Method for applying individual identifier of flip-chip package device using rear surface protective thermosetting resin layer

Abstract

To simplify a method for applying a small piece with an individual identifier formed on a stable material to a flip-chip package device.SOLUTION: A method for applying a small piece having an individual identifier to a flip-chip package device includes forming unique information to be associated with a flip-chip package device on a small piece as an individual identifier, and fixing the small piece with the individual identifier formed to the flip-chip package device by using a rear surface protective thermosetting resin layer of an IC chip. The rear surface protective thermosetting resin layer can be formed by thermally curing a rear surface protective thermosetting resin tape pasted to a rear surface of wafer with an IC chip formed.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present invention relates to a method for imparting an identifier to a flip chip package device using a thermosetting resin layer for back surface protection. More specifically, the present invention relates to a method for imparting an identifier related to improving the security of a flip chip package device using a thermosetting resin layer for back surface protection.

Background Art

[0002] In the information society, edge devices that stably and rapidly process large-scale data on the device side rather than on the cloud side are currently attracting attention. When performing data processing on the cloud side, there are problems such as the communication cost increasing as the amount of data increases, it being difficult to perform real-time high-speed processing in information processing via the network, or the existence of confidential information that cannot be cited in the cloud. To address these problems, edge devices have come to be attracting attention.

[0003] In information management of confidential information, security threats due to attacks from the outside, etc. are an issue. Against various attacks on IC chips, etc. in edge devices, defense by software countermeasures alone is insufficient, and defense by hardware countermeasures is required. However, effective countermeasures for hardware security countermeasures of edge devices are not known.

[0004] As a secure and reliable individual identification technology required for adding security, an artifact metric that authenticates an artifact using unique features of the artifact has been proposed. For example, conventionally, a method is known in which an identifier composed of an authentication structure using an optically readable random pattern is directly formed and provided on a device such as a semiconductor package (for example, a QFP (Quad Flat Package) or a BGA (Ball Grid Array package)) (Patent Documents 1 to 3). Patent Documents 1 to 3 disclose that a random pattern is formed by means such as attaching fine particles (tagants) to an object or spraying liquid ink particles onto the object, and the pattern is used for authenticity determination of the object. Patent Document 4 discloses that a countermeasure against forgery is performed by forming an uneven structure as an authentication structure on an object to be authenticated (Second Embodiment, Third Embodiment, FIGS. 5 and 6).

[0005] As a hardware security countermeasure for edge devices, the practical application of a technique for producing an individual identification structure for the purpose of adding physical security to a package device composed of an IC chip or the like and a technique for providing the individual identification structure to the package device are required. Although Patent Documents 1 to 4 disclose methods for directly forming and providing an identifier (individual identification structure) on the surface of an object, the practical application of a technique for forming and providing an identifier on a package device using surface mounting technology is not mentioned.

[0006] Furthermore, the above-mentioned conventional technologies have problems in terms of durability, reading reliability, versatility, etc. of the formed pattern. Specifically, regarding durability, the adhesive force of the tagant or ink on the surface of the object has deteriorated over time, resulting in reduced durability. Regarding reading reliability, the acquired image has changed due to physical or chemical changes in the object itself for some reason. Regarding versatility, the range of material selection for tags, inks, etc. to be applied is limited depending on the state and material of the object surface.

[0007] Patent Document 5 discloses a method of providing an object with an individual identifier formed on a stable material, rather than directly forming a random pattern on the object with a tagant or ink as in Patent Documents 1 to 4 described above, and providing an object having the individual identifier. In Patent Document 5, a small piece having an individual identifier formed thereon is provided on the package of a semiconductor package device.

Prior Art Documents

Patent Documents

[0008]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Patent Document 5

Summary of the Invention

Problems to be Solved by the Invention

[0009] In Patent Document 5 described above, a technique is disclosed in which a small piece in which unique information associated with a package device is formed as an individual identifier is surface-mounted on the upper surface of the package using a thermosetting resin. However, Patent Document 5 does not mention the practical application of a technique for providing an individual identifier to a device in which an IC chip is directly mounted on a substrate, such as a flip-chip package device. Further, in Patent Document 5, the surface mounting of the small piece having the individual identifier on the package device was performed using a thermosetting resin such as an epoxy-based material for the package, so the process of surface-mounting the small piece having the individual identifier on the package device had to be separately performed after the completion of the package device manufacturing process.

[0010] The present invention has been made to solve such problems, and one of its objectives is to provide a flip-chip package device with a small piece having an identifier formed on a stable material. Another objective is to simplify the process of providing a flip-chip package device with a small piece having an identifier formed thereon.

Means for Solving the Problems

[0011] A method for attaching a small piece having an identifier formed thereon to a flip-chip package device according to one aspect of the present invention includes forming unique information associated with the flip-chip package device as an identifier on the small piece, and fixing the small piece having the identifier formed thereon using a thermosetting resin layer for protecting the back surface of an IC chip mounted on the flip-chip package device.

Effects of the Invention

[0012] According to the present invention, a small piece having an identifier such as a fine pattern formed thereon can be attached to the back surface side of an IC chip mounted on a flip-chip package device by a process of thermosetting a thermosetting resin for protecting the back surface formed on the back surface of the wafer at the wafer stage. And since the small piece is attached to the back surface of the IC chip mounted on the flip-chip package device, in the flip-chip package device using the IC chip, a small piece as an identifier can be attached to the upper surface of the package device. Therefore, according to the present invention, the process of attaching a small piece as an identifier to a flip-chip package device can be simplified.

Brief Description of the Drawings

[0013]

Figure 1A

Figure 1B

Figure 2

Figure 3

Figure 4

Figure 5

BEST MODE FOR CARRYING OUT THE INVENTION

[0014] A flip chip package device is a semiconductor package device having a structure in which an IC chip is flip-chip mounted on an organic substrate and a connection portion is sealed with an underfill resin. The flip chip package device can achieve a thinner package compared to semiconductor packages such as QFP that mount the circuit formation surface of the IC chip upward.

[0015] FIG. 1A is a diagram exemplarily showing the structure of a flip chip package device. As exemplified in FIG. 1A, the flip chip package device 10 mounts the IC chip 20 in an inverted state with the circuit formation surface facing downward, and directly fixes and mounts the electrode terminals formed on the circuit formation surface to the electrodes on the substrate 30 by soldering or the like, and the connection portion is sealed with the underfill resin 40.

[0016] In the flip chip package device, since the back surface of the IC chip 20 forms the package upper surface, a back surface protection thermosetting resin layer 50 is formed on the back surface of the IC chip 20 to protect the back surface of the IC chip 20. Incidentally, although not limiting, for example, the thickness of the IC chip is about 100 μm, and the thickness of the thermosetting resin layer for back surface protection is about 25 μm to 50 μm.

[0017] In this specification, as a means for adding physical security to the IC chip 20, a small piece having a predetermined thickness (for example, 100 μm or less or 10 μm or less) with an identifier is provided (applied, adhered, or joined) to the back surface of the IC chip 20 of the flip chip package device on the thermosetting resin layer formed for back surface protection, and a proposed structure is provided.

[0018] FIG. 1B conceptually shows a process in which the applying device 60 forms an identifier 71 on a small piece 70. On the small piece 70 mounted on the IC chip 20, information to be applied to the object (for example, information that can distinguish the flip chip package device 10 from other flip chip package devices) is formed as the identifier 71 by the applying device 60. Forming the information to be applied to the object as the identifier 71 on the small piece 70 may be performed according to the prior art as disclosed in Patent Documents 1 to 4, or may be performed by other methods.

[0019] The small piece 70 is made of an inorganic material (glass, silicon, quartz, metal, etc.) or a durable organic material, and has an identifier 71 on its surface. When the small piece 70 is peeled off from an object such as the flip chip package device 10, it is desirable to have a vulnerability such that it is destroyed at the time of peeling in order to prevent reuse and duplication.

[0020] The identifier 71 is optically readable information, and can indicate specific information by characters, symbols, signs, figures, and / or a fine random uneven shape pattern. In order for the reader 90 described later to easily find the presence of the identifier 71, an alignment mark may be formed around the identifier 71 of the small piece 70. The alignment marks may be placed so as to be scattered on the back surface of the IC chip 20 of the flip chip package device 10, and serve as a mark for facilitating the reader 90 to detect the identifier 71.

[0021] FIG. 2 is a diagram schematically showing a method of assigning an individual identifier 71 to an IC chip 20 mounted on a flip chip package according to the present embodiment.

[0022] FIG. 2(a) shows a step of bonding a thermosetting resin tape 51 for back surface protection to the back surface side of a semiconductor wafer 80 having an electronic circuit and connection electrodes of the IC chip 20 formed on the upper surface. In FIG. 2(a), the wafer 80 is placed on a laminator with the back surface side of the wafer facing upward, and a thermosetting resin tape 51 for forming a thermosetting resin layer for back surface protection is attached to the back surface of the wafer. The thermosetting resin tape 51 for back surface protection has an adhesive layer formed on one side. In this example, the thermosetting resin tape 51 for back surface protection for forming a thermosetting resin layer for back surface protection of the IC chip is adhered to the back surface of the wafer 80 using a laminator.

[0023] FIG. 2(b) shows a step of mounting a small piece 70 having an individual identifier formed thereon on the thermosetting resin tape 51 for back surface protection attached to the back surface of the wafer 80 by a mounter. In the present embodiment, the small piece 70 having the individual identifier 71 formed by using the manufacturing method exemplified in FIG. 1B or the like is mounted in this step in a region corresponding to each IC chip on the back surface side of the wafer.

[0024] FIG. 2(c) shows a step of heating and thermosetting the thermosetting resin tape 51 for back surface protection attached to the back surface of the wafer to form a thermosetting resin layer 50 for back surface protection. By heating and thermosetting the thermosetting resin tape 51 for back surface protection to form a thermosetting resin layer, a thermosetting resin layer for back surface protection in which the small piece 70 mounted at a position corresponding to each IC chip 20 on the thermosetting resin tape 51 for back surface protection in the step of FIG. 2(b) is fixed is formed.

[0025] Since the thermosetting resin layer 50 for back surface protection formed by the thermosetting in this heating step can be printed by a laser or an inkjet printer, marking can be performed in a region corresponding to each IC chip.

[0026] Figure 2(d) shows the laser marking process. In this laser marking process, information such as the unique symbol of each IC chip can be printed on the area corresponding to each IC chip. In the method of the present embodiment, since the small piece 70 in which the information unique to each IC chip is formed as an individual identifier is fixed to the area corresponding to each IC chip on the back surface of the wafer 80, the information of the individual identifier 71 can be read by the reader 90, and information for associating the read unique information with each IC chip can be obtained.

[0027] Thereafter, as shown in Figure 2(e), the wafer 80 is attached to the dicing tape 52 and diced by a blade or the like to form chips, whereby the IC chip 20 with the small piece 70 fixed to the back surface side as illustrated in Figure 2(f) is completed. The small piece 70 is fixed on the thermosetting resin layer 50 for protecting the back surface of the IC chip 20, and the unique symbol 53 is marked. Thus, according to the method of the present embodiment, the thermosetting resin layer 50 for protecting the back surface of the IC chip 20 is provided with the small piece 70 in which, for example, the unique information associated with the IC chip 20 is formed as an individual identifier. As described above, in the flip chip package device, the IC chip 20 is mounted (i.e., flip-mounted) on the substrate 30 with the back surface facing upward, so that the information formed on the small piece 70 can be read by the reader from the upper surface of the package device (the back surface of the IC chip).

[0028] Although not limited, for example, the size of the IC chip 20 created in the present embodiment is such that the chip size is about several mm square to several tens of mm square, and the size of the small piece 70 is about 1 mm square to 3 mm square. As will be described later, the small piece 70 fixed to the thermosetting resin layer for protecting the back surface of the IC chip 20 desirably does not protrude as much as possible from the surface of the thermosetting resin layer for protecting the back surface from the viewpoint of handling. Specifically, the protruding amount is desirably within several μm and may be zero.

[0029] Figure 3 is a flowchart of the method of this embodiment. Step 301 is a step of forming, as an individual identifier 71, unique information associated with a flip chip package device on which an IC chip is mounted by an attaching device on the small piece 70. As described with reference to FIG. 1B, on the small piece 70 fixed to the region corresponding to each IC chip, unique information serving as information associated with each IC chip is formed as the individual identifier 71.

[0030] Step 302 is a step of bonding a thermosetting resin tape for back surface protection to the back surface of the wafer on which the IC chip is formed. This step is carried out, for example, using a well-known laminator as described above.

[0031] Step 303 is a step of mounting the small piece 70 on which the individual identifier 71 is formed on each region corresponding to the IC chip on the thermosetting resin tape bonded to the back surface of the wafer. This step is carried out, for example, using a mounter as described above.

[0032] Step 304 is a step of heating the wafer to thermoset the thermosetting resin tape and fixing the small piece 70 as a thermosetting resin layer. This step is carried out, for example, using a well-known baking device.

[0033] Step 305 is a marking step of performing marking on each region corresponding to the IC chip on the back surface of the wafer. This step is carried out, for example, by laser marking.

[0034] Step 306 is a step of reading the information of the individual identifier formed on the small piece 70 fixed on each region corresponding to the IC chip of the wafer. By this step, the information of each IC chip can be associated with the individual identifier. Note that the reading of the information of the individual identifier of the small piece 70 may be carried out after the flip chip package is completed.

[0035] Process 307 is a process of dicing a wafer into chips. This diced IC chip 20 is flip-chip mounted on a substrate in Process 308 to complete a flip-chip package device.

[0036] FIG. 4 shows a flip-chip package device 100 on which an IC chip 20 manufactured by the method of the embodiment of the present disclosure is mounted. As shown in FIG. 4, in the flip-chip package device 100 on which the IC chip 20 manufactured by the method of the present embodiment is mounted, a small piece 70 fixed to the back surface protection thermosetting resin layer 50 of the IC chip 20 is observable from above.

[0037] Here, an example has been described in which the back surface protection thermosetting resin layer 50 is formed by thermosetting a tape formed of a thermosetting resin, but the back surface protection thermosetting resin layer 50 may be formed by other methods.

[0038] The thermosetting resin used in this embodiment may be a resin that is difficult to repair easily, such as a thermosetting epoxy-based material. In each figure, it should be understood that the dimensions such as the actual size and thickness have been changed in order to clearly show the positional relationship of each component.

[0039] The reader 90 performs optical reading on the small piece 70 attached to the flip-chip package device to obtain an optical image or a white interference image of the individual identifier 71 of the flip-chip package device 100 (object), and can perform individual identification based on the optical image or the white interference image. When the individual identifier 71 adopts a structure located on the adhesive surface side between the small piece 70 and the back surface protection thermosetting resin layer of the flip-chip package device 100, individual identification by reading an optical image such as a white interference image of the individual identifier 71 can be achieved by making the small piece 70 of transparent quartz or glass. Alternatively, when using infrared light, it can be made of silicon.

[0040] When fixing the small piece 70 to the thermosetting resin layer 50 for protecting the back surface of the IC chip, it is not preferable for the small piece 70 to protrude from the surface of the thermosetting resin layer 50 for back surface protection in terms of handling properties and durability. Since the thermosetting resin tape 51 for back surface protection before the thermosetting treatment is flexible, when mounting the small piece 70 on the thermosetting resin tape 51 for back surface protection in the process described in Fig. 2(b) (process 302 in Fig. 3), it is desirable to perform a heat treatment in a state where the small piece 70 is pushed into the thermosetting resin tape 51 for back surface protection by pressing from above.

[0041] In this embodiment, in process 302 of Fig. 3, when mounting the small piece 70 on the thermosetting resin tape 51 for back surface protection, by pressing from above, as shown in Fig. 5(a), the small piece 70 is fixed in a state of being pushed into the thermosetting resin layer 50 for back surface protection. Thereby, the amount by which the small piece 70 protrudes from the surface of the thermosetting resin layer can be reduced. At this time, the small piece 70 may have a protrusion amount of zero by being completely pushed into the thermosetting resin tape for back surface protection.

[0042] Also, as another embodiment, as shown in Fig. 5(b), the protrusion amount may be reduced by making the thickness of the small piece 70 as thin as possible. In this case, the small piece 70 may be thinned in advance by chemical mechanical polishing (CMP) or the like.

[0043] The small piece 70 forming the individual identifier 71 is preferably made of a physically and chemically stable material such as silicon or quartz. The small piece 70 formed of such a material is resistant to deterioration over time and has the advantage of high anti-cloning property because if it is forcibly peeled off, the individual identifier 71 itself will break. Furthermore, by adopting a transparent small piece 70, optical reading by the reader 90 becomes possible.

[0044] The fixed small piece 70 has an adhesive strength that is sufficient to prevent peeling or, even if peeled, cause destruction, thereby enabling the anti-cloning property of the flip chip package device 100 to be obtained. In this case, the adhesive strength is desirably 1 MPa or more, and more desirably 10 MPa or more.

[0045] (Summary) As described with reference to FIG. 1B, the small piece 70 having the individual identifier 71 is formed separately from the flip chip package device 100 that is the object, and is applied to the back surface of the IC chip 20 mounted on the flip chip package device. At this time, the small piece 70 having the individual identifier 71 and the flip chip package device are fixed so that they cannot be separated from each other so that the correspondence relationship therebetween is not changed. Generally, the package device contains various organic substances for the package, etc., but the present invention does not depend on the composition of the contained substances, and generally provides a method for fixing so that they cannot be separated and a flip chip package device to which the individual identifier 71 is given thereby. Specifically, a small piece 70, which is a substantially plate-shaped or substantially block-shaped authentication structure in which the individual identifier 71 is formed, is mounted on a thermosetting resin tape for protecting the back surface of the IC chip mounted on the flip chip package device and thermosetting is performed so that it cannot be separated and is firmly fixed by thermosetting.

[0046] Although the principles of the present invention have been described with reference to exemplary embodiments above, those skilled in the art will understand that various embodiments can be realized by making changes in the configuration and details without departing from the gist of the present invention.

Explanation of Reference Numerals

[0047] 10, 100 ··· Flip chip package device 20 ··· IC chip 30 ··· Substrate 40 ··· Underfill resin 50 ··· Thermosetting resin layer for back surface protection 51 ··· Thermosetting resin tape for back surface protection 52 ··· Dicing tape 60... Applying device 70... Small piece 71... Individual identifier 80... Wafer 90... Reader

Claims

1. A method of attaching a small piece having an individual identifier to a flip-chip package device, comprising: forming the unique information associated with the flip-chip package device as the individual identifier on the small piece; fixing the formed small piece to a thermosetting resin layer for protecting the back surface of an IC chip mounted on the flip-chip package device. The method according to claim 1, further comprising:

2. The method according to claim 1, wherein the individual identifier includes characters, symbols, signs, figures, and / or a fine random uneven shape pattern.

3. The method according to claim 1, wherein the thermosetting resin layer for protecting the back surface is formed by a thermosetting resin tape for protecting the back surface, which is attached to the back surface of the wafer on which the IC chip is formed.

4. The method according to claim 3, wherein the small piece is fixed by thermosetting the thermosetting resin tape.

5. The method according to claim 3, further comprising reading the unique information of the small piece fixed to each region corresponding to the IC chip of the thermosetting resin layer for protecting the back surface of the wafer.

Images