Method and system for decoupling inoperative passive elements on a semiconductor chip

Abstract

The present invention teaches a method and system for disconnecting shorted decoupling capacitors, wherein a semiconductor chip having a plurality of redundant decoupling capacitors. Each of the capacitors is coupled, by means of a link, to a bus having a predetermined voltage. Each link is accessible to light emissions, in planar view. The system comprises a tester for testing the operability of each of the capacitors. In a preferred embodiment, the tester comprises a heating element and a high voltage stress testing element. Under thermal and voltage stress, an infrared signal identifying shorted decoupling capacitors is generated by shorted decoupling capacitors. The system further comprises a sensor for sensing the infrared signal. In one embodiment of the present invention, the sensor comprises an emission microscope for multilevel inspection ("EMMI"). Each inoperable capacitor is decoupled from the bus by disintegrating the link with a laser in response to the infrared signal. In an alternate embodiment, the link is disintegrated by an acid etch comprising H 2 SO 4 , H 2 SO 4 and H 2 O 2 , or H 2 PO 4 .

What is claimed is: 
     
       1. A method for decoupling inoperative elements on a semiconductor chip comprising the steps of: providing said semiconductor chip having a plurality of redundant passive elements, each of said elements coupled to a bus by means of a link, said bus associated with a predetermined voltage;   testing each of said elements for operability, said testing generating a signal identifying which of said elements are inoperable: and   decoupling each of said inoperable elements externally from said bus in response to said signal.   
     
     
       2. A method for decoupling inoperative elements, according to claim 1, wherein at least one of said elements is a decoupling capacitor. 
     
     
       3. A method for decoupling inoperative elements, according to claim 2, wherein said link comprises substantially low resistive characteristics. 
     
     
       4. A method for decoupling inoperative elements, according to claim 3, wherein said predetermined voltage is substantially in the range of 3 Volts and 5 Volts, and said testing comprises the step of: applying a voltage along said bus substantially in the range of 7 Volts and 8 Volts for a time substantially in the range of 1 minute and 48 hours.   
     
     
       5. A method for decoupling inoperative elements, according to claim 4, wherein said testing further comprises the step of: heating said semiconductor chip to a temperature substantially in the range of 120° C. and 140° C. for a time substantially in the range 1 hour and 48 hours.   
     
     
       6. A method for decoupling inoperative elements, according to claim 5, wherein said testing further comprises the step of: sensing a light emission from each of said inoperative elements.   
     
     
       7. A method for decoupling inoperative elements, according to claim 6, wherein said light emission is substantially within the infrared wavelength spectrum. 
     
     
       8. A method for decoupling inoperative elements, according to claim 7, wherein said sensing is accomplished by means of an emission microscope for multilevel inspection. 
     
     
       9. A method for decoupling inoperative elements, according to claim 7, wherein said decoupling comprises the step of: disintegrating said link of said inoperable element in response to said infrared light emission.   
     
     
       10. A method for decoupling inoperative elements, according to claim 9, wherein said disintegrating is performed by exposing said link to external energy substantially in the range of 0.1 μWatt and 10 mWatt. 
     
     
       11. A method for decoupling inoperative elements, according to claim 10, wherein said external energy is generated by a laser. 
     
     
       12. A method for decoupling inoperative elements, according to claim 9, wherein said disintegrating is performed by means of an acid etch. 
     
     
       13. A method for decoupling inoperative elements, according to claim 12, wherein said acid etch comprises at least one of H 2  SO 4 , H 2  SO 4  diluted with H 2  O 2 , and H 2  PO 4 . 
     
     
       14. A system for decoupling inoperative elements on a semiconductor chip, the semiconductor chip having a plurality of redundant passive elements, each of said elements coupled to a bus by means of a link, said bus associated with a predetermined voltage; the system comprising: a. a base for mounting the semiconductor chip, and for providing operative power to the semiconductor chip;   b. means for evaluating the operability of each of said elements, said means for evaluating generating a signal identifying which of said elements are inoperable; and   c. means for externally decoupling each of said inoperable elements from said bus by disintegrating said link, said means for externally decoupling responsive to said signal.   
     
     
       15. A system for decoupling inoperative elements, according to claim 14, where said link comprises substantially low resistive characteristics and is accessible to light. 
     
     
       16. A system for decoupling inoperative elements, according to claim 15, wherein at least one of said elements is a decoupling capacitor. 
     
     
       17. A system for decoupling inoperative elements, according to claim 16, wherein said predetermined voltage is substantially in the range of 3 Volts and 5 Volts, and said means for evaluating comprises a stressing element coupled to said bus for applying a voltage substantially in the range of 7 Volts and 8 Volts for a time substantially in the range of 1 minute and 48 hours. 
     
     
       18. A system for decoupling inoperative elements, according to claim 17, wherein said means for evaluating comprises a heating element for heating said semiconductor chip to a temperature substantially in the range between 120° C. and 140° C. for a time substantially in the range between 1 hour and 48 hours. 
     
     
       19. A system for decoupling inoperative elements, according to claim 18, wherein said means for evaluating comprises a sensor for sensing a light emission from each of said inoperative elements. 
     
     
       20. A system for decoupling inoperative elements, according to claim 19, wherein said light emission is substantially within the infrared wavelength spectrum. 
     
     
       21. A system for decoupling inoperative elements, according to claim 20, wherein said sensor comprises an emission microscope for multilevel inspection. 
     
     
       22. A system for decoupling inoperative elements, according to claim 20, wherein said means for externally decoupling comprises a generator for generating energy externally, substantially in the range of 0.1 μWatt and 10 mWatt, to disintegrate said link in response to said infrared light emission. 
     
     
       23. A system for decoupling inoperative elements, according to claim 22, wherein said generator comprises a laser. 
     
     
       24. A system for decoupling inoperative elements, according to claim 20, wherein said means for externally decoupling comprises an applicator for applying acid to disintegrate said link in response to said infrared light emission. 
     
     
       25. A system for decoupling inoperative elements, according to claim 24, wherein said acid comprises at least one of H 2  SO 4 , H 2  SO 4  diluted with H 2  O 2 , and H 2  PO 4 . 
     
     
       26. An automated system for decoupling inoperative capacitors on a semiconductor chip, the semiconductor chip having a plurality of redundant capacitors, each of said capacitors coupled to a bus by a link, said bus associated with a predetermined voltage, said link comprising substantially low resistive characteristics and being accessible to light emissions; the system comprising: a. means for testing the operability of each of said capacitors, said means for testing generating an infrared signal identifying which of said capacitors are inoperative, said means for testing comprising: (1) a heating element for heating said semiconductor chip to a temperature substantially in the range between 120° C. and 140° C. for a time substantially in the range between 1 hour and 48 hours;   (2) a stressing element coupled to said bus for applying substantially in the range of 7 Volts and 8 Volts for a time substantially in the range of 1 minute and 48 hours; and     b. a sensor for sensing said infrared signal from each of said inoperative capacitors; and   c. a laser for externally decoupling each of said inoperative capacitors from said bus by disintegrating said link, said laser responsive to said signal and having a power range substantially between 0.1 μWatt and 10 mWatt. .Iadd.   
     
     
       27.  A method for decoupling a passive element coupled to a conductor through a link, the method comprising: providing the passive element, conductor, and link on a semiconductor chip;   testing the passive element for operability;   responsive to inoperability of the passive element, generating a signal identifying the passive element as inoperable;   sensing the identifying signal; and   decoupling the inoperable passive element externally from the chip in response to the identifying signal. .Iaddend..Iadd.28. The method of claim 27, wherein the step of testing the passive element for operability comprises applying a voltage to the conductor. .Iaddend..Iadd.29. The method of claim 27, wherein the step of providing the conductor on the chip comprises providing the conductor on the chip in association with an operating voltage, wherein the step of testing the passive element for operability comprises applying a voltage to the conductor that is substantially greater than the operating voltage. .Iaddend..Iadd.30. The method of claim 29, wherein the operating voltage is in a range between 3 Volts and 5 Volts, wherein the step of applying the voltage to the conductor comprises applying the voltage to the conductor substantially in a range between 7 Volts and 8 Volts for a period of time up to 48 hours.   
     
     
        .Iaddend..Iadd.31.  The method of claim 27, wherein the step of testing the passive element for operability comprises heating the semiconductor chip. .Iaddend..Iadd.32. The method of claim 31, wherein the step of heating the semiconductor chip comprises heating the semiconductor chip to a temperature substantially in a range between 120° C. and 140° C. for a period of time up to 48 hours. .Iaddend..Iadd.33. The method of claim 27, wherein the step of generating the signal identifying the passive element as inoperable comprises generating an electromagnetic emission from the inoperable passive element. .Iaddend..Iadd.34. The method of claim 33, wherein the generated electromagnetic emission is substantially within the light spectrum. .Iaddend..Iadd.35. The method of claim 27, wherein the step of sensing the identifying signal comprises sensing the identifying signal with an emission microscope for multilevel inspection. .Iaddend..Iadd.36. The method of claim 27, wherein the step of decoupling the inoperable passive element comprises disintegrating the link in response to the identifying signal. .Iaddend..Iadd.37. The method of claim 36, wherein the step of disintegrating the link comprises exposing the link to external energy sufficient to disintegrate the link. 
     
     
        .Iaddend..Iadd.38.  The method of claim 37, wherein the step of exposing the link to external energy comprises exposing the link to external energy substantially in a range between 0.1 μWatt and 10 mWatt. .Iaddend..Iadd.39. The method of claim 37, wherein the step of exposing the link to external energy comprises exposing the link to a laser beam. .Iaddend..Iadd.40. The method of claim 36, wherein the step of disintegrating the link comprises etching the link away with an etchant. .Iaddend..Iadd.41. The method of claim 40, wherein the etchant comprises at least one of H 2  SO 4 , H 2  SO 4  diluted with H 2  O 2 , and H 2  PO 4 . .Iaddend..Iadd.42. The method of claim 27 wherein the steps of testing, sensing, and decoupling are automated. .Iaddend..Iadd.43. A method for decoupling inoperable passive elements from a conductor, the method comprising: providing on a semiconductor chip the conductor coupled to each of a plurality of passive elements on the chip through one of a plurality of links on the chip;   testing the passive elements for operability;   responsive to inoperability of some of the passive elements, generating a signal associated with each inoperable passive element identifying the location on the chip of the inoperable passive element;   sensing each inoperable passive element's associated location identifying signal;   determining each inoperable passive element's location from its associated location identifing signal;   locating each inoperable passive element in accordance with its determined location; and   destroying the link coupled to each located inoperable passive element from a position external to the chip. .Iaddend..Iadd.44. The method of claim 43, wherein the step of testing the passive elements for operability comprises applying a voltage to the conductor. .Iaddend..Iadd.45. The method of claim 43, wherein the step of providing the conductor comprises providing the conductor in association with an operating voltage, wherein the step of testing the passive elements for operability comprises applying a voltage to the conductor that is substantially greater than the operating voltage. .Iaddend..Iadd.46. The method of claim 45, wherein the operating voltage is in a range between 3 Volts and 5 Volts, wherein the step of applying the voltage to the conductor comprises applying the voltage to the conductor substantially in a range between 7 Volts and 8 Volts for a period of time up to 48 hours. .Iaddend..Iadd.47. The method of claim 43, wherein the step of testing the passive elements for   
     
     
        operability comprises heating the semiconductor chip. .Iaddend..Iadd.48. The method of claim 47, wherein the step of heating the semiconductor chip comprises heating the semiconductor chip to a temperature substantially in a range between 120° C. and 140° C. for a period of time up to 48 hours. .Iaddend..Iadd.49. The method of claim 43, wherein the step of generating the location identifying signal associated with each inoperable passive element comprises generating an electromagnetic emission from each inoperable passive element. .Iaddend..Iadd.50. The method of claim 49, wherein the generated electromagnetic emissions are substantially within the light spectrum. .Iaddend..Iadd.51. The method of claim 43, wherein the step of sensing each inoperable passive element's location identifying signal comprises sensing each inoperable passive element's location identifying signal with an emission microscope for multilevel inspection. .Iaddend..Iadd.52. The method of claim 43, further comprising storing each inoperable passive element's location in a computer memory. .Iaddend..Iadd.53. The method of claim 43, wherein the step of destroying the link coupled to each located inoperable passive element comprises exposing each link to external energy sufficient to disintegrate each link. .Iaddend..Iadd.54. The method of claim 53, wherein the step of exposing each link to external energy comprises exposing each link to external energy substantially in a range between 0.1 μWatt and 10 mWatt. .Iaddend..Iadd.55. The method of claim 53, wherein the step of exposing each link to external energy comprises exposing each link to a laser beam. .Iaddend..Iadd.56. The method of claim 43, wherein the step of destroying the link coupled to each located inoperable passive element comprises etching each link away with an etchant. .Iaddend..Iadd.57. The method of claim 56, wherein the etchant comprises at least one of H 2  SO 4 , H 2  SO 4  diluted with H 2  O 2 , and H 2  PO 4 . .Iaddend..Iadd.58. The method of claim 43 wherein the steps of testing, determining, locating, and destroying are automated. .Iaddend..Iadd.59. A system for decoupling an inoperable passive element on a semiconductor chip from a conductor on the chip, the passive element being coupled to the conductor through a link, the system comprising: an evaluator for evaluating the operability of the passive element and for receiving a signal generated by the passive element identifying the passive element as inoperable; and   decoupler external to the chip for decoupling the inoperable passive element from the conductor by disintegrating the link in response to the identifying signal. .Iaddend..Iadd.60. The system of claim 59, wherein the evaluator comprises a stressing element coupled to the conductor for applying a voltage thereto. .Iaddend..Iadd.61. The system of claim 60, wherein the conductor is associated with an operating voltage, wherein the voltage applied to the conductor is substantially greater than the operating voltage. .Iaddend..Iadd.62. The system of claim 61 wherein the operating voltage is in a range between 3 Volts and 5 Volts, wherein the voltage applied to the conductor is in a range between 7 Volts and 8 Volts. .Iaddend..Iadd.63. The system of claim 59, wherein the evaluator comprises a heating element for heating the semiconductor chip. .Iaddend..Iadd.64. The system of claim 63, wherein the heating element heats the semiconductor chip to a temperature substantially in a range between 120° C. and 140° C. for a period of time up to 48 hours. .Iaddend..Iadd.65. The system of claim 59, wherein the evaluator comprises a sensor for receiving an electromagnetic emission from the passive element identifying the passive element as inoperable.   
     
     
        .Iaddend..Iadd.66.  The system of claim 65, wherein the received electromagnetic emission is substantially within the light spectrum. .Iaddend..Iadd.67. The system of claim 59, wherein the decoupler comprises a generator for generating energy externally from the chip to disintegrate the link in response to the identifying signal. .Iaddend..Iadd.68. The system of claim 67, wherein the generator generates energy substantially in a range between 0.1 μWatt and 10 mWatt. .Iaddend..Iadd.69. The system of claim 67, wherein the generator comprises a laser generator. .Iaddend..Iadd.70. The system of claim 59, wherein the decoupler comprises an applicator for applying an etchant to disintegrate the link in response to the identifying signal. .Iaddend..Iadd.71. The system of claim 70, wherein the etchant comprises at least one of H 2  SO 4 , H 2  SO 4  diluted with H 2  O 2 , and H 2  PO 4 . .Iaddend..Iadd.72. The system of claim 59, wherein the evaluator comprises an automated sensor for sensing the identifying signal, determining the inoperable passive element's location therefrom, and storing the 
     
     
        determined location. .Iaddend..Iadd.73.  The system of claim 72, wherein the decoupler is coupled to the evaluator, wherein the decoupler comprises an automated decoupler responsive to the stored location of the inoperable passive element for disintegrating the link. .Iaddend..Iadd.74. A recovery system for recovering a semiconductor die made at least partially inoperable by an inoperable passive element shorting first and second conductors on the die together, the system comprising: a link coupled in series with the inoperable passive element between the first and second conductors;   a tester for determining the inoperable status of the inoperable passive element; and   a decoupler responsive to the tester for destroying the link to interrupt the shorting together of the conductors. .Iaddend..Iadd.75. The recovery system of claim 74, wherein the link comprises a material of minimal electrical resistance. .Iaddend..Iadd.76. The recovery system of claim 74, wherein the tester comprises an emission microscope for multilevel inspection. .Iaddend..Iadd.77. The recovery system of claim 74, wherein the decoupler is selected from a group comprising a laser and an etchant. .Iaddend.