Electricity: measuring and testing – Fault detecting in electric circuits and of electric components – Of individual circuit component or element
Reexamination Certificate
1998-02-05
2001-06-19
Metjahic, Safet (Department: 2858)
Electricity: measuring and testing
Fault detecting in electric circuits and of electric components
Of individual circuit component or element
C324S754090, C324S1540PB
Reexamination Certificate
active
06249132
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to an inspection method and apparatus for inspecting the characteristics of an object and, more particularly, to an inspection method and apparatus for inspecting the physical characteristics, e.g., electrical characteristics of an object. In the present invention, components or finished products in various fields can be used as objects. For example, in the electronic field, the present invention can be applied to an object such as an integrated circuit formed on a semiconductor wafer, an IC chip, a printed board, or an electronic component such as an LCD.
Especially, the present invention can be applied to improve the inspection method and apparatus for inspecting the electrical characteristics of an integrated circuit formed on a semiconductor wafer (to be referred to as a wafer hereinafter).
Conventionally, an inspection method comprising the inspection step of inspecting the characteristics of an object and the unloading step of unloading the object which has undergone the inspection step, and an inspection apparatus for practicing the inspection method are used in various fields. When the inspection step is to be performed in a low-temperature environment, the surface of the object must be prevented from moisture condensation during inspection. Various techniques for this purpose, e.g., techniques of making the inspection chamber atmosphere cold and dry have been developed (Jpn. Pat. Appln. KOKAI Publication Nos. 60-180135, 62-54144, and 63-207928, and Jpn. Pat. Appln. KOKOKU Publication No. 7-111995). After inspection of the characteristics of the object in this atmosphere, the object is automatically unloaded by a convey mechanism.
The object which has undergone the inspection step is conveyed from the inspection chamber to a room-temperature environment. During or after this convey step, the object which has been cooled at the low temperature is moved to an environment at a high dew point. As a result, moisture condensation takes place on the surface of the object, so dust tends to attach to the surface. The present invention has as its object to prevent or minimize this moisture condensation to prevent or minimize dust attaching to the surface of the object.
The prior arts and their problems will be described in more detail by using a probe test apparatus in the semiconductor field.
FIGS. 5 and 6
show the conventional probe test apparatus in the semiconductor field. This probe test apparatus comprises a loader chamber
1
in which a convey mechanism for conveying and prealigning a wafer W is arranged, and a prober chamber
2
in which a means for inspecting the electrical characteristics of the wafer W conveyed from the loader chamber
1
is arranged. Fork
3
and a subchuck
4
are disposed in the loader chamber
1
. While the wafer W is being conveyed by the fork
3
, the subchuck
4
prealigns the wafer W with reference to the orientation flat. A main chuck
5
and an alignment mechanism
6
are disposed in the prober chamber
2
. The main chuck
5
on which the wafer W has been mounted aligns the wafer W with respect to probes
7
A of a probe card
7
in cooperation with the alignment mechanism
6
while moving in the X, Y, Z, and &thgr; directions. The probes
7
A electrically contact bonding pads on the wafer W and send an electrical signal from the bonding pads to a test section (not shown) through a test head T, so the test section inspects the electrical characteristics of the wafer W. The probe card
7
is detachably attached to a head plate
8
which constitutes the ceiling of the prober chamber
2
.
In an apparatus having a partition
9
between the loader chamber
1
and the prober chamber
2
, a loading/unloading port
9
A for the wafer W is formed in the partition
9
, and an opening/closing door
10
(
FIG. 1
) is attached to the loading/unloading port
9
A. This opening/closing door
10
is kept closed during inspection and opened when the wafer W is conveyed by the fork
3
between the loader chamber
1
and the prober chamber
2
.
The wafer W is inspected by room-temperature inspection, low-temperature inspection, or high-temperature inspection. For this purpose, the main chuck
5
has a temperature adjustment means. The temperature of the wafer W is set within a wide range from, e.g., −several ten ° C. to +160° C. using the temperature adjustment means. When the wafer W is to be inspected at a low temperature of −40° C., the temperature adjustment means cools the wafer W on the main chuck
5
to −40° C. In this case, dry air at a dew point of −40° C. or less is supplied to the prober chamber
2
to prevent moisture condensation and icing on the surface of the wafer W. After inspection, the fork
3
pick up the wafer W from the main chuck
5
and unload the wafer W from the prober chamber
2
to the loader chamber
1
.
When the wafer is inspected at a low temperature and then unloaded from the prober chamber
2
to the loader chamber
1
in the probe apparatus, moisture condensation takes place on the wafer surface (sometimes moisture freezes to result in icing). Dust tends to attach to the wafer surface due to moisture and contaminates the surface.
This is a common problem for inspection systems which perform the step of inspecting an object in a low-temperature environment and then conveying it to an environment at a higher temperature, e.g., room temperature.
BRIEF SUMMARY OF THE INVENTION
It is an object of the present invention to solve the above problem.
According to the first aspect of the present invention, there is provided an inspection method comprising the inspection step of inspecting predetermined characteristics of an object, the inspection step including inspection at least at a temperature not more than room temperature, and the unloading step of unloading the object which has undergone the inspection step, the unloading step including heating the object to a temperature at which moisture condensation does not occur on a surface of the object during and after the unloading step.
In the present invention, the “object” includes components or finished products in various fields. In, e.g., the electronic field, an integrated circuit formed on a semiconductor wafer, an IC chip, a printed board, or an electronic device such as an LCD can be exemplified as the object.
In the present invention, “inspection at least at a temperature not more than room temperature” includes, in addition to inspection at room temperature or less, a combination of inspection at room temperature or less and inspection at another temperature, e.g., a combination of inspection at room temperature or less and inspection at room temperature, or a combination of inspection at room temperature or less and inspection of room temperature or more.
In the present invention, the means for the “process of heating the object” can be selected from heating means using radiation heat from electric heating, heating means for spraying a gas (e.g., air) heated using electric heating or a vortex tube, and the like, in accordance with the nature of the object or desired heating speed.
The heating means can be set operative not only during the unloading step but also throughout the loading step, the inspection step, and the unloading step.
The timing of this process can also be set at any stage of the unloading step, or throughout the unloading step. When the unloading step is performed in the same environment as that in the inspection chamber, the heating step may be performed immediately after the unloading step.
According to the second aspect of the present invention, in the method of the first aspect, the heating step includes spraying a gas heated to a predetermined temperature to the object which has undergone the inspection step.
In the present invention, the “gas” used in the heating step can be selected from air, an inert gas, and the like in accordance with the nature of the object.
According to the third aspect of the present invention, in the method of the first aspect, the heating st
Hollington Jermele M.
Metjahic Safet
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
Tokyo Electron Limited
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