JP2695797B2 - Small size measurement method - Google Patents

Small size measurement method

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Publication number
JP2695797B2
JP2695797B2 JP25362487A JP25362487A JP2695797B2 JP 2695797 B2 JP2695797 B2 JP 2695797B2 JP 25362487 A JP25362487 A JP 25362487A JP 25362487 A JP25362487 A JP 25362487A JP 2695797 B2 JP2695797 B2 JP 2695797B2
Authority
JP
Japan
Prior art keywords
pattern
measurement
waveform
scanning waveform
edge position
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Fee Related
Application number
JP25362487A
Other languages
Japanese (ja)
Other versions
JPH0197357A (en
Inventor
誠 加藤
哲夫 横山
純太郎 有馬
寿宏 古屋
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Hitachi Ltd
Original Assignee
Hitachi Ltd
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Hitachi Ltd filed Critical Hitachi Ltd
Priority to JP25362487A priority Critical patent/JP2695797B2/en
Publication of JPH0197357A publication Critical patent/JPH0197357A/en
Application granted granted Critical
Publication of JP2695797B2 publication Critical patent/JP2695797B2/en
Anticipated expiration legal-status Critical
Expired - Fee Related legal-status Critical Current

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  • Exposure Of Semiconductors, Excluding Electron Or Ion Beam Exposure (AREA)
  • Length-Measuring Devices Using Wave Or Particle Radiation (AREA)

Description

【発明の詳細な説明】 〔産業上の利用分野〕 本発明は半導体表面パターン等の微細パターンの線幅
測定方式に係り、特に高精度で、ノイズ等にも強い微小
寸法測定方式に関する。 〔従来の技術〕 近年、半導体の微細化が進み、その製造工程の管理に
用いられる線幅測定には、従来の光学式の測定では分解
能が不足となり、高分解能を利用した走査電子顕微鏡
(Scanning Electron Microscope、以下SEMと略す)が
用いられるようになつてきている。SEMによる半導体表
面の画像に2つのカーソルを重ねて表示し、オペレータ
が半導体表面パターンの両端にカーソるを移動させ、そ
の間隔を倍率で割つたものを線幅とするマニユアル(手
動)測長が主として行われているが、測定の高速化,属
人性の排除を行うため各種自動測長方式が検討されてい
る。自動測長では電子線を半導体表面のパターンに垂直
に走査し、その走査波形より、線幅の測長を行う。具体
的には、第6図(a)において、試料表面1上を走査
し、同図(b)に示した走査波形3より、同図(a)の
パターン端点2の位置を求め、この間隔を求める。この
パターン端点2を走査波形3より求めるために、種々の
方式が考えられている。例えば、日本学術振興会第132
委員会第89回研究会資料pp5〜8で論じられている方式
がある。この方式は直線近似法と呼ばれるが第2図の走
査波形3を底部近似直線4と傾斜部近似直線5で近似
し、その交点の位置を測定エツジ位置6とするものであ
る。また、他の代表的な方式としては、しきい値法と呼
ばれる方式がある。(例えば、「微小線幅測定装置」、
日本学術振興会第132委員会第85回研究会資料)このし
きい値法では第3図の走査波形3に対し、しきい値7を
設定し、走査波形3がしきい値7をとる点を測定エツジ
位置9とするものである。このしきい値は、材質形状に
応じて決めることができ、しきい値8をとれば、測定エ
ツジ位置10が得られる。他に、本方式に関連するものと
して、例えば、特開昭58−117404号,同55−同55−6370
4号,同57−96206号がある。 〔発明が解決しようとする問題点〕 上記従来技術のうち、最初に説明した直線近似法につ
いては、第2図(a)の測定エツジ位置6と第6図のパ
ターン端点2の関係は必ずしも一致するものではなく、
材質や断面形状の違いにより変化するという点に配慮さ
れていない。また、後に説明したしきい値法において
は、雑音の影響により不正確となることがある。具体的
には、第4図において雑音印加の走査波形11に対して、
しきい値12を定めると、測定エツジ位置13,測定エツジ
位置14,測定エツジ位置15の3点が対応し不確定さが残
ることになる点問題があつた。 本発明の目的は、材質や断面形状の違いに対応でき、
かつ雑音の影響も少ない微小寸法測定方式を提供するこ
とにある。 〔問題点を解決するための手段〕 上記目的は、直線近似法において、横近似直線を、材
質,形状に応じて上下させ、傾斜部近似直線との交点
を、測定エツジ位置とすることにより達成される。 〔作用〕 材質・形状に応じて横近似直線を、あらかじめ決めて
おいた量だけ上下させることにより、材質・形状の変化
に左右されない測定エツジ位置を得る。また、しきい値
法と異なり、傾斜部を直線で近似しているので、雑音の
影響が少ない。 〔実施例〕 第1図は本発明による測長SEMシステムの実施例のハ
ードウエア構成図である。SEMの鏡体17中の電子銃18よ
り放出された電子線19は、電子レンズ系20により偏向さ
れ、試料台21上の試料22に入射する。電子線19の入射に
応じて試料22より2次電子23が放出され、検出器24で補
足され信号となり、デイスプレイ25上の画像を形成す
る。この信号は、キーボード27により入力される指示に
より、計算機26で処理される。 第7図は計算機26における測長処理手順を示すフロー
チヤートである。ブロツク71では走査波形を読みこむ。
このブロツク72では、しきい値の設定を行う。 このしきい値の設定には、種々の方法があるが、その
一例を第8図を用いて説明する。走査波形3は、第6図
(a)の試料表面1に対する走査波形として典型的なも
のであり、最大値ピーク81,最小値暗部82,上部平坦部9
3,底部84,傾斜部85よりなる。最大値ピーク81の高さ、
最小値暗部82の深さ,傾斜部85の傾斜は主に形状を反映
し、上部平坦部83と底部84の相対的な関係は主に材質を
反映することが知られている。これら波形の特徴点の信
号値、すなわち最大値86,最小値87,上部平坦部の信号値
88,底部の信号値89より、しきい値7を決める。最大値8
6をImax,最小値87をImin,上部平坦部の信号値88をIt,底
部の信号値89をIb,しきい値7をIthで表わすと、例え
ば、 のように決めることができる。この決め方は、あらかじ
め、真のエツジ位置のわかつている試料に対して測定実
験を行い決める方法と理論的に走査波形を計算して決め
る方法がある。 次に、ブロツク73では、第5図の走査波形3を傾斜部
近似直線5で近似する。このためには、傾斜部の波形を
最小二乗法等で近似を行えば良い。 次にブロツク74では、ブロツク72で求めたしきい値7
と、ブロツク73で求めた傾斜部近似曲線5の交点を測定
エツジ位置16とすることによりエツジ決定を行う。ブロ
ツク75では、測定結果を第1図のデイスプレイ25に表示
する。 〔発明の効果〕 本発明によれば、SEMにより半導体表面パターン等の
微細形状の線幅測定を、形状や材質の変化に対応し、か
つ雑音にも影響されず行えるので、高精度の線幅測定を
行える効果がある。
Description: BACKGROUND OF THE INVENTION The present invention relates to a method for measuring the line width of a fine pattern such as a semiconductor surface pattern, and more particularly to a method for measuring a fine dimension which is highly accurate and resistant to noise and the like. [Prior Art] In recent years, the miniaturization of semiconductors has progressed, and the resolution of conventional optical measurement has become insufficient for line width measurement used for control of the manufacturing process, and a scanning electron microscope (Scanning microscope) using high resolution has been used. Electron Microscope (hereinafter abbreviated as SEM) has come to be used. A manual (manual) length measurement, in which two cursors are superimposed on the image of the semiconductor surface by SEM and the cursor is moved to both ends of the semiconductor surface pattern and the interval is divided by the magnification, and the line width is obtained. Although mainly performed, various automatic length measurement methods are being studied in order to speed up the measurement and eliminate personality. In the automatic length measurement, an electron beam is scanned perpendicularly to the pattern on the semiconductor surface, and the line width is measured from the scanning waveform. Specifically, in FIG. 6 (a), the surface of the sample 1 is scanned, and the position of the pattern end point 2 in FIG. 6 (a) is obtained from the scanning waveform 3 shown in FIG. 6 (b). Ask for. Various methods have been considered to determine the pattern end point 2 from the scanning waveform 3. For example, Japan Society for the Promotion of Science 132
There is a scheme discussed in the 89th meeting of the committee, pp5-8. This method is referred to as a straight line approximation method, in which the scanning waveform 3 in FIG. 2 is approximated by a bottom approximation line 4 and a slope approximation line 5, and the position of the intersection is set as a measurement edge position 6. Another typical method is a method called a threshold method. (For example, "micro line width measuring device",
In this threshold method, the threshold value 7 is set for the scanning waveform 3 in FIG. 3, and the scanning waveform 3 takes the threshold value 7 in this threshold method. Is the measurement edge position 9. This threshold value can be determined according to the material shape. If the threshold value 8 is set, the measurement edge position 10 can be obtained. Others related to the present method are disclosed in, for example, JP-A-58-117404 and JP-A-55-6370.
No. 4 and No. 57-96206. [Problems to be Solved by the Invention] Among the above-described prior arts, in the linear approximation method described first, the relationship between the measurement edge position 6 in FIG. 2A and the pattern end point 2 in FIG. Not to do
No consideration is given to the fact that it changes depending on the material and cross-sectional shape. Further, in the threshold method described later, inaccuracy may be caused by the influence of noise. Specifically, in FIG. 4, with respect to the scanning waveform 11 with noise applied,
When the threshold value 12 is determined, there is a problem that three points of the measurement edge position 13, the measurement edge position 14, and the measurement edge position 15 correspond to each other, and uncertainty remains. The object of the present invention is to be able to cope with differences in materials and cross-sectional shapes,
Another object of the present invention is to provide a micro-size measuring method which is less affected by noise. [Means for Solving the Problems] The above object is achieved by, in the straight-line approximation method, raising and lowering the horizontal approximation line according to the material and shape, and setting the intersection with the inclined portion approximation line as the measurement edge position. Is done. [Operation] By moving the horizontal approximate straight line up and down by a predetermined amount according to the material and shape, a measurement edge position that is not affected by changes in the material and shape is obtained. Also, unlike the threshold method, the slope is approximated by a straight line, so that the influence of noise is small. Embodiment FIG. 1 is a hardware configuration diagram of an embodiment of a length measuring SEM system according to the present invention. An electron beam 19 emitted from an electron gun 18 in an SEM mirror 17 is deflected by an electron lens system 20 and enters a sample 22 on a sample stage 21. Secondary electrons 23 are emitted from the sample 22 in response to the incidence of the electron beam 19 and are captured by the detector 24 to become a signal, thereby forming an image on the display 25. This signal is processed by the computer 26 according to an instruction input from the keyboard 27. FIG. 7 is a flow chart showing the length measurement processing procedure in the computer 26. At block 71, a scanning waveform is read.
In this block 72, a threshold value is set. There are various methods for setting the threshold, one example of which will be described with reference to FIG. The scanning waveform 3 is a typical scanning waveform for the sample surface 1 shown in FIG. 6 (a), and includes a maximum peak 81, a minimum dark area 82, and an upper flat area 9
3, consisting of a bottom portion 84 and an inclined portion 85. The maximum peak 81 height,
It is known that the depth of the minimum dark part 82 and the inclination of the inclined part 85 mainly reflect the shape, and the relative relationship between the upper flat part 83 and the bottom part 84 mainly reflects the material. The signal values of the characteristic points of these waveforms, that is, the maximum value 86, the minimum value 87, and the signal value of the upper flat portion
Threshold value 7 is determined from 88, the signal value 89 at the bottom. Maximum value 8
6 is I max , the minimum value 87 is I min , the signal value 88 of the upper flat portion is I t , the signal value 89 of the bottom portion is I b , and the threshold value 7 is I th . Can be decided as follows. This determination method includes a method in which a measurement experiment is performed on a sample having a true edge position and a method in which the scanning waveform is theoretically calculated. Next, in a block 73, the scanning waveform 3 in FIG. For this purpose, the waveform of the inclined portion may be approximated by the least square method or the like. Next, at block 74, the threshold value 7 obtained at block 72 is obtained.
The edge is determined by setting the intersection of the slope approximated curve 5 obtained by the block 73 as the measured edge position 16. At block 75, the measurement result is displayed on the display 25 of FIG. [Effects of the Invention] According to the present invention, the line width of a fine shape such as a semiconductor surface pattern can be measured by a SEM in response to a change in shape or material and without being affected by noise. There is an effect that measurement can be performed.

【図面の簡単な説明】 第1図は、本発明の一実施例のハードウエア構成図、第
2図は、直線近似法の説明図、第3図は、しきい値法の
説明図、第4図は、しきい値法を雑音印加走査波形に適
用した図、第5図は、本発明の原理説明図、第6図は測
定試料の断面図と典型的な走査波形図、第7図は本発明
の一実施例のソフトウエアのフローチヤート、第8図
は、しきい値決定法の説明図である。
BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a hardware configuration diagram of one embodiment of the present invention, FIG. 2 is an explanatory diagram of a linear approximation method, FIG. 4 is a diagram in which the threshold value method is applied to a noise-applied scanning waveform, FIG. 5 is a diagram illustrating the principle of the present invention, FIG. 6 is a cross-sectional view of a measurement sample and a typical scanning waveform diagram, and FIG. FIG. 8 is a flowchart of the software according to an embodiment of the present invention. FIG. 8 is an explanatory diagram of a threshold value determining method.

───────────────────────────────────────────────────── フロントページの続き (72)発明者 古屋 寿宏 茨城県勝田市市毛882番地 株式会社日 立製作所那珂工場内 (56)参考文献 特開 昭61−99809(JP,A) 特開 昭60−161514(JP,A) 特開 昭58−117405(JP,A) 特開 昭58−117404(JP,A) 特開 昭57−96207(JP,A)   ────────────────────────────────────────────────── ─── Continuation of front page    (72) Inventor Toshihiro Furuya               882 Ma, Katsuta-shi, Ibaraki Pref.               Inside the Naka Factory                (56) References JP-A-61-99809 (JP, A)                 JP-A-60-161514 (JP, A)                 JP-A-58-117405 (JP, A)                 JP-A-58-117404 (JP, A)                 JP-A-57-96207 (JP, A)

Claims (1)

(57)【特許請求の範囲】 1.微細パターン上を電子線で走査し、この走査によつ
て得られた電気信号の、パターンのエツジ部分に特徴的
な波形を、側壁部の斜め直線と、波形の底部レベル,頂
部レベル,最大値,最小値等の波形の特徴及び、外部よ
り与えたパラメータの組により定まる水平直線で近似
し、これら2直線の交点を以つてパターン端部となし、
2の操作を両側壁部に施し、2つのパターン端部の間隔
を以つてパターン幅とすることを特徴とする微小寸法測
定方式。
(57) [Claims] The fine pattern is scanned with an electron beam, and a characteristic waveform of an edge portion of the pattern of an electric signal obtained by the scanning is represented by an oblique straight line on a side wall, a bottom level, a top level, and a maximum value of the waveform. , Approximation with a horizontal straight line determined by a set of parameters such as waveform characteristics, minimum value, etc., and an externally given parameter.
2. The micro-dimension measuring method, wherein the operation 2 is performed on both side walls, and a pattern width is determined by an interval between two pattern ends.
JP25362487A 1987-10-09 1987-10-09 Small size measurement method Expired - Fee Related JP2695797B2 (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
JP25362487A JP2695797B2 (en) 1987-10-09 1987-10-09 Small size measurement method

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
JP25362487A JP2695797B2 (en) 1987-10-09 1987-10-09 Small size measurement method

Publications (2)

Publication Number Publication Date
JPH0197357A JPH0197357A (en) 1989-04-14
JP2695797B2 true JP2695797B2 (en) 1998-01-14

Family

ID=17253940

Family Applications (1)

Application Number Title Priority Date Filing Date
JP25362487A Expired - Fee Related JP2695797B2 (en) 1987-10-09 1987-10-09 Small size measurement method

Country Status (1)

Country Link
JP (1) JP2695797B2 (en)

Also Published As

Publication number Publication date
JPH0197357A (en) 1989-04-14

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