In this paper we will review typical applications of photoluminescence (PL) metrology in high volume LED manufacturing environments. PL is a well-established method for analysis of semiconductor properties. The technique is non-contact, non-destructive and rapid. We will describe the principles of the measurement and review PL data from LED process wafers. We will discuss how PL measurement results like peak wavelength, dominant wavelength and PL intensity are obtained. We will summarize the accuracy, precision, stability and other considerations of the measurement. Finally, metrology considerations for manufacturing LEDs on large diameter substrates, including the possibility of 8” silicon substrates, will be presented.
Photoluminescence (PL) technique has demonstrated the powerful capability for practical application to wafer
inspections in III-V compound semiconductor production. This paper describes the principle and the physics behind the
variation of PL wavelength with laser excitation power density. We discuss the effect of GaN cap thickness on the PL
measurements. This is especially relevant to LED manufacturers where thick GaN caps are commonly used and to PL
metrology of InGaN MQW laser structures. A methodology was proposed to select the most appropriate laser and set of
excitation conditions to achieve matching between PL and electroluminescence (EL) wavelengths for common Blue and
Green LED structures.
Selective area epitaxial (SAE) growth of strained SiGe:B (Boron) in the recessed source/drain (S/D) region of an MOS device is known to improve Si-PMOS performance due to enhancement of hole mobility and reduction of S/D resistance. However, the process may be adversely affected by pattern loading effects, SiGe relaxation, dislocation formation, dopant precipitation and contamination. These effects, if not controlled, will deteriorate device performance and yield. A nondestructive, in-line SAE process monitoring approach on patterned wafers is especially desired. A specialized, contact-less, carrier lifetime-based Room Temperature - Photoluminescence (RT-PL) method meets this demand. The RT-PL tool, which uses a novel excitation path design to achieve carrier confinement, device-suitable probing depth, submicron scanning resolution and a micron probe size, offers a quick, non-destructive assessment of strain, defects and contamination for SAE. In this paper, a systematic evaluation of blanket and selective growth layers is illustrated using layers with a Ge content of 15-25%, undoped and B-doped at ~1020 cm-3 concentration. For the as-grown conditions, we observed that SiGe remains in an unrelaxed state without extended dislocations being formed. These results suggest that SiGe composition could be further modified to optimize the associated mobility enhancement. Uniformity variations associated with SiGe composition and B-doping were identified. Excessive boron precipitation, metallic particle-originated defects and large contamination regions induced by processing tools were also exposed. The multiple and unique insights enabled through the RT-PL technique provide significant benefits towards decreasing process development and integration time, maintaining SiGe process in control and reducing device fabrication costs.