Abstract:
An apparatus is provided to cool high-performance instruments within a semiconductor test head using direct facility water. The direct facility water cooling apparatus consists of an air chamber, a first base to receive and removably mount the instrument within the air chamber, a test head inlet in fluid communication with the first base and a facility water supply, a test head discharge in fluid communication with the first base and a facility drain, and a fan in fluid communication with the air chamber inlet to induce the flow of air from the air chamber inlet to the air chamber outlet.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims priority to and the benefit of U.S. Provisional Patent Application No. 60/780,910, filed on Mar. 9, 2006, the entire contents of which are incorporated by reference herein. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates generally to thermal regulation within automatic testing equipment (“ATE”) used to test semiconductor devices and, more particularly, to a system for temperature control of one or more instruments in the test head within the testing equipment. 
     BACKGROUND OF THE INVENTION 
     In manufacturing a semiconductor device, testing equipment is typically used for quality control of a finally produced device. In such testing equipment a test head consists of one or more instruments which perform a variety of tests on the device. The temperature control of these instruments is usually accomplished using either a liquid chiller or an air-cooling system. However such test equipment is typically limited in cooling capacity and unsuitable for cooling high-end, high-performance instruments. 
     Improved testing equipment would be realized if three main functional requirements of the cooling system could be achieved: high-performance, scalability and compactness. High-performing cooling systems would enable high-end instrument development and could be leveraged to improve reliability of tests conducted. A cooling system that scales according to cooling capacity required by the test head is also desirable. Such a system would allow users of low-power instruments to avoid the cost of excess cooling capacity needed by a test head populated with high-power instruments. Finally, a cooling system that can be integrated into a test head would enable a “tester-in-a-test head” system architecture that is compact and easy to work with. 
     A test head that uses facility water for cooling purposes presents its own unique challenges. Bio-growth and freezing are typically prevented by the addition of chemicals to the facility water. This can leave traces of glycol or polyglycol behind making the water inappropriate for use with bare aluminum. Facility water is generally cooled to a temperature lower than ambient temperature of a laboratory or manufacturing facility. With relative humidity ranges between 30-60%, the dew point at an extreme temperature-relative humidity combination can be above the entering water temperature. As a consequence, water often condenses on the external plumbing surfaces. Facility water may also be undesirable for direct cooling because of the persistent presence of dissolved salts and particles as well as the threat of corrosion to the plumbing. Thus, facility water has been typically employed as a primary loop fluid while another coolant was employed in a secondary, or process loop. This arrangement is similar to a heat exchanger with a dedicated test head coolant loop. Systems developed by Agilent, Schlumberger, Advantest, LTX and Teradyne are examples of this mode. 
     Typically, such secondary loops are placed in large and expensive cabinets. These cabinets are bulky, and are usually fixed within a section of the room. As a consequence, such systems are frequently dependent on process loop placement and are expensive, cumbersome arrangements. 
     SUMMARY OF THE INVENTION 
     Thus, a need exists for a high-performance cooling system capable of using direct facility water in the test head. 
     In satisfaction of this need, an embodiment of the present invention provides an apparatus for cooling an instrument in a semiconductor device test head consisting of an air chamber having an air chamber inlet and an air chamber outlet. The apparatus also consists of a first base having a first base inlet and a first base outlet to receive and removably mount the instrument within the air chamber so that the instrument is exposed to the air chamber, a test head inlet in fluid communication with the first base inlet and a facility water supply, a test head discharge in fluid communication with the first base outlet and a facility drain, and a fan in fluid communication with the air chamber inlet to induce the flow of air from the air chamber inlet to the air chamber outlet. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       These and other aspects of this invention will be readily apparent from the detailed description below and the appended drawings, which are meant to illustrate and not to limit the invention and in which: 
         FIGS. 1 ,  2  and  3  are schematic diagrams of an exemplary cooling system for cooling a test head according to embodiments of the present invention; 
         FIG. 4  is a schematic diagram of exemplary cooling system for directly preheating cooling water injected into a test head; and 
         FIG. 5  is a schematic diagram of an exemplary system for indirectly preheating water injected into a test head in accordance with an embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     The systems and apparatus for cooling test head instruments by directly coupling the test head to a facility water supply will now be described with respect to various embodiments. However, the skilled artisan will readily appreciate that the systems described herein are merely exemplary and that variations can be made without departing from the spirit and scope of the invention. In this description, like numbers refer to similar elements within various embodiments of the present invention. 
     Embodiments of the present invention provide systems that use direct facility water to cool instruments within a test head of a testing apparatus. This may be accomplished by coupling the test head directly to a facility water supply. In other embodiments, the system is structured to allow air flow through spaces between the instruments within the test head. This may be accomplished by spacing the instruments sufficiently apart in an air chamber. Air flows from an air chamber inlet, through spaces between the instruments and discharges through an air chamber outlet. Flow of air may be induced by the use of fans. 
       FIG. 1  is a schematic diagram of an exemplary cooling system  10  for cooling a test head  100  having an inlet  102  and a discharge  104 , according to an embodiment of the present invention. Test head  100  may be used to house various instruments to test a semiconductor device. According to such an embodiment, inlet  102  is connected directly to a facility water supply. Discharge  104  is configured to remove cooling water from test head  100 , such as by a pump or gravity drain. In some embodiments, discharge  104  may be configured to return the cooling water back to the facility water line. 
       FIG. 2  is a schematic diagram of an exemplary cooling system  20  for cooling test head  100 . System  20  is similar in many respects to system  10  except that system  20  includes a fluid polishing and monitoring system (“FMPS”)  106  interposed between inlet  102  and test head  100 . FMPS  106  may be configured to include one or more components to condition the fluid entering test head  100 , such as for biogrowth inhibition, deionization, heating and particulate filtration. Such components may be arranged within FMPS  106  to allow fluid entering from inlet  102 . Two or more components associated with FMPS  106  may be arranged serially or in parallel. In some embodiments, the fluid entering from inlet  102  may be allowed to flow through a select number of components. In other embodiments, redundant units of each type of component may be installed. 
       FIG. 3  is a schematic diagram of an exemplary cooling system  30  for cooling test head  100 . In the illustrated embodiment, system  30  includes test head  100 , inlet  102 , outlet  104  and FPMS  106 . Test head  100  includes a supply manifold  202 , a plurality of inlet channels  204   a - 204   l , a plurality of instruments  206   a - 206   l  under test, and a return manifold  210 . As illustrated, FPMS  106  includes a particulate filtration component  212 , a deionization component  214 , an in-line heating component  216 , a pressure boosting component  218 , a flow rate regulation component  210 , and a bio-growth inhibition component  222 . Although FMPS  106  is illustrated as providing six components, those skilled in the art will appreciate that FMPS  106  may include more or less components each of which may provide one or more functions. 
     As illustrated, supply manifold  202  is configured to collect and forward incoming facility water to instruments  206   a - 206   l  within test head  100 . Return manifold  210  collects the facility water that has passed through instruments  206   a - 206   l  and forwards it to discharge  104 . 
     Instruments ( 206   a - 206   l ) generally comprise circuit boards or channel cards that may be mounted on one or more bases within test head  100  in order to interface with the tested semiconductor device in a controlled fashion. 
     Particulate filtration component  212  may be configured to ensure the facility water is free from particles greater than a predetermined size. For example, particulate filtration component  212  may be configured to remove particles greater than 1,000, 100 or 10 microns. Deionization component  214  may be used to remove dissolved salts. 
     In-line heating component  216  may be configured to minimize condensation on external plumbing surfaces. In various embodiments, in-line heating component  216  is responsive to ambient temperature and relative humidity measurements. In some embodiments, in-line heating component  216  may be configured to limit the water temperature rise, for example, by about 1.0 degree centigrade. 
     Pressure boosting component  218  may be configured to maintain a relatively consistent flow rate inside test head  100 . In an embodiment, pressure boosting component  218  may be a single booster pump or a plurality of booster pumps connected either in series, parallel or a combination thereof. A variety of pumps may be used including, for example, a magnetic drive pump. Each such drive pump typically occupies about 4″×4″×4″ of space and has a 10 pounds/sq. inch boost capacity. Flow regulator  220  may be used to throttle fluid flow through inlet  102 . Additionally, bio-growth inhibition component  222  may be used to treat facility water with bio-growth inhibitors. 
       FIG. 4  is a schematic diagram of exemplary cooling system  40  for directly preheating cooling water injected into test head  100  in accordance with an embodiment of the present invention. System  40  includes test head  100 , inlet  102 , discharge  104 , pressure boosting component  218 , a temperature sensor  402 , a by pass valve  404 , and a preheat line  406 . Although not shown, it should be apparent to one skilled in the art that FMPS  106  may be included in system  40  without departing from the principles of the invention. 
     As illustrated, temperature sensor  402  is configured to track the temperature of incoming facility water. Temperature sensor  402  provides feedback in the form of an input signal to by pass valve  404 . By pass valve  404  is provided to adjust the ratio of outgoing facility water to incoming facility water at inlet  102 . The remainder of the outgoing facility water is directed towards the discharge  104 . Preheat line  406  is configured to mix the outgoing facility water with the incoming facility water from inlet  102 . Check valves (not shown) may be used to prevent a backflow of the outgoing facility water. 
       FIG. 5  is a schematic diagram of an exemplary cooling system  50  for indirectly preheating water injected into test head  100  in accordance with an embodiment of the present invention. System  50  includes test head  100 , inlet  102 , discharge  104 , temperature sensor  402 , by pass valve  404 , a heat exchanger  504 , a heat exchanger inlet  502 , and a heat exchanger discharge  506 . 
     As illustrated, heat exchanger inlet  502  directs the outgoing facility water to heat exchanger  504 . Heat exchanger discharge  506  is configured to return the outgoing facility water from heat exchanger  504  back to discharge  104 . 
     In operation, facility water is pumped directly into test head  100  as illustrated in  FIG. 1 . Incoming facility water flows from the tap in the manufacturing facility through inlet  102  to test head  100 . After performing its function within test head  100 , the facility water flows towards discharge  104 . As illustrated in  FIG. 2 , FPMS  106  may be provided in-line with facility water cooling system in accordance with an embodiment of the present invention. 
     Referring now to  FIG. 3 , the facility water from inlet  102  passes through FPMS  106 , and internal components  212 - 222 . Internal components  212 - 222  perform several facility water conditioning activities such as particulate filtration, deionization, heating, pressure boosting, flow rate regulation, and bio-growth inhibition before forwarding the facility water to test head  100 . 
     The facility water flow rate is controlled by the combination of pressure boosting component  218  and flow rate regulator  220 . The facility water is then collected in supply manifold  202  and subsequently forwarded through paths  204   a - 204   l  provided to direct the flow of incoming water to instruments  206   a - 206   l . After distribution of the facility water to cool instruments  206   a - 206   l , return paths  208   a - 208   l  carry the facility water to return manifold  210 . The collected facility water is then forwarded to discharge  104  connecting test head  100  to facility water drain. 
     Those skilled in the art will recognize the many benefits and advantages afforded by the present invention. The invention provides the user with a semiconductor testing system that utilizes direct facility water for the liquid cooling portion. Thus, the invention enables high-power instruments operating on a semiconductor device to be cooled using a scalable liquid cooling system. The apparatus is also compact thus enabling it to be packaged within the tester. 
     While the invention has been particularly shown and described with references to certain embodiments, it will be understood by those skilled in the art that various changes in form and detail may be made therein without departing from the spirit and scope of the invention.