Electricity: measuring and testing – Impedance – admittance or other quantities representative of... – Lumped type parameters
Reexamination Certificate
1999-06-03
2001-10-30
Nguyen, Vinh P. (Department: 2858)
Electricity: measuring and testing
Impedance, admittance or other quantities representative of...
Lumped type parameters
C324S537000, C324S661000, C324S662000
Reexamination Certificate
active
06310482
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to an exposure system and more particularly to a capacitance gauge tracking apparatus used for an exposure system, a method for tracking a surface of a semiconductor device using the same, a leveling apparatus having a tracking apparatus and a leveling method, and to a semiconductor device made thereby.
2. Description of the Related Art
In a photolithography exposure system used in manufacturing of semiconductor devices, light beams are radiated on a photoresist layer overlying a semiconductor device substrate through a mask having predetermined transparent regions to expose predetermined regions in the photoresist layer. In order to form an accurate predetermined pattern in the photoresist during an exposure process, it is important to constantly control the exposure distance between the photoresist covered semiconductor device substrate and the light source of the exposure apparatus. The semiconductor device substrate should be leveled with respect to the light source by controlling the tilt degree and the position of the substrate mounted on a stage of the exposure system. That is, the focus distance between the substrate and the light source and/or the degree of tilt of the substrate should be controlled.
A prior art apparatus for leveling a substrate by controlling its focus distance or degree of tilt has a sub-unit for tracking the surface of the substrate to measure a distance between the surface of the substrate and the light source, such as an exposure slit. A capacitance gauge tracking apparatus that measures air capacitance (i.e., the capacitance between the probe and the substrate where the probe does not physically contact the substrate surface) may be used for tracking the surface of the semiconductor device substrate. In the capacitance gauge tracking apparatus, a probe tracks the surface of the substrate by being moved over the surface. A gauge measures a distance between the surface of the semiconductor device substrate and an exposure slit based on the signal from the probe. The measured signal from the gauge is fed back to an exposure system controller, such as a leveling apparatus stage controller. The controller positions a stage on which the substrate is mounted based on the measured signal. The photoresist layer on the semiconductor device substrate is then exposed by the light source of the exposure system.
FIG. 1
schematically shows a vertical structure formed on a semiconductor device substrate
10
, and
FIG. 2
schematically shows the result of tracking the surface of the semiconductor device substrate
10
using a capacitance gauge tracking apparatus.
Referring to
FIG. 1
, as the level of integration of semiconductor devices becomes higher, a step of a conductive layer
20
, such as a storage node, becomes greater. That is, in order to ensure sufficient capacitance to operate a memory cell in a cell array area of the semiconductor device, a thick conductive layer
20
, such as a doped polycrystalline silicon layer should be formed. A thick insulating layer
30
is required to overcome the large step of the thick conductive layer
20
. However, the insulating layer
30
is relatively thin in a portion
31
covering the upper portion of the conductive layer
20
, and relatively thick in a portion
33
burying the gap between the conductive layers
20
or in a portion covering a peripheral circuit area of the semiconductor device where the conductive layer
20
is not formed.
Referring to
FIG. 2
, when the surface of the semiconductor substrate is tracked by the capacitance gauge tracking apparatus, a measured value output by the apparatus oscillates in accordance with a position of the probe over the surface of the semiconductor substrate
10
. The measured value may be a voltage value or a focus value (i.e., the measured voltage value converted by the apparatus to a distance between the substrate and the light source). That is, the focus value oscillates with a period (shown as “P”, in
FIGS. 1 and 2
) corresponding to the period of oscillation in the thickness of the insulating layer
30
.
Therefore, a change in the thickness of the insulating layer
30
can have an effect on the substrate position value, such as the focus value, measured by the capacitance gauge tracking apparatus. Although there is no substantial change in the height of the surface of the semiconductor substrate
10
covered by layers such as
20
,
30
, etc., the value measured by the capacitance gauge tracking apparatus may oscillate instead to indicate a substrate of a varying height of being relatively steady to indicate a substrate of a constant height. Thus, a tracking error is present in the signal output by the tracking apparatus to the stage controller. The signal output by the tracking apparatus erroneously indicates the state of the surface of the semiconductor substrate
10
. The tracking error may cause the surface of the semiconductor substrate
10
to be misaligned with respect to the light source, such as the exposure slit of the exposure apparatus, by the stage controller of the leveling apparatus. That is, leveling failure or error may occur due to the tracking error. The leveling failure may greatly reduce a focus margin of the exposure process. The reduction in the focus margin may reduce an exposure process margin to generate an exposure failure which would lead to the eventual failure of the semiconductor device.
SUMMARY OF THE INVENTION
In view of the foregoing, it would be desirable to provide a capacitance gauge tracking apparatus and a leveling apparatus using the same, used for an exposure system for manufacturing a semiconductor device in which the tracking error can be reduced or prevented from being generated to suppress a reduction in a focus margin and leading to a more precise exposure system.
It would also be desirable to provide a method for tracking a surface of a semiconductor device and a method of leveling the semiconductor device in which a tracking error can be reduced or prevented from being generated to suppress reduction in a focus margin and leading to a more precise exposure process.
According to one embodiment of the present invention, there is provided a capacitance gauge tracking apparatus used for an exposure system for manufacturing a semiconductor device including a ground unit, a probe unit and a gauge unit.
The ground unit is electrically connected to a semiconductor device substrate. The probe unit is spaced apart from the semiconductor device substrate and receives a constant current of at least two different frequency bands to thereby track the surface of the semiconductor device substrate. The gauge unit measures the capacitance between the ground unit and the probe unit.
In a preferred aspect of this embodiment, the probe unit comprises at least one first probe to which a constant current of a first frequency is applied and at least one second probe to which a constant current of a second frequency is applied. The preferred constant current of the first frequency is approximately 50 Hz or less, and the preferred constant current of the second frequency is approximately 50~500 Hz.
According to another embodiment of the present invention, there is provided a leveling apparatus of an exposure system for manufacturing a semiconductor device including a stage, a stage driving unit, a ground unit, a probe unit, a gauge unit and a stage controller.
The stage is used for mounting a semiconductor device substrate. The stage driving unit is electrically connected to the stage and drives the stage to level the semiconductor device substrate. The ground unit is electrically connected to the semiconductor device substrate. The probe unit is spaced apart from the semiconductor device substrate and receives a constant current of at least two different frequency bands to thereby track the surface of the semiconductor device substrate. The gauge unit measures the capacitance between the ground unit and the probe unit. The stage controller is
Law Offices of Eugene M Lee, P.L.L.C.
Nguyen Vinh P.
Patel Paresh
Samsung Electronics Co,. Ltd.
LandOfFree
Capacitance gauge tracking apparatus used for exposure... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Capacitance gauge tracking apparatus used for exposure..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Capacitance gauge tracking apparatus used for exposure... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2603616