Abstract: A substrate holder for vertical furnaces is configured to support substrates in slots at inner portions of the substrates, rather than solely at the edges. The holder allows sufficient clearance above substantially the entire front face of the substrate that a substrate deflection or bow, induced by thermal stresses during loading and unloading of the substrate holder into and out of the furnace, can be accommodated without the substrate touching the support members of the substrate holder. A relationship is established such that, for given loading/unloading temperatures, a minimum amount of free space in the wafer slots is provided to avoid substrate scratching. Conversely, for a given amount of free space in the wafer slots, the relationship provides maximum loading and/or unloading temperatures to avoid scratching.