Specific Process Knowledge/Thin film deposition/Deposition of Silicon Oxide/SiO2 disk and granule source tests in Temescal October 2026: Difference between revisions

[[Specific Process Knowledge|Specific Process Knowledge]] / [[Specific Process Knowledge/Thin film deposition|Thin film deposition]] / [[Specific Process Knowledge/Thin film deposition/Deposition of Silicon Oxide|Deposition of Silicon Oxide]]

= SiO₂ disk and granule source tests in Temescal, October 2026 =

Two source-loading configurations were tested in the Temescal electron-beam evaporator on 22 and 23 October 2026. Each run used four solid, circular SiO₂ disks in a graphite liner and a nominal thickness setpoint of 600 nm at 1 Å/s. Run 1 used the disks alone. Run 2 used new disks with SiO₂ granules between the stack and liner wall. Both runs used a HULA (high uniformity lift-off assembly) holder.

The disks alone developed a narrow cavity that penetrated the entire stack. Adding granules and changing to a horizontal figure-eight sweep produced a more manageable deposition: repeated small rate spikes persisted, but the run finished without the major instability or growing liner-exposure concern described for Run 1. The deepest penetration stopped at the interface between the third and fourth disks.

The report follows the experimental sequence using source photographs, schematics, visual observations and instrument recordings. The power curves retain the recorded values without smoothing. Run 1 heating-timer pauses are excluded from the main comparison and are separate from source instability. These exploratory tests document source behaviour and provide a basis for further process development.

=== Common tooling-file settings ===

| Maximum power / O₂ flow setting || 10% / 5%

| Rate / thickness setpoint || 1 Å/s (0.1 nm/s) / 600 nm

'''Note.''' Density is a controller input, not measured film density. O₂ = 5% is the instrument setting, not gas composition or partial pressure. Run 2 was reported as RT/unheated, but its logged thermocouple temperature rose from 22.0 to 61.6 °C during deposition. The TC channel is not an independent sample-surface temperature measurement. Power is recorded as percent of full scale.

Source loading, sweep geometry and the temperature condition changed together, so this is not a single-variable comparison. The logs also show different rise/soak settings, including soak-2 levels of 2.8% in Run 1 and 5.0% in Run 2. Thickness milestones refer to the QCM indication, not local source erosion depth. The deposition-only comparison excludes repeated conditioning in Run 1.

The final logged values confirm that both depositions reached the intended 600 nm range. The approximately 11% difference from ellipsometry therefore remains a calibration question rather than an unrecorded extra 50 nm of indicated deposition. Relative to the post-ramp summaries, the differences are approximately +10.70% and +11.24%.

The similar offsets motivate checking QCM calibration and sample position within the HULA holder before selecting a new tooling factor. QCM thickness conversion depends on density and tooling geometry [2]. The entered 2.648 g/cm³ is a controller setting; the recorded thickness alone does not identify which calibration input needs adjustment.

 

'''Note.''' At 1 Å/s, 600 nm corresponds to 100 min. The logged shutter-open totals are consistent with this scale. Run 1’s heating-timer pauses increase elapsed time but are not included in the main comparison of deposition behaviour.

== Processing and physical interpretation ==

[[File:Eves_SiO2_Temescal_202610_Fig09_Power_active_time.png|thumb|center|900px|Figure 9. Power plotted against cumulative time in the sustained DEPOSIT phases. Alarm pauses and conditioning are removed from the time axis. The first 120 s after each restart remain as gaps in the curve; those seconds are still part of the deposition-phase clock. This time axis differs from elapsed wall-clock time. All-phase wall-clock plots and the complete raw records are included in the accompanying package.]]

Run 1 was interrupted by alarms when the 30-minute heating allowance expired. The main plots use sustained DEPOSIT phases, exclude repeated rise/soak sequences, and omit a fixed 120 s recovery interval after each restart. These exclusions are shown as gaps. Three isolated zero-power DEPOSIT-labelled records preceding restart ramps are also excluded. The initial startup is retained.

 

 

 

== Conclusions and next experiments ==

The combination of disks, surrounding granules and a horizontal figure-eight sweep gave more stable operation in the second test and left the fourth disk unpenetrated. Both configurations produced transparent SiO₂ films with Cauchy-model ellipsometry thicknesses close to 0.67 µm. The combined configuration is a reasonable starting point for further source optimization.

A HULA (high uniformity lift-off assembly) holder was used in both runs. The SiO₂ film thicknesses were obtained by Cauchy-model ellipsometry. Figure 5 records visual mental descriptions through the top chamber window, where brightness, contrast and shadowing affect interpretation. Final penetration depths were established after venting.

[2] DTU Nanolab LabAdviser, “Temescal processing / Good to know about the Temescal”. QCM conversion, tooling calibration and source monitoring. Accessed 27 October 2026.

[3] DTU Nanolab LabAdviser, “Evaporation of SiO₂ in Temescal-2”. Related local process information, accessed 27 October 2026. Its earlier tests are separate from this comparison.