JP3374742B2 - Method of forming metallized layer of pedestal for semiconductor pressure sensor - Google Patents

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 semiconductor pressure sensor pedestal, which is formed by joining a semiconductor pressure sensor chip having a diaphragm and a pedestal.

[0002]

2. Description of the Related Art Generally, a semiconductor pressure sensor measures a pressure in a low pressure region, and as shown in FIG. 3, a semiconductor pressure sensor having a diaphragm 11 formed in a thin shape by forming a recess. Chip 1 is glass pedestal 2
To the center by anodic bonding, etc.
PPS or PBT with metal pipe 4 such as 2 alloy
Etc. are installed in the plastic package 3. The aluminum pad on the surface of the semiconductor pressure sensor chip 1 and the lead 5 are connected by a wire 6 made of gold or aluminum. In addition, 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 the material of the glass pedestal 2,
For example, Pyrex glass (made by Corning, product number # 7
740) is used.

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, and the glass pedestal 2 has this through hole 2
1 and the through hole 41 of the metal pipe 4 are arranged to face each other and are joined to the metal pipe 4. In order to bond the glass pedestal 2 and the metal pipe 4, the metallization layer 8 is formed on the surface of the glass pedestal 2 which is not bonded to the semiconductor pressure sensor chip 1.
Is formed.

To form 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, as shown in FIG. As shown in FIG. 3, 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 (lowermost layer) / Ni / Au (uppermost layer), Ti
(Bottom layer) / Ni / Au (top layer), Ti (bottom layer) /
Examples include Pt / Au (uppermost layer). After that, FIG.
As shown in (c), the glass pedestal 2 is attached to the flat plate 10
Remove from.

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

[0006]

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

If 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 obtained. ), High bias (about 50
Since 0 V to 800 V) is applied, between the portion of the bonding surface of the semiconductor pressure sensor chip 1 with the glass pedestal 2 near the through hole 21 and the metallization layer 8 formed on the upper end of the inner wall of the through hole 21. However, there is a problem in that the semiconductor pressure sensor chip 1 is destroyed due to discharge.

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. 6A, the metallization layer 8
The surface to be formed is roughened, and as shown in FIG. 6B, the wax 20 is filled in the through holes 21 at the stage where the glass pedestal 2 is placed in close contact with the flat plate 10. 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 for filling the wax 20 into the through hole 21 is as follows.
For example, the wax is ejected from the needle tip using a dispenser or the like. Thereafter, as shown in FIG. 6C, the metallized layer 8 is formed on the surface roughened by sputtering or vapor deposition. After completing the formation of the metallized layer 8,
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 holes 21. By doing so, the metallized layer 8 is prevented from being formed in the through hole 21.

However, in this case, the through hole 21
An extra step of filling the wax 20 into the inside increases, resulting in an increase in cost. Further, when the wax is scattered on the surface of the glass pedestal 2 other than inside the through hole 21, the metallized layer 8 is formed on the wax, and the adhesive force of the metallized layer 8 to the surface of the glass pedestal 2 is increased. descend.
Further, after the metallized layer 8 is formed, the wax 20 filled in the through holes 21 is melted and removed. When the residue of the wax 20 wraps around on the surface of the glass pedestal 2 that is bonded to the semiconductor pressure sensor chip 1. Therefore, the bonding quality between the glass pedestal 2 and the semiconductor pressure sensor chip 1 is significantly affected. That is, voids (voids) are generated without joining, and the joining strength is reduced. Cleaning with a molten organic solvent (acetone, isopropyl alcohol, etc.) may be considered to remove the residue of the wax 20, but the number of cleaning steps increases and quality control such as confirmation of the residue level after cleaning is difficult. In particular, when the wax 20 is opaque, there is a problem that the visual inspection cannot be performed and the cleaning property cannot be evaluated.

The present invention has been made in view of the above points, and an object thereof is that a metallized layer is not formed on the inner wall of the through hole of the pedestal, the number of steps is not increased, and the bonding reliability is improved. Another object of the present invention is to provide a method of forming a metallized layer of a pedestal for a semiconductor pressure sensor having good properties.

[0011]

The invention according to claim 1 is
It has a semiconductor pressure sensor chip having a diaphragm formed thin by forming a recess, and a pedestal in which a through hole for introducing pressure to the diaphragm is formed and which is joined to the semiconductor pressure sensor chip. A method of forming a metallization layer on the surface of the pedestal of the semiconductor pressure sensor that is not joined to the semiconductor pressure sensor chip, the method having a cross-sectional shape that is substantially the same as the shape of the through hole. A surface on which a plurality of pins having a length equal to or greater than the depth are fixed by a thin linear member so as to be arranged corresponding to the arrangement of the through holes of the pedestal, and each of the plurality of pins forms a metallized layer of the pedestal The metallized layer is formed by sputtering or vapor deposition from the surface side on which the metallized layer is to be formed with the pin inserted into the through hole from the side. And it is characterized in and.

According to a second aspect of the present invention, in the first aspect of the invention, when forming the metallized layer, sputtering or vapor deposition is performed while rotating the pedestal.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION An example of an embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a process drawing showing a method for forming a metallized layer of a semiconductor pressure sensor pedestal according to an example of an embodiment of the present invention. First, as shown in FIG. 1A, a disk-shaped glass pedestal 2 (diameter of about 100 mm to 1
The through-hole 21 is formed in 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.
Surface roughening is performed on one surface of the glass pedestal 2. That is, one surface of the glass pedestal 2 is polished with a coarse grindstone or is sprayed with a sandblast method to roughen the surface so that metal is easily attached when forming a metallized layer described later. deep.

Next, as shown in FIG. 1B, the glass pedestal 2 is placed on the flat plate 10 with its roughened surface facing upward. Then, a plurality of columnar pins 30 having a cross-sectional shape substantially the same as the shape of the through hole 21 of the glass pedestal 2 and having a length equal to or greater than the depth of the through hole 21 correspond to the arrangement of the through hole 21. Are fixed by a thin metal wire 40 as a thin wire member so that each of the plurality of pins 30 is formed from the surface side of the glass pedestal 2 on which the metallized layer 8 is formed through the through hole 21.
The pin 30 is inserted until it reaches the flat plate 10. Each through hole 21 is blocked by the plurality of pins 30.

In this state, as shown in FIG. 1C, the metallized layer 8 is formed on the roughened surface side of the glass pedestal 2 by sputtering or vapor deposition. In the case of sputtering, a pressure of 10 ^-2 Torr to 10 ^-4 Torr is applied around the target (a plate used as the material of the metallized layer 8) and a few hundred V is applied between the substrate and the vacuum container (ground) and the target.
A voltage of several KV is applied to generate plasma. 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 by this method, a plurality of metal layers are laminated to form the metallized layer 8. An example of the metallized layer 8 is Cr (bottom layer) / N
Examples include i / Au (uppermost layer), Ti (lowermost layer) / Ni / Au (uppermost layer), Ti (lowermost layer) / Pt / Au (uppermost layer). Note that the sputtering is performed from the direction of the surface on which the metallized layer is formed (the surface on which the surface is roughened). At this time, since the metal wire 40 fixing the plurality of pins 30 is a thin member, the metallization layer 8 is not uneven due to the shielding of the metal wire 40. Then, Figure 1
As shown in (d), the pin 30 is taken out from the through hole 21.

FIG. 2 is a process chart showing a method of forming a metallized layer of a semiconductor pressure sensor pedestal according to another embodiment of the present invention. In this embodiment, as shown in FIG. 2B in the above-described embodiment, the flat plate 10 is installed on the rotary table 50. A bearing 52 is provided on the upper surface of the rotary table 50, and the flat plate 10 placed on the rotary table 50 can be rotated by the motor 51. Therefore, when performing sputtering or vapor deposition, as shown in FIG. 2C, the flat plate 10 is rotated. After the formation of the metallized layer 8 is completed, the rotation of the flat plate 10 is stopped,
The pin 30 is taken out from the through hole 21. Since the other steps are the same as those in the above-described embodiment, the description will be omitted. In the present embodiment, since the flat plate 10 is rotated, that is, the pedestal 2 is rotated to perform sputtering and vapor deposition, even if the metal wire 40 becomes slightly thick, the metallized layer 8 will not be uneven.

In the glass pedestal 2 on which the metallized layer 8 is formed as described above, the surface on which the metallized layer 8 is formed is joined to the metal pipe 4 via the solder 9 as shown in FIG. The surface is bonded to the semiconductor pressure sensor chip 1 by anodic bonding. As the conditions for anodic bonding, 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 causes atomic bonding by electrostatic attraction. Of.

According to the above embodiment, the inner wall 22 of the through hole 21 of the glass pedestal 2 is formed with the metallized layer 8 because the through hole 21 is blocked by the pin 30 during the process of forming the metallized layer 8. Is not formed, and is formed only on the joint surface with the metal pipe 4. Therefore, when the glass pedestal 2 and the semiconductor pressure sensor chip 1 are anodically bonded, the semiconductor pressure sensor chip 1 is not destroyed by discharge, and an extra step such as filling with wax is not added. In addition, the reliability of joining the glass pedestal 2 to the semiconductor pressure sensor chip 1 and the metal pipe 4 is also improved.

[0019]

As described above, according to the first aspect of the present invention, a semiconductor pressure sensor chip having a diaphragm formed thin by forming a recess, and a pressure for introducing pressure to the diaphragm. A through hole is formed,
A method of forming a metallized layer on a surface of a pedestal of a semiconductor pressure sensor having a pedestal bonded to the semiconductor pressure sensor chip, the surface not being bonded to the semiconductor pressure sensor chip, the shape of the through hole A plurality of pins having a cross-sectional shape substantially the same as the above and having a length equal to or greater than the depth of the through hole, are fixed by a thin wire member so as to be arranged corresponding to the arrangement of the through hole of the pedestal, Each of the plurality of pins was inserted into the through hole from the side of the pedestal on which the metallized layer is formed, and with the pins inserted, the metallized layer was formed by sputtering or vapor deposition from the side of the metallized layer forming surface. Therefore, the metallized layer is not formed on the inner wall of the through hole of the pedestal, and the number of steps does not increase,
A method of forming a metallized layer of a pedestal for a semiconductor pressure sensor having good bonding reliability can be provided.

According to the invention of claim 2, in the invention of claim 1, when forming the metallization layer, sputtering or vapor deposition is performed while rotating the pedestal, so that a more uniform metallization layer is formed. Can be formed.

[Brief description of drawings]

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

FIG. 2 is a process drawing showing a method for forming a metallized layer of a semiconductor pressure sensor pedestal according to another embodiment of the present invention.

FIG. 3 is a schematic view showing a state in which the pedestal according to the above is joined to a semiconductor pressure sensor chip and a metal pipe.

FIG. 4 is a schematic configuration diagram of a semiconductor pressure sensor.

FIG. 5 is a process drawing showing a method for forming a metallized layer of a semiconductor pressure sensor pedestal according to a conventional example.

FIG. 6 is a schematic view showing a state in which the pedestal according to the above is joined to a semiconductor pressure sensor chip and a metal pipe.

FIG. 7 is a process chart showing a method for forming a metallized layer of a pedestal for a semiconductor pressure sensor according to another conventional example.

[Explanation of symbols]

1 Semiconductor pressure sensor chip 2 glass pedestal 3 plastic packages 4 metal pipes 5 leads 6 wires 7 lid 8 Metallized layer 9 solder 10 Flat plate 11 diaphragm 12 Strain gauge resistance 13 overcoat 20 wax 21 through holes 22 Inner wall 30 pin 40 metal wire 50 turntable 51 motor 52 bearing

Continuation of the front page (56) Reference JP-A-4-120264 (JP, A) JP-A-4-120263 (JP, A) JP-A-4-120262 (JP, A) JP-A-11-241964 (JP , A) JP-A-11-241963 (JP, A) JP-A-11-21595 (JP, A) JP-A-10-30972 (JP, A) JP-A-58-83335 (JP, A) 64-8977 (JP, U) (58) Fields investigated (Int.Cl. ⁷ , DB name) G01L 9/00 C23C 14/04 H01L 29/84

Claims (2)

(57) [Claims] 1. A semiconductor pressure sensor chip having a diaphragm formed thin by forming a recess and a through hole for introducing pressure to the diaphragm are formed and bonded to the semiconductor pressure sensor chip. A method of forming a metallization layer on a surface of a semiconductor pressure sensor having a pedestal, which is not joined to the semiconductor pressure sensor chip of the pedestal, and has a cross-sectional shape substantially the same as the shape of the through hole. Then, a plurality of pins having a length equal to or greater than the depth of the through holes are fixed by a thin wire member so as to be arranged corresponding to the arrangement of the through holes of the pedestal, and each of the plurality of pins is metalized on the pedestal. The metallization layer is formed by sputtering or vapor deposition from the surface side on which the metallization layer is to be formed, with the pin inserted into the through hole from the surface side on which the layer is to be formed. A method of forming a metallized layer of a pedestal for a semiconductor pressure sensor, characterized in that. 2. The method for forming a metallized layer for a semiconductor pressure sensor pedestal according to claim 1, wherein the metallized layer is formed by performing sputtering or vapor deposition while rotating the pedestal.