Method of compensating for effects of mechanical stresses in a microcircuit

Abstract

A method for manufacturing an integrated circuit includes forming in a substrate a measuring circuit sensitive to mechanical stresses and configured to supply a measurement signal representative of mechanical stresses exerted on the measuring circuit. The measuring circuit is positioned such that the measurement signal is also representative of mechanical stresses exerted on a functional circuit of the integrated circuit. A method of using the integrated circuit includes determining from the measurement signal the value of a parameter of the functional circuit predicted to mitigate an impact of the variation in mechanical stresses on the operation of the functional circuit, and supplying the functional circuit with the determined value of the parameter.

1 . A device, comprising:
 a semiconductor substrate;   a functional circuit formed in the semiconductor substrate and configured to be variable, with respect to an operating parameter of the functional circuit, in response to variations in a control signal at a control signal input of the functional circuit; and   a measuring circuit configured to detect mechanical stresses exerted on the functional circuit, to determine a value of the control signal according to a value of the detected mechanical stresses, and to differentiate between mechanical stresses exerted on the functional circuit along two different axes.   
     
     
         2 . The device of  claim 1 , wherein the measuring circuit is configured to be substantially insensitive to mechanical stresses exerted on the functional circuit except stresses exerted along a selected axis. 
     
     
         3 . The device of  claim 1 , wherein the measuring circuit is configured to control, by selection of the value of the control signal, a variation of the operating parameter that is inversely related to a variation of the operating parameter provoked by a change in mechanical stresses exerted on the functional circuit. 
     
     
         4 . The device of  claim 1 , wherein the measuring circuit comprises a first component, having a low sensitivity to the mechanical stresses, and a second component having a relatively higher sensitivity to the mechanical stresses, wherein the first component includes a transistor with an octagonal-shape annular gate enclosing a source or drain of the transistor. 
     
     
         5 . The device of  claim 1 , wherein the measuring circuit comprises a first component, having a low sensitivity to the mechanical stresses, and a second component having a relatively higher sensitivity to the mechanical stresses, wherein the first component includes a resistor formed, in the semiconductive substrate, of branches connected in parallel, each branch including two elongated N+-doped regions connected in series and having respective orientations distanced by 30 to 60°. 
     
     
         6 . The device of  claim 1 , wherein the measuring circuit comprises two transistors, one being more sensitive to the mechanical stresses than the other, the measurement signal representative of mechanical stresses exerted on the integrated circuit being derived from a difference in voltage across the respective transistors or from a difference in a current flowing through the respective transistors. 
     
     
         7 . The device of  claim 1 , wherein the measuring circuit comprises:
 an oscillator having components sensitive to the mechanical stresses;   a frequency measuring circuit configured to measure a frequency of an output signal of the oscillator, the frequency of the output signal being representative of the mechanical stresses exerted on the integrated circuit; and   an additional oscillator formed of components substantially insensitive to the mechanical stresses, the measuring circuit being configured to produce the measurement signal representative of the mechanical stresses based on a difference in frequency between respective output frequencies of the oscillator and the additional oscillator.   
     
     
         8 . The device of  claim 1 , wherein the measuring circuit includes a MOS transistor with a rectangular gate, the MOS transistor being sensitive to the mechanical stresses and configured to generate the measurement signal. 
     
     
         9 . A device, comprising:
 a semiconductor substrate;   a functional circuit formed in the semiconductor substrate and configured to be variable, with respect to an operating parameter of the functional circuit, in response to variations in a control signal at a control signal input of the functional circuit; and   a measuring circuit configured to detect mechanical stresses exerted on the functional circuit, to determine a value of the control signal according to a value of the detected mechanical stresses, and to be substantially insensitive to mechanical stresses exerted on the functional circuit except stresses exerted along a selected axis   
     
     
         10 . The device of  claim 9 , wherein the measuring circuit is configured to control, by selection of the value of the control signal, a variation of the operating parameter that is inversely related to a variation of the operating parameter provoked by a change in mechanical stresses exerted on the functional circuit. 
     
     
         11 . The device of  claim 9 , wherein the measuring circuit comprises a first component, having a low sensitivity to the mechanical stresses, and a second component having a relatively higher sensitivity to the mechanical stresses, wherein the first component includes a transistor with an octagonal-shape annular gate enclosing a source or drain of the transistor. 
     
     
         12 . The device of  claim 9 , wherein the measuring circuit comprises a first component, having a low sensitivity to the mechanical stresses, and a second component having a relatively higher sensitivity to the mechanical stresses, wherein the first component includes a resistor formed, in the semiconductive substrate, of branches connected in parallel, each branch including two elongated N+-doped regions connected in series and having respective orientations distanced by 30 to 60°. 
     
     
         13 . The device of  claim 9 , wherein the measuring circuit comprises two transistors, one being more sensitive to the mechanical stresses than the other, the measurement signal representative of mechanical stresses exerted on the integrated circuit being derived from a difference in voltage across the respective transistors or from a difference in a current flowing through the respective transistors. 
     
     
         14 . The device of  claim 9 , wherein the measuring circuit comprises:
 an oscillator having components sensitive to the mechanical stresses;   a frequency measuring circuit configured to measure a frequency of an output signal of the oscillator, the frequency of the output signal being representative of the mechanical stresses exerted on the integrated circuit; and   an additional oscillator formed of components substantially insensitive to the mechanical stresses, the measuring circuit being configured to produce the measurement signal representative of the mechanical stresses based on a difference in frequency between respective output frequencies of the oscillator and the additional oscillator.   
     
     
         15 . The device of  claim 9 , wherein the measuring circuit includes a MOS transistor with a rectangular gate, the MOS transistor being sensitive to the mechanical stresses and configured to generate the measurement signal 
     
     
         16 . A method, comprising:
 forming a functional electronic circuit configured to be variable, with respect to an operating parameter of the functional circuit, in response to variations in a control signal at a control signal input of the functional circuit; and   forming in the semiconductor substrate a measuring circuit configured to detect mechanical stresses exerted on the semiconductor substrate, to determine a value of the control signal according to a value of the detected mechanical stresses, and to differentiate between mechanical stresses exerted on the functional circuit along two different axes.   
     
     
         17 . The method of  claim 16 , wherein the measuring circuit is configured to be substantially insensitive to mechanical stresses exerted on the functional circuit except stresses exerted along a selected axis. 
     
     
         18 . The method of  claim 16 , wherein forming the measuring circuit comprises forming a first component, having a low sensitivity to the mechanical stresses, and forming a second component having a relatively higher sensitivity to the mechanical stresses, wherein forming the first component includes forming a transistor with an octagonal-shape annular gate enclosing a source or drain of the transistor. 
     
     
         19 . A method, comprising:
 obtaining a measurement signal representative of mechanical stresses exerted on a measuring circuit of an integrated circuit formed in a semiconductor substrate, the measuring circuit being in a position of the integrated circuit such that the measurement signal is also representative of mechanical stresses exerted on a functional circuit of the integrated circuit,   determining from the measurement signal a value of a parameter of the functional circuit; and   supplying the functional circuit with the value of the parameter, wherein obtaining the measurement signal includes differentiating between mechanical stresses exerted on the functional circuit along two different axes.   
     
     
         20 . The method of  claim 19 , wherein the measuring circuit is substantially insensitive to mechanical stresses exerted on the functional circuit except stresses exerted along a selected axis. 
     
     
         21 . The method of  claim 19 , comprising
 comparing a value of each measurement signal with extreme values, and   if the value of the measurement signal is not between the extreme values, activating a warning signal.   
     
     
         22 . The method of  claim 19 , comprising
 obtaining first and second measurements of the mechanical stresses;   determining a variation rate between the first and second measurements;   comparing the variation rate with a threshold value corresponding to a removal of the integrated circuit package; and   activating a warning signal if a variation rate exceeds the threshold value.