JP3642250B2

JP3642250B2 - Method for judging polishing conditions of semiconductor substrate

Info

Publication number: JP3642250B2
Application number: JP2000049396A
Authority: JP
Inventors: 健夫加藤; 秀樹坂本; 英之近藤
Original assignee: 三菱住友シリコン株式会社
Priority date: 2000-02-25
Filing date: 2000-02-25
Publication date: 2005-04-27
Anticipated expiration: 2020-02-25
Also published as: JP2001239459A

Description

【０００１】
【発明の属する技術分野】
本発明は、シリコンウェーハに代表される半導体基板の研磨条件の良否を判定する方法に関する。更に詳しくは半導体基板の表面の最終的な面質を決定する仕上げ研磨条件を判定する方法に関するものである。
【０００２】
【従来の技術】
半導体デバイスの高集積化、高機能化及びウェーハの大口径化の要求に伴い、ウェーハ表面のマイクロラフネスや平坦度で評価されるシリコンウェーハの表面の面質は益々重要視されてきている。この最終的な面質を決定するプロセスとして、シリコンウェーハの研磨工程、特に仕上げ研磨工程が挙げられる。従ってシリコンウェーハの表面の面質を高めるためには、仕上げ研磨における研磨条件を最適にする必要がある。そのために摩耗した研磨パッドの交換時期、或いは新規な研磨パッドの慣らし運転時間、新規な研磨パッドや新規な研磨スラリーの適否等の研磨条件を的確に判定する方法が求められている。
【０００３】
従来、研磨条件の良否は、主として研磨レートの大小により判定している。研磨レートは単位時間当りの研磨によるウェーハ表面の取り代（stock removal）である。この方法では研磨した取り代やそれに費やした研磨時間により研磨パッドの摩耗状態、研磨スラリーを評価している。
また仕上げ研磨の良否は、パーティクルカウンタを用いて研磨後の基板表面に光を照射し、そのヘイズ値の多寡により基板表面のマイクロラフネスを測定した後、或いは原子間力顕微鏡（Atomic Force Microscope、以下、ＡＦＭという。）を用いて基板表面のマイクロラフネスを測定した後、このマイクロラフネスに基づいて判定している。
更に別の方法としては、研磨後の基板表面に酸化膜を形成し、この酸化膜の耐圧特性から仕上げ研磨条件の良否を判定している。
【０００４】
【発明が解決しようとする課題】
しかし、研磨レートにより研磨条件の良否を判定する方法では、この方法を仕上げ研磨に適用した場合、仕上げ研磨による取り代が小さいため、研磨レートを測定するのが困難であり、良否判定が難しい問題点があった。また、パーティクルカウンタやＡＦＭを用いてマイクロラフネスを測定した後、この値から研磨条件の良否を判定する方法や、或いは基板表面の酸化膜耐圧特性から研磨条件の良否を判定する方法では、研磨条件の良否の要因を特定することが難しく、また研磨後の基板を加工する必要があり、時間とコストがかかる問題点があった。
本発明の目的は、半導体基板の研磨の最適な条件を見い出し得る半導体基板の研磨条件の判定方法を提供することにある。
本発明の別の目的は、仕上げ研磨不良に起因する問題を非破壊で迅速に評価する半導体基板の研磨条件の判定方法を提供することにある。
【０００５】
【課題を解決するための手段】
請求項１に係る発明は、同一の工程を経て製造された複数の半導体基板を用意し、前記複数の半導体基板のそれぞれに対して研磨パッド又は研磨スラリーのいずれか一方又は双方を変えた異なる複数の研磨条件で研磨し、研磨したこれらの半導体基板の表面粗さを非接触法により測定し、その５μｍ〜１ｍｍの空間波長成分領域の波長成分強度の大小により、上記複数の研磨条件のそれぞれの良否を判定する半導体基板の研磨条件の判定方法である。
請求項１に係る発明では、異なった複数の研磨条件で研磨した複数の半導体基板の表面粗さを非接触法により測定し、そのときの空間波長成分領域が５μｍ〜１ｍｍの範囲の波長成分強度の値を各基板間で比較して波長成分強度の値が小さい研磨条件を良好な条件であると判定する。
【０００６】
請求項２に係る発明は、半導体基板の表面粗さを非接触法により測定し、その５μｍ〜１ｍｍの空間波長成分領域の第１波長成分強度を測定し、上記半導体基板を所定の研磨条件で研磨し、この研磨した半導体基板の表面粗さを上記非接触法により測定し、その５μｍ〜１ｍｍの空間波長成分領域の第２波長成分強度を測定し、第１波長成分強度と第２波長成分強度を比較することにより、上記研磨条件の良否を判定する半導体基板の研磨条件の判定方法である。
請求項２に係る発明では、ある研磨条件で単一の半導体基板を研磨し、その研磨前後における第１波長成分強度と第２波長成分強度の比較から、上記研磨条件が良好であったか否か判定する。
【０００７】
【発明の実施の形態】
本発明の実施の形態について説明する。
本発明の判定する研磨条件は、半導体基板の表面の最終的な面質を決定する仕上げ研磨条件である。本発明ではこの研磨条件における研磨パッドの摩耗状態又は研磨スラリーの良否を判定する。
仕上げ研磨は通常、片面研磨方法によって行われる。図２に基づいて片面研磨方法について述べる。この研磨装置２０は回転定盤２１と基板保持具２２を備える。回転定盤２１は大きな円板であり、その底面中心に接続されたシャフト２３によって回転する。回転定盤２１の上面には研磨パッド２４が貼付けられる。基板保持具２２は加圧ヘッド２２ａとこれに接続して加圧ヘッド２２ａを回転させるシャフト２２ｂからなる。加圧ヘッド２２ａの下面には研磨プレート２６が取付けられる。研磨プレート２６の下面には複数枚の半導体基板１０が貼付けられる。回転定盤２１の上部には研磨スラリー２７を供給するための配管２８が設けられる。この研磨装置２０により半導体基板１０を研磨する場合には、加圧ヘッド２２ａを下降して半導体基板１０に所定の圧力を加えて基板１０を押さえる。配管２８から研磨スラリー２７を研磨パッド２４に供給しながら、加圧ヘッド２２ａと回転定盤２１とを同一方向に回転させて、基板１０の表面を平坦に研磨する。
【０００８】
本発明の非接触表面粗さ測定法としては、前述のＡＦＭ以外に、マルチビーム干渉法（Multi-Beam Interferometry）、低出力光学顕微鏡（Low power optical Microscope）、高出力光学顕微鏡（High power optical Microscope）、微分干渉顕微鏡（Differential Interference Microscope）、位相差顕微鏡(Phase-Contrast Microscope)、円錐レーザ走査型光学顕微鏡（cone-focal laser Scanning Optical Microscope）、走査型電子顕微鏡（Scanning Electron Microscope）、透過型電子顕微鏡（Transmission Electron Microscope）、反射型電子顕微鏡（Reflection Electron Microscope）、電界イオン顕微鏡（Field Ion Microscope）、走査型トンネル顕微鏡（Scanning Tunneling Microscope）等が挙げられる。
【０００９】
本実施の形態では微分干渉法に基づいた装置について説明する。
上記研磨装置で研磨したときの仕上げ研磨条件のうち、研磨パッドの摩耗状態と研磨スラリーの良否を図１に示す検査装置１１で半導体基板１０表面のマイクロラフネスの特定波長域成分を検査することにより判定する。この検査装置１１は、レーザ発振器１２と、基板１０表面上を移動可能に形成された移動測定ヘッド１３と、基板１０に照射したレーザ光の反射偏光を検出する検出器１４ａ、１４ｂと、ノンポラライジングビームスプリッタ１６と、ポラライジングビームスプリッタ１７とを備える。レーザ発振器１２より発振されたレーザ光は、図示しない偏光板、１／４波長板により光量の制御が行われ、円偏光となる。円偏光は実線矢印に示すように、ノンポラライジングビームスプリッタ１６を通った後、移動測定ヘッド１３のペンタプリズム１３ａに入射する。移動測定ヘッド１３は１００ｍｍの範囲で移動可能に構成され、その位置情報は１μｍ又は０．２μｍの分解能で図示しないコンピュータに取込まれる。入射光はペンタプリズム１３ａで９０°下方に反射され、ノマルスキプリズム１３ｂでＰ偏光、Ｓ偏光に分離され、対物レンズ１３ｃを通って基板１０表面で結像する。基板１０表面で反射されたＰ偏光及びＳ偏光は再びノマルスキプリズム１３ｂで合成され、破線矢印で示すように、ペンタプリズム１３ａ、ノンポラライジングビームスプリッタ１６を経て、ポラライジングビームスプリッタ１７にて各偏光成分に分離され検出器１４ａ、１４ｂにより偏光成分の強度が電圧にて検出される。この検出された各偏光成分の強度から表面粗さプロファイルを測定し、更にプロファイルをフーリエ変換することにより波長成分強度（Power Spectral Density、以下、ＰＳＤという。）が算出される。
【００１０】
請求項１に係る判定方法では、同一の工程を経て製造された、基板間に差異のないと考えられる複数の半導体基板に対して、上記研磨装置により異なった複数の研磨条件で研磨を行い、それぞれ研磨した半導体基板の表面に上記レーザ発振器より発振されたレーザ光を照射する。ここで異なった複数の研磨条件とは、材質の異なる研磨パッド、同一材質でも摩耗程度の異なる研磨パッド、性状の異なる研磨スラリーを用いた場合をいう。材質の異なる研磨パッド又は性状の異なる研磨スラリーとは、従来使用していた研磨パッド、研磨スラリーとは異なる新規に採用された研磨パッド、研磨スラリーをいう。同一材質でも摩耗程度の異なる研磨パッドとは、同一製品であっても新品の研磨パッド、摩耗程度が中位、或いは摩耗が極端に進んだ研磨パッドをいう。研磨条件が異なると、研磨前に同一の表面を有していた複数の半導体基板も研磨後には、各表面のマイクロラフネスや平坦度が変化する。
【００１１】
このように異なった複数の研磨条件でそれぞれ研磨した複数の半導体基板の表面にレーザ光を照射すると、研磨後のウェーハ表面特性であるマイクロラフネスや平坦度の程度に応じて異なった反射偏光を生ずる。この反射偏光より検出された各偏光成分から表面粗さプロファイルを測定し、更にプロファイルをフーリエ変換して５μｍ〜１ｍｍの空間波長成分領域のＰＳＤを測定し、その大小を比較することにより、複数の研磨条件毎にその研磨パッド、研磨スラリーの良否を判定する。空間波長成分領域を５μｍ〜１ｍｍにするのはこの領域では波長成分が緩やかに減少していき、研磨状態を評価するのに適しているからである。５μｍ未満の波長成分は、研磨後表面に対する短時間の化学的エッチングによって左右されるため、研磨パッド、研磨スラリーの良否判定には向かず、１ｍｍを越えると仕上げ研磨では殆ど粗さ成分が変化せず、他の要因で粗さ成分が決まるためである。この空間波長成分領域は好ましくは１０μｍ〜１００μｍである。
【００１２】
請求項２に係る判定方法では、単一の半導体基板の研磨前後における第１ＰＳＤ及び第２ＰＳＤをそれぞれ測定し、両ＰＳＤの比較により当該研磨条件の良否を判定する。この方法は異なった研磨条件の判定のみならず、同一条件で大量に半導体基板を研磨しているときの抜取り検査にも適する。即ち、仕上げ研磨が良好な場合のＰＳＤと、不良な場合のＰＳＤを予め測定しておき、これらのＰＳＤに対して、サンプリングした半導体基板から得られたＰＳＤを比較することにより、当該研磨条件を半導体基板を破壊することなく、迅速に評価することができる。仕上げ研磨後にこの方法を用いれば、従来仕上げ研磨不良に起因した、基板表面に残存するスクラッチ、酸化膜耐圧不良などの種々の問題を未然に防止することができる。
【００１３】
【実施例】
次に本発明の実施例を比較例とともに説明する。
＜実施例１＞
通常の粗研磨を終えた半導体基板であるシリコンウェーハを４枚用意し、シリコンウェーハ毎に同一の研磨スラリーを用いて研磨パッドを変えて仕上げ研磨を行った。この仕上げ研磨に用いた研磨スラリーはＳｉＯ₂の研磨粒子が分散した市販されている仕上げ研磨用スラリー原液を純水で３０倍に希釈して調製した（これを研磨スラリーＡという。）また研磨パッドにはそれぞれ同一製品であるが、使用履歴の異なる４種類を用意した（これらを研磨パッドＡ、研磨パッドＢ、研磨パッドＣ及び研磨パッドＤという。）。研磨パッドＡは一度も使用されていないパッド、研磨パッドＢは１０時間使用されたパッド、研磨パッドＣは１５０時間使用されたパッド、研磨パッドＤは１０時間使用されているが何らかの理由で仕上げ研磨がうまく行われないパッドである。４枚のシリコンウェーハの仕上げ研磨を各研磨パッド毎に図２に示す研磨装置により研磨圧力１．１８×１０⁴Ｐａで各１０分間行った。仕上げ研磨を終えた４枚のシリコンウェーハの表面を図１に示す微分干渉式表面プロファイラを用いて、表面粗さプロファイルを測定し、空間波長成分領域が１０〜１００μｍの範囲のＰＳＤを求めた。このＰＳＤの積分した値を表１に示す。単位は任意単位（a.u.：arbitary unit）であって、次に述べる実施例及び比較例も同じである。
【００１４】
＜比較例１＞
実施例１の仕上げ研磨を終えたシリコンウェーハ表面を光散乱式パーティクルカウンタによりヘイズ値を測定した。その結果を表１に示す。
＜比較例２＞
実施例１の仕上げ研磨を終えたシリコンウェーハ表面をＡＦＭにより１０μｍ×１０μｍの領域の平均マイクロラフネス（average microroughness、以下、Ｒａという。）を測定した。その結果を表１に示す。
【００１５】
【表１】

【００１６】
表１から明らかなように、比較例１及び２の測定結果に比較して実施例１の測定結果は、各研磨条件の差が顕著に現れ、仕上げ研磨の良否を良く反映していた。特に、１０時間使用した研磨パッドＢによる研磨は通常良好な研磨が行われるという事実が比較例１及び２に比べて実施例１で最も良く示され、実施例１の測定方法が研磨パッドの摩耗状態、良否状態を的確に判定していた。
【００１７】
＜実施例２＞
実施例１と同じシリコンウェーハを更に４枚用意した。シリコンウェーハ毎に同一の研磨パッドを用いて研磨スラリーを変えて仕上げ研磨を行った。研磨パッドは実施例１の研磨パッドＢを用い、研磨スラリーは種類の異なる市販されている仕上げ研磨用スラリー原液を純水で３０倍に希釈して調製した（以下、これらを研磨スラリーＡ、Ｂ及びＣという。）。４枚のシリコンウェーハの仕上げ研磨を各研磨スラリー毎に実施例１と同様に行った。仕上げ研磨を終えた４枚のシリコンウェーハの表面を微分干渉式表面プロファイラを用いて、表面粗さプロファイルを測定し、空間波長成分領域が１０〜１００μｍの範囲のＰＳＤを求めた。このＰＳＤの積分した値を表２に示す。
【００１８】
＜比較例３＞
実施例２の仕上げ研磨を終えたシリコンウェーハ表面を光散乱式パーティクルカウンタによりヘイズ値を測定した。その結果を表２に示す。
＜比較例４＞
実施例２の仕上げ研磨を終えたシリコンウェーハ表面をＡＦＭにより１０μｍ×１０μｍの領域のＲａを測定した。その結果を表２に示す。
【００１９】
【表２】

【００２０】
表２から明らかなように、比較例３及び４の測定結果に比較して実施例２の測定結果は、各研磨条件の差が顕著に現れ、研磨スラリーによる仕上げ研磨の良否を良く反映していた。
【００２１】
【発明の効果】
以上述べたように、本発明では、研磨に用いる研磨パッドの摩耗状態や研磨スラリーに基づく研磨条件の良否を半導体基板表面のマイクロラフネスの特定波長域成分により判定することにより、研磨条件を最適化することができ、研磨パッド、研磨スラリーの最適な組合わせを迅速に決定することができる。また、仕上げ研磨の状態を研磨前後のＰＳＤ値の変化によって評価し、研磨布やスラリーの性質等の研磨条件を変化させることでスラリーや研磨パッドの開発に役立てることもできる。
更に、酸化膜耐圧特性による研磨条件の判定と異なり、仕上げ研磨不良に起因する問題を非破壊で迅速に防止して、低コストで研磨条件を判定することができる。
【図面の簡単な説明】
【図１】半導体基板表面の検査装置の構成図。
【図２】半導体基板の片面研磨装置の構成図。
【符号の説明】
１０半導体基板
１１検査装置
１２レーザ発振器
１３移動測定ヘッド
１３ａペンタプリズム
１３ｂノマルスキプリズム
１３ｃ対物レンズ
１４ａ、１４ｂ検出器
１６ノンポラライジングビームスプリッタ
１７ポラライジングビームスプリッタ
２０片面研磨装置
２１回転定盤
２２基板保持具
２２ａ加圧ヘッド
２２ｂシャフト
２３シャフト
２４研磨パッド
２６研磨プレート
２７研磨スラリー
２８配管[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for determining the quality of polishing conditions for a semiconductor substrate typified by a silicon wafer. More specifically, the present invention relates to a method for determining final polishing conditions for determining the final surface quality of a semiconductor substrate.
[0002]
[Prior art]
With the demand for higher integration and higher functionality of semiconductor devices and larger wafer diameters, the surface quality of silicon wafers evaluated by the microroughness and flatness of the wafer surface has become increasingly important. As a process for determining the final surface quality, a silicon wafer polishing step, particularly a finish polishing step, may be mentioned. Therefore, in order to improve the surface quality of the surface of the silicon wafer, it is necessary to optimize the polishing conditions in the final polishing. Therefore, there is a need for a method for accurately judging the polishing conditions such as the replacement timing of a worn polishing pad, the running-in time of a new polishing pad, the suitability of a new polishing pad and a new polishing slurry, and the like.
[0003]
Conventionally, the quality of polishing conditions is mainly determined by the magnitude of the polishing rate. The polishing rate is the stock removal of the wafer surface by polishing per unit time. In this method, the abrasion state of the polishing pad and the polishing slurry are evaluated based on the polishing allowance and the polishing time spent on it.
In addition, the quality of final polishing is determined by irradiating the polished substrate surface with light using a particle counter and measuring the microroughness of the substrate surface based on the haze value, or by atomic force microscope (hereinafter referred to as atomic force microscope). , AFM)), and the microroughness of the substrate surface is measured, and then the determination is made based on the microroughness.
As yet another method, an oxide film is formed on the surface of the substrate after polishing, and the quality of the final polishing conditions is judged from the pressure resistance characteristics of the oxide film.
[0004]
[Problems to be solved by the invention]
However, in the method of judging the quality of the polishing conditions based on the polishing rate, when this method is applied to finish polishing, it is difficult to measure the polishing rate because the machining allowance by finish polishing is small, and it is difficult to judge pass / fail There was a point. In addition, after measuring the microroughness using a particle counter or AFM, the method for judging the quality of the polishing conditions from this value, or the method for judging the quality of the polishing conditions from the oxide film pressure resistance characteristics of the substrate surface, It is difficult to specify the quality factor, and it is necessary to process the polished substrate, which requires time and cost.
An object of the present invention is to provide a method for determining the polishing conditions of a semiconductor substrate that can find the optimum conditions for polishing the semiconductor substrate.
Another object of the present invention is to provide a method for determining a polishing condition for a semiconductor substrate, which can quickly and non-destructively evaluate a problem caused by defective final polishing.
[0005]
[Means for Solving the Problems]
The invention according to claim 1 is provided with a plurality of different semiconductor substrates prepared through the same process, wherein one or both of a polishing pad and a polishing slurry are changed for each of the plurality of semiconductor substrates. The surface roughness of these polished semiconductor substrates was measured by a non-contact method, and each of the plurality of polishing conditions was determined by the magnitude of the wavelength component intensity in the spatial wavelength component region of 5 μm to 1 mm. This is a method for determining the polishing conditions of a semiconductor substrate for determining pass / fail.
In the invention according to claim 1, the surface roughness of a plurality of semiconductor substrates polished under a plurality of different polishing conditions is measured by a non-contact method, and the wavelength component intensity in which the spatial wavelength component region is in the range of 5 μm to 1 mm. Is compared between the substrates, and the polishing condition with a small value of the wavelength component intensity is determined to be a good condition.
[0006]
In the invention according to claim 2, the surface roughness of the semiconductor substrate is measured by a non-contact method, the first wavelength component intensity in the spatial wavelength component region of 5 μm to 1 mm is measured, and the semiconductor substrate is subjected to predetermined polishing conditions. Polishing, measuring the surface roughness of the polished semiconductor substrate by the non-contact method, measuring the second wavelength component intensity of the spatial wavelength component region of 5 μm to 1 mm, the first wavelength component intensity and the second wavelength component This is a method for determining the polishing conditions of a semiconductor substrate for determining the quality of the polishing conditions by comparing strengths.
In the invention according to claim 2, a single semiconductor substrate is polished under a certain polishing condition, and it is determined whether or not the polishing condition is good by comparing the first wavelength component intensity and the second wavelength component intensity before and after the polishing. To do.
[0007]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described.
The polishing conditions determined by the present invention are finish polishing conditions that determine the final surface quality of the surface of the semiconductor substrate. In the present invention, the abrasion state of the polishing pad or the quality of the polishing slurry is determined under these polishing conditions.
Final polishing is usually performed by a single-side polishing method. A single-side polishing method will be described with reference to FIG. The polishing apparatus 20 includes a rotating surface plate 21 and a substrate holder 22. The rotating surface plate 21 is a large disk and is rotated by a shaft 23 connected to the center of the bottom surface. A polishing pad 24 is affixed to the upper surface of the rotating surface plate 21. The substrate holder 22 includes a pressure head 22a and a shaft 22b that is connected to the pressure head 22a and rotates the pressure head 22a. A polishing plate 26 is attached to the lower surface of the pressure head 22a. A plurality of semiconductor substrates 10 are attached to the lower surface of the polishing plate 26. A pipe 28 for supplying the polishing slurry 27 is provided on the upper part of the rotating surface plate 21. When the semiconductor substrate 10 is polished by the polishing apparatus 20, the pressure head 22 a is lowered and a predetermined pressure is applied to the semiconductor substrate 10 to hold the substrate 10. While supplying the polishing slurry 27 from the pipe 28 to the polishing pad 24, the pressure head 22a and the rotating surface plate 21 are rotated in the same direction to polish the surface of the substrate 10 flatly.
[0008]
In addition to the above-mentioned AFM, the non-contact surface roughness measurement method of the present invention includes a multi-beam interferometry, a low power optical microscope, and a high power optical microscope. ), Differential Interference Microscope, Phase-Contrast Microscope, cone-focal laser Scanning Optical Microscope, Scanning Electron Microscope, Transmission Electron A microscope (Transmission Electron Microscope), a reflection electron microscope (Reflection Electron Microscope), a field ion microscope (Field Ion Microscope), a scanning tunneling microscope (Scanning Tunneling Microscope), etc. are mentioned.
[0009]
In this embodiment, an apparatus based on differential interference is described.
Among the final polishing conditions when the polishing is performed by the polishing apparatus, the wear state of the polishing pad and the quality of the polishing slurry are inspected by inspecting the specific wavelength region component of the microroughness on the surface of the semiconductor substrate 10 with the inspection apparatus 11 shown in FIG. judge. This inspection apparatus 11 includes a laser oscillator 12, a moving measurement head 13 formed so as to be movable on the surface of the substrate 10,

detectors

14a and 14b for detecting reflected polarized light of the laser light irradiated on the substrate 10, and a non-polarizer. A rising beam splitter 16 and a polarizing beam splitter 17 are provided. The laser light oscillated from the laser oscillator 12 is controlled in light quantity by a polarizing plate and a quarter wavelength plate (not shown), and becomes circularly polarized light. As indicated by the solid line arrow, the circularly polarized light passes through the non-polarizing beam splitter 16 and then enters the pentaprism 13 a of the moving measurement head 13. The moving measurement head 13 is configured to be movable within a range of 100 mm, and its position information is taken into a computer (not shown) with a resolution of 1 μm or 0.2 μm. Incident light is reflected 90 ° downward by the pentaprism 13a, separated into P-polarized light and S-polarized light by the Nomarski prism 13b, and forms an image on the surface of the substrate 10 through the objective lens 13c. The P-polarized light and the S-polarized light reflected by the surface of the substrate 10 are again synthesized by the Nomarski prism 13b, passed through the pentaprism 13a, the non-polarizing beam splitter 16, and each polarized beam splitter 17 as shown by the broken line arrows. Separated into polarized components, the

detectors

14a and 14b detect the intensity of the polarized components with voltage. A surface roughness profile is measured from the detected intensity of each polarization component, and the profile is further subjected to Fourier transform to calculate a wavelength component intensity (hereinafter referred to as PSD).
[0010]
In the determination method according to claim 1, a plurality of semiconductor substrates manufactured through the same process and considered to have no difference between the substrates are polished under a plurality of polishing conditions by the polishing apparatus, The surface of the polished semiconductor substrate is irradiated with laser light oscillated from the laser oscillator. Here, the plurality of different polishing conditions means a case where polishing pads made of different materials, polishing pads made of the same material but having different wear levels, and polishing slurries having different properties are used. The polishing pad having a different material or the polishing slurry having a different property refers to a polishing pad and a polishing slurry which are newly employed and are different from the polishing pad and the polishing slurry which have been conventionally used. A polishing pad having the same material but having a different degree of wear refers to a new polishing pad, even if it is the same product, a polishing pad having a middle degree of wear, or an extremely advanced wear. If the polishing conditions are different, the microroughness and flatness of each surface also change after polishing even for a plurality of semiconductor substrates having the same surface before polishing.
[0011]
When laser light is irradiated onto the surfaces of a plurality of semiconductor substrates that have been polished under a plurality of different polishing conditions in this way, different reflected polarized light is produced depending on the degree of microroughness and flatness, which are wafer surface characteristics after polishing. . A surface roughness profile is measured from each polarization component detected from this reflected polarized light, and the profile is further subjected to Fourier transform to measure a PSD of a spatial wavelength component region of 5 μm to 1 mm. The quality of the polishing pad and polishing slurry is determined for each polishing condition. The reason why the spatial wavelength component region is set to 5 μm to 1 mm is that the wavelength component gradually decreases in this region, which is suitable for evaluating the polishing state. Wavelength components of less than 5 μm are affected by short-time chemical etching on the surface after polishing, so they are not suitable for judging the quality of polishing pads and polishing slurries. This is because the roughness component is determined by other factors. This spatial wavelength component region is preferably 10 μm to 100 μm.
[0012]
In the determination method according to the second aspect, the first PSD and the second PSD before and after polishing of a single semiconductor substrate are respectively measured, and the quality of the polishing condition is determined by comparing both PSDs. This method is suitable not only for determining different polishing conditions but also for sampling inspection when a large number of semiconductor substrates are polished under the same conditions. That is, the PSD when the final polishing is good and the PSD when the final polishing is poor are measured in advance, and the PSD obtained from the sampled semiconductor substrate is compared with these PSDs to determine the polishing conditions. It is possible to evaluate quickly without destroying the semiconductor substrate. If this method is used after finish polishing, various problems such as scratches remaining on the substrate surface and defective oxide film breakdown voltage due to conventional finish polishing failure can be prevented.
[0013]
【Example】
Next, examples of the present invention will be described together with comparative examples.
<Example 1>
Four silicon wafers, which are semiconductor substrates that have undergone normal rough polishing, were prepared, and finish polishing was performed by changing the polishing pad using the same polishing slurry for each silicon wafer. The polishing slurry used for the final polishing was prepared by diluting a commercially available final polishing slurry stock solution in which SiO ₂ abrasive particles were dispersed 30 times with pure water (this is called polishing slurry A). Are the same products, but four types having different usage histories were prepared (referred to as polishing pad A, polishing pad B, polishing pad C, and polishing pad D). The polishing pad A is a pad that has never been used, the polishing pad B is a pad that has been used for 10 hours, the polishing pad C is a pad that has been used for 150 hours, and the polishing pad D has been used for 10 hours. Is a pad that does not work well. Final polishing of four silicon wafers was performed for each polishing pad with a polishing apparatus shown in FIG. 2 at a polishing pressure of 1.18 × 10 ⁴ Pa for 10 minutes. The surface roughness profile was measured on the surface of the four silicon wafers after the finish polishing using the differential interference type surface profiler shown in FIG. 1, and the PSD having a spatial wavelength component region in the range of 10 to 100 μm was obtained. Table 1 shows the integrated values of this PSD. The unit is an arbitrary unit (au), and the same applies to Examples and Comparative Examples described below.
[0014]
<Comparative Example 1>
The haze value was measured on the surface of the silicon wafer after finishing polishing in Example 1 using a light scattering particle counter. The results are shown in Table 1.
<Comparative example 2>
The average microroughness (hereinafter referred to as Ra) of an area of 10 μm × 10 μm was measured on the surface of the silicon wafer after the finish polishing in Example 1 by AFM. The results are shown in Table 1.
[0015]
[Table 1]

[0016]
As is clear from Table 1, the measurement results of Example 1 compared with the measurement results of Comparative Examples 1 and 2 showed a significant difference in each polishing condition, and well reflected the quality of finish polishing. In particular, the fact that the polishing with the polishing pad B used for 10 hours usually shows good polishing is best shown in Example 1 as compared with Comparative Examples 1 and 2, and the measurement method of Example 1 shows the abrasion of the polishing pad. The state and the pass / fail state were accurately determined.
[0017]
<Example 2>
Four more silicon wafers as in Example 1 were prepared. The final polishing was performed by changing the polishing slurry using the same polishing pad for each silicon wafer. As the polishing pad, the polishing pad B of Example 1 was used, and the polishing slurry was prepared by diluting commercially available final polishing slurry stocks of different types 30 times with pure water (hereinafter referred to as polishing slurries A and B). And C). Final polishing of four silicon wafers was performed in the same manner as in Example 1 for each polishing slurry. The surface roughness profile was measured on the surface of the four silicon wafers after finishing polishing using a differential interference type surface profiler, and a PSD having a spatial wavelength component region in the range of 10 to 100 μm was obtained. Table 2 shows the integrated values of this PSD.
[0018]
<Comparative Example 3>
The haze value was measured on the surface of the silicon wafer after finishing polishing in Example 2 using a light scattering type particle counter. The results are shown in Table 2.
<Comparative example 4>
Ra of the region of 10 μm × 10 μm was measured by AFM on the surface of the silicon wafer after finishing polishing in Example 2. The results are shown in Table 2.
[0019]
[Table 2]

[0020]
As is clear from Table 2, the measurement results of Example 2 are significantly different from the measurement results of Comparative Examples 3 and 4 and reflect the quality of the final polishing with the polishing slurry. It was.
[0021]
【The invention's effect】
As described above, in the present invention, the polishing conditions are optimized by determining the wear state of the polishing pad used for polishing and the quality of the polishing conditions based on the polishing slurry based on the specific wavelength region component of the microroughness of the semiconductor substrate surface. And the optimum combination of polishing pad and polishing slurry can be quickly determined. Further, the state of final polishing can be evaluated by changing the PSD value before and after polishing, and the polishing conditions such as the properties of the polishing cloth and slurry can be changed, which can be used for the development of slurry and polishing pad.
Further, unlike the determination of the polishing conditions based on the oxide film pressure resistance characteristics, the problem caused by the final polishing failure can be quickly prevented in a non-destructive manner, and the polishing conditions can be determined at a low cost.
[Brief description of the drawings]
FIG. 1 is a configuration diagram of a semiconductor substrate surface inspection apparatus.
FIG. 2 is a configuration diagram of a single-side polishing apparatus for a semiconductor substrate.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 Semiconductor substrate 11 Inspection apparatus 12 Laser oscillator 13 Moving measurement head

13a Penta prism

13b Nomarski prism

13c Objective lens

14a, 14b Detector 16 Non-polarizing beam splitter 17 Polarizing beam splitter 20 Single-side polishing apparatus 21 Rotating surface plate 22 Holding substrate Tool 22a Pressure head 22b Shaft 23 Shaft 24 Polishing pad 26 Polishing plate 27 Polishing slurry 28 Piping

Claims

Preparing a plurality of semiconductor substrates manufactured through the same process, polishing each of the plurality of semiconductor substrates under a plurality of different polishing conditions by changing either one or both of a polishing pad and a polishing slurry, The surface roughness of a plurality of polished semiconductor substrates is measured by a non-contact method, and the quality of each of the plurality of polishing conditions is determined based on the magnitude of the wavelength component intensity in the spatial wavelength component region of 5 μm to 1 mm. A method for judging polishing conditions.

The surface roughness of the semiconductor substrate is measured by a non-contact method, the first wavelength component intensity in the spatial wavelength component region of 5 μm to 1 mm is measured, the semiconductor substrate is polished under predetermined polishing conditions, and the polished semiconductor substrate By measuring the surface roughness of the film by the non-contact method, measuring the second wavelength component intensity in the spatial wavelength component region of 5 μm to 1 mm, and comparing the first wavelength component intensity and the second wavelength component intensity A method for determining polishing conditions of a semiconductor substrate for determining whether or not the polishing conditions are good.