JPH01259569A - Manufacture of semiconductor pressure sensor - Google Patents

Abstract

PURPOSE:To improve junction strength by performing solder junction of a pedestal and a substrate without in advance segregating element ions generated from the inside of the pedestal on the junction surface to be soldered of this pedestal at the time of anodic bonding. CONSTITUTION:A silicon chip 7 is positioned on one side of the support bases 5, a + electrode 13 is set on one side surface of the silicon chip 7 in a contact state, while a - electrode 14 is set on the other side of the support bases 5 (a surface of a metallized layer 8) through a dummy glass 15; they undergo anodic bonding. Consequently, Na<+> to be precipitated from the pedestals 5 at the time of anodic bonding is segregated on one side 15' of the dummy glass 15 so that N<+> stops segregating on the surface of the metallized layer 8. Later, the dummy glass 15 is removed and the end face on the diasilicon chip side of the pedestals 5 is soldered with a substrate 1 through the metallized layer 8. Thereby, the junction strength of the pedestals 4 with the substrate 1 is increased.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a diaphragm type semiconductor pressure sensor.

[Conventional technology]

A diaphragm type semiconductor pressure sensor (for example, a silicon pressure sensor) utilizes the so-called piezoresistance effect in which the resistance value of a resistance element changes due to stress caused by deformation of a diaphragm.

This type of pressure sensor is known, for example, from Japanese Patent Application Laid-Open No. 55-19864.
As disclosed in Japanese Unexamined Patent Publication No. 62-72178, a reference pressure chamber is formed inside the sensor housing, and a passage for introducing the pressure to be measured into the reference pressure chamber and a passage sensitive to the pressure to be measured are disclosed. A diaphragm type semiconductor (for example, a silicon chip) is provided.

Some devices measure pressure by detecting this with a strain gauge attached to the diaphragm when the diaphragm senses the pressure to be measured.

Such pressure sensors usually consist of a sensor housing consisting of a cap and a base, a pedestal having a passage for introducing the pressure to be measured is bonded onto the base, and a diaphragm type semiconductor chip with a strain gauge is mounted on the pedestal. A structure is adopted in which the joints are arranged in correspondence with the openings of the four-person passageway to be measured. In order to adopt such a structure, for example, when using a silicon chip as a diaphragm type semiconductor,
The pedestal for supporting the diaphragm is also made of a material having a coefficient of thermal expansion equal to or similar to that of silicon, such as Pyrex glass, and the silicon chip is bonded onto this pedestal by anodic bonding. In addition, when joining a pedestal and a base, a metallized layer is provided on the side of the pedestal to be joined, and high melting point soldering is performed through this metallized layer, thereby bonding the pedestal onto the base. Note that, like the pedestal, the base is also made of a material having a coefficient of thermal expansion that is the same as or similar to that of silicon.

[Problem to be solved by the invention]

As mentioned above, when manufacturing this type of pressure sensor, first the diaphragm-type silicon chip on one side of the pedestal is bonded by anodic bonding, and then the other side of the pedestal is soldered onto the base via a metallized layer. do.

Among these work processes, the anodic bonding process is
As shown in FIG. 4 (FIG. 4 is a diagram showing the conventional anodic bonding process), the (+) pole 13 is set on one surface of the diaphragm-type silicon chip 7 aligned with one surface of the pedestal 5, and the Anodic bonding was performed by setting a (-) electrode 14 on the metallized layer 8 side previously formed on the other surface of the metallization layer 5 .

By the way, in such an anodic bonding process, Na+ in the Pyrex glass (pedestal) 5 is segregated by the anodic bonding to the metallized surface 8, and the metallized surface 8 is contaminated with Na+. The diagrams shown in FIGS. 4 and 5 represent the Na concentration distribution of the pedestal after anodic bonding (A/B) in terms of X-ray intensity, with the horizontal axis corresponding to the length of the pedestal 5, and the vertical axis represents the X-ray intensity. As shown in the solid line graph in the same figure, the closer to the metallized surface 8 side of the pedestal 5, the greater the Na concentration inside the pedestal, and Nap is precipitated on the metallized surface 8.

This Na+ contamination causes a reduction in the bonding strength during solder bonding between the pedestal 5 and the base. However, in the past, this Na
No special consideration was given to contamination. Therefore, for example, if this type of pressure sensor is placed in a harsh operating environment such as in an automobile.

It has become difficult to obtain sufficient sealing performance and mechanical strength between the joint between the pedestal and the base, and improvements have been desired.

The present invention has been made in view of the above points, and its purpose is to improve the joint strength by soldering between the pedestal and the base after the anodic bonding process,
Furthermore, the purpose is to improve the reliability of the pressure sensor.

[Means to solve the problem]

In the present invention, when a diaphragm-type semiconductor chip and a pedestal are anodically bonded, elemental ions (Nap in the case of Pyrex glass) generated from the pedestal are bonded to the pedestal and the base (through metallization) after the anodic bonding process. This was done after discovering that it had a negative effect on soldering (soldered joints), and the following measures were adopted to solve the problem.

That is, in order to achieve the above object, the present invention includes a step of bonding a semiconductor chip to one surface of a pedestal by anodic bonding, and a step of bonding the pedestal with the semiconductor chip onto a substrate by soldering via a metallized layer. In the method of manufacturing a semiconductor pressure sensor using a pedestal, etc., when a pedestal is soldered to a base, elemental ions generated from inside the pedestal are segregated in advance on the surface of the pedestal to be soldered during the anodic bonding step. The pedestal and the base are soldered to each other so as not to cause any damage.

As a specific method for preventing elemental ions generated during anodic bonding from segregating on the surface of the pedestal to be soldered, for example, there is the following method.

That is, in the anodic bonding process, one electrode (+ electrode) for bonding is set on the surface of the semiconductor chip positioned on one surface of the pedestal, and a dummy member made of the same material as the pedestal is placed on the other surface of the pedestal. The other electrode for anodic bonding is set on one end surface of this dummy member, and in this state anodic bonding is performed between the semiconductor chip and the pedestal. In the subsequent step of soldering the pedestal and the base, the dummy member used in the anodic bonding step is removed, and the pedestal surface, which is the surface from which the dummy member has been removed, is soldered to one surface of the base.

Alternatively, in the anodic bonding process, the (+) electrode for anodic bonding is set on the semiconductor chip side in the same way as above, and on the other hand, the pedestal is extended beyond a preset length and the extended end face is used for anodic bonding. (-) electrode is set, and in this state, anodically bonding is performed between the semiconductor chip and the pedestal. The subsequent step of soldering the pedestal and the base is performed by cutting out the extension of the pedestal and soldering the cut surface of the pedestal to one side of the base.

[Effect]

According to the present invention, during anodic bonding between a semiconductor chip and a pedestal, elemental ions (for example, Nap when the pedestal is made of Pyrex glass) are not segregated on the solder joint surface of the pedestal (the surface to be joined with the base). With this consideration, in the process of soldering the pedestal and the base, contamination of elemental ions can be eliminated, and a good solder joint between the pedestal and the base can be achieved.

In addition, as specific methods for preventing elemental ions from segregation on the surface to be soldered to the pedestal, we have provided examples of methods such as attaching a dummy member to the pedestal or extending the pedestal, but the effects of these methods will be discussed in the [Example] section. Explain in detail.

〔Example〕

Embodiments of the present invention will be described based on the drawings.

FIG. 1 is a longitudinal sectional view showing an example of a diaphragm type semiconductor pressure sensor to which the present invention is applied, and FIGS.
The figures show specific examples showing a part of the manufacturing process of the semiconductor pressure sensor.

In FIG. 1, 1 is a base, 2 is a cap that is placed on the base, and these elements 1 and 2 constitute a sensor housing H. A pressure introduction hole 3 is provided in the base 1, and a pressure introduction pipe 4 is fixed to the lower surface of the base 1 using a brazing agent (for example, silver solder) so as to communicate with the pressure introduction hole 3.

Reference numeral 5 denotes a pedestal for supporting the silicon chip 7, and the pedestal 5 is made of a member having the same or similar coefficient of thermal expansion as the silicon chip 7, such as Pyrex glass #7740. The base 1 is also made of a material having a coefficient of thermal expansion that is the same as or similar to that of the silicon chip 7. Further, a pressure introduction hole 6 is provided through the pedestal 5 in the axial direction.

The silicon chip 7 has a semiconductor strain gauge (not shown) arranged on one surface using, for example, a diffused resistor, and has a diaphragm 7a obtained by processing a recess on the back surface, and is bonded to the pedestal 5 by anodic bonding. be done. In this case, the silicon chip 7 is disposed with the diaphragm 7a facing the opening of the pressure introduction hole 6 of the pedestal 5 while maintaining sealing properties. Furthermore, the pedestal 5 is placed on the base 1 by soldering via a metallized layer 8, which will be described later.

In this case, the pressure introduction hole 6 on the diaphragm support 5 side and the pressure introduction hole 3 on the base plate 1 side are aligned and bonded.

The metallized layer 8 is made of 500 to 1500 Ti, Cr, or N, which allows the first layer to bond well with the material of the support base 5.
Adhesive layer such as i-0r, 1000 to 4000 Ni or Pt, where the second layer prevents interlayer diffusion of multilayer materials;
It is composed of three layers: a diffusion prevention layer such as Mo, and a third layer serving as a surface oxidation protective layer such as Au of 1000 to 1500 to protect the surface from oxidation.

Reference numeral 9 denotes a lead pin disposed on the base 1, and the lead pin 9 is inserted into the hermetic seal glass 10 while penetrating the base 1.
It is sealed with. In this way, the sensor housing H becomes airtight, and the inside of the housing H becomes the reference pressure chamber (
The vacuum chamber) is set to 11 °S.

One end of the lead pin 9 is connected to the strain gauge on the silicon chip 7 side via a thin metal wire 12, and the other end is electrically connected to an external circuit.

A pressure sensor having such a configuration has a pressure introduction pipe 4. The pressure to be measured is guided to the silicon chip 7 side through the pressure introduction holes 3 and 6, and when the silicon diaphragm 7a senses the pressure to be measured, the strain gauge outputs an output according to the degree of sensitivity to the external circuit ( (amplifier circuit) to measure pressure. In addition, the amplifier circuit,
The temperature compensation circuit may be integrated and formed on the silicon chip 7 side instead of being externally attached.

Next, a method for manufacturing a semiconductor pressure sensor, which is the gist of this embodiment, will be explained.

The semiconductor pressure sensor of this embodiment basically consists of a step of forming a pedestal 5 having a pressure introduction passage 6 from Pyrex glass, a step of forming a silicon chip 7 having a silicon diaphragm 7a, and one surface of the pedestal 5. The pressure sensor is manufactured through a process of bonding the silicon chip 7 by anodic bonding, and a process of bonding the other surface of the diaphragm support 5 to the substrate 1 via the metallized layer 8 by soldering. Among these steps, anodic bonding between the silicon chip 7 and the pedestal 5 is performed as follows.

A specific example of this anodic bonding will be explained based on FIGS. 2 and 3.

FIGS. 2 and 3 show the anodic bonding state between the silicon chip 7 and the pedestal 5 and the change in Na concentration before and after the anodic bonding (A/B) using X-ray intensity.

In the example shown in FIG. 2, one pedestal 5 is formed to the specified dimensions (here, the length is 5.0 layers wn), and a metallized layer 8 is preliminarily deposited on its negative surface. When the silicon chip 7 is bonded to the other surface (the side opposite to the metallized layer) of the pedestal 5 by anodic bonding, it is performed as follows.

That is, when performing anodic bonding, as shown in the figure, the silicon chip 7 is aligned on one side of the support base 5, and the (+) electrode 1 is placed on one side of the silicon chip 7.
Set 3 in contact state.

Further, a (-) electrode 14 is set on the other surface of the support base 5 (the surface of the metallized layer 8) via a dummy glass 15, and anodic bonding is performed. Here, dummy glass 15
The length is about 2m, and its negative side is the 8th metallized layer,
The other surface (-) contacts the pole 14.

According to such anodic bonding, Na precipitated from the pedestal 5 during anodic bonding is on one surface of the dummy glass 15 [one surface on the (-) electrode 14 side].
It is possible to prevent Na from segregating on the 8th surface of the metallized layer.

If the Na concentration distribution inside the pedestal 5 and the dummy glass 15 at this time is expressed in terms of X-ray intensity, it will be as shown in the solid line graph in Figure 2. ).

That is, when the dummy glass 15 is used, the Na concentration inside the pedestal 5 remains at 50 CPS, the same as before the anodic bonding, while the Na concentration inside the dummy glass 15 shifts to the (-) electrode 14 side. The concentration increases as the concentration increases, and finally Na is segregated at one end 15' of the dummy glass.

In this embodiment, after this anodic bonding, the dummy glass 15 is removed, and the end surface of the pedestal 50 on the side opposite to the silicon chip is bonded to the substrate 1 through the metallized layer 8.
According to this method, Na segregation (contamination) does not occur on the surface of the pedestal 5 to be soldered, and a good high-melting point solder bond between the pedestal 5 and the base 1 can be achieved. As a result, the bonding strength between the pedestal 5 and the base 1 increases, and the reliability of the sensor can be improved.

Next, an example of an anodic bonding process that replaces the method shown in FIG. 2 will be explained based on FIG. 3.

In Figure 3, during the anodic bonding process,
The length of the diaphragm support base 5 is set to the specified length (for example, 5.
(approximately 0 mm) (this extended portion 5' is approximately 2 m long and is formed by extending it in advance by an amount greater than dummy glass 1 in Figure 1).
5).

When performing anodic bonding, the silicon chip 7 and the (+) pole 13 are set in the same manner as shown in FIG. Set it in a contact state. According to such an anodic bonding process, Na is segregated on the end face of the extension portion 5' of the pedestal 5.

If the Nafi degree distribution of the pedestal 5 at this time is expressed in terms of X-ray intensity, it will be as shown in the solid line graph in FIG.

That is, in this case, the Na concentration is
' rises as it approaches the end and finally reaches the extension part 5'
Na inside precipitates on the end face, while other Na inside the pedestal 5
The concentration is almost the same as before anodic.

After this anodic bonding process, the pedestal 5
is cut at a set length 5a, a metallized layer 8 is deposited on this cut surface 5a, and the cut surface Sa side is soldered to the substrate 1 side.

In this embodiment, the pedestal extension 5' in which Na is segregated is cut, and the pedestal cut surface 5a without segregation in Na is soldered to the base 1 via the metallized layer 8.
As in the case where the pedestal 5 and the base 1 are used, a good high melting point solder joint can be made between the pedestal 5 and the base 1.

Note that such a measure to prevent Na+ segregation on the pedestal can be applied to a relative pressure sensor as well as the absolute pressure sensor of each embodiment described above.

〔Effect of the invention〕

As described above, according to the present invention, the solder joint between the pedestal and the base is performed after the anodic bonding process without contamination of elemental ions, so the strength of the soldered joint between the pedestal and the base is improved, In turn, the reliability of the pressure sensor can be improved.

[Brief explanation of the drawing]

FIG. 1 is a vertical cross-sectional view showing an example of a semiconductor pressure sensor to which the present invention is applied; FIGS. 2 and 3 are explanatory diagrams showing an example of the anodic bonding process in the semiconductor pressure sensor manufacturing method of the invention; Figure 4 is an explanatory diagram showing an example of the conventional anodically bonding process, and Figure 5 is the Naf of the pedestal when a silicon chip is anodically bonded to the pedestal.
It is a graph showing i degrees in terms of X-ray intensity. 1... Base, 5... Pedestal, 5'... Pedestal extension,
7... Semiconductor chip, 7a... Diaphragm, 8.
... Metallized layer, 13.14... Electrode for anodic bonding, 15... Dummy member (dummy glass)
.

Claims (1)

[Claims] 1. A step of forming a diaphragm with a strain gauge that is sensitive to the pressure to be measured on a semiconductor chip, a step of bonding the semiconductor chip to one surface of a pedestal by anodically bonding, and a step of bonding the semiconductor chip. In the method of manufacturing a semiconductor pressure sensor through a step of later joining the other surface of the pedestal to the base by soldering via a metallized layer, when the pedestal is soldered to the base, the previous step A method for manufacturing a semiconductor pressure sensor, characterized in that solder bonding is performed by preventing elemental ions generated from inside the pedestal from being segregated on the surface of the pedestal to be soldered during anodically bonding. 2. A step of forming a diaphragm with a strain gauge that is sensitive to the pressure to be measured on the semiconductor chip, a step of bonding this semiconductor chip to one surface of the pedestal by anodically bonding, and a step of bonding the semiconductor chip to one surface of the pedestal after bonding the semiconductor chip to the other surface of the pedestal. In a method for manufacturing a semiconductor pressure sensor through a step of soldering a surface onto a substrate by soldering through a metallized layer, in the step of anodically bonding the semiconductor chip and the pedestal, the step of bonding the semiconductor chip to the pedestal includes: One electrode for anode bonding is set on the surface of the positioned semiconductor chip, a dummy member made of the same material as the pedestal is placed on the other surface of the pedestal, and a dummy member made of the same material as the pedestal is placed on one end surface of the dummy member. The other electrode for anodically bonding is set, and anodically bonding is performed between the semiconductor chip and the pedestal in this state, and the solder bonding between the pedestal and the base is performed after the anodically bonding. A method for manufacturing a semiconductor pressure sensor, characterized in that the dummy member is removed and the pedestal surface, which is the surface from which the dummy member has been removed, is soldered to one surface of the base. 3. A process of forming a diaphragm with a strain gauge that is sensitive to the pressure to be measured on the semiconductor chip, a process of bonding this semiconductor chip to one surface of the pedestal by anodically bonding, and a process of bonding the pedestal with the semiconductor chip with a metallized layer. In the method of manufacturing a semiconductor pressure sensor through a step of bonding the semiconductor chip and the pedestal to a substrate by soldering through a substrate, in the step of anodically bonding the semiconductor chip and the pedestal, the semiconductor chip positioned on one surface of the pedestal is One electrode for anode bonding ink is set on the surface of the pedestal, and the other electrode is set on the extended end surface of the pedestal by extending it beyond a preset length, and in this state, the semiconductor chip and Anodically bonding is performed with the pedestal, and the pedestal and the base are soldered together by cutting an extension of the pedestal after the anodically bonding, and soldering the cut surface of the pedestal and one surface of the base. A method for manufacturing a semiconductor pressure sensor, characterized in that the method is carried out by attaching. 4. A method of manufacturing a semiconductor pressure sensor according to any one of claims 1 to 3, wherein the semiconductor chip is a silicon chip and the pedestal is made of Pyrex glass.