MCEE201/601 – Report#1

Oxidation, Ion-Implantation and RTP/Furnace Processing

Abstract

The Lab course’s goal is to perform how to design, fabricate and characterize a simple P-type-metal oxide-semiconductor (PMOS) device. In this lab report, details about the oxidation, ion implantation and rapid thermal processing (RTP), which are some of main processes of PMOS fabrication procedure, is reported. Three specific wafers, but similar at initiation (lightly doped N-type Silicon) were marked C1, C2 and C3 to be used in order to monitor our different process steps. The process began with RCA cleaning followed by wet oxidization and mask pattering in order to prepare wafers for ion-implantation. The C1 wafer was step-etched for upcoming evaluation. Ion-implantation was performed on all the three wafers with Boron as a dopant. Afterwards, C1 and C3 wafers went through Rapid Thermal Annealing to activate bombarded dopant. Sheet resistance (R_s) measurement via 4-point probe technique was executed on C1 wafer to evaluate the minimum oxide thickness of ion-implantation mask based on R_s. In order to increase the junction depth, furnace thermal processing was done on C2 wafer. Steam oxide was grown and etched on C2 wafer as well. Groove and Stain technique was performed on C2 wafer for junction depth (X_j) measurements. Athena software was used for better understanding and also to make some comparison between measured and simulated values such as dopant profile, minimum mask oxide thickness, and junction depth and sheet resistance.

1. Introduction

Microfabrication course is about the theory behinds common methods and techniques for semiconductor device fabrication with focus on transistors. In Lab session, all these methods practically shown by operating different tools, different processing steps and final characterization for better understanding of what the course is about. The PMOS transistor has been chosen to be design and fabricate in the lab from beginning (wafer preparation) to the end (electrical measurement). 

The first transistor was developed in 1947 as a low cost, low dimensional active component to replace vacuum tube bulbs. The first material was germanium and gradually transistors made by other semiconductors such as Silicon (Si) and Gallium Arsenide (GaAs).  The Si has gradually become the most dominant material in semiconductor industry since it is abundant element, cheap to produce, has good electrical properties and high quality silicon dioxide (SiO₂) can be easily grown on it.   SiO₂ has good dielectric properties and can act as oxide mask also can be selectively etched.

Transistors have huge applications; they are the main component on integrated circuits (IC). The PMOS is a type of transistor which based on Si with controlling oxidation. Figure 1 shows a schematic of simple PMOS.