Method of sharing a test resource at a plurality of test sites, automated test equipment, handler for loading and unloading devices to be tested and test system

A method of sharing a test resource at a plurality of test sites executes respective test flows at the plurality of test sites with an offset in time, the respective test flows accessing the test resource at a predetermined position in the test flow.

BACKGROUND OF THE INVENTION

Embodiments of the invention concern a method of sharing a test resource at a plurality of test sites testing a plurality of devices, an automated test equipment, a handler for loading and unloading devices to be tested to/from a plurality of test sites of an automated test equipment, and a system for testing a system for testing a plurality of devices.

Components, for example memory elements and integrated circuits (IC), need to be tested. During testing these devices under test (DUTs) are exposed to various types of stimulus signals, and responses from such devices are measured, processed and compared to an expected response. Such testing may be carried out by automated test equipment (ATE) which usually performs such tasks according to a device-specific test program or test flow.

Examples for such automated test equipment are the Verigy V93000 series and the Verigy V5000 series, the first being a platform for testing system-on-a-chip, system-on-a-package and high-speed memory devices. The latter is for testing memory devices including flash memory and multi-chip packages at wafer sort and final test.

Such automated test equipment may comprise multiple sites, each receiving a device under test thereby allowing the testing of a plurality of devices at the same time. Such automated test equipment may comprise a device handler having a gripping mechanism for simultaneously placing a plurality of devices to be tested into the test sites and for removing the devices from the test sites after the test is completed. The automated test equipment provides for respective resources allowing the testing of the devices, and in a multi-site test, the respective ATE resources are accessible to all sites. While there are resources which are provided at each site, there are also resources in an automated test equipment, such as RF resources for RF measurements and the like, which are expensive but which are used only during short periods of a test program or test flow executed at a respective test site. In one conventional approach, at each test site of an automated test equipment, such a specific resource, for example, a resource for performing RF measurements, may be provided which, however, is quite expensive. Alternatively, a single resource may be provided in the automated test equipment and resource multiplexing in common test flows executed at the respective test site might be performed. However, this adds to test time overhead. Also, the test flows or test programs may be modified to generate circular test flows which are executed in such a manner that those portions of a test flow accessing the specific resources do not overlap while simultaneously executing the test flows at the respective test sites, however, this involves the development of different test flows per site which increases the complexity of the test preparation.

SUMMARY

According to an embodiment, a method of sharing among a plurality of test sites a specific test resource for executing a specific test at a device may have the steps of: executing respective test flows at the plurality of test sites with an offset in time, wherein the respective test flows access the test specific resource at a predetermined position in the test flow to execute a specific test at a device held in a test site.

Another embodiment may have a computer-readable medium including computer executable instructions for carrying out the method of sharing among a plurality of test sites a specific test resource for executing a specific test at a device, the method having the steps of: executing respective test flows at the plurality of test sites with an offset in time, wherein the respective test flows access the test specific resource at a predetermined position in the test flow to execute a specific test at a device held in a test site, when executing the instructions on a computer.

According to another embodiment, an automated test equipment may have: a plurality of test sites, each test site being configured to receive a device to be tested; a specific test resource configured to be selectively connected to one of the test sites and to execute a specific test at a device held in a test site; and a tester configured to start execution of respective test flows at the test sites with an offset in time, wherein the respective test flows includes a portion accessing the specific test resource, the offset in time being selected such that portions in the test flows accessing the specific test resource do not overlap, and wherein the tester is configured to connect the specific test resource to the test site at which the portion accessing the specific test resource is currently executed.

According to another embodiment, a test system for testing a plurality of devices may have: an automated test equipment that may have: a plurality of test sites, each test site being configured to receive a device to be tested; a specific test resource configured to be selectively connected to one of the test sites and to execute a specific test at a device held in a test site; and a tester configured to start execution of respective test flows at the test sites with an offset in time, wherein the respective test flows include a portion accessing the specific test resource, the offset in time being selected such that portions in the test flows accessing the specific test resource do not overlap, and wherein the tester is configured to connect the specific test resource to the test site at which the portion accessing the specific test resource is currently executed; and a handler for loading and unloading devices to be tested to/from a plurality of test sites of an automated test equipment, the handler including: a mechanism configured to load devices to be tested to respective test sites of an automated test equipment and configured to unload devices tested from the test sites; and a controller configured to control the mechanism to load the devices with an offset in time.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1is a schematic view illustrating a conventional approach for testing a plurality of devices using an automated test equipment100as it is schematically shown inFIG. 1.

The automated test equipment100comprises a plurality of test sites102,104,106and108. It is noted that inFIG. 1an automated test equipment is shown having four test sites. Further, a handling mechanism110is provided for loading110adevices to be tested to the respective test sites102to108and for unloading110bdevices tested from the respective test sites102to108.

The automated test equipment comprises a specific resource112, for example, a RF resource for executing respective RF measurements at the devices held in the respective test sites102to108. Further, a multiplexer114is provided for selectively switching the resource112to the respective test sites102to108. At the respective test sites102to108, the automated test equipment100has loaded respective test flows116to122which may be the same or which may be different. Each of the test flows comprises a first portion118ato122aand a second portion118bto122b. The first portion116ato122aof the respective test flows116to122executes respective tests at the devices under test provided at the respective test sites102to108using test resources wherein each site102to108comprises respective test resources so that the portions116ato122aof the tests can be carried out in parallel. The second portions116bto122bof the respective test flows116to122access the specific test resource112, for example, for executing RF tests with regard to the devices provided at the respective test site. Since the automated test equipment100comprises only a single specific test resource112, the second portions116bto122bof the respective test flows116to122cannot be executed in parallel.

Rather, the portions116bto122bof the test flows116to122access the test resource112in a sequential manner and the test recourse112is connected via the multiplexer114to one of the test sites102to108and, more specifically, to that test site at which currently the second portion of the test flow116to122is executed.

More specifically, at a time t1the handler110loads110adevices to be tested into the test sites102to108and the automated test equipment100starts executing the first portion116ato122aof the respective test flows or test programs116to122until the time t2. During the time period between t1and t2, testing of the devices is done in parallel, as outlined above, as all test flows access resources provided at each test site102to108. At the time t2, the parallel testing is completed and now access is made to the specific resource112provided only once for all test sites102to108. During the time period between t2and t3the first program flow116executed at site102executes its second portion116b. At that time, the specific resource112is connected via multiplexer114to site102currently executing that part of the test flow accessing the RF resource112. At the time t3testing at the first site102is completed and testing at the second site104is started by executing the second portion118bof test flow118. At this time, the resource112is connected via the multiplexer114to the second site104so that the second portion118bmay access the resource112. In a similar manner, between times t4and t5and between t5and t6, the second portions120band122bof the test flows120and122at test sites106and108are executed.

It is noted thatFIG. 1shows an example where a single test resource112is provided, however, it might well be that, for example, two specific test resources112are provided which are shared among two of the four test sites. Also, more than the four test sites might be provided. Also, test flows might be slightly different, for example, the respective portions116bto122baccessing the specific resource112might be provided at the beginning of the test or somewhere in the middle of the test flow.

At time t6all devices arranged at the sites102to108are tested and handler110is again activated to unload110bthe tested devices from the system shown inFIG. 1. The process is then repeated, i.e., new devices to be tested are loaded110ato the now empty sites102to108and test flow execution is carried out as specified above. While the approach described inFIG. 1reduces the costs associated with testers providing at each site a specific test resource112, it is readily apparent that the reduced costs are achieved by an increase in test time or by the addition of test time overhead. To be more specific, despite the fact that testing of the device at the first site102is already completed at time t3, all devices are removed from the tester together at the time t6. Thus, during the time period t3to t6, the test site102is idle. Thus, it is, for example, not possible to replace a device at site102after the test is complete by a new device, rather, it is to be waited until all devices are tested.

FIG. 2shows a schematic view of a second conventional approach for sharing a specific test resource, however, rather than using a multiplexed approach, the conventional approach shown inFIG. 2uses circular test flows. InFIG. 2, those elements having the same functionality as corresponding elements described inFIG. 1are associated with the same reference signs.

As can be seen fromFIG. 2, rather than using a test flow at the respective test sites102to108having a first portion and a second portion, in accordance with the approach shown inFIG. 2, each test flow is segmented into four portions1161to1164,1181to1184,1201to1204and1221to1224. The respective portions1164to1224, are those portions of the respective test flows116to122accessing the specific resource112. The respective portions of the test flows are arranged in such a manner that when testing in parallel at the respective test sites102to108, the portions are arranged in such a manner that those portions1164to1224accessing the specific device112, do not overlap. Thus, during the time period of t1to t4, at the first site102, the portions116ato1163accessing test resources associated with the test site102are executed and during the time period between t4and t5, the single resource112is accessed by portion1164. At the second test site104, the resource112is accessed at the time period between t1and t2, at the third test site106, the resource112is accessed during the time period t2and t3, and at the fourth test site122, the resource112is accessed during the time period between t3and t4. Again, the multiplexer114connects the resource112selectively to those test sites currently executing the test flow portion1164to1224accessing the test source112.

When compared to the approach inFIG. 1, it is to be seen that test execution is faster and at the time t5all devices were tested and can be removed by handler110, so that no idle times at the respective test sites exist. However, as can also be seen fromFIG. 2, the respective test flows to be executed at the sites102to108are quite complex, i.e., test program complexity is greatly increased, and becomes even more complicated when assuming that conventional automated test equipment comprises many more test sites than those shown in the example ofFIG. 2. In other words, with increasing number of test sites, the test program complexity increases accordingly.

To avoid the problems associated with prior art approaches, such as providing the expensive and rarely used specific resources112at each test site of an automated system, the additional test time overhead as described with regard toFIG. 1, or the test program complexity as described in the example ofFIG. 2, embodiments of the invention suggest a novel approach for sharing a specific test resource among a plurality of test sites of an automated test equipment. Embodiments of the invention call the approach a “pipelined test flow”. As will be discussed in further detail below, embodiments of the invention overcome the above problems of prior art approaches by shifting the times of loading and unloading the devices to the tested into the test sites, by shifting the execution of multiple site test flows (the same test flows or different test flows at the respective test sites) in time, and by sequentially sharing test resources. Further, the invention provides an automated test equipment with the ability to execute the test site flows shifted in time to enable a pipelined test flow execution. Also, embodiments of the invention provide a handler with the ability to load and unload parts into sites in a time-shifted way.

FIG. 3is a block diagram of a test system in accordance with embodiments of the invention. The test system124comprises an automated test equipment100operating in accordance with the principles of embodiments of the invention. The automated test equipment comprises four test sites102to108, respective resources RI, RII, RIIIand RIV, each of the just-mentioned resources being associated with a respective one of the test sites102to108. More specifically, resources RIbelong to test sites102, resources RIIbelong to test site104, resources RIIIbelong to test site106and resources RIV, belong to test site108. Also, the specific resource112to be shared among all test sites102to108is shown together with its associated multiplexer114. The automated test equipment also comprises a tester126receiving via an input IN respective signals and out-putting via the output OUT respective test output signals. The tester provides at the respective test sites102to108, the test flows or test programs to be executed with regard to devices to be tested. The test programs may be the same or may be different at the respective test sites. In accordance with embodiments of the invention, the tester126of the automated test equipment is configured to start executing the respective test flows at the different test sites102to108with an offset in time, as will be described in further detail below.

The system124further comprises the handler110comprising a controller128and a mechanism130for loading/unloading devices to the automated test equipment100, more specifically to/from the respective test sites102to108. A mechanism130comprises a first part130aalong which a gripping mechanism130bmay be moved (see arrow132) for allowing loading/unloading devices to be tested and devices which were tested, respectively, via respective grippers134to140. In accordance with embodiments of the invention, the controller128of the handler118is configured such that the gripping mechanism130bloads/unloads the devices to the respective test sites102to108of the automated test equipment100with an offset in time, as will also be described in further detail below.

FIG. 4illustrates a schematic view of a method according to embodiments of the invention. InFIG. 4, the respective actions taken by the handler are indicated by reference signs110a1to110a4and110b1to110b4. The respective test flows are indicated by reference signs116to122. The portions116ato122aaccessing resources associated with the respective test sites are indicated as well as portions116bto122baccessing the single resource112via multi-plexer114are indicated.

FIG. 4shows a part of the operation of a test system as is shown inFIG. 3and the approach in accordance with embodiments of the invention will be described below. In accordance with the principles of embodiments of the invention, the times of loading110a1to110a4and unloading110b1to110b4of the devices to be tested at the respective test sites102to108are shifted in time. As can be seen, at time t1handler110loads110a1a device to test site102.

Loading of devices to the other test sites104to108is shifted in time, so that at time t2a device is loaded110a2to site104, at time t3a device is loaded110a3to site106and at time t4a device is loaded110a4to site108.

At the respective sites102to108, the test programs or test flows116to122are provided by the tester of the automated test equipment, however, in accordance with the principles of embodiments of the invention, executing the respective test flows at the different sites102to108is shifted in time in a manner as is shown inFIG. 4. More specifically, start of the respective test flow portions116ato122ais shifted in a similar manner as is the loading of the devices so that the test flow at site102starts at time the test flow at site104starts at time t2, the test flow at site106starts at time t3and the test flow at site108starts at time t4. The portions116bto122bwithin the respective test flows are arranged in such a manner that due to the time difference, when starting the execution of the respective test flows at the test sites102to108, the portion's116bto122bare executed in a non-overlapping manner. This allows using the single resource112and coupling same to the respective test sites102to108via the multiplexer114at those times at which at the respective test sites the test flow portion116bto122baccessing element112are executed. More specifically, during the time period between the t4and t5, the single resource112is coupled to the first site102, during the time period between t5and t6, the resource112is coupled to the second site104, during the time period between t6and t7, the resource112is coupled to the third site106and during the time period between and is the resource112is coupled to site108.

As outlined above, the handler places the respective devices to the different sites with an offset in time and, in a similar manner, is able to remove or unload tested devices from the respective sites with an offset in time. The handler is configured in such a manner that devices can be removed from the sites once a test is completed. More specifically, following the test complete t5, handler110removes110b1the tested device from site102and places a new device to be tested at site102, so that the test flow can again be executed at time t6. In a similar manner, removal of tested devices and loading of new devices to be tested is done at the other sites104to108. More specifically, a time t6a tested device is removed110b2from site104and a new device to be tested is inserted so that test flow execution can again be started at time t7. At time t7, a tested device is removed from test site106and a new one is inserted, thereby allowing execution of the test flow at site106at time t8again. In a similar manner, at time t8a tested device from site108is removed110b4and a new device is loaded thereby allowing starting execution of the test flow at site108again at time t9.

Thus, in accordance with the principles of embodiments of the invention, it is not necessary to provide expensive resources, like an RF resource112, at each of the test sites102to108of an automated test equipment, thereby allowing a reduction in costs. Also, the problems of test flow complexity and test time overhead are avoided by allowing the handler to place respective devices to the test site with an offset in time and remove the respective devices which were tested from the test sites also with an offset in time, thereby avoiding idle times at the respective test sites102to108as new devices can already be loaded into the test site and testing can be started. Also, by allowing the automated test equipment to start execution of the respective test programs in a time shifted way, the use of a common resource112for respective portions116bto122bof the test program is allowed.

In the embodiment described inFIG. 4, a test system is assumed similar to the one shown inFIG. 3, i.e., a test system having an automated test equipment with four test sites and four grippers of the handler. The invention is not limited to such embodiments, rather the automated test equipment may have less test sites or more test sites. The gripping mechanism of the handler110may have a corresponding number of gripping elements allowing loading/unloading of devices to the respective test sites. Alternatively, the handler may be configured with less grippers which are controlled in such a manner that the grippers sequentially receive devices to be tested and place the devices, e.g. one or more devices with subsequent moves, at the respective sites.

Also, the test flow does not require the specific portion116bto122baccessing the single device112to be positioned towards the end of the test flow, rather any position within the test flow is possible as long as the staggered execution of the test flows in the respective test sites does result in an overlap of those portions of the test flows accessing the single device112. WhileFIG. 4shows an embodiment in which each test site executes the same test flow, it is noted that also different test flows can be provided with the respective test sites102to108.

In addition, the invention is not limited to embodiments in accordance with which only a single specific resource112is to be shared among a plurality of test sites, rather; it might well be that a plurality of specific test resources112are provided, each being shared between a subset of test sites. For example, inFIG. 4, a second resource may be provided wherein the first resource is shared among sites102and104and a second one is shared among sites106and108.

While embodiments of the invention described above show starting the execution of respective test flows at subsequent test sites, it is noted that the test flows may be started in a non-sequential manner. For example, when looking atFIG. 4, it is possible to start loading and executing the test flow at test site102at time t2or a later time and to start loading and executing the test flow at site106at time t1.

Also the invention is not limited to embodiments in which all of the test sites share one or more specific resources. For example, test sites102and104may execute the same or different test flows requiring access to resource112while the remaining test sites do not require access to resource112when testing the device placed here. In this situation, the device112is only shared among sites102and104, so that only loading/unloading of devices to be tested and starting execution of the test flows at sites102and104is shifted in time, while, for example, testing at sites106and108may start concurrently with testing at site102or at any desired starting time.

Further, it is noted that the above described method, in accordance with embodiments of the invention, can be implemented in hardware or in software. In addition, the implementation can be in a digital storage medium, for example a disc or a CD comprising electronically readable control signals, which can act together with a programmable computer system, for executing the method according to embodiments of the invention. Generally, the invention is also a computer program product having a program code for executing the method according to embodiments of the invention being stored on a machine readable carrier and executed when the computer program product runs on a computer. In other words, the invention is also a computer program having program codes for carrying out the method when the computer program runs on a computer.