Automating photolithography in the fabrication of integrated circuits

Abstract

Automated photolithography of integrated circuit wafers is enabled with a processor connected to a Rayleigh derator, a form factor generator, a logic synthesizer, a layout generator, a lithography module and a wafer process. The Rayleigh derator receives manufacturing information resulting from yield data in the wafer process, and this manufacturing data is then used to derate the theoretical minimum feature size available for etching wafer masks given a known light source and object lens numerical aperture. This minimum feature size is then used by a form factor generator in sizing transistors in a net list to their smallest manufacturable size. A logic synthesizer then converts the net list into a physical design using a layout generator combined with user defined constraints. This physical design is then used by the mask lithography module to generate wafer masks for use in the semiconductor manufacturing. Manufacturing data including process and yield parameters is then transferred back to the Rayleigh processor for use in the designing of subsequent circuits. In this way, a direct coupling exists between the measurement of wafer process parameters and the automated sizing of semiconductor devices, enabling the production of circuits having the smallest manufacturable device sizes available for the given lithography and wafer process.

1. A method for automating the manufacture of an integrated circuit by means of a computer having a processor, a display, input means, output means, and a memory storing information, said method comprising the steps of:
 measuring at least one process parameter for a wafer process;    storing said parameter in said memory;    electing a light source by said input means;    utilizing information stored in said memory to determine a wavelength and a numerical aperture associated with said selected light source;    determining a select minimum device feature size which can be manufactured in the wafer process based on said process parameter and said determined wavelength and numerical aperture;    reading a net list stored in said memory for said integrated circuit to determine, for a given device in said circuit, based on the select minimum device feature size, a minimum manufacturable feature size;    repeating the previous step for the other devices in said circuit;    sizing the individual devices of the integrated circuit in accordance with said minimum manufacturable feature sizes to produce sizing information; and    obtaining said sizing information through said output means to complete the design of said integrated circuit.    
     
     
       2. The method according to  claim 1  further comprising the step of manufacturing said integrated circuit having said devices in accordance with said minimum manufacturable feature sizes. 
     
     
       3. The method according to  claim 2  wherein the select minimum device feature size relates to optical parameters of photolithography equipment used in the manufacture of the integrated circuit. 
     
     
       4. The method according to  claim 3  wherein the select minimum device feature size is determined according to the formula: 
       R   =       k   ⁢           ⁢   λ     NA           
       where R is said select minimum device feature size, λ is a light source wavelength, NA is a numerical aperture value, and k is the value of a Rayleigh constant. 
     
     
       5. The method according to  claim 1  wherein a manufacturing constant is generated from said measured process parameter. 
     
     
       6. The method according to  claim 5  wherein said manufacturing constant is generated by applying weighting functions to the measured process parameter. 
     
     
       7. The method according to  claim 5  wherein said manufacturing constant is a derating value which reflects variations in said process parameter. 
     
     
       8. The method according to  claim 5  wherein the minimum manufacturable device feature size is determined by multiplying the select minimum device feature size by said manufacturing constant. 
     
     
       9. The method according to  claim 1  wherein the measuring of the process parameter is performed automatically. 
     
     
       10. The method according to  claim 1  wherein the measuring of the process parameter is performed continuously. 
     
     
       11. The method according to  claim 3  wherein the optical parameters include aperture and wavelength associated with said photolithography equipment. 
     
     
       12. The method according to  claim 3  wherein an enhanced Hg arc light is used in the photolithography equipment resulting in a minimum manufacturable feature size of no more than a quarter of a micron. 
     
     
       13. The method according to  claim 3  wherein a KrF laser light is used in the photolithography equipment resulting in a minimum manufacturable feature size of no more than an eighth of a micron. 
     
     
       14. A method for automating the manufacture of a semiconductor device having a feature size below approximately 0.3 microns by means of a computer having processor, a display, input means, output means, and a memory storing information, said method comprising the steps of:
 measuring at least one process parameter for a wafer process;    storing said parameter in said memory;    selecting a light source by said input means;    utilizing information stored in said memory to determine a wavelength and a numerical aperture associated with said selected light source;    determining a select minimum device feature size below approximately 0.3 microns which can be manufactured in the wafer process based on said process parameter and said determined wavelength and numerical aperture;    reading a net list stored in said memory for said integrated circuit to determine, for a given device in said circuit, based on the select minimum device feature size, a minimum manufacturable feature size below approximately 0.3 microns;    repeating the previous step for the other devices in said circuit;    sizing individual devices of the integrated circuit in accordance with said minimum manufacturable feature sizes to produce sizing information; and    obtaining said sizing information through said output means to complete the design of said integrated circuit.    
     
     
       15. The method for automating the manufacture of an integrated circuit according to  claim 14 , further comprising the step of manufacturing said integrated circuit having said devices in accordance with said minimum manufacturable feature sizes. 
     
     
       16. The method according to  claim 14  wherein the select minimum device feature size relates to optical parameters of photolithography equipment used in the manufacture of the integrated circuit. 
     
     
       17. The method according to  claim 16  wherein the select minimum device feature size is determined according to the formula: 
       R   =       k   ⁢           ⁢   λ     NA           
       where R is said select minimum device feature size, λ is a light source wavelength, NA is a numerical aperture value, and k is the value of a Rayleigh constant. 
     
     
       18. The method according to  claim 14  wherein a manufacturing constant is generated from said measured process parameter. 
     
     
       19. The method according to  claim 14  wherein said manufacturing constant is generated by applying weighting functions to the measured process parameters. 
     
     
       20. A method for automatically manufacturing an integrated circuit by means of a computer having a processor, a display, input means, output means, and a memory for storing information, said method comprising the steps of:
   measuring at least one process parameter for a wafer process;        storing said parameter in said memory;        selecting a light source by said input means;        utilizing information stored in said memory to determine a wavelength and a numerical aperture associated with said selected light source;        determining a select minimum device feature size which can be manufactured in the wafer process based on said process parameter and said determined wavelength and numerical aperture;        manufacturing the integrated circuit in accordance with the determined device feature size;        evaluating the manufactured integrated circuit in light of the stored process parameter; and        storing a new process parameter in said memory based on the evaluation of the manufactured integrated circuit.     
     
     
       21. The method according to  claim 20 , wherein a manufacturing constant is generated from said measured process parameter. 
     
     
       22. The method according to  claim 21 , wherein said manufacturing constant is generated by applying weighting functions to the measured process parameter. 
     
     
       23. The method according to  claim 21 , wherein said manufacturing constant is a derating value which reflects variations in said process parameter. 
     
     
       24. The method according to  claim 21 , wherein the minimum device feature size is determined by multiplying the select minimum device feature size by said manufacturing constant. 
     
     
       25. The method according to  claim 20 , wherein the measuring of the process parameter is performed continuously. 
     
     
       26. The method according to  claim 20 , wherein the measuring of the process parameter is performed automatically. 
     
     
       27. The method according to  claim 20 , wherein evaluating the manufactured integrated circuit is performed by taking wafer- test measurements on finished integrated circuits.   
     
     
       28. The method according to  claim 20 , wherein evaluating the manufactured circuit is performed by taking wafer- test measurements on in - line wafers during manufacturing.   
     
     
       29. The method according to  claim 20 , wherein the step of evaluating the manufactured integrated circuit includes determining the wafer yield. 
     
     
       30. The method according to  claim 29 , wherein the step of evaluating the manufactured circuit comprises balancing the benefits of small device geometries against the benefits of higher wafer yields. 
     
     
       31. The method according to  claim 20 , wherein the steps of measuring at least one process parameter through storing a new device parameter comprise an automated process feedback loop. 
     
     
       32. The method according to  claim 20 , wherein the steps of measuring at least one process parameter through storing a new device parameter comprise a continuous process feedback loop. 
     
     
       33. A system for automatically manufacturing an integrated circuit comprising:
   computer means including a processor, a display, input means, output means, and a memory storing information;        means for measuring at least one process parameter for a wafer process;        means for storing said parameter in said memory;        means for selecting a light source by said input means;        means for utilizing information stored in said memory to determine a wavelength and a numerical aperture associated with said selected light source;        means for determining a select minimum device feature size which can be manufactured in the wafer process based on said process parameter and said determined wavelength and numerical aperture;        means for manufacturing the integrated circuit in accordance with the determined device feature size;        means for evaluating the manufactured integrated circuit in light of the stored process parameter; and        means for storing a new process parameter in said input memory based on the evaluation of the manufactured integrated circuit.     
     
     
       34. The system according to  claim 33 , wherein the means for measuring the process parameter enables continuous measurement. 
     
     
       35. The system according to  claim 33 , wherein the means for measuring the process parameter enables automatic measurement. 
     
     
       36. A method for manufacturing an integrated circuit, comprising the steps of:
   designing the integrated circuit using a first processor based system, including a first memory, coupled to the first processor, storing      a light source library of information related to a given light source, and an aperture library containing information for numerical apertures; and        having a k constant register for storing a derating constant;          a second memory, coupled to the first processor, for storing a minimum device feature size;        a third memory, coupled to the first processor, storing a netlist database of circuit components; and        a fourth memory, coupled to the first processor, storing:      a V   T    library of threshold voltages for various MOS transistors, and        a C   GOX    library of gate oxide capacitances of various MOS transistors; and        having a μ memory storing a mobility constant μ;          calculating the minimum device feature size using the stored contents of the first memory;        storing the minimum device feature size in the second memory;        using the fourth memory to calculate a size for each circuit component in the third memory based on the minimum device feature size stored in the second memory; and        producing the integrated circuit in a production system controlled by a second processor system according to the calculated circuit component sizes.     
     
     
       37. A method of manufacturing integrated circuits, comprising the steps of:
 ( a )  determining a minimum manufacturable feature size using a feature size subroutine that utilizes  
 ( i )  a first memory including  
   a light source library of information related to a given light source, and an aperture library of information for numerical apertures; and    
   having a k constant register for storing a derating constant; and    
 
 ( ii )  a second memory for storing the minimum manufacturable device feature size;    
   ( b )  sizing circuit elements using a form factor subroutine that utilizes  
 ( i )  a third memory storing a netlist database of circuit components; and    
 ( ii )  a fourth memory including  
   a V   T    library for storing threshold voltages for various MOS transistors, and    
   a C   GOX    library for storing gate oxide capacitances of various MOS transistors; and    
   having a μ memory for storing a mobility constant μ;    
 
   ( c )  generating a set of wafer masks based on the sized circuit elements; and      ( d )  producing the integrated circuits based on the set of wafer masks.     
     
     
       38. The method of  claim 37 , wherein the first memory further has a constant register (m) for receiving and storing data relating to variations in the manufacturing of the integrated circuits. 
     
     
       39. The method of  claim 38 , further comprising the step of measuring the produced integrated circuits for variations due to manufacturing. 
     
     
       40. The method of  claim 39 , further comprising the step of updating the constant register ( m )  with the data relating to variations in the manufacturing of the integrated circuits.   
     
     
       41. A method for automating the manufacture of an integrated circuit by means of a computer having a processor, a display, input means, output means, and a memory storing information, said method comprising the steps of:
   measuring at least one process parameter for a wafer process;        storing said parameter in said memory;        selecting a light source by said input means;        utilizing information stored in said memory to determine a wavelength and a numerical aperture associated with said selected light source;        determining a select minimum device feature size which can be manufactured in the wafer process based on said process parameter and said determined wavelength and numerical aperture;        reading a net list stored in said memory for said integrated circuit to determine, for a given device in said circuit, based on the select minimum device feature size, a minimum manufacturable feature size;        repeating the previous step for the other devices in said circuit;        sizing the individual devices of the integrated circuit in accordance with said minimum manufacturable feature sizes to produce sizing information; and        obtaining said sizing information through said output means to complete the design of said integrated circuit.     
     
     
       42. The method according to  claim 41  further comprising the step of manufacturing said integrated circuit having said devices in accordance with said minimum manufacturable feature sizes. 
     
     
       43. The method according to  claim 42  wherein the select minimum device feature size relates to optical parameters of photolithography equipment used in the manufacture of the integrated circuit. 
     
     
       44. The method according to  claim 43  wherein the select minimum device feature size is determined according to the formula: 
       R   =       k   ⁢           ⁢   λ     NA           
       
         where R is said select minimum device feature size, λ is a light source wavelength, NA is a numerical aperture value, and k is the value of a Rayleigh constant. 
       
     
     
       45. The method according to  claim 41  wherein a manufacturing constant is generated from said at least one measured process parameter. 
     
     
       46. The method according to  claim 45  wherein said manufacturing constant is generated by applying weighting functions to the at least one measured process parameter. 
     
     
       47. The method according to  claim 45  wherein said manufacturing constant is a derating value which reflects variations in said process parameter. 
     
     
       48. The method according to  claim 45  wherein the minimum manufacturable device feature size is determined by multiplying the select minimum device feature size by said manufacturing constant. 
     
     
       49. The method according to  claim 41  wherein the measuring of the at least one process parameter is performed automatically. 
     
     
       50. The method according to  claim 41  wherein the measuring of the at least one process parameter is performed continuously. 
     
     
       51. The method according to  claim 43  wherein the optical parameters include aperture and wavelength associated with said photolithography equipment. 
     
     
       52. The method according to  claim 43  wherein an enhanced Hg arc light is used in the photolithography equipment resulting in a minimum manufacturable feature size of no more than a quarter of a micron. 
     
     
       53. The method according to  claim 43  wherein a KrF laser light is used in the photolithography equipment resulting in a minimum manufacturable feature size of no more than an eighth of a micron. 
     
     
       54. A method for automating the manufacture of a semiconductor device having a feature size below approximately  0 . 3  microns by means of a computer having a processor, a display, input means, output means, and a memory storing information, said method comprising the steps of:
   measuring at least one process parameter for a wafer process;        storing said parameter in said memory;        selecting a light source by said input means;        utilizing information stored in said memory to determine a wavelength and a numerical aperture associated with said selected light source;        determining a select minimum device feature size below approximately  0 . 3  microns which can be manufactured in the wafer process based on said process parameter and said determined wavelength and numerical aperture;        reading a net list stored in said memory for said integrated circuit to determine, for a given device in said circuit, based on the select minimum device feature size, a minimum manufacturable feature size below approximately  0 . 3  microns;        repeating the previous step for the other devices in said circuit;        sizing individual devices of the integrated circuit in accordance with said minimum manufacturable feature sizes to produce sizing information; and        obtaining said sizing information through said output means to complete the design of said integrated circuit.     
     
     
       55. The method for automating the manufacture of an integrated circuit according to  claim 53 , further comprising the step of manufacturing said integrated circuit having said devices in accordance with said minimum manufacturable feature sizes. 
     
     
       56. The method according to  claim 54  wherein the select minimum device feature size relates to optical parameters of photolithography equipment used in the manufacture of the integrated circuit. 
     
     
       57. The method according to  claim 56  wherein the select minimum device feature size is determined according to the formula: 
       R   =       k   ⁢           ⁢   λ     NA           
       
         where R is said select minimum device feature size, λ is a light source wavelength, NA is a numerical aperture value, and k is the value of a Rayleigh constant. 
       
     
     
       58. The method according to  claim 54  wherein a manufacturing constant is generated from said measured process parameter. 
     
     
       59. The method according to  claim 54  wherein said manufacturing constant is generated by applying weighting functions to the measured process parameters. 
     
     
       60. A system for automating the manufacture of an integrated circuit by means of a computer having a processor, a display, input means, output means, and a memory storing information, said system comprising:
   means for measuring at least one process parameter for a wafer process;        means for storing said parameter in said memory;        means for selecting a light source by said input means;        means for utilizing information stored in said memory to determine a wavelength and a numerical aperture associated with said selected light source;        means for determining a select minimum device feature size which can be manufactured in the wafer process based on said process parameter and said determined wavelength and numerical aperture;        means for reading a net list stored in said memory for said integrated circuit to determine, for a given device in said circuit, based on the select minimum device feature size, a minimum manufacturable feature size;        means for repeatedly applying the means for reading to the other devices in said circuit;        means for sizing the individual devices of the integrated circuit in accordance with said minimum manufacturable feature sizes to produce sizing information; and        means for obtaining said sizing information through said output means to complete the design of said integrated circuit.     
     
     
       61. A system for automating the manufacture of a semiconductor device having a feature size below approximately  0 . 3  microns by means of a computer having a processor, a display, input means, output means, and a memory storing information, said system comprising:
   means for measuring at least one process parameter for a wafer process;        means for storing said parameter in said memory;        means for selecting a light source by said input means;        means for utilizing information stored in said memory to determine a wavelength and a numerical aperture associated with said selected light source;        means for determining a select minimum device feature size below approximately  0 . 3  microns which can be manufactured in the wafer process based on said process parameter and said determined wavelength and numerical aperture;        means for reading a net list stored in said memory for said integrated circuit to determine, for a given device in said circuit, based on the select minimum device feature size, a minimum manufacturable feature size below approximately  0 . 3  microns;        means for repeatedly applying the means for reading to the other devices in said circuit;        means for sizing the individual devices of the integrated circuit in accordance with said minimum manufacturable feature sizes to produce sizing information; and        means for obtaining said sizing information through said output means to complete the design of said integrated circuit.