Ion‐Implanted Photoresist and Damage‐Free Stripping

Abstract

The surface of positive photoresist is hardened by the ion implantation process and becomes very difficult to remove thereafter. To investigate this phenomenon, the following aspects of photoresist were investigated: (i) the effectiveness of low-energy plasma ashing, (if) surface states by XPS, and (iii) outgassing during the ion implantation process. For photoresists without ion implantation, the ion bombardment energy dependence of the ashing rate was found to have two regions: the radical-mode ashing region and the reactive ion etching (RIE) mode ashing region. On the other hand, photoresist following an ion implantation process was found to be entirely covered with a hardened surface layer exhibiting only RIE-mode characteristics. This is why a plasma ashing process with low ion bombardment energy for suppression of damage on the wafer surface cannot work effectively in this case. When the photoresist is baked at a high temperature in a nitrogen ambience, the ratio between the carbon (C1~) peak area and the oxygen (O1,) peak area (C/O ratio) in the x-ray photoelectron spectroscopy data increases, indicating that carbonization has occurred. The ericial C/O ratio of carbonized photoresist that can be removed by sulfuric acid/hydrogen peroxide mix (SPM) is i0. However, an ion-implanted photoresist, with a C/O ratio of three, cannot be removed by SPM. Outgassing from the photoresist during the ion implantation process contains hydrogen as its main component. Our results indicate that an ion-implanted photoresist is difficult to remove because of an inactive high-polymer layer formed on the surface which has an extremely low hydrogen concentration, not because of carbonization in the surface. Therefore, the hydrogen concentration in the photoresist surface is considered to be critical to the efficiency of photoresist ashing. Since outgassing from photoresist during the ion implantation process contains hydrogen as its main component, the hardened surface layer must be supplied with hydrogen compounds in order to effectively remove the ion-implanted photoresist without damaging the substrate.

Effects of Sputtering Metal Deposition Parameters in the Photoresist used as a Sacrificial Layer in Micro-electromechanical System Devices

“…When ionized argon plasma sputters against aluminum target produces a positively charged argon ions that impinge the photoresist layer. Several papers have reported that if the photoresist is under argon ions an outgassing of hydrogen by decomposition of C-H bond is produced [6][7][8][9]. This decomposition produces a corrugated form of the photoresist layer that increases the roughness and makes the photoresist useless as a sacrificial layer.…”

Relationship between Oxygen Additive Amount and Photoresist Removal Rate Using H Radicals Generated on an Iridium Hot-Wire Catalyst

“…Photoresists must eventually be removed. Conventional methods use chemicals or oxygen plasma to remove photoresists [1][2][3][4][5][6]. Chemicals are not only environmentally unfriendly but also expensive.…”

Photoresist Removal Using H Radicals Generated by Iridium Hot-Wire Catalyst

“…Photoresists have to be removed at the end of the process. In the removal of photoresist, there are some problems, such as the environmental impacts and the costs of the chemicals because hazardous chemicals are usually used for removal [1][2][3]. As one of the removal methods without the chemicals, the removal method by an ashing, in which photoresist was decomposed to oxide-carbon compounds by using the oxygen plasma [4][5][6][7], is used to remove photoresists in some cases.…”