HOLDING DEVICE FOR AN INTEGRATED CIRCUIT CHIP

Abstract: A holding device for an integrated circuit chip (60) includes a thermally conductive body (10) provided with a cavity (12) in which are arranged thermoelectric modules (14, 15) having located thereon a conductive pad (16) on which is mounted a further thermoelectric module (18) in contact with a thermally conductive block (20). The block (20) extends into a gas chamber (50) located in the body (10) and having upper and lower thermally insulative, slotted plates (24, 27). A socket (22) mounted on the lower plate (22) receives, via the slot in the upper plate (27), an integrated circuit chip (60). The thermoelectric modules (14, 15, 18) serve to rapidly heat and cool the chip. Dry nitrogen gas supplied via an inlet (30) to the gas chamber (50) is directed towards the chip (60) by inclined edges of the slot in the upper plate (27), thereby inhibiting condensation during cooling of the chip (60).

Description: HOLDING DEVICE FOR AN INTEGRATED CIRCUIT CHIP Technical Field , This invention relates to holding devices for integrated circuit chips, of the kind including socket means for releasably mounting a chip. Background Art Two operations frequently undertaken in con¬ nection with the manufacture of integrated circuit chips are failure analysis and temperature characterization. Failure analysis, which is a post-mortem examination of failed I.C. chips to determine the causes of failure, is an important procedure in semiconductor manufacturing. By ' sing failure analysis, corrective actions may be taken in production processing, device design, test or application to eliminate the cause or prevent recurrence of the failure reported. Failure analysis typically consists of inserting a decapped I.C. chip into a test socket, subjecting the chip to extreme temperatures (in the range of about -60°C. to +150 β C.) and performing electrical tests to determine (1) whether opens, shorts or abnormal characteristics exist between pairs of pins, pins and die or substrate, or pins and device package (2) the threshold voltages of transis¬ tors, clock signals, and (3), in general, the operating characteristics of the I.C. chip. Testing is accom¬ plished, typically, at an analytical probing test sta¬ tion with the aid of in-circuit probing equipment such as a micromanipulator which allows visual inspection of the individual circuits on a chip under high magnifi- cation (of up to 2000X) and probing of the circuits by means of tungsten probe tips. Closely related to failure analysis is tem¬ perature characterization of the I.C. chip. This is an electrical verification procedure by which a newly de- signed chip, immediately after fabrication, is subjected _0..-H to extremes of temperature to ensure that the chip meets all the required electrical parameters. In an article by D. A. Zeskind, "Thermoelec¬ tric Heat Pumps Cool Packages Electronically" , Elec- tronics, July 31, 1980, pages 104-113, the concept of utilizing thermoelectric modules in connection with hot and cold wafer-holding chucks for semiconductor testing is mentioned. Such thermoelectric modules utilize the Peltier effect and consist of a number of Peltier couples, formed by joining p-doped and n-doped semi¬ conductor elements, connected electrically in series and thermally in parallel by means of copper connecting strips. The couples are embedded between ceramic face¬ plates to electrically insulate the connecting strips from external surfaces. Passage of an electrical cur¬ rent through the module heats all Peltier couple junc¬ tions attached to one faceplate and cools all the junc¬ tions attached to the other faceplate thereby pumping heat from one faceplate to the other. It is found that when integrated circuit chips are cooled to the low temperatures utilized in failure analysis and temperature characterization operations, condensation of water vapor on the chips tends to occur, thereby impairing microprobing of the microcircuits on the chip. Disclosure * of the Invention It is an object of the present invention to provide a holding device for an integrated circuit chip, of the kind specified, which is simple, inexpensive, reliable and portable and which is capable of rapidly heating, cooling and stabilizing the temperature of an integrated circuit chip during temperature characteri¬ zation and failure analysis, wherein the problem of water vapor condensation during cooling is alleviated. Therefore, according to the present invention, there is provided a holding device for an integrated circuit chip, of the kind specified, characterized by a thermally conductive member adapted for thermal com¬ munication with the mounted chip, thermoelectric means in thermal communication with said thermally conductive member and adapted to selectively heat or cool said thermally conductive member, and gas flow means adapted to direct a flow of gas to the neighborhood of the mounted chip. It will be appreciated that in a holding de- vice according to the invention the provision of gas flow means enables a flow of dry gas to inhibit conden¬ sation of water vapor on the integrated circuit chip. Preferably the device includes a body member formed of a thermally conductive material, the gas flow means including a gas chamber located within the body member, inlet means adapted to supply gas to the gas chamber and direction control means adapted to direct the gas from the chamber towards the chip. Brief Description of the Drawings One embodiment of the invention will now be described by way of example with reference to the accom¬ panying drawings, in which: Fig. 1 is an exploded perspective view of an integrated circuit chip holding device; and Fig. 2 is an assembled view of the integrated circuit chip holding device of Fig. 1. Best Mode for Carrying Out the Invention Turning now to Figs . 1 and 2 of the drawings, an integrated circuit chip holding device includes a thermal body or block 10 constructed of a high thermal conductivity material such as aluminum, which is easily machinable, inexpensive and durable. In the embodiment shown, the external dimensions of the thermal block 10 are about 15 x 13 x 9 cms. Thermal block 10 serves as a heat sink during the cooling operation and a heat source OMPI during the heating operation of an I.C. chip 60. During the heating operation, the block 10 will absorb heat from the ambient air which is then transferred to the chip. During the cooling operation, the thermal block 10 will absorb heat from the chip. In order to maximize heat transfer to/from the environment, the thermal block 10 is provided with a number of vertical flanges 11 made in the walls of the block 10 creating a finned structure as shown in Fig. 1. The flanges 11 increase the surface area of the block 10, thereby enhancing convection and radiation of heat to the surrounding environment during the cooling operation and absorption of heat from the ambient during the heating operation of the chip. The thermal block 10 has a rectangular cavity 12, illustratively, of dimensions 6 9 cms. and a flat floor 13. Embedded at the center of floor 13 is a thermocouple TC. for measuring the temperature of block 10. Arranged flush against the cavity floor 13 are a pair of commercially available thermoelectric modules 14 and 15. The thermoelectric modules 14 and 15 each have a pair of upper and lower ceramic faceplates 14A and 14B and 15A and 15B, respectively, constructed of a metal¬ lized ceramic material hav.ing a high electrical insula¬ tion and thermal conduction. Embedded between the faceplates 14A and 14B of thermoelectric module 14 and between faceplates 15A and 15B of thermoelectric module 15 are a number of Peltier couples 14C and 15C, respec¬ tively, which are connected electrically in series and thermally in parallel. When a low voltage of up to about 8 volts is applied to the thermoelectric modules 14 or 15, by connecting the wires 14D and 14E of module 14 and wires 15D and 15E of module 15 to a suitable power source, causing a current flow of about 1-15 amps therein, these modules, due to Peltier effect, behave like a heat pump by absorbing heat from one end (top or bottom) of the module and rejecting heat at the other end. Reversing the current in modules 14 and 15 rever¬ ses the direction of heat flow. In the embodiment in Figs. 1 and 2, the modules 14 and 15 have the approxi¬ mate dimensions 3 x 3 x 0.4 centimeters and are sold as Part No. CP 1.4-71-06L by Material Electronic Products Corporation, Trenton, New Jersey. The modules 14 and 15 may be connected together, in series or parallel, and operated by a single power supply. Overlying modules 14 and, 15 is a pad 16 made of a material having high thermal conductivity, such as copper, to distribute heat evenly over the entire pad. Heat from pad 16 can then be uniformly transferred by modules 14 and 15 downward during the cooling operation or upward during the heating operation of the chip. In the embodiment shown, the dimensions of pad 16 are approximately 4.5 x 8 x 0.5 cm. A thermocouple TC„ is inserted in pad 16 through a hole drilled therein as shown in Fig. 1 to monitor the heat flow across the pad. The pad 16 is rigidly fastened to the thermal block 10 by means of screws 17A and 17B (Fig. 2 ) and securely holds the modules 14 and 15 against the block 10 to eliminate any vibrations. The combination of the thermoelectric modules 14 and 15 and the pad 16 constitutes the first stage of a two-stage heat pumping mechanism and will hereinafter be referred to by this name. To insure good thermal contact between the thermoelectric modules 14 and 15 and the block 10, a thin coating of a heat conductive compound such as zinc oxide crystals in silicon grease is applied to the lower faceplates 14B and 15B of modules 14 and 15, respec- tively. Similarly, to insure good thermal contact between the modules 14 and 15 and the pad 16, the upper faceplates 14A and 15A of modules 14 and 15, respec¬ tively, are coated with the just-mentioned heat conduc¬ tive compound. Arranged atop pad 16, in a central portion thereof, is another thermoelectric module 18. In the exemplary embodiment shown, module 18 is of the same type and size as modules 14 and 15 and has an upper ' faceplate 18A and a lower faceplate 18B embedded between which are a number of -Peltier couples 18C. Module 18 is connected to a power supply (not shown) to enable it to function as a heat pump. The upper and lower faceplates 18A and 18B, respectively, of module 18 are coated with a thin layer of the heat conductive compound discussed above in connection with the modules 14 and 15, to enhance thermal contact between the lower faceplate 18B and the pad 16 and the upper faceplate 18A and the block 20. Block 20 overlies the thermoelectric module 18 and is affixed to pad 16, securing the module 18 against the pad 16, by means of screws 19A and 19B (Fig. 2). Block 20 is made of a high thermal conductivity mater¬ ial, such as copper, and has a configuration as shown in Fig. 1 to receive an I.C. chip socket 22 having a rec¬ tangular cavity therein, and a flat contact area 21 for the I.C. chip to make uniform contact with. A thermo- couple C 3 is mounted in a hole drilled in block 20 to measure accurately the temperature of the I.C. chip resting on the contact area 21 within socket 22. The configuration of block 20 is designed to insure that socket 22 will be received with zero insertion force and, when the apparatus is assembled, will not vibrate. Another design feature of block 20 is that the contact area 21 is chosen to be as large as needed to match the particular I.C. chip to be tested. Also, since block 20 is rigidly mounted, during the probing operation, the block 20 will not allow the socket to move as a result of stresses introduced into the socket by the probe tips, j The combination of the thermoelectric module 18 and block 20 comprise the second stage of the two- stage heat pumping mechanism, and will be referred to by this name hereinafter. The socket 22 is a commonly available insu¬ lating socket of a size and configuration and having pin holes 22A to receive a 24, 28, 40 or 64 pin chip 60 with zero insertion force. Socket 22 may be provided with a mechanical latch (not shown) for rigid attachment of the socket 22 to the block 20. Alternatively, socket 22 may be fastened to block 20 by screws 23A and 23B (Fig. 2). Attached to socket 22 is a cable 40 consis¬ ting of wires connecting to each of the socket pins. The bottom cover plate 24 is made of a ther¬ mally insulating material such as plexiglass, and is attached to the thermal block 10 by screws 25A and 25B (Fig. 2) to thermally seal cavity 12 and minimize con- vective currents due to the flow of gases from the outside which deleteriously affect the heat pumping process. Additionally, the empty space of cavity 12 may be filled with a thermally insulative material, such as styrofoam, for a more efficient heat pumping process. Cover plate 24 is provided with a rectangular slot 26 (Fig. 1) to permit the upper portion of block 20 to pass therethrough as shown in Fig. 2. The top cover plate 27, which is also made of a thermally insulative material like plate 24, is at¬ tached to the thermal block 10 by screws 28A and 28B such that the separation between plates 24 and 27 is approximately one-half inch (about 1.3 cm). Cover plate 27 is provided with a slot for inserting/removing the I.C. chip 60 as shown in Fig. 2. The edges 29 of this slot are sloped inward (bottom-to-top) to direct the flow of dry nitrogen gas, introduced through the gas inlet 30 of block 10, toward the top of the I.C. chip area. By forcing dry nitrogen gas in the chamber 50 between the bottom cover plate 24 and the top cover plate 27 and the region where the I.C. chip 60 is inser¬ ted detrimental condensation of water vapor on the chip during the cooling operation is avoided. As shown in Fig. 1, the thermal block 10 is provided with hole 31 to receive the cable 40, holes 32 and 33 to receive the appropriate pair of wires 14D, 14E, 15D or 15E from the serially/parallely connected thermoelectric modules 14 and 15, holes 34 and 35 to receive wires 18D and 18E from the thermoelectric module 18, and holes 36-38 to receive the thermocouples TC. , TC,, and TC_ , respectively. Cable 40 is electrically connected to appropriate external electrical I.C. chip testing devices (not shown) . Thermocouples TC. , TC,, and TC. are connected to suitable temperature recorders. The wires emerging from holes 32-35 are connected to suitable D.C. power supplies to activate the thermo¬ electric modules 14, 15 and 18. MODE OF OPERATION The operation of the apparatus will be des¬ cribed in two parts: (1) the cooling operation " , and (2) ' the heating operation. Cooling Operation The cooling operation will now be explained with reference to the assembled device shown in Fig. 2. The I.C. chip 60 to be cooled is inserted into socket 22 so that the metal bar on the chip is flush against the contact area 21 of the block 20. Dry nitrogen gas is then introduced through the inlet 30, maintaining a positive gas pressure inside the chamber 50. The power supplies which activate modules 18, 14 and 15 are turned on, causing currents to flow in all the modules in a direction such that heat will be pumped from the I.C. chip 60 to the thermal block 10 (which in this particu¬ lar operation functions as a heat sink) . The performance characteristics- of the first and second stage thermoelectric modules are a function of such module parameters as the operative current, the base temperature of the module, and the coefficient of performance. For example, using Melcor CP1.4-71-06 modules at room temperature and a voltage of 6 volts causing a current flow of 2.5 amps through each module, the rate of ' Tieat transferred by the modules will be about 17 wa-tts and the temperature differential between the upper and lower faceplates of each module will be about 20°C. The second stage thermoelectric module 18 will absorb heat from the I.C chip 60 via the block 20 at the upper end of the module and reject heat at the lower end of the module to the pad 16. This rejected heat, due to the high thermal conductivity of pad 16, will be readily distributed uniformly throughout pad 16, thereby raising the temperature of pad 16. The first stage thermoelectric modules 14 and 15 will, in turn, absorb heat from pad 16 and transfer it to the block 10. By means of thermocouples TC. , TC_ and TC_, the temperatures of the heat block 10, the pad 16 and the block 20 are monitored. Using these temperatures, the operating currents of the thermoelectric modules 14, 15 and 18 are adjusted by means of suitable current regulators (not shown) to the optimum values thereby maximizing the efficiency of this two-stage heat-pumping mechanism. As a result of this heat transfer mechanism and since the I.C. chip 60 generally has a small thermal inertia and the block 10 has a large heat-absorption capacity, the chip will cool rapidly well below the ambient typically in a minute or two. If the heat load of the I.C. chip 60 is high, i.e., the chip is powered, due to the load's thermal inertia it will, of course, take a longer time to cool the chip. Also, when the heat load of the chip is high, additional cooling to dissipate heat from the block 10 is advantageous. This may be accomplished by circulating air around the block 10 or by immersing the block 10 in a cold liquid bath. Alternatively, the block 10 may be cooled by forming cooling channels therein and forcing a coolant through these channels. By using this two-stage heat-pumping action, the I.C. chip may be cooled to a temperature of about -55°C. O PI Heating Operation In this mode of operation, the thermal block 10 functions as a reservoir/source of heat which is transferred to the I.C. chip 60, thereby rapidly heating the chip. To heat the I.C. chip 60 mounted on socket 22, the currents in the various thermoelectric modules are reversed by reversing, for example, the polarities. The operating currents of the first and second stage thermoelectric modules are adjusted to obtain optimal heat transfer. Heat from block 10 is pumped upward by the first stage thermoelectric modules 14 and 15 to pad 16 where it is quickly and uniformly distributed. The second stage thermoelectric module 18 will, in turn, transfer heat from pad 16 to the block 20r Block 20 quickly conducts heat to the I.C. chip 60 in contact with the contact area 21, thereby heating the chip. In this mode of operation, temperatures of over 100°C. may be achieved in a very short time. Using the operational modes described above, it is possible to rapidly heat or cool I.C. chips in a test socket in the wide temperature range of about -55°C. to 105°C. to an accuracy of +1°C. without the problems of condensation of moisture or frosting on the chip, and chip vibration. To obtain temperatures higher than about 105°C, the embodiment shown above may be modified by introducing a resistance heater element in the first stage, for example, inside pad 16. By direct¬ ly heating pad 16 in this manner, heat from pad 16 can be rapidly transferred by the second stage of the heat pump to the I.C. chip 60, thereby raising the temper¬ ature of the chip to the desired value. Also, by in¬ creasing the number of stages of the heat pumping mech- ι anism of this invention to, for example, four stages by means of a cascade of thermoelectric modules, the chip may be cooled to a temperature of about -75°C. and heated to about 120°C. or more. In a modified embodiment there may be only a single stage heat pumping apparatus consisting of one or both of the thermoelectric modules 14 and 15 in direct contact with the block 20 (i.e. without the need for pad 16 and module 18). OMPΪ

Claims: CLAIMS : 1. A holding device for an integrated cir¬ cuit chip (60), including socket means (22) for releas- ably mounting said chip (60), characterized by a ther¬ mally conductive member (20) adapted for thermal com- munication with the mounted chip (60), thermoelectric means (14, 15, 18) in thermal communication with said thermally conductive member (20) and adapted to selec¬ tively heat or cool said thermally conductive member (20), and gas flow " means (27, 29, 30) adapted to direct a flow of gas to the neighborhood of the mounted chip (60). 2. A device according to claim 1, charac¬ terized in that said thermoelectric means includes first and second thermoelectric stages (14, 15; 18), said second thermoelectric stage (18) being in thermal communication with said thermally conductive member (20) and with a thermally conductive pad (16), and said first thermoelectric stage (14, 15 Y being in thermal communi¬ cation with said thermally conductive pad (16). 3. A device according to claim 2, charac¬ terized in that said first thermoelectric stage includes a pair of thermoelectric modules (14, 15). 4. A device according to claim 3, charac¬ terized by a body member (10) of thermally conductive material, said body member (10) including a cavity (12) having said thermoelectric means (14, 15, 16) located therein. 5. A device according to claim 4 , charac¬ terized in that said gas flow means includes a gas chamber ( 50 ) , located within said body member (10) , inlet means ( 30 ) adapted to supply gas to said gas 5. (concluded) chamber (50) and direction control means (29) adapted to direct the gas from said chamber (50) towards said chip (60). 6. A device according to claim 5, charac¬ terized by a slotted member (27) having a slot providing access for mounting said chip (60) in said socket means (22), said direction control means being formed by in- clined edges (29) of said slot. 7. A device according to claim 6, charac¬ terized in that said gas chamber (50) is located between said slotted member (27) and a thermally insulative member (24) having a slot (26) permitting a portion of said thermally conductive member (20) to pass there¬ through, said cavity (12) being disposed beneath said thermally insulative member (24). 8. A device according to claim 7, charac¬ terized in that said thermally conductive pad (16) is rigidly attached by screws (17A, 17B) to a lower surface of said cavity (12), in that said thermally conductive member (20) is rigidly attached by screws (19A, 19B) to said thermally conductive pad (16), in that said socket means (22) is rigidly attached by screws (23A, 23B) to said thermally insulative member (24) and in that said slotted member (27) and said thermally insulative member (24) are rigidly attached to said body member (10) by screws (28A, 28B; 25A, 25B) . 9. A device according to claim 8, charac¬ terized in that temperature monitoring devices are pro¬ vided on said body member (10) adjacent the lower sur¬ face of said cavity (12); on said thermally conductive pad (16); and on said thermally conductive member (20). CMPI 10. A device according to any one of the preceding claims, characterized in that said gas is dry nitrogen gas.

Inventors: PERCHAK ROBERT MATTHEW, PERCHAK, ROBERT, MATTHEW
Applicants: NCR CO, NCR CORPORATION
Application year: 1983
Main classification: H01L23
IPC codes: H01L21, H01L23