Most gases used in the semiconductor industry are

supplied at a constant pressure, typically above

atmosphere, and are delivered to a process at or below

atmosphere. Ion implant gases are now mostly supplied at

sub-atmospheric pressure using SDS or VAC source gas

technology.

These SDS gases are supplied at a sub-atmospheric

pressure that decreases as the gas is consumed. This is

a critical difference for the mass flow controller, as inlet

pressure, was typically constant. Changing inlet pressure

can impact an MFC’s capability to both meter and control

flow accurately, as well as achieve set-point within an

allowable time. The wider the range of inlet pressure that

an MFC can control and meet performance criteria is

critical to SDS gas utilization and tool uptime.

The

πMFC-LP was specifically designed for SDS source

gases and similar applications. It controls rapidly and

accurately from initial SDS pressures of 650 Torr down

to pressures well below 10 Torr at the MFC. The digital

control electronics have been tuned to provide typical

response times of less than 2 seconds. With its ability

to accurately meter and control gas flow over this wide

pressure range, the SDS source utilization is maximized

resulting in fewer bottle changeouts, increased up-time

and ultimately lower cost of ownership. See Figure 1 for

typical SDS gas utilization as a function of pressure.

Figure 1 —

SDS Gas Use Rate Efficiency

Note: Unless otherwise specified, dimensions are nominal values in inches (mm referenced).

The

πMFC multi-gas feature allows the user to configure

an MFC off-the-shelf for its intended gas further lowering

costs through reduced inventory requirements. This feature

is enabled through a web browser utility accessed through

the device’s Ethernet port. The configuration utility uses a

standard web browser – no special software is required.