A new failure mechanism by corrosion of tungsten in a tungsten plug process

Bothra, S.; Sur, H.; Liang, V.

doi:10.1016/s0026-2714(98)00191-7

Cited by 21 publications

(17 citation statements)

References 3 publications

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“…Tungsten has a high potential for applications as a good corrosion resistant metallic component in steel alloys due to its ability to form passive oxide film layer on its metal surface . Tungsten and its alloys are widely used to produce corrosion resistant products for automotive, electronics, aerospace and military industries .…”

Section: Introductionmentioning

confidence: 99%

In situmonitoring of the electrochemical dissolution of tungsten

Krebsz

Kollender

Hassel

2017

Phys. Status Solidi A

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In the present work, which is aimed to monitor in situ the electrochemical dissolution of tungsten by using a Flow-Type Scanning Droplet Cell Microscope (FT-SDCM) and Inductively Coupled Plasma Mass Spectrometry (ICP-MS), novel results are reported. The anodic oxide growth and its dissolution on the surface of W have been monitored in situ.The results of this current study show the importance of coupling electrochemical experiments to ICP-MS.

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Section: Introductionmentioning

confidence: 99%

In situmonitoring of the electrochemical dissolution of tungsten

Krebsz

Kollender

Hassel

2017

Phys. Status Solidi A

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“…Because the hydroxide ions react with tungsten trioxide ͑WO 3 ͒ formed on the tungsten surface. 6 Thus, the following experiments were performed by solution D with a pH of 5.0 for tungsten layer cleaning.…”

Section: Resultsmentioning

confidence: 99%

Nonoxidative Aqueous Cleaning Solutions for Tungsten Layers

Park

Kim

Lee

et al. 2009

J. Electrochem. Soc.

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Aqueous cleaning solutions were developed for postetch cleaning of tungsten layers to replace the amine-based organic strippers. They are composed of tetramethylammonium hydroxide, HF, and two additives. Even the cleaning recipes without a strong oxidant, such as hydrogen peroxide, could remove postetch residues formed by reactive ion etching and they also had the same particle removal efficiency compared to ammonium and hydrogen peroxide mixture known as RCA Standard Clean. The concentration of metal ion on the wafer surface after cleaning by them was under 10 10 atoms/cm 2 . The effects of the cleaning could be explained by applying Pan's double-layer model ͓J. Electrochem. Soc., 148, G315 ͑2001͔͒. In fact, these cleaning solutions made it possible to decrease the resistances of tungsten bit lines and metal contacts and contributed to yield enhancement.As devices shrink, it is imperative to introduce metal layers such as tungsten and copper to enhance device performance and reduce a chip size of memory in the semiconductor industry. 1,2 Particularly, the tungsten layer has been widely used as a bit line material and, recently, the gate stack of memory has been changed to the tungsten gate stack to obtain low sheet resistance and reduce the chip size in many chip makers. [3][4][5] The cleaning processes after tungsten layer etching require removal of unwanted etch residues without corrosion of the tungsten layers. 6 However, classical RCA cleaning chemicals with a strong oxidant, such as hydrogen peroxide ͑H 2 O 2 ͒, 7 are not appropriate because of tungsten oxidation, followed by dissolution into highly acidic or basic solutions. 8,9 And they could not completely remove metallic etch residues, which have been observed to form a thin residue layer along the gate edge with transmission electron microscopy images of the poly metal gate after cleaning. 10 Thus, organic amine-based strippers with effective removal efficiency of etch residues were evaluated and applied to the postetch cleaning process of tungsten but could hardly remove particles and metal ions contaminated from the previous processes. 11 These contaminants on the silicon wafer surface provide a source of killing defects to affect the yield and characteristics of devices. [12][13][14] In this study, we have developed a nonoxidative cleaning solution for the tungsten layer, which could not only strip metallic etch polymers but also remove Si particles up to over 70% and prevent the readsorption of metal ions at well-controlled pH without tungsten loss. Furthermore, the resistance of contacts and bit lines could be lower and also yield could be increased when applied to the tungsten bit line and contact processes. ExperimentalA variety of the cleaning compositions were evaluated to find the best cleaning efficiency for tungsten layers as shown in Table I. They are composed of tetramethylammonium hydroxide ͑TMAH͒, HF, and two additives. One additive is a kind of ammonium salt conjugated with an anion of an inorganic acid and was added to the cleaning so...

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“…As evidence linking the corrosion phenomena to charging, Bothra et al demonstrated that the corrosion by solvent stripping was suppressed if the charge was discharged by electrical grounding with an electrical microprobe. 1) We consider that the grounding procedure using the electrical microprobe not only caused the electrical discharge but also mechanically peeled off the surface deposition induced by the plasma process. In order to prove our conjecture, we carried out three different contact procedures prior to the immersion in the aqueous amine stripper as shown in Fig.…”

Section: Resultsmentioning

confidence: 99%

“…In the zero margin design, the misalignment of the metal layer and the W via plugs can expose the W plugs after dry etching of the metal layer. Recently, Bothra et al 1) reported that W plugs which were partially exposed were corroded by a solvent stripping process which is usually carried out to remove residual photoresist and deposited material after reactive ion etching and ashing. They concluded that the significant amount of positive charging in the Al electrode/W plug stack structure occurred during plasma etching, and the charges enhanced the electrochemical oxidation of W in the stripping solvent.…”

Section: Introductionmentioning

confidence: 99%

Mechanism of Tungsten Plug Corrosion during Chemical Stripping Process: Scanning Maxwell-Stress Microscopy and Electrochemical Potentiometry Studies

Matsukawa¹,

Murata

Kotani

et al. 2002

Jpn. J. Appl. Phys.

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Corrosion of W plugs in LSI interconnects during chemical solvent stripping was investigated by scanning Maxwell-stress microscopy (SMM). The surface potential of TiN, Al and W, of which the interconnects are composed, was measured by SMM, and the changes in electrostatic charging and work functions through the processes were estimated. After immersion in aqueous amine stripper, which actually caused the W plug corrosion, the work functions of the Al and W films were comparable. Due to the similarity of the work function to the electrochemical reduction potential, we consider that the corrosion protection of the Al/W contact becomes inactive in the aqueous amine stripper. This is also supported by the electrode potential measurement in the aqueous amine stripper, for which the Al potential exhibited a higher value than that of W only for the films after O 2 ashing. We consider that the W plug corrosion is caused by the electrochemical interaction between the aqueous amine stripper and the material deposited on the Al by O 2 ashing.

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A new failure mechanism by corrosion of tungsten in a tungsten plug process

Cited by 21 publications

References 3 publications

In situmonitoring of the electrochemical dissolution of tungsten

In situmonitoring of the electrochemical dissolution of tungsten

Nonoxidative Aqueous Cleaning Solutions for Tungsten Layers

Mechanism of Tungsten Plug Corrosion during Chemical Stripping Process: Scanning Maxwell-Stress Microscopy and Electrochemical Potentiometry Studies

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