US 7571637 B2
A design structure for an on-chip real-time moisture detection circuitry for monitoring ingress of moisture into an integrated circuit chip during the operational lifetime of the chip. The moisture detection circuitry includes one or more moisture-sensing units and a common moisture monitor for monitoring the state of each moisture-sensing units. The moisture monitor can be configured to provided a real-time moisture-detected signal for signaling that moisture ingress into the integrated circuit chip has occurred.
1. A design structure embodied in a machine readable medium used in a design process for an integrated circuit chip, the design structure comprising:
functional circuitry that is located on the integrated circuit chip when the integrated circuit chip is produced; and
moisture-detecting circuitry, which is embedded within layers of the integrated circuit chip when the integrated circuit chip is produced, that includes:
a moisture-sensing unit for generating a sense signal that varies as a function of moisture within said moisture-sensing unit; and
a moisture monitor in electrical communication with said moisture-sensing unit, said moisture sensing unit including:
a memory for storing a first value, said first value stored in said memory at a first time; and
a comparator for comparing a second value of said sense signal to said first value, said second value being provided by said moisture-sensing unit subsequent to said first value being stored in said memory.
2. The design structure of
3. The design structure of
4. The design structure of
5. A design structure embodied in a computer readable medium for performing a method of detecting ingress of moisture into an integrated circuit chip, the design structure comprising:
a moisture-sensing unit embedded within layers of the integrated circuit chip when the integrated circuit chip is produced, said moisture-sensing unit, when embodied in the integrated circuit chip, for generating a sense signal in response to moisture present in the integrated circuit chip;
a means for storing a first value in a memory of the integrated circuit chip;
a means for comparing, aboard the integrated circuit chip, a second value of said sense signal to said first value; and
a means for generating a warning if said second value is lower than said first value by a predetermined amount.
The present disclosure generally relates to the field of moisture detection in an integrated circuit. In particular, the present disclosure is directed to a design structure for an on-chip real-time moisture sensor for and method of detecting moisture ingress in an integrated circuit chip.
The ingress of moisture into an integrated circuit (IC) chip can have a negative impact on the performance and reliability of circuitry aboard the chip. When moisture ingresses into the active chip circuitry, both the performance and reliability of IC chip significantly degrades. Severe moisture penetration can cause significant failures in the operation of the IC chip.
One method utilized today for detecting moisture in integrated circuits is a gas detection operation, which is performed during the manufacturing test and packaging stage of the IC fabrication process. However, this gas detection operation uses off-chip mechanisms and, thus, it does not provide a on-chip moisture detection scheme for the IC when it is installed in a finished product and operating in the field. During the lifetime of an IC chip, the package may crack because of, for example, severe temperature changes and other mechanical stress factors that can cause the chip moisture seal to break. If the chip seal breaks, moisture ingression into the chip may occur, which can result in IC chip malfunction and/or failure.
This may be especially true for large packaged integrated circuits used in severe temperature environments, such as IC chips for automobile, aircraft, and spacecraft applications. Additionally, because of advances in IC technology there may be increased current leakage and increased integration density of the circuits and, thus, much heat may be generated in an integrated circuit system. In particular, the temperature of the IC package may be ramped from room temperature to higher than 100° C. The large swing in temperature may cause tiny cracks in the IC package and in the die cover layer. These cracks may allow moisture invasion that leads to degradation of the IC chip performance and reliability.
In one embodiment a design structure embodied in a machine readable medium used in a design process for an integrated circuit chip is provided. The design structure includes functional circuitry; and moisture-detecting circuitry that includes: a moisture-sensing unit for generating a sense signal that varies as a function of moisture within the moisture-sensing unit; and a moisture monitor in electrical communication with the moisture-sensing unit, the moisture monitor including: a memory for storing a first value, the first value stored in the memory at a first time; and a comparator for comparing a second value of the sense signal to the first value, the second value being provided by the moisture-sensing unit subsequent to the first value being stored in the memory.
In another embodiment, a design structure embodied in a computer readable medium for performing a method of detecting ingress of moisture into an integrated circuit chip is provided. The design structure includes a means for storing a first value in a memory of the integrated circuit chip; a means for generating, aboard the integrated circuit chip, a second value of the sense signal to the first value; and a means for generating a warning if the second value is lower than the first value by a predetermined amount.
For the purpose of illustrating the invention, the drawings show aspects of one or more embodiments of the invention. However, it should be understood that the present invention is not limited to the precise arrangements and instrumentalities shown in the drawings, wherein:
The present invention is directed to a design structure for an on-chip real-time moisture sensor for and method of detecting moisture ingress in an integrated circuit chip. Referring now to the drawings,
Each moisture-sensing unit 104 may include an active device that has at least one measurable electrical characteristic that changes as a function of the moisture level of its environment. In one example, each moisture-sensing unit 104 may include a low-k capacitor, such as, but not limited to a metal-insulator-metal (MIM) capacitor, e.g., a copper/low-k (Cu/low-k) capacitor, as shown in
As mentioned above, in addition to utilizing MIM capacitors, such as MIM capacitors 200 a-d, one or more of moisture-sensing units 104 (
A low-k capacitor, such as each of MIM capacitors 200 a-d (
Referring again to
Each moisture-sensing unit 410 may include one or more moisture sensitive elements, such as a low-k capacitor C1, which may be, for example, a Cu/low-k MIM capacitor (e.g., any one of MIM capacitors 200 a-d of
More particularly, FETs P1, P3 form a current mirror. FET P1 may be controlled via a control signal 434 from moisture monitor 412 and is the charging current source device of moisture-sensing unit 410. FET P2 is controlled via a control signal 416. When FET P2 is turned on, capacitor C1 is charged and a voltage, which is measurable, is developed at voltage node Vc. A control signal 418 may be used to activate TG 414, which allows the voltage at voltage node Vc (e.g., the Vc sense signal 415) to be passed to moisture monitor 412. FET N1 is controlled via a control signal 420. When FET N1 is turned on as a reset, capacitor C1 is discharged and the voltage at voltage node Vc falls to about ground (about 0.0 volts). FET N1 and FET P2 are not turned on at the same time. Each respective moisture-sensing unit 410 have a unique set of control signals 416, 418, and 420, and each provide a unique Vc sense signal 415 to moisture monitor 412 via each respective TG 414. Control signals 416, 418, and 420 for each moisture-sensing unit 410 are supplied by an internal or external controller or processor (not shown) that is associated with the IC chip upon which moisture-detecting circuitry 400 is installed.
In this example, a core element of the moisture sensor circuitry of each moisture-sensing unit 410 is low-k capacitor C1. When capacitor C1 is charged by a current pulse, the voltage on voltage node Vc across the capacitor C1 approximately equals (I×T)/C; where I is the charging current, T is the pulse duration (e.g., provided at control signal 416 at FET P2), and C is the capacitance of capacitor C1. In one example, the selections of I, T and C usually follows up the formula of (I×T)/C=0.5 Vdd to 0.75 Vdd. Moisture ingression increases the leakage paths and film polarization, which results in an increased leakage current and film k-value that is reflected by an increased capacitance value. When the moisture penetrates into the IC chip, the voltage across capacitor C1, here voltage Vc, may decrease because of the following two factors: (1) as moisture increases, the effective capacitor dielectric constant (k) increases and, thus, the capacitance increases and (2) as moisture increases, the leakage current of the capacitor increases, which is equivalent to adding a resistor in parallel to the capacitor and, thus, the real charging current is reduced.
Moisture monitor 412 may include a current source circuit 430 that provides the control signal 434 that is common to all moisture-sensing units 410 of moisture-detecting circuitry 400. Current source circuit 430 may be formed of a p-type FET P3 and a constant current source 432 that may be connected in series between the power supply and ground. Constant current source 432 supplies a constant current I0. In one example, constant current source 432 may be a FET device that is controlled to provide a constant current. FET P3 of current source circuit 430 and FET P1 of each moisture-sensing unit 410 form a current mirror scheme that has a current ratio of K for supplying a constant current as a function of current I0 to each moisture-sensing unit 410.
Moisture monitor 412 may further include an analog-to-digital converter (A/D) 436. The input of A/D 436 may be the Vc-1 through Vc-n sense signals 415 of the respective moisture-sensing units 410-1 through 410-n, which are electrically connected together, but only one of which is activated at any given time. A control signal 438 is provided for sampling A/D 436, which performs an analog-to-digital conversion operation for receiving an analog input voltage and generating a digital equivalent thereof. The output of A/D 436 feeds an input of a TG 440 that is controlled via a control signal 442. TG 440 may be, for example, a pass transistor. An output of TG 440 feeds an input of an on-chip storage device, such as a read only memory (ROM) 444. A set of control signals 446 are provided to ROM 444 for providing addressing thereto and read control thereof. The storage capacity of ROM 444 is at least suitable for storing a unique Vc value for each moisture-sensing unit 410 within moisture-detecting circuitry 400.
In one example, ROM 444 may be a TaN resistor-based read only memory as described with reference to U.S. patent application Ser. No. 11/161,332, entitled, “Phase-change TaN resistor based triple-state/multi-state read only memory.” Each moisture-sensing unit 410 is assigned an address within ROM 444. In one example, when there are ten moisture-sensing units 410 within moisture-detecting circuitry 400, ROM 444 contains at least ten unique storage locations. Control signals 438, 442, 446 for moisture monitor 412 are supplied by an internal or external controller or processor (not shown) that is associated with the integrated circuit upon which moisture-detecting circuitry 400 is installed.
ROM 444 supplies a digital output of one or more bits to a digital-to-analog converter (D/A) 448, which performs a digital-to-analog conversion operation for receiving a digital input and generating an analog voltage equivalent thereof. An output of D/A 448 feeds an input of a divider 450, which may be voltage divider circuit for generating any user-defined fraction of its input voltage. Divider 450 may provide a divide ratio according to Monte Carlo simulation results to set a margin in order to avoid false alarm. In one example, the output of divider 450 may be 95% of its input voltage value that is supplied by D/A 448. The combination of D/A 448 and divider 450 provides a threshold voltage Vt to which the Vc-1 through Vc-n sense signals 415 of moisture-sensing units 410-1 through 410-n, respectively, are compared.
A comparator 452, which may be a standard analog voltage comparator device, may be provided within moisture monitor 412 for comparing the Vc-1 through Vc-n sense signals 415 of moisture-sensing units 410-1 through 410-n, respectively, to the threshold voltage Vt from divider 450. The output of comparator 452 feeds a TG 452, which may be a pass transistor, that provides a logic one or zero to an input of a latch 456. Latch 456 may be a clocked latch for storing the moisture warning status of moisture-detecting circuitry 400 and generating a moisture-detected signal 458. Latch 456 may be a single bit latch for reading one at a time the moisture warning status of each moisture-sensing unit 410. Alternatively, latch 456 may be a multi-bit register for capturing the moisture warning status of all moisture-sensing units 410, which may be read in parallel, and wherein each bit corresponds to a corresponding respective one of moisture-sensing units 410. Latch 456 may be fed by a clock signal (not shown) and reset signal (not shown).
The operation of moisture detecting circuitry, such as moisture detecting circuitry 400, for detecting ingress of moisture into an integrated circuit chip may be as follows. For each moisture-sensing unit 410, at the beginning of a chip power-up process and when the chip is dry and undamaged, each FET N1 of each moisture-sensing unit 410 is turned on via each respective signal 420 and capacitor C1 is discharged and, thus, voltage node Vc of each moisture-sensing unit 410 may be set to around ground (i.e., to around 0.0 volts). Additionally, all the bits of latch 456 may be reset to a state that is defined as a “normal” state. For example, the moisture alarm is not active when moisture-detected signal 458 of latch 456 is a high logic state. Subsequently, a pulse that has an accurate pulse width of T is applied to the gate of each FET P2 of each moisture-sensing unit 410 via each respective signal 416. In doing so, each FET P2 of each moisture-sensing unit 410 is turned on and each respective capacitor C1, which is the moisture sensor, is charged with (K×current I0) for the time period of T and each respective voltage node Vc is at a certain voltage level. At the completion of this operation, each capacitor C1 of each moisture-sensing unit 410 is in a charged state and the voltage at each voltage node Vc reflects the condition of each capacitor C1 in a dry and undamaged condition, which may be a reference Vc value.
Subsequently, the Vc value of capacitor C1 of each moisture-sensing unit 410 is converted to the digital data by the analog to digital converter A/D 436 and the digital data are stored within ROM 444 as a reference Vc value for that moisture-sensing unit when the IC chip is in a dry and undamaged condition (e.g., reference Vc value may be stored prior to deploying the integrated circuit chip into in-situ operation). In particular, the voltage value at Vc sense signal 415 of each moisture-sensing unit 410 is stored one at a time within ROM 444. More specifically, TG 414 of the selected moisture-sensing unit 410 may be turned on via its respective signal 418 and, thus, the Vc sense signal 415 of the selected moisture-sensing unit 410 is presented at the input of A/D 436 of moisture monitor 412. A trigger signal 438 may be applied to A/D 436, which initiates the analog-to-digital conversion operation and then the control signal 442 may be applied to TG 440, which transmits the output of A/D 436 to ROM 444. The output of A/D 436 is then stored in one location of ROM 444 that is defined by control signals 446 of ROM 444. The data (e.g., corresponding to each Vc sense signal 415) that is stored in ROM 444 serves as a reference Vc value for a later moisture detection operation.
For example, in a periodic moisture detection operation (e.g., after the IC chip has been deployed into in-situ operation), comparator 452 compares an actual real-time voltage Vc (i.e., an actual Vc voltage that may be a function of moisture that is present in the IC chip) of a selected moisture-sensing unit 410 to voltage Vt of divider 450, which is the stored reference Vc value for the selected moisture-sensing unit 410 minus a certain voltage margin. When the actual voltage Vc is higher than voltage Vt, the output of comparator 452 may be, for example, at a certain state, such as a logic high, which may be the “normal” state. However, when voltage Vc is lower than voltage Vt, the output of comparator 452 may be, for example, at a logic low. In both cases, TG 454 transmits the logic signal from comparator 452 to latch 456 which reflects the moisture status of the given moisture-sensing unit 410. In the case wherein the actual Vc voltage of a given moisture-sensing unit 410 falls below the voltage Vt at comparator 452, moisture-detected signal 458 of latch 456 may be set to a logic low, in effect generating a moisture alarm. The bits of latch 456 correspond to the respective moisture-sensing unit 410 that are installed at different locations of the chip. The time difference from the initial use of the integrated circuit in the field to when a moisture alarm is detected at moisture-detected signal 458 of latch 456 may indicate the moisture ingression speed. As seen, moisture-detecting circuitry 400 provides a single level of moisture warning that is based on an analog comparison of one or more actual voltage Vc values to a single threshold voltage Vt. However, in other embodiments, moisture-detecting circuitry may be configured to provide multiple levels of moisture warning, as exemplified in
The one or more moisture-sensing units 510 of
Voltage Vt1 may feed a corresponding comparator 552, voltage Vt2 may feed a corresponding comparator 562, and voltage Vt3 may feed a corresponding comparator 572. Comparators 552, 562, and 572 are also fed by the selected Vc sense signal 515, as shown in
The operation of moisture-detecting circuitry 500 of
The one or more moisture-sensing units 610 of
The operation of moisture-detecting circuitry 600 of
The one or more moisture-sensing units 710 of
Moisture monitor 712 of
The respective outputs of A/Ds 736-1 through 736-n feed a set of respective inputs IN-1 through IN-n of a digital comparator 740 and the output of REF A/D 732 feeds an input IN-REF of digital comparator 740. Each digital value at inputs IN-1 through IN-n is compared to input IN-REF of digital comparator 740. A set of outputs 1 through n of digital comparator 740 feed a set of latches 744-1 through 744-n, respectively. Each latch 744 may be substantially the same as latch 456 of moisture monitor 412 of moisture-detecting circuitry 400 of
The operation of moisture-detecting circuitry 700 may be similar to the moisture-detecting circuitry that is described in
Design process 810 may include using a variety of inputs; for example, inputs from library elements 830 which may house a set of commonly used elements, circuits, and devices, including models, layouts, and symbolic representations, for a given manufacturing technology (e.g., different technology nodes, 32 nm, 45 nm, 90 nm, etc.), design specifications 840, characterization data 850, verification data 860, design rules 870, and test data files 885 (which may include test patterns and other testing information). Design process 810 may further include, for example, standard circuit design processes such as timing analysis, verification, design rule checking, place and route operations, etc. One of ordinary skill in the art of integrated circuit design can appreciate the extent of possible electronic design automation tools and applications used in design process 810 without deviating from the scope and spirit of the invention. The design structure of the invention is not limited to any specific design flow.
Design process 810 preferably translates an embodiment of the invention as shown in IC chip 100, along with any additional integrated circuit design or data (if applicable), into a second design structure 890. Design structure 890 resides on a storage medium in a data format used for the exchange of layout data of integrated circuits (e.g. information stored in a GDSII (GDS2), GL1, OASIS, or any other suitable format for storing such design structures). Design structure 890 may comprise information such as, for example, test data files, design content files, manufacturing data, layout parameters, wires, levels of metal, vias, shapes, data for routing through the manufacturing line, and any other data required by a semiconductor manufacturer to produce an embodiment of the invention as shown in
Exemplary embodiments have been disclosed above and illustrated in the accompanying drawings. It will be understood by those skilled in the art that various changes, omissions and additions may be made to that which is specifically disclosed herein without departing from the spirit and scope of the present invention.