Substrate supporting apparatus

A substrate supporting apparatus, comprising:

• a rotatable chuck for supporting a substrate, defining a plurality of first injecting ports and a plurality of second injecting ports, the first injecting ports connecting to a gas pipe for supplying gas to the substrate and sucking the substrate by Bernoulli effect, the second injecting ports connecting to another gas pipe for supplying gas to the substrate and lifting the substrate;
• a plurality of locating pins disposed at the top surface of the rotatable chuck, the plurality of locating pins being divided into a first group of locating pins and a second group of locating pins, every locating pin being driven by an independent cylinder, the cylinders which drive the first group of locating pins connecting to a gas pipe, the cylinders which drive the second group of locating pins connecting to another gas pipe;
• a hollow shaft, an inner wall of the hollow shaft defining four gas grooves, each gas groove configured to supply gas to a corresponding one of the gas pipes for supplying gas to the substrate and sucking the substrate by Bernoulli effect, the another gas pipe for supplying gas to the substrate and lifting the substrate, the gas pipe connecting to the cylinders which drive the first group of locating pins, or the another gas pipe connecting to the cylinders which drive the second group of locating pins;
• a rotary spindle, being set in the hollow shaft and a spacing formed between an outer wall of the rotary spindle and the inner wall of the hollow shaft;
• two pairs of seal rings, wherein one pair of seal rings is disposed at opposite sides of one gas groove which supplies gas to the cylinders for driving the first group of locating pins, one pair of seal rings is disposed at opposite sides of one gas groove which supplies gas to the cylinders for driving the second group of locating pins;
• wherein the hollow shaft defines an exhaust port between two adjacent gas grooves, wherein one gas groove supplies gas to the cylinders for driving the first group of locating pins or the second group of locating pins, one gas groove supplies gas to the first injecting ports or the second injecting ports, wherein the outer wall of the rotary spindle defines a blocking wall corresponding to the exhaust port of the hollow shaft and a recess matching the gas groove which supplies gas to the first injecting ports or the second injecting ports.