Electricity: measuring and testing – Electrostatic field – Using modulation-type electrometer
Reexamination Certificate
2000-10-18
2002-10-15
Le, N. (Department: 2858)
Electricity: measuring and testing
Electrostatic field
Using modulation-type electrometer
C324S750010, C324S765010
Reexamination Certificate
active
06466027
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an apparatus for measuring an electrostatic charge and particularly to an apparatus for measuring an electrostatic charge born on a semiconductor device.
2. Description of the Related Art
A semiconductor device is commonly produced by: forming a plurality of semiconductor devices on a substrate of Si (silicon) or GaAs (gallium arsenide); sawing or machining the substrate into individual semiconductor devices (each referred to as a die) by the dicing process; mounting the die in a package and connecting electrodes formed on the die to external leads using gold wires; and finally completing the manufacturing procedure by sealing the package in, for example, resin.
Quality deficiencies in semiconductor devices have been caused by failures in the processes of forming semiconductor devices on a substrate: for example, failure in the photolithography to form a pattern of a designed size; and penetration fault of a contact hole to be penetrated through an insulator layer to connect upper and lower wiring layers.
Recently, the tendency of decreasing a size of a semiconductor device has carried about a deteriorated immunity from static electricity of a semiconductor device. As a result, quality deficiencies caused by static electricity have increased in addition to those caused by faulty processes as described above.
The present inventor et al. have disclosed an apparatus for measuring an electrostatic charge to track the sources of the deficiencies in Japanese Patent Publication No. 2908240.
The measuring apparatus will be set forth with reference to the drawings below.
FIG. 1
is a schematic diagram of the apparatus described in the quoted literature. A dielectric substance
4
of a known dielectric constant surrounds a metal rod
14
. Grounded metal plate
15
covers dielectric substance
4
.
The wiring arranged between an object to be measured and dielectric substance
4
is positionally fixed with respect to dielectric substance
4
to keep the relative position unchanged, thereby preventing measured values from being varied by a deformation of the wiring. Since metal plate
15
shields metal rod
14
from an external electromagnetic wave, the measurement of the electrostatic charge is screened from an electromagnetic induction. Furthermore, dielectric substance
4
is configured so as to set up a distributed capacity along the path through which the charge to measured conducts. This configuration of dielectric substance
4
allows the distributed capacitor to be charged delaying successively from the proximity of the object to be measured, thereby preventing voltmeter
5
from being instantaneously applied with a high electric tension of the object. In this way, the electrostatic charge to be measured is prevented from leaking through voltmeter
5
to the ground.
FIGS.
2
(
a
) and
2
(
b
) represent an example in which the above-described measuring apparatus is applied to the manufacturing process of an LSI.
In this example, an electric charge was measured that was created at a lead terminal caused by dynamic friction when LSI
16
was slid on a sloped metal rail
17
and carried from the top to the bottom, as is shown in FIG.
2
(
a
).
Such a carrying system has been often employed in a process step of manufacturing an LSI. The measurement is carried out by two procedures: the preliminary procedure and the measurement procedure. The preliminary procedure is performed, as is shown in
FIG. 1
, by connecting metal plate
15
arranged outermost of the measuring apparatus to the ground potential; connecting voltmeter
5
between the top end of inner metal rod
14
and the ground potential; and sufficiently discharging the capacitor made up of metal rod
14
, metal plate
15
and dielectric substance
4
by shortcircuiting metal rod
14
and metal plate
15
.
Next, the measurement procedure is carried out, as is shown in enlarged exploded FIG.
2
(
b
), by bringing the pointed bottom tip of metal rod
14
into contact with lead terminal
18
of LSI
16
that has slid down on metal rail
17
; and observing the value indicated in voltmeter
5
and calculating electric charge caused by the dynamic friction Q from the equation Q=CV.
Lately, the tendency toward miniaturizing a semiconductor device such as an MR head (magneto-resistive head) for reading magnetic data in semiconductor ICs (a DRAM, a processor and a CCD) and a hard-disk has been rapidly advanced.
Miniaturizing of semiconductor devices entails high susceptibility to an electrostatic charge created on a semiconductor device while it is manufactured, assembled and practically used. For this reason, there is an urgent need to improve a technique for measuring an electrostatic charge born on a semiconductor device to protect the device from problems caused by the electric charge.
The traditional measuring apparatus employing a coulomb meter has been difficult to measure an electrostatic charge induced within the semiconductor device, while it has been useful for the measurement of an electrostatic charge externally charged on the sample to be subjected to the measurement.
However, there are many process steps in a manufacturing line in which an electric charge is induced in a product, for example, the step of adsorption by a nozzle and the step of mounting a semiconductor device to a substrate. Since the traditional measuring apparatus is unable to measure an electric charge charged on a product from an external source, for example, from a charged human body, a problem encountered has been that it is impossible to track the source of a defect of a product presumably caused by a charge induced within the product. As a result, it has been impossible to eliminate deficiencies arising from electrostatic charge charged in a manufacturing line.
The background of the above-described problem is that in the front-end techniques since 1997, the products such as a hard disk of a high storing density, a liquid crystal display for displaying a picture of a high definition and a plasma display as well as an electronic device have suffered from troubles due to an electrostatic charge and such troubles take place very frequently not only in a manufacture line but also in an assembly line.
For example, the wiring rule of a large-scale integrated circuit is now going down to less than 0.25 &mgr;m and will presumably reach 0.18 &mgr;m in 2000. Furthermore, the area of each pixel in a picture CCD has been miniaturized in order to improve fineness of a picture.
A storing density of a hard disk, on the other hand, has been increased to as high as 5-15 GBit/inch
2
, which has enabled the realization of a miniaturized head for read and/or write.
In the field of the liquid crystal display (LCD) as well, improvement of the resolution has been advanced through miniaturization of a display pixel. As the digital broadcast becomes full-fledged and the high-vision TV becomes widespread in the near future, the pixels in the picture display such as a plasma display will be miniaturized entailing susceptibleness to an electrostatic charge.
The minimum quantity of the static electricity that affects a miniaturized semiconductor device is not included in the range of the precision of the above-described traditional apparatus. Thus, an improvement of the apparatus is required.
In Southeast Asia where manufacture sites have shifted to as well as in Japan, U.S.A. and Europe, problems caused by static electricity in manufacture lines and markets have been occurring in rapid succession. Thus, there is an urgent need to eliminate such problems. For this reason, it is necessary to provide for measurement of an electrostatic charge with improved precision and simplicity.
It is an object of the present invention to provide an apparatus capable of measuring an electrostatic charge induced within a test sample while the conventional method has been capable of measuring only an externally charged electrostatic charge. The present invention is specifically directed to eliminating pro
Hayes & Soloway P.C.
Kerveros James
Le N.
NEC Corporation
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