JPH01102333A - Semiconductor pressure sensor - Google Patents

Abstract

PURPOSE:To enable the impression of a negative voltage necessary for an anodic junction processing from a surface region wherein no metallized layer exists, by providing this region in a part of an end face wherein the metallized layer of a glass pedestal is to be provided. CONSTITUTION:By the impression of a voltage at the time of anodic junction, positive sodium ions are concentrated uniformly on and near a through hole 3 which is kept at a negative potential by a steel ball 5 attached on the inside of a region 40 wherein a metallized layer 4 of a glass pedestal 2 does not exist. On the other side negative oxygen ions migrate so that they gather uniformly toward a junction interface with a silicon chip 1. As the result, the chip 1 and the pedestal 2 are bonded firmly by the anodic junction, while the deposition of sodium on the interface of the pedestal 2 with the metallized layer 4 is eliminated. The mechanical bonding strength of the metallized layer 4 and the pedestal 2 is not lowered, and therefore there is no possibility that this lowering affects adversely a sealing property and adhesion on the occasion of soldering. Accordingly, the impression of a negative voltage necessary for an anodic junction processing can be executed from the surface region 40.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a pressure sensor using a silicon chip on which a piezoresistor is formed as a displacement-electrical conversion element for pressure detection, and is particularly applicable to automobiles. The present invention relates to a semiconductor pressure sensor suitable for an absolute pressure sensor for engine control.

[Conventional technology]

BACKGROUND ART In recent years, systems for detecting and controlling intake pressure of the engine have come into practical use in automobile gasoline engines, etc., and for this reason, absolute pressure sensors have become widely used.

The absolute pressure sensor for detecting intake pressure is as follows:
Conventionally, semiconductor pressure sensors have been mainly used due to their reliability, small size, light weight, and cost.

By the way, the conventional technology for this semiconductor pressure sensor is, for example, as described in Japanese Patent Laid-Open No. 62-72178, a piezoresistive element is formed on one surface of a silicon chip formed in the shape of a diaphragm, and a displacement-electrical conversion element is formed. In this conventional technology, a glass member is interposed between the silicon chip and the metal pedestal, and anodic bonding is performed between the silicon and the glass in order to obtain the hermetic properties necessary for assembling the silicon chip. By using solder brazing bonding between glass and metal via a metallized layer, a physical bond can be obtained without using adhesives, and the necessary hermetic properties can be maintained. There is.

[Problem that the invention seeks to solve]

The above-mentioned conventional technology does not take into account the movement of sodium ions associated with anodic bonding, and has problems in maintaining necessary mechanical strength and sealing properties at the bonded portion between the glass member and the metal pedestal.

In other words, the anodic bonding method used to bond such a silicon member and a glass member utilizes the movement of ions within the glass member and uses an example of the bonding conditions: N2 atmosphere,
325 °C and an applied voltage of 1000 V), but when this is applied to the assembly of a semiconductor pressure sensor, a glass pedestal with a metallized layer formed on one joint surface is used, and the silicon chip that becomes the pressure sensing element is , the surface of the glass pedestal on which the metallized layer is not formed will be anodically bonded, and at this time, a positive voltage is applied to the silicon chip and a negative voltage is applied to the metallized layer, and the anode Will be combined.

Therefore, at this time, sodium ions (Na'') move within the glass pedestal, and sodium precipitates at the interface with the metallized layer, which is on the negative potential side.As a result, ripple-like formations occur on the metallized surface due to the precipitation of sodium. This may cause streaks or liquid stickiness to occur, and may also cause damage to the adhesion between the metallized layer and the glass pedestal.

For this reason, in the conventional technology, after anodic bonding and before proceeding to brazing the glass pedestal and metal pedestal, a series of cleaning operations are required to remove sodium on the metallized layer surface, which increases costs. Not only does it become difficult to maintain reliability, but the strength of the brazed joint between the glass pedestal and metal pedestal decreases due to a decrease in the adhesion of the metallized layer, and as mentioned above, it becomes difficult to maintain the necessary mechanical strength and sealing performance. The problem is the retention of

The purpose of the present invention is to obtain sufficient reliability at low cost,
It is an object of the present invention to easily provide a semiconductor pressure sensor that can be sufficiently applied to absolute pressure sensors for automobile engines that require high reliability.

[Means for solving problems]

The above purpose is to attach a part of the joint surface between the glass pedestal and the metal pedestal.
When a region where no metallized layer is present is provided and anodic bonding is performed, an electric field is applied between this region and the silicon chip.

[Effect]

During the anodic bonding process between the silicon chip and the glass pedestal, sodium ions move toward the interface with the electrode to which a negative voltage is applied, so no sodium precipitation occurs at the interface with the metallized layer, and therefore cleaning is possible. Even if sodium removal work such as treatment is not performed sufficiently, there is no risk of the strength of the metallized layer decreasing, and the sealing performance and mechanical strength are sufficiently maintained.

〔Example〕

EMBODIMENT OF THE INVENTION Hereinafter, the semiconductor pressure sensor according to the present invention will be explained in detail with reference to illustrated embodiments.

Fig. 3 shows an embodiment in which the present invention is applied to an absolute pressure sensor for controlling an automobile engine. A diaphragm-shaped silicon chip 1 is anodically bonded to a glass pedestal 2, and the glass pedestal 2 is further attached to a metal pedestal 9 by soldering via a metallized layer. A lead pin 12 is fixed, and a sensing member 10 is welded and fixed to this using a laser or the like; 14 is a wire that electrically connects the piezoresistor of the silicon chip l and the lead pin 12;
15 is a cap that covers the sensing member 10 and partitions the cavity 52 by fixing it to the base 13; 16 is a low melting point metal (Pb/S) welded to the cap 15 to vacuum-seal the interior of the cavity 52; This is a sealing solder consisting of n solder, etc.).

Therefore, by communicating the hole provided in the center of the metal pedestal 9 with the intake pipe of the engine, the intake air pressure passes through the hole 3 of the glass pedestal 2 and acts on the back surface of the silicon chip 1.
The difference between the vacuum pressure in the chamber 52 and the vacuum pressure in the chamber 52 is taken out from the lead pin 12 as an electric signal, and functions as an absolute pressure sensor.

Next, details of the sensing member 10 in this embodiment will be explained with reference to FIGS. 1 and 2.

First, in FIG. 1, a silicon chip 1 has a piezoresistive element formed by diffusion on one side and a diaphragm 100 thinned by forming a recess on the other side. Reference numeral 2 denotes a cylindrical glass pedestal, and a through hole 3 is provided in the center. Reference numeral 4 denotes a metallized layer, in which the vicinity of the through hole 3 is covered with a mask or the like at the center of one end surface of the glass pedestal 2, and a three-layer structure of a Tl thin film, a Ni thin film, and an Au thin film is coated with vacuum from the glass pedestal 2 side. It is formed by vapor deposition or sputtering, and therefore, a ring-shaped non-metalized region 40 is formed around the through hole 3. Reference numeral 5 indicates a steel ball that serves as an electrode member for voltage application, 6 an electrode member that also serves as a seat for the steel ball 5, 7 a jig made of quartz glass for insulation, and 30 a power source for anodic bonding.

When the silicon chip 1 and the glass pedestal 2 are anodically bonded, the electrode member 6, the steel ball 5, the glass pedestal 2, and the silicon chip 1 are placed in an insulating jig 7 made of quartz glass as shown in the figure. These are set one on top of the other in order, and then wired and heated so that a positive potential is applied to the silicon chip 1 and a negative potential is applied to the electrode member 6. Then, when the overall temperature reaches 325'C, a voltage (approximately 1000V) is applied from the power supply 30 to perform anodic bonding. In other words, the through hole 3 of the glass pedestal 2
A negative potential is applied to the region 40 near the metallized layer 4 through the steel ball 5, thereby causing sodium ions to gather only near the periphery of the through hole 3 in the region 40 where the metallized layer 4 is not provided, thereby performing anodic bonding. This is what we do.

FIG. 1 also shows the state of movement of mobile ions within the glass pedestal 2 caused by anodic bonding between the silicon chip 1 and the glass pedestal 2, and as is clear from this, the application of voltage during anodic bonding causes Positive sodium ions are evenly concentrated in the vicinity of the through hole 3, which is maintained at a negative potential by the steel ball 5 attached inside the region 40 where the metallized layer 4 of the glass pedestal 2 does not exist; The oxygen ions (0=) move evenly to the bonding interface with the silicon chip l. As a result, the silicon chip l and the glass pedestal 2 are firmly bonded by anodic bonding, and there is no precipitation of sodium at the interface between the glass pedestal 2 and the metallized layer 4. Since the mechanical adhesive strength of the pedestal 2 is not reduced, there is no possibility that the sealing performance, adhesive strength, etc. during solder bonding will be adversely affected.

After completing the anodic bonding process between the silicon chip 1 and the glass pedestal 2, the process proceeds to the solder bonding process with the metal pedestal 9, which will be explained below with reference to FIG.

In FIG. 2, 7 is a jig made of quartz glass, 8 is a solder sheet, and 9 is a metal pedestal, which is made of an Fe--Ni alloy having a coefficient of thermal expansion similar to that of the glass pedestal 2. Here, the jig 7 is simply a jig for positioning during soldering, and is not included in the sensing member 10.
A Ni plating layer 50 for solder bonding is applied to the surface. Note that the silicon chip 1 is anodically bonded as explained in FIG.

In the solder bonding process, each member is first set in a jig 7 made of quartz glass so that the metal pedestal 9, the solder sheet 8, and the glass pedestal 2 are stacked on top of each other in this order. these are,
Solder bonding is achieved by heating the solder sheet 8 to its melting point temperature. Note that the solder sheet 8 has A u / S n
Made of solder or Pb/Sn solder with a thickness of approximately 25 μm
sheets are used. And the temperature at the time of soldering is
The temperature is 320°C in the former case and 230''C in the latter case.

As explained in FIG. 1, in this embodiment, the metallized layer 4 is not affected by sodium ions even by anodic bonding, so solder bonding can be easily performed.
Since the sensing member 10 with sufficient mechanical strength and sufficient sealing performance can be obtained, high reliability can be easily maintained.

In addition, a series of cleaning operations such as removing sodium from the surface of the metallized layer 4 prior to solder bonding becomes unnecessary, the manufacturing time and process are shortened, and it is suitable for mass production, and a significant cost reduction can be expected.

Furthermore, since the adhesion of the metallized layer 4 to the glass pedestal 2 is not impaired, the reliability of the airtightness at the solder joint is sufficient, and in the embodiment shown in FIG. A highly reliable absolute pressure sensor without any leakage can be easily provided.

FIG. 4 shows another embodiment of the present invention, and the feature of this embodiment is that an electrode member for applying a negative potential for anodic bonding the silicon chip 1 to the glass pedestal 2,
In place of the steel ball 5 in the embodiment shown in FIG. 1, an electrode metal member 60 having a cylindrical convex portion in the center is used.

During the anodic bonding process, the electrode metal member 60, the glass pedestal 2, and the silicon chip 1 are set in the quartz glass jig 7 so as to be stacked in this order, and then the silicon chip 1 is placed on the positive side, and the member 60 is placed on top of each other in this order. The wires are wired and heated so that a potential that becomes negative is applied, a predetermined temperature is maintained, and a voltage is applied by the power source 30 to perform anodic bonding.

According to this embodiment, the surface of the glass pedestal 2 near the through hole 3 and the electrode metal member 60 come into surface contact, so that sodium ions move more easily than in the embodiment shown in FIG.

Furthermore, the end face of the through hole 3 of the glass pedestal 2 is less likely to be chipped.

FIG. 5 shows yet another embodiment of the present invention, and the feature of this embodiment is that on the end face of the glass pedestal 2 on which the metallized layer 4 is provided, a region 40 where the metallized layer is not formed. is located in a ring shape on the outer periphery, and accordingly, the electrode member 61 for anodic bonding is also formed in a ring shape. According to this embodiment, when anodic bonding is performed by applying a voltage as shown in the figure, the sodium ions move so as to gather uniformly on the outer circumference of the end surface of the glass pedestal 2, but at this time, according to this embodiment, Since the contact area between the glass pedestal 2 and the ring-shaped electrode member 61 for negative potential can be increased, sodium ions can move more easily than in the embodiment shown in FIG.

In both of the embodiments shown in FIGS. 4 and 5, precipitation of sodium at the interface between the glass pedestal 2 and the metallized layer 4 is suppressed, so there is no risk of deterioration in reliability.

Next, a more specific example of the anodic bonding process in the above-described assembly process of the sensing member 10 will be described in the sixth section.
This will be explained using figures.

In the embodiment shown in FIG. 6, a plurality of sensing members 10 can be processed simultaneously, and a disk-shaped jig 70 having a plurality of insertion holes is used as an assembly jig made of quartz glass. A weight electrode 62 having a shape similar to that of the embodiment shown in FIG. 4 is used for applying a negative voltage, 31 is an iron disc-shaped assembly board, and 63 is an electrode serving as a common terminal for applying a negative voltage. It is a board. A jig 70 is attached to this electrode plate 63.
Similarly, holes are provided at corresponding positions corresponding to the plurality of insertion holes formed in the hole.

During the anodic bonding process, a quartz glass jig 10 is fixed to an iron substrate 31, and into each of its insertion holes,
After setting the silicon chip 1 and the glass pedestal 2, the electrode plate 63 for applying a negative voltage is attached to the quartz glass jig 32.
This electrode plate 63 is fixed so as to match each insertion hole of the electrode plate 63, and the weight electrode 62 is dropped from above into each insertion hole of the jig 70 from each hole of the electrode plate 63,
A region 40 (
(see FIG. 4) so that the convex portion of the weight electrode 62 comes into contact with it. Then, heat it to a predetermined temperature, and as shown in the figure,
If voltage is applied from the power supply 30 with the substrate 31 being positive and the electrode plate 63 being negative, the silicon chip l and the glass pedestal 2 are anodic bonded, and the plurality of sensing members lO are anodic bonded simultaneously. be able to.

In the above embodiments, titanium and nickel were used as metallization N4 in order from the glass pedestal side.

A three-layer structure of gold is used, and as a result, the occurrence of solder joint defects due to surface oxidation can be sufficiently suppressed.

〔Effect of the invention〕

According to the present invention, the application of a negative voltage necessary for anodic bonding can be applied to a part of the end face of the glass pedestal where the metallized layer is to be provided, by providing a surface area where no metallized layer is present. Since no voltage is applied to the metallized layer during the anodic bonding process, sodium ions do not precipitate at the interface of the metallized layer, and the adhesion of the metallized layer, which is the base of the solder bond, is improved. As a result, sufficient mechanical strength and
In addition, a semiconductor pressure sensor with a high degree of sealing performance can be easily provided. Furthermore, since there is no need for a series of cleaning operations after anodic bonding, the operating time can be shortened and costs can be reduced.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram of an anodic bonding process in an embodiment of a semiconductor pressure sensor according to the present invention, FIG. 2 is an explanatory diagram of a soldering process, and FIG. 3 is an embodiment in which the present invention is applied to an absolute pressure sensor. The cross-sectional view of the example, FIG. 4 and FIG. 5 are respectively explanatory diagrams of anodic bonding processing in an embodiment of the present invention, and FIG. 6 is a case in which a plurality of sensing members are simultaneously subjected to anodic bonding processing according to an embodiment of the present invention. FIG. 1--------Silicon chip, 2--------Glass pedestal, 3--Through hole, 4--11--Metallized layer, 5--1111 Steel ball , 6------
-Electrode member, 7--Jig, 8--Solder sheet, 9--Metal pedestal, io--Sensing member. Fig. 1 1: Nurikon drying and whelk 5 nisshi-ru 2: nifusu 6 ゛ catty 6: duck r
5 cedar holes 3: 1 through hole 7: Kenka "Last 4"
:Nutarais “4o: Too
: '5' Iafura Ku 2nd figure 4o, Raizume 50 : Ni metal 1st layer 3rd layer +6 4th figure 5th figure 6th figure

Claims (1)

[Claims] 1. By using a glass pedestal, a pressure sensing element made of a silicon chip can be attached to a metal pedestal through anodic bonding between silicon and glass and a metallized layer between glass and metal. In a semiconductor pressure sensor, a surface area where no metallized layer is formed is provided on the joint surface of the glass pedestal and the metal pedestal, and an electrode brought into contact with the surface area and the pressure detection A semiconductor pressure sensor characterized in that the anodic junction is formed by an electric field generated by a voltage applied between elements. 2. The semiconductor according to claim 1, wherein the metallized layer has a three-layer structure, and each of the three layers has a composition of titanium, nickel, and gold in order from the glass pedestal side. pressure sensor.