Template for measuring edge width and method of using

Details Template for measuring edge width and method of using Template for measuring edge width and method of using

1999-01-29

2002-12-31

Gutierrez, Diego (Department: 2859)

Geometrical instruments

Gauge

Template

C033S555100, C033S0010BB

Reexamination Certificate

active

06499222

ABSTRACT:

FIELD OF THE INVENTION
The present invention generally relates to a template for measuring a distance from an edge of a disk and a method of using the template and more particularly, relates to a template for measuring a distance from a wafer edge after an edge bead rinse process to determine how well the process is centered with the wafer and a method of using the template.
BACKGROUND OF THE INVENTION
Spin-on-glass (SOG) is frequently used for gap fill and planarization of inter-level dielectrics (ILD) in multi-level metalization structures. It is a suitable material for use in low-cost fabrication of IC circuits. Most commonly used SOG materials are of two basic types; an inorganic type of silicate based SOG and an organic type of siloxane based SOG. One of the commonly used organic type SOG materials is a silicon oxide based polysiloxane which is featured with radical groups replacing or attaching to oxygen atoms. Based on these two basic structures, the molecular weight, the viscosity and the desirable film properties of SOG can be modified and adjusted to suit the requirement of specific IC fabrication process.
SOG film is typically applied to a pre-deposited oxide surface as a liquid to fill gaps and steps on the substrate. Similar to the application method for photoresist films, a SOG material can be dispensed onto a wafer and spun at a rotational speed which determines the thickness of the SOG layer desired. After the film is evenly applied to the surface of the substrate, it is cured at a temperature of approximately 400° C. and then etched back to obtain a smooth surface in preparation for a capping oxide layer on which a second interlevel metal may be patterned. The purpose of the etch-back step is to leave SOG between metal lines but not on top of the metal, while the capping oxide layer is used to seal and protect SOG during further fabrication processes. The siloxane based SOG material is capable of filling 0.15 micron gaps and therefore it can be used advantageously in 0.25 micron technology,
When fully cured, silicate SOG has similar properties like those of silicon dioxide. Silicate SOG does not absorb water in significant quantity and is thermally stable. However, one disadvantage of silicate SOG is the large volume shrinkage during curing. As a result, the silicate SOG retains high stress and cracks easily during curing and further handling. The cracking of the SOG layer can cause a serious contamination problem for the fabrication process. The problem can sometimes be avoided by the application of only a thin layer, i.e., 1000~2000 Å of the silicate SOG material.
In the current SOG coating process, a solvent edge rinse and a solvent backside rinse process are utilized to remove unwanted SOG deposited on the wafer edge and on the backside of the wafer. This is shown in FIGS.
1
~
3
. A semiconductor wafer
10
which has a flat side
12
is shown in FIG.
1
. After a SOG coating process, a SOG layer
14
is blanket deposited on the top surface
16
of the wafer. The layer is deposited as a dielectric layer for insulating between metal lines. In order to process the wafer in subsequent fabrication steps, the wafer must be positioned in reaction chambers for various processes such as etching or deposition. In most of the process chambers, the wafer is positioned on a platform and held down on the edge by a wafer clamp. The function of the wafer clamp is to prevent the wafer from moving during the process when reactant gases or etching gases may be flowing into the reaction chamber. To enable the wafer clamp to function properly, the edge portion of the wafer of approximately 2~4 mm wide must be cleaned without any coated material. The edge area
22
on wafer
10
is shown in FIG.
1
.
In present wafer fabrication technology, the SOG layer deposited at unintended areas of the wafer can be removed in two different processes. The first process is a solvent edge rinse which is shown in FIG.
2
. In this process, wafer
10
is placed on a platform (not shown) and spun at a predetermined rotational speed along a spin axis
26
. The rotational speed of the wafer can be suitably adjusted for each specific application depending on the thickness of the layer to be removed and the type of chemical solution used. As shown in
FIG. 2
, a chemical solution injector
28
is used to inject chemical solution
32
onto the top edge
34
of the wafer. The chemical solution
38
deflected from the edge
34
of the wafer hits the chamber wall
42
and drains to the bottom of the process chamber. The solvent edge rinse process is effective in removing a limited area, i.e., a width of 2~4 mm, on the top edge of the wafer of an unwanted coating material such as SOG or photoresist.
The second cleaning process is a solvent backside rinse such as that shown in FIG.
3
. The backside
48
of wafer
10
can be cleaned by this process. A cleaning solution
52
is injected from a spray nozzle
54
onto the backside
48
of the wafer. The process is also known as a centrifugal spray cleaning process wherein a chemical solution, i.e., normally a good solvent for the coating layer is pressure-fed and injected directly onto the backside of a spinning wafer. The process can be effectively used to reduce the volume of fresh chemical consumed and is normally faster than an immersion process. After the injected chemical solution
52
hits the bottom surface
48
of the wafer, the chemical solution
56
reflects from the backside
48
of the wafer and drains into the bottom of the process tank (not shown). During a normal backside rinse process, the sprayed chemical solution
52
is only capable of rinsing the backside
48
of the wafer and, none of the chemical solution
52
can reach the top surface
16
.
After an edge bead rinse process is conducted on a processed silicon wafer
10
, the concentricity of the rinse process must be determined in order to assure the quality of the IC dies (not shown) on the wafer
10
. Traditionally, this is carried out by using a straight ruler
20
as shown in FIG.
4
. The scales
24
on the straight ruler
20
is used to measure the edge rinse width
30
. The measurement of the edge rinse width
30
may also be performed by using a caliper (not shown).
The measurement process for the edge rinse width
30
is an important step in the quality control of the edge bead rinse process. For instance, as shown in
FIG. 5
, when the concentricity of the SOG coating layer
14
is off in relationship to the wafer
10
, serious quality problems occur in the numerous IC dies that are located on the edge of the wafer
10
. Quality problems arising out of particle contamination may also result due to cracked SOG material. For instance, as shown in
FIG. 5
, portion
36
of the SOG coating layer resulting from a narrow edge rinse width
40
may cause SOG layer cracking issue in a subsequent process where wafer
10
is held down by a clamp ring (not shown). The excess SOG coating layer
36
when clamped under a ring crack and may cause serious particle contamination problem in a process chamber. On the other hand, at the opposite edge of the wafer
10
, an excessively wide area
44
of the edge rinse width occurs in portion
46
of the SOG coating layer. The excessive removal of the SOG coating layer
14
results in some of the IC dies located in the area being damaged by a water jet that was used in the edge bead rinse process. The IC dies are damaged even when a small corner of the die is hit by the high velocity water jet.
A reliable measurement tool and a method for using such tool are therefore important issues in ascertaining the reliability of an edge bead rinse process. The concentricity of the edge bead rinse process in relationship to the wafer must be determined with high accuracy in order to calibrate the edge bead rinse apparatus, i.e., the position of the rinse nozzle. The calibration may be performed both at the beginning of an edge bead rinse process as a step in the set-up procedure, and during subsequent processes for checking reliability, i.e., the conce

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