JP4202703B2 - Polishing equipment - Google Patents

Description

【００２５】
上記表１中のリンス時間とは、研磨後に行われる水研磨に要する時間をいう。すなわち、砥粒の除去を目的として、スラリの代わりに水を用いて小さい荷重で研磨する際に要する時間のことをいう。
【００２６】
図３はウェーハチャック表面の面粗さを縦軸に、気泡の量を横軸に取り、砥粒の付着の有無を調べた本研磨実験の実験結果である。同図の横軸は、右方向に行くほどセラミック中の気泡が少ないことを表している。同図から、気泡の少ないポアフリー材を使用し、表面粗さが１μｍ以下である場合に砥粒がチャック表面に付着しないことが分かる。
【００２７】
一方、図４は従来セラミック材のウェーハチャックを用いて連続研磨加工を実施したときのウェーハ加工精度（ＳＦＱＲ）の変化状況を示した図である。ここでＳＦＱＲとは、研磨されたウェーハから所定寸法（２５ｍｍ角）の４角形を複数サンプリングし、各サンプルについて所望のウェーハ厚との差を求め、各サンプルの値の平均値を算出することにより求められるウェーハ平坦度の指標である。図４より、３枚目に研磨されたウェーハのＳＦＱＲは０．１２μｍであるのに対し、１１枚目に研磨されたウェーハのＳＦＱＲは０．３２μｍ、２５枚目に研磨されたウェーハのＳＦＱＲは０．７１μｍとなり、連続研磨するに従いウェーハ加工精度（ＳＦＱＲ）が劣化することがわかる。なお、ウェーハ加工順２６枚目においてウェーハチャック表面の研磨を行ったため、２７枚目に研磨されたウェーハのＳＦＱＲは０．１１μｍと回復している。
【００２８】
上記砥粒付着実験結果および上記連続研磨加工実験結果からわかるように、従来セラミック材で構成されたウェーハチャックを用いて連続研磨加工したときはチャック表面への砥粒付着が発生し、連続加工中にウェーハ加工精度が劣化する。
【００２９】
これに対して気泡が少なくかつ表面粗さがRmax：１μｍ以下のセラミック材で構成されたチャックを用い連続研磨加工を行ったときには、最後まで平坦度を維持することができた。
【００３０】
以上のような本発明者達の実験に基づく知見から、本発明者達は、セラミック材であって、そのセラミック材中の気泡の直径が１μｍ以下、気泡の数量が１００，０００個／ｍｍ^３以下のセラミック材料により構成されたチャックが、耐磨耗性に優れ、かつ、砥粒や加工粉の付着が少なく連続研磨加工を実施したときにウェーハ加工精度を維持できることを見出した。
【００３１】
また、ウェーハチャックをセラミック材で構成したときでもチャック表面に”ポケット”が存在しなくなったため、加工粉が入り込むことにより発生する加工粉のウェーハ裏面へのキズやウェーハ裏面への再付着を防止でき、また、研磨砥粒がチャック表面に付着しても”アンカー効果”が発生しないので簡単に剥離できることを見出した。
【００３２】
そこで、以下、材質中の気泡の直径が１μｍ以下、気泡の数量が１００，０００個／ｍｍ^３以下のポアフリー材を使用してウェーハチャックを作成する場合について図５を用いて説明する。図５は本発明にかかわるピンチャック１７の平面図である。チャックの加工方法は作成するウェーハチャックの形状によって異なるが、ここでは図５に示した形状のピンチャック１７を例に説明する。
【００３３】
はじめに図５を参照して全体の構成を簡単に説明する。図５は本発明のピンチャック１７の構成で、ピンチャック１７は、チャックベース２５と、ピン１４と、シール部１２と、排気穴２４等とから構成されている。
【００３４】
図５中、符号２５は円板状のチャックベースであり、このチャックベース２５の上面に高さ０．２ｍｍの円柱状のピン１４を複数形成している。更に、このチャックベース２５の上面であってピン１４の周りに、高さ０．２ｍｍのリング状のシール部１２を設けている。このシール部１２に囲まれた凹部を真空吸着部１３とし、真空吸着部１３の中央下端にはチャックベース２５を上面から下面に貫通する排気穴２４を穿設している。そして、この排気穴２４の下端開口部を図示しない真空ポンプに接続する。
【００３５】
このピンチャック１７は以下の方法により作成する。まずＳｉＣであって気泡の直径１μｍ以下、気泡の数量１００，０００個／ｍｍ^３以下のポアフリー材により形成した直径３００ｍｍ厚さ１０ｍｍの円板の下面を、従来材料のＳｉＣにより形成した直径３００ｍｍ厚さ２０ｍｍの円板の上面に接着剤等により接着する。ピンチャック１７に用いる材料はＳｉＣに限らず、アルミナ等を用いることもできる。共にＳｉＣにより形成したのは線膨張係数を等しくし、ピンチャック１７が熱膨張により歪まないようにするためである。
【００３６】
なお、上記ポアフリー材としては、例えばＳｉＣ、アルミナ等が用いられ、用途に応じて例えばサファイア、チタニア、窒化珪素、ジルコニア、窒化アルミ等の種類がある。上記ピンチャック１７の作成に用いるポアフリー材としては、上記条件を満たし、かつ安価なＳｉＣが好適である。
【００３７】
次に真空吸着部１３、ピン１４及びシール部１２を、ポアフリー材により形成した円板の上面に形成する。真空吸着部１３、ピン１４及びシール部１２の形成方法は、特に限定されるものではないが、ビーズブラスト処理などにより形成することができる。ビーズブラスト処理は、例えばウェーハチャック上面のピン１４とシール部１２とが形成されるべき位置に樹脂被覆層を保護膜として形成した後に、エアーブラスト機によって圧縮空気を利用してアルミナ、ＳｉＣ等の球形の粒体（ビーズ）を噴射することにより行う。このときのビーズの粒径は、１〜１０μｍ程度であることが望ましい。これにより樹脂被覆層の保護膜がビーズの衝撃を吸収し、ピン１４とシール部１２が形成されるべき部分は除去されないが、保護膜の無い真空吸着部１３が形成されるべき部分が約０．２ｍｍ除去され真空吸着部１３、ピン１４及びシール部１２が形成される。なお、樹脂被覆層の材料としては、シリコン樹脂、フッ素樹脂、ポリエーテルスルホン樹脂等、被膜形成能のある公知の樹脂を用いることができる。
【００３８】
その後、ウェーハ接触部に相当するピン１４とシール部１２の上面に研削または、研磨加工を施すことにより、ピンチャック上面の表面粗さをRmax：１μｍ以下にする。なお、研磨加工に用いる研磨砥粒の粒径は０．１〜３０μｍであることが望ましい。
【００３９】
本実施の形態ではポアフリー材により形成した直径３００ｍｍ、厚さ１０ｍｍの円板を、従来材料により形成した直径３００ｍｍ、厚さ２０ｍｍの円板の上面に接着剤により接着したものにビーズブラスト処理を行い、ピンチャック１７を作成した。しかし、従来材料により形成した直径３００ｍｍ、厚さ３０ｍｍの円板にビーズブラスト処理を行った後に、ピン１４とシール部１２との表面にＣＶＤ（chemical vapor deposition化学気相蒸着）等により、気泡の直径１μｍ以下、気泡の数量１００，０００個／ｍｍ^３以下のセラミックの薄膜を形成してピンチャックを作成しても良い。また、本実施の形態では本発明をピンチャックに適用する場合について説明したが、本発明の適用はこれに限られるものではなく、吸着面が平坦な通常のチャックや、リングチャック、及び、ホールチャック等にも適用できる。
【００４０】
次に、上記した構成を有するピンチャック１７によって、ウェーハを研磨する方法について図２を用いて以下に説明する。
まず、ピンチャック１７を用いた研磨装置について簡単に説明する。図２において、定盤２３は略円板形状であって水平に保持し、上面に研磨クロス２０を貼付している。定盤２３の下部には、スピンドルを垂直に連結し、スピンドルは図示しない定盤回転モータの回転軸に連結され、定盤２３を回転可能としている。一方、研磨ヘッド２１は、シャフト２６、フレーム２７、エアバック２８、ピンチャック１７、及びリテーナリング２２等から構成される。図中、符号１７はピンチャックであり、このピンチャック１７の上面に円板形状の板ゴム及び板バネよりなるエアバック２８を固定し、エアバック２８の外周をフレーム２７に固定する。そしてフレーム外周にリテーナリング２２を配置し、中央上方には研磨ヘッド昇降用シリンダに連結されたシャフト２６を固定している。
【００４１】
次に上記した構成を有する研磨装置によりウェーハを研磨する方法について説明する。ピンチャック１７にウェーハ１６を吸着させた後、研磨ヘッド回転用モータと定盤回転用モータを駆動させることにより、研磨ヘッド２１と定盤２３とを相対回転させる。そして、研磨クロス２０とウェーハ１６との間に研磨液を供給する。この研磨液としては、ＳｉＣ、ＳｉＯ等の直径１２ｎｍ程度の砥粒とアルカリ溶液を混合したスラリなどを用いることができる。
【００４２】
不図示の研磨ヘッド昇降用シリンダを駆動させ、ウェーハ１６が研磨クロス２０に接するまで研磨ヘッド２１を下降させる。ウェーハ１６及びリテーナリング２２を研磨クロス２０に対して押圧した状態で、研磨液を供給しながら研磨ヘッド２１と定盤２３とを相対回転させ、５分間ウェーハ１６の研磨を行う。
【００４３】
この際、加工粉や砥粒がウェーハ１６の裏面に廻り込むが、本発明のウェーハチャックの表面にはポケットが存在しないため、ポケットに砥粒が入り込むことはない。そのため、従来のようにポケットに入り込んだ砥粒がアンカーとなり、その周りに他の砥粒が凝縮を起こすという現象は発生しない。
【００４４】
上記のように”アンカー効果”が発生しないため、研磨砥粒がチャック表面に廻り込んだ場合であっても、ウェーハ加工毎に行われる洗浄のみによって研磨砥粒を簡単に除去することができる。したがって、従来のように凝縮した砥粒を除去するためにピンチャック１７を研磨する必要がないため、加工基準面の精度が劣化せず、連続研磨加工を実施してもウェーハ加工精度を維持できる。
【００４５】
なお、被研磨物に関しては本発明を実施するにあたり何ら制限は無く、シリコン等の半導体ウェーハのみならず、液晶基板等の平坦面を有する被研磨物に対しても本発明を適用することができる。
【００４６】
このように本願発明は、上記実施の形態に限定されるものではなく、ウェーハチャックの大きさや形状、製造方法、被研磨物などに関し、発明の要旨の範囲内において、種々の応用、変形を加えることが可能である。
【００４７】
【発明の効果】
本発明のウェーハ研磨装置によれば、加工圧等による変形とウェーハへのメタル汚染とを防止することができるセラミック材でウェーハチャックを構成したときでも、チャック表面に”ポケット”が存在しなくなった。そのため、加工粉がウェーハチャックとウェーハとの隙間に入り込むことにより発生するウェーハ裏面へのキズやウェーハ裏面への加工粉の再付着を防止できる。また、研磨砥粒がチャック表面に付着しても”アンカー効果”が発生せず簡単に除去することができる。
【００４８】
また、上記のようにウェーハチャックに研磨砥粒が固着することがないため、ウェーハを連続研磨加工した場合であっても、ウェーハ研磨精度の維持が可能である。
【図面の簡単な説明】
【図１】ウェーハチャックの要部拡大縦断面図である。
【図２】本発明にかかわるウェーハチャックを用いた研磨ヘッドの縦断面図である。
【図３】表面粗さを縦軸に、気泡の量を横軸に取り、ウェーハチャックへの砥粒付着の有無を調べた研磨実験の実験結果である。
【図４】従来セラミック材によるウェーハチャックを用いて連続研磨加工を実施したときのウェーハ加工精度（ＳＦＱＲ）の変化状況を示した図である。
【図５】本発明にかかわるピンチャックの平面図である。
【符号の説明】
１１…ウェーハチャック
１１a…ウェーハチャック表面
１２…シール部
１３…真空吸着部
１４…ピン
１５…加工粉
１６…ウェーハ
１７…ピンチャック
１８…気泡
１９…加工キズ
２０…研磨クロス
２１…研磨ヘッド
２２…リテーナリング
２３…定盤
２４…排気穴
２５…チャックベース
２６…シャフト
２７…フレーム
２８…エアバック。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a substrate fixing device that adsorbs a substrate having a flat surface such as a semiconductor wafer or a liquid crystal substrate, and in particular, a pin chuck or a ring chuck that can improve a substrate support portion and prevent damage to the substrate or deterioration of flatness. The present invention relates to a substrate fixing apparatus and a manufacturing method thereof.
[0002]
[Prior art]
In the process of manufacturing a mirror surface wafer used as a raw material wafer for manufacturing a semiconductor device, a polishing process is performed to maintain the flatness of the wafer. Further, in the process of manufacturing an integrated circuit on a semiconductor wafer, a CMP (Chemical Mechanical Polishing) process is usually performed to flatten the front surface or the back surface of the wafer. In these polishing steps, the wafer is polished by a wafer polishing apparatus and finished into a wafer with extremely high flatness.
[0003]
As a wafer polishing device generally used in the polishing process, a disk-shaped surface plate with a polishing cloth affixed to the surface, and a wafer chuck that holds one surface of the wafer to be polished and presses the other surface of the wafer against the polishing cloth Is widely known in which polishing is performed by supplying a slurry between a wafer and a polishing cloth and rotating the wafer and a surface plate relative to each other.
[0004]
Further, as this wafer chuck, a pin chuck that has a small contact area with the wafer and little damage to the wafer is generally used. However, when the wafer is vacuum-sucked using this pin chuck, there is a problem that the surface of the wafer that slides on the pin and contacts the wafer chuck is damaged. In order to solve this problem, for example, Japanese Patent Laid-Open No. 10-144777 discloses a chuck configuration for reducing damage to the chuck contact surface of the wafer.
[0005]
In this chuck configuration, the wafer contact portion of the pin chuck pin is chamfered or the pin wafer contact portion is formed in a spherical shape. Further, the wafer contact portion of the pin chuck is made of a material whose hardness is lower than that of the wafer.
[0006]
[Problems to be solved by the invention]
Since the wafer chuck surface for polishing is used as a reference surface for processing, the flatness greatly affects the flatness of the wafer after processing. Therefore, the wafer chuck surface of the pin chuck is processed with high precision by grinding or lapping, and is kept at a high flatness.
[0007]
However, if the tip of the pin is chamfered or processed into a spherical surface, the height of each pin, that is, the flatness deteriorates. Further, if the material of the wafer chuck is made of a material whose hardness is lower than that of the wafer, the wafer chuck is worn by repeated contact with the wafer and the flatness of the wafer chuck is deteriorated. Further, in actual processing, the processing powder of the workpiece is scratched between the wafer and the wafer chuck, and the wafer is scratched.
[0008]
The invention according to the present application has been made to solve the above-described problems, and the first object thereof is to damage the wafer without deteriorating the flatness of the wafer chuck surface. An object of the present invention is to provide a wafer chuck capable of reducing the wafer processing accuracy and maintaining the wafer processing accuracy at a high level.
[0009]
The second object of the invention according to the present application is to prevent the occurrence of “pockets” on the chuck surface, so that the machining powder enters the “pocket” and the machining powder scratches the wafer back surface or re-appears on the wafer back surface. It is an object of the present invention to provide a wafer chuck that can prevent adhesion.
[0010]
A third object of the invention according to the present application is to provide a wafer chuck that does not generate an “anchor effect” even if the abrasive grains adhere to the chuck surface and can easily remove the abrasive grains.
[0011]
[Means for Solving the Problems]
In order to achieve the above object, the first invention according to the present application is to hold one surface of an object to be polished by vacuum suction using a vacuum pump and bring the other surface of the object into contact with a polishing cloth. A polishing apparatus including a substrate fixing device to be used, wherein a material of a portion of the substrate fixing device that is in contact with the object to be polished is a ceramic material having a diameter of bubbles contained in the material of 1 μm or less. A polishing apparatus including a substrate fixing apparatus.
[0012]
The second invention according to the present application is a substrate fixing device that holds one surface of an object to be polished by vacuum suction using a vacuum pump and causes the other surface of the object to be in contact with a polishing cloth. a polishing device comprising the material of the portion in contact with the workpiece of the substrate fixing device, 1 [mu] m or less diameter of the bubbles contained in the material, and the quantity of the bubbles 100,000 / mm ³ A polishing apparatus including a substrate fixing device, which is the following ceramic pore-free material.
[0013]
Furthermore, a third invention according to the present application is a substrate fixing device that holds one surface of an object to be polished by vacuum suction using a vacuum pump and causes the other surface of the object to be in contact with a polishing cloth. comprising a polishing device comprising, on the surface of the portion in contact with the workpiece of the substrate fixing device, the diameter of the bubbles is provided the following ceramic thin film 1μm by CVD, the substrate fixing device, characterized in that Polishing apparatus .
[0014]
Further, the fourth invention of the present application, the surface roughness of the wafer contact portion of the substrate fixing device Rmax: 1 [mu] m or less and to have, in the first to third having a substrate fixing device, characterized in that A polishing apparatus according to any one of the inventions.
[0015]
Furthermore, a fifth invention according to the present application includes a pin chuck that holds one surface of an object to be polished by vacuum suction using a vacuum pump and contacts the other surface of the object to be polished with a polishing cloth. A polishing apparatus comprising a pin chuck, wherein a material of a portion of the pin chuck that contacts the object to be polished is a ceramic material having a bubble diameter of 1 μm or less contained in the material. Device .
[0017]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the wafer chuck according to the present application will be described in detail based on the drawings. However, the materials, dimensions, shapes, and the like of the component parts described in the following embodiments are merely illustrative examples, and are not intended to limit the scope of the present invention unless otherwise specifically described. In the following embodiments, a wafer chuck for fixing a silicon wafer is described as a specific example. However, the present invention is not limited to this, and various semiconductor substrates, liquid crystal glass substrates, and the like are fixed. Needless to say, the present invention can also be applied to a substrate fixing device.
[0018]
As shown in FIG. 1, in wafer processing, a wafer chuck 11 is used for the purpose of fixing the wafer 16 and simultaneously using it as a reference surface for wafer processing. The material of the wafer chuck 11 is optimally a ceramic material in order to prevent deformation due to processing pressure or the like and metal contamination of the wafer 16. However, when the wafer 16 is fixed by the processing (hard) wafer chuck 11 and the wafer 16 is processed, the back surface of the wafer 16 is scratched, or dust adheres to the surface of the wafer chuck 11 and the processing reference surface. There is a problem that the flatness of the steel changes and the processing accuracy deteriorates.
[0019]
The present inventors have found through research that these problems are caused by the following causes. That is, the ceramic material has many minute bubbles 18 in the material as shown in FIG. 1 due to the problem of the manufacturing method such as sintering, and the wafer chuck surface 11a also has minute holes. The minute holes on the wafer chuck surface 11a become pockets of the machining powder 15 generated by the machining, and the machining powder 15 enters the pocket. The processing powder 15 is attached to or scratched on the chuck surface of the wafer 16 to contaminate or scratch the wafer 16. Further, when the processing powder 15 protrudes from the processing reference surface, the unevenness is transferred to the wafer processing surface, and processing accuracy deteriorates.
[0020]
The above phenomenon occurs when the bubbles 18 in the material come out on the chuck surface by processing, and the bubbles 18 become pockets. Similarly, if the wafer chuck surface 11a has a processing scratch 19 or the like, the processing scratch 19 Will become a pocket and similar problems will occur.
[0021]
Further, when abrasive grains are used for polishing or the like, a phenomenon of abrasive grain condensation occurs. When a small amount of abrasive grains enters the pocket on the surface of the wafer chuck 11, other loose abrasive grains gather and adhere to the small amount of abrasive grains that have entered the pocket, causing condensation. At this time, the abrasive grains that have entered the pocket serve as anchors, and it becomes difficult to remove the abrasive grains that have condensed and hardened on the wafer chuck surface 11a. For this reason, the accuracy of the processing reference surface is deteriorated and the wafer processing accuracy is deteriorated.
[0022]
In particular, since the periphery of the wafer chuck surface 11a is evacuated during wafer polishing, the wafer chuck surface 11a is easily dried, and during the standby, the polishing liquid does not flow and is easily dried, so that abrasive grains are likely to condense on the wafer chuck surface 11a. Further, the abrasive grains condensed due to adhesion can be removed by polishing the wafer chuck surface 11a. However, since the anchor portion due to a small amount of abrasive grains entering the pocket remains as a root, the abrasive grain is again put on the anchor portion. Adheres and tends to condense.
[0023]
Therefore, the present inventors focused on the pore-free material, which is a ceramic material with few bubbles, based on the above investigation of the cause, and by controlling the amount and surface roughness of the bubbles contained in the ceramic material, An attempt was made to solve the above problem.
[0024]
Therefore, first, a comparative polishing experiment was conducted under the conditions shown in Table 1 to examine the presence or absence of abrasive grains by using the amount of bubbles in the ceramic material and the surface roughness of the material as a standard. FIG. 2 shows the peripheral form of the polishing head 21 of the single wafer polishing machine used in this polishing experiment, and a pin chuck 17 was used as a wafer chuck.
[Table 1]

[0025]
The rinse time in Table 1 above refers to the time required for water polishing performed after polishing. That is, it means the time required for polishing with a small load using water instead of slurry for the purpose of removing abrasive grains.
[0026]
FIG. 3 shows the results of this polishing experiment in which the surface roughness of the wafer chuck surface is plotted on the vertical axis and the amount of bubbles is plotted on the horizontal axis, and the presence or absence of abrasive grains is examined. The horizontal axis in the figure represents that the number of bubbles in the ceramic decreases as it goes to the right. From the figure, it can be seen that when a pore-free material with few bubbles is used and the surface roughness is 1 μm or less, the abrasive grains do not adhere to the chuck surface.
[0027]
On the other hand, FIG. 4 is a diagram showing a change state of wafer processing accuracy (SFQR) when continuous polishing is performed using a conventional ceramic wafer chuck. Here, SFQR is obtained by sampling a plurality of squares of a predetermined dimension (25 mm square) from a polished wafer, obtaining a difference from a desired wafer thickness for each sample, and calculating an average value of the values of each sample. This is an index of required wafer flatness. From FIG. 4, the SFQR of the third polished wafer is 0.12 μm, whereas the SFQR of the eleventh polished wafer is 0.32 μm, and the SFQR of the 25th polished wafer is It can be seen that the wafer processing accuracy (SFQR) deteriorates with continuous polishing. Since the surface of the wafer chuck was polished in the 26th wafer processing order, the SFQR of the 27th wafer was recovered to 0.11 μm.
[0028]
As can be seen from the results of the above-mentioned abrasive grain adhesion experiment and the above-mentioned continuous polishing process experimental results, when continuous polishing was performed using a wafer chuck made of a conventional ceramic material, abrasive grains adhered to the chuck surface, and during continuous processing In addition, the wafer processing accuracy deteriorates.
[0029]
On the other hand, when continuous polishing was performed using a chuck made of a ceramic material with few bubbles and a surface roughness of Rmax: 1 μm or less, the flatness could be maintained until the end.
[0030]
From the knowledge based on the experiments of the inventors as described above, the inventors of the present invention are ceramic materials, the diameter of bubbles in the ceramic material is 1 μm or less, and the number of bubbles is 100,000 / mm ^3. It has been found that chucks made of the following ceramic materials have excellent wear resistance and can maintain wafer processing accuracy when continuous polishing is performed with less adhesion of abrasive grains and processing powder.
[0031]
In addition, even when the wafer chuck is made of a ceramic material, there are no “pockets” on the chuck surface, so it is possible to prevent scratches on the wafer back surface and reattachment to the wafer back surface caused by the processing powder entering. Further, it has been found that even if abrasive grains adhere to the chuck surface, the “anchor effect” does not occur, so that the abrasive can be easily peeled off.
[0032]
Therefore, a case where a wafer chuck is formed using a pore-free material having a bubble diameter of 1 μm or less and a quantity of bubbles of 100,000 / mm ³ or less will be described below with reference to FIG. FIG. 5 is a plan view of the pin chuck 17 according to the present invention. The chuck processing method varies depending on the shape of the wafer chuck to be created. Here, the pin chuck 17 having the shape shown in FIG. 5 will be described as an example.
[0033]
First, the overall configuration will be briefly described with reference to FIG. FIG. 5 shows a configuration of the pin chuck 17 according to the present invention. The pin chuck 17 includes a chuck base 25, a pin 14, a seal portion 12, an exhaust hole 24, and the like.
[0034]
In FIG. 5, reference numeral 25 denotes a disc-shaped chuck base, and a plurality of cylindrical pins 14 having a height of 0.2 mm are formed on the upper surface of the chuck base 25. Further, a ring-shaped seal portion 12 having a height of 0.2 mm is provided on the upper surface of the chuck base 25 and around the pin 14. A concave portion surrounded by the seal portion 12 is referred to as a vacuum suction portion 13, and an exhaust hole 24 that penetrates the chuck base 25 from the upper surface to the lower surface is formed at the lower center of the vacuum suction portion 13. The lower end opening of the exhaust hole 24 is connected to a vacuum pump (not shown).
[0035]
The pin chuck 17 is produced by the following method. First, the lower surface of a 300 mm diameter and 10 mm diameter disk made of a pore-free material made of SiC and having a bubble diameter of 1 μm or less and a number of bubbles of 100,000 / mm ³ or less is 300 mm in diameter formed by SiC of the conventional material. Adhere to the upper surface of a 20 mm thick disc with an adhesive or the like. The material used for the pin chuck 17 is not limited to SiC, and alumina or the like can also be used. The reason why both are formed of SiC is to make the linear expansion coefficient equal and prevent the pin chuck 17 from being distorted by thermal expansion.
[0036]
In addition, as said pore free material, SiC, an alumina, etc. are used, for example, there exist types, such as a sapphire, a titania, a silicon nitride, a zirconia, an aluminum nitride, according to a use. As a pore-free material used for the production of the pin chuck 17, SiC that satisfies the above conditions and is inexpensive is suitable.
[0037]
Next, the vacuum suction part 13, the pin 14, and the seal part 12 are formed on the upper surface of a disk formed of a pore-free material. Although the formation method of the vacuum suction part 13, the pin 14, and the seal | sticker part 12 is not specifically limited, It can form by bead blasting etc. In the bead blasting process, for example, after a resin coating layer is formed as a protective film at a position where the pin 14 and the seal portion 12 on the upper surface of the wafer chuck are to be formed, an air blasting machine is used to compress alumina or SiC. This is done by spraying spherical particles (beads). In this case, the bead particle size is desirably about 1 to 10 μm. Thereby, the protective film of the resin coating layer absorbs the impact of the beads, and the portion where the pin 14 and the seal portion 12 are to be formed is not removed, but the portion where the vacuum suction portion 13 without the protective film is to be formed is about 0. 2 mm is removed, and the vacuum suction part 13, the pin 14, and the seal part 12 are formed. In addition, as a material of the resin coating layer, a known resin capable of forming a film, such as a silicon resin, a fluororesin, or a polyethersulfone resin, can be used.
[0038]
Thereafter, the surface roughness of the upper surface of the pin chuck is reduced to Rmax: 1 μm or less by grinding or polishing the upper surfaces of the pins 14 corresponding to the wafer contact portion and the seal portion 12. In addition, it is desirable that the grain size of the abrasive grains used for the polishing process is 0.1 to 30 μm.
[0039]
In this embodiment, a bead blasting process is performed on a 300 mm diameter and 10 mm thick disk formed of a pore-free material and bonded to an upper surface of a 300 mm diameter and 20 mm thick disk formed of a conventional material with an adhesive. A pin chuck 17 was prepared. However, after a bead blasting process is performed on a disk having a diameter of 300 mm and a thickness of 30 mm made of a conventional material, the surface of the pin 14 and the seal portion 12 is subjected to bubble formation by CVD (chemical vapor deposition) or the like. A pin chuck may be formed by forming a ceramic thin film having a diameter of 1 μm or less and a quantity of bubbles of 100,000 / mm ³ or less. Further, in the present embodiment, the case where the present invention is applied to a pin chuck has been described. However, the application of the present invention is not limited to this, and a normal chuck having a flat suction surface, a ring chuck, and a hole can be used. It can also be applied to chucks.
[0040]
Next, a method for polishing a wafer with the pin chuck 17 having the above-described configuration will be described with reference to FIG.
First, a polishing apparatus using the pin chuck 17 will be briefly described. In FIG. 2, the surface plate 23 has a substantially disc shape and is held horizontally, and the polishing cloth 20 is stuck on the upper surface. A spindle is vertically connected to a lower portion of the surface plate 23, and the spindle is connected to a rotation shaft of a surface plate rotation motor (not shown) so that the surface plate 23 can be rotated. On the other hand, the polishing head 21 includes a shaft 26, a frame 27, an air bag 28, a pin chuck 17, a retainer ring 22, and the like. In the figure, reference numeral 17 denotes a pin chuck. An air bag 28 made of a disc-shaped plate rubber and a plate spring is fixed to the upper surface of the pin chuck 17, and the outer periphery of the air bag 28 is fixed to the frame 27. A retainer ring 22 is disposed on the outer periphery of the frame, and a shaft 26 connected to a polishing head raising / lowering cylinder is fixed above the center.
[0041]
Next, a method for polishing a wafer with the polishing apparatus having the above-described configuration will be described. After the wafer 16 is attracted to the pin chuck 17, the polishing head 21 and the surface plate 23 are rotated relative to each other by driving the polishing head rotation motor and the surface plate rotation motor. Then, a polishing liquid is supplied between the polishing cloth 20 and the wafer 16. As this polishing liquid, slurry in which abrasive grains having a diameter of about 12 nm such as SiC and SiO and an alkaline solution are mixed can be used.
[0042]
A polishing head lift cylinder (not shown) is driven to lower the polishing head 21 until the wafer 16 contacts the polishing cloth 20. While the wafer 16 and the retainer ring 22 are pressed against the polishing cloth 20, the polishing head 21 and the surface plate 23 are relatively rotated while supplying the polishing liquid, and the wafer 16 is polished for 5 minutes.
[0043]
At this time, the processing powder and abrasive grains move around the back surface of the wafer 16, but since there are no pockets on the surface of the wafer chuck of the present invention, the abrasive grains do not enter the pockets. Therefore, unlike the conventional case, the phenomenon that the abrasive grains that have entered the pockets become anchors and other abrasive grains condense around the anchors does not occur.
[0044]
Since the “anchor effect” does not occur as described above, even when the polishing abrasive grains wrap around the chuck surface, the polishing abrasive grains can be easily removed only by cleaning performed every time the wafer is processed. Therefore, since it is not necessary to polish the pin chuck 17 in order to remove the condensed abrasive grains as in the conventional case, the accuracy of the processing reference surface does not deteriorate, and the wafer processing accuracy can be maintained even if continuous polishing processing is performed. .
[0045]
It should be noted that there is no restriction on the object to be polished, and the present invention can be applied not only to semiconductor wafers such as silicon but also to objects to be polished having a flat surface such as a liquid crystal substrate. .
[0046]
As described above, the present invention is not limited to the above-described embodiment, and various applications and modifications are made within the scope of the present invention with respect to the size and shape of the wafer chuck, the manufacturing method, the object to be polished, and the like. It is possible.
[0047]
【The invention's effect】
According to the wafer polishing apparatus of the present invention, even when a wafer chuck is made of a ceramic material that can prevent deformation due to processing pressure or the like and metal contamination of the wafer, there is no “pocket” on the chuck surface. . Therefore, it is possible to prevent scratches on the back surface of the wafer and reattachment of the processing powder to the back surface of the wafer caused by the processing powder entering the gap between the wafer chuck and the wafer. Further, even if abrasive grains adhere to the chuck surface, the “anchor effect” does not occur and can be easily removed.
[0048]
Further, since the abrasive grains do not adhere to the wafer chuck as described above, the wafer polishing accuracy can be maintained even when the wafer is continuously polished.
[Brief description of the drawings]
FIG. 1 is an enlarged longitudinal sectional view of a main part of a wafer chuck.
FIG. 2 is a longitudinal sectional view of a polishing head using a wafer chuck according to the present invention.
FIG. 3 is an experimental result of a polishing experiment in which the surface roughness is plotted on the vertical axis and the amount of bubbles is plotted on the horizontal axis, and the presence or absence of abrasive grains adhering to the wafer chuck is examined.
FIG. 4 is a diagram showing a change state of wafer processing accuracy (SFQR) when continuous polishing is performed using a wafer chuck made of a conventional ceramic material.
FIG. 5 is a plan view of a pin chuck according to the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 11 ... Wafer chuck 11a ... Wafer chuck surface 12 ... Seal part 13 ... Vacuum adsorption part 14 ... Pin 15 ... Processing powder 16 ... Wafer 17 ... Pin chuck 18 ... Bubble 19 ... Processing scratch 20 ... Polishing cloth 21 ... Polishing head 22 ... Retainer Ring 23 ... surface plate 24 ... exhaust hole 25 ... chuck base 26 ... shaft 27 ... frame 28 ... air bag.

Claims (5)

A polishing apparatus comprising a substrate fixing device for holding one surface of an object to be polished by vacuum suction using a vacuum pump and contacting the other surface of the object to be polished with a polishing cloth,
The material of the portion in contact with the workpiece of the substrate fixing device, the polishing apparatus diameter of air bubbles contained in the material is less ceramic material 1 [mu] m, comprising a substrate fixing device, characterized in that. A polishing apparatus comprising a substrate fixing device for holding one surface of an object to be polished by vacuum suction using a vacuum pump and contacting the other surface of the object to be polished with a polishing cloth,
The material of the portion of the substrate fixing device that contacts the object to be polished is a ceramic pore-free material in which the diameter of bubbles contained in the material is 1 μm or less and the number of bubbles is 100,000 / mm ³ or less. A polishing apparatus comprising a substrate fixing device . A polishing apparatus comprising a substrate fixing device for holding one surface of an object to be polished by vacuum suction using a vacuum pump and contacting the other surface of the object to be polished with a polishing cloth,
Wherein the surface of the portion in contact with the object to be polished, the diameter of the bubble by CVD has provided the following ceramic film 1 [mu] m, a polishing apparatus having a substrate fixing device, characterized in that the substrate fixing device. The polishing apparatus according to claim 1 , further comprising a substrate fixing device, wherein a surface roughness of a wafer contact portion of the substrate fixing device is Rmax: 1 μm or less. A polishing apparatus comprising a pin chuck that holds one surface of an object to be polished by vacuum suction using a vacuum pump and abuts the other surface of the object to be polished on a polishing cloth,
The material of the portion in contact with the workpiece of the pin chuck, the polishing apparatus diameter of air bubbles contained in the material is less ceramic material 1 [mu] m, it comprises a pin chuck according to claim.

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