Patent ID: 7416165

Claim:
A diaphragm valve in a vacuum exhaustion system, the diaphragm valve comprising: a first body having a flow-in passage and a flow-out passage; a valve seat disposed between the flow-in passage and the flow-out passage, wherein the valve seat comprises a ring-shaped valve seat body and a ring-shaped holding body, wherein the first body includes a valve seat body accommodating part that accommodates the valve seat body and a holding body accommodating part that accommodates the holding body, wherein the valve seat body accommodating part and the holding body accommodating part are formed concentrically at a lower part of a valve chamber of the first body centering around the flow-in passage, and wherein the holding body is provided with a plurality of communication bores that communicate with the out-flow passage, and the holding body is fitted around the valve seat body and is also fitted in the valve chamber of the first body; a diaphragm installed in the first body and permitted to rest on, and move away from, the valve seat, wherein the ring-shaped holding body fitted around the ring-shaped valve seat body is disposed in the valve chamber so as to be accommodated by the holding body accommodating part of the first body, and wherein an outer periphery of the diaphragm is disposed above an outer periphery of the ring-shaped holding body so that the diaphragm and the ring-shaped holding body are pressed against the first body by a bonnet by way of a gasket disposed above the outer periphery of the diaphragm so as to keep the valve chamber air-tight; and a driving means provided on the first body for allowing the diaphragm to rest on and move away from the valve seat, wherein synthetic resin films of a predetermined thickness coat fluid-contacting parts of the body and the diaphragm, wherein the synthetic resin films are fluorine-containing resin films that are 50 to 100 μm thick and the fluid-contacting parts coated by the synthetic resin films include surfaces of the flow-in passage, the flow-out passage, the valve seat of the first body, and also a lower surface of the diaphragm, and wherein the synthetic resin films are heat resistant approximately up to 150° C. against monosilane gas, diborane gas, phosphine gas and arsine gas.