JP2004225063A - Non-cyanide silver plating solution, silver plating method and bump forming method using the same - Google Patents
Non-cyanide silver plating solution, silver plating method and bump forming method using the same Download PDFInfo
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- JP2004225063A JP2004225063A JP2003010599A JP2003010599A JP2004225063A JP 2004225063 A JP2004225063 A JP 2004225063A JP 2003010599 A JP2003010599 A JP 2003010599A JP 2003010599 A JP2003010599 A JP 2003010599A JP 2004225063 A JP2004225063 A JP 2004225063A
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- 238000007747 plating Methods 0.000 title claims abstract description 104
- BQCADISMDOOEFD-UHFFFAOYSA-N Silver Chemical compound [Ag] BQCADISMDOOEFD-UHFFFAOYSA-N 0.000 title claims abstract description 84
- 229910052709 silver Inorganic materials 0.000 title claims abstract description 83
- 239000004332 silver Substances 0.000 title claims abstract description 83
- 238000000034 method Methods 0.000 title claims abstract description 18
- LFAGQMCIGQNPJG-UHFFFAOYSA-N silver cyanide Chemical compound [Ag+].N#[C-] LFAGQMCIGQNPJG-UHFFFAOYSA-N 0.000 claims abstract description 33
- LSNNMFCWUKXFEE-UHFFFAOYSA-N Sulfurous acid Chemical compound OS(O)=O LSNNMFCWUKXFEE-UHFFFAOYSA-N 0.000 claims abstract description 9
- YIROYDNZEPTFOL-UHFFFAOYSA-N 5,5-Dimethylhydantoin Chemical compound CC1(C)NC(=O)NC1=O YIROYDNZEPTFOL-UHFFFAOYSA-N 0.000 claims abstract description 5
- IJBYGVAJNSNXJI-UHFFFAOYSA-N 5,5-dimethylimidazolidine-2,4-dione;silver Chemical compound [Ag].CC1(C)NC(=O)NC1=O IJBYGVAJNSNXJI-UHFFFAOYSA-N 0.000 claims abstract description 5
- 239000004065 semiconductor Substances 0.000 claims description 6
- 238000009713 electroplating Methods 0.000 claims description 4
- GEHJYWRUCIMESM-UHFFFAOYSA-L sodium sulfite Chemical compound [Na+].[Na+].[O-]S([O-])=O GEHJYWRUCIMESM-UHFFFAOYSA-L 0.000 claims description 4
- BHZRJJOHZFYXTO-UHFFFAOYSA-L potassium sulfite Chemical group [K+].[K+].[O-]S([O-])=O BHZRJJOHZFYXTO-UHFFFAOYSA-L 0.000 claims description 3
- 235000019252 potassium sulphite Nutrition 0.000 claims description 3
- 239000007788 liquid Substances 0.000 claims description 2
- 235000010265 sodium sulphite Nutrition 0.000 claims description 2
- 238000002161 passivation Methods 0.000 abstract description 8
- 238000010586 diagram Methods 0.000 abstract 1
- KWYUFKZDYYNOTN-UHFFFAOYSA-M Potassium hydroxide Chemical compound [OH-].[K+] KWYUFKZDYYNOTN-UHFFFAOYSA-M 0.000 description 9
- 238000001556 precipitation Methods 0.000 description 6
- 230000000052 comparative effect Effects 0.000 description 5
- 230000000694 effects Effects 0.000 description 4
- 239000010931 gold Substances 0.000 description 4
- 238000005259 measurement Methods 0.000 description 4
- 229920002120 photoresistant polymer Polymers 0.000 description 4
- SQGYOTSLMSWVJD-UHFFFAOYSA-N silver(1+) nitrate Chemical group [Ag+].[O-]N(=O)=O SQGYOTSLMSWVJD-UHFFFAOYSA-N 0.000 description 4
- 230000003746 surface roughness Effects 0.000 description 4
- XFXPMWWXUTWYJX-UHFFFAOYSA-N Cyanide Chemical compound N#[C-] XFXPMWWXUTWYJX-UHFFFAOYSA-N 0.000 description 3
- 239000003570 air Substances 0.000 description 3
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 3
- 229910052760 oxygen Inorganic materials 0.000 description 3
- 239000001301 oxygen Substances 0.000 description 3
- 239000002244 precipitate Substances 0.000 description 3
- 230000015572 biosynthetic process Effects 0.000 description 2
- WJRBRSLFGCUECM-UHFFFAOYSA-N hydantoin Chemical compound O=C1CNC(=O)N1 WJRBRSLFGCUECM-UHFFFAOYSA-N 0.000 description 2
- 229940091173 hydantoin Drugs 0.000 description 2
- 238000004519 manufacturing process Methods 0.000 description 2
- 239000000203 mixture Substances 0.000 description 2
- 239000002245 particle Substances 0.000 description 2
- 238000005185 salting out Methods 0.000 description 2
- 229910001961 silver nitrate Inorganic materials 0.000 description 2
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 2
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 description 1
- 229910021607 Silver chloride Inorganic materials 0.000 description 1
- 150000001875 compounds Chemical class 0.000 description 1
- 238000000151 deposition Methods 0.000 description 1
- 230000008021 deposition Effects 0.000 description 1
- 208000028659 discharge Diseases 0.000 description 1
- PCHJSUWPFVWCPO-UHFFFAOYSA-N gold Chemical compound [Au] PCHJSUWPFVWCPO-UHFFFAOYSA-N 0.000 description 1
- 229910052737 gold Inorganic materials 0.000 description 1
- 229910052751 metal Inorganic materials 0.000 description 1
- 239000002184 metal Substances 0.000 description 1
- 230000002250 progressing effect Effects 0.000 description 1
- 229910052710 silicon Inorganic materials 0.000 description 1
- 239000010703 silicon Substances 0.000 description 1
- 229940100890 silver compound Drugs 0.000 description 1
- 150000003379 silver compounds Chemical class 0.000 description 1
- HKZLPVFGJNLROG-UHFFFAOYSA-M silver monochloride Chemical compound [Cl-].[Ag+] HKZLPVFGJNLROG-UHFFFAOYSA-M 0.000 description 1
- RHUVFRWZKMEWNS-UHFFFAOYSA-M silver thiocyanate Chemical compound [Ag+].[S-]C#N RHUVFRWZKMEWNS-UHFFFAOYSA-M 0.000 description 1
- TZMGLOFLKLBEFW-UHFFFAOYSA-M silver;sulfamate Chemical compound [Ag+].NS([O-])(=O)=O TZMGLOFLKLBEFW-UHFFFAOYSA-M 0.000 description 1
- 238000004544 sputter deposition Methods 0.000 description 1
- LSNNMFCWUKXFEE-UHFFFAOYSA-L sulfite Chemical class [O-]S([O-])=O LSNNMFCWUKXFEE-UHFFFAOYSA-L 0.000 description 1
- 231100000331 toxic Toxicity 0.000 description 1
- 230000002588 toxic effect Effects 0.000 description 1
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- Electroplating And Plating Baths Therefor (AREA)
- Electroplating Methods And Accessories (AREA)
Abstract
【課題】ノジュールのような突起状物を形成することなく、平滑な銀めっき表面を実現できるとともに、不動態膜の存在する被めっき表面であっても段差を生じることなく銀めっき処理が施せ、光沢のある銀めっき処理が可能な非シアン系銀めっき液及び銀メッキ方法を提供する。
【解決手段】ジメチルヒダントイン銀錯体を銀濃度で１〜７５ｇ／Ｌと、亜硫酸塩を０．１〜１０．０ｇ／Ｌと、ジメチルヒダントインを５０〜２５０ｇ／Ｌとを含有し、ｐＨ７〜１３であることを特徴とする非シアン系銀めっき液とした。
【選択図】 なしAn object of the present invention is to achieve a smooth silver plating surface without forming protrusions such as nodules, and to perform a silver plating process without generating a step even on a surface to be plated having a passivation film. Provided are a non-cyanide silver plating solution and a silver plating method capable of performing shiny silver plating.
The silver complex contains 1 to 75 g / L of dimethylhydantoin silver, 0.1 to 10.0 g / L of sulfite, 50 to 250 g / L of dimethylhydantoin, and has a pH of 7 to 13. A non-cyanide silver plating solution characterized by the following facts.
[Selection diagram] None
Description
【０００１】
【発明の属する技術分野】
本発明は、非シアン系の銀めっき液に関するもので、特に、ノジュールなどの突起状物を形成することなく平滑なめっき処理面を形成するとともに、光沢のある銀めっき処理を施せ、半導体チップ表面に銀バンプを形成する場合に好適な非シアン系銀めっき液及び銀めっき方法に関する。
【０００２】
【従来の技術】
従来から、めっき業界で実用化されている銀めっき液は、その優れためっき特性から主にシアン系の銀めっき液が使用されている。このシアン系銀めっき液は、めっき表面における析出粒子が非常に細かく、平滑な銀めっき処理が行えるものである。
【０００３】
ところが、このシアン系銀めっき液は毒性があり、作業環境、排出処理の点で問題がある。そのため、近年では、シアンを含まない非シアン系銀めっき液の開発が盛んに行われている。この非シアン系銀めっき液としては、例えば、硝酸銀、ヒダントイン銀、スルファミン酸銀、塩化銀、チオシアン酸銀等を主組成としたものが知られている（例えば、特許文献１〜４参照）
【０００４】
【特許文献１】特開平１０−１２１２８９号公報
【特許文献２】特開平９−２５６１８５号公報
【特許文献３】特開平９−２５６１８６号公報
【特許文献４】特開平９−２５６１８７号公報
【０００５】
これら従来の非シアン系銀めっき液は、銀めっき処理後の表面が比較的粗い状態で仕上がる傾向がある。そして、場合によってはノジュールと呼ばれる突起状物を形成する場合がある。また、銀めっき浴中の銀の沈殿を抑制することや、或いは発生した銀の沈殿物を溶解させるため、酸素又は空気をめっき浴に供給しなければならなく、めっき処理操作が簡単に行えない。
【０００６】
さらに、被めっき物表面に不動態膜が存在している場合、不動態膜のある部分と存在しない部分とを含む表面を銀めっき処理すると、ある程度の厚みの銀めっきでその表面を被覆しても、不動態膜のある部分における境界付近に段差を生じてしまう傾向がある。
【０００７】
近年、半導体製造において、金バンプの代わりに銀により形成した銀バンプを形成することが行われるが、上記のような非シアン系銀めっき液を用いて銀バンプを形成すると、理想的な形状を形成することが困難な場合があった。特に、バンプサイズが極小化する昨今においては、ノジュールのような突起状物を形成する銀メッキ処理では実用できないという問題を生じていた。
【０００８】
【発明が解決しようとする課題】
本発明は、以上のような事情のもとになされたもので、ノジュールのような突起状物を形成することなく、平滑な銀めっき表面を実現できるとともに、不動態膜の存在する被めっき表面であっても段差を生じることなく銀めっき処理が施すことができ、光沢のある銀めっきが処理できる非シアン系銀めっき液及び銀メッキ方法を提供することを目的とする。
【０００９】
【課題を解決するための手段】
かかる課題を解決するため、本発明者は、ヒダントイン系化合物を用いた非シアン系銀めっき液について鋭意研究した結果、本発明の非シアン系銀めっき液を想到するに至った。
【００１０】
本発明の非シアン系銀めっき液は、ジメチルヒダントイン銀錯体を銀濃度で１〜７５ｇ／Ｌと、亜硫酸塩を０．１〜１０．０ｇ／Ｌと、ジメチルヒダントインを５０〜２５０ｇ／Ｌとを含有し、ｐＨ７〜１３であるものとした。
【００１１】
本発明の非シアン系銀めっき液は、めっき界面における銀の析出状態をスムーズに進行させることができる亜硫酸塩を含み、所定のｐＨに調整していることが大きな特徴である。この本発明の非シアン系銀めっき液によれば、銀の析出が被めっき表面の性状に影響されることなく、被めっき表面の全面で均一的に銀の析出が進行し、銀の析出粒子も細かく、ノジュールのような突起状物を形成することなく、平滑な銀めっき処理をすることが可能となる。また、本発明の非シアン系銀めっき液では、被めっき表面に不動態膜が存在していても、ある程度の厚みの銀めっきを行うと、その不動態膜の境界でも段差を生じることが無くなる。さらに、本発明の非シアン系銀めっき液は、銀めっき液中の銀の沈殿を抑制するために或いは発生した銀の沈殿物を溶解させるために酸素又は空気をめっき液に供給する必要がなく、長期間安定的に銀めっき処理を行うことができる。
【００１２】
本発明の非シアン系銀めっき液は、めっき液中の銀化合物がジメチルヒダントイン銀錯体の形で存在し、その時の銀濃度が１〜７５ｇ／Ｌである。１ｇ／Ｌ未満であると、所要の電流密度での銀めっき処理が行えず、めっき効率の低下を生じ、実用的でなくなる。また、７５ｇ／Ｌを超えると、塩析を生じやすくなるからである。
【００１３】
また、本発明の非シアン系銀めっき液では、ジメチルヒダントインが５０〜２５０ｇ／Ｌであるが、５０ｇ／Ｌ未満であるとめっき効率の低下が生じ、２５０ｇ／Ｌを超えると塩析が生じて実用的でなくなる。
【００１４】
そして、本発明の非シアン系銀めっき液では、亜硫酸塩が０．１〜１０ｇ／Ｌであるが、０．１ｇ／Ｌ未満であると、銀の析出粒子を微細化する効果が小さくなり、ノジュールのような突起状物の形成を抑制する効果が小さくならからである。１０ｇ／Ｌを超えると、銀の還元が起こり始め、銀の沈殿物を発生し易くなる。なお、この亜硫酸塩は、本発明の非シアン系銀めっき液でのめっき界面における銀の析出状態をスムーズに進行させるもので、このような作用を奏するのは、亜硫酸特有の比較的激しくない、いわゆるマイルドな還元能力によるものと考えられる。
【００１５】
そしてまた、本発明の非シアン系銀めっき液では、ｐＨが７〜１３であるが、ｐＨ７未満であると、銀めっき液がけん濁する傾向となり、ｐＨ１３を超えると析出した銀が無光沢となるからである。
【００１６】
本発明の非シアン系めっき液で用いる亜硫酸塩は、亜硫酸カリウム、亜硫酸ナトリウムが好ましい。これらの亜硫酸塩を用いると、ノジュールのような突起状物を形成することなく平滑なめっき表面を実現でき、析出した銀は光沢性を有したものとなるからである。
【００１７】
上記した本発明に係る非シアン系銀めっき液を用いて銀めっき処理を行う場合には、電流密度０．１〜１０Ａ／ｄｍ２、液温３０〜９０℃の条件で電解めっきすることが好ましい。電流密度が０．１Ａ／ｄｍ２未満になると、析出効率が低下しすぎ、１０Ａ／ｄｍ２を超えると、突起状物が発生し易くなり、析出する銀も無光沢になりやすくなる。
【００１８】
そして、本発明の非シアン系銀めっき液を用いて上記しためっき処理条件に基づき、半導体チップ表面に電解めっきを行って銀バンプを形成することが好ましいものである。本発明の非シアン系銀めっき液で銀めっき処理を行うと、突起状物を形成することなく平滑なめっき表面を形成でき、極小化傾向のバンプについても理想的な形状をした銀バンプを形成することができる。さらに、従来の非シアン系銀めっき液と異なり、酸素や空気の供給を行う必要がないため、容易に半導体製造工程に適用でき、長期間安定して銀めっき処理を行うことができる。
【００１９】
【発明の実施の形態】
本発明の好ましい実施形態について、以下に示す実施例及び比較例により説明する。
【００２０】
実施例：本発明に係る非シアン系銀めっき液として、表１に示す各組成のめっき液を建浴した。
【００２１】
【表１】
表１に示すの各実施例の非シアン系銀めっき液は、次ぎのようにして製造した。まず、ジメチルヒダントイン銀を表１に示す銀濃度となるように純水に投入し、そして、亜硫酸カリウムを表１に示す各濃度となるように投入し、その後水酸化カリウムを用い表１に示す各ｐＨ値となるように調整した。また、めっき液温は６０℃とした。
【００２３】
比較例：比較として、次の非シアン系銀めっき液を作製した。比較例の非シアン系銀めっき液は、硝酸銀を銀濃度で３０ｇ／Ｌ、ジメチルヒダントインを２００ｇ／Ｌを純水に投入し、水酸化カリウムを用いてｐＨ１０．０に調整したものである。また、めっき液温は６０℃とした。
【００２４】
上記した実施例及び比較例の非シアン系銀めっき液を用い、厚さ２μｍで、一辺の長さが１００μｍの正方形状のバンプ形成パターンを有するフォトレジストを、Ａｕのスパッタ皮膜を備えたウェハの表面に配置して、その表面に銀めっき処理を行った。
【００２５】
非シアン系銀めっき処理条件は、液温６０℃で、電流密度１Ａ／ｄｍ２、
めっき厚みは５０μｍとした。そして、銀めっき処理して得られた各サンプルの銀バンプについて、表面粗さＲａ及びめっき処理段差（測定装置：ＫＬＡ ｐｒｏｆｉｌｅｒ Ｐ−１１）、外観（金属顕微鏡：ＮＩＫＯＮ ＭＯＤＥＬ ＯＰＴＩＰＨＯＴＯ−８８）、及び光沢度（ＧＡＭ光沢度計 ｄｉｇｉｔａｌ ｄｅｎｓｉｔｏｍａｔｅｒ ＭＯＤＥＬ １４４）を調べることにより、銀めっき評価を行った。
【００２６】
ここで、図１に示す銀バンプの概略断面図を用いて、上記した各測定の測定位置について説明する。図１に示すように、銀めっき処理はシリコンウェハ１表面上に、スパッタリングで被覆されたＡｕ皮膜２の表面を被めっき面として、そのＡｕ皮膜表面に、一辺１００μｍの正方形状のバンプパターンを有したフォトレジスト３をコーティングしたものを準備した。各銀メッキ液で厚み５０μｍ銀メッキ処理を行うと、図１のようにフォトレジスト３の上部（不導体被膜表面上）にまで広がった状態の銀バンプ４が形成される。表面粗さは、矢印Ａの部分において測定し、めっき処理段差ＢはＡ部分とフォトレジスト３の上部にメッキされた部分との表面の高さの相違を測定したものである。光沢度は、銀バンプ４上部表面にて測定した。表２にその測定結果を示す。
【００２７】
【表２】
表２に示すように、比較例の銀めっき液では、銀バンプの表面にノジュールといわれる突起状物が形成されていることが観察され、表面粗さも高い数値を示した。また、不動態膜の境界部分では、５０μｍ厚の銀めっき処理を行ったにも関わらず、１．５μｍもの厚みの段差が形成されていた。そして、光沢度値も０．３であり、半光沢状の銀めっき表面であった。
【００２９】
これに対し、実施例１〜２７までの銀めっき液では、銀バンプ表面にはノジュール等の突起物も形成されていなく、非常に平滑な表面であることが観察され、表面粗さも０．１〜０．４μｍ程度の低い数値で平滑な表面であることが確認された。また、不動態膜の境界部分では、５０μｍ厚の銀めっき処理を行うと、０．１〜０．４μｍ程度の段差しか形成されていなかった。そして、光沢度値も０．７〜１．３であり、光沢状の銀めっき表面であることが確認された。
【００３０】
【発明の効果】
以上説明したように、本発明の非シアン系銀めっき液によると、ノジュールのような突起状物を形成することなく、平滑な銀めっき表面を実現できるとともに、不動態膜の存在する被めっき表面であっても段差を生じることなく銀めっき処理が施せる。そのため、半導体チップに銀バンプを形成する場合に特に好適なものといえる。
【図面の簡単な説明】
【図１】銀バンプを形成したウェハの概略断面図。[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a non-cyanide silver plating solution, in particular, to form a smooth plating surface without forming projections such as nodules, and to apply a glossy silver plating process to the semiconductor chip surface. The present invention relates to a non-cyanide silver plating solution and a silver plating method suitable for forming a silver bump on a silver plate.
[0002]
[Prior art]
Conventionally, as a silver plating solution practically used in the plating industry, a cyan silver plating solution is mainly used because of its excellent plating characteristics. In this cyan silver plating solution, the precipitated particles on the plating surface are very fine, and a smooth silver plating process can be performed.
[0003]
However, this cyan silver plating solution is toxic and has problems in working environment and discharge treatment. Therefore, in recent years, non-cyanide-based silver plating solutions containing no cyanide have been actively developed. As the non-cyanide silver plating solution, for example, those having a main composition of silver nitrate, silver hydantoin, silver sulfamate, silver chloride, silver thiocyanate, and the like are known (for example, see Patent Documents 1 to 4).
[0004]
[Patent Document 1] JP-A-10-112289 [Patent Document 2] JP-A-9-256185 [Patent Document 3] JP-A 9-256186 [Patent Document 4] JP-A 9-256187 [0005] ]
These conventional non-cyanide silver plating solutions tend to be finished with a relatively rough surface after silver plating. In some cases, a projection called a nodule may be formed. Further, in order to suppress the precipitation of silver in the silver plating bath or to dissolve the generated silver precipitate, oxygen or air must be supplied to the plating bath, and the plating operation cannot be easily performed. .
[0006]
Furthermore, when a passivation film is present on the surface of the object to be plated, when the surface including the passivation film and the non-existence portion is subjected to silver plating, the surface is covered with silver plating having a certain thickness. Also, there is a tendency that a step is generated near the boundary in a certain portion of the passivation film.
[0007]
In recent years, in semiconductor manufacturing, silver bumps formed of silver are formed instead of gold bumps. When silver bumps are formed using a non-cyanide silver plating solution as described above, an ideal shape is obtained. It was sometimes difficult to form. In particular, in recent years when the bump size is minimized, there has been a problem that the silver plating process for forming a protrusion like a nodule cannot be used.
[0008]
[Problems to be solved by the invention]
The present invention has been made in view of the above circumstances, and can realize a smooth silver plating surface without forming protrusions such as nodules, and a plating surface on which a passive film exists. It is an object of the present invention to provide a non-cyanide silver plating solution and a silver plating method capable of performing silver plating without generating a step and performing glossy silver plating.
[0009]
[Means for Solving the Problems]
In order to solve such a problem, the present inventors have intensively studied a non-cyanide silver plating solution using a hydantoin-based compound, and as a result, have come to think of a non-cyanide silver plating solution of the present invention.
[0010]
The non-cyanide silver plating solution of the present invention comprises a silver dimethylhydantoin complex in a silver concentration of 1 to 75 g / L, a sulfite of 0.1 to 10.0 g / L, and a dimethylhydantoin of 50 to 250 g / L. Contained and had a pH of 7 to 13.
[0011]
The major feature of the non-cyanide silver plating solution of the present invention is that it contains a sulfite capable of smoothly progressing the silver precipitation state at the plating interface, and is adjusted to a predetermined pH. According to the non-cyanide silver plating solution of the present invention, silver precipitation proceeds uniformly over the entire surface of the surface to be plated, without being affected by the properties of the surface to be plated. Also, it is possible to perform a smooth silver plating process without forming protrusions such as nodules. Further, in the non-cyanide silver plating solution of the present invention, even if a passivation film is present on the surface to be plated, if silver plating of a certain thickness is performed, no step occurs at the boundary of the passivation film. . Further, the non-cyanide silver plating solution of the present invention does not need to supply oxygen or air to the plating solution in order to suppress silver precipitation in the silver plating solution or to dissolve generated silver precipitates. Silver plating can be stably performed for a long period of time.
[0012]
In the non-cyanide silver plating solution of the present invention, the silver compound in the plating solution is present in the form of a dimethylhydantoin silver complex, and the silver concentration at that time is 1 to 75 g / L. If the amount is less than 1 g / L, silver plating at a required current density cannot be performed, resulting in a reduction in plating efficiency, which is not practical. On the other hand, if it exceeds 75 g / L, salting out tends to occur.
[0013]
In the non-cyanide silver plating solution of the present invention, the dimethylhydantoin content is 50 to 250 g / L, but if it is less than 50 g / L, the plating efficiency is reduced, and if it exceeds 250 g / L, salting out occurs. It is not practical.
[0014]
In the non-cyanide silver plating solution of the present invention, the amount of sulfite is 0.1 to 10 g / L, but if it is less than 0.1 g / L, the effect of miniaturizing silver precipitation particles is reduced, This is because the effect of suppressing the formation of protrusions such as nodules is small. If it exceeds 10 g / L, silver starts to be reduced and silver precipitates are easily generated. Note that this sulfite is one that smoothly promotes the precipitation state of silver at the plating interface in the non-cyanide silver plating solution of the present invention, and such an effect is relatively intense peculiar to sulfurous acid. This is probably due to the so-called mild reduction ability.
[0015]
Further, in the non-cyanide silver plating solution of the present invention, the pH is 7 to 13. However, when the pH is less than 7, the silver plating solution tends to become turbid, and when the pH exceeds 13, the precipitated silver becomes dull. Because it becomes.
[0016]
The sulfite used in the non-cyanide plating solution of the present invention is preferably potassium sulfite or sodium sulfite. If these sulfites are used, a smooth plating surface can be realized without forming nodules such as nodules, and the deposited silver has gloss.
[0017]
When silver plating is performed using the above-described non-cyanide silver plating solution according to the present invention, it is preferable to perform electrolytic plating under the conditions of a current density of 0.1 to 10 A / dm 2 and a solution temperature of 30 to 90 ° C. . When the current density is less than 0.1 A / dm 2 , the deposition efficiency is too low, and when the current density is more than 10 A / dm 2 , projections tend to be generated, and the deposited silver tends to be dull.
[0018]
Then, it is preferable that the surface of the semiconductor chip is subjected to electrolytic plating to form silver bumps on the basis of the above plating conditions using the non-cyanide silver plating solution of the present invention. When silver plating is performed with the non-cyanide silver plating solution of the present invention, a smooth plating surface can be formed without forming projections, and a silver bump having an ideal shape can be formed even for a bump having a tendency to be minimized. can do. Furthermore, unlike the conventional non-cyanide silver plating solution, there is no need to supply oxygen or air, so that it can be easily applied to a semiconductor manufacturing process and silver plating can be stably performed for a long period of time.
[0019]
BEST MODE FOR CARRYING OUT THE INVENTION
Preferred embodiments of the present invention will be described with reference to the following examples and comparative examples.
[0020]
Example : As a non-cyanide silver plating solution according to the present invention, plating solutions having respective compositions shown in Table 1 were bathed.
[0021]
[Table 1]
The non-cyanide silver plating solution of each example shown in Table 1 was produced as follows. First, dimethylhydantoin silver is added to pure water so as to have a silver concentration shown in Table 1, and potassium sulfite is added so as to have each concentration shown in Table 1. Thereafter, potassium hydroxide is used as shown in Table 1 using potassium hydroxide. It adjusted so that it might be each pH value. The plating solution temperature was 60 ° C.
[0023]
Comparative Example : For comparison, the following non-cyanide silver plating solution was prepared. The non-cyanide silver plating solution of the comparative example was prepared by charging silver nitrate at a silver concentration of 30 g / L and dimethylhydantoin at a concentration of 200 g / L in pure water, and adjusting the pH to 10.0 using potassium hydroxide. The plating solution temperature was 60 ° C.
[0024]
Using the non-cyanide silver plating solution of the above-described Examples and Comparative Examples, a photoresist having a square-shaped bump formation pattern having a thickness of 2 μm and a side length of 100 μm was formed on a wafer having a sputtered Au film. It was arranged on a surface, and the surface was subjected to silver plating.
[0025]
The conditions for the non-cyanide silver plating treatment are a liquid temperature of 60 ° C., a current density of 1 A / dm 2 ,
The plating thickness was 50 μm. Then, the surface roughness Ra and the plating step (measurement device: KLA profiler P-11), the appearance (metal microscope: NIKON MODEL OPTIPHOTO-88), and the gloss of the silver bump of each sample obtained by the silver plating process. The silver plating was evaluated by examining the degree (GAM gloss meter digital densitometer model 144).
[0026]
Here, the measurement position of each measurement described above will be described with reference to the schematic cross-sectional view of the silver bump shown in FIG. As shown in FIG. 1, in the silver plating process, a surface of a Au film 2 coated by sputtering is formed on a surface of a silicon wafer 1 and a surface of the Au film has a square bump pattern of 100 μm on a side. A photoresist 3 coated was prepared. When a silver plating treatment with a thickness of 50 μm is performed with each silver plating solution, a silver bump 4 is formed which spreads over the photoresist 3 (on the surface of the nonconductive film) as shown in FIG. The surface roughness was measured at the portion indicated by the arrow A, and the plating step B measured the difference in surface height between the portion A and the portion plated on the photoresist 3. The gloss was measured on the upper surface of the silver bump 4. Table 2 shows the measurement results.
[0027]
[Table 2]
As shown in Table 2, in the silver plating solution of the comparative example, it was observed that a protrusion called a nodule was formed on the surface of the silver bump, and the surface roughness also showed a high numerical value. Further, at the boundary portion of the passivation film, a step having a thickness of 1.5 μm was formed despite the silver plating treatment having a thickness of 50 μm. The gloss value was 0.3, and the surface was a semi-gloss silver-plated surface.
[0029]
On the other hand, in the silver plating solutions of Examples 1 to 27, no projections such as nodules were formed on the surface of the silver bump, and it was observed that the surface was very smooth, and the surface roughness was 0.1%. It was confirmed that the surface was smooth with a low value of about 0.4 μm. In addition, at the boundary portion of the passivation film, when a silver plating process with a thickness of 50 μm was performed, no step of about 0.1 to 0.4 μm was formed. The gloss value was also 0.7 to 1.3, and it was confirmed that the surface was a glossy silver-plated surface.
[0030]
【The invention's effect】
As described above, according to the non-cyanide silver plating solution of the present invention, a smooth silver plating surface can be realized without forming projections such as nodules, and a surface to be plated on which a passive film exists. Even in this case, the silver plating process can be performed without generating a step. Therefore, it can be said that it is particularly suitable when silver bumps are formed on a semiconductor chip.
[Brief description of the drawings]
FIG. 1 is a schematic sectional view of a wafer on which silver bumps are formed.
Claims (4)
電流密度０．１〜１０Ａ／ｄｍ２、液温３０〜９０℃の条件で電解めっきするものである銀めっき方法。A method of silver plating using the non-cyanide silver plating solution according to claim 1 or 2,
A silver plating method for performing electrolytic plating under the conditions of a current density of 0.1 to 10 A / dm 2 and a liquid temperature of 30 to 90 ° C.
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP2003010599A JP2004225063A (en) | 2003-01-20 | 2003-01-20 | Non-cyanide silver plating solution, silver plating method and bump forming method using the same |
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| JP2003010599A JP2004225063A (en) | 2003-01-20 | 2003-01-20 | Non-cyanide silver plating solution, silver plating method and bump forming method using the same |
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Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2012092434A (en) * | 2010-09-21 | 2012-05-17 | Rohm & Haas Electronic Materials Llc | Cyanide-free silver electroplating solutions |
| CN103741178A (en) * | 2014-01-20 | 2014-04-23 | 厦门大学 | Solution for directly electroplating surface of silicon with smooth and compact thin silver film and electroplating method |
| CN107313084A (en) * | 2017-08-10 | 2017-11-03 | 佛山市南博旺环保科技有限公司 | A kind of alkaline non-cyanide plate silver plating solution and silver-coating method |
-
2003
- 2003-01-20 JP JP2003010599A patent/JP2004225063A/en active Pending
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2012092434A (en) * | 2010-09-21 | 2012-05-17 | Rohm & Haas Electronic Materials Llc | Cyanide-free silver electroplating solutions |
| CN103741178A (en) * | 2014-01-20 | 2014-04-23 | 厦门大学 | Solution for directly electroplating surface of silicon with smooth and compact thin silver film and electroplating method |
| CN107313084A (en) * | 2017-08-10 | 2017-11-03 | 佛山市南博旺环保科技有限公司 | A kind of alkaline non-cyanide plate silver plating solution and silver-coating method |
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