CN114106704A

CN114106704A - A green and environmentally friendly titanium metal polishing liquid

Info

Publication number: CN114106704A
Application number: CN202111540483.0A
Authority: CN
Inventors: 谢顺帆; 赵群; 何彦刚; 杨露瑶; 梅旭鲲; 孟妮; 张祥龙; 李相辉
Original assignee: Hebei University of Technology
Current assignee: Hebei University of Technology
Priority date: 2021-12-16
Filing date: 2021-12-16
Publication date: 2022-03-01

Abstract

The present invention is a kind of green and environment-friendly titanium metal polishing liquid. The titanium polishing liquid includes abrasives, oxidants, alkaline oxides, surfactants, complexing agents and corrosion inhibitors. The corrosion inhibitor is nicotinic acid, and the surface The active agent is an organic surfactant that does not contain sodium ions. The formula of the present invention does not introduce new external sodium ions, and can be applied to polishing in the semiconductor field, thereby reducing the number of metal ions. A good titanium surface can be obtained by introducing a small amount of nicotinic acid. When the concentration of nicotinic acid is 0.05 wt%, excellent surface quality can be obtained, and at the same time, it has a good removal rate.

Description

Green environment-friendly titanium metal polishing solution

Technical Field

The invention relates to a titanium polishing solution capable of inhibiting corrosion and scratch of a titanium metal surface and a preparation method thereof.

Background

At present, titanium is widely applied in the fields of aerospace, biomedicine, integrated circuits and the like due to relatively rich content, higher strength, better stability and better biocompatibility. In the IC field and the biomedical field, extremely high requirements are made on the surface quality of titanium and titanium alloy. Relevant researches show that the reduction of the surface roughness can effectively reduce the occurrence of cracks and prolong the service life of the material. Good surfaces can only be obtained by chemical mechanical polishing techniques.

A Chemical Mechanical Polishing (CMP) technique, which is a technique that can finally realize local and global planarization of a wafer by the interaction of mechanical action and chemical action. CMP technology was first introduced by Walsh et al in 1965 and was first used to manufacture high quality glass surfaces such as military telescopes. In the chemical mechanical polishing process, grinding is mainly performed through the combined action among the polishing head, the polishing pad and the polishing liquid, the polishing head and the polishing pad mainly provide the mechanical grinding function, and the polishing liquid mainly plays a chemical role. The polished wafer and the polishing pad move relatively, and the purposes of quickly removing materials and obtaining a high-quality surface are achieved by utilizing the grinding of nano-grade abrasive materials in the polishing solution and the oxidation corrosion of chemical additives such as oxidizing agents, complexing agents and the like.

From the introduction of chemical mechanical polishing techniques to the present, CMP has been developed from the original application mainly to Integrated Circuits (ICs) to the processing fields of memory disks, precision ceramics, metal alloys (titanium alloys, etc.) having special uses in the aerospace field, etc., which have special requirements for surfaces. Particularly, as the IC manufacturing technology node is continuously reduced, the research and development of the polishing solution in the direction of low pressure and low abrasive material becomes important. And the polishing solution is used as an recyclable consumable in the field of high-precision manufacturing, so that the market demand is very huge, and the treatment work after the waste liquid is discharged is very difficult, so that the environment-friendly titanium metal chemical mechanical polishing solution is especially important.

The chemical corrosion in the metal polishing solution is a main factor causing metal surface defects, the presence of chemical additives such as hydrogen ions or hydroxyl ions and complexing agents in the polishing solution causes the surface defects of titanium in the polishing process, and partial researchers research that a metal corrosion inhibitor BTA, TTA and the like is added to inhibit the surface defects after the chemical mechanical polishing of the titanium, so that the environmental pollution is large.

Disclosure of Invention

Aiming at the problems, the invention aims to provide the green and environment-friendly titanium polishing solution capable of inhibiting corrosion and scratch of the surface of the titanium wafer and the preparation method thereof, so that the quality of the titanium surface after chemical mechanical polishing is improved, and the influence on the environment is minimized.

The technical scheme adopted by the invention for solving the technical problems is as follows:

the green environment-friendly titanium metal polishing solution can inhibit corrosion and metal pollution on the surface of a titanium wafer, and comprises an abrasive, an oxidant, an alkaline oxide, a surfactant, a complexing agent and a corrosion inhibitor, and is characterized in that the corrosion inhibitor is nicotinic acid, and the surfactant is an organic surfactant without sodium ions.

The polishing solution comprises the following components in percentage by mass: silica sol: 1 wt% -10 wt%; oxidizing agent: 0.1 wt% -2 wt%; basic compound (b): 0.01 wt% -0.1 wt%; complexing agent: 0.1 wt% -5 wt%; corrosion inhibitor: 0.01 wt% -0.2 wt%; surfactant (b): 0.01 wt% -0.1 wt%; the balance of deionized water.

The complexing agent comprises potassium citrate, and the complexing agent also can comprise any one of potassium tartrate and glycine;

the oxidant is hydrogen peroxide; the alkaline compound is any one of tetramethyl ammonium hydroxide, tetraethyl ammonium hydroxide, polyaspartic acid and ammonia water; the surfactant is polyvinylpyrrolidone, fatty alcohol-polyoxyethylene ether and dodecylbenzene sulfonic acid, preferably fatty alcohol-polyoxyethylene ether.

The preparation process of the green environment-friendly titanium metal polishing solution comprises the following steps: the preparation process needs to be matched with a stirrer for use, and the specific process is as follows:

1) respectively dissolving a complexing agent, a corrosion inhibitor and a surfactant into a 1 wt% diluent state;

2) filtering 1 wt% of the diluent in the step 1), wherein the aperture of a filter element is 500 nm;

3) carrying out two-stage filtration on the silica sol, wherein the filter element aperture of a filter element used in the two-stage filtration is 500nm and 300 nm;

4) mixing by a stirrer, controlling the rotating speed to be 80-120r/min, stirring for 30-60min, controlling the temperature to be 30-50 ℃, and adding deionized water, a complexing agent (1 wt% solution), a corrosion inhibitor (1 wt% solution), a surfactant (1 wt% solution), silica sol, an alkaline compound and hydrogen peroxide into the raw materials in sequence. The addition of the substances is carried out according to the required proportion, and the 1 wt% solution means that the corresponding components are dissolved in water in advance, the mass of large particles is ignored after filtration, solid chemicals cannot be directly added into silica sol, the problems of gelation and the like occur, and the total mass input of the 1 wt% solution is required when the target mass of the components to be added is calculated according to the mass of solutes in the 1 wt% solution during later addition.

Compared with the prior art, the invention has the beneficial effects that:

nicotinic acid, also known as niacin, is one of the 13 vitamins that are essential to the human body. The application adopts nicotinic acid as a corrosion inhibitor, the molecular structure of the nicotinic acid is composed of a carboxyl (-COOH) and a pyridine group, titanium is an oxygen-philic element, after the nicotinic acid is added, the carboxyl and the titanium surface can form a coordinate bond, the corrosion process is retarded in an adsorption film forming mode, the corrosion inhibition effect is achieved, the harm to a human body is small in the using process, the toxicity of the nicotinic acid is small compared with BTA and the like, the influence on the environment is small, and the titanium metal polishing solution is green and environment-friendly.

The formula of the invention does not introduce new external sodium ions, can be applied to the polishing in the semiconductor field (in the polishing process in the semiconductor field, strict requirements are provided for the content of metal ions, especially sodium ions), and the number of the metal ions is reduced.

According to the method, a good titanium surface can be obtained by introducing a small amount of nicotinic acid (0.05 wt%), the surface quality can be excellent when the concentration of the nicotinic acid is 0.05 wt%, the surface can not be optimized when the content of the nicotinic acid is continuously increased, and the removal rate can be reduced due to excessive introduction of the corrosion inhibitor.

The preparation method provided by the invention adopts a filtering technology, so that the number of large particles in the polishing solution can be obviously reduced, and the occurrence of scratches on the surface of the titanium wafer can be effectively avoided.

Drawings

FIG. 1 is a flow chart of the preparation of polishing solution.

FIG. 2 is a graph comparing the number of large particles (. gtoreq.0.5 μm) in the slurry under different process conditions.

FIG. 3 is a graph comparing surface quality (Sq) after titanium polishing under different process conditions.

FIG. 4 is a graph of the titanium surface quality Sq results for different niacin contents in example 1.

FIG. 5 is a graph showing the effect of different organic acids on the surface quality Sq of titanium.

FIG. 6 is an AFM test of titanium after 0.05 wt% citric acid and phytic acid, nicotinic acid as corrosion inhibitors in accordance with the present invention.

Detailed Description

The present invention is further explained with reference to the following examples and drawings, but the scope of the present invention is not limited thereto.

Example 1

The green environment-friendly titanium metal polishing solution comprises an abrasive, an oxidant, an alkaline oxide, a surfactant, a complexing agent and a corrosion inhibitor, wherein the corrosion inhibitor is nicotinic acid, and the surfactant is an organic surfactant without sodium ions.

The polishing solution comprises the following components in percentage by mass: silica sol: 5 wt%; oxidizing agent: 1 wt%; basic compound (b): 0.08 wt%; complexing agent: 1 wt%; corrosion inhibitor: 0.01 wt% -0.1 wt%; surfactant (b): 0.05 wt%. The complexing agent comprises potassium citrate; the oxidant is hydrogen peroxide; the alkaline compound is tetramethyl ammonium hydroxide; the surfactant is fatty alcohol-polyoxyethylene ether.

The preparation process of the polishing solution comprises the following steps:

2) filtering 1 wt% of the diluent in the step 1), wherein the aperture of a filter element is 500 nm; the mass concentration of the solution after filtration is 1 wt%, the purpose of filtration is to prevent the polishing result from being influenced by incompatible trace impurities in the dissolving process or large particles introduced in the preparation process, the content of the large particles is less, and the quality is ignored. The "1 wt% complexing agent" in the above formula refers to the content of potassium citrate in the polishing solution, and the "1 wt% diluent" is to dissolve each component in advance (for example, if 1g potassium citrate is required in the polishing solution, 100g potassium citrate solution (1 wt%) needs to be added).

4) mixing by a stirrer, controlling the rotating speed at 100r/min, stirring for 50min, controlling the temperature at 40 ℃, and adding deionized water, a complexing agent (1 wt% solution), a corrosion inhibitor (1 wt% solution), a surfactant (1 wt% solution), silica sol, an alkaline compound and hydrogen peroxide into the raw materials in sequence. The polishing solution obtained through the four steps has 9625 large particles (not less than 0.5 μm) per milliliter.

In the embodiment, different nicotinic acid addition concentrations are set, and the test data on the influence of the nicotinic acid addition concentration on the titanium surface performance are shown in a table 4, wherein the data in the table show that the surface quality Sq is 1.5nm when the nicotinic acid is not added, and the surface quality Sq is controlled within 0.29nm when the nicotinic acid addition concentration is 0.04-0.2%. The concentration of nicotinic acid is 0.05 wt% to obtain the optimal surface, and the cost is low.

The removal rate of the polishing solution in the embodiment is lower than 100nm/min, is between 30 and 70nm/min, and is about 60nm/min when the mass concentration is 5 wt%.

Example 2

The steps of this example are the same as example 1, except that step 2 is not performed in this example, and the amount of the added corrosion inhibitor, nicotinic acid, is 0.05 wt%. The test results are as follows: large particle test equipment: ACCUSIZer780APS type Large particle tester (PSS780) manufactured by PSS particle sizer corporation, USA; surface quality test equipment: agilent model 5600LS Atomic Force Microscope (AFM) manufactured by Agilent technologies, Inc.

The experimental results are as follows: the number of large particles (not less than 0.5 mu m) per milliliter is 12685;

titanium surface quality (Sq): 0.94, under the same condition, the corrosion inhibitor is citric acid and the like, the titanium surface quality is worse, and the Sq is 1.73.

Comparing example 1 with example 2, it can be seen that, under the same conditions, if the large particles in the polishing solution are not removed, the wafer surface is scratched, and the surface quality is seriously affected.

Example 3

The steps of this example are the same as example 1, except that the amount of the added corrosion inhibitor, nicotinic acid, is 0.05 wt%, the complexing agent is a mixture of potassium citrate and glycine, and the two are added according to a ratio of 1: 1.

Example 4

The steps of this example are the same as example 1, except that the amount of the added nicotinic acid as the corrosion inhibitor is 0.05 wt%, and the surfactant is polyvinylpyrrolidone.

Comparative example 1

The steps of this example are the same as example 1, except that 0.05 wt% of citric acid and phytic acid are used as corrosion inhibitors instead of nicotinic acid, and the obtained polishing solution is tested for titanium surface quality under the same conditions, and the experimental results are shown in fig. 5. As is obvious from figure 5, the nicotinic acid can obviously reduce the surface quality of titanium metal by being used as a corrosion inhibitor, and has obvious effect.

Comparative example 2

The composition and content of each substance in the comparative example are the same as those in example 1, except that no corrosion inhibitor is added in the comparative example, and step 2) and step 3) are not performed in the preparation process. The test results are as follows:

the experimental results are as follows: the number of large particles (not less than 0.5 mu m) per milliliter is 34319;

titanium surface quality (Sq): 3.44 nm.

Because the raw materials are not filtered and the corrosion inhibitor is not added, the number of large particles is too large, scratches are generated on the surface of the wafer in the polishing process, and the surface quality is seriously influenced. Comparing comparative example 2 and example 2, it can be seen that the surface quality is greatly improved when the nicotinic acid corrosion inhibitor is added, and the citric acid added on the basis of comparative example 2 as the corrosion inhibitor has a certain protection effect on the titanium surface, but the effect is far less than that of the nicotinic acid. And because of the property of the activator, the removal rate of titanium is reduced, and nicotinic acid is selected as the corrosion inhibitor.

Nothing in this specification is said to apply to the prior art.

Claims

1. a green and environment-friendly titanium metal polishing liquid, this titanium polishing liquid comprises abrasive, oxidant, alkaline oxide, tensio-active agent, complexing agent and corrosion inhibitor, it is characterized in that, described corrosion inhibitor is nicotinic acid, The surfactant is an organic surfactant without sodium ions.

2. An environmentally friendly titanium metal polishing liquid, wherein the mass percentage of each component in the polishing liquid is: silica sol: 1wt%-10wt%; oxidizing agent: 0.1wt%-2wt%; basic compound : 0.01wt%-0.1wt%; complexing agent: 0.1wt%-5wt%; corrosion inhibitor: 0.01wt%-0.2wt%; surfactant: 0.01wt%-0.1wt%; balance of deionized water;

The complexing agent includes potassium citrate;

The oxidant is hydrogen peroxide; the basic compound is any one of tetramethylammonium hydroxide, tetraethylammonium hydroxide, polyaspartic acid and ammonia; the surfactant is polyvinylpyrrolidone, fatty alcohol polyoxyethylene ether and At least one of dodecylbenzenesulfonic acid.

3. The polishing liquid according to claim 1 or 2, wherein the surfactant is a fatty alcohol polyoxyethylene ether, and the complexing agent further comprises potassium tartrate or glycine.

4. The polishing liquid according to claim 1 or 2, wherein the mass percentage of the niacin is 0.04-0.1%.

5. The polishing liquid according to claim 1 or 2, characterized in that, after adding nicotinic acid, the carboxyl group forms a coordination bond with the titanium surface, and the corrosion process is blocked by the mode of adsorption film formation to achieve corrosion inhibition.

6. the preparation method of the arbitrary described green and environment-friendly type titanium metal polishing liquid of claim 1-5, is characterized in that, the process of this preparation method is:

1) dissolving the complexing agent, the corrosion inhibitor and the surfactant into a diluent state of 1 wt% respectively;

2) filter the 1wt% diluent in step 1), the filter element aperture is 500nm, and the filtered liquid is respectively recorded as the 1wt% solution of the corresponding function;

3) Two-stage filtration is performed on the silica sol, and the filter element apertures of the filter elements used in the two-stage filtration are 500 nm and 300 nm;

4) Use a mixer for mixing, the speed is controlled at 80-120r/min, the stirring time is 30-60min, the temperature is controlled at 30-50°C, and the order of adding raw materials is deionized water, complexing agent, corrosion inhibitor, surface active agent, silica sol, alkaline compound, hydrogen peroxide; when adding in step 4), the complexing agent, corrosion inhibitor, and surfactant are added according to the mass of the solute in the 1wt% solution to calculate the target mass of the component that needs to be added. % total mass input of solution.