KR100623963B1 - Metal CMP Slurry And Metal Polishing Method Using Thereof - Google Patents

Abstract

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a CMP slurry composition for polishing metal wires containing a metal oxidant, wherein deionized water is used as a solvent, a metal oxide and an inorganic acid, an organic acid compound having two or more carboxyl groups, deionized water, a metal oxidant, an alkali compound, and a fatty acid. It relates to a metal wire polishing slurry composition comprising a.

The CMP slurry composition for polishing metal wires according to the present invention is a slurry composition that can be used immediately without additional process such as mixing an oxidant before use, and can have stable polishing performance even after long time standing. In addition, the pattern polishing characteristics such as oxide erosion and oxide loss are excellent, and defects in the semiconductor manufacturing process can be significantly reduced, thereby improving the yield of the semiconductor manufacturing process.

Slurries, metal oxidants, fatty acids, abrasives, CMP

Description

Slurry composition for metal wiring polishing and metal wiring polishing method using the same {Metal CMP Slurry And Metal Polishing Method Using Thereof}

The present invention relates to a slurry composition for polishing metal wires excellent in oxide erosion or oxide loss as well as a high removal rate and a low defect property, and a method for polishing metal wires using the same. will be.

Recently, due to high integration and multilayering of semiconductor technology, oxide erosion or oxide loss characteristics are highlighted in metal layer polishing CMP.

In general, the semiconductor CMP process is a polishing method in which a wafer surface is planarized using a polishing pad and a slurry during semiconductor manufacturing. The wafer surface is contacted on a polishing pad made of polyurethane and mixed with rotation and linear motion. An orbital motion or the like is performed, and mechanically and chemically polishing is performed by supplying a CMP slurry between the polishing pad and the wafer.

In this case, the slurry includes an abrasive to impart physical polishing properties and an etchant or oxidant to impart chemical polishing properties. This combination of mechanical and chemical properties provides a smooth surface by selectively polishing the protruding portions on the wafer surface. In addition, the CMP slurry may be divided into an insulating layer polishing slurry and a metal layer polishing CMP slurry depending on the polishing target. In addition, according to the semiconductor process, the insulating layer polishing slurry may be classified into an interlayer dielectric (ILD), an inter metal layer dielectric (IMD) process, and a shallow trench isolation (STI) process. It can be used in the formation of interconnects and tungsten contacts / via plugs of tungsten, aluminum or copper wiring or in a dual damascene process.

When the slurry is divided by the above criteria, the metal layer polishing CMP slurry is generally composed of an abrasive, an oxidizing agent, an oxidizing aid, a dispersant, a pH adjusting agent, other additives, and the like. Among the components, the abrasive is for polishing the mechanical properties, the oxidizing agent and the oxidizing aid are for promoting the oxidation of the metal layer to weaken the strength of the metal layer to promote polishing, the dispersant is to improve the dispersion stability of the slurry. In addition, the pH adjusting agent has a role of adjusting the pH range in which oxidation can occur well according to the properties of the metal layer to be polished.

For example, tungsten polishing slurries generally have an oxide film at a pH of 4 or less, and the tungsten slurry serves to maintain a pH of 4 or less. In addition, the alumina polishing slurry has a property of forming an oxide film at a pH of 4 to 10 and serves to maintain a pH of 4 to 10.

Finally, various additives are added to improve and supplement the physical and polishing properties of the slurry.

The most commonly used oxidant of CMP slurry for polishing metal layers is a peroxide compound, and hydrogen peroxide is most frequently used. However, since hydrogen peroxide needs to be mixed and used immediately before polishing, the mixing ratio should be checked each time before mixing, and there is a problem that a facility such as a tank for mixing is required in the actual production process.

Accordingly, the present invention has been made in order to solve the problems of the prior art, it is convenient in use by adding all the compounds needed for slurry production without storing the oxidizing agent, etc., the stability of the dispersion stability and polishing performance of The purpose is to provide an excellent slurry composition for polishing metal wires.

In order to achieve the above object, the present invention uses a deionized water as a solvent, and metal oxide polishing, characterized in that it comprises a metal oxide and inorganic acid, an organic acid compound having two or more carboxyl groups, deionized water, metal oxidizing agents, alkali compounds, and fatty acids It provides a slurry composition for.

Based on the total weight of the composition, 1 to 25% by weight when the metal oxide is silica (SiO₂), 0.5 to 10% by weight when alumina (Al₂O₃), ceria (CeO₂), or zirconia (ZrO₂), the inorganic acid is 0.1 to 5% by weight, the organic acid compound is 0.1 to 3% by weight, the fatty acid is 0.01 to 3% by weight, the alkali compound is 0.05 to 5% by weight, and the metal oxidizing agent comprises 0.1 to 10% by weight It is done.

The specific surface area of the metal oxide is characterized in that 150 to 400 m 2 / g.

The inorganic acid is characterized in that at least one selected from the group consisting of nitric acid (sulfuric acid), sulfuric acid (sulfuric acid), hydrochloric acid, phosphoric acid (phosphoric acid).

The organic acid compound is citric acid (citric acid), glutaric acid (glutaric acid), malic acid (maleic acid), maleic acid (maleic acid), oxalic acid (oxalic acid), phthalic acid (phthalic acid), succinic acid, tartaric acid (tartaric acid) is characterized in that at least one selected from the group consisting of.

The fatty acid is characterized in that one or more selected from the group consisting of polyglycerin Fatty Acid Ester (KM-70), sucrose fatty acid ester, polysorbate.

The metal oxidant is characterized in that at least one selected from the group consisting of iron nitrate, iron perchlorate, magnesium perchlorate.

The alkali compound is characterized in that at least one selected from the group consisting of potassium hydroxide (KOH), calcium hydroxide (CaOH), ammonium hydroxide (NH₄OH), tetramethylammonium hydroxide.

The present invention also provides a metal wire polishing method, wherein the slurry composition for polishing metal wire is used for polishing a polishing object composed of tungsten.

As the metal oxide, silica (SiO₂) or alumina (Al₂O₃), ceria (CeO₂), or zirconia (ZrO₂) may be used, and in the case of silica, it is preferable to include 1 to 25% by weight based on the total weight of the composition. . It is more preferable that it is 2-12 weight%. In addition, when the metal oxide is alumina (Al₂O₃), ceria (CeO₂), or zirconia (ZrO₂), it is preferable to include 0.5 to 10% by weight based on the total weight of the composition. It is more preferable that it is 1 to 6 weight%. If more is added, not only the defects of scratch and defect increase, but also the dispersion stability characteristics become weak. Dispersion stability is influenced by the degree of dispersion and pH, especially the content of metal oxides. In addition, when an amount smaller than the above range is added, it may not have a polishing rate required in the semiconductor process and thus may not be applicable.

The specific surface area of the metal oxide of the abrasive used in the present invention is preferably a metal oxide having a range of 150 m 2 / g to 400 m 2 / g. If the specific surface area value is smaller than the above value, the metal layer polishing rate is lowered and the insulating layer polishing rate is increased. In this case, the difference in polishing rate between the metal layer and the insulating layer is reduced, resulting in poor oxide erosion or oxide loss characteristics. In addition, when the specific surface area value is larger than the above value, it is difficult to disperse the metal oxide, which results in poor scratch characteristics and the like.

In addition, when a mixture of two or more kinds of metal oxides having different specific surface areas of the metal oxides in the above ranges may have a very high metal layer polishing rate. For example, when a slurry is prepared by mixing silica having a specific surface area of 200 m 2 / g and silica having 300 m 2 / g, the polishing rate may be 1.5 times higher than that of using a single specific surface area of silica. Therefore, in order to prepare a slurry having a high polishing rate, it is preferable to use two or more metal oxides having different specific surface areas.

In addition, the inorganic acid used in the present invention may use general inorganic acids such as nitric acid, sulfuric acid, hydrochloric acid, and phosphoric acid, and one or more of these may be selected and used. have. The inorganic acid serves to adjust the pH of the slurry, the pH of the tungsten polishing slurry is preferably 2 to 4, the pH of the aluminum and copper polishing slurry is preferably in the range of 3 to 5. If the pH is high or low outside the above range, the polishing rate is lowered, so that it is not applicable to the actual semiconductor process, or the degree of corrosion and dissolution becomes severe, which causes the semiconductor to greatly reduce the reliability.

In addition, the inorganic acid serves as an oxidizer to oxidize the metal layer. The metal layer oxidized by the oxidant forms an oxide film. The oxide film thus formed has a very weak strength. Therefore, in order to have a high polishing rate, the rapid formation of the oxide film and the continuous formation become important. Although the inorganic oxidizing agent added in the present invention is slightly different depending on the type, 0.1 to 5% by weight is added, and more preferably 0.5 to 2% by weight is added.

Next, the organic acid compound having two or more carboxyl groups may be citric acid, glutaric acid, malic acid, maleic acid, oxalic acid, phthalic acid, It is preferable to use at least one selected from the group consisting of succinic acid and tartaric acid. The addition amount is 0.1 to 3 weight%, more preferably 0.2 to 1 weight%.

The organic acid compound having two or more carboxyl groups can be expected to chelate (chelate) effect to assist in preventing the re-adsorption of the separated oxide film while chemically removing the metal oxide film generated during the metal layer polishing CMP process. Therefore, it is possible to have a stable removal rate of the metal layer. Therefore, in order to have a role of more effective organic acid, an organic acid having two or more carboxyl groups is preferable. In addition, if the addition amount is more than the pH of the slurry is too low, the polishing rate is lowered or the polishing rate uniformity may indicate a problem in the use of the slurry, if less than the above-mentioned addition amount is expected while adding the organic acid It is difficult to expect an increase in the oxide film removal efficiency.

Next, fatty acids play three roles in CMP slurries. First, fatty acids play a role in preventing the evaporation of the slurry and improving the stability and dispersion stability such as scratches and defects. The second is to react with the surface charge of the insulating layer to reduce the polishing rate of the insulating layer. The third helps to maintain the dispersed state of the dispersed metal oxide.

The fatty acid used in the slurry is preferably at least one selected from the group consisting of Polyglycerin Fatty Acid Ester (KM-70), sucrose fatty acid ester, and polysorbate. More preferably, it is preferable to add 0.1 to 2 weight%. When it is added in excess of the above range, the fatty acid reacts not only with the insulating layer but also with the surface of the metal layer, which adversely acts to widen the difference in polishing rates between the insulating layer and the metal layer. In addition, too much addition of water solubility causes problems in uniform mixing due to solubility with the slurry. In addition, when the fatty acid is added in less than the above range, it becomes difficult to achieve the purpose of reducing the polishing defects such as the scratches expected by adding the fatty acid.

Next, the metal oxidant oxidizes the metal layer surface to form an oxide film. The surface of the oxidized metal layer is much weaker than before the oxide film is formed, and thus the smooth polishing process is performed. Iron nitrate, iron perchlorate, magnesium perchlorate can be used as the metal oxidant. Such a metal oxidant can be stably maintained in a slurry, and thus has no advantage in that it does not need to be separately packaged and manufactured without UV or decomposition over time like conventional peroxide compounds.

The metal oxidant adds 0.1% to 10% by weight, more preferably 0.2% to 5% by weight. If less than this range is added, the oxidation effect of the metal oxidant is reduced and the polishing rate of the metal layer is low and cannot be used. There is no increase in the polishing rate when the excess amount is added outside the above range, and only the impurity content of the slurry is increased.

Next, the alkali compound added in the present invention may be potassium hydroxide (KOH), calcium hydroxide (CaOH), ammonium hydroxide (NH₄OH), tetramethylammonium hydroxide, and the like, together with the above-mentioned inorganic acid. It is used for the purpose of adjusting the pH of the slurry. Used together with the inorganic acid serves to stably adjust the pH of the slurry. PH characteristics of the slurry for each polishing object are the same as those mentioned above for the inorganic acid. Although there are some differences depending on the kind of alkali compound and the object of the metal layer to be polished, 0.05 to 5% by weight, more preferably 0.1 to 3% by weight is added.

Hereinafter, the present invention will be described in more detail with reference to specific examples. However, the following examples are merely for illustrative purposes and do not limit the scope of the present invention.

Example 1

(1) Preparation of Slurry Composition

Commercial fumed silica (specific surface area 300 m 2 / g) or ceria (specific surface area 200 m 2 / g) 0.8 kg, 50 kg, 100 kg, 300 kg, DI water 965.2 kg, 916 kg, 866 kg, 666 kg, nitric acid 2.0 kg, iron nitrate 20.0kg, malic acid 6.0kg, polyglycerol fatty acid ester 2.0kg, TMAH (tetramethylammonium hydroxide) 4.0kg was added and dispersed through a high pressure disperser to prepare a slurry, and then 1㎛ CMP depth filter (Depth filter) It was prepared by filtration.

   * Specific surface area is based on the value measured by BET measurement.

(2) Polishing evaluation

After polishing for 1 minute in the following conditions the results are shown in Table 1.

o Grinder model: UNIPLA211 (SEMICONTECH)

o Polishing condition:

Pad type: IC1400 / SubaIV Stacked (Rodel)

Platen Speed: 24rpm

-Spindle Speed: 80rpm

Wafer Pressure: 3psi

-Back Pressure: 0psi

-Temperature: 25 ℃

Slurry flow: 200 ml / min

o Polishing target:

The sample wafer is a W blanket wafer, and 1000-degree deposition of P-TEOS (poly-tetraethylorthosilicate) on a poly-Si substrate, followed by titanium nitride (TiN) and tungsten (W), respectively. It was produced by depositing 450 Å and 9,000 Å. The W pattern wafer was manufactured in the same way, and the pattern density was 90%.

Abrasive / DIW (Deionized Water) W grinding speed P-TEOS Polishing Speed μ-scratch (> 0.2 μm) Silica (0.8kg) / DIW (965.2kg) 2,250 Å / min 10 Å / min 10 ea Silica (50 kg) / DIW (916 kg) 3,720 Å / min 22 Å / min 12 ea Silica (100 kg) / DIW (866 kg) 4,230 Hz / min 25 Å / min 11 ea Silica (300kg) / DIW (666kg) 4,400 Å / min 38 Å / min 32 ea Ceria (0.8kg) / DIW (965.2kg) 2,860 Å / min 12 Å / min 9 ea Ceria (50 kg) / DIW (916 kg) 3,940 Å / min 20 Å / min 15 ea Ceria (100 kg) / DIW (866 kg) 4,570 Å / min 28 Å / min 17 ea Ceria (300kg) / DIW (666kg) 4,610 Å / min 37 Å / min 42 ea Alumina (100kg) / DIW (666kg) 4,610 Å / min 37 Å / min 42 ea

(P-TEOS is poly-tetraethylorthosilicate)

As the content of the abrasive increases, the polishing rate increases, but the µ-scratch increases, which makes the semiconductor chip less reliable and cannot be used. Therefore, an appropriate amount of abrasive content must be added.

Example 2

Commercial fumed silica (fumed silica, specific surface area 300㎡ / g and 200㎡ / g ratio 1: 1, 2: 1, 1: 2, 1: 0, 0: 1) 50kg, deionized water 916kg, nitric acid 2.0kg , 6.0 kg of malic acid, 2.0 kg of polyglycerin fatty acid ester, 4.0 kg of tetramethylammonium hydroxide (TMAH), and 20.0 kg of iron nitrate were added and dispersed through a high pressure disperser to prepare a slurry, followed by 1 μm depth for CMP. It was prepared by filtration using a filter (Depth filter).

Abrasive Mixing Ratio W grinding speed P-TEOS Polishing Speed Oxide erosion 200㎡ / g 300㎡ / g One One 5,870 Å / min 24 Å / min 220Å One 2 5,720 Å / min 26 Å / min 230 yen 2 One 5,920 Å / min 25 Å / min 230 yen One 0 3,130 Å / min 25 Å / min 360Å 0 One 3,720 Å / min 22 Å / min 320Å

When the abrasive is mixed, the W polishing rate is greatly increased, but the P-TEOS polishing rate is not greatly increased, so that the difference in polishing rate between the insulating layer and the metal layer is increased, thereby reducing the amount of oxide erosion, thereby increasing the reliability of the semiconductor chip.

Example 3

50 kg of fumed silica (specific surface area 300㎡ / g), deionized water 916kg, nitric acid 2.0kg, malic acid 8.0kg, polyglycerin fatty acid ester or sucrose fatty acid ester 0.05g, 5.0g, 25g, tetramethylammonium hydroxide 4.0 kg of side (tetramethylammonium hydroxide, TMAH) and 20.0 kg of iron nitrate were added and dispersed through a high pressure disperser to prepare a slurry, followed by filtration using a 1 μm CMP depth filter. Polishing evaluations were evaluated immediately after preparation and 90 days after preparation.

fatty acid W grinding speed P-TEOS Polishing Speed μ-scratch (> 0.2 μm) 0 days 90 days Polyglycerin Fatty Acid Ester (0.5kg) 3,250 Å / min 3,320 Å / min 40 Å / min 38ea Polyglycerin Fatty Acid Ester (5.0kg) 3,760 Å / min 3,560 Å / min 20 Å / min 10ea Polyglycerin Fatty Acid Ester (25kg) 3,390 Å / min 3,190 Å / min 15 Å / min 12ea Sucrose Fatty Acid Esters (0.5kg) 3,170 Å / min 3,650 Å / min 50 Å / min 44ea Sucrose Fatty Acid Esters (5.0kg) 3,420 Å / min 3,550 Å / min 20 Å / min 11ea Sucrose fatty acid ester (25 kg) 3,050 Å / min 3,280 Å / min 20 Å / min 10ea

From the results of the experiment, the addition of an appropriate amount of fatty acids has advantages such as maintaining the uniform polishing rate, improving the polishing rate selectivity due to the lowering of the insulating layer, and reducing the μ-scratch even when the slurry is stored for a long time.

Example 4

Commercially available fumed silica (specific surface area 300㎡ / g) 50kg, deionized water 916kg, nitric acid 2.0kg, malic acid 0.5kg, 7.0kg, 15kg, or maleic acid 0.6kg, 5.0kg, 20kg, polyglycerin fatty acid ester 2.0 kg, tetramethylammonium hydroxide (TMAH) 4.0kg, iron nitrate 20.0kg was added and dispersed through a high pressure disperser to prepare a slurry, and then filtered using a 1㎛ CMP depth filter (Depth filter) Prepared.

Organic acid compounds W grinding speed W polishing uniformity Malic acid (0.5kg) 2,480 Å / min 3.8% Malic acid (7.0kg) 3,620 Å / min 2.2% Malic acid (15 kg) 3,060 Å / min 6.5% Maleic Acid (0.6kg) 3,100 Å / min 2.3% Maleic Acid (5.0kg) 3,850 Å / min 1.2% Maleic Acid (20kg) 2,980 Å / min 7.2%

  * Non-Uniformity

In the above test results, when an appropriate amount of organic acid is added above or below W polishing uniformity is worse, the polishing process cannot proceed. In addition, the W polishing rate is lowered, so an appropriate amount of organic acid should be added.

Example 5

50 kg of fumed silica (specific surface area 300㎡ / g), deionized water 916kg, nitric acid 2.0kg, malic acid 6.0kg, polyglycerin fatty acid ester 2.0kg, tetramethylammonium hydroxide (TMAH) 0.1kg , 2.0kg, 40.0kg or KOH 2.0kg, 20.0kg iron nitrate was added and dispersed through a high pressure disperser to prepare a slurry, and then filtered by using a depth filter for 1㎛ CMP (Depth filter).

Alkaline compounds W grinding speed P-TEOS Polishing Speed TMAH (0.1kg) 1,720 Å / min 20 Å / min TMAH (2.0kg) 3,670 Å / min 25 Å / min TMAH (40kg) 2,270 Å / min 45 Å / min KOH (2.0kg) 3,760 Å / min 15 Å / min

If the alkali compound is added in less than the appropriate range from the above embodiment, the W polishing rate is lowered, and when a large amount of the alkali compound is added, the polishing rate of W is increased, but the polishing rate of P-TEOS is increased, so that the selectivity of the polishing rate relative to the insulating layer is lowered. It can increase.

Example 6

50 kg of fumed silica (specific surface area 300㎡ / g), deionized water 916kg, nitric acid 2.0kg, malic acid 6.0kg, polyglycerin fatty acid ester 2.0kg, tetramethylammonium hydroxide (TMAH) 4.0kg , 0.5kg iron nitrate, 15.0kg, 60kg or 20kg iron perchlorate, or 20kg magnesium perchlorate was added and dispersed through a high pressure disperser to prepare a slurry, and then filtered using a 1㎛ depth filter for CMP Prepared.

Metal oxidant W grinding speed Oxide erosion Oxide loss Iron Nitrate (0.5kg) 2,640 Hz / min 460 yen 20Å Iron Nitrate (15kg) 3,540 Å / min 320Å 50Å Iron Nitrate (60Kg) 3,620 Å / min 480 yen 150Å Iron overchloride (20Kg) 3,320 Å / min 360Å 50Å Magnesium Perchlorate (20Kg) 3,150 Å / min 330 yen 60Å

From the above embodiment, the metal oxidant has a disadvantage in that the W polishing rate is lowered if it is added in less than an appropriate range, and the oxide loss is reduced. Therefore, the W polishing rate, oxide erosion, and oxide loss required in the semiconductor process can be obtained when an appropriate amount is added. In addition, the reliability of the semiconductor chip due to metal contamination when the addition is excessive.

Example 7

50 kg of fumed silica (specific surface area 300㎡ / g), deionized water 916kg, 0.5kg nitric acid, 2.0kg, 5.0kg, malic acid 6.0kg, polyglycerin fatty acid ester 2.0kg, tetramethylammonium hydroxide (tetramethylammonium) 4.0 kg of hydroxide, TMAH) and 20.0 kg of iron nitrate were added and dispersed through a high pressure disperser to prepare a slurry, and then filtered by using a 1 μm depth filter for CMP.

Inorganic acids W grinding speed P-TEOS Polishing Speed Nitric acid (0.5kg) 2,260 Å / min 25 Å / min Nitric acid (2.0kg) 3,750 Å / min 30 Å / min Nitric acid (5.0kg) 2,400 Å / min 25 Å / min

 When the inorganic acid is added to less or more than the appropriate range from the above embodiment, the polishing rate of W is lowered, and in particular, when the excess amount is added, the polishing rate of the insulating layer P-TEOS is increased, thereby lowering the selectivity. This makes it impossible to apply to fine pattern wafers.

The present invention improves oxide erosion and oxide loss by increasing the difference with the polishing rate of the metal layer due to the decrease in polishing rate of the insulating layer when fatty acid is added, and W polishing slurry that reduces polishing defects such as μ-scratch even during long-term storage. The composition of.

Claims (6)

A slurry composition for polishing metal wires, comprising deionized water as a solvent, a metal oxide and an inorganic acid, an organic acid compound having two or more carboxyl groups, deionized water, a metal oxidant, an alkali compound, and a fatty acid. In claim 1, Based on the total weight of the composition, 1 to 25% by weight when the metal oxide is silica (SiO₂), 0.5 to 10% by weight when alumina (Al₂O₃), ceria (CeO₂), or zirconia (ZrO₂), the inorganic acid is 0.1 to 5% by weight, the organic acid compound is 0.1 to 3% by weight, the fatty acid is 0.01 to 3% by weight, the alkali compound is 0.05 to 5% by weight, and the metal oxidizing agent comprises 0.1 to 10% by weight A slurry composition for polishing metal wires. In claim 1, The specific surface area of the metal oxide is a metal wire polishing slurry composition, characterized in that 150 to 400 m 2 / g. In claim 1, The metal oxide is a polishing slurry composition, characterized in that for use by mixing two or more metal oxides having different specific surface area. In claim 1, The inorganic acid is at least one selected from the group consisting of nitric acid, sulfuric acid, hydrochloric acid, and phosphoric acid, and the organic acid compound is citric acid or glutaric acid. one or more selected from the group consisting of glutaric acid, malic acid, maleic acid, maleic acid, oxalic acid, phthalic acid, succinic acid, tartaric acid, The fatty acid is at least one selected from the group consisting of Polyglycerin Fatty Acid Ester (KM-70), sucrose fatty acid ester, and polysorbate, and the metal oxidizing agent is iron nitrate or iron perchlorate. perchlorate) and one or more selected from the group consisting of magnesium perchlorate, wherein the alkali compounds are potassium hydroxide (KOH), calcium hydroxide (CaOH), A slurry composition for polishing metal wires, characterized in that at least one selected from the group consisting of ammonium sulfide (NH₄OH), tetramethylammonium hydroxide. The metal wiring polishing method according to any one of claims 1 to 5, wherein the slurry composition for polishing metal wirings is used for polishing a polishing object composed of tungsten.