Getting the Most Heat onto Your Wafer
When you’re working in a vacuum, you’ve got a problem: convection is gone. There’s no air to carry the heat around. You’re left with radiation, and that’s where things get tricky. If you’re designing an infrared heater for wafers, your main enemy is “leakage.” You don’t want your precious energy drifting off into the chamber walls. You want it hitting the substrate. Period. Why we go with gold You might be tempted to use polished aluminum or stainless steel. Don’t. They soak up way too much energy. We use high-purity gold coatings instead. Why? Because gold is a beast when it comes to the infrared spectrum—it bounces back over 98% of that radiation. By wrapping the heating element in gold, we basically tell the heat, “Don’t go to the vacuum pumps or the housing. Go back to the wafer.” It means every watt you pay for actually does the work. Focusing the heat But just reflecting the light isn’t enough. We want to aim it. By curving that gold shield, we can create a concentrated “hot zone.” It’s a huge win for your workflow. You hit your target temperatures faster, and the heat stays uniform across the whole wafer. The best part? You get that intense heat density without having to crank the voltage so high that you blow out your filament. The catch Now, here’s the thing: gold is fancy, but it’s fragile. You can’t just go in There with an abrasive scrub pad or some harsh chemicals to clean the reflectors. Do that, and you’ll strip the coating right off. Once that happens, your efficiency tanks. Also, because the heat is so focused, you have to keep an eye on the thermal mass of your substrate. If you aren’t careful, you’ll end up with local hot spots. If you’re building a system for high-throughput annealing, this gold-coated setup is the way to go. It cuts down your ramp-up time and stops you from wasting power. Just a pro tip: double-check your mounting brackets. You don’t want any mechanical friction rubbing against those coated surfaces.