JP4567295B2 - Wafer scratch analysis method - Google Patents

Description

となる。次にパーティクル１０の位置を表す式は
【数２】

となる。これを展開して表現すると、
【数３】

となり、（ｘ_ｄ、ｙ_ｄ）について解くと、
【数４】

となる。こうして（４ａ）、（４ｂ）式で示すように、パーティクル１０の軌道を時間ｔの関数として求めることが可能となる。
【００３１】
［２］スクラッチに基づく研磨装置のパラメータの演算
上記［１］ではスクラッチの軌道について考えたが、スクラッチに基づいて研磨装置が有するパラメータを演算することができる。
【００３２】
図３は（ｘ、ｙ）座標で考えたｒ_ｄ、ρ、ρ_ｓを示す図である。
【００３３】
研磨後、ウェーハ５にスクラッチが形成されているものとして、次のように各値を定義する。
【００３４】
・スクラッチ２０上の一点と固定面３ａの中心Ｏ_２との間の距離…ｒ_ｄ
・スクラッチ２０上の一点における曲率半径…ρ
・スクラッチ２０上の一点における曲率円中心Ｑと固定面３ａの中心Ｏ_２との間の距離…ρ_ｓ
【００３５】
（ｘ、ｙ）座標で表示した上記（４ａ）、（４ｂ）式は時間ｔの媒介変数表示になっており、両式から時間ｔを消去する必要がある。そのために、スクラッチの一点に対してｒ_ｄ、ρ、ρ_ｓ、という量を導入する。上記（４ａ）、（４ｂ）式より、下記（５）式が求められる。但し、ξ＝Ｒ_ｄ／Ｒ_ｏ、ζ＝（α−β）／αとする。
【数５】

【００３６】
（５ａ）、（５ｂ）、（５ｃ）式において、ｒ＾_ｄ、ρ＾、ρ＾_ｓは、ウェーハ上のスクラッチ上の三点Ａ、Ｂ、Ｃの座標を用いた曲率円フィッティングから演算される。したがって上記（５ａ）、（５ｂ）、（５ｃ）式より、ζ及びξを解くことが可能である。この計算ではζの６次方程式が得られるため、ζの解は最多で６個存在しうる。この解法には、例えばニュートンラフソン（Newton-Raphson）法を用いる。こうして求めたζ及びξを用いて、ζ＝（α−β）／α及びξ＝Ｒ_ｄ／Ｒ_ｏを解き、β／α及びＲ_ｄを得ることができる。
【００３７】
［３］曲率半径ρ等の求め方
次に上述したｒ_ｄ、ρ、ρ_ｓの求め方について説明する。
【００３８】
図４はｒｄ、ρ、ρ_ｓの求め方を説明するための図であり、ウェーハ５に固定した座標系で考えたｒ_ｄ、ρ、ρ_ｓを示している。
【００３９】
スクラッチ軌道は実際には円ではないので、曲率半径ρはスクラッチ上の一点に対して定義される。このため、図４に示すように、スクラッチ上の三点Ａ、Ｂ、Ｃの座標から曲率円中心Ｑ（ｘ_ｏ、ｙ_ｏ）を求める場合、その曲率は三点の中心であるＢ点に帰属させる。
【００４０】
曲率円中心Ｑ（ｘ_ｏ、ｙ_ｏ）は、ウェーハ５に固定した座標系における三点Ａ（ｘ_Ａ、ｙ_Ａ）、Ｂ（ｘ_Ｂ、ｙ_Ｂ）、Ｃ（ｘ_Ｃ、ｙ_Ｃ）を用いて、次のように表される。
【数６】

（６ａ）、（６ｂ）式から、Ｂ点に対応するρは、
【数７】

により求められる。
【００４１】
また、ρ_ｓ、ｒ_ｄを求めるには、ウェーハ５に固定した座標系からプレート３に固定した座標系への変換が必要になる。プレート３の中心Ｏ_２とウェーハ５の中心Ｏ_３との距離をｒ_ｗｃと定義すると、図４からその変換を含めて、ρ_ｓ、ｒ_ｄは、
【数８】

により求められる。
【００４２】
［４］実施例
各研磨工程においてウェーハ５をプレート３に固定するにあたり、プレート３に対するウェーハ５の位置を定める必要がある。そこでウェーハ５のノッチやオリフラがプレート３に対して所定方向を向くようにして、ウェーハ５をプレート３の固定面３ａに固定する。ウェーハ５を固定した後にプレート３を下盤２の研磨面２ａ上に配置し、下盤２及びプレート３を回転させてウェーハ５の研磨を行う。このようにして複数の研磨工程を行う。
【００４３】
全研磨工程が終了すると、パーティクルカウンタ等で各ウェーハ５を測定し、スクラッチが存在する場合はその位置を取得する。
【００４４】
取得したスクラッチの位置を用いて、上記［３］で説明した方法によりｒ_ｄ、ρ、ρ_ｓを求め、［２］で説明した方法によりζを求めてβ／αを求める。また同じくξを求めてＲ_ｄを求める。
【００４５】
本発明者らはソフトウェアを作成することによって本発明を実現した。このソフトフェアは、パーティクルカウンタで測定した所定の座標データファイルを読み込み、ＬＰＤマップを表示し、ＬＰＤのスクラッチ部分を画面表示するものである。更にＬＰＤマップに表示されたスクラッチ上の三点を指示することで、そのスクラッチのβ／α、Ｒ_ｄ、ρ、ρ_ｓを算出するものである。
【００４６】
本発明によれば、ウェーハに形成されたスクラッチを解析することによって、スクラッチ形成に関わる研磨装置を特定することができる。結果として研磨工程を改善することが可能になる。
【００４７】
［５］解析事例１
次に本発明によって求めたβ／αに基づいてスクラッチ形成に関わる研磨装置を特定する事例について説明する。
【００４８】
４段階の研磨工程（第１〜第４の研磨工程）でウェーハを研磨した後にウェーハを測定した結果、図５に示すようなスクラッチが形成されていた。各研磨工程ではそれぞれ異なる研磨装置が用いられており、表１に示すように、各研磨装置のβ／αは、上限値（β／α）_ｍａｘ及び下限値（β／α）_ｍｉｎの範囲内に含まれる。
【００４９】
【表１】

【００５０】
図５に示すウェーハ５の各スクラッチ２１〜２３を本発明によって解析したところ、表２に示す結果が得られた。
【００５１】
【表２】

【００５２】
表２で示すように、スクラッチ２１に基づいて求められたβ／αの値は“0.803691”である。表１を見ると、この値は第４研磨工程におけるβ／αの範囲に含まれる。したがってスクラッチ２１の形成に第４研磨工程で用いられる研磨装置が関わった、ということを特定できる。
【００５３】
また表２で示すように、スクラッチ２２に基づいて求められたβ／αの値は“0.895741”である。表１を見ると、この値は第３研磨工程におけるβ／αの範囲に含まれる。したがってスクラッチ２２の形成に第３研磨工程で用いられる研磨装置が関わった、ということを特定できる。
【００５４】
また表２で示すように、スクラッチ２３に基づいて求められたβ／αの値は“0.603993”である。表１を見ると、この値は第４研磨工程におけるβ／αの範囲に含まれる。したがってスクラッチ２３の形成に第４研磨工程で用いられる研磨装置が関わった、ということを特定できる。
【００５５】
なお表１に示す例では、第２研磨工程のβ／α（0.848〜0.875）が第４研磨工程のβ／α（0.583〜0.875）の一部に含まれている。このような場合は、同じバッチで処理された複数ウェーハのスクラッチに基づいて各β／αを求め、β／αの分布を調べることによって、各ウェーハのスクラッチが第２、第４の何れの研磨工程で形成されたのか、を特定できる。例えばβ／αの分布が0.848〜0.875に集中していれば、スクラッチの形成に第２研磨工程で用いられる研磨装置が関わった、ということを特定でき、β／αの分布が0.583〜0.875に分散していれば、スクラッチの形成に第４研磨工程で用いられる研磨装置が関わった、ということを特定できる。
【００５６】
［６］解析事例２
次に本発明によって求めたＲｄを用いることによって、パーティクルの発生源を推定する事例について説明する。
【００５７】
図６（ａ）〜（ｃ）は所定数のウェーハに形成された各スクラッチを解析した場合に得られるＲ_ｄの分布を示す図である。
【００５８】
所定数のウェーハを研磨した後に、各ウェーハに形成されたスクラッチに基づいてＲ_ｄを求めＲ_ｄの分布を求めると、大別して図６（ａ）〜（ｃ）のような結果が得られる。
【００５９】
図６（ａ）に示すような分布が得られた場合、つまり小さいＲ_ｄほど度数が大きく、大きいＲ_ｄほど度数が小さい場合は、クロスの中心近傍に供給されるスラリーに不純物が含まれていると推定される。
【００６０】
また図６（ｂ）に示すような分布が得られた場合、つまりＲ_ｄに関わらず度数がほぼ等しい場合は、ダスト等が大気中からクロスに一様に降下していると推定される。
【００６１】
また図６（ｃ）に示すような分布が得られた場合、つまりＲ_ｄの一点及びその近傍における度数が大きい場合は、ダスト等が下盤の特定部分すなわち中心からＲ_ｄ離れた位置で発生していると推定される。
【図面の簡単な説明】
【図１】図１は研磨装置の全体及び各部分を示す図である。
【図２】図２は研磨面の中心Ｏ_１を原点とする座標系（Ｘ、Ｙ）と、固定面の中心Ｏ_２を原点とする座標系（ｘ、ｙ）とを示す図である。
【図３】図３は（ｘ、ｙ）座標で考えたｒ_ｄ、ρ、ρ_ｓを示す図である。
【図４】図４はｒ_ｄ、ρ、ρ_ｓの求め方を説明するための図である。
【図５】図５はスクラッチが形成されたウェーハを示す図である。
【図６】図６（ａ）〜（ｃ）は所定数のウェーハに形成された各スクラッチを解析した場合に得られるＲ_ｄの分布を示す図である。
【符号の説明】
１ 研磨装置
２ 下盤
２ａ 研磨面
３ プレート
３ａ 固定面
５ ウェーハ[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a wafer scratch analysis method for analyzing a scratch formed on a wafer in accordance with the operation of a polishing apparatus, and in particular, determines a parameter of the polishing apparatus based on the scratch and identifies a polishing apparatus involved in scratch formation. About things.
[0002]
[Prior art]
A polishing apparatus for a semiconductor wafer or the like is shown in FIG. FIG. 1A shows a perspective view of the entire polishing apparatus, and FIG. 1B shows the positional relationship between the lower plate and the plate when the polishing apparatus is viewed from the upper part of FIG. FIG. 1C shows the positional relationship between the plate and the wafer when the plate is viewed from the lower plate side of FIG.
[0003]
A polishing apparatus 1 shown in FIG. 1 includes a lower board 2, a plurality of plates 3, and a slurry supply pipe 4. Lower plate 2 has a polishing surface 2a of the cross (also referred to as a polishing cloth) is stuck, rotates in an arrow A direction shown in the drawings the center O ₁ as the center of rotation by a rotation mechanism (not shown). Plate 3 has a fixing surface 3a, the rotation mechanism (not shown), for example, the center roller and the guide roller, by rotating in the arrow B direction shown in the drawings the center O ₂ as the center of rotation. The plate 3 is movable in a direction substantially perpendicular to the polishing surface 2a. One or more wafers 5 are fixed around the center O ₂ of the fixing surface 3 a of the plate 3. A plurality of plates 3 are provided around the center O ₁ of the polishing surface 2 a so that the polishing surface 2 a of the lower plate 2 and the fixed surface 3 a of the plate 3 face each other. The slurry supply pipe 4 is provided with the supply port 4a facing the polishing surface 2a of the lower board 2.
[0004]
FIG. 1 (b) shows a state in which four plates 3 are provided on the polishing surface 2a, and FIG. 1 (c) shows a state in which five wafers 5 are fixed to the fixed surface 3a. However, the number of plates 3 and wafers 5 with respect to the polishing apparatus 1 is not particularly limited, and is determined according to the size of the polishing apparatus 1 and the wafers 5.
[0005]
The polishing apparatus 1 operates as follows. When a constant load is applied to the plate 3 in the lower plate 2 direction while the polishing surface 2a of the lower plate 2 and the wafer 5 are in contact, the wafer 5 is pressed against the polishing surface 2a. In this state, the lower board 2 and the plate 3 rotate. At this time, slurry (also referred to as abrasive grains) is supplied from the slurry supply pipe 4 onto the polishing surface 2a. In this way, the surface of each wafer 5 fixed to the plate 3 is polished.
[0006]
Usually, polishing of a wafer is performed through a plurality of processes. Specifically, the process is gradually shifted from the process of performing rough polishing to the process of performing fine polishing, and in each process, a polishing apparatus corresponding to the degree of polishing is used. That is, a plurality of polishing apparatuses are used for polishing one wafer.
[0007]
Incidentally, solid foreign matters (hereinafter referred to as “particles”) may adhere to the polished surface 2a. When the lower plate 2 and the plate 3 rotate, the particles and the wafer are relatively displaced. As a result, the surface of the wafer 5 may be scraped by particles to form an arc-shaped scratch. Conventionally, there has been a technique for measuring the position of surface foreign matters represented by such scratches and dirt, displaying the measurement results on a map, and classifying and analyzing the number density and aggregation state of the surface foreign matters.
[0008]
For example, Patent Document 1 below describes a technique for determining whether mirror polishing is good or not as one technique for analyzing scratches. According to this technique, a mirror-polished wafer is subjected to HF cleaning to remove surface oxides, and SC-1 cleaning is performed to etch scratches to form pits, which are measured by a particle counter. . The quality of the mirror polishing is determined according to the measured LPD density.
[0009]
[Patent Document 1]
Japanese Patent Laid-Open No. 11-145088
[Problems to be solved by the invention]
Scratches degrade the oxide film breakdown voltage of the wafer, which causes a reduction in wafer manufacturing yield and reliability. Therefore, it is necessary to suppress the formation of scratches, and for that purpose, it is necessary to improve the conditions of the polishing process in which the scratches are formed and the polishing apparatus itself.
[0011]
For example, it is assumed that a wafer is observed after all of a plurality of polishing processes are completed, and a scratch is found. In this case, the polishing apparatus involved in the formation of the scratch must be specified.
[0012]
Many of the particles adhering to the cloth are so small that they cannot be recognized by the human eye, and no particle can be found by examining the polishing apparatus itself. However, in the conventional scratch analysis technology, there is no one that specifies a polishing apparatus involved in scratch formation. Therefore, conventionally, it has not been possible to identify a polishing apparatus in which a scratch is formed.
[0013]
The present invention has been made in view of such circumstances, and by determining the parameters of the polishing apparatus based on the scratches formed on the wafer, the polishing apparatus related to scratch formation is identified and contributes to the improvement of the polishing process. This is a problem to be solved.
[0014]
[Means, actions and effects for solving the problems]
In order to solve the above problems, the first invention is:
A plate having a rotation center at one point on a fixed surface for fixing the wafer and a lower plate having a rotation center at one point on the polishing surface for polishing the wafer, and fixing the wafer around the rotation center of the fixed surface When a plurality of polishing apparatuses that polish a wafer by placing a plate around the rotation center of the polishing surface and rotating the lower plate and the plate are used, the solid foreign matter adhered to the polishing surface In the wafer scratch analysis method for analyzing the scratch formed on the wafer,
Before each polishing, fixing step for fixing the wafer relative to the plate;
After a plurality of polishings, in the wafer removed from the plate, the scratch formed on the wafer is measured, and using the measured three positions on the scratch and the scratch trajectory formula, the rotational speed of the plate and the A ratio calculating step for determining the ratio of the rotation speed of the lower board;
And a specifying step of specifying a polishing apparatus that has formed a scratch on a wafer using the ratio obtained in the ratio calculating step.
[0015]
The second invention is the first invention,
After said identifying step, a distance calculating step of calculating a distance R _d between the rotation center of the polishing surface of the polishing apparatus to form a scratch on the wafer and the solid contaminants,
Performs the distance calculation step for each of a plurality of scratches, characterized by comprising an estimating step of estimating a source of solid contaminants, the use of the distribution of the distance R _d of solid contaminants.
The third invention is the first invention,
The said ratio calculating step, and a distance [rho _s between the rotation center of the fixing surface curvature circle center at one point on the scratch, and the distance r _d between the center of rotation of the fixed surface and a point on the scratch, one point on the scratch And calculating the ratio of the rotation speed of the plate and the rotation speed of the lower board.
It is characterized by.
[0016]
The first invention will be described with reference to FIGS. Has a fixed surface 3a for fixing the wafer 5, the plate 3 to rotate about one point O ₂ on the fixing surface has a polished surface 2a of polishing the wafer 5, a point O ₁ on the polishing surface 2a A lower plate 2 having a rotation center, the wafer 5 is fixed around the rotation center O ₂ of the fixed surface 3a, and the plate 3 is provided around the rotation center O ₁ of the polishing surface 2a. When the polishing apparatus 1 that polishes the wafer 5 by rotating 3 is used, scratches may be formed on the wafer due to solid foreign substances adhering to the polishing surface 2a.
[0017]
In the first invention, first, the wafer 5 is fixed by positioning relative to the plate 3 before the wafer 5 is polished. After the wafer 5 is polished by the polishing apparatus 1, as shown in FIG. The distance ρ _s between the center of curvature circle Q at one point on the formed scratch 20 and the rotation center O ₂ of the fixed surface 3a, and the distance between one point on the scratch 20 and the rotation center O ₂ of the fixed surface 3a. and r _d, with a radius of curvature ρ at a point on the scratch 20, determining the ratio beta / alpha of the rotational speeds of alpha and footwall second plate 3 beta.
[0018]
In the second invention, obtains a distance R _d between the rotation center O ₁ and solid contaminants (particles) 10 of the polishing surface 2a shown in FIG.
[0019]
According to the first and second aspects of the present invention, it is possible to identify a polishing apparatus related to scratch formation by analyzing scratches formed on the wafer. As a result, the polishing process can be improved.
[0023]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of a wafer scratch analysis method according to the present invention will be described below with reference to the drawings.
[0024]
The following [1] to [3] explain the concept of the present invention, the following [4] explains specific examples of the present invention, and the following [5] and [6] are obtained by the present invention. An analysis example using numerical values will be described.
[0025]
[1] Formulation of Scratch Trajectory In the present invention, the parameters (ratio between the rotation speed of the lower plate and the rotation speed of the plate, the position of the particles) possessed by the polishing apparatus are obtained based on the scratch existing on the wafer. By determining the parameters of the polishing apparatus, it is possible to identify the polishing apparatus involved in scratch formation. What is important in obtaining the parameters of the polishing apparatus based on the scratch is “formation of the scratch trajectory”. First, “scratch trajectory formulation” will be described.
[0026]
FIG. 2 is a diagram showing a coordinate system (X, Y) whose origin is the center O ₁ of the polishing surface and a coordinate system (x, y) whose origin is the center O _{2 of the} fixed surface. The state which projected the plate 3 on the grinding | polishing surface 2a is shown.
[0027]
Here, each value is defined as follows.
-Angular velocity of plate 3 ... α
-Angular velocity of lower board 2 ... β
- distance between the center _{O 1} and particle 10 of the polishing surface 2a ... _{R d}
The distance between-the center _{O 1} of the polishing surface 2a and the center _{O 2} of the fixing surface 3a ... _{R o}
[0028]
The scratch is obtained as a locus left on the wafer 5 when the particles 10 existing on the polishing surface 2 a move as the lower plate 2 and the plate 3 rotate. As shown in Figure 2 represents the location of the particle 10 in the vector R _d. Underline Characters marked with indicate a vector. R _d is moved together with the polishing surface 2a. Also representative of the position of the center _{O 2} of the plate in R _o.
[0029]
As shown in FIG. 3, since the wafer 5 is fixed to the plate 3, the scratch trajectory to be obtained is desired to be obtained by (x, y) coordinates. As shown in FIG. 2, a vector drawn from the center O ₂ of the plate 3 to the particle 10 is expressed as a component r _d ′ in fixed (X, Y) coordinates, and moves with the rotation of the plate 3 (x represents those components denoted at y) coordinates r _d.
[0030]
During the time t, the lower board 2 rotates by an angle βt, and the particle 10 rotates with the rotation of the lower board 2. Further, the plate 3 rotates by an angle αt, and the wafer 5 rotates with the rotation of the plate 3. First, r _d and r _d ′ are rotated by an angle αt.

It becomes. Next, the expression for the position of the particle 10 is:

It becomes. Expanding and expressing this,
[Equation 3]

And solving for (x _d , y _d )
[Expression 4]

It becomes. Thus, as shown by the equations (4a) and (4b), the trajectory of the particle 10 can be obtained as a function of time t.
[0031]
[2] Calculation of parameters of polishing apparatus based on scratch In the above [1], the trajectory of the scratch was considered, but the parameters of the polishing apparatus can be calculated based on the scratch.
[0032]
FIG. 3 is a diagram showing r _d , ρ, and ρ _s considered in (x, y) coordinates.
[0033]
Assuming that scratches are formed on the wafer 5 after polishing, each value is defined as follows.
[0034]
And distance between a point on the scratch 20 with the center O ₂ of the fixing surface 3a ... r _d
-The radius of curvature at one point on the scratch 20 ... ρ
The distance between the center of curvature circle Q at one point on the scratch 20 and the center O ₂ of the fixed surface 3 a ... ρ _s
[0035]
The above equations (4a) and (4b) displayed in the (x, y) coordinates are parameter display of time t, and it is necessary to delete time t from both equations. For this purpose, the quantities r _d , ρ, ρ _s are introduced for one point of the scratch. From the above equations (4a) and (4b), the following equation (5) is obtained. However, ξ = R _d / R _o and ζ = (α−β) / α.
[Equation 5]

[0036]
In equations (5a), (5b), and (5c), r ^ _d , rho ^, rho ^ _s are calculated from curvature circle fitting using the coordinates of three points A, B, and C on the scratch on the wafer. The Therefore, ζ and ξ can be solved from the above equations (5a), (5b), and (5c). In this calculation, since a sixth-order equation of ζ is obtained, there can be a maximum of six solutions of ζ. For example, the Newton-Raphson method is used for this solution. Using ζ and ξ thus obtained, ζ = (α−β) / α and ξ = R _d / R _o can be solved to obtain β / α and R _d .
[0037]
[3] How to determine the radius of curvature ρ, etc. Next, how to determine the above-mentioned r _d , ρ, ρ _s will be described.
[0038]
4 rd, [rho, is a diagram illustrating how to obtain ρ _s, r _d was considered in a fixed coordinate system on the wafer _5, [rho, shows a [rho _s.
[0039]
Since the scratch trajectory is not actually a circle, the radius of curvature ρ is defined for a point on the scratch. Therefore, as shown in FIG. 4, when the curvature circle center Q (x _o , y _o ) is obtained from the coordinates of the three points A, B, C on the scratch, the curvature is at the point B, which is the center of the three points. Attach.
[0040]
The center of curvature Q (x _o , y _o ) is defined by three points A (x _A , y _A ), B (x _B , y _B ), C (x _C , y _C ) in the coordinate system fixed to the wafer 5. It is expressed as follows.
[Formula 6]

From equations (6a) and (6b), ρ corresponding to point B is
[Expression 7]

It is calculated by.
[0041]
Further, to obtain [rho _s, r _d is converted from a fixed coordinate system on the wafer 5 to the fixed coordinate system to the plate 3 is required. When the distance between the center _{O 2} and the center _{O 3} of the wafer 5 of plate 3 is defined as _{r wc,} including the conversion from FIG. 4, ρ _{s, r d} is
[Equation 8]

It is calculated by.
[0042]
[4] Embodiment In fixing the wafer 5 to the plate 3 in each polishing step, it is necessary to determine the position of the wafer 5 with respect to the plate 3. Therefore, the wafer 5 is fixed to the fixed surface 3 a of the plate 3 such that the notch and orientation flat of the wafer 5 are directed in a predetermined direction with respect to the plate 3. After fixing the wafer 5, the plate 3 is placed on the polishing surface 2a of the lower plate 2, and the lower plate 2 and the plate 3 are rotated to polish the wafer 5. Thus, a plurality of polishing steps are performed.
[0043]
When the entire polishing process is completed, each wafer 5 is measured with a particle counter or the like, and if there is a scratch, the position is acquired.
[0044]
Using the acquired scratch position, r _d , ρ, and ρ _s are obtained by the method described in [3] above, and ζ is obtained by the method described in [2] to obtain β / α. Similarly, ξ is obtained to obtain R _d .
[0045]
The inventors have realized the present invention by creating software. This software reads a predetermined coordinate data file measured by a particle counter, displays an LPD map, and displays a scratch portion of the LPD on the screen. Further, by specifying three points on the scratch displayed on the LPD map, β / α, R _d , ρ, and ρ _s of the scratch are calculated.
[0046]
According to the present invention, it is possible to identify a polishing apparatus related to scratch formation by analyzing scratches formed on a wafer. As a result, the polishing process can be improved.
[0047]
[5] Analysis example 1
Next, an example in which a polishing apparatus related to scratch formation is specified based on β / α obtained by the present invention will be described.
[0048]
As a result of measuring the wafer after polishing the wafer in the four stages of polishing processes (first to fourth polishing processes), a scratch as shown in FIG. 5 was formed. Different polishing apparatuses are used in the respective polishing steps. As shown in Table 1, β / α of each polishing apparatus is within the range of the upper limit (β / α) _max and the lower limit (β / α) _min . include.
[0049]
[Table 1]

[0050]
When the scratches 21 to 23 of the wafer 5 shown in FIG. 5 were analyzed according to the present invention, the results shown in Table 2 were obtained.
[0051]
[Table 2]

[0052]
As shown in Table 2, the value of β / α obtained based on the scratch 21 is “0.803691”. Looking at Table 1, this value is included in the range of β / α in the fourth polishing step. Therefore, it can be specified that the polishing apparatus used in the fourth polishing step is involved in forming the scratch 21.
[0053]
Further, as shown in Table 2, the value of β / α obtained based on the scratch 22 is “0.895741”. Looking at Table 1, this value is included in the range of β / α in the third polishing step. Therefore, it can be specified that the polishing apparatus used in the third polishing step is involved in forming the scratch 22.
[0054]
Further, as shown in Table 2, the value of β / α obtained based on the scratch 23 is “0.603993”. Looking at Table 1, this value is included in the range of β / α in the fourth polishing step. Therefore, it can be specified that the polishing apparatus used in the fourth polishing step is involved in forming the scratch 23.
[0055]
In the example shown in Table 1, β / α (0.848 to 0.875) in the second polishing step is included as part of β / α (0.583 to 0.875) in the fourth polishing step. In such a case, each β / α is obtained based on the scratches of a plurality of wafers processed in the same batch, and the β / α distribution is examined. Whether it was formed in the process can be specified. For example, if the β / α distribution is concentrated in the range of 0.848 to 0.875, it can be specified that the polishing apparatus used in the second polishing step is involved in the formation of the scratch, and the β / α distribution is in the range of 0.583 to 0.875. If it is dispersed, it can be specified that the polishing apparatus used in the fourth polishing step is involved in the formation of scratches.
[0056]
[6] Analysis example 2
Next, an example of estimating a particle generation source by using Rd obtained by the present invention will be described.
[0057]
FIGS. 6A to 6C are diagrams showing the distribution of _Rd obtained when analyzing each scratch formed on a predetermined number of wafers.
[0058]
After polishing the predetermined number of wafers, the determining the distribution of R _d seeking R _d on the basis of the scratches formed on the wafer, the results shown in FIG. 6 roughly (a) ~ (c) is obtained.
[0059]
If the shown distribution was obtained FIG. 6 (a), the words small R _d as power is large, when the frequency the larger R _d is small, it contains impurities in the slurry supplied to the vicinity of the center of the cross It is estimated that
[0060]
Also if the distribution as shown in FIG. 6 (b) is obtained, that is, when power regardless of R _d is substantially equal to, dust or the like is estimated to be uniformly lowered to cross from the atmosphere.
[0061]
In addition, when the distribution shown in FIG. 6C is obtained, that is, when the frequency at one point of R _d and the vicinity thereof is large, dust or the like is generated at a specific portion of the lower board, that is, at a position away from R _d. It is estimated that
[Brief description of the drawings]
FIG. 1 is a diagram showing an entire polishing apparatus and parts thereof.
FIG. 2 is a diagram showing a coordinate system (X, Y) whose origin is the center O _{1 of the} polishing surface and a coordinate system (x, y) whose origin is the center O _{2 of the} fixed surface.
FIG. 3 is a diagram showing r _d , ρ, and ρ _s considered in (x, y) coordinates.
FIG. 4 is a diagram for explaining how to obtain r _d , ρ, and ρ _s ;
FIG. 5 is a view showing a wafer on which scratches are formed.
FIGS. 6A to 6C are diagrams showing distributions of R _d obtained when analyzing each scratch formed on a predetermined number of wafers.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Polishing apparatus 2 Lower board 2a Polishing surface 3 Plate 3a Fixed surface 5 Wafer

Claims (3)

A plate having a rotation center at one point on a fixed surface for fixing the wafer and a lower plate having a rotation point at one point on the polishing surface for polishing the wafer, and fixing the wafer around the rotation center of the fixed surface Then, when a plurality of polishing apparatuses that polish a wafer by placing a plate around the rotation center of the polishing surface and rotating the lower plate and the plate are used, the solid foreign matter adhered to the polishing surface In the wafer scratch analysis method for analyzing the scratch formed on the wafer,
Before each polishing, fixing step for fixing the wafer relative to the plate;
After a plurality of polishings, in the wafer removed from the plate, the scratch formed on the wafer is measured, and using the measured three positions on the scratch and the scratch trajectory formula, the rotational speed of the plate and the A ratio calculating step for determining the ratio of the rotation speed of the lower board;
And a specifying step of specifying a polishing apparatus that has formed a scratch on the wafer using the ratio obtained in the ratio calculating step. A distance calculating step of calculating a distance Rd between the center of rotation of the polishing surface and the solid foreign matter in the polishing apparatus in which a scratch is formed on the wafer after the specific step;
The wafer scratch according to claim 1, further comprising: an estimation step of performing the distance calculation step for each of a plurality of scratches and estimating a solid foreign matter generation source using a distribution of the solid foreign matter distance Rd. analysis method. In the ratio calculation step, the distance ρs between the center of curvature circle at one point on the scratch and the rotation center of the fixed surface, the distance rd between one point on the scratch and the rotation center of the fixed surface, and the curvature at one point on the scratch. The wafer scratch analysis method according to claim 1, wherein a radius ρ is obtained, and a ratio between a rotational speed of the plate and a rotational speed of the lower plate is obtained.

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