JP4885376B2

JP4885376B2 - Grinding wheel

Info

Publication number: JP4885376B2
Application number: JP2001203115A
Authority: JP
Inventors: 将昭鈴木
Original assignee: Disco Corp
Current assignee: Disco Corp
Priority date: 2001-07-04
Filing date: 2001-07-04
Publication date: 2012-02-29
Anticipated expiration: 2021-07-04
Also published as: JP2003019671A

Description

【０００１】
【発明の属する技術分野】
本発明は、それに限定されるものではないが、特に半導体ウエーハの片面を研削するのに好都合に使用される研削ホイールに関する。
【０００２】
【従来の技術】
当業者には周知の如く、半導体デバイスの製造においては、半導体ウエーハの片面を研削して半導体ウエーハを所要厚さにせしめる片面研削が遂行されている。かかる研削には、平坦な保持面を有するチャックテーブルとこれに対向して配設された回転軸とを具備する研削機が使用される。半導体ウエーハはその研削すべき片面を露呈せしめて（従って、反対側の面をチャックテーブルに密接せしめて）チャックテーブル上に保持され、回転軸の先端には研削ホイールが装着される。研削ホイールは環状基台とこの基台の下面に装着された砥石手段とから構成されている。砥石手段は、通常、周方向に間隔をおいて配設され周方向に弧状に延びる複数個の砥石から構成されている。基台には周方向に間隔をおいて複数個の冷却液流動孔が形成されている。冷却液流動孔の各々は基台の上面から下面まで基台を貫通して延び、その下端は基台の下面に装着されている砥石手段の半径方向内側に位置せしめられている。チャックテーブルは比較的低速（例えば１００乃至３００ｒｐｍ）で回転せしめられ、回転軸及びこれに装着された研削ホイールは比較的高速（例えば４０００乃至５０００ｒｐｍ）で回転せしめられ、そして研削ホイールの砥石手段を半導体ウエーハの片面に押圧せしめて前進せしめることによって半導体ウエーハの片面の研削が遂行される。かかる研削の際には、回転軸に配設されている冷却液流路を通して研削ホイールの冷却液流動孔に純水の如き冷却液が供給され、基台の下面に開口している冷却液流動孔から冷却液が流出せしめられる。
【０００３】
【発明が解決しようとする課題】
而して、本発明者の経験によれば、上述した形態の従来の研削ホイールを使用した研削においては、供給される冷却液が研削ホイールの砥石手段及び被研削物即ち半導体ウエーハの研削面の冷却に充分効果的に利用されず、これに起因して研削効率が必ずしも充分ではなく、研削ホイールにおける砥石手段の摩滅が比較的大きい、ことが判明した。
【０００４】
本発明は上記事実に鑑みてなされたものであり、その主たる技術的課題は、研削ホイールに改良を加えて、供給される冷却液を研削ホイール及び被研削物の冷却に充分効果的に利用できるようになすことである。
【０００５】
【課題を解決するための手段】
本発明者は従来の研削ホイールを使用した研削を検討したところ、研削ホイールが比較的高速で回転せしめられることに起因して、冷却液の相当量が砥石手段及び被研削物の冷却に充分に利用されることなく半径方向外方に向かって流動してしまうことを認識した。そして、かかる認識に基づき、研削ホイールの基台の形態に改良を加えて、更に詳しくは基台の内周面を独特な形態にすると共に、周方向に連続して延在し且つ半径方向内方に開放された冷却液溜を形成して、研削ホイールの基台に供給された冷却液の半径方向外方への流動を上記冷却液溜によって一旦阻止した後に砥石手段及び被研削物に向けて溢れ出すようになすことによって、上記主たる技術的課題を達成することができることを見出した。
【０００６】
即ち、本発明によれば、上記主たる技術的課題を達成する研削ホイールとして、環状基台と、該基台の下面に装着された砥石手段とから構成された研削ホイールにおいて、
該基台の内周面は、鉛直に下方に延びる上部垂下面、該上部垂下面の下端から水平に半径方向外方に延びる後退面、該後退面の半径方向外側端から下方に向かって半径方向外方に傾斜して延びる上部傾斜面、該上部傾斜面の下端から鉛直に下方に延びる中間垂下面、該中間垂下面の下端から、該上部傾斜面の下方を、水平に半径方向内方に延びる突出面、該突出面の半径方向内側端から鉛直に下方に延びる下部垂下面、及び該下部垂下面の下端から下方に向かって半径方向外方に傾斜して延びる下部傾斜面を含んでおり、該上部傾斜面と該突出面との間に周方向に連続して延在せしめられ且つ半径方向内方に開放されている冷却液溜が規定されており、
該基台には、更に、その上面から該冷却液溜に連通する複数個の連通切欠が形成されている、
ことを特徴とする研削ホイールが提供される。
【０００７】
好適実施形態においては、該砥石手段は周方向に間隔をおいて配設され周方向に弧状に延びる複数個の砥石から構成されている。
【０００８】
【発明の実施の形態】
以下、添付図面を参照して、本発明に従って構成された研削ホイールの好適実施形態について、更に詳細に説明する。
【０００９】
図１及び図２を参照して説明すると、全体を番号２で示す研削ホイールは基台４と砥石手段６とから構成されている。アルミニュームの如き適宜の金属から形成することができる基台２は全体として環状であり、実質上水平である環状上面８、実質上水平である環状下面１０及び実質上鉛直である円筒状外周面１２を有する。
【００１０】
基台４の内周には半径方向内方に開放された冷却液溜１４が形成されていることが重要である。図示の実施形態においては、基台４の内周面は実質上鉛直に下方に延びる上部垂下面１６、この上部垂下面１６の下端から実質上水平に半径方向外方に延びる後退面１８、後退面１８の半径方向外側端から下方に向かって半径方向外方に傾斜して延びる上部傾斜面２０、上部傾斜面２０の下端から実質上鉛直に下方に延びる中間垂下面２２、この中間垂下面２２の下端から、従って上記上部傾斜面２０の下方を、実質上水平に半径方向内方に延びる突出面２４、突出面２４の半径方向内側端から実質上鉛直に下方に延びる下部垂下面２６、及び下部垂下面２６の下端から下方に向かって半径方向外方に傾斜して延びる下部傾斜面２８を含んでいる。そして、上部傾斜面２０と突出面２４との間に、断面形状が略直角三角形状の冷却液溜１４が規定されている。後述する連通切欠が形成されている部位を除いて、上記上部垂下面１６、後退面１８、上部傾斜面２０、中間垂下面２２、突出面２４、下部垂下面２６及び下部傾斜面２８は周方向に連続して延在せしめられており、上記冷却液溜１４も周方向に連続して延在せしめられている。
【００１１】
図１を参照することによって明確に理解される如く、基台４には上面８から内周面における上記後退面１８及び上部傾斜面２０まで延びる連通切欠３０が周方向に間隔をおいて複数個、更に詳しくは等角度間隔をおいて６個形成されており、基台４の上面は連通切欠３０を介して上記冷却液溜１４に連通せしめられている。連通切欠３０の各々は略半円形状であり、半径方向内側が開放されている。基台４には、更に、上面８から実質上鉛直に下方に延びる盲ねじ孔３２が周方向に間隔をおいて複数個形成されている。図示の実施形態においては、等角度間隔をおいて６個の盲ねじ孔３２が形成されており、周方向に見て盲ねじ孔３２の各々は隣接する連通切欠３０の中間に位置せしめられている。
【００１２】
図１及び図２を参照して説明を続けると、上記砥石手段６は基台４の下面１０に配設されている。更に詳述すると、図示の実施形態においては、基台１０の下面には周方向に連続して延びる環状溝３４が形成されている。砥石手段６は周方向に間隔をおいて周方向に弧状に延びる複数個（図示の場合は２７個）の砥石３６から構成されており、砥石３６の各々は適宜の接着剤によってその上部を溝３４内に固着することによって基台１０の下面に固定されている。砥石３６の各々は、例えばダイヤモンド砥粒をビトリファイドの如き適宜の結合剤によって結合することによって形成されたものでよい。砥石３６の各々の横断面形状は矩形でよい。周方向に間隔をおいて配設された複数個の砥石３６に代えて、所望ならば、周方向に連続して延びる環状砥石から砥石手段６を構成することもできる。
【００１３】
図３は図１及び図２に図示する研削ホイール２を使用して半導体ウエーハ３８の片面を研削する様式を簡略に図示している。片面を研削すべき半導体ウエーハ３８は、研削すべき片面を上面として上方に露呈せしめた状態で、チャックテーブル４０上に保持される。チャックテーブル４０は、少なくともその中央主部は多孔質材料から形成され或いは多数の吸引孔を有し、半導体ウエーハ３８を真空吸着することができる形態のものであるのが好適である。
【００１４】
チャックテーブル４０の上方には回転軸４２が配設されており、かかる回転軸４２の先端即ち下端に研削ホイール２が装着される。更に詳述すると、回転軸４２の下端には装着フランジ４４が一体に形成されており、この装着フランジ４４の下面には比較的大径の円形凹部４６が形成されている。回転軸４２には上下方向に延びて円形凹部４６に開口している冷却液流路４８が形成されている。回転軸４２の下端、従って装着フランジ４４には付加部材５０が固定されている。付加部材５０は円形凹部４６の内径と実質上同一の外径を有する上部と装着フランジ４４の外径と実質上同一の外径を有する下部とを有し、その上部が円形凹部４６内に挿入せしめられ、上部と下部との間に規定されている環状肩面が装着フランジ４４の下面に当接せしめられる。装着フランジ４４にはその外周面から円形凹部４６まで半径方向に延びる貫通孔が周方向に間隔をおいて形成されており、付加部材５０の上部にはその外周面から半径方向に延びる盲ねじ孔が周方向に間隔をおいて形成されており、装着フランジ４４の貫通孔を通して付加部材５０の盲ねじ孔に締結ボルト５１を螺合することによって、装着フランジ４４に付加部材５０が固定される。付加部材５０の上部の外周面と装着フランジ４４の円形凹部４６の内周面との間には合成ゴム製でよい密封リング５２が配設され、付加部材５０の環状肩面と装着フランジ４４の下面との間にも合成ゴム製でよい密封リング５４が配設されている。付加部材５０の上面にはその中央から放射状に延びる複数個（図の場合は６個）の溝５６が形成され、そしてまたかかる溝５６の各々の外側端部から実質上鉛直に延び下面に開口している穴５８が形成されている。溝５６及び穴５８は回転軸４２に形成されている上記冷却液流路４８に連通せしめられている。
【００１５】
図１乃至図３を参照して説明を続けると、研削ホイール２は付加部材５０の下面に装着される。装着フランジ４４及び付加部材５０には周方向に間隔をおいて実質上鉛直に延びる複数個（図示の場合は６個）の貫通孔が形成されている。かかる貫通孔を通して、研削ホイール２の基台４の上面に形成されている上記盲ねじ孔３２に締結ボルト６０を螺合することによって、付加部材５０の下面に、従って回転軸４２の下端に研削ホイール２が装着される。研削ホイール２の基台４に形成されている上記連通切欠３０の各々は、付加部材５０に形成されている上記穴５８の各々に整合せしめられる。従って、研削ホイール２の基台４に形成されている上記冷却液溜１４は、基台４に形成されている連通切欠３０並びに付加部材５０に形成されている穴５８及び溝５６を介して、回転軸４２に形成されている冷却液流路４８に連通せしめられている。
【００１６】
半導体ウエーハ３８の片面を研削する際には、チャックテーブル４０が１００乃至３００ｒｐｍ程度でよい比較的低速で回転せしめられると共に、回転軸４２が４０００乃至５０００ｒｐｍ程度でよい比較的高速で回転せしめられ、そして、研削ホイール２を半導体ウエーハ３８の片面に押圧せしめて漸次加工せしめ、かくして半導体ウエーハ３８の片面が研削ホイール２によって、更に詳しくはその砥石手段６によって研削される。かかる研削の際には、回転軸４２の冷却液流路４８を通して常温の純水でよい冷却液が供給される。冷却液は回転軸４２の冷却液流路４８から付加部材５０に形成されている溝５６及び穴５８を通って流動し、次いで研削ホイール２の基台４に形成されている連通切欠３０を通って冷却液溜１４に流入する。研削ホイール２は比較的高速で回転せしめられている故に、冷却液には相当大きな遠心力が作用し、これによって冷却液は半径方向外方に流動せんとする。しかしながら、本発明に従って構成された研削ホイール２においては、半径方向内方に開放された冷却液溜１４が配設されている故に、半径方向外方に流動せしめられる傾向を有する冷却液が一旦冷却液溜１４に滞留せしめられ、半径方向外方への流動が抑制される。そして、冷却液溜１４に滞留せしめられた後に冷却液溜１４から溢れ出し、冷却液溜１４の下方を下方に向かって半径方向外方に傾斜して延在している下部傾斜面２８に沿って流下して、砥石手段６及びこれによって研削されている半導体ウエーハ３８の片面上に導かれる。本発明に従って構成された研削ホイール２においては、研削ホイール２の高速回転に起因して半径方向外方に流動せしめられる冷却液が、冷却液溜１４に一旦滞留された後に所要部位、即ち研削が遂行されている部位、に供給される故に、冷却液が半径方向外方に過剰に流動せしめられて無駄に消費されることが防止乃至抑制され、冷却液が充分効果的に利用される。
【００１７】
実施例
図１及び図２に図示するとおりの形態の研削ホイールを製作した。基台はアルミニュームから形成した。基台の外径Ｄ１は２９０ｍｍ、基台の高さＨ１は１７ｍｍ、上面内径Ｄ２は１５８ｍｍ、下面内径Ｄ３は１７８ｍｍであった。基台の内周における上部垂下面の高さＨ２は２．５ｍｍ、後退面の幅Ｗ１は３．８ｍｍ、上部傾斜面の傾斜角度αは２０度、上部傾斜面の長さＬ１は８．８ｍｍ、中間垂下面の高さＨ３は１．６ｍｍ、突出面の幅Ｗ２は６．３ｍｍ、下部垂下面の高さＨ４は１．６ｍｍ、下部傾斜面の傾斜角度βは４５度、下部傾斜面の長さＬ２は１１．３ｍｍであった。基台の下面には周方向に等間隔をおいて２７個の砥石を固着した。砥石の各々の周方向長さＬ３は２０ｍｍ、厚さＴ１は４．０ｍｍ、基台の下面からの突出長さＬ４は５．２ｍｍであり、各砥石の周方向間隔Ｇ１は２．２ｍｍであった。砥石の各々は粒径４０乃至６０μm のダイヤモンド粒子をビトリファイドによって結合して形成したものであり、ダイヤモンド粒子の集中度は７５であった。
【００１８】
株式会社ディスコから商品名「ＤＦＧ８４１」として販売されている研削機（サーフェイスグラインダー）の回転軸に上記研削ホイールを装着し、直径６インチのシリコンウエーハの片面研削を遂行した。かかる研削において、回転軸の回転速度は４８００ｒｐｍで、チャックテーブルの回転速度は２００ｒｐｍで、研削ホイールを８μm ／秒の下降速度で２００μm 下降せしめ、シリコンウエーハの片面を２００μm の深さに渡って研削した。冷却水として２４℃の純水を回転軸の冷却水流路を通して３０００ｃｃ／分供給した。
【００１９】
１８０枚のシリコンウエーハの片面研削を遂行した後に、研削ホイールにおける砥石の摩滅量（突出長さの減少量）を測定したところ下記表１に示すとおりであった。また、シリコンウエーハの研削体積合計値を砥石摩滅体積合計値で除した研削比を求めたところ下記表１に示すとおりであった。
【００２０】
比較例
比較のために、基台の形状が図４に図示するとおりであることを除いて、実施例において使用した研削ホイールと同一である研削ホイールを使用して、実施例と同様にして１８０枚のシリコンウエーハの片面の研削を遂行した。研削ホイールの基台の外径Ｄ４は２９０ｍｍ、高さＨ５は１７ｍｍ、上面内径Ｄ５は１３８ｍｍ、下面内径Ｄ６は１７８ｍｍであった。基台の上面内周縁部には深さＸ１が１．９ｍｍで横断面形状が三角形状である環状溝が形成され、そしてまた基台には周方向に等間隔をおいて溝から基台の下面まで延びる１２個の孔が形成されていた。孔は下方に向かって半径方向外方に傾斜して延びており、傾斜角γは２５度で孔の直径Ｄ７は２ｍｍであった。
【００２１】
実施例と同様にして、研削ホイールにおける砥石の摩滅量（突出長さの減少量）及び研削比を求めたところ下記表１に示すとおりであった。
【００２２】
【表１】

【００２３】
【発明の効果】
本発明の研削ホイールにおいては、供給される冷却液が研削ホイール及び被研削物の冷却に充分効果的に利用され、砥石の摩滅が低減せしめられ研削比が向上せしめられる。
【図面の簡単な説明】
【図１】本発明に従って構成された研削ホイールの好適実施形態を、一部を切り欠いて示す斜面図。
【図２】図１に示す研削ホイールの部分拡大断面図。
【図３】図１に示す研削ホイールを使用して半導体ウエーハの片面を研削する様式を図示する断面図。
【図４】比較例において使用した従来の研削ホイールを示す部分拡大断面図。
【符号の説明】
２：研削ホイール
４：基台
６：砥石手段
１４：冷却液溜
２０：上部傾斜面
２４：突出面
３０：連通切欠
３６：砥石[0001]
BACKGROUND OF THE INVENTION
The present invention relates to, but is not limited to, a grinding wheel that is advantageously used to grind one side of a semiconductor wafer.
[0002]
[Prior art]
As is well known to those skilled in the art, in the manufacture of semiconductor devices, single-side grinding is performed to grind one side of a semiconductor wafer so that the semiconductor wafer has a required thickness. For such grinding, a grinding machine including a chuck table having a flat holding surface and a rotating shaft disposed to face the chuck table is used. The semiconductor wafer is held on the chuck table with its one surface to be ground exposed (hence, the opposite surface is in close contact with the chuck table), and a grinding wheel is mounted on the tip of the rotating shaft. The grinding wheel is composed of an annular base and grindstone means mounted on the lower surface of the base. The grindstone means is usually composed of a plurality of grindstones that are arranged at intervals in the circumferential direction and extend in an arc shape in the circumferential direction. A plurality of coolant flow holes are formed in the base at intervals in the circumferential direction. Each of the coolant flow holes extends through the base from the upper surface to the lower surface of the base, and the lower end thereof is positioned radially inward of the grindstone means attached to the lower surface of the base. The chuck table is rotated at a relatively low speed (for example, 100 to 300 rpm), the rotating shaft and the grinding wheel attached thereto are rotated at a relatively high speed (for example, 4000 to 5000 rpm), and the grinding wheel means of the grinding wheel is a semiconductor. Grinding of one side of the semiconductor wafer is performed by pressing against one side of the wafer and moving it forward. In such grinding, a coolant such as pure water is supplied to the coolant flow hole of the grinding wheel through the coolant flow path disposed on the rotating shaft, and the coolant flowing in the bottom surface of the base is opened. Coolant flows out of the hole.
[0003]
[Problems to be solved by the invention]
Thus, according to the inventor's experience, in the grinding using the conventional grinding wheel of the above-described form, the supplied coolant is used for the grinding wheel means of the grinding wheel and the grinding surface of the object to be ground, that is, the semiconductor wafer. It has been found that the grinding efficiency is not necessarily sufficient due to the fact that the grinding efficiency is not sufficient due to the fact that the grinding wheel is not sufficiently effective for cooling, and that the grinding wheel means in the grinding wheel is relatively worn.
[0004]
The present invention has been made in view of the above-mentioned facts, and the main technical problem thereof is to improve the grinding wheel and use the supplied coolant sufficiently effectively for cooling the grinding wheel and the object to be ground. Is to do so.
[0005]
[Means for Solving the Problems]
The present inventor examined grinding using a conventional grinding wheel, and due to the fact that the grinding wheel was rotated at a relatively high speed, a considerable amount of coolant was sufficient for cooling the grinding wheel means and the object to be ground. Recognized that it would flow radially outward without being used. Based on this recognition, the shape of the base of the grinding wheel is improved, and more specifically, the inner peripheral surface of the base is made into a unique shape, continuously extending in the circumferential direction, and in the radial direction. A coolant reservoir that is open to the outside is formed, and the coolant that is supplied to the base of the grinding wheel is prevented from flowing radially outward by the coolant reservoir, and then directed toward the grinding wheel means and the object to be ground. It has been found that the main technical problems can be achieved by overflowing.
[0006]
That is, according to the present invention, as a grinding wheel for achieving the main technical problem, in the grinding wheel constituted by an annular base and a grindstone means mounted on the lower surface of the base,
The inner peripheral surface of the base has an upper hanging surface extending vertically downward, a receding surface extending radially outward from the lower end of the upper hanging surface, and a radius downward from the radially outer end of the receding surface. An upper inclined surface extending obliquely outward in the direction, an intermediate hanging surface extending vertically downward from the lower end of the upper inclined surface, and a lower portion of the intermediate hanging lower surface of the upper inclined surface horizontally inward in the radial direction A projecting surface extending downward, a lower hanging surface extending vertically downward from a radially inner end of the projecting surface, and a lower inclined surface extending obliquely outwardly from the lower end of the lower hanging surface. A cooling liquid reservoir is defined that extends continuously between the upper inclined surface and the projecting surface in the circumferential direction and is opened radially inward;
The base is further formed with a plurality of communication notches communicating with the coolant reservoir from the upper surface thereof.
A grinding wheel is provided.
[0007]
Preferred in embodiments, the grinding wheel means is constituted by a plurality of wheels extending arcuately disposed at intervals in the circumferential direction circumferentially.
[0008]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, with reference to the accompanying drawings, a preferred embodiment of a grinding wheel constructed according to the present invention will be described in more detail.
[0009]
Referring to FIGS. 1 and 2, the grinding wheel denoted as a whole by the number 2 is composed of a base 4 and a grindstone means 6. The base 2 which can be formed from a suitable metal such as aluminum is generally annular, an annular upper surface 8 which is substantially horizontal, an annular lower surface 10 which is substantially horizontal and a cylindrical outer peripheral surface which is substantially vertical. Twelve.
[0010]
It is important that a cooling liquid reservoir 14 opened radially inward is formed on the inner periphery of the base 4. In the illustrated embodiment, the inner peripheral surface of the base 4 has an upper hanging surface 16 that extends substantially vertically downward, a receding surface 18 that extends radially outward from a lower end of the upper hanging surface 16, and a receding surface. An upper inclined surface 20 extending obliquely outward in the radial direction downward from the radially outer end of the surface 18, an intermediate hanging surface 22 extending substantially vertically downward from the lower end of the upper inclined surface 20, and the intermediate hanging surface 22 A projecting surface 24 extending radially inwardly from the lower end of the upper inclined surface 20, and a lower hanging surface 26 extending substantially vertically downward from a radially inner end of the projecting surface 24; A lower inclined surface 28 that extends downwardly from the lower end of the lower drooping surface 26 in a radially outward direction is included. And between the upper inclined surface 20 and the protrusion surface 24, the cooling liquid reservoir 14 whose cross-sectional shape is a substantially right triangle shape is prescribed | regulated. The upper hanging surface 16, the retreating surface 18, the upper inclined surface 20, the intermediate hanging surface 22, the projecting surface 24, the lower hanging surface 26, and the lower inclined surface 28 are arranged in the circumferential direction except for a portion where a communication notch described later is formed. The cooling liquid reservoir 14 is also continuously extended in the circumferential direction .
[0011]
As clearly understood by referring to FIG. 1, the base 4 has a plurality of communication cutouts 30 extending from the upper surface 8 to the receding surface 18 and the upper inclined surface 20 on the inner peripheral surface at intervals in the circumferential direction. More specifically, six are formed at equiangular intervals, and the upper surface of the base 4 is communicated with the cooling liquid reservoir 14 through a communication notch 30. Each of the communication cutouts 30 has a substantially semicircular shape, and the inside in the radial direction is open . The base 4 further includes a plurality of blind screw holes 32 extending substantially vertically downward from the upper surface 8 at intervals in the circumferential direction. In the illustrated embodiment, six blind screw holes 32 are formed at equal angular intervals, and each of the blind screw holes 32 is positioned in the middle of the adjacent communication notch 30 when viewed in the circumferential direction. Yes.
[0012]
Continuing with reference to FIGS. 1 and 2, the grindstone means 6 is disposed on the lower surface 10 of the base 4. More specifically, in the illustrated embodiment, an annular groove 34 extending continuously in the circumferential direction is formed on the lower surface of the base 10. The grindstone means 6 is composed of a plurality (27 in the illustrated case) of grindstones 36 extending in an arc shape in the circumferential direction with an interval in the circumferential direction, and each of the grindstones 36 is grooved in the upper part by an appropriate adhesive. It is fixed to the lower surface of the base 10 by being fixed in the interior 34. Each of the grindstones 36 may be formed by, for example, bonding diamond abrasive grains with an appropriate binder such as vitrified. Each cross-sectional shape of the grindstone 36 may be rectangular. In place of the plurality of grindstones 36 spaced apart in the circumferential direction, if desired, the grindstone means 6 can be constituted by an annular grindstone that extends continuously in the circumferential direction.
[0013]
FIG. 3 schematically illustrates a manner in which one side of the semiconductor wafer 38 is ground using the grinding wheel 2 illustrated in FIGS. 1 and 2. The semiconductor wafer 38 to be ground on one side is held on the chuck table 40 with the one side to be ground exposed upward. It is preferable that the chuck table 40 has at least a central main portion formed of a porous material or has a plurality of suction holes so that the semiconductor wafer 38 can be vacuum-sucked.
[0014]
A rotating shaft 42 is disposed above the chuck table 40, and the grinding wheel 2 is attached to the tip, that is, the lower end of the rotating shaft 42. More specifically, a mounting flange 44 is integrally formed at the lower end of the rotating shaft 42, and a circular recess 46 having a relatively large diameter is formed on the lower surface of the mounting flange 44. The rotating shaft 42 is formed with a coolant flow path 48 that extends in the vertical direction and opens into a circular recess 46. An additional member 50 is fixed to the lower end of the rotating shaft 42, and thus to the mounting flange 44. The additional member 50 has an upper portion having an outer diameter substantially the same as the inner diameter of the circular recess 46 and a lower portion having an outer diameter substantially the same as the outer diameter of the mounting flange 44, and the upper portion is inserted into the circular recess 46. The annular shoulder surface defined between the upper part and the lower part is brought into contact with the lower surface of the mounting flange 44. A through hole extending in the radial direction from the outer peripheral surface to the circular recess 46 is formed in the mounting flange 44 at intervals in the circumferential direction, and a blind screw hole extending in the radial direction from the outer peripheral surface is formed in the upper portion of the additional member 50. Are formed at intervals in the circumferential direction, and the additional member 50 is fixed to the mounting flange 44 by screwing the fastening bolt 51 into the blind screw hole of the additional member 50 through the through hole of the mounting flange 44. A sealing ring 52, which may be made of synthetic rubber, is disposed between the upper outer peripheral surface of the additional member 50 and the inner peripheral surface of the circular recess 46 of the mounting flange 44, and the annular shoulder surface of the additional member 50 and the mounting flange 44. A sealing ring 54, which may be made of synthetic rubber, is also disposed between the lower surface. The upper surface of the additional member 50 is formed with a plurality of (six in the figure) grooves 56 extending radially from the center thereof, and also extends substantially vertically from the outer end of each of the grooves 56 and opens to the lower surface. A hole 58 is formed. The groove 56 and the hole 58 are communicated with the coolant channel 48 formed in the rotating shaft 42.
[0015]
If the description is continued with reference to FIGS. 1 to 3, the grinding wheel 2 is mounted on the lower surface of the additional member 50. The mounting flange 44 and the additional member 50 are formed with a plurality of (six in the illustrated example) through-holes extending substantially vertically at intervals in the circumferential direction. Through such holes, by screwing the fastening bolt 60 into the blind threaded hole 32 formed in the upper surface of the base 4 of the grinding wheel 2, the lower surface of the additional member 50, thus the lower end of the rotary shaft 4 2 A grinding wheel 2 is mounted. Each of the communication notches 30 formed on the base 4 of the grinding wheel 2 is aligned with each of the holes 58 formed in the additional member 50. Therefore, the cooling liquid reservoir 14 formed on the base 4 of the grinding wheel 2 passes through the communication notch 30 formed in the base 4 and the hole 58 and the groove 56 formed in the additional member 50. It is caused to communicate with the cooling fluid channel 48 formed on the rotating shaft 4 2.
[0016]
When grinding the one surface of the semiconductor wafer 38, together with the chuck table 40 is rotated at a relatively low speed may be about 100 to 300 rpm, the rotating shaft 4 2 is rotated at a relatively high speed may be about 4000 to 5000 rpm, Then, gradually allowed processed brought presses the grinding e i Lumpur 2 on one surface of the semiconductor wafer 38, thus the one side grinding wheel 2 of the semiconductor wafer 38 is ground more particularly by the grinding wheel means 6. During such grinding, good cooling liquid with pure water at room temperature through the cooling fluid channel 48 of the rotary shaft 4 2 is supplied. The coolant flows through the groove 56 and hole 58 are formed from a cooling liquid channel 48 of the rotary shaft 4 2 to the additional member 50, then the communication notch 30 formed in the base 4 of the grinding wheel 2 And flows into the coolant reservoir 14. Since the grinding wheel 2 is rotated at a relatively high speed, a considerable centrifugal force acts on the coolant, thereby causing the coolant to flow radially outward. However, in the grinding wheel 2 configured according to the present invention, the cooling liquid reservoir 14 opened radially inward is disposed, so that the cooling liquid having a tendency to flow radially outward is once cooled. The liquid is retained in the liquid reservoir 14 and the outward flow in the radial direction is suppressed. Then, after being retained in the cooling liquid reservoir 14, it overflows from the cooling liquid reservoir 14, and extends along a lower inclined surface 28 that extends downwardly in a radially outward direction below the cooling liquid reservoir 14. Then, it is guided onto one side of the grindstone means 6 and the semiconductor wafer 38 being ground thereby. In the grinding wheel 2 configured according to the present invention, the coolant that is caused to flow radially outward due to the high-speed rotation of the grinding wheel 2 is once retained in the coolant reservoir 14, so that a required portion, that is, grinding is performed. Since the cooling liquid is supplied to the portion where it is performed, it is prevented or suppressed that the cooling liquid is caused to flow excessively outward in the radial direction and is wasted, and the cooling liquid is used sufficiently effectively.
[0017]
Example A grinding wheel having the configuration shown in FIGS. 1 and 2 was produced. The base was made of aluminum. The outer diameter D1 of the base was 290 mm, the height H1 of the base was 17 mm, the upper surface inner diameter D2 was 158 mm, and the lower surface inner diameter D3 was 178 mm. The height H2 of the upper hanging surface on the inner periphery of the base is 2.5 mm, the width W1 of the receding surface is 3.8 mm, the inclination angle α of the upper inclined surface is 20 degrees, and the length L1 of the upper inclined surface is 8.8 mm. The height H3 of the intermediate hanging surface is 1.6 mm, the width W2 of the protruding surface is 6.3 mm, the height H4 of the lower hanging surface is 1.6 mm, the inclination angle β of the lower inclined surface is 45 degrees, and the lower inclined surface The length L2 was 11.3 mm. Twenty-seven grindstones were fixed to the lower surface of the base at equal intervals in the circumferential direction. Each grindstone has a circumferential length L3 of 20 mm, a thickness T1 of 4.0 mm, a protrusion length L4 from the lower surface of the base of 5.2 mm, and a circumferential distance G1 of each grindstone is 2.2 mm. It was. Each of the grindstones was formed by bonding diamond particles having a particle diameter of 40 to 60 μm by vitrification, and the degree of concentration of diamond particles was 75.
[0018]
The grinding wheel was mounted on the rotating shaft of a grinding machine (surface grinder) sold under the trade name “DFG841” from DISCO Corporation, and single-side grinding of a 6-inch diameter silicon wafer was performed. In such grinding, the rotation speed of the rotating shaft is 4800 rpm, the rotation speed of the chuck table is 200 rpm, the grinding wheel is lowered by 200 μm at a descending speed of 8 μm / sec, and one side of the silicon wafer is ground over a depth of 200 μm. . Pure water at 24 ° C. was supplied as cooling water at 3000 cc / min through the cooling water passage of the rotating shaft.
[0019]
After performing 180-sided silicon wafer single-side grinding, the wear amount of the grinding wheel (decrease in protrusion length) in the grinding wheel was measured, and as shown in Table 1 below. Further, the grinding ratio obtained by dividing the total grinding volume of the silicon wafer by the total grinding wheel volume was found to be as shown in Table 1 below.
[0020]
Comparative Example For comparison, the grinding wheel is identical to the grinding wheel used in the example except that the shape of the base is as shown in FIG. Similarly, grinding of one side of 180 silicon wafers was performed. The grinding wheel base had an outer diameter D4 of 290 mm, a height H5 of 17 mm, an upper surface inner diameter D5 of 138 mm, and a lower surface inner diameter D6 of 178 mm. An annular groove having a depth X1 of 1.9 mm and a cross-sectional shape of a triangle is formed on the inner peripheral edge of the upper surface of the base, and the base is spaced from the groove to the base at equal intervals in the circumferential direction. Twelve holes extending to the lower surface were formed. The hole was inclined downward and extended radially outward, the inclination angle γ was 25 degrees, and the hole diameter D7 was 2 mm.
[0021]
In the same manner as in the example, the wear amount of the grinding wheel (the reduction amount of the protrusion length) and the grinding ratio in the grinding wheel were determined and as shown in Table 1 below.
[0022]
[Table 1]

[0023]
【Effect of the invention】
In the grinding wheel of the present invention, the supplied coolant is sufficiently effectively used for cooling the grinding wheel and the object to be ground, so that the abrasion of the grindstone is reduced and the grinding ratio is improved.
[Brief description of the drawings]
FIG. 1 is a perspective view showing a preferred embodiment of a grinding wheel constructed according to the present invention, with a part cut away.
2 is a partially enlarged sectional view of the grinding wheel shown in FIG.
3 is a cross-sectional view illustrating a manner in which one side of a semiconductor wafer is ground using the grinding wheel shown in FIG. 1;
FIG. 4 is a partially enlarged sectional view showing a conventional grinding wheel used in a comparative example.
[Explanation of symbols]
2: Grinding wheel 4: Base 6: Whetstone means 14: Coolant reservoir 20: Upper inclined surface 24: Protruding surface 30: Communication notch 36: Whetstone

Claims

In a grinding wheel composed of an annular base and grinding wheel means mounted on the lower surface of the base,
The inner peripheral surface of the base has an upper hanging surface extending vertically downward, a receding surface extending radially outward from the lower end of the upper hanging surface, and a radius downward from the radially outer end of the receding surface. An upper inclined surface extending obliquely outward in the direction, an intermediate hanging surface extending vertically downward from the lower end of the upper inclined surface, and a lower portion of the intermediate hanging lower surface of the upper inclined surface horizontally inward in the radial direction A projecting surface extending downward, a lower hanging surface extending vertically downward from a radially inner end of the projecting surface, and a lower inclined surface extending obliquely outwardly from the lower end of the lower hanging surface. A cooling liquid reservoir is defined that extends continuously between the upper inclined surface and the projecting surface in the circumferential direction and is opened radially inward;
The base is further formed with a plurality of communication notches communicating with the coolant reservoir from the upper surface thereof.
A grinding wheel characterized by that.

2. The grinding wheel according to claim 1 , wherein the grinding wheel means is composed of a plurality of grinding wheels which are disposed at intervals in the circumferential direction and extend in an arc shape in the circumferential direction.