DE102008030425A1 - LED lighting system for an electrical test system - Google Patents

Abstract

LED illumination for a microscope optics optical test device (8) for producing a microscopic image is described, wherein the LED illumination comprises a plurality of LED units (1, 2, 3) for test object illumination at different positions on the tester. The LED lighting has at least two differently positioned LED lighting units (1, 2, 3) for generating different types of lighting, each serving a lighting in the distant dark field, a lighting in the near dark field, and the lighting in the bright field.

Description

The The invention relates generally to the testing of electronic assemblies, as well as the examination of Devices that are applied for example on a wafer. In general, the objects positioned on a support become so tested that they are driven under a microscope and the object position can be determined by optical analysis.

Based on recorded data, the contact position for the electrical Measurement determined. Subsequently become the positions for approached the electrical measurement. A chuck / workpiece carrier with Wafers and measuring needles are moved towards each other until the electric Contact is made securely.

For the determination of measuring positions is the safe detection of the different necessary objects to be measured. When electrically testing Semiconductor chips, for example, applied to a wafer is an optical analysis on a microscopic picture necessary to determine the required measuring positions with sufficient accuracy to be able to.

in the The state of the art has been for a microscope insert standard lighting regularly corresponding Halogen lights used. When using the microscope dark field illumination will the for the brightfield used lighting deflected to the lens edge, so that the lens is an annular Light emission arises. This kind of darkfield lighting is, however very inefficient. additionally depends on that Image in the dark field also from the object surface, so with normally provided dark field illuminations only an insufficient one optical image of the test object or electrically tested Chips is possible.

in the Prior art testing systems have been so far with a usual Microscope illumination offered, but the lighting device is not optimal.

Of the Invention is based on the object microscope-based tests equip electronic assemblies with optimized lighting.

The solution This task is done by the combination of features accordingly Claim 1. Advantageous embodiments are the dependent claims remove.

Of the Invention is based on the finding that methods based on build up microscopic pictures, instead of lighting with halogen lamps light emitting diodes (LED) are used can. These are optimally positioned in the lighting system, whereby for different Lighting types a combination of LEDs or LED groups is formed. The individual associated lighting units can positioned at different positions in the lighting system be.

The Lighting system consists of a combination of different positioned LEDs as light sources, wherein advantageously a LED lighting unit for the Brightfield lighting, an LED lighting unit for the near Dark field illumination and another LED illumination unit for the distance Darkfield lighting in charge is.

It is also advantageous, white radiating LEDs, although other colors such as red, green or blue possible are.

A LED lighting to generate a bright field is optimally sideways in the Imaged beam path coupled and is thus in the direction of illumination positioned in front of the lens of the system. For the representation of dark field illuminations are the LED units each in the illumination direction behind the lens positioned and form an annular or square frame around the illumination beam path. To generate a lighting with near dark field, a frame with a smaller diameter is provided and for illumination in the distant dark field is a frame with a larger diameter intended. The individual LEDs are advantageous over a frame or a ring equally distributed.

It is advantageous, the emission direction of individual LEDs by attaching lenses to influence specifically. The lenses are designed in such an optimized way that they are in a range of +/- 10 ° around a surface normal radiate.

Of the Image beam path advantageously has the same diameter like an object to be imaged.

in the The following is a schematic of the invention not limiting Figure describes an embodiment of the invention.

The FIG. 1 shows a measurement setup for an LED lighting system, wherein three separately positioned lighting units for each three different types of lighting are optimally positioned.

The system consists of a combination of different light sources for the bright field, the near dark field and the distant dark field illumination. The light sources used are white LEDs (light-emitting diodes). Their light is guided via optics onto the object to be viewed with the camera. This is the bright field illumination 3 generated by the coupling of the light beams via a beam splitter in the imaging beam path.

A dark field illumination is optimized by direct lighting arrangements 1 . 2 relative to the imaging beam path 4 behind the lens 7 generated. White light emitting LEDs are also used as the light source for the near and the far dark field.

The Lighting for the generation of a near dark field consists of LEDs and a Optics, with the LEDs and the optics on a ring with the ring width from 1 to 5 mm are positioned around the imaging beam path. The imaging beam path has the diameter of the image to be imaged Object.

at the use of line scan cameras for optical detection of the imaged Object is the cross section of the usable beam path accordingly the figure rectangular educated. In this case, the illumination of the near dark field is inside a frame with the frame width of 1 to 5 mm around the rectangular Cross section of the beam path positioned around.

The used LEDs have a lens for generating a beam lobe with an opening of +/- 10 ° from the surface normal calculated from. At the edge of this opening angle is the light intensity on about 50% compared dropped off an angle of 0 °. The angle of 0 ° is identical to the solder on the radiating surface of an LED.

The Lenses of the LEDs are to realize this radiation characteristic centered around polished so that the resulting flat surface, the size of the LED chip has. The polished surfaces own in about the same lot as the radiating chip surface.

The optics for the refraction of the illumination beam of the near and far dark field illumination consists of a Fresnel lens 16 with a focal length of f = A, as indicated in the figure.

Becomes no additional Optics are used, so the LEDs are bent so that for a sufficient number LEDs the lot of radiant surface on the illuminated Object is directed.

It is also advantageous, the three separate lighting units also to turn on and off separately. Thus, the lighting for the generation of a bright field, for the near dark field and for the far-off darkfield will be activated separately.

For each Lighting circle or frame, the light intensity can be fed through the in the light-emitting diodes electric current can be varied.

Of the particular advantage of this lighting system is that LEDs have a very long life, so for long Time no change of light sources will be required. LEDs are very compact, allowing small LEDs directly between lens and image Object are placeable. The object can be illuminated almost directly in the dark field which improves the quality of the object illumination and the automatic image analysis is simplified.

The figure shows an object to be illuminated and tested in the form of the wafer 14 , This one is on a chuck 15 applied and can be moved relative to the microscope with appropriate drive. Within the microscope assembly are lighting units 1 . 2 . 3 provided in different positions, so that different types of lighting are possible. These can be activated individually or in total. The bright field illumination 3 can be via a beam splitter 6 the imaging beam path 4 be initiated. From the object, wafers 14 , Back reflected beams are from the camera 5 recorded and fed to an image analysis. Based on this, a lighting control or a lighting adjustment can take place. The higher-level control of the test system can via the drive control by means of the measuring units, consisting of measuring plate 10 , Spider 11 , Measuring card 12 , Measuring needle 13 , the wafer or the electronic components applied to the wafer by appropriate contacting with the measuring needle tips 13 check.

Claims (14)

LED illumination for an optical test instrument with microscope optics ( 8th ) for generating a microscopic image, wherein the LED illumination comprises a plurality of LED units ( 1 . 2 . 3 ) for test object illumination at different positions on the tester. LED lighting according to claim 1, wherein at least 2 differently positioned LED lighting units ( 1 . 2 . 3 ) are available for generating different types of lighting. LED lighting system according to claim 2, wherein three different types of lighting are provided, - at least one LED lighting unit ( 1 ) for illumination in the distant dark field, - at least one LED illumination unit ( 2 ) for near dark field illumination, and - at least one LED illumination unit ( 3 ) for a lighting in the bright field. LED lighting system according to one of claims 1 to 3, in which white LEDs are used. LED lighting system according to one of claims 1 to 4, wherein the illumination in the far dark field in the observation direction behind the lens ( 16 ) is arranged, consists of a plurality of LEDs and is arranged annularly around the imaging beam path. LED lighting system according to one of claims 1 to 5, wherein the illumination in the near dark field in the observation direction behind the lens ( 16 ) is arranged, consists of a plurality of LEDs and is arranged annularly around the imaging beam path within the illuminated dark field illumination ring. LED lighting system according to one of claims 1 to 6, wherein the illumination in the bright field in the viewing direction by a coupling in the imaging beam path ( 4 ) of the tester in front of the lens ( 16 ) is provided. LED lighting system according to one of claims 1 to 7, wherein the imaging beam path ( 4 ) and / or are formed of LED lighting rings rectangular. LED lighting system according to claim 8, wherein a Illumination frame in the near dark field with an edge length of about 1-5 mm is set. LED lighting system according to one of claims 1 to 9, in which LEDs have auxiliary lenses and in operation on the solder the radiating surface emit at an angle of up to +/- 10 °. LED lighting system according to claim 10, wherein the attaching lenses in their strength so rejuvenated are that the rejuvenated Area about the area of an LED chip. LED lighting system according to one of claims 3 to 11, in which in the dark field illumination, a Fresnel lens with a focal length (A) is present. LED lighting system according to one of claims 1 to 12, in which the different lighting units ( 1 . 2 . 3 ) are independently switchable. LED lighting system according to one of the preceding Claims, where the radiated color of the LEDs is red, green or blue.