Pressure differential measuring tool

Details Pressure differential measuring tool Pressure differential measuring tool

2002-10-05

2004-11-23

Lefkowitz, Edward (Department: 2855)

Measuring and testing

Fluid pressure gauge

Diaphragm

Reexamination Certificate

active

06820491

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to process tools for the fabrication of integrated circuits on semiconductor wafer substrates. More particularly, the present invention relates to a tool for measuring the pressure difference between atmospheric or ambient air in a semiconductor fabrication facility and an indexer in a process tool to prevent influx of potential wafer-contaminating particles into the indexer.
BACKGROUND OF THE INVENTION
Generally, the process for manufacturing integrated circuits on a silicon wafer substrate typically involves deposition of a thin dielectric or conductive film on the wafer using oxidation or any of a variety of chemical vapor deposition processes; formation of a circuit pattern on a layer of photoresist material by photolithography; placing a photoresist mask layer corresponding to the circuit pattern on the wafer; etching of the circuit pattern in the conductive layer on the wafer; and stripping of the photoresist mask layer from the wafer. Each of these steps, particularly the photoresist stripping step, provides abundant opportunity for organic, metal and other potential circuit-contaminating particles to accumulate on the wafer surface.
In the semiconductor fabrication industry, minimization of particle contamination on semiconductor wafers increases in importance as the integrated circuit devices on the wafers decrease in size. With the reduced size of the devices, a contaminant having a particular size occupies a relatively larger percentage of the available space for circuit elements on the wafer as compared to wafers containing the larger devices of the past. Moreover, the presence of particles in the integrated circuits compromises the functional integrity of the devices in the finished electronic product. When the circuits on a wafer are submicron in size, the smallest quantity of contaminants can significantly reduce the yield of the wafers. For instance, the presence of particles during deposition or etching of thin films can cause voids, dislocations, or short-circuits which adversely affect performance and reliability of the devices constructed with the circuits. Accordingly, technological advances in recent years in the increasing miniaturization of semiconductor circuits necessitate correspondingly stringent control of impurities and contaminants in the plasma process chamber. Currently, mini-environment based IC manufacturing facilities are equipped to control airborne particles much smaller than 1.0 &mgr;m, as surface contamination continues to be of high priority to semiconductor manufacturers. To achieve an ultra-clean wafer surface, particles must be removed from the wafer. Particle-removing and contamination-preventing methods are therefore of utmost importance in the fabrication of semiconductors.
During the photolithography step of semiconductor production, light energy is applied through a reticle mask onto a photoresist material previously deposited on the wafer to define circuit patterns which will be etched in a subsequent processing step to define the circuits on the wafer. Because these circuit patterns on the photoresist represent a two-dimensional configuration of the circuit to be fabricated on the wafer, minimization of particle generation and uniform application of the photoresist material to the wafer are very important. By minimizing or eliminating particle generation during photoresist application, the resolution of the circuit patterns, as well as circuit pattern density, is increased.
Photoresist materials are coated onto the surface of a wafer by dispensing a photoresist fluid typically on the center of the wafer as the wafer rotates at high speeds within a stationary bowl or coater cup. The coater cup catches excess fluids and particles ejected from the rotating wafer during application of the photoresist. The photoresist fluid dispensed onto the center of the wafer is spread outwardly toward the edges of the wafer by surface tension generated by the centrifugal force of the rotating wafer. This facilitates uniform application of the liquid photoresist on the entire surface of the wafer.
Spin coating of photoresist on wafers is carried out in an automated track system using wafer handling equipment which transport the wafers between the various photolithography operation stations, such as vapor prime resist spin coat, develop, baking and chilling stations. Robotic handling of the wafers minimizes particle generation and wafer damage. Automated wafer tracks enable various processing operations to be carried out simultaneously. Two types of automated track systems widely used in the industry are the TEL (Tokyo Electron Limited) track and the SVG (Silicon Valley Group) track.
The various processing steps used in the fabrication of devices on a wafer substrate are carried out sequentially in multiple processing systems. An example of such a processing system is an automated track-type semiconductor fabrication apparatus which may be obtained from the Tokyo Electron Co., of Tokyo, Japan, and is generally indicated by reference numeral
1
in the schematic of FIG.
1
. The apparatus
1
includes an enclosure
2
and a track
3
which transports semiconductor wafer substrates
12
(
FIG. 2
) among multiple process stations where the substrates
12
are subjected to various treatments during the fabrication process. The apparatus
1
includes a spin coater station
4
, further shown in
FIG. 2
, and multiple hot/cold plate stations
5
,
6
, and
7
, respectively, arranged in series. The track
3
transports wafer containers
11
, each of which contains multiple wafer substrates
12
, from upstream process stations (not shown) to the spin coater station
4
, in which a coating layer of photoresist material, for example, is applied to the surface of the substrates
12
. Next, the track
3
transports the wafer containers
11
and coated wafer substrates
12
into and out of the hot/cold plate stations
5
,
6
,
7
for conversion of the spin-coated material coated on the substrates
12
into a low dielectric constant material, according to the knowledge of those skilled in the art.
In typical operation of the apparatus
1
, the wafer container
11
, which may be a SMIF (standard mechanical interface) pod, for example, contains the multiple wafer substrates
12
and is loaded into an indexer
10
of the spin coater station
4
. Each of the wafer substrates
12
is individually transferred from the wafer container
11
and placed on a wafer support
15
in a process chamber
14
. During the photoresist coating process, the wafer support
15
is rotated at high speeds as the liquid photoresist (not shown) is dispensed onto the substrate
12
through a dispensing opening (not shown) in the top of the process chamber
14
. The photoresist is uniformly distributed on the surface of the rotating substrate
12
, after which the coated substrate
12
is transferred back into the wafer container
11
. After all of the substrates
12
in the wafer container
11
have undergone the coating process, the wafer container
11
, containing the coated substrates
12
, is removed from the indexer
10
, and the track
3
distributes the wafer container
11
to the next station in the apparatus
1
.
During the photoresist application process in the process chamber
14
, the high rotational speed of the wafer support
15
generates photoresist powder particles in the process chamber
14
. While most of these particles are removed by operation of a vacuum exhaust line (not shown), a small quantity of the particles remain in the process chamber
14
. Due to the top dispensing opening (not shown) provided in the top of the process chamber
14
, the pressure of air inside the process chamber
14
equalizes with the pressure of ambient or atmospheric air surrounding the process chamber
14
. Thus, in the event that the pressure of the air or gas in the indexer
10
is lower than the atmospheric pressure of the air or gas in the process chamber
14
, the particles tend to flow with the turbulent gas or air from the hig

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