Plasma-Damage-Induced Leakage Prevention Using Ozone Followed by SPM Solution Cleaning for Ion-Implanted Photoresist Strip

Abstract

During the device fabrication, thin dielectric layers experience a wide range of photoresist ͑PR͒ strip processes after various implantations carried out with the thin dielectric layers exposed. Degradation of the thin dielectric layers by the PR strip process using O 2 plasma is well known to cause yield reduction and reliability deterioration. This paper investigates a PR strip method using ozone ͑O 3 ͒ followed by sulfuric-peroxide mixture ͑SPM͒ solution cleaning and finds it significantly effective in PR strip performance even at the damaged PR by high-dose and high-energy implantations. The method dramatically reduces gate leakage current, resulting in significant improvement in gate oxide integrity. The PR strip technology is significantly effective for the reduction of plasma damage-induced dark current and white pixel defects of a 1.3 mega-pixel complementary metal oxide semiconductor image sensor fabricated with 0.18 m technology node.Plasma damage on large scale integration is receiving a lot of attention as the technology strongly requires even more stringent control than ever for damage free process. 1 The plasma damage is well known to degrade the thin dielectric layers by generating electron hole pairs ͑EHP͒ in oxide and trap charges at Si-SiO 2 interface, resulting in gate oxide leakage current, threshold voltage ͑V th ͒ shift, and deterioration of gate oxide reliability. 2 Many studies have focused on the shift of electrical characteristics and device reliability caused by the plasma charging damage during the exposure of the thin dielectric layers to plasma. [1][2][3][4] The demand for low-plasma-induced leakage imposes a challenge on the complementary metal oxide semiconductor ͑CMOS͒ image sensor technology also. The plasma damage could induce the trap charges onto the Si-SiO 2 interface on photodiode ͑PD͒ area of CMOS image sensor pixel and cause an extreme leakage current. The leakage current in the PD area is well known to be one of the most critical sources of the dark current and white pixel defects. [5][6][7][8] The dark current and white pixel defects are important means for characterizing the performance of an image sensor and correlated with the reduction of the amount of white pixel defects in dark. 6 Recently, many works have been reported to reduce the plasma damage induced dark current in CMOS image sensor. 9 The O 2 plasma has been widely used for the photoresist ͑PR͒ strip process after the implantations implemented with the thin dielectric layers exposed, providing a serious source of plasma damage. This is why many companies have tried to develop PR strip process without using plasma, such as ozone alone, ozone injected water, ozone injected SPM, and SPM alone. However, the PR strip using SPM alone or ozone injected SPM showed an extreme PR residue even for the low dose implantations, because the chemical solution cleaning alone cannot break the PR surface hardened by ion bombardment during the implantations. This is why the SPM solution cleaning has been used only for the remov...

Thermally Activated Gas-Phase Chemical Reactions in a Single-Wafer Wet Clean Process

“…Prior studies with plasmaless ozone ashing have been done on both photoresist and implanted photoresist, but material loss and interactions between ashing and wet clean were not well characterized (10,11). Other studies have shown reduced mobile ion density and reduced gate leakage current benefits with plasma-less ozone ashing relative to remote oxygen plasma systems (12,13). One plasma-less ozone study at 300 °C showed a low silicon oxidation rate of ~1.3 Å/min, which would correspond to <1 Å/min silicon loss, but implanted photoresist removal was not characterized (14).…”

Removal of ion-implanted photoresists on GaAs using two organic solvents in sequence

“…Heavily implanted photoresists have been removed via dry plasma ashing with a subsequent wet chemical treatment at elevated temperatures [17,18]. However, it is thought that the introduction of plasma ashing and a wet treatment results in material loss and surface damage of III-V semiconductors as well as increases both the manufacturing cost and environmental issues, preventing the application of this technique in the next-generation semiconductor manufacturing process [19][20][21]. In this study, therefore, the facile removal of three different types of implanted photoresists (I-line, ArF, and KrF) on GaAs wafers was investigated.…”

TiO2Nanotubes Formed in Aqueous Media: Relationship between Morphology, Electrochemical Properties and Photoelectrochemical Performance for Water Oxidation

“…3,[6][7][8][9][10][11] TiO 2 nanotubes can be obtained by anodization in aqueous electrolytes as well as in organic media containing fluoride ions. [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15] The latter one is the most commonly used to fabricate films for photoelectrochemical applications due to its simplicity for controlling the morphology (tube diameter and length) through operational variables. TiO 2 nanotubes formed in fluoride containing aqueous electrolytes are typically short due to the high chemical etching produced by fluoride ions during their growth.…”