Patent Application
20080035921
An enable signal (e.g., a logical 1) is applied to an enable input 7 for the degradation monitor circuit 2 in order to initialize a process for detecting semiconductor device 1 degradation over time. First, the semiconductor device 1 (including the degradation monitor circuit 2) is subjected to a first operating condition. For example, the first operating condition may comprise a first supply voltage (e.g., 1 volt) applied to the semiconductor device 1. A first value for a first parameter (e.g., resistance) of a circuit within degradation monitor circuit 2 (e.g., see process sensitive circuit(s) in
If the differential value is greater than the predetermined threshold value then a notification is sent via the output 8 to indicate that the semiconductor device 1 has degraded and a system interrupt (i.e., to disable the semiconductor device 2) may be performed. The degradation monitor circuit 2 may suggest a change (i.e., change to the operating condition) for the semiconductor device 1 to ensure operability (i.e., to account for degradation). For example, the suggested change may comprise, inter alia, to lower an operating frequency, raise an operating voltage, change a workload, etc. The notification and suggested change may be sent to a user (e.g., a computer operator) of the semiconductor device 1 so that the user may manually change the first operating condition to a second operating condition (e.g., the first supply voltage of 1 volt is changed to a supply voltage of 1.1 volts). Alternatively, the suggested change may be sent to a system comprising the semiconductor device 1 (e.g., a computer comprising the semiconductor device 1) so that the system may automatically change the first operating condition to a second operating condition (e.g., the first supply voltage of 1 volt is changed to a supply voltage of 1.1 volts). For example, if the semiconductor device 1 is a CPU in a computer system, then the suggested change may be sent to the computer system so that the computer system may automatically make the suggested change to the operating condition. Upon making the suggested change from the first operating condition to the second operating condition (e.g., the first supply voltage of 1 volt is changed to a supply voltage of 1.1 volts) the aforementioned process may be performed again using the second operating condition to determine more semiconductor device 1 degradation. Additionally, the aforementioned process may be performed periodically.
If the differential value is less than the predetermined threshold value then a determination is made that the semiconductor device 1 has not degraded and the semiconductor device 1 is again operated at normal conditions at the first operating condition. The aforementioned measurement process may be performed again at a later time (e.g., periodically) to determine if the semiconductor device 1 has degraded at the later time.
Note that any operating condition for the semiconductor device 1 may be changed to perform the aforementioned process. For example, a temperature for the semiconductor device 1 may be changed by directing a heating source (e.g., a heater) or a cooling source (e.g., a fan, a heat sink, etc) at the semiconductor device 1 (i.e., subjecting the semiconductor device 1 to the operating condition).
After the semiconductor device 1 including the process sensitive circuit(s) 15 is subjected to a first operating condition. For example, the first operating condition may comprise a first supply voltage (e.g., 1 volt) applied to the semiconductor device 1. A first value for a first parameter (e.g., with respect to a ring oscillator circuit a first parameter may comprise a frequency) of one of the process sensitive circuit(s) 15 is measured at a first time and is stored in memory unit 21. The first parameter is measured by the measurement circuits 17. Additionally, the measurement circuits 17 convert all measured parameters to digital values. For example, if one of process sensitive circuit(s) 15 produces a voltage, then an analog to digital converter within measurement circuits 17 is used to convert an analog voltage to a digital number. Likewise, if one of process sensitive circuit(s) 15 produces a frequency (e.g., ring oscillator circuit), then the measurement circuits 17 would convert the analog frequency to a digital number. After the first value for a first parameter is measured and stored in memory unit 21, the semiconductor device 1 is operated under normal conditions. After the semiconductor device 1 is operated under normal conditions for a specified time, a second value for the first parameter of the process sensitive circuit(s) 15 is measured again at a second time (i.e., at the first operating condition) and stored in memory unit 21. The comparison circuit 20 compares the first value to the second value and the calculation circuit 24 calculates a differential value between the first value and the second value. The comparison circuit 20 may comprise comparator circuitry (e.g., digital comparators) to compare a given process sensitive circuit's current value (i.e., second value) to its initial value (i.e., first value). For example, at the beginning of its life a ring oscillator might have a measured frequency of 1 GHz but after running for a while it might now have a measured frequency of 900 MHz. The differential value between the first value and the second value is compared (i.e., by the comparison circuit 24) to a predetermined threshold value stored in memory unit 21.
If the differential value is greater than the predetermined threshold value then a notification may be sent via the output 8 to indicate that said semiconductor device 1 has degraded. The condition change circuit 28 may use a pre-calculated algorithm to produce a system interrupt (i.e., for the semiconductor device 2) and suggest a change (i.e., calculated by the calculation circuit 24) to the operating condition for the semiconductor device 2 to ensure operability and account for degradation. For example, condition change circuit 28 could ask a system operating the semiconductor device 2 to lower its operating frequency, raise its voltage, change its workload, etc. The notification and suggested change may be sent to a user of the semiconductor device 1 so that the user may manually change the first operating condition to a second operating condition (e.g., the first supply voltage of 1 volt is changed to a supply voltage of 1.1 volts). Alternatively, the suggested change may be sent to a system comprising the semiconductor device 1 so that the system may automatically change the first operating condition to a second operating condition (e.g., the first supply voltage of 2 volts is changed to a supply voltage of 1 volt). For example, if the semiconductor device 1 is a CPU in a computer system, then the suggested change may be sent to the computer system so that the computer system may automatically make the suggested change. Upon making the suggested change from the first operating condition to the second operating condition (e.g., the first supply voltage of 2 volts is changed to a supply voltage of 1 volt) the aforementioned process is performed again using the second operating condition to determine further degradation.
If the differential value is less than the predetermined threshold value then a determination is made that the semiconductor device 1 has not degraded and the semiconductor device 1 is again operated at normal conditions.
The aforementioned measurement process may be performed again at a later time (e.g., periodically) to determine if the semiconductor device 1 has degraded at the later time. Additionally the aforementioned process may be performed using a plurality of circuit within the process sensitive circuits 15 as illustrated by the following example of implementation for the degradation monitor circuit 2 of
In the example a process degradation monitor circuit 2 comprises two circuits: a ring oscillator circuit comprising regular threshold voltage (RVT) devices and a ring oscillator circuit comprising high threshold voltage devices (HVT) as the process sensitive circuits 15. After the semiconductor device 1 is manufactured it is tested. During the test the control circuit 12 will test (either in parallel or sequentially) the RVT circuit and the HVT circuit. In the example, the RVT circuit and the HVT circuit are tested sequentially. The control circuit 12 will enable the RVT circuit and the measurement circuit 17 will measure a frequency of its output. The measurement circuit 17 measures a value of 1 GHz for a parameter (i.e., frequency) of the RVT circuit. The value (i.e., 1 GHz) is stored in the memory unit 21. Next, the control circuit 12 enables the HVT circuit and the measurement circuit 17 measures a value of 0.5 GHz. This value is also stored in the memory unit 21. These two values (1 GHz and 0.5 GHz) are stored as time T0 valued measurements for each circuit.
The semiconductor device 1 is now put into operation and periodically (e.g., during boot-up, every hour, every day, etc), the process degradation monitor circuit 2 interrogates the RVT circuit and the HVT circuit. Every time the control circuit 12 enables the RVT circuit and the HVT circuit, the measurement circuit 17 measures output values, the comparison circuit 20 compares values, the calculation circuit 24 calculates a delta frequency from time T0, and the condition change circuit 28 provides semiconductor device 1 recommendations. For example, the process degradation monitor circuit 2 re-measures the HVT circuit and the RVT circuit and compares the re-measure values to the T0 values. Currently, the HVT circuit measures 0.5 GHz and the RVT circuit measures 0.9 GHz. The process degradation monitor circuit 2 compares the current HVT circuit value of 0.5 GHz to the T0 value of 0.5 GHz and because there is no change there are no system changes recommended. The RVT circuit T0 value of 1.0 GHz is compared to the 0.9 MHz current value. Based on a delta of 10% between the T0 value and the current value, the condition change circuit 28 will send signals to the system requesting either the system to slow down or the operating voltage to be raised, etc.
In step 40, the process is initiated. In step 42, the semiconductor device 1 is subjected to a first operating condition. In step 44, a first value for a parameter of a first circuit within the process sensitive circuits 15 is measured. In step 46, the semiconductor device 1 is operated at normal conditions. In step 50, a second value for the parameter of the first circuit within the process sensitive circuits 15 is measured. In step 52, a differential value between the first value and the second value is determined. In step 54, the differential value is compared to a predetermined threshold value. In step 56, it is determined if the differential value exceeds the predetermined threshold value.
If in step 56, it is determined that the differential value exceeds the predetermined threshold value then in step 58, the condition change circuit 28 indicates that the semiconductor device 1 has degraded. In step 60, the semiconductor device is subjected to a second operating condition and step 44 is repeated.
If in step 56, it is determined that the differential value does not exceed the predetermined threshold value then step 42 is repeated.
While embodiments of the present invention have been described herein for purposes of illustration, many modifications and changes will become apparent to those skilled in the art. Accordingly, the appended claims are intended to encompass all such modifications and changes as fall within the true spirit and scope of this invention.
