Peter G. Borden

Junction depth measurement using carrier illumination

Carrier Illumination™ (CI) is a new method recently developed to meet the need for a non-destructive, high throughput junction depth measurement on patterned wafers. A laser beam creates a quasi-static excess carrier profile in the semiconductor underlying the activated junction. The excess carrier profile is fairly constant below the junction, and drops rapidly in the junction, creating a steep index of refraction gradient at the junction edge. Interference with light reflected from this index gradient provides a signal that is analyzed to determine the junction depth. The paper summarizes evaluation of performance in full NMOS and PMOS process flows, on both bare and patterned wafers. The aims have been to validate (1) performance in the presence of underlying layers typically found at the source/drain (S/D) process steps and (2) measurement on patterned wafers. Correlation of CI measurements to SIMS and transistor drive current are shown. The data were obtained from NMOS structures using As S/D and LDD...

A novel method to form nano-gridlines on textured CZ silicon wafers

We report a novel method to form metal nano-gridlines on textured Czochralski (CZ) silicon. This involves the deposition of tensile stressed silicon nitride under conditions that cause cracks at the base of the pyramid features. The crack width is adjusted with buffered BHF and the opening is self-aligned with the nitride as a mask. Subsequently, the metal lines are plated within the cracks, forming conductors with submicron dimensions. The metal grid provides a conduction path parallel to the emitter, relaxing sheet resistance requirements for a diffused emitter.

Characterizing Via Bottom Integrity in Cu/Low‐κ Processes

One of the most challenging aspects of Cu damascene fabrication is obtaining uniformly clear via hole bottoms following etch and clean. Residues and excess CuOx growth are common sources of high resistance and electro‐migration failure. In this paper we describe a method of characterizing via bottoms in dense 0.12 um via structures that have been etched and cleaned prior to barrier/seed deposition. The technique used in this study is a non‐destructive laser measurement method that is sensitive to the absorption of residues and oxides in the via bottom.

Opportunities and Risks in Semiconductor Metrology

New metrology opportunities are constantly emerging as the semiconductor industry attempts to meet scaling requirements. The paper summarizes some of the key FEOL and BEOL needs. These must be weighed against a number of considerations to ensure that they are good opportunities for the metrology equipment supplier. The paper discusses some of these considerations.

Non‐destructive Characterizing of Lateral Doping Effects

As channel lengths decrease, device performance becomes increasingly sensitive to lateral doping effects. We report on methods of non‐contact measurement of lateral diffusion and implant straggle using a combination of a bar mask pattern and Carrier Illumination™ measurements, in which one laser beam generates excess carriers and a second laser beam reflects from the excess carrier distribution. Doped region width is extracted from measurements in structures with a range of pitches and fills from 0 to 100%. The method may be applied to both pre‐ and post‐annealed structures, with orthogonal bar patterns used to determine the vector components of lateral doping. Lateral resolution of 0.5 nm is demonstrated. Both vertical and lateral diffusion distance are obtained. Data presented shows that the ratio of lateral to vertical diffusion depends on implant and anneal conditions. Measurements of high‐current single‐wafer implants show implant angle uniformity of better than ±1°.

In-situ particle monitoring: today's technology drivers

In situ particle monitors (ISPMs) have seen rapidly increased acceptance in semiconductor production because they provide automated, 100% inspection of particle levels during process at a low cost per inspection point. As productivity enhancement tools, ISPM use is only justified when it increases productivity of the host tool. The sensors provide an indirect measure of wafer contamination, and are of greatest value when they provide a particle count that correlates to yield and has identifiable causes. Manufacturing integration has now become the key factor driving the future of ISPM technology. This paper will discuss some of these factors, including correlation, sensor placement, impact on sensor design, application of expertise to qualification and maintenance, and gauge capability.