JP3750466B2 - Semiconductor wafer finish polishing method - Google Patents

Description

【００１５】
表１より明らかなように比較例１に対して実施例１ではＲｍｓ値が減少しており、短時間の研磨でウェーハ表面のラフネスが低減していることが判る。
また、図２より比較例１に対して実施例１では空間周波数１×１０^-2〜１×１０^-1（μｍ^-1）の範囲でのＰＳＤ強度が小さくなっており、マイクロラフネスが低減されていることがわかる。
【００１６】
【発明の効果】
以上述べたように、本発明によれば、半導体ウェーハの仕上げ研磨を圧縮率５％以上の表層がスウェードからなる研磨布とアルカリ性であってポリビニルアルコール又はヒドロキシエチルセルロースのいずれか一方またはその双方からなる添加有機物の含有率が１０ｐｐｍ未満の研磨スラリーの組合せで研磨した後に、圧縮率５％以上の表層がスウェードからなる研磨布とアルカリ性であってポリビニルアルコール又はヒドロキシエチルセルロースのいずれか一方またはその双方からなる添加有機物の含有率が１０ｐｐｍ以上の研磨スラリーを用いてウェーハを更に研磨するようにしたので、ウェーハ表面のマイクロラフネスを短時間で低減し、かつ最終的な面質を安定にすることができる。
【図面の簡単な説明】
【図１】 半導体基板の片面研磨装置の構成図。
【図２】 実施例１及び比較例１の空間周波数における表面粗さパワースペクトルを示す図。
【符号の説明】
１０ 片面研磨装置
１１ 回転定盤
１２ ウェーハ保持具
１２ａ 加圧ヘッド
１２ｂ シャフト
１３ シャフト
１４ 研磨布
１６ 研磨プレート
１７ 半導体ウェーハ
１８ 研磨スラリー
１９ 配管[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for finishing polishing a semiconductor wafer represented by a silicon wafer.
[0002]
[Prior art]
In general, the manufacturing process of a semiconductor wafer includes a slicing process for slicing a single crystal ingot to obtain a thin disk-shaped wafer, and a chamfering process for chamfering the outer periphery to prevent cracking and chipping of the wafer obtained by the slicing process. A polishing process for planarizing the wafer, an etching process for removing chamfering and processing distortion remaining on the lapped wafer, a polishing process for mirroring the surface of the wafer, and cleaning the polished wafer. And a cleaning process for removing abrasives and foreign matters adhering to the surface. In this mirror polishing process, a polishing slurry is used between the polishing cloth and the wafer, and the wafer is polished by a so-called mechanochemical polishing method (mechanical chemical composite polishing method). This is a method that combines the mechanical action of mechanical polishing and the chemical action of etching, and synergistically obtains high-efficiency, high-precision surface quality. It depends on the distribution of elements. In addition, the mirror polishing process includes a rough polishing process for removing surface irregularities due to etching and a final polishing process for determining the final surface quality of the wafer surface after the rough polishing.
Conventionally, in this final polishing process, a relatively soft cloth with a compression ratio of 5% or more is used as the polishing cloth, and a liquid in which SiO ₂ fine particles and other abrasive grains are suspended in a weak alkaline liquid is used as the polishing slurry. The The finish polishing slurry usually further contains 10 ppm or more of added organic matter, and this added organic matter has the effect of suppressing and controlling the chemical reaction, increasing the liquid viscosity, and preventing haze and scratches.
[0003]
[Problems to be solved by the invention]
However, in the above-described finish polishing using the polishing cloth and the polishing slurry, the removal efficiency of the unevenness of the wavelength component in the range of 5 μm to 1 mm due to the etching remaining after the rough polishing is poor, and the microroughness in this range is reduced. It took a long time to polish.
Further, the polishing slurry used for finish polishing is affected by a natural oxide film grown on the polishing surface and organic substances attached during polishing. For this reason, there is a problem that the time for starting the polishing reaction is delayed, and the surface quality becomes unstable in a short time polishing.
An object of the present invention is to provide a semiconductor wafer finish polishing method that reduces the microroughness of the wafer surface in a short time and stabilizes the final surface quality.
[0004]
[Means for Solving the Problems]
According to a first aspect of the present invention, there is provided a method for final polishing a semiconductor wafer in which a polishing slurry is interposed between a semiconductor wafer and a polishing cloth to polish the wafer to determine a final surface quality of the wafer surface. After polishing the wafer with a polishing slurry in which the surface layer of 5% or more is made of suede and alkaline, and the content of the added organic substance consisting of one or both of polyvinyl alcohol and hydroxyethyl cellulose is less than 10 ppm, The wafer is further polished using a polishing slurry having a surface layer with a compressibility of 5% or more and a polishing cloth made of suede and alkaline, and containing at least 10 ppm of an added organic substance made of polyvinyl alcohol or hydroxyethyl cellulose. Of semiconductor wafers characterized by It is a raised polishing method.
In the invention according to claim 1, paying attention to the compressibility of the polishing cloth and the organic matter contained in the polishing slurry, the polishing cloth comprising a suede surface layer having a compressibility of 5% or more, which is different from the combination used in the conventional finish polishing. And a polishing slurry having a surface layer with a compressibility of 5% or more and a polishing cloth made of suede and having a content of additive organics of 10 ppm or more. A final polishing is performed to further polish the wafer using. In the combination of the previous stage polishing, the polishing reaction start is accelerated by using a polishing slurry having an additive organic substance content of less than 10 ppm that suppresses chemical reaction, and the remaining after rough polishing by using a relatively soft polishing cloth. The removal efficiency of the unevenness of the wavelength component in the range of 5 μm to 1 mm due to the etching to be performed can be increased, and the final surface quality of the wafer is stabilized by the short-time polishing.
[0005]
In the combination of the subsequent polishing , the microroughness can be further reduced by performing polishing corresponding to conventional finish polishing.
[0006]
Further, when the polishing slurry contains the organic substance, the polishing reaction can be more effectively suppressed and controlled.
[0007]
DETAILED DESCRIPTION OF THE INVENTION
Next, an embodiment of the present invention will be described.
Polishing cloth of the present invention include scan Wade. Base fabric of the scan Wade is polyurethanes is usually used. The compressibility of the polishing cloth is determined by a method based on JIS L-1096. Specifically using known automatic compression rate measuring unit, the thickness T ₁ of Part 1 minute after measured by adding the initial load ^{_{L 0 (300g / cm 2)}} , simultaneously load and the measured L ₁ (1800 g / cm ² ), and after 1 minute, the thickness T ₂ is measured, and the compression rate is obtained by the following formula (1) based on the T ₁ and T ₂ .
[0008]
Compression rate (%) = {(T ₁ −T ₂ ) / T ₁ } × 100 (1)
A single-side polishing method is usually used for the finish polishing method of the present invention. A single-side polishing method will be described with reference to FIG. The polishing apparatus 10 includes a rotating surface plate 11 and a wafer holder 12. The rotating surface plate 11 is a large disk and is rotated by a shaft 13 connected to the center of the bottom surface. A polishing cloth 14 is affixed to the upper surface of the rotating surface plate 11. The wafer holder 12 includes a pressure head 12a and a shaft 12b connected to the pressure head 12a and rotating the pressure head 12a. A polishing plate 16 is attached to the lower surface of the pressure head 12a. A plurality of semiconductor wafers 17 are attached to the lower surface of the polishing plate 16. A pipe 19 for supplying the polishing slurry 18 is provided on the upper part of the rotating surface plate 11. When the semiconductor wafer 17 is polished by the polishing apparatus 10, the pressure head 12 a is lowered and a predetermined pressure is applied to the semiconductor wafer 17 to hold the wafer 17. While supplying the polishing slurry 18 from the pipe 19 to the polishing pad 14, the pressure head 12 a and the rotating surface plate 11 are rotated in the same direction to polish the surface of the wafer 17 flatly.
[0009]
Next, finish polishing by such an apparatus will be described .
[0010]
The first polishing cloth Ken compression ratio of 5% or more of the surface layer is Ru suede Tona to Migakununo, the content of the added organic matter be alkaline in the polishing slurry to polish the wafer using a Migaku Ken slurry of less than 10 ppm. It is preferred that The compression ratio 10-20% of the surface layer is polished wafers with the content of the added organic matter a Migaku Ken cloth and alkaline Ru suede Tona is a Migaku Ken slurry of less than 10 ppm. If the additive organic content exceeds 10 ppm, the chemical reaction suppressing effect becomes too strong, resulting in a problem that the polishing rate is lowered and the roughness removal efficiency is lowered. By polishing with this combination , the removal efficiency of the wavelength component of 5 μm to 1 mm of the irregularities on the wafer surface can be enhanced, and the influence of the natural oxide film and the attached organic matter grown on the polished surface can be quickly removed.
[0011]
Then, following the polishing, the content of the compression ratio of 5% or more of the surface layer is added organics a Migaku Ken cloth and alkaline Ru suede Tona to polish the wafer using the above Migaku Ken slurry 10 ppm. It is preferable to polish the wafer using a polishing slurry having a surface layer with a compression rate of 10 to 20% and a polishing cloth made of suede and alkaline, and an additive organic content of 100 ppm to 1%. In performing this Migaku Ken can be further reduced microroughness of the wafer surface.
[0012]
【Example】
Next, examples of the present invention will be described.
< Example 1 >
First, a silicon wafer that has been subjected to a rough polishing step is prepared as a semiconductor wafer, and a polishing cloth whose surface layer is made of suede and a polishing cloth having a compressibility of 5% or more and SiO ₂ abrasive particles to which an organic substance is added are commercially available. A polishing pressure of 1.96 × 10 ⁴ Pa using a polishing apparatus shown in FIG. 1 using an alkaline polishing slurry prepared by diluting an alkaline polishing slurry stock solution with pure water so that the content of the added organic material is 100 ppm or more , the finish polishing was Tsu 3 minutes row at a relative speed 1.0m / s of the polishing pad and the wafer. Diluting a polishing slurry stock solution of alkaline to continue stomach abrasive particles of the SiO ₂ to the silicon wafer surface layer is not compressibility consisting suede was added 5% or more of the polishing cloth and organic matter is commercially available was dispersed in pure water Then, final polishing was further performed for 3 minutes under the same polishing conditions as above using the alkaline polishing slurry to which no organic matter was added .
[0013]
<Comparative Example 1>
A commercially available alkaline solution in which a coarsely polished silicon wafer was prepared in the same manner as in Example 1, and a polishing cloth having a surface layer made of suede and having a compressibility of 5% or more and SiO ₂ abrasive particles to which no organic matter was added was dispersed. 1 using a polishing slurry shown in FIG. 1 using an alkaline polishing slurry prepared by diluting a stock slurry for polishing with pure water to which organic substances are not added , a polishing pressure of 1.96 × 10 ⁴ Pa, and a relative speed of a polishing cloth and a wafer Final polishing was performed at 1.0 m / s for 6 minutes.
<Comparison evaluation>
The surface roughness power spectrum (Power Spectral Density, hereinafter referred to as PSD) is measured on the surface of the finished silicon wafer using an optical non-contact profiler, and the square root average of wavelength of 100 μm or less is obtained from the obtained PSD. The roughness (root-mean-square roughness, hereinafter referred to as Rms) was obtained. The PSD obtained in Example 1及 beauty Comparative Example 1 in FIG. 2, showing the Rms in Table 1. Incidentally, in FIG. 2 shows the PSD obtained from another in the final polishing prior to the wafer surface having been subjected to the rough polishing step of the PSD curve of Example 1及 beauty Comparative Example 1 and the reference value.
Note that PSD is obtained by decomposing a surface roughness profile into components for each spatial frequency by Fourier transform. Rms is the square root of the PSD integrated in a certain spatial frequency range.
[0014]
[Table 1]

[0015]
Table 1 has decreased Rms value in the embodiment 1 than against obvious Comparative Example 1 As it can be seen that the roughness of the wafer surface in a short time of polishing is reduced.
Further, in the embodiment 1 with respect to Comparative Example 1 from 2 has become small PSD strength in the range of spatial frequencies ^{1 × 10 -2 ~1 × 10 -1} (μm -1), microroughness is reduced You can see that
[0016]
【The invention's effect】
As described above, according to the present invention, final polishing of a semiconductor wafer is performed with a polishing cloth having a surface layer made of suede having a compression rate of 5% or more and alkaline, and is made of one or both of polyvinyl alcohol and hydroxyethyl cellulose. After polishing with a combination of polishing slurries with an additive organic content of less than 10 ppm, the surface layer with a compressibility of 5% or more is a polishing cloth made of suede and alkaline, and consists of one or both of polyvinyl alcohol and hydroxyethyl cellulose. Since the wafer is further polished using a polishing slurry having an additive organic content of 10 ppm or more, the microroughness of the wafer surface can be reduced in a short time and the final surface quality can be stabilized.
[Brief description of the drawings]
FIG. 1 is a configuration diagram of a single-side polishing apparatus for a semiconductor substrate.
FIG. 2 shows the surface roughness power spectrum in a spatial frequency of Example 1及 beauty Comparative Example 1.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 Single-side polish apparatus 11 Rotating surface plate 12 Wafer holder 12a Pressure head 12b Shaft 13 Shaft 14 Polishing cloth 16 Polishing plate 17 Semiconductor wafer 18 Polishing slurry 19 Piping

Claims (1)

In a final polishing method for a semiconductor wafer, in which a polishing slurry is interposed between a semiconductor wafer and a polishing cloth to polish the wafer and determine a final surface quality of the surface of the wafer,
Polishing the wafer using a polishing slurry having a surface layer with a compressibility of 5% or more and a polishing cloth made of suede and alkaline and containing less than 10 ppm of an added organic substance made of either polyvinyl alcohol or hydroxyethyl cellulose Then, the surface layer having a compressibility of 5% or more is a polishing cloth made of suede, and the polishing slurry is alkaline, and the content of the added organic substance consisting of either one or both of polyvinyl alcohol and hydroxyethyl cellulose is 10 ppm or more. A method for final polishing a semiconductor wafer, further comprising polishing the wafer .

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