Who makes fab materials, masks, gases for AI data centers

This is the consumables layer of chip fabrication, sitting alongside fab equipment as an input to the advanced-node foundry step: photoresist and masks used to pattern each layer, CMP slurries and other process chemicals, sputtering targets for deposition steps, and the specialty gases used throughout the process. Unlike fab equipment, which is a durable capital good, these are consumed and repurchased continuously in step with wafer output, making this sub-layer's volume a closer real-time read on actual fab utilization than equipment order books are. Several of the specific sub-categories here (see the child parts) carry meaningful supplier concentration — a handful of firms dominate advanced-node photoresist, for instance — which the taxonomy breaks out separately because the investor-relevant dynamics differ materially by material type. For investors, the general pattern across this whole sub-layer is that AI accelerator dies, being larger and more process-step-intensive than typical logic chips, consume more of each material per finished wafer than a conventional chip would, adding a second source of demand growth beyond wafer start volume alone.