AuGe & AuSi Eutectic Services
361 °C / 363 °C Die Attach & Ohmic Contacts
At Nanosystems JP Inc., we deposit and pattern gold-germanium (AuGe 88/12) and gold-silicon (AuSi, typically ~97/3 wt%, commonly cited 96.8 Au / 3.2 Si) eutectics, the fluxless, high-temperature die-attach metallurgies of GaAs, SiC, and hermetic package work, and the base of the AuGe/Ni/Au ohmic contact system for n-GaAs. These eutectic compositions are typically formed by PVD evaporation rather than conventional electroplating. 4 to 12 inch wafers, from a single wafer.
GaAs die attach standard
classic Si die attach
GaAs, SiC, InP, Si
prototype to production
The top of the solder ladder
AuSi 363 °C and AuGe 361 °C sit above AuSn 278 °C and indium 157 °C, so a die attached with AuGe or AuSi can be designed to stay solid through the lower-temperature reflows that follow; each assembly's thermal history is checked at engineering review.
Fluxless gold eutectics
for the joints that must not move
When a die must stay solid through the reflows that follow it, run hot in service, or sit in a hermetic package for long service lives, the industry reaches for gold-based eutectics. Three properties keep AuGe and AuSi irreplaceable.
Highest Practical Solder Hierarchy
Melting at 361 °C and 363 °C, AuGe and AuSi joints stay solid through AuSn attach at 278 °C, SnAg reflow around 250 °C, and every rework cycle below. That makes them the first joint in multi-step assemblies, the die attach that everything else is built on top of, and the choice for devices whose junction temperatures would creep past ordinary solders' service limits.
Fluxless and Hermetic-Clean
Like AuSn, these gold-rich alloys bond without flux: no residue, no voiding from flux volatiles, and no cleaning chemistry inside a package that will be hermetically sealed. The joints are rigid, high-modulus, and thermally conductive, exactly what a power die or a hermetic header wants underneath it.
The n-GaAs Ohmic Contact System
AuGe is more than die attach: alloyed AuGe/Ni/Au is the standard ohmic contact to n-type GaAs, the metallization under decades of MESFETs, HEMTs, and MMICs. We deposit the stack by evaporation and lift-off and can alloy it by rapid thermal annealing in the same flow, to your contact recipe.
Evaporation-only metallurgies,
deposited as engineered stacks
Neither alloy has a practical plating chemistry, so both are built the AuSn way: alternating layers evaporated to the target composition, patterned by lift-off or deposited blanket on die backsides, homogenizing into the eutectic on the first melt.
Complete AuGe / AuSi
fabrication parameters
| Parameter | AuGe (88/12) | AuSi (97/3) |
|---|---|---|
| Eutectic Temperature | 361 °C | 363 °C |
| Wafer Sizes | 4 to 12 inch (100 to 300 mm) | |
| Substrates | GaAs, Si, SiC, InP; others on request | |
| Deposition | Stacked-layer evaporation; composition by layer thickness ratio | |
| Patterning | Lift-off (±0.5 µm) or blanket backside | |
| Die-Attach Layer Thickness | 1 to 5 µm typical | |
| Ohmic Contact Stack | AuGe/Ni/Au, 0.1 to 0.3 µm typical | N/A |
| RTA Alloying | Available in flow, per recipe | N/A |
| Composition Control | Layer thickness ratio at deposition | |
| Backside Processing | Thinned-wafer handling available | |
| Inspection | Profilometry + SEM standard; cross-section on request | |
| Minimum Lot | From 1 wafer; R&D runs to repeat lots on one baseline recipe | |
AuGe and AuSi across GaAs,
SiC, and hermetic packaging
GaAs MMIC Die Attach
AuGe die attach for GaAs power amplifiers and MMICs in telecom, radar, and satellite hardware, the fluxless, high-hierarchy joint that hermetic microwave packages are built on, with thermal conduction the die's dissipation depends on.
n-GaAs Ohmic Contacts
Alloyed AuGe/Ni/Au ohmic contacts for MESFET, HEMT, and MMIC front-ends, evaporated, lift-off patterned, and RTA alloyed to your recipe, with the low, stable contact resistance decades of III-V manufacturing established.
SiC & High-Temperature Power
Gold-eutectic die attach for SiC and other wide-bandgap devices whose junction temperatures overrun ordinary solders, keeping the joint solid and conductive where the device actually operates.
Hermetic Headers & TO Packages
AuSi and AuGe attach into hermetic headers, TO cans, and ceramic packages, fluxless joints with no flux residues or polymer dielectrics in the joint, in the package styles that space, defense, and sensing programs still qualify.
Laser & LED Bar Attach
High-hierarchy eutectic attach for laser bars and LED arrays where subsequent AuSn or solder steps follow, the first, hottest joint in a multi-metallurgy optical assembly.
Hi-Rel Space & Defense
Gold-eutectic joints carry decades of qualification heritage in space and defense hardware. We support new builds and legacy-process reproduction from single-wafer lots with full process documentation.
What makes our AuGe / AuSi capability
different
The AuSn playbook, applied
Stacked-layer evaporation, layer-ratio composition control, lift-off patterning: the discipline proven on our AuSn flow runs these alloys the same way.
Die attach and ohmic in one flow
Backside die-attach metallization and front-side AuGe/Ni/Au contacts, with RTA alloying, run as one program instead of two separate procurements.
Evaporation-only alloys, done properly
These metallurgies cannot be plated, and services built around plating avoid them. Evaporation and lift-off are the standard route for this service, so AuGe and AuSi are standard work, not exceptions.
Thermal hierarchy engineered
We ask what comes after this joint, AuSn, SnAg, rework, and place your attach at the right rung of the ladder, with the companion metallurgies available on the same UBM.
Compound-substrate handling
GaAs and InP wafers, thinned backsides, and fragile die-attach-ready substrates are handled with adapted chucking and thermal budgets, the routine case in this application space.
From 1 wafer, no minimum lot
Prototype on a single wafer, verify composition and wetting, then scale on the same recipe with the prototype data as baseline. That prototype data becomes the baseline for repeat production.
Start your project.
Initial response typically within one business day.
Share your process requirements, substrate, and production volume. A Nanosystems JP Inc. engineer will give an initial response typically within one business day. Full quote typically within 7-10 business days, subject to project complexity and NDA requirements.