JP5583331B2 - Polishing pad - Google Patents

Description

  The present invention relates to a polishing pad having a foam structure suitable for polishing a semiconductor wafer such as a silicon wafer.

  A chemical mechanical polishing (CMP) technique is used for planarization processing of a semiconductor wafer or the like, and various CMP apparatuses using the CMP technique have been proposed. FIG. 3 is a schematic configuration diagram of a conventional CMP apparatus. A polishing slurry 3 is supplied from a slurry supply device 4 to a polishing pad 2 attached to the surface of the surface plate 1. For example, a semiconductor wafer 5 as an object to be polished is held by a polishing head 6 via a backing film 7. When a load is applied to the polishing head 6, the semiconductor wafer 5 is pressed against the polishing pad 2.

  The slurry 3 supplied onto the polishing pad 2 spreads on the polishing pad 2 and reaches the semiconductor wafer 5. The surface plate 1 and the polishing head 6 rotate in the same direction and move relatively as indicated by an arrow A, and the slurry 3 enters between the polishing pad 2 and the semiconductor wafer 5 to perform polishing. . Reference numeral 8 denotes a dresser for conspicuous the surface of the polishing pad 2.

As such a polishing pad 2, one using foamed polyurethane having excellent wear resistance or the like is known (for example, see Patent Document 1).
JP-A-2005-236200

  In a polishing pad having a foam structure, the characteristics of the bubbles such as the distribution and size of bubbles (pores) are the flatness of the object to be polished, the polishing rate, or the end face where the outer edge of the object to be polished is excessively polished ( This greatly affects polishing performance such as roll-off.

  In particular, the stability of the polishing rate is impaired due to variations in the characteristics of the bubbles. For this reason, a polishing pad with improved flatness and end face sagging that has become increasingly severe in recent years without maintaining the stability of the polishing rate and impairing the productivity is desired.

  As a result of diligent research to achieve the above object, the inventors of the present invention have found that a polishing pad having a foam structure has an area ratio of air bubbles within a certain range, thereby stabilizing the polishing rate and polishing objects. The present inventors have found that the flatness and the edge of the end face can be improved.

That is, the polishing pad of the present invention, the surface has an abrasive layer which is pressed against the semiconductor wafer, the polishing layer has a foam structure, a polishing pad for polishing the semiconductor wafer, in the surface, cell diameter 0.1mm larger bubble area ratio of, 10% or less than 4%, the area ratio, the ratio der of the area of the bubble to the area of the surface (pores) is, the cell diameter 1 The number of bubbles having a diameter of 5 mm or more and 2.0 mm or less is 25 or more and 50 or less per 50 mm × 50 mm area of the surface, and the number of bubbles having a bubble diameter of 2.5 mm or more and 3.5 mm or less. , 5 or less per area .

  The area ratio means the ratio of the area of bubbles (pores) to the area of the surface, that is, the ratio of the area of bubbles to the total area of the surface.

  If the area ratio of the bubbles is less than 4%, the slurry cannot be retained sufficiently, and the polishing rate decreases. Conversely, if the area ratio exceeds 10%, the resin area between the bubbles decreases and the rigidity in the load direction decreases. By doing so, the polishing pad is easily elastically deformed, and as a result, the flatness is deteriorated, which is not preferable.

  If the number of bubbles having a bubble diameter of 1.5 mm or more and 2.0 mm or less is less than 25, the polishing rate is lowered and clogging is likely to occur. The end face of the polished article becomes large, which is not preferable.

  Further, when the number of bubbles having a bubble diameter of 2.5 mm or more and 3.5 mm or less exceeds 5, it is not preferable because the end face of the object to be polished becomes large.

In one embodiment, the back pressure is 20 mmH ₂ O or more and 30 mmH ₂ O or less when one layer of the polishing layer is formed and air having a flow rate of 30 liters / minute is passed through the polishing pad.

In another embodiment, the polishing layer has a density of 0.4 g / cm ³ or more and 0.6 g / cm ³ .

  In still another embodiment, the surface roughness Ra of the polishing layer is 5 μm or more and 10 μm or less.

  This surface roughness Ra is the surface roughness of the region other than the bubbles that are open on the surface.

According to the polishing pad of the present invention, the area ratio of the bubbles having a bubble diameter larger than 0.1 mm on the surface of the polishing layer having a foam structure is in a certain range, so that the polishing target is not impaired without impairing the stability of the polishing rate. can improve the flatness of the object, further, bubble cell diameter is 1.5mm or more 2.0mm or less, and, with a range of number of bubbles bubble diameter is 2.5mm or more 3.5mm or less Therefore , it is possible to improve the end face droop without impairing the stability of the polishing rate.

According to the present invention, on the surface of the polishing layer having a foam structure, the area ratio of the bubbles having a bubble diameter larger than 0.1 mm is in a certain range, and further, the bubbles having a bubble diameter of 1.5 mm to 2.0 mm, In addition, since the number of bubbles having a bubble diameter of 2.5 mm or more and 3.5 mm or less is set within a certain range , the flatness and end of the surface of the object to be polished can be improved without impairing the stability of the polishing rate. it can.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  The polishing pad of this embodiment is made of foamed polyurethane, and an isocyanate-terminated prepolymer that is an isocyanate group-containing compound and an aromatic amine that is an active hydrogen-containing compound are mixed and stirred together with a foaming agent (water) to obtain a predetermined mold. And then cured by reaction to obtain a foamed polyurethane molded body.

  Further, the foamed polyurethane molding is cut into a sheet having a predetermined thickness, and punched out to obtain a polishing pad.

  The isocyanate-terminated prepolymer is obtained by reacting a polyisocyanate and a polyol under commonly used conditions. This isocyanate-terminated prepolymer may be a commercially available one, or may be synthesized from a polyol and a polyisocyanate.

  Examples of the polyisocyanate include 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, 4,4′-diphenylmethane diisocyanate, naphthalene-1,5-diisocyanate, and the like.

  Examples of the polyol include polyether polyols such as poly (oxytetramethylene) glycol and poly (oxypropylene) glycol, polycarbonate polyols, and polyester polyols.

  For polishing, an ether-based polyol that does not cause hydrolysis is preferable. As an ether-based polyol, -O- bonds such as PPG (polypropylene glycol), PTMG (polytetramethylene ether glycol), and PEG (polyethylene glycol) are used. Among them, a PTMG system having good physical properties (tensile properties) is preferable. In particular, PTMG having a molecular weight MW = 500 to 5000 is preferable.

  As an aromatic amine which is an active hydrogen-containing compound, for example, as a diamine compound, 3,3′-dichloro-4,4′-diaminodiphenylmethane (MOCA), chloroaniline-modified dichlorodiaminodiphenylmethane, 3,5-bis ( And methylthio) -2,4-toluenediamine and 3,5-bis (methylthio) -2,6-toluenediamine.

In the polishing pad of this embodiment, the area ratio of bubbles having a bubble diameter larger than 0.1 mm on the surface is 4% or more and 10% or less. The number of bubbles having a bubble diameter of 1.5 mm or more and 2.0 mm or less is 25 or more and 50 or less per 50 mm × 50 mm area of the surface, and the bubble diameter is 2.5 mm or more and 3.5 mm or less. the number of certain bubbles, per the area, Ru der 5 or less.

Furthermore, it is preferable that the back pressure when air having a flow rate of 30 liters / minute is passed through the polishing pad is 20 mmH ₂ O or more and 30 mmH ₂ O or less.

The density is preferably 0.4 g / cm ³ or more and 0.6 g / cm ³ , and the surface roughness Ra of the polishing layer is preferably 5 μm or more and 10 μm or less.

  Hereinafter, the present invention will be described in more detail based on examples.

By the above manufacturing method, a polishing pad having a thickness of 1 mm to 1.3 mm made of four types of foamed polyurethanes of Examples 1 and 2 and Comparative Examples 1 and 2 was manufactured, and the area ratio of bubbles (pores) on the surface to be the polishing surface , Surface roughness Ra, number per unit area (50 mm × 50 mm) of bubbles having a bubble diameter of 1.5 mm to 2.0 mm, number per unit area of bubbles having a bubble diameter of 2.5 mm to 3.5 mm, air permeability APR was measured. The results are shown in Table 1 below.

研磨パッドの表面における気泡径および気泡の数は、研磨パッドの表面を撮像した画像を、画像解析ソフトウェアであるＷｉｎＲｏｏｆ Ｖｅｒ５．６．２（三谷商事製）を用いて、図１に示すように、円形近似した気泡の部分１０とパッドの部分１１とに２値化して計測し、気泡径の分布および面積率を算出した。

As shown in FIG. 1, the bubble diameter and the number of bubbles on the surface of the polishing pad are obtained by using an image analysis software WinRoof Ver5.6.2 (manufactured by Mitani Corp.) as an image obtained by imaging the surface of the polishing pad. The bubble portion 10 and the pad portion 11 that were approximated in a circular shape were binarized and measured, and the bubble diameter distribution and area ratio were calculated.

  The measurement range was set at 3 locations of 4 × 4 mm, and the binarization determination method was 88% by the P tile method.

  The bubbles to be measured were larger than the bubble diameter of 0.1 mm.

  The air permeability (aeration resistance value APR) was measured by measuring the back pressure when air having a flow rate of 30 liters / minute was passed through the polishing pad 12, as shown in FIG.

In each of Examples 1 and 2 and Comparative Examples 1 and 2 , the area ratio of the bubbles is in the range of 4% to 10%. Regarding the surface roughness Ra, Examples 1 and 2 are 5 μm. Examples 1 and 2 are in a preferred range of 25 to 50 in terms of the number per unit area (50 mm × 50 mm) of bubbles having a bubble diameter of 1.5 mm to 2.0 mm. Examples 1 and 2 and Comparative Example 2 are in the preferred range of 5 or less for the number of bubbles with a bubble diameter of 2.5 mm to 3.5 mm per unit area. 1 , 2 and Comparative Example 1 are in a preferable range of ₂₀ mmH ₂ O to 30 mmH ₂ O.

That is, all the items of the bubble area ratio, the surface roughness Ra, the number of bubbles having a bubble diameter of 1.5 mm to 2.0 mm, the number of bubbles having a bubble diameter of 2.5 mm to 3.5 mm, and the air permeability APR The preferred range is only in Example 1 , and items other than the surface roughness Ra are in the preferred range in Example 2. The number of bubbles having a bubble diameter of 1.5 mm to 2.0 mm and the ventilation It is Comparative Example 2 that items other than the property APR are in a preferable range, which is the surface roughness Ra, the number of bubbles having a bubble diameter of 1.5 mm to 2.0 mm, and the bubbles having a bubble diameter of 2.5 mm to 3.5 mm. It is Comparative Example 1 that items other than the number are in the preferred range.

Next, the silicon wafer was polished using the polishing pads of Examples 1 and 2 and Comparative Examples 1 and 2 in Table 1, and the standard deviation (RRσ) of the polishing rate and the average of flatness (GBIR) (GBIR_AVG) The average of the flatness (SFQR) (SFQR_AVG) and the average of the end face deflection (ROLLOFF_AVG) were measured.

  The polishing conditions are as follows. The flatness is measured using ADE9500 (manufactured by Japan ADE Co., Ltd.), and ROLLOFF (ROA) is measured using LER-310M (manufactured by Kobelco Research Institute, Ltd.). Measured.

Polishing condition slurry: NP6220 colloidal slurry (1:19 dilution) (Nitta Haas)
Wafer: 200mm etched wafer P (100)
Load: 75-250g / cm ²
Rotation speed: 30rpm
The measurement results and the determination results are shown in Table 2 below.

表２における研磨レートＲＲ（μｍ／ｍｉｎ）の標準偏差σ、平坦度の平均ＧＢＩＲ＿ＡＶＧ（μｍ）、平坦度の平均ＳＦＱＲ＿ＡＶＧ（μｍ）、端面だれの平均ＲＯＬＬＯＦＦ＿ＡＶＧ（μｍ）の各項目の判定基準を、下記表３に示す。

In Table 2, the standard deviation σ of the polishing rate RR (μm / min), the average GBIR_AVG (μm) of flatness, the average SFQR_AVG (μm) of flatness, and the average roll-off average ROLLOFF_AVG (μm) Shown in Table 3 below.

表３に示すように、研磨レートの標準偏差については、０．０３未満を◎、０．０３以上０．０５未満を○、０．０５以上０．０７未満を△、０．０７≦を×と判定した。

As shown in Table 3, with respect to the standard deviation of the polishing rate, ３ is less than 0.03, ○ is 0.03 or more and less than 0.05, Δ is 0.05 or more and less than 0.07, and 0.07 ≦ is ×. It was determined.

  Regarding the average GBIR_AVG of flatness, less than 1.25 was evaluated as ◎, 1.25 or more and less than 1.35 as ◯, 1.35 or more and less than 1.45 as Δ, and 1.45 or more as ×.

  Regarding the average flatness SFQR_AVG, less than 0.12 was evaluated as ◎, 0.12 or more and less than 0.15 as ◯, 0.15 or more and less than 0.18 as Δ, and 0.18 or more as ×.

Regarding the average ROLLOFF_AVG of the end face, it was determined that ０．４ is less than 0.4, ◯ is 0.4 or more and less than 0.45, Δ is 0.45 or more and less than 0.5, and x is 0.5 or more.
Furthermore, for each of the examples and comparative examples , comprehensive determination was performed in four stages of ◎, ○, Δ, and × according to the comprehensive determination criteria in Table 4 below. The results are also shown in Table 2.

総合判定では、表２に示される研磨レートＲＲ（μｍ／ｍｉｎ）の標準偏差σ、平坦度の平均ＧＢＩＲ＿ＡＶＧ（μｍ）、平坦度の平均ＳＦＱＲ＿ＡＶＧ（μｍ）、端面だれの平均ＲＯＬＬＯＦＦ＿ＡＶＧ（μｍ）についての◎、○、△、×の４段階の判定結果に対して、◎は３点、○は２点、△は１点、×は０点を割り当て、その合計点が、０点〜１点は×、２点〜４点は△、５点〜７点は○、８点〜１１点は◎と総合判定した。

In the comprehensive judgment, the standard deviation σ of the polishing rate RR (μm / min) shown in Table 2, the average flatness GBIR_AVG (μm), the average flatness SFQR_AVG (μm), and the average ROLLOFF_AVG (μm) of the end face. ◎, ○, △, × for the four-step judgment results, ◎ is assigned 3 points, ○ is 2 points, △ is 1 point, × is 0 points, the total score is 0 points to 1 point X, 2 to 4 points were evaluated as Δ, 5 to 7 points as ◯, and 8 to 11 points as ◎.

In Example 1 in which all items are in the preferred range, as shown in Table 2, the standard deviation σ of the polishing rate RR (μm / min), the average flatness GBIR_AVG (μm), the average flatness SFQR_AVG (μm) All of the average ROLLOFF_AVG (μm) of the end face were excellent.

In Example 2 , in which items other than the surface roughness Ra are in a preferable range, as shown in Table 2, all except the standard deviation σ of the polishing rate RR (μm / min) are good, and the overall judgment is also good. there were.

Thus, the area ratio of bubbles, the number of bubbles having a bubble diameter of 1.5 mm to 2.0 mm, the number of bubbles having a bubble diameter of 2.5 mm to 3.5 mm, and the items of air permeability APR are in the preferred range. In Examples 1 and 2 , it can be seen that the polishing rate is also stable, and the flatness and edge droop can be improved.

  The present invention is useful as a polishing pad used for polishing a silicon wafer or the like.

It is a schematic view of a polishing pad surface showing the distribution measurement of air bubbles. It is a figure for demonstrating the air permeability measurement method. Schematic configuration diagram of CMP equipment

Explanation of symbols

2 Polishing pad 5 Semiconductor wafer

Claims (4)

A polishing pad for polishing the semiconductor wafer , the surface having a polishing layer pressed against the semiconductor wafer , the polishing layer having a foam structure,
In the surface cell diameter 0.1mm larger bubble area ratio of, 10% or less than 4%, the area ratio, Ri proportion der of the area of the bubble to the area of the surface (pores)
The number of bubbles having a bubble diameter of 1.5 mm or more and 2.0 mm or less is 25 or more and 50 or less per 50 mm × 50 mm area of the surface, and the bubble diameter is 2.5 mm or more and 3.5 mm or less. A polishing pad , wherein the number of bubbles is 5 or less per area . 2. The polishing according to claim 1, wherein the back pressure is 20 mmH ₂ O or more and 30 mmH ₂ O or less when one layer of the polishing layer is formed and air having a flow rate of 30 liters / minute is passed through the polishing pad. pad. Density of the polishing layer, the polishing pad according to claim 1 or 2 is 0.4 g / cm ³ or more 0.6 g / cm ^3. The polishing pad according to any one of claims 1 to 3, wherein the polishing layer has a surface roughness Ra of 5 µm or more and 10 µm or less .

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