Abrading – Precision device or process - or with condition responsive... – By optical sensor
Reexamination Certificate
2001-05-02
2002-10-01
Rachuba, M. (Department: 3723)
Abrading
Precision device or process - or with condition responsive...
By optical sensor
C451S041000, C451S287000, C451S526000
Reexamination Certificate
active
06458014
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a polishing body, polishing apparatus, polishing apparatus adjustment method and polished film thickness or polishing endpoint measurement method which are suitable for use in the polishing of semiconductor devices in a method for manufacturing semiconductor devices such as ULSI devices, etc., and to a semiconductor device manufacturing method.
2. Discussion of the Related Art
As semiconductor integrated circuits have become finer and more highly integrated, the individual processes involved in semiconductor manufacturing processes have become more numerous and complicated. However, the surfaces of semiconductor devices are not always flat. The presence of step differences on the surfaces of semiconductor devices leads to step breakage of wiring and local increases in resistance, etc., and thus causes wiring interruptions and drops in electrical capacitance. Furthermore, in insulating films such step differences also lead to a deterioration in the withstand voltage and the occurrence of leaks.
Meanwhile, as semiconductor integrated circuits have become finer and more highly integrated, the wavelengths of light sources in semiconductor exposure apparatuses used in photolithography have become shorter, and the numerical aperture or so-called NA of the projection lenses used in such semiconductor exposure apparatuses has become larger. As a result, the focal depth of the projection lenses used in such semiconductor exposure apparatuses has become substantially shallower. In order to deal with such increasing shallowness of the focal depth, there is a demand for even greater planarization of the surfaces of semiconductor devices than that achieved so far.
Specifically, planarization techniques such as that shown in
FIG. 1
have become essential in semiconductor manufacturing processes. A semiconductor device
14
, and inter-layer insulating film
12
comprising SiO
2
and a metal film
13
comprising Al are formed on the surface of a silicon wafer
11
. FIG.
1
(
a
) shows an example of the planarization of an inter-layer insulating film
12
on the surface of the semiconductor device. FIG.
1
(
b
) shows an example in which a so-called damascene is formed by polishing a metal film
13
on the surface of the semiconductor device.
A chemical mechanical polishing or chemical mechanical planarization (hereafter referred to as “CMP”) technique is widely used as a method for planarizing the surfaces of such semiconductor devices. Currently, the CMP technique is the sole method that can be used to planarize the entire surface of a silicon wafer.
CMP was developed on the basis of silicon wafer mirror surface polishing methods.
FIG. 2
is a schematic structural diagram of a polishing (planarization) apparatus used in CMP. This polishing apparatus is constructed from a polishing member
15
, an object of polishing holding part (hereafter referred to as a “polishing head” in some instances)
16
, and a polishing agent supply part
18
. Furthermore, a silicon wafer
17
which is the object of polishing is attached to the polishing head
16
, and the polishing agent supply part
18
supplies a polishing agent (slurry)
19
. The polishing member
15
is formed by attaching a polishing body (hereafter referred to as a “polishing pad” in some instances)
21
to the surface of a platen
20
.
The silicon wafer
17
is held by the polishing head
16
, so that they are caused to oscillate while being rotated, and is pressed against the polishing body
21
of the polishing member
15
with a specified pressure. The polishing member
15
is also rotated, so that a relative motion is performed between the polishing member
15
and the silicon wafer
17
. In this state, the polishing agent
19
is supplied to the surface of the polishing body
21
from the polishing agent supply part
18
. The polishing agent
19
diffuses over the surface of the polishing body
21
, and enters the space between the polishing body
21
and the silicon wafer
17
as the polishing member
15
and silicon wafer
17
move relative to each other, so that the polishing surface of the silicon wafer
17
is polished. Specifically, good polishing is accomplished by a synergistic effect of the mechanical polishing caused by the relative motion of the polishing member
15
and silicon wafer
17
and the chemical action of the polishing agent
19
.
The relationship between the amount of polishing of a silicon wafer and the above-mentioned polishing conditions is given by an empirical formula known as the formula of Preston, which is indicated by Equation (1).
R=K×P×V (1)
Here, R is the amount of polishing of the silicon wafer, P is the pressure per unit area with which the silicon wafer is pressed against the polishing body, V is the relative linear velocity caused by the relative motion between the polishing member and the silicon wafer, and k is a proportionality constant.
Conventionally, the endpoint of CMP polishing has been determined by time control using the formula of Preston on the basis of the polishing rate calculated by means of film thickness measurement using an ellipsometer, etc., after polishing several tens of dummy samples and performing a cleaning process. In CMP, however, variation occurs in the polishing rate because of the temperature distribution of the polishing body and local differences in the polishing agent supply conditions. Furthermore, because of variations in the surface conditions of the polishing body, the polishing rate drops with the number of wafers processed, and there are differences in the polishing rate due to individual differences between polishing bodies, etc. Accordingly, it is difficult to determine the endpoint of polishing by performing a specified amount of polishing using time control.
Furthermore, the time control method requires polishing work using as many as several tens of dummy samples in order to determine the polishing rate. Accordingly, this polishing work results in increased costs, and is therefore undesirable for stabilizing the semiconductor device manufacturing process and reducing production costs.
Accordingly, methods in which the endpoint of polishing is determined while measuring the motor torque or vibration, etc., in situ have been proposed as a substitute for endpoint determination by time control. Such methods are effective in the case of CMP wherein the material of the object of polishing varies (e.g., CMP of wiring materials or CMP in which there are stopper layers). However, in the case of silicon wafers having complicated patterns, there is little variation in the material of the object of polishing. Accordingly, there are cases in which it is difficult to ascertain the endpoint. Furthermore, in the case of CMP of inter-layer insulating films, it is necessary to control the inter-wiring capacitance. Accordingly, control of the residual film thickness is required rather than control of the polishing endpoint. It is difficult to measure the film thickness using a method in which the endpoint is ascertained by in-situ measurement of the motor torque or vibration, etc.
Recently, optical measurements, especially in-situ endpoint detection and in-situ film thickness measurement based on the measurement of spectroscopic reflections, have come to be viewed as effective means of solving the above-mentioned problems. For instance, one example of such measurement is described in U.S. Pat. No. 5,433,651. For such in-situ measurements, a common method is a method in which an opening part
22
used for measurement is formed in the platen
20
and polishing body
21
a shown in
FIG. 2
, and the surface of the object of polishing is observed by means of a polished-state measuring device
23
that measures the polished state via this opening part
22
. Although not shown in
FIG. 2
, a transparent window is generally installed in the polishing body
21
, etc., in order to close off the opening part. By installing such a window, it is possible to allow the
Ihsikawa Akira
Miyaji Akira
Senga Tatsuya
Ushio Yoshijiro
Morgan & Lewis & Bockius, LLP
Nikon Corporation
Rachuba M.
Thomas David B.
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