Electricity: measuring and testing – Measuring – testing – or sensing electricity – per se – With rotor
Reexamination Certificate
1998-11-20
2001-01-09
Metjahic, Safet (Department: 2858)
Electricity: measuring and testing
Measuring, testing, or sensing electricity, per se
With rotor
C324S754090, C333S033000
Reexamination Certificate
active
06172497
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a high-frequency wave measurement substrate used for measuring electrify characteristics of semiconductor elements, semiconductor element package or circuit boards which use a microstrip line in high frequencies such as microwaves and millimeter waves, more particularly to a wide-band low-loss high-frequency wave measurement substrate whose measurable frequency band is enhanced.
2. Description of the Related Art
For measurement and evaluation of electric characteristics of a semiconductor element, a semiconductor element package or circuit board in a high-frequency band such as a microwave or a millimeter wave, a wafer probe is used at the measuring instrument side, which comes in contact with a coplanar line to enable its highly accurate measurement. On the other hand, a microstrip line is usually used as a transmission line at an input/output part of a measurement object such as a fast digital or high-frequency circuit for radio communication apparatuses using high-frequency wave signals, a high-frequency semiconductor element, and a package for housing such a high-frequency semiconductor element. Consequently measurement of electric characteristics in a high-frequency wave using a wafer probe needs a line converter to cope with a connection between the coplanar line of the wafer probe and the microstrip line of the measurement object. The line converter is required to transmit high-frequency wave signals without so much loss thereby to extract the characteristics of the object very accurately.
Conventionally, the line converter has been generally designed to have such a structure that the widths of signal and ground conductors of the coplanar line portion correspond to the sizes required by a wafer probe head. One end of the converter is connected to one end of the microstrip line so that the signal conductor width is changed smoothly on both sides-. The ground conductor of the coplanar line is thus connected to the ground conductor of the microstrip line via a through conductor such as a through-hole and a via hole.
FIG. 16
shows a top view of the structure of a conventional line converter. A conductor film is applied to almost the entire of the bottom surface of a dielectric substrate
1
having a relative dielectric constant of 9.6 and a thickness of 200 &mgr;m to form a ground conductor. Then, the width of the signal conductor
2
of the microstrip line portion and the width of the signal conductor
3
of the coplanar line portion are set to 190 &mgr;m and 160 &mgr;m, respectively, and the interval between the signal conductor
3
of the coplanar line portion and the ground conductors
4
and
4
′ is set to 135 &mgr;m. The ground conductors
4
and
4
′ are electrically connected to the ground conductor formed on the bottom surface via 150 &mgr;m diameter through-holes
5
and
5
′ which are through conductors. The structure of each ground conductor of the coplanar line portion is thus formed like a through-hole pad. If the electric characteristics are measured and extracted from those two ground conductors of the same shape formed as described above and placed so as to face each other symmetrically like an object and its mirror image via the microstrip line portion, the frequency characteristics as shown in
FIG. 17
are obtained.
In
FIG. 17
, the lateral axis indicates frequencies in units of GHz, and the ordinate axis indicates transmission coefficients in units of dB used as evaluation indices for the amount of transmitted signals of all the input signals. The characteristic curve indicates the frequency characteristics for transmission coefficients. From this measurement result it is found that the higher the frequency is, the smaller the transmission coefficient is and the more the amount of transmitted signals is reduced.
In addition to such a high-frequency wave measurement substrate composed as described above, there is also another type high-frequency wave measurement substrate disclosed as “Microstrip Line portion Measurement Jig” in Japanese Registered Utility Model Publication JP-Z2 2507797. Unlike the above measurement substrate, this jig is formed by converting the coplanar line and the microstrip line without using any through conductors such as through-holes and via holes. According to JP-Z2 2507797, a measurement jig (measurement substrate)
10
is structured as shown in
FIG. 18
(top view) so that the tip of a microstrip line
12
provided on an dielectric substrate
11
which has a ground conductor on its bottom surface is stepped or tapered. Its width is thus matched with the width of a center conductor of a probe head
13
and connected to the center conductor. Then, around the tip of the microstrip line
12
is formed an equivalent ground with a semi-circular or an approximate semi-circular fan-shaped radial stub
14
thereby to correspond to two ground line conductors of a probe head
13
. In addition, the radius of a radial stub
14
is decided to be an effective length of about ½ wavelength of the lower limit of the measurement frequency.
The utility model has proved that measured data can be reproduced very well with such a configuration of the measurement jig, since no connecting means is used between the ground conductors for connecting the probe head
13
to the measurement jig
10
using an element whose characteristics are varied like the ribbon bonding and the through conductor described above.
It may be said that the principle of the equivalent ground formed with this semi-circular or fan-shaped radial stub
14
is equivalent to a general phenomenon of the radial stub to occur in a high-frequency wave circuit.
In other words, on the basis of IEEE TRANSACTIONS ON MICROWAVE THEORY AND TECHNIQUES, VOL. 36, NO. 7, JULY 1988 “A Coplanar Probe to Microstrip Transition”, a reactance value X of a radial stub
15
shaped as shown in
FIG. 19
(top view) will be represented in the following expressions, wherein h is a thickness of the substrate on which this radial stub
15
is formed, r
1
and r
2
are inner and outer diameters of the radial stub
15
, &thgr; is a radial center angle, &egr;
re
is an effective relative dielectric constant in the case where a high frequency wave signal transmits a radial along a radius, &lgr;
0
is a free space wavelength of the high frequency wave signal.
X
=
h
2
π
r
1
Z
0
(
r
1
)
360
θ
·
cos
(
θ
1
-
ψ
2
)
sin
(
ψ
1
-
ψ
2
)
(
1
)
tan
θ
1
=
N
0
(
kr
1
)
J
0
(
kr
1
)
(
2
)
tan
ψ
1
=
-
N
i
(
kr
1
)
J
i
(
kr
1
)
,
(
i
=
1
,
2
)
(
3
)
Z
0
(
r
1
)
=
120
π
ϵ
re
·
J
0
2
(
kr
1
)
+
N
0
2
(
kr
1
)
J
i
2
(
kr
1
)
+
N
i
2
(
kr
1
)
(
4
)
k
=
2
π
ϵ
re
λ
0
(
5
)
In the above expressions, J
i
(x) and N
i
(x) are i-order Bessel functions.
According to the principle, the operation of the radial stub in a high-frequency wave goes into an almost perfect reflection state, so that the radial stub can be regarded to be an equivalent ground. Accordingly the radial stub with such an effect is usable as an equivalent ground in a high-frequency wave measurement substrate. The radial stub
14
disclosed in JP-Z2 2507797 uses such effect, and characteristics of a high-frequency wave measurement substrate of the radial stub are extracted.
FIG. 22
is a top view indicating a conventional high-frequency wave measurement substrate which uses a radial stub. The conventional high-frequency wave measurement substrate is formed as a fan-shaped radial stub having inner and outer diameters of 215 &mgr;m and 580 &mgr;m, respectively, and a center angle of 230° in such a manner that firstly a metallic film as a ground conductor is coated almost all over the bottom surface of an dielectric substrate
21
having a relative dielectric constant of 9.6 and a thicknes
Hogan & Hartson LLP
Kyocera Corporation
Metjahic Safet
Tang Minh
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