【０００１】
【発明の属する技術分野】
本発明は、板状体、例えば液晶ディスプレイ用ガラス基板、フォトマスク用ガラス基板、磁気ディスク用ガラス基板、シリコンウェハ等、特に液晶ディスプレイ用ガラス基板の片側を支持し、その反対側の表面を研磨する片面研磨装置に用いる加圧定盤に関するものである。
【０００２】
【従来の技術】
液晶ディスプレイ用ガラス基板、フォトマスク用ガラス基板、磁気ディスク用ガラス基板、シリコンウェハ等に使用する基板の製造直後の表面は、完全な平滑面ではなく、多少のうねりやマイクロコルゲーション、凹凸、キズ等を有している。よって、通常、これらの基板は研磨により平滑な面に加工される。
【０００３】
従来、一般的に行われているオスカー式研磨機等による片面研磨は、上部の加圧定盤に、基板が収まる開口穴を開けた基板ホルダーを貼り付け、基板を基板ホルダーに保持した状態で、酸化セリウム等の微粉からなる研磨材を水に懸濁させてスラリーとした研磨液を供給しつつ、回転する下側の研磨盤の盤面に貼着された研磨布に片面を押しつけて、研磨加工する方法で行われる。
【０００４】
尚、オスカー式研磨機においては、上側の加圧定盤と下側の研磨盤の揺動運動および回転によって基板の研磨面を均一に研磨している。即ち、通常、加圧定盤は揺動自在なアームに自転可能に取り付けられ、この加圧定盤には基板を保持するための保持具が取り付けられている。
【０００５】
この保持具は加圧定盤の下面に接着材または粘着材によって貼着される発泡弾性体等のバックアップ部材とバックアップ部材の下面側に接着材によって貼着されるベークライト等の保持板、即ち、基板ホルダーよりなる。この基板ホルダーの中央部には、基板の大きさおよび形状に合わせた形状の開口穴が形成されている。基板が基板ホルダーに開けられた開口穴に保持された状態で、基板の下側の、研磨布を貼り付けた研磨盤を回転させ、研磨布に加圧定盤で基板の研磨面を押圧し研磨を行う。
【０００６】
例えば、特開平５−１２３９６３号公報に示される液晶用大型マスク基板のように無欠陥、高精度が要求される場合は加圧定盤側に軟質の布を貼り付けるという方法が開示されている。
【０００７】
また、特開平６−２３８５５９号公報には、基板ホルダー側面部にまで軟質の布を貼り付け基板の端面部におけるクラック、割れ、キズの発生を防止する方法が開示されている。
【０００８】
更に、特開平７−１３６９２７号公報には、軟質の布に親水性物質を塗り布の乾燥をなくし布の劣化を抑制し交換による工数を削減する方法が開示されている。
【０００９】
一方、加圧定盤側に基板を保持するための基板ホルダーを用いない片面研磨機において、基板の片面を研磨する際、上側の加圧定盤に貼着したバックパッドと通称する多孔質軟質樹脂よりなる厚さ１ｍｍ程度の発泡シートに、基板を密着させた状態で、該バックパッドと下側の研磨盤に貼着した研磨布の間に、研磨対象である基板を挟み込み、研磨材を供給しながら、研磨布に押し付け、下側の研磨盤を回転させることによって基板の片面を研磨する。
【００１０】
詳しくは、両面粘着シートを予め全面に貼ったバックパッドを、加圧定盤下面側にもう一方の粘着面により貼り付けた後で、基板の非研磨面側をバックパッド下面側に密着固定させる。バックパッドに適量の水を含ませ、加圧ローラ等を用いて、基板を密着させると水の表面張力およびバックパッドの粘着性で、基板がバックパッド下面側に固定される。密着固定した基板の研磨面側を、加圧定盤で回転する研磨盤上に両面粘着シートで貼り付けられた研磨布に、加圧定盤にて押圧して研磨する。
【００１１】
【発明が解決しようとする課題】
バックパッドを加圧定盤下面に貼着する際、バックパッドと下面の間に気泡が残り局部的な凸部となり、そのことが原因で、研磨後の基板表面には局部的な凹みによる研磨ムラが発生し欠陥となるという問題があった。
【００１２】
【課題を解決するための手段】
本発明者は、この問題を解決する方法を検討した結果、加圧定盤下面を多数の線状の凹みを有する状態、および磨り面状とし、気泡が残ることを防止することが効果的であることがわかった。
【００１３】
即ち、本発明は多孔質樹脂製の発泡シートからなるバックパッドにより保持した板状体を、回転する研磨盤上の研磨布に加圧定盤にて押圧して、板状体表面を研磨する片面研磨装置に用いる加圧定盤において、加圧定盤の下面は内面部から外周部まで繋がった多数の線状の凹みを有することを特徴とする片面研磨装置に用いる研磨用加圧定盤である。
【００１４】
更に、本発明は、多孔質樹脂製の発泡シートからなるバックパッドにより保持した板状体を、回転する研磨盤上の研磨布に加圧定盤にて押圧して、板状体表面を研磨する片面研磨装置に用いる加圧定盤において、下面が磨り面状であることを特徴とする片面研磨装置に用いる加圧定盤である。
【００１５】
更に、本発明は、多孔質樹脂製の発泡シートからなるバックパッドにより保持した板状体を、回転する研磨盤および研磨布に加圧定盤にて押圧して、板状体表面を研磨する片面研磨装置に用いる加圧定盤において、下面に内面部から外周部まで繋がった多数の線状の凹みを有し、かつ下面が磨り面状であることを特徴とする片面研磨装置に用いる加圧定盤である。
【００１６】
更に本発明は、線状の凹みのサイズが幅０．０５ｍｍ以上、１ｍｍ以下、深さが０．０１ｍｍ以上、１ｍｍ以下の範囲であることを特徴とする上記の片面研磨装置に用いる加圧定盤である。
【００１７】
更に、本発明は、磨り面状の凹凸のサイズが１μｍ以上、１００μｍ以下の範囲であることを特徴とする上記の片面研磨装置に用いる加圧定盤である。
【００１８】
片面研磨装置において、基板の片面を研磨する際、上側に加圧定盤、バックパッドと通称する多孔質樹脂よりなる発泡シートおよび基板を保持するためのホルダーを配し、下側に研磨盤および研磨布を配し、バックパッドと研磨布の間に研磨対象である基板を挟み込み、加圧定盤で基板の片面を下側の回転する研磨盤および研磨布に押圧し研磨する。加圧定盤の下面に凹凸があると、研磨後の基板に凹凸が転写し研磨面が平滑で無くなるので、加圧定盤下面は高精度の平面度が必要とされ、凹凸無きよう表面加工される。即ち、研磨用加圧定盤は下面を高精度の平面度とするため磨き込まれ滑らかな鏡面状態となっている。
【００１９】
本発明者が鋭意調査したところ、バックパッドを加圧定盤下面に貼り付ける際に、両面粘着シートと加圧定盤下面の貼り付け面の間に数ｍｍ程度の気泡が多数発生し、該気泡の大きさは、バックパッドの厚み約０．４〜１ｍｍと同程度の大きさであることが判った。これは加圧定盤下面が高精度の平面度とするため磨き込まれ滑らかな鏡面状態となっているため、両面粘着シートを加圧定盤の下面に貼り付けた際に、空気の逃げる隙間が無く、貼り付け面に空気が閉じこめられ、エアーの噛みこみによる気泡が発生するためであり、かなり慎重に作業しても気泡の発生を無くすことは困難である。更に調査したところ、バックパッドの厚みと同程度の大きさの気泡が発生することにより、バックパッド上に凸部が生じ、バックパッドの凸部が原因で研磨作業時の研磨圧に局部的な異常が生じ、研磨後の基板の表面に、局部的な凹みによる研磨ムラが発生し欠陥となることが判った。
【００２０】
そこで、気泡の発生を防止する方法として、加圧定盤の下面に内面部から外周部までつながった多数の線状の凹みを加工する、下面の全面を磨り面状にする、あるいは両方の加工を同時に行うこととした。即ち、加圧定盤に粘着シートを貼り付ける際に、多数の線状の凹み、あるいは、磨り面による隙間より空気を逃がし、気泡の発生を無くすこととした。下面に線状の凹みを付ける場合は、下面内面部から外周部まで抜けるように凹みを付けないと、隙間があっても行き止まりとなるため空気は逃げ場を失い、問題となる気泡が発生する。線状の凹みの数が多いほど、空気を逃がす効果が大きくなるので、線状の凹みは多い方が好ましいが、加圧定盤の平面度を損い、研磨後の基板の平面度に影響するほど多いことは好ましくない。線状の凹みによる加圧定盤下面のパターンは下面内面部から外周部まで凹みが繋がっていれば問わないが、線状の凹みが一点に集中するとその部分が大きな凹みとなり好ましくない。
【００２１】
本発明における加圧定盤下面の線状の凹みのサイズは、幅が０．０５ｍｍ以上、１ｍｍ以下、深さが０．０１ｍｍ以上、１ｍｍ以下の範囲であることが好ましい。幅、０．０５ｍｍ、深さ、０．０１ｍｍより小さいと空気を逃がす効果が無く、幅、１ｍｍ、深さ、１ｍｍより大きいと加圧定盤の平滑性を損ない、研磨後の基板の平滑性を低化させる。
【００２２】
一方、本発明における加圧定盤下面を磨り面状とした際の凹凸のサイズは、１μｍ以上、１００μｍ以下の範囲であることが好ましい。１μｍより小さいと、空気を逃がす効果が無く、１００μｍより大きいと、加圧用研磨定盤の平滑性を損ない、研磨後の基板の平滑性を低下させる。
【００２３】
加圧定盤の下面の加工方法としては、固定砥石で平面度を出す研削加工と遊離砥粒で平面度をだすラッピング加工等が挙げられる。研磨用加圧定盤下面に線状の凹みを多数加工するには切削加工が適している。ラッピング加工は、研磨砥粒（研磨剤）を挟んだ状態で、摺動運動（摺り合わせ）を行い、加工物を微少切削しながら研磨することによって、加工物をより平坦に仕上げていく遊離砥粒加工であり、研磨定盤下面を梨地状の磨り面に加工する際に、遊離砥粒の粒径を調整し所定の凹凸のサイズを得ることが可能である。
【００２４】
【発明の実施の形態】
図３は、本発明の加圧定盤を用いる片面研磨装置の主要部の側面図である。
【００２５】
ガラス基板４を片面研磨する際は、上側に加圧定盤１を配し、研磨対象であるガラス基板４を挟み込んだ下側の研磨盤５を回転させることによって研磨する。
【００２６】
図３に示すように、加圧定盤１の下面に、両面粘着シート６でバックパッド７と通称する軟質樹脂からなる発泡シートを貼り付け、更に、バックパッド７の下面側にガラス基板４の非研磨面側を密着固定する。ガラス基板４のバックパッド７への固定はバックパッド７に水を含ませ、ガラス基板４を接触させると水の表面張力およびバックパッド７の粘着性で、ガラス基板４が強く密着しバックパッド７に固定する。自転軸８を中心に回転可能な加圧定盤１を加圧し、固定したガラス基板４の下面側である研磨面を、回転駆動軸９を中心に回転する研磨盤５に、両面粘着シート６’で貼り付けた研磨布１０に加圧し押しつけることで研磨加工を行う。
【００２７】
本発明の研磨用加圧定盤１の下面の、貼着時に空気を逃がすための表面加工の例を、図１および図２に示す。図１は、下面に多数の凹みを設けた本発明の研磨用加圧定盤の平面図である。図２の（ａ）は、下面に磨り面状加工を施した加圧定盤の平面図である。（ｂ）は、図２の（ａ）において、Ａ−Ａ’で示される部分の断面図である。
【００２８】
図１の（ａ）〜（ｄ）に示すように加圧定盤１の下面に加圧定盤外周に達する多数の線状の凹み２を付けることよりなる表面加工を行う。下面の多数の線状の凹み２は、下面の内面部から外周部まで繋がっていれば、パターンは問わない。
【００２９】
または、図２の（ａ）および（ａ）に図示したＡ−Ａ’の断面図（ｂ）に示すように、加圧定盤１の下面を磨り面状加工面３にする表面加工を行う。
【００３０】
磨り面とは、細かい凹凸を擁し手触りがザラザラした梨地面であり、例えば、遊離砥粒（研磨剤）を挟んだ状態で摺動運動（すりあわせ）を行い、加工物を微少切削しながら研磨することによって、加工物をより平坦に仕上げていく遊離砥粒加工であるラッピング加工により形成する。
【００３１】
【実施例】
実施例１
鏡面状態にまで滑らかに表面加工された直径７０ｃｍの加圧定盤１の下面を、研削砥石で、外周へ向け、幅０．７ｍｍ、深さ０．５ｍｍ線状の凹みが抜けるように多数加工し、両面粘着シート６を使用して、厚さ１ｍｍのバックパッド７を貼り付けたところ、エアーの噛みこみによる気泡は、直径１ｍｍの物が２個発生したのみで、非常に良好な貼付の状態が得られた。貼着したバックバッド７に、研磨対象である基板、板厚、０．７ｍｍ、サイズ、３６０ｍｍ×４６０ｍｍの液晶ディスプレイ向け基板４を密着固定させ、片面研磨機により、研磨圧１００ｇ／ｃｍ２、研磨時間３００秒／枚の条件で研磨加工したところ、凹みによる研磨ムラのない非常に良好な研磨面が得られた。
実施例２
鏡面状態にまで滑らかに表面加工された直径７０ｃｍの加圧定盤１の下面を、凹凸のサイズ７０μｍで磨り面状に全面ラッピング加工し、両面粘着シート６を使用して、厚さ１ｍｍのバックパッド７を貼り付けたところ、気泡は、直径１ｍｍのものが２個発生したのみで、非常に良好な貼付の状態が得られた。貼着したバックバッド７に、前記基板を密着固定させ、片面研磨機により実施例１と同様の条件で研磨加工したところ、凹みによる研磨ムラのない非常に良好な研磨面が得られた。
比較例１
鏡面状態にまで滑らかに表面加工された直径７０ｃｍの加圧定盤１の下面を加工しないで、両面粘着シート６を使用して、厚さ１ｍｍのバックパッド７を貼り付けたところ、直径、最小１ｍｍから最大１８ｍｍのエアーの噛みこみによる気泡が１９ヶ所発生し、バックパッド７上に該気泡による凸部が多数発生した。貼着したバックパッド７に、前記基板を４密着固定させ、片面研磨機により実施例１と同様の条件で研磨加工したところ、バックパッドの凸部の影響により、研磨面に欠陥である凹みによる研磨ムラが発生した。
比較例２
鏡面状態にまで滑らかに表面加工された直径７０ｃｍの加圧定盤１の下面を研削砥石で下面の外周へ向け線状の凹みが抜けないように加工し、両面粘着シートを使用して、厚さ１ｍｍのバックパッドを貼り付けたところ、数ｍｍから１０数ｍｍのエアーの噛みこみが１２ヶ所発生し、バックパッド７上にエアーの噛み込みによる凸部が多数発生した。貼着したバックバッド７に該基板４を貼り付け、片面研磨機により実施例１と同様の条件で研磨加工したところ、バックパッド７の凸部の影響により研磨面に欠陥である凹みによる研磨ムラが発生した。
【００３２】
【発明の効果】
本発明により、加圧定盤とバックパッドを両面粘着シートを使用して貼り付けた際に、加圧定盤の下面と粘着シートの貼付部位に、エアーの噛みこみによる気泡の発生が殆ど無くなることにより、バックパッド上に凸部が発生せず、研磨後の基板に局部的に発生する凹みによる研磨ムラが無くなる。
【図面の簡単な説明】
【図１】（ａ）〜（ｄ）は、本発明の実施例において、下面に多数の凹みを設けた研磨用加圧定盤の平面図である。
【図２】（ａ）は、本発明の実施例において、下面に磨り面状加工を施した加圧定盤の平面図である。（ｂ）は、図２（ａ）において、Ａ−Ａ’で示される部分の断面図である。
【図３】本発明の加圧定盤を用いる片面研磨装置の主要部の側面図である。
【符号の説明】
１ 加圧定盤
２ 線状の凹み
３ 磨り面状加工面
４ ガラス基板[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention supports a plate-shaped body, for example, a glass substrate for a liquid crystal display, a glass substrate for a photomask, a glass substrate for a magnetic disk, a silicon wafer, etc., and particularly, supports one side of a glass substrate for a liquid crystal display and polishes the surface on the opposite side. And a pressure platen used in a single-side polishing apparatus.
[0002]
[Prior art]
The surface of a glass substrate for a liquid crystal display, a glass substrate for a photomask, a glass substrate for a magnetic disk, a substrate for a silicon wafer, etc. immediately after production is not a completely smooth surface, but has some undulations, microcorrugations, irregularities, scratches, etc. have. Therefore, these substrates are usually processed into a smooth surface by polishing.
[0003]
Conventionally, single-side polishing with an Oscar-type polishing machine or the like, which is generally performed, attaches a substrate holder having an opening hole for accommodating the substrate to an upper pressure platen, and holds the substrate in the substrate holder. Abrasives made of fine powders such as cerium oxide are suspended in water, and a slurry is supplied as a slurry, while one side is pressed against a polishing cloth stuck on the surface of a rotating lower polishing plate to perform polishing. It is performed by a processing method.
[0004]
In the Oscar-type polishing machine, the polished surface of the substrate is uniformly polished by the swinging motion and rotation of the upper pressure platen and the lower polishing plate. That is, usually, the pressure plate is rotatably attached to a swingable arm, and a holder for holding the substrate is attached to the pressure plate.
[0005]
This holder is a backup member such as a foamed elastic body adhered to the lower surface of the pressure platen by an adhesive or an adhesive, and a holding plate such as bakelite adhered to the lower surface side of the backup member by an adhesive, that is, Consists of a substrate holder. An opening hole having a shape corresponding to the size and shape of the substrate is formed in the center of the substrate holder. While the substrate is held in the opening hole opened in the substrate holder, rotate the polishing plate on the lower side of the substrate, on which the polishing cloth is attached, and press the polishing surface of the substrate on the polishing cloth with a pressure platen. Perform polishing.
[0006]
For example, when a defect-free and high precision is required as in a large mask substrate for a liquid crystal disclosed in Japanese Patent Application Laid-Open No. 5-123396, a method of attaching a soft cloth to the pressure platen side is disclosed. .
[0007]
Also, Japanese Patent Application Laid-Open No. 6-238559 discloses a method in which a soft cloth is stuck to the side surface of a substrate holder to prevent cracks, breaks, and scratches from occurring at the end surface of the substrate.
[0008]
Further, Japanese Patent Application Laid-Open No. Hei 7-136927 discloses a method in which a soft cloth is coated with a hydrophilic substance, drying of the cloth is suppressed, deterioration of the cloth is suppressed, and the number of steps for replacement is reduced.
[0009]
On the other hand, in a single-side polishing machine that does not use a substrate holder for holding a substrate on the pressing platen side, when polishing one surface of the substrate, a porous soft material commonly called a back pad attached to the upper pressing platen is used. A substrate to be polished is sandwiched between the back pad and a polishing cloth adhered to a lower polishing plate in a state where the substrate is brought into close contact with a foam sheet having a thickness of about 1 mm made of a resin. One side of the substrate is polished by pressing against the polishing cloth and rotating the lower polishing plate while supplying.
[0010]
In detail, after the back pad on which the double-sided adhesive sheet has been pasted on the entire surface is pasted on the lower surface side of the pressure platen with the other adhesive surface, the non-polished surface side of the substrate is firmly fixed to the lower surface side of the back pad. . When a suitable amount of water is contained in the back pad and the substrate is brought into close contact with a pressure roller or the like, the substrate is fixed to the lower surface of the back pad by the surface tension of water and the adhesiveness of the back pad. The polished surface side of the substrate fixedly adhered is polished by pressing with a pressure plate against a polishing cloth adhered with a double-sided adhesive sheet on a polishing plate rotating with a pressure plate.
[0011]
[Problems to be solved by the invention]
When attaching the back pad to the lower surface of the pressure platen, air bubbles remain between the back pad and the lower surface to become local convex portions, and as a result, the substrate surface after polishing is polished by local dents. There is a problem that unevenness occurs and becomes a defect.
[0012]
[Means for Solving the Problems]
The present inventor has studied a method for solving this problem, and as a result, it is effective to form a state in which the lower surface of the pressure platen has a number of linear depressions and a polished surface to prevent air bubbles from remaining. I found it.
[0013]
That is, in the present invention, the plate-like body held by the back pad made of a foamed sheet made of a porous resin is pressed against a polishing cloth on a rotating polishing plate with a pressure platen to polish the surface of the plate-like body. A pressure platen for use in a single-side polishing apparatus, wherein a lower surface of the pressure plate has a number of linear recesses connected from an inner surface portion to an outer peripheral portion. It is.
[0014]
Further, the present invention provides a polishing method for polishing a plate-shaped body held by a back pad made of a foamed sheet made of a porous resin against a polishing cloth on a rotating polishing plate with a pressure platen, thereby polishing the surface of the plate-shaped body. A pressure platen used in a single-side polishing apparatus, wherein the lower surface is a polished surface.
[0015]
Further, in the present invention, the plate-like body held by the back pad made of a porous sheet made of a porous resin is pressed against a rotating polishing plate and a polishing cloth with a pressure platen to polish the plate-like body surface. In a pressure platen used for a single-side polishing machine, a lower surface has a large number of linear recesses connected from an inner surface to an outer periphery, and the lower surface has a polished surface, and is a polishing plate used for a single-side polishing device. It is a pressure platen.
[0016]
Further, in the present invention, the size of the linear recess is in the range of 0.05 mm or more and 1 mm or less in width, and the depth is in the range of 0.01 mm or more and 1 mm or less. It is a board.
[0017]
Further, the present invention is the pressure platen used in the above-mentioned single-side polishing apparatus, wherein the size of the polished surface irregularities is in the range of 1 μm or more and 100 μm or less.
[0018]
In the single-side polishing apparatus, when polishing one side of the substrate, a pressure platen on the upper side, a foam sheet made of a porous resin commonly referred to as a back pad and a holder for holding the substrate are arranged, a polishing platen on the lower side and A polishing cloth is arranged, a substrate to be polished is sandwiched between the back pad and the polishing cloth, and one surface of the substrate is pressed against a lower rotating polishing plate and polishing cloth with a pressure platen to perform polishing. If there is unevenness on the lower surface of the pressure platen, the unevenness will be transferred to the polished substrate and the polished surface will not be smooth, so the lower surface of the pressure platen must have high precision flatness and surface processing so that there is no unevenness Is done. In other words, the polishing pressure platen is polished in order to make the lower surface have high-precision flatness, and is in a smooth mirror surface state.
[0019]
The present inventors have conducted extensive research and found that when the back pad is attached to the lower surface of the pressure platen, a large number of air bubbles of about several mm are generated between the double-sided adhesive sheet and the attached surface of the lower surface of the pressure platen. The size of the bubbles was found to be about the same as the thickness of the back pad of about 0.4 to 1 mm. This is because the lower surface of the pressure platen is polished to obtain a high-precision flatness and has a smooth mirror surface, so that when the double-sided adhesive sheet is attached to the lower surface of the pressure platen, the air escape space This is because air is trapped on the application surface and air bubbles are generated due to air entrapment, and it is difficult to eliminate the generation of air bubbles even when working very carefully. Further investigation revealed that bubbles having a size approximately the same as the thickness of the back pad generated a convex portion on the back pad, and the convex portion of the back pad caused local pressure on the polishing pressure during the polishing operation. It was found that an abnormality occurred, and polishing unevenness due to a local depression occurred on the surface of the polished substrate, resulting in a defect.
[0020]
Therefore, as a method of preventing the generation of air bubbles, a number of linear dents connected from the inner surface to the outer periphery are formed on the lower surface of the pressure platen, the entire lower surface is polished, or both are processed. At the same time. That is, when sticking the pressure-sensitive adhesive sheet to the pressure platen, air is released from a large number of linear dents or gaps formed by the polished surface to eliminate bubbles. In the case where a linear depression is formed on the lower surface, if the depression is not formed so as to pass from the inner surface to the outer periphery of the lower surface, even if there is a gap, a dead end occurs, so that the air loses a refuge and a problematic bubble is generated. The greater the number of linear dents, the greater the effect of escaping air.Therefore, it is preferable that the number of linear dents is large, but the flatness of the pressure platen is impaired and the flatness of the polished substrate is affected. It is not preferable that the number is too large. The pattern of the lower surface of the pressure platen due to the linear depressions is not limited as long as the depressions are connected from the inner surface to the outer periphery of the lower surface. However, if the linear depressions are concentrated at one point, the portions become large and are not preferable.
[0021]
The size of the linear recess on the lower surface of the pressure platen in the present invention is preferably in the range of 0.05 mm or more and 1 mm or less and the depth of 0.01 mm or more and 1 mm or less. When the width is smaller than 0.05 mm, depth, or 0.01 mm, there is no effect of releasing air. When the width is larger than 1 mm, depth, or 1 mm, the smoothness of the pressure plate is impaired, and the smoothness of the substrate after polishing is reduced. Is lowered.
[0022]
On the other hand, in the present invention, the size of the unevenness when the lower surface of the pressure platen is polished is preferably in the range of 1 μm or more and 100 μm or less. When it is smaller than 1 μm, there is no effect of releasing air, and when it is larger than 100 μm, the smoothness of the polishing platen for pressing is impaired, and the smoothness of the polished substrate is reduced.
[0023]
Examples of the processing method of the lower surface of the pressure platen include grinding processing for obtaining flatness with a fixed grindstone and lapping processing for obtaining flatness with free abrasive grains. Cutting is suitable for forming many linear depressions on the lower surface of the polishing platen. The lapping process is a loose grinding process that performs a sliding motion (grinding) with polishing abrasive grains (abrasives) sandwiched between them and grinds the workpiece while cutting it finely, thereby finishing the workpiece more evenly. This is a graining process. When the lower surface of the polishing platen is machined into a matt-like polished surface, it is possible to adjust the particle size of the free abrasive grains to obtain a predetermined uneven size.
[0024]
BEST MODE FOR CARRYING OUT THE INVENTION
FIG. 3 is a side view of a main part of a single-side polishing apparatus using the pressure platen of the present invention.
[0025]
When the glass substrate 4 is polished on one side, the pressure platen 1 is arranged on the upper side, and the lower polishing plate 5 sandwiching the glass substrate 4 to be polished is rotated to polish.
[0026]
As shown in FIG. 3, a foam sheet made of a soft resin commonly called a back pad 7 with a double-sided pressure-sensitive adhesive sheet 6 is adhered to the lower surface of the pressure platen 1. Closely fix the non-polished surface side. When the glass substrate 4 is fixed to the back pad 7, the back pad 7 is impregnated with water. When the glass substrate 4 is brought into contact with the back pad 7, the surface tension of the water and the tackiness of the back pad 7 cause the glass substrate 4 to strongly adhere to the back pad 7. Fixed to. The pressurizing platen 1 rotatable about the rotation shaft 8 is pressed, and the polishing surface, which is the lower surface side of the fixed glass substrate 4, is attached to the polishing plate 5 rotating about the rotation drive shaft 9 by the double-sided adhesive sheet 6. Polishing is performed by pressing and pressing against the polishing cloth 10 pasted in '.
[0027]
FIGS. 1 and 2 show examples of the surface processing of the lower surface of the polishing pressure platen 1 of the present invention for releasing air at the time of sticking. FIG. 1 is a plan view of a polishing pressure platen of the present invention in which a number of depressions are provided on a lower surface. FIG. 2A is a plan view of a pressure platen having a polished surface processed on the lower surface. FIG. 2B is a cross-sectional view of a portion indicated by AA ′ in FIG.
[0028]
As shown in FIGS. 1A to 1D, surface processing is performed by forming a large number of linear recesses 2 reaching the outer periphery of the pressure platen 1 on the lower surface of the pressure platen 1. The pattern of the many linear recesses 2 on the lower surface is not limited as long as it is connected from the inner surface to the outer periphery of the lower surface.
[0029]
Alternatively, as shown in the cross-sectional view (b) of AA ′ shown in (a) and (a) of FIG. 2, surface processing is performed to make the lower surface of the pressure platen 1 a polished surface processing surface 3. .
[0030]
The polished surface is a pear surface having fine irregularities and a rough texture, for example, performing a sliding motion (grinding) with free abrasive grains (abrasive) sandwiched therebetween, and polishing while finely cutting a workpiece. By doing so, the workpiece is formed by lapping, which is free abrasive grain processing for finishing the workpiece more flat.
[0031]
【Example】
Example 1
The lower surface of the pressure platen 1 having a diameter of 70 cm, which has been smoothly surface-polished to a mirror surface state, is machined with a grinding wheel toward the outer periphery so that a linear recess of 0.7 mm in width and 0.5 mm in depth comes out. Then, when the back pad 7 having a thickness of 1 mm was stuck using the double-sided pressure-sensitive adhesive sheet 6, only two bubbles having a diameter of 1 mm were generated due to the entrapment of air. The condition was obtained. A substrate to be polished, a substrate having a thickness of 0.7 mm, a size of 360 mm × 460 mm, and a substrate 4 for a liquid crystal display, which are to be polished, are fixedly adhered to the attached back pad 7, and the polishing pressure is 100 g / cm 2 by a single-side polishing machine. When the polishing was performed under the condition of 300 seconds / sheet, a very good polished surface without polishing unevenness due to the dent was obtained.
Example 2
The lower surface of the pressure platen 1 having a diameter of 70 cm, which has been smoothly surface-polished to a mirror surface state, is entirely wrapped in a polished surface shape with an uneven size of 70 μm. When the pad 7 was stuck, only two bubbles having a diameter of 1 mm were generated, and a very good stuck state was obtained. The substrate was adhered and fixed to the attached back pad 7 and polished by a single-side polishing machine under the same conditions as in Example 1. As a result, a very good polished surface without polishing unevenness due to the depression was obtained.
Comparative Example 1
A back pad 7 having a thickness of 1 mm was adhered using a double-sided adhesive sheet 6 without processing the lower surface of the pressure platen 1 having a diameter of 70 cm, which was smoothly processed to a mirror surface state. Nineteen bubbles were generated due to air entrapment from 1 mm to a maximum of 18 mm, and a large number of convex portions due to the bubbles were generated on the back pad 7. The substrate was adhered and fixed to the back pad 7 adhered to the back pad 4 and polished by a single-side polishing machine under the same conditions as in Example 1. Polishing unevenness occurred.
Comparative Example 2
The lower surface of the pressure platen 1 having a diameter of 70 cm, which has been smoothed to a mirror surface, is processed with a grinding wheel so that a linear dent does not come out toward the outer periphery of the lower surface. When a back pad having a thickness of 1 mm was attached, air entrapment of several mm to several tens of mm occurred in 12 places, and a large number of convex portions were formed on the back pad 7 due to air entrapment. The substrate 4 was adhered to the back pad 7 and polished by a single-side polishing machine under the same conditions as in Example 1. Polishing unevenness was caused by a dent which was a defect on the polished surface due to the influence of the convex portion of the back pad 7. There has occurred.
[0032]
【The invention's effect】
According to the present invention, when the pressure platen and the back pad are pasted together using a double-sided pressure-sensitive adhesive sheet, almost no air bubbles are generated due to air entrapment on the lower surface of the pressure platen and the region where the pressure-sensitive adhesive sheet is pasted. As a result, no convex portion is generated on the back pad, and polishing unevenness due to a locally generated dent on the polished substrate is eliminated.
[Brief description of the drawings]
1 (a) to 1 (d) are plan views of a polishing pressure plate having a large number of depressions on a lower surface in an embodiment of the present invention.
FIG. 2A is a plan view of a pressure platen having a polished surface formed on a lower surface in an embodiment of the present invention. FIG. 2B is a cross-sectional view of a portion indicated by AA ′ in FIG.
FIG. 3 is a side view of a main part of a single-side polishing apparatus using the pressure platen of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Pressing platen 2 Linear recess 3 Polished surface 4 Glass substrate
