JPH06260477A - Selective etching method - Google Patents
Selective etching methodInfo
- Publication number
- JPH06260477A JPH06260477A JP7113793A JP7113793A JPH06260477A JP H06260477 A JPH06260477 A JP H06260477A JP 7113793 A JP7113793 A JP 7113793A JP 7113793 A JP7113793 A JP 7113793A JP H06260477 A JPH06260477 A JP H06260477A
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Abstract
Description
【０００１】[0001]
【産業上の利用分野】本発明は加工物の表面を微細に加
工する方法、特に高選択比な選択エッチング方法に関す
る。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for finely processing the surface of a workpiece, and more particularly to a selective etching method with a high selection ratio.
【０００２】[0002]
【従来の技術】従来技術として、被加工物をエッチング
溶液中に浸した状態でレーザー光を照射し、照射領域の
温度上昇に伴う化学反応の促進で、エッチング用のマス
クなしでエッチング加工した方法がある（R.J.von Gutf
eld et al.:Appl.Phys.Lett.40(4)1982 p.352 ）。この
方法ではエッチング溶液中に、高密度に反応種（エッチ
ャント）が存在しているために化学反応が速やかに起こ
り、エッチング速度が非常に高いという特徴がある。2. Description of the Related Art As a conventional technique, a method in which an object to be processed is irradiated with a laser beam in a state of being immersed in the solution, and a chemical reaction is accelerated with a rise in temperature of an irradiation region to perform etching processing without a mask for etching. There is (RJ von Gutf
eld et al .: Appl. Phys. Lett. 40 (4) 1982 p. 352). This method is characterized in that the reactive species (etchants) are present in the etching solution at a high density, so that a chemical reaction occurs quickly and the etching rate is very high.
【０００３】[0003]
【発明が解決しようとする課題】しかしながら、エッチ
ング溶液中に高密度の反応種が存在することは、レーザ
ー光未照射部分においてもエッチングが徐々に進行し、
特に微細加工にとって重要な加工精度が悪化するという
問題がある。即ち選択比が低い。これを完全に抑えるた
めにはエッチング溶液及び被加工材料の温度を可能な限
り下げればよい（理想は絶対零度）が、そのために大掛
かりな冷却機構が必要となり、実現は容易でなく現実的
ではない。本発明は上記の問題を鑑みてなされたもので
あり、室温において局部加熱部分と未加熱部分とで高選
択比なエッチングが可能な加工方法を提供することを目
的とする。However, the presence of a high density of reactive species in the etching solution means that the etching gradually progresses even in the portion not irradiated with laser light,
In particular, there is a problem that the processing accuracy, which is important for fine processing, deteriorates. That is, the selection ratio is low. In order to completely suppress this, the temperature of the etching solution and the material to be processed should be lowered as much as possible (ideally, absolute zero), but this requires a large-scale cooling mechanism, which is not easy and not realistic. . The present invention has been made in view of the above problems, and an object of the present invention is to provide a processing method capable of performing etching with a high selective ratio between a locally heated portion and an unheated portion at room temperature.
【０００４】[0004]
【課題を解決するための手段】上記の課題を解決するた
め本発明の構成は、常温ではほとんど反応しない反応溶
液と被加工材料との組合せで、局所加熱により前記反応
溶液中に浸した前記被加工材料の所定の領域を局所加熱
して、前記反応溶液と接している該加熱領域部分に前記
反応溶液との反応生成物を形成する反応工程と、前記局
所加熱により温度上昇した、前記反応生成物の形成され
た前記被加工材料を冷却する冷却工程と、冷却された前
記被加工材料の前記反応生成物を再び局所加熱により前
記反応生成物を溶液中に飛散させる飛散工程とからなる
ことを特徴とする。また、その関連発明の構成は、前記
局所加熱としてパルスレーザー光を用いることを特徴と
し、第二関連発明の構成は、前記反応生成物が前記被加
工材料の酸化物であることを特徴とする。第三関連発明
の構成は、前記被加工材料がシリコンであり、前記反応
生成物がシリコン酸化物であり、前記反応溶液が純水あ
るいは塩酸水溶液であることを特徴とする。第四関連発
明の構成は、前記被加工材料が複合化合物であり、前記
反応生成物が反応前の酸化物とは異なる酸化物であるこ
とを特徴とする。In order to solve the above-mentioned problems, the structure of the present invention is a combination of a reaction solution which hardly reacts at room temperature and a material to be processed. A reaction step of locally heating a predetermined region of the processing material to form a reaction product of the reaction solution in the heating region portion in contact with the reaction solution; and the reaction generation of which the temperature is raised by the local heating. A cooling step of cooling the processed material on which an object is formed, and a scattering step of scattering the reaction product into a solution by locally heating the reaction product of the cooled processed material again. Characterize. The configuration of the related invention is characterized by using pulsed laser light as the local heating, and the configuration of the second related invention is characterized in that the reaction product is an oxide of the material to be processed. . The structure of the third related invention is characterized in that the material to be processed is silicon, the reaction product is silicon oxide, and the reaction solution is pure water or an aqueous hydrochloric acid solution. The structure of the fourth related invention is characterized in that the material to be processed is a composite compound, and the reaction product is an oxide different from the oxide before the reaction.
【０００５】[0005]
【作用】パルスレーザー等で局所加熱を被加工材料に施
すと、その領域は被加工材料の融点近傍まで温度上昇す
る。このため反応溶液中の反応種と被加工材料は化学反
応を起こすことができ、反応物を形成する。この場合、
被加工材料と反応種とは室温で化学反応しない組合せを
選択してあるので、未加熱部分は反応を起こさない。化
学反応の代表である酸化反応は活性化エネルギーが高
く、室温での酸化は自然酸化膜が形成され、高々その厚
さは数nm程度であるのみで、ほとんど進行しない。そし
て、エネルギー照射で上昇した温度を冷却させ、再び局
所加熱を同じ箇所に施すと、形成されていた化学反応物
は急激な加熱によって熱膨張し、もとの被加工材料との
熱膨張係数が異なるために反応物は界面で剥離を生じて
溶液中に分散する。即ちエッチングが行われる。剥離分
散した反応物は溶液中ですぐ冷却されるので被加工物に
再付着することはない。この反応・分散を必要なだけ繰
り返すことで室温中で選択エッチングが行われる。When the material to be processed is locally heated by a pulse laser or the like, the temperature of the region rises to near the melting point of the material to be processed. Therefore, the reactive species in the reaction solution and the material to be processed can cause a chemical reaction to form a reactant. in this case,
Since the combination of the material to be processed and the reactive species does not chemically react at room temperature, the unheated portion does not react. The oxidation reaction, which is a typical chemical reaction, has a high activation energy, and the oxidation at room temperature forms a natural oxide film, and the thickness thereof is about several nm at most, and it hardly progresses. When the temperature raised by energy irradiation is cooled and local heating is applied again to the same location, the formed chemical reaction product thermally expands due to rapid heating, and the coefficient of thermal expansion with the original material to be processed is increased. Due to the difference, the reactants peel at the interface and disperse in the solution. That is, etching is performed. The exfoliated and dispersed reaction product is cooled immediately in the solution, so that it does not redeposit on the work piece. By repeating this reaction and dispersion as many times as necessary, selective etching is performed at room temperature.
【０００６】[0006]
【発明の効果】本発明によれば、局部加熱によってのみ
可能となる活性化エネルギーの高い化学反応を用いるこ
とで必要な部分のみ反応を施し、同部分の局部加熱によ
る剥離分散の工程を繰り返すことで非常に高選択比なエ
ッチング加工が実現する。また、局部加熱で加熱するの
で微細な加工に対処できる。EFFECTS OF THE INVENTION According to the present invention, a chemical reaction having a high activation energy, which can be achieved only by local heating, is used to carry out a reaction only on a necessary portion, and a step of peeling and dispersing the same portion by local heating is repeated. With this, etching processing with a very high selection ratio is realized. In addition, since it is heated by local heating, fine processing can be dealt with.
【０００７】[0007]
【実施例】以下、本発明を具体的な実施例に基づいて説
明する。図１に本発明を適用した第一実施例の主な工程
における過程断面図を示す。図１（ａ）で、被加工材料
であるシリコン基板１０が反応溶液としての純水２０中
に局部加熱を行いやすいように水面に平行に配置されて
いる。純水２０中には反応種である水分子２１がある。
このシリコン基板１０の表面のエッチングしたい所定の
領域にパルスレーザー３０を集束して真上から照射させ
る。こうすることでシリコン基板１０の表面は融点近傍
まで温度上昇する。このため、照射領域におけるシリコ
ンは水中の反応種である水分子と酸化反応を起こすのに
必要なエネルギーを受取り、シリコン酸化物（SiO2）を
形成する（図１(b))。このメカニズムはシリコンＬＳＩ
プロセスのウエット酸化と同じである。このときレーザ
ーの未照射領域ではほとんど温度上昇しないので酸化反
応は進行しない（自然酸化膜が形成される程度）。これ
は例えばシリコンのアルカリエッチングにおける活性化
エネルギーが０．５８ｅＶでエッチング液では室温でも
エッチング反応が進むが、酸化反応の活性化エネルギー
は１．３ｅＶと高いために室温程度では純水と酸化反応
を起こさないためである。EXAMPLES The present invention will be described below based on specific examples. FIG. 1 shows process sectional views in the main steps of the first embodiment to which the present invention is applied. In FIG. 1A, a silicon substrate 10 which is a material to be processed is arranged in parallel with a water surface in pure water 20 as a reaction solution so as to facilitate local heating. In the pure water 20, there are water molecules 21 that are reactive species.
The pulsed laser 30 is focused on a predetermined region of the surface of the silicon substrate 10 to be etched and irradiated from directly above. By doing so, the temperature of the surface of the silicon substrate 10 rises to near the melting point. Therefore, silicon in the irradiation region receives energy necessary for causing an oxidation reaction with water molecules that are reactive species in water, and forms silicon oxide (SiO 2 ) (FIG. 1 (b)). This mechanism is silicon LSI
It is the same as wet oxidation in the process. At this time, the temperature hardly rises in the non-irradiated region of the laser, so that the oxidation reaction does not proceed (a natural oxide film is formed). For example, the activation energy in alkali etching of silicon is 0.58 eV, and the etching reaction proceeds even at room temperature with an etching solution, but the activation energy of the oxidation reaction is as high as 1.3 eV. This is to prevent it from happening.
【０００８】さて、レーザー照射で形成されたシリコン
酸化膜は、その状態のままでは形成されるだけである。
そこでこの基板を一旦冷却させる（冷却工程、図１
(c))。Now, the silicon oxide film formed by laser irradiation is only formed in that state.
Therefore, this substrate is once cooled (cooling step, FIG.
(c)).
【０００９】そして再び溶液中でパルスレーザーを所定
の酸化した部分に照射すると、今度は酸化物（SiO2）が
急激に加熱され熱膨張する。このとき母材のシリコン基
板との熱膨張率が異なるために酸化膜との界面で剥離が
生じて酸化膜は反応溶液である純水中に分散する（飛散
工程、図１(d))。冷却工程の時にも剥離が生じるように
も考えられるが、この時は自然冷却と言えるので剥離を
生じる程の歪みが生じず、飛散工程の再加熱時のみ局所
的な急激な加熱で歪んで剥離する。When the pulsed laser is again irradiated in the solution to the predetermined oxidized portion, the oxide (SiO 2 ) is rapidly heated and thermally expanded. At this time, since the coefficient of thermal expansion of the base material is different from that of the silicon substrate, peeling occurs at the interface with the oxide film, and the oxide film is dispersed in pure water as a reaction solution (scattering step, FIG. 1D). It is considered that peeling may occur even during the cooling process, but at this time it can be said that natural cooling does not cause distortion that causes peeling, and only when reheating in the scattering process, distortion occurs due to local rapid heating and peeling. To do.
【００１０】図２は本発明を適応した第二実施例の主な
工程の断面図を示す。図２はシリコンの例と同様、被加
工材料である複合酸化物のＰＺＴ（ジルコン酸・チタン
酸鉛）基板１０’で、やはり反応溶液である純水２０中
に局部加熱が行いやすいように水面と平行になるよう配
置されている。そこでエッチングを行いたい所定の部分
にパルスレーザーを照射させ、反応を起こさせる（図２
(a))。この場合、被加工材料がＰＺＴであるので、組成
としてはZr（ジルコニア）とTi（チタン）とPb（鉛）と
Ｏ（酸素）とで成り立っており、これらをレーザー照射
で次のように分解・酸化させる。FIG. 2 is a sectional view showing the main steps of the second embodiment to which the present invention is applied. FIG. 2 shows a PZT (lead zirconate / titanate) substrate 10 ′ of a composite oxide, which is a material to be processed, similarly to the example of silicon, in which pure water 20 which is also a reaction solution makes it easy to perform local heating on the water surface. It is arranged to be parallel to. Therefore, a predetermined portion to be etched is irradiated with a pulse laser to cause a reaction (Fig. 2
(a)). In this case, since the material to be processed is PZT, the composition consists of Zr (zirconia), Ti (titanium), Pb (lead), and O (oxygen), which are decomposed by laser irradiation as follows. -Oxidize.
【００１１】まず、レーザー照射で温度上昇が生じる
と、それぞれの金属原子に純水より酸素原子が供給され
てPbO2とZrO2とTiO2が生じる。このうちPbO2とTiO2は低
融点材料なので反応工程中に溶液中に溶融・昇華してし
まう。ZrO2１５は高融点材料であるのでそのまま固体と
して残存する（図２(b))。そして一旦ＰＺＴ基板を冷却
させ、再びパルスレーザーを照射して局所加熱を行う
と、今度はZrO2１５が単独で存在するために反応工程時
より加熱されて相転移温度１１７０℃に到り、結晶構造
が単斜晶から正方晶に変化する。この相転移は体積収縮
が伴うため、下地のＰＺＴ基板との界面で剥離を生じて
ZrO2１５は溶液中に分散し、エッチングがなされる（図
２(c))。First, when the temperature rises due to laser irradiation, oxygen atoms are supplied from pure water to the respective metal atoms to produce PbO 2 , ZrO 2 and TiO 2 . Of these, PbO 2 and TiO 2 are low-melting materials, so they melt and sublime in the solution during the reaction process. Since ZrO 2 15 is a high melting point material, it remains as a solid as it is (FIG. 2 (b)). Then, once the PZT substrate was cooled and pulsed laser was irradiated again to perform local heating, this time, since ZrO 2 15 was present alone, it was heated from the reaction step and reached the phase transition temperature of 1170 ° C. The structure changes from monoclinic to tetragonal. Since this phase transition is accompanied by volume contraction, peeling occurs at the interface with the underlying PZT substrate.
ZrO 2 15 is dispersed in the solution and etched (FIG. 2 (c)).
【００１２】この実施例では反応溶液として純水を用い
たが、塩酸水溶液でも同様に効果がある。さらに被加工
材料としては、反応溶液と常温では反応せず、熱膨張係
数が反応生成物と異なるものであれば良く、例えばアル
ミやステンレスのような金属であっても構わない。ま
た、対象とする材料によってはパルスレーザー照射の集
中度を変化させて昇温の程度を調節してもよい。Although pure water was used as the reaction solution in this example, an aqueous hydrochloric acid solution is also effective. Further, the material to be processed may be a material that does not react with the reaction solution at room temperature and has a coefficient of thermal expansion different from that of the reaction product, and may be a metal such as aluminum or stainless steel. Further, depending on the target material, the degree of temperature rise may be adjusted by changing the degree of concentration of pulsed laser irradiation.
【００１３】以上のように本発明はわずかな簡単な工程
で望む箇所にのみエッチングを施すことができ、かなり
微細な構造にも対処できる利点がある。As described above, the present invention has an advantage that only a desired portion can be etched by a few simple steps and a considerably fine structure can be dealt with.
【図１】本発明を適用した第一実施例の主な工程におけ
る模式断面図。FIG. 1 is a schematic cross-sectional view in main steps of a first embodiment to which the present invention is applied.
【図２】本発明を適応した第二実施例の主な工程におけ
る模式断面図。FIG. 2 is a schematic cross-sectional view in a main step of a second embodiment to which the present invention is applied.
１０ 被加工材料（Si基板） １１ レーザー照射領域 １２ 反応生成物の酸化物（SiO2） １４ 剥離された酸化物 ２０ 反応溶液（純水） ２１ 反応種（水分子） ３０ 局所加熱（パルスレーザー照射） １０’被加工材料（ＰＺＴ基板） １１’レーザー照射領域 １５ 反応生成物の酸化物（ZrO2）10 Work Material (Si Substrate) 11 Laser Irradiation Area 12 Oxide of Reaction Product (SiO 2 ) 14 Exfoliated Oxide 20 Reaction Solution (Pure Water) 21 Reactive Species (Water Molecule) 30 Local Heating (Pulse Laser Irradiation) ) 10 'Workpiece material (PZT substrate) 11' Laser irradiation area 15 Oxide of reaction product (ZrO 2 )
Claims (5)
加工材料との組合せで、局所加熱により前記反応溶液中
に浸した前記被加工材料の所定の領域を局所加熱して、
前記反応溶液と接している該加熱領域部分に前記反応溶
液との反応生成物を形成する反応工程と、 前記局所加熱により温度上昇した、前記反応生成物の形
成された前記被加工材料を冷却する冷却工程と、 冷却された前記被加工材料の前記反応生成物を再び局所
加熱により前記反応生成物を溶液中に飛散させる飛散工
程とからなることを特徴とする選択エッチング方法。1. A combination of a reaction solution which hardly reacts at room temperature and a material to be processed, by locally heating a predetermined region of the material to be processed immersed in the reaction solution by local heating,
A reaction step of forming a reaction product of the reaction solution in the heating region portion in contact with the reaction solution, and cooling the work material on which the reaction product is formed, the temperature of which has been raised by the local heating. A selective etching method comprising: a cooling step; and a scattering step in which the reaction product of the cooled material to be processed is again locally heated to scatter the reaction product in a solution.
用いることを特徴とする請求項１に記載の選択エッチン
グ方法。2. The selective etching method according to claim 1, wherein pulsed laser light is used as the local heating.
物である、 ことを特徴とする請求項１および請求項２に記載の選択
エッチング方法。3. The selective etching method according to claim 1, wherein the reaction product is an oxide of the material to be processed.
徴とする請求項３に記載の選択エッチング方法。4. The selective etching method according to claim 3, wherein the material to be processed is silicon, the reaction product is silicon oxide, and the reaction solution is pure water or an aqueous hydrochloric acid solution. .
ることを特徴とする請求項３に記載の選択エッチング方
法。5. The selective etching method according to claim 3, wherein the material to be processed is a composite compound, and the reaction product is an oxide different from the oxide before the reaction.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP7113793A JPH06260477A (en) | 1993-03-05 | 1993-03-05 | Selective etching method |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP7113793A JPH06260477A (en) | 1993-03-05 | 1993-03-05 | Selective etching method |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| JPH06260477A true JPH06260477A (en) | 1994-09-16 |
Family
ID=13451900
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP7113793A Pending JPH06260477A (en) | 1993-03-05 | 1993-03-05 | Selective etching method |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPH06260477A (en) |
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2009119848A1 (en) * | 2008-03-28 | 2009-10-01 | 国立大学法人大阪大学 | Method of etching |
| JP2009542022A (en) * | 2006-07-03 | 2009-11-26 | フラウンホッファー−ゲゼルシャフト・ツァー・フォデラング・デル・アンゲワンテン・フォーシュング・エー．ファウ． | Liquid jet-guided etching method and use thereof to remove material from solids |
| JP5024048B2 (en) * | 2005-11-18 | 2012-09-12 | 三菱瓦斯化学株式会社 | Wet etching method and wet etching apparatus |
-
1993
- 1993-03-05 JP JP7113793A patent/JPH06260477A/en active Pending
Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP5024048B2 (en) * | 2005-11-18 | 2012-09-12 | 三菱瓦斯化学株式会社 | Wet etching method and wet etching apparatus |
| JP2009542022A (en) * | 2006-07-03 | 2009-11-26 | フラウンホッファー−ゲゼルシャフト・ツァー・フォデラング・デル・アンゲワンテン・フォーシュング・エー．ファウ． | Liquid jet-guided etching method and use thereof to remove material from solids |
| WO2009119848A1 (en) * | 2008-03-28 | 2009-10-01 | 国立大学法人大阪大学 | Method of etching |
| JP5306328B2 (en) * | 2008-03-28 | 2013-10-02 | 国立大学法人大阪大学 | Etching method |
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