WO2012019425A1

WO2012019425A1 - Chemo-mechanical polishing liquid

Info

Publication number: WO2012019425A1
Application number: PCT/CN2011/001214
Authority: WO
Inventors: 王晨; 何华锋
Original assignee: 安集微电子（上海）有限公司
Priority date: 2010-08-11
Filing date: 2011-07-25
Publication date: 2012-02-16
Also published as: CN102373012A; CN102373012B

Abstract

Disclosed is a chemo-mechanical polishing liquid comprising water, an abrasive filler, a compound capable of etching tungsten, a tungsten-etching inhibitor, and a regulator for a substrate profile, wherein the tungsten-etching inhibitor is an amide comprising a double bond. The said polishing liquid possesses a very high tungsten polishing rate and, at the same time, a very low tungsten static etch rate.

Description

Chemical mechanical polishing liquid

The present invention relates to a chemical mechanical polishing liquid, and in particular to a chemical mechanical polishing liquid for tungsten. technical background

With the continuous development of semiconductor technology and the increasing number of interconnect layers of large-scale integrated circuits, the planarization technology of conductive layers and dielectric layers has become particularly critical. In the 1980s, the chemical mechanical polishing (CMP) technology pioneered by IBM was considered the most effective method for global planarization.

Chemical mechanical polishing (CMP) is a combination of chemical action, mechanical action, and both. It usually consists of a polishing table with a polishing pad and a polishing head for carrying the chip. The polishing head holds the chip and then presses the front side of the chip against the polishing pad. When chemical mechanical polishing is performed, the polishing head moves linearly on the polishing pad or in the same direction of motion as the polishing table. At the same time, the slurry containing the abrasive is dropped onto the polishing pad and laid flat on the polishing pad by centrifugation. The surface of the chip achieves global planarization under both mechanical and chemical effects.

The main mechanism of chemical mechanical polishing (CMP) of metal layers is considered as follows: The oxidant first oxidizes the surface of the metal into a film, and the abrasive film represented by silica and alumina mechanically removes the oxide film to produce a new metal surface. Continued to be oxidized, these two effects work together.

Metal tungsten, one of the chemical mechanical polishing (CMP) targets, has high electron current resistance at high current density and can form a good ohmic contact with silicon, so it can be used as a filler metal for contact windows and via holes. Diffusion barrier. There are several methods for chemical mechanical polishing (CMP) of tungsten:

In 1991, FB Kaufman et al. reported the use of potassium ferricyanide for tungsten chemical mechanical polishing ("Chemical Mechanical Polishing for Fabricating Patterned W Metal Features as Chip Interconnects", Journal of the Electro Chemical Society, Vol. 138, No. 11 , November 1991).

U.S. Patent 5,340,370 discloses a formulation for tungsten chemical mechanical polishing (CMP) containing 0.1 M potassium ferricyanide, 5% silica, and acetate as a pH buffer. Since potassium ferricyanide decomposes highly toxic hydrogen cyanide under ultraviolet light or sunlight, and in an acidic medium, it is widely used.

U.S. Patent No. 5,527,423, U.S. Patent No. 6,008,119, U.S. Patent No. 6,284,151 discloses the like Fe (N0 _{₃₎ 3,} aluminum system, a method for tungsten-mechanical polishing (CMP) of. The polishing system has an advantage in terms of static etch rate, but due to the use of alumina as an abrasive, there are significant deficiencies in product defects. At the same time, the high concentration of ferric nitrate makes the pH of the polishing liquid strongly acidic, which seriously corrodes the equipment, and at the same time, generates rust and contaminates the polishing pad. In addition, high concentrations of iron ions act as mobile metal ions, which seriously reduce the reliability of semiconductor components.

U.S. Patent No. 5,225, 034, U. However, in this type of method, the amount of silver nitrate is large (greater than 2%), resulting in excessive polishing solution cost, unstable abrasive, easy precipitation, and rapid decomposition of hydrogen peroxide.

U.S. Patent 5,958,288 discloses the use of ferric nitrate as a catalyst and hydrogen peroxide as an oxidant for tungsten chemical mechanical polishing. It should be noted that: In this patent, a number of transitions are mentioned. The metal element, which was confirmed to be significantly effective by experiments, was only iron. Therefore, the actual implementation effect and scope of the invention are limited. Although the method greatly reduces the amount of ferric nitrate, since the iron ions still exist and the Fenton reaction occurs with the hydrogen peroxide, the hydrogen peroxide rapidly and violently decomposes and fails, so the polishing solution has a problem of poor stability.

U.S. Patent No. 5,980,775 and U.S. Patent No. 6,068,787, each of which is incorporated herein by reference to U.S. Patent No. 5,958, 288, incorporates an organic acid as a stabilizer to improve the rate of decomposition of hydrogen peroxide. However, the decomposition rate is still high, and the hydrogen peroxide concentration is usually reduced by more than 10% in two weeks, causing the polishing rate to decrease and the polishing liquid to gradually decompose and fail. The static corrosion rate of tungsten in the system of iron and hydrogen peroxide is very fast, which directly affects the yield of production. Therefore, it is necessary to further add a static corrosion inhibitor of tungsten.

CN98809580.7 The tungsten corrosion inhibitor used in the hydrogen peroxide addition system is:

2,3,5-trimethylpyrazine, porphyrin, pyridazine, pyrazine; reduced glutathione, thiophene, sulfhydryl N-oxypyridine, thiamine hydrochloride, tetraethyl disulfide tetradecyl Lamb; isostearyl ethyl imino gun, cetyltrimethylammonium hydroxide, 2-heptadecyl-4-ethyl-2-oxazoline-4-methanol, trisyl chloride Methylammonium, 4,4-dimethyloxazoline, tetrabutylammonium hydroxide, dodecylamine, tetramethylammonium hydroxide and combinations thereof; glycine, aminopropylsilanol, aminopropyl a siloxane, or a mixture of aminopropylsilanol and aminopropyl siloxane.

CN200610077360.7 The tungsten corrosion inhibitor used in the hydrogen peroxide addition system is: a nitrogen-containing heterocycle, an alkylammonium-forming compound, an aminoalkyl group, an amino acid or a combination thereof; a nitrogen-containing functional heterocycle, a sulfide , alkyl ammonium ion; 2-ethyl-3, 5-dimethylpyrazine, 2-acetylpyrrole, histidine and combinations thereof; 2-mercaptobenzimidazole, cystine amine, and mixtures thereof a compound that forms an alkylammonium ion; a naturally occurring amino acid, a synthetic amino acid, and mixtures thereof.

Chemical mechanical polishing liquid containing silver ion, sulfate ion, oxidant, tungsten corrosion inhibitor There is a high tungsten polishing speed, but on the entire surface of the silicon wafer, usually the edge speed of the silicon wafer is faster. The polishing speed is slower toward the center of the silicon wafer, and the profile of the silicon wafer is "V" shaped. On the contrary, the chemical mechanical polishing liquid containing iron and hydrogen peroxide goes to the center of the silicon wafer, and the polishing speed is faster, and the profile view of the silicon wafer is "Λ" shape. This results in uneven polishing speed on the silicon wafer. In general, it is desirable that the ideal profile is "one-by-one," so that the overall wafer is polished at a uniform rate, which is advantageous for improving the yield of the production. The present invention and the above five US patents: 5225034, 5354490 The main differences between 5980775, 6068787 and 5958288 are: 1) they do not use acrylamide; 2) they are not found, nor can they be inferred: the combination of hydrogen peroxide, silver ion and sulfate has an effect on improving the polishing effect of tungsten. The effect of this combination on increasing the polishing speed of tungsten is unexpected to those skilled in the art.

The main difference between the present invention and the above-mentioned patents CN98809580.7, CN200610077360.7 is: 1) The invention uses a double bond-containing amide (acrylamide) as a tungsten corrosion inhibitor, acrylamide is an amide substance, and contains a double The amide of the bond is structurally different from the two patents mentioned above. 2) The system of the present invention is a system of hydrogen peroxide plus silver ions. The above two patents are systems containing hydrogen peroxide plus iron ions, which differ from the above two patents.

Summary of invention

The technical problem solved by the invention is to provide a new polishing liquid, improve the chemical mechanical polishing speed of tungsten, improve the uniformity of the polishing speed on the whole silicon wafer, and realize an optimized profile. The chemical mechanical polishing liquid of the present invention comprises: water, an abrasive, a compound capable of eroding tungsten, a tungsten corrosion inhibitor, and a substrate profile modifier, wherein the tungsten corrosion inhibitor is a double bond-containing Amide. Preferably, the substrate is a silicon wafer.

In the present invention, the tungsten corrosion inhibitor is acrylamide in an amount of 0.01% to 0.5% by mass. In the present invention, the compound capable of eroding tungsten contains one or more oxidizing agents. The oxidizing agent is a peroxide, preferably hydrogen peroxide. The hydrogen peroxide content is 0.1 to 5% by mass, preferably 1 to 2% by mass.

In the present invention, the compound capable of eroding tungsten further contains one or more additives which can significantly increase the polishing speed of tungsten, and the additive contains silver ions and sulfate ions. The silver ions are derived from a silver salt, preferably from one or more of silver fluoride, silver perchlorate, silver sulfate, and/or silver nitrate. The silver salt is 0.05% by weight to 0.3% by weight.

In the present invention, the sulfate ion is derived from a sulfate, preferably a non-metallic sulfate, and the non-metal sulfate is preferably ammonium sulfate.

In the present invention, silver sulfate itself can provide both silver ions and sulfate ions, but there is a technical limitation in the single use of silver sulfate: the molar ratio of silver ions to sulfate ions is fixed, but actually, this The ratio needs to be adjustable. For example, the amount of sulfate is required to be larger than the amount of silver ions. These excess sulfates can be provided by other sulfates, such as ammonium sulfate and potassium sulfate. In the present invention, the substrate profile modifier is a transition metal salt. The addition of a small amount of transition metal salt can significantly improve the uniformity of polishing speed and improve the profile of substrates such as silicon wafers.

(profile). The substrate profile modifier is typically selected from the group consisting of iron salts. The iron salt is preferably iron nitrate. In the polishing solution, the concentration of ferric nitrate is calculated as iron: l~15 ppm.

The chemical mechanical polishing liquid of the present invention may further contain an organic acid stabilizer. Its use is mainly used to stabilize silver ions and prevent or slow the discoloration of silver ions under strong light conditions. The chemical mechanical polishing liquid of the present invention may further contain a pH adjuster. The chemical mechanical polishing liquid of the present invention has a pH of 0.5 to 5. The positive progress of the present invention is: The present invention provides a new polishing liquid for chemical mechanical polishing, which significantly improves the polishing speed of tungsten, reduces the static etch rate of tungsten, and improves the whole silicon. The uniformity of polishing speed on the wafer improves the profile of the wafer, which is beneficial to improve the yield of production. DRAWINGS

Figure 1 is a graph of the tungsten removal rate profile for Comparative Example 17 and Example 6.

Summary of the invention

Preparation Examples Table 1 shows the formulations of the chemical mechanical polishing liquids of the present invention in Examples 1 to 11 and Comparative Examples 1 to 17, according to the components listed in Table 1 and their contents, uniformly mixed in deionized water, using pH. A chemical mechanical polishing solution can be prepared by adjusting the pH to the desired pH. Table 1 Formulations of the chemical mechanical polishing liquids of the present invention Examples 1 to 11 and Comparative Examples 1 to 17

Organic acid transition gold

Oxidation

Abrasive wt% component 1 wt component 2 wt wt% propylene PH

Amide (wt%) (wt%)

(wt%)

Dioxygen

Comparative Example 1 Silica Sol 1 2 2.5

Water

Dioxygen

Comparative Example 2 Silica Sol 1 Silver nitrate 0.2 2 2.5

Water

Sulfuric acid

Comparative Example 3 Silica Sol 1 Silver nitrate 0.2 0.01 2 2.5

Manganese water

Sulfuric acid

Comparative Example 4 Silica Sol 1 Silver nitrate 0.2 0.02 2 2.5

Manganese water

Sulfuric acid

Comparative Example 5 Silica Sol 1 Silver nitrate 0.2 0.1 2 2.5

Manganese water

Sulfuric acid

Comparative Example 6 Silica Sol 1 Silver nitrate 0.2 0.1 2 2.5

Ammonium water

Sulfuric acid

Comparative Example 7 Silica Sol 1 Silver nitrate 0.2 0.5 2 2.5

Potassium water

Sulfuric acid

Comparative Example 8 Silica Sol 1 Silver nitrate 0.2 0.5 2 2.5

Manganese water

Dioxygen

Comparative Example 9 Silica Sol 1 Silver Sulfate 0.2 2 2.5

Water

Sulfuric acid

Comparative Example 10 Silica Sol 1 Silver nitrate 0.2 0.01 2 0.07 2.5

Manganese water

Sulfuric acid

Comparative Example 11 Silica Sol 1 Silver nitrate 0.2 0.02 2 0.01 2.5

Manganese water

Sulfuric acid

Comparative Example 12 Silica Sol 1 Silver nitrate 0.2 0.1 2 0.5 2.5

Manganese water

Sulfuric acid

Comparative Example 13 Silica Sol 1 Silver nitrate 0.2 0.1 2 0.1 2.5

Ammonium water

Sulfuric acid

Comparative Example 14 Silica Sol 1 Silver nitrate 0.2 0.5 2 0.2 2.5

Potassium water Dioxygen sulfate

Comparative Example 15 Silica Sol 1 Silver sulphate 0.2 0.5 2 0.06 2.5

Manganese water

Dioxygen

Comparative Example 16 Silica Sol 1 Silver Sulfate 0.2 2 0.4 2.5

Water

Sulfuric acid

Comparative Example 17 Silica Sol 0.5 Silver nitrate 0.2 0.1 2 0.1 3

Ammonium water

Gas phase dioxane

Example 1 0.1 Succinic acid

Silver sulfate 0.05 0.1 0.01 0.5 Silicon water Water 1:00 PM 5 ppm Gas phase dioxygen sulfate Dioxygen Fe citric acid Example 2 0.1 Silver nitrate 0.1 0.005 3 0.1 5

Silicon, potassium, water, 2:00 PM, 10 ppm, gas phase, dioxygen sulfate, dioxygen, Fe

Example 3 2 Succinic acid

Silver nitrate 0.15 0.1 4 0.1 2 Silicon silicate Ammonium water 8 ppm 5 ppm

Dioxygen Fe 10

Example 4 Succinic acid

Alumina 10 Silver sulfate 0.2 1 0.1 3

Water pm 5 ppm sulfuric acid dioxygen Fe

Example 5 Alumina 6 0.1 Succinic acid

Silver nitrate 0.3 0.5 2 0.5

Zinc water 5 ppm 50 sulfuric acid dioxygen Fe 10

Example 6 0.5 2 0.1 2 0.1 malonic acid

Silica sol silver nitrate 0. 3

Ammonium water pm 80 ppm

Dioxygen Femalonic acid Example 7 Cerium oxide 2 Silver sulfate 0.2 2 0.1 100 4

Water 5 ppm

PPm sulfuric acid Dioxygen Fe succinic acid Example 8 Cerium oxide 2 Silver nitrate 0.2 0.3 5 0.3 4

Potassium water 5 ppm 50 ppm sulfuric acid dioxygen Fe

Example 9 0.5 5 citric acid

Cerium oxide 2 silver nitrate 0.3 0.5 4

Ammonium water 3 ppm 50 ppm sulfuric acid dioxygen Fe 15

Example 10 2 2 0.1 citric acid

Silica sol 1 silver fluoride 0.2 0. 1.9

Ammonium water pm 50 ppm perchloric acid sulfuric acid dioxygen Fe

Silica sol 1 0.2 0.2 2 malonic acid Example 11 0.1 1.9

Silver ammonium water 5 ppm 50 ppm

Effect embodiment 1

Polishing conditions: Polishing machine is Logitech (UK) 1PM52 type, polytex polishing pad, 4cm X 4cm square wafer (Wafer), grinding pressure 4psi, grinding table rotation speed 70rev/min, grinding head rotation speed 150rev/min, polishing The droplet acceleration is 100 ml/min.

Table 2 Comparative Example for Tungsten Polishing 1~16

Tungsten polishing rate (A/min) Tungsten static corrosion rate (A/min) Comparative example 1 200

Comparative example 2 353 Comparative example 3 821 83

Comparative example 4 1465 78

Comparative example 5 2238 91

Comparative example 6 2500 72

Comparative example 7 2285 70

Comparative example 8 2485 81

Comparative example 9 2310 80

Comparative example 10 810 2

Comparative example 11 1450 10

Comparative example 12 2100 0

Comparative example 13 2430 1

Comparative example 14 2170 1

Comparative example 15 2301 2

Comparative example 16 2010 0

Comparative Example 1 shows that the polishing rate of tungsten is very low only in the presence of hydrogen peroxide.

Comparative Example 2 shows that: in combination with hydrogen peroxide and silver nitrate, the polishing rate of tungsten is very low.

Comparative examples 3 to 9 show that the combination of silver ions, sulfate groups and hydrogen peroxide in the presence of sulfate can significantly increase the polishing rate of tungsten.

Comparative Examples 10 - 16 show that the addition of acrylamide can significantly suppress the static corrosion rate of tungsten while still maintaining a high polishing rate of tungsten. Effect Example 2

Polishing conditions are: 8-inch industrial machine, 200mm wafer, pressure 3.8 psi. IC1000 polishing Pad.

As shown in Fig. 1, the polishing solution containing silver ion, sulfate, hydrogen peroxide, and erosion inhibitor has a high tungsten polishing speed, but the profile of the silicon wafer is slow in the middle, and the polishing uniformity needs to be improved. Example 6 Under the same conditions, the addition of a trace amount of a metal salt can significantly improve the polishing uniformity of tungsten, improve the profile, and improve the yield of the product.

Claims

Rights request

A chemical mechanical polishing liquid comprising: water, an abrasive, a compound capable of etching tungsten, a tungsten corrosion inhibitor, and a substrate profile modifier, wherein the tungsten corrosion inhibitor is an amide containing a double bond .

The chemical mechanical polishing liquid according to claim 1, wherein the tungsten etching inhibitor is acrylamide.

The chemical mechanical polishing liquid according to claim 1, wherein the tungsten etching inhibitor is contained in an amount of 0.01% to 0.5% by mass.

4. The chemical mechanical polishing liquid according to claim 1, wherein the tungsten etchable compound comprises one or more oxidizing agents.

The chemical mechanical polishing liquid according to claim 4, wherein the oxidizing agent is a peroxide.

The chemical mechanical polishing liquid according to claim 5, wherein the peroxide is hydrogen peroxide.

The chemical mechanical polishing liquid according to claim 6, wherein the hydrogen peroxide content is 0.1 to 5% by mass.

8. The chemical mechanical polishing fluid according to claim 4, wherein the tungsten etchable compound further comprises one or more additives.

9. The chemical mechanical polishing liquid according to claim 8, wherein the additive comprises silver ions and sulfate ions.

10. The chemical mechanical polishing liquid according to claim 9, wherein the silver ions are derived from a silver salt.

The chemical mechanical polishing liquid according to claim 10, wherein the silver ion is derived from one or more of silver fluoride, silver perchlorate, silver sulfate, and/or silver nitrate.

The chemical mechanical polishing liquid according to claim 10, wherein the silver salt is 0.05% by weight to 0.3% by weight.

The chemical mechanical polishing liquid according to claim 9, wherein the sulfate ion is derived from a sulfate.

The chemical mechanical polishing liquid according to claim 13, wherein the sulfate ion is derived from a non-metal sulfate.

The chemical mechanical polishing liquid according to claim 14, wherein the non-metal sulfate is ammonium sulfate.

The chemical mechanical polishing liquid according to claim 1, wherein the substrate profile modifier is a transition metal salt.

The chemical mechanical polishing liquid according to claim 16, wherein the transition metal salt is an iron salt.

The chemical mechanical polishing liquid according to claim 17, wherein the iron salt is iron nitrate.

The chemical mechanical polishing liquid according to claim 18, wherein the iron nitrate concentration is calculated as iron: l ~ 15 ppm.

20. The chemical mechanical polishing liquid according to claim 1, wherein the chemical mechanical polishing liquid further comprises an organic acid.

The chemical mechanical polishing liquid according to claim 1, wherein the chemical mechanical polishing liquid has a pH of 0.5 to 5.