JP3652053B2 - Method for forming thin film on substrate for electronic circuit - Google Patents

Description

ここで、
ｖ：基板上昇速度、η：レジスト液の粘度、ρ：レジスト液の密度、
ｇ：重力加速度、γ：レジスト液の表面張力
この式は、もちろん、液切縁部では成立しないし、液の蒸発速度が無限大であるとして求められている。この関係式は、概略定性的にいうと、上昇速度が速いと膜厚は厚くなり上昇速度が遅いと膜厚は薄くなることを示している。１枚の基板について上方部と下方部とで膜厚を均一にする１次速度制御は、蒸発速度などを考慮すると、線形でなく当然一定でない。しかし、一定速度の運動Ｕ４（図１６、ステップＳ１３）に従って上昇させれば現在要求されている膜厚精度が許容範囲に入ることは、本発明の試作装置（図に示す実施形態の装置）から判明している。
【００６０】
図１８（ａ）は、把持部即ち上縁部を残してほとんど全部が液浸（又は液漬）した状態の基板２がステップＳ１１で停止した状態を示している。この下限停止状態から基板２は、一定の高速で上昇を始める。この高速は、前記式により定められるが、１秒間に２５ｍｍの速度で上昇される。インバータモータ４４には、１秒間に１００ヘルツの信号が入力され、そのヘルツ数に比例する平均速度で基板２が上昇する。
【００６１】
図１８（ｂ）は、基板の下端縁部が僅かな上下幅だけ液浸している状態を示している。この状態は、図１９（ａ），図２０（ａ）に示すように、有効な第１縦メニスカスＭ１が形成されている状態である。レジスト液の表面張力により形成される第１縦メニスカスＭ１は、基板２の両面側にできている。基板２には、概ね一定厚さの膜厚部分Ｔ１と液面近くのメニスカスにより膨らみを持っているため一定でない厚さの膜厚部分Ｔ２が形成されている。有効な第１縦メニスカスＭ１とは、膜厚部分Ｔ２が表面張力及び重力の影響で液面Ｓ側に引っ張られ下方へ流動する量が有効量になっている状態のメニスカスをいう。
【００６２】
図１８（ｃ）は、基板の下端縁が僅かに遠方の液面よりも高い位置に位置している状態を示している。表面張力がなければ、基板２は液から完全に離脱しているはずの上昇状態である。しかし、図１９（ｂ），図２０（ｂ）に示すように、依然として有効な第２縦メニスカスＭ２が表面張力により形成されている状態である。第２縦メニスカスＭ２も基板２の両面側にできている。膜厚部分Ｔ２は、図２０（ｂ）に示すように、図２０（ａ）に示す状態よりも、更に流動性を強めている。前記と同様に、有効な第２縦メニスカスＭ１とは、膜厚部分Ｔ２が表面張力及び重力の影響で液面Ｓ側に引っ張られ下方へ流動する量が有効量になっている状態のメニスカスをいう。
【００６３】
このような状態は、基板２の速度が遅ければ遅いほど長く維持される。このような状態が維持されている時の基板２の上昇速度は、図１６に運動Ｕ５（ステップＳ１４）として示されている。運動Ｕ５の速度は、液切時上昇速度設定つまみ２０１により、運動Ｕ４の速度の１００分の１から１０分の１の範囲で設定できる。より具体的いうと、インバータモータ４４には数ヘルツ／秒の信号が入力されている。運動Ｕ５の速度は、運動Ｕ４の速度の約２０分の１に設定されている。
この。基板２は、１部が液面Ｓより上方に出ている。
【００６４】
このような有効な第２メニスカスＭ２が形成されている状態では、図２１に示すように、横メニスカスＭ３が形成されている。図２１は、３様の横メニスカスＭ３ａ，Ｍ３ｂ，Ｍ３ｃが示されている。横メニスカスＭ３は、図で左側に進行している。基板２の下端線と液面Ｓとが完全に平行なら、メニスカスの進行方向は定まらないが、機械誤差、基板２の成形誤差の範囲で必ずその平行性は崩れている。もし両側にメニスカスが発生してもいずれか一方は消滅しあるいは他方に吸収され、必ず、１個のメニスカスが片側から反対側へ進行し、膜厚部分Ｔ２を走査して液面側に吸収する。
【００６５】
横メニスカスＭ３が走っているいる間に、基板２は僅かに上昇する。従って、横メニスカスＭ３ａと横メニスカスＭ３ｂと横メニスカスＭ３ｃとは、僅かに形態が異なっているが、作用上は実質的に同じである。即ち、メニスカスを介して膜厚部分Ｔ２が、液面側に引っ張られる作用が継続している限り、実質的に同じである。基板２の遅さの程度は、メニスカスＭ３が一方側で発生し、他方側まで走りつくことができる程度の遅さである。上昇速度が速い場合には、横メニスカスＭ３は途中で切れて消滅する。
【００６６】
速度が運動Ｕ５の状態にある時間幅（液切過程の時間、前記メニスカスが継続されている時間）は、有効縦メニスカス及び横メニスカスが形成されうる時間帯でよい。具体的には、粘度が４０ｃｐｓ以下で、基板２の下端部の幅は、数ｍｍ以下であり、遠方の液面と基板２の下端線との間の距離は２〜３ｍｍ程度である。このような横メニスカスを介して、膜厚部分Ｔ２の膨らみは、メニスカスの走査過程で取り除かれる。その取除状況は、実施例として後述する。
【００６７】
基板２の下縁が液面Ｓを離脱した後は、工程サイクルを短縮させるために、速度を上昇させる（運動Ｕ６、ステップＳ１５）。また、レジスト液循環用ポンプ３１を起動してレジスト液の循環を開始する（ステップ１６、図１６中動作Ｐ１）。レジスト液の循環による液面の振動はもはや基板２の抵抗層形成に影響を及ぼさない。
【００６８】
昇降台５４は、上限位置検出用光センサー７６の動作（ステップ１７）により上限位置で停止する（運動Ｕ７、ステップＳ１８）。停止状態は、原点復帰状態である。以上に述べたフローチャート中で、転輪６２は全く動作していない。この実施形態では、把持解消された基板２は人手により機外に持ち出されるが、機種により自動化される。運転停止のために制御電源スイッチ８１を再度押せば、レジスト液循環用ポンプ３１その他の機器を停止させ運転終了とする（ステップＳ２３）。そうでない場合は、次の基板２をエアチャック爪７１に把持させて工程サイクルを継続する（ステップＳ５）。
【００６９】
上記工程サイクルは、機内外に基板２を持ち込み取り出す手作業を除いて全自動化されている。レジスト液として用いられている揮発性溶媒とレジスト層形成物質との混合比率は、粘度の継続的計量によりリアルタイムで検出される。粘度の変化と希釈液の追加のタイミングがずれ粘度が変化する場合がある。このような場合は、基板上昇速度可変用つまみ８３ａをまわして、１次制御速度を変更する。
【００７０】
本発明は、上記実施形態に限られることはなく、本発明の趣旨の範囲内で、設計変更が行われる。たとえば、液切角度θは零に限定されないが、大きくないことが好ましい。θは、限りなく零に近い角度でよく、あるいは、３度ほどの角度に設定してもよい。この場合でも、液切過程の上昇速度は遅く設定されている。
【００７１】
図２２は、本発明の実施例と従来例を示している。液切過程の基板上昇速度は、図２２（ａ）では１ヘルツ、同（ｂ）では３ヘルツ、同（ｃ）では５ヘルツ、同（ｄ）では７ヘルツ、同（ｅ）では従来通り１００ヘルツである。同（ｅ）の塗布ずみ基板は、図中指示位置断面を図２５に示すように、下端縁部で膨らみ部２０３が両面に形成されている。
【００７２】
図２２（ａ）〜（ｄ）に示す部分２０４は、レジスト液が全くといってもよい程度に、基板２に付着されていない部分である。図２２（ｃ）に示される基板２のレジスト液非付着部分２０４は、規則正しく縁にそって（メニスカスの進行方向に）形成されている。幅３００ｍｍの基板で、このようなレジスト液非付着部分２０４の個数は約５０である。レジスト液付着部分２０５とレジスト液非付着部分２０４とが、図２３に示すように、規則正しく交互に波打って並んでいる。図２２（ｃ）中の２箇所の指示位置断面を図２４（ａ），（ｂ）に示すように、レジスト液付着部分２０５はそれより中央（内側）よりの部分２０６の膜厚より薄く、レジスト液非付着部分２０４の膜厚は実質的に零である。上昇速度が７ヘルツの場合は、レジスト液非付着部分２０４の面積は少なくなる。サイズについて説明すると、図２４で、基板２の厚さは１〜３ｍｍであり、部分２０６の膜厚は、１０ミクロン程度である（図は、誇張して描かれている。）。
【００７３】
図２３に示すように交互に波打って膜厚が形成される理由は、次のように推定される。横メニスカスの移動により下端縁部の液がメニスカスの進行方向に誘導されて移動する場合の運動量とこの移動を阻止しようとする反作用と自らの上面張力により振動が発生して基板面の液面に波状の盛り上がりが生じ、同時に、縦メニスカスにより下方へその盛り上がり部は引っ張られて液面側に吸収されるのであると、推定される。
【図面の簡単な説明】
【図１】図１は、本発明による浸漬式基板面抵抗層形成装置の概念を示し、斜軸投影図である。
【図２】図２は、理想的な基板を示す正面図である。
【図３】図３は、図３は本発明による浸漬式基板面抵抗層形成装置の実施形態を示す正面図である。
【図４】図４は、レジスト液タンクとレジスト液循環用系を示し、正面図である。
【図５】図５は、図４の平面図である。
【図６】図６は、図４の側面図である。
【図７】図７は、昇降手段を取り出して示す正面図である。
【図８】図８は、図７の側面図である。
【図９】図９は、傾動手段を示す正面図である。
【図１０】図１０は、図９の平面図である。
【図１１】図１１は、把持手段を示す側面図である。
【図１２】図１２は、図３の１部を拡大した正面図である。
【図１３】図１３は、制御回路図である。
【図１４】図１４は、制御回路の１部の回路図である。
【図１５】図１５は、シーケンサ９１のシーケンス回路図である。
【図１６】図１６は、動作チャート図である。
【図１７】図１７は、フローチャート図である。
【図１８】図１８（ａ），（ｂ），（ｃ）は、液切過程を解説するための３態様の概念図である。
【図１９】図１９（ａ），（ｂ）は、図１８（ｂ），（ｃ）の側面断面図である。
【図２０】図２０（ａ），（ｂ）は、図１９（ａ），（ｂ）を拡大して横メニスカスを示す断面図である。
【図２１】図２１は、縦メニスカスを示す断面図である。
【図２２】図２２（ａ），（ｂ），（ｃ），（ｄ），（ｅ）は、それぞれの膜厚を比較して示す正面図である。
【図２３】図２３は、図２２（ｃ）の断面図である。
【図２４】図２４（ａ），（ｂ）は、それぞれの膜厚を比較して示す側面断面図である。
【図２５】図２５従来のものの膜厚を示す側面断面図である。
【符号の説明】
１…レジスト液タンク
２…基板
３…液切角度設定手段
４…昇降手段
７…傾動手段
８…上昇速度制御手段
１１ａ…レジスト層（１１ａ）
９３…速度コントローラ（９３）
Ｒ…下縁
Ｓ…レジスト液面[0001]
[Technical field to which the invention belongs]
The present invention relates to an electronic circuit substrate and a thin film forming method thereof. More specifically, the present invention relates to an electronic circuit substrate and a thin film forming method thereof for applying a predetermined amount of liquid to the electronic circuit substrate when the electronic circuit substrate is dipped in a photosensitive resist solution (resistance solution) and pulled up.
[0002]
[Prior art]
The manufacturing process of a substrate such as an electrode substrate includes a step of applying a liquid such as a photosensitive resist solution to the substrate to form a thin film on the substrate surface. Such a process requires extreme cost reductions in terms of yield, production efficiency, and the like, and also requires high density.
[0003]
Under such a demand, a uniform thickness of the thin film is required. It is also required that the resist material can be applied in a uniform thickness even after the substrate material is moved up and down and dried in an immersion manner. The relational expression between the rising speed and the thickness of the thin film is well known. However, the formula relating to the film thickness at the lower edge of the substrate material to be drained is not known.
[0004]
Generally, the thickness of the liquid cutting edge is increased. Reducing the thickness of the liquid drain is related to the overall uniformity. As a known means for satisfying such a relationship, a technique described in JP-A-8-51268 is known. This known technique is excellent in terms of ensuring liquid drainage because the liquid is drained by inclining the lower end edge line for liquid drainage with respect to the liquid surface. Further, in this known technique, the meniscus formed between the liquid surface and the lower edge of the substrate material moves quickly, so that the liquid draining time is short and the production efficiency is high.
[0005]
However, the thickness of one side of the lower end edge portion tends to be thicker than the other portion at the last hit of the meniscus. It's not that you just cut off the thickened part. That is, various inconveniences occur in later processing steps. For example, when the portion is not well dried at the time of exposure, the resist solution adheres to the film for exposure and adhesion with the film is deteriorated, resulting in a problem that the pattern becomes unclear. Furthermore, since the portion that should be peeled off in the copper pattern forming process is thickly applied, the resist is not peeled off and the resist remains, causing residual copper, and causing gaps during subsequent laminating presses, causing defects. There's a problem.
[0006]
[Problems to be solved by the invention]
The present invention has been made based on such a technical background, and achieves the following objects.
[0007]
The objective of this invention is providing the thin film formation method of the board | substrate for electronic circuits by which a film thickness is made more uniform.
[0008]
Another object of the present invention is to provide a method for forming a thin film on an electronic circuit substrate with a better yield.
[0009]
Another object of the present invention is to provide a method for forming a thin film on an electronic circuit substrate that has a better yield and does not substantially reduce the production efficiency.
[0010]
Still another object of the present invention is to provide a method for forming a thin film on a substrate for electronic circuits in which the film thickness at the lower end is reduced.
[0011]
Still another object of the present invention is to provide a method for forming a thin film on a substrate for an electronic circuit in which the film thickness at the lower end is substantially zero microns.
[0012]
Still other objects of the present invention will be more specifically clarified through the following description of embodiments.
[0013]
[Means for Solving the Problems]
The thin film forming method for an electronic circuit substrate according to the present invention is an electronic circuit substrate in which a thin film is formed on the surface by applying a liquid to the surface while being lifted and lowered from the resist solution in a generally vertical plane. In the method for forming a thin film on an electronic circuit board, the film thickness of the thin film is formed thinner than the film thickness closer to the inside than the edge portion at the lower edge portion on the side to be edged with the resist solution.
Pulling up the electronic circuit board from the resist solution in the ascending process;
Reducing the rising speed in the process of draining the resist solution from the edge of the circuit board for electronic circuit;
The lower end line of the edge cutting edge is substantially horizontal;
The rising speed of the liquid draining process is 1/100 to 1/10 of the maximum rising speed until the liquid draining process,
The liquid has a viscosity of 25 degrees Celsius and 40 cps or less, the average ascent rate is 10 mm to 70 mm per second, and the ascending rate of the liquid draining process is 0.1 mm to 1.0 mm. .
[0014]
Such a thin film thickness is formed while the meniscus formed by gravity and surface tension between the liquid surface and the edge runs slowly from one side to the opposite side. Since the shape of the meniscus is substantially constant between the beginning and the end of the run, and the speed is also substantially constant, the amount of liquid drained from the edge to the liquid surface side is substantially constant per time. However, the thickness changes in a wave shape, and the film thickness is measured to be substantially zero in a thin portion. Since the substantially zero thickness portion is regularly distributed in a dotted manner in this way, the thickness of the portion sandwiched between the zero thickness portions is greater than the thickness inside the edge that is the liquid drainage portion. It will be formed thin.
[0015]
In the case where the edge portion is formed thinly, the contact with the pattern during exposure is good and the resolution of image formation is high. If the thinly formed portion is corrugated, the adhesion is better.
[0016]
In the liquid draining process in which the liquid cutting edge portion of the circuit board is drained from the liquid, the rising speed is reduced. The speed is extremely reduced to 1/10 or 1/100 of the maximum ascent speed. Such a slow increase increases the time for draining and at the same time slows down the movement speed of the meniscus. The slow movement speed of the meniscus avoids the phenomenon of pushing up the flowing liquid, so that the film thickness of the edge can be reduced. When the lower end line of the edge cutting edge is horizontal, the meniscus speed is further reduced.
[0017]
Since the viscosity coefficient of the liquid is 40 cps or less and low, liquid draining is improved. Experiments have confirmed that the average ascent rate is 10 mm to 70 mm per second, particularly preferably 10 mm to 30 mm, and the ascending rate in the liquid draining process is preferably 0.1 mm to 1.0 mm. Since the meniscus portion formed between the liquid cutting edge and the liquid surface moves in only one direction from one side to the other side, liquid cutting is performed uniformly.
[0018]
The time required for the draining process is not shorter than the time required for the meniscus portion to move from one side to the other side.
[0019]
【The invention's effect】
In the electronic circuit board and the photosensitive resist film forming method according to the present invention, the meniscus is moved sufficiently slowly, so that the liquid is sufficiently drained at the entire lower end edge. Therefore, the film thickness does not increase locally at the lower edge. This eventually increases the yield. Since the rising speed is lowered only in the draining process, the production efficiency is not lowered.
[0020]
Embodiment
The embodiment will be described in detail below. FIG. 1 is an oblique projection showing a configuration of an immersion substrate surface resist layer (hereinafter simply referred to as a resist layer) forming apparatus for carrying out an electronic circuit substrate and a method for forming a photosensitive resist film thereof according to the present invention. As this apparatus, the same apparatus as the above-mentioned known apparatus can be used. This apparatus includes a resist solution tank 1 in which a resist solution is circulated in an overflow manner and the liquid level is maintained at a constant level. The resist liquid tank 1 is open on the liquid surface side, that is, on the upper side.
[0021]
The immersion type substrate surface resist layer forming apparatus includes a lifting / lowering means 4 for lifting / lowering a gripping means 70 (not shown in FIG. 1, which will be described in detail later) that supports and grips an electronic circuit substrate (hereinafter referred to as a substrate) 2. And a liquid drain angle setting means 3 (details will be described later) for holding and fixing the substrate at a tilt angle position where the lower edge of the substrate is tilted with respect to the liquid surface of the resist liquid at a liquid drain angle θ. In the present invention, the liquid draining angle θ is preferably set to substantially zero at the time of implementation. Substantially zero means zero within the range of mechanical error. However, it does not necessarily have to be zero.
[0022]
Moreover, the immersion type substrate surface resist layer forming apparatus includes an elevating speed control means 5 (not shown in FIG. 1 and described later in detail) for controlling the elevating speed of the gripping means. In addition, the immersion type substrate surface resist layer forming apparatus includes a resist solution circulating means 30 (FIG. 4), a tilting means 7 (not shown in FIG. 1 and will be described in detail later) for tilting the substrate being lifted, and a rising speed. A control means 8 (not shown in FIG. 1 and will be described in detail later), a control operation panel 9 (FIG. 3), and other means are provided.
[0023]
As shown in FIG. 2, the substrate 2 includes an insulating substrate 10 and a conductive layer 11 attached to one or both surfaces of the insulating substrate 10. The insulating substrate 10 is made of an insulating material such as glass or epoxy resin. Although copper is used for the conductive layer 11, it can be replaced with silver or gold. A resistance layer 11a is formed on the conductive layer 11 by a method described later.
[0024]
FIG. 3 shows the appearance of the main body casing 12. The main casing 12 is substantially closed by six wall plates and forms a working space therein. A control panel 9 is provided on the front right side of the main casing 12. An opening / closing door 13 is provided at the center of the front surface of the main casing 12. The open / close door 13 composed of two transparent plates that are both vertically open and close opens and closes in the vertical direction. A plurality of caster wheels 14 are attached to the lower end surface of the floor wall. A ventilation fan (not shown) is provided on the back side of the main casing 12.
[0025]
Below, the resist solution tank 1, liquid drain angle setting means 3, elevating means 4, elevating speed control means 5, elevating speed control means 8, tilting means 7, tilting means 70, etc. provided inside the main body casing 12 are provided. The means will be described individually below.
[Resist liquid tank 1]
The resist solution tank 1 is provided at a lower portion of the main body casing 12. As shown in FIGS. 4, 5, and 6, the resist solution tank 1 includes a substrate immersion tank 20 and an overflow tank 21. The substrate immersion tank 20 and the overflow tank 21 are partitioned by a weir forming plate 22.
[0026]
The upper end of the weir forming plate 22 is set lower than the upper edge of the four circumferences of the resist solution tank 1. The bottom surface of the substrate immersion tank 20 is slightly inclined. As shown in FIG. 4, a resist solution discharge pipe 23 opened to the lowest position of the bottom of the overflow tank 21 is attached.
[0027]
[Resist solution circulating means 30]
The resist solution circulation means 30 is provided in the resist solution circulation path including the resist solution tank 1 as shown in FIGS. As the resist solution circulation pump 31, a circulation path sealed magnet pump having a known structure in which a liquid feeding internal rotating body is rotationally driven by a magnet rotor outside the circulation path is used. One end of a pressure feeding pipe 32 is connected to the discharge port of the resist solution circulation pump 31.
[0028]
The other end of the pressure feeding pipe 32 is connected to the inlet of the filter 33. One end of a supply pipe 34 is connected to the outlet of the filter 33. The other end of the supply pipe 34 is connected to the upper part of the substrate immersion tank 20 and is opened in the substrate immersion tank 20. One end of a return pipe 35 is connected to a return port opened at the bottom wall of the overflow tank 21. The other end of the return pipe 35 is connected to the suction port of the resist solution circulation pump 31.
[0029]
[Elevating means 4 / Elevating speed control means 5]
As shown in FIG. 7, the motor mounting base 41, the lower bearing guide rail mounting base 42, and the upper bearing guide rail mounting base 43 are attached to the back wall of the main body casing 12. An inverter motor 44 is fixedly provided on the motor mounting base 41. The rotation speed can be freely controlled by controlling the inverter by a program. Specifically, it is driven by an input pulse of 1, 2, 3,... 100 hertz (integer value hertz up to 100) per second, and the hertz number can be arbitrarily set between 1 and 100. . Instead of the inverter motor 44, a DC servo motor or an AC servo motor can be used.
[0030]
A lift screw ball screw shaft 46 is vertically coupled to the output shaft of the inverter motor 44 via a speed reducer. The ball screw shaft 46 for driving up and down is supported by a bearing whose lower part is attached to the lower bearing guide rail mounting base 42 and whose upper part is supported by a bearing attached to the upper bearing guide rail mounting base 43. Guide rails 49 and 50 are provided on both sides in parallel with the ball screw shaft 46 for driving up and down.
[0031]
The upper and lower ends of the guide rails 49 and 50 are fixed to fixed bases 51 and 52 attached to both sides of the lower bearing guide rail mounting base 42 and the upper bearing guide rail mounting base 43, respectively. A lifting platform 54 is supported so as to be movable up and down through a ball nut storage box in which a ball nut is stored in a ball screw shaft 46 for driving up and down.
[0032]
Four linear bearings 55 are attached to the lifting platform 54 and are guided by the guide rails 49 and 50 so as to be lifted and lowered with ease. The lift 54 is driven by a lift drive ball screw shaft 46 and is guided by guide rails 49 and 50 on both sides, and can be lifted and lowered silently and without vibration.
[0033]
As described above, the lifting means is constituted by the inverter motor 44, the lifting drive ball screw shaft 46, the guide rails 49, 50, and the like. The raising / lowering control means 5 is comprised by the program etc. which are not shown in figure which control the inverter motor 44 and an inverter.
[0034]
[Liquid drain angle setting means 3 and tilting means 7]
As shown in FIGS. 9 and 10, as shown in FIGS. 9 and 10, a liquid drain angle setting means 3 for gripping the substrate by tilting the liquid lower angle θ with respect to the liquid surface of the resist liquid to provide a liquid drain angle setting means 3 is provided. . A liquid drain angle setting motor 60 is fixed on the elevator 54. A rotating wheel 62 is rotatably attached to an eccentric shaft 61 that is attached to the output shaft of the liquid cutting angle setting motor 60.
[0035]
A tilting shaft 63 is provided in the horizontal direction on the lifting platform 54. A tilting table 64 is rotatably provided on the tilting shaft 63. A tilt guide body 65 is fixed to the right side surface of the tilt table 64. The tilting table 64 is always pulled by the other end of the tension spring 66 whose one end is fixed to the lifting table 54, and the tilting table 64 is constantly urged by a counterclockwise rotational force in FIG. The tension spring 66 functions so as to bring the roller wheel 62 into contact with the upper side surface of the tilt guide body 65.
[0036]
The liquid cutting angle setting motor 60 can be programmed to rotate once after the eccentric shaft 61 receives an input of one signal and stops halfway, and is stopped at a rotational angle position of the eccentric shaft 61 and stopped. Can be programmed to fix in position. In order to fix the rotational position in this way, for example, a DC control type servo motor having a servo system is used as the liquid drain angle setting motor 60.
[0037]
The DC control type servo motor is a motor of a type that controls the intermittent time of a constant current that flows intermittently, and can be stopped almost completely at a certain rotation angle position. As described above, the liquid drain angle setting means 3 includes the eccentric shaft 61 having the fixing means, the wheel 62, the tilt guide body 65, and the tilt shaft 63.
[0038]
The fixing means is a liquid cutting angle setting motor 60 having the servo function and has a function of maintaining a specific rotational position constant, but other means such as mechanically gripping and fixing means. Can be changed. The tilting means 7 includes a liquid cutting angle setting motor 60, an eccentric shaft 61, a roller wheel 62, and a tilt guide body 65. Both means share a liquid drain angle setting motor 60, a roller wheel 62, a tilting shaft 63, and a tilting guide body 65.
[0039]
[Gripping means 70]
10, 11 and 12 show a gripping means 70 for gripping and supporting the substrate 2 in a vertical plane. Two pairs of gripping means 70 are provided on the tilting table 64. The pair of gripping means 70 has two air chuck claws 71 each having one to two gripping claws. The air chuck claw 71 is mounted in the pressurized air supply / discharge unit 72 and is driven by an air cylinder (not shown).
[0040]
The pressure air is connected to the supply and discharge ports 73 and 74 of the pressure air supply and discharge unit 72. The gripping claws of the air chuck claw 71 are moved forward and backward in opposition to each other by the pressure air supplied and discharged by one air cylinder. The air chuck claw 71 can always hold the substrate 2 at the same position with respect to the lifting platform 54.
[0041]
[Upper and lower limit setting means]
Upper / lower limit setting means including a sensor for setting an upper limit raising / lowering position and a lower limit raising / lowering position of the lifting platform 54 is provided. As shown in FIG. 7, the upper limit position detection optical sensor 76 and the lower limit position detection optical sensor 77 are fixed to the lower bearing guide rail mounting base 42 and the upper bearing guide rail mounting base 43.
[0042]
A slowdown light sensor 78 is provided between the upper limit position detection light sensor 76 and the lower limit position detection light sensor 77 at a position closer to the lower limit position detection light sensor 77. After the position is detected by the optical sensor 78, the descending speed of the lifting platform 54 becomes slow. An overrun prevention limit switch 79 is provided below the lower limit position detecting optical sensor 77.
[0043]
[Control Panel 9]
FIG. 12 shows the control operation panel 9. A control operation panel 9 provided on the front surface of the main casing 12 includes a power indicator lamp 80, a control power switch 81, an automatic operation switch 82, a substrate raising speed variable knob 83a, a liquid drain angle setting knob 83b, a substrate. In addition to a size switching switch 84, a door opening / closing switch 85, and a resist solution circulation pump operation start switch 86, a forced stop switch 87, a manual raising switch 88, and a manual lowering switch 89 are provided. .
[0044]
These switches have the same configuration as that of the known invention, but the present invention further includes a rising speed setting knob 201 at the time of draining. With this knob 201, the ascending speed is selected in the range of 1 to 100 Hertz, and the speed of the inverter motor 44 is set when the liquid is drained.
[0045]
In addition, an alarm buzzer 90 that operates in the event of an abnormal operation is provided. The automatic operation switch 82 is turned on during automatic operation. When the automatic operation switch 82 that is lit is pressed once, the automatic operation switch 82 is turned off and the automatic mode is switched to the manual mode. While the lamp is lit, manual operation cannot be performed by the manual manual raising switch 88 and the manual lowering switch 89.
[0046]
[Climbing speed control circuit 8]
FIG. 13 shows a control mechanism including the ascending speed control circuit 8. The sequencer 91 operates in response to an operation command from the control power switch 81 and the automatic operation switch 82. A speed change command 92 for the ascending speed V and the descending speed expressed as a function of time is output from the sequencer 91 in a time series and is input to the speed controller 93.
[0047]
The speed controller 93 can cause the inverter 90 to output the frequency signal 94 based on the speed change command 92. The frequency signal 94 outputs an alternating current having a predetermined frequency to the inverter motor 44. The speed controller 93 includes a substrate rising speed varying knob 83a, a liquid draining angle setting knob 83b, and a liquid draining upward speed setting knob 201, respectively, and a rising speed signal 95, a liquid draining angle signal 96, and a liquid draining upward speed signal. 202 is input. The speed controller 93 performs calculation for converting the ascending speed signal 95, the liquid draining angle signal 96, and the liquid draining ascending speed signal 202 into an output signal 94, and outputs it.
[0048]
A tilt angle setting signal 97 is output from the sequencer 91 to the angular position controller 98 in time series. The angle position controller 98 that receives the signal via the sequencer 91 based on the liquid drain angle signal 96 of the liquid drain angle setting knob 83 b supplies a drive current to the liquid drain angle setting motor 60.
[0049]
The resist solution circulation pump 31 operates and stops in response to an on / off signal 99 output from the sequencer 91. The air cylinder 100 that operates the gripping means 70 reciprocates the chuck pawl 71 by opening and closing an electromagnetic on-off valve that operates in response to an on / off signal 100 a output from the sequencer 91.
[0050]
FIG. 14 shows the wiring between the main operating devices time-series by the sequencer 91 and the three-phase power source. The inverter motor 44 is supplied with power from the three-phase power source 101 via the inverter 90. The resist solution circulation pump 31 circulates the solution at a constant flow rate. The electromagnetic brake 102, which is supplied with voltage from two phases of the three-phase power supply and operates, brakes and stops the inverter motor 44 in an emergency.
[0051]
As shown in FIG. 15, as other devices operated by the sequencer 91, a ventilation fan 103 for releasing the resist solution diluent ethyl acetate and methyl ethyl ketone to the outside of the apparatus, and a liquid drain angle setting motor 60. A rotation counter 104 for controlling the rotation position, an integrator 105 for the rotation angle, and a door controller 106 for controlling the open / close door 13 are provided.
[0052]
[Immersion type substrate surface resist layer forming method]
Next, a resistance layer forming method based on the above-described configuration of the first embodiment will be described together with operations and actions with reference to a flowchart shown in FIG. The control power switch 81 is pressed to start the operation of the apparatus (step S0). By this start, the lifting platform 54 and the eccentric shaft 61 are returned to the machine origin (in this embodiment, set by the upper limit position detecting optical sensor 16) (step S1), and the substrate immersion tank 20 and the resist solution circulation pump 31 are connected. The circulation of the resist solution begins (step S2). The resist solution contains a photo-etching photosensitive material in a volatile diluent. The viscosity is 34 cps at 25 degrees C.
[0053]
The overflow is confirmed and it is confirmed that a resist solution circulation path is formed. From the control panel 9, the substrate rising speed variable knob 83 a, the liquid cutting angle setting knob 83 b, the liquid cutting rising speed setting knob 201, and the substrate size switching switch 84, the substrate rising speed, the liquid cutting angle, and the liquid cutting time are set. The rising speed and the substrate size are input (step S3). The substrate rising speed V, the rising speed at the time of liquid removal, and the liquid cutting angle θ are changed only in special cases such as when the concentration of the resist solution changes and the viscosity resistance fluctuates. The liquid cutting angle θ is set to zero.
[0054]
There are only several substrate sizes as vertical and horizontal sizes, and vertical dimensions are input. There are only four vertical dimensions (height dimensions) of 265 mm, 350 mm, 420 mm, and 530 mm. In the present embodiment, which is designed for manual use, the lifting platform 54 is not automatically lowered. Two foot pedals are available. A grip signal is sent from the foot pedal to the solenoid valve that operates the air cylinder 100 (step S4), the two pairs of grip means 70 are closed, and the two substrates 2 and 2 are sandwiched between the grip means 70 (step S5). After the set time set by the timer in the sequencer 91, the elevator 54 starts to descend (step S7).
[0055]
Prior to the start of the descent, the resist solution circulation pump 31 stops (step S6). The initial lowering motion is represented by the motion U1 shown in FIG. In FIG. 16, the horizontal axis represents the elapsed time, and the vertical axis represents the operation mode. The wheel 62 is not operating. A slow-down signal output from the slow-down light sensor 78 that reacts when the elevator 54 descends to the set height position is input to the sequencer 91 (step S8), a slow-down command is issued (step S9), and the elevator 54 Then, the substrate 2 descending slowly sinks below the resist liquid surface (see U2 in FIG. 16).
[0056]
Such a slow motion U2 keeps the liquid level quiet. A stop signal output from the lower limit position detecting optical sensor 77 that reacts when the elevator 54 is lowered to the lower limit height position is input to the sequencer 91 (step S10), a stop command is issued, and the inverter motor 44 is stopped (motion state). U3, step S11).
[0057]
Next, in the operation method according to the present invention, the tilt command is not issued in principle from the sequencer 91. That is, the angular position controller 98 does not supply a drive current to the liquid drain angle setting motor 60. Step S12 is omitted.
[0058]
After a while, an ascending command is issued, and the substrate starts to rise together with the lifting platform 54. This rising speed is determined by the viscosity of the resist solution and the film thickness to be formed on the substrate. The well-known mathematical relationship between the rising speed, the viscosity of the resist solution, and the film thickness h formed on the substrate is as follows when the surface tension cannot be ignored.
[0059]
[Expression 1]

here,
v: substrate rising speed, η: resist solution viscosity, ρ: resist solution density,
g: Gravitational acceleration, γ: Surface tension of resist solution
Of course, this equation does not hold at the edge of the liquid, and it is required that the liquid evaporation rate is infinite. This relational expression indicates that, in terms of qualitative terms, the film thickness increases when the rising speed is fast, and the film thickness decreases when the rising speed is slow. The primary speed control for making the film thickness uniform between the upper part and the lower part of one substrate is not linear and naturally not constant in consideration of the evaporation speed and the like. However, from the prototype device of the present invention (the device of the embodiment shown in the figure) that the presently required film thickness accuracy falls within the allowable range if it is raised according to the constant speed motion U4 (FIG. 16, step S13). It turns out.
[0060]
FIG. 18A shows a state in which the substrate 2 in a state where almost all of the substrate 2 is immersed (or immersed) leaving the gripping portion, that is, the upper edge portion, is stopped in step S11. From this lower limit stop state, the substrate 2 starts to rise at a constant high speed. This high speed is determined by the above equation, but is increased at a speed of 25 mm per second. A signal of 100 hertz is input to the inverter motor 44 per second, and the substrate 2 is raised at an average speed proportional to the hertz number.
[0061]
FIG. 18B shows a state where the lower edge of the substrate is immersed by a slight vertical width. This state is a state in which an effective first vertical meniscus M1 is formed as shown in FIGS. 19 (a) and 20 (a). The first vertical meniscus M1 formed by the surface tension of the resist solution is formed on both sides of the substrate 2. The substrate 2 has a film thickness portion T1 having a substantially constant thickness and a film thickness portion T2 having a non-uniform thickness because the substrate 2 has a bulge due to a meniscus near the liquid surface. The effective first vertical meniscus M1 refers to a meniscus in which the film thickness portion T2 is pulled toward the liquid surface S due to the influence of surface tension and gravity and the amount flowing downward is an effective amount.
[0062]
FIG. 18C shows a state in which the lower edge of the substrate is located at a position slightly higher than the distant liquid surface. If there is no surface tension, the substrate 2 is in an elevated state that should be completely detached from the liquid. However, as shown in FIGS. 19B and 20B, the effective second vertical meniscus M2 is still formed by the surface tension. The second vertical meniscus M2 is also formed on both sides of the substrate 2. As shown in FIG. 20 (b), the film thickness portion T2 has a stronger fluidity than the state shown in FIG. 20 (a). Similarly to the above, the effective second vertical meniscus M1 is a meniscus in which the film thickness portion T2 is pulled to the liquid surface S side by the influence of surface tension and gravity and the amount flowing downward is an effective amount. Say.
[0063]
Such a state is maintained longer as the speed of the substrate 2 is slower. The rising speed of the substrate 2 when such a state is maintained is shown as motion U5 (step S14) in FIG. The speed of the motion U5 can be set within a range from 1/100 to 1/10 of the speed of the motion U4 by using the rising speed setting knob 201 at the time of draining. More specifically, a signal of several hertz / second is input to the inverter motor 44. The speed of the motion U5 is set to about 1/20 of the speed of the motion U4.
this. A part of the substrate 2 protrudes above the liquid level S.
[0064]
In a state where such an effective second meniscus M2 is formed, as shown in FIG. 21, a lateral meniscus M3 is formed. FIG. 21 shows three horizontal meniscuses M3a, M3b, and M3c. The horizontal meniscus M3 proceeds to the left in the figure. If the lower end line of the substrate 2 and the liquid surface S are completely parallel, the meniscus traveling direction is not determined, but the parallelism is always broken within the range of mechanical error and substrate 2 forming error. If a meniscus is generated on both sides, one of them disappears or is absorbed by the other, and one meniscus always advances from one side to the other side, scans the film thickness portion T2 and absorbs it on the liquid surface side. .
[0065]
While the horizontal meniscus M3 is running, the substrate 2 rises slightly. Accordingly, the lateral meniscus M3a, the lateral meniscus M3b, and the lateral meniscus M3c are slightly different in form, but are substantially the same in operation. That is, the film thickness portion T2 is substantially the same as long as the action of pulling the film thickness portion T2 to the liquid surface side continues through the meniscus. The degree of slowness of the substrate 2 is slow enough that the meniscus M3 is generated on one side and can run to the other side. When the rising speed is fast, the lateral meniscus M3 is cut off and disappears.
[0066]
The time width in which the speed is in the state of the motion U5 (the time of the draining process, the time during which the meniscus is continued) may be a time zone in which the effective vertical meniscus and the horizontal meniscus can be formed. Specifically, the viscosity is 40 cps or less, the width of the lower end portion of the substrate 2 is several mm or less, and the distance between the distant liquid surface and the lower end line of the substrate 2 is about 2 to 3 mm. Through such a horizontal meniscus, the swelling of the film thickness portion T2 is removed in the meniscus scanning process. The removal status will be described later as an example.
[0067]
After the lower edge of the substrate 2 leaves the liquid level S, the speed is increased in order to shorten the process cycle (movement U6, step S15). Further, the resist solution circulation pump 31 is activated to start circulation of the resist solution (step 16, operation P1 in FIG. 16). The vibration of the liquid level due to the circulation of the resist solution no longer affects the formation of the resistance layer of the substrate 2.
[0068]
The lifting platform 54 stops at the upper limit position by the operation of the upper limit position detection optical sensor 76 (step 17) (movement U7, step S18). The stop state is a home position return state. In the flowchart described above, the wheel 62 does not operate at all. In this embodiment, the unresolved substrate 2 is taken out of the machine by hand, but is automated depending on the model. If the control power switch 81 is pressed again to stop the operation, the resist solution circulation pump 31 and other devices are stopped to end the operation (step S23). Otherwise, the next substrate 2 is held by the air chuck claw 71 and the process cycle is continued (step S5).
[0069]
The above process cycle is fully automated except for the manual operation of bringing the substrate 2 into and out of the machine. The mixing ratio of the volatile solvent used as the resist solution and the resist layer forming substance is detected in real time by continuously measuring the viscosity. In some cases, the viscosity changes due to a change in the viscosity and the timing of adding the diluent. In such a case, the primary control speed is changed by turning the substrate raising speed varying knob 83a.
[0070]
The present invention is not limited to the above embodiment, and design changes are made within the scope of the gist of the present invention. For example, the liquid drain angle θ is not limited to zero, but is preferably not large. θ may be an angle close to zero as much as possible, or may be set to an angle of about 3 degrees. Even in this case, the rising speed of the liquid draining process is set to be slow.
[0071]
FIG. 22 shows an embodiment of the present invention and a conventional example. The substrate rising speed during the draining process is 1 hertz in FIG. 22 (a), 3 hertz in (b), 5 hertz in (c), 7 hertz in (d), and 100 in FIG. Hertz. As shown in FIG. 25, the coated substrate (e) has a bulging portion 203 formed on both sides at the lower edge.
[0072]
A portion 204 shown in FIGS. 22A to 22D is a portion that is not attached to the substrate 2 to such an extent that the resist solution can be said at all. The resist solution non-adhered portion 204 of the substrate 2 shown in FIG. 22C is regularly formed along the edge (in the meniscus traveling direction). The number of such resist solution non-adhering portions 204 is about 50 on a substrate having a width of 300 mm. As shown in FIG. 23, the resist solution adhering portion 205 and the resist solution non-adhering portion 204 are regularly and alternately waved and arranged. As shown in FIGS. 24 (a) and 24 (b), as shown in FIGS. 24 (a) and 24 (b), the resist solution adhering portion 205 is thinner than the film thickness of the portion 206 from the center (inner side). The film thickness of the resist solution non-adhered portion 204 is substantially zero. When the rising speed is 7 Hz, the area of the resist solution non-adhered portion 204 is reduced. The size will be described. In FIG. 24, the thickness of the substrate 2 is 1 to 3 mm, and the thickness of the portion 206 is about 10 microns (the drawing is exaggerated).
[0073]
The reason why the film thickness is formed by alternately waving as shown in FIG. 23 is estimated as follows. The movement of the lateral meniscus causes the momentum when the liquid at the lower edge is guided to move in the direction of meniscus movement, the reaction to prevent this movement, and the vibration of the upper surface tension, causing vibration on the substrate surface. It is presumed that a wave-like swell occurs, and at the same time, the swelled part is pulled downward by the vertical meniscus and absorbed on the liquid surface side.
[Brief description of the drawings]
FIG. 1 is a perspective view showing a concept of an immersion type substrate surface resistance layer forming apparatus according to the present invention.
FIG. 2 is a front view showing an ideal substrate.
FIG. 3 is a front view showing an embodiment of an immersion type substrate surface resistance layer forming apparatus according to the present invention.
FIG. 4 is a front view showing a resist solution tank and a resist solution circulation system.
FIG. 5 is a plan view of FIG. 4;
FIG. 6 is a side view of FIG. 4;
FIG. 7 is a front view showing the lifting means taken out.
FIG. 8 is a side view of FIG. 7;
FIG. 9 is a front view showing tilting means.
FIG. 10 is a plan view of FIG. 9;
FIG. 11 is a side view showing gripping means.
FIG. 12 is an enlarged front view of a part of FIG. 3;
FIG. 13 is a control circuit diagram.
FIG. 14 is a circuit diagram of a part of the control circuit.
FIG. 15 is a sequence circuit diagram of the sequencer 91;
FIG. 16 is an operation chart.
FIG. 17 is a flowchart.
18 (a), (b), and (c) are conceptual diagrams of three modes for explaining the liquid draining process. FIG.
19 (a) and 19 (b) are side cross-sectional views of FIGS. 18 (b) and 18 (c).
20 (a) and 20 (b) are cross-sectional views showing enlarged horizontal meniscuses in FIGS. 19 (a) and 19 (b).
FIG. 21 is a cross-sectional view showing a vertical meniscus.
22 (a), (b), (c), (d), and (e) are front views showing a comparison of film thicknesses.
FIG. 23 is a cross-sectional view of FIG. 22 (c).
24 (a) and 24 (b) are side cross-sectional views showing a comparison of film thicknesses.
25 is a side sectional view showing the film thickness of the conventional one in FIG.
[Explanation of symbols]
1 ... Resist solution tank
2 ... Board
3 ... Liquid drain angle setting means
4 ... Lifting means
7 ... Tilting means
8 ... Ascent speed control means
11a: Resist layer (11a)
93 ... Speed controller (93)
R ... Bottom edge
S: Resist liquid level

Claims (4)

A substrate for an electronic circuit in which a thin film is formed on the surface by applying a liquid to the surface while being lifted and lowered from the resist liquid in a generally vertical plane, and a lower edge portion on the side to be cut off from the resist liquid In the method for forming a thin film of an electronic circuit board, wherein the film thickness of the thin film is formed thinner than the film thickness closer to the inside than the edge,
Pulling up the electronic circuit board from the resist solution in the ascending process;
Reducing the rising speed in the process of draining the resist solution from the edge of the circuit board for electronic circuit ;
The lower end line of the edge cutting edge is substantially horizontal ;
The rising speed of the liquid draining process is 1/100 to 1/10 of the maximum rising speed until the liquid draining process,
The liquid has a viscosity of 25 degrees Celsius and 40 cps or less, the average rising speed is 10 mm to 70 mm in 1 second, and the rising speed of the liquid draining process is 0.1 mm to 1.0 mm. A method for forming a thin film on an electronic circuit board. In claim 1,
A method of forming a thin film on an electronic circuit board, characterized in that the film thickness of the thin film changes in a wavy shape in the horizontal direction along the edge at the edge that is cut off from the resist solution. In claim 1 or 2 ,
The electronic circuit board is not separated from the liquid surface until the meniscus portion formed between the liquid cutting edge and the liquid surface finishes moving from one side to the other side. Forming method. 3. The method for forming a thin film on an electronic circuit board according to claim 1 , wherein the time required for the liquid draining process is not shorter than the time required for the meniscus portion to move from one side to the other side.

Images