Temperature-controlled semiconductor wafer chuck system

Details Temperature-controlled semiconductor wafer chuck system Temperature-controlled semiconductor wafer chuck system

1999-01-26

2003-06-24

Sherry, Michael (Department: 2829)

Electricity: measuring and testing

Fault detecting in electric circuits and of electric components

Of individual circuit component or element

C324S1540PB

Reexamination Certificate

active

06583638

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates generally to a semiconductor wafer platform, or chuck, used to support, and by means of applied vacuum, hold, a wafer for testing in a prober station. More specifically, the invention relates to a temperature-controlled semiconductor wafer chuck which directly heats or cools the semiconductor wafer for, and during, manufacture, testing, characterization, and failure analysis of semiconductor wafers and other components at hot and cold temperatures.
2. Description of the Related Art
In the conventional manufacture of semiconductor devices, semiconductor wafers are first produced. Each semiconductor wafer can contain many individual electronic devices or electronic circuits, which are known as dies. Each die is electrically tested by connecting it to suitable test equipment. Probe pins, which are connected to the test equipment, are brought into contact with the die to be tested. This generally occurs at a prober station, which conventionally includes a prober stage supporting a wafer chuck, which in turn supports the wafer. The prober station in production applications is usually an automated testing apparatus, and such stations are well known. Alternatively the prober station can be such as will facilitate manual testing by a human operator; and in the latter case also includes a means for magnifying the wafer for observation by testing personnel, which can be employed in confirming accurate probe placement. In either case a conventional prober station also includes means for micropositioning of the prober stage, and accordingly the chuck and a wafer supported thereon, with respect to test probes etc.
It is often required to control the temperature of the die during testing, and for this purpose the semiconductor wafer chuck can be a temperature-controlled chuck. In many cases such chucks are required to be able to both heat and cool the wafer. Many types of temperature-controlled chucks are known and are widely commercially available. The simplest form consists of a chuck incorporating a heater element; and the heater heats the chuck. This design relies on natural convection to cool the chuck. This method of cooling can be too slow for many commercial production test requirements.
Temperature-controlled chucks that incorporate heaters and heat sinks are also available. Heaters can take several forms, such as plate heaters, coil heaters, mica heaters, thin film heaters, peltier elements or heater rods incorporated into the chuck. Another method involves casting the heater rods into an element of the chuck structure. Cooling is provided by a heat sink that is cooled by a recirculating fluid, or in other designs by passing a fluid through the chuck without recirculating it. The fluid can be a liquid or a gas, usually air in the latter case. The liquid or air can be chilled for greater cooling effect in passing through the chuck, and can be recirculated for greater efficiency. A chuck cooled by means of a fluid chilled to a temperature below ambient temperature enables wafer probing at temperatures below ambient. In general, current conventional heat-sink designs incorporate simple cooling channels cross-drilled and capped in the chuck base.
In order to increase their performance, the density and complexity of semiconductor devices is increasing. Feature sizes, i.e. line widths, pad areas etc. are becoming increasingly smaller. This has led to certain new requirements for temperature-controlled chucks.
As an example, the number of probe pins to be connected to each individual die is increasing. Each of these probe pins can exert a pressure of up to several ounces on each of the test pads. With a high number of probe pins, which can be several hundred over a 1 square inch area or less, the supporting chuck is put under a relatively high load due to the applied force. This force can cause the chuck to deform. Bending and displacement of the chuck, even by relatively minute amounts, can, in turn, result in the test probe pins moving off the test pads.
A solid chuck, for example, not one that is temperature controlled, can provide the structural strength required for this probing. However, insufficient rigidity can be a problem for current temperature-controlled chuck designs. Conventionally, incorporating heating and cooling means reduces the structural strength of the chuck. Current temperature-controlled chuck design is limited to less than optimal performance in providing both the thermal performance and mechanical stability required for these high probe force applications. What is needed is a temperature-controlled chuck that has good thermal performance and also a high degree of structural strength in resisting loads induced by probe pins.
For accurate positioning of the probe pins on each die, the wafer chuck must remain mechanically stable. In addition to deformation resulting from applied load forces, heating and cooling of the temperature-controlled chuck can lead to changes in the height, leveling and planarity of the top surface of the chuck, which can in turn require re-calibration of the probe station, repositioning of probe pins, and re-focusing of microscopes. Current temperature-controlled chuck designs provide less than desirable mechanical stability over the needed temperature ranges. What is needed is a temperature-controlled chuck design that will minimize changes in height, leveling and planarity over the temperature range of the chuck during testing.
As mentioned, wafer chucks are usually mounted in probe stations that, amongst other functions, position the wafer chuck such that the semiconductor die is brought into contact with the probe pins. The chuck is mounted on a prober stage that can be moved, manually or automatically, with extreme accuracy. These prober stages in particular can be sensitive to changes in temperature. Current temperature-controlled chucks provide various means of thermal insulation between the chuck and the prober stage. Over time however, thermal energy can be conducted to or from the prober stage. In cases where the temperature deviates significantly from ambient this can cause inaccuracies of positioning or damage to the prober station or prober stage. What is needed is a system that mitigates or eliminates this and the other problems discussed above.
SUMMARY OF THE INVENTION
In a first aspect of the invention, a temperature-controlled semiconductor wafer chuck system is provided which incorporates a wafer chuck having a top surface and a bottom surface, the chuck being configured for mounting on a prober stage of a wafer probe station, the system comprising a heat sink incorporating a cooler, which further comprises a fluid conduit which distributes a coolant fluid substantially uniformly through the heat sink for removing thermal energy therefrom. The heat sink further comprises pillars disposed in the fluid conduit and configured to transfer force across the fluid conduit, whereby forces applied to the top surface of the chuck are transferred through the heat sink incorporated in the chuck to the prober stage, without substantial deformation of the chuck.
In another aspect of the invention it provides a temperature-controlled semiconductor wafer chuck system including a chuck further including a chuck top plate comprising a top surface of the chuck, a chuck bottom plate comprising a bottom surface of the chuck, a first heater disposed between the heat sink and the top surface of the chuck and a second heater disposed between the heat sink and the bottom surface of the chuck. With this configuration the temperature of the top surface of the chuck and the bottom surface of the chuck can be independently controlled. In a more detailed aspect the top and bottom surfaces can be independently maintained at different desired temperatures. This is done by independently controlling the first and second heaters as required to independently add heat to the chuck adjacent the top and bottom surfaces respectively, and removing heat through the heat sink as required b

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