Polishing solution and preparation method thereof

Abstract

The invention relates to the technical field of chemical mechanical polishing, in particular to a polishing solution and a preparation method thereof, and the polishing solution comprises the following components by weight: 600-850 parts of silica sol; 2-6 parts of a metal chelating agent; 3-7 parts of a pH regulator; 0.01 to 0.10 part of a surfactant; 1-10 parts of organic amine; 125 to 380 parts of deionized water; the surfactant is selected from at least one of fatty alcohol ether phosphate, fatty alcohol-polyoxyethylene ether, alkylphenol polyoxyethylene ether and nonylphenol polyoxyethylene ether. According to the polishing solution provided by the invention, through the synergistic effect of the surfactant and other components in the polishing solution, not only is the removal rate improved, but also a corrosion inhibition protection layer can be formed on the surface of a silicon wafer, and chemical corrosion generated on the surface of the silicon wafer due to too strong chemical action is reduced, so that the surface of the silicon wafer is prevented from being damaged; therefore, the polishing quality is improved while the removal rate is increased.

Description

Technical Field

[0001] The invention relates to the technical field of chemical mechanical polishing, and in particular to a polishing liquid and a preparation method thereof. Background Art

[0002] Silicon wafers are the main substrate material for integrated circuits (ICs), and their surface roughness is one of the important factors affecting the etching line width of integrated circuits. With the continuous improvement of the integration of integrated circuits and the continuous reduction of feature sizes, the requirements for the processing accuracy and surface quality of silicon wafers are becoming higher and higher. At present, the Semiconductor Industry Association (SIA) has the following requirements for silicon wafers with feature sizes of 0.065 to 0.13 μm: global flatness (GBIR) less than 2 μm, surface roughness reaching nanometer and sub-nanometer levels, and very little residual stress and damage layer on the surface or no damage, that is, higher requirements are put forward for the surface flatness, surface roughness, surface defects, etc. of silicon wafer processing.

[0003] At present, the use of chemical mechanical polishing (CMP) technology to planarize the surface of silicon wafers has become one of the essential process steps in the era of deep submicron integrated circuit manufacturing technology. The chemical mechanical polishing process is to keep the silicon wafer and the polishing table / polishing pad rotating under a certain downward pressure, input the polishing liquid onto the polishing pad, and obtain high-quality polished silicon wafers under the synergistic effect of chemistry and mechanics.

[0004] The polishing liquid currently used for polishing silicon wafers usually includes abrasives, metal chelating agents, and corrosive agents (inorganic bases or organic bases), etc. When polishing silicon wafers, there is a problem of slow removal rate. Summary of the invention

[0005] The object of the present invention is to provide a polishing liquid which can improve the polishing rate through the synergistic effect of various components.

[0006] The technical solution adopted by the present invention to solve the technical problem is:

[0007] A polishing liquid, comprising the following components in parts by weight:

[0008]

[0009] The surfactant is selected from at least one of fatty alcohol ether phosphate, fatty alcohol polyoxyethylene ether, alkylphenol polyoxyethylene ether and nonylphenol polyoxyethylene ether.

[0010] Preferably, the mass concentration of the silica sol is 30%.

[0011] Preferably, the particle size of the silica sol is in the range of 20-200 nm.

[0012] Preferably, the silica sol includes a first silica sol with a particle size of 20 nm, a second silica sol with a particle size of 50 nm, and a third silica sol with a particle size of 70 nm.

[0013] Preferably, the mass ratio of the first silica sol, the second silica sol and the third silica sol is (5-7):(1-5):1.

[0014] Preferably, the metal chelating agent is selected from at least one of diethylenetriaminepentaacetic acid, ethylenediaminetetraacetic acid, aminotriacetic acid, and hydroxyethylenediphosphonic acid.

[0015] Preferably, the pH regulator is selected from at least one of potassium hydroxide, tetraethylammonium hydroxide, tetramethylammonium hydroxide, diethylenetriamine, triethylenetetramine, tartaric acid, citric acid, glycine and lactic acid.

[0016] Preferably, the organic amine is selected from at least one of tetramethylammonium hydroxide, tetraethylammonium hydroxide, tetrapropylammonium hydroxide, tetrabutylammonium hydroxide, trimethylbenzylammonium hydroxide, trimethylhydroxyethylammonium hydroxide, dimethyldihydroxyethylammonium hydroxide, diethylamine, triethylamine, ethylenediamine, monoethanolamine, diethanolamine, triethanolamine, isopropanolamine, diisopropanolamine or triisopropanolamine.

[0017] Preferably, the pH value of the polishing liquid is 5-13.

[0018] Another object of the present invention is to provide a method for preparing the polishing liquid as described above, comprising the following steps:

[0019] S1: Dissolve the pH regulator, metal chelating agent, organic amine and surfactant in deionized water according to the formula to obtain a premixed solution;

[0020] S2: Under stirring, the premixed liquid is added into the silica sol to obtain a polishing liquid.

[0021] The beneficial effects of the present invention are:

[0022] The polishing liquid provided by the present invention, through the synergistic effect of the surfactant and other components in the polishing liquid, not only helps to improve the removal rate, but also can form a corrosion inhibition protective layer on the surface of the silicon wafer, reduce the chemical corrosion of the silicon wafer surface caused by excessive chemical action, and thus avoid damage to the silicon wafer surface, thereby improving the removal rate while improving the polishing quality. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] The present invention is further described below in conjunction with the accompanying drawings and embodiments.

[0024] Figure 1 is a schematic diagram of silicon wafer removal rate of Examples 1-4 of the present invention;

[0025] Figure 2 It is a schematic diagram of the silicon wafer removal rate of Examples 5-8 of the present invention. DETAILED DESCRIPTION

[0026] The present invention is now further described in detail. The embodiments described below are exemplary and intended to be used to explain the present invention, but cannot be understood as limiting the present invention. All other embodiments obtained by ordinary technicians in this field without creative work based on the embodiments of the present invention belong to the scope of protection of the present invention.

[0027] In order to solve the problem that the surface of the silicon wafer is easily damaged when the silicon wafer is polished in the prior art, the present invention provides a polishing liquid, which comprises the following components in parts by weight:

[0028]

[0029] Specifically, during the chemical mechanical polishing process, the role of the polishing liquid is to react chemically with the surface of the wafer through chemical reagents, and then remove the reactants produced by the chemical reaction through the mechanical friction of the abrasive. Through the dual coupling of chemical corrosion and mechanical grinding, the surface defects of the wafer are removed at the atomic level, thereby achieving precise surface processing of the wafer; therefore, the composition of the polishing liquid plays a decisive role in the rate and effect of chemical mechanical polishing.

[0030] To ensure the removal rate, the present invention preferably introduces a surfactant into the polishing liquid so that the surfactant is adsorbed on the surface of the silicon wafer and the silicon dioxide particles to form an adsorption layer, which not only increases the removal rate but also protects the surface of the silicon wafer from chemical and mechanical corrosion, thereby avoiding damage to the surface of the silicon wafer.

[0031] The present invention further preferably selects at least one of the surfactants from fatty alcohol ether phosphate, fatty alcohol polyoxyethylene ether, alkylphenol polyoxyethylene ether and nonylphenol polyoxyethylene ether, so as to form a thin film adsorption layer as a corrosion inhibition protective layer on the surface of the silicon wafer through synergistic action with other components in the polishing liquid, thereby reducing chemical corrosion on the surface of the silicon wafer caused by excessive chemical action, thereby avoiding damage to the surface of the silicon wafer and improving the polishing quality.

[0032] As an abrasive in the polishing liquid, silica sol is used to remove the softened layer on the surface of the silicon wafer produced by the action of chemical reagents by repeatedly grinding, rolling and sliding on the surface of the silicon wafer during the polishing process; therefore, silica sol plays an important role in the chemical mechanical barrel process; in order to take into account both the polishing quality and the polishing rate, the preferred mass concentration of silica sol in the present invention is 30%.

[0033] Furthermore, the preferred particle size range of the silica sol in the present invention is 20-200 nm.

[0034] In order to further avoid scratches on the surface of the silicon wafer, ensure the polishing quality and improve the polishing rate, the silica sol of the present invention is preferably a composite silica sol. Specifically, the silica sol preferably includes a first silica sol with a particle size of 20 nm, a second silica sol with a particle size of 50 nm, and a third silica sol with a particle size of 70 nm. It is further preferred that the mass ratio of the first silica sol, the second silica sol and the third silica sol is (0-7):(1-5):1.

[0035] The present invention further preferably selects at least one of the metal chelating agent from diethylenetriaminepentaacetic acid, ethylenediaminetetraacetic acid, aminotriacetic acid and hydroxyethylidenediphosphonic acid, so as to improve the polishing rate by complexation and self-passivation effect while ensuring the polishing quality.

[0036] In order to adjust the formation rate and removal rate of the passivation film on the surface of the silicon wafer, thereby improving the polishing effect, the preferred pH regulator of the present invention is selected from at least one of potassium hydroxide, tetraethylammonium hydroxide, tetramethylammonium hydroxide, diethylenetriamine, triethylenetetramine, tartaric acid, citric acid, glycine, and lactic acid.

[0037] The present invention introduces organic amines and utilizes N atoms to polarize silicon on the surface of the substrate, thereby improving the polishing rate; specifically, the present invention preferably uses at least one of the organic amines selected from tetramethylammonium hydroxide, tetraethylammonium hydroxide, tetrapropylammonium hydroxide, tetrabutylammonium hydroxide, trimethylbenzylammonium hydroxide, trimethylhydroxyethylammonium hydroxide, dimethyldihydroxyethylammonium hydroxide, diethylamine, triethylamine, ethylenediamine, monoethanolamine, diethanolamine, triethanolamine, isopropanolamine, diisopropanolamine or triisopropanolamine.

[0038] In addition, the present invention can accelerate the removal rate of the silicon wafer surface and improve the polishing rate by adopting a suitable pH regulator and an organic amine addition ratio.

[0039] In order to take into account both the polishing effect and the stability of the polishing liquid, the pH value of the polishing liquid of the present invention is preferably 5-13, and further preferably 10-13.

[0040] Since the chemical mechanical polishing process involves both chemical reaction and mechanical process, the result is the result of the coupling of chemical reaction and mechanical process, which has a certain complexity. The selection and proportion of various additives in the polishing liquid will affect the surface quality of the silicon wafer. Moreover, it should be emphasized that due to the complexity of the process, the same additive may play different roles in different polishing liquid composition systems. The polishing liquid provided by the present invention can reduce surface damage, improve polishing quality and increase polishing rate through the synergistic effect of various components.

[0041] Another object of the present invention is to provide a method for preparing the polishing liquid as described above, the preparation method comprising the following steps:

[0042] S1: Dissolve the pH regulator, metal chelating agent, organic amine and surfactant in deionized water according to the formula to obtain a premixed solution;

[0043] S2: Under stirring, the premixed liquid is added to the silica sol to obtain a polishing liquid.

[0044] The preparation method of the polishing liquid provided by the present invention has a simple preparation process; the prepared polishing liquid, through the synergistic effect of the surfactant and other components in the polishing liquid, can not only improve the removal rate, but also form a corrosion inhibition protective layer on the surface of the silicon wafer, thereby reducing chemical corrosion on the surface of the silicon wafer caused by excessive chemical action, thereby avoiding damage to the surface of the silicon wafer and improving the polishing quality.

[0045] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, specific embodiments of the present invention are described in detail below.

[0046] Example 1

[0047] Prepare 1000g polishing liquid:

[0048] Take 6g potassium hydroxide, 4g diethylenetriaminepentaacetic acid, 0.05g fatty alcohol polyoxyethylene ether, and 3g triethylamine and dissolve them in 230.95g DIW to make a premix; then add the premix to 756g colloidal silicon dioxide with a particle size of 70nm and a concentration of 30% under stirring to obtain a 01 polishing liquid with a pH of about 12.

[0049] First, take the prepared 01 polishing liquid, use the Zhiling 1280 polishing machine, the polishing pad is: SUBA800 flat pad, the polishing pressure is: 280kg, the polishing head / disc speed is: 30 / 29rpm, and the circulation flow is 3L / min. The temperature of the polishing disk is controlled at 30±8℃, and the liquid dilution ratio is 1:20 for polishing. The polishing test results are shown in Table 1.

[0050] Example 2

[0051] Prepare 1000g polishing liquid:

[0052] Take 5g potassium hydroxide, 4g diethylenetriaminepentaacetic acid, 0.05g fatty alcohol polyoxyethylene ether, and 3g triethylamine and dissolve them in 231.95g DIW to make a premix; then add the premix to 756g colloidal silicon dioxide with a particle size of 70nm and a concentration of 30% under stirring to obtain 02 polishing liquid with a pH of about 12.

[0053] First, take the prepared 02 polishing liquid, use the Zhiling 1280 polishing machine, the polishing pad is: SUBA800 flat pad, the polishing pressure is: 280kg, the polishing head / disc speed is: 30 / 29rpm, and the circulation flow is 3L / min. The temperature of the polishing disk is controlled at 30±8℃, and the liquid dilution ratio is 1:20 for polishing. The polishing test results are shown in Table 1.

[0054] Example 3

[0055] Prepare 1000g polishing liquid:

[0056] Take 6g potassium hydroxide, 5g diethylenetriamine pentaacetic acid, 0.05g fatty alcohol polyoxyethylene ether, and 2g triethylamine and dissolve them in 230.95g DIW to make a premix; then add the premix to 756g colloidal silicon dioxide with a particle size of 70nm and a concentration of 30% under stirring to obtain 03 polishing liquid with a pH of about 12.

[0057] First, take the prepared 03 polishing liquid, use the Zhiling 1280 polishing machine, the polishing pad is: SUBA800 flat pad, the polishing pressure is: 280kg, the polishing head / disc speed is: 30 / 29rpm, and the circulation flow rate is 3L / min. The temperature of the polishing disk is controlled at 30±8℃, and the liquid dilution ratio is 1:20 for polishing. The polishing test results are shown in Table 1.

[0058] Example 4

[0059] Prepare 1000g polishing liquid:

[0060] Take 6g potassium hydroxide, 5g diethylenetriamine pentaacetic acid, 0.05g fatty alcohol polyoxyethylene ether, and 2g triethylamine and dissolve them in 230.95g DIW to make a premix; then add the premix to 756g colloidal silicon dioxide with a particle size of 70nm and a concentration of 30% under stirring to obtain 04 polishing liquid with a pH of about 12.

[0061] First, take the prepared 04 polishing liquid, use the Zhiling 1280 polishing machine, the polishing pad is: SUBA800 flat pad, the polishing pressure is: 280kg, the polishing head / disc speed is: 30 / 29rpm, and the circulation flow is 3L / min. The temperature of the polishing disk is controlled at 30±8℃, and the liquid dilution ratio is 1:20 for polishing. The polishing test results are shown in Table 1.

[0062] Table 1

[0063]

[0064] It can be seen from Examples 1-2 that different results are achieved on the removal rate of silicon wafers by using silica sol with a particle size of 70 nm and different amounts of potassium hydroxide. By comparison, it can be found that under the same conditions of other additive ratios, increasing the amount of potassium hydroxide used and increasing its chemical corrosion effect can accelerate the removal rate of silicon wafers.

[0065] It can be seen from Examples 3-4 that, in comparison with the results of Examples 1-2, the ratio of diethylenetriaminepentaacetic acid to triethylamine was changed based on the 6g potassium hydroxide implementation group, and the polishing results were compared. It was shown that when the ratio of diethylenetriaminepentaacetic acid to triethylamine was 5 / 2, the silicon wafer removal rate was the fastest. Figure 1 , detailed polishing rates are shown in Table 2.

[0066] Table 2

[0067]

[0068] Example 5

[0069] Prepare 1000g polishing liquid:

[0070] Take 3g potassium hydroxide, 2g ethylenediaminetetraacetic acid, 0.05g fatty alcohol polyoxyethylene ether, and 10g isopropanolamine and dissolve them in 284.95g DIW to make a premix; then add the premix into 700g colloidal silica with particle sizes of 20nm, 50nm, and 70nm and a concentration of 30% under stirring. The mass ratios of the three particle sizes of colloidal silica are 5:4:1, respectively, to obtain 05 polishing liquid with a pH of about 12.

[0071] First, take the prepared 05 polishing liquid, use the Zhiling 1280 polishing machine, the polishing pad is: SUBA800 flat pad, the polishing pressure is: 280kg, the polishing head / disc speed is: 30 / 29rpm, and the circulation flow is 3L / min. The temperature of the polishing disk is controlled at 30±8℃, and the liquid dilution ratio is 1:25 for polishing. The polishing test results are shown in Table 3.

[0072] Example 6

[0073] Prepare 1000g polishing liquid:

[0074] Take 3g potassium hydroxide, 2g ethylenediaminetetraacetic acid, 0.05g fatty alcohol polyoxyethylene ether, and 10g isopropanolamine and dissolve them in 284.95g DIW to make a premix; then add the premix into 700g colloidal silica with particle sizes of 20nm, 50nm, and 70nm and a concentration of 30% under stirring. The ratios of the three particle sizes of colloidal silica are 6:3:1, respectively, to obtain 06 polishing liquid with a pH of about 12.

[0075] First, take the prepared 06 polishing liquid, use the Zhiling 1280 polishing machine, the polishing pad is: SUBA800 flat pad, the polishing pressure is: 280kg, the polishing head / disc speed is: 30 / 29rpm, and the circulation flow rate is 3L / min. The temperature of the polishing disk is controlled at 30±8℃, and the liquid dilution ratio is 1:25 for polishing. The polishing test results are shown in Table 3.

[0076] Example 7

[0077] Prepare 1000g polishing liquid:

[0078] Take 3g potassium hydroxide, 2g ethylenediaminetetraacetic acid, 0.05g fatty alcohol polyoxyethylene ether, and 10g isopropanolamine and dissolve them in 284.95g DIW to make a premix; then add the premix into 700g colloidal silica with particle sizes of 20nm, 50nm, and 70nm and a concentration of 30% under stirring. The ratios of the three particle sizes of colloidal silica are 7:2:1, respectively, to obtain 07 polishing liquid with a pH of about 12.

[0079] First, take the prepared 07 polishing liquid, use the Zhiling 1280 polishing machine, the polishing pad is: SUBA800 flat pad, the polishing pressure is: 280kg, the polishing head / disc speed is: 30 / 29rpm, and the circulation flow is 3L / min. The temperature of the polishing disk is controlled at 30±8℃, and the liquid dilution ratio is 1:25 for polishing. The polishing test results are shown in Table 3.

[0080] Example 8

[0081] Prepare 1000g polishing liquid:

[0082] Take 3g potassium hydroxide, 2g ethylenediaminetetraacetic acid, 0.05g fatty alcohol polyoxyethylene ether, and 10g isopropanolamine and dissolve them in 284.95g DIW to make a premix; then add the premix into 700g colloidal silica with particle sizes of 50nm and 70nm and a concentration of 30% under stirring. The ratio of the three particle sizes of colloidal silica is 5:5, and 08 polishing liquid is obtained, and its pH is about 12.

[0083] First, take the prepared 08 polishing liquid, use the Zhiling 1280 polishing machine, the polishing pad is: SUBA800 flat pad, the polishing pressure is: 280kg, the polishing head / disc speed is: 30 / 29rpm, and the circulation flow is 3L / min. The temperature of the polishing disk is controlled at 30±8℃, and the liquid dilution ratio is 1:25 for polishing. The polishing test results are shown in Table 3.

[0084] Table 3

[0085]

[0086] It can be seen from Examples 5 and 8 that, under the conditions of fixed potassium hydroxide and other additives, by introducing colloidal silica with a smaller particle size into the polishing liquid of two colloidal silicas with a particle size of 50 and 70 nm, different results are achieved on the removal rate of silicon wafers. By comparison, it can be found that under the same conditions of other additive ratios, changing the ratio of colloidal silica and increasing its mechanical action can accelerate the removal rate of silicon wafers.

[0087] By comparing Examples 5-7, it can be seen that in the colloidal silica with a concentration of 30%, the polishing liquid system with a particle size ratio of 20nm, 50nm, and 70nm of 6:3:1 respectively has the fastest silicon wafer removal rate. Figure 2 , detailed polishing rates are shown in Table 4.

[0088] Table 4

[0089] Example 5 Example 6 Example 7 Example 8 1st run (μm / min) 0.75 0.81 0.78 0.73 2nd run (μm / min) 0.73 0.8 0.767 0.721 3rd run (μm / min) 0.72 0.78 0.742 0.717 4th run (μm / min) 0.7 0.76 0.725 0.7 5th run (μm / min) 0.68 0.743 0.707 0.692 6th run (μm / min) 0.69 0.738 0.7 0.684 7th run (μm / min) 0.68 0.73 0.687 0.672 8th run (μm / min) 0.66 0.713 0.678 0.664 9th run (μm / min) 0.654 0.702 0.657 0.652 10th run (μm / min) 0.648 0.689 0.630 0.632 Average (μm / min) 0.691 0.747 0.708 0.686

[0090] Comparative Example 1

[0091] The difference between this comparative example and Example 3 is that the fatty alcohol polyoxyethylene ether is replaced by sodium polyacrylate.

[0092] After testing, the removal rate was 0.632μm / min; there were slight scratches on the surface of the polished silicon wafer.

[0093] Comparative Example 2

[0094] The difference between this comparative example and Example 3 is that diethylenetriaminepentaacetic acid is replaced by ethylenediaminetetramethylenephosphonic acid.

[0095] After testing, the removal rate was 0.588μm / min; there were no obvious scratches on the surface of the polished silicon wafer.

[0096] In the present invention, the polishing rate is calculated by detecting the average value of the thickness change of the silicon wafer before and after polishing.

[0097] Based on the above ideal embodiments of the present invention, the relevant staff can make various changes and modifications without departing from the technical concept of the present invention through the above description. The technical scope of the present invention is not limited to the contents of the specification, and its technical scope must be determined according to the scope of the claims.

Claims

1. A polishing liquid, characterized in that: According to parts by weight, it includes the following components: The surfactant is selected from at least one of fatty alcohol ether phosphate, fatty alcohol polyoxyethylene ether, alkylphenol polyoxyethylene ether and nonylphenol polyoxyethylene ether.

2. The polishing liquid according to claim 1, characterized in that The mass concentration of the silica sol is 30%.

3. The polishing liquid according to claim 1, characterized in that The particle size of the silica sol is in the range of 20-200 nm.

4. The polishing liquid according to claim 3, characterized in that The silica sol includes a first silica sol with a particle size of 20 nm, a second silica sol with a particle size of 50 nm, and a third silica sol with a particle size of 70 nm.

5. The polishing liquid according to claim 4, characterized in that The mass ratio of the first silica sol, the second silica sol and the third silica sol is (5-7):(1-5):

1.

6. The polishing liquid according to claim 1, characterized in that The metal chelating agent is selected from at least one of diethylenetriaminepentaacetic acid, ethylenediaminetetraacetic acid, aminotriacetic acid, and hydroxyethylidene diphosphonic acid.

7. The polishing liquid according to claim 1, characterized in that The pH regulator is selected from at least one of potassium hydroxide, tetraethylammonium hydroxide, tetramethylammonium hydroxide, diethylenetriamine, triethylenetetramine, tartaric acid, citric acid, glycine, and lactic acid.

8. The polishing liquid according to claim 1, characterized in that The organic amine is selected from at least one of tetramethylammonium hydroxide, tetraethylammonium hydroxide, tetrapropylammonium hydroxide, tetrabutylammonium hydroxide, trimethylbenzylammonium hydroxide, trimethylhydroxyethylammonium hydroxide, dimethyldihydroxyethylammonium hydroxide, diethylamine, triethylamine, ethylenediamine, monoethanolamine, diethanolamine, triethanolamine, isopropanolamine, diisopropanolamine or triisopropanolamine.

9. The polishing liquid according to any one of claims 1 to 8, characterized in that The pH value of the polishing liquid is 5-13.

10. A method for preparing a polishing liquid according to any one of claims 1 to 9, characterized in that: The steps include: S1: Dissolve the pH regulator, metal chelating agent, organic amine and surfactant in deionized water according to the formula to obtain a premixed solution; S2: Under stirring, the premixed liquid is added into the silica sol to obtain a polishing liquid.

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