Dry‑etching process is widely adopted in chip manufacturing. The silicon wafer is placed as the positive electrode at the bottom of the etching chamber. The gas distribution plate with dense tiny through‑holes, serving as the negative electrode, is mounted on top of the chamber. With proper voltage applied and acidic plasma etching gas introduced, micro‑fabrication is performed on the silicon wafer inside the high‑temperature chamber according to circuit patterns defined by lithography, so as to etch the wafer surface to the designed line width and depth and form micro‑integrated circuits.
The upper and lower electrodes are in direct contact with plasma. While etching the silicon wafer, plasma also wears out both electrodes. Electrodes suffer gradual physical and chemical corrosion from etching gas. Once worn to a certain level, electrodes must be replaced to guarantee uniform etching. The evenly‑distributed holes on the upper electrode (shower head / gas distribution plate) will deviate in dimension due to etching‑gas corrosion and need replacement when tolerance limits are exceeded.
The showerhead (gas distribution plate / upper electrode / silicon electrode / gas homogenizing plate) is one of the core components for etching and thin‑film deposition in semiconductor wafer manufacturing. It is mounted close to the top of the reaction zone, featuring numerous fine holes as gas inlets to inject reaction gas evenly into the chamber. As a consumable part kept in stock, machining the dense micro‑holes on showerhead faces the following challenges, which are common bottlenecks in semiconductor equipment manufacturing.
– Material Challenge— Showerheads are usually made of hard‑brittle materials including monocrystalline silicon, SiC and high‑purity alumina ceramic. These materials feature high hardness and high brittleness, which easily cause hole‑edge chipping, cracking and rapid tool wear.
– Precision Challenge — To ensure uniform gas distribution, the quality of massive micro‑holes on shower heads directly determines chip process yield. Hole diameter tolerance, roundness, surface roughness and positional accuracy are all at micron‑level.
– Structural Challenge — Shower‑head micro‑holes feature small diameter and high depth‑to‑diameter ratio. Hole diameters range from Φ0.3 mm to Φ0.8 mm with depth‑to‑diameter ratio up to 55:1. Small and deep holes result in poor chip evacuation, high risk of drill breakage and difficulty in stable machining quality.
Solution Analysis
◎ Tests on φ0.45 mm PCD micro‑drill machining monocrystalline silicon show minimal hole‑edge chipping. Under microscope inspection, hole roundness tolerance is less than 0.005 mm, dimensional accuracy within ±0.003 mm, and surface roughness ≤Ra0.2 μm, meeting customer requirements.
◎ In preliminary tests, the drill presents slight edge wear after machining 3500 holes and remains usable.
◎ Worldia PCD micro‑drills are divided into four series (WZ1, WZ2, WZ3 and WZ‑X) according to processed materials and application scenarios, with diameter range of φ0.1‑φ1.0 mm. The solid PCD drills adopt self‑centering design, supporting maximum depth‑to‑diameter ratio up to 57:1. Chip‑flutes are manufactured by integral grinding for smooth chip evacuation. Machined hole‑wall finish can reach Ra0.2 μm or better with little hole‑edge chipping. The PCD drill tip delivers excellent wear resistance, long tool life and high dimensional consistency. The products satisfy micro‑hole machining demands for monocrystalline silicon, polycrystalline silicon, SiC, ceramics, fused silica and other materials in semiconductor industry.