used for ablation and microstructure fabrication.

As product designs become thinner and shorter, manufacturing technology must make a breakthrough. Today, high-pulse energy picosecond lasers are gradually being used in the optoelectronics and semiconductor industries due to low processing thermal effects and better accuracy. Compared to nanosecond lasers, high-pulse energy picosecond lasers are a powerful tool for microstructure processing and can process a wide range of material samples, including brittle materials (glass, sapphire), metals, or composite materials.

However, since the pulse of the picosecond laser is approximately equal to the thermal effect conduction rate (4ps), after most targets are excited by the laser, because the thermal conduction is slower than the pulsed laser, the target is vaporized and volatilized directly from the solid state. Smaller, the accuracy of material removal can be effectively improved (less burrs). Therefore, the picosecond laser mechanism is quite different from the traditional nanosecond laser. Laser cutting fluids suitable for traditional nanosecond lasers do not provide protection as expected. Therefore, how to choose the appropriate picosecond laser cutting fluid has become an urgent task for the industry.

The present invention relates to a solution that can be used to form a protective layer for picosecond laser processing. Due to the short pulse of the picosecond laser, most target materials are directly vaporized from the solid state when excited by the laser, and because the thermal shadow area generated by the picosecond laser is small, the accuracy of material removal can be improved, effectively reducing The phenomenon of burrs.

According to the present invention, a solution is proposed for forming a protective layer as a picosecond laser process. The solution includes a water-soluble resin and a solvent. The solvent includes water and an organic solvent, and the weight ratio of the solid content of the solution is 0.5% or more and less than 3%.

According to the present invention, a method for manufacturing a solution for forming a protective layer for wafer picosecond laser processing is proposed, which comprises mixing a water-soluble resin and a solvent. The solvent includes water and an organic solvent, and the weight ratio of the solid content of the solution is 0.5% or more and less than 3%.

In order to have a better understanding of the above and other aspects of the present invention, the following specific examples are given below in conjunction with the accompanying drawings to make a detailed description as follows:

100‧‧‧Semiconductor wafer

100a‧‧‧Semiconductor wafer surface

10‧‧‧ substrate

11‧‧‧ semiconductor layer

12‧‧‧Semiconductor wafer

13‧‧‧cut road

14‧‧‧ protective layer

X, Y, Z‧‧‧ Coordinate axes

FIG. 1 is a top view of a semiconductor wafer according to an embodiment of the present invention.

Fig. 2 is a cross-sectional view of the semiconductor wafer of Fig. 1 taken along line A-A '.

FIG. 1 is a top view of a semiconductor wafer 100 according to an embodiment of the present invention. Fig. 2 is a cross-sectional view of the semiconductor wafer 100 of Fig. 1 taken along line A-A '. In this embodiment, the semiconductor wafer includes a substrate 10 and a semiconductor layer 11. The semiconductor layer 11 is disposed on the substrate 10, and as shown in FIG. 1, the semiconductor wafer 100 is in the first figure (at the position of reference numeral 12). The semiconductor wafer 12 formed by the layer 11 is, for example, an integrated circuit (IC) or a large-scale integration (LSI). In addition, as shown in FIGS. 1 and 2, the plurality of semiconductor wafers 12 are separated by a scribe line 13, and the scribe line 13 is in a grid shape, for example.

In this embodiment, the semiconductor layer 11 includes an insulating film (not shown) and a functional film (not shown) on the surface of the semiconductor wafer 100a, and the insulating film of the semiconductor layer 11 is, for example, SiO ₂ ) is composed of a low dielectric constant (Low k) insulating film, an inorganic material, or an organic material. The inorganic material is, for example, SiOF or BSG (SiOB), and the organic material is, for example, polyfluorene or parylene.

In one embodiment, in order to prevent the semiconductor wafer 100 from being cut into a semiconductor wafer by a dicing blade, defects, scratches, or debris may be generated, and the insulating film formed on the wafer surface may be peeled off, and a laser is applied along the dicing track 13. In addition, in order to effectively prevent the substrate 10 from melting or thermally decomposing and generating silicon vapor after laser processing, these vapors are condensed and deposited on the semiconductor wafer surface 100a, or other debris generated after laser processing is deposited on the semiconductor wafer surface 100a. A protective layer 14 is formed on the surface 100a of the semiconductor wafer. As shown in FIGS. 1 and 2, the protective layer 14 may cover the substrate 10, the semiconductor layer 11, and the scribe line 13.

In the embodiment of the present invention, high-pulse energy picosecond laser processing is applied along the cutting path 13, and the pulse length of the pulse laser of the picosecond laser processing is 1 picosecond to 999 picoseconds (ps). . The protective layer 14 is made of a solution including a water-soluble resin and a solvent. A water-soluble resin is used as a base material of the protective layer 14. In addition, the thickness of the protective layer 14 formed by the solution is 0.005 to 0.65 micrometers (μm).

In one embodiment, the weight-average molecular weight of the water-soluble resin is 900,000-1,500,000, and includes, for example, polyvinyl alcohol, polyvinyl pyrrolidone (PVP), and five or more oxyethylene recurring units. ) Polyethylene glycol, polyoxyethylene, methyl cellulose, ethyl cellulose, hydroxypropyl cellulose, polyacrylic acid, polyvinyl alcohol-polyacrylic block polymer, polyvinyl alcohol-polyacrylate block polymerization Materials, polyglycerin (polyglycerin), and water-soluble resin may include the foregoing single material, or include a combination of two or more. However, the present invention is not limited to this, as long as the material can be dissolved in a solvent such as water, and a protective layer can be formed after coating and drying.

In one embodiment, the protective layer 14 formed on the semiconductor wafer surface 100a can be rinsed with water after the picosecond laser processing. Considering the ability of the protective layer 14 to wash water, the water-soluble resin may include a resin having only one ether bond or a hydroxyl group as a polar group, such as the aforementioned polyvinyl alcohol or polyethylene glycol water-soluble resin. If it has a polar group, such as a carboxyl group or a tertiary amine, the water-soluble resin tends to be firmly fixed on the semiconductor wafer surface 100a, and may remain on the semiconductor wafer surface 100a after being rinsed with water. In contrast, if a resin having only one ether bond or a hydroxyl group as a polar group has relatively weak adhesion, it can effectively avoid that the semiconductor wafer surface 100a still retains its residue after being rinsed with water. In one embodiment, the degree of polymerization or molecular weight of the water-soluble resin is preferably low. Taking polyvinyl alcohol as an example, the molecular weight is preferably about 300. However, although a water-soluble resin having a high degree of polymerization or a high molecular weight is less likely to be washed away from the semiconductor wafer surface 100a by water, it can be used Plasticizer to avoid this situation. The plasticizer will be described later.

The solvent used in the solution for preparing the protective layer 14 may be in the form of a mixture of water and an organic solvent. In addition, the weight ratio of the solid content of the solution for preparing the protective layer 14 is 0.5% or more and less than 3%, more preferably 0.5% or more and 2.8% or less. In another embodiment, the weight ratio of the solid content of the solution is 0.5 to 2.5%. Here, the weight ratio of the solid content of the solution is defined as: water-soluble resin / (water-soluble resin + solvent) × 100%.

The organic solvent is, for example, ethanol, an ester, an alkylene glycol, an alkylene glycol monoalkyl ether, or an alkylene glycol monoalkyl ether acetate. To further illustrate, examples of organic solvents include isopropylalcohol, ethanol, propylene glycol monomethyl ether acetate (PGMEA), propylene glycol monomethyl ether (PGME), and alkyl carbonate Alkyl carbonates, such as butene carbonate, propylene carbonate, glycerine carbonate, or vinyl carbonate. These organic solvents may be used alone or in combination of two or more thereof. In this embodiment, the alkylene glycol monoalkyl ether is, for example, propylene glycol monomethyl ether.

In one implementation, the solvent used in preparing the solution of the protective layer 14 is a solvent having a weight ratio (water / organic solvent) of 3 to 17 of water to the organic solvent. If the water content is too high (that is, water / organic solvent> 17), it will be difficult to store and uneven coating. If the content of water is too low (that is, water / organic solvent <3), the cost of the process will be too high and it is not economical. In another embodiment, the solvent used in preparing the solution of the protective layer 14 may be a solvent having a weight ratio of water to organic solvents of 3-10. In again In one embodiment, the solvent used in the solution for preparing the protective layer 14 may be a solvent having a weight ratio of water to organic solvents of 3-7.

In the embodiment of the present invention, the solvent used in the solution for preparing the protective layer 14 is a solvent whose weight ratio (H ₂ O / PGME) of water to propylene glycol monomethyl ether is 3-17. If the water content is too high (that is, H ₂ O / PGME> 17), it will be difficult to store and the coating will be uneven. If the water content is too low (that is, H ₂ O / PGME <3), the process cost will be too high and it will not be economical. In another embodiment of the present invention, the solvent used in the solution for preparing the protective layer 14 is a solvent having a weight ratio (H ₂ O / PGME) of water to propylene glycol monomethyl ether of 3-10. In another embodiment of the present invention, the solvent used in the solution for preparing the protective layer 14 is a solvent having a weight ratio (H ₂ O / PGME) of water to propylene glycol monomethyl ether of 3 to 7.

In addition to the water-soluble resin described above, other mixing agents may be dissolved and applied to the solution forming the protective layer 14. For example, the solution may include a water-soluble laser absorber, a plasticizer, and a surfactant.

The water-soluble laser absorber is used in combination with a water-soluble resin. The water-soluble laser absorber may be, for example, a water-soluble dye, a water-soluble pigment, or a water-soluble ultraviolet absorber. The above materials are all water-soluble and can be uniformly stored in the protective layer 14. In addition, the water-soluble laser absorbent has a strong affinity with the semiconductor wafer surface 100a, so that the protective layer 14 can be firmly adhered to the semiconductor wafer surface 100a. Furthermore, the solution with the above materials should have a high storage capacity during the storage process, and there should be no unfavorable conditions, such as phase separation or precipitation, and good coating performance. If a water-soluble laser absorber such as a pigment is used, the protective layer 14 The laser absorptivity will change, or the storage performance and coating performance will be poor, making it difficult to form a protective layer 14 with a uniform thickness.

In one embodiment, the water-soluble dye is selected from the group consisting of azo dyes (monoazo and polyazo dyes), metal complex salt azo dyes, pyrazolone azo dye, and stilbazo azo. Dyes (stilbene azo dye), thiazole azo dye, anthraquinone dye (anthraquinone derivative, anthrone derivative), indigo dye (indigo derivative, thioindigo derivative), phthalocyanine Dyes, carbonium dyes (diphenylmethane dyes, triphenylmethane dyes, xanthene dyes, acridine dyes), quinoneimine dyes (azine dyes, azine dyes, thiazole dyes), times Methyl dyes (cyanine dyes, azomethine dyes), quinoline dyes, nitroso dyes, benzoquinone dyes and naphthoquinone dyes, naphthoyl Naphthalimide dye, perinone dye, and other dyes.

In one embodiment, the water-soluble pigment is considered as a food additive in consideration of environmental load, such as Food Red No. 2, Food Red No. 40, Food Red No. 102, Food Red No. 104, Food Red No. 105, Food Red No. 106, Food Yellow NY, Food Yellow No. 4 Tartrazine Yellow, Food Yellow No. 5, Food Yellow No. 5 Sunset Yellow FCF, Food Orange AM (Food Orange AM), Food Zhu No. 1, Food Zhu No. 4, Food Zhu 101, Food Blue 1, Food Blue 2, Food Green 3, Food Melon Color B, Food Egg Color 3

In one embodiment, the water-soluble ultraviolet absorber is, for example, 4,4'-2. Carboxybenzophenone, benzophenone-4-carboxylic acid, 2-carboxyanthraquinone, 1,2-naphthalenedicarboxylic acid, 1,8-naphthalenedicarboxylic acid, 2,3-naphthalenedicarboxylic acid, 2 1,6-naphthalenedicarboxylic acid, 2,7-naphthalenedicarboxylic acid, sodium salt, potassium salt, ammonium salt, and its quaternary ammonium salt, 2,6-anthraquinone disulfonic acid sodium salt, 2,7- Anthraquinone disulfonic acid sodium salt and ferulic acid.

In the present invention, the above-mentioned water-soluble laser absorbent is used in an amount to ensure a desired laser absorption capacity. If a laser with a wavelength of 355 nm is used for processing, for example, the solid absorption coefficient k (g absorption coefficient k) of the solution forming the protective layer 14 ranges from 3 × 10 ^-3 to 2.5 × 10 ^-1 abs‧L / g- Within cm (abs: absorbance). If the g absorption coefficient k is lower than the above range, the laser absorption capacity of the protective layer 14 is low, so that the thermal decomposition of the protective layer 14 generated by laser irradiation is significantly slower than that of the substrate 10 (for example, a silicon substrate), and the substrate 10 is thermally decomposed. The vapor pressure of the product easily causes the film to peel off, and debris is formed at the outer peripheral portion of the semiconductor wafer 100. If the g absorption coefficient k is higher than the above range, when a laser is applied, thermal decomposition of the protective layer 14 is more likely to occur due to laser reflection from the substrate 10, and the processing width of the laser is larger than the diameter of the laser focal point. It is not appropriate to cut with the cutting line 13 having a small line width.

If the above-mentioned water-soluble laser absorber is selected and used, the wavelength of the laser used is within its maximum absorption wavelength range, and a small amount of use can ensure the g absorption coefficient k in the above range. If you choose to use a water-soluble laser absorbent that does not meet the above conditions, you must use a large amount to ensure the g absorption coefficient k in the above range. However, if the water-soluble laser absorbent is used in too large an amount, when the solution containing the water-soluble laser absorbent is coated and dried to form the protective layer 14, A phase separation occurs between the soluble laser absorbent and the water-soluble resin. If the amount of the water-soluble laser absorbent used is too small, the water-soluble laser absorbent may be unevenly distributed on the protective layer 14. Therefore, when a water-soluble laser absorbent is generally selected, 100 g of a water-soluble resin is used, and 0.01 to 10 g of a water-soluble laser absorber is used to ensure a g absorption coefficient k within the above range.

The plasticizer is used to enhance the ability of the protective layer 14 to be washed away by water after laser processing. In particular, the plasticizer can be applied when a high molecular weight water-soluble resin is used. In addition, the plasticizer can suppress carbonization of the water-soluble resin due to laser irradiation. In one embodiment, water-soluble low-molecular-weight compounds can be used as plasticizers, such as ethylene glycol, triethylene glycol, tetraethylene glycol, ethanolamine, and glycerol. The plasticizer may contain one, two or more of the above-mentioned compounds in combination. The amount of plasticizer used is based on the principle that no phase separation will occur between the plasticizer and the water-soluble resin after solution coating and drying. For example, 100 grams of a water-soluble resin can be mixed with 75 grams or less of a plasticizer, in one embodiment, for example, 20 to 75 grams of a plasticizer.

Surfactants can be used to enhance coating properties and enhance the storage stability of solutions. Any nonionic, cationic, anionic, or amphoteric surfactant can be used as long as the surfactant is water-soluble.

Nonionic surfactants are, for example, nonylphenol-based, higher alcohol-based, polyol-based, polyoxyalkylene glycol-based, polyoxyethylene alkyl ester-based, polyoxyethylene alkyl-based Ether group, polyoxyethylene alkylphenol ether group or polyoxyethylene sorbitan alkyl ester group. Cationic surfactants are for example Quaternary ammonium and ammonium salts. Anionic surfactants are, for example, alkylbenzenesulfonic acid and its salts, alkyl sulfate salts, methyl taurate, and ether sulfonates. Amphoteric surfactants are, for example, imidazoline betaines, amidopropyl betaines, and aminodipropionate surfactants. The surfactant of the embodiment of the present invention may be selected from one, a combination of two or more of the above-mentioned surfactants. Depending on the preparation solution, the amount of surfactant can be 10 ppm or hundreds of ppm.

In the embodiment of the present invention, the content of the internal solids (such as the water-soluble resin, water-soluble laser absorbent, etc.) of the solution used to form the protective layer 14 of the laser cutting blade should be based on the type of water-soluble resin used. , Degree of polymerization or molecular weight, so that the solution has appropriate coating properties. If the solid content is too high, for example, coating may be difficult, resulting in uneven formation of the protective layer 14 or residual air bubbles. If the solid content is too low, the solution is liable to drip down when the solution is coated on the surface of the semiconductor wafer 100a, and it is not easy to control the thickness of the protective layer 14 formed after the solution is dried.

After the aforementioned solution is applied onto the surface 100a of the semiconductor wafer to be processed, the applied solution is dried to form the protective layer 14. The semiconductor wafer 100 includes a plurality of semiconductor wafers 12 divided by grid-shaped scribe lines 13, and these scribe lines 13 are irradiated with a laser beam through a protective layer 14 to form trenches. The thickness of the protective layer 14 on the scribe line 13 is, for example, 0.1 to 5 μm . These semiconductor wafer surfaces 100a to be processed usually have many dents and protrusions, and a scribe line 13 is formed in these dents. Therefore, if the thickness of the protective layer 14 is small, the thickness of the protective layer 14 on these protrusions is very small, so that debris may enter the protective layer 14 and be deposited on the surface of the semiconductor wafer 12. On the other hand, too large a thickness of the protective layer 14 does not bring special advantages, and it is more time-consuming to rinse the protective layer 14 with water after laser processing.

When the protective layer 14 formed by the solution of the embodiment of the present invention is formed on the semiconductor wafer surface 100a, a protective tape may be adhered to the back surface of the semiconductor wafer 100. Next, the surface 100 a of the semiconductor wafer is irradiated with the laser beam through the protective layer 14 (dicing track 13).

The following proposes a solution for forming the protective layer 14 as a picosecond laser process according to the present invention. The experimental and comparative examples can perform picosecond laser processing steps under the following processing conditions: Machine manufacturer: A.L.S.I

Wavelength: 1064nm

Output: 7 ~ 8W

In the following examples and comparative examples, polyvinyl pyrrolidone (PVP) is used as the water-soluble resin, and the solvent is water and propylene glycol monomethyl ether (PGME).

First, select the ingredients according to the following Tables 1 and 2, and mix the above ingredients, add them to a mixer equipped with a stirrer, and stir at room temperature and 500 rpm for 1 hour, then prepare for forming Solution for protective layer 14 for wafer dicing. Then, the semiconductor wafer 100 of the protective layer 14 formed by the solution is mounted on a laser processing device that meets the above specifications to perform picosecond laser processing, and observe the dicing performance.

The components of the embodiment are shown in Table 1:

The components of the comparative example are shown in Table 2:

It should be noted that the steps of performing picosecond laser processing in the experimental example and the comparative example include performing under three conditions of low power (such as 0.37W), medium power (such as 0.7W), and high power (such as 1.7W) The results are in accordance with Tables 1 and 2.

Among them, 6 ml of solution is taken for thick film, and it is rotated at 600 rpm for 50 seconds; 6 ml of solution is taken for thin film, and it is rotated at 5000 rpm and 50 seconds at 600 rpm and 50 seconds.

Referring to the results of Tables 1 and 2, the cutting performance of the protective layer formed by the solutions prepared in Examples 1 to 5 is significantly better than that of the protective layer formed by the solutions prepared in Comparative Examples 1 to 4. That is, when the solution used to form the protective layer 14 for wafer picosecond laser processing has a solid content weight ratio of 0.5% or more but less than 3%, the semiconductor wafer 100 may be processed by the picosecond laser processing. Render better Cutting performance.

Referring to the results of Table 2, since the weight ratio of the solid content in Comparative Example 1 is not in the range of 0.5% or more and less than 3%, the cut surface of the film or the thick film is not good. In Comparative Examples 2 to 3, since the weight ratio of the solid content was further increased and was not within the range of 0.5% or more and less than 3%, the cutting surface of the film or thick film had burrs or even corners. In Comparative Example 4, since no water-soluble resin was added, a film could not be formed regardless of the thin film or thick film conditions.

Following the above description, the solution of the embodiment of the present invention can form a protective layer on the wafer to be processed by the laser, so that the laser irradiates the surface of the wafer through the protective layer, and effectively avoids condensed silicon vapor or other via laser. Debris generated after processing is deposited on the surface of the semiconductor wafer, causing a reduction in quality. At the same time, the solution of the embodiment of the present invention is suitable for picosecond laser processing, so that the accuracy of material removal can be improved, and the phenomenon of burrs can be effectively reduced.

In summary, although the present invention has been disclosed as above with the embodiments, it is not intended to limit the present invention. Those with ordinary knowledge in the technical field to which the present invention pertains can make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, the protection scope of the present invention shall be determined by the scope of the attached patent application.

Claims (10)

A solution for forming a protective layer for picosecond laser processing. The solution includes: a water-soluble resin; and a solvent, wherein the solvent includes water and an organic solvent, and the weight ratio of the water to the organic solvent is 3 ~ 17, and the weight ratio of the solid content of the solution is 0.5% or more and less than 3%. The solution according to item 1 of the scope of the patent application, wherein the weight ratio of the solid content of the solution is 0.5% to 2.5%. The solution according to item 1 of the scope of patent application, wherein the organic solvent includes isopropanol, propylene glycol monomethyl ether acetate, propylene glycol monomethyl ether, butene carbonate, propylene carbonate, glycerol carbonate, and At least one of ethylene carbonate. The solution according to item 1 of the patent application scope, wherein the water-soluble resin includes polyvinyl alcohol, polyvinylpyrrolidone, polyethylene glycol having five or more oxyethylene repeating units, polyoxyethylene, methyl fiber Cellulose, ethyl cellulose, hydroxypropyl cellulose, polyacrylic acid, polyvinyl alcohol-polyacrylic block polymer, polyvinyl alcohol-polyacrylate block polymer, or polyglycerin. The solution according to item 1 of the patent application scope further includes a water-soluble laser absorbent, wherein the water-soluble laser absorbent includes at least one of a water-soluble dye, a water-soluble pigment, and a water-soluble ultraviolet absorber. . The solution according to item 1 of the patent application range, wherein the weight-average molecular weight of the water-soluble resin is 900,000-1,500,000. The solution according to item 1 of the scope of patent application, wherein the thickness of the protective layer is 0.005 to 0.08 microns. The solution according to item 1 of the patent application range, wherein the pulse length of the pulse laser processed by the picosecond laser is 1 picosecond to 999 picoseconds. The solution according to item 1 of the scope of patent application, wherein the viscosity of the solution is 4 to 21 mPas. A method for manufacturing a solution for forming a protective layer for wafer picosecond laser processing includes mixing a water-soluble resin and a solvent, wherein the solvent includes water and an organic solvent, and a weight ratio of the water to the organic solvent is 3-17, and the weight ratio of the solid content of the solution is 0.5% or more and less than 3%.