Electricity: measuring and testing – Fault detecting in electric circuits and of electric components – Of individual circuit component or element
Reexamination Certificate
1998-10-30
2001-10-30
Metjahic, Safet (Department: 2858)
Electricity: measuring and testing
Fault detecting in electric circuits and of electric components
Of individual circuit component or element
C324S755090, C324S762010
Reexamination Certificate
active
06310483
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a high-frequency probe such that one end of a conductor is pressed to an electrode of a device-under-test (DUT) arranged on a device stage and the other end is connected to the external conductor through a coaxial connector connected to another end of this inner conductor. And in particular, the present invention relates to a high-frequency probe that makes it possible to measure the device not having a ground electrode on a surface of the device-under-test (DUT), to correspond to a device having narrowly-pitched electrodes or multiple pins, and to secure durability by simplification of point conciseness.
Conventionally, in this type of high-frequency probe, as shown in
FIGS. 1A through 1C
, and
FIG. 2
, at an end of a probe
100
, a signal contact
101
and ground contacts
102
and
102
A are contacted with three corresponding device electrodes arranged on the surface of the device-under-test (DUT)
120
, which is called as coplanar type. These device electrodes are aligned in a row in the horizontal direction on the surface of the device-under-test (DUT)
120
. Normally, as inner conductor
103
positioned in the center of the probe
100
becomes the signal contact
101
, and contacts to a signal electrode
113
of the device-under-test (DUT)
120
. In addition, a outer conductor
104
of the probe
100
is formed as ground contacts
102
and
102
A on the left and right of the signal contact
101
at the end of the probe
100
, and contacts to ground electrodes
118
of the device-under-test (DUT)
120
.
As shown in
FIG. 3
, let thickness of the signal electrode
113
of the device-under-test (DUT)
120
be represented by “tsig” and let the thickness of the ground electrode
118
be represented by “tgnd”. Usually, as shown in
FIGS. 4A through 4C
, combination of these thicknesses “tsig” and “tgnd” is “tsig=tgnd” (FIG.
4
A), “tsig>tgnd” (FIG.
4
B), and “tsig<tgnd” (FIG.
4
C). This means that the end of the probe
100
must have elasticity since a uniform pressure amount is necessary for the signal electrode
113
and ground electrode
118
at the end of the probe
100
.
Nevertheless, it is difficult to make a coaxial line of the probe
100
have the elasticity. Therefore, with using members having the elasticity as the inner conductor
103
and outer conductor
104
, the signal contact
101
and ground contacts
102
and
102
A are made to have the elasticity.
In this type of construction, the signal electrode and ground electrode of the device-under-test (DUT) should have the same arranged intervals as those of the probe contacts and should exist on the same plane as that of the probe contacts. Nevertheless, some probe contacts have such construction that the signal electrode and ground electrode are vertically aligned with defining a device stage as the reference ground against a case that the ground electrodes do not exist on the device surface, for example, they are on the back surface. In this case of longitudinal construction, so as to absorb unevenness of height of the device electrodes, a large vertically-movable range is necessary, and hence simple alignment cannot deal with this problem.
In addition, in case the ground electrodes and signal electrode are on a device surface and the arranged intervals of electrodes of a coplanar type device-under-test (DUT) are the same as those of the probe contacts, contact is possible. Nevertheless, distribution of electric force lines at the time of contact differs according to dispersion of electrode height, and in consequence, characteristic impedance of the probe varies. Hence, accurate measurement cannot be performed.
Although the impedance does not change due to electrode height (thickness) at the time of contact if end faces of the ground device electrodes of the device-under-test (DUT) is made to coincide with the end faces of the ground contacts, mutual alignment is difficult. From the viewpoint of the device side, since two ground electrodes should be provided for one signal electrode on the same plane so as to correspond to conventional probe contacts, the size of the device becomes large, and hence cost also increases.
In particular, compound devices such as GaAs devices have wafer cost more expensive than that of silicon. For this reason, in mass-production devices, both of cost reduction and security of high-frequency characteristics are realized by not providing ground electrodes on the same plane, making a chip area small and making wafer thickness thin, and assigning the back side to a ground electrode surface.
If the signal electrode and ground electrodes of the device-under-test (DUT) are apart from each other, the probe contacts can contact to them by making intervals of the probe contacts coincide with those of the device-under-test (DUT). Nevertheless, since the distance between the signal contact and ground contacts changes at an end part of the probe, impedance mismatching arises, and hence accurate measurement cannot be performed.
In order to reduce the influence of this mismatching, electrode length should be shortened. Nevertheless, so as to make the probe have the elasticity, the probe contacts should have some extent of length and thinness. By elongating the probe contacts, the characteristics get worse due to impedance mismatching. Furthermore, thin probe contacts are easily broken by overdrive at the time of contact.
On the other hand, since a body over from a coaxial connector positioning in a base part to the end part has predetermined size, this probe can be applied to device electrodes with inclining the probe against the plane so as to shorten the length of the relatively thin probe contacts. Nevertheless, since the probe contacts deeply bite into the device electrodes due to reduction of the elasticity and overdrive of the probe contacts, damage to the probe contacts becomes large.
In addition, usually, a device having a good high-frequency characteristic has a backside used as a whole-surface ground so as to obtain a good grounding characteristic. In particular, in LSIs (large scale integrated circuits) described later, line width becomes small, and hence the ground surface is approached to the signal lines on the surface by making the device thin so as to obtain a predetermined impedance characteristic, for example, 50&OHgr;. In consequence, the ground electrodes are not on the same plane as that of the signal electrode, and the ground surface exists at a near position in the plane. Therefore, if the ground surface is formed on the whole surface of the backside, the probe having the above-described construction cannot contact.
In addition, conventional probe contacts have such structure that the ground electrode, signal electrode, and ground electrode are horizontally aligned in this order in the direction being perpendicular to the pressure direction at the time of contact to device electrodes. Therefore, this type of probe cannot deal with a case that signal electrodes are aligned in narrow pitches like those of LSI. Although probes that can deal with narrowly-pitched electrodes or multiple pins exist, the ground electrodes are not structurally stretched to the end of each probe. Therefore, since the impedance mismatching, crosstalk between signal electrodes, and the like arise, they cannot be used in high-frequency domains.
As described above, conventional high-frequency probes have the following problems.
A first problem is that correspondence is very difficult or impossible if the signal electrode and ground electrodes of a device-under-test (DUT) such as a microstrip type are not arranged in the same plane.
Its reason is that, since the probe contacts contacting to the device electrodes are horizontally aligned on the same plane and the pitches of the probe contacts coincide with the pitches of device electrodes in such alignment, the probe contacts cannot contact to the device electrodes not having this construction.
A second problem is that, if the signal electrode and ground electrodes of a device-und
Hayakawa Satoshi
Inoue Hirobumi
Matsunaga Kouji
Tanehashi Masao
Taura Toru
Kerveros James
Metjahic Safet
NEC Corporation
Ostrolenk Faber Gerb & Soffen, LLP
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