JP4931196B2 - Electroless copper plating bath, electroless copper plating method, and ULSI copper wiring formation method - Google Patents
Electroless copper plating bath, electroless copper plating method, and ULSI copper wiring formation method Download PDFInfo
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Description
本発明は、ＵＬＳＩのトレンチ埋め込みによるダマシン法銅配線形成において、トレンチ内のボイド等の欠陥の形成を可及的に防止しつつ、効率的な埋め込みが可能な無電解銅めっき浴、無電解銅めっき方法、及びＵＬＳＩ銅配線形成方法に関する。 The present invention relates to an electroless copper plating bath and an electroless copper capable of efficiently filling a damascene copper wiring formed by embedding ULSI trenches while preventing defects such as voids in the trenches as much as possible. The present invention relates to a plating method and a ULSI copper wiring forming method.
近年のＵＬＳＩの高速化、高集積化を支えるキーテクノロジーのひとつとしてＵＬＳＩ銅配線形成プロセスであるダマシン法がある。ダマシン法では、基板に形成した配線パターンのトレンチを電気銅めっきにより埋め込み配線を形成する。このプロセスでは、めっき浴中に含まれる数種の添加剤によりトレンチ底部から優先的に銅が析出する「ボトムアップ効果」により、微細で高アスペクト比のトレンチヘの完全な銅埋め込みが実現される。 One of the key technologies that support the recent high speed and high integration of ULSI is the damascene method, which is a ULSI copper wiring formation process. In the damascene method, a wiring having a wiring pattern formed on a substrate is buried by electrolytic copper plating. In this process, complete copper embedding into a fine, high aspect ratio trench is achieved by a “bottom-up effect” in which copper is preferentially deposited from the bottom of the trench by several additives contained in the plating bath.
これらの添加剤効果については盛んに研究が行われており、トレンチ埋め込み時に析出促進剤がトレンチ底部で濃縮し、その結果としてボトムアップ効果が発現するものと解釈されている（非特許文献１参照）。一方、最近では今後のさらなる微細化に対応しうる埋め込み配線形成法として、無電解めっき法を用いたプロセスの開発も注目されている。 Active research has been conducted on the effects of these additives, and it is interpreted that the precipitation accelerator is concentrated at the bottom of the trench when the trench is buried, and as a result, the bottom-up effect is expressed (see Non-Patent Document 1). ). On the other hand, recently, development of a process using an electroless plating method has attracted attention as a method for forming an embedded wiring that can cope with further miniaturization in the future.
無電解めっき法によるトレンチ埋め込みでは、析出抑制剤のトレンチ内部での消費によりボトムアップ効果を発現させた高アスペクト比トレンチの埋め込みが報告されている（非特許文献２参照）。しかしながら、この方法では電気めっきに比べてトレンチ埋め込み速度が非常に遅く、ボトムアップ効果のトレンチサイズ依存性も顕著である。 In trench embedding by electroless plating, it has been reported that a high aspect ratio trench is embedding in which a bottom-up effect is manifested by the consumption of a deposition inhibitor inside the trench (see Non-Patent Document 2). However, in this method, the trench filling speed is very slow compared to electroplating, and the trench size dependence of the bottom-up effect is remarkable.
なお、本発明に関連する先行技術文献情報としては、以下のものがある。
本発明は、上記事情に鑑みなされたもので、トレンチ内のボイド等の欠陥の形成を可及的に防止しつつ、効率的な埋め込みが可能な無電解銅めっき浴、無電解銅めっき方法、及びＵＬＳＩ銅配線形成方法を提供することを目的とする。 The present invention has been made in view of the above circumstances, and while preventing the formation of defects such as voids in trenches as much as possible, an electroless copper plating bath capable of efficient filling, an electroless copper plating method, And it aims at providing the ULSI copper wiring formation method.
本発明者は、無電解めっきにおいても電気めっきと同様に析出促進剤によるボトムアップ効果を発現させることができれば、より効果的な埋め込みが期待できると考え、無電解銅めっき浴における析出促進剤として報告されている８−ヒドロキシ−７−ヨード−５−キノリンスルホン酸（ＨＩＱＳＡ）を用いた無電解銅めっき浴について検討を重ねた結果、水溶性銅塩、還元剤としてホルマリン、パラホルムアルデヒド、グリオキシル酸、グリオキシル酸塩、ホスフィン酸、ホスフィン酸塩、次亜リン酸又は次亜リン酸塩、錯化剤、析出抑制剤としてポリエチレングリコール、ポリプロピレングリコール又はエチレングリコール−プロピレングリコール共重合体、析出促進剤として８−ヒドロキシ−７−ヨード−５−キノリンスルホン酸を含有し、Ｎａイオンを含有しない無電解銅めっき浴を用いてトレンチへの埋め込みめっきを実施すれば、トレンチ内にボイド等を形成せずにトレンチの埋め込みが可能であると共に、被めっき面に形成される銅めっき皮膜表面の平滑性が高いことを見出し、本発明をなすに至った。 The present inventor believes that more effective embedding can be expected if the bottom-up effect due to the deposition accelerator can be expressed in electroless plating as well as electroplating, and as a deposition accelerator in an electroless copper plating bath. As a result of repeated studies on the reported electroless copper plating bath using 8-hydroxy-7-iodo-5-quinolinesulfonic acid (HIQSA), water-soluble copper salt, formalin, paraformaldehyde, glyoxylic acid as a reducing agent , Glyoxylate, phosphinic acid, phosphinate, hypophosphorous acid or hypophosphite , complexing agent, precipitation inhibitor as polyethylene glycol, polypropylene glycol or ethylene glycol-propylene glycol copolymer, as precipitation accelerator Contains 8-hydroxy-7-iodo-5-quinoline sulfonic acid If the electroless copper plating bath that does not contain Na ions is used to fill the trench, the trench can be buried without forming a void or the like in the trench and formed on the surface to be plated. As a result , the present inventors have found that the smoothness of the surface of the copper plating film is high.
即ち、本発明は、以下の無電解銅めっき浴、無電解銅めっき方法及びＵＬＳＩ銅配線形成方法を提供する。
［１］ （Ａ）水溶性銅塩、（Ｂ）還元剤としてホルマリン、パラホルムアルデヒド、グリオキシル酸、グリオキシル酸塩、ホスフィン酸、ホスフィン酸塩、次亜リン酸又は次亜リン酸塩、（Ｃ）錯化剤、（Ｄ）めっき析出抑制剤としてポリエチレングリコール、ポリプロピレングリコール又はエチレングリコール−プロピレングリコール共重合体、及び（Ｅ）めっき析出促進剤として８−ヒドロキシ−７−ヨード−５−キノリンスルホン酸を含有し、Ｎａイオンを含有しないことを特徴とする無電解銅めっき浴。
［２］ 上記（Ｂ）成分の還元剤がグリオキシル酸又はその塩であることを特徴とする［１］記載の無電解銅めっき浴。
［３］ 上記（Ｂ）成分の還元剤がホルマリン又はパラホルムアルデヒドであることを特徴とする［１］記載の無電解銅めっき浴。
［４］ ［１］乃至［３］のいずれかに記載の無電解銅めっき浴を用いることを特徴とする無電解銅めっき方法。
［５］ ［１］乃至［３］のいずれかに記載の無電解銅めっき浴を用いた無電解銅めっきにより、トレンチに銅めっきを埋め込んで銅配線を形成することを特徴とするＵＬＳＩ銅配線形成方法。
That is, the present invention provides the following electroless copper plating bath, electroless copper plating method, and ULSI copper wiring formation method.
[1] (A) Water-soluble copper salt, (B) Formalin, paraformaldehyde, glyoxylic acid, glyoxylate, phosphinic acid, phosphinate, hypophosphorous acid or hypophosphite as reducing agent, (C) Complexing agent, (D) polyethylene glycol, polypropylene glycol or ethylene glycol-propylene glycol copolymer as plating deposition inhibitor, and (E) 8-hydroxy-7-iodo-5-quinolinesulfonic acid as plating deposition accelerator. An electroless copper plating bath characterized by containing Na ions.
[2] The electroless copper plating bath according to [1], wherein the reducing agent of the component (B) is glyoxylic acid or a salt thereof.
[3] The electroless copper plating bath according to [1], wherein the reducing agent of the component (B) is formalin or paraformaldehyde.
[ 4 ] An electroless copper plating method using the electroless copper plating bath according to any one of [1] to [3] .
[ 5 ] ULSI copper wiring, wherein copper wiring is formed by embedding copper plating in a trench by electroless copper plating using the electroless copper plating bath according to any one of [1] to [3] Forming method.
本発明によれば、ボイド等の欠陥の形成を可及的に防止しつつ、トレンチの効率的な埋め込みが可能であり、更に、微細なトレンチへの均一な付着が難しい乾式法によるシード層形成をせずに、全工程を湿式工程で構成して、より均一かつ確実にトレンチの埋め込みめっきを施すことが可能である。 According to the present invention, it is possible to efficiently fill a trench while preventing the formation of defects such as voids as much as possible, and further, it is possible to form a seed layer by a dry method in which uniform adhesion to a fine trench is difficult. It is possible to perform the buried plating of the trench more uniformly and reliably by configuring the whole process by a wet process without performing the above process.
以下、本発明について、更に詳しく説明する。
まず、本発明の第１の発明の無電解銅めっき浴について説明する。
Hereinafter, the present invention will be described in more detail.
First, the electroless copper plating bath according to the first aspect of the present invention will be described.
本発明の第１の発明において、無電解銅めっき浴は、（Ａ）水溶性銅塩、（Ｂ）還元剤、（Ｃ）錯化剤、（Ｄ）めっき析出抑制剤としてポリエチレングリコール、ポリプロピレングリコール又はエチレングリコール−プロピレングリコール共重合体、（Ｅ）めっき析出促進剤として８−ヒドロキシ−７−ヨード−５−キノリンスルホン酸を含有する。 In the first invention of the present invention, the electroless copper plating bath comprises (A) a water-soluble copper salt, (B) a reducing agent, (C) a complexing agent, and (D) a plating deposition inhibitor as polyethylene glycol, polypropylene glycol. Alternatively, it contains 8-hydroxy-7-iodo-5-quinolinesulfonic acid as an ethylene glycol-propylene glycol copolymer and (E) plating deposition accelerator.
（Ａ）成分の水溶性銅塩としては、例えば、硫酸銅、塩化銅、硝酸銅などを用いることができ、その濃度は銅イオン基準で０．０１〜０．１ｍｏｌ／Ｌが好ましい。特に、硫酸銅を好適に用いることができ、この場合、ＣｕＳＯ4・５Ｈ2Ｏを２．５〜２５ｇ／Ｌの濃度で用いることができる。 As the water-soluble copper salt of the component (A), for example, copper sulfate, copper chloride, copper nitrate and the like can be used, and the concentration is preferably 0.01 to 0.1 mol / L based on the copper ion. In particular, copper sulfate can be suitably used. In this case, CuSO 4 .5H 2 O can be used at a concentration of 2.5 to 25 g / L.
（Ｂ）成分の還元剤としては、例えば、ホルマリン、パラホルムアルデヒド、グリオキシル酸又はその塩、ホスフィン酸又はその塩、次亜リン酸又はその塩、ジメチルアミンボランなどを用いることができるが、塩を用いる場合はナトリウム塩以外の塩を用いる。その濃度は０．０１〜０．２５ｍｏｌ／Ｌ、特に０．０１〜０．１ｍｏｌ／Ｌが好ましい。特に、グリオキシル酸を好適に用いることができ、この場合、２〜１５ｇ／Ｌの濃度で用いることができる。 As the reducing agent of component (B), for example, formalin, paraformaldehyde, glyoxylic acid or a salt thereof, phosphinic acid or a salt thereof, hypophosphorous acid or a salt thereof, dimethylamine borane, and the like can be used. When used, a salt other than sodium salt is used. The concentration is preferably 0.01 to 0.25 mol / L, particularly 0.01 to 0.1 mol / L. In particular, glyoxylic acid can be preferably used, and in this case, it can be used at a concentration of 2 to 15 g / L.
（Ｃ）成分の錯化剤としては、エチレンジアミン四酢酸又はその塩、酒石酸又はその塩、エチレンジアミン、クエン酸又はその塩などを用いることができるが、塩を用いる場合はナトリウム塩以外の塩を用いる。その濃度は０．０１〜０．２ｍｏｌ／Ｌ、特に０．０５〜０．１ｍｏｌ／Ｌが好ましい。特に、エチレンジアミン四酢酸を好適に用いることができ、この場合、５〜２０ｇ／Ｌの濃度で用いることができる。 As the complexing agent for component (C), ethylenediaminetetraacetic acid or a salt thereof, tartaric acid or a salt thereof, ethylenediamine, citric acid or a salt thereof can be used. . The concentration is preferably 0.01 to 0.2 mol / L, particularly 0.05 to 0.1 mol / L. In particular, ethylenediaminetetraacetic acid can be preferably used, and in this case, it can be used at a concentration of 5 to 20 g / L.
本発明の第１の発明の無電解銅めっき浴には、（Ｄ）成分のめっき析出抑制剤としてポリエチレングリコール、ポリプロピレングリコール又はエチレングリコール−プロピレングリコール共重合体が含まれ、これらは平均分子量（ＧＰＣによるポリスチレン換算値）が１，０００〜２０，０００のものが好ましい。その濃度は０．１〜１００ｐｐｍ、特に０．５〜５ｐｐｍ、とりわけ１〜２ｐｐｍが好ましい。これらめっき析出抑制剤の添加は、ボイド等の形成抑制と、めっきにより形成される皮膜の平滑化に効果的である。 The electroless copper plating bath of the first invention of the present invention contains polyethylene glycol, polypropylene glycol or ethylene glycol-propylene glycol copolymer as a plating precipitation inhibitor of component (D), which has an average molecular weight (GPC). (Polystyrene equivalent value) is preferably 1,000 to 20,000. The concentration is preferably from 0.1 to 100 ppm, particularly preferably from 0.5 to 5 ppm, particularly preferably from 1 to 2 ppm. The addition of these plating precipitation inhibitors is effective in suppressing formation of voids and the like and smoothing of the film formed by plating.
本発明の第１の発明の無電解銅めっき浴には、（Ｅ）成分のめっき析出促進剤として８−ヒドロキシ−７−ヨード−５−キノリンスルホン酸（ＨＩＱＳＡ）を含有する。このＨＩＱＳＡの添加は、トレンチのボトムからのめっき成長効果（ボトムアップ効果）の促進に効果的である。その濃度は０．１〜２０ｐｐｍ、特に１〜１０ｐｐｍ、とりわけ２〜５ｐｐｍが好ましい。 The electroless copper plating bath according to the first aspect of the present invention contains 8-hydroxy-7-iodo-5-quinolinesulfonic acid (HIQSA) as a plating deposition accelerator of the component (E). The addition of HIQSA is effective in promoting the plating growth effect (bottom-up effect) from the bottom of the trench. The concentration is preferably 0.1 to 20 ppm, particularly 1 to 10 ppm, particularly 2 to 5 ppm.
なお、上記（Ｄ）成分と（Ｅ）成分の比が（Ｄ）成分：（Ｅ）成分＝１：１０〜１０：１、特に１：５〜５：１、とりわけ１：２〜２：１（いずれも質量比）であることが、ボイド等の形成抑制と、めっき析出速度の両立の点から好ましい。 The ratio of the component (D) to the component (E) is (D) component: (E) component = 1: 10 to 10: 1, particularly 1: 5 to 5: 1, especially 1: 2 to 2: 1. (Mass ratio) is preferable from the viewpoint of coexistence of formation suppression of voids and the plating deposition rate.
次に、本発明の第２の発明の無電解銅めっき浴について説明する。
本発明の第２の発明において、無電解銅めっき浴は、（Ａ）水溶性銅塩、（Ｂ）還元剤としてグリオキシル酸又はその塩、（Ｃ）錯化剤、及び（Ｄ）めっき析出抑制剤としてポリエチレングリコール、ポリプロピレングリコール又はエチレングリコール−プロピレングリコール共重合体を含有する。
Next, the electroless copper plating bath according to the second aspect of the present invention will be described.
In the second invention of the present invention, the electroless copper plating bath comprises (A) a water-soluble copper salt, (B) glyoxylic acid or a salt thereof as a reducing agent, (C) a complexing agent, and (D) plating precipitation suppression. The agent contains polyethylene glycol, polypropylene glycol or ethylene glycol-propylene glycol copolymer.
この、第２の発明の無電解銅めっき浴においては、（Ｂ）成分の還元剤として、グリオキシル酸又はその塩を用いるが、塩を用いる場合はナトリウム塩以外の塩を用いる。その濃度は０．０１〜０．２５ｍｏｌ／Ｌ、特に０．０１〜０．１ｍｏｌ／Ｌが好ましい。特に、グリオキシル酸を好適に用いることができ、この場合、２〜１５ｇ／Ｌの濃度で用いることができる。 In the electroless copper plating bath of the second invention, glyoxylic acid or a salt thereof is used as the reducing agent for component (B), but when a salt is used, a salt other than the sodium salt is used. The concentration is preferably 0.01 to 0.25 mol / L, particularly 0.01 to 0.1 mol / L. In particular, glyoxylic acid can be preferably used, and in this case, it can be used at a concentration of 2 to 15 g / L.
一方、（Ａ）成分の水溶性銅塩、（Ｃ）成分の錯化剤、（Ｄ）成分のめっき析出抑制剤は、上述した第１の発明の無電解銅めっき浴と同様のものを、同様の濃度で用いることが可能である。 On the other hand, the water-soluble copper salt of the component (A), the complexing agent of the component (C), and the plating precipitation inhibitor of the component (D) are the same as the electroless copper plating bath of the first invention described above. It is possible to use the same concentration.
なお、この第２の発明の場合であっても、めっき浴に、（Ｅ）成分である８−ヒドロキシ−７−ヨード−５−キノリンスルホン酸（ＨＩＱＳＡ）を添加することが可能である。 Even in the case of the second invention, it is possible to add 8-hydroxy-7-iodo-5-quinolinesulfonic acid (HIQSA) as the component (E) to the plating bath.
本発明の無電解銅めっき浴においては（第１の発明及び第２の発明のいずれの場合においても）、ｐＨ調整剤としてテトラメチルアンモニウムハイドロオキサイド等のめっき浴にＮａイオンを供給しないものを用い、ｐＨを６〜１３、特に１０〜１３として用いることが好ましい。 In the electroless copper plating bath of the present invention (in either case of the first invention or the second invention), a pH adjuster that does not supply Na ions to a plating bath such as tetramethylammonium hydroxide is used. The pH is preferably 6 to 13, particularly 10 to 13.
更に、本発明の無電解銅めっき浴は（第１の発明及び第２の発明のいずれの場合も）、Ｎａイオンを含有しないものである。そのため、めっき浴に添加する各成分としては、めっき浴にＮａイオンを供給しないものを用いる。 Furthermore, the electroless copper plating bath of the present invention (in either case of the first invention or the second invention) does not contain Na ions. Therefore, as each component added to the plating bath, one that does not supply Na ions to the plating bath is used.
本発明において、無電解銅めっきは、上述した無電解銅めっき浴を用い、無電解銅めっきにおける従来公知の条件を適用することができるが、めっき析出速度とめっき浴の安定性の点から、めっき温度は、４０〜８０℃、特に６０〜７０℃とすることが好ましい。めっき浴は、必要に応じ、エアバブリング等の方法で攪拌することができる。なお、前処理として触媒付与処理が必要な場合の触媒付与処理も従来公知の方法が適用できる。 In the present invention, the electroless copper plating uses the above-described electroless copper plating bath, and conventionally known conditions in the electroless copper plating can be applied. From the viewpoint of plating deposition rate and the stability of the plating bath, The plating temperature is preferably 40 to 80 ° C, particularly 60 to 70 ° C. The plating bath can be stirred by a method such as air bubbling as necessary. In addition, a conventionally well-known method can be applied also to the catalyst provision process when a catalyst provision process is required as pre-processing.
本発明のめっき浴は、ＵＬＳＩ（超大規模集積回路）等の銅配線形成における、トレンチへの銅めっきの埋め込み、いわゆるダマシン法によるシリコン基板への銅配線形成に好適であり、特に、幅５０〜１，０００ｎｍ、特に２００〜６００ｎｍ、アスペクト比（幅／深さ）０．５〜５、特に１〜２．５のトレンチをボイド等の欠陥を形成することなく、十分なめっき速度で効率的に埋め込むことができる。更に、トレンチ埋め込みにより基板上に形成されるめっき皮膜の平滑性が良好となる。その結果、その後のＣＭＰ（ケミカルメカニカルポリッシング）などにより施される平坦化工程における欠陥の発生をも可及的に防止することができる。 The plating bath of the present invention is suitable for embedding copper plating in a trench in forming copper wiring such as ULSI (ultra-large scale integrated circuit), and forming copper wiring on a silicon substrate by a so-called damascene method. A trench having a thickness of 1,000 nm, particularly 200 to 600 nm, and an aspect ratio (width / depth) of 0.5 to 5, particularly 1 to 2.5 is efficiently formed at a sufficient plating speed without forming defects such as voids. Can be embedded. Furthermore, the smoothness of the plating film formed on the substrate by filling the trench is improved. As a result, it is possible to prevent as much as possible the occurrence of defects in the planarization process performed by subsequent CMP (chemical mechanical polishing) or the like.
また、第２の発明のめっき浴の場合、幅１００〜５００ｎｍ、特に１００〜１５０ｎｍ、アスペクト比（幅／深さ）０．５〜３、特に２〜３のトレンチに効果的であり、これらのトレンチをボイド等の欠陥を形成することなく、十分なめっき速度で効率的に埋め込むことができる。 In the case of the plating bath of the second invention, it is effective for trenches having a width of 100 to 500 nm, particularly 100 to 150 nm, and an aspect ratio (width / depth) of 0.5 to 3, particularly 2 to 3. The trench can be efficiently filled at a sufficient plating speed without forming defects such as voids.
以下、実施例、比較例及び参考例を示して本発明を具体的に説明するが、本発明は下記の実施例に制限されるものではない。 EXAMPLES Hereinafter, although an Example , a comparative example, and a reference example are shown and this invention is demonstrated concretely, this invention is not restrict | limited to the following Example.
［実施例１］
表１に示される無電解銅めっき浴を用い、Ｃｕ／Ｔａ／ＳｉＯ2／Ｓｉ基板上に形成された幅２００〜６００ｎｍ、アスペクト比２．５〜０．６のトレンチをめっきにより埋め込み、めっき後のトレンチの断面を電界放射型走査電子顕微鏡（ＦＥ−ＳＥＭ）で観察した。ＳＥＭ像を図１に示す。なお、図示したトレンチの幅は２００ｎｍ、アスペクト比は２．５である（以下の図２〜４のＳＥＭ像において同じ）。また、この無電解銅めっき浴を用い、銅箔上にめっき皮膜を形成し、重量法によりめっき析出速度を測定したところ、３．５μｍ・ｈｒ-1であった。
[Example 1]
Using an electroless copper plating bath shown in Table 1, trenches having a width of 200 to 600 nm and an aspect ratio of 2.5 to 0.6 formed on a Cu / Ta / SiO 2 / Si substrate are embedded by plating. The cross section of the trench was observed with a field emission scanning electron microscope (FE-SEM). An SEM image is shown in FIG. The illustrated trench has a width of 200 nm and an aspect ratio of 2.5 (the same applies to the SEM images of FIGS. 2 to 4 below). Moreover, when this electroless copper plating bath was used, a plating film was formed on the copper foil, and the plating deposition rate was measured by a weight method, which was 3.5 μm · hr −1 .
［比較例１］
ＨＩＱＳＡ及びＰＥＧを用いなかった以外は、実施例１と同様にしてトレンチを埋め込み、めっき後のトレンチの断面を観察した。ＳＥＭ像を図２に示す。また、実施例１と同様にめっき析出速度を測定したところ、３．３μｍ・ｈｒ-1であった。
[Comparative Example 1]
Except that HIQSA and PEG were not used, the trench was embedded in the same manner as in Example 1, and the cross section of the trench after plating was observed. An SEM image is shown in FIG. Moreover, when the plating deposition rate was measured in the same manner as in Example 1, it was 3.3 μm · hr −1 .
［比較例２］
ＰＥＧを用いなかった以外は、実施例１と同様にしてトレンチを埋め込み、めっき後のトレンチの断面を観察した。ＳＥＭ像を図３に示す。また、実施例１と同様にめっき析出速度を測定したところ、４．０μｍ・ｈｒ-1であった。
[Comparative Example 2]
Except for not using PEG, the trench was embedded in the same manner as in Example 1, and the cross section of the trench after plating was observed. An SEM image is shown in FIG. Moreover, when the plating deposition rate was measured in the same manner as in Example 1, it was 4.0 μm · hr −1 .
［比較例３］
グリオキシル酸の代わりにホルムアルデヒドを０．０４ｍｏｌ／Ｌの濃度で用い、ｐＨを水酸化ナトリウムで調整した以外は、実施例１と同様にしてトレンチを埋め込み、めっき後のトレンチの断面を観察した。ＳＥＭ像を図４に示す。また、実施例１と同様にめっき析出速度を測定したところ、５．８μｍ・ｈｒ-1であった。
[Comparative Example 3]
A trench was embedded in the same manner as in Example 1 except that formaldehyde was used at a concentration of 0.04 mol / L instead of glyoxylic acid and the pH was adjusted with sodium hydroxide, and the cross section of the trench after plating was observed. An SEM image is shown in FIG. Moreover, when the plating deposition rate was measured in the same manner as in Example 1, it was 5.8 μm · hr −1 .
［実施例２］
表２に示される無電解銅めっき浴を用い、Ｃｕ／Ｔａ／ＳｉＯ2／Ｓｉ基板上に形成された幅２００〜６００ｎｍ、アスペクト比２．５〜０．６のトレンチをめっきにより埋め込み、めっき後のトレンチの断面を電界放射型走査電子顕微鏡（ＦＥ−ＳＥＭ）で観察した。ＳＥＭ像を図５に示す。なお、図示したトレンチの幅は１００ｎｍ、アスペクト比は３である（以下の図６のＳＥＭ像において同じ）。また、この無電解銅めっき浴を用い、銅箔上にめっき皮膜を形成し、重量法によりめっき析出速度を測定したところ、１０．６μｍ・ｈｒ-1であった。
[Example 2]
Using an electroless copper plating bath shown in Table 2, trenches having a width of 200 to 600 nm and an aspect ratio of 2.5 to 0.6 formed on a Cu / Ta / SiO 2 / Si substrate are filled by plating. The cross section of the trench was observed with a field emission scanning electron microscope (FE-SEM). An SEM image is shown in FIG. The illustrated trench has a width of 100 nm and an aspect ratio of 3 (the same applies to the SEM image of FIG. 6 below). Moreover, when this electroless copper plating bath was used, a plating film was formed on the copper foil, and the plating deposition rate was measured by a weight method, which was 10.6 μm · hr −1 .
実施例１，２と比較例１〜３とを比べると、ＨＩＱＳＡ及びＰＥＧの双方を用いていない比較例１では、トレンチ内にボイドが発生し、また、めっき皮膜の表面の無数の突起が形成された平滑性の低いものとなっている。ＰＥＧを用いなかった（ＨＩＱＳＡを用いた）比較例２も、ボイドの発生と、めっき表面の平滑性は改善されていない。一方、ＨＩＱＳＡ及びＰＥＧの双方を用い、ｐＨ調整に水酸化ナトリウムを用いたＮａイオンを含むめっき浴を用いた比較例３では、平滑性は改善されるが、やはりボイドが発生した。これに対し、実施例１，２においては、トレンチが欠陥なく埋め込まれ、トレンチを埋め込んだめっき皮膜の表面も平滑である。 When Examples 1 and 2 are compared with Comparative Examples 1 to 3, in Comparative Example 1 in which neither HIQSA nor PEG is used, voids are generated in the trenches, and numerous protrusions are formed on the surface of the plating film. The smoothness is low. In Comparative Example 2 in which PEG was not used (HIQSA was used), the generation of voids and the smoothness of the plating surface were not improved. On the other hand, in Comparative Example 3 using both HIQSA and PEG and using a plating bath containing Na ions using sodium hydroxide for pH adjustment, the smoothness was improved, but voids were still generated. On the other hand, in Examples 1 and 2, the trench is buried without a defect, and the surface of the plating film in which the trench is buried is also smooth.
更に、実施例１，２のめっき浴のめっき析出速度はＨＩＱＳＡ及びＰＥＧの双方を用いていない比較例１と遜色ないめっき析出速度が確保され、効率的なめっきによるトレンチ埋め込みが可能であることが確認された。 Furthermore, the plating deposition rate of the plating baths of Examples 1 and 2 is as high as that of Comparative Example 1 that does not use both HIQSA and PEG, and the trench filling by efficient plating is possible. confirmed.
ＨＩＱＳＡとＰＥＧとを併用した本発明の無電解銅めっき浴における、トレンチへの埋め込み性能の向上は、ＰＥＧ消費によりトレンチ内部に生じる濃度勾配による開口部での顕著なめっき析出抑制作用に加え、その濃度勾配によりトレンチ内部でのＨＩＱＳＡのめっき析出促進作用がトレンチ外部に比較して顕著になったためであると考えられる。 In the electroless copper plating bath of the present invention in which HIQSA and PEG are used in combination, the improvement of the embedding performance in the trench is in addition to the remarkable plating precipitation suppressing action in the opening due to the concentration gradient generated inside the trench due to the consumption of PEG. This is probably because the HIQSA plating deposition promoting action inside the trench became more prominent than the outside of the trench due to the concentration gradient.
［参考例１］
表３に示される無電解銅めっき浴を用い、Ｃｕ／Ｔａ／ＳｉＯ2／Ｓｉ基板上に形成された幅１００〜５００ｎｍ、アスペクト比０．５〜３のトレンチをめっきにより埋め込み、めっき後のトレンチの断面を電界放射型走査電子顕微鏡（ＦＥ−ＳＥＭ）で観察した。ＳＥＭ像を図６に示す。また、この無電解銅めっき浴を用い、銅箔上にめっき皮膜を形成し、重量法によりめっき析出速度を測定したところ、１．１μｍ・ｈｒ-1であった。
[ Reference Example 1 ]
Using an electroless copper plating bath shown in Table 3, a trench having a width of 100 to 500 nm and an aspect ratio of 0.5 to 3 formed on a Cu / Ta / SiO 2 / Si substrate is buried by plating, and the trench after plating Was observed with a field emission scanning electron microscope (FE-SEM). An SEM image is shown in FIG. Moreover, when this electroless copper plating bath was used, a plating film was formed on the copper foil, and the plating deposition rate was measured by a weight method, which was 1.1 μm · hr −1 .
参考例１においては、還元剤としてグリオキシル酸を用い、ＨＩＱＳＡを用いていないが、この場合であってもトレンチが欠陥なく埋め込まれる。 In Reference Example 1 , glyoxylic acid is used as the reducing agent and HIQSA is not used, but even in this case, the trench is buried without any defects.
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