WO2016208553A1 - 半導体デバイス電極の製造方法 - Google Patents

半導体デバイス電極の製造方法 Download PDF

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WO2016208553A1
WO2016208553A1 PCT/JP2016/068327 JP2016068327W WO2016208553A1 WO 2016208553 A1 WO2016208553 A1 WO 2016208553A1 JP 2016068327 W JP2016068327 W JP 2016068327W WO 2016208553 A1 WO2016208553 A1 WO 2016208553A1
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metal
thin film
silicide
semiconductor device
electrode
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PCT/JP2016/068327
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English (en)
French (fr)
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大見　俊一郎
政広　泰
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国立大学法人東京工業大学
田中貴金属工業株式会社
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Priority to US15/574,942 priority Critical patent/US20180174850A1/en
Priority to KR1020177035199A priority patent/KR20180002837A/ko
Publication of WO2016208553A1 publication Critical patent/WO2016208553A1/ja

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Definitions

  • the present invention relates to a method for manufacturing a silicide electrode in a semiconductor device such as a MOSFET.
  • a gate electrode and a source / drain region are formed on a silicon substrate, and then a silicide electrode is formed in the source / drain region in order to form a metal / semiconductor junction.
  • the silicide electrode is formed by depositing a metal thin film on the substrate by sputtering or the like and then heat-treating it to diffuse silicon into the metal thin film and silicidize.
  • titanium silicide (TiSi 2 ) and cobalt silicide (CoSi 2 ) are generally known in the past.
  • NiSi nickel silicide
  • platinum silicide (PtSi) that does not cause a phase transition in the heat treatment during silicidation is also expected.
  • a metal thin film of silicide such as Ni and heat-treat it.
  • this heat processing temperature is based also on a metal, it is about 300 degreeC or more and about 600 degreeC. Therefore, there is a concern about the formation of an insulating film due to oxidation of the metal as silicidation progresses in the heat treatment process.
  • the surface form of the silicide electrode may be deteriorated due to oxidation of the metal, which may increase the electrical resistance.
  • the second metal compound film may be referred to as a Cap layer (cap layer)).
  • TiN titanium nitride
  • TiC titanium carbide
  • the present invention has been made based on the above background, and relates to a method of forming a silicide electrode on a silicon substrate.
  • the present invention relates to the formation of an insulating film by oxidation of a first metal thin film formed during silicidation. Provided is one that can more effectively suppress changes in surface morphology.
  • the present inventors examined the constituent material of the Cap layer for protecting the first metal in order to solve the above problems. As a result, the present inventors have conceived the present invention that hafnium (Hf) is particularly effective as the second metal.
  • the present invention provides a step of forming a first thin film made of a first metal on a substrate containing Si, and a second thin film made of a compound of a second metal on the first thin film.
  • a semiconductor device electrode comprising: a step of forming; and a step of forming a first metal silicide electrode by heat treatment, wherein the second metal is applied with hafnium (Hf).
  • Hf hafnium
  • the first metal thin film for manufacturing the silicide electrode is formed on the Si portion of the substrate.
  • a Si substrate is usually used as a device substrate, and a source / drain is formed. Therefore, a diffusion layer is formed by doping a corresponding region with a dopant.
  • the first thin film is formed on this source / drain region.
  • the diffusion layer is formed by a conventional general method.
  • the gate electrode is also formed in accordance with the prior art.
  • the first metal constituting the silicide electrode is preferably Ti, Co, Ni, Pt or an alloy thereof.
  • consideration is given to the versatility of Ti silicide and Co silicide, Ni silicide characteristics for extremely reducing the junction depth, and the good heat resistance of Pt silicide.
  • the silicide of an alloy of Pt and Hf (PtHf) also has a work function near midgap with respect to Si (n-Si or p-Si) constituting the substrate, and is useful from the viewpoint that the barrier height can be reduced. This is a silicide electrode.
  • the film thickness of the first thin film is determined by the junction depth required for the device and is not related to the suppression of oxidation of the first metal, which is the subject matter of the present invention. Therefore, the thickness of the first thin film is not limited by the present application.
  • the method for forming the first metal thin film is not particularly limited, and any of a physical method such as a sputtering method and a vacuum evaporation method and a chemical method such as a chemical vapor deposition method (CVD method) can be applied.
  • the sputtering method is preferable.
  • the thin film is formed by magnetron sputtering, ion beam sputtering, electron cyclotron resonance (ECR) sputtering, mirrortron sputtering, radio frequency (RF) sputtering, direct current (DC) sputtering, or the like.
  • Hf is applied as the second metal.
  • Hf has a characteristic that it is relatively easy to develop and maintain an amorphous phase during compound formation, and structural changes due to crystallization hardly occur even when heated. . Therefore, when compared with TiN or the like conventionally used as a Cap layer, the Hf compound has high heat resistance and excellent barrier performance against the first thin film.
  • HfN As specific examples of Hf compounds, HfN, HfW, HfB, and the like can be applied. Among these Hf compounds, HfN is more preferable because it can form a film having high amorphous phase and high heat resistance. In addition, HfN has good etching properties and has an advantage that the removal process after silicidation can be simplified.
  • the thickness of the Hf compound thin film is preferably 10 nm or more and 20 nm or less. This is because the film has high oxidation resistance and is difficult to crystallize.
  • the method for forming the Hf compound thin film is not particularly limited as in the case of the first thin film, but the sputtering method is preferred. Reactive sputtering is applied to form a nitride film.
  • the first metal is silicided by heat treatment (annealing).
  • This heat treatment is preferably performed at 400 ° C. or higher and 600 ° C. or lower. This is because the heat treatment temperature can reduce the resistivity.
  • the heat treatment atmosphere is preferably a non-oxidizing atmosphere (vacuum atmosphere, inert gas atmosphere, reducing atmosphere).
  • the heat treatment is preferably performed using a rapid heat treatment apparatus.
  • the Hf compound thin film which is the second thin film, serves to barrier the first metal during silicidation by annealing, and thus completes its role upon completion of annealing.
  • the removal of the Hf compound thin film is preferably by wet etching.
  • Preferred etching solutions include dilute hydrofluoric acid and buffered hydrofluoric acid.
  • the etching solution is selected according to the type of the first metal, and examples thereof include dilute hydrofluoric acid, aqua regia, and sulfuric acid.
  • the first metal silicide electrode is formed on the substrate.
  • the subsequent steps follow conventional processes.
  • the present invention optimizes the constituent material of the second metal compound (Cap layer) that suppresses the oxidation of the first metal thin film to be silicided when manufacturing the silicide electrode of the semiconductor device.
  • the Hf compound applied in the present invention has a barrier performance superior to that of the prior art, and can cope with the manufacture of a miniaturized / thinned silicide film.
  • First Embodiment As a preliminary test, Pt is formed as a first metal to form Pt silicide on an Si substrate, and a case where a HfN thin film is formed thereon and not formed is used. The surface morphology of the silicide electrode after annealing was examined.
  • FIG. 1 shows a comparative test process according to this embodiment.
  • a Si substrate p-Si (100)
  • a Pt thin film was formed to a thickness of 10 nm by sputtering.
  • the HfN thin film was formed on the Pt thin film.
  • the HfN thin film was formed by reactive sputtering using a Hf target and setting the film formation atmosphere to Kr / N 2 (film thickness 20 nm).
  • the comparative example was subjected to silicidation without forming this HfN thin film.
  • silicidation was performed by heat treatment.
  • the silicidation conditions were a processing temperature of 450 ° C., a processing atmosphere in nitrogen gas, and a processing time of 30 minutes.
  • FIG. 2 is a photograph showing the observation results.
  • the silicide film of the comparative example in which the Cap layer made of HfN was not applied had irregularities formed on the surface, and was judged to be morphologically defective.
  • such a morphological defect was not found in the silicide film of this embodiment. It was confirmed that the barrier effect by the HfN thin film worked effectively during the annealing for silicidation.
  • the RMS of the Pt silicide alloy film of this embodiment to which the Cap layer was applied was 2 .26 nm.
  • the RMS of the Pt silicide film of the comparative example in which the Cap layer was not applied was 3.12 nm.
  • FIG. 3 schematically illustrates a process for forming a CBKR structure while applying an HfN thin film.
  • a change in interface resistance was also examined when annealing with a forming gas (N 2 /4.9% H 2 ) was performed after forming the CBKR structure.
  • Table 1 shows the measurement results of the interface resistance between the silicide electrode and the Al electrode by the BKR method.
  • the contact resistance can be reduced by applying the HfN thin film as the Cap layer in manufacturing the silicide electrode.
  • the FGA is originally an operation for improving the electrical contact between Al and the silicide electrode to improve the interface resistance. It was confirmed that the application of the Cap layer made of the HfN thin film can maintain the action of the FGA, and the contact resistance can be greatly reduced by both.
  • the present invention when manufacturing a silicide electrode, a higher quality than the conventional one can be manufactured.
  • the present invention is suitable as a process for manufacturing a silicide electrode in various semiconductor devices such as MOSFETs.

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Abstract

本発明は、Ｓｉを含む基板上に第１の金属からなる第１の薄膜を形成する工程と、前記第１の薄膜の上に、第２の金属の化合物からなる第２の薄膜を形成する工程と、熱処理することで第１の金属のシリサイドからなる電極を形成する工程と、を含む半導体デバイス電極の製造方法において、前記第２の金属はハフニウム（Ｈｆ）を適用することを特徴とする半導体デバイス電極の製造方法である。この第２の金属の化合物としては、ＨｆＮ、ＨｆＷ、ＨｆＢ等が好適である。本発明によれば、シリコン基板上にシリサイド電極を形成する際、シリサイド化する予定の金属薄膜の酸化を有効に抑制することができる。

Description

半導体デバイス電極の製造方法
　本発明は、ＭＯＳＦＥＴ等の半導体デバイスにおいて、シリサイド電極を製造するための方法に関する。
　ＭＯＳＦＥＴ等の半導体デバイスにおいては、シリコン基板上にゲート電極とソース／ドレイン領域が形成され、その後、金属／半導体接合を形成するために前記ソース／ドレイン領域にシリサイド電極を形成する。シリサイド電極の製造は、基板にスパッタリング法等で金属薄膜を蒸着した後、熱処理をしてシリコンを金属薄膜に拡散させてシリサイド化することで形成される。シリサイド電極の構成に関しては、古くはチタンシリサイド（ＴｉＳｉ２）やコバルトシリサイド（ＣｏＳｉ２）が一般に知られている。また、デバイスの微細化・薄型化に対応するため、ソース／ドレイン領域における接合深さの極浅化が可能なＳｉ消費量の少ないシリサイドとしてニッケルシリサイド（ＮｉＳｉ）が用いられている。更に、シリサイド化の際の熱処理における相転移の恐れのない白金シリサイド（ＰｔＳｉ）も期待されている。
　上記の通り、シリサイド電極の製造にあたっては、Ｎｉ等のシリサイド化する金属の薄膜を形成し、これを熱処理することが必要となる。この熱処理温度は金属にもよるが、３００℃以上６００℃程度である。そのため、熱処理過程でシリサイド化の進行と共に、当該金属の酸化による絶縁膜形成が懸念される。また、当該金属の酸化によりシリサイド電極の表面形態が悪化し、電気抵抗を上昇させるおそれもある。
　シリサイド電極製造時の絶縁膜形成やシリサイド膜の形態悪化を抑制するため、従来から、熱処理前にシリサイド化する金属（第１の金属）の薄膜の上に他の金属（第２の金属）の化合物膜を形成し、第１の金属の酸化を抑制する手法が提案されている（以下、この第２の金属の化合物膜をＣａｐ層（キャップ層）と称するときがある。）。Ｃａｐ層となる金属化合物としては、これまで、窒化チタン（ＴｉＮ）、炭化チタン（ＴｉＣ）等の有用性が報告されている。
特開平７－３８１０４号公報 特開平９－１５３６１６号公報
　近年の半導体デバイスの設計においては、微細化・薄型化に対応する要求がより高くなっており、シリサイド電極もこの傾向に追随する必要がある。そのため、第１の金属の膜厚の低減やコンタクトエリアの狭小化が図られているが、その様な中でシリサイド電極の低抵抗化および平坦化のためにはキャップ層のバリア能力の向上が必要となる。
　本発明は、上記のような背景のもとなされたものであり、シリコン基板上にシリサイド電極を形成する方法に関し、シリサイド化の際に形成した第１の金属薄膜の酸化による絶縁膜の形成・表面形態の変化をより有効に抑制することができるものを提供する。
　本発明者等は、上記課題を解決すべく、第１金属を保護するためのＣａｐ層の構成材料について検討を行った。そしてその結果、第２の金属としてハフニウム（Ｈｆ）が特に有効であるとして本発明に想到した。
　即ち、本発明は、Ｓｉを含む基板上に第１の金属からなる第１の薄膜を形成する工程と、前記第１の薄膜の上に、第２の金属の化合物からなる第２の薄膜を形成する工程と、熱処理することで第１の金属のシリサイドからなる電極を形成する工程と、を含む半導体デバイス電極の製造方法において、前記第２の金属はハフニウム（Ｈｆ）を適用することを特徴とする半導体デバイス電極の製造方法である。以下、本発明に係る半導体デバイス電極の製造方法について説明する。
　シリサイド電極を製造するための第１の金属の薄膜は、基板のＳｉ部分の上に形成される。シリサイド電極の適用が想定されるＭＯＳＦＥＴでは、通常、デバイスの基板としてＳｉ基板を使用し、ソース／ドレインを形成するため、対応する領域にドーパントをドープして拡散層を形成する。第１の薄膜は、このソース／ドレイン領域の上に形成される。拡散層の形成方法は従来からの一般的な手法でなされる。また、ソース／ドレイン領域の形成と共に、ゲート電極の形成も従来技術に従ってなされる。
　シリサイド電極を構成する第１の金属は、Ｔｉ、Ｃｏ、Ｎｉ、Ｐｔのいずれか又はこれらの合金が好ましい。上記の通り、ＴｉシリサイドやＣｏシリサイドの汎用性、接合深さの極浅化を図るためのＮｉシリサイド特性、更に、Ｐｔシリサイドの良好な耐熱性を考慮するものである。また、ＰｔとＨｆとの合金（ＰｔＨｆ）のシリサイドも基板を構成するＳｉ（ｎ－Ｓｉ又はｐ－Ｓｉ）に対してｍｉｄｇａｐ付近の仕事関数を有し、障壁高さを小さくできるといった観点から有用なシリサイド電極である。
　第１の薄膜の膜厚に関しては、デバイスに対して要求される接合深さ等により決定されるものであり、本発明の主題事項である第１の金属の酸化抑制とは無関係である。よって、第１の薄膜の膜厚は、本願で制限されることはない。
　第１の金属の薄膜形成の方法は特に限定されるものではなく、スパッタリング法や真空蒸着法等の物理的方法や、化学気相蒸着法（ＣＶＤ法)等の化学的方法のいずれも適用できるが、好ましくはスパッタリング法である。薄膜形成におけるスパッタリング形式については特に制限は無く、マグネトロンスパッタ、イオンビームスパッタ、電子サイクロトロン共鳴（ＥＣＲ）スパッタ、ミラートロンスパッタ、高周波（ＲＦ）スパッタ、直流（ＤＣ）スパッタ等で薄膜形成を行う。
　そして、第１の薄膜を形成した後、その上に第２の金属の化合物の薄膜を形成する。本発明では、この第２の金属としてＨｆを適用する。本発明者等によれば、Ｈｆは、化合物形成の際に、非晶質相の発現とその維持が比較的容易であり、加熱を受けても結晶化による構造変化が生じ難いという特性がある。そのため、従来からＣａｐ層として使用されてきたＴｉＮ等と比較したとき、Ｈｆ化合物は耐熱性が高く、第１の薄膜に対するバリア性能が優れている。
　そして、Ｈｆの化合物の具体例としては、ＨｆＮ、ＨｆＷ、ＨｆＢ等を適用することができる。これらＨｆ化合物の中でも、非晶質相の発現性が高く耐熱性の良好な膜が形成できるＨｆＮがより好ましい。また、ＨｆＮは、エッチング性も良好であり、シリサイド化後の除去工程を簡潔にすることができるというメリットもある。
　このＨｆ化合物薄膜の厚さとしては、１０ｎｍ以上２０ｎｍ以下とするのが好ましい。酸化耐性が高く、かつ結晶化しにくい膜厚だからである。
　Ｈｆ化合物薄膜の形成方法についても、第１の薄膜と同様に特に制約はないが、スパッタリング法が好ましい。窒化物膜を形成することから、反応性スパッタリングが適用される。
　第２の薄膜であるＨｆ化合物薄膜を形成した後、熱処理（アニール）により第１の金属をシリサイド化する。この熱処理は、４００℃以上６００℃以下で行うのが好ましい。抵抗率を低減できる熱処理温度だからである。熱処理雰囲気は、非酸化性雰囲気（真空雰囲気、不活性ガス雰囲気、還元雰囲気）とするのが好ましい。また、熱処理は高速熱処理装置を用いて行うことが好ましい。
　アニール後は、第２の薄膜を除去する工程を含むことが好ましい。第２の薄膜であるＨｆ化合物薄膜は、アニールによるシリサイド化の際に第１の金属をバリアするためのものであるので、アニール完了によりその役目を完了するからである。Ｈｆ化合物薄膜の除去は、ウエットエッチングによるのが好ましい。好ましいエッチング液としては、希フッ酸、緩衝フッ酸等が挙げられる。
　また、Ｈｆ化合物薄膜の除去と共に、アニール後のシリサイド化していない未反応の第１の金属も除去することが好ましい。この未反応の第１金属の除去もエッチングによるが、エッチング液は第１の金属の種類に応じて選択され、希フッ酸、王水、硫酸等が挙げられる。
　以上の工程により、基板上に第１の金属のシリサイド電極が形成される。半導体デバイスを製造するに当たり、その後の工程は従来プロセスに従う。
　本発明は、半導体デバイスのシリサイド電極の製造の際、シリサイド化する第１の金属薄膜の酸化を抑制する第２の金属の化合物（Ｃａｐ層）の構成材料を最適化するものである。本発明で適用するＨｆ化合物は、従来技術よりも優れたバリア性能を有し、微細化・薄膜化されたシリサイド膜製造にも対応可能である。
第１実施形態における評価試験のための試料の製造工程を説明する図。 第１実施形態で製造したシリサイド（ＰｔＳｉ）電極の表面形態の写真。 第２実施形態で製造したＣＢＫＲ構造の製造工程を説明する図。
　以下、本発明の実施形態について説明する。
第１実施形態：本実施形態では、予備的試験としてＳｉ基板の上にＰｔシリサイドを形成するために第１の金属としてＰｔを成膜し、その上にＨｆＮ薄膜を形成した場合としない場合におけるアニーリング後のシリサイド電極の表面形態を検討した。
　図１に本実施形態に係る比較試験の工程を示す。本実施形態では、Ｓｉ基板（ｐ－Ｓｉ（１００））を用意し、洗浄後、スパッタリング法にてＰｔ薄膜を１０ｎｍ成膜した。
　そして、本実施形態では、Ｐｔ薄膜の上にＨｆＮ薄膜を形成した。ＨｆＮ薄膜は、Ｈｆターゲットを用い、成膜雰囲気をＫｒ／Ｎ２とする反応性スパッタリングにて成膜した（膜厚２０ｎｍ）。比較例については、このＨｆＮ薄膜を形成することなくシリサイド化に供した。
　次に、熱処理によりシリサイド化を行った。シリサイド化の条件は、処理温度として４５０℃とし、処理雰囲気は窒素ガス中とし、処理時間を３０分間とした。
　Ｐｔシリサイド形成後、エッチングによりＨｆＮ膜及び未反応のＰｔを除去してデバイスとした。まず、希フッ酸（１％）でＨｆＮを除去した後、希釈王水（ＨＣｌ：ＨＮＯ３：Ｈ２Ｏ＝３：２：１、温度４０℃）により未反応Ｐｔを除去した。その後、７５０℃で処理雰囲気窒素ガス中とした熱処理を３０秒間行った。
　以上のようにしてシリサイド膜を形成したＳｉ基板について、シリサイド膜の表面形態をＳＥＭにて観察した。図２は、この観察結果を示す写真である。図２から分かるように、ＨｆＮからなるＣａｐ層を適用しなかった比較例のシリサイド膜は、表面に凹凸が形成されており形態的不良と判定された。これに対し、本実施形態のシリサイド膜にはかかる形態的不良は見られなかった。シリサイド化のためのアニールの際、ＨｆＮ薄膜によるバリア効果が有効に作用したことが確認できた。
　これらのシリサイド合金膜について、ＡＦＭ（原子間力顕微鏡）により自乗平均表面粗さ（ＲＭＳ）を測定したところ（走査幅３μｍ）、Ｃａｐ層を適用した本実施形態のＰｔシリサイド合金膜のＲＭＳは２．２６ｎｍであった。これに対してＣａｐ層を適用しない比較例のＰｔシリサイド膜のＲＭＳは３．１２ｎｍであった。
第２実施形態：ここでは、ＨｆＮ薄膜の有用性に関し、実際の半導体デバイス素子の製造工程への効果を再現・評価するため、クロスブリッジケルビン抵抗法（ｃｒｏｓｓ-ｂｒｉｄｇｅ Ｋｅｌｖｉｎ ｒｅｓｉｓｔａｎｃｅ：以下、ＣＢＫＲと称する）による４端子ケルビンテスト構造におけるコンタクト抵抗（界面接触抵抗）を評価した。図３は、ＨｆＮ薄膜を適用しつつＣＢＫＲ構造を形成するための工程を概略説明するものである。尚、この評価試験では、ＣＢＫＲ構造を形成後、フォーミングガス（Ｎ２／４．９％Ｈ２）によるアニール（Ｆｏｒｍｉｎｇ　Ｇａｓ　Ａｎｎｅａｌ：ＦＧＡ）を行った場合の界面抵抗の変化も検討した。表１は、ＢＫＲ法によるシリサイド電極とＡｌ電極との界面抵抗の測定結果を示す。
Figure JPOXMLDOC01-appb-T000001
　表１から、シリサイド電極製造の際のＣａｐ層としてＨｆＮ薄膜を適用すること、でコンタクト抵抗が低減できることが確認できる。また、ＦＧＡとの関連についてであるが、本来、ＦＧＡは、Ａｌとシリサイド電極との電気的接触を改善し界面抵抗を良好にする操作である。ＨｆＮ薄膜からなるＣａｐ層の適用は、ＦＧＡの作用を維持することができ、両者によりコンタクト抵抗は大きく低減できることが確認できた。
　本発明によれば、シリサイド電極を製造するに際し、従来以上に高品質のものを製造することができる。本発明は、ＭＯＳＦＥＴ等の各種半導体デバイスにおけるシリサイド電極の製造プロセスとして好適である。

Claims (4)

  1. 　Ｓｉを含む基板上に第１の金属からなる第１の薄膜を形成する工程と、
    　前記第１の薄膜の上に、第２の金属の化合物からなる第２の薄膜を形成する工程と、
    　熱処理することで第１の金属のシリサイドからなる電極を形成する工程と、を含む半導体デバイス電極の製造方法において、
    　前記第２の金属はハフニウム（Ｈｆ）を適用することを特徴とする半導体デバイス電極の製造方法。
  2. 　第２の金属の化合物は、ＨｆＮ、ＨｆＷ、又はＨｆＢである請求項１記載の半導体デバイス電極の製造方法。
  3. 　第１の金属は、Ｔｉ、Ｃｏ、Ｎｉ、Ｐｔのいずれか又はこれらの合金である請求項１又は請求項２記載の半導体デバイス電極の製造方法。
  4. 　熱処理後、第２の薄膜を除去する工程を含む請求項１～請求項３のいずれかに記載の半導体デバイス電極の製造方法。
     
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KR20180002837A (ko) 2018-01-08

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