In-Situ Low-Angle Cross Sectioning: Bevel Slope Flattening due to Self-Alignment Effects

TL;DR

This paper investigates how self-alignment effects during in-situ low-angle cross sectioning cause significant slope flattening, with experimental results showing a wide range of achievable shallow slopes.

Contribution

It provides a detailed analysis of self-alignment effects in in-situ low-angle cross sectioning and quantifies how mask edge chamfering influences slope flattening.

Findings

Achieved slope angles as low as 0.014° in experiments.

Demonstrated slope angles between 0.031° and 0.32° by varying ion impact angles.

Showed consistent slope flattening due to self-alignment effects.

Abstract

Low-angle cross sections are produced inside an Auger microprobe using the equipped depth profile ion sputter gun. Simply the sample is partly covered by a mask. Utilizing the edge of this mask the sample is sputtered with ions. Due to the shading of the mask a cross section is produced in the sample. The slope of this cross section is considerably shallower than given by the geometrical setup. This is attributed to self-alignment effects, which are due to missing sputter cascades in the transition area between sputtered and shaded sample regions and a chamfering of the mask edge. These self-alignment effects are studied here using a 104.6 nm thick SiO2 layer thermally grown on a Si substrate. In this study on one hand for a fixed ion impact angle of 15.8{\deg} as function of the sputter time several in-situ low-angle cross sections were produced. This way slope angles between an ultimate low slope angle of 0.014{\deg} and 0.085{\deg} were achieved. On the other hand for a fixed sputter time the ion impact angle was varied between 14.8{\deg}and 70.8{\deg}. For these samples cross section slope angles between 0.031{\deg}and 0.32{\deg}are observed. These results demonstrate the distinct slope flatting of in-situ cross sectioning.