CN102516876A - Polishing composition for silicon wafer polishing and preparation method thereof - Google Patents

Abstract

The invention discloses a polishing composition for silicon wafer polishing and a preparation method thereof, belonging to the technical field of chemical mechanical polishing. The polishing composition is composed of functionalized silica sol, silicic acid modifier, polishing pad protection agent, alkaline compound, surfactant and deionized water, wherein, by weight percentage, the abrasive is 0.05-50 wt%, silicon The acid modifier is 0.001-10wt%, the polishing pad protection agent is 0.001-1wt%, the basic compound is 0.001-10wt%, the surfactant is 0.001-1wt%, and the balance is deionized water. The functionalized silica sol contained in the present invention can reduce the amount of exposed Si-OH, reduce the reactivity of silica particles to generate silicic acid after polishing, and make silica particles less susceptible to silicon dioxide in the polishing process. The acid is deposited on the surface of the polishing pad, which reduces the chance of blocking the pores of the polishing pad compared with conventional polishing fluids.

Description

A polishing composition for silicon wafer polishing and its preparation method

technical field

The invention belongs to the technical field of chemical mechanical polishing (CMP), and in particular relates to a polishing composition for silicon wafer polishing and a preparation method thereof.

Background technique

Semiconductor materials, mainly silicon materials, are the most important basic functional materials in the electronic information industry, and occupy a very important position in the national economy and military industry. More than 95% of the world's semiconductor devices are made of silicon materials, and 85% of integrated circuits are also made of silicon materials. At present, IC technology has entered the era of nanoelectronics with a line width of less than 0.1 μm, and the requirements for the surface processing quality of silicon single crystal polished wafers are getting higher and higher. Traditional polishing fluids can no longer meet the requirements of silicon single wafer polishing. In order to ensure higher machining accuracy such as warpage, local surface flatness, and surface roughness of silicon polishing wafers, it is necessary to develop new polishing fluids and polishing processes. Obtaining silicon wafers with higher surface processing precision is an important link in the manufacture of integrated circuits, which is directly related to the pass rate of integrated circuits.

Pure chemical polishing has slow polishing rate, high surface precision, low damage, and good integrity, but it cannot correct the surface accuracy, and the polishing consistency is poor; pure mechanical polishing has good consistency and high surface flatness. The polishing rate is high, but the damage layer is deep and the surface accuracy is low; chemical mechanical polishing (CMP) can not only obtain a more perfect surface, but also obtain a high polishing rate, which is the only way to achieve global planarization. A traditional CMP system consists of the following three parts: a rotating silicon wafer holding device, a workbench carrying a polishing pad, and a polishing liquid (slurry) supply system. During polishing, the rotating workpiece is applied with a certain pressure on the polishing pad that rotates with the worktable. The polishing liquid flows between the workpiece and the polishing pad, and a chemical reaction occurs on the surface of the workpiece. The chemical reactants formed on the surface of the workpiece are formed by the abrasive. Mechanical friction is removed. In the alternating process of chemical film formation and mechanical film removal, a very thin layer of material is removed from the surface of the workpiece through the joint action of chemistry and machinery, and ultra-precision surface processing is finally realized. Therefore, in order to achieve high-efficiency and high-quality polishing, it is necessary to achieve a good match between the chemical action process and the mechanical action process.

In order to achieve the goals of fast polishing rate, less surface defects and high flatness of silicon wafer polishing liquid, various methods have been tried at home and abroad, and some progress has been made.

People such as Sasaki disclose a kind of silicon wafer polishing composition (patent EP0371147B1, JP09324174) containing the silica sol modified by silane coupling agent; WO2004042812); Patents US5876490 and US3922393 adopt ceria-coated and alumina-coated silica particles; patent US4664679 adopts a modification method for reducing silanol groups on the surface of colloidal silica. These treatments have achieved a certain effect on the control of defects, but for the new generation of single crystal silicon polishing fluid with higher requirements, the above methods still have certain limitations.

Contents of the invention

The invention overcomes the problems of many surface defects, low removal rate, many metal residues and difficult cleaning which are easily caused by the traditional silicon wafer polishing liquid during the polishing process, and also prolongs the service life of the polishing pad.

The invention discloses a silicon wafer polishing composition which can prolong the service life of the polishing pad, has high polishing rate, less surface defects, high flatness, less metal ion pollution of the silicon wafer after polishing and is easy to clean.

In order to achieve the above object, the present invention adopts functionalized silica sol, silicic acid modifier, and polishing pad protective agent, so that the abrasives in the polishing composition can maintain a good dispersion state, have good stability, and reduce the polishing cost. The deposition of silicic acid substances in the process reduces the wear of the polishing pad during the polishing process.

The polishing composition for silicon wafer polishing is composed of functionalized silica sol, silicic acid modifier, polishing pad protector, alkaline compound, surfactant and deionized water, wherein, by weight percentage , abrasive (silicon dioxide) is 0.05-50wt%, silicic acid modifier is 0.001-10wt%, polishing pad protection agent is 0.001-1wt%, basic compound is 0.001-10wt%, surfactant is 0.001-1wt% %, the balance is deionized water, and the functionalized silica sol is aminated silica sol.

In the aminated silica sol, the particle size of the silica particles is 1-500nm; the aminated silica sol is obtained by modifying the silica sol with an aminosilane coupling agent, that is, adding the silica sol with stirring, In the reaction kettle with heating function, control the reaction kettle at 20-95°C, add aminosilane coupling agent, the mass ratio of colloidal silicon dioxide to aminosilane coupling agent is 100-1000, and stir at constant temperature for 1-3 hours to obtain Aminated silica sol.

Among them, the aminosilane coupling agent used for modification is γ-aminopropyltriethoxysilane (KH-550), γ-aminopropyltrimethoxysilane (A-1110), N-β (ammonia Ethyl)-γ-aminopropyltrimethoxysilane (A-1120), N-β(aminoethyl)-γ-aminopropylmethyldimethoxysilane (KBM-602), N-β( Aminoethyl)-γ-aminopropyltriethoxysilane, N-β(aminoethyl)-γ-aminopropylmethyldiethoxysilane, anilinomethyltriethoxysilane, aniline One or more of methyltrimethoxysilane, aminoethylpropyltrimethoxysilane (A-1130).

The silicic acid modifier is an organic polymer containing a hydroxyl group, an ether group, a carboxyl group or an amide group, such as hydrogenated hydrolyzed starch solution (HSH), polyethylene oxide (PEO), polypropylene oxide (PPO), polypropylene One or more of vinyl acid, polyvinyl alcohol (PVA), polyacrylic acid (PAA), polyacrylamide (PAM).

Described polishing pad protective agent is polyhydric alcohol, is ethylene glycol (EG), propylene glycol (PG), butanediol (BG), hexanediol (HG), diethylene glycol (DEG), triethylene glycol One or more of (TEG), polyethylene glycol (PEG), polypropylene glycol (PPG), glycerol (GLY).

Described alkaline compound is potassium hydroxide (KOH), sodium hydroxide (NaOH), ammonium carbonate (NC), ammonium bicarbonate (NHC), potassium bicarbonate (KHC), potassium carbonate (KC), sodium bicarbonate ( NaHC), sodium carbonate (NaC), tetramethylammonium hydroxide (TMAH), ammonia (NH ₃ ), methylamine (MA), dimethylamine (DMA), trimethylamine (TMA), ethyl Amine (EA), diethylamine (DEA), triethylamine (TEA), isopropanolamine (MIPA), aminopropanol (AP), tetraethylamine (TEAH), ethanolamine (MEA), di Ethylenetriamine (DTA), Triethylenetetramine (TTA), Hydroxyethylethylenediamine (AEEA), Hexamethylenediamine (HDA), Diethylenetriamine (DETA), Triethylene One or more of tetramine (TETA), piperazine anhydrous (PIZ), piperazine hexahydrate (PHA).

The surfactant is one or more of nonionic surfactants, anionic surfactants or cationic surfactants. Nonionic surfactants are polydimethylsiloxane (PDMS), polyoxyethylene (9) lauryl ether (AEO-9), fatty alcohol polyoxyethylene ether (AEO), nonylphenol polyoxyethylene ether ( One or more of NP10), octylphenol polyoxyethylene ether (OP-10), polyoxypropylene polyoxyethylene block copolymer (EO-PO); the anionic surfactant is dodecylbenzenesulfonate Sodium dodecyl sulfonate (SDBS), sodium dodecyl sulfonate (K-12), sodium α-olefin sulfonate (AOS), sodium diisooctyl sulfonate (AOT), fatty alcohol (10) polyoxygen One or more of ethylene (AEO-10), fatty alcohol polyoxyethylene ether sodium sulfate (AES); cationic surfactants are tetradecyl dimethyl benzyl ammonium chloride, dodecyl trimethyl Trimethylammonium Chloride (TDBAC), Guar Hydroxypropyltrimethylammonium Chloride (C-162), Dodecyltrimethylammonium Bromide (DTAB), Dodecyldimethylbenzyl Bromide One or more of the base ammonium (DDBA).

The specific steps for preparing the polishing composition for silicon wafer polishing are:

1) Weigh each component according to the stated ratio, and disperse the functionalized silica sol in deionized water;

2) Under stirring conditions, add silicic acid modifier, polishing pad protective agent, and surfactant in sequence;

3) adding a basic compound, and adjusting the pH of the polishing composition to 8.5-12;

4) Filter the polishing composition with a filter element with a pore size of 0.5 μm to remove large particles of impurities in the polishing composition, that is, to obtain the polishing composition of the present invention.

Compared with the prior art, the present invention has the following advantages:

1) The functionalized silica sol contained in the present invention can reduce the amount of exposed Si-OH, reduce the reactivity of silica particles to generate silicic acid after polishing, and make the silica particles difficult to Deposited on the surface of the polishing pad by the action of silicic acid, compared with conventional polishing fluids, it reduces the chance of blocking the pores of the polishing pad;

2) The selected amino-modified silica sol is a composite particle with mechanical and chemical effects. While having the mechanical effect of silica particles, it also has the chemical effect of amino groups. The chemical and chemical effects in the polishing process The mechanical action is more balanced and the polishing effect is better;

3) The hydroxyl, ether group, carboxyl or amido organic macromolecule contained in the present invention can carry out association reaction with silicic acid group, which weakens the silicic acid generated in the polishing process to polymerize into large particles, and reduces the deposition on the polishing pad. The molecular weight of the silicic acid polymer reduces the chance of the pores of the polishing pad being blocked by the polysilicic acid generated after polishing, and prolongs the service life of the polishing pad;

4) The silicic acid modifier contained in the present invention makes the generated silicic acid more easily detach from the polishing surface, accelerates the exposure of the fresh surface to be polished, and improves the removal rate in the polishing process;

5) The polyhydric alcohol polishing pad protective agent contained in the present invention can form a protective film on the polishing pad, which can reduce the wear of the polishing pad in the polishing process and play the role of protecting the polishing pad;

6) The raw materials used in the polishing composition of the present invention are readily available and easy to carry out large-scale industrial production.

Description of drawings

Fig. 1 is an optical profiler (ZYGO) photo of a polished silicon wafer when the components of the polishing composition of the present invention are well matched (Example 6).

2 is an optical profiler (ZYGO) photo of a polished silicon wafer when the components of the polishing composition of the present invention are poorly matched (Example 3).

3 is an optical profiler (ZYGO) photo of a polished silicon wafer when ordinary silica sol is used in the polishing composition of the present invention and no silicic acid modifier and polishing pad protective agent are added (Comparative Example 3).

Detailed ways

Below by embodiment and comparative example (do not add functionalized silica sol, silicic acid modifier and polishing pad protective agent in the composition of the present invention) the present invention will be further elaborated, certainly should not be construed as limiting this invention in any case the scope of the invention.

(1) Preparation Examples

Preparation of amino functionalized silica sol:

Put the silica sol into the reaction kettle with stirring and heating functions, control the reaction kettle at 20-95°C, add aminosilane coupling agent, the mass ratio of colloidal silica to aminosilane coupling agent is 100～ 1000, stirring at constant temperature for 1 to 3 hours to obtain aminated silica sol.

Examples 1-9

The polishing composition was prepared. According to the specific polishing implementation requirements, 6000g of polishing composition was configured for each example for polishing experiments, as shown in Table 1.

Among them, the preparation method of the aminated silica sol used in Examples 1 to 3 is as follows: the particle size of the silica sol used in the examples is 40nm, the reaction kettle is heated to 95°C, and KH550 aminosilane is added to couple agent, the mass ratio of colloidal silica to aminosilane coupling agent was 200, and stirred at constant temperature for 3 hours to obtain aminated silica sol.

The preparation method of the aminated silica sol used in Examples 4 to 6 is as follows: the particle size of the silica sol used in the examples is 25nm, the reaction kettle is heated to 25°C, and A-1110 aminosilane is added to couple agent, the mass ratio of colloidal silica to aminosilane coupling agent is 400, and stirred at constant temperature for 3 hours to obtain aminated silica sol.

The preparation method of the aminated silica sol used in Examples 7 to 9 is as follows: the particle size of the silica sol used in the examples is 75nm, the reaction kettle is heated to 45°C, and A-1120 aminosilane is added to couple agent, the mass ratio of colloidal silica to aminosilane coupling agent was 600, and stirred at constant temperature for 3 hours to obtain aminated silica sol.

Comparative example 1-3

In the comparative example, except that the functionalized silica sol, the silicic acid modifier and the polishing pad protection agent described in the present invention are not added, other configuration comparative examples are the same as the embodiment configuration process, wherein comparative example 1 and embodiment 1 ; Comparative Example 2 and Example 4; Comparative Example 3 and Example 5; Comparative Example 4 corresponds to Example 8, as shown in Table 1.

(two) test embodiment

The polishing composition after configuration is used for polishing experiment, and polishing experiment parameter is as follows:

Polishing machine: single-sided polishing machine, equipped with 4 polishing heads, each polishing head can polish 4 silicon wafers;

Polishing pressure: 32kPa;

Polishing turntable speed: 90 rpm;

Polishing head speed: 100 rpm;

Specifications of polished silicon single wafer: P type <100>, diameter 100mm, resistivity: 0.1～100.Ω·cm;

Polishing time: 20min;

Polishing pad: DOW company SUB600 polishing pad;

Polishing fluid flow rate: 230ml/min;

Polishing temperature: 20°C

Surface quality inspection of polished silicon wafers: use ZYGO New View 7200 profiler to detect the surface roughness of polished silicon wafers, 2X eyepiece, 50X objective lens, and the test range is 0.07×0.05mm ² .

Polishing pad service life (usage time) calculation: Polishing pad service life refers to the actual polishing time from the beginning of using the polishing pad to when the polishing rate is 10% lower than the maximum rate during the use of the polishing pad.

Polishing average rate: The polishing removal rate is calculated by the change of the thickness of the center part of the silicon wafer before and after polishing. It is the average value of the difference in the center thickness of the four silicon wafers. It can be measured by a micrometer. Ratio, the average polishing rate is the average polishing rate during the service life of the polishing pad.

As can be seen from the polishing test results of the examples and comparative examples in Table 1, compared with the conventional polishing composition, the polishing composition of the present invention is due to containing functionalized silica sol, silicic acid modifier, polishing pad protective agent And it has high polishing removal rate, excellent surface quality of silicon wafer and long service life of polishing pad.

As can be seen from the foregoing examples, the surface roughness of the silicon wafer after polishing using the polishing composition of Example 6 under the polishing process conditions of the present invention is as low as 1.678nm, the service life of the polishing pad reaches 45h, and the removal rate reaches 1.22 μm/ min.

The above examples fully demonstrate that the polishing composition of the present invention is a polishing material for CMP with excellent performance, especially suitable for polishing silicon wafers.

The following table shows the components and content of the polishing composition in each embodiment (using the content of each component in the diluent, the concentrated solution of the polishing composition of the present invention can be obtained by concentrating 10, 20, 30, and 40 of the diluent) and its The roughness of the polished silicon wafer surface, the average rate of polishing and the service time of the polishing pad. The type of each component in the table is replaced by the abbreviation in brackets after the substance in the summary of the invention part of the specification.

The above is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any person skilled in the art within the technical scope disclosed in the present invention can easily think of changes or Replacement should be covered within the protection scope of the present invention. Therefore, the protection scope of the present invention should be determined by the protection scope of the claims.

The preparation and test of table 1 embodiment and comparative example

Claims (10)

1. A polishing composition for silicon wafer polishing, characterized in that: it is made up of functionalized silica sol, silicic acid modifier, polishing pad protective agent, alkaline compound, tensio-active agent and deionized water , wherein, by weight percentage, the abrasive is 0.05-50wt%, the silicic acid modifier is 0.001-10wt%, the polishing pad protection agent is 0.001-1wt%, the basic compound is 0.001-10wt%, and the surfactant is 0.001-10wt%. 1 wt%, the balance is deionized water, and the functionalized silica sol is aminated silica sol. 2. The polishing composition according to claim 1, characterized in that: the aminated silica sol is obtained by modifying silica sol with an aminosilane coupling agent. 3. The polishing composition according to claim 1, characterized in that: in the aminated silica sol, the particle size of the silica particles is 1-500 nm. 4. The polishing composition according to claim 1, characterized in that: the aminated silica sol is prepared by the following method: the silica sol is added into a reactor with stirring and heating functions, and the reactor Control the temperature at 20-95°C, add aminosilane coupling agent, the mass ratio of colloidal silica to aminosilane coupling agent is 100-1000, stir at constant temperature for 1-3 hours to obtain aminated silica sol. 5. The polishing composition according to claim 4, characterized in that: the aminosilane coupling agent used for modification is γ-aminopropyltriethoxysilane, γ-aminopropyltrimethoxysilane, N-β(aminoethyl)-γ-aminopropyltrimethoxysilane, N-β(aminoethyl)-γ-aminopropylmethyldimethoxysilane, N-β(aminoethyl)- γ-aminopropyltriethoxysilane, N-β(aminoethyl)-γ-aminopropylmethyldiethoxysilane, anilinomethyltriethoxysilane, anilinomethyltrimethoxy Silane, one or more of aminoethylpropyltrimethoxysilane. 6. The polishing composition according to claim 1, characterized in that: the silicic acid modifier is an organic polymer containing a hydroxyl group, an ether group, a carboxyl group or an amide group, and is a hydrogenated hydrolyzed starch solution, polyethylene oxide One or more of alkane, polypropylene oxide, polyvinyl acid, polyvinyl alcohol, polyacrylic acid, and polyacrylamide. 7. The polishing composition according to claim 1, characterized in that: the polishing pad protective agent is a polyhydric alcohol, which is ethylene glycol, propylene glycol, butanediol, hexanediol, diethylene glycol, triethylene glycol One or more of glycol, polyethylene glycol, polypropylene glycol, and glycerol. 8. The polishing composition according to claim 1, characterized in that: the alkaline compound is potassium hydroxide, sodium hydroxide, ammonium carbonate, ammonium bicarbonate, potassium bicarbonate, potassium carbonate, sodium bicarbonate, carbonic acid Sodium, tetramethylammonium hydroxide, ammonia, methylamine, dimethylamine, trimethylamine, ethylamine, diethylamine, triethylamine, isopropanolamine, aminopropanol, tetraethylamine amine, ethanolamine, diethylenetriamine, triethylenetetramine, hydroxyethylethylenediamine, hexamethylenediamine, diethylenetriamine, triethylenetetramine, anhydrous piperazine, six One or more of water piperazines. 9. The polishing composition according to claim 1, characterized in that: the surfactant is one or more of nonionic surfactants, anionic surfactants or cationic surfactants. Nonionic surfactants are polydimethylsiloxane, polyoxyethylene (9) lauryl ether, fatty alcohol polyoxyethylene ether, nonylphenol polyoxyethylene ether, octylphenol polyoxyethylene ether, polyoxypropylene One or more of polyoxyethylene block copolymers; anionic surfactants are sodium dodecylbenzenesulfonate, sodium dodecylsulfonate, sodium α-olefin sulfonate, diisooctyl succinate One or more of sodium ester sulfonate, fatty alcohol (10) polyoxyethylene, fatty alcohol polyoxyethylene ether sodium sulfate; cationic surfactant is tetradecyl dimethyl benzyl ammonium chloride, lauryl One of Alkyl Trimethyl Ammonium Chloride, Guar Gum Hydroxypropyl Trimethyl Ammonium Chloride, Dodecyl Trimethyl Ammonium Bromide, Dodecyl Dimethyl Benzyl Ammonium Bromide or Several kinds. 10. The preparation method of the polishing composition for silicon wafer polishing according to any one of claims 1 to 9, characterized in that the specific steps are: 1) Weigh each component according to the stated ratio, and disperse the functionalized silica sol in deionized water; 2) Under stirring conditions, add silicic acid modifier, polishing pad protective agent, and surfactant in sequence; 3) adding a basic compound, and adjusting the pH of the polishing composition to 8.5-12; 4) Filter the polishing composition with a filter element with a pore size of 0.5 μm to remove large particles of impurities in the polishing composition, that is, to obtain the polishing composition.

Images