CN100425405C - Freezing nanometer abrasive polishing pad and its prepn. method - Google Patents

Abstract

Aiming at the shortcomings of traditional polishing pads such as low efficiency, high cost, poor uniformity and reliability, and weak process control ability in the polishing process, the present invention proposes a frozen nano-abrasive polishing pad and its preparation method to adapt to the current polishing process. processing needs. The invention uses liquid as a binder to bond nano-abrasives by freezing to form a polishing pad, which can be used for polishing various thin workpieces, and is especially suitable for processing heat-sensitive materials, soft materials, crystal materials, and the like. The invention has the advantages of simple manufacture, low processing cost, high processing efficiency, strong process control ability, and environmental protection.

Description

Frozen nano abrasive polishing pad and preparation method thereof

technical field

The invention relates to a nano-abrasive polishing pad and a preparation method thereof, in particular to a polishing pad formed by bonding nano-abrasives through freezing by using liquid as a binder.

Background technique

As we all know, the traditional CMP (Chemical Mechanical Polishing) system is composed of three parts: a rotating workpiece holding device, a workbench carrying a polishing pad, and a polishing liquid (slurry) supply system. During polishing, the rotating workpiece is pressed against the polishing pad that rotates with the worktable with a certain pressure, while the polishing liquid composed of submicron or nanometer abrasives and chemical liquid flows between the workpiece and the polishing pad, and produces chemical on the surface of the workpiece. The reaction, the chemical reactants formed on the surface of the workpiece are removed by the mechanical friction of the abrasive grains. Due to the selection of free abrasives that are softer than the workpiece or have the same hardness as the workpiece, in the alternating process of chemical film formation and mechanical film formation, a very thin layer of material is removed from the surface of the workpiece through the joint action of chemistry and machinery to achieve ultra-precision surface processing. . Although this traditional CMP technology is widely used in ultra-precision surface processing, it also shows certain shortcomings in practical applications: (1) The traditional CMP is based on three-body (free abrasive, polishing pad and silicon wafer) wear Mechanism, process parameters are many, the processing process is unstable, it is difficult to realize automatic control, and the production efficiency is low. (2) Since the polishing pad is an organic fabric with certain elasticity, the selectivity to material removal during polishing is not high, resulting in defects such as over polishing, dishing, and nitride corrosion. . (3) After polishing, a part of free abrasives will be inlaid on the surface of the film layer, which is not easy to clean. Moreover, the composition of the slurry is complex, and the removal of residual slurry on the polished surface is a difficult problem in post-CMP cleaning. (4) Due to the uneven distribution of abrasive particles between the polishing pad and the workpiece, the material removal rate of each part of the workpiece is inconsistent, which affects the surface flatness. Especially for large-size workpieces, this effect is more prominent. (5) During the polishing process, the polishing pad undergoes plastic deformation and gradually becomes smooth, or the micropore surface of the polishing pad surface is blocked, which reduces the ability to accommodate slurry and remove waste, resulting in a decrease in material removal rate over time. Continuous conditioning and wetting of the polishing pad is required to restore its surface roughness and porosity. In addition, the uneven wear of the polishing pad makes the polishing process unstable and difficult to optimize parameters. (6) The cost of consumables such as CMP slurry, polishing pads, and dressing discs accounts for about 70% of the total cost of CMP, while the cost of polishing slurry accounts for 60% to 80% of the consumables. (7) Polishing slurry management and waste slurry treatment are also quite troublesome.

To sum up, the requirements for efficiency, cost, uniformity, reliability, and process control capability of CMP planarization are getting higher and higher. At present, when polishing pads are used for finishing, there is an urgent need for a polishing pad with strong adaptability, convenient manufacture, and low grinding heat, which uses fixed abrasives instead of free abrasives and polishing pads in traditional CMP.

Contents of the invention

The purpose of the present invention is to provide a frozen nano-abrasive polishing pad and a preparation method thereof, so as to meet the needs of current CMP finishing.

Technical scheme of the present invention is:

A frozen nano-abrasive polishing pad is characterized in that it is mainly composed of nano-abrasives, additives and a liquid that acts as a bond after freezing, wherein the abrasives account for 10% to 70% of the total weight of the polishing pad, and the additives account for 5% of the total weight ~9%, the balance is the liquid that eventually freezes.

The additive is composed of polyhydroxydiamine, alkyl alcohol polyoxyethylene ether, edetate disodium salt and carboxymethyl cellulose, or is composed of polyhydroxydiamine, alkyl alcohol polyoxyethylene ether, It is composed of disodium salt of ethylenediaminetetraacetic acid and polyethylene glycol, and their proportioning relationship is: polyhydroxydiamine accounts for 2% to 3% of the weight of the entire polishing pad, and alkyl alcohol polyoxyethylene ether accounts for the entire weight of the polishing pad. 2%-3% by weight, disodium ethylenediaminetetraacetic acid accounts for 0.5%-1% of the weight of the entire polishing pad, and carboxymethyl cellulose or polyethylene glycol accounts for 0.5%-2% of the weight of the entire polishing pad.

The nano-abrasive is one or a combination of Al ₂ O ₃ , SiC, Cr ₂ O ₃ , SiO ₂ , CeO ₂ and diamond powder.

The liquid that finally freezes is water.

A kind of preparation method of frozen nano-abrasive polishing pad of above-mentioned frozen emery wheel, it is characterized in that comprising the following steps:

a. First, mix the well-proportioned nano-abrasives, additives and liquid evenly to obtain the liquid or colloidal raw materials to be frozen in which the abrasives are in a dispersed and suspended state and put them into the mold;

b, then above-mentioned mold is put into freezing equipment, freezes under the condition of minus 1 to minus 70 degrees, and the raw material to be frozen in the mold is completely solidified into a solid to obtain the frozen nano-abrasive polishing pad identical with the shape of the mold.

Beneficial effects of the present invention:

1. It is simple to manufacture and easy to form, and can be manufactured into various shapes.

2. It is suitable for forming abrasive grains of various materials and particle sizes.

3. The grinding heat generated during the processing is very small, which is beneficial to prevent the thermal stress of the parts being ground, and it is easy to use. It can be ensured that the grinding wheel is not damaged by adding a cooling device to the grinding head and filling liquid nitrogen. Will self-melt due to ambient temperature.

4. The bonding strength can fully meet the requirements of use. When the liquid freezes, its hardness and strength are quite large, which not only ensures the strength of the combination of abrasive grains and ice, but also the ice itself can participate in certain cutting. Blocks of ice are hard and strong enough to crack steel plates, as evidenced by the destruction of the Titanic ship on floating ice in the sea.

5. It can realize self-lubricating grinding, and no lubricant is added during the processing, which is beneficial to environmental protection and adapts to the current development direction of green manufacturing.

6. Provide effective processing tools for the manufacture of ultra-thin crystal materials.

7. It provides a brand-new processing tool for high-precision surface processing of soft materials and non-metallic parts, which will definitely lead to changes in material processing methods and is conducive to the development of new uses for such materials.

8. It is easy to use and can be made and used immediately.

9. The operation process is simple, and the self-sharpening of the abrasive tool can be realized. There is no downtime problem caused by replacing and trimming the polishing pad and cleaning the polishing slurry, and there is no maintenance and disposal problem of the polishing liquid.

10. It can work at high speed, and the speed can reach hundreds of revolutions, which is conducive to improving the processing efficiency and overcoming the shortcomings of traditional CMP with too high speed and abrasive spillage.

11. Due to the use of fixed abrasive polishing pads, there are no free abrasive particles, so it can be considered to be based on a two-body wear mechanism.

12. It has excellent planarization ability, which can quickly remove the oxide film on the protruding part, while the oxide film on the low-lying part is not affected by mechanical action, and has strong selective removal ability for uneven surface materials, and the surface morphology is highly and flattened The film thickness ratio can reach 200:1.

13. In chip multilayer wiring, direct high-density plasma (HDP) shallow trench isolation (STI) polishing becomes possible, eliminating the need for reactive ion etching (RIE) process.

14. Small in-wafer non-uniformity (WIW-UN) and in-chip non-uniformity (WID-NU) can be achieved.

15. With polishing self-stop function (Self-stopping). Being very insensitive to overpolishing, only minimal dishing and erosion occurs, equivalent to an automatic cessation of the polishing action.

16. The abrasive utilization rate is high, effectively reducing the pollution of impurity particles on the polishing surface, the processed surface is easy to clean, and the waste liquid treatment is simple, which can effectively reduce the cost.

17. There are few process variables, the processing process is stable, repeatable, and easy to realize automatic control.

18. Computer-controlled chemical reactions and/or medical reactions can be realized.

19. According to different additives, the invention can also be used to manufacture non-CMP grinding tools, which can be used for final polishing of crystal, glass and other industries.

Description of drawings

Fig. 1 is a schematic diagram of the mold structure of the frozen nanoabrasive polishing pad of the present invention.

Fig. 2 is a schematic diagram of the frozen nanoabrasive polishing pad of the present invention.

Detailed ways

The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

As shown in Figure 1 and 2.

Embodiment one.

A kind of ultra-thin material polishing CMP frozen polishing pad, by 500 grams of nanometer SiO ₂ (or nanometer CeO ₂ ) abrasive, 70 grams of additives (it consists of 25 grams of polyhydroxy diamines, 20 grams of alkyl alcohol polyoxyethylene ethers, EDTA disodium salt 10 grams, carboxymethyl cellulose (CMC) or polyethylene glycol (dispersant) 15 grams) and the water (or concentration is the hydrous ethanol of 45) composition of remainder 440, use Before mixing the three evenly to form a colloidal mixture in which the abrasive is dispersed and suspended, press it into the polishing pad mold, and then put it together with the mold in a low-temperature test box for 45 minutes and freeze at minus 40 degrees. Keep warm for 15 minutes. When using it, it should be demolded first, and then quickly installed on the power head with cooling device or liquid nitrogen to start use. Using this polishing pad to process single crystal silicon wafers can make the surface roughness Ra=2.01nm , which is nearly 14 times more efficient than traditional CMP.

Embodiment two.

A kind of CMP frozen polishing pad for supersoft material polishing, by 100 grams of nanometer CeO ₂ (or nanometer SiO ₂ ) abrasive, 60 grams of additives (it consists of 20 grams of polyhydroxydiamine, 20 grams of alkyl alcohol polyoxyethylene ether , EDTA disodium salt 10 grams, carboxymethyl cellulose (CMC) or polyethylene glycol (dispersant) 10 grams) according to the proportion of setting and the water of the 850 of surplus (or concentration is 32 water-containing ethanol), before use, mix the three evenly to form a colloidal mixture in which the abrasive is dispersed and suspended, then press it into the polishing pad mold, and then put it into a low-temperature test box together with the mold and freeze it for 50 Minutes, and keep warm for 60 minutes at minus 30 degrees. When using, it should be demolded first, and then quickly installed on the power head with cooling device or liquid nitrogen to start up and use. Using this polishing pad to process 1mm aluminum plate can make the surface roughness value reach Ra=3.03nm, which is nearly 10 times higher than the traditional CMP efficiency.

Embodiment three.

A kind of superhard material polishing CMP frozen polishing pad, by the nano-diamond abrasive material of 700 grams (or nano-Al2O3 abrasive material, nano-SiC abrasive material, nano-Cr2O3 abrasive material), the additive of 80 grams (it is made of polyhydroxy diamine 30 grams, alkyl Alcohol polyoxyethylene ether 25 grams, ethylenediaminetetraacetic acid disodium salt 10 grams, carboxymethyl cellulose (CMC) or polyethylene glycol (dispersant) 15 grams and 230 liquid (or concentration of 90 aqueous ethanol ) composition, the three are mixed uniformly before use to form a colloidal mixture in which the abrasive is dispersed and suspended, and then pressed into the polishing pad mold, and then put into a low-temperature test box together with the mold to freeze for 35 minutes, and Keep it warm for 30 minutes at minus 70 degrees. When using it, it should be demolded first, and then quickly installed on the power head with cooling device or liquid nitrogen to start use. Using this polishing pad to process CVD diamond thick film can make The surface roughness value reaches Ra=4.05nm, which is nearly 12 times higher than the traditional CMP efficiency.

Embodiment four.

This embodiment is basically the same as Embodiments 1 to 3, except that the added additives do not contain components that react chemically with the processed object.

Claims (5)

1. A frozen nano-abrasive polishing pad is characterized in that it is mainly composed of nano-abrasives, additives and frozen liquid that acts as a bond, wherein the abrasives account for 10% to 70% of the total weight of the polishing pad, and the additives account for 10% of the total weight. 5% to 9%, and the balance is the liquid that finally freezes. 2. The frozen nano-abrasive polishing pad according to claim 1, characterized in that the additive is made of polyhydroxydiamine, alkyl alcohol polyoxyethylene ether, edetate disodium salt and carboxymethyl fiber element, or composed of polyhydroxydiamine, alkyl alcohol polyoxyethylene ether, edetate disodium salt and polyethylene glycol, and their ratio relationship is: polyhydroxydiamine accounts for 1% of the weight of the entire polishing pad 2% to 3%, alkyl alcohol polyoxyethylene ether accounts for 2% to 3% of the weight of the entire polishing pad, disodium salt of edetate accounts for 0.5% to 1% of the weight of the entire polishing pad, carboxymethyl fiber Sodium or polyethylene glycol accounts for 0.5% to 2% of the weight of the entire polishing pad. 3. The frozen nano-abrasive polishing pad according to claim 1, characterized in that the nano-abrasive is one or one of Al ₂ O ₃ , SiC, Cr ₂ O ₃ , SiO ₂ , CeO ₂ and diamond powder more than one combination. 4. The frozen nanoabrasive polishing pad according to claim 1, characterized in that the liquid that finally freezes is water. 5. A method for preparing the frozen nano-abrasive polishing pad according to claim 1, characterized in that it comprises the following steps: a. First, mix the well-proportioned nano-abrasives, additives and liquid evenly to obtain the liquid or colloidal raw materials to be frozen in which the abrasives are in a dispersed and suspended state and put them into the mold; b, then above-mentioned mold is put into freezing equipment, freezes under the condition of minus 1 to minus 70 degrees, and the raw material to be frozen in the mold is completely solidified into a solid to obtain the frozen nano-abrasive polishing pad identical with the shape of the mold.

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