CN111378973A

CN111378973A - Chemical mechanical polishing solution and application thereof

Info

Publication number: CN111378973A
Application number: CN201811654601.9A
Authority: CN
Inventors: 王晨; 何华锋; 李星
Original assignee: Anji Microelectronics Technology Shanghai Co ltd
Current assignee: Anji Microelectronics Technology Shanghai Co ltd; Anji Microelectronics Shanghai Co Ltd
Priority date: 2018-12-28
Filing date: 2018-12-28
Publication date: 2020-07-07
Also published as: TW202033692A; TWI824092B

Abstract

The invention provides a chemical mechanical polishing solution, which comprises silicon dioxide abrasive particles, a halogen-containing oxidizing agent, a polishing rate accelerator and water. Wherein, the surface of the silicon dioxide grinding particles is grafted with an organic matter with a sulfonic group at the molecular terminal. The invention also provides an application of the chemical mechanical polishing solution in copper and silicon polishing. The invention has the advantages that: 1) the polishing solution disclosed by the invention uses the oxidant containing halogen, so that the polishing solution has high polishing rate to copper and silicon; 2) according to the polishing solution disclosed by the invention, the silicon dioxide abrasive particles with sulfonic groups at the molecular terminals are grafted on the surface, so that the stability of the colloid of the polishing solution is greatly improved; 3) the method reduces the residue of the grinding particles on the surface of the wafer in the polishing process, improves the polishing quality, reduces the polishing defects and improves the yield of products.

Description

Chemical mechanical polishing solution and application thereof

Technical Field

The invention relates to the field of chemical mechanical polishing, in particular to a chemical mechanical polishing solution and application thereof in copper and silicon polishing.

Background

The TSV (Through-Silicon-Via) technology is a latest technology for realizing interconnection between chips by making vertical conduction between the chips and between the wafers. Different from the conventional IC packaging bonding and bump stacking technology, the TSV has the advantages that the stacking density of chips in the three-dimensional direction can be maximized, the overall dimension is minimized, and the interconnection is shortened, so that the chip speed is increased, and the power consumption is reduced. The back-thinning technique in the TSV technology requires chemical mechanical polishing, and the polishing solution used in the TSV technology requires very high polishing rates for both silicon and copper materials.

Generally, under alkaline conditions, higher silicon polishing rates can be achieved, for example:

US2002032987 discloses a polishing liquid using alcohol amine as an additive to increase the removal rate of polysilicon, wherein the additive is preferably 2- (dimethylamino) -2-methyl-1-propanol.

US2002151252 discloses a polishing solution containing complexing agents with multiple carboxylic acid structures for increasing the polysilicon removal rate, wherein the preferred complexing agents are EDTA (ethylenediaminetetraacetic acid) and DTPA (diethyltriaminepentaacetic acid).

European patent EP1072662 discloses a polishing liquid for an organic substance containing a lone pair of electrons and a double bond generating delocalized structure to improve the removal rate of polysilicon, and preferably, the compound is a guanidine compound or a salt thereof.

US2006014390 discloses a polishing liquid for increasing the removal rate of polysilicon, which comprises 4.25-18.5 wt% of an abrasive and 0.05-1.5 wt% of an additive. Wherein the additive is mainly selected from organic bases such as quaternary ammonium salt, quaternary ammonium base, ethanolamine and the like. In addition, the polishing liquid contains a nonionic surfactant, such as a homo-or copolymerization product of ethylene glycol or propylene glycol.

The chinese patent CN101497765A significantly improves the polishing speed of silicon by utilizing the synergistic effect of biguanide and azole.

Generally, using an oxidizing agent under acidic conditions, a high copper polishing rate can be achieved by utilizing the high oxidation potential of the oxidizing agent (hydrogen peroxide) under acidic conditions, and the property of copper to coordinate and dissolve easily under acidic conditions, such as:

chinese patent CN1705725A discloses a polishing solution for polishing copper metal surface, which is between 2.5 and 4.0, and removes the surface of copper metal under the action of oxidant (hydrogen peroxide, etc.), chelating agent and passivating agent.

Chinese patent CN1787895A discloses a CMP composition comprising a fluid agent as well as an oxidizing agent, a chelating agent, an inhibitor, an abrasive and a solvent. Under acidic conditions, such CMP compositions advantageously increase material selectivity in a CMP process, which can be used to polish the surface of copper components on semiconductor substrates without dishing or other adverse planarization defects in the polished copper.

Chinese patent CN01818940A discloses that a copper polishing slurry can be formed by further combining with an oxidizing agent, such as hydrogen peroxide, and/or a corrosion inhibitor, such as benzotriazole, to increase the removal rate of copper. This higher polishing rate is achieved while maintaining local PH stability and significantly reducing global and local corrosion.

In addition, polishing of copper is sometimes also performed under alkaline conditions, such as:

chinese patent CN1644640A discloses an aqueous composition for polishing copper under alkaline conditions, which comprises 0.001 to 6% by weight of a nonferrous metal inhibitor, 0.05 to 10% by weight of a complexing agent for the metal, 0.01 to 25% by weight of a copper removing agent for accelerating the removal of copper, 0.5 to 40% by weight of an abrasive, etc., and the removal rate of copper is increased by the interaction of imidazole, a BTA, which are copper removing agents.

Chinese patent CN1398938A discloses a chemical mechanical global planarization polishing solution for multilayer copper wiring of a very large scale integrated circuit, which is used for improving the removal rate of copper and comprises the following components: 18 to 50 percent by weight of abrasive, 0.1 to 10 percent by weight of chelating agent, 0.005 to 25 percent by weight of complexing agent, 0.1 to 10 percent by weight of active agent, 1 to 20 percent by weight of oxidizing agent, and deionized water.

However, the above patent does not disclose a polishing liquid having both high polishing rates of copper and silicon. In fact, it is very difficult to achieve high polishing rates of copper and silicon simultaneously. This is because, although a high copper polishing rate can be obtained by polishing under acidic conditions, the polishing rate for silicon is generally low. The reason is that under acidic conditions, the oxidizing agent oxidizes the surface of elemental silicon to silica, which is more difficult to remove than silicon. Polishing under alkaline conditions, if no oxidizing agent is added, although very high silicon polishing rates can be achieved, the polishing rate for copper is generally low. The reason is that copper needs to be oxidized before it can be easily removed. However, if an oxidant such as hydrogen peroxide is added, the surface of the elemental silicon is oxidized into silicon dioxide by the hydrogen peroxide, which is more difficult to remove. In addition, under alkaline conditions, oxidants such as hydrogen peroxide are unstable and can be rapidly decomposed and become ineffective.

In addition, the polishing solution disclosed in the above patent has a problem that: at high ionic strength, for example, when a large amount of potassium ions (>0.1mol/Kg) is added, the average particle size of the abrasive particles gradually increases, resulting in instability of the polishing solution and easy sedimentation and delamination. Therefore, the utility model can be used in a very short time after production, thereby bringing great inconvenience to the production and use links.

Currently, the abrasive particles used in Chemical Mechanical Polishing (CMP) solutions are usually silicon dioxide, including silica sol (colloidal silica) and fumed silica (fumed silica). They are solids in themselves, but can be dispersed homogeneously in aqueous solution without settling, and can even retain long-term stability of 1 to 3 years.

The stability (no sedimentation) of the abrasive particles in the aqueous phase can be explained by the theory of the electric double layer-since each particle surface carries the same charge, they repel each other and do not agglomerate.

According to the Stern model, colloidal ions generate Zeta potential on the tangent plane when moving. Zeta potential is an important indicator of colloid stability, since colloid stability is closely related to electrostatic repulsion between particles. The decrease in Zeta potential decreases the electrostatic repulsive force, causing the inter-particle van der waals attractive force to dominate, causing aggregation and sedimentation of the colloid. The level of ionic strength is an important factor affecting the Zeta potential.

The stability of the colloid is influenced by many other factors besides the zeta potential, such as temperature, pH, surfactant type, molecular weight of additives, etc. In the aspect of temperature, at higher temperature, the irregular thermal motion of particles is intensified, the probability of mutual collision is increased, and the agglomeration is accelerated; in the aspect of pH value, the pH value is more stable than neutral under strong alkaline and strong acidic conditions, wherein the alkalinity is the most stable, and the pH value is the least stable in a range of 4-7; in the aspect of the types of the surfactants, some surfactants can play a role of a dispersing agent to improve the stability of colloid, and some surfactants can reduce the surface charge of the nano particles, reduce electrostatic repulsion, destroy the stability of the colloid and accelerate sedimentation, and in the surfactants, an anionic surfactant is favorable for the stability of the nano particles, and a cationic surfactant is easy to reduce the stability; in terms of the molecular weight of the additive, too long polymer long chains sometimes entangle nanoparticles, increase the viscosity of the dispersion, deteriorate the stability of colloids, and accelerate particle aggregation.

In view of this, colloidal stability can be improved by modifying the surface of silica and grafting organic molecules. Currently, the grafting method is usually to form a specific structure by condensation of a silane coupling agent and hydroxide bonds on the surface of silica. The silane coupling agent is usually dispersed particles with amino groups on the surface and positive charges, or dispersed particles with epoxy groups. However, such positively charged silica abrasive grains are easily bonded to the surface of a negatively charged silicon wafer and easily remain on the surface of the silicon wafer, thereby deteriorating polishing effects and increasing difficulty in cleaning.

Disclosure of Invention

In order to solve the problems, the invention provides a chemical mechanical polishing solution, wherein a halogen-containing oxidizing agent is used in the polishing solution, and an organic matter with a sulfonic group at the molecular terminal is grafted on the surface of an abrasive particle, so that the obtained polishing solution has higher polishing rate of silicon and copper and higher stability.

Specifically, in one aspect, the present invention provides a chemical mechanical polishing solution comprising silica abrasive particles, a halogen-containing oxidizing agent, a polishing rate accelerator, and water. Wherein, the surface of the silicon dioxide grinding particles is grafted with an organic matter with a sulfonic group at the molecular terminal.

Preferably, the content of the grinding particles is 5-30% by mass.

Preferably, the surface charge of the abrasive particles forms a voltage between-30 millivolts and-70 millivolts.

Preferably, the halogen-containing oxidizing agent comprises one or more of potassium bromate, potassium iodate, potassium chlorate, and ammonium periodate.

Preferably, the halogen-containing oxidizing agent is potassium bromate.

Preferably, the content of the halogen-containing oxidant is 0.5-4% by mass.

Preferably, the polishing rate accelerator is a nitrogen-containing organic compound.

Preferably, the nitrogen-containing organic compound comprises one or more of piperazine, ethylenediamine, amino acids, EDTA (ethylenediaminetetraacetic acid).

Preferably, the content of the nitrogen-containing organic compound is 0.1-4% by mass.

Preferably, the pH of the chemical mechanical polishing solution is 10 to 12.

In another aspect, the invention provides a use of the chemical mechanical polishing solution in copper and silicon polishing.

The technical principle of improving the stability of the polishing solution colloid is as follows: 1) after an organic matter with a sulfonic group at the molecular terminal is grafted on the surface of the silicon dioxide grinding particles, the silicon dioxide particles are negatively charged, and are not easy to agglomerate due to mutual electrostatic repulsion, so that the colloid stability is increased. 2) The polishing solution disclosed by the invention is alkaline, under an alkaline condition, the surface of a silicon wafer is negatively charged, and electrostatic repulsion is generated between the negatively charged grinding particles, so that the adsorption quantity of the grinding particles on the surface of the wafer is reduced.

Compared with the prior art, the invention has the advantages that: 1) the polishing solution disclosed by the invention uses the oxidizing agent containing halogen, and has a high polishing rate to copper and silicon, so that the polishing solution can be used for polishing two materials of copper and silicon simultaneously; 2) according to the polishing solution disclosed by the invention, the silicon dioxide abrasive particles with sulfonic groups at the molecular terminals are grafted on the surface, so that the stability of the colloid of the polishing solution is greatly improved; 3) the method reduces the residue of the grinding particles on the surface of the wafer in the polishing process, improves the polishing quality, reduces the polishing defects and improves the yield of products.

Detailed Description

The advantages of the present invention are further illustrated by the following specific examples, but the scope of the present invention is not limited to the following examples.

Table 1 shows the components and contents of polishing solutions of examples 1 to 10 of the present invention and comparative examples 1 to 3. According to the components and the mixture ratio in the table 1, the components are mixed evenly, and water is used for complementing the mass percent to 100 percent. The pH was adjusted to a desired value with nitric acid, KOH or tetramethylammonium hydroxide to obtain polishing solutions of examples and comparative examples in Table 1.

In table 1, abrasive particle type a is a conventional silica abrasive particle, and abrasive particle type B is a silica abrasive particle having a surface grafted with an organic substance having a sulfonic acid group at the end.

TABLE 1 polishing solution formulations for inventive examples 1-10 and comparative examples 1-3

Wafers containing silicon and copper materials were polished with the chemical mechanical polishing solutions of examples 1-10 and comparative examples 1-3, respectively. The polishing conditions were: polishing was performed using a Logitech table top polisher, using a Fujibo polishing pad, at a polishing pressure of 3 psi. The polishing rates of the polishing liquids for silicon and copper in each example were obtained. Further, the polishing liquids of the respective examples were allowed to stand at ordinary temperature for 30 days, and then the particle diameters of the silica abrasive particles therein were measured, and the increase of the average value thereof from the average particle diameter of the original silica abrasive particles was calculated. The results of the above-mentioned increase in polishing rates of silicon and copper and average particle size of the silica abrasive grains are shown in Table 2.

TABLE 2 polishing results of the polishing liquids of examples 1 to 10 of the present invention and comparative examples 1 to 3

As seen from Table 2, the polishing of the examples of the present invention has higher abrasive grain stability while having higher polishing rates for silicon and copper, compared to the comparative examples. The polishing solution of comparative example 1 has a high polishing rate for polysilicon, but has a very low polishing rate for copper because of the absence of an oxidizing agent, and the average particle size of the abrasive grains slightly increases after the polishing solution of comparative example 1 is left to stand for 30 days. The polishing solution of the comparative example 2 is based on the comparative example 1, and hydrogen peroxide is added as an oxidant, so that the polishing rate of copper is obviously improved, but the hydrogen peroxide oxidizes the surface of silicon into silicon oxide, so that the polishing rate of the polishing solution to the silicon is obviously reduced. The polishing liquid of comparative example 2 was allowed to stand for 30 days, and the average particle diameter of the abrasive grains also slightly increased. Comparative example 3 the oxidizing agent in comparative example 2 was replaced by potassium bromate, and the polishing solution had a higher polishing rate for both copper and polysilicon, but because of the high potassium ion concentration in the polishing solution of comparative example 3, the colloid double layer of the abrasive particles was compressed, the colloid stability decreased, and the average particle size of the abrasive particles increased substantially after 30 days of standing.

From examples 1 to 12, it can be seen that, in an alkaline environment, by using a halogen oxidizing agent in combination with piperazine, ethylenediamine, or amino acid, EDTA as a polishing rate accelerator, a polishing solution having a high polishing rate for both silicon and copper can be obtained, and the polishing solution also has a high stability, and does not cause aggregation of abrasive particles even after standing for 30 days. Moreover, it can be seen from examples 1-12 that different polishing rates for copper and silicon can be obtained by changing the mixture ratio of the abrasive particles, the oxidizer and the polishing rate accelerator, for example, a polishing solution with a suitably low polishing rate for copper but a high polishing rate for silicon can be obtained by adding less abrasive particles in example 3; in example 5, by increasing the content of the abrasive grains and decreasing the content of the oxidizing agent and the polishing rate accelerator, a polishing liquid having a polishing rate of copper equivalent to that of silicon can be obtained; in example 4, a polishing liquid having high polishing rates of copper and silicon was obtained by increasing the content of the abrasive grains, the content of the oxidizing agent and the content of the polishing rate accelerator at the same time. Therefore, the polishing solution suitable for different polishing objects and polishing environments can be obtained by controlling the specific content of each component of the polishing solution. Moreover, when the polishing solution is used for polishing silicon and copper, the polishing solution cannot be attached to the surface of a wafer, so that the cleanliness of the surface of the polished wafer can be improved, and convenience is brought to a subsequent cleaning process. Moreover, the polishing solution has good stability, long storage period and higher commodity value.

It should be noted that the contents in the present invention are all contents by mass percentage, if not specifically stated.

It should be noted that the embodiments of the present invention have been described in terms of preferred embodiments, and not by way of limitation, and that those skilled in the art can make modifications and variations of the embodiments described above without departing from the spirit of the invention.

Claims

1. A chemical mechanical polishing solution comprises silica abrasive particles, a halogen-containing oxidizing agent, a polishing rate accelerator, and water. Wherein, the silicon dioxide grinding particles are negatively charged, and an organic matter with a sulfonic group at the molecular terminal is grafted on the surface.

2. The chemical mechanical polishing solution according to claim 1,

the content of the silicon dioxide grinding particles is 5-30% by mass.

3. The chemical mechanical polishing solution according to claim 1,

the surface charge of the silica abrasive particles results in a voltage of-30 millivolts to-70 millivolts.

4. The chemical mechanical polishing solution according to claim 1,

the oxidant containing halogen comprises one or more of potassium bromate, potassium iodate, potassium chlorate and ammonium periodate.

5. The chemical mechanical polishing solution according to claim 4,

the halogen-containing oxidant is potassium bromate.

6. The chemical mechanical polishing solution according to claim 1,

the content of the halogen-containing oxidant is 0.5-4% by mass.

7. The chemical mechanical polishing solution according to claim 1,

the polishing rate accelerator is a nitrogen-containing organic compound.

8. The chemical mechanical polishing solution according to claim 7,

the nitrogen-containing organic compound comprises one or more of piperazine, ethylenediamine, amino acid and EDTA (ethylene diamine tetraacetic acid).

9. The chemical mechanical polishing solution according to claim 7,

the mass percentage content of the nitrogen-containing organic compound is 0.1-4%.

10. The chemical mechanical polishing solution according to claim 1,

the pH value of the chemical mechanical polishing solution is 10-12.

11. Use of a chemical mechanical polishing liquid according to any one of claims 1 to 10 for copper and silicon polishing.