Robert D. Rathmell

Implant Angle Repeatability on Optima MD

A very sensitive channeling implant has been used to quantify the repeatability of implant angles for the Optima MD over a period exceeding one month. Sensitivity of sheet resistance to variation in vertical and horizontal beam angles was measured for 500 keV P++ at a dose of 5E13 /cm2 near orientations tilt/twist of 0°/0° and 35.26°/0° for (100) wafers. Sensitivity to tilt in the vertical plane at both conditions was at least a 10% change in Rs for a 0.5° change in tilt at a tilt of 0.75° away from the channel (i.e. at 0.75°/0° and 34.5°/0°), where the variation in Rs was linear with tilt. Horizontal angle sensitivity resulted in a 7.5% change in Rs for a 0.5° change in angle, but was less sensitive to smaller angle variation, since Rs varied roughly as a second order function near the channel. Sensitivity to tilt is reduced by about a factor of 3 for implants at 0°/0° compared to 0.75°/0° with a similar response at 35.26°/0° compared to 34.5°/0°. Implants were carried out using wafers from a single boul...

Implant Angle Control on Optima MD

Implant angle control is increasingly important with each new device node. Some devices have demonstrated a sensitivity of threshold voltage of about 100 mV/deg for implant angle and require implant angles to be held within +/− 0.2° for process control. There are many sources of angle variation in single wafer implanters. Mechanical orientation can usually be controlled to high precision, but an accurate control of the implant angle requires knowledge of the actual beam angle relative to the surface or crystal planes of the wafer. In‐situ methods to measure beam angles in both the horizontal and vertical planes are required and it is necessary that these methods be calibrated to the surface or crystal planes of the wafer to achieve the required angle control. Optima MD has incorporated methods to automatically measure beam angles prior to implant in both planes, and correct for any deviation from the desired implant angle. The symmetric parallelizing lens that corrects angles without bending the beam enab...

Vertical Beam Angle Control: an Advancement/Requirement in Modern Ion Implant Manufacturing

As the industry moves to the new technology nodes of 45 nm and 32 nm devices, implant angle control becomes even more crucial for consistent device performance. Commercial single wafer ion implanters are able to measure and correct the horizontal incident angle of the ion beam. But the vertical beam angle (VBA) control has become a very important parameter as well. In this work the authors demonstrate the impact of a tilt variation for a 65 nm and a 45 nm MOS transistor generated by different beam setups on one machine. Comparisons are made for each technology with a controlled angle variation of ±4°. The Vt‐distribution should be reduced with better incident angle control allowing faster development of a new transistor node base line using the new VBA control technique from Axcelis.

Optima MD: Mid‐Dose, Hybrid‐Scan Ion Implanter

The emergence of higher‐dose and lower‐energy halo and source‐drain extension implants for 90 and 65‐nm nodes drove the design of Axcelis’ Optima MD ion implanter. The Optima MD extends the proven process performance of traditional medium‐current implanters over an energy range of 1 keV to 250 keV for singly‐charged ion species with beam currents ranging from 1 pμA to 4800 pμA. The Optima MD comprises a hybrid‐scan beamline architecture, a new endstation, and a new control system that offers the user more flexibility in data acquisition and statistical process control. The beamline has the capability to provide milliamp beam currents in the low energy (<5 keV) range. The use of an aggressive final deceleration (decel) in combination with a final angular energy filter (AEF) enables this productivity improvement of higher beam currents while mitigating the risk of energy contamination. In this paper the new beam transport system that reduces space charge blowup and maintains focus control at low energies is...