JP4046407B2 - Sputtering method and wiring formation method - Google Patents

Description

このようなパーセンテージを各電流階級毎に度数としてグラフで示したのが図８である。図８において、Ｓ₀ のような各棒状部は、純Ｔｉターゲットを用いる反応性スパッタ法でＴｉＯＮ膜５６を形成した場合の度数を示し、Ｓ₁ のような各棒状部は、酸素含有量２０［ｗｔ％］のＴｉターゲットを用いる反応性スパッタ法でＴｉＯＮ膜５６を形成した場合の度数を示す。
【００４８】
図８によれば、ＴｉＯＮ膜５６を純Ｔｉターゲットを用いる反応性スパッタ法で形成する場合（Ｓ₀ ）に比べて酸素含有量２０［ｗｔ％］のＴｉターゲットを用いる反応性スパッタ法で形成する場合（Ｓ₁ ）の方がリーク電流及びリーク電流ばらつきのいずれも小さく、耐熱性が高いことがわかる。
【００４９】
図９は、図６に関して前述した配線形成法においてバリア膜としてのＴｉＯＮ膜５６を酸素含有量２０［ｗｔ％］のＴｉターゲットを用いる反応性スパッタ法で形成した場合Ｌ₃ と、酸素含有量３５［ｗｔ％］のＴｉターゲットを用いる反応性スパッタ法で形成した場合Ｌ₄ についてコンタクト抵抗Ｒｃとそのばらつきがコンタクトサイズに依存する様子を図７と同様にして示すものである。
【００５０】
図１０は、図６に関して前述した配線形成法においてバリア膜としてのＴｉＯＮ膜５６を酸素含有量２０［ｗｔ％］のＴｉターゲットを用いる反応性スパッタ法で形成した場合Ｓ₃ と、酸素含有量１５［ｗｔ％］のＴｉターゲットを用いる反応性スパッタ法で形成した場合Ｓ₄ とについて４５０［℃］アニール処理後のリーク電流の度数分布を図８と同様にして示すものである。
【００５１】
図９によれば、Ｔｉターゲットの酸素含有量が３５［ｗｔ％］より大きくなると、コンタクト抵抗及びコンタクト抵抗ばらつきのいずれも大きくなることがわかる。また、図１０によれば、Ｔｉターゲットの酸素含有量が１５［ｗｔ％］より小さくなると、リーク電流及びリーク電流ばらつきがいずれも大きくなり、耐熱性が低下することがわかる。従って、Ｔｉターゲットの酸素含有量は、１５〜３５［ｗｔ％］とするのが好ましい。
【００５２】
図１３〜１９は、この発明に係るスパッタ法の他の応用例として多層配線形成法を示すものである。この例では、Ｗ密着膜及び反射防止膜をこの発明に係るスパッタ法により形成する。
【００５３】
図１３の工程では、例えばシリコンからなる半導体基板５０の表面に不純物ドープ領域５０ａを覆ってシリコンオキサイド等の絶縁膜５２をＣＶＤ法等により形成する。そして、絶縁膜５２には、周知のホトリソグラフィ及び選択的ドライエッチング処理により不純物ドープ領域５０ａに達する接続孔５２ａを形成する。
【００５４】
図１４の工程では、接続孔５２ａの内面及び絶縁膜５２を覆ってこの発明に係る反応性スパッタ法によりＷ密着膜としてのＴｉＯＮ膜８０を形成する。ＴｉＯＮ膜８０は、一例として図１の直流スパッタ装置を用いて前述のＴｉＯＮ膜５６と同様の条件で１００［ｎｍ］の厚さに形成することができる。この場合、ＴｉＯＮ膜８０を形成する前に接続孔５２ａの内面及び絶縁膜５２を覆って例えば１０〜２０［ｎｍ］の厚さのＴｉ膜（抵抗低減膜）をスパッタ法等により形成してもよい。
【００５５】
次に、接続孔５２ａを埋めるようにＴｉＯＮ膜８０の上にＷ層８２をブランケットＣＶＤ法により形成する。Ｗ層８２は、一例として５００［ｎｍ］の厚さに形成することができる。成膜条件は、
ＷＦ₆ 流量：５０［ｓｃｃｍ］
圧力：４０［Ｔｏｒｒ］
基板温度：４００［℃］
とすることができる。
【００５６】
図１５の工程では、絶縁膜５２の上面側でＴｉＯＮ膜８０が露呈するまでＷ層８２をエッチバックすることにより接続孔５２ａ内にＷ層８２の残存部からなる接続プラグ８２ａを形成する。Ｗ層８２を平坦状に除去する方法としては、エッチバック処理の代りにＣＭＰ（化学機械研磨）処理を用いてもよい。また、ＴｉＯＮ膜８０は、絶縁膜５２の上面側で除去し、接続孔５２ａ内にのみ残存させるようにしてもよく、この場合には接続プラグ８２ａ及びＴｉＯＮ膜８０の残存部を覆ってＴｉ等の配線下地膜を形成してもよい。
【００５７】
図１６の工程では、接続プラグ８２ａ及びＴｉＯＮ膜８０の露呈部を覆ってＡｌ系金属（Ａｌ又はＡｌ合金）層８４をスパッタ法等により形成する。Ａｌ系金属層８４としては、例えば３５０〜４００［ｎｍ］の厚さのＡｌ−Ｓｉ−Ｃｕ合金層をスパッタ法で形成することができる。
【００５８】
次に、Ａｌ系金属層８４の上に反射防止膜としてのＴｉＯＮ膜８６をこの発明に係る反応性スパッタ法により形成する。ＴｉＯＮ膜８６は、一例として図１のスパッタ装置を用いて前述のＴｉＯＮ膜５６と同様の条件で５０［ｎｍ］の厚さに形成することができる。この場合、ＴｉＯＮ膜８６を形成する前にＡｌ系金属層８４を覆って例えば１０［ｎｍ］の厚さのＴｉ膜（Ａｌ系金属表面の酸化を防止する膜）をスパッタ法等により形成してもよい。
【００５９】
図１７の工程では、ホトリソグラフィ処理により所望の配線パターニングに従ってエッチングマスクとしてのレジスト層（図示せず）をＴｉＯＮ膜８６の上に形成する。このとき、Ａｌ系金属層８４の表面からの光反射がＴｉＯＮ膜８６により抑制されるので、寸法精度よくレジスト層をパターニングすることができる。
【００６０】
次に、形成したレジスト層をマスクとする選択的ドライエッチング処理によりＴｉＯＮ膜８０、Ａｌ系金属層８４及びＴｉＯＮ膜８６を含む積層をパターニングして接続プラグ８２ａにつながる配線層８８を形成する。配線層８８は、ＴｉＯＮ膜８０の残存部からなるＴｉＯＮ膜８０ａと、Ａｌ系金属層８４の残存部からなるＡｌ系金属層８４ａと、ＴｉＯＮ膜８６の残存部からなるＴｉＯＮ膜８６ａとを含むもので、接続プラグ８２ａ及び接続孔底部のＴｉＯＮ膜８０ｂを介して不純物ドープ領域５０ａに接続される。
【００６１】
図１８の工程では、絶縁膜５２の上に配線層８８を覆って層間絶縁膜９０を形成する。絶縁膜９０は、配線段差を緩和するように平坦状に形成するのが好ましい。このためには、例えばプラズマＣＶＤ法によりシリコンオキサイド膜を形成した後、水素シルセスキオキサン樹脂膜を回転塗布し、塗布膜に熱処理を施してセラミック状のシリコンオキサイド膜とし、更にその上にプラズマＣＶＤ法によりシリコンオキサイド膜を形成することができる。
【００６２】
次に、絶縁膜９０には、ホトリソグラフィ及び選択的ドライエッチング処理により配線層８８の一部に達する接続孔９０ａを形成する。
【００６３】
図１９の工程では、図１４〜１７に関して前述したのと同様の処理により接続孔９０ａを介して配線層８８につながる上層配線を形成する。上層配線は、Ｗ密着膜としてのＴｉＯＮ膜９２ａと、Ｗからなる接続プラグ９４ａと、Ａｌ系金属層９６ａと、反射防止膜としてのＴｉＯＮ膜９８ａとにより構成される。接続プラグ９４ａにつながる配線層１００は、配線パターニングの結果として残存するＴｉＯＮ膜９２ａ、Ａｌ系金属層９６ａ及びＴｉＯＮ膜９８ａを含んでいる。
【００６４】
上記した実施形態によれば、スパッタリングターゲット２８として酸素含有量が１５〜３５［ｗｔ％］のＴｉターゲットを用いると共にＡｒガス、Ｎ₂ ガス又はＡｒ＋Ｎ₂ の混合ガスを用いて酸化チタン又は酸化窒化チタンからなるスパッタ膜を形成するようにしたので、酸素ガスの供給量はゼロ又は微量でよく、シート抵抗、反射率、耐熱性等の膜特性のばらつきを低減することができる。また、酸素ガスを殆ど使用しないことから安全性が向上するため、クライオポンプ３２の使用が可能になり、短時間で高真空に到達することができる。この結果、良質な（結晶粒径が大きく、大きさのばらつきが小さいためマイグレーションに強い）アルミニウム成膜が可能となる。
【００６５】
その上、この発明に係る反応性スパッタ法によりバリア膜としてのＴｉＯＮ膜５６、Ｗ密着膜としてのＴｉＯＮ膜８０ａ，９２ａ、反射防止膜としてのＴｉＯＮ膜６０，８６ａ，９８ａ等を形成するようにしたので、ＴｉＯＮ膜のシート抵抗、反射率、耐熱性等の特性ばらつきを低減することができ、しかも耐熱性の向上により図２０の９ａ，９ｂのようなＷのしみ出しを抑制することができる。従って、信頼性の高い微細配線を歩留りよく形成することができる。
【００６６】
【発明の効果】
以上のように、この発明によれば、スパッタリングターゲットとして酸素含有量が１５〜３５［ｗｔ％］のチタンターゲットを用いて酸化窒化チタンからなるスパッタ膜を形成するようにしたので、スパッタ膜の特性ばらつきが低減されると共に安全性が向上する効果が得られる。
【００６７】
また、配線形成プロセスにおいて、この発明に係るスパッタ法によりバリア膜、密着膜又は反射防止膜としてのＴｉＯＮ膜を形成するようにしたので、耐熱性良好な配線を歩留りよく形成できる効果も得られる。
【図面の簡単な説明】
【図１】 この発明を実施する際に使用されるスパッタ装置を示す概略構成図である。
【図２】 スパッタリングターゲットの製法を示すフローチャートである。
【図３】 酸素含有量１０［ｗｔ％］のチタンターゲットを用いたスパッタ処理におけるスパッタ時間と膜厚、比抵抗との関係を示すグラフである。
【図４】 酸素含有量２０［ｗｔ％］のチタンターゲットを用いたスパッタ処理におけるスパッタ時間と膜厚、比抵抗との関係を示すグラフである。
【図５】 酸素含有量３０［ｗｔ％］のチタンターゲットを用いたスパッタ処理におけるスパッタ時間と膜厚、比抵抗との関係を示すグラフである。
【図６】 この発明のスパッタ法の一応用例として配線形成法を説明するための基板断面図である。
【図７】 バリア膜としてのＴｉＯＮ膜を純Ｔｉターゲットを用いる反応性スパッタ法で形成した場合と、酸素含有量２０［ｗｔ％］のＴｉターゲットを用いる反応性スパッタ法で形成した場合とについてコンタクトサイズとコンタクト抵抗、コンタクト抵抗ばらつきとの関係を示すグラフである。
【図８】 バリア膜としてのＴｉＯＮ膜を純Ｔｉターゲットを用いる反応性スパッタ法で形成した場合と、酸素含有量２０［ｗｔ％］のＴｉターゲットを用いる反応性スパッタ法で形成した場合とについて４５０［℃］アニール処理後のリーク電流の度数分布を示すグラフである。
【図９】 バリア膜としてのＴｉＯＮ膜を酸素含有量２０［ｗｔ％］のＴｉターゲットを用いる反応性スパッタ法で形成した場合と、酸素含有量３５［ｗｔ％］のＴｉターゲットを用いる反応性スパッタ法で形成した場合とについてコンタクトサイズとコンタクト抵抗、コンタクト抵抗ばらつきとの関係を示すグラフである。
【図１０】 バリア膜としてのＴｉＯＮ膜を酸素含有量２０［ｗｔ％］のＴｉターゲットを用いる反応性スパッタ法で形成した場合と、酸素含有量３５［ｗｔ％］のＴｉターゲットを用いる反応性スパッタ法で形成した場合とについて４５０［℃］アニール処理後のリーク電流の度数分布を示すグラフである。
【図１１】 リーク電流測定に用いられるテスト素子を示す平面図である。
【図１２】 図１１の素子のＸ−Ｘ’線に沿う断面図である。
【図１３】 この発明のスパッタ法の他の応用例としての多層配線形成法における接続孔形成工程を示す基板断面図である。
【図１４】 図１３の工程に続くＴｉＯＮ膜形成及びＷ層形成工程を示す基板断面図である。
【図１５】 図１４の工程に続くエッチバック工程を示す基板断面図である。
【図１６】 図１５の工程に続くＡｌ系金属層形成及びＴｉＯＮ膜形成工程を示す基板断面図である。
【図１７】 図１６の工程に続く配線パターニング工程を示す基板断面図である。
【図１８】 図１７の工程に続く層間絶縁膜形成及び接続孔形成工程を示す基板断面図である。
【図１９】 図１８の工程に続く上層配線形成工程を示す基板断面図である。
【図２０】 従来の多層配線形成法を説明するための基板断面図である。
【符号の説明】
２０：スパッタ室、２２：アノード電極、２４：被処理ウエハ、２６：カソード電極、２８：スパッタリングターゲット、３０：直流電源、３２：クライオポンプ、３４：高周波電源、３６：マッチング回路、５０：半導体基板、５０ａ：不純物ドープ領域、５２，９０：絶縁膜、５２ａ，９０ａ：接続孔、５６，６０，８０，８０ａ，８６，８６ａ，９２ａ，９８ａ：ＴｉＯＮ膜、８２：Ｗ層、８２ａ，９４ａ：接続プラグ、５８，８４，８４ａ，９６ａ：Ａｌ系金属層、６２，８８，１００：配線層。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a sputtering method and wiring formation. To the law In particular, by using a titanium (Ti) target having an oxygen content of 15 to 35 [wt%] as a sputtering target, variations in film characteristics are reduced and safety is improved.
[0002]
[Prior art]
Conventionally, in the field of wiring formation such as LSI, it is known to use a TiN (titanium nitride) film as an antireflection film, a W (tungsten) adhesion film, or a barrier film.
[0003]
FIG. 20 shows an example of a multilayer wiring structure using a TiN film as an antireflection film and a W adhesion film. An insulating film 2 is formed on the surface of the semiconductor substrate 1 so as to cover the impurity doped region 1 a, and a connection hole 2 a reaching the impurity doped region 1 a is formed in the insulating film 2. A TiN film 3 is formed to cover the inner surface of the connection hole 2a and the insulating film 2, and a W layer is formed on the TiN film 3 by a blanket CVD (chemical vapor deposition) method so as to fill the connection hole 2a. Is done. The TiN film 3 is formed as an adhesion film for improving adhesion with the W layer. By etching back the W layer until the TiN film 3 is exposed, a connection plug 4 consisting of the remaining portion of the W layer is formed in the connection hole 2a.
[0004]
An Al (aluminum) alloy layer 5 and a TiN film 6 are sequentially formed so as to cover the connection plug 4 and the exposed portion of the TiN film 3, and then the stack including the layer 5 and the film 6 is patterned by photolithography and selective etching. The wiring layer W comprising the Al alloy layer 5 and the TiN film 6 remaining by ₁ Is connected to the connection plug 4. In the photolithography process, since the TiN layer 6 acts as an antireflection film when forming a resist layer as an etching mask, the register layer can be patterned with high dimensional accuracy.
[0005]
On the upper surface of the substrate, the wiring layer W ₁ An insulating film 7 is formed to cover the insulating film 2, and the insulating film 7 includes a wiring layer W ₁ A connection hole 7a that reaches a part of is formed. In the connection hole 7a, a connection plug 9 made of W is formed through the TiN film 8 in the same manner as described above. On the insulating film 7, the wiring layer W made of the Al alloy layer 10 and the TiN film 11 is formed as described above. ₂ Is connected to the connection plug 9.
[0006]
The TiN film 8 is useful as a W adhesion film like the TiN film 3, and the TiN film 11 is useful as an antireflection film like the TiN film 6. The TiN films 3, 6, 8, and 11 are usually formed by reactive sputtering.
[0007]
[Problems to be solved by the invention]
According to the above-described prior art, since the heat resistance of the TiN films 3 and 8 formed by the reactive sputtering method is not sufficient, the oozing of W 4a and 9a occurs during the deposition of W, and the impurity bleed region is caused by the oozing of W 4a. There is a disadvantage that the PN junction between 1a and the substrate 1 is broken, or the resistance (via resistance) of the interlayer connection portion increases due to the seepage of W 9a.
[0008]
As a method for improving the barrier property of the TiN film, 100 [ppm] to 5 [%] nitrogen and / or 1000 [ppm] to 14 [%] oxygen are included as a sputtering target in the reactive sputtering process. A method using a titanium target is known (see, for example, JP-A-5-179435). However, using such a method is not sufficient to prevent the oozing 4a and 9a.
[0009]
Therefore, the inventor studied a wiring formation process using a TiON (titanium oxynitride) film instead of the TiN films 3, 6, 8, and 11. In such a wiring formation process, the TiON film was formed by a reactive sputtering method. That is, Ar + N in the sputtering chamber ₂ + O ₂ Then, a TiON film was formed by sputtering a titanium target. However, due to the extremely high reactivity of titanium to oxygen, a film property distribution was observed along the oxygen flow path. For example, the sheet resistance of the TiON film is high at a position close to the oxygen inlet, and decreases as the distance from the oxygen inlet is increased. This indicates that the oxygen content of the TiON film changes along the oxygen flow path, and the characteristics such as the reflectance of the TiON film also change according to such a change in the oxygen content. Therefore, there is a problem that variations in film properties such as sheet resistance, reflectance, and heat resistance are large.
[0010]
In addition, since oxygen gas that imparts flammability is used, it is necessary to give sufficient consideration to safety, and particularly in an exhaust system that uses a cryopump, there is a risk of explosion due to ozone generation.
[0011]
An object of the present invention is to provide a novel sputtering method with small variations in film characteristics and high safety. Ruko It is in.
[0012]
Another object of the present invention is to provide a novel wiring forming method capable of forming a wiring having a barrier film, an adhesion film and / or an antireflection film with a high yield.
[0013]
[Means for Solving the Problems]
In the sputtering method according to the present invention, an object to be processed and a sputtering target are disposed in a sputtering chamber, and the sputtering chamber is maintained at a predetermined pressure by an exhaust unit while introducing a processing gas into the sputtering chamber. A sputtering method for forming a sputtered film composed of sputtered particles on the surface of the object to be processed by releasing sputtered particles from the sputtering target by irradiation with ions of the processing gas, wherein the processing gas is used as the processing gas. Nikko Elementary gas or inert gas (Eg argon gas) The sputtered film is formed by using a mixed gas of nitrogen gas and a titanium target having an oxygen content in the range of 15 to 35 [wt%] as the sputtering target. Acid A titanium oxynitride film is formed.
[0014]
According to the sputtering method of the present invention, a titanium target having an oxygen content of 15 to 35 [wt%] is used as the sputtering target. When the oxygen content exceeds 35 [wt%], the sheet resistance of the sputtered film increases and the variation in sheet resistance also increases. When the oxygen content is less than 15 [wt%], the heat resistance of the sputtered film becomes insufficient. In this invention, since the oxygen content is 15 to 35 [wt%], sheet resistance and its variation can be made practically sufficient and practically sufficient heat resistance can be obtained.
[0016]
In the sputtering method according to the present invention, since a titanium target containing an appropriate amount of oxygen is used as the sputtering target, the amount of oxygen gas supplied to the sputtering chamber may be substantially zero, and even if supplied, the amount may be small. For this reason, variations in film properties such as sheet resistance, reflectance, and heat resistance are reduced. In addition, safety is improved, and even if a cryopump is used as an exhaust means, there is no danger of explosion due to ozone generation.
[0017]
In the wiring forming method according to the present invention, a TiON film as a barrier film, an adhesion film or an antireflection film is formed by the sputtering method of the present invention. For this reason, a TiON film having good heat resistance is obtained, and variations in characteristics such as sheet resistance, reflectance, and heat resistance of the TiON film are reduced.
[0018]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 shows a schematic configuration of a sputtering apparatus used for carrying out the present invention.
[0019]
In the sputtering chamber 20, an anode electrode 22 that holds a processing target wafer 24 such as a semiconductor wafer is disposed. In the sputtering chamber 20, a cathode electrode 26 with a sputtering target 28 mounted on the lower surface is disposed above the anode electrode 22.
[0020]
The conducting wire Qa connected to the anode electrode 22 is led out from the sputtering chamber 20 through the insulating member Pa, and is connected to the positive pole of the DC power source 30 with variable voltage. The conducting wire Qk connected to the cathode electrode 26 is led out from the sputtering chamber 20 via the insulating member Pk and connected to the negative pole of the DC power supply 30.
[0021]
During the sputtering process, a processing gas G is introduced into the sputtering chamber 20 from a gas inlet 20 a provided in the upper part of the sputtering chamber 20. As the processing gas G, for example, Ar (argon) gas, N ₂ (Nitrogen) gas or Ar gas and N ₂ A gas mixture with the gas is supplied. A cryopump 32 as an evacuation unit is connected to an exhaust port 20 b provided in the lower part of the sputtering chamber 20, and the inside of the sputtering chamber 20 is maintained at a predetermined pressure by evacuation by the cryopump 32. In such a state, when the DC voltage of the DC power supply 30 is set to a predetermined value that can be discharged, the processing gas G is ionized by the DC discharge, and the sputtered particles are released from the target 28 by irradiation of the ions of the processing gas G. The released sputtered particles adhere to the surface of the wafer 24 and form a sputtered film.
[0022]
In the sputtering apparatus of FIG. 1, a high frequency power supply 34 and a matching circuit 36 can be connected instead of the DC power supply 30 and sputtering can be performed by high frequency discharge.
[0023]
As the sputtering target 28, a titanium target having an oxygen content of 15 to 35 [wt%] is used. Such a titanium target is obtained by powder metallurgy as shown in FIG. 2 using commercially available high-purity titanium powder (purity 99.99 [%]) and high-purity titanium oxide powder (purity 99.99 [%]) as raw materials. Can be formed.
[0024]
In the powder metallurgy method shown in FIG. 2, in step 40, the titanium powder and the titanium oxide powder are weighed so that the oxygen content becomes 15 to 35 [wt%]. In step 42, the measured titanium powder and titanium oxide powder are mixed uniformly. In step 44, the mixed powder of titanium and titanium oxide is compression-molded and sintered to obtain a titanium target material made of a sintered body.
[0025]
In the process of step 44, a hot press or a hot isostatic press that can be formed in vacuum is used as the compression molding means. The treatment temperature at this time is preferably 1200 to 1500 [° C.] in order to obtain a crystal structure of titanium oxide, and the press pressure is 200 to 200 to achieve a high density of relative density 80 [%] or more. 400 [kg / cm ² ] Is preferable.
[0026]
The titanium target material thus formed is finished into a predetermined shape and dimensions (for example, a disk shape having a diameter of 100 [mm] × thickness of 6 [mm]) by machining. The titanium target thus processed is attached as a sputtering target 28 to a Cu (copper) cooling plate as the cathode electrode 26 by metal bonding.
[0027]
Using the titanium target obtained as described above, a sputtering process was performed with the sputtering apparatus of FIG. 1 to form a titanium oxide film. The sputtering conditions at this time are
Sputtering power supply: DC power supply 30
Power: 0.5 [kW]
Sputtering pressure: 5 × 10 ^-3 [Torr]
Sputtering gas: Argon
It was.
[0028]
3 to 5 show the relationship between the sputtering time, the specific resistance, and the film thickness of the titanium oxide film obtained by the above sputtering process. FIG. 3 shows the case where the oxygen content of the titanium target is 10 [wt%]. FIG. 4 shows a case where the oxygen content of the titanium target is 20 [wt%], and FIG. 5 shows a case where the oxygen content of the titanium target is 30 [wt%].
[0029]
When the sputtering time was 3 [min], the specific resistances of the titanium oxide films in FIGS. 3, 4 and 5 were 335, 470 and 540 [μΩcm], respectively. According to FIGS. 3 to 5, the specific resistance of the titanium oxide film increases as the oxygen content of the titanium target increases, and the thickness of the titanium oxide film increases linearly as the sputtering time increases. It can be seen that the specific resistance of the titanium oxide film is almost constant with respect to the change in sputtering time.
[0030]
FIG. 6 shows a wiring formation method as an application example of the sputtering method according to the present invention. In this example, the barrier film and the antireflection film are formed by the sputtering method according to the present invention.
[0031]
For example, an insulating film 52 such as silicon oxide is formed on the surface of the semiconductor substrate 50 made of silicon so as to cover the impurity doped region 50a by a CVD method or the like. Then, a connection hole 52a reaching the impurity doped region 50a is formed in the insulating film 52 by known photolithography and selective dry etching.
[0032]
Next, a TiON film 56 as a barrier film is formed so as to cover the connection hole 52a and the insulating film 52 by the reactive sputtering method according to the present invention. As an example, the TiON film 56 is formed by using the DC sputtering apparatus shown in FIG.
Sputtering target 28: Ti target having an oxygen content of 20 [wt%]
Process gas G: Ar gas and N ₂ Gas mixed with gas at 4: 6
The film can be formed to a thickness of 50 [nm] under the following conditions. In this case, a small amount of O is added to the processing gas G to supplement oxygen. ₂ Gas may be added. In order to improve the contact performance, a resistance reduction film may be formed covering the connection hole 52a and the insulating film 52 before the TiON film 56 is formed. As the resistance reduction film, a refractory metal film is suitable. For example, a Ti film 54 having a thickness of 20 [nm] can be formed by sputtering or the like.
[0033]
Next, an Al-based metal layer 58 is formed on the TiON film 56 so as to fill the connection hole 52a. As the Al-based metal layer 58, for example, an Al—Cu alloy layer having a thickness of 500 [nm] can be formed. In order to form the Al-based metal layer 58 so as to fill the connection hole 52a, a reflow sputtering method in which the substrate is heated during sputtering, a reflow method in which the substrate is heated after sputtering, or the like can be used.
[0034]
Next, a TiON film 60 as an antireflection film is formed so as to overlap the Al-based alloy layer 58 by the reactive sputtering method according to the present invention. For example, the TiON film 60 can be formed to a thickness of 30 [nm] using the DC sputtering apparatus shown in FIG. 1 under the same conditions as those for forming the TiON film 56 described above. In this case, before the TiON film 60 is formed, a Ti film as an antioxidant film may be formed on the Al-based metal layer 58 to a thickness of 10 [nm] by sputtering, for example.
[0035]
Next, the laminated layer including the Ti film 54, the TiON film 56, the Al-based metal layer 58, and the TiON film 60 is patterned by photolithography and selective dry etching to form the wiring layer 62. The wiring layer 62 includes the Ti film 54, the TiON film 56, the Al-based alloy layer 58, and the TiON film 60 that remain as a result of the wiring patterning, and is connected to the impurity doped region 50a through the connection hole 52a.
[0036]
FIG. 7 shows a case where the TiON film 56 as a barrier film is formed by the reactive sputtering method using a pure Ti target in the wiring formation method described above with reference to FIG. 6, and the reaction using a Ti target having an oxygen content of 20 [wt%]. This shows how the contact resistance Rc and its variation depend on the contact size for the case of forming by the reactive sputtering method.
[0037]
The contact resistance Rc corresponds to the resistance between the wiring layer 62 and the impurity doped region 50a in FIG. 6, and the contact size corresponds to the diameter of the connection hole 52a in FIG. In FIG. 7, L ₀ Shows the change in contact resistance when the TiON film 56 is formed by reactive sputtering using a pure Ti target. ₁ Shows the change in contact resistance when the TiON film 56 is formed by reactive sputtering using a Ti target having an oxygen content of 20 [wt%].
[0038]
According to FIG. 7, when the TiON film 56 is formed by reactive sputtering using a pure Ti target (L ₀ In the case of forming by reactive sputtering using a Ti target having an oxygen content of 20 [wt%] compared to (L) ₁ ) Shows that both the contact resistance and the contact resistance variation are smaller.
[0039]
When the TiON film 56 is formed by reactive sputtering using a Ti target having an oxygen content of 20 [wt%], a small variation in contact resistance indicates a small variation in the oxygen content in the TiON film. Yes. Therefore, when the TiON film 60 as an antireflection film is formed by a reactive sputtering method using a Ti target having an oxygen content of 20 [wt%], the variation in reflectance is reduced.
[0040]
8 shows a case where the TiON film 56 as a barrier film is formed by the reactive sputtering method using a pure Ti target in the wiring formation method described above with reference to FIG. 6, and a reaction using a Ti target having an oxygen content of 20 [wt%]. 2 shows a frequency distribution of leakage current after annealing at 450 [° C.] with respect to the case of forming by the reactive sputtering method.
[0041]
In order to measure the leakage current, test elements 70 as shown in FIGS. 11 and 12 were respectively formed in 64 chip regions on one main surface of the semiconductor wafer. Then, the leakage current was measured for each test element 70 (each chip region) with the measurement circuit shown in FIG.
[0042]
The test element 70 has an elongated P-type well region 74 formed on the surface of a semiconductor substrate 72 made of silicon, and N formed in a line on the surface of the region 74. ⁺ Type impurity doped regions 76 (1), 76 (2)... 76 (m). An insulating film 75 such as silicon oxide is formed on the surface of the substrate. On the insulating film 75, wiring layers 78 (1), 78 (2)... 78 (n) are formed in a line. . Each of the wiring layers 78 (1) to 78 (n) is formed in the same manner as the wiring layer 62 described above with reference to FIG.
[0043]
The wiring layer 78 (1) is connected to the P-type well region 74, and one end of the wiring layer 78 (2) is N ⁺ Connected to mold region 76 (1). A PN junction formed between the regions 74 and 76 (1) is interposed between the wiring layers 78 (1) and 78 (2).
[0044]
The other end of the wiring layer 78 (2) is N ⁺ One end of a wiring layer 78 (3) (not shown) is connected to a part of the mold region 76 (2) and the other part of the region 76 (2). N in the same way ⁺ Numerous N up to mold area 76 (m) ⁺ The mold regions are connected in series by a number of wiring layers up to the wiring layer 78 (n). The number n of the wiring layers 78 (1) to 78 (n) is N ⁺ If the number of mold regions 76 (1) to 76 (m) is m, then m + 1.
[0045]
In the test element 70, the number of contact portions CN corresponding to the connection holes was 5000, and the diameter of each connection hole was 0.25 [μm]. After forming the wiring layers 78 (1) to 78 (n), the test element 70 was annealed at 450 [° C.]. In the measurement circuit of FIG. 12, the voltage V = 5 [V] is applied between the wiring layers 78 (1) -78 (n) so that the PN junction between the regions 74-76 (1) is biased in the reverse direction. The reverse leakage current was measured with an ammeter A.
[0046]
Such a leakage current measurement was performed for each of the 64 test elements on the wafer, and the measured values were obtained. Each measured value is 10 ^-Ten [A] stand, 10 ^-9 [A] stand, 10 ^-8 [A] stand, 10 ^-7 [A] It was determined which of the above four current classes belonged, and the current classes determined to belong were counted. For each current class, the number of counts was N, and the percentage was obtained by the following equation (1).
[0047]
[Expression 1]

FIG. 8 is a graph showing such a percentage as a frequency for each current class. In FIG. 8, S ₀ Each bar-like portion indicates the frequency when the TiON film 56 is formed by reactive sputtering using a pure Ti target, and S ₁ Each of the rod-like parts as described above indicates the frequency when the TiON film 56 is formed by a reactive sputtering method using a Ti target having an oxygen content of 20 [wt%].
[0048]
According to FIG. 8, when the TiON film 56 is formed by reactive sputtering using a pure Ti target (S ₀ ) In comparison with a reactive sputtering method using a Ti target having an oxygen content of 20 [wt%] (S ₁ ) Is smaller in both the leakage current and the variation in leakage current, indicating that the heat resistance is higher.
[0049]
9 shows a case where a TiON film 56 as a barrier film is formed by a reactive sputtering method using a Ti target having an oxygen content of 20 [wt%] in the wiring formation method described above with reference to FIG. _Three And a reactive sputtering method using a Ti target having an oxygen content of 35 [wt%] L _Four FIG. 8 shows the state in which the contact resistance Rc and its variation depend on the contact size in the same manner as in FIG.
[0050]
FIG. 10 shows a case where the TiON film 56 as a barrier film is formed by the reactive sputtering method using a Ti target having an oxygen content of 20 [wt%] in the wiring formation method described above with reference to FIG. _Three And a reactive sputtering method using a Ti target having an oxygen content of 15 [wt%] S _Four 8 shows the frequency distribution of leakage current after annealing at 450 [° C.] in the same manner as in FIG.
[0051]
According to FIG. 9, it can be seen that when the oxygen content of the Ti target is greater than 35 [wt%], both the contact resistance and the contact resistance variation increase. Moreover, according to FIG. 10, when the oxygen content of the Ti target is smaller than 15 [wt%], it can be seen that both the leakage current and the variation in the leakage current are increased and the heat resistance is lowered. Therefore, the oxygen content of the Ti target is preferably 15 to 35 [wt%].
[0052]
13 to 19 show a multilayer wiring forming method as another application example of the sputtering method according to the present invention. In this example, the W adhesion film and the antireflection film are formed by the sputtering method according to the present invention.
[0053]
In the process of FIG. 13, for example, an insulating film 52 such as silicon oxide is formed on the surface of the semiconductor substrate 50 made of silicon so as to cover the impurity doped region 50a by a CVD method or the like. Then, a connection hole 52a reaching the impurity doped region 50a is formed in the insulating film 52 by known photolithography and selective dry etching.
[0054]
In the process of FIG. 14, a TiON film 80 as a W adhesion film is formed by the reactive sputtering method according to the present invention so as to cover the inner surface of the connection hole 52a and the insulating film 52. As an example, the TiON film 80 can be formed to a thickness of 100 [nm] under the same conditions as the TiON film 56 described above using the DC sputtering apparatus of FIG. In this case, a Ti film (resistance reduction film) having a thickness of, for example, 10 to 20 [nm] may be formed by sputtering or the like so as to cover the inner surface of the connection hole 52a and the insulating film 52 before the TiON film 80 is formed. Good.
[0055]
Next, a W layer 82 is formed on the TiON film 80 by a blanket CVD method so as to fill the connection hole 52a. For example, the W layer 82 can be formed to a thickness of 500 [nm]. Deposition conditions are
WF ₆ Flow rate: 50 [sccm]
Pressure: 40 [Torr]
Substrate temperature: 400 [° C]
It can be.
[0056]
In the step of FIG. 15, the W layer 82 is etched back until the TiON film 80 is exposed on the upper surface side of the insulating film 52, thereby forming the connection plug 82a consisting of the remaining portion of the W layer 82 in the connection hole 52a. As a method for removing the W layer 82 in a flat shape, a CMP (Chemical Mechanical Polishing) process may be used instead of the etch back process. Further, the TiON film 80 may be removed on the upper surface side of the insulating film 52 so as to remain only in the connection hole 52a. In this case, Ti or the like is covered to cover the connection plug 82a and the remaining portions of the TiON film 80. A wiring base film may be formed.
[0057]
In the step of FIG. 16, an Al-based metal (Al or Al alloy) layer 84 is formed by sputtering or the like so as to cover the exposed portions of the connection plug 82a and the TiON film 80. As the Al-based metal layer 84, for example, an Al—Si—Cu alloy layer having a thickness of 350 to 400 [nm] can be formed by sputtering.
[0058]
Next, a TiON film 86 as an antireflection film is formed on the Al-based metal layer 84 by the reactive sputtering method according to the present invention. As an example, the TiON film 86 can be formed to a thickness of 50 [nm] using the sputtering apparatus of FIG. In this case, before forming the TiON film 86, a Ti film having a thickness of, for example, 10 nm (film for preventing oxidation of the Al-based metal surface) is formed by sputtering or the like so as to cover the Al-based metal layer 84. Also good.
[0059]
In the step of FIG. 17, a resist layer (not shown) as an etching mask is formed on the TiON film 86 according to desired wiring patterning by photolithography. At this time, light reflection from the surface of the Al-based metal layer 84 is suppressed by the TiON film 86, so that the resist layer can be patterned with high dimensional accuracy.
[0060]
Next, a layer including the TiON film 80, the Al-based metal layer 84, and the TiON film 86 is patterned by selective dry etching using the formed resist layer as a mask to form a wiring layer 88 connected to the connection plug 82a. The wiring layer 88 includes a TiON film 80a composed of the remaining portion of the TiON film 80, an Al-based metal layer 84a composed of the remaining portion of the Al-based metal layer 84, and a TiON film 86a composed of the remaining portion of the TiON film 86. Thus, the impurity doped region 50a is connected via the connection plug 82a and the TiON film 80b at the bottom of the connection hole.
[0061]
In the process of FIG. 18, an interlayer insulating film 90 is formed on the insulating film 52 so as to cover the wiring layer 88. The insulating film 90 is preferably formed in a flat shape so as to alleviate the wiring step. For this purpose, for example, after forming a silicon oxide film by a plasma CVD method, a hydrogen silsesquioxane resin film is spin-coated, a heat treatment is performed on the coated film to form a ceramic silicon oxide film, and a plasma is further formed thereon. A silicon oxide film can be formed by a CVD method.
[0062]
Next, a connection hole 90a reaching a part of the wiring layer 88 is formed in the insulating film 90 by photolithography and selective dry etching.
[0063]
In the process of FIG. 19, an upper layer wiring connected to the wiring layer 88 through the connection hole 90a is formed by the same process as described above with reference to FIGS. The upper layer wiring is composed of a TiON film 92a as a W adhesion film, a connection plug 94a made of W, an Al-based metal layer 96a, and a TiON film 98a as an antireflection film. The wiring layer 100 connected to the connection plug 94a includes a TiON film 92a, an Al-based metal layer 96a, and a TiON film 98a remaining as a result of wiring patterning.
[0064]
According to the above-described embodiment, a Ti target having an oxygen content of 15 to 35 [wt%] is used as the sputtering target 28 and Ar gas, N ₂ Gas or Ar + N ₂ Since a sputtered film made of titanium oxide or titanium oxynitride is formed using a mixed gas of oxygen, the supply amount of oxygen gas may be zero or a very small amount, and variations in film characteristics such as sheet resistance, reflectance, and heat resistance Can be reduced. Moreover, since oxygen is hardly used, safety is improved, so that the cryopump 32 can be used, and a high vacuum can be reached in a short time. As a result, it is possible to form a high quality aluminum film (strong in migration due to a large crystal grain size and small variation in size).
[0065]
In addition, a TiON film 56 as a barrier film, TiON films 80a and 92a as W adhesion films, TiON films 60, 86a and 98a as antireflection films, and the like are formed by the reactive sputtering method according to the present invention. Therefore, it is possible to reduce variations in characteristics such as sheet resistance, reflectance, and heat resistance of the TiON film, and to suppress the seepage of W as shown in 9a and 9b in FIG. 20 by improving the heat resistance. Therefore, highly reliable fine wiring can be formed with high yield.
[0066]
【The invention's effect】
As described above, according to the present invention, a titanium target having an oxygen content of 15 to 35 [wt%] is used as a sputtering target. Acid Since the sputtered film made of titanium oxynitride is formed, it is possible to reduce the variation in characteristics of the sputtered film and improve the safety.
[0067]
Moreover, in the wiring formation process, since the TiON film as the barrier film, the adhesion film or the antireflection film is formed by the sputtering method according to the present invention, the effect that the wiring with good heat resistance can be formed with high yield can be obtained.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram showing a sputtering apparatus used when carrying out the present invention.
FIG. 2 is a flowchart showing a method for manufacturing a sputtering target.
FIG. 3 is a graph showing the relationship between sputtering time, film thickness, and specific resistance in a sputtering process using a titanium target having an oxygen content of 10 [wt%].
FIG. 4 is a graph showing the relationship between sputtering time, film thickness, and specific resistance in a sputtering process using a titanium target having an oxygen content of 20 [wt%].
FIG. 5 is a graph showing the relationship between sputtering time, film thickness, and specific resistance in a sputtering process using a titanium target having an oxygen content of 30 [wt%].
FIG. 6 is a cross-sectional view of a substrate for explaining a wiring formation method as one application example of the sputtering method of the present invention.
FIG. 7 shows a contact between a TiON film as a barrier film formed by a reactive sputtering method using a pure Ti target and a reactive sputtering method using a Ti target having an oxygen content of 20 [wt%]. It is a graph which shows the relationship between size, contact resistance, and contact resistance variation.
8 shows a case where a TiON film as a barrier film is formed by a reactive sputtering method using a pure Ti target and a case where it is formed by a reactive sputtering method using a Ti target having an oxygen content of 20 [wt%]. [° C.] A graph showing the frequency distribution of leakage current after annealing.
FIG. 9 shows a case where a TiON film as a barrier film is formed by a reactive sputtering method using a Ti target having an oxygen content of 20 [wt%] and a reactive sputtering using a Ti target having an oxygen content of 35 [wt%]. It is a graph which shows the relationship between contact size, contact resistance, and contact resistance dispersion | variation about the case where it forms by a method.
FIG. 10 shows a case where a TiON film as a barrier film is formed by a reactive sputtering method using a Ti target having an oxygen content of 20 [wt%] and a reactive sputtering using a Ti target having an oxygen content of 35 [wt%]. It is a graph which shows the frequency distribution of the leakage current after a 450 [degreeC] annealing process about the case where it forms by a method.
FIG. 11 is a plan view showing a test element used for leak current measurement.
12 is a sectional view taken along line XX ′ of the element shown in FIG.
FIG. 13 is a cross-sectional view of a substrate showing a connection hole forming step in a multilayer wiring forming method as another application example of the sputtering method of the present invention.
FIG. 14 is a cross-sectional view of the substrate showing a TiON film formation and W layer formation step subsequent to the step of FIG. 13;
FIG. 15 is a cross-sectional view of the substrate showing an etch-back process following the process of FIG. 14;
16 is a substrate cross-sectional view showing an Al-based metal layer formation and a TiON film formation step subsequent to the step of FIG.
17 is a substrate cross-sectional view showing a wiring patterning step subsequent to the step of FIG. 16. FIG.
18 is a substrate cross-sectional view showing an interlayer insulating film formation and connection hole formation step subsequent to the step of FIG.
19 is a substrate cross-sectional view showing an upper layer wiring forming process following the process of FIG. 18;
FIG. 20 is a cross-sectional view of a substrate for explaining a conventional multilayer wiring formation method.
[Explanation of symbols]
20: Sputtering chamber, 22: Anode electrode, 24: Wafer to be processed, 26: Cathode electrode, 28: Sputtering target, 30: DC power source, 32: Cryo pump, 34: High frequency power source, 36: Matching circuit, 50: Semiconductor substrate 50a: impurity doped region, 52, 90: insulating film, 52a, 90a: connection hole, 56, 60, 80, 80a, 86, 86a, 92a, 98a: TiON film, 82: W layer, 82a, 94a: connection Plug, 58, 84, 84a, 96a: Al-based metal layer, 62, 88, 100: wiring layer.

Claims (4)

The object to be processed and the sputtering target are disposed in the sputtering chamber, and the processing gas is introduced into the sputtering chamber while the sputtering chamber is maintained at a predetermined pressure by the exhaust unit, and the processing gas is irradiated with ions. A sputtering method for forming a sputtered film made of sputtered particles on the surface of the object to be processed by releasing sputtered particles from a sputtering target,
The sputtering by using the titanium target having an oxygen content in the range of 15 to 35 [wt%] as a sputtering target with a mixed gas of nitrogen gas or inert gas and nitrogen gas in said process gas sputtering and forming an acid titanium nitride film as the film. Forming an insulating film covering the connected portion on the substrate, and then forming a connection hole reaching the connected portion in the insulating film;
Forming a titanium oxynitride film as a barrier film by covering the inner surface of the connection hole and the insulating film by the sputtering method according to claim 1;
Forming a wiring material layer covering the titanium oxynitride film so as to fill the connection hole;
Forming a wiring layer comprising a remaining portion of the stack by patterning a stack including the titanium oxynitride film and the wiring material layer. Forming an insulating film covering the connected portion on the substrate, and then forming a connection hole reaching the connected portion in the insulating film;
Forming a titanium oxynitride film as an adhesion film by covering the inner surface of the connection hole and the insulating film by the sputtering method according to claim 1;
Forming a conductive material layer on the titanium oxynitride film so as to fill the connection hole;
Removing the conductive material layer in a flat shape and leaving at least part of the titanium oxynitride film and part of the conductive material layer as connection plugs inside the connection hole;
Forming a wiring layer on the insulating film so as to be connected to the connection plug. Forming a wiring material layer on an insulating film covering the substrate;
Forming a titanium oxynitride film as an antireflection film by covering the wiring material layer by the sputtering method according to claim 1;
Forming a wiring layer comprising a remaining portion of the stack by patterning a stack including the wiring material layer and the titanium oxynitride film by photolithography and selective etching.

Images