The Role of Ion Mass on End-of-Range Damage in Shallow Preamorphizing Silicon
- PDF / 2,669,492 Bytes
- 6 Pages / 612 x 792 pts (letter) Page_size
- 65 Downloads / 214 Views
The Role of Ion Mass on End-of-Range Damage in Shallow Preamorphizing Silicon Mark H. Clark1, Kevin S. Jones2, Tony E. Haynes3, Charles J. Barbour4, Kenneth G. Minor5 and Ebrahim Andideh6 1,2 University of Florida, Dept of Materials Science and Engineering, Gainesville, FL 32611-6130, U.S.A. 3 Oak Ridge National Laboratory, Oak Ridge, TN, 37831-6048, U.S.A. 4 Sandia National Laboratories, Albuquerque, NM, 87185-1056, U.S.A. 5 Sandia National Laboratories, Albuquerque, NM, 87185-1056, U.S.A. 6 Intel Corporation, Portland, OR, 97124, U.S.A. ABSTRACT Preamorphization is commonly used to form shallow junction in silicon CMOS devices. The purpose of this experiment was to study the effect of the preamorphizing species’ mass on the interstitial concentration at the end-of-range (EOR). Isovalent species of Si, Ge, Sn and Pb were compared. Silicon wafers with a buried boron marker layer (4700 Å deep) were amorphized using implants of 22 keV 28Si+, 32 keV 73Ge+, 40 keV 119Sn+ or 45 keV 207Pb+, which resulted in similar amorphous layer depths. All species were implanted at a dose of 5x1014 /cm2. Cross-sectional transmission electron microscopy (XTEM) was used to measure amorphous layer depths (approximately 400 Å). Post-implantation anneals were performed at 750 0C for 15 minutes. Plan-view transmission electron microscopy (PTEM) was used to observe and quantify the EOR defect population upon annealing. Secondary ion mass spectrometry (SIMS) was used to monitor the transient enhanced diffusion (TED) of the buried boron marker layer resulting from the EOR damage introduced by the amorphizing implants. Based upon the SIMS results Florida Object Oriented Process Simulator (FLOOPS) calculated the resulting time average diffusivity enhancements. Results showed that increasing the ion mass over a significant range (28 to 207 AMU) not only affects the quantity and type of damage that occurs at the EOR, but results in a reduced diffusivity enhancement. INTRODUCTION Increasing the packing density, speed, and power efficiency of future devices requires the vertical and lateral scaling down of device dimensions. One of the most challenging problems of device scaling is forming shallow source and drain junctions. With each successive generation, the junction depth for the source and drain is slated to shrink with the gate length. A 70 nm gate in 2008 will require a junction depth as shallow as 20 nm [1]. Currently, ion implantation is the most commonly used technique for forming shallow junctions, due to its superior dose control. Shallow n+-p junctions are formed relatively easily by arsenic implantation. Since arsenic is a heavy ion, it has a small projected range and does not experience serious ion channeling in crystalline silicon. On the other hand, shallow p+-n junctions are difficult to form due to the small atomic mass of boron, which is commonly used as J3.6.1
the p-type dopant. When boron is implanted into crystalline silicon, channeling of the implanted boron ion occurs, resulting in a dopant profile channeling tail, and con
Data Loading...
