the ink chambers are typically formed in the thick film layer and the nozzle holes are formed in the nozzle plate a fluid supply slot 26 is formed through the thickness t of the semiconductor substrate 12 to provide a fluid supply path for flow of fluid to the fluid chambers 24 and heater resistors 14 the fluid supply slot 26 may be provided by an elongate slot or individual holes through the thickness t of the substrate 12 methods for making fluid supply slots 26 are known and include mechanical abrasion chemical etching and dry etching techniques a particularly advantageous method for forming a fluid supply slot 26 is a deep reactive ion etching drie process generally as described in u s pat no 6 402 301 to powers et al the disclosure of which is incorporated by reference as if fully set forth herein while the fluid supply slot 26 is shown as having substantially vertical walls the walls of the fluid supply slot 26 are typically slightly tapered so that the fluid supply slot 26 is wider on one end than on the other end with reference to fig2 11 an exemplary method for making micro fluid ejection devices according to one embodiment of the disclosure is illustrated the method includes providing a substrate 12 having a thickness ranging from about 200 to about 800 microns or more a plurality of layers including insulative conductive and resistive materials are deposited on the device surface 16 of the substrate to provide a plurality of heater resistors 14 thereon and electrical tracing to the heater resistors 14 the substrate 12 may also include.