Study of Dopant Activation in Silicon Employing Differential Hall Effect Metrology (DHEM)

Abhijeet Joshi,Bulent M Basol

doi:10.1109/jeds.2022.3148048

Abstract

Differential Hall Effect Metrology (DHEM) technique was used to characterize highly n-type doped Si epi layers deposited on p-type Si wafers. Total dopant concentration, doping depth profile and post deposition annealing condition were changed for various sample sets and influence of such changes on the resistivity, mobility and carrier concentration depth profiles were studied. It was determined that samples annealed at 900 ∘C had higher activation compared to those annealed at 700 ∘C. Gradation in doping depth profiles did not result in similar gradation in resistivity values. Carrier concentration at the near-surface region was found to be lower in all samples. It is shown that electrical properties of films forming ultra-shallow junctions can be studied in detail and correlated with process parameters using DHEM data obtained at sub-nm depth resolution.

Highlights

IN advanced node transistors the contact resistance dominates parasitic resistance and negatively impacts power consumption and speed of devices
We present a study of active dopant depth profiles through n-type, highly doped Si films using Differential Hall Effect Metrology (DHEM) technique
As applied to measurements on Si, the traditional DHE technique makes repeated Van der Pauw/Hall effect measurements after the electrically active thickness of the layer is reduced in steps, typically by surface oxidation followed by chemical etching in hydrofluoric acid (HF)

Summary

INTRODUCTION

IN advanced node transistors the contact resistance dominates parasitic resistance and negatively impacts power consumption and speed of devices. Increasing the carrier concentration in S/D requires development of doping and annealing techniques and evaluation of dopant activation, especially in the near-surface regions of the films. In this contribution, we present a study of active dopant depth profiles through n-type, highly doped Si films using Differential Hall Effect Metrology (DHEM) technique. Calibration establishing a relationship between the thickness of the anodically formed oxide and the applied anodic voltage determines the depth scale, which is very dependable under fixed measurement conditions (20oC and standard pressure). At this time DHEM has the capability to controllably convert 2-5Å of Si into oxide before each measurement step, which gives it a depth resolution of well below 1nm

EXPERIMENTAL DETAILS

RESULTS AND DISCUSSION

CONCLUSION