Abstract:
A large range of commercial VLSI Deep Submicron circuits are used in aeronautics for designs of electronic cards. Due to miniaturization, a continually increasing level of integration and the use of new materials in the foundries, the main failure mechanisms change whilst other ones appear. The lifetimes linked to these failure mechanisms are suspected of being shorter and shorter, so that predicting the lifetime becomes a significant challenge for the reliability of Deep Submicron (DSM) semiconductors. A new approach is proposed here, based on analyzing the technology so as to determine the potential risks to reliability with respect to the specific use of DSM components for avionics applications.

Description:
BACKGROUND OF THE INVENTION AND PROBLEM STATEMENT  
       [0001]    The present invention belongs to the field of electronic component manufacturing processes. It relates more specifically to a method for selecting electronic components, in particular deep submicron semiconductors. 
         [0002]    With technological advances in miniaturization and the introduction of new materials, predicting the lifetime and failure rate of deep submicron (DSM) semiconductors has acquired great importance. 
         [0003]    Integrated circuit manufacturers manage these problems based on goals of low cost and high performance for the mass market, with a component lifetime criterion of 10 years in use (operating conditions, 0.1% cumulative failures, 90% confidence). This approach does not satisfy the requirements for long-term high reliability and lifetime encountered in professional electronic systems such as aeronautics, space, defense, health, transport, energy or industrial installations. 
         [0004]    The following table presents the example of long-term reliability required in the aerospace and energy industries: 
         [0000]    
       
         
               
               
             
               
               
               
               
               
             
               
               
               
               
               
             
           
               
                   
                   
               
               
                   
                 Requirements for the equipment 
               
             
          
           
               
                   
                 Application 
                   
                 Failure rate 
                 Lifetime 
               
               
                   
                   
               
             
          
           
               
                   
                 Space satellite 
                 10 
                 FITs 
                 15 years 
               
               
                   
                 Civil avionics 
                 100 
                 FITs 
                 30 years 
               
               
                   
                 Nuclear power plant 
                 10-100 
                 FITs 
                 60 years 
               
               
                   
                   
               
             
          
         
       
     
         [0005]    In most of these applications, these failure rates and lifetime specifications are achieved through redundancy of the printed circuits and equipment. 
         [0006]    However, any solution must be based on knowledge of the component&#39;s failure rate in relation to the mission&#39;s profile and the assurance of a fairly good level of reliability. With this knowledge, the necessary redundancy can be prepared so that a failure rate and lifetime margin can be obtained which respect the specifications of the equipment in question. 
         [0007]    Today it is envisaged to use a large range of commercial off-the-shelf (“COTS”) deep-submicron-generation components in their design. The main advantages of these components compared to specific components are their high performance levels and low price, but their reliability in severe environments is still questionable. 
         [0008]    Generally, the components&#39; qualification reports and technical data sheets provided by the integrated circuit manufacturers are used to estimate the components&#39; failure rate, in use, based on Accelerated Tests (AT) and Acceleration Factors (AF). 
         [0009]    The accelerated tests are carried out at the component level and are generally mentioned in the manufacturer&#39;s qualification report. 
         [0010]    The activation energy depends on the failure mechanism and the degradation models. The failure mechanism is determined by the technological and design choices. Thus, choosing a small gate length with a SiON gate oxide will favor a charge injection mechanism in the gate. Taking a default activation energy can result in a greatly distorted estimate of the component&#39;s reliability. For example, an overestimated activation energy in an acceleration factor leads to an underestimation of the failure rate in use. 
         [0011]    Integrated circuit manufacturers rarely take into account environmental conditions, long-term use and other parameters linked to professional electronics, because these parameters do not concern products intended for the mass market. In these severe conditions, a factor of 4 can even be obtained for commercial off-the-shelf (“COTS”) components ( FIG. 1  and  FIG. 2 ). 
         [0012]    As a result, knowledge of acceleration factor models and parameters based on the technology is essential for estimating reliability. 
         [0013]    Unfortunately, professional electronics are only a very small market for circuits with very large-scale integration (“VLSI”) and information is not available for these markets. To overcome this problem a dedicated reliability analysis at the silicon level must be performed for each electronic component in order to collect basic information and build a reliability prediction. 
         [0014]    An initial step of the method consists of gathering basic information about the component: manufacturer, foundry and if possible data relating to the manufacturing process and the technology. 
         [0015]    When the required information is not available in the literature, the component is studied using a process of reverse engineering at the silicon level. 
         [0016]    The research is carried out to draw up the component&#39;s identity card with regard to the final foundry steps (“Back End Of Line”—BEOL) and initial foundry steps (“Front End Of Line”—FEOL), where at least the following information is extracted:
       The technological generation or node (half-step parameter),   Number of metal layers, materials and dimensions of the metallization and interconnections,   Transistor material and dimensions,   Substrate type (Silicon on insulator or “massive bulk” silicon).       
 
         [0021]    A next step consists of analyzing the component&#39;s sensitivity relative to its mission profile, such as the examples of aeronautics mission profiles illustrated in the following table. 
         [0000]    
       
         
               
               
               
             
               
               
               
             
           
               
                   
               
               
                 Profile 
                 Use 
                   
               
             
          
           
               
                 example 
                 Storage 
                 Application 
               
               
                   
               
               
                 1 
                 10% operating cycle 
                 90% operating cycle 
               
               
                   
                 25° C. 
                 25/70° C., V DD   
               
               
                   
                 no polarization 
               
               
                   
                 no assembly 
               
               
                 2 
                 99% operating cycle 
                 1% operating cycle 
               
               
                   
                 25° C. 
                 −55/125° C., V DD   
               
               
                   
                 no polarization 
               
               
                   
                 assembled 
               
               
                   
               
             
          
         
       
     
         [0022]    These profiles must be taken into account when estimating reliability. 
         [0023]    For example, compared to operational situations the emergence of failure mechanisms activated by the voltage, such as electromigration and the burnout of the gate oxide, are unlikely in non-powered storage conditions. 
         [0024]    Regardless of the mission profile, some materials and architectures are known to be more sensitive to certain mechanisms. For example, the porosity of low-k oxide makes it easier for the oxide of the inter-layer dielectric (ILD) to fail. In addition, during the BEOL step there are large variances between the thermal expansion coefficients of the copper in double damascening, of the diffusion layer and of the dielectric oxides of the intermediate layer, which makes the technology more sensitive to damage by migration under constraints. 
         [0025]    In Silicon On Insulator (SOI) technology, the insulator layer prevents dissipation by Joule effect to spread through the substrate, which induces a thermal acceleration of the silicon&#39;s failure mechanisms. 
         [0026]    On the other hand, for the same gate length the consumption of dynamic power is lower in SOI technology than in bulk substrates, which offsets these thermal weaknesses. 
         [0027]    Finally, gate oxides with high permittivity values seem to be more sensitive to the instability mechanisms of the threshold voltage in temperature than the traditional SiON oxide, due to a greater physical thickness, a larger number of interfaces and the initial presence of mobile charges in the oxide. 
         [0028]    The sensitivity analysis provides an indication of the silicon&#39;s failure mechanisms that are the most likely to occur. 
         [0029]    By elimination the predominant mechanisms to be studied are selected, as well as the qualification report tests that must be the subject of a subsequent analysis. 
         [0030]    The predominant failure mechanisms of the circuits also provide information about the time dependency of the failure. Some of these are typical of the bottom of the reliability bath curve and some others are defined as wear-out mechanisms ( FIG. 3 ). 
         [0031]    In the first case, the reliability is best described by a constant instantaneous failure rate (designated by A and expressed in FITs—“Failure in Time”), whereas for the mechanism of failure by wear-out, it is the lifetime that is talked of instead: “Time to Failure” (TTF) in hours, the time at which the probability of failure F(t) reaches the specified value, e.g. 10 −7  or 10 −9  for some aeronautical applications. 
         [0032]    Manufacturers of integrated circuits generally deduce an instantaneous failure rate from a high-temperature operating life (HTOL) test through the χ 2  estimator. 
         [0033]    The main advantage of this estimator is to extrapolate a failure rate from a small sample to a large quantity of components with a known confidence coefficient ( FIG. 4 ). This method is still acceptable for the failure mechanism occurring when the failure rate is constant and independent of the duration of the test. 
         [0034]    However, this calculation is no longer suitable for wear mechanisms, simply because the failure rate increases with time. 
       OBJECTIVES OF THE INVENTION  
       [0035]    The objective of this invention is therefore to propose a method responding to the problem outlined above. 
       DESCRIPTION OF THE INVENTION  
       [0036]    To remedy this problem, the invention envisages a Method for estimating the lifetime (TTF APPLI ) of a deep-submicron-generation integrated electronic component, linked to a wear mechanism occurring in previously defined special conditions of use, said component being of a deep submicron type, with very large-scale integration (VLSI), commercially available off the shelf, 
         [0037]    characterized in that it is assumed that the same sample population always experiences a failure due to the following two mechanisms:
       a failure mechanism, the most predominant during the period of useful life, described by an exponential law,   a wear mechanism, the most critical, represented by a Weibull distribution at the end of the previous period,       
 
         [0040]    and in that the method comprises the following steps: 
         [0041]    Step  101 —of receiving and storing predefined elements of technical information about the component, in particular the power supply voltage(s), technological data (node, FEOL and BEOL description), the technical description of the encapsulation and the addressing data for the component, 
         [0042]    Step  106 —of analyzing the component&#39;s sensitivity with regard to specific conditions of use, 
         [0043]    Step  116 —of selecting the most probable bottom of the bath and wear mechanisms, and associated accelerated tests. 
         [0044]    According to various advantageous implementations, possibly used in conjunction, the method comprises the following steps in addition: 
         [0045]    Step  109 —of calculating the rate of failures (λ TEST ), based on the results of the accelerated tests on the component&#39;s lifetime, 
         [0046]    Step  111 —of calculating an estimated lifetime for the component in test conditions (TTF TEST ), 
         [0047]    Step  112 —of determining an acceleration factor used for analyzing the results of at least one accelerated test of the component in relation to the latter&#39;s technology and the mission profile. 
         [0048]    Step  108 —of acquiring and storing the results of at least one accelerated test of the component&#39;s lifetime, if such test results are not available; the type of test is chosen according to a mechanism of failure by wear. In this step, for the failure mechanisms such as those known under the names HCl, NBTI and EM, and in order to take the fastest components into account, the test bench comprises a means of very local heating/cooling of the component. 
         [0049]    Step  103 —of studying the component using a process of reverse engineering, so as to determine, in particular, the technological data of the component at the level of the component&#39;s housing, the BEOL and FEOL parameters. 
         [0050]    Step  105 —of establishing an identity card for the component according to a series of predefined criteria (technology, failure mechanisms inherent in the technology, etc.). 
         [0051]    Step  102 —of characterizing environmental data corresponding to the specific conditions of use planned for the component, in particular the electrical and thermal mission profile. 
         [0052]    Step  110 —of identifying failure mechanisms observed at the time of failures under test conditions. 
         [0053]    Advantageously, in Step  111 :
       the probability of failures is described by a bimodal distribution (Eq. 1) in which λ TEST  is the failure rate under test conditions, TTF TEST     —     R %  the mean value of the time to failure for components that have survived after t=t TEST  and β the Weibull slope of the wear mechanism:       
 
         [0000]    
       
         
           
             
               
                 
                   
                     
                       F 
                       component 
                     
                      
                     
                       ( 
                       t 
                       ) 
                     
                   
                   = 
                   
                     { 
                     
                       
                         
                           
                             1 
                             - 
                             
                                
                               
                                 
                                   - 
                                   
                                     λ 
                                     test 
                                   
                                 
                                 · 
                                 t 
                               
                             
                           
                         
                         
                           
                             
                               if 
                                
                               
                                   
                               
                                
                               
                                 t 
                                 
                                   0 
                                    
                                   % 
                                 
                               
                             
                             ≤ 
                             t 
                             ≤ 
                             
                               t 
                               test 
                             
                           
                         
                       
                       
                         
                           
                             1 
                             - 
                             
                                
                               
                                 - 
                                 
                                   
                                     ( 
                                     
                                       t 
                                       
                                         TTF 
                                         
                                           test 
                                           - 
                                           
                                             R 
                                              
                                             
                                               u 
                                               ‵ 
                                             
                                           
                                         
                                       
                                     
                                     ) 
                                   
                                   β 
                                 
                               
                             
                           
                         
                         
                           
                             
                               if 
                                
                               
                                   
                               
                                
                               
                                 t 
                                 test 
                               
                             
                             ≤ 
                             t 
                             ≤ 
                             
                               t 
                               
                                 100 
                                  
                                 % 
                               
                             
                           
                         
                       
                     
                   
                 
               
               
                 
                   ( 
                   1 
                   ) 
                 
               
             
           
         
       
       
         
           
             the most unfavorable case is considered, in which the most critical failure mechanism occurs just after the test period, because of the continuity of the two distributions, resulting in there being the same probability of the component&#39;s failure described by the exponential law and by the Weibull distribution, and therefore in TTF TEST     —     R %  being calculated by (Eq. 2): 
           
         
       
     
         [0000]    
       
         
           
             
               
                 
                   
                     TTF 
                     
                       TEST_R 
                        
                       % 
                     
                   
                   = 
                   
                     
                       
                         ( 
                         
                           t 
                           TEST 
                         
                         ) 
                       
                       
                         1 
                         - 
                         
                           1 
                           β 
                         
                       
                     
                     
                       λ 
                       TEST 
                       
                         1 
                         β 
                       
                     
                   
                 
               
               
                 
                   ( 
                   2 
                   ) 
                 
               
             
           
         
       
       
         
           
             the mean time to failure TTF TEST  is thus calculated for all the mechanisms of failure by wear studied, with relevant Weibull slopes, typical of each wear mechanism; their value is chosen according to the technological analysis. 
           
         
       
     
         [0057]    More specifically, in this case, the method also includes a step: 
         [0058]    Step  113 ,  114 —of calculating the effective failure rates λ APPLI  and lifetime TTF APPLI  in use, according to the acceleration factor AF i  specific to mechanism i, from the failure rate λ TEST  and lifetime TTF TEST  measured during the accelerated tests, by applying the formulas: 
         [0000]    
       
         
           
             
               
                 
                   
                     
                       λ 
                       APPLICATION 
                     
                     = 
                     
                       
                         λ 
                         TEST 
                       
                       
                         AF 
                         i 
                       
                     
                   
                    
                   
                     
 
                   
                    
                   
                     
                       TTF 
                       APPLICATION 
                     
                     = 
                     
                       
                         TTF 
                         
                           TEST_R 
                            
                           % 
                         
                       
                       · 
                       
                         AF 
                         i 
                       
                     
                   
                 
               
               
                 
                   
                     ( 
                     3 
                     ) 
                   
                    
                   
                     ( 
                     4 
                     ) 
                   
                 
               
             
           
         
       
     
     
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
         [0059]    The goals and advantages of the invention will be better understood in reading the description and drawings of a particular embodiment, given as a non-limiting example, for which the drawings show: 
           [0060]      FIG. 1  (already mentioned): FPGA acceleration factor between the rate of failures in use and the rate of failures in test conditions for different activation energies for the TDDB (“Time Dependent Dielectric Failure”: time-based burnout of the dielectric) failure mechanism of the gate oxide (2 nm thick SiON gate oxide), 
           [0061]      FIG. 2  (already mentioned): FPGA failure rate under conditions of use for different activation energies for the TDDB failure mechanism of the gate oxide (2 nm SiON gate oxide), 
           [0062]      FIG. 3  (already mentioned): bath curve of the failure rate and failure mechanisms of silicon, 
           [0063]      FIG. 4  (already mentioned): methodology for estimating the failure rate (according to the state of the art), 
           [0064]      FIG. 5 : probability of failures of the component as a function of time, 
           [0065]      FIG. 6 : component reliability bath curve for two components under conditions of use (30 years, 70° C., 3.3 V, 50% operating cycle), 
           [0066]      FIG. 7 : methodology for estimating the failure rate in a method as described. 
       
    
    
     DETAILED DESCRIPTION OF AN EMBODIMENT OF THE INVENTION  
       [0067]    The following description of the method for calculating the reliability of deep submicron components is presented over several technologies. 
         [0068]    The method as described is notably intended to be implemented automatically by a suitable electronic device. 
         [0069]    The goal of the method is to estimate a life span for a deep-submicron-generation integrated component, based on the calculation of the failure rate provided by the manufacturer. 
         [0070]    It is assumed that the same sample population always experiences a failure due to:
       the most predominant mechanism during the period of useful life, described by an exponential law,   the most critical wear mechanism, represented by a Weibull distribution at the end of the previous period.       
 
         [0073]    As a result, the probability of failures can be described by a bimodal distribution (1) in which λ TEST  is the failure rate under test conditions, TTF TEST     —     R %  the mean value of the time to failure for components that have survived after t=t TEST  and β the Weibull slope of the wear mechanism. 
         [0000]    
       
         
           
             
               
                 
                   
                     
                       F 
                       component 
                     
                      
                     
                       ( 
                       t 
                       ) 
                     
                   
                   = 
                   
                     { 
                     
                       
                         
                           
                             1 
                             - 
                             
                                
                               
                                 
                                   - 
                                   
                                     λ 
                                     test 
                                   
                                 
                                 · 
                                 t 
                               
                             
                           
                         
                         
                           
                             
                               if 
                                
                               
                                   
                               
                                
                               
                                 t 
                                 
                                   0 
                                    
                                   % 
                                 
                               
                             
                             ≤ 
                             t 
                             ≤ 
                             
                               t 
                               test 
                             
                           
                         
                       
                       
                         
                           
                             1 
                             - 
                             
                                
                               
                                 - 
                                 
                                   
                                     ( 
                                     
                                       t 
                                       
                                         TTF 
                                         
                                           test 
                                           - 
                                           
                                             R 
                                              
                                             
                                               u 
                                               ‵ 
                                             
                                           
                                         
                                       
                                     
                                     ) 
                                   
                                   β 
                                 
                               
                             
                           
                         
                         
                           
                             
                               if 
                                
                               
                                   
                               
                                
                               
                                 t 
                                 test 
                               
                             
                             ≤ 
                             t 
                             ≤ 
                             
                               t 
                               
                                 100 
                                  
                                 % 
                               
                             
                           
                         
                       
                     
                   
                 
               
               
                 
                   ( 
                   1 
                   ) 
                 
               
             
           
         
       
     
         [0074]    The most unfavorable case is also considered, in which the most critical failure mechanism occurs just after the test period. Indeed, at the intersection of the two distributions (point  1  in  FIG. 5 ) there is the same probability of failure of the component described by the exponential law and by the Weibull distribution. 
         [0075]    By continuity, the following can be expressed: 
         [0000]    
       
         
           
             
               
                 
                   
                     TTF 
                     
                       TEST_R 
                        
                       % 
                     
                   
                   = 
                   
                     
                       
                         ( 
                         
                           t 
                           TEST 
                         
                         ) 
                       
                       
                         1 
                         - 
                         
                           1 
                           β 
                         
                       
                     
                     
                       λ 
                       TEST 
                       
                         1 
                         β 
                       
                     
                   
                 
               
               
                 
                   ( 
                   2 
                   ) 
                 
               
             
           
         
       
     
         [0076]    A time to fail is thus calculated for all the mechanisms of failure by wear studied, with relevant Weibull slopes. The Weibull slope is typical of a wear mechanism. 
         [0077]    It depends on the technology, such that its value is chosen according to the technological analysis. 
         [0078]    A good estimate of the lifetime and the failure rate depends on the accuracy of the acceleration factor. 
         [0079]    For a given silicon failure mechanism, the literature contains various models generally linked to the generation node and the polarization. 
         [0080]    For example, the gate oxide&#39;s burnout time can be modeled according to four degradation laws:
       Model E is used for an application with a low electrical field,   Models 1/E and E 0.5  are used for a high electrical field;   The voltage power law is associated with a behavior not conforming to the Arrhenius law in temperature for a gate oxide less than 3 nm thick.       
 
         [0084]    In addition, the material and the dimensions of scale have implications for the choice of the model&#39;s parameters. For example, the activation energy of the gate oxide&#39;s burnout mechanism will be different for the oxides in silicon (SiO 2 ), nitrided oxides (SiON) and oxides with a high permittivity value. 
         [0085]    As a result, estimating the failure rate and the lifetime entails first of all knowing the physical aspects of the failure involved and then, for a specific failure mechanism, setting up a large database of acceleration factor data and models with all the appropriate parameters that cover the entire variety of deep submicron components. 
         [0086]    The effective failure rates and lifetime in use are then calculated with the factor AF i  specific to mechanism i, from the failure rate and lifetime measured during accelerated tests (Eq. 3). 
         [0000]    
       
         
           
             
               
                 
                   
                     
                       λ 
                       APPLICATION 
                     
                     = 
                     
                       
                         λ 
                         TEST 
                       
                       
                         AF 
                         i 
                       
                     
                   
                    
                   
                     
 
                   
                    
                   
                     
                       TTF 
                       APPLICATION 
                     
                     = 
                     
                       
                         TTF 
                         
                           TEST_R 
                            
                           % 
                         
                       
                       · 
                       
                         AF 
                         i 
                       
                     
                   
                 
               
               
                 
                   
                     ( 
                     3 
                     ) 
                   
                    
                   
                     ( 
                     4 
                     ) 
                   
                 
               
             
           
         
       
     
         [0087]    The methodology used in the method for estimating the failure rate as described is illustrated in  FIG. 7 . 
         [0088]    As seen in this figure, the method comprises the following steps: 
         [0089]    step  101 —of receiving and storing predefined elements of technical information about the component, in particular the power supply voltage(s), technological data (node, FEOL and BEOL description) and the addressing data for the component, 
         [0090]    step  102 —of characterizing environmental data corresponding to the specific conditions of use planned for the component, in particular the electrical and thermal mission profile. 
         [0091]    step  104 —of determining whether the technical data received in step  101  are sufficient, in particular for determining a theoretical failure rate, and if not: 
         [0092]    step  103 —of studying the component using a process of reverse engineering, so as to determine, in particular, the technological data of the component at the level of the component&#39;s housing, the BEOL and FEOL parameters. 
         [0093]    Then a step  105 —of establishing an identity card for the component according to a series of predefined ‘criteria (technology, failure mechanisms inherent in the technology, etc.). 
         [0094]    The results of this step  105  and step  102  are used as input in a step  115 —of selecting a model of damage for the component and its parameters, 
         [0095]    and simultaneously in a step  106 —of analyzing the component&#39;s sensitivity with regard to special conditions of use. 
         [0096]    This step  106  allows the most effective bottom of the bath and wear mechanisms, and associated accelerated tests, to be selected in a step  116 . 
         [0097]    In a step  107 , it is determined whether the results of accelerated tests as determined in step  116  are available, if not, in a step  108 , tests to be operated on the user&#39;s side for spotlighting the mechanisms sought, if such test results are not available in the manufacturer&#39;s qualification report, are determined and implemented. 
         [0098]    Then in a step  109  the failure rate (λ TEST ) is calculated, based on the results of the accelerated tests of the component&#39;s lifetime. 
         [0099]    In a step  110  the failure mechanisms observed at the time of failures under test conditions are identified. 
         [0100]    If the mechanism is a wear mechanism, the continuity of the failure function is used, and in a step  111  an estimated lifetime of the component in test conditions (TTF TEST ) is calculated. 
         [0101]    Then in a step  112  the acceleration factors used to analyze the results of the accelerated test for the component is determined. 
         [0102]    Finally, in steps  113  (for a bottom of the bath curve mechanism) and  114  (for a wear mechanism), the effective failure rate λ APPLI  and lifetime TTF APPLI  in use are calculated, according to the appropriate acceleration factor AF, from the failure rate λ TEST  and lifetime TTF TEST  measured during the accelerated tests, by applying equations 3 and 4. 
         [0103]    Example of Application 
         [0104]    The interest of such an approach is demonstrated by an example of application with two similar components of the same technological generation and from two different foundries. 
         [0105]    The components are called A and B. 
         [0106]    The two components are subject to an avionics type of mission profile, in this case 3 years storage, not powered, at 25° C., then during 30 years, a junction temperature of 70° C., powered at 3.3 V twelve hours a day. 
         [0107]    The failure mechanism studied is a mechanism by wear, the electromigration in interconnections of the final foundry steps (“BEOL”). 
         [0108]    First, information is collected about the manufacturing processes of the foundries where the components were manufactured. 
         [0109]    The information available from the foundries is not sufficient and a destructive physical analysis is carried out to obtain the required data. 
         [0110]    The two components have the same foundry BEOL steps, with 3 layers of metallization and exactly the same interconnections dimension. However, component A has interconnections made of aluminum whereas component B is manufactured in copper with the help of a double damascene method. 
         [0111]    These data are collected in the following table. 
         [0000]    
       
         
               
               
               
             
               
               
               
             
               
               
               
             
           
               
                   
                   
               
               
                   
                 Component 
                   
               
             
          
           
               
                   
                 A 
                 B 
               
               
                   
                   
               
             
          
           
               
                 Number of layers of metallization 
                 3 
                 3 
               
               
                 Nature of the metallization 
                 2 Al 
                 2 Cu 
               
               
                   
                 1 TiW 
                 1 TiW 
               
               
                 Nature of the interconnection holes 
                 W 
                 Cu 
               
               
                 Diffusion layer 
                 Ti/TiN 
                 Ta/TaN 
               
               
                 Cap 
                 SiN x   
                 SiN x   
               
               
                 Intermediate layer oxide 
                 SiO 2   
                 Low permittivity 
               
               
                   
                   
                 oxide 
               
               
                   
               
             
          
         
       
     
         [0112]    Considering the mission profile, no risk was detected in the storage situation (component not powered). 
         [0113]    However, a reliability risk located in the 3 rd  level has been identified for component A. 
         [0114]    The metallization width is close to 2 μm and as a result creates a rapid diffusion path through the border of the grains, which can induce a migration of metal grains in a polarization state. 
         [0115]    For this failure mechanism, a high-temperature lifetime test of the oxide was carried out on 87 samples of component A and 87 samples of component B during 2000 hrs, at 125° C. (junction) and 3.96 V. 
         [0116]    No failure was observed during the tests. The maximum failure rate under the test conditions can be calculated by equation 5, assuming a 60% confidence level. 
         [0000]    
       
         
           
             
               
                 
                   
                     
                       λ 
                       TEST 
                     
                     = 
                     
                       
                         
                           χ 
                           
                             1 
                             - 
                             α 
                           
                           2 
                         
                          
                         
                           ( 
                           
                             
                               2 
                                
                               
                                   
                               
                                
                               c 
                             
                             + 
                             2 
                           
                           ) 
                         
                       
                       
                         2 
                         · 
                         N 
                         · 
                         
                           t 
                           TEST 
                         
                       
                     
                   
                    
                   
                     
 
                   
                    
                   
                     
                       λ 
                       TEST 
                     
                     = 
                     
                       5300 
                        
                       
                           
                       
                        
                       FITs 
                     
                   
                 
               
               
                 
                   ( 
                   5 
                   ) 
                 
               
             
           
         
       
     
         [0117]    The probability of failure after the test conditions of the test is close to 1%. 
         [0118]    This indicates that 99% of the 87 samples could break down through the electromigration mechanism; this value will be taken into consideration for calculating the lifetime. Assuming a Weibull slope of 6 for the structure Al/Ti/TiN/SiO 2 , the average time to failure (“TTF”) taking the test conditions into account can be estimated by equation 6: 
         [0000]    
       
         
           
             
               
                 
                   
                     TTF 
                     
                       TEST_R 
                        
                       % 
                     
                   
                   = 
                   
                     
                       
                         
                           ( 
                           
                             t 
                             TEST 
                           
                           ) 
                         
                         
                           1 
                           - 
                           
                             1 
                             β 
                           
                         
                       
                       
                         λ 
                         TEST 
                         
                           1 
                           β 
                         
                       
                     
                     = 
                     
                       
                         
                           
                             ( 
                             2000 
                             ) 
                           
                           
                             1 
                             - 
                             
                               1 
                               6 
                             
                           
                         
                         
                           
                             ( 
                             
                               5 
                               , 
                               
                                 3 
                                 · 
                                 
                                   10 
                                   
                                     - 
                                     6 
                                   
                                 
                               
                             
                             ) 
                           
                           
                             1 
                             6 
                           
                         
                       
                       ≈ 
                       
                         4300 
                          
                         
                             
                         
                          
                         h 
                       
                     
                   
                 
               
               
                 
                   ( 
                   6 
                   ) 
                 
               
             
           
         
       
     
         [0119]    The most representative acceleration factor for the electromigration test is the Black model. 
         [0120]    This model emphasizes the influence of the power supply voltage through the current density expressed by a power law and the impact of the temperature with an Arrhenius model (Eq. 7). 
         [0000]    
       
         
           
             
               
                 
                   TTF 
                   = 
                   
                     A 
                     · 
                     
                       J 
                       
                         - 
                         n 
                       
                     
                     · 
                     
                        
                       
                         
                           E 
                           A 
                         
                         
                           k 
                           · 
                           T 
                         
                       
                     
                   
                 
               
               
                 
                   ( 
                   7 
                   ) 
                 
               
             
           
         
       
     
         [0121]    TTF is the time to failure, A is a constant, J is the current density, E A  is the activation energy, k is the Boltzmann constant and T is the temperature. 
         [0122]    In addition, the relationship between the electrical power supply and the current density can be expressed by equation 8. 
         [0123]    Parameter f is the frequency (Hz), ε 0  is the dielectric constant in a vacuum, ε ox  is the dielectric constant of the oxide, V DD  is the voltage of the power supply and d is the minimum pitch between the metallizations. 
         [0000]    
       
         
           
             
               
                 
                   J 
                   = 
                   
                     f 
                     · 
                     
                       ɛ 
                       0 
                     
                     · 
                     
                       ɛ 
                       ox 
                     
                     · 
                     
                       
                         V 
                         DD 
                       
                       d 
                     
                   
                 
               
               
                 
                   ( 
                   8 
                   ) 
                 
               
             
           
         
       
     
         [0124]    According to (7) and (8), the acceleration factors for the two components can be obtained by equation 9: 
         [0000]    
       
         
           
             
               
                 
                   AF 
                   = 
                   
                     
                       
                         ( 
                         
                           
                             V 
                             appli 
                           
                           
                             V 
                             test 
                           
                         
                         ) 
                       
                       
                         - 
                         n 
                       
                     
                     · 
                     
                        
                       
                         
                           Ea 
                           k 
                         
                         · 
                         
                           ( 
                           
                             
                               1 
                               
                                 T 
                                 test 
                               
                             
                             - 
                             
                               1 
                               
                                 T 
                                 appli 
                               
                             
                           
                           ) 
                         
                       
                     
                   
                 
               
               
                 
                   ( 
                   9 
                   ) 
                 
               
             
           
         
       
     
         [0125]    and the parameters of the model are listed in the following table: 
         [0000]    
       
         
               
               
               
               
               
             
               
               
               
               
               
             
           
               
                   
                   
               
               
                   
                   
                   
                   
                 AF 
               
               
                   
                 Component 
                 n 
                 E A   
                 electromigration 
               
               
                   
                   
               
             
             
               
                   
               
             
          
           
               
                   
                 A 
                 2.02 
                 0.58 
                 21.7 
               
               
                   
                 B 
                 1.1 
                 0.89 
                 80.9 
               
               
                   
                   
               
             
          
         
       
     
         [0126]    Finally, the failure rate and the lifetime of the component can be calculated for the two components with regard to the electromigration mechanism. 
         [0127]    The resulting reliability parameters for components A and B in the conditions of use (87 samples) are indicated in the following table: 
         [0000]    
       
         
               
               
               
             
               
               
               
             
           
               
                   
                   
               
               
                   
                 30 years, 70° C., 3.3 V, 50% op. cycle 
                   
               
             
          
           
               
                   
                 TTF 1%   
                 TTF 63.2%   
               
               
                 Component 
                 (years) 
                 (years) 
               
               
                   
               
               
                 A 
                 10 
                 21 
               
               
                 B 
                 37 
                 80 
               
               
                   
               
             
          
         
       
     
         [0128]    Although component A and component B have the same function, the same architecture and the same generation node, it was found that component B was more suitable than component A for the avionics application described, as shown in  FIG. 6 . 
         [0129]    The variation in reliability is explained by the different nature of the metallization in the area of the foundry BEOL steps. 
         [0130]    The proposed methodology was applied for a wear mechanism: electromigration. 
         [0131]    In order to estimate a complete reliability for the component, the same methodology must be applied for all the silicon&#39;s other failure mechanisms. 
         [0132]    The extreme diversity of designs, manufacturing solutions and the very different mission profiles of very large-scale integration (“VLSI”) circuits in professional systems cause a great divergence between the existing approaches based on standard qualification tests and the actual and extremely varied capabilities of deep submicron technologies. 
         [0133]    This is also true for components from the same technology node. 
         [0134]    Given that there is no standard wear for a deep submicron component and a specific mission profile, it is necessary to carry out a specific reliability analysis for each deep submicron component. 
         [0135]    The method of the invention is based on a technological analysis which helps to identify the main failure mode and the wear mechanism. 
         [0136]    An appropriate failure rate is deduced in order to establish a realistic prediction of the lifetime. 
         [0137]    This new approach allows a correct choice of the accelerated test and an accurate calculation of the acceleration factor validating the lifetime prediction.