JP6330241B2 - Vacuum-sealed module and manufacturing method thereof - Google Patents

Description

  The present invention relates to a vacuum-sealed module that houses a semiconductor chip (hereinafter referred to as a chip) that requires vacuum mounting, such as an infrared sensor or a tuning-fork type crystal resonator, and a manufacturing method for fixing the chip in the module. is there.

  FIG. 6 shows a conventional vacuum sealed module. This module includes a substrate 100 on which a wiring pattern is formed, a chip 101 made of a silicon semiconductor fixed to the substrate 100 and formed with an infrared sensor, and a cap 104 for vacuum-sealing the chip 101. The chip 101 is fixed to the substrate 100 by a resin adhesive 102 typified by silver paste or the like, and the circuit inside the chip 101 is a conductive pad (illustrated) that is an external terminal of the vacuum-sealed module by a bonding wire 103. Not connected).

  Patent Document 1 discloses a technique for sealing an infrared sensor in a vacuum sealed module. In other words, a sufficient area for attaching a getter for adsorbing and removing a gas is secured on the inner side surface of the cap that covers the chip. The infrared sensor is attached to the semiconductor substrate so as to close the window, the lens that transmits infrared, and the detection surface capable of detecting infrared toward the window. A sensor chip attached to the semiconductor substrate in an electrically connected state, a cap that covers the sensor chip, and a vacuum in a space that is provided on the inner surface of the cap and surrounded by the cap, the semiconductor substrate, and the lens And a getter that adsorbs and removes the gas that lowers the temperature.

  Patent Document 2 discloses a technique for sealing a surface wave element in a vacuum sealed module. That is, the surface acoustic wave device can be easily mounted on the surface, the surface wave element support structure is simplified, the device manufacturing process is simplified, the device has high performance, high quality, downsizing, and cost reduction. A surface wave device is provided. A surface acoustic wave element (chip) having a crossed finger electrode (IDT) formed on a piezoelectric substrate is arranged so that the bottom surface of the surface mount container faces the IDT formation surface. At this time, a conductive pad having elasticity is interposed between the two so as to be squeezed to obtain electrical conduction. Further, with the pressing force applied to the chip by the drawn cap, the cap is welded to the container, and the container is hermetically sealed.

JP 2010-197335 A

JP 7-154185 A

In the conventional example described above, as shown in FIG. 6, the chip 101 is fixed to the substrate 100 with a resin adhesive 102. Such an adhesive has a problem that it generates outgas and it is difficult to maintain the degree of vacuum. In addition, a die bonding process for fixing the chip 101 with the adhesive 102 and a wire bonding process for obtaining electrical continuity between the chip 101 and the substrate 100 are necessary, and the manufacturing process becomes complicated. It was.
The present invention has been made under such circumstances, and provides a vacuum sealed module that can easily achieve and maintain the degree of vacuum that requires the inside, and a method for manufacturing the same.

  One aspect of the vacuum-sealed module of the present invention includes a substrate on which a conductive pad is formed, a chip that is flip-chip mounted so that an external terminal is connected to the conductive pad, one end is opened, and the other end is closed. And a cap for vacuum-sealing the peripheral portion of the one end side to the substrate so as to cover the chip, and the other end side of the cap evacuates the cap. Among them, after being bonded to the substrate, the sensor element is bent inward due to a pressure difference when moved to atmospheric pressure, and the sensor element is pressed. A concave portion is formed on the back surface of the element chip, and the element chip may be positioned with reference to the concave portion by combining the top of the bent portion of the cap and the concave portion. The substrate has an optical lens at a central portion of the region covered with the cap, and positioning of the element chip with respect to the optical axis of the optical lens is performed with respect to the top of the bent portion of the cap and the element chip. You may make it carry out by positioning with a recessed part.

  Further, one aspect of a method for manufacturing a vacuum-sealed package of the present invention includes a step of flip-chip mounting a chip on a substrate on which a conductive pad is formed so that an external terminal is connected to the conductive pad. A step of adhering a peripheral portion of the one end side to the substrate so as to cover the chip, and vacuum-sealing the cap, which is a cylindrical body having one end opened and the other end closed. The other end of the substrate is bent inward by a pressure difference when the cap is bonded to the substrate in a vacuum and then transferred to atmospheric pressure, and the chip is pressed against the substrate. It is characterized by fixing.

  The present invention can easily achieve a degree of vacuum of about 1 Pa that requires the inside of the vacuum-sealed module, and can maintain this degree of vacuum over a long period of time.

1 is a cross-sectional view of a vacuum sealed module according to Example 1. FIG. FIG. 2 is a cross-sectional view of a vacuum sealed module showing a state before the chip of FIG. 1 is fixed. Sectional drawing (a) and the top view (b) explaining the detail of the vacuum sealing type module shown in FIG. Sectional drawing of the vacuum-sealing type module which concerns on Example 2. FIG. FIG. 6 is a cross-sectional view of a vacuum sealed module according to a third embodiment. Sectional drawing of the conventional vacuum sealing type module.

  Hereinafter, embodiments of the invention will be described with reference to examples.

The first embodiment will be described with reference to FIGS.
For example, an infrared sensor is formed on the chip mounted on the vacuum sealed module in this embodiment.
As shown in FIG. 1, the vacuum-sealed module includes a substrate 2 on which conductive pads are formed, a chip 1 that is flip-chip mounted so that external terminals 3 are connected to the conductive pads, and one end side is It is a cylindrical body that is open and closed at the other end 41, and has a cap 4 that is vacuum-sealed by adhering the peripheral portion of the one end to the substrate 2 so as to cover the chip 1. The other end side 41 (closed side) of the cap 4 is bent inward due to a pressure difference when the cap 4 is bonded to the substrate 2 in a vacuum and then transferred to atmospheric pressure. The chip 1 is pressed and fixed to the substrate 2. This bent portion is referred to as a bent portion 42.

As shown in FIG. 3, in the vacuum-sealed module, bumps 3 that are external terminals of the chip 1 are flip-chip connected to conductive pads 23 formed on the surface of the substrate 2 so that electrical connection between them is achieved. Done. An external connection terminal 21 is provided on the back surface of the substrate 2. The external connection terminal 21 is electrically connected to the conductive pad 23 by an internal wiring 22 formed inside the substrate 2.

Further, the chip 1 is pressed and fixed to the substrate 2 by a bent portion 42 formed by a pressure difference generated during the module manufacturing process on the closed side 41 of the other end of the cap 4.
The cap 4 attached to the substrate 2 has a quadrilateral shape when viewed from above, and the chip 1 has a substantially quadrilateral shape. The bending portion 42 that fixes the chip 1 has the deepest portion 5 at the intersection of the diagonal 6 of the quadrilateral of the cap 4. Therefore, in order to effectively use the pressing force of the bending portion 42, it is optimal to align the center portion of the chip 1 with the deepest portion 5. The cap may have other shapes such as a cylindrical shape, or may be made of metal.

Next, a manufacturing method of the vacuum sealed module in this embodiment will be described. The conductive pad 23 is formed on the substrate 4 such as glass, and the chip 1 such as silicon is flip-chip mounted so that the bump (external terminal) 3 is connected to the conductive pad 23. This step is performed under normal atmospheric pressure. In the next step, the cylindrical cap 4 with one end open and the other end 41 closed is covered with the chip 1 so that the peripheral portion on one end side of the cap 4 is adhered to the substrate 2 and vacuum sealed. Stop. The step of bonding the cap 4 such as silicon to the substrate 2 is performed in a vacuum, and in the next step, the cap 4 is moved from the vacuum to the atmospheric pressure. Due to the pressure difference at this time, the other end 41 of the cap 4 is bent inward, and the chip 1 is pressed and fixed to the substrate 2.

  FIG. 2 shows a state where the module is placed in a vacuum and the process of bonding the cap 4 to the substrate 1 is finished. When this is moved under atmospheric pressure, the other end 41 of the cap 4 bends due to the pressure difference as shown in FIG. In order to convert such a pressure difference into a force for accurately fixing the chip 1, the side surface of the cap 4 is prevented from falling down and moved from the other end side 41 to the main surface of the substrate 2 (a). If the thickness (b) of the other end side 41 and the distance (c) from the other end side 41 to the back surface of the chip 1 are set to appropriate values, the deepest portion 5 ( The depth of d) can be set to an appropriate value.

In this embodiment, anodic bonding can be used as means for connecting the substrate 2 and the cap 4. Anodic bonding means that when glass and a polished surface of a silicon substrate subjected to crystal anisotropic etching are superposed and voltage is applied while heating, strong bonding by covalent bonding can be achieved.
As described above, since the chip does not use an adhesive for mounting on the substrate, it can easily achieve the degree of vacuum that requires the inside of the vacuum-sealed module, and this degree of vacuum can be maintained for a long time. Can be maintained across. In addition, the chip can be efficiently dissipated from the cap.

Next, Embodiment 2 will be described with reference to FIG.
This embodiment is characterized by the shape of the chip. As in the first embodiment, the module includes a substrate 2 on which conductive pads are formed, a chip 1 that is flip-chip mounted so that external terminals 3 are connected to the conductive pads, and one end side that is open and the other end side 41. Is a closed cylindrical body, and has a cap 4 that is vacuum-sealed by adhering the peripheral portion on the one end side to the substrate 2 so as to cover the chip 1. The other end 41 is bent inward due to a pressure difference when the cap 4 is bonded to the substrate 2 in a vacuum and then moved to atmospheric pressure. Fix to 2. Flip chip mounting is performed under normal atmospheric pressure, and the process of connecting the cap in the next process to the substrate is performed in a vacuum sealing device.

  In this embodiment, a recess 11 that is substantially similar to the bent portion 42 is formed on the back surface of the chip 1. The top 8 of the cap bending portion 42 generated by the pressure difference from the atmospheric pressure and the deepest portion 12 of the recess 11 are combined, so that the chip 1 can be positioned by the self-alignment effect with the recess 11 as a reference. is there.

Next, Example 3 will be described with reference to FIG.
This embodiment is characterized in that an infrared sensor is formed using the chip used in the second embodiment.
As in the second embodiment, the module includes a substrate 2 on which conductive pads are formed, a chip 1 that is flip-chip mounted so that external terminals 3 are connected to the conductive pads, and one end side that is open and the other end side 41. Is a closed cylindrical body, and has a cap 4 that is vacuum-sealed by adhering the peripheral portion on the one end side to the substrate 2 so as to cover the chip 1. The other end 41 is bent inward due to a pressure difference when the cap 4 is bonded to the substrate 2 in a vacuum and then moved to atmospheric pressure. Fix to 2. Flip chip mounting is performed under normal atmospheric pressure, and the process of bonding the cap of the next process to the substrate is performed in a vacuum apparatus.

In this embodiment, a concave portion substantially similar to the bending portion 42 is formed on the back surface of the chip 1. Then, the top portion 8 of the cap bending portion 42 generated by the pressure difference from the atmospheric pressure is combined with the deepest portion of the concave portion, so that the chip 1 can be positioned by the self-alignment effect with reference to the concave portion.
In this embodiment, the substrate 2 has a window portion 21, and the lens 7 is formed so as to cover the window portion 21. The substrate 2 is made of glass. Alumina or the like normally used for semiconductor packages may be used. The window portion 21 is configured to introduce infrared rays through the central portion of the substrate 2. The lens 7 is for collecting infrared rays, and chalcogenide glass, germanium, silicon, zinc sulfide can be used as a material.

The lens 7 is arranged so that a line (optical axis) passing through the center passes through the center of the chip 1 and its focal length is equal to the distance to the chip 1. The chip 1 detects infrared rays by converting light energy from the outside into heat energy. The cap 4 is for vacuum-sealing the chip 1.
As described above, in this embodiment, the optical lens is provided at the center of the region covered with the cap of the substrate, and the chip is positioned relative to the optical axis of the optical lens. And positioning.

1 ... chip (semiconductor substrate)
2 ... Substrate 3 ... Bump (external terminal)
DESCRIPTION OF SYMBOLS 4 ... Cap 5 ... Deepest part of bending part 6 ... Diagonal line 7 ... Optical lens 8 ... Top part of bending part 11 ... Recessed part 12 ... Deepest part of a recessed part 21 ... External connection terminal 22 ... Internal wiring 23 ... Conductive pad 41 ... Other end side of cap 42 ... Flexed part of cap

Claims (4)

A substrate on which a conductive pad is formed, a chip that is flip-chip mounted so that an external terminal is connected to the conductive pad, and a cylindrical body that is open at one end and closed at the other end so as to cover the chip And a cap for vacuum-sealing the peripheral portion of the one end side to the substrate, and the other end side of the cap is under atmospheric pressure after the cap is bonded to the substrate in a vacuum. A vacuum-sealed module characterized in that it is bent inward by a pressure difference when transferred, and the chip is pressed by this bending to fix it to the substrate. The recess is formed on the back surface of the chip, and the chip is positioned with reference to the recess by combining the top of the bent portion of the cap and the recess. Vacuum sealed module. The substrate has an optical lens at the center of the region covered with the cap, and the positioning of the chip with respect to the optical axis of the optical lens is performed by using the top of the bent portion of the cap and the recess of the chip. The vacuum-sealed module according to claim 2, wherein the positioning is performed by positioning. A step of flip-chip mounting the chip on the substrate on which the conductive pad is formed so that an external terminal is connected to the conductive pad, and a cap that is a cylindrical body whose one end is opened and the other end is closed, A step of adhering a peripheral portion of the one end side to the substrate so as to cover the chip and vacuum-sealing, and the other end side of the cap adheres the cap to the substrate in a vacuum. A vacuum-sealed module characterized in that after being moved to atmospheric pressure, the chip is bent inward by a pressure difference, and the chip is pressed against the substrate by a bending force and fixed to the substrate. Manufacturing method.

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