Electricity: measuring and testing – Fault detecting in electric circuits and of electric components – Of individual circuit component or element
Utility Patent
1998-05-04
2001-01-02
Nguyen, Vinh P. (Department: 2858)
Electricity: measuring and testing
Fault detecting in electric circuits and of electric components
Of individual circuit component or element
Utility Patent
active
06169409
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a prober for testing the electrical characteristics of an object to be tested, at a low temperature.
A conventional prober for testing the electrical characteristics of an object at a low temperature will now be described in connection with an example the prober for testing the electrical characteristics of integrated circuits formed on a semiconductor wafer. In the loader chamber
1
, a fork
3
and a sub-chuck
4
are provided. A wafer W is placed by the fork
3
, on the sub-chuck
4
, where the wafer W is pre-aligned with respect to the orientation flat of the wafer W. In the prober chamber
2
, a main chuck
5
and an alignment mechanism
6
are provided. The alignment mechanism
6
moves the main chuck
5
in the X, Y and &thgr; directions, so as to align an electrode of an IC chip formed on the wafer W placed on the main chuck
5
, with a probe
7
A of a probe card
7
situated above the main chuck
5
. An insert ring
9
is fixed to a head plate
8
which constitute a ceiling surface of the prober chamber
2
, and the probe card
7
is detachably mounted to the insert ring
9
. In order to test the electrical characteristics of the wafer W, the aligned main chuck
5
is moved in the X, Y and Z directions, so as to bring the electrode pads of the IC chips into electrical contact with the probe
7
A one after another. Thus, each time the electrical contact is made, the electrical characteristics of the IC chips are tested via a test head T.
The testing of an object may be carried out at room temperature, low temperature or high temperature. Therefore, the main chuck
5
is equipped with a temperature adjusting mechanism for carrying out the test at necessary temperature. With the temperature adjusting mechanism, the temperature of the wafer W placed on the main chuck
5
is set in, for example, a range from several tens of ° C. below zero to room temperature, or a wide range from several tens of ° C. below zero to 160° C. In the case where an IC chip is tested at a low temperature of −40° C., the wafer W placed on the main chuck
5
is cooled down to −40° C. by the temperature adjusting mechanism. In the case of such a low-temperature test, a dry gas having a dew point much lower than −40° C., for example, dry air having a dew point of −70° C., is supplied into the prober chamber
2
, so as to prevent condensing or icing from occurring on the surface of the wafer W during the low-temperature test. In order to shut the prober chamber
2
from outside, a shutting plate
10
is mounted on the insert ring
9
on the outer side of the probe card
7
, and thus a space S defined by the probe card
7
, the plate
10
and the insert ring
9
is created.
The space S in the insert ring in the conventional prober is shut off from outside by the plate
10
, and is separated from the prober chamber
2
by the probe card
7
. With this structure, even if the dry air is supplied into the prober chamber
2
during the low-temperature testing, the space S cannot be easily ventilated. As a result, the air having a high dew point in the prober chamber
2
remains in the space S. Consequently, if the air contained in the space S and having a high dew point leaks into the probe chamber
2
during the low-temperature test, and the air is brought into contact with the wafer W cooled at a low temperature, for example, −40° C., the moisture carried in the air condenses and ices instantaneously on the surface of the wafer W, and the connection between the probe
7
A and the electrode pad of the IC chip is blocked. This results in the lowering of the reliability of the test. Particularly, in the test environment where the dew point is as low as −70° C., if air having a high humidity enters the prober chamber
2
, the condensing and icing phenomena of the moisture of the air become further prominent.
BRIEF SUMMARY OF THE INVENTION
An object of the present invention is to provide a low-temperature testing method for a prober for testing the electrical characteristics of an object at low temperature, and a prober for performing such a test method.
Another object of the present invention is to a low-temperature testing method appropriate for testing the electrical characteristics of integrated circuits formed on a semiconductor wafer (to be called simply “a wafer”) at low temperature, and a prober for performing such a test method.
Still another object of the present invention is to provide a low-temperature testing method capable of preventing the condensing and icing occurring on the surface of a semiconductor wafer during a low-temperature test, thereby achieving a highly reliable test, and a prober for performing such a test method, designed to solve the above-described problem of the prior art technique.
According to the first aspect of the present invention, there is provided a method of testing electrical characteristics of an object to be tested, at a predetermined low temperature, in a prober comprising:
a prober chamber;
a main chuck on which the object is placed in the prober chamber, the main chuck including a temperature adjusting mechanism for cooling the object to the predetermined low temperature;
a probe card with probes for testing the electrical characteristics of the object as being brought into contact with electrical pads of the object placed on the main chuck;
a ring-like member fixed to an upper portion of the prober chamber, for detachably supporting the probe card; and
a plate provided for the ring-like member, at a position outward of the probe card, the plate creating a space defined by the ring-like member between the probe card and the plate itself,
the method comprising:
(a) supplying dry gas which does not condense at the predetermined low temperature at which the object is tested, to the prober chamber;
(b) replacing a gas in the space with the dry gas;
(c) cooling the object to be tested to the predetermined low temperature by the temperature adjusting mechanism; and
(d) testing the electric characteristics of the object at the low temperature.
According to the second aspect of the present invention, there is provided a testing method according to the first aspect, wherein the step (b) is carried out by supplying the dry gas which does not condense at the predetermined low temperature at which the object is tested, to the space from an outside of the prober chamber.
According to the third aspect of the present invention, there is provided a testing method according to claim
1
, wherein the step (b) is carried out by supplying the dry gas supplied to the prober chamber in the step (a), to the space via the probe card.
According to the fourth aspect of the present invention, there is provided a prober comprising:
a main chuck on which an object is placed in the prober chamber, the main shuck including a temperature adjusting mechanism for cooling the object to the predetermined low temperature;
a prober chamber in which the main chuck is placed, the prober chamber is filled with dry gas which does not condense at the predetermined low temperature;
a probe card with probes for testing the electrical characteristics of the object as being brought into contact with electrical pads of the object placed on the main chuck;
a ring-like member fixed to an upper portion of the prober chamber, for detachably supporting the probe card; and
a plate provided for the ring-like member, at a position outward of the probe card, the plate creating a space defined by the ring-like member between the probe card and the plate itself; and
a dry gas supplying mechanism for supplying a dry gas which does not condense at the predetermined low temperature to the space, thereby replacing the gas in the space with the dry gas.
According to the fifth aspect of the present invention, there is provided a prober according to the fourth aspect, wherein the dry gas supply mechanism is of a type for supplying dry gas which does not condense at the predetermined low temperature at which the object is tested, t
Nguyen Vinh P.
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
Tokyo Electron Limited
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