Wafer Prober

 

 

Electroglas 2001X Prober

The Electroglas Automatic Wafer Probing System is a precision instrument which moves wafers through the test process quickly, accurately, and safely. The instrument operates in a specific sequence which combines pre-programmed instructions and operator control guided by menus and prompts. A typical 2000X Series wafer prober showing some options.

The hart of the 2000 Series prober is the Electroglas linear reluctance stepper motor, an electromagnetic X-Y positioning system consisting of a platen and traveling forcer, or positioner. Mounted on the forcer is a Z-stage supporting a chuck top which transports the wafer for probing. The Z stage has a 200-mil range. The forcer operates in both the X- and Y- axis independently or simultaneously.

The forcer is supported by a cushion of air and moves over the waffle-pattern ferromagnetic surface of the platen in steps of 1 micron (.039mils). Because all bearing is provided by air and all drive pulses are magnetic, error caused by wearing of parts in conventional mechanical positioner is eliminated.

The 2000 Series prober is microprocessor-controlled; movement modes and parameters are programmed by keyboard. Entry procedures are required primarily for setup. Once the parameters and modes are set, wafer probing becomes automatic with little operator intervention. All parameter and operating ode entries are to CMOS RAM with lithium battery (average life, 2 years). If power is interrupted, there is no loss of operating status.

As of Prober Vision 2 software REV DB, a set of Machine-Dependent Variables (MDVs) in battery-backed RAM is retained with the particular prober. These are not overwritten by download of setup files generated on another prober. On the present EPROM and disk system, the first 32K bytes of memory are battery backed. A 6 Kbytes section of this battery-backed RAM is reserved exclusively for the MDVs. In order to ensure the integrity and validity of the data contained in the non-volatile memory, a Cyclic Redundancy Code (CRC) is generated on the MDV segment. The CRC is checked on power-up.

Operation of the Base Unit follows four general steps:

1)LOAD 2)ALIGN 3)PROBE 4)UNLOAD

Under operator control, the wafer is coarse-aligned, vacuum-locked on the Chuck Assembly, and transported to a predetermined location for final precision alignment.

Depending on programming, the prober can then perform any of several probing operations such as scanning, testing, or examination. Specific die can be probed, or the entire wafer can be probed according to chosen pattern. In addition, die may be inked during the probe to indicate which do not meet test criteria. After the probing operation, the Chuck Assembly automatically is returned to the load area for unlading.

WAFER PROER BASE UNIT

The Base Unit is an independent wafer probing unit which performs manual load, semiautomatic alignment, automatic probe, and manual unload operations. It includes four assemblies:

1) Base Assembly

4) Power/Control Assembly (PCM)

 

2) Monitor Console

5) Power Supply Module (PSM)

3) Operator Console

 

 

 

The Electroglas model 1034X is the world's most popular wafer prober. It incorporates greater X, Y, and Z axis performance, and more innovative electronic/mechanical features than any other prober available. Its production oriented operator controls and clean styling result from Electroglas' twenty years experience in the design and manufacture of high speed probers.

High speed, friction free motion

At the heart of the model 1034X is the exclusive Electroglas X-Y motion system, featuring fast, simple operation and low maintenance requirements. The unique, frictionless air bearing, linear reluctance, solid state high speed motion system offers fast, accurate X-Y positioning with extreme mechanical simplicity.

Programmed and controlled X and Y motion is produced with only one moving part, a 'forcer', which carries the Z stage. Conversion of rotary motion to linear motion through lead screws and related mechanical hardware is completely eliminated.

The electromagnetic forcer moves smoothly and quietly over a ferromagnetic platen on a frictionless air bearing. There is no wear and tear to affect system performance, overall reliability or accuracy, and no rquirement for periodic overhaul and replacement or parts. Precise, digitally controlled acceleration/deceleration is achieved with an accuracy of + .0005 in (.127 mm) over 5- or 6 inch (127- or 152- mm) stage travel.

Operator oriented control

The 1034X is designed to give semiconductor manufactures a prober of significantly greater throughput capacity, by reducing wafer load and alignment time and by improving the manual prober functions.

In the model 1034X, wafers are loaded and unloaded outside the probe ring area without disturbing the probe ring or optics. When loaded, wafers are rapidly aligned on any device in the matrix area via automatic gross positioning, manual or motorized Theta alignment, and a multifunction joystick that provides twenty separate manual commands in a single control.

In addition, safety interlocks allow indexing and jog movements while leaving the chuck in the up position. The operator is free to command stage movement without first lowering the chuck. Internal prober electronics automatically lower the chuck, initiate stage movement, and raise the chuck once stage movement in completed. This exclusive Electroglas feature saves significant operator alignment time.

To further simplify operation, the 1034X is equipped with an indicating panel that constantly advises the status of all prober functions. At one glance, direction, check and prober status are immediately known by the operator.

Inch and metric indexing

To eliminate costly conversions, the 1034X provides both inch and metric indexing as standard equipment. The desired index mode is selected by simply pushing a switch. This feature also includes a selectable alignment for various wafer sizes. You can select one- to five- inch wafers (25 mm to 127 mm) and the 1034X will limit its alignment scan distance to the selected wafer size. Long alignment scan distances no longer must be tolerated on small wafers., and the wafer will always remain in view while alignment is accomplished.

Simple, multifunctional joystick control

To reduce operator fatigue and improve productivity, the 1034X is designed with all manual commands for X, Y, and Z motion conveniently combined in a single joystick control. A three-position rotary switch on the joystick selects the mode of stage motion: JOG, INDEX, or SCAN. Movement of the stick in any direction activates that mode in either "single slow" (first position), or "multi-fast" (second position) speeds. This allows twenty separate stage commands in one control. A button on top of the joystick activates the multi-fast condition.

All probe related elements on one casting

To minimize vibration at the probe point interface, all probe-related elements have been mounted on a single, rigid, internal casting. This includes the vacuum chuck, X, Y, Z, and Theta drive assemblies, probe ring support stand, and microscope supports. By structurally tying these elements together, and vibrations inherent to the system are eliminated and overall probe tip-to-wafer movement is reduced to an insignificant level.

Swing-away casting

For maintenance and servicing, the model 1034X offers the ultimate in accessibility. Cover casting can be taken off without removing a single screw. The entire right side of the prober module is hinged to swing completely clear of interior components. In addition, its entire logic card cage can be removed in 30 seconds without tools. the interior of the power module is just as easy to reach. Its swing-away top cover allows free access to all components.

Separate power module

The prober and power modules are separate to provide convenient maintenance.

Quick change probe ring assembly

Probe ring assemblies are easy to change. The oversized ring plate (with extra room for special test circuitry) is suspended on three precision alignment posts. Rings incorporate "quick release" knobs for instant replacement. Adjustable probe ring inserts, fixed-point probe card arrays, or special test heads may be mounted easily on the flat planar surface of each 1034X assembly.

Built-in inking

The built-in delayed inking system eliminates the need for external accessory boxes. It provides for one edge sensor and six inkers. Inkers are programmable for "one-behind" or "two behind" as well as conventional "in-place" inking.

External control and coordinate reporting options

Electroglas offers options for the 1034X to facilitate test site probing, wafer mapping, and online computer control through IEEE-488 and RS-232 interfaces. Separate data sheets are published for these options and should be requested separately.

Accessories and options

Accessories include ring inserts, probe heads, inkers, edge sensors, probe tips, extender cables, TV optics, special optics, illuminators, planarizer, R&K adapters, magnetic inkers, work station tables, high frequency hardware, conversion kits, and various chuck top sizes.

Z stage options

High-speed-motor driven programmable, high speed motor driven, and pneumatic Z stages are available on 1034X probers.

High speed, fast Z axis cycle types are used to reduce mean time between device indexing. They are useful in probe test applications where maximum device throughput is desired. The stroke of the high speed Z stage is fixed at .016 inch (.406 mm). Probe contact over-travel is controlled by setting the height of the probe card carrier.

The programmable Z stage provides not only high speed Z axis cycle time but an adaptive function as well to control after-contact Z travel. When used in conjunction with an edge sensor, the axis stroke can be programmed to provide constant over-travel regardless of variations in wafer thickness. The desired over-travel may be selected in one-mil (or optionally one-half-mil) increments, resulting in uniform probe pressure to any die on the wafer surface, a condition critical to obtaining highest possible yields. In addition, a "short stroke" feature of the 1 mil-increment programmable Z limits the down stroke to .006 inches (.152 mm) below probe contact, further decreasing cycle time.

Programmable Z stages are available with high torque motors and heavy duty bearings to accommodate 1) the extra mass of temperature controlled chucks 2) the cumulative pressure of high density probe applications and 3) the increased load bearing requirement at the perimeter of 5-inch (127 mm) wafers.

High speed and programmable Z stages are available with manual or motorized Theta control, and Theta limit.

The pneumatic Z stage is recommended for applications in which unusually high mass is handled, Z-axis time is not critical, and programmable over-travel is not required. The pneumatic Z stage comes with manual Theta control only.

Required utilities

  • กค Electrical: 110 VAC, 60 HZ, 1 phase, 1 kw, 220 VAC, 50 HZ, 1 phase, 1 kw
  • กค Air: 2.5 cfm at 85 psi
    Compressed air must be filtered to 5 micron maximum, free from water and other contaminants.
  • กค Vacuum: 18 to 25 inches Hg, 457 to 635 mm Hg

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