Shrinking pattern sizes dictate that scanner-to-scanner variations for HVM products shrink proportionally. This paper shows the ability to identify (a subset of) root causes for mismatch between ArF immersion scanners using scanner metrology. The root cause identification was done in a Samsung HVM factory using a methodology (Proximity Matching Budget Breakdown or PromaBB) developed by ASML. The proper identification of root causes<sup>-1</sup> helps to select what combination of scanner control parameters should be used to reduce proximity differences of critical patterns while minimizing undesirable side effects from cross-compensation. Using PromaBB, the difference between predicted and measured CD mismatch was below 0.2nm. PromaBB has been proposed for HVM implementation at Samsung in combination with other ASML fab applications: Pattern Matcher Full Chip (PMFC), Image Tuner and FlexWave.
We report that, based on our experimental data, lens heating (LH) impact on wafer image can be effectively controlled by using a computational method (cASCAL) on critical device layers with no request on tool time. As design rule shrinks down, LH control plays a key role in preventing the image deterioration caused by the LH-induced wavefront distortion during exposure. To improve LH prediction accuracy, 3-dimension structure of mask stack (M3D) is considered in calculating the electro-magnetic (EM) field that passes through the mask for full chip. Additionally, lens specific calibration (LSC) is performed on individual scanners to take the lens-to-lens variation into account. In data comparisons, we show that cASCAL performs very well as an ASCAL substitute, and that M3D and LSC improve the LH prediction accuracy of cASCAL.
The beam combination method using stimulated Brillouin scattering phase conjugate mirrors is a promising technique
for solid state lasers of high power/energy operating with high repetition rate. The key technology of this method is the
phase control of the SBS waves. In the previous works, the principle of this phase control technique was demonstrated experimentally. As a next step, in this work, amplifiers have been added to the beam combination system. Inserting the amplifiers, a stabilized phase difference has been obtained with a fluctuation less than λ/50 at 44 mJ total output energy and 10 Hz repetition rate.
We have introduced the additional prepulse with main pulse to generate the stimulated Brillouin scattering (SBS) and
investigated the effect of this technique. In general, temporal pulse shape deformation takes place when the pulse is
reflected from the medium breeding SBS. This deformation of the SBS wave can cause optical breakdown in the optical
components and consequently it leads to low reflectivity and low fidelity of the phase conjugated wave in the SBS
medium. It has been shown that there is optimum prepulse time delay and minimum energy for preserving the SBS
waveform. This method is so simple that it can be applied to other systems and utilized in many applications easily, such
as high-power laser and optical isolator applications employing several SBS cells.
We have found that it is possible to preserve the temporal waveform of the reflected wave generated from stimulated
Brillouin scattering (SBS) by using a prepulse technique. In this work, the fundamental research has been carried out to
preserve the deformed pulse shape reflected from SBS medium. It is well known that the reflected SBS wave has a steep
rising edge. If one employs SBS cells in series, the rising edge of the pulse shape becomes steeper every time it reflects
at every SBS cell. This deformation of the SBS wave can cause the undesirable effects when we employ several SBS
cells in series, such as an optical breakdown in the optical components and the lower reflectivity and lower fidelity of the
phase conjugated wave in the SBS medium. A prepulse energy of 5 mJ and a time delay of 5 ns have been measured to
be the optimum values under this experimental condition. This prepulse method is useful in developing a multistage
system employing several SBS cells in series for high-power laser applications.
We report that the phase of backward Stokes waves can be independently controlled, which is necessary for a beam combination laser using stimulated Brillouin scattering-phase conjugate mirrors (SBS-PCM). The phase control is achieved by a self-generated density modulation without seeding the Stokes beam. Theoretical analysis shows that the phase fluctuation is mainly due to the pump energy fluctuation and is inversely proportional to the pump energy. We have achieved that the relative phase difference between two Stokes waves via SBS is smaller than λ/4 for all the pump pulses.