Jorge Luque

CF A 2Σ+–X 2Π and B 2Δ–X 2Π study by broadband absorption spectroscopy in a plasma etch reactor: Determination of transition probabilities, CF X 2Π concentrations, and gas temperatures

Broadband absorption spectroscopy was applied to study the CF A 2Σ+–X 2Π and B 2Δ–X 2Π transitions in a plasma etch reactor. We report a previously unobserved band, which is assigned as CF A 2Σ+–X 2Π (3,0). This band is significantly broadened by predissociation, and we estimate the average collision-free lifetime of the CF A 2Σ+ v′=3 level to be 0.30±0.08 ps. Experimental relative oscillator strength measurements, together with ab initio calculations, Rydberg–Klein–Rees-based wave functions and experimental lifetimes were used to calculate a full set of transition probabilities for the CF A 2Σ+–X 2Π and B 2Δ–X 2Π bands. The maximum observed number densities of CF X 2Π were ∼2×1013 cm−3 with sensitivity to measure to 1010 cm−3. The excited state and ground state temperatures were determined by comparing the spectra to simulations. The ground state rotational temperature was 450±30 K and the vibrational temperature was 850±80 K near the substrate surface. The CF B 2Δ excited state rotational temperatures a...

Gas temperature measurement in CH4/CO2 dielectric-barrier discharges by optical emission spectroscopy

The gas temperatures were determined by optical emission in a dielectric-barrier discharge at atmospheric pressure. The feed gases were either pure CH4 to yield higher hydrocarbons or CH4/CO2 mixtures to yield synthesis gas (H2/CO). The monitored emission was from the CH radical A 2Δ–X 2Π electronic system and the gas temperature range characterized was from 300 to 600 K. The technique described in this article enables the measurement of the neutral gas temperature in the discharge that is not accessible via conventional methodology using thermocouples. A bimodal rotational population distribution in the CH A 2Δ v′=0 state was determined in the investigated gas mixtures of CO2/CH4 and in pure methane. Most of the rotational population was at temperatures from 300 to 600 K depending on experimental conditions, which are only slightly higher than the set temperature of the reactor. A small fraction of the emitting species was found to have a much higher rotational temperature of ∼4000 K for the pure methane...

Advanced process control for poly-Si gate etching using integrated CD metrology

Advanced integrated metrology capability is actively being pursued in several process areas, including etch, to shorten process cycle times, enable wafer-level advanced process control (APC), and improve productivity. In this study, KLA-Tencors scatterometry-based iSpectra Spectroscopic CD was integrated on a Lam 2300 Versys Star silicon etch system. Feed-forward control techniques were used to reduce critical dimension (CD) variation. Pre-etch CD measurements were sent to the etch system to modify the trim time and achieve targeted CDs. CDs were brought to within 1 nm from a starting CD spread of 25 nm, showing the effectiveness of this process control approach together with the advantages of spectroscopic CD metrology over conventional CD measurement techniques.

Broadband absorption and ab initio results on the CF C 2Σ+–X 2Π system

Broadband absorption spectra and ab initio calculations are combined to complete and reinterpret part of the vacuum ultraviolet spectra of the CF radical. We have found a new band at 190.8 nm which we have assigned to the CF C 2Σ+–X 2Π (1,0) transition. Ab initio calculations show that the band at 186.6 nm formerly assigned as CF C′ 2Σ+–X 2Π (0,0) by White et al. [J. Mol. Spectrosc. 75, 318 (1979)] corresponds to the CF C 2Σ+–X 2Π (2,0) band. The CF C 2Σ+ state is heavily perturbed by the A 2Σ+ state and by repulsive 2Σ+ states. The observed predissociation pattern for the C 2Σ+ (v′=0,1,2) states is well reproduced by the calculations. Information on the CF C 2Σ+–X 2Π and D 2Π–X 2Π electronic transition moments and corresponding oscillator band strengths is also presented.

Advanced process control applied to 90-nm lithography and etch

In this paper, we demonstrate how understanding and controlling lithography through etch, using appropriate integrated metrology, can improve process results, reducing across-wafer CD variability. A spectroscopic CD tool was used to generate CD, profile, and film thickness information from wafers exposed on a 248 nm ASML track/scanner cluster. Using this data, detailed intrafield and interfiled wafermaps were generated. Based on this information, dose, focus, and intensity uniformity corrections were fed back to the track/scanner cluster as offsets for subsequent exposures. In parallel and as a complement to this control loop, CD and profile information was also fed forward to a Lam 2300 Versys Star silicon etch system as input for the etch process optimization step. Following etch, the wafers were moved into the integrated CD metrology module on the etch platform, whereupon post-etch CD/profile measurements were made to verify the effect of the lithography correction, effectiveness of optimized etch process parameters, and magnitude of the lithography-to-etch CD bias.