Patent Publication Number: US-2019195700-A1

Title: MIDDLE-OF-LINE (MOL) METAL RESISTOR TEMPERATURE SENSORS  FOR LOCALIZED TEMPERATURE SENSING OF ACTIVE SEMICONDUCTOR AREAS IN INTEGRATED CIRCUITS (ICs)

Description:
PRIORITY APPLICATION 
     The present application is a divisional of and claims priority to U.S. patent application Ser. No. 15/246,006, now U.S. Pat. No. ______, filed Aug. 24, 2016 and entitled “MIDDLE-OF-LINE (MOL) METAL RESISTOR TEMPERATURE SENSORS FOR LOCALIZED TEMPERATURE SENSING OF ACTIVE SEMICONDUCTOR AREAS IN INTEGRATED CIRCUITS (ICs),” which is incorporated herein by reference in its entirety. 
    
    
     BACKGROUND 
     I. Field of the Disclosure 
     The technology of the disclosure relates generally to temperature sensing in an integrated circuit (IC), and more particularly to providing on-chip temperature sensors in an IC chip for sensing the temperature of semiconductor devices in the IC chip. 
     II. Background 
     Accurate measurement of ambient temperature is important in many applications such as instruments, controllers, and monitoring systems. Temperature is also important for the performance of circuits. For example, one way to increase the performance of circuits in an integrated circuit (IC) is to increase supply voltage. However, as supply voltage increases, temperature within the IC may also increase. Rising temperatures in an IC may eventually cause carrier mobility degradation, and thus actually slow down operation of the IC, increase resistivity, and/or cause circuit failures. The problem has become especially critical as voltage scaling has slowed down and the number of active components per unit area in an IC has increased. Thus, it is desired to measure temperature in an IC to control thermal dissipation. Thus, as an example, the measured temperature can be used as a factor to control voltage scaling of supply voltages to increase supply voltages to increase performance when desired or possible, but also decrease supply voltages when temperature exceeds desired limits. 
     Smart temperature sensors can be fabricated on-chip in standard complementary metal oxide semiconductor (CMOS) technology within an IC to measure temperatures in the IC. On-chip temperature sensors can offer digitized temperature values to other circuits in the IC at low cost and small form factor. For example, the sensed temperature may be provided as an input to a voltage scaling circuit that controls scaling of a supply voltage based on temperature. In this manner, adaptive voltage scaling can be performed based on temperature to increase supply voltage to increase performance when there is temperature margin, and decrease supply voltage to decrease performance when the temperature exceeds a desired temperature value. This can also protect circuits and components in the IC from being damaged due to excessively high temperatures. 
     Conventional on-chip temperature sensors use vertically formed parasitic bipolar junction transistors (BJTs), because a base-emitter voltage (Vbe) potential of BJTs in forward-active regions is inversely proportional to temperature. This is referred to as complementary-to-absolute-temperature (CTAT). There are deficiencies in BJT temperature sensors that have become increasingly problematic. For example, the relationship between the temperature and the power level of a BJT temperature sensor becomes increasingly non-linear as power densities increase in ICs. However at the same time, precision in temperature measurement has become increasingly important in thermal management of ICs. Further, BJT temperature sensors consume a large area that makes it more difficult to scale down the size of BJTs. Also, it may be important to isolate BJT temperature sensors from other operational transistors in an IC to avoid parasitic capacitances and noise from the BJTs affecting metal oxide semiconductor (MOS) field-effect transistor (FET) (MOSFET) operation. For these reasons, it may only be possible to locate a BJT temperature sensor within 5-10 micrometers (μm) away from an area of interest in the IC. However, it may be important to locate temperature sensing devices much closer to specific areas and devices of interest for temperature monitoring, because certain localized areas may be known to be hot spots that have a disproportionately high temperature as compared to other areas in the IC. 
     SUMMARY OF THE DISCLOSURE 
     Aspects disclosed herein include middle-of-line (MOL) metal resistor temperature sensors for localized temperature sensing of active semiconductor areas in integrated circuits (ICs). In this regard, in certain aspects disclosed herein, one or more metal resistors are fabricated in a MOL layer of an IC to sense ambient temperature in the IC. The MOL layer is formed above and adjacent to an active semiconductor area in a front-end-of-line (FEOL) portion of the IC that includes devices, such as MOS field-effect transistors (MOSFETs) for example. Resistance of the metal resistor changes as a function of an ambient temperature in the active semiconductor area, because heat generated by the devices in the active semiconductor area cause atoms in the MOL layer to vibrate, thus freeing captive electrons to become carriers of current through the metal resistor. Thus, the voltage of the metal resistor will change as a function of ambient temperature of the metal resistor, which can be sensed to measure the ambient temperature around devices in the active semiconductor layer adjacent to the metal resistor. The metal resistor can also be coupled through contacts formed in the MOL layer to interconnect lines in interconnect layer(s) to be coupled to a voltage source and on-chip temperature sensing circuit in the IC configured to sense temperature as a function of the voltage across the metal resistor. A higher power-consuming current source is not required to sense temperature in the MOL metal resistor temperature sensor like provided in BJT temperature sensors to measure temperature. The sensed temperature may be used to control operations in the IC that are affected by temperature, such as voltage supply scaling as an example. 
     Thus, by fabricating a metal resistor in the MOL layer in the IC, the metal resistor can advantageously be localized adjacent and very close to semiconductor devices, such as transistors, to more accurately sense temperature around the semiconductor devices. This is opposed to BJT temperature sensors that are located farther away in the IC (e.g., 10 times farther away) from complementary MOS (CMOS) devices due to the size and area constraints of BJTs. Also, by providing the metal resistor in the MOL layer, the same fabrication processes used to create contacts in the MOL layer can also be used to fabricate the metal resistor in the MOL layer. Further, because the MOL layer is already provided in the IC to provide contacts between the semiconductor devices in the active semiconductor layer and the interconnect layers, additional area may not be required to provide the metal resistors in the IC. 
     In this regard, in one exemplary aspect, a MOL temperature sensor for an IC is provided. The MOL temperature sensor comprises an active semiconductor layer. The MOL temperature sensor also comprises a metal resistor having a resistance and comprising a first metal material disposed in an MOL layer disposed above the active semiconductor layer. The MOL temperature sensor also comprises a first contact disposed above the metal resistor in the MOL layer, the first contact electrically coupled to a first contact area of the metal resistor. The MOL temperature sensor also comprises a second contact disposed above the metal resistor in the MOL layer, the second contact electrically coupled to a second contact area of the metal resistor, wherein the metal resistor has a resistance between the first contact area and the second contact area. The MOL temperature sensor also comprises a first interconnect disposed in a first interconnect layer above the MOL layer in the active semiconductor layer, the first interconnect layer electrically coupled to the first contact to electrically couple the first interconnect to the first contact area of the metal resistor. The MOL temperature sensor also comprises a second interconnect disposed in a second interconnect layer above the MOL layer in the active semiconductor layer, the second interconnect layer electrically coupled to the second contact to electrically couple the second interconnect to the second contact area of the metal resistor 
     In another exemplary aspect, a MOL metal resistor temperature sensor is provided. The MOL metal resistor temperature sensor comprises a means of forming an active semiconductor layer. The MOL metal resistor temperature sensor also comprises a means for forming a MOL layer above the means for providing the active semiconductor layer. The MOL metal resistor temperature sensor also comprises a means for forming a resistance disposed in the means for forming the MOL layer, the means for forming the resistance further comprising a means for providing the resistance between a first means for providing a first contact area and a second means for providing a second contact area. The MOL metal resistor temperature sensor also comprises a first contacting means disposed above the means for providing the resistance for electrically coupling to the first means for providing the first contact area. The MOL metal resistor temperature sensor also comprises a second contacting means disposed above the means for providing the resistance for electrically coupling to the second means for providing the second contact area. The MOL metal resistor temperature sensor also comprises a first means for electrically coupling to the first contacting means, the first means for electrically coupling disposed in a first interconnect layer above the means for forming the MOL layer. The MOL metal resistor temperature sensor also comprises a second means for electrically coupling to the second contacting means, the second means for electrically coupling disposed in a second interconnect layer above the means for forming the MOL layer. 
     In another exemplary aspect, a method of sensing temperature in a semiconductor die for an IC is provided. The method comprises forming a substrate. The method also comprises forming an active semiconductor layer above the substrate. The method also comprises forming at least one semiconductor device in the active semiconductor layer. The method also comprises forming a middle-of-line (MOL) layer above the active semiconductor layer. The method also comprises forming a MOL layer above the active semiconductor layer, comprising forming a metal resistor having a resistance and comprising a first metal material in the MOL layer. The first metal resistor comprises a first contact area and a second contact area and has a resistance between the first contact area and the second contact area. The method also comprises forming a first contact above the metal resistor in the MOL layer and in contact with the first contact area of the metal resistor. The method also comprises forming a second contact above the metal resistor in the MOL layer and in contact with the second contact area of the metal resistor. The method also comprises forming at least one interconnect layer above the MOL layer. The method also comprises forming a first interconnect in the at least one interconnect layer electrically coupled to the first contact, to electrically couple the first interconnect to the first contact area of the metal resistor. The method also comprises forming a second interconnect in the at least one interconnect layer electrically coupled to the second contact, to electrically couple the second interconnect to the second contact area of the metal resistor. 
     In another exemplary aspect, an is provided. The IC comprises an active semiconductor layer. The IC also comprises a MOL layer disposed above the active semiconductor layer. The IC also comprises a MOL temperature sensor comprising a metal resistor disposed in the MOL layer, the metal resistor having a resistance that changes as a function of a change in an ambient temperature of the metal resistor. The IC also comprises a voltage source electrical coupled to the metal resistor. The voltage source is configured to apply a first voltage to the metal resistor. The IC also comprises a voltage detector circuit configured to sense a second voltage as a function of the ambient temperature of the metal resistor when the first voltage is applied to the metal resistor. The IC also comprises a measurement circuit configured to measure the ambient temperature of the metal resistor based on a voltage level of the sensed voltage, and generate a temperature signal on an output node representing an ambient temperature value of the metal resistor. 
    
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
         FIG. 1  is a diagram illustrating a cross-sectional, side view of an integrated circuit (IC) that includes a middle-of-line (MOL) metal resistor temperature sensor fabricated in an MOL layer adjacent to an active semiconductor layer in the IC for localized sensing of ambient temperature of a metal resistor and the active semiconductor layer adjacent to the metal resistor as a function of a change in a resistance in the metal resistor; 
         FIG. 2  is a chart illustrating an exemplary relationship between resistance in ohms (Ω) and temperature in Celsius (C) of a metal resistor; 
         FIG. 3  is a diagram of the MOL metal resistor temperature sensor in  FIG. 1  as part of an on-chip temperature sensing system for sensing ambient temperature of the metal resistor and the active semiconductor layer adjacent to the metal resistor; 
         FIG. 4  is a flowchart illustrating an exemplary process of the on-chip temperature sensing system in  FIG. 3  for sensing ambient temperature of the metal resistor and the active semiconductor layer adjacent to the metal resistor; 
         FIG. 5  is a flowchart illustrating an exemplary process of fabricating a MOL metal resistor temperature sensor in an IC, such as the MOL metal resistor temperature sensor in the IC in  FIG. 1 ; 
         FIGS. 6A-6F  are exemplary process stages of fabricating a MOL metal resistor temperature sensor in an IC, such as the MOL metal resistor temperature sensor in the IC in  FIG. 1 ; 
         FIG. 7  is a schematic diagram of a generalized representation of an exemplary computer system that can be provided in a system-on-a-chip and include MOL metal resistor temperature sensors and related temperature sensing systems, and according to the examples disclosed herein; and 
         FIG. 8  is a block diagram of an exemplary wireless communications device that includes radio-frequency (RF) components and MOL metal resistor temperature sensors and related temperature sensing systems according to the examples disclosed herein, and according to the exemplary aspects disclosed herein. 
     
    
    
     DETAILED DESCRIPTION 
     With reference now to the drawing figures, several exemplary aspects of the present disclosure are described. The word “exemplary” is used herein to mean “serving as an example, instance, or illustration.” Any aspect described herein as “exemplary” is not necessarily to be construed as preferred or advantageous over other aspects. 
     In another exemplary aspect, a method of sensing temperature in a semiconductor die for an integrated circuit (IC) is provided. The method comprises forming a substrate. The method also comprises forming an active semiconductor layer above the substrate. The method also comprises forming at least one semiconductor device in the active semiconductor layer. The method also comprises forming a middle-of-line (MOL) layer above the active semiconductor layer. The method also comprises forming a metal resistor having a resistance and comprising a first metal material in the MOL layer, the first metal resistor comprising a first contact area and a second contact area and having a resistance between the first contact area and the second contact area. The method also comprises forming a first contact above the metal resistor in the MOL layer and in contact with the first contact area of the metal resistor. The method also comprises forming a second contact above the metal resistor in the MOL layer and in contact with the second contact area of the metal resistor. The method also comprises forming at least one interconnect layer above the MOL layer. The method also comprises forming a first interconnect in the at least one interconnect layer electrically coupled to the first contact, to electrical couple the second interconnect to the first contact area of the metal resistor. The method also comprises forming a second interconnect in the at least one interconnect layer electrically coupled to the second contact, to electrical couple the second interconnect to the second contact area of the metal resistor. 
     In another exemplary aspect, an IC. The IC comprises an active semiconductor layer. The IC also comprises a MOL layer disposed above the active semiconductor layer. The IC also comprises a MOL temperature sensor comprising a metal resistor disposed in the MOL layer, the metal resistor having a resistance that changes as function of change in ambient temperature of the metal resistor. The IC also comprises a voltage source electrical coupled to the metal resistor, the voltage source configured to apply a voltage to metal resistor. The IC also comprises a voltage detector circuit configured to sense a voltage of the metal resistor generated in response to the voltage provided to the metal resistor and the ambient temperature of the metal resistor. The IC also comprises a measurement circuit configured to measure ambient temperature of the metal resistor based on a voltage level of the sensed voltage, and generate a temperature signal on an output node representing the ambient temperature value of the metal resistor. 
     In this regard,  FIG. 1  is a diagram illustrating a cross-sectional, side view of a semiconductor die  100  for an IC  102  that includes a MOL metal resistor temperature sensor  104 . The MOL metal resistor temperature sensor  104  is provided on-chip in the IC  102  in this example. The MOL metal resistor temperature sensor  104  includes a metal resistor  106  that is fabricated from a metal material provided in a MOL layer  108  in a MOL area  110  of the semiconductor die  100 . The metal resistor  106  has a resistance based on the metal material and the sizing of the metal resistor  106 . The MOL layer  108  is formed above and adjacent to one or more active semiconductor layers  112  in a front-end-of-line (FEOL) area  114  of the semiconductor die  100  disposed on a substrate  116 . The active semiconductor layers  112  include semiconductor devices  118 , such as a MOS field-effect transistor (MOSFET) shown in  FIG. 1  for example. In this example, the MOSFET is a FinFET  120  that includes a Fin  122  of a width ‘W fin ’ providing a conductive channel with a gate material  124  disposed adjacent to the Fin  122  to provide a gate (G). 
     With continuing reference to  FIG. 1 , the resistance of the metal resistor  106  changes as a function of ambient temperature around the metal resistor  106 , because heat generated by the semiconductor devices  118  in the active semiconductor layers  112  adjacent to the MOL layer  108  causes atoms in the MOL layer  108  to vibrate, thus freeing captive electrons to become carriers of current Ic through the metal resistor  106 . Thus, when a voltage Vdd from a voltage source is applied to the metal resistor  106 , current Ic will flow through the metal resistor  106  as a function of ambient temperature. The change in ambient temperature of the metal resistor  106  can be sensed and measured. For example,  FIG. 2  is chart  200  illustrating an exemplary relationship between resistance in ohms (Ω) and temperature in Celsius (C) of the metal resistor  106  in  FIG. 1 . As shown therein, the resistance of the metal resistor  106  changes approximately 0.24 ohms per degree Celsius for a semiconductor device  118  having a W/L ratio of 0.5 micrometers (μm)/0.5 μm, wherein ‘W’ is the width of the gate (G) and ‘L’ is the length of the gate (G) of the IC  102 . 
     With reference back to  FIG. 1 , because the metal resistor  106  is disposed in the MOL layer  108  immediately adjacent to the active semiconductor layers  112  in this example, voltage of the metal resistor  106  can also be used to measure the temperature in the active semiconductor layers  112  and the semiconductor devices  118  disposed therein. Thus, by fabricating the metal resistor  106  in the MOL layer  108 , the metal resistor  106  can advantageously be localized adjacent and very close to the semiconductor devices  118  in the active semiconductor layers  112 , such as the FinFET  120 , to more accurately sense temperature around the semiconductor devices  118 . This is opposed to BJT temperature sensors that are located farther away in an IC (e.g., 10 times farther away) from CMOS devices due to the size and area constraints of BJTs. The sensed temperature may be used to control operations in the IC  102  that are affected by temperature, such as voltage supply scaling as an example. 
     With continuing reference to  FIG. 1 , to provide connectivity to the MOL metal resistor temperature sensor  104  to be able to direct the voltage Vdd to the metal resistor  106  for sensing ambient temperature of the metal resistor  106 , a first contact  126 ( 1 ) and a second contact  126 ( 2 ) are provided in the MOL layer  108 . The first contact  126 ( 1 ) is electrically coupled to a first contact area  128 ( 1 ) of the metal resistor  106 . The second contact  126 ( 2 ) is electrically coupled to a second contact area  128 ( 2 ) of the metal resistor  106 . For example, the first and second contacts  126 ( 1 ),  126 ( 2 ) may be conductive contact pads made out of a Tungsten (W) material. In this example, the first and second contacts  126 ( 1 ),  126 ( 2 ) physically contact the respective first and second contact areas  128 ( 1 ),  128 ( 2 ). The metal resistor  106  has a resistance R between the first contact area  128 ( 1 ) and the second contact area  128 ( 2 ). First and second vertical interconnect accesses (vias)  130 ( 1 ),  130 ( 2 ) are fabricated in an interconnect layer  132  in an interconnect area  134  of the semiconductor die  100  in aligned contact with the first and second contacts  126 ( 1 ),  126 ( 2 ) to provide electrical connectivity between the metal resistor  106  and the interconnect layer  132 . For example, the interconnect layer  132  is shown as a metal 1 (M1) layer directly above the MOL layer  108 . First and second interconnects  136 ( 1 ),  136 ( 2 ) are formed in the interconnect layer  132  above and in contact with the first and second vias  130 ( 1 ),  130 ( 2 ). For example, the first and second interconnects  136 ( 1 ),  136 ( 2 ) may be metal lines  138 ( 1 ),  138 ( 2 ) that were fabricated from a conductive material disposed in trenches formed in a dielectric material  141 . In this manner, connectivity to the MOL metal resistor temperature sensor  104  is provided through the metal lines  138 ( 1 ),  138 ( 2 ) in this example. 
     Thus, by fabricating the metal resistor  106  in the MOL layer  108  in the IC  102 , the metal resistor  106  can advantageously be localized adjacent and very close to the semiconductor devices  118  in the active semiconductor layers  112 , such as transistors, to more accurately sense temperature around the semiconductor devices  118 . For example, the MOL layer  108  may have a thickness T of approximately eighteen (18) nanometers (nm) or less, which may be a thickness ratio of approximately 0.26 or less to the thickness of the semiconductor layers  112 . This is opposed to BJT temperature sensors for example that are located in an IC farther away (e.g., 10 times farther away) from semiconductor devices due to the size and area constraints of BJTs. Further, because the MOL layer  108  is already provided in the IC  102  to provide contacts between the semiconductor devices  118  in the semiconductor layers  112  and the interconnect layer  132 , additional area may not be required to provide the metal resistor  106  in the  102 . For example, the metal resistor  106  may be approximately a W/L of 0.21 μm/0.21 μm, as opposed to for example, W/L of 3.0 μm/3.0 μm as a typical area required for a BJT temperature sensor. A metal pitch P of the metal lines  138 ( 1 ),  138 ( 2 ) in the IC  102  in  FIG. 1  is unaffected by the fabrication of the metal resistor  106  in the MOL layer  108  in this example, because the metal resistor  106  can be much smaller than the metal pitch P. Similarly, the alignment of the metal resistor  106  to the gate (G) of the FinFET  120  in the example of  FIG. 1  is not critical, because the metal resistor  106  can be much smaller than the gate (G). 
     The metal resistor  106  can be formed from any conductive material desired. As examples, the metal resistor  106  can be formed from Tungsten Silicide (WSiX), Titanium Nitride (TiN), and Tungsten (W). The metal resistor  106  should have a sufficient resistance to he sensitive to changes in ambient temperature. For example, the resistance of the metal resistor  106  may be at least 400 ohms per W/L μm of the semiconductor devices  118 . Thus, small ambient temperature change results will result in a larger resistance change in the metal resistor  106  to provide for accurate temperature sensing. However, small ambient temperature change results may not result in larger resistance changes in the first and second contacts  126 ( 1 ),  126 ( 2 ) or the metal lines  138 ( 1 ),  138 ( 2 ), because these components are usually fabricated to have lower resistances (e.g., 1.0 ohm per W/L μm) to provide a lower contact and interconnect resistance to avoid impacting performance of the semiconductor devices  118 . Also, by disposing the metal resistor  106  in the MOL layer  108 , it may be efficient from a fabrication process standpoint to form the metal resistor  106  from the same material as a work function material  140  disposed adjacent to the gate (G) of the FinFET  120 . 
       FIG. 3  is a diagram of the MOL metal resistor temperature sensor  104  in  FIG. 1  as part of an on-chip temperature sensing system  300  for sensing ambient temperature of the metal resistor  106 , and thus the ambient temperature of the active semiconductor layers  112  adjacent to the metal resistor  106  in the MOL layer  108 . Common components between  FIG. 1  and  FIG. 3  are illustrated in  FIG. 3  with common element numbers, and thus will not be re-described.  FIG. 4  is a flowchart illustrating an exemplary process  400  of the on-chip temperature sensing system  300  in  FIG. 3  sensing ambient temperature to the metal resistor  106  and the active semiconductor layers  112  adjacent to the metal resistor  106 .  FIG. 3  and  FIG. 4  will be discussed in conjunction with each other. 
     In this regard, as shown in  FIG. 3 , a voltage source  302  is provided that is electrically coupled to the first interconnect  136 ( 1 ) of the MOL metal resistor temperature sensor  104  to provide a first voltage Vdd to the metal resistor  106  (block  402  in  FIG. 4 ). As previously discussed, the metal resistor  106  has a resistance that changes as a function of the change in ambient temperature of the metal resistor  106 . The second interconnect  136 ( 2 ) is electrically coupled to a voltage divider node  304  in a voltage detector circuit  306  provided in the form of a voltage divider circuit  308  in this example. A reference resistor Rref is also coupled between a ground node (GND) and the voltage divider node  304 . Thus, the resistance of the metal resistor  106  that changes as a function of ambient temperature will control the amount of current Ic flowing to the voltage divider node  304 , which will divide the first voltage Vdd between the metal resistor  106  and the reference resistor Rref to provide a second voltage Vtemp as Vdd*resistance of reference resistor Rref/(resistance of metal resistor  106 +resistance of reference resistor Rref). The voltage divider circuit  308  is configured to detect the second voltage Vtemp at the voltage divider node  304  generated in response to the first voltage Vdd applied to the metal resistor  106  (block  404  in  FIG. 4 ). The second voltage Vtemp will change as a function of ambient temperature of the metal resistor  106 . 
     With continuing reference to  FIG. 3 , a measurement circuit  310  can be provided in the on-chip temperature sensing system  300  to receive the second voltage Vtemp and measure the ambient temperature of the metal resistor  106  as a function of a voltage level of the second voltage Vtemp (block  406  in  FIG. 4 ). The measurement circuit  310  is configured to generate a temperature signal (temp)  312  on an output node  314  representing an ambient temperature value of the metal resistor  106  (block  408  in  FIG. 4 ). For example, the measurement circuit  310  could be an analog-to-digital (A/D) circuit configured to generate the temperature signal (temp)  312  as a digital temperature value by converting the second voltage Vtemp into a digital temperature value. As another example, the measurement circuit  310  could be an operational amplifier circuit configured to generate the temperature signal (temp)  312  as a differential analog temperature signal by comparing the second voltage Vtemp to a reference voltage or a feedback voltage. The temperature signal (temp)  312  can be directed to other circuits  316  configured to provide operations in the IC  102  based on the ambient temperature, such as voltage scaling for example. 
       FIG. 5  is a flowchart illustrating an exemplary process  500  of fabricating a MOL metal resistor temperature sensor in an IC, such as the MOL metal resistor temperature sensor  104  in the IC  102  in  FIGS. 1 and 3 .  FIGS. 6A-6F  are exemplary process stages  600 ( 1 )- 600 ( 6 ) of fabricating a MOL metal resistor temperature sensor in an IC, such as the MOL metal resistor temperature sensor  104  in the IC  102  in  FIGS. 1 and 3 . The exemplary process  500  in  FIG. 5  and the exemplary process stages  600 ( 1 )- 600 ( 6 ) to fabricate a MOL metal resistor temperature sensor  604  in  FIGS. 6A-6F  will now be described. 
     As illustrated in processing stage  600 ( 1 ) in  FIG. 6A , a first step of fabricating a MOL metal resistor temperature sensor  604  in an IC  602  is to form a substrate  616  (block  502  in  FIG. 5 ). An active semiconductor layer  612  is formed above the substrate  616  as shown in  FIG. 6A  (block  504  in  FIG. 5 ). Further, as shown in  FIG. 6A , at least one semiconductor device  618  is formed in the active semiconductor layer  612  (block  506  in  FIG. 5 ). In this example, PFETs  619 ( 1 ) and a NFETs  619 ( 2 ) are formed in the active semiconductor layer  612 . As shown therein, sources (S), drains (D), and gates (G) are formed for the PFETs  619 ( 1 ) and NFETs  619 ( 2 ). Next, a MOL layer  608  is formed above the active semiconductor layer  612  (block  508  in  FIG. 5 ). In this example, the middle MOL layer  608  is comprised of a first insulating layer  642  followed by a metal material layer  644 , with another second insulating layer  646  disposed on the metal material layer  644 . The first and second insulating layers  642 ,  646  in this example are oxide layers. The metal material layer  644  may be formed of any conductive material that will provide a desired resistance, such as tungsten. As previously discussed, the metal material layer  644  may be formed from the same work function material used to create a gate (G) in the active semiconductor layer  612 . The first insulating layer  642  is configured to insulate the MOL layer  608  from the active semiconductor layer  612  and the semiconductor devices  618  fabricated therein. The metal material layer  644  will be processed to form a metal resistor as will be discussed in more detail below. 
     Next, as shown in a second process stage  600 ( 2 ) in  FIG. 6B , to prepare the metal resistor to be formed in the MOL layer  608 , a photoresist layer  648  is disposed on top of the MOL layer  608 , and more particularly the second insulating layer  646 . Next, as shown in the next process stage  600 ( 3 ) in  FIG. 6C , a hard mask  650  is disposed on the photoresist layer  648  to prepare the metal resistor to be formed from the metal material layer  644 . The hard mask  650  is sized to be of the desired size of the metal resistor to be formed. As previously discussed, the hard mask  650  may be placed so that the metal resistor is formed from the metal material layer  644  adjacent to a semiconductor device  618  in the active semiconductor layer  612 , such as a gate (G) to be affected by the ambient heat generated from the semiconductor device  618 . The photoresist layer  648  in the IC  602  is then processed by exposure to light. As shown in the process stage  600 ( 5 ) in  FIG. 6E , the photoresist layer  648 , the second insulating layer  646 , and the metal material layer  644  are removed except under the area where the hard mask  650  was disposed in process stage  600 ( 4 ) in  FIG. 6D . After the exposure of the photoresist layer  648 , the second insulating layer  646  and the metal material layer  644  that are not underneath the hard mask  650  are removed. The remaining metal material layer  644  forms a metal resistor  606  that has a first contact area  628 ( 1 ) and a second contact area  628 ( 2 ) for providing electrical contacts to the metal resistor  606  as part of the MOL metal resistor temperature sensor  604 . For example, the second insulating layer  646  may be removed by a chemical etch process or other removal process. The metal material layer  644  may be removed by a different chemical etch process or other removal process. 
     Next, as shown in process stage  600 ( 6 ) in  FIG. 6F , another insulating layer  652 , which may be another oxide layer, is disposed over the remaining first insulating layer  642 , the metal resistor  606 , and the second insulating layer  646  to prepare contacts to be formed in the MOL layer  608 . In subsequent processing steps, to continue with fabrication of the MOL metal resistor temperature sensor  604 , a first contact is formed above the metal resistor  606  in the MOL layer  608  and is in contact with the first contact area  628 ( 1 ) (block  510  in  FIG. 5 ). A first contact is also formed above the metal resistor  606  in the MOL layer  608  and in contact with the second contact area  628 ( 2 ) (block  512  in  FIG. 5 ). At least one interconnect layer is formed above the MOL layer  608  (block  514  in  FIG. 5 ). A first interconnect is formed in the at least one interconnect layer electrically coupled to the first contact, to electrically couple the first interconnect to the first contact area  628 ( 1 ) of the metal resistor  606  (block  516  in  FIG. 5 ). A second interconnect is formed in the at least one interconnect layer electrically coupled to the second contact, to electrically couple the second interconnect to the second contact area  628 ( 2 ) of the metal resistor  606  (block  518  in  FIG. 5 ). As previously discussed, vias may be formed in the interconnect layer above the MOL layer  608  to electrically couple contacts connected to the first and second contact areas  628 ( 1 ),  628 ( 2 ) of the metal resistor  606  to the first and second interconnects to form a circuit with the metal resistor  606  to form the MOL metal resistor temperature sensor  604 . 
     In other aspects, a MOL metal resistor temperature sensor can include a means of forming an active semiconductor layer. For example, this means may be the active semiconductor layers  112  in the IC  102  in  FIG. 1 or 3 . The MOL metal resistor temperature sensor can also include a means for forming a MOL layer above the means for providing the active semiconductor layer. For example, the means for forming a MOL layer can be the MOL layer  108  in the IC  102  in  FIG. 1 or 3 . The MOL metal resistor temperature sensor can also include a means for forming a resistance disposed in the means for forming the MOL layer. For example, the means for forming a resistance may be the metal resistor  106  in  FIG. 1 or 3 . The means for forming a resistance can include a means for providing the resistance between a first means for providing a first contact area and a second means for providing a second contact area. For examples, the first means for providing a first contact area and the second means for providing a second contact area may be the first and second contact areas  128 ( 1 ),  128 ( 2 ) in  FIG. 1 or 3 , respectively. The MOL metal resistor temperature sensor can also include a first contacting means disposed above the means for providing the resistance for electrically coupling to the first means for providing the first contact area, and a second contacting means disposed above the means for providing the resistance for electrically coupling to the second means for providing the second contact area. For example, these means may be the first and second contacts  126 ( 1 ),  126 ( 2 ) in  FIG. 1 or 3 , respectively. The MOL metal resistor temperature sensor can also include a first means for electrically coupling to the first contacting means, the first means for electrically coupling disposed in a first interconnect layer above the means for forming the MOL layer, and a second means for electrically coupling to the second contacting means, the second means for electrically coupling disposed in a second interconnect layer above the means for forming the MOL layer. For example, these means can be the first and second interconnects  136 ( 1 ),  136 ( 2 ) in  FIG. 1 or 3 , respectively. The first and second interconnects  136 ( 1 ),  136 ( 2 ) in  FIG. 1 or 3  can be the metal lines  138 ( 1 )  138 ( 2 ), respectively. 
     MOL metal resistor temperature sensors for localized temperature sensing of active semiconductor areas in integrated circuits (ICs), and according to any of the examples disclosed herein, may be provided in or integrated into any processor-based device. Examples, without limitation, include a set top box, an entertainment unit, a navigation device, a communications device, a fixed location data unit, a mobile location data unit, a mobile phone, a cellular phone, a smart phone, a tablet, a phablet, a computer, a portable computer, a desktop computer, a personal digital assistant (PDA), a monitor, a computer monitor, a television, a tuner, a radio, a satellite radio, a music player, a digital music player, a portable music player, a digital video player, a video player, a digital video disc (DVD) player, a portable digital video player, and an automobile. 
     In this regard,  FIG. 7  illustrates an example of a processor-based system  700  that includes a CPU  702  that includes one or more processors  704 . The processor-based system  700  may be provided as a system-on-a-chip (SoC)  706 . The CPU  702  may have a cache memory  708  coupled to the processor(s)  704  for rapid access to temporarily stored data. The CPU  702  may include the MOL metal resistor temperature sensor  104  and on-chip temperature sensing system  300  in  FIG. 3  to measure temperature of semiconductor devices in the CPU  702  and to allow control of operations that affect temperature, such as voltage scaling, to be performed based on the measured temperature. The CPU  702  is coupled to a system bus  710  and can intercouple peripheral devices included in the processor-based system  700 . The processor(s)  704  in the CPU  702  can communicate with these other devices by exchanging address, control, and data information over the system bus  710 . Although not illustrated in  FIG. 7 , multiple system buses  710  could be provided, wherein each system bus  710  constitutes a different fabric. For example, the CPU  702  can communicate bus transaction requests to a memory in a memory system  714  as an example of a slave device. In this example, the memory controller  712  is configured to provide memory access operations in the memory system  714 . 
     Other devices can be connected to the system bus  710 . As illustrated in  FIG. 7 , these devices can include the memory system  714 , one or more input devices  718 , one or more output devices  720 , one or more network interface devices  722 , and one or more display controllers  724 , as examples. The input device(s)  718  can include any type of input device, including but not limited to input keys, switches, voice processors, etc. The output device(s)  720  can include any type of output device, including but not limited to audio, video, other visual indicators, etc. The network interface device(s)  722  can be any devices configured to allow exchange of data to and from a network  726 . The network  726  can be any type of network, including but not limited to a wired or wireless network, a private or public network, a local area network (LAN), a wireless local area network (WLAN), a wide area network (WAN), a BLUETOOTH™ network, and the Internet. The network interface device(s)  722  can be configured to support any type of communications protocol desired. 
     The CPU  702  may also be configured to access the display controller(s)  724  over the system bus  710  to control information sent to one or more displays  728 . The display(s)  728  can include any type of display, including but not limited to a cathode ray tube (CRT), a liquid crystal display (LCD), a plasma display, etc. The display controller(s)  724  sends information to the display(s)  728  to be displayed via one or more video processors  730 , which process the information to be displayed into a format suitable for the display(s)  728 . 
       FIG. 8  illustrates an example of a wireless communications device  800  which can include RF components in which MOL metal resistor temperature sensors detect temperature changes, including but not limited to the MOL metal resistor temperature sensor  104  and the on-chip temperature sensing system  300  in  FIG. 3 . In this regard, the wireless communications device  800 , may be provided in an integrated circuit (IC)  806 . The wireless communications device  800  may include or be provided in any of the above referenced devices, as examples. As shown in  FIG. 8 , the wireless communications device  800  includes a transceiver  804  and a data processor  808 . The IC  806  and/or the data processor  808  may include the MOL metal resistor temperature sensor  104  and on-chip temperature sensing system  300  in  FIG. 3  to measure temperature of semiconductor devices in the CPU  702  in  FIG. 7  and to allow control of operations that affect temperature, such as attenuation levels, frequency rates as examples to be performed based on the measured temperature. The data processor  808  may include a memory (not shown) to store data and program codes. The transceiver  804  includes a transmitter  810  and a receiver  812  that support bi-directional communication. In general, the wireless communications device  800  may include any number of transmitters and/or receivers for any number of communication systems and frequency bands. All or a portion of the transceiver  804  may be implemented on one or more analog ICs, RF ICs (RFICs), mixed-signal ICs, etc. 
     A transmitter or a receiver may be implemented with a super-heterodyne architecture or a direct-conversion architecture. In the super-heterodyne architecture, a signal is frequency-converted between RF and baseband in multiple stages, e.g., from RF to an intermediate frequency (IF) in one stage, and then from IF to baseband in another stage for a receiver. In the direct-conversion architecture, a signal is frequency converted between RF and baseband in one stage. The super-heterodyne and direct-conversion architectures may use different circuit blocks and/or have different requirements. In the wireless communications device  800  in  FIG. 8 , the transmitter  810  and the receiver  812  are implemented with the direct-conversion architecture. 
     In the transmit path, the data processor  808  processes data to be transmitted and provides I and Q analog output signals to the transmitter  810 . In the exemplary wireless communications device  800 , the data processor  808  includes digital-to-analog-converters (DACs)  814 ( 1 ) and  814 ( 2 ) for converting digital signals generated by the data processor  808  into the I and Q analog output signals, e.g., I and Q output currents, for further processing. 
     Within the transmitter  810 , lowpass filters  816 ( 1 ),  816 ( 2 ) filter the I and Q analog output signals, respectively, to remove undesired images caused by the prior digital-to-analog conversion. Amplifiers (AMP)  818 ( 1 ),  818 ( 2 ) amplify the signals from the lowpass filters  816 ( 1 ),  816 ( 2 ), respectively, and provide I and Q baseband signals. An upconverter  820  upconverts the I and Q baseband signals with I and Q transmit (TX) local oscillator (LO) signals through mixers  824 ( 1 ),  824 ( 2 ) from a TX LO signal generator  822  to provide an upconverted signal  826 . A filter  828  filters the upconverted signal  826  to remove undesired images caused by the frequency upconversion as well as noise in a receive frequency band. A power amplifier (PA)  830  amplifies the upconverted signal  826  from the filter  828  to obtain the desired output power level and provides a transmit RF signal. The transmit RF signal is routed through a duplexer or switch  832  and transmitted via an antenna  834 . 
     In the receive path, the antenna  834  receives signals transmitted by base stations and provides a received RF signal, which is routed through the duplexer or switch  832  and provided to a low noise amplifier (LNA)  836 . The duplexer or switch  832  is designed to operate with a specific RX-to-TX duplexer frequency separation, such that RX signals are isolated from TX signals. The received RF signal is amplified by the LNA  836  and filtered by a filter  838  to obtain a desired RF input signal. Downconversion mixers  840 ( 1 ),  840 ( 2 ) mix the output of the filter  838  with I and Q receive (RX) LO signals (i.e., LO_I and LO_Q) from an RX LO signal generator  842  to generate I and Q baseband signals. The I and Q baseband signals are amplified by amplifiers (AMP)  844 ( 1 ),  844 ( 2 ) and further filtered by lowpass filters  846 ( 1 ),  846 ( 2 ) to obtain I and Q analog input signals, which are provided to the data processor  808 . In this example, the data processor  808  includes analog-to-digital-converters (ADCs)  848 ( 1 ),  848 ( 2 ) for converting the analog input signals into digital signals to be further processed by the data processor  808 . 
     In the wireless communications device  800  in  FIG. 8 , the TX LO signal generator  822  generates the I and Q TX LO signals used for frequency upconversion, while the RX LO signal generator  842  generates the I and Q RX LO signals used for frequency downconversion. Each LO signal is a periodic signal with a particular fundamental frequency. A transmit (TX) phase-locked loop (PLL) circuit  850  receives timing information from the data processor  808  and generates a control signal used to adjust the frequency and/or phase of the TX LO signals from the TX LO signal generator  822 . Similarly, a receive (RX) phase-locked loop (PLL) circuit  852  receives timing information from the data processor  808  and generates a control signal used to adjust the frequency and/or phase of the RX LO signals from the RX LO signal generator  842 . 
     Those of skill in the art will further appreciate that the various illustrative logical blocks, modules, circuits, and algorithms described in connection with the aspects disclosed herein may be implemented as electronic hardware, instructions stored in memory or in another computer-readable medium and executed by a processor or other processing device, or combinations of both. The master and slave devices described herein may be employed in any circuit, hardware component, integrated circuit (IC), or IC chip, as examples. Memory disclosed herein may be any type and size of memory and may be configured to store any type of information desired. To clearly illustrate this interchangeability, various illustrative components, blocks, modules, circuits, and steps have been described above generally in terms of their functionality. How such functionality is implemented depends upon the particular application, design choices, and/or design constraints imposed on the overall system. Skilled artisans may implement the described functionality in varying ways for each particular application, but such implementation decisions should not be interpreted as causing a departure from the scope of the present disclosure. 
     The various illustrative logical blocks, modules, and circuits described in connection with the aspects disclosed herein may be implemented or performed with a processor, a Digital Signal Processor (DSP), an Application Specific Integrated Circuit (ASIC), a Field Programmable Gate Array (FPGA) or other programmable logic device, discrete gate or transistor logic, discrete hardware components, or any combination thereof designed to perform the functions described herein. A processor may be a microprocessor, but in the alternative, the processor may be any conventional processor, controller, microcontroller, or state machine. A processor may also be implemented as a combination of computing devices, e.g., a combination of a DSP and a microprocessor, a plurality of microprocessors, one or more microprocessors in conjunction with a DSP core, or any other such configuration. 
     The aspects disclosed herein may be embodied in hardware and in instructions that are stored in hardware, and may reside, for example, in Random Access Memory (RAM), flash memory, Read Only Memory (ROM), Electrically Programmable ROM (EPROM), Electrically Erasable Programmable ROM (EEPROM), registers, a hard disk, a removable disk, a CD-ROM, or any other form of computer readable medium known in the art. An exemplary storage medium is coupled to the processor such that the processor can read information from, and write information to, the storage medium. In the alternative, the storage medium may be integral to the processor. The processor and the storage medium may reside in an ASIC. The ASIC may reside in a remote station. In the alternative, the processor and the storage medium may reside as discrete components in a remote station, base station, or server. 
     It is also noted that the operational steps described in any of the exemplary aspects herein are described to provide examples and discussion. The operations described may be performed in numerous different sequences other than the illustrated sequences. Furthermore, operations described in a single operational step may actually be performed in a number of different steps. Additionally, one or more operational steps discussed in the exemplary aspects may be combined. It is to be understood that the operational steps illustrated in the flow chart diagrams may be subject to numerous different modifications as will be readily apparent to one of skill in the art. Those of skill in the art will also understand that information and signals may be represented using any of a variety of different technologies and techniques. For example, data, instructions, commands, information, signals, bits, symbols, and chips that may be referenced throughout the above description may be represented by voltages, currents, electromagnetic waves, magnetic fields or particles, optical fields or particles, or any combination thereof. 
     The previous description of the disclosure is provided to enable any person skilled in the art to make or use the disclosure. Various modifications to the disclosure will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other variations without departing from the spirit or scope of the disclosure. Thus, the disclosure is not intended to be limited to the examples and designs described herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.