Gate Oxide Cleans on Single Wafer Tool

Abstract

Pre gate oxide and especially "Double Gate Oxide" cleans are the most critical surface preparation steps in the semiconductor industry. This paper describes the key parameters to perform this kind of operations on a fully integrated single wafer cleaning tool. This switch from conventional batch cleaning tool enables significant defect density reduction and therefore yield enhancement. Nonetheless the main challenge of the double gate oxide clean is the prevention and the control of photo lithography resist lift off during the wet etch. This clean is also composed of two other steps, less critical. Nonetheless special care has been considered in the surface preparation in order to avoid any electrical mobility degradation.

Photo Lithography - Surface Preparation Interactions

“…But it has become more and more challenging since the deep UV resists' introduction and the continuous transistors' shrinking dimensions (figure 1 right). Moreover, although the transition from batch to single wafer tools enables a significant defectivity's reduction, it also increases the resist lift off [4] due to increased chemicals' concentration to maintain high enough tools' productivity. To keep such sensitive patterning in wet, a better understanding and innovative solutions have to be found.…”

Characterization of the Descum Process for Various Silicon Substrates Doping

“…The descum process is used to remove organic residue remaining after photolithography steps in the integrated circuit manufacturing process (1,2,3). This process provides a clean surface for subsequent process steps such as wet etch, implant, and dry etch (4).…”

Dependency of the Underlying Surface Condition on Dielectric Film Removal at Wafer Edge

“…6 Until recently, many semiconductor companies had been using batch cleaning systems [7][8][9][10] that are used for a wet process. However, the adoption of a single wafer spin tool 6,[11][12][13][14][15][16][17][18][19][20][21][22][23][24][25] has become mainstream for the cleaning process on the back side, frontside, and wafer edge etching because the process control and flexibility are considered to be superior to that of batch systems. 6,11,12 For edge etching using a single wafer spin tool, chemical liquids are supplied toward the edge of the front of the wafer from the wafer back side by diffraction.…”

“…However, the adoption of a single wafer spin tool 6,[11][12][13][14][15][16][17][18][19][20][21][22][23][24][25] has become mainstream for the cleaning process on the back side, frontside, and wafer edge etching because the process control and flexibility are considered to be superior to that of batch systems. 6,11,12 For edge etching using a single wafer spin tool, chemical liquids are supplied toward the edge of the front of the wafer from the wafer back side by diffraction. The chemical liquid is not supplied to the front edge directly; therefore, we postulated that the chemical liquid flow or infiltration depends on the wettability of the underlying surface.…”