Sealing method and structure of sealing part

Abstract

To provide a sealing method for performing proper sealing with a sealing member and further, introducing sufficient pressure transmission oil into a sensor chip.SOLUTION: A sealing method includes the steps of: forming a sensor chip 22 on a wafer; sticking a dicing tape to the wafer; cutting out the sensor chip 22; peeling off the dicing tape; accumulating pressure transmission oil 25 in a counterbore 27; sucking the pressure transmission oil 25 into an oil introduction path 23 by a reduced pressure injection method; and sealing an introduction port 26 with a sealing member 24. In the step of accumulating the pressure transmission oil 25 in the counterbore 27, a volume of the pressure transmission oil 25 that at least fills the oil introduction path 23 is accumulated in the counterbore 27.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a sealing method and a sealing structure for sealing an inlet for introducing oil formed in a sensor chip of a pressure sensor. [Background technology]

[0002] Sensor chips used in recent pressure sensors are formed on a semiconductor wafer, cut out from the semiconductor wafer, and formed through a process of introducing pressure transmission oil from an inlet, sealing the inlet, etc. The introduction of pressure transmission oil may be performed by a reduced pressure injection method, as described in Patent Document 1, for example. The process from when the sensor chip is formed on the semiconductor wafer until the inlet for the pressure transmission oil is sealed is performed as shown in FIGS. 12(A) to (D) and 13(A) to (C).

[0003] A semiconductor wafer 1 shown in Fig. 12(A) has a plurality of chip regions 2 formed thereon to become sensor chips. Two chip regions 2 are depicted in Fig. 12(A). Although not shown, each chip region 2 is formed with a sensor diaphragm that receives the pressure to be measured, a pressure chamber whose wall is the sensor diaphragm, and the like. An oil introduction path, indicated by reference symbol 3 in Fig. 12(A), is connected to the pressure chamber. The oil introduction path 3 has an introduction port 4 that opens to the outer surface 1a of the semiconductor wafer 1. The hole diameter of the introduction port 4 is larger than the other portion of the oil introduction path 3 that extends within the semiconductor wafer 1.

[0004] After the chip regions 2 are formed on the semiconductor wafer 1, a dicing tape 5 is attached to the outer surface 1a of the semiconductor wafer 1 as shown in Fig. 12(B). Then, as shown in Fig. 12(C), each chip region 2 is cut out from the semiconductor wafer 1 by a cutter (not shown), and then the dicing tape 5 is peeled off to form individual sensor chips 6 as shown in Fig. 12(D). Next, as shown in Fig. 13(A), the sensor chip 6 is held by a jig (not shown) with the inlet 4 of the oil inlet path 3 facing upward, and pressure transmission oil 7 is dripped onto the upper surface 6a of the sensor chip 6.

[0005] Thereafter, the sensor chip 6 is loaded into a vacuum chamber (not shown), and the vacuum chamber is depressurized to a predetermined vacuum level. This depressurization creates a vacuum in the oil introduction path 3 of the sensor chip 6, and pressure transmission oil 7 is sucked into the oil introduction path 3, as shown in Fig. 13(B). Next, as shown in Fig. 13(C), a sealing member 8 such as a solder ball is placed on the introduction port 4 of the oil introduction path 3, and is melted and solidified. The sealing member 8 solidifies to seal the oil introduction path 3. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] JP 2018-159593 A Summary of the Invention [Problem to be solved by the invention]

[0007] The conventional sealing methods shown in FIGS. 12(A) to (D) and 13(A) to (C) have the following two problems. The first problem is that when the dicing tape 5 is peeled off, the tape glue 9 of the dicing tape 5 may adhere to the boundary between the upper surface 6a of the sensor chip 6 and the inlet 4 of the oil inlet path 3, as shown in FIG. 12(D). If the tape glue 9 adheres to the opening edge of the inlet 4, the tape glue 9 will hinder the spreading of the solder when the sealing member 8 is melted. When the sealing member 8 is properly melted and solidified, its outer shape is approximately circular in plan view, but if the tape glue 9 adheres to the inlet 4, an abnormal part 10 is generated in which a part of the outer edge of the sealing member 8 is recessed, as shown in FIG. 14. Furthermore, when the sealing member 8 is properly melted, it spreads on the upper surface 6a of the sensor chip 6 like a normal part indicated by reference numeral 11 in FIG. 15, but if the tape glue 9 adheres to the inlet 4, an abnormal part 12 is generated in which the sealing member does not spread. If an abnormality occurs in the shape of the sealed part by the sealing member 8, the pressure resistance strength of the sensor chip 6 may be insufficient against the pressure applied to the sensor diaphragm.

[0008] The second problem is that after the pressure transmission oil 7 is dripped onto the upper surface 6a of the sensor chip 6, in the process of loading the sensor chip 6 into a vacuum chamber and depressurizing it, the pressure transmission oil 7 may spill from the upper surface 6a of the sensor chip 6 due to slight vibrations or air currents that occur during transportation or evacuation. That is, if the pressure transmission oil 7 is dripped onto the upper surface 6a of the sensor chip 6 as shown in FIG. 13(A), and then the pressure transmission oil 7 spills, the pressure transmission oil 7 held on the upper surface 6a decreases as shown in FIG. 16(A). If the pressure transmission oil 7 decreases in this way, the oil 7 introduced into the oil introduction path 3 becomes insufficient as shown in FIG. 16(B). If the oil 7 is insufficient, air bubbles are mixed into the sensor chip 6, which deteriorates the temperature characteristics, pressure characteristics, etc. of the sensor chip 6, and the pressure resistance performance decreases.

[0009] An object of the present invention is to provide a sealing method and a sealing structure in which sealing by a sealing member is performed correctly and pressure transmitting oil is sufficiently introduced into the sensor chip. [Means for solving the problem]

[0010] In order to achieve this object, the sealing method of the present invention includes the steps of forming a sensor chip of a pressure sensor on a wafer, the sensor chip having an inlet for pressure transmission oil and a countersink surrounding the inlet, a step of attaching a dicing tape to the outer surface of the wafer on which the countersink is formed, a step of cutting out the sensor chip from the wafer, a step of peeling off the dicing tape from the wafer, a step of storing the pressure transmission oil in the countersink including the inlet, a step of sucking the pressure transmission oil from the inlet into an oil inlet path in the sensor chip by a reduced pressure injection method, and a step of sealing the inlet with a sealing member, and in the step of storing the pressure transmission oil in the countersink, at least a volume of the pressure transmission oil sufficient to fill the oil inlet path is stored in the countersink.

[0011] The sealing structure of the present invention comprises an oil inlet passage formed in a sensor chip of a pressure sensor and through which pressure transmission oil is sucked in, a countersink formed on the outer surface of the sensor chip so as to surround an inlet of the oil inlet passage, and a sealing member positioned within the formation area of ​​the countersink and sealing the inlet, and the volume of the countersink may be a volume capable of storing at least an amount of the pressure transmission oil to fill the oil inlet passage.

[0012] In the sealing portion structure of the present invention, the countersink may have a multi-stage structure including a bottom portion where the oil inlet passage opens, and an intermediate portion formed above the bottom portion so that the opening width is wider than that of the bottom portion.

[0013] In the sealing portion structure of the present invention, a bottom surface of the countersink may be formed in a tapered shape that gradually becomes deeper toward the inlet of the oil inlet passage.

[0014] In the sealing portion structure of the present invention, the countersink may be formed with a protrusion formed on the outer surface of the sensor chip so as to surround the inlet of the oil inlet path as an inner wall. Effect of the Invention

[0015] According to the present invention, it is possible to provide a sealing method and a sealing structure in which sealing by a sealing member is performed correctly and pressure transmitting oil is sufficiently introduced into the sensor chip. [Brief description of the drawings]

[0016] [Figure 1] FIG. 1 is a cross-sectional view of a sealing structure according to the present invention. [Diagram 2] FIG. 2 is a plan view of the sealing portion structure. [Diagram 3] FIG. 3 is a flow chart for explaining the sealing method according to the present invention. [Figure 4] FIG. 4 is a cross-sectional view of a semiconductor wafer and a sensor chip for explaining a sealing method. [Diagram 5] FIG. 5 is a cross-sectional view of the sensor chip for explaining the sealing method. [Figure 6] FIG. 6 is a plan view of a captured image of the sealing structure according to the present invention. [Figure 7] FIG. 7 is a cross-sectional view obtained by copying an image of a cross section of a sealing structure according to the present invention. [Figure 8] FIG. 8 is a plan view of a sensor chip showing a modified example of the counterbore. [Figure 9] FIG. 9 is a cross-sectional view of a sensor chip showing a modified example of the counterbore. [Figure 10] FIG. 10 is a cross-sectional view of a sensor chip showing a modified example of the counterbore. [Figure 11] FIG. 11 is a cross-sectional view of a sensor chip showing a modified example of the counterbore. [Figure 12] FIG. 12 is a cross-sectional view of a semiconductor wafer and a sensor chip for explaining a conventional sealing method. [Figure 13] FIG. 13 is a cross-sectional view of a sensor chip for explaining a conventional sealing method. [Figure 14] FIG. 14 is a plan view of a captured image of a conventional sealing structure. [Figure 15]FIG. 15 is a cross-sectional view that is a copy of an image of a cross section of a conventional sealing structure. [Figure 16] FIG. 16 is a cross-sectional view of a sensor chip for explaining a defect caused by a conventional sealing method. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0017] BEST MODE FOR CARRYING OUT THE DISCLOSURE Hereinafter, one embodiment of a sealing method and a sealing portion structure according to the present invention will be described in detail with reference to Figs. The sealing portion structure 21 shown in Fig. 1 is a structure in which an oil introduction path 23 formed in a sensor chip 22 for a pressure sensor is sealed by a sealing member 24. Only a part of the sensor chip 22 for a pressure sensor is shown in Fig. 1. Although not shown, the sensor chip 22 is formed with a sensor diaphragm for receiving the pressure of the fluid to be measured and a pressure chamber whose wall is made up of the sensor diaphragm.

[0018] The oil inlet path 23 is a passage for introducing pressure transmission oil 25 to the pressure chamber, and extends into the sensor chip 22 from an inlet 26 that opens toward the outside of the sensor chip 22. The inlet 26 is formed as a recess with a larger hole diameter than the portion of the oil inlet path 23 that extends inside the sensor chip 22. The inlet 26 is a circular recess into which a solder ball (not shown), which is the base material of the sealing member 24, fits.

[0019] A countersink 27 is formed on the outer surface 22a of the sensor chip 22 so as to surround the inlet 26 of the oil introduction path 23. The inlet 26 of the oil introduction path 23 opens to a bottom surface 27a of the countersink 27. The opening shape of the countersunk hole 27 in this embodiment is circular, as shown in Fig. 2. The inlet 26 of the oil inlet passage 23 is located at the center of the countersunk hole 27 when viewed from a direction perpendicular to the outer surface 22a of the sensor chip 22. The sealing member 24 is disposed within the formation area of ​​the countersunk hole 27 to seal the inlet 26.

[0020] The countersink 27 extends from the circular opening edge toward the inside of the sensor chip 22 so that the inside diameter is approximately constant. The volume of the countersink 27, i.e., the opening area and depth, is determined based on the volume of the pressure transmission oil 25 introduced into the oil introduction passage 23. In other words, the volume of the countersink 27 is a volume that allows at least an amount of the pressure transmission oil 25 to fill the oil introduction passage 23 to be stored in the countersink 27. The "amount to at least fill the oil introduction passage" here means an amount sufficient to fill all the space including the pressure chamber in the sensor chip 22 and the oil introduction passage 23. A tape adhesive 28a of a dicing tape 28 (see FIG. 4(B)) described later is attached to the opening edge of the countersunk hole 27 shown in FIG.

[0021] Next, a sealing method for realizing the above-mentioned sealing portion structure 21 will be described in detail with reference to the flow chart shown in FIG. 3 and the cross-sectional views of each process shown in FIGS. In order to realize the sealing portion structure 21, in step S1 of the flowchart in Fig. 3, a plurality of chip regions 32 are formed on a semiconductor wafer 31 as shown in Fig. 4(A). The chip regions 32 become the sensor chips 22. That is, the sensor chips 22 are fabricated in the semiconductor wafer 31.

[0022] Inside the chip region 32, although not shown, a sensor diaphragm, a pressure chamber whose wall is formed by the sensor diaphragm, an oil introduction passage 23 connected to the pressure chamber, and the like are formed. An introduction port 26 of the oil introduction path 23 and a countersink 27 are formed on an outer surface 31a of the semiconductor wafer 31.

[0023] After the chip region 32 is formed on the semiconductor wafer 31, as shown in FIG. 4(B), a dicing tape 28 is attached to the outer surface 31a of the semiconductor wafer 31 on which the recess 27 is formed (step S2). Thereafter, as shown in FIG. 4(C), the semiconductor wafer 31 is divided into chip regions 32 by a cutter (not shown) to cut out the sensor chips 22 (step S3), and then, as shown in FIG. 4(D), the dicing tape 28 is peeled off to extract the individual sensor chips 22 (step S4). When the dicing tape 28 is peeled off from the outer surface 22a, the tape glue 28a may adhere to the opening edge of the countersunk hole 27.

[0024] After the sensor chip 22 is cut from the semiconductor wafer 31 in this way, the sensor chip 22 is held in a jig (not shown) in a position in which the countersunk 27 is located on top as shown in FIG. 5(A), and pressure transmission oil 25 is dripped into the countersunk 27 (step S5). At this time, the pressure transmission oil 25 is supplied so that the inlet 26 of the oil introduction path 23 and the inside of the countersunk 27 are filled with the pressure transmission oil 25 and the pressure transmission oil 25 rises due to surface tension. Then, the sensor chip 22 is loaded into a vacuum chamber (not shown), and the inside of the vacuum chamber is depressurized by evacuation to a predetermined degree of vacuum (step S6). That is, the pressure transmission oil 25 is introduced into the sensor chip 22 by a so-called depressurized injection method.

[0025] After the pressure transmission oil 25 has been dripped, vibrations during transportation may be transmitted to the pressure transmission oil 25, or the pressure transmission oil 25 may be pushed by an air flow during decompression, causing the pressure transmission oil 25 to spill over the sensor chip 22. However, even in such cases, the pressure transmission oil 25 remains in the countersink 27 as shown in FIG. 5(B). When the inside of the vacuum chamber is depressurized to a predetermined vacuum level, pressure transmitting oil 25 is sucked into oil introduction passage 23 of sensor chip 22, as shown in FIG. 5(C).

[0026] By carrying out this evacuation step S6, all spaces including the pressure chambers and the oil introduction passages 23 in the sensor chip 22 are filled with the pressure transmission oil 25. After the introduction of the pressure transmission oil 25 is completed in this manner, the sensor chip 22 is removed from the vacuum chamber, and the introduction port 26 of the oil introduction path 23 is sealed with the sealing member 24 (step S7), as shown in Fig. 1. In this sealing process, a solder ball, which is the base material of the sealing member 24, is inserted into the introduction port 26 and melted by heating with, for example, laser light, and then solidified.

[0027] Since no tape glue 28a is attached to the opening edge of the introduction port 26, the solder properly wets and spreads around the introduction port 26. As a result, as shown in Fig. 6, the outer edge of the sealing member 24 becomes substantially circular when viewed from above. Also, as shown in Fig. 7, the outer periphery 24a of the sealing member 24 properly wets and spreads along the opening edge of the introduction port 26 to the bottom surface 27a of the countersunk portion 27. In this way, the sealing member 24 properly melts and the shape of the sealing member becomes as designed, thereby obtaining high pressure resistance as designed.

[0028] Therefore, according to this embodiment, it is possible to provide a sealing method and a sealing structure in which sealing by the sealing member is performed correctly and pressure transmitting oil is sufficiently introduced into the sensor chip.

[0029] (Modification of countersink) The countersink 27 can be formed as shown in Figures 8 to 11. In Figures 8 to 11, the same or equivalent members as those described with reference to Figures 1 to 7 are designated by the same reference numerals, and detailed description thereof will be omitted as appropriate. 8 is formed in a rectangular shape when viewed from a direction perpendicular to outer surface 22a of sensor chip 22. Inlet port 26 of oil inlet passage 23 is positioned in the center of bottom surface 27a of countersunk 27 formed in a rectangular shape. Even when the opening shape of the countersunk 27 is thus rectangular, it is possible to provide a sealing method and a sealing portion structure 21 in which sealing by the sealing member 24 is properly performed and pressure transmission oil 25 is sufficiently introduced into the sensor chip 22. The opening shape of the countersunk 27 is not limited to a circle or a rectangle, and may be a triangle, a polygon having 5 or more sides, or the like.

[0030] The countersink 27 shown in Figure 9 is formed to have a multi-stage structure including a bottom 33 where the inlet 26 of the oil inlet passage 23 opens, and an intermediate portion 34 formed above the bottom 33 so that the opening width is wider than that of the bottom 33. A bottom surface 27 a of the countersink 27 shown in FIG. 10 is formed in a tapered shape that gradually becomes deeper toward the inlet 26 of the oil inlet passage 23 . 11, a protrusion 35 is formed on outer surface 22a of sensor chip 22, surrounding inlet 26 of oil inlet passage 23. Countersink 27 of sensor chip 22 is formed with protrusion 35 as its inner wall. Even when the cross-sectional shape of the countersink 27 is formed as shown in Figures 9 to 11, it is possible to provide a sealing method and a sealing structure in which sealing by the sealing member is performed correctly and pressure transmission oil is sufficiently introduced into the sensor chip. [Explanation of symbols]

[0031] 21...sealing structure, 22...sensor chip, 25...pressure transmission oil, 26...inlet, 27...counterbore, 27a...bottom, 31...semiconductor wafer, 22a...outer surface, 23...oil inlet path, 28...dicing tape, 33...bottom, 34...middle portion, 35...protrusion, S1...sensor area formation step, S2...dicing tape attachment step, S3...sensor chip cutting step, S4...dicing tape peeling step, S5...pressure transmission oil dripping step, S6...vacuum drawing step, S7...sealing step.

Claims

1. forming a sensor chip of a pressure sensor having an inlet for pressure transmission oil and a counterbore surrounding the inlet on a wafer; attaching a dicing tape to the outer surface of the wafer on which the recess is formed; cutting the sensor chip from the wafer; Peeling the dicing tape from the wafer; storing the pressure transmission oil in the countersink including the inlet; a step of drawing the pressure transmission oil from the inlet into an oil inlet passage in the sensor chip by a decompression type injection method; and sealing the inlet with a sealing member. A sealing method, characterized in that in the step of storing the pressure transmission oil in the countersink, at least a volume of the pressure transmission oil that fills the oil introduction passage is stored in the countersink.

2. an oil introduction passage formed in a sensor chip of the pressure sensor and through which pressure transmission oil is drawn; a countersink formed on an outer surface of the sensor chip so as to surround an inlet of the oil inlet passage; a sealing member disposed within the area where the countersink is formed and sealing the introduction port; A sealing structure, characterized in that the volume of the countersink is a volume that is large enough to store at least an amount of the pressure transmission oil that fills the oil introduction passage.

3. The sealing structure according to claim 2, A sealing structure characterized in that the countersink has a multi-stage structure including a bottom portion where the oil inlet passage opens and an intermediate portion formed above the bottom portion so that the opening width is wider than that of the bottom portion.

4. The sealing structure according to claim 2, A sealing structure, characterized in that a bottom surface of the countersink is formed in a tapered shape that gradually becomes deeper toward the inlet of the oil inlet passage.

5. The sealing structure according to claim 2, A sealing structure, characterized in that the countersink is formed with a protrusion formed on the outer surface of the sensor chip so as to surround the inlet of the oil inlet path as an inner wall.

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