JP2011002259A - Method for measuring stress, sensor for measuring stress and device for evaluating residual stress - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for measuring stress which measures the stress given to a substrate and a measuring object to which the substrate is fixed, based on a change in the resistance of a via chain, utilizing that a reversible resistance change is found out when the stress is given to the substrate provided with the via chain.SOLUTION: The prescribed substrate 10, on which the via chain 15 and pads 17 and 18 connected thereto are provided is fixed to the measuring object and electrical resistance between the pads, is measured; thereby the change in the resistance of the via chain 15 corresponding to the amplitude of the stress given to the measuring object is made detectable from outside in the condition that this stress is given also to the substrate 10, simultaneously. By understanding beforehand the relation between the change in the stress and the change in the resistance of the via chain 15, the stress value can be acquired from the resistance value of the via chain 15. The stress given to the measuring object can be measured with good sensitivity, on the basis of the property that the resistance changes greatly, compared with the case of a piezo resistance effect, with respect to the same stress.

Description

  The present invention relates to a stress measurement method for measuring stress applied to a substrate or a measurement object to which the substrate is fixed, based on a resistance change of a via chain provided on the substrate by a semiconductor manufacturing process.

  In semiconductor devices such as LSIs, miniaturization and multilayering of wiring are progressing with the aim of further speeding up and power saving along with downsizing and high integration. Then, in order to further reduce the resistance of the wiring with miniaturization, a copper wiring is adopted instead of the aluminum wiring, and, along with the adoption of the copper wiring, as an interlayer insulating film, a film for reducing the capacitance between the wirings A low dielectric constant film (low-k film) in which holes are introduced to reduce the dielectric constant is used.

  With the introduction of new technology accompanying such miniaturization and multilayering of wiring, problems that affect the operation of the formed circuit are likely to occur in the manufacturing process. It is required to appropriately verify and evaluate whether or not defects occur during or after the manufacturing process and whether or not the electrical characteristics as designed can be ensured.

  In recent years, in manufacturing such semiconductor devices, TEG (Test Element Group) has been used at each stage of wafers and packages to evaluate wiring performance and process influence, analyze defects, and the like. As one of the evaluation patterns for multilayer wiring in this TEG, there is provided a via chain in which a large number of wirings arranged in a plurality of layers are connected between each layer through vias and connected in series. By measuring the resistance and the like of this via chain, it is possible to confirm whether the wiring, vias, insulating film, etc. are functioning as originally designed.

  Examples of such conventional semiconductor device evaluation methods using via chains include Japanese Patent Laid-Open No. 3-36747 (Patent Document 1), Japanese Patent Application Laid-Open No. 2004-228510 (Patent Document 2), and Japanese Patent Application Laid-Open No. 2004-335914. There are some which are indicated by a gazette (patent documents 3).

  On the other hand, in a semiconductor device, stress is applied to a substrate (chip) due to a packaging process such as molding, a wiring process such as wire bonding, and a temperature change or pressure application after manufacturing, which may change electrical characteristics. For this reason, it is necessary to appropriately evaluate the stress applied to the substrate, and a mechanism for measuring the stress has been demanded. In recent years, it has been difficult to measure stress from outside the device, but in recent years, a diffused resistance element, that is, a stress detector utilizing the piezoresistive effect is formed on the semiconductor substrate itself, and the stress applied to the substrate is measured as an electrical signal. Some have been proposed, and examples thereof include those disclosed in Japanese Unexamined Patent Application Publication No. 2005-209827 (Patent Document 4) and Japanese Unexamined Patent Application Publication No. 2009-65052 (Patent Document 5).

  In addition, such a semiconductor provided with a diffused resistor element is not limited to measuring the stress of the semiconductor substrate itself, but is also generally used as a semiconductor sensor provided with only a diffused resistor element on the substrate, that is, only having a stress measuring function. Has been used. Examples of such conventional stress measurement sensors include those disclosed in Japanese Patent Laid-Open No. 10-132675 (Patent Document 6) and Japanese Patent Laid-Open No. 2006-258664 (Patent Document 7).

JP-A-3-36747 JP 2004-228510 A JP 2004-335914 A JP 2005-209827 A JP 2009-65052 A Japanese Patent Laid-Open No. 10-132675 JP 2006-258664 A

  Conventionally, evaluation of electrical characteristics and the like of a semiconductor device has been performed by the method described in Patent Documents 1 to 3, but only a wiring pattern such as a via chain detects and evaluates stress applied to a semiconductor substrate. However, it was necessary to separately measure the diffused resistance element as shown in Patent Documents 4 and 5 on the substrate.

  However, the measurement of stress using a diffusion resistance element portion formed on a semiconductor substrate as disclosed in Patent Documents 4 to 7 shows that the resistance change of the diffusion resistance element portion corresponding to the change in stress is caused by the piezoresistance effect. Due to its nature, it is extremely small, such as only a few percent change from the resistance value at zero stress, so the detection sensitivity is not excellent, and various measures are required for measurement, making it difficult to measure. It was. Further, the diffusion resistance element portion is formed as a diffusion layer on the semiconductor substrate, and thus has a problem that it is easily restricted by the manufacturing process and the arrangement on the substrate is limited.

  The present invention has been made in order to solve the above-described problems. By utilizing the fact that a reversible resistance change was found when stress was applied to a substrate provided with a via chain, the substrate and this substrate were A stress measurement method for measuring stress applied to a fixed measurement object based on a resistance change of the via chain, a stress measurement sensor that can be fixed to the measurement object and a stress value can be obtained from the resistance change of the via chain, and Another object of the present invention is to provide a residual stress evaluation device that is provided with a via chain that changes resistance in response to stress and can measure and evaluate stress applied to a substrate.

  In the stress measuring method according to the present invention, a via chain formed by connecting a large number of wirings arranged on a substrate across a plurality of layers via an insulating film between layers via vias and connecting them in series is an outer layer. One connection pad connected to the external wiring is connected to one end of the chain, and the other connection pad connected to the external wiring is connected to the external wiring and the other end of the chain are connected. The substrate is fixed to the measurement object, and the resistance between the one connection pad and the other connection pad is measured in a state where stress is applied to the measurement object, and the stress in the substrate acquired in advance is measured. Based on the rate of resistance change corresponding to the change, the value of the stress applied to the measurement object is obtained.

  As described above, in the present invention, regarding the via chain used for the evaluation of the electrical characteristics of the wiring on the substrate of the semiconductor device in which the wiring is miniaturized and multi-layered, the inventor applied stress to the substrate having such a via chain. In addition, the resistance value of the via chain changes greatly corresponding to the magnitude of the applied stress, and the phenomenon that the resistance value returns to the original resistance value when the stress is released is found on the predetermined substrate. By fixing a device with a via chain and a pad connected to it to the measurement object and measuring the electrical resistance between the pads, the stress applied to the measurement object is simultaneously applied to the substrate. The resistance change of the via chain corresponding to the thickness can be detected from the outside, and the relationship between the stress change and the resistance change of the via chain is grasped in advance. You can get the value of the stress from the resistance value of the chain, based on the large nature of resistance changes compared with the piezo resistance effect for the same stress, enabling the measurement of the stress applied to the sensitivity measuring object.

  In addition, the stress measurement method according to the present invention, if necessary, when the stress applied to the substrate in a state of being fixed to the measurement object is in a tensile direction with respect to the via chain, When the stress value is obtained based on the ratio of the resistance change corresponding to the stress change in the tension direction with respect to the via chain, and the stress applied to the substrate in the fixed state to the measurement object is in the compression direction with respect to the via chain Is to obtain the stress value based on the ratio of the resistance change corresponding to the stress change in the compression direction with respect to the via chain in the substrate obtained in advance.

  As described above, according to the present invention, in a substrate with a via chain, the stress applied to the substrate has a stress change and a via chain resistance change in each of a tensile direction and a compression direction with respect to the via chain. When the direction of the stress applied to the substrate is the tension direction based on the fact that the relationship is different, the stress is obtained using the relationship between the change in stress and the resistance change in the tension direction obtained in advance. Further, when the direction of the stress applied to the substrate is the compression direction, the stress is obtained by using the relationship between the change in the stress and the resistance change in the compression direction acquired in advance, and the direction of the stress is applied. Corresponding to the resistance change of different via chains, the stress applied to the substrate can be obtained appropriately, and the response to the measurement object can be applied very accurately. It can be performed of the measurement.

  Further, the stress measuring method according to the present invention includes a via chain formed by connecting a plurality of wirings arranged on a substrate over a plurality of layers via an insulating film between each layer via vias and connecting them in series. The one end of the chain connected to the external wiring disposed on the outer layer is connected to one end of the chain, and the other end of the chain connected to the external wiring connected to the outer wiring is connected to the other end of the chain. The resistance between the one connection pad and the other connection pad is measured in a state where stress is applied to the substrate, and based on the ratio of the resistance change corresponding to the stress change in the substrate obtained in advance. The value of the stress applied to is obtained.

  As described above, in the present invention, a via chain and a pad connected to the via chain are provided on a predetermined substrate, and the electrical resistance between the pads is measured in a situation where stress can be directly applied to the substrate. The resistance change of the via chain corresponding to the size can be detected, and the stress value can be obtained from the resistance value of the via chain by grasping the relationship between the stress change and the resistance change of the via chain in advance. On the other hand, the stress directly applied to the substrate can be measured with high sensitivity based on the property that the resistance changes greatly compared to the case of the piezoresistance effect. The stress measurement method of the present invention may measure the stress generated by an external force applied to the substrate. In this case, the external force may be applied to a part away from the via chain or may be applied on the via chain. Moreover, it can also be set as the structure which provides a press pad in the part which adds external force.

  Further, in the stress measurement method according to the present invention, if necessary, the measurement in the state where the stress is applied is the measurement of the residual stress in the device mounting state of the substrate, and the ratio of the resistance change is the device of the substrate. This is the ratio of the resistance change obtained before mounting.

  As described above, in the present invention, a via chain and a pad connected to the via chain are provided separately from the main electronic circuit on the substrate of the semiconductor device, and the electrical resistance between the pads in the device mounting state is measured. When stress is applied to the board, the via chain resistance change corresponding to the magnitude of this stress can be detected from the outside, and the relationship between the stress change and the via chain resistance change must be known in advance. The stress value can be obtained from the resistance value of the via chain, and based on the property that the resistance changes greatly compared to the case of the piezoresistive effect for the same stress, the stress can be measured with high sensitivity and added to the board in the device mounted state Stress can be accurately evaluated.

  In addition, the stress measuring method according to the present invention is used, if necessary, with the substrate being a low-k insulating film as the insulating film and a copper wiring being arranged over the plurality of layers. It is.

  As described above, in the present invention, the interlayer insulating film in the substrate is a low dielectric constant film and the wiring is a copper wiring, and a via chain consisting of wiring and vias to be remarkably miniaturized is an extremely small region on the order of μm of the substrate. If the space for the pad that can be connected to the outside is secured, the measurement range can be set appropriately regardless of the stress measurement target. Stress can be measured, and stress measurement can be appropriately performed from a minute level to a level of a general strain gauge.

  Further, in the stress measurement method according to the present invention, if necessary, the substrate is formed of a 90 nm node multilayer wiring, the via diameter is about 0.13 μm, and the pitch of each via is about 0.33 μm. In addition, the number of vias in the via chain is 20,000 to 100,000.

  As described above, in the present invention, in a multilayer wiring board of 90 mm node, stress is applied to the via chain in the tensile direction with respect to the via chain in which a large number of vias are arranged with diameters and intervals corresponding to the size of the wiring. The resistance change of the via chain is measured based on the fact that the resistance of the via chain decreases as the stress increases as the stress increases, and the change in stress and the resistance change of the via chain are measured. By obtaining the stress using the relationship, the stress value can be determined appropriately from the resistance value of the via chain that shows the opposite trend of the increase and decrease of the stress applied to the substrate, and the influence from the outside other than the stress can be obtained. The stress can be measured without receiving it.

  In addition, in the stress measurement method according to the present invention, if necessary, the substrate has a multi-layer wiring of 250 nm nodes, the diameter of each via is about 0.25 μm, and the pitch of each via is about 1 μm. The number of vias in the via chain is 20,000 to 100,000.

  As described above, in the present invention, in a multilayer wiring board having a 250 mm node, a number of vias are arranged at diameters and intervals corresponding to the size of the wiring to form a via chain. The resistance change of the via chain is measured based on the fact that the resistance of the via chain increases and decreases with a large change rate as the stress increases and decreases as the stress increases and decreases. By obtaining the stress using the relationship with the resistance change of the chain, the stress value can be appropriately obtained from the resistance value of the via chain that shows the same change tendency as the increase and decrease of the stress applied to the substrate, Stress can be measured efficiently with high sensitivity.

  In addition, the stress measurement sensor according to the present invention is a via chain formed by connecting a number of wirings arranged on a substrate over a plurality of layers via an insulating film between each layer via vias and connecting them in series. Is connected to one end of the chain and the other end of the chain connected to the external wiring and connected to the other end of the chain connected to the external wiring and connected to the external wiring. Thus, the resistance between the one connection pad and the other connection pad can be measured and fixed to the measurement object.

  As described above, in the present invention, a sensor having a via chain and a pad connected to the via chain on a predetermined substrate is fixed to a measurement object as a sensor, and the value of the electrical resistance between the pads changes according to the magnitude of the stress. By measuring the resistance change of the via chain corresponding to this stress while stress is applied to the object to be measured at the same time as the measurement object, By using this relationship, the stress value can be easily obtained from the resistance value of the via chain, and the stress applied to the measurement object can be measured efficiently. In addition to the sensor for measuring the stress applied to the object to be measured, when the external force can be directly received by the substrate, it is not necessary to fix the substrate to another object. It can be set as the sensor which can obtain | require the value of the produced stress, and the value of external force.

  Further, the device for evaluating residual stress according to the present invention is a via formed by connecting a large number of wirings arranged on a substrate across a plurality of layers via an insulating film between each layer via vias and connecting them in series. The chain is connected to one end of the chain and the other end of the chain connected to the external wiring and connected to the other end of the chain connected to the external wiring and connected to the external wiring. Thus, the stress detection unit is not electrically connected to the main electronic circuit unit on the board, and the resistance between the one connection pad and the other connection pad can be measured from the outside, and is in a mounted state. Is.

  Thus, in the present invention, a via chain and a pad connected to the via chain are provided separately from the main electronic circuit on the substrate of the semiconductor device, and the value of the electrical resistance between the pads is obtained, so that the substrate is mounted in the device mounted state. If a change in the resistance of the via chain corresponding to this stress is measured from the outside when stress is applied to the via, the resistance of the via chain can be determined using the relationship between the change in stress and the resistance change of the via chain ascertained in advance. The stress value can be easily obtained from the value, the stress applied to the substrate can be appropriately measured, and the residual stress in the semiconductor device having the same structure can be accurately evaluated.

It is a top view of the sensor used with the stress measuring method concerning a 1st embodiment of the present invention. It is a schematic sectional drawing of the sensor used with the stress measuring method which concerns on the 1st Embodiment of this invention. It is a schematic plan view of the via chain part in the sensor used with the stress measuring method which concerns on the 1st Embodiment of this invention. It is a schematic cross section of a via chain portion in the sensor used in the stress measurement method according to the first embodiment of the present invention. It is a partial notch top view of the device for evaluation used with the stress measuring method concerning a 2nd embodiment of the present invention. It is a schematic sectional drawing of the device for evaluation used with the stress measuring method which concerns on the 2nd Embodiment of this invention. It is application state explanatory drawing as a memory device of the via chain on the board | substrate which concerns on other embodiment of this invention. It is a board | substrate addition state explanatory drawing of the stress used as the tension direction with respect to the via chain in the Example of this invention. It is a board | substrate addition state explanatory drawing of the stress which becomes a compression direction with respect to the via chain in the Example of this invention. It is a graph which shows the relationship between the stress in the case of a 90 nm node in the Example of this invention, and resistance. It is a graph which shows the relationship between the stress in the case of a 250 nm node in the Example of this invention, and resistance.

(First embodiment of the present invention)
Hereinafter, a stress measurement method according to a first embodiment of the present invention will be described with reference to FIGS.
In each of the drawings, the stress measuring method according to the present embodiment uses the sensor 1 having the via chain 15 on the substrate 10, and the sensor 1 is fixed to the stress measuring object 50 and applied to the measuring object 50. Is to measure.

  The sensor 1 includes a via chain 15 formed by connecting a plurality of wirings 11 arranged on a substrate 10 across a plurality of layers via insulating films 13 between each layer via vias 12 and connecting them in series. A first connection pad 17 disposed on the outer layer and connected to one end of the via chain 15; a second connection pad 18 disposed on the outer layer and connected to the other end of the via chain 15; It is the structure provided with the exterior body 16 to protect.

  In the sensor 1, the first connection pad 17 and the second connection pad 18 are connected to the external wirings 17a and 18a, respectively, so as to be electrically connected to the terminal portions 17b and 18b on the surface of the exterior body 16, and the terminal portions 17b and 18b. By connecting to an external measuring device, the resistance between the first connection pad 17 and the second connection pad 18 can be measured, and the object to be measured with the terminal portions 17b and 18b facing outward 50.

  The substrate 10, the wiring 11, the via 12 and the insulating film 13 in the sensor 1 may be configured in the same manner as a general semiconductor device. However, when the wiring is miniaturized due to a design requirement, the wiring is a copper wiring. It is preferable to employ a low dielectric constant film (low-k film) as the insulating film 13. The sensor 1 is formed by providing a plurality of wiring layers on a semiconductor substrate 10 made of silicon or the like with an insulating film 13 interposed therebetween as in a general semiconductor device. If so, the substrate 10 is not limited to a semiconductor such as silicon, but may be a polyimide or glass substrate.

  The wiring 11 is used in a wiring state generally adopted in a semiconductor device such as a 90 nm node and a 250 nm node. For example, in the case of a 90 nm node, each via diameter is about 0.13 μm, each via pitch is about 0.33 μm, and in the case of a 250 nm node. Each via diameter is about 0.25 μm, and the pitch of each via is about 1 μm. In the formation of the via 12, in the case of copper wiring, copper plating of the via portion is appropriately performed, adhesion with the adjacent copper wiring is ensured, and copper migration to the low-k film is suppressed. For this purpose, a known seed layer or barrier metal technique can be used.

  The via chain 15 is a known one formed by connecting a large number of wirings 11 arranged on a substrate 10 across a plurality of layers via insulating films 13 between each layer via vias 12 and connecting them in series. In the case of this embodiment, since the number of connections is very large, it is arranged in a space-saving manner as a zigzag folded pattern.

  The number of vias in the via chain 15 is 20,000 to 100,000, and the resistance of the via chain 15 (resistance between connection pads) increases as the number of vias, that is, the number of interconnected wirings increases. 200 kΩ to 1 MΩ when not applied. In addition, the resistance value of the via chain 15 in a state where the stress is not applied can be appropriately adjusted according to the measurement situation depending on the wiring length, the number of wirings connected (number of vias), the via diameter, and the like.

  Each of the connection pads 17 and 18 is a known metal pad disposed on the outer layer, and is connected to both ends of the via chain 15 formed on the inner layer side and connected to the external wiring, and is connected to the via chain. 15 resistances can be measured.

  A general via chain is used for evaluating electrical characteristics of wiring on a substrate of a semiconductor device in which wiring is miniaturized and multilayered. For such via chain, the present inventor has attached to a substrate having a via chain. When stress is applied, the resistance value of the via chain changes greatly at a rate of change of several tens to several hundred percent from the initial value corresponding to the magnitude of the applied stress, and the initial resistance value when the stress is removed. The phenomenon of returning to (1) was found by an experiment described later.

  Using this phenomenon, if the resistance between the first connection pad 17 and the second connection pad 18 on the substrate 10 fixed to the measurement object 50 is measured in a state where stress is applied to the measurement object 50, Based on the ratio of the resistance change corresponding to the stress change in the substrate 10 acquired in advance, the value of the stress applied to the measurement object 50 is obtained.

  It is noted that the relationship between the stress change and the resistance change of the via chain 15 is different depending on whether the direction of the stress applied to the substrate 10 is the tensile direction or the compression direction with respect to the via chain 15. However, when the stress applied to the substrate 10 in a state of being fixed to the measurement object 50 is in the pulling direction with respect to the via chain 15 in correspondence with such a property, The stress value is obtained based on the ratio of the resistance change corresponding to the stress change in the pulling direction with respect to the via chain 15. On the other hand, when the stress applied to the substrate 10 in the fixed state to the measurement object 50 is in the compression direction with respect to the via chain 15, the stress change in the compression direction with respect to the via chain 15 in the substrate 10 obtained in advance is changed. The stress value is determined based on the corresponding resistance change rate.

  However, the stress in the pulling direction refers to an external force that bends the substrate 10 in such a direction that, for example, the substrate surface side with the via chain 15 is a peak side and the opposite surface side of the substrate is a valley side. Is applied to the surface of the substrate 10 with the via chain 15 in the direction in which the surface of the substrate 10 is stretched together with the via chain, and the stress in the compression direction is, for example, the via chain 15 When an external force is applied to bend the substrate 10 in such a direction that the substrate surface side with the valley is the trough side and the opposite surface side of the substrate is the crest side, the substrate surface with the via chain 15 will be compressed together with the via chain. It refers to the same stress that occurs in the direction.

  Next, the implementation state of the measurement by the stress measurement method according to the present embodiment will be described. For the substrate 10 forming the sensor 1, the stress in the pulling direction and the compressing direction with respect to the via chain 15 is changed with a test apparatus or the like in advance, and the resistance change state corresponding to this change is obtained. Keep track of the relationship.

  Prior to measurement, the sensor 1 is fixed to the measurement target portion of the measurement target 50 in a state where no stress is applied to the measurement target 50 and the sensor 1 itself is not stressed. To do. A device capable of measuring the resistance between the pads is connected to each connection pad 17, 18 of the sensor 1 via a predetermined external wiring.

  When the measurement object 50 is deformed by receiving an external force, or the measurement object 50 itself is deformed by an internal change (such as heat generation) to generate stress, the stress is also applied to the substrate 10 forming the sensor 1. When stress is applied to the substrate 10 with the via chain 15 in this way, the electrical resistance between the connection pads being measured, that is, the resistance value of the via chain 15 is greatly changed in accordance with the magnitude of the stress applied to the substrate 10. The value is different from the state where no stress is applied.

  Since it is possible to determine whether the stress applied to the substrate 10 is in the tension direction or the compression direction with respect to the via chain 15 from the deformation state of the measurement object 50 and the positional relationship between the sensor 1 and the measurement object 50. The stress in the measurement object 50 can be obtained from the obtained resistance value and the known relationship between the stress and the resistance according to the direction of the stress.

  As described above, in the stress measurement method according to the present embodiment, the sensor 1 including the via chain 15 and the pads 17 and 18 connected to the via chain 15 on the substrate 10 is fixed to the measurement object 50, and the pads 17 and 18. By measuring the electrical resistance between them, that is, the resistance of the via chain 15, while the stress applied to the measurement object 50 is simultaneously applied to the substrate 10, the resistance change of the via chain 15 corresponding to the magnitude of this stress is externally applied. By knowing the relationship between the stress change and the resistance change of the via chain 15 in advance, the stress value can be obtained from the resistance value of the via chain 15 as compared with the case of the piezoresistive effect for the same stress. The stress applied to the measurement object 50 can be measured with high sensitivity based on the property that the resistance greatly changes.

  In addition, the resistance change due to the stress change is caused by the via chain 15, the piezoresistance effect is not used, and the resistance detection part is not provided with a diffusion layer on the semiconductor substrate. In addition to increasing the degree of freedom of the manufacturing environment, the substrate 10 does not need to be a semiconductor, and a substrate material capable of multilayer wiring other than the semiconductor can be used, and an optimum material corresponding to the measurement environment can be selected.

  In the stress measurement method according to the embodiment, the sensor 1 to be used is configured to protect the substrate 10 by covering the substrate 10 with the exterior body 16. However, the present invention is not limited thereto, and the substrate and wiring are appropriately protected in the semiconductor manufacturing process. If an outermost protective film can be provided, it can be used without the outer package 16 made of plastic or ceramic.

  In the stress measurement method according to the embodiment, the sensor 1 is fixed to another object to be the measurement object 50 and measures the stress applied to the measurement object 50. When an external force is directly applied, it is not necessary to fix the substrate to the measurement object, so that a sensor that can obtain the value of the stress generated by the external force and the value of the external force can be configured using only the substrate.

(Second embodiment of the present invention)
A second embodiment of the present invention will be described with reference to FIGS.
In each of the drawings, the stress measurement method according to the present embodiment uses the evaluation device 2 configured by providing the substrate 20 inside the semiconductor device with the main electronic circuit 24 and the via chain 25 separately, and this evaluation device. The stress applied to the substrate 20 is measured using the second substrate 20 as a measurement object.

  In the stress measurement method according to the present embodiment, the measurement of the evaluation device 2 is not performed by attaching a sensor having a via chain on a substrate to a predetermined measurement object as in the first embodiment. A semiconductor device having a similar configuration by providing a via chain 25 on the substrate 20 and obtaining stress applied to the substrate 20 from its resistance value, thereby enabling stress measurement on the mounted substrate 20 that is difficult to measure from the outside. Therefore, the residual stress in the device mounting state of the substrate can be appropriately evaluated.

  The evaluation device 2 includes a semiconductor substrate 20, a main electronic circuit 24 formed on the substrate 20, and a large number of wirings arranged on the substrate 20 through a plurality of layers via insulating films. The via chain 25 connected in series, the first connection pad 27 arranged on the outer layer and connected to one end of the via chain 25, and the other end of the via chain 25 arranged on the outer layer are connected. A second connection pad 28, an exterior body 26 that covers and protects these parts, and a terminal part 29 that allows the main electronic circuit 24 and each connection pad 27, 28 to be electrically connected to the outside.

  In this evaluation device 2, the first connection pad 27 and the second connection pad 28 are connected to the external wirings 27 a and 28 a, respectively, and are electrically connected to the terminal part 29, and the terminal part 29 is connected to an external measuring device. Thus, the resistance between the first connection pad 27 and the second connection pad 28 can be measured.

  The evaluation device 2 may have a structure similar to that of a general semiconductor device except that it includes a via chain 25. However, when the wiring is miniaturized due to a design requirement, the wiring is a copper wiring and an insulating film is combined. It is preferable to employ a low dielectric constant film (low-k film). The via size and arrangement interval are the same as those in the first embodiment.

  Regarding the structure of the via chain 25 and the connection pads 27 and 28 and the mechanism for obtaining the stress from the resistance between the first connection pad 27 and the second connection pad 28, that is, the resistance of the via chain 25, the first It is the same as that of the embodiment, and the description is omitted.

  Next, the implementation state of the measurement by the stress measurement method according to the present embodiment will be described. For the substrate 20 before being mounted as a device, the stress applied to the substrate 20 is changed by a test apparatus or the like as in the first embodiment, and a resistance change state corresponding to this change is obtained. Keep track of the relationship.

  Then, like the general semiconductor device, the main electronic circuit 24 and the connection pads 27 and 28 of the substrate 20 are connected to the terminal portions 29, respectively, and the substrate 20 is covered with an exterior body 26 such as a resin or ceramic, and the evaluation device Completed state as 2.

  The measurement with respect to the evaluation device 2 is performed by connecting a measurement device to the terminal portion 29 that is electrically connected to the connection pads 27 and 28 in a state where the evaluation device 2 is supported so that no external force is applied. taking measurement.

  If some stress is applied to the substrate 20 through the manufacturing process, the electrical resistance between the pads being measured, that is, the resistance value of the via chain 25 on the substrate 20 is not applied to the stress before mounting. 20 shows a value greatly changed corresponding to the magnitude of the stress applied to 20. The stress in the substrate 20 can be obtained from the obtained resistance value and the known relationship between the stress and the resistance.

  Since this evaluation device 2 has the same structure as a product type semiconductor device having the same main electronic circuit and is in a device mounting state through the same manufacturing process, the stress generated in the evaluation device 2 is It can be considered that the same occurs in the semiconductor device. If the stress evaluation for the evaluation device 2 is appropriately performed, it can be regarded that the stress evaluation is performed for the semiconductor device in the same manner, and the device design, the manufacturing process, etc. can be improved. It will be connected.

  As described above, in the stress measurement method according to the present embodiment, the via chain 25 and the pads 27 and 28 connected to the via chain 25 are provided on the semiconductor substrate 20 separately from the main electronic circuit 24, and the pads between the pads in the device mounting state are provided. By measuring the electrical resistance, it is possible to detect a change in resistance of the via chain 25 corresponding to the magnitude of the stress from the outside when stress is applied to the substrate 20 in the device mounting state. By grasping the relationship with the resistance change of the via chain 25, the stress value can be obtained from the resistance value of the via chain 25, and the resistance changes greatly compared to the case of the piezoresistance effect for the same stress. The stress can be measured with high sensitivity, and the stress applied to the substrate 20 in the device mounting state can be accurately evaluated.

  In the stress measurement method according to each of the first and second embodiments, the via chains 15 and 25 are provided on the substrates 10 and 20 to be used for the stress measurement. Since the via chain formed with respect to the size of the substrate (chip) is extremely small, multiple via chains are provided on the substrate in a range where the connection pads connecting to the via chain can be arranged, and the stress applied to the substrate is reduced. It is also possible to enable measurement at multiple points.

  The mechanism for detecting the resistance change corresponding to the stress change in the via chains 15 and 25 on the substrates 10 and 20 used in the stress measurement method according to each of the first and second embodiments is used for stress measurement. In addition to using it, a pressure sensor that measures external force / atmospheric pressure, etc., or a change across a predetermined threshold of resistance of a via chain corresponding to a stress change accompanying an operation input such as pressing against a substrate is detected to turn on an external device, It can also be used as a switch for controlling OFF. Further, as shown in FIG. 7, a large number of via chains 35 serving as such switches are arranged on the substrate 30 while being connected in a linear or matrix form, and it is determined which of the via chains has undergone a resistance change due to stress. In addition, if a mechanism for applying stress to each via chain location based on predetermined input information is provided, one or more via chains corresponding to the input information maintain the state in which the resistance is changed. It can also be used as a kind of memory device.

  In the stress measurement method of the present invention, the fact that the substrate provided with the via chain used as a resistance change detection portion corresponding to the stress change changes the resistance of the via chain by the applied stress was actually confirmed. The experiment will be described.

  As an example of a substrate to be used as a sensor or a semiconductor device in the present invention, a substrate manufactured by the same manufacturing process as that of a semiconductor was used as a structure similar to a general semiconductor device. The substrate of this embodiment is a silicon substrate, the wiring is copper wiring, and the insulating film is a low dielectric constant film (low-k film), which has a 90 nm node (first embodiment) and a 250 nm node. Each (second example) was manufactured and subjected to experiments.

  In the case of the first embodiment having a 90 nm node, the wiring is connected so that the number of vias in the via chain on the substrate is 100,000, each via diameter is about 0.13 μm, and the pitch of each via is about 0.33 μm. It is said. In this case, the resistance of the via chain (resistance between the connection pads) is 1 MΩ in a state where no stress is applied.

  On the other hand, in the case of the second embodiment in which the node is 250 nm, the wiring is connected so that the number of vias in the via chain on the substrate is 100,000, each via diameter is about 0.25 μm, and the pitch of each via is about 1 μm. It is said. Also in this case, the resistance of the via chain (resistance between the connection pads) becomes 1 MΩ in a state where no stress is applied.

  In any of the embodiments, the thickness of the Low-K film portion is 0.5 to 0.8 μm, and a plurality of via chains are arranged in an independent manner as a zigzag pattern.

  For applying stress to the substrate, out of the four fulcrums arranged side by side, the middle fulcrum connected to the load cell of the apparatus is brought into contact with the fulcrum at both ends on the opposite side. A four-point bending apparatus was used in which the stresses in the pulling direction and the compressing direction with respect to the via chain were switched and applied to the substrate by switching the surfaces. As for the fulcrum positions for supporting the substrate in the four-point bending apparatus, the distance between the fulcrums at both ends is 24 mm, and the distance between each fulcrum is 8 mm.

  In the experiment, a fulcrum is brought into contact with four locations of the substrate with a four-point bending device, and the load is intended to bend the substrate so that the substrate surface side with the via chain is a peak side and the opposite surface side of the substrate is a valley side. And applying stress to the intermediate portion of the substrate surface sandwiched between the two intermediate fulcrums in the direction of extending the substrate surface together with the via chain, that is, in the tensile direction with respect to the via chain (see FIG. 8). On the contrary, a load is applied to the substrate so that the substrate surface side with the via chain is a trough side and the opposite surface side of the substrate is a crest side. In addition, an operation (see FIG. 9) for applying a stress in the compressing direction with respect to the via chain, that is, the direction of pressing and shrinking was performed. In each case where a known stress was applied to each of the tension direction and the compression direction, the resistance change between the pads accompanying the stress change was measured.

  The measurement is performed for each of the stresses in the tensile direction and the compression direction for each example, and the area on the substrate sandwiched between two intermediate fulcrums in the four-point bending apparatus while changing the stress by adjusting the load. With respect to the via chain disposed in the electrode, the resistance of the via chain was measured by applying the electrode of the measuring device to pads connected to both ends of the via chain. In order to avoid the influence due to the difference in the position of the via chain on the substrate, the resistance is measured simultaneously for two via chains located slightly apart on the substrate, and the total value is adopted as the measurement result. Then, the same measurement is performed three times by changing both via chains. However, the positions and combinations of via chains to be measured are the same for the 90 nm node substrate and the 250 nm node substrate.

  Results of measuring the resistance change for each stress in the tensile direction and the compressive direction three times for each of the 90 nm node substrate and the 250 nm node substrate by changing the set of via chains (A, B, C) In addition, FIGS. 10 and 11 show graphs in which the change in the average value of the resistance measurement results for three times with respect to the stress is shown with the horizontal axis as the stress and the vertical axis as the rate of change in resistance. For the stress, a positive value indicates the tensile direction and a negative value indicates the compression direction.

  From FIG. 10, in the case of 90 nm node wiring, the resistance value decreases as the stress increases in both the tensile direction and the compressive direction, and the degree of the decrease is when the stress is applied in the tensile direction. The result is larger than that in the compression direction. And the resistance change rate from the state where stress is not applied has reached several tens of percent.

  Further, from FIG. 11, in the case of the wiring of the 250 nm node, contrary to the case of the wiring of the 90 nm node, the resistance value increases as the stress increases in both the tensile direction and the compression direction. The degree of increase is greater when the stress is applied in the tension direction than in the compression direction. In any direction, the rate of resistance change with respect to the stress change is larger than in the case of the 90 nm node wiring, and the rate of resistance change from the state where no stress is applied reaches several hundred percent.

  In this way, when the stress is applied to the board with the via chain, the change in the resistance value of the via chain varies depending on the board design, but in either case, it corresponds to the magnitude of the applied stress. As a result, the resistance value changes greatly, and when the stress is released, the phenomenon of returning to the original resistance value is confirmed, and the resistance change corresponding to the stress is reproducible for the board manufactured with the same design. It is clear that this can be used for stress measurement.

1 Sensor 10, 20, 30 Substrate 11, 21 Wiring 12, 22 Via 13, 23 Insulating film 15, 25, 35 Via chain 16, 26 Exterior body 17, 27 First connection pad 18, 28 Second connection pad 2 For evaluation Device 24 Main electronic circuit 29 Terminal section 50 Measurement object

Claims (9)

A via chain formed by connecting a large number of wirings arranged on multiple layers across the substrate via an insulating film between each layer via vias and connecting them in series is arranged on the outer layer and connected to the external wiring The board is fixed to the measurement object with one connection pad connected to one end of the chain and the other connection pad disposed on the outer layer and connected to the external wiring connected to the other end of the chain. And
The resistance between the one connection pad and the other connection pad is measured in a state where stress is applied to the measurement object, and based on the resistance change ratio corresponding to the stress change in the substrate obtained in advance. A stress measuring method characterized by obtaining a value of stress applied to an object to be measured. In the stress measuring method according to claim 1,
When the stress applied to the substrate in a fixed state to the object to be measured is in the tensile direction with respect to the via chain, the resistance change corresponding to the stress change in the tensile direction with respect to the via chain in the substrate acquired in advance. Obtain the stress value based on the ratio of
When the stress applied to the substrate in a fixed state to the measurement object is in the compression direction with respect to the via chain, the resistance change corresponding to the stress change in the compression direction with respect to the via chain in the substrate acquired in advance. A stress measurement method characterized in that a stress value is obtained based on the ratio. A via chain formed by connecting a large number of wirings arranged on multiple layers across the substrate via an insulating film between each layer via vias and connecting them in series is arranged on the outer layer and connected to the external wiring One connection pad and one end of the chain are connected, and another connection pad disposed on the outer layer and connected to the external wiring is connected to the other end of the chain,
The resistance between the one connection pad and the other connection pad is measured in a state where stress is applied to the substrate, and based on the ratio of the resistance change corresponding to the stress change in the substrate obtained in advance. A stress measurement method characterized by obtaining a value of stress applied to the substrate. In the stress measurement method according to claim 3,
The measurement in the state where the stress is applied is measurement of residual stress in the device mounting state of the substrate, and the ratio of the resistance change is a ratio of the resistance change acquired before mounting the device on the substrate. And stress measurement method. In the stress measuring method according to any one of claims 1 to 4,
The stress measurement method characterized in that the substrate is used with a low-k insulating film as an insulating film and a copper wiring as a wiring arranged over the plurality of layers. In the stress measurement method according to claim 5,
In the substrate, the wiring is a multi-layer wiring of 90 nm nodes, each via diameter is about 0.13 μm, each via pitch is about 0.33 μm, and the number of vias in the via chain is 20,000 to 100,000 A stress measurement method characterized by being used. In the stress measurement method according to claim 5,
In the substrate, the wiring is a multi-layer wiring of 250 nm node, each via diameter is about 0.25 μm, each via pitch is about 1 μm, and the number of vias in the via chain is 20,000 to 100,000. A stress measurement method characterized by being used. A via chain formed by connecting a large number of wirings arranged on multiple layers across the substrate via an insulating film between each layer via vias and connecting them in series is arranged on the outer layer and connected to the external wiring And one end of the chain is connected to one end of the chain, and the other end of the chain connected to the external wiring disposed on the outer layer is connected to the other end of the chain.
A stress measuring sensor, wherein a resistance between the one connection pad and another connection pad is measurable and fixed to a measurement object. A via chain formed by connecting a large number of wirings arranged on multiple layers across the substrate via an insulating film between each layer via vias and connecting them in series is arranged on the outer layer and connected to the external wiring One connection pad is connected to one end of the chain, and another connection pad disposed on the outer layer and connected to the external wiring is connected to the other end of the chain. The stress detection unit is not connected
A residual stress evaluation device characterized in that a resistance between the one connection pad and another connection pad can be measured from the outside to be mounted.

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