Camera based two-point vision alignment for semiconductor device testing handlers

A guiding plate based vision alignment system for a test handler includes cameras, configured to view the position difference between a tested device and the corresponding contactor. A pick-and-place handler is configured to move the device. A guiding plate is configured to actuate guiding plate with one translation alignment feature and one rotation alignment feature to correct the position offset between the tested device and the corresponding contactor.

BACKGROUND OF THE INVENTION

The present invention relates generally to the field of automated test handlers for semi-conductor devices. Specifically, the present invention relates to a vision alignment system for a semiconductor device test handler.

The following description of the background of the invention is provided simply as an aid in understanding the invention and is not admitted to describe or constitute prior art to the invention.

Semiconductor devices are subject to numerous tests before they are shipped to a wholesaler and/or end consumer. Manufacturers of semiconductor devices spend a significant amount of time testing devices prior to shipment. Therefore, it is desirable to speed up the semiconductor testing procedure by several methods.

Generally, a semiconductor device is tested using a testing handler. Testing handlers are configured to process and test a large amount of semiconductor devices. One aspect of semiconductor testing involves applying a testing contactor to the surface of a semiconductor device to carryout testing on the device. Aligning the semiconductor device with the testing contactor is an important step in the testing process for many reasons. First, proper alignment insures that the testing is carried out appropriately. In addition, the ability to quickly and automatically align a semiconductor device and a testing contactor allows for testing to proceed at an efficient rate.

Accordingly, there is a need for a system and method of efficiently and accurately aligning semiconductor devices with testing contactors.

SUMMARY OF THE INVENTION

According to one embodiment of the invention, a vision alignment system for a test handler includes several components. Cameras are configured to view the position difference between a tested device and the corresponding contactor. A pick-and-place handler is configured to move the tested device to the corresponding contactor. A guiding plate with one translation slot and one rotation slot to correct the position offset between the tested device and the corresponding contactor with the two alignment circle features on the device holder.

According to another embodiment of the invention, a device holder for holding and guiding the tested device to the corresponding contactor has two circular guiding features. The first guide feature determines the x and y position of the device holder. The second guiding feature determines the angle of the device holder. A method for calibrating a contactor begins by determining the contactor position in handler coordinate with a contactor-view camera in the guiding plate coordinate. The device holder position in guiding coordinate is determined by the two circular guiding features on the device holder and aligned by the two slots on the guiding plate. Next, the tested device position to the device holder circle features is determined by another device-view camera. Therefore, the offset between the tested device and the corresponding contactor is determined.

According to still another embodiment of the invention, a method for aligning a tested device in a test handler uses a guiding plate with two guiding slots and a device holder with two circle features to position the tested device.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Embodiments of the present invention will be described below with reference to the accompanying drawings. It should be understood that the following description is intended to describe exemplary embodiments of the invention, and not to limit the invention.

FIG. 1shows an alignment vision system1according to one embodiment of the invention. A test handler10for testing semiconductor devices has a handling side and an imaging side. The handling side of the test handler10includes a pick and place handler30, a guiding plate230with three actuators235and a controller40. The imaging side of the test handler10includes a contactor-view camera210and a device-view camera110with a lighting system20. The imaging side of the test handler10includes a vision alignment processor240, having a memory245is operatively connected to the device-view camera110and the contactor-view camera210.

As shown inFIG. 1, the pick and place handler30spans across both the handling side and the imaging side of the test handler10. The pick and place handler30positions a device holder150and/or a tested device “DUT”250(FIGS. 2 and 3) so that the contactor-view camera210or the device-view camera110can capture high contrast images of the subject devices.

The controller40is operatively connected to all the components in the test handler10and the vision alignment processor240. Accordingly, the vision alignment controller240controls and coordinates all imaging related operations that take place in the test handler10.

The lighting system20provides high contrast lighting for the contactor-view camera210and the device-view camera110. According to one embodiment, the lighting system20is comprised of two separate lighting devices (one for the contactor-view camera210and one for the device-view camera110), each controlling a three channel programmable LED array. In order to achieve high contrast, the lighting system20is configured to provide lighting in the range of zero (0°) to ninety (90°) degrees relative to the subject of the cameras110,210. The lighting system20comprises a lighting processor which is configured to execute trained vision recipes. These recipes are executed by the lighting system20in order to provide lighting according to user desired configurations.

The contactor-view camera210is configured to capture images for the purposes of determining the contactor position in the handler coordinate system. The contactor-view camera210may be a CCD or CMOS camera.

Similarly, the device-view camera110is configured to capture images of a DUT250and the device holder150. The device-view camera1100may be a CCD or CMOS camera.

The images captured by the device-view camera110are analyzed by a vision alignment processor240. The vision alignment processor240is configured to execute vision alignment software and transforms the images captured by the device-view camera110to determine whether the position of a DUT250needs adjustment so that it will mate accurately with a testing contactor260. The vision alignment controller240is also configured to control a guiding plate230to effectively provide information to change the position of the DUT250.

Operation of the vision alignment system1will now be described. The vision alignment system1operates in at least two modes. The vision alignment system1is configured to calibrate itself based on a given testing contactor260and device holder150. In addition, the vision alignment system1is configured to align DUTs250with a testing contactor260for the purpose of carrying out testing.

The calibration operation of the vision alignment system1is as follows. First, as shown inFIG. 5, a double sided visible glass target with a high contrast dot array (a training device) in a device holder150with two alignment circle features (guiding features) is imaged by a device view camera110(Step1000). The positions of the alignment circle features on the device holder150in the training device coordinate system are recorded (Step1010). The guiding plate230is positioned to the contactor position using three actuators235(Step1020). Next, two guiding features120(guiding circles) are inserted on to the guiding plate230(Step1030). As shown inFIG. 2, guiding slots220receive the guiding features120. The training device is locked the guiding plate230and the device holder150is released from the guiding plate230(Step1040). The contactor-view camera210images and records the position of the guiding plate230in the training device coordinate system21(Step1050). Accordingly, the calibrated transform from the contactor nominal position to the device holder with the guiding plate and the three actuator nominal positions is established, a guiding coordinate system is established and the vision alignment system is calibrated and ready to begin DUT250alignment to the corresponding contactor260.

The vision alignment procedure executed by the vision alignment system1is described as follows. First, a guiding coordinate system and transforms must be obtained from the calibration process described above. A DUT250is positioned by the device holder150so that it is observed by the vision device-view camera110(Step2000). The vision device-view camera110captures images of the position of the DUT250relative to the two circular guiding features120(Step2010). Using the pre-calibrated transform the offset between the device and contactor is determined (Step2020). The offset calculation is then converted to linear motion commands for the three actuators235in order to position the guiding plate230(Step2030). Next, the guiding plate230is locked and the device150with device holder250is inserted on to the contactor260through the guiding plate230(Step2040).

For example,FIG. 4shows a DUT250having a difference in position relative to a device holder150and further to the corresponding contactor based on the previous calibration. As shown, the DUT250is positioned differently from the device holder150in the X and Y direction. In addition, the angular position of the DUT is different from that of the device holder150. Accordingly, a guiding plate230acts upon the movable guiding slots220(via chamfered spring pushers200(a) and200(b)) to move the DUT250so that the position offset detected by the vision alignment processor240is eliminated (Step2030). As a result, the DUT250is now aligned to accurately mate with a testing contactor260.

According to one embodiment of the invention, the guiding plate230has two guiding slots220. The first guide slot220(a) is configured with two guiding surfaces (x,y) and a spring200(a) to ensure touching between a guiding circle on the device holder and the guiding slot220(a) on the guiding plate, the first (i.e., translational) guiding feature225(a) moves the DUT250horizontally or vertically relative to the handler coordinate system. The second guide slot220(b) is configured with one guiding surface (θ) and a spring200(b) to ensure touching between a guiding circle on the device holder and the guiding slot220(b) on the guiding plate, the second (i.e., rotational) guiding feature225(b) adjusts the angular positioning of the DUT250.

According to the embodiments of the invention described above, several advantages are realized. For example, the present invention simplifies the aligning process by using a pre-calibrated guiding plate instead of directly actuating on the device holder. As a result, the complexity involved with alignment procedures are greatly reduced which in turn reduces costs and increase the reliability. Moreover, the present invention can be applied across a large a number of device handlers, providing a scalable solution for testing firms.