Tungsten chemical mechanical polishing solution and application thereof

Abstract

A tungsten chemical mechanical polishing solution includes abrasive particles, a catalyst, a stabilizer, an oxidizer, a corrosion inhibitor, and a substituted pinacol borate, with the balance being water. The substituted pinacol borate used in the tungsten chemical mechanical polishing solution of the present invention increases the stability of the polishing solution and improves the removal rate.

Description

Technical Field

[0001] This invention relates to the field of chemical mechanical polishing (CMP) technology, specifically to a chemical mechanical polishing slurry for tungsten plugs in semiconductor manufacturing and its application. Background Technology

[0002] Chemical Mechanical Polishing (CMP), proposed by Monsanto in the US in 1965 and applied to semiconductor manufacturing by IBM in 1991, has become an indispensable processing technology for integrated circuits, very large-scale integrated circuits, and microelectromechanical systems (MEMS). Compared with traditional purely mechanical or purely chemical polishing methods, CMP avoids the surface damage caused by purely mechanical polishing and the disadvantages of purely chemical polishing, such as slow polishing speed, poor surface smoothness, and poor polishing consistency, through the combined action of chemicals and mechanics. It utilizes the "soft abrasion, hard abrasion" principle in wear, that is, using a softer material for polishing to achieve high-quality surface polishing. Under certain pressure and in the presence of polishing fluid, the workpiece being polished moves relative to the polishing pad. Through the organic combination of the abrasive action of nanoparticles and the corrosive action of oxidants, a flat surface is formed on the surface of the workpiece being polished.

[0003] Integrated circuits consist of hundreds of millions of active elements formed on a silicon substrate. These elements are interconnected through multiple layers of interconnects, in which tungsten has been used to form metal plugs that connect different conductive layers. Tungsten deposited by chemical vapor deposition can fill very small contact windows and inter-layer connection holes, and can also cover the entire wafer surface.

[0004] Currently, tungsten chemical mechanical polishing slurries use silane coupling agents to modify and stabilize abrasives, and then add other additives to improve surface quality. However, the introduction of multiple additives increases the instability of the polishing slurry itself and the gold impurity content. Therefore, it is necessary to develop new tungsten chemical mechanical polishing slurries to meet these ongoing needs. Summary of the Invention

[0005] This invention provides a tungsten chemical mechanical polishing slurry with high slurry stability and fast polishing rate.

[0006] Another object of the present invention is to provide the application of this tungsten chemical mechanical polishing slurry in the chemical mechanical polishing of tungsten plugs.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0008] A tungsten chemical mechanical polishing slurry includes abrasive particles, a catalyst, a stabilizer, an oxidant, a corrosion inhibitor, and a substituted pinacol ester of borate.

[0009] In a preferred embodiment, the tungsten chemical mechanical polishing slurry comprises 0.1% to 10% by mass of abrasive particles, 0.001% to 0.1% of catalyst, 0.02% to 0.5% of stabilizer, 0.5% to 3.5% of oxidant, 0.005% to 5% of corrosion inhibitor, and 0.01% to 0.1% of substituted pinacol borate, with the balance being water.

[0010] In a more preferred embodiment, the tungsten chemical mechanical polishing slurry comprises 0.1% to 10% abrasive particles, 0.005% to 0.05% catalyst, 0.05% to 0.2% stabilizer, 0.5% to 3.5% oxidant, 0.05% to 3% corrosion inhibitor, and 0.02% to 0.05% substituted pinacol borate, with the balance being water.

[0011] In one specific embodiment, the substituted pinacol ester of borate has the chemical formula (I) shown.

[0012]

[0013] Learn the structure:

[0014] Wherein: R group is selected from one of pyrazolyl and its derivatives, phenyl and its derivatives, pyrimidinyl and its derivatives, pyridinyl and its derivatives, and isoxazolyl and its derivatives; preferably pyrazolyl and its derivatives.

[0015] In one specific implementation, the grinding particles are nano-silica gel bodies; preferably, the particle size of the nano-silica gel bodies is 40-150 nm.

[0016] In one specific implementation, the catalyst is ferric nitrate.

[0017] In one specific implementation, the oxidant is hydrogen peroxide.

[0018] In one specific embodiment, the stabilizer is an organic acid selected from one or more of citric acid, malonic acid, tartaric acid, succinic acid, succinic acid, succinic acid, and oxalic acid, preferably malonic acid.

[0019] In one specific embodiment, the corrosion inhibitor is selected from one or more of glycine, lysine, arginine, piperazine and its derivatives, triazole and its derivatives, pyridine and its derivatives, diethylenetriamine, tetraethylenepentamine, 1,5,7-triazabicyclo[4.4.0]dec-5-ene (TBD), 7-methyl-1,5,7-triazabicyclo[4.4.0]dec-5-ene (MTBD), 1,5-diazabicyclo[4.3.0]-5-nonene (DBN), and 1,8-diazabicycloundec-7-ene (DBU); preferably glycine; more preferably, the amount of glycine used is 500-30000 ppm.

[0020] In one specific implementation, the pH of the polishing solution is 2-3.

[0021] On the other hand, the aforementioned tungsten chemical mechanical polishing slurry is used in the chemical mechanical polishing of tungsten plugs.

[0022] By adopting the above technical solution, compared with the prior art, the present invention has the following beneficial effects:

[0023] (1) The borate pinacol ester substituted in the polishing liquid of the present invention hydrolyzes in deionized water to form boric acid compound, which reacts with the silanol on the surface of the subsequently added silica sol particles to form Si-OB bond, thereby making the grinding particles exist stably in the slurry.

[0024] (2) The small molecule pinacol formed by the hydrolysis of the substituted borate pinacol ester in the polishing liquid of the present invention acts as a wetting agent and dispersant in the polishing of the slurry, which is beneficial to the stability of the slurry.

[0025] (3) In tungsten chemical mechanical polishing, due to the electron deficiency of boron, the abrasive particles bound to boron atoms are electrostatically attracted to the negative charge on the surface of the tungsten wafer. The abrasive particles are pulled toward the surface of the tungsten wafer, increasing the contact area and helping to improve the removal rate. Detailed Implementation

[0026] To better understand the technical solution of the present invention, the following embodiments will further illustrate the method provided by the present invention. However, the present invention is not limited to the listed embodiments, but should also include any other well-known modifications within the scope of the claims of the present invention.

[0027] A tungsten chemical mechanical polishing slurry comprises 0.1%–10% abrasive particles, 0.001%–0.1% catalyst, 0.02%–0.5% stabilizer, 0.5%–3.5% oxidant, 0.005%–5% corrosion inhibitor, and 0.01%–0.1% substituted pinacol borate ester, with the balance being water.

[0028] In a preferred embodiment, the tungsten chemical mechanical polishing slurry comprises 0.1%–10% abrasive particles, 0.005%–0.05% catalyst, 0.05%–0.2% stabilizer, 0.5%–3.5% oxidant, 0.05%–3% corrosion inhibitor, and 0.02%–0.05% substituted pinacol borate, with the balance being water.

[0029] Specifically, the substituted pinacol ester of borate has the chemical structure shown in formula (I):

[0030]

[0031] Wherein: R group is selected from one of pyrazolyl and its derivatives, phenyl and its derivatives, pyrimidinyl and its derivatives, pyridinyl and its derivatives, and isoxazolyl and its derivatives; preferably pyrazolyl and its derivatives.

[0032] Specifically, the substituted pinacol ester of borate is selected from any one of the following structures A to L, preferably from...

[0033]

[0034] The following is a substituted pinacol ester of borate with the structure D.

[0035] Specifically, the amount (by mass percentage, based on the total mass of the polishing slurry) of the substituted pinacol ester borate is 0.001% to 0.1%, for example, including but not limited to 0.001%, 0.002%, 0.003%, 0.004%, 0.005%, 0.008%, 0.011%, 0.014%, 0.017%, 0.02%, 0.023%, 0.026%, 0.029%, 0.032%, 0.035%, 0.038%, 0.041%, 0.044%, 0.047%, 0.05%, 0.06%, 0.07%, 0.08%, 0.09%, and 0.1%, preferably 0.02% to 0.05%.

[0036] The grinding particles are nano-silica gel particles, preferably with a particle size of 40-150nm, such as including but not limited to 40nm, 45nm, 50nm, 55nm, 60nm, 65nm, 70nm, 75nm, 80nm, 85nm, 90nm, 95nm, 100nm, 105nm, 110nm, 115nm, 120nm, 125nm, 130nm, 135nm, and 140nm.

[0037] The key to this invention lies in the hydrolysis of the substituted borate pinacol ester in deionized water to form substituted boric acid, which reacts with the silanol on the surface of the subsequently added silica sol particles to form Si-OB bonds, thereby making the grinding particles stable in the slurry.

[0038] Another key aspect of this invention is that the small molecule pinacol formed by the hydrolysis of the substituted borate pinacol ester acts as a wetting agent and dispersant in slurry polishing, which can further improve the stability of the slurry.

[0039] Another key aspect of this invention lies in the fact that during tungsten chemical mechanical polishing, the surface of the tungsten wafer is negatively charged. Due to the electron deficiency of boron, the abrasive particles bound to the boric acid compound are electrostatically attracted to the surface of the tungsten wafer, and the abrasive particles are pulled toward the surface of the tungsten wafer, thereby increasing the contact area between the abrasive particles and the tungsten wafer and improving the removal rate of the tungsten wafer.

[0040] The present invention will be further explained and illustrated below through more specific embodiments, but these do not constitute any limitation.

[0041] The abrasive particles were purchased from Fuso's PL series silica sol, specifically PL-3 and PL-5, from Japan.

[0042] The substituted pinacol esters were all purchased from Sigma-Aldrich (Shanghai) Trading Co., Ltd.

[0043] The aminopropylmethyldiethoxysilane (KH-902) was purchased from Beijing Innocare Technology Co., Ltd.

[0044] Unless otherwise specified, all other raw materials and reagents used in the embodiments and comparative examples of this invention can be purchased through commercial channels.

[0045] Polishing slurry preparation steps:

[0046] The substituted borate pinacol ester was added to an appropriate amount of deionized water and stirred for 10 minutes. The pH was then adjusted to 2-3 with nitric acid. Silica sol particles were then slowly added while stirring. Following this, a tungsten chemical mechanical polishing slurry was prepared by simple stirring and mixing according to Table 1. After thorough mixing, the pH was adjusted to 2.0-3.0 with nitric acid or KOH. Hydrogen peroxide was added before use, and the mixture was stirred thoroughly. The remaining amount was made up with water, resulting in the various embodiments and comparative examples of this invention.

[0047] Table 1. Composition of polishing fluid in Comparative Examples 1-3 and Examples 1-9

[0048]

[0049]

[0050] During the preparation of the polishing slurry, Comparative Examples 1 and 2 exhibited agglomeration during the addition of silica sol, while Comparative Examples 3 and Examples 1-9 maintained stable appearance. The average particle size of the abrasive particles in the tungsten chemical mechanical polishing slurries of Comparative Examples 1-3 and Examples 1-8 was measured, and the results are listed in Table 2.

[0051] Table 2. Particle size of polishing slurry after settling in Comparative Examples 1-3 and Examples 1-8

[0052]

[0053] To verify the polishing effect of the polishing slurry of the present invention, tungsten blank wafers and silicon oxide blank wafers were polished using the polishing slurries of Comparative Example 3 and Examples 1-9, respectively. The polishing conditions were as follows: the polishing machine was a 12” Reflexion LK, the polishing pad was an IC1000, the polishing pressure was 3 psi, the rotation speed of the polishing head and polishing disc was 93 / 87 rpm, the polishing slurry flow rate was 250 mL / min, and the polishing time was 60 s.

[0054] The conductivity of the tungsten-coated film was measured using a four-probe conductivity meter before and after polishing, and the thickness of the tungsten-coated film was calculated accordingly. The tungsten polishing rate was obtained by dividing the difference in thickness of the tungsten-coated film before and after polishing by the polishing time. The polishing rate of the silicon oxide-coated film was measured using a non-metallic film thickness gauge in a similar manner. The polishing effects of Comparative Example 3 and Examples 1-9 are shown in Table 3.

[0055] Table 3 shows the polishing test results of Comparative Examples 3 and Examples 1-9.

[0056]

[0057]

[0058] In summary, when the tungsten chemical mechanical polishing slurry of the present invention is applied to the chemical mechanical polishing of tungsten blanks, the added substituted borate pinacol ester has multiple functions: it can replace the silane coupling agent to improve the stability of the polishing slurry, and it can also increase the polishing rate through electrostatic interaction.

[0059] Although the present invention has been described in detail through the above preferred embodiments, it should be understood that the present invention is not limited to these embodiments and various modifications, variations and alterations can be made without departing from the spirit and scope of the present invention. The scope of the present invention should be limited only by the claims and their equivalents.

Claims

1. A tungsten chemical mechanical polishing slurry, characterized in that, It comprises 0.1% to 10% (by mass) grinding particles, 0.001% to 0.1% catalyst, 0.02% to 0.5% stabilizer, 0.5% to 3.5% oxidant, 0.005% to 5% corrosion inhibitor, and 0.001% to 0.1% substituted pinacol borate, with the balance being water; The substituted pinacol ester of borate is selected from any one of the following structures A to L. The preparation steps of the tungsten chemical mechanical polishing slurry include: adding substituted borate pinacol ester to an appropriate amount of deionized water, stirring for 10 minutes, then adjusting the pH to 2-3 with nitric acid, and then slowly adding silica sol particles while stirring. Finally, the tungsten chemical mechanical polishing slurry is prepared by simple stirring and mixing according to the proportion.

2. The tungsten chemical mechanical polishing slurry according to claim 1, characterized in that, It comprises 0.1% to 10% grinding particles, 0.005% to 0.05% catalyst, 0.05% to 0.2% stabilizer, 0.5% to 3.5% oxidant, 0.05% to 3% corrosion inhibitor and 0.02% to 0.05% substituted pinacol ester of borate, with the balance being water.

3. The tungsten chemical mechanical polishing slurry according to claim 1 or 2, characterized in that, The grinding particles are nano-silica gel.

4. The tungsten chemical mechanical polishing slurry according to claim 3, characterized in that, The particle size of the nano-silica gel is 30-150 nm.

5. The tungsten chemical mechanical polishing slurry according to claim 1 or 2, characterized in that, The catalyst is ferric nitrate.

6. The tungsten chemical mechanical polishing slurry according to claim 1 or 2, characterized in that, The oxidant is hydrogen peroxide.

7. The tungsten chemical mechanical polishing slurry according to claim 1 or 2, characterized in that, The stabilizer is an organic acid, selected from one or more of citric acid, malonic acid, tartaric acid, succinic acid, succinic acid, and oxalic acid.

8. The tungsten chemical mechanical polishing slurry according to claim 7, characterized in that, The stabilizer is malonic acid.

9. The tungsten chemical mechanical polishing slurry according to claim 1 or 2, characterized in that, The corrosion inhibitor is selected from one or more of glycine, arginine, piperazine and its derivatives, triazole and its derivatives, pyridine and its derivatives, diethylenetriamine, tetraethylenepentamine, 1,5,7-triazidobicyclo[4.4.0]dec-5-ene, 7-methyl-1,5,7-triazabicyclo[4.4.0]dec-5-ene, 1,5-diazabicyclo[4.3.0]-5-nonene, and 1,8-diazabicycloundec-7-ene.

10. The tungsten chemical mechanical polishing slurry according to claim 9, characterized in that, The corrosion inhibitor is glycine.

11. The tungsten chemical mechanical polishing slurry according to claim 10, characterized in that, The dosage of glycine is 500-30000 ppm.

12. The tungsten chemical mechanical polishing slurry according to claim 1 or 2, characterized in that, The pH of the polishing solution is 2-3.

13. The application of the tungsten chemical mechanical polishing slurry according to any one of claims 1-12 in tungsten chemical mechanical polishing.

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