JP2016151563A - Semiconductor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a semiconductor device capable of increasing detection accuracy of a stress to which the semiconductor device is subjected.SOLUTION: A semiconductor device comprises: a semiconductor substrate; an electronic circuit provided on the semiconductor substrate; a metal pattern provided on the semiconductor substrate; and an air bridge structure including a columnar part located lateral to the metal pattern and a just above part connected to the columnar part and located just above the metal pattern and formed in a conductor without contacting with the metal pattern. The metal pattern and the air bridge structure are not electrically in contact with the electronic circuit.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a semiconductor device.

  Patent Document 1 discloses a method for detecting stress using whiskers generated in a wiring pattern inside a semiconductor device. Specifically, the Al wiring formed on the Si substrate is deformed by migration due to stress, and a defect is detected by short-circuiting to another Al wiring arranged in parallel.

JP-A-11-260878

  In the method disclosed in Patent Document 1, stress can be detected only when the whisker grows in the lateral direction, and thus there is a problem that the detection accuracy of the stress applied to the semiconductor device is low.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a semiconductor device that can improve the accuracy of detection of stress received by the semiconductor device.

  A semiconductor device according to the invention of the present application includes a semiconductor substrate, an electronic circuit provided on the semiconductor substrate, a metal pattern provided on the semiconductor substrate, and a columnar portion located beside the metal pattern. An air bridge structure which is connected to the columnar part and located immediately above the metal pattern, and is formed of a conductor without contacting the metal pattern, the metal pattern and the air bridge The structure is characterized in that it is not in electrical contact with the electronic circuit.

  Another semiconductor device according to the invention of the present application is provided with an electronic circuit, a package formed of an insulator covering the electronic circuit, a semiconductor substrate provided on the package, and a semiconductor substrate provided on the semiconductor substrate. And a metal pattern.

  According to the present invention, it becomes possible to detect whiskers extending in the upward direction, thereby increasing the accuracy of detecting stress applied to the semiconductor device.

1 is a plan view of a semiconductor device according to a first embodiment. It is sectional drawing in the broken-line part of FIG. It is a figure which shows the stress which arises during use of a semiconductor device. It is a figure which shows that the whisker generate | occur | produced. It is a figure which shows a monitoring part etc. It is a figure which shows a cap etc. It is a figure which shows having provided a part of columnar part between the electronic circuit and the metal pattern. It is a figure which shows a shielding wall. It is a figure which shows the modification of a metal pattern. It is a figure which shows another modification of a metal pattern. It is a figure which shows another modification of a metal pattern. It is a figure which shows another modification of a metal pattern. It is a figure of a saddle type air bridge structure. It is a figure of a dome type air bridge structure. It is a table | surface which shows the result of a heating experiment. It is a top view which shows the whisker detection circuit which concerns on Embodiment 2, and its periphery structure. It is sectional drawing in the broken line of FIG. FIG. 6 is a cross-sectional view of a whisker detection circuit according to a third embodiment. It is a figure which shows a whisker. FIG. 6 is a plan view of a semiconductor device according to a fourth embodiment. It is sectional drawing in the broken line of FIG. It is sectional drawing of the whisker detection circuit which concerns on a modification. It is sectional drawing of the whisker detection circuit which concerns on another modification. FIG. 9 is a plan view of a semiconductor device according to a fifth embodiment. It is sectional drawing in the broken line of FIG. It is sectional drawing of the whisker detection circuit which concerns on a modification. It is sectional drawing of the whisker detection circuit which concerns on another modification. FIG. 10 is a plan view of a semiconductor device according to a sixth embodiment. It is sectional drawing in the broken line of FIG. It is a top view of the semiconductor device which concerns on a modification. It is a top view of the semiconductor device which concerns on another modification. It is sectional drawing of a whisker detection circuit.

  A semiconductor device according to an embodiment of the present invention will be described with reference to the drawings. The same or corresponding components are denoted by the same reference numerals, and repeated description may be omitted.

Embodiment 1 FIG.
FIG. 1 is a plan view of a semiconductor device 10 according to the first embodiment of the present invention. The semiconductor device 10 includes a frame 12. A semiconductor substrate 14 and a cap 15 are provided on the frame 12. The frame 12 and the cap 15 constitute a package. Only the frame portion of the cap 15 is shown, and the lid portion is omitted. The semiconductor substrate 14 is formed of a compound semiconductor such as GaAs or SiC.

  A terminal 16 extending from the cap 15 to the outside is fixed to the cap 15. The terminal 16 includes a first terminal 16a, a second terminal 16b, a third terminal 16c, and a fourth terminal 16d.

  An electronic circuit 20 and a wiring pattern 22 are provided on the semiconductor substrate 14. The electronic circuit 20 includes, for example, a power amplification element. The wiring pattern 22 is, for example, an Au pattern formed of Au on the semiconductor substrate 14. The wiring pattern 22 and the electronic circuit 20 are electrically connected. The wiring pattern 22 is connected to the terminal 16 by a wire 24 made of, for example, Au.

  A metal pattern 30 is provided on the semiconductor substrate 14. The metal pattern 30 is made of Al. An air bridge structure 32 is formed on the metal pattern 30. The air bridge structure 32 is formed of a conductor such as Au. The metal pattern 30 and the air bridge structure 32 will be described with reference to FIG.

  2 is a cross-sectional view taken along a broken line in FIG. The metal pattern 30 includes metal patterns 30a, 30b, 30c, 30d, and 30e. The air bridge structure 32 includes a columnar portion 32a and a directly upper portion 32b. The columnar part 32a is located beside the metal patterns 30b, 30c, and 30d. The directly upper portion 32b is connected to the columnar portion 32a and is located immediately above the metal patterns 30b, 30c, 30d. Since gaps are provided between the upper part 32b and the metal patterns 30b, 30c, and 30d, the upper part 32b does not contact the metal pattern 30.

  A barrier metal 40 is provided on the metal patterns 30a and 30e. A columnar portion 32 a is provided on the barrier metal 40. The barrier metal 40 is formed of, for example, Ti / Mo / Ti, W, WN, Ta, or TaN in order to prevent mutual diffusion between the metal patterns 30a and 30e and the air bridge structure 32.

  The thickness t1 of the semiconductor substrate 14 is, for example, 30 to 600 μm. The thickness t2 of the metal patterns 30a, 30b, 30c, 30d, and 30e is, for example, 0.1 to 10 μm.

  Returning to the description of FIG. The metal pattern 30a (the leftmost metal pattern) is connected to the first terminal 16a by a wire. Thereby, the air bridge structure 32 and the 1st terminal 16a are electrically connected. The metal pattern 30b (second metal pattern from the left) is connected to the second terminal 16b by a wire, and the metal pattern 30c (third metal pattern from the left) is connected to the third terminal 16c by a wire, and the metal pattern 30d ( The fourth metal pattern from the left is connected to the fourth terminal 16d by a wire.

  The metal pattern 30 and the air bridge structure 32 constitute a “whisker detection circuit” for detecting whiskers. Since the whisker detection circuit is provided at a position away from the electronic circuit 20, it does not come into electrical contact with the electronic circuit 20.

  An energized semiconductor device may be subjected to excessive environmental stress (temperature, humidity, temperature change) exceeding a product rating, for example. FIG. 3 is a diagram illustrating stress generated during use of the semiconductor device. When the semiconductor device is subjected to stress due to a high temperature of, for example, 280 ° C. or higher, a thermal stress 50 is generated due to a difference in thermal expansion coefficient between the semiconductor substrate 14 and the metal pattern 30b. FIG. 4 is a diagram showing that whiskers 52 are generated from the metal pattern 30b by this thermal stress. When the whisker 52 grows, the metal pattern 30b and the air bridge structure 32 are short-circuited. Similar to the metal pattern 30b, whiskers can occur in the metal patterns 30c and 30d.

  A method for detecting the presence or absence of whiskers will be described. FIG. 5 is a diagram illustrating the monitoring unit 60 and the like. The monitoring unit 60 is connected to the first to fourth terminals 16a, 16b, 16c, and 16d. The monitoring unit 60 includes a monitor circuit 60a that monitors whether any two of the first to fourth terminals 16a, 16b, 16c, and 16d are open or short-circuited. The investigation result in the monitor circuit 60a is displayed on the display unit 60b. In FIG. 5, the inside of the semiconductor device is shown for convenience of explanation, but actually, as shown in FIG. 6, the cap 15 covers the whisker detection circuit, the electronic circuit 20, and the like.

  By using the monitoring unit 60, it is possible to monitor whether any two terminals are open or short-circuited. As a result, it is possible to instantaneously detect that the whisker has grown due to the high temperature stress of the semiconductor device.

  When the occurrence of whiskers is detected by the monitoring unit 60, a system having a redundant system can be switched to another circuit. In addition, a whisker detection circuit can be used for investigating the cause when the semiconductor device is destroyed. Specifically, the history of thermal stress can be examined nondestructively by confirming electrical open or electrical short between terminals. In addition, the whisker detection circuit can be integrated with another circuit on one semiconductor substrate, so that it can be incorporated in a semiconductor device of a small package. Further, since the whisker detection circuit is electrically unrelated to the electronic circuit 20, it does not affect the electrical characteristics of the electronic circuit 20. That is, even if a whisker is detected by the whisker circuit, it does not affect the operation of the electronic circuit 20.

  Without using the monitoring unit 60, the entire cap 15 may be removed from the frame 12, or the lid portion of the cap 15 may be opened, and the appearance of whiskers may be observed to investigate the stress history of the semiconductor device. If a problem occurs in the electronic circuit 20 or the like, the cause of the problem can be specified by investigating the occurrence of whiskers.

  The metal patterns 30a and 30e function as a base part formed of the same material as the metal patterns 30b, 30c, and 30d on the semiconductor substrate. That is, the metal patterns 30 a and 30 e function as a base part of the air bridge structure 32. The metal patterns 30a and 30e may be formed of the same material as the metal patterns 30b, 30c, and 30d because the air bridge structure 32 and the first terminal 16a may be connected. The columnar part and the semiconductor substrate 14 may be brought into contact by omitting the metal patterns 30a and 30e and the barrier metal 40 and extending the columnar part 32a downward.

  Whisker may grow not only upward but also laterally. Therefore, by arranging metal patterns in parallel, whiskers grown laterally from one metal pattern are brought into contact with another metal pattern. For example, when the metal pattern 30b and the metal pattern 30c are short-circuited, it can be determined that there is lateral whisker growth. Further, by positioning the columnar portion 32a beside the metal patterns 30b, 30c, and 30d, whiskers grown in the horizontal direction come into contact with the columnar portion 32a, and the occurrence of the whiskers can be detected.

  As described above, whiskers may grow not only in the upward direction but also in the lateral direction. Therefore, it should be prevented that whiskers extending from the metal pattern 30 reach the electronic circuit 20 and affect the operation of the electronic circuit 20. Therefore, it is possible to surround the metal pattern 30 with the columnar portion of the air bridge structure so that the whisker grown in the lateral direction does not contact the electronic circuit 20. Further, it is possible to prevent whiskers grown in the lateral direction from coming into contact with the wiring pattern 22. A part of the columnar part may be provided between the electronic circuit 20 and the metal pattern 30 without surrounding the metal pattern 30 with the columnar part. FIG. 7 is a diagram showing that a part of the columnar part is provided between the electronic circuit 20 and the metal pattern 30. A part of the columnar part is a protective wall 32c. The protective wall 32 c is provided on the semiconductor substrate 14.

  A shielding wall surrounding the metal pattern 30 may be provided so that whiskers extending from the metal pattern do not reach the electronic circuit 20. FIG. 8 is a view showing the shielding wall 33. Although the height of the shielding wall 33 needs to be high enough to prevent the whisker from growing in the lateral direction, it is preferable that the height of the shielding wall 33 be equal to the thickness of the metal pattern so as not to disturb the wire connection. The shielding wall 33 is formed of an insulating film, resin, or metal film. The shielding wall may be provided between the electronic circuit 20 and the metal pattern 30 without surrounding the metal pattern with the shielding wall.

  FIG. 9 is a diagram illustrating a modification of the metal pattern. A part of the metal pattern 30b is a narrow part 30f that is narrower than the other part. The narrow portion 30f is a portion where a V-shaped cut is formed in a plan view. The narrow portion 30f is immediately below the air bridge structure 32 indicated by a broken line. When the semiconductor device receives stress, the stress concentrates on the narrow portion 30f, and whiskers are generated from the narrow portion 30f. Therefore, since the place where a whisker is generated can be limited, the whisker can be easily found when the whisker is visually observed (appearance observation). In addition, whisker (electric short) can be reliably detected by growing a whisker extending upward just below the air bridge structure. The narrow portion is not particularly limited as long as it is formed in a part of the metal pattern so that the width is narrower than other portions in plan view. For example, you may form a U-shaped narrow part like the narrow part 30g of FIG.

  FIG. 11 is a diagram showing another modification of the metal pattern. A concave portion 30h is formed in the metal pattern 30b. When the semiconductor device is stressed, the stress is concentrated in the recess 30h and a whisker is generated in the recess 30h. Therefore, the place where a whisker is generated can be limited. The shape of the recess is not particularly limited. For example, you may form a recessed part like the recessed part 30i of FIG. In addition, the number and shape of the metal patterns 30 can be arbitrarily set. As described above, the stress detection accuracy can be increased by positioning the narrow portion or the concave portion directly below the air bridge structure.

  The material of the metal pattern 30 is not limited to Al. The material of the metal pattern 30 is determined according to what kind of “stress received by the semiconductor device” is desired to be detected. The temperature at which the whisker is generated can be adjusted by alloying Al or the like with Ta, Pd, In, or the like. Further, the whisker generation temperature can be adjusted by changing the size or thickness of the metal pattern 30. The thickness of the metal pattern is, for example, about 0.1 to 10 μm.

  Various modifications can be made to the shape of the air bridge structure. For example, as shown in FIG. 13, a bowl-shaped air bridge structure 70 may be provided. Further, as shown in FIG. 14, a dome-shaped air bridge structure 72 may be provided. In Embodiment 1 of the present invention, the columnar portion 32a of the air bridge structure is distinguished from the barrier metal 40 and the metal patterns 30a and 30e. However, the columnar portion 32a, the barrier metal 40 and the metal patterns 30a and 30e are collectively included in the columnar portion. You may think.

  These modifications can also be applied to semiconductor devices according to the following embodiments. It should be noted that the semiconductor device according to the following embodiment has much in common with the first embodiment, and therefore the description will focus on the differences from the first embodiment.

Embodiment 2. FIG.
There is a threshold for the temperature at which whiskers are generated. That is, whiskers are generated when the semiconductor device reaches a certain temperature or higher. FIG. 15 is a table showing the relationship between the temperature obtained by conducting the heating experiment and the generation of whiskers. The heating experiment was conducted by holding a sample obtained by vacuum-depositing a 0.5 μm thick Al film (pure Al) on a 30 μm thick GaAs substrate at 125 ° C. to 330 ° C. for 1 hour. did. The presence or absence of whisker generation was confirmed with an optical microscope (or SEM). This heating experiment shows that there is a threshold value for the whisker generation temperature.

  FIG. 16 is a plan view showing the whisker detection circuit according to the second embodiment and the surrounding structure. The metal patterns 80a, 80b, 80c and the air bridge structure 82 constitute a first whisker detection circuit, the metal patterns 80d, 80e, 80f and the air bridge structure 84 constitute a second whisker detection circuit, and the metal patterns 80g, 80h, 80i and the air bridge structure 86 constitute a third whisker detection circuit.

  The metal patterns 80a, 80b, and 80c are configured to generate whiskers at 280 ° C., the metal patterns 80d, 80e, and 80f are configured to generate whiskers at 330 ° C., and the metal patterns 80g, 80h, and 80i are configured to be 380 ° C. Is configured to generate whiskers. That is, the whisker generation temperatures of the first to third whisker detection circuits are different. When the metal patterns 80a to 80i have Al as a main material, whisker generation temperature is adjusted by alloying Al or adjusting the size or thickness of Al.

  17 is a cross-sectional view taken along the broken line in FIG. When the semiconductor device is subjected to thermal stress of 280 ° C. or higher, whiskers 90 are generated. When the semiconductor device is subjected to thermal stress of 330 ° C. or higher, whiskers 90 and 92 are generated. When the semiconductor device is subjected to thermal stress of 380 ° C. or higher, whiskers 90, 92, and 94 are generated. In this way, it is possible to easily detect how much thermal stress the semiconductor device has been subjected to. Since the degree of thermal stress can be detected in multiple stages, the accuracy of detecting the stress applied to the semiconductor device can be increased.

  A feature of the semiconductor device of the second embodiment is that a whisker detection circuit having a plurality of metal patterns, a plurality of air bridge structures, and different whisker generation conditions of the plurality of metal patterns is provided. Various modifications can be made without departing from this feature.

Embodiment 3 FIG.
FIG. 18 is a cross-sectional view of a whisker detection circuit according to the third embodiment. The difference from the second embodiment is that the heights of the upper portions 100a, 102a, 104a of the plurality of air bridge structures 100, 102, 104 are not uniform. The distance from the upper part 100a to the metal pattern 105b immediately below the upper part 100a is h1. The distance from the upper part 102a to the metal pattern 105e immediately below the upper part 102a is h2. The distance from the upper part 104a to the metal pattern 105h immediately below the upper part 104a is h3. h2 is larger than h1, and h3 is larger than h2. That is, the distance from the upper part to the metal pattern immediately below the upper part is not uniform.

  The longer the heating time of the semiconductor device, the longer the whisker grows upward. When the heating time is about 1 minute, the whisker height is h1, and when it is about 5 minutes, the whisker height is h2, and when it is about 10 minutes, the whisker height is h3. Therefore, as shown in FIG. 19, when the heating time is 1 minute, the metal pattern 105 b and the air bridge structure 100 are short-circuited by the whisker 106. When the heating time is 5 minutes, the metal pattern 105e and the air bridge structure 102 are short-circuited by the whisker 108. When the heating time is 10 minutes, the metal pattern 105h and the air bridge structure 104 are short-circuited.

  Therefore, it is possible to easily detect how long the semiconductor device has been subjected to stress at a temperature equal to or higher than a predetermined threshold. As described above, since the whisker detection circuit according to the third embodiment measures the time during which heat stress is applied, it is preferable that all the metal patterns 105a to 105i are formed of the same material. The distance from the upper part of the air bridge to the metal pattern immediately below the upper part can be arbitrarily set. The number of whisker detection circuits can also be set arbitrarily.

Embodiment 4 FIG.
FIG. 20 is a plan view of a semiconductor device according to the fourth embodiment. The metal pattern 150 is made of Sn. 21 is a cross-sectional view taken along the broken line in FIG. The metal pattern 150 includes metal patterns 150a, 150b, 150c, 150d, and 105e. Stress that causes high temperature and high humidity inside the semiconductor device (for example, 60 ° C./90% or more (60 ° C./90% or more means that the temperature is 60 ° C. or more and the humidity is 90% or more)) When received, the surface of the metal pattern 150 made of Sn is oxidized and the volume expands. Therefore, a compressive stress 152 is generated on the surface of the metal pattern 150c. Due to this compressive stress, whiskers 154 are generated from the metal pattern 150c, and the metal pattern 150c and the air bridge structure 32 are short-circuited. By detecting this short circuit by a monitoring unit or appearance observation, it is possible to detect the stress applied to the semiconductor device.

  By forming the metal pattern 150 with Sn, it is possible to detect how much the semiconductor device has been subjected to stress due to temperature and humidity. In order to adjust the whisker generation temperature, Sn or Bi may be added to Sn for alloying, or the size or thickness of the metal pattern may be changed. Note that the thickness of the metal pattern 150 is varied in the range of 0.1 to 10 μm, for example.

  FIG. 22 is a cross-sectional view of a whisker detection circuit according to a modification. The metal pattern 160a generates whiskers at a temperature of 30 ° C. or higher and 90% or higher, the metal pattern 160b generates whiskers at a temperature of 40 ° C. or higher and 90% or higher, and the metal pattern 160c has a humidity of 60 ° C. and 90% or higher. A whisker is generated. The whisker generation temperature is adjusted by alloying Sn or adjusting the size and thickness. By investigating the presence or absence of the whiskers 162, 164, 166, the stress applied to the semiconductor device can be accurately detected.

  FIG. 23 is a cross-sectional view of a whisker detection circuit according to another modification. The distances between the upper portions 100a, 102a, and 104a of the air bridge and the metal patterns 170a, 170b, and 170c were not uniform. When the predetermined high temperature and high humidity state continues for 10 hours, the metal pattern 170 a and the air bridge structure 100 are short-circuited by the whisker 172. When the predetermined high temperature and high humidity state continues for 100 hours, the metal pattern 170b and the air bridge structure 102 are short-circuited by the whisker 174. When the predetermined high temperature and high humidity state continues for 1000 hours, the metal pattern 170 c and the air bridge structure 104 are short-circuited by the whisker 174. In this way, it is possible to measure the time during which high temperature and high humidity stress is applied.

Embodiment 5 FIG.
FIG. 24 is a plan view of the semiconductor device according to the fifth embodiment. The metal pattern 200 is made of Zn. 25 is a cross-sectional view taken along the broken line in FIG. The metal pattern 200 includes metal patterns 200a, 200b, 200c, 200d, and 200e. When a semiconductor device is repeatedly subjected to a stress of a sudden temperature change (for example, a temperature change from −40 ° C. to 85 ° C.), an expansion / compression stress 202 is generated due to a difference in thermal expansion coefficient between the semiconductor substrate 14 and the metal pattern 200 To do. Due to the expansion and compression stress, whiskers 204 are generated from the metal pattern 200d, and the metal pattern 200d and the air bridge structure 32 are short-circuited. By detecting this short circuit by a monitoring unit or external observation, it is possible to detect stress (abrupt temperature change) applied to the semiconductor device.

  By forming the metal pattern with Zn, it can be determined whether the semiconductor device has been subjected to stress due to temperature change. In order to adjust the temperature at which whiskers are generated, Bi or Pb or the like may be added to Zn for alloying, or the size or thickness of the metal pattern may be changed. The thickness of the metal pattern is varied in the range of 0.1 to 10 μm, for example.

  FIG. 26 is a cross-sectional view of a whisker detection circuit according to a modification. When the metal pattern 210a undergoes a temperature change from −40 ° C. to 85 ° C., the whisker 212 grows. When the metal pattern 210b is subjected to a temperature change from −55 ° C. to 125 ° C., the whisker 214 grows. When the metal pattern 210c undergoes a temperature change from −65 ° C. to 175 ° C., the whisker 216 grows. The whisker generation temperature is adjusted by alloying Zn or adjusting the size and thickness. By investigating the presence or absence of the whiskers 212, 214, 216, it is possible to accurately detect the stress applied to the semiconductor device.

  FIG. 27 is a cross-sectional view of a whisker detection circuit according to another modification. The distances between the upper portions 100a, 102a, and 104a of the air bridge and the metal patterns 220a, 220b, and 220c were not uniform. The metal pattern 220a and the air bridge structure 100 are short-circuited by the whisker 222 when subjected to stress due to a predetermined temperature change 10 times. When the stress due to a predetermined temperature change is received 100 times, the metal pattern 220b and the air bridge structure 102 are short-circuited by the whisker 224. The metal pattern 220 c and the air bridge structure 104 are short-circuited by the whisker 226 when subjected to stress due to a predetermined temperature change 1000 times. Thus, the number of times of stress due to temperature change can be measured by utilizing the property that whiskers grow according to the number of times of stress due to temperature change.

Embodiment 6 FIG.
FIG. 28 is a plan view of a semiconductor device according to the sixth embodiment. A frame 12 and a cap 15 (package) formed of an insulator cover the electronic circuit. Metal patterns 300a, 300b, and 300c are exposed on the surface of the package. 29 is a cross-sectional view taken along the broken line in FIG. On the cap 15, semiconductor substrates 302a, 302b, and 302c are provided. The semiconductor substrates 302a, 302b, and 302c are made of, for example, GaAs or SiC. Metal patterns 300a, 300b, and 300c are provided on the semiconductor substrates 302a, 302b, and 302c, respectively. The metal pattern 300a is Al, the metal pattern 300b is Sn, and the metal pattern 300c is Zn.

  When the semiconductor device is subjected to stress at a high temperature (for example, 280 ° C. or higher), whiskers 304 are generated due to the stress caused by the difference in thermal expansion coefficient between the semiconductor substrate 302a and the metal pattern 300a. When the semiconductor device is subjected to stress of high temperature and high humidity (for example, 60 ° C./90% or more), the whisker 306 is generated due to the stress caused by the volume expansion of the metal pattern 300b. When the semiconductor device is repeatedly subjected to environmental stress due to rapid temperature changes (for example, −40 ° C. to 85 ° C.), whiskers 308 are generated due to the expansion and compression stress resulting from the difference in thermal expansion coefficient between the semiconductor substrate 302c and the metal pattern 300c. .

  Therefore, by observing the appearance of the metal patterns 300a, 300b, and 300c and confirming the presence or absence of whiskers, the history of environmental stress received by the semiconductor device can be examined nondestructively. Whisker generation conditions can be adjusted by alloying a metal such as Al, Sn, or Zn with Ta, Pd, In, Bi, Pd, or the like. In addition, whisker generation conditions can be adjusted by changing the size or thickness of the metal. The thickness range is, for example, 0.1 to 10 μm.

  FIG. 30 is a plan view of a semiconductor device according to a modification. By providing narrow portions in the metal patterns 310a, 310b, and 310c, stress can be concentrated on the narrow portions, and the locations where whiskers are generated can be limited.

  FIG. 31 is a plan view of a semiconductor device according to another modification. The metal patterns 312a and 312b are patterns mainly composed of Al. The metal pattern 312a generates whiskers when heated at 280 ° C., and the metal pattern 312b generates whiskers when heated at 380 ° C.

  The metal patterns 312c and 312d are patterns mainly composed of Sn. The metal pattern 312c generates whiskers when high temperature and high humidity are maintained for 10 hours. The metal pattern 312d generates whiskers when high temperature and high humidity are maintained for 1000 hours.

  The metal patterns 312e and 312f are patterns mainly composed of Zn. The metal pattern 312e generates whiskers when there is a temperature change from −40 ° C. to 85 ° C. The metal pattern 312f generates whiskers when there is a temperature change from −65 ° C. to 175 ° C.

  As described above, by providing a plurality of metal patterns having different whisker generation conditions, it is possible to improve the accuracy of detecting the stress applied to the semiconductor device. Note that the semiconductor substrate provided under the metal pattern may have the same planar shape as the metal pattern, or may have a large area so that a plurality of metal patterns can be formed.

  FIG. 32 is a cross-sectional view of a whisker detection circuit according to another modification. Whiskers grow longer in the vertical direction depending on the time of stress. Therefore, a short whisker 304 on the left side is generated at the beginning. When the stress application time is long, the whisker 304 is slightly longer at the center, and when the stress application time is longer, the long whisker 304 is on the right side. Therefore, by confirming the height of the whisker, it is possible to know the time during which stress is received.

  Although Al, Sn, and Zn are exemplified as the metal pattern material, other materials such as Ag may be used. Note that the features of the embodiments described so far may be combined as appropriate.

  DESCRIPTION OF SYMBOLS 10 Semiconductor device, 12 Frame, 14 Semiconductor substrate, 15 Cap, 16 Terminal, 20 Electronic circuit, 22 Wiring pattern, 24 Wire, 30 Metal pattern, 32 Air bridge structure, 32a Columnar part, 32b Directly upper part, 32c Protective wall, 33 Shielding wall, 52 whiskers, 60 monitoring section, 72 air bridge structure

Claims (15)

A semiconductor substrate;
An electronic circuit provided on the semiconductor substrate;
A metal pattern provided on the semiconductor substrate;
An air bridge structure having a columnar part located beside the metal pattern, and an upper part directly connected to the columnar part and located immediately above the metal pattern, and not formed in contact with the metal pattern and formed of a conductor; With
The metal pattern and the air bridge structure are not in electrical contact with the electronic circuit. A first terminal electrically connected to the air bridge structure and extending to the outside;
The semiconductor device according to claim 1, further comprising a second terminal electrically connected to the metal pattern and extending to the outside. A plurality of the metal patterns;
A plurality of air bridge structures;
The semiconductor device according to claim 1, wherein the plurality of metal patterns have different whisker generation conditions. A plurality of the metal patterns;
A plurality of air bridge structures;
The height of the portion directly above the plurality of air bridge structures is non-uniform so that the distance from the top portion to the metal pattern directly below the top portion is non-uniform. The semiconductor device according to claim 1 or 2.   The semiconductor device according to claim 1, wherein the columnar portion is between the electronic circuit and the metal pattern.   The semiconductor device according to claim 1, further comprising a shielding wall surrounding the metal pattern so that whiskers extending from the metal pattern do not reach the electronic circuit.   The semiconductor device according to claim 1, further comprising an Au pattern formed of Au on the semiconductor substrate and electrically connected to the electronic circuit. A base portion formed of the same material as the metal pattern on the semiconductor substrate;
A barrier metal provided on the base part,
The semiconductor device according to claim 1, wherein the columnar portion is provided on the barrier metal. A part of the metal pattern is a narrow part narrower than the other part in plan view,
The semiconductor device according to claim 1, wherein the narrow portion is located immediately below the upper portion. A concave portion is formed in the metal pattern,
The semiconductor device according to claim 1, wherein the concave portion is located immediately below the upper portion. Electronic circuit,
A package formed of an insulator covering the electronic circuit;
A semiconductor substrate provided on the package;
And a metal pattern provided on the semiconductor substrate. A plurality of the semiconductor substrates;
A plurality of the metal patterns;
The semiconductor device according to claim 11, wherein conditions for generating whiskers of the plurality of metal patterns are different. The metal pattern is formed of Al, Sn or Zn,
The semiconductor device according to claim 1, wherein the semiconductor substrate is formed of a compound semiconductor.   13. The semiconductor device according to claim 11, wherein a part of the metal pattern is a narrow part narrower than another part in a plan view.   The semiconductor device according to claim 11, wherein a recess is formed in the metal pattern.

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