KR100425261B1 - High Purity Slurry for Polishing Metal Layers of Semiconductor Devices - Google Patents

Abstract

The present invention relates to a slurry for polishing a metal layer of a semiconductor device, and more particularly, to a high purity slurry for polishing a metal layer of a semiconductor device including a metal oxide fine powder, manganese nitrate, hydrogen peroxide, polyacrylic acid, and deionized water. By using the polishing slurry of the CMP process while maintaining a high polishing rate to prevent defects due to metal or metal ions, it is possible to long-term storage of the slurry.

Description

High Purity Slurry for Polishing Metal Layers of Semiconductor Devices

The present invention relates to a slurry for polishing a metal layer of a semiconductor device, and more particularly to a high purity slurry for polishing a metal layer of a semiconductor device including a metal oxide fine powder, manganese nitrate, hydrogen peroxide, polyacrylic acid, and deionized water.

Chemical Mechanical Polishing (called "CMP") is a process in which semiconductors are subjected to orbital motions in which rotating and linear motions are mixed in contact with a polishing pad after adding a slurry containing an abrasive to the surface of a semiconductor wafer. To planarize the wafer surface.

Polishing slurries (hereinafter referred to as "CMP slurries") used in the CMP process are generally water-soluble suspensions and are composed of abrasives such as fine silica or alumina powders, oxidizing agents, pH adjusters, stabilizers and the like. The basic mechanism of CMP with the metal layer to be polished is an iterative and continuous reaction of oxidizing the metal layer on the wafer surface with an oxidant in the CMP slurry and then removing the oxide. That is, CMP slurries achieve better and optimized planarization by selectively etching exposed portions of the wafer surface through physical and chemical action.

The composition of the CMP slurry is an important factor in determining the efficiency of the CMP process, and its performance is determined by the role of the oxidizing agent, abrasive, and other additives contained in the slurry. CMP slurries should be chosen to meet the polishing rates required to polish metal layers while minimizing corrosion, erosion, scratches and contamination of the surface to be polished. In addition, the CMP slurry should be capable of selective polishing rate control for different abrasive layers such as titanium nitride or titanium.

As an example of a commercially available CMP slurry, US Pat. No. 5,244,534 discloses that slurry added with alumina and hydrogen peroxide and potassium or ammonium hydroxide is effective for polishing between tungsten and the insulating layer. In addition, U. S. Patent No. 5,209, 816 discloses CMP slurries containing perchloric acid, hydrogen peroxide, abrasives and the like.

However, most conventional CMP slurries contain metal ions because they use metal-based oxidants. If these metal ions remain on the wafer surface, not only will the electrical performance of the gate or contact within the wafer change, but also the performance of the dielectric layer. Such a change causes the long term reliability of the integrated circuit. Therefore, a slurry that minimizes metal ion contamination of the wafer should be used. However, the nonmetallic oxidants have some problems due to the low polishing rate during tungsten polishing. If the tungsten polishing rate is slow, the polishing time may be long, and thus, the SiO ₂ layer may be over-polishing or corrosion may occur. In particular, corrosion causes problems in resolution in subsequent photolithography processes. In addition, the semiconductor manufacturing cost increases as the polishing rate decreases. Therefore, there is a need to develop a new CMP slurry that can minimize wafer contamination by metal ions while maintaining a high polishing rate.

Therefore, the present invention can maintain a high polishing rate by the continuous recharge of the oxidizing power while minimizing the metal or metal ion content of the slurry by using manganese nitrate and hydrogen peroxide as the oxidant, and at the same time by stabilizing the manganese ion by polyacrylic acid An object of the present invention is to provide a slurry for polishing a metal layer of a semiconductor device in which the dispersion stability of the slurry is maximized.

That is, an object of the present invention is to provide a high purity slurry for polishing a metal layer of a semiconductor device comprising fine metal oxide powder, manganese nitrate, hydrogen peroxide, polyacrylic acid, and deionized water.

Hereinafter, the high purity slurry for polishing a metal layer of the present invention will be described in more detail.

Polishing slurry of the present invention is prepared containing a fine metal oxide powder, manganese nitrate, hydrogen peroxide, polyacrylic acid, and deionized water, preferably

1.0 to 15% by weight fine metal oxide powder;

Manganese nitrate 0.01-0.05 wt%;

1-3% by weight of hydrogen peroxide; And

Polyacrylic Acid 0.001 ~ 0.01 wt%

It is prepared to include.

The metal oxide fine powder used in the present invention serves as an abrasive, and metal oxide fine powders commonly used in CMP slurries may be used as long as the object of the present invention is not impaired. Preferably, silica (SiO ₂ ) or alumina is used. (Al ₂ O ₃ ), ceria (CeO ₂ ), and titania (TiO ₂ ).

The content of the fine metal oxide powder is preferably 1.0 to 15% by weight relative to the total slurry, the outside of the content can not achieve the object of the present invention.

The manganese nitrate used in the present invention makes the wafer polishing desired by oxidizing the electrons of the metal layer deposited on the wafer surface while the number of manganese ions is (II) to (I) during the CMP process. At this time, the hydrogen peroxide used together serves to oxidize the reduced manganese ion again. This reaction mechanism is described in detail by taking an example of a reaction with tungsten commonly used as a material for metal wiring:

4Mn ²⁺ + W + 2H ₂ O → 4Mn ⁺ + WO ₂ + 4H ⁺

6Mn ²⁺ + W + 3H ₂ O → 6Mn ⁺ + WO ₃ + 6H ⁺

Manganese (I) produced from Schemes 1 and 2 can be reoxidized to manganese (II) by hydrogen peroxide and nitrate ions according to Schemes 3 and 4 below, thereby restoring polishing activity to maintain a high polishing rate. Will be:

2Mn ⁺ + 2H ⁺ + 3H ₂ O ₂ → 2Mn ²⁺ + O ₂ + 4H ₂ O

_{^{3Mn + + 4H + + NO 3}} - → 3Mn 2+ + NO + 2H 2 O

Meanwhile, the tungsten oxides WO ₂ and WO ₃ generated during the CMP process according to Schemes 1 and 2 are removed by silica or alumina, which is an abrasive in the slurry, to expose a new tungsten layer. Oxidation occurs.

According to the present invention, the manganese nitrate used as the oxidizing agent is continuously recharged the oxidative power consumed by the reaction of the metal layer by hydrogen peroxide and nitrate as described above, even if only a small amount of manganese nitrate is added to the slurry, I can keep it. For example, when 0.03% by weight of manganese nitrate is added to the entire slurry to polish the tungsten layer, the polishing rate may be 3,500 Pa / min or more.

In the present invention, the content of manganese nitrate may have a sufficient polishing rate required by CMP when added in an amount of 0.01 to 0.05% by weight relative to the total slurry, and more preferably 0.02 ~ in consideration of defects and storage stability including polishing rate. It is preferably added at 0.04% by weight. On the other hand, when considering the content of manganese nitrate as described above, the content of hydrogen peroxide is preferably 1 to 3% by weight relative to the total slurry, it can not achieve the object of the present invention outside the content.

Polyacrylic acid used in the present invention serves to stabilize the manganese ion. Manganese (II) agglomerates the abrasive in the slurry through polymerization of manganese (II) in an aqueous solution or reaction with an abrasive in an aqueous solution, as shown in Scheme 5 below, thereby lowering the dispersion stability of the slurry and causing storage problems when used for a long time or during polishing. It may cause defects such as scratches:

Mn (H ₂ O) ₂ ²⁺ ↔ Mn (H ₂ O) (OH) ⁺ + H ⁺ →...

→ (H ₂ O) MnOMn (H ₂ O) ⁺ + H ₂ O → MnO ₂ + Mn (OH) ₂ + Mn (HO ₂ ) +.

However, in the present invention, such a problem could be solved by stabilizing Mn ²⁺ ions using polyacrylic acid. That is, the present inventors COOH present in the poly acrylic ^acid-has been found that ions to stabilize the Mn ²⁺ ion to form a chemical structure such as the following formula (1) and Mn ²⁺ ions:

In addition, the polyacrylic acid has the effect of further improving the dispersion stability of the slurry by increasing the absolute value of the slurry zeta-potential value in addition to the stabilization effect of the manganese ions as described above. For example, CMP slurries that use silica as an abrasive have an isoelectric point in the range of pH 3-4, resulting in poor long-term dispersion stability. In addition, due to agglomeration of the abrasive, defects caused by scratches during polishing and the like have a non-uniform polishing rate. However, this problem can be solved by polishing by adding 0.001 to 0.01 wt% of polyacrylic acid to the slurry to which manganese nitrate is added.

For example, 0.03% by weight of manganese nitrate and 0.005% by weight of polyacrylic acid are added to a slurry made of silica, and the slurry is free of polyacrylic acid after centrifugation at 120 rpm for 120 minutes in a centrifuge. As a result, it was observed that the upper layer was cleared and the abrasive particles were precipitated in the lower layer, but the slurry to which polyacrylic acid was added could not be observed and the dispersion stability was improved.

In the present invention, the content of the polyacrylic acid is preferably 0.001 to 0.01 wt%, more preferably 0.003 to 0.008 wt% based on the total slurry.

In addition to the above components, nitric acid and / or acetic acid may be added to the polishing slurry of the present invention as needed to maintain the pH of the slurry to about 3 to facilitate oxidation of the metal layer as needed. The content of the pH adjusting agent is preferably from 0.03 to 0.1% by weight relative to the total composition, it can not achieve the object of the present invention outside the above range.

Since the high purity slurry of the semiconductor device metal layer polishing of the present invention having the composition as described above has a metal or metal ion content of 500 ppm or less, the possibility of defects caused by the metal or metal ion in the CMP process is minimized.

The polishing slurry of the present invention is particularly effective for polishing tungsten layers, but can be applied evenly to polishing conductive layers and wiring materials of semiconductors such as titanium, titanium nitride, and aluminum in addition to tungsten.

Hereinafter, the present invention will be described in more detail with reference to examples, but these examples are for illustrative purposes only and should not be construed as limiting the present invention.

Example 1

50 g of fine silica powder (Aerosil 90G, manufactured by Degussa), 928.95 g of deionized water, 0.2 g of manganese nitrate, 0.05 g of polyacrylic acid, 0.4 g of nitric acid, and 0.4 g of acetic acid were mixed by stirring at 2,000 rpm for 90 minutes in a 2 L polyethylene flask. The mixture was dispersed once at 1,200 psi by high pressure dispersion to make a slurry. The slurry thus obtained was filtered using a 1 µm depth filter, and then 20 g of hydrogen peroxide (50%) was added and stirred to complete a slurry for polishing a metal layer.

After polishing the tungsten-deposited 6-inch wafer using the polishing slurry thus prepared for 1 minute under the following conditions, the polishing rate was measured from the change in thickness removed by polishing.

[Abrasive performance evaluation method]

Grinding machine model: 6EC (Strasbaugh)

o Polishing condition:

-Pad Type: IC1000 / SubaⅣ Stacked (Rodel)

-Flattening Speed: 60rpm

Quill speed: 90 rpm

Pressure: 8 psi

Background Pressure: 0psi

Temperature: 25 ℃

Slurry flow rate: 200 ml / min

o Polishing target: 6-inch wafer with tungsten

Example 2

Except that 0.4g of manganese nitrate was added in Example 1, the polishing slurry was prepared in the same manner as in Example 1 and the polishing performance was evaluated. The results are shown in Table 1 below.

Example 3

A polishing slurry was prepared in the same manner as in Example 1 except that alumina was used as an abrasive instead of silica in Example 1, and the polishing performance was evaluated. The results are shown in Table 1 below.

Example 4

A polishing slurry was prepared in the same manner as in Example 2 except that alumina was used instead of silica as an abrasive in Example 2, and the polishing performance was evaluated. The results are shown in Table 1 below.

Example 5

Except that 0.01g of polyacrylic acid was added in Example 1, the polishing slurry was prepared in the same manner as in Example 1, and the polishing performance was evaluated. The results are shown in Table 1 below.

Example 6

Except that 0.1g of polyacrylic acid was added in Example 1, the polishing slurry was prepared in the same manner as in Example 1, and the polishing performance was evaluated. The results are shown in Table 1 below.

Example 7

After 6 months long storage of the polishing slurry prepared in Example 1 was evaluated for the polishing performance. The results are shown in Table 1 below.

Comparative Example 1

Except not adding manganese nitrate in Example 1 to prepare a polishing slurry in the same manner as in Example 1 and evaluated the polishing performance. The results are shown in Table 1 below.

Comparative Example 2

A polishing slurry was prepared in the same manner as in Comparative Example 1 except that alumina was used as the abrasive in Comparative Example 1, and the polishing performance was evaluated. The results are shown in Table 1 below.

Comparative Example 3

A polishing slurry was prepared in the same manner as in Example 1 except that hydrogen peroxide water was not added in Example 1, and the polishing performance was evaluated. The results are shown in Table 1 below.

Comparative Example 4

Except that polyacrylic acid was not added in Example 1, the polishing slurry was prepared in the same manner as in Example 1, and the polishing performance was evaluated. The results are shown in Table 1 below.

division abrasive Manganese Nitrate (g) Hydrogen peroxide (g) Polyacrylic acid (g) Scratch ^* () Polishing Speed (Å / min) Example 1 SiO ₂ 0.2 g 10 g 0.05g 20 3,600 Example 2 SiO ₂ 0.4g 10 g 0.05g 22 3,620 Example 3 Al ₂ O ₃ 0.2 g 10 g 0.05g 25 3,870 Example 4 Al ₂ O ₃ 0.4g 10 g 0.05g 26 3,900 Example 5 SiO ₂ 0.2 g 10 g 0.01 g 23 3,610 Example 6 SiO ₂ 0.2 g 10 g 0.1g 18 3,580 Example 7 SiO ₂ 0.2 g 10 g 0.05g 22 3,590 Comparative Example 1 SiO ₂ - 10 g 0.05g 28 1,320 Comparative Example 2 Al ₂ O ₃ - 10 g 0.05g 35 1,450 Comparative Example 3 SiO ₂ 0.2 g - 0.05g 31 1,010 Comparative Example 4 SiO ₂ 0.2 g 10 g - 105 2,450

* Scratch is more than 0.3㎛ scratch.

As described in detail above, using the polishing slurry of the present invention can prevent defects due to metal or metal ions while maintaining a high polishing rate during the CMP process, and the slurry can be stored for a long time.

Claims (4)

delete Based on the total weight of the composition, 1.0 to 15% by weight fine metal oxide powder; Manganese nitrate 0.01-0.05 wt%; 1-3% by weight of hydrogen peroxide; And Polyacrylic Acid 0.001 ~ 0.01 wt% High purity slurry for polishing a metal layer of a semiconductor device comprising a. The method of claim 2, The slurry further comprises 0.03 to 0.1% by weight of nitric acid and / or acetic acid as the pH adjusting agent, based on the total weight of the composition. The fine powder of the metal oxide of claim ₂ is a fine powder of at least one metal oxide selected from the group consisting of silica (SiO ₂ ), alumina (Al ₂ O ₃ ), ceria (CeO ₂ ) and titania (TiO ₂ ). A high purity slurry for polishing a metal layer of a semiconductor device.