# Patent

## Title
Edge crack detection system

## Abstract

According to an exemplary embodiment, a method of detecting edge cracks in a die under test is provided. The method includes the following operations: receiving a command signal; providing power from the command signal; providing a response signal based on the command signal; and self-destructing based on the command signal.

## Background
CROSS-REFERENCE TO RELATED APPLICATIONS
This application is a continuation of U.S. patent application Ser. No. 14/288,462, entitled “Edge Crack Detection System,” filed May 28, 2014, which is incorporated herein by reference in its entirety.


BACKGROUND
During die sawing process, dies often suffer from edge cracks. A traditional method for edge crack detection is visual inspection which cannot be realized after wafer-level packing process, such as tape and reel (TnR). Therefore, there is a need to develop new method for edge crack detection.



BRIEF DESCRIPTION OF THE DRAWINGS
Aspects of the present disclosure are best understood from the following detailed description when read with the accompanying figures. It is noted that, in accordance with the standard practice in the industry, various features are not drawn to scale. In fact, the dimensions of the various features may be arbitrarily increased or reduced for clarity of discussion.
FIG. 1 is a block diagram illustrating an exemplar edge crack detection system in accordance with some embodiments.
FIG. 2 is a flow chart for a method of detecting edge cracks in a die under test in accordance with some embodiments.
FIG. 3 is a flow chart for a method of detecting edge cracks in a die under test in accordance with some embodiments.
FIG. 4 is a block diagram illustrating a wafer including chips having the exemplar RFID tag in accordance with some embodiments.
FIG. 5 is a block diagram illustrating the exemplar edge crack detection system using tape and reel packing in accordance with some embodiments.
FIG. 6 is a block diagram illustrating another exemplar RFID tag in accordance with some embodiments.



DETAILED DESCRIPTION
The following disclosure provides many different embodiments, or examples, for implementing different features of the provided subject matter. Specific examples of components and arrangements are described below to simplify the present disclosure. These are, of course, merely examples and are not intended to be limiting. For example, the formation of a first feature over or on a second feature in the description that follows may include embodiments in which the first and second features are formed in direct contact, and may also include embodiments in which additional features may be formed between the first and second features, such that the first and second features may not be in direct contact. In addition, the present disclosure may repeat reference numerals and/or letters in the various examples. This repetition is for the purpose of simplicity and clarity and does not in itself dictate a relationship between the various embodiments and/or configurations discussed.
Further, spatially relative terms, such as “beneath,” “below,” “lower,” “above,” “upper” and the like, may be used herein for ease of description to describe one element or feature's relationship to another element(s) or feature(s) as illustrated in the figures. The spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. The apparatus may be otherwise oriented (rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein may likewise be interpreted accordingly.
The disclosure describes a method which uses a RFID reader and a RFID tag to detect edge crack in a die under test. The RFID tag includes a tag antenna and a tag processor. The tag processor is disposed under a seal ring of the die. The tag antenna is disposed outside the seal ring of the die. The RFID reader sends a command signal to the RFID tag. When the die under test has no edge cracks, the tag antenna and the tag processor encircling the die under test are workable to send a response signal to the RFID reader. That is, when receiving the response signal, the RFID reader determines that the die under test has no edge cracks. Additionally, after determining the die has no edge cracks, the RFID reader sends a self-destruction command to destroy or disable the RFID tag, so the method does no impact normal operation of the die. When the edge cracks damaging the die under test, the tag antenna or the tag processor occur, the RFID reader cannot get any response signal.
In details, the method may include the following operations: the tag antenna converts between electromagnet wave and electric signal; the tag processor provides a response signal through the tag antenna; the RFID reader receives the response signal; if the tag antenna does not work, the RFID reader does not receive any signal from the RFID tag; if the RFID reader receives the response signal from the RFID tag, the RFID reader sends a self-destruction command to make the RFID tag self-destruct.
The edge crack detection system may be applied to any RF bands, for example: low frequency (LF) at 120-135 kHz; high frequency (HF) at 13.56 MHz; ultra high frequency (UHF) at 433 MHz or 860-960 MHz; microwave at 2450 MHz.
FIG. 1 is a block diagram illustrating an exemplar edge crack detection system in accordance with some embodiments. As shown in FIG. 1, a system 100 is provided. The system 100 includes a RFID reader 110 and a RFID tag 120 wireless connected to the RFID reader 110. The RFID tag 120 is physically connected to a die under test 130.
The RFID tag 120 may include an antenna 122 outside the seal ring 131 of the die 130. The antenna 122 may have a width of 1 micrometer. The RFID tag 120 may include a processor 124 disposed under a seal ring 131 of the die 130. The processor 124 may have a width of 10 micrometer and a length of 500 micrometer.
The RFID reader 110 provides a command signal 111. The RFID tag 120 receives the command signal 111. The RFID tag 120 produces power from the command signal 111 and provides a response signal 121 based on the command signal 111. The RFID reader 110 receives the response signal 121 so that the RFID reader 110 determines the workability of the RFID tag 120 as well as the die under test 130.
The RFID reader 110 provides the command signal 111 regarding the RFID tag's self-destruction based on the response signal 121. The RFID tag 120 receives the command signal 111 and self-destructs based on the command signal 111. The RFID tag may further compare the command signal 111 with a lookup table (not shown) to determine whether to provide the response signal 121 or to self-destruct. For example, the command signal 111 and the lookup table (not shown) may both include two digits. The two digits representing the RFID tag's self-destruction may refer to “00”, and the two digits of the command signal 111 representing the RFID tag's response or workability may refer to “11”.
Moreover, the RFID reader 110 determines that the die under test 130 has no edge cracks when receiving the response signal 121 indicating the workability of the RFID tag 120. After the self-destruction of the RFID tag 120, the RFID tag 120 no longer provides the response signal 121 and has no impact to the die under test 130. Additionally, the RFID reader 110 provides the command signal 111 in the form of electromagnet wave, and the RFID tag 120 provides the response signal 121 in the form of electromagnet wave as well.
FIG. 2 is a flow chart for a method of detecting edge cracks in a die under test in accordance with some embodiments. As shown in FIGS. 1 and 2, a method 200 is provided. The method 200 includes the following operations: receiving a command signal 111 (202); providing power from the command signal 111 (204); providing a response signal 121 based on the command signal 111 (206); and self-destructing based on the command signal 111 (208). The method 200 further includes comparing the command signal 111 with a lookup table (not shown) to determine whether to provide the response signal 121 or to self-destruct.
FIG. 3 is a flow chart for a method of detecting edge cracks in a die under test in accordance with some embodiments. As shown in FIGS. 1 and 3, a method 300 is provided. The method 300 includes the following operations: by using a RFID reader 110 to provide a command signal 111 regarding a RFID tag's response (302); by using the RFID tag 120 to receive the command signal 111 and produce power from the command signal 111 (304); by using the RFID tag 120 to provide a response signal 121 based on the command signal 111 (306); by using the RFID reader 110 to receive the response signal 121 and provides the command signal 111 regarding the RFID tag's self-destruction based on the response signal 121 (308); and by using the RFID tag 120 to receive the command signal 111 and to self-destruct based on the command signal 111 (310).
Furthermore, the method 300 may further include disposing a processor 124 of the RFID tag 120 under a seal ring 131 of the die 130. The method 300 may further include disposing an antenna 122 of the RFID tag 120 outside a seal ring 131 of the die 130. The method 300 may further include determining that the die 130 has no edge cracks when receiving the response signal 121. The method 300 may further include no longer providing the response signal 121 after the self-destruction of the RFID tag 120. The method 300 may further include having no impact to the die 130 after the self-destruction of the RFID tag 120. The method 300 may further include by using the RFID tag 120 to compare the command signal 111 with a lookup table to determine whether to provide the response signal 121 or to self-destruct. The operation 302 may further include providing the command signal 111 in the form of electromagnet wave. The operation 302 may further include providing the response signal 121 in the form of electromagnet wave.
Next, more details of the exemplar edge crack detection system will be depicted. FIG. 4 is a block diagram illustrating a wafer including chips having the exemplar RFID tag in accordance with some embodiments. As shown in FIG. 4, a wafer 400 is provided. The wafer 400 has a plurality of chips separated by a plurality of scribe lines. For example, the first chip 402 and the second chip 404 are separated by the scribe line 410.
The first chip 402 includes a RFID tag 420 and a die under test 430. The RFID tag 420 is physically connected to a die under test 430. The RFID tag 420 is not limited to the shape in FIG. 4, and may include an antenna (not shown) encircling the die under test 430. The antenna may have a width of 1 micrometer. The RFID tag 420 may further include a processor disposed under a seal ring of the die under test 430. The processor may have a width of 10 micrometer and a length of 500 micrometer. The second chip 404 includes another RFID tag 440 and another die under test 450. The function of the RFID tag 440 and the die under test 450 is similar to the RFID tag 420 and the die under test 430, and is not repeated herein.
The wafer 400 will be diced at those scribe lines to produce individual chips. For example, the wafer 400 will be cut along the scribe line 410 to produce the first chip 402 and the second chip 404. In the embodiment, the dicing is performed using techniques, for example, physical sawing or laser sawing.
FIG. 5 is a block diagram illustrating the exemplar edge crack detection system using tape and reel packing in accordance with some embodiments. As shown in FIG. 5, the chips are placed on tape and reel 508 for distribution to the client. However, during tape and reel packing, cracks damaging the chips easily occur. By using the exemplar edge crack detection system 510 including a RFID reader 502 and a RFID tag 420 wirelessly connected to the RFID reader 502, the chips with cracks can be easily detected.
In the embodiment, during tape and reel packing, a crack 506 occurs in the first chip 402, and damages the RFID tag 420 and the die under test 430. When the tool 504 for tape and reel asks the RFID reader 502 to provide a command signal 503, the RFID tag 420 is unable to receive the command signal 503 and transmit any response signal. Then, the tool 504 for tape and reel connected to the RFID reader 502 cannot get any response signal. Therefore, the tool 504 for tape and reel determines failure of the first chip 402.
In the embodiment, no crack occurs in the second chip 404. When the die under test 450 has no edge cracks, the RFID tag 440 connected to the die 450 is workable to send a response signal to the RFID reader 502. That is, when receiving the response signal, the RFID reader 502 determines that the die 450 under test has no edge cracks. Additionally, after determining the die 450 has no edge cracks, the RFID reader 502 sends a self-destruction command to destroy or disable the RFID tag 440, so the method does no impact normal operation of the die 450.
FIG. 6 is a block diagram illustrating an exemplar RFID tag in accordance with some embodiments. The RFID tag 120 may be configured as shown in FIG. 6. The RFID tag 120 includes an antenna 602, an analog front end (AFE) 610, a MCU and a memory 630. The analog front end (AFE) 610 includes an envelope detector 611, a rectifier 612, a voltage regulator 613, a reset unit 614, and a modulator 615. The RFID tag 120 is connected to a die under test.
The antenna 602 receives the command signal 603. The rectifier 612 and the voltage regulator 613 produce power 618 from the command signal 603. The reset unit 614 sends a reset signal 619 to initialize the MCU 620. The envelope detector 611 extracts a demodulated signal 616 and a clock 617 from the command signal 603. The MCU 620 provides a control signal 621 to the modulator 615 based on the demodulated signal 616. Via the antenna 602, the modulator 615 modulates the control signal 621 and sends the response signal 121 to a RFID reader (not shown). The response signal 121 may carry information about workability of the RFID tag 120 as well as the die under test. After the workability is confirmed, the MCU 620 further performs self-destructing based on the demodulated signal 616 and the data in the memory 630.
According to an exemplary embodiment, a method of detecting edge cracks in a die under test is provided. The method includes the following operations: receiving a command signal; providing power from the command signal; providing a response signal based on the command signal; and self-destructing based on the command signal.
According to an exemplary embodiment, a method of detecting edge cracks in a die under test is provided. The method includes the following operations: by using a RFID reader to provide a command signal regarding a RFID tag's response; by using the RFID tag to receive the command signal and produce power from the command signal; by using the RFID tag to provide a response signal based on the command signal; by using the RFID reader to receive the response signal and provides the command signal regarding the RFID tag's self-destruction based on the response signal; and by using the RFID tag to receive the command signal and to self-destruct based on the command signal.
According to an exemplary embodiment, an edge crack detection system for a die under test is provided. The system includes a RFID reader and a RFID tag. The RFID reader provides a command signal. The RFID tag is wireless connected to the RFID reader, receives the command signal, produces power from the command signal, and provides a response signal based on the command signal. The RFID reader receives the response signal and provides the command signal regarding the RFID tag's self-destruction based on the response signal, and the RFID tag receives the command signal and self-destructs based on the command signal.
The foregoing outlines features of several embodiments so that those skilled in the art may better understand the aspects of the present disclosure. Those skilled in the art should appreciate that they may readily use the present disclosure as a basis for designing or modifying other processes and structures for carrying out the same purposes and/or achieving the same advantages of the embodiments introduced herein. Those skilled in the art should also realize that such equivalent constructions do not depart from the spirit and scope of the present disclosure, and that they may make various changes, substitutions, and alterations herein without departing from the spirit and scope of the present disclosure.

## Claims

1. A method of detecting edge cracks in a die under test, comprising:
encircling a die under test with an antenna of a radio frequency identification (RFID) tag, the antenna being disposed outside of a seal ring of the die under test;
receiving a first command signal at the RFID tag;
based on the first command signal, transmitting a response signal using the RFID tag;
receiving a second command signal at the RFID tag after the transmitting of the response signal; and
self-destructing the RFID tag based on the second command signal.

2. The method of claim 1, further comprising disposing a processor of the RFID tag under the seal ring of the die under test.

3. The method of claim 1, wherein the antenna completely encircles the die under test, and the seal ring surrounds an entire periphery of the die under test.

4. The method of claim 1, further comprising determining whether to perform the self-destructing of the RFID tag based on a comparison of the second command signal to a lookup table.

5. The method of claim 1, wherein the response signal is transmitted as an electromagnetic wave.

6. The method of claim 1, further comprising discontinuing the transmitting of the response signal after the self-destructing of the RFID tag.

7. A method of detecting edge cracks in a die under test, comprising:
transmitting a first command signal to a radio frequency identification (RFID) tag, the RFID tag including an antenna that encircles a die under test;
receiving a response signal from the RFID tag; and
transmitting a second command signal to the RFID tag based on the response signal, the second command signal comprising an indication that commands the RFID tag to perform a self-destruction process.

8. The method of claim 7, further comprising determining that the die under test has no edge cracks based on the receiving of the response signal from the RFID tag.

9. The method of claim 7, wherein the first command signal is transmitted as an electromagnetic wave.

10. An edge crack detection system comprising:
a die under test; and
a radio frequency identification (RFID) tag comprising an antenna that completely encircles the die under test, the RFID tag being configured to
receive a first command signal via the antenna,
based on the first command signal, transmit a response signal,
receive a second command signal after the transmitting of the response signal, and
self-destruct based on the second command signal.

11. The edge crack detection system of claim 10, wherein the antenna is disposed outside of a seal ring of the die under test.

12. The edge crack detection system of claim 11, wherein the RFID tag comprises a processor disposed under the seal ring.

13. The edge crack detection system of claim 11, wherein the seal ring surrounds an entire periphery of the die under test.

14. The edge crack detection system of claim 10, wherein
the RFID tag is configured to wirelessly connect to an RFID reader,
the RFID tag is configured to receive the first and second command signals from the RFID reader, and
the RFID tag is configured to transmit the response signal to the RFID reader.

15. The edge crack detection system of claim 10, wherein the RFID tag is configured to determine whether to perform the self-destructing based on a comparison of the second command signal to a lookup table.

16. The edge crack detection system of claim 10, wherein the RFID tag is configured to transmit the response signal as an electromagnetic wave.

17. The edge crack detection system of claim 10, wherein the RFID tag is configured to discontinue the transmitting of the response signal after the self-destructing.

18. An edge crack detection system comprising:
a radio frequency identification (RFID) reader configured to
connect wirelessly to an RFID tag,
transmit a first command signal to the RFID tag, the RFID tag including an antenna that encircles a die under test,
receive a response signal from the RFID tag, and
transmit a second command signal to the RFID tag based on the response signal, the second command signal comprising an indication that commands the RFID tag to perform a self-destruction process.

19. The edge crack detection system of claim 18, wherein the RFID reader is configured to determine that the die under test has no edge cracks based on the receiving of the response signal from the RFID tag.

20. The edge crack detection system of claim 18, wherein the RFID reader is configured to transmit the first command signal as an electromagnetic wave.