JPH11248572A - Method for forming metalizing layer of pedestal for semiconductor sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for forming a metalizing layer of a pedestal for a semiconductor pressure sensor of good joint reliability wherein no metalizing layer is formed on an inner wall of a through hole of the pedestal, with no increase in the number of processes. SOLUTION: In a method for forming a metalizing layer 8 on a surface on the side not jointing a semiconductor pressure sensor chip 1 of a pedestal 2 of a semiconductor pressure sensor comprising the semiconductor pressure sensor chip 1 provided with a diaphragm 11 formed in thin-wall by forming a recessed part, and a pedestal 2 which is, with a through hole 21 for introducing a pressure into the diaphragm 11, jointed to the semiconductor pressure sensor ship 1, the metalizing layer 8 is formed by sputtering or vapor-deposition after an inside wall 22 of the through hole 21 is mirror-finished.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for forming a metallized layer of a pedestal for a semiconductor pressure sensor formed by joining a semiconductor pressure sensor chip having a diaphragm formed thereon and a pedestal.

[0002]

2. Description of the Related Art In general, a semiconductor pressure sensor measures a pressure in a micro pressure region. As shown in FIG. 3, a semiconductor pressure sensor having a diaphragm 11 formed thin by forming a concave portion. Chip 1 is glass pedestal 2
To the center by Kovar or 4
PPS or PBT on which metal pipe 4 such as 2 alloy is arranged
And so on, in a plastic package 3. The aluminum pad on the surface of the semiconductor pressure sensor chip 1 and the lead 5 are connected by a gold or aluminum wire 6. Note that 7
Is a lid of the plastic package 3, 12 is a strain gauge resistor formed on the semiconductor pressure sensor chip 1, and 13 is an overcoat for protecting the surface of the semiconductor pressure sensor chip 1. As a material of the glass pedestal 2,
For example, Pyrex glass (Corning's product number # 7
740).

A through hole 21 for applying pressure to the diaphragm 11 of the semiconductor pressure sensor chip 1 is formed in the center of the glass pedestal 2.
1 and the through-hole 41 of the metal pipe 4 are joined to the metal pipe 4 in such an arrangement that they face each other. In order to join the glass pedestal 2 and the metal pipe 4, a metallization layer 8 is formed on the surface of the glass pedestal 2 on the side not joined to the semiconductor pressure sensor chip 1.
Is formed.

In forming the metallized layer 8 on the glass pedestal 2, first, as shown in FIG. 4A, the surface on which the metallized layer 8 is to be formed is roughened, and then, FIG. As shown in (1), the glass pedestal 2 is placed in close contact with the flat plate 10, and the metallized layer 8 is formed on the surface roughened by sputtering or vapor deposition. Examples of the metallized layer 8 include Cr (bottom layer) / Ni / Au (top layer), Ti
(Bottom layer) / Ni / Au (top layer), Ti (bottom layer) /
Pt / Au (top layer) and the like. Then, FIG.
(C) As shown in FIG.
Remove from

[0005] Then, the metal pipe 4 and the glass pedestal 2 are joined by solder (tin, tin-antimony alloy, lead, tin-lead alloy, gold-silicon alloy, tin-silver alloy, etc.) 9 via the metallized layer 8. Is done. A of the uppermost layer of the metallized layer 8
The solder 9 can be applied to the surface of u.

[0006]

However, according to the method for forming the metallized layer 8 on the glass pedestal 2 as described above, the surface of the glass pedestal 2 that is in contact with the flat plate 10 is not metallized. However, metal particles adhere to the inner wall of the through hole 21 and the metallized layer 8 is formed.

When the metallized layer 8 is formed on the inner wall of the through hole 21, as shown in FIG. 5, when the glass pedestal 2 and the semiconductor pressure sensor chip 1 are anodically bonded, a high temperature (about 300 ° C. to 400 ° C.) is applied. ) In high bias (about 50
0 V to 800 V) is applied between the metallization layer 8 formed at the upper end of the inner wall of the through-hole 21 and the portion near the through-hole 21 on the joint surface of the semiconductor pressure sensor chip 1 with the glass pedestal 2. As a result, there is a problem that a discharge occurs and the semiconductor pressure sensor chip 1 is broken.

In order to solve such a problem, there is a method of filling the through hole 21 of the glass pedestal 2 with the wax 20 when forming the metallized layer 8 as shown in FIG. That is, as shown in FIG.
6B, the wax 20 is filled in the through holes 21 at the stage where the glass pedestal 2 is closely mounted on the flat plate 10 as shown in FIG. 6B. The wax 20 used is one that melts with heat of about 100 ° C. to 150 ° C., but the type of the wax 20 may be appropriately changed depending on the temperature applied when the metallized layer 8 is formed. The method of filling the wax 20 into the through hole 21 is as follows.
For example, this is performed by discharging wax from the needle tip using a dispenser or the like. Thereafter, as shown in FIG. 6C, a metallized layer 8 is formed on the surface roughened by sputtering or vapor deposition. After the formation of the metallized layer 8 is completed,
As shown in FIG. 6D, the glass pedestal 2 is removed from the flat plate 10, and the glass pedestal 2 is heated to melt and remove the wax 20 filled in the through hole 21. This prevents the metallized layer 8 from being formed in the through hole 21.

However, in this case, the through holes 21
The step of filling the inside of the wax 20 is extraly increased, and the cost is increased. Also, if the wax scatters on the surrounding glass pedestal 2 surface other than in the through hole 21, the metallized layer 8 will be formed on the wax, and the adhesive strength of the metallized layer 8 to the surface of the glass pedestal 2 will be reduced. descend.
Further, after the metallized layer 8 is formed, the wax 20 filled in the through-hole 21 is melted and removed, but when the residue of the wax 20 wraps around the surface of the glass pedestal 2 to be joined to the semiconductor pressure sensor chip 1. This significantly affects the bonding quality between the glass pedestal 2 and the semiconductor pressure sensor chip 1. In other words, the bonding strength is reduced due to voids being generated without bonding. Washing with a molten organic solvent (acetone, isopropyl alcohol, etc.) may be considered to remove the residue of the wax 20, but the number of washing steps is increased, and quality control such as checking the residue level after washing is difficult. In particular, when the wax 20 is opaque, there is a problem that a visual inspection cannot be performed and a cleaning property cannot be evaluated.

[0010] The present invention has been made in view of the above points, and an object thereof is to form a metallized layer on the inner wall of a through-hole of a pedestal without increasing the number of steps and improving the bonding reliability. It is an object of the present invention to provide a method for forming a metallized layer of a pedestal for a semiconductor pressure sensor having good easiness.

[0011]

According to the first aspect of the present invention,
A semiconductor pressure sensor chip having a diaphragm formed in a thin shape by forming a concave portion, and a pedestal formed with a through hole for introducing pressure to the diaphragm and joined to the semiconductor pressure sensor chip. A method of forming a metallized layer on the surface of the pedestal of the semiconductor pressure sensor, which is not bonded to the semiconductor pressure sensor chip, after mirroring the inner wall of the through hole, forming the metallized layer by sputtering or vapor deposition. It is characterized by doing so.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a process chart showing a method for forming a metallized layer of a pedestal for a semiconductor pressure sensor according to an example of an embodiment of the present invention. First, as shown in FIG. 1A, a disk-shaped glass pedestal 2 (with a diameter of about 100 mm
The through-hole 21 is formed at an area of 50 mm and a thickness of about 0.5 mm to 3 mm) by an ultrasonic processing method or the like. Through hole 2
The size of 1 is about 0.6 mm to 1.5 mm in diameter.

Here, for example, buffered hydrofluoric acid (BH)
The inner wall 22 of the through hole 21 is mirror-finished by immersing the glass pedestal 2 in the liquid F). At this time, it is desirable that the surface roughness of the inner wall 22 is set to RMAX 0.05 μm or less.

Next, as shown in FIG. 1B, one surface of the glass pedestal 2 is roughened. In other words, one surface of the glass pedestal 2 is polished with a coarse grindstone, or sprayed by sandblasting to roughen the surface, so that metal can easily adhere when forming a metallized layer described later. deep.

Next, as shown in FIG. 1C, the glass pedestal 2 is placed on the flat plate 10 with the roughened surface facing upward. Then, a metallized layer 8 is formed on the roughened surface of the glass pedestal 2 by sputtering or vapor deposition.
In the case of sputtering, a pressure around a target (a plate used as a material of the metallized layer 8) is increased to 10 ⁻² Torr.
A voltage of several hundred V to several KV is applied between the substrate and the vacuum vessel (ground) and the target at a pressure of 10 ^-4 Torr to generate plasma. The ions in the plasma bounce off the atoms on the target surface and adhere to the substrate (glass) to form a film. By changing the target in this manner, a plurality of metal layers are stacked, and the metallized layer 8 is formed. Examples of the metallized layer 8 include:
Cr (bottom layer) / Ni / Au (top layer), Ti (bottom layer) / Ni / Au (top layer), Ti (bottom layer) / Pt /
Au (top layer) and the like. The surface on which the metallized layer is formed by sputtering (surface on which surface roughening has been performed)
From the direction.

As shown in FIG. 2, the surface of the glass pedestal 2 on which the metallized layer 8 is formed is joined to the metal pipe 4 via the solder 9 while the metallized layer 8 is formed, as shown in FIG. The surface is bonded to the semiconductor pressure sensor chip 1 by anodic bonding. The conditions for the anodic bonding are as follows: heating to about 400 ° C. in a vacuum atmosphere and applying a DC voltage of about 500 V to 800 V so that the semiconductor pressure sensor chip 1 side becomes a positive electrode, the atomic bonding is performed by electrostatic attraction. It is.

According to the above-described embodiment, the inner wall 22 of the through hole 21 of the glass pedestal 2 is mirror-finished so as not to have irregularities. It is difficult to form a metallized layer on the inner wall 22 of the hole 21. Therefore, when the glass pedestal 2 and the semiconductor pressure sensor chip 1 are anodic-bonded, the semiconductor pressure sensor chip 1 is not broken by electric discharge, and an extra step such as filling with wax is not increased. Further, the joining reliability between the glass pedestal 2 and the semiconductor pressure sensor chip 1 or the metal pipe 4 is also improved.

[0018]

As described above, according to the first aspect of the present invention, a semiconductor pressure sensor chip having a diaphragm formed in a thin shape by forming a concave portion, and a semiconductor pressure sensor chip for introducing pressure to the diaphragm. A through hole is formed,
A method of forming a metallized layer on a surface of a semiconductor pressure sensor having a pedestal joined to the semiconductor pressure sensor chip and a surface of the pedestal not joined to the semiconductor pressure sensor chip, wherein an inner wall of the through hole is provided. After metallization, a metallized layer is formed by sputtering or vapor deposition.Therefore, the metallized layer is not formed on the inner wall of the through hole of the pedestal, and the number of processes is not increased, and a semiconductor pressure sensor having high bonding reliability is provided. The method for forming the metallized layer of the pedestal can be provided.

[Brief description of the drawings]

FIG. 1 is a process diagram showing a method for forming a metallized layer of a pedestal for a semiconductor pressure sensor according to one embodiment of the present invention.

FIG. 2 is a schematic diagram showing a state where the pedestal according to the above is joined to a semiconductor pressure sensor chip and a metal pipe.

FIG. 3 is a schematic configuration diagram of a semiconductor pressure sensor.

FIG. 4 is a process chart showing a method of forming a metallized layer of a pedestal for a semiconductor pressure sensor according to a conventional example.

FIG. 5 is a schematic view showing a state where the pedestal according to the above is joined to a semiconductor pressure sensor chip and a metal pipe.

FIG. 6 is a process chart showing a method of forming a metallized layer of a pedestal for a semiconductor pressure sensor according to another conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Semiconductor pressure sensor chip 2 Glass pedestal 3 Plastic package 4 Metal pipe 5 Lead 6 Wire 7 Lid 8 Metallization layer 9 Solder 10 Flat plate 11 Diaphragm 12 Strain gauge resistance 13 Overcoat 20 Wax 21 Through hole 22 Inner wall (mirror surface)

Claims (1)

[Claims] 1. A semiconductor pressure sensor chip having a diaphragm formed thin by forming a concave portion, and a through hole for introducing pressure to the diaphragm are formed and joined to the semiconductor pressure sensor chip. A method of forming a metallized layer on a surface of the semiconductor pressure sensor having a pedestal on a side of the pedestal that is not bonded to the semiconductor pressure sensor chip, wherein after mirroring an inner wall of the through hole, sputtering or vapor deposition is performed. A method for forming a metallized layer of a pedestal for a semiconductor pressure sensor, wherein the metallized layer is formed by: