WO2012051787A1 - Chemical mechanical polishing liquid - Google Patents

Abstract

Disclosed is a chemical mechanical polishing liquid for the planarization of a blocking layer, which comprises at least one kind of abrasive particle, a metal chelating agent, a silicon dioxide polishing promoter, a composite metal anticorrosive, an auxiliary cleaning constituent and an oxidant. During polishing of the blocking layer, the polishing liquid can effectively remove particle residues on the surface of wafers and metal compound residues on polishing pads, and has relatively good stability.

Description

 Chemical mechanical polishing liquid

Technical field

 The present invention relates to a chemical mechanical polishing liquid.

technical background

 In the copper process of the Damascene process, the purpose of the planarization of the barrier layer is to remove the barrier metal and dielectric material on the surface of the wafer and to control the thickness of the metal copper and the interlayer dielectric within the scope of the process to form an interconnection. One-stage polishing directly determines the electrical performance and reliability of the device, especially the efficiency of planarization after entering the 45-nanometer process, the removal rate of various materials, the amount of surface contaminants, the size of residual particles, and surface defects. The degree of adsorption and surface adsorption characteristics have higher requirements, especially for metal corrosion and surface contaminant control has reached new height and precision. Generally speaking, the mechanical strength is weak in the 45nm process. Low dielectric material, and covered with a silicon dioxide layer to protect the dielectric layer from damage during polishing, and the thickness of the barrier layer is further reduced. At about 100 angstroms, the residual of surface particles is also reduced to below 100 or even lower. In addition, the polishing uniformity at the wafer level and the slice level is as low as possible (<3%), and it is absolutely forbidden to produce various forms of corrosion on the metal. Phenomenon. The surface roughness and morphology of copper metal should meet the requirements. In addition, as the global semiconductor industry lowers the cost requirements, the comprehensive use cost of CMP slurry should be reduced to a certain level to ensure polishing performance. After reaching the standard, the concentration of the slurry can further reduce the cost.

Summary of invention

SUMMARY OF THE INVENTION The object of the present invention is to provide a barrier polishing liquid having a high polishing rate, an adjustable selection ratio, a surface contamination index meeting requirements, and a low cost in the above background. The invention provides a chemical mechanical polishing liquid for flattening a metal copper interconnection barrier layer, which comprises:

 a: an abrasive granule,

 b : a metal chelating agent,

 c: , a silica polishing accelerator.

 d : combination metal corrosion inhibitor,

 e: an auxiliary cleaning agent

 f: an oxidant

 Wherein the abrasive particles are silica sol or a fumed silica aqueous dispersion having a particle size of from 20 to 250 nm, most preferably from 30 to 150 nm. The content of the abrasive grains is 2 to 30% by weight, preferably 5 to 20% by weight.

 Wherein, the metal chelating agent is a mono- or polybasic organic acid or an organic phosphine such as HEDP (hydroxyethylidene diphosphonic acid), PBTCA (2-phosphonobutane-1, 2,4-tricarboxylic acid), HPAA (2) - hydroxyphosphonoacetic acid), oxalic acid, malonic acid, succinic acid, citric acid, tartaric acid, and the like. The concentration of the metal chelating agent is from 0.01 to 1% by weight, most preferably from 0.1 to 0.5% by weight.

 Wherein the oxidizing agent is a peroxide or a persulfide. The concentration of the oxidizing agent is 0.01 to 1% by weight. Wherein, the combined metal corrosion inhibitor is: an azole compound such as BTA (benzotriazole) or a derivative of BTA; and a water-soluble polymer such as polyacrylic acid or an acrylic copolymer. The concentration of BTA and its derivatives is 0.01-0.5 wt%, and the optimum is 0.1-0.2%; the concentration of the water-soluble polymer is 0.01%-0.5 wt%, and the optimum is 0.05-0.2%.

 Wherein, the silica polishing accelerator is a quaternary ammonium salt or a quaternary ammonium base, specifically tetramethylammonium halide, tetraethylammonium halide, tetrapropylammonium halide, tetrabutylammonium halide, tetramethylhydrogenated ammonium , tetraethylammonium hydroxide, tetrapropylammonium hydroxide, tetrabutylhydrogen peroxide: ammonium, and the like. Preferred are tetrabutylammonium fluoride, tetrapropylammonium bromide, tetramethylammonium hydroxide, tetrabutylammonium hydroxide. The concentration of the silica polishing accelerator is from 10 ppm by mass to 0.5% by mass, preferably from 100 ppm to 0.2% by mass.

The present invention also includes an auxiliary cleaning agent, specifically one or more anthracene phosphate ester anionic surfactants, for example: alkyl phosphate diethanolamine salt, alkyl phosphate triethanolamine salt, phosphoric acid Ammonium decyl phosphatidyl ammonium salt, potassium decyl phosphate, potassium tetradecyl phosphate, potassium cetyl phosphate, and the like. The auxiliary cleaning agent is contained in an amount of from 0.005 to 0.2% by weight, preferably from 0.01 to 0.1% by weight.

 The polishing liquid of the present invention has a pH of from 2 to 5, preferably from 2.5 to 3.5.

 Abrasive particles are a source of mechanical force for the slurry and are primarily used to remove residual metal oxides and dielectric materials.

 The beneficial effects of the present invention are as follows: The present invention comprises a metal chelating agent capable of sequestering oxidized metal copper ions to form a water-soluble substance, which is discharged with the polishing liquid to prevent metal compounds from remaining on the polishing pad and the wafer surface; the oxidizing agent can oxidize Metallic copper to ionic state, easy to be removed by abrasive mechanical force; metal corrosion inhibitor system can protect metal copper surface, avoid corrosion, protect metal metal copper of recess from oxidation, ensure no defects and material erosion on the entire wafer surface In addition, it can adjust the sensitivity of copper removal to hydrogen peroxide; silica polishing accelerator can improve the removal rate of silica, adjust the polishing selectivity ratio of oxide to metal; auxiliary cleaning component can ensure the polished wafer Easy to clean and reduce the amount of particulate residue.

DRAWINGS

 Figure 1 shows the surface of a wafer without the addition of an auxiliary cleaning alkyl phosphate;

 Figure 2 is a wafer surface after adding a surfactant alkyl phosphate;

 Figure 3 shows the effect of the amount of water-soluble polymer added on the removal rate of copper; Figure 4 shows the sensitivity of Cu to the change of hydrogen peroxide concentration in the presence of water-soluble polymer.

Summary of the invention

The invention is further illustrated by the following specific embodiments. Chemical mechanical polishing conditions: Logteek PM50 polishing machine

 Downforce: 1.5psi

 Polishing head speed: 90 rpm

 Polishing plate speed: 70 rpm

 Polishing fluid flow rate: 100 ml / min

 Polishing time: 2 minutes

 Polished sheet: PETEOS, metal crucible, metallic copper, BD1, etc.

Table 1 Example 1-12 Implementation Silica polishing

 Abrasive combined corrosion inhibitor complexing agent oxidant cleaning aid PH example light accelerator

 Water soluble poly

 Azole corrosion inhibitor

 Compound

Reference

Polishing 3 liquid

 0.2% double

1 10% SiO ₂ 0.2% BTA 0.2% citric acid 3 oxygen water

 0.2% double

. 2 10% SiO ₂ 0.2% BTA 0.2% citric acid 0.]%TBAH 3 Oxygen water

 0.2% double

3 10% SiO ₂ 0.2% BTA 0.1% PAA 0.2% citric acid 0.1% TBAH 3 Oxygen water

 0.2% double 0.05% twelve

4 10% SiO ₂ 0.2% BTA 0.1% PAA 0.2% citric acid 0.]% TBAH 3 Oxygen phosphate phosphate ammonium salt

0.01% lemon 0.2% double 0.05% twelve 垸

5 30% SiO ₂ 0.5% BTA 0.01% PAA 0.1% TBAH 5

 Oxygen phosphate phosphate hinge salt

 0.05% decyl phosphorus

0.2% double

6 2%Si0 ₂ 0.01%BTA 0.5%PAA 0.5% citric acid 0.5% bismuth ester triethanol hinge 2

 ±卜

 0.2% double 0.05% hexadecane

1 10% SiO ₂ 0.2%% BTA 0.1% PAA 0.5% HEDP 0.1% TBAH 3 Oxygen water. Phosphate hinge salt

0.2% double 0.05% twelve

8 10% SiO ₂ 0.2% BTA 0.1% PAA 0.5% PBTCA 0.1 % TBAH 3 Oxygen phosphate phosphate potassium salt

 0.005% fourteen

0.2% double

 9 2%SiO 2 0.5% BTA 0.01% PAA 1% malonic acid 0.5% TMAH alkyl phosphate 2 oxygen water

 Potassium salt

 0.2% hexadecane

0.01% C2 0.2% Double

10 30% SiO2 0.01% BTA 0.5% PAA 0.01% TBAF Potassium Phosphate Potassium 5 Acid Oxygen Water: t Bu 0.]% phosphate

30% smoke 0.01% Ding 0.2% double

 11 0.1%BTA 0.1%PAA Ο.ΟΓ/oTPABr 5 Silica powder Acid Oxygen water

 Phosphate salt

0.1% propylene 0.05% phosphate

2% smoke

 12 0.2% BTA acid maleic acid 1% tartaric acid 0.1% TBAH 0.2% base 12 fluorenyl 2 silicon powder

 Copolymer phosphate hinge

Table 2 Comparison of the effects of the embodiments 1~12 with the prior art

 As can be seen from Table 2, the prior art polishing liquid causes a large range of particle residue and metal residue after polishing, and the present inventions 1 to 12 have excellent problems in the prior art. solve.

 The beneficial effects of the present invention are further explained below with reference to the accompanying drawings:

See Figure 1, for the addition of the auxiliary cleaning agent guanyl phosphate ester active agent, after polishing and cleaning, wafer table There were foggy deposits on the surface. After SEM analysis, no large particles remained. Referring to Figure 2, after the addition of decyl phosphate, the misty substance on the surface of the wafer disappeared, and no residual particulate matter was found, indicating that the anionic active agent alkyl phosphate salt can change the surface electrical properties of the particles, making the cleaning process more Easy to be cleaned 3⁄4J removed, improving wafer cleanliness.

 Referring to Figure 3, after the addition of PAA (polyacrylic acid), the removal rate of copper is suppressed to varying degrees, and the ability to correct the butterfly depression on the graphic wafer can be adjusted.

 Referring to Figure 4, in the presence of PAA (polyacrylic acid), the metal copper removal rate is more sensitive to the oxidant concentration, so that the adjustment of the process parameters can be used to adjust the thickness of the copper on-line. In summary, the invention adopts a composite anti-corrosion inhibitor to effectively protect the metal from corrosion during the polishing process, and can correct the surface defects of the front process to achieve the planarization effect, and the organic solvent is used to change the slurry and the polishing pad and the wafer. The adsorption behavior between the two to reduce the level of metal residues on the polishing pad, further improve the life of the polishing pad and increase productivity.

Claims

Rights request A polishing liquid for chemical mechanical polishing of a copper interconnect barrier layer, comprising: an abrasive particle, a metal chelating agent, a silica polishing accelerator, a combined metal corrosion inhibitor, and an auxiliary cleaning agent And an oxidizing agent.  The chemical mechanical polishing liquid according to claim 1, wherein the abrasive particles are silica sol and/or fumed silica aqueous dispersion.  The chemical mechanical polishing liquid according to claim 1, wherein the abrasive particles have a particle diameter of 20 to 250 nm.  The chemical mechanical polishing liquid according to claim 3, wherein the abrasive particles have a particle diameter of 30 to 150 nm.  The chemical mechanical polishing liquid according to claim 1, wherein the abrasive particles are contained in an amount of 2 to 30% by weight.  The chemical mechanical polishing liquid according to claim 5, wherein the abrasive particles are contained in an amount of 5 to 20% by weight.  The chemical mechanical polishing liquid according to claim 1, wherein the metal chelating agent is an organic carboxylic acid and/or an organic phosphine.  The chemical mechanical polishing liquid according to claim 1, wherein the metal chelating agent is selected from the group consisting of: hydroxyethylidene diphosphonic acid, 2-phosphonic acid butane-1, 2, 4-three One or more of a carboxylic acid, 2-hydroxyphosphonoacetic acid, oxalic acid, malonic acid, succinic acid, citric acid, and tartaric acid.  The chemical mechanical polishing liquid according to claim 1, wherein the metal chelating agent has a concentration of 0.01 to 1% by weight.  The chemical mechanical polishing liquid according to claim 9, wherein the metal chelating agent has a concentration of 0.1 to 0.5% by weight.  The chemical mechanical polishing liquid according to claim 1, wherein the oxidizing agent is a peroxide and/or a persulfide. The chemical mechanical polishing liquid according to claim 1, wherein the oxidizing agent The concentration is 0.01-lwt%.  The chemical mechanical polishing liquid according to claim 1, wherein the combined metal corrosion inhibitor comprises: an azole compound and a water-soluble polymer.  The chemical mechanical polishing liquid according to claim 13, wherein the azole compound is benzotriazole or a derivative thereof; and the water-soluble polymer is polyacrylic acid and a salt thereof or an acrylic copolymer. .  The chemical mechanical polishing liquid according to claim 13, wherein the concentration of the azole compound is from 0.01 to 0.5% by weight.  The chemical mechanical polishing liquid according to claim 13, wherein the water-soluble polymer has a concentration of 0.05 to 0.5% by weight.  The chemical mechanical polishing liquid according to claim 1, wherein the silica polishing accelerator is selected from the group consisting of tetra-sodium halide, tetraethylammonium halide, tetrapropylammonium halide, tetrabutyl. One or more of ammonium halide, tetramethylammonium hydroxide, tetraethylammonium hydroxide, tetrapropylammonium hydroxide and tetrabutylammonium hydroxide.  The chemical mechanical polishing liquid according to claim 17, wherein the silica polishing accelerator is one selected from the group consisting of tetrabutylammonium fluoride, tetrapropylammonium bromide and tetrabutylammonium hydroxide. Kind or more.  The chemical mechanical polishing liquid according to claim 1, wherein the silica polishing accelerator has a concentration of from 10 ppm by mass to 0.5% by mass.  The chemical mechanical polishing liquid according to claim 19, wherein the concentration of the silica polishing accelerator is from 10,000 ppm to 0.2% by mass.  The chemical mechanical polishing liquid according to claim 1, wherein the auxiliary cleaning agent is an anionic surfactant. The chemical mechanical polishing liquid according to claim 21, wherein the anionic surfactant is selected from the group consisting of alkyl phosphate diethanolamine salts, mercapto phosphate triethanolamine salts, and decyl dodecyl phosphate. Phosphate ammonium salt, potassium dodecyl phosphate, potassium tetradecyl phosphate and sixteen The chemical mechanical polishing liquid according to claim 1, wherein the auxiliary cleaning agent is contained in an amount of 0.005 to 0.2% by weight.  The chemical mechanical polishing liquid according to claim 23, wherein the auxiliary cleaning agent is contained in an amount of from 0.01 to 0.1% by weight.  The chemical mechanical polishing liquid according to claim 1, wherein the chemical mechanical polishing liquid has a pH of from 2 to 5.  The chemical mechanical polishing liquid according to claim 25, wherein the chemical mechanical polishing liquid has a pH of 2.5 to 3.5.