Abrading – Precision device or process - or with condition responsive... – Controlling temperature
Reexamination Certificate
2002-07-05
2003-10-28
Hail, III, Joseph J. (Department: 3723)
Abrading
Precision device or process - or with condition responsive...
Controlling temperature
49, 49, 49, 49, 49, 49, 49, 49
Reexamination Certificate
active
06638141
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to the chemical-mechanical polishing (CMP) technique. More particularly, the invention relates to a CMP method and a CMP apparatus which are preferably used for the planarization processes for substrates or wafer in semiconductor device fabrication.
2. Description of the Related Art
Recently, the CMP process has been attracting our attention as one of the planarization techniques in semiconductor device fabrication field. This is because the CMP process makes it possible to planarize globally a deposited film of films over a whole semiconductor wafer or substrate, which has been difficult to be realized with the use of any other conventional planarization techniques, such as the etch back process. The planarization of deposited film(s) is an essential process to enhance the integration scale (i.e., density) and miniaturization of semiconductor integrated circuit devices. Thus, it is said that the CMP process is one of the most important techniques.
FIG. 1
shows schematically a prior-art polishing apparatus for the CMP process.
The apparatus of
FIG. 1
comprises a circular rotating platen
101
having a polishing pad
102
on its surface. The bottom of the platen
101
is fixed to a vertical rotating shaft
105
. The shaft
105
is rotatable around its axis with a first driving mechanism (not shown). Thus, the platen
101
is rotatable in a horizontal plane by way of the shaft
105
. The pad
102
is rotatable along with the platen
101
.
A slurry supply tube
103
is mounted at a specific position over the platen
101
in such a way that the outlet of the tube
103
is oriented toward the pad
102
. The tube
103
is used to supply a polishing slurry
104
onto the pad
102
in the form of drops.
A substrate holder
110
is movably provided over the platen
101
to hold or carry a substrate (e.g., a semiconductor wafer)
106
having a target film (not shown) to be polished on its surface. The holder
110
has a cylindrical body
111
with an inverted U-shaped cross section. The body
111
has a cylindrical inner space.
A vertical spindle
112
is fixed to the top of the substrate holder
111
. The spindle
112
is rotatable around its axis with a second driving mechanism (not shown). Thus, the holder
101
is rotatable in a horizontal plane and movable vertically and horizontally by way of the spindle
112
.
A circular plate
113
is fixed horizontally in the inner wall of the holder body
111
. The plate
113
is located at an elevated position from the bottom end of the body
111
by a specific distance. A backing film
114
, which is made of a resin, is attached to the lower surface of the plate
113
.
The holder
110
holds or carries the substrate
106
by way of the backing film
114
and the plate
113
. The holder
110
is horizontally rotatable and vertically movable with the second driving mechanism while holding the substrate
106
.
Next, the operation of the prior-art polishing apparatus of
FIG. 1
(i.e., the CMP process with the apparatus) is explained below.
First, a substrate
106
having a target film on its surface is held with the substrate holder
110
in such a way that the target film is oriented to the lower side. This is performed in the state where the holder
110
is sufficiently apart from the platen
101
.
Next, a polishing slurry
104
is supplied onto the surface of the polishing pad
102
by way of the slurry supply tube
103
in the form of drops while rotating the platen
101
in a horizontal plane, as shown in FIG.
1
. Due to the rotation of the platen
101
, the slurry
104
supplied onto the pad
102
is automatically distributed uniformly on the surface of the pad
102
.
Thereafter, the holder
110
is moved toward the pad
102
while rotating the holder
110
in the same direction as the rotating platen
101
until the target film (not shown) of the substrate
106
is attached to the surface of the pad
102
. In this state, the surface area of the target film reacts chemically with potassium hydroxide (KOH) contained in the slurry
104
, thereby forming a soft layer (not shown) on the target film. The soft layer thus formed is mechanically polished with grains contained in the slurry
104
. As a result, the CMP process advances.
In this way, with the CMP process, the target film on the substrate
106
is polished by both a chemical action (formation of a soft layer) and a mechanical action (polishing with grains).
In general, the polishing rate (i.e., polishing speed) in the CMP process varies dependent upon various factors, such as the temperature of the polishing surface, the pressing force against the polishing pad
102
, the backing pressure against the plate
113
, the rotation speeds of the platen
101
and the holder
110
, the surface roughness of the pad
102
, the distribution status of the slurry
104
, and the density of the grains in the slurry
104
.
With the prior-art apparatus of
FIG. 1
, there is a problem that the polishing rate is likely to be non-uniform due to the above-describe factors in the polishing plane. For example, if the desired or designed polishing rate is 500±50 nm/min, the actual polishing rate tends to have a dispersion as much as 50 to 100 nm/min over the whole substrate
106
. To avoid this problem, a variety of improvements has been made so far.
For example, the Japanese Non-Examined Patent Publication No. 11-33897 published in 1999 discloses a polishing apparatus for CMP. This apparatus comprises temperature detection means for detecting the temperature of a substrate and substrate heating means for heating a substrate, which are located in substrate holding means for holding a substrate. The substrate is heated with the substrate heating means in such a way that the in-plane temperature of the substrate is uniform. This apparatus makes it possible to uniformize the temperature as one of the factors affecting the polishing rate over the whole substrate.
The Japanese Non-Examined Patent Publication No. 11-121409 published in 1999 discloses another polishing apparatus for CMP. This apparatus comprises heaters arranged concentrically in a top ring (i.e., substrate holding means). The heat quantities from the respective heaters are adjusted to control the in-plane temperature distribution of the substrate in the radial directions. This apparatus makes it possible to control the in-plane polishing rate of a substrate.
With the prior-art apparatus of
FIG. 1
, as explained above, the polishing rate (i.e., the polishing speed) is likely to be non-uniform within the polishing surface. Therefore, there is a problem that a satisfactory or sufficient flatness is difficult to be realized over the whole substrate. The insufficient flatness will cause exposure error due to discrepancy in depth of focus in the lithography process and/or reliability degradation of wiring lines formed over uneven surfaces.
With the polishing apparatus disclosed by the Publication No. 11-33897, the temperature may be uniformized over the whole substrate. However, any other factors affect the polishing rate. Thus, there is a problem that satisfactory flatness of the substrate is not always formed over the whole substrate.
With the polishing apparatus disclosed by the Publication No. 11-121409, there is a problem as follows.
In general, heat is generated by friction within the polishing period to thereby raise (or fluctuate) the temperature of the polishing surface. Like this, with the apparatus of the Publication No. 11-121409, there is a possibility that temperature fluctuation of the polishing surface occurs due to friction heat within the polishing period and as a result, a desired polishing rate or speed is unable to be generated. Therefore, a problem that satisfactory flatness of the substrate is not always formed over the whole substrate occurs.
SUMMARY OF THE INVENTION
Accordingly, an object of the present invention is to provide a polishing method and a polishing apparatus for CMP that uniformize substantially the polishing
Hail III Joseph J.
Katten Muchin Zavis & Rosenman
McDonald Shantese
NEC Electronics Corporation
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