MgO Deposition: (CpEt) 2 Mg + H 2 O April 2014 A. O’Mahony, A. Mane, J. Elam

Early Attempt at Uniform MgO 70 cycles (EtCp) 2 Mg/H 2 O: o C MgO measured on Si and MCP MCP located at centre of 9 x MCP holder Expected GPC 1.4 Å/cycle: Up to 2x higher GPC on back of MCP compared to front Non-uniformity in thickness will affect MCP gain Precursor flow Growth per cycle ( Å/cycle ) Location on MCP (cm) Front of MCP Back of MCP

20 μm monitor MCPs 10 μm dummy MCPs Optimized Process Wedged holder with 9 x 9” holder for 53 mm MCPs 30 cycles (EtCp) 2 Mg/H 2 O: o C inlet outlet top bottom Substrate Layout:

MgO thickness measured: On Si positioned beneath 9 MCP holder (8 x 8” Si) On front and back surfaces of MCP – 5 points in each direction (2 x 2” MCP) Measurement of MgO Thickness Inlet Centre Outlet top Thickness measurement on MCP inlet to outlettop to bottom

Si along length of reactor, 9 x MCPs: 1 monitor (centre) Si std variation = 4%, GPC = 1.3 Å/cycle (direction: inlet-outlet) Si std variation = 13%, GPC = 1.5 Å/cycle (direction: top-bottom) Higher GPC on MCPs than on Si but good uniformity on both MCP surfaces Run MgO: (CpEt) 2 Mg + H 2 O Precursor flow Thickness on Si (8 x 8” Si) Thickness on Centre MCP (2 x 2” MCP) MCP front MCP back Precursor flow

Si along length of reactor, 9 x MCPs: inlet and outlet monitors Si std variation = 9.0%, GPC = 1.3 Å/cycle (direction: inlet-outlet) Si std variation = 9.8%, GPC = 1.5 Å/cycle (direction: top-bottom) Run MgO: (CpEt) 2 Mg + H 2 O Thickness on Si (8 x 8” Si) Precursor flow Thickness on Inlet MCP (2 x 2” MCP) MCP front MCP back Thickness on Outlet MCP (2 x 2” MCP) MCP front MCP back

Reproducible MgO thickness on Si with 9 x MCPs Slight depletion in precursor at outer most point of holder (run 2) Decrease in MgO thickness from inlet to outlet but good uniformity across MCP top and bottom surfaces for all 3 monitor MCPs All data: Runs 1 + 2

Conclusions Uniform deposition on individual MCPs (front and back surfaces) located at inlet, centre and outlet positions Decrease in MgO thickness across reactor but precursor depletion only evident at outermost point on outlet MCP Challenges: Scaling to larger batches of 2 x 2” MCPs or 8 x 8” MCP Substrates – require NiCr coated substrates for process optimization (need reflective surface for ellipsometry to measure thickness)