Chemical mechanical polishing solution for polishing silicon wafer as well as preparation method and application of chemical mechanical polishing solution

Abstract

The invention relates to a chemical mechanical polishing solution for polishing a silicon wafer as well as a preparation method and application of the chemical mechanical polishing solution. The chemical mechanical polishing solution comprises a water-soluble small molecule containing a morpholine ring and an amido side chain at the same time. According to the polishing solution, the water-soluble micromolecules containing the morpholine ring and the amino side chain are added into the polishing solution, so that the surface flatness of the silicon wafer is effectively improved on the premise that the polishing rate of the silicon wafer is remarkably increased, the requirement for silicon wafer planarization in production is met, and the processing efficiency of the silicon wafer is ensured.

Description

Technical Field

[0001] The invention belongs to the field of polishing liquid, and particularly relates to a chemical mechanical polishing liquid for polishing silicon wafers, and a preparation method and application thereof. Background Art

[0002] With the development of the integrated circuit industry, advanced process technology has put forward higher requirements on the surface flatness and polishing efficiency of silicon wafers. Chemical mechanical polishing (CMP) and double-sided chemical mechanical polishing (DSP) and other technologies can achieve high flatness of silicon wafers.

[0003] CMP technology is a combination of chemical and mechanical action, with advantages such as fast processing speed, high grinding quality, and reliable processing results. However, during the processing, it is difficult to balance the polishing rate and surface flatness of silicon wafers. The CMP process is complex and has many influencing factors, including the type of material on the workpiece surface, the composition of the polishing liquid, the pressure of the polishing head, etc.

[0004] Therefore, a technical solution is needed that can increase the polishing rate of silicon wafers and improve the surface flatness of silicon wafers. Summary of the invention

[0005] The technical problem to be solved by the present invention is to provide a chemical mechanical polishing liquid for silicon wafer polishing and a preparation method and application thereof, and in particular to a chemical mechanical polishing liquid and a preparation method thereof for significantly improving the polishing rate and surface flatness of silicon wafers.

[0006] The invention provides a chemical mechanical polishing liquid, which comprises water-soluble small molecules containing a morpholine ring and an amino side chain.

[0007] The raw material components of the chemical mechanical polishing liquid of the present invention include water-soluble small molecules containing both morpholine rings and amine side chains. The polishing liquid containing both morpholine rings and amine side chains is added to chemically mechanically polish silicon wafers, which effectively improves the surface flatness of silicon wafers while significantly improving the polishing rate.

[0008] The chemical mechanical polishing liquid comprises water-soluble small molecules containing both morpholine rings and amine side chains, abrasives, alkaline compounds, and water; wherein the weight percentage of the water-soluble small molecules containing both morpholine rings and amine side chains in the polishing liquid is 0.005-0.5%.

[0009] Preferably, the chemical mechanical polishing solution comprises, by weight percentage:

[0010]

[0011] Preferably, the water-soluble small molecule containing a morpholine ring and an amine side chain includes one or more of 4-aminomorpholine, 4-(2-aminoethyl)morpholine, N-aminopropylmorpholine, and 2-(aminomethyl)morpholine.

[0012] Preferably, the abrasive includes one or more of inorganic particles, organic particles, and organic-inorganic composite particles.

[0013] Preferably, the inorganic particles include one or more of metal oxide particles, nitride particles, carbide particles, and diamond particles; the organic particles include one or more of polymethyl methacrylate PMMA particles, poly (meth) acrylic acid particles, and polyacrylonitrile particles.

[0014] Preferably, the oxide particles include one or more of silicon dioxide, cerium oxide, aluminum oxide, and zirconium oxide; the nitride particles include one or both of silicon nitride and boron nitride; and the carbide particles include one or both of silicon carbide and boron carbide.

[0015] Further preferably, the abrasive is silicon dioxide particles among oxide particles, more preferably, colloidal silicon dioxide particles.

[0016] Preferably, the abrasive is abrasive in the form of primary particles, abrasive in the form of secondary particles formed by a plurality of primary particles, or a mixture of abrasive in the form of primary particles and abrasive in the form of secondary particles. More preferably, at least a portion of the abrasive is in the form of secondary particles.

[0017] There is no particular restriction on the average primary particle size of abrasive grain. From the perspective of polishing rate, the average primary particle size of abrasive grain is preferably more than 20nm, more preferably more than 30nm, and particularly preferably more than 40nm. From the perspectives of aspects such as wafer surface defects and polishing liquid storage stability after polishing, the average primary particle size of abrasive grain is preferably below 100nm, more preferably below 80nm, and further preferably below 70nm. The average primary particle size of abrasive grain can be measured by, for example, the BET method, for example, the Flow Sorb II 2300 specific surface area measuring instrument developed by Micromeritics Instrument Corporation can be used.

[0018] There is no particular restriction on the average secondary particle size of abrasive particles. From the perspective of polishing rate, the average secondary particle size of abrasive particles is preferably more than 40nm, more preferably more than 50nm, and particularly preferably more than 60nm. From the perspectives of wafer surface defects after polishing and the storage stability of polishing liquid, the average secondary particle size of abrasive particles is preferably less than 200nm, more preferably less than 180nm, and further preferably less than 160nm. The average secondary particle size of abrasive particles can be measured by, for example, dynamic light scattering, for example, the Zetasizer Lab nanoparticle size analyzer developed by Malvern Panalytical can be used.

[0019] The alkaline compound plays a role in adjusting the pH value of the polishing liquid.

[0020] Preferably, the alkaline compound includes one or more of alkali metal hydroxides, carbonates, bicarbonates, nitrogen-containing organic alkaline compounds, and nitrogen-containing inorganic alkaline compounds.

[0021] Preferably, the alkaline compound includes one or more of ammonia water, potassium hydroxide, sodium hydroxide, tetramethylammonium hydroxide, and potassium carbonate.

[0022] The water plays a role in dissolving and carrying other components of the polishing liquid; the water includes ion exchange water (deionized water), pure water, ultrapure water, distilled water and the like.

[0023] Preferably, the components further include one or more of water-soluble polymers, chelating agents, surfactants, preservatives, and mildew inhibitors.

[0024] The water-soluble polymer plays a role in simultaneously improving the surface roughness and flatness of the polishing object.

[0025] Preferably, the water-soluble polymer includes one or more of vinyl alcohol polymers and cellulose derivatives; wherein the weight percentage of the water-soluble polymer is 0.005% to 0.5%.

[0026] Preferably, the vinyl alcohol polymer comprises polyvinyl alcohol, polyethylene glycol, polyvinyl acetate, polyacrylate, polyvinyl sulfonic acid, etc., and the weight average molecular weight range is 1×10 3 -2×10 5 g / mol. Cellulose derivatives include hydroxyethyl cellulose, carboxymethyl cellulose, etc., with a weight average molecular weight range of 1×10 5 -1.5×10 6 g / mol.

[0027] The chelating agent forms a complex with metal impurities in the polishing liquid to capture the metal impurities, thereby playing a role in inhibiting the metal impurities from contaminating the polishing object.

[0028] Preferably, the chelating agent includes one or more of carboxylic acid, organic phosphonic acid and organic sulfonic acid chelating agents, wherein the weight percentage of the chelating agent is 0.0005% to 0.1%.

[0029] Further, the carboxylic acid chelating agent includes one or more of ethylenediaminetetraacetic acid, sodium ethylenediaminetetraacetate, nitrilotriacetic acid, ammonium nitrilotriacetate, hydroxyethylethylenediaminetriacetic acid, diethylenetriaminepentaacetic acid, triethylenetetraaminehexaacetic acid, polyacrylic acid, polymethacrylic acid, hydrolyzed polymaleic anhydride, etc. The organic phosphonic acid chelating agent includes one or more of 2-aminoethylphosphonic acid, aminotrimethylenephosphonic acid, diethylenetriaminepentamethylenephosphonic acid, ethylenediaminetetramethylenephosphonic acid, triethylenetetraaminehexamethylphosphonic acid, hydroxyethyl-1,1-diphosphonic acid, etc. The organic sulfonic acid chelating agent includes one or more of ethylenediaminetetramethylenesulfonic acid, aminoethanesulfonic acid, aminopropanesulfonic acid, etc.

[0030] The surfactant plays a role in improving the stability of the polishing solution and optimizing the surface defects and surface roughness of the silicon wafer after polishing.

[0031] Preferably, the surfactant includes one or more of a nonionic surfactant, a cationic surfactant, and an anionic surfactant; wherein the weight percentage of the surfactant is 0.0001% to 0.1%.

[0032] Furthermore, the surfactant includes one or more of alkyl betaine, alkyl amine oxide, polyoxyethylene alkyl ether, polyoxyethylene alkylamine, alkyl alkanolamide, polyoxyethylene fatty acid ester, sorbitan fatty acid ester and the like.

[0033] The preservative and mildew preventer play a role in maintaining the effectiveness and stability of the polishing liquid, and can be used alone or in combination.

[0034] The preservatives and mildew preventers both include isothiazolin compounds, parabens, parahydroxybenzoates, etc. Preferably, the preservatives and mildew preventers include 1,2-benzisothiazolin-3-one, 2-methyl-4-isothiazolin-3-one, etc.

[0035] Preferably, the weight percentage of the preservative is 0.001% to 0.1%;

[0036] Preferably, the mass percentage of the mildew inhibitor is 0.001% to 0.1%.

[0037] The preparation method of the chemical mechanical polishing liquid of the present invention is not particularly limited. For example, the components of the polishing liquid can be mixed by stirring, ultrasonic dispersion, homogeneous mixing, etc. There is no particular restriction on the mixing method of these components. For example, all the components can be mixed at one time, or they can be mixed in a set order. From the perspective of preparing a chemical mechanical polishing liquid with better stability, the preferred preparation method is: preferentially mix the abrasive slurry, alkaline compounds and water, adjust the pH to 10-12, and then add a water-soluble small molecule containing both a morpholine ring and an amine side chain (add a water-soluble polymer, a chelating agent, a preservative and a mildew inhibitor, etc.), and stir and mix evenly.

[0038] The invention provides a method for preparing a chemical mechanical polishing liquid, comprising: mixing various components to obtain the polishing liquid.

[0039] Furthermore, the polishing liquid is diluted with deionized water with a mass of 10-50 times the mass of the deionized water.

[0040] The invention provides an application of the chemical mechanical polishing liquid in polishing silicon wafers.

[0041] Beneficial Effects

[0042] The present invention provides a chemical mechanical polishing liquid capable of effectively improving the flatness of a silicon wafer while increasing the polishing rate of the silicon wafer, and a preparation method and use thereof, wherein the components of the chemical mechanical polishing liquid include water-soluble small molecules containing both a morpholine ring and an amine side chain. The present invention effectively improves the surface flatness of a silicon wafer while significantly increasing the polishing rate of the silicon wafer by adding water-soluble small molecules containing both a morpholine ring and an amine side chain to the polishing liquid, thereby meeting the need for flattening of silicon wafers in production and ensuring the processing efficiency of silicon wafers. DETAILED DESCRIPTION

[0043] The present invention will be further described below in conjunction with specific embodiments. It should be understood that these embodiments are only used to illustrate the present invention and are not intended to limit the scope of the present invention. In addition, it should be understood that after reading the content taught by the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms fall within the scope limited by the appended claims of the application equally.

[0044] It should be noted that the process equipment or devices not specifically specified in the following examples are all conventional equipment or devices in the art. In addition, it should be understood that the scope of protection of the present invention is not limited to the specific embodiments described below, and one or more method steps mentioned in the present invention do not exclude the presence of other method steps before and after the combination step or the insertion of other method steps between these explicitly mentioned steps, unless otherwise specified. It should also be understood that the terms used in the examples of the present invention are intended to describe specific embodiments, not to limit the scope of protection of the present invention. The test methods for which specific conditions are not specified in the following examples are generally carried out under conventional conditions or under the conditions recommended by the manufacturers.

[0045] In the following embodiments and comparative examples of the present application, a specific polishing process condition is adopted, specifically:

[0046] Polishing object: 300mm diameter (100) surface silicon wafer;

[0047] Polishing equipment: Tianjin Huahai Qingke Universal-300X;

[0048] Polishing pad: Polyurethane polishing pad SPM-3100 manufactured by NITTA DuPont, Japan;

[0049] Polishing speed ratio: 123:119rpm;

[0050] Polishing liquid flow rate: 300mL / min;

[0051] Polishing pressure: 3.0psi.

[0052] Example 1

[0053] In this embodiment, a method for preparing a novel chemical mechanical polishing liquid is provided, comprising the following steps:

[0054] 35% by mass of colloidal silica (average secondary particle size 110 nm), 1.6% by mass of tetramethylammonium hydroxide (TMAH), 1% by mass of potassium carbonate, 0.3% by mass of 4-aminomorpholine and ion exchange water were stirred and mixed at room temperature (25°C) for 30 minutes to obtain a polishing liquid.

[0055] The polishing liquid obtained by the above process needs to be diluted by 30 times by mass and added with ion exchange water for polishing experiments.

[0056] The chemical structure of 4-aminomorpholine is

[0057] Example 2

[0058] In this embodiment, a method for preparing a novel chemical mechanical polishing liquid is provided, comprising the following steps:

[0059] 4-(2-aminoethyl)morpholine was used to replace 4-aminomorpholine in Example 1, and the rest of the parts remained the same as in Example 1.

[0060] The chemical structure of 4-(2-aminoethyl)morpholine is

[0061] Example 3

[0062] In this embodiment, a method for preparing a novel chemical mechanical polishing liquid is provided, comprising the following steps:

[0063] N-aminopropylmorpholine was used to replace 4-aminomorpholine in Example 1, and the rest of the parts were completely the same as those in Example 1. The chemical structural formula of N-aminopropylmorpholine is

[0064] Example 4

[0065] In this embodiment, a method for preparing a novel chemical mechanical polishing liquid is provided, comprising the following steps:

[0066] 2-(Aminomethyl)morpholine was used to replace 4-aminomorpholine in Example 1, and the rest of the parts remained the same as in Example 1.

[0067] The chemical structure of 2-(aminomethyl)morpholine is

[0068] Comparative Example 1

[0069] The difference between this comparative example and Example 1 is that: no water-soluble small molecule containing both a morpholine ring and an amine side chain is used, that is, no 4-aminomorpholine is used; the rest of the parts are completely the same as Example 1.

[0070] Comparative Example 2

[0071] The difference between this comparative example and Example 1 is that diethylenetriamine is used to replace the 4-aminomorpholine in Example 1; the rest of the parts are completely the same as Example 1.

[0072] The chemical structure of diethylenetriamine is

[0073] Comparative Example 3

[0074] The difference between this comparative example and Example 1 is that triethylenetetramine is used to replace 4-aminomorpholine in Example 1; the rest of the parts are completely the same as Example 1.

[0075] The chemical structure of triethylenetetramine is

[0076] Comparative Example 4

[0077] The difference between this comparative example and Example 1 is that: W =2.5×10 5 Polyvinyl pyrrolidone replaced 4-aminomorpholine in Example 1; the rest of the components remained the same as in Example 1.

[0078] The chemical structure of polyvinyl pyrrolidone

[0079] Comparative Example 5

[0080] The difference between this comparative example and Example 1 is that: W =5×10 4 Poly-N-vinylacetamide replaces 4-aminomorpholine in Example 1; the rest remains the same as in Example 1.

[0081] The chemical structure of poly-N-vinyl acetamide is

[0082] The performance of CMP (Chemical Mechanical Polishing) polishing slurry is generally evaluated by measuring the polishing rate of silicon wafers and the surface flatness of the silicon wafer after polishing. The polishing rate and the surface flatness of the silicon wafer are measured using a bare die geometry metrology system (WaferSight2+, KLA Tencor, Milpitas, CA, USA).

[0083] The polishing rate of the chemical mechanical polishing solution obtained in Examples 1-4 and Comparative Examples 1-6 was tested by measuring the mass of the silicon wafer before and after polishing. The polishing rate was calculated by measuring the mass difference before and after polishing of the silicon wafer and dividing it by the polishing time.

[0084] The polishing rate test results are shown in Table 1. The polishing rate of each example in Table 1 is a ratio based on the polishing rate of the CMP polishing liquid of Comparative Example 1 being 100%, and a larger value indicates a higher polishing rate.

[0085] The chemical mechanical polishing liquid obtained in Examples 1-4 and Comparative Examples 1-6 was subjected to a silicon wafer flatness test, and the specific operation was as follows: TTV and SFQR were used as evaluation indicators for the flatness of the silicon wafer surface. TTV (Total thickness variation) refers to the difference between the highest point and the lowest point of the silicon wafer surface morphology relative to the reference back side. SFQR (Site flatness front least-squares range) refers to dividing a plurality of sites in an area between the center and the edge of the silicon wafer by 1 mm, and measuring the difference between the highest point and the lowest point of the silicon wafer surface morphology within the site relative to the least squares reference plane. ΔTTV and ΔSFQR are obtained by subtracting the TTV (or SFQR) of the silicon wafer after polishing from the TTV (or SFQR) before polishing, which can indicate the improvement of the surface flatness of the silicon wafer before and after polishing.

[0086] The results of the silicon wafer surface flatness test are shown in Table 1. The ΔTTV, ΔSFQR values ​​and polishing rates of each example in Table 1 are based on the ΔTTV (-0.2553 μm), ΔSFQR value (-0.07653 μm) and polishing rate (590 nm / min) of the CMP polishing solution used in Comparative Example 1, and the relative changes of each example are calculated according to this ratio. The larger the ratio value, the better the improvement of the silicon wafer flatness and the greater the improvement of the polishing rate.

[0087] Table 1

[0088]

[0089]

[0090] It can be seen from Table 1 that the chemical mechanical polishing liquid obtained by the preparation method of the present application can achieve ΔTTV, ΔSFQR and polishing rate values ​​higher than those of the comparative polishing liquid. This shows that the chemical mechanical polishing liquid of water-soluble small molecules containing both morpholine rings and amino side chains provided by the present application can effectively improve the surface flatness of silicon wafers while significantly improving the polishing rate of silicon wafers.

Claims

1. A chemical mechanical polishing liquid, characterized in that: The polishing liquid comprises water-soluble small molecules containing a morpholine ring and an amine side chain.

2. The chemical mechanical polishing solution according to claim 1, characterized in that: By weight percentage, the components include:

3. The chemical mechanical polishing solution according to claim 1, characterized in that: The water-soluble small molecules containing a morpholine ring and an amine side chain include one or more of 4-aminomorpholine, 4-(2-aminoethyl)morpholine, N-aminopropylmorpholine, and 2-(aminomethyl)morpholine.

4. The chemical mechanical polishing solution according to claim 2, characterized in that: The abrasive includes one or more of inorganic particles, organic particles, and organic-inorganic composite particles; the alkaline compound includes one or more of alkali metal hydroxides, carbonates, bicarbonates, nitrogen-containing organic alkaline compounds, and nitrogen-containing inorganic alkaline compounds.

5. The chemical mechanical polishing solution according to claim 2, characterized in that: The inorganic particles include one or more of oxide particles, nitride particles, carbide particles, and diamond particles; the organic particles include one or more of polymethyl methacrylate PMMA particles, poly (meth) acrylic acid particles, and polyacrylonitrile particles; The oxide particles include one or more of silicon dioxide, cerium oxide, aluminum oxide, and zirconium oxide; the nitride particles include one or two of silicon nitride and boron nitride; the carbide particles include one or two of silicon carbide and boron carbide; The alkaline compound includes one or more of ammonia water, potassium hydroxide, sodium hydroxide, tetramethylammonium hydroxide and potassium carbonate.

6. The chemical mechanical polishing solution according to claim 2, characterized in that: The abrasive material is abrasive grains in the form of primary particles, abrasive grains in the form of secondary particles, or a mixture of abrasive grains in the form of primary particles and abrasive grains in the form of secondary particles; The average primary particle size of the abrasive is greater than 20 nm; the average secondary particle size of the abrasive is greater than 40 nm.

7. The chemical mechanical polishing solution according to claim 2, characterized in that: The components also include one or more of water-soluble polymers, chelating agents, surfactants, preservatives, and mildew inhibitors.

8. The chemical mechanical polishing solution according to claim 7, characterized in that: The water-soluble polymer includes one or more of vinyl alcohol polymers and cellulose derivatives; wherein the weight percentage of the water-soluble polymer is 0.005% to 0.5%; The chelating agent includes one or more of carboxylic acid, organic phosphonic acid, and organic sulfonic acid chelating agents, wherein the weight percentage of the chelating agent is 0.0005% to 0.1%; The surfactant includes one or more of a nonionic surfactant, a cationic surfactant, and an anionic surfactant; wherein the weight percentage of the surfactant is 0.0001% to 0.1%; The weight percentage of the preservative is 0.001% to 0.1%; The mass percentage of the mildew inhibitor is 0.001% to 0.1%.

9. A method for preparing a chemical mechanical polishing liquid, comprising: Mix all components to obtain a polishing solution.

10. Use of the chemical mechanical polishing liquid according to claim 1 in polishing silicon wafers.

Images