JP7067524B2 - Wafer flatness measuring machine selection method and measuring method - Google Patents

Wafer flatness measuring machine selection method and measuring method Download PDF

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JP7067524B2
JP7067524B2 JP2019077332A JP2019077332A JP7067524B2 JP 7067524 B2 JP7067524 B2 JP 7067524B2 JP 2019077332 A JP2019077332 A JP 2019077332A JP 2019077332 A JP2019077332 A JP 2019077332A JP 7067524 B2 JP7067524 B2 JP 7067524B2
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理 大西
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Shin Etsu Handotai Co Ltd
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本発明は、ウェーハのフラットネス測定機の選定方法及びそれにより選定されたフラットネス測定機を用いたウェーハのフラットネスの測定方法に関する。 The present invention relates to a method for selecting a wafer flatness measuring machine and a method for measuring wafer flatness using the flatness measuring machine selected thereby.

Ｓｉ単結晶ウェーハは集積回路の原料として広く用いられている。集積回路に求められる性能が向上するにつれて、Ｓｉ単結晶ウェーハの厚み分布（平坦度）もより一層良好なものが求められる。Ｓｉ単結晶ウェーハの平坦度測定には、ＫＬＡ－Ｔｅｎｃｏｒ社（ケーエルエー・テンコール社）のＷａｆｅｒＳｉｇｈｔに代表されるような、Ｓｉ単結晶ウェーハの表面と裏面の変位量を個別に計測し、平坦度として算出される測定機が多く用いられている（特許文献１）。 Si single crystal wafers are widely used as raw materials for integrated circuits. As the performance required for integrated circuits improves, the thickness distribution (flatness) of Si single crystal wafers is also required to be even better. For the flatness measurement of the Si single crystal wafer, the displacement amount of the front surface and the back surface of the Si single crystal wafer, as represented by WaferSight of KLA-Tencor, is individually measured and used as the flatness. Many calculated measuring instruments are used (Patent Document 1).

測定機の精度や機差もデザインルールの狭小化に伴い向上してきた。しかしながら、Ｓｉ単結晶ウェーハに求められる平坦度が一層タイトになるにつれ、製造装置の工程能力に余力が無くなり、フラットネス測定機の測定精度の機差がＳｉ単結晶ウェーハの歩留まりを左右する状況となっている。 The accuracy and difference of measuring machines have also improved with the narrowing of design rules. However, as the flatness required for Si single crystal wafers becomes tighter, the process capacity of the manufacturing equipment becomes scarce, and the difference in measurement accuracy of the flatness measuring machine affects the yield of Si single crystal wafers. It has become.

特開２０１３－２３８５９５号公報Japanese Unexamined Patent Publication No. 2013-238595

一定の歩留まりを確保するため、特に悪い検査値を出力する装置を用いないことも可能だが、根拠のない測定機選定となるため、本来必要とされる真の平坦度を知ることもできなくなってしまう。更にそれによって、生産技術開発の方向性をも見失うこととなる。よって、真の値に近い値を出力する測定機を選別し機差を低減することが必要となるが、現段階でその術はない。 In order to secure a certain yield, it is possible not to use a device that outputs particularly bad test values, but since the selection of measuring instruments is unfounded, it becomes impossible to know the true flatness that is originally required. It ends up. Furthermore, by doing so, the direction of production technology development will be lost. Therefore, it is necessary to select a measuring machine that outputs a value close to the true value and reduce the machine difference, but there is no such technique at this stage.

本発明は、このような事情に鑑みてなされたもので、複数のフラットネス測定機のなかから測定精度の高いフラットネス測定機を選定し、信頼性及び測定精度の高いウェーハの平坦度測定を可能にするウェーハのフラットネス測定機の選定方法を提供することを目的とする。 The present invention has been made in view of such circumstances, and a flatness measuring machine having high measurement accuracy is selected from a plurality of flatness measuring machines to measure the flatness of a wafer having high reliability and measurement accuracy. It is an object of the present invention to provide a method for selecting a flatness measuring machine for a wafer, which enables it.

上記目的を達成するために、本発明は、複数のフラットネス測定機の中から測定精度の高いフラットネス測定機を選定する方法であって、
予めフラットネスの異なる複数のウェーハを準備し、
該複数のウェーハの厚み分布を、前記複数のフラットネス測定機において、それぞれ複数回測定し、
該複数回測定した複数のウェーハの厚み分布から、それぞれのウェーハの厚み分布の差分プロファイル、該差分プロファイルのＬｉｎｅ ＳＦＱＲ、前記測定毎のＥＳＦＱＲの少なくともいずれかの値を算出し、
前記差分プロファイルの前記複数のウェーハの平均プロファイル中の最大値と最小値の差、前記Ｌｉｎｅ ＳＦＱＲの最大値の前記複数のウェーハの平均値、前記ＥＳＦＱＲの前記測定毎の最大値の前記複数のウェーハの平均値の少なくともいずれかが所定の値より小さいフラットネス測定機、及び／又は、
前記ＥＳＦＱＲのうち、前記複数回測定において得られた前記ＥＳＦＱＲ同士の相関関係から、相関度が所定の値より大きいフラットネス測定機、
を選ぶことで、測定精度の高い測定機を選定することを特徴とするウェーハのフラットネス測定機の選定方法。 In order to achieve the above object, the present invention is a method of selecting a flatness measuring machine having high measurement accuracy from a plurality of flatness measuring machines.
Prepare multiple wafers with different flatness in advance,
The thickness distributions of the plurality of wafers were measured a plurality of times by the plurality of flatness measuring machines.
From the thickness distributions of the plurality of wafers measured a plurality of times, at least one of the difference profile of the thickness distribution of each wafer, the line SFQR of the difference profile, and the ESFQR for each measurement is calculated.
The difference between the maximum value and the minimum value in the average profile of the plurality of wafers of the difference profile, the average value of the plurality of wafers of the maximum value of the Line SFQR, and the plurality of wafers of the maximum value for each measurement of the ESFQR. A flatness measuring instrument in which at least one of the average values of is smaller than a predetermined value, and / or
Among the ESFQRs, a flatness measuring machine having a degree of correlation greater than a predetermined value based on the correlation between the ESFQRs obtained in the plurality of measurements.
A method for selecting a wafer flatness measuring machine, which is characterized by selecting a measuring machine with high measurement accuracy by selecting.

本発明のウェーハのフラットネス測定機の選定方法であれば、複数のフラットネス測定機のなかから、測定機の表面側と裏面側のシステムの個体差が少ない、測定精度の高いフラットネス測定機を選定することができるため、従来よりも信頼性及び測定精度の高いウェーハの平坦度測定が可能となる。また、そのような測定機を用いて測定を行えば、ウェーハの平坦度測定の機差を低減することが可能となる。 According to the method for selecting the flatness measuring machine for the wafer of the present invention, the flatness measuring machine having high measurement accuracy has little individual difference between the front side and the back side systems of the measuring machine from among a plurality of flatness measuring machines. Therefore, it is possible to measure the flatness of the wafer with higher reliability and measurement accuracy than before. Further, if the measurement is performed using such a measuring machine, it is possible to reduce the machine difference in the flatness measurement of the wafer.

このとき、前記複数のフラットネス測定機において、それぞれ複数回測定する際に、前記ウェーハを表裏反転させる前と後でそれぞれ１回以上測定することが好ましい。 At this time, when measuring a plurality of times in each of the plurality of flatness measuring machines, it is preferable to perform the measurement at least once before and after the wafer is turned upside down.

このような方法であれば、より確実に測定精度の高い測定機を選定することが可能となる。 With such a method, it is possible to more reliably select a measuring machine with high measurement accuracy.

また、前記複数のフラットネス測定機において、それぞれ複数回測定する際に、前記ウェーハを回転させることで投入角度を変更して複数回測定することが好ましい。 Further, in the plurality of flatness measuring machines, when each measurement is performed a plurality of times, it is preferable to rotate the wafer to change the loading angle and perform the measurement a plurality of times.

このような方法であっても、より確実に測定精度の高い測定機を選定することが可能となる。 Even with such a method, it is possible to more reliably select a measuring machine with high measurement accuracy.

また、本発明はウェーハのフラットネス測定機の選定方法で選定されたフラットネス測定機を用いてウェーハのフラットネスを測定することを特徴とするウェーハのフラットネスの測定方法を提供する。 Further, the present invention provides a method for measuring the flatness of a wafer, which comprises measuring the flatness of a wafer by using the flatness measuring machine selected in the method for selecting a flatness measuring machine for a wafer.

このようなウェーハのフラットネスの測定方法であれば、測定精度の高いフラットネス測定機を用いて測定を行うことができるため、信頼性及び測定精度の高いウェーハの平坦度測定が可能である。 With such a method for measuring the flatness of a wafer, since the measurement can be performed using a flatness measuring machine having high measurement accuracy, it is possible to measure the flatness of the wafer with high reliability and measurement accuracy.

本発明のウェーハのフラットネス測定機の選定方法であれば、複数のフラットネス測定機のなかから、測定機の表面側と裏面側のシステムの個体差が少ない、測定精度の高いフラットネス測定機を選定することができるため、従来よりも信頼性及び測定精度の高いウェーハの平坦度測定が可能となる。また、そのような測定機を用いて測定を行えば、ウェーハの平坦度測定の機差を低減して精度の高い測定をすることが可能となる。 According to the method for selecting the flatness measuring machine for the wafer of the present invention, the flatness measuring machine having high measurement accuracy has little individual difference between the front side and the back side systems of the measuring machine from among a plurality of flatness measuring machines. Therefore, it is possible to measure the flatness of the wafer with higher reliability and measurement accuracy than before. Further, if the measurement is performed using such a measuring machine, it is possible to reduce the machine difference in the flatness measurement of the wafer and perform the measurement with high accuracy.

ＥＳＦＱＲｍａｘの平均値の測定機平均からのずれを示す図である。It is a figure which shows the deviation from the measuring machine average of the average value of ESFQRmax. ノッチ角度毎のＥＳＦＱＲｍａｘの全ウェーハの平均値の測定機平均からのずれを示す図である。It is a figure which shows the deviation from the measuring machine average of the average value of all wafers of ESFQRmax for each notch angle. 一般的なウェーハのフラットネス測定機を示す概略図である。It is a schematic diagram which shows the flatness measuring machine of a general wafer. テストウェーハのシェイプと表裏反転する前と後の厚み分布の差分プロファイル（ΔＴＨＫ）の関係を示す図である。It is a figure which shows the relationship between the shape of a test wafer and the difference profile (ΔTHK) of the thickness distribution before and after inverting. それぞれの測定機の通常測定時のＥＳＦＱＲと反転測定時のＥＳＦＱＲとの自己相関を示す図である。It is a figure which shows the autocorrelation of ESFQR at the time of normal measurement and ESFQR at the time of inversion measurement of each measuring machine.

以下、本発明について詳細に説明するが、本発明はこれらに限定されるものではない。 Hereinafter, the present invention will be described in detail, but the present invention is not limited thereto.

上記のように、ウェーハのフラットネス測定機には測定精度の機差が存在し、そのような機差を示す複数のフラットネス測定機のなかから、真の値に近い値を出力する測定機を選別することは困難であった。 As described above, there is a difference in measurement accuracy among wafer flatness measuring machines, and among a plurality of flatness measuring machines showing such a difference, a measuring machine that outputs a value close to the true value. Was difficult to sort out.

本発明者は、創意工夫を重ねた結果、複数回測定した複数のウェーハの厚み分布から、それぞれのウェーハの厚み分布の差分プロファイル、差分プロファイルのＬｉｎｅ ＳＦＱＲ、測定毎のＥＳＦＱＲの少なくともいずれかの値を算出し、差分プロファイルの複数のウェーハの平均プロファイル中の最大値と最小値の差、Ｌｉｎｅ ＳＦＱＲの最大値の複数のウェーハの平均値、ＥＳＦＱＲの測定毎の最大値の複数のウェーハの平均値の少なくともいずれかが所定の値より小さい、及び／又は、ＥＳＦＱＲ同士の相関度が所定の値より大きいフラットネス測定機を選べば、測定精度の高い測定機を選定することができることを見出し、本発明を完成させるに至った。 As a result of repeated ingenuity, the present inventor has obtained at least one of the difference profile of the thickness distribution of each wafer, the line SFQR of the difference profile, and the ESFQR for each measurement from the thickness distribution of a plurality of wafers measured a plurality of times. The difference between the maximum and minimum values in the average profile of multiple wafers in the difference profile, the average value of multiple wafers with the maximum value of Line SFQR, and the average value of multiple wafers with the maximum value for each measurement of ESFQR. We have found that if at least one of the above is smaller than a predetermined value and / or a flatness measuring machine in which the degree of correlation between ESFQRs is larger than a predetermined value is selected, a measuring machine with high measurement accuracy can be selected. The invention was completed.

即ち、本発明は、複数のフラットネス測定機の中から測定精度の高いフラットネス測定機を選定する方法であって、
予めフラットネスの異なる複数のウェーハを準備し、
該複数のウェーハの厚み分布を、前記複数のフラットネス測定機において、それぞれ複数回測定し、
該複数回測定した複数のウェーハの厚み分布から、それぞれのウェーハの厚み分布の差分プロファイル、該差分プロファイルのＬｉｎｅ ＳＦＱＲ、前記測定毎のＥＳＦＱＲの少なくともいずれかの値を算出し、
前記差分プロファイルの前記複数のウェーハの平均プロファイル中の最大値と最小値の差、前記Ｌｉｎｅ ＳＦＱＲの最大値の前記複数のウェーハの平均値、前記ＥＳＦＱＲの前記測定毎の最大値の前記複数のウェーハの平均値の少なくともいずれかが所定の値より小さいフラットネス測定機、及び／又は、
前記ＥＳＦＱＲのうち、前記複数回測定において得られた前記ＥＳＦＱＲ同士の相関関係から、相関度が所定の値より大きいフラットネス測定機、
を選ぶことで、測定精度の高い測定機を選定することを特徴とするウェーハのフラットネス測定機の選定方法である。 That is, the present invention is a method of selecting a flatness measuring machine having high measurement accuracy from a plurality of flatness measuring machines.
Prepare multiple wafers with different flatness in advance,
The thickness distributions of the plurality of wafers were measured a plurality of times by the plurality of flatness measuring machines.
From the thickness distributions of the plurality of wafers measured a plurality of times, at least one of the difference profile of the thickness distribution of each wafer, the line SFQR of the difference profile, and the ESFQR for each measurement is calculated.
The difference between the maximum value and the minimum value in the average profile of the plurality of wafers of the difference profile, the average value of the plurality of wafers of the maximum value of the Line SFQR, and the plurality of wafers having the maximum value for each measurement of the ESFQR. A flatness measuring instrument in which at least one of the average values of is smaller than a predetermined value, and / or
Among the ESFQRs, a flatness measuring machine having a degree of correlation greater than a predetermined value based on the correlation between the ESFQRs obtained in the plurality of measurements.
This is a method for selecting a wafer flatness measuring machine, which is characterized in that a measuring machine having high measurement accuracy is selected by selecting.

このようなウェーハのフラットネス測定機の選定方法であれば、複数のフラットネス測定機のなかから、測定機の表面側と裏面側のシステムの個体差が少ない、測定精度の高いフラットネス測定機を選定することができるため、従来よりも信頼性及び測定精度の高いウェーハの平坦度測定が可能となる。また、そのような測定機を用いて測定を行えば、ウェーハの平坦度測定の機差を低減することが可能となる。 With this method of selecting a wafer flatness measuring machine, among multiple flatness measuring machines, there is little individual difference between the systems on the front side and the back side of the measuring machine, and the flatness measuring machine with high measurement accuracy. Therefore, it is possible to measure the flatness of the wafer with higher reliability and measurement accuracy than before. Further, if the measurement is performed using such a measuring machine, it is possible to reduce the machine difference in the flatness measurement of the wafer.

本発明のウェーハのフラットネス測定機の選定方法では、まず、予めフラットネスの異なる複数のウェーハを準備する。 In the method for selecting a wafer flatness measuring machine of the present invention, first, a plurality of wafers having different flatness are prepared in advance.

次に、複数のウェーハの厚み分布を、複数のフラットネス測定機において、それぞれ複数回測定する。ここで、上記のようにそれぞれ複数回測定する際に、ウェーハを表裏反転させる前と後とでそれぞれ１回以上測定することとすることができる。また、それぞれ複数回測定する際に、ウェーハを回転させることで投入角度を変更して複数回測定することもできる。これらの方法であれば、より確実に測定精度の高い測定機を選定することが可能となる。 Next, the thickness distribution of the plurality of wafers is measured a plurality of times by a plurality of flatness measuring machines. Here, when the measurement is performed a plurality of times as described above, the measurement can be performed once or more before and after the wafer is turned upside down. Further, when each measurement is performed a plurality of times, the loading angle can be changed by rotating the wafer to perform the measurement a plurality of times. With these methods, it is possible to more reliably select a measuring machine with high measurement accuracy.

次に、複数回測定した複数のウェーハの厚み分布から、それぞれのウェーハの厚み分布の差分プロファイル、該差分プロファイルのＬｉｎｅ ＳＦＱＲ、測定毎のＥＳＦＱＲの少なくともいずれかの値を算出する。
そして、差分プロファイルの複数のウェーハの平均プロファイル中の最大値と最小値の差、Ｌｉｎｅ ＳＦＱＲの最大値の複数のウェーハの平均値、ＥＳＦＱＲの測定毎の最大値の複数のウェーハの平均値の少なくともいずれかが所定の値より小さいフラットネス測定機、及び／又は、ＥＳＦＱＲのうち、複数回測定において得られたＥＳＦＱＲ同士の相関関係から、相関度が所定の値より大きいフラットネス測定機を選ぶことで、測定精度の高い測定機を選定する。 Next, at least one of the difference profile of the thickness distribution of each wafer, the Line SFQR of the difference profile, and the ESFQR for each measurement is calculated from the thickness distributions of the plurality of wafers measured a plurality of times.
Then, at least the difference between the maximum value and the minimum value in the average profile of the plurality of wafers of the difference profile, the average value of the plurality of wafers of the maximum value of Line SFQR, and the average value of the plurality of wafers of the maximum value for each measurement of ESFQR. Select a flatness measuring machine whose degree of correlation is larger than a predetermined value from the correlation between ESFQRs obtained in multiple measurements among the flatness measuring machines in which one is smaller than a predetermined value and / or ESFQR. Then, select a measuring machine with high measurement accuracy.

以下、ウェーハを表裏反転させる前と後でそれぞれ１回ずつ測定する場合を例として、より詳細に説明するが、それぞれのウェーハについて複数回測定すれば、測定方法、回数は限定されるものではない。 Hereinafter, a case of measuring once before and after inverting the wafer will be described in more detail, but if each wafer is measured a plurality of times, the measurement method and the number of times are not limited. ..

ウェーハの平坦度を測定する際には、ウェーハの表裏面の変位量を個別に計測する必要がある。図３は一般的なウェーハのフラットネス測定機を示す概略図である。通常は、ウェーハＷの表面はフラットネス測定機１００の表面側のシステム１０１で、裏面は裏面側のシステム１０２でそれぞれ変位量を測定し、両者の差から厚みの平坦度を算出している。 When measuring the flatness of a wafer, it is necessary to individually measure the amount of displacement on the front and back surfaces of the wafer. FIG. 3 is a schematic view showing a general wafer flatness measuring machine. Normally, the front surface of the wafer W is measured by the system 101 on the front surface side of the flatness measuring machine 100, and the back surface is measured by the system 102 on the back surface side, respectively, and the flatness of the thickness is calculated from the difference between the two.

これに対して、ウェーハを表裏反転させた後の測定は、ウェーハを反転させてウェーハの表面を裏面側のシステムで、ウェーハの裏面を表面側のシステムで変位量を測定し、両者の変量の差から厚みの平坦度を算出する。ウェーハの厚みデータはｒ－ｔｈｅｔａ（θ）座標系で表現することができるが、表裏反転させた後の測定の厚み平坦度を出力する際には、反転測定を考慮して、ウェーハの厚みデータのｔｈｅｔａの位相を反転させればよい。 On the other hand, in the measurement after inverting the wafer, the displacement is measured by inverting the wafer and using the system on the back side of the wafer and the system on the front side of the back of the wafer. The flatness of the thickness is calculated from the difference. Wafer thickness data can be expressed in the r-theta (θ) coordinate system, but when outputting the thickness flatness of the measurement after flipping the front and back, the wafer thickness data is taken into consideration for the flip measurement. The phase of theta may be inverted.

次に、差分プロファイルの複数のウェーハの平均プロファイル中の最大値と最小値の差、Ｌｉｎｅ ＳＦＱＲの最大値の複数のウェーハの平均値、ＥＳＦＱＲの測定毎の最大値の複数のウェーハの平均値、複数回測定において得られたＥＳＦＱＲ同士の相関関係の相関度の基準によりフラットネス測定機を選定する方法について説明する。これらの基準のうち、少なくともいずれか一つの基準によりフラットネス測定機を選定する。 Next, the difference between the maximum value and the minimum value in the average profile of the multiple wafers of the difference profile, the average value of the multiple wafers of the maximum value of Line SFQR, the average value of the multiple wafers of the maximum value for each measurement of ESFQR, A method of selecting a flatness measuring machine based on the criteria of the degree of correlation between ESFQRs obtained in multiple measurements will be described. A flatness measuring machine is selected based on at least one of these criteria.

［差分プロファイルの平均プロファイル中の最大値と最小値の差］
上記のようにして表裏反転させる前の通常測定による厚みの平坦度（厚み分布）と表裏反転させた後のウェーハ反転測定による厚みの平坦度を比較した場合、表裏反転とはいえども同一の測定機で測定しているため、測定結果は同一となり、両者の差は０になることが望ましい。しかしながら、一般的なフラットネス測定機は、ウェーハの表裏面を個別に測定する表面側と裏面側のシステムに個体差があることから、この差は必ずしも０にならないことが多く、この差の大きさは大小さまざまである。 [Difference between maximum and minimum values in the average profile of the difference profile]
When comparing the flatness of the thickness (thickness distribution) by the normal measurement before the front and back inversion and the flatness of the thickness by the wafer inversion measurement after the front and back inversion as described above, the same measurement is performed even if the front and back are inverted. Since the measurement is performed by the machine, it is desirable that the measurement results are the same and the difference between the two is zero. However, in a general flatness measuring machine, since there is an individual difference between the front side and the back side systems that individually measure the front and back surfaces of the wafer, this difference is often not always 0, and the difference is large. The size varies.

また、このような表裏反転測定によるウェーハの厚み分布から算出される差分プロファイルは、元々のウェーハのシェイプと相関が有ることが分かり、このことから、フラットネス測定機の表裏面の各変位量測定システムのウェーハシェイプに対する変位量測定のダイナミックレンジ等によるシステム差を表すことができることに想到した。以上のことから、通常測定とウェーハ反転測定との厚み分布の差分プロファイルの最大値と最小値の差（高低差）から測定機の良し悪しを判断することができる。例えば、差分プロファイルの高低差が０に近い測定機は、測定したウェーハの差分プロファイルとシェイプとの相関度が低く、測定精度が高いといえ、差分プロファイルの高低差が大きい測定機は、測定したウェーハの差分プロファイルとシェイプとの相関度が高く測定精度が低いといえる。
従って、複数のフラットネス測定機の中から、差分プロファイルの複数のウェーハの平均プロファイルをとり、その平均プロファイル中の最大値と最小値の差が所定の値よりも小さいフラットネス測定機を選ぶことで、差分プロファイルの最大値と最小値の差が平均的に小さい、即ち、測定精度の高い測定機を選定することができる。ここで、平均プロファイルは、複数のウェーハの厚みデータのｒ－ｔｈｅｔａ（θ）座標に基づいて、複数のウェーハの差分プロファイルの対応する座標の平均をとればよい。 In addition, it was found that the difference profile calculated from the thickness distribution of the wafer by such front-back inversion measurement has a correlation with the original wafer shape, and from this, each displacement amount measurement of the front and back surfaces of the flatness measuring machine was found. I came up with the idea that it is possible to express the system difference due to the dynamic range of displacement measurement for the wafer shape of the system. From the above, it is possible to judge the quality of the measuring machine from the difference (height difference) between the maximum value and the minimum value (height difference) of the difference profile of the thickness distribution between the normal measurement and the wafer inversion measurement. For example, a measuring machine in which the height difference of the difference profile is close to 0 has a low degree of correlation between the measured difference profile and the shape, and the measurement accuracy is high. It can be said that the degree of correlation between the difference profile of the wafer and the shape is high and the measurement accuracy is low.
Therefore, from among a plurality of flatness measuring machines, take an average profile of a plurality of wafers having a difference profile, and select a flatness measuring machine in which the difference between the maximum value and the minimum value in the average profile is smaller than a predetermined value. Therefore, it is possible to select a measuring machine having a small difference between the maximum value and the minimum value of the difference profile on average, that is, having high measurement accuracy. Here, the average profile may be the average of the corresponding coordinates of the difference profiles of the plurality of wafers based on the r-theta (θ) coordinates of the thickness data of the plurality of wafers.

差分プロファイルと元々のウェーハのシェイプとの相関、及び、測定機の測定精度の機差が生じることについては、以下のような理由が考えられる。例えば、ＷａｆｅｒＳｉｇｈｔに代表されるような光学干渉式の変位量測定機の場合、ウェーハそのもののシェイプ（ソリや凹凸）によってウェーハ像を正確に結像出来ないことが起こりえる。また、フラットネス測定機においてウェーハを保持するグリッパーは力学的にウェーハを変形させることが知られているため、グリッパーによる変形とウェーハそのもののシェイプが干渉した場合、そのソリ量や凹凸は更に大きくなることが容易に想像できる。更に、光学干渉式の測定においては、測定対象のウェーハよりも大きな口径のレンズやミラーといった光学部品が用いられるが、これらの形状個体差がウェーハシェイプと干渉し、理想的な結像が行えない部位がウェーハには存在すると考えられる。このような不確定要素によって、差分プロファイルと元々のウェーハのシェイプとの相関、測定機の測定精度の機差は発生すると考えられる。また、これらのことから、測定精度の低い測定機では、本来一致するはずの、ウェーハを表裏反転させる前と後の厚み分布が一致せず、差分プロファイルを算出してもウェーハのシェイプの影響が残り、差分プロファイルの複数のウェーハの平均プロファイル中の最大値と最小値の差が大きくなってしまうと考えられる。 The following reasons can be considered for the correlation between the difference profile and the original wafer shape and the difference in measurement accuracy of the measuring machine. For example, in the case of an optical interferometry type displacement measuring machine such as WaferSight, it may not be possible to accurately image a wafer image due to the shape (warp or unevenness) of the wafer itself. Further, since it is known that the gripper that holds the wafer in the flatness measuring machine dynamically deforms the wafer, if the deformation by the gripper interferes with the shape of the wafer itself, the amount of warpage and unevenness become larger. Can be easily imagined. Further, in the optical interference type measurement, optical components such as lenses and mirrors having a diameter larger than that of the wafer to be measured are used, but these individual differences in shape interfere with the wafer shape, and ideal imaging cannot be performed. The site is considered to be present on the wafer. It is considered that such uncertainties cause a correlation between the difference profile and the original wafer shape, and a machine difference in the measurement accuracy of the measuring machine. In addition, from these facts, in a measuring machine with low measurement accuracy, the thickness distribution before and after flipping the wafer, which should originally match, does not match, and even if the difference profile is calculated, the influence of the wafer shape is affected. It is considered that the difference between the maximum value and the minimum value in the average profile of the plurality of wafers in the difference profile becomes large.

［Ｌｉｎｅ ＳＦＱＲの最大値の平均値］
この場合、上記のように、［通常測定による厚み分布のプロファイル］－［ウェーハ反転測定による厚み分布のプロファイル］の引き算から表裏反転測定における厚み分布の差分プロファイルを得、得られた差分プロファイルのＬｉｎｅ ＳＦＱＲの最大値（Ｌｉｎｅ ＳＦＱＲｍａｘ）を算出する。差分プロファイルのＬｉｎｅ ＳＦＱＲとは、例えば直径３００ｍｍのＳｉ単結晶ウェーハの場合、ｒ－ｔｈｅｔａ座標系で表現されたウェーハの差分プロファイルの角度１度毎に半径１１８ｍｍ～１４８ｍｍの差分プロファイルを出力したのちに、これに最小二乗線を適用した際の、最小二乗線からの差分プロファイルの変位のレンジ（Ｍａｘ－Ｍｉｎ）とすることができる。ひとつの円盤状データからは３６０個のＬｉｎｅ ＳＦＱＲが得られるが、その最大値がＬｉｎｅ ＳＦＱＲｍａｘとなる。
このように算出されたＬｉｎｅ ＳＦＱＲｍａｘも、上記差分プロファイルの複数のウェーハの平均プロファイル中の最大値と最小値の差と同様に、フラットネス測定機の表面側と裏面側のシステムの個体差やウェーハのシェイプが変位量測定に影響を及ぼしているかどうかの指標とすることができる。このため、複数のフラットネス測定機の中から、上記Ｌｉｎｅ ＳＦＱＲｍａｘの複数のウェーハの平均値が所定の値よりも小さいフラットネス測定機を選ぶことで測定精度の高い測定機を選定することができる。 [Average value of the maximum value of Line SFQR]
In this case, as described above, the difference profile of the thickness distribution in the front-back inversion measurement is obtained from the subtraction of [Profile of thickness distribution by normal measurement]-[Profile of thickness distribution by wafer inversion measurement], and the line of the obtained difference profile is obtained. The maximum value of SFQR (Line SFQRmax) is calculated. The line SFQR of the difference profile is, for example, in the case of a Si single crystal wafer having a diameter of 300 mm, after outputting the difference profile having a radius of 118 mm to 148 mm for each angle of the difference profile of the wafer expressed by the r-theta coordinate system. , The range of displacement of the difference profile from the minimum squared line (Max-Min) when the minimum squared line is applied to this. From one disk-shaped data, 360 Line SFQRs can be obtained, and the maximum value thereof is Line SFQRmax.
The Line SFQRmax calculated in this way is also the individual difference of the system on the front side and the back side of the flatness measuring machine and the wafer, as well as the difference between the maximum value and the minimum value in the average profile of the plurality of wafers of the above difference profile. It can be used as an index of whether or not the shape of is affecting the displacement measurement. Therefore, a measuring machine having high measurement accuracy can be selected by selecting a flatness measuring machine in which the average value of the plurality of wafers of the Line SFQRmax is smaller than a predetermined value from the plurality of flatness measuring machines. ..

［ＥＳＦＱＲの測定毎の最大値の平均値］
この場合、複数のウェーハの表裏反転させる前と後の厚み分布において、それぞれ厚み分布のＥＳＦＱＲの最大値（ＥＳＦＱＲｍａｘ）の平均値を算出する。ここでＥＳＦＱＲとは、例えば直径３００ｍｍのＳｉ単結晶ウェーハの場合、半径１１８ｍｍ～１４８ｍｍ、角度５度の領域における裏面基準の厚み分布に対して最小二乗面を適用し、最小二乗面からの変位のレンジ（Ｍａｘ－Ｍｉｎ）とすることができる。ひとつの円盤状の厚み分布のデータからは７２個のＥＳＦＱＲが得られるが、その最大値がＥＳＦＱＲｍａｘとなる。ＥＳＦＱＲｍａｘを、複数のウェーハについて表裏反転させる前と後とでそれぞれ算出し、それらのＥＳＦＱＲｍａｘの複数のウェーハの平均値を求める。
このように算出されたＥＳＦＱＲｍａｘの複数のウェーハの平均値も、上記と同様に、フラットネス測定機の表面側と裏面側のシステムの個体差やウェーハのシェイプが変位量測定に影響を及ぼしているかどうかの指標とすることができる。このため、複数のフラットネス測定機の中から、ＥＳＦＱＲｍａｘの複数のウェーハの平均値が所定の値よりも小さいフラットネス測定機を選ぶことで測定精度の高い測定機を選定することができる。 [Average value of maximum values for each measurement of ESFQR]
In this case, the average value of the maximum value (ESFQRmax) of the ESFQR of the thickness distribution is calculated for each of the thickness distributions before and after the front-to-back inversion of the plurality of wafers. Here, the ESFQR is, for example, in the case of a Si single crystal wafer having a diameter of 300 mm, the minimum squared surface is applied to the thickness distribution based on the back surface in a region having a radius of 118 mm to 148 mm and an angle of 5 degrees, and the displacement from the minimum squared surface is applied. It can be in the range (Max-Min). 72 ESFQRs can be obtained from the data of one disk-shaped thickness distribution, and the maximum value is ESFQRmax. ESFQRmax is calculated before and after flipping the front and back of a plurality of wafers, and the average value of the plurality of wafers of the ESFQRmax is obtained.
As for the average value of multiple wafers of ESFQRmax calculated in this way, does the individual difference between the front side and back side systems of the flatness measuring machine and the shape of the wafer affect the displacement measurement in the same manner as above? It can be used as an index. Therefore, a measuring machine having high measurement accuracy can be selected by selecting a flatness measuring machine in which the average value of the plurality of wafers of ESFQRmax is smaller than a predetermined value from the plurality of flatness measuring machines.

［ＥＳＦＱＲ同士の相関関係の相関度］
この場合、上記のように算出された表裏反転させる前と後のそれぞれの厚み分布のＥＳＦＱＲ同士の相関関係から、その相関度を求める。上記記載したように、表裏反転させた後の測定の厚み分布からＥＳＦＱＲを算出する際に、ｒ－ｔｈｅｔａ座標におけるｔｈｅｔａの位相を表裏反転させる前の通常測定と合わせるため、平坦度プロファイルデータおよびＥＳＦＱＲのｔｈｅｔａ座標を反転させ、表裏反転させる前と後のＥＳＦＱＲの自己相関を算出する。
同一ウェーハの対応する領域のＥＳＦＱＲは、表裏反転させる前後の異なる測定においても同一の値を示すはずであるため、測定精度が高い測定機であれば、複数回測定において得られたＥＳＦＱＲ同士の相関関係の相関度は高くなるはずである。このため、複数のフラットネス測定機の中から、上記相関度が所定の値よりも大きいフラットネス測定機を選ぶことで測定精度の高い測定機を選定することができる。 [Correlation degree of correlation between ESFQRs]
In this case, the degree of correlation is obtained from the correlation between the ESFQRs of the respective thickness distributions before and after the flipping calculated as described above. As described above, when calculating ESFQR from the thickness distribution of the measurement after flipping the front and back, the flatness profile data and ESFQR are used to match the phase of theta in the r-theta coordinates with the normal measurement before flipping the front and back. Theta coordinates of the above are inverted, and the autocorrelation of ESFQR before and after the inversion is calculated.
The ESFQRs in the corresponding regions of the same wafer should show the same value even in different measurements before and after flipping, so if the measuring machine has high measurement accuracy, the correlation between ESFQRs obtained in multiple measurements The degree of correlation of the relationship should be high. Therefore, it is possible to select a measuring machine having high measurement accuracy by selecting a flatness measuring machine having a correlation degree larger than a predetermined value from a plurality of flatness measuring machines.

また、複数のウェーハの厚み分布を、複数のフラットネス測定機において、それぞれ複数回測定する際に、ウェーハを回転させることで投入角度を変更して複数回測定する場合、差分プロファイルの複数のウェーハの平均プロファイルは、異なる角度間の差分プロファイルを算出し、それらを複数のウェーハについて平均すればよい。またこのとき、差分プロファイルのＬｉｎｅ ＳＦＱＲは、上記算出した異なる角度間の差分プロファイルを基に、上記記載の表裏反転測定時と同様に算出することができる。またこのとき、ＥＳＦＱＲの測定毎の最大値の平均値は、上記記載の表裏反転測定時と同様に算出することができ、ＥＳＦＱＲ同士の相関関係は、投入角度を考慮して、厚み分布のｔｈｅｔａ座標を回転させて、対応する領域のＥＳＦＱＲの相関関係を求めればよい。 Further, when the thickness distribution of a plurality of wafers is measured multiple times by a plurality of flatness measuring machines, when the loading angle is changed by rotating the wafer and the measurement is performed multiple times, a plurality of wafers having a difference profile are measured. For the average profile of, the difference profile between different angles may be calculated and averaged for a plurality of wafers. At this time, the Line SFQR of the difference profile can be calculated in the same manner as in the case of the front-back inversion measurement described above, based on the difference profile between the different angles calculated above. At this time, the average value of the maximum values for each measurement of ESFQR can be calculated in the same manner as in the case of the front-back inversion measurement described above, and the correlation between ESFQRs is theta of the thickness distribution in consideration of the charging angle. The coordinates may be rotated to obtain the correlation of ESFQR in the corresponding region.

また、上記の方法により、測定精度の高いフラットネス測定機に選定されなかったフラットネス測定機は、表裏反転測定等の複数回測定を行っても同一の平坦度の結果が出るように測定機の調整を行えばよい。また、調整後の測定機の評価については、上記と同様に、複数のウェーハの厚み分布を測定し、差分プロファイルの複数のウェーハの平均プロファイル中の最大値と最小値の差、Ｌｉｎｅ ＳＦＱＲの最大値の複数のウェーハの平均値、ＥＳＦＱＲの測定毎の最大値の複数のウェーハの平均値の少なくともいずれかが所定の値よりも小さいこと、及び／又は、複数回測定において得られたＥＳＦＱＲ同士の相関関係の相関度が所定の値よりも大きいことにより判断することができる。 In addition, the flatness measuring machine that was not selected as a flatness measuring machine with high measurement accuracy by the above method is a measuring machine so that the same flatness result can be obtained even if multiple measurements such as front-back inversion measurement are performed. You just have to make adjustments. Regarding the evaluation of the adjusted measuring machine, the thickness distribution of multiple wafers is measured in the same manner as above, the difference between the maximum value and the minimum value in the average profile of the multiple wafers of the difference profile, and the maximum line SFQR. At least one of the mean value of multiple wafers of the value, the mean value of multiple wafers of the maximum value for each measurement of ESFQR is smaller than a predetermined value, and / or the ESFQRs obtained by multiple measurements It can be determined by the fact that the degree of correlation of the correlation is larger than a predetermined value.

また、上記選定方法により選定されたフラットネス測定機を用いてウェーハのフラットネスを測定すれば、測定精度の高いフラットネス測定機を用いて測定を行うため、信頼性及び測定精度の高いウェーハの平坦度測定が可能となる。 Further, if the flatness of the wafer is measured using the flatness measuring machine selected by the above selection method, the measurement is performed using the flatness measuring machine having high measurement accuracy, so that the wafer has high reliability and measurement accuracy. Flatness measurement is possible.

以下、実施例を示し、本発明をより具体的に説明するが、本発明は下記の実施例に制限されるものではない。 Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited to the following examples.

［実施例１］
フラットネス測定機を５台（測定機（Ｍ／＃）Ａ～Ｅ）、この５台のフラットネス測定機から測定精度の高い測定器を選定するために用いる直径３００ｍｍのテストウェーハを１５枚準備した。この際、結晶スラブからウェーハを切り取る際に発生するソーマークや熱変形によるお椀状のシェイプを持つテストウェーハを用いた。 [Example 1]
Five flatness measuring machines (measuring machines (M / #) A to E), and 15 test wafers with a diameter of 300 mm used to select a measuring device with high measurement accuracy from these five flatness measuring machines are prepared. bottom. At this time, a test wafer having a bowl-shaped shape due to saw marks and thermal deformation generated when the wafer was cut from the crystal slab was used.

準備した１５枚のテストウェーハの表面をフラットネス測定機の表面側変位量測定システムでそれぞれ測定し、テストウェーハの裏面を裏面側変位量測定システムでそれぞれ測定し、表裏面の変位量の通常測定を行った。そして、両者の差分から、それぞれのテストウェーハの厚み分布を得、それぞれのテストウェーハのＥＳＦＱＲを算出した。ここでＥＳＦＱＲは、半径１１８ｍｍ～１４８ｍｍ、角度５度の領域における裏面基準の厚み分布に対して最小二乗面を適用したときの、最小二乗面からの変位のレンジ（Ｍａｘ－Ｍｉｎ）である。
また、上記と同様のテストウェーハの表面を上記と同様のフラットネス測定機の裏面側変位量測定システムで測定し、テストウェーハの裏面を表面側変位量測定システムで測定し、表裏面の変位量の反転測定を行った。そして、両者の差分から、それぞれのテストウェーハの反転測定における厚み分布を得、それぞれのテストウェーハの反転測定におけるＥＳＦＱＲを算出した。この際、ｒ－ｔｈｅｔａ座標におけるｔｈｅｔａの位相を通常測定と合わせるため、厚み分布およびＥＳＦＱＲのｔｈｅｔａ座標を反転させた。 The front surface of the prepared 15 test wafers is measured by the front surface displacement measurement system of the flatness measuring machine, the back surface of the test wafer is measured by the back surface displacement measurement system, and the displacement of the front and back surfaces is normally measured. Was done. Then, the thickness distribution of each test wafer was obtained from the difference between the two, and the ESFQR of each test wafer was calculated. Here, ESFQR is a range of displacement (Max-Min) from the least squares surface when the least squares surface is applied to the thickness distribution of the back surface reference in a region having a radius of 118 mm to 148 mm and an angle of 5 degrees.
Further, the front surface of the test wafer similar to the above is measured by the back surface side displacement measurement system of the flatness measuring machine similar to the above, the back surface of the test wafer is measured by the front surface side displacement measurement system, and the displacement amount of the front and back surfaces is measured. Inversion measurement was performed. Then, the thickness distribution in the inversion measurement of each test wafer was obtained from the difference between the two, and the ESFQR in the inversion measurement of each test wafer was calculated. At this time, in order to match the phase of theta in the r-theta coordinates with the normal measurement, the thickness distribution and theta coordinates of ESFQR were inverted.

上記通常測定及び反転測定を５台のフラットネス測定機で行った。 The above-mentioned normal measurement and inversion measurement were performed with five flatness measuring machines.

［通常測定による厚み分布のプロファイル］－［ウェーハ反転測定による厚み分布のプロファイル］の引き算から、それぞれのテストウェーハについて、通常測定と反転測定との厚み差分プロファイル（ΔＴＨＫ）を得、得られた差分プロファイルに対して外周３０ｍｍ、 ２ｍｍＥＥにおけるＬｉｎｅ ＳＦＱＲの最大値（Ｌｉｎｅ ＳＦＱＲｍａｘ）を算出した。ここでＬｉｎｅ ＳＦＱＲは、１度毎に半径１１８ｍｍ～１４８ｍｍの差分プロファイルを出力したのちに、これに最小二乗線を適用したときの、最小二乗線からの差分プロファイルの変位のレンジ（Ｍａｘ－Ｍｉｎ）である。ひとつの円盤状データからは３６０個のＬｉｎｅ ＳＦＱＲが得られるが、その最大値をＬｉｎｅ ＳＦＱＲｍａｘとした。
また、表裏反転時（通常測定及び反転測定）のＥＳＦＱＲの自己相関を算出した。 From the subtraction of [Profile of thickness distribution by normal measurement]-[Profile of thickness distribution by wafer inversion measurement], the thickness difference profile (ΔTHK) between normal measurement and inversion measurement was obtained for each test wafer, and the difference obtained. The maximum value (Line SFQRmax) of Line SFQR at an outer circumference of 30 mm and 2 mm EE was calculated with respect to the profile. Here, Line SFQR outputs a difference profile with a radius of 118 mm to 148 mm for each degree, and then applies the least squares line to this, and the range of displacement of the difference profile from the least squares line (Max-Min). Is. 360 Line SFQRs can be obtained from one disk-shaped data, and the maximum value thereof is defined as Line SFQRmax.
In addition, the autocorrelation of ESFQR at the time of front-back inversion (normal measurement and inversion measurement) was calculated.

以下の表１に、ＥＳＦＱＲの自己相関（傾き、切片、及び、決定係数Ｒ２）、差分プロファイルのＬｉｎｅ ＳＦＱＲｍａｘの全ウェーハの平均値（ΔＴＨＫ Ｌｉｎｅ ＳＦＱＲｍａｘ）を示す。また図５に、それぞれの測定機の通常測定時のＥＳＦＱＲと反転測定時のＥＳＦＱＲとの自己相関を示す。 Table 1 below shows the autocorrelation of ESFQR (slope, intercept, and coefficient of determination R2 ) and the average value (ΔTHK Line SFQRmax) of all wafers of Line SFQRmax of the difference profile. Further, FIG. 5 shows the autocorrelation between the ESFQR at the time of normal measurement and the ESFQR at the time of inversion measurement of each measuring machine.

Figure 0007067524000001
Figure 0007067524000001

通常測定及び反転測定における厚みの差分プロファイルのＬｉｎｅ ＳＦＱＲｍａｘの全ウェーハの平均値が小さいもの、ＥＳＦＱＲの自己相関の相関度を示す決定係数Ｒ２が高いものの順にそれぞれ５台の装置のデータを並べ、最も測定機の表裏面の測定システムの差が小さい測定機を選出した結果、測定機Ｅが最も好調で測定機Ｄが最も不調であると判断された。 The data of each of the five devices are arranged in the order of the one with the smallest average value of all wafers in the line SFQRmax of the thickness difference profile in the normal measurement and the inversion measurement, and the one with the highest determination coefficient R2 indicating the degree of autocorrelation of ESFQR. As a result of selecting the measuring machine having the smallest difference between the measuring systems on the front and back sides of the measuring machine, it was determined that the measuring machine E was the best and the measuring machine D was the worst.

また、表裏反転させる前と後のそれぞれ厚み分布における、ＥＳＦＱＲの最大値であるＥＳＦＱＲｍａｘを算出し、それぞれのフラットネス測定機においてＥＳＦＱＲｍａｘの全ウェーハの平均値を求めた。図１にＥＳＦＱＲｍａｘの全ウェーハの平均値の測定機平均からのずれ（ＥＳＦＱＲｍａｘのずれ）を示す。ここで、測定機平均とは、すべてのフラットネス測定機の、ＥＳＦＱＲｍａｘの全ウェーハの平均値を平均したものである。 In addition, ESFQRmax, which is the maximum value of ESFQR in the thickness distribution before and after inversion, was calculated, and the average value of all wafers of ESFQRmax was obtained in each flatness measuring machine. FIG. 1 shows the deviation (deviation of ESFQRmax) from the measuring machine average of the average value of all wafers of ESFQRmax. Here, the measuring machine average is the average value of all the wafers of ESFQRmax of all the flatness measuring machines.

上記で最も不調と判断された測定機Ｄは同一サンプルを測定しても最も高いＥＳＦＱＲｍａｘの全ウェーハの平均値を示した。 The measuring machine D judged to be the most malfunctioning above showed the average value of all wafers with the highest ESFQRmax even when the same sample was measured.

また、図１に示したＥＳＦＱＲｍａｘの全ウェーハの平均値を比較した場合、測定機Ｂが最も平均値に近い値を示しているが、表裏反転による自己相関において、測定機Ｂは測定機Ｅの自己相関より劣っている（表１参照）。このことより、平均値に近い値を示していることは、測定機自体の自己相関性、すなわち健全性が保たれていることとは言えず、自己相関の良し悪しが測定機の健全性を比較する重要な指標となる。 Further, when comparing the average values of all the wafers of ESFQRmax shown in FIG. 1, the measuring machine B shows the value closest to the average value, but in the autocorrelation due to the inversion of the front and back, the measuring machine B is the measuring machine E. Inferior to autocorrelation (see Table 1). From this, it cannot be said that the autocorrelation of the measuring instrument itself, that is, the soundness is maintained, that the value close to the average value is shown, and the good or bad of the autocorrelation determines the soundness of the measuring instrument. It is an important indicator to compare.

また、表裏反転する前と後の厚み分布の差分プロファイルの１５枚のウェーハの平均プロファイルの最大値と最小値の差も、上記で最も不調と判断された測定機Ｄで最も大きな値を示した。この結果から、測定機Ｄが最もウェーハシェイプの影響を強く受け、更に差分プロファイルの高低差が大きいことから表裏面の変位量測定システム差が大きいと判断された。一方、測定機Ｅは最もウェーハシェイプの影響を受けにくく、差分プロファイルの高低差も小さいことから表裏面の変位量測定システム差が小さいと判断できた。
これらのことは、図４に示したテストウェーハのシェイプと表裏反転する前と後の厚み分布の差分プロファイル（ΔＴＨＫ）の関係からも確認できる。図４には、例として、１５枚のテストウェーハのうちの５枚のテストウェーハ（Ｓ／＃０１～０５）のウェーハシェイプと、それぞれのテストウェーハを５台の測定機（Ｍ＃Ａ～Ｅ）で表裏反転測定したときのΔＴＨＫとの関係を示している。図４において、シェイプ及びΔＴＨＫの濃淡は高低差を表している。このとき、測定機の測定精度が高い場合は表裏反転する前と後の厚み分布に差がないと考えられるため、ウェーハシェイプによらず、ΔＴＨＫ中の高低差は小さくなり、濃淡の変化は少なくなる。図４から明らかなように、ＥＳＦＱＲの自己相関から測定精度が高いと判断された測定機Ｅは、様々なシェイプのテストウェーハについて、平坦なΔＴＨＫを示した。一方、最も不調であると判断された測定機Ｄでは、ΔＴＨＫがウェーハシェイプの影響を大きく受けていることが分かる。 In addition, the difference between the maximum value and the minimum value of the average profile of the 15 wafers in the difference profile of the thickness distribution before and after the flipping was also the largest value in the measuring machine D judged to be the most malfunctioning above. .. From this result, it was judged that the displacement amount measuring system difference between the front and back surfaces is large because the measuring machine D is most strongly influenced by the wafer shape and the height difference of the difference profile is large. On the other hand, since the measuring machine E is least affected by the wafer shape and the height difference of the difference profile is small, it can be judged that the displacement amount measuring system difference between the front and back surfaces is small.
These can be confirmed from the relationship between the shape of the test wafer shown in FIG. 4 and the difference profile (ΔTHK) of the thickness distribution before and after the inversion. In FIG. 4, as an example, the wafer shapes of 5 test wafers (S / # 01-05) out of 15 test wafers and 5 measuring machines (M # A to E) for each test wafer are shown. ) Shows the relationship with ΔTHK when the front-back inversion measurement is performed. In FIG. 4, the shades of shape and ΔTHK represent height differences. At this time, if the measurement accuracy of the measuring machine is high, it is considered that there is no difference in the thickness distribution before and after the flipping, so the height difference in ΔTHK is small and the change in shade is small regardless of the wafer shape. Become. As is clear from FIG. 4, the measuring machine E judged to have high measurement accuracy from the autocorrelation of ESFQR showed a flat ΔTHK for the test wafers of various shapes. On the other hand, it can be seen that ΔTHK is greatly affected by the wafer shape in the measuring machine D, which is determined to be the most malfunctioning.

上記の結果から、複数枚のウェーハを測定した際の表裏面差分プロファイルの平均プロファイルの最大値と最小値との差、同差分プロファイルのＬｉｎｅ ＳＦＱＲの最大値、表裏反転させて得られる厚み形状をｔｈｅｔａで補正したＥＳＦＱＲの相関係数や傾き、切片等（図５、表１参照）に一定の閾値を設け、閾値より大きい又は小さい測定機を選別することによって、真の値に近く測定精度の高い測定機を選別することができることが示された。 From the above results, the difference between the maximum and minimum values of the average profile of the front and back difference profiles when measuring multiple wafers, the maximum value of Line SFQR of the same difference profile, and the thickness shape obtained by inverting the front and back are obtained. By setting a certain threshold value for the correlation coefficient, slope, intercept, etc. of ESFQR corrected by theta (see Fig. 5, Table 1) and selecting measuring machines that are larger or smaller than the threshold value, the measurement accuracy is close to the true value. It was shown that high measuring machines can be sorted.

［実施例２］
実施例１と同様のテストウェーハのセットと測定機（Ｍ／＃ Ａ～Ｅ）を用い、テストウェーハの通常測定を行った。ここで、実施例２では、測定の際、テストウェーハを回転させることで投入角度（ノッチ角度）を変更した。実施例１と同様にＥＳＦＱＲｍａｘを算出し、投入角度とＥＳＦＱＲｍａｘの全ウェーハの平均値との関係を評価した。図２に、ノッチ角度毎のＥＳＦＱＲｍａｘの全ウェーハの平均値の測定機平均からのずれを示す。 [Example 2]
Using the same test wafer set and measuring machine (M / # A to E) as in Example 1, normal measurement of the test wafer was performed. Here, in the second embodiment, the charging angle (notch angle) was changed by rotating the test wafer at the time of measurement. ESFQRmax was calculated in the same manner as in Example 1, and the relationship between the charging angle and the average value of all wafers of ESFQRmax was evaluated. FIG. 2 shows the deviation of the mean value of ESFQRmax for each notch angle from the average value of all wafers from the measuring machine average.

測定精度の高い装置であれば、ノッチ角度によるＥＳＦＱＲｍａｘの変動は無いことが理想的だが、実際は、図２に示すノッチ角度毎のＥＳＦＱＲｍａｘの全ウェーハの平均値のように測定機への投入角度によって、ＥＳＦＱＲｍａｘの全ウェーハの平均値は変動することが分かった。更に、下記表２に示すように、ＥＳＦＱＲｍａｘの全ウェーハの平均値の変動の大きさとＥＳＦＱＲｍａｘの全ウェーハ及び全ノッチ角度の平均値の絶対値の大小関係も一致していた。このことから、全ウェーハ及びノッチ角度の平均値が所定の値より小さいものを選べば、ノッチ角度によるＥＳＦＱＲｍａｘの変動が無く、測定精度の高い測定機を選定することができることが明らかとなった。また、投入角度によるＥＳＦＱＲｍａｘの全ウェーハの平均値の変動（ＥＳＦＱＲｍａｘのバラツキ）からも装置の良し悪しが判断できると言える。 Ideally, if the device has high measurement accuracy, the ESFQRmax does not fluctuate depending on the notch angle, but in reality, it depends on the input angle to the measuring machine like the average value of ESFQRmax for each notch angle shown in FIG. , It was found that the average value of all the wafers of ESFQRmax fluctuates. Further, as shown in Table 2 below, the magnitude relationship between the magnitude of the fluctuation of the average value of all wafers of ESFQRmax and the absolute value of the average value of all wafers and all notch angles of ESFQRmax also matched. From this, it was clarified that if the average value of all wafers and notch angles is smaller than a predetermined value, the ESFQRmax does not fluctuate depending on the notch angle, and a measuring machine with high measurement accuracy can be selected. Further, it can be said that the quality of the device can be judged from the fluctuation of the average value of all wafers of ESFQRmax depending on the charging angle (variation of ESFQRmax).

Figure 0007067524000002
Figure 0007067524000002

なお、本発明は、上記実施形態に限定されるものではない。上記実施形態は例示であり、本発明の特許請求の範囲に記載された技術的思想と実質的に同一な構成を有し、同様な作用効果を奏するものは、いかなるものであっても本発明の技術的範囲に包含される。 The present invention is not limited to the above embodiment. The above-described embodiment is an example, and any one having substantially the same structure as the technical idea described in the claims of the present invention and having the same effect and effect is the present invention. Is included in the technical scope of.

１００…フラットネス測定機、
１０１…表面側のシステム、 １０２…裏面側のシステム。 100 ... Flatness measuring machine,
101 ... front side system, 102 ... back side system.

Claims (4)

複数のフラットネス測定機の中から測定精度の高いフラットネス測定機を選定する方法であって、
予めフラットネスの異なる複数のウェーハを準備し、
該複数のウェーハの厚み分布を、前記複数のフラットネス測定機において、それぞれ複数回測定し、
該複数回測定した複数のウェーハの厚み分布から、それぞれのウェーハの厚み分布の差分プロファイル、該差分プロファイルのＬｉｎｅ ＳＦＱＲ、前記測定毎のＥＳＦＱＲの少なくともいずれかの値を算出し、
前記差分プロファイルの前記複数のウェーハの平均プロファイル中の最大値と最小値の差、前記Ｌｉｎｅ ＳＦＱＲの最大値の前記複数のウェーハの平均値、前記ＥＳＦＱＲの前記測定毎の最大値の前記複数のウェーハの平均値の少なくともいずれかが所定の値より小さいフラットネス測定機、及び／又は、
前記ＥＳＦＱＲのうち、前記複数回測定において得られた前記ＥＳＦＱＲ同士の相関関係から、相関度が所定の値より大きいフラットネス測定機、
を選ぶことで、測定精度の高い測定機を選定することを特徴とするウェーハのフラットネス測定機の選定方法。 It is a method of selecting a flatness measuring machine with high measurement accuracy from multiple flatness measuring machines.
Prepare multiple wafers with different flatness in advance,
The thickness distributions of the plurality of wafers were measured a plurality of times by the plurality of flatness measuring machines.
From the thickness distributions of the plurality of wafers measured a plurality of times, at least one of the difference profile of the thickness distribution of each wafer, the line SFQR of the difference profile, and the ESFQR for each measurement is calculated.
The difference between the maximum value and the minimum value in the average profile of the plurality of wafers of the difference profile, the average value of the plurality of wafers of the maximum value of the Line SFQR, and the plurality of wafers of the maximum value for each measurement of the ESFQR. A flatness measuring instrument in which at least one of the average values of is smaller than a predetermined value, and / or
Among the ESFQRs, a flatness measuring machine having a degree of correlation greater than a predetermined value based on the correlation between the ESFQRs obtained in the plurality of measurements.
A method for selecting a wafer flatness measuring machine, which is characterized by selecting a measuring machine with high measurement accuracy by selecting. 前記複数のフラットネス測定機において、それぞれ複数回測定する際に、前記ウェーハを表裏反転させる前と後でそれぞれ１回以上測定することを特徴とする請求項１に記載のウェーハのフラットネス測定機の選定方法。 The wafer flatness measuring machine according to claim 1, wherein when each of the plurality of flatness measuring machines is measured a plurality of times, the wafer is measured one or more times before and after the wafer is turned upside down. Selection method. 前記複数のフラットネス測定機において、それぞれ複数回測定する際に、前記ウェーハを回転させることで投入角度を変更して複数回測定することを特徴とする請求項１に記載のウェーハのフラットネス測定機の選定方法。 The flatness measurement of a wafer according to claim 1, wherein when each of the plurality of flatness measuring machines is measured a plurality of times, the wafer is rotated to change the loading angle and the measurement is performed a plurality of times. How to select a machine. 請求項１から請求項３のいずれか一項に記載のウェーハのフラットネス測定機の選定方法で選定されたフラットネス測定機を用いてウェーハのフラットネスを測定することを特徴とするウェーハのフラットネスの測定方法。 Flatness of a wafer characterized by measuring the flatness of a wafer by using a flatness measuring machine selected by the method for selecting a flatness measuring machine for a wafer according to any one of claims 1 to 3. How to measure ness.
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