BACKGROUND OF THE INVENTION
FIELD OF THE INVENTION
The present invention relates to an apparatus for automatically testing, calibrating and characterizing test adapters for semiconductor devices. The semiconductor devices are preferably integrated semiconductor circuits.
During the testing, calibration and characterization processes, the radio-frequency characteristics of the test adapters are investigated, in particular. However, it is also possible to investigate direct-current characteristics.
A test adapter may be, for example, what is referred to as a test card, by means of which semiconductor chips are tested at wafer level. Another example of a test adapter is a socket board, into which individual modules are introduced for testing.
In test systems for testing, say, semiconductor chips at wafer level, test cards are used, as is known, as test adapters. These test cards produce the electrical connection between contact points on the semiconductor chips in a wafer to be tested and at least one test channel in the test system. Reference is had, in this context, to FIG. 9 which shows a plan view of one possible exemplary arrangement of contact surfaces 2 in an edge area 3 of a motherboard of a test card 1. It should be understood, however, that other configurations of a test card are also feasible as an example of a test adapter. The contact surfaces 2 produce a contact with the test channels in the test system, and are preferably located on a number of circles with different radii in the edge region 3. A large number of contact needles are provided on the lower face of the test card 1, and are to fit such that they reliably make contact with the contact points on the chip at wafer level to be tested. These contact needles are preferably located in the inner area of the test card. In this case, each contact surface 2 has at least one associated contact needle. This means that the contact needles are electrically related with the associated contact surfaces 2 in a precisely defined manner.
In the socket boards mentioned initially, the contact surfaces 2 are arranged in the form of a square, rather than in the circular configuration above.
In general, test adapters such as test cards are matched to different semiconductor devices to be tested, that is, to their contact points. The appropriate different test adapters are therefore required for different types of semiconductor devices. The test adapters therefore make it possible to use the same test system even for different types of semiconductor devices.
We have, however, identified the fact that the electrical characteristics of the test adapters used for testing semiconductor devices have a considerable influence on the test results, and hence also on the test yield. In other words, the electrical calibration and/or characterization of test adapters is an important element, which should not be underestimated, in the analysis of an overall test system.
In the past, scarcely any investigations have been carried out into the influence of test adapters on various electrical parameters, such as line impedance, signal delay times, signal rise times or crosstalk between their various channels in different test systems, due to the large number of channels, which is currently around 1600 for test cards and will amount to 3200 in the near future. In other words, the influence of test adapters on signal performance and signal integrity in test systems has scarcely been considered so far.
In the current state of the art only a single appliance exists, which has not yet been described in any great detail, on the market, which allows semiautomatic measurement of the line impedance and of the signal delay times in test cards. In that case, electrical contact is made with the test card to be investigated via an interface board, which produces the connection between a test head of a test system and the test card even during normal operation of the test card. That appliance can therefore be used only with test systems provided with this interface board and not in general form for test cards for test systems with a different type of interface board, as well. Furthermore, only a relatively small subset of the channels can be measured automatically with the known appliance, as well. If it is intended to evaluate the channels of a different subset, then a manual change must be made to contact plugs for this subset. The measurement of crosstalk effects between the channels of different subsets is thus likewise impossible with the known appliance. Thus, until now, such a measurement could be carried out only manually and, due to the large number of channels, this was associated with an extremely long time penalty.
SUMMARY OF THE INVENTION
It is accordingly an object of the invention to provide an apparatus for automated testing, calibration and characterization of different test adapters, which overcomes the above-mentioned disadvantages of the heretofore-known devices and methods of this general type and which allows for any desired channels of the test adapter to be measured automatically.
With the foregoing and other objects in view there is provided, in accordance with the invention, an apparatus for automated testing, calibration and characterization of test adapters for semiconductor devices. The novel apparatus comprises:
a holder for holding a test adapter;
at least one probe head adjustably disposed relative to the holder, the probe head having two or more contact pins whose with an adjustable spacing distance therebetween; and
an adjustment device configured to adjust the probe head relative to the holder.
In other words, the objects of the invention are achieved in the context of an apparatus of the type mentioned initially, by a holder for the test adapter and at least one probe head, which can be adjusted with respect to the holder and has at least two contact pins (whose spacing is adjustable).
The distance between the at least two contact pins on a probe head can be matched to the distance, which differs with different test adapters to be calibrated or wherein, between the contact surfaces for signals and the associated shields.
The holder can in this case hold test adapters with different diameters.
The apparatus according to the invention thus has, in particular, the holder which can rotate to hold test adapters with different diameters. This holders allows the test adapter to be rotated in a defined manner in the apparatus. A stepping motor or the like may be used as the drive for this rotation of the holder.
Furthermore, the apparatus according to the invention has one or more robot arms, which can be moved in a horizontal direction, running parallel to the plane of the test adapter, and also in a direction at right angles to this. In this case, a probe head is fit on each robot arm.
These robot arms and the rotation of the holder allow the probe heads and their contact pins to be positioned on the contact surfaces of the test adapter.
The apparatus can be matched directly to widely differing test adapters by appropriately controlling the position of the robot arms.
The rotation of the holder and the position of the robot arms and probe heads can be controlled from a central computer. This allows fully automated contact to be made with all channels, and a corresponding fully automated investigation to be carried out of the various electrical parameters of the test adapter.
The apparatus according to the invention can thus be matched directly to different test adapters and measurement tasks. Since, furthermore, it operates in a fully automated manner, it can carry out any desired electrical calibration and characterization of test adapters of widely differing types.
Other features which are considered as characteristic for the invention are set forth in the appended claims.
Although the invention is illustrated and described herein as embodied in an apparatus for automated testing, calibration and characterization of test adapters, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims.
The construction and method of operation of the invention, however, together with additional objects and advantages thereof will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.