JPS58102124A - Semiconductor pressure sensor - Google Patents

Abstract

PURPOSE:To prevent poor hermetical sealing and adverse effect of strain due to residual stress, by using a glass material which includes a filler and has a reversible property with respect to the repetition of the heating and fusing, as a bonding agent which bonds a pressure sensitive pellet and a seat. CONSTITUTION:The pressure sensitive pellet 11 comprising a piezoelectric resistance gage 13 and a diaphragm 12 is bonded to the silicon seat 14 by a glass bonding layer 15. A filler is mixed in the glass bonding layer 15. The glass bonding layer 15 comprises a glass material which has reversible property with respect to repetition of heating and fusing and has a thickness of 50mum-130mum. In this constitution, the thickness l of the glass bonding layer 15a is specified within the range of 50mum-130mum. Therefore decrease in bonding force due to the size of the filler element and the breakdown of the diaphragm due to the rise T of the glass bonding layer can be prevented.

Description

Detailed Description of the Invention @@0 Technical Field The present invention relates to a semiconductor pressure sensor having a diaphragm structure with high dose characteristics and high lI#ltl characteristics.

BACKGROUND TECHNOLOGY When a semiconductor crystal is strained by stress during pressure, its resistance value changes, which is known as the piezo effect.

Various semiconductor pressure sensors have been developed by effectively utilizing this piezo effect phenomenon, and by combining it with semiconductor XC technology in recent years, compact pressure sensors with superior performance have been realized.

1fg is a schematic diagram showing a semiconductor diffusion diaphragm type pressure sensor O structure developed for high-precision industrial use. This sensor consists of 10
At the center of the pellet 1 at the g+s mouth, approximately 4~
The diameter of the diaphragm is machined to a thickness of 7 Oam1i, and a diaphragm 7 ram 1 is provided, and a piezoresistance gauge S is provided by thermally diffusing boron (2) into a rectangular shape on the surface of this diaphragm i. have And this bellet 1 is stand 11
After being fixed on 44, the package jK was mounted,
It is interconnected to the electrode lead by a metal wire 6. In addition, the pipe r-mori, which is connected to the through-hole of the pedestal 40 and is thrown with sand, introduces fluid pressure to the diaphragm portion. The heavy pedestal 4 functions as a strain barrier to prevent O from the outside, especially from the package 5, from being transmitted to the vinyl resistance gauge 1.To, b, with this structure, -sO~
It has achieved a high performance of 0.211 FB over a wide temperature range of 85°C.

However, such a high fw industrial pressure sensor requires a special package structure as described above, and therefore its cost is extremely high. Not only Oku package,
Although the element part also uses silicon material, mass production is possible.
It has become commonplace to not take advantage of C technology. In addition, in recent years, there have been many requests for 4I to find p-semiconductor pressure in the development of microcomputers, but in this case, it is more important to lower the price than to improve the performance! Ii is covered.

Therefore, recently, low-cost semiconductor pressure sensors having the structures shown in BE(p) to BE(C) have been developed. In this Senna, one part of the pressure-sensitive diamond 7 and four parts of the pedestal shown in FIG. 1 can be mass-produced by using a silicon diffusion process. In Figure 3-), 4 Oguchi, 300s1
A 40 μm thick diaphragm 11 is formed in the center of the silicon pellet (1 thick silicon pellet) from the back side, and a diffused resistance strain gauge 11 is installed on the surface of this diaphragm 11.
is provided. These are constructed in a similar manner to that shown in FIG. 1, and are adapted to be sensitive to fluid pressures of 2 to 4 f/as' in the above animal. Therefore, Pellet 71 is mounted on a glass 15 on a pedestal 14 made of silicon.
The adhesive layer is 9, and the 9 through-holes are provided on this stand W114.
#6 The fluid pressure is introduced into the diaphragm 12. This pedestal 14, like the previous pedestal 4, prevents stress other than fluid pressure from being applied to the strain gauge IJ formed on the pellet II, and is designed to be as thick as possible. . In addition, generally through hole 1
- Due to limitations in processing technology, etc., a pedestal 14 is used. In the pressure sensor having such a structure, as shown in FIGS. 2(b), (c) and K, four pellets 11 are formed in a matrix on a silicon wafer li, and through holes 16 are formed in this silicon wafer IrK. The structure is manufactured by bonding nine wafer-shaped bases II via a glass cage and then cutting them into individual pellets at the position shown in the center of Itlml (C). In this case, Berrett's expansion device can be achieved using a single semiconductor device, which is almost the same as a conventional bipolar IC, and the diaphragm can also be formed by an etching technique using an alkaline S product. Due to this, the pressure is high? 011 writing fluency has improved significantly, and great progress has been made towards becoming a 70-year-old.

However, in order for this type of intercropping to be effective, the following conditions must be met. That is, as shown in 3rd IQ(b)K, it is necessary to airtightly bond the pellet wafer 110 to the base wafer IJ without deteriorating the device characteristics, and conventionally solder glass has been used solely from the viewpoint of creep characteristics. I'm here. Incidentally, in the structure shown in No. 111, since the pellet 1 and the base 4 are bonded individually for each element, the coefficient of thermal expansion of the adhesive is slightly different from that of silicon.
However, there is almost no risk of deterioration of the airtightness or the properties of the card.
. Therefore, Toshiba Hang Karasu 503, which has a thermal expansion coefficient of 80×10/'C1 and a working temperature of 1 s20° C., is used as the adhesive. In this case, even if consideration is given to the coefficient of thermal expansion of silicon, the permissible temperature of the wiring@go is
The above-mentioned soldering process is carried out with emphasis on the fact that the working temperature for glass bonding is lower than 50°C. At this time, the pellet IK strain stress is applied due to the difference in thermal expansion coefficient between the solder glass and silicon.
The thickness of the glass adhesive layer was reduced to 3.
Efforts are being made to ensure element characteristics by making the device as thin as possible and suppressing the strain stress as low as possible.

One point of the background art However, when bonding is performed in units of sea urchins as shown in FIG. 2(b), the coefficient of thermal expansion of solder glass as an adhesive becomes large. That is, first, since the bonding area is large, residual stress is generated locally in the sea urchin during bonding. Due to the influence of residual stress, when the pellet is cut from the P1 wafer, cracks occur in the glass bond and the airtightness is likely to occur. Since the residual stress is uniform, the above residual stress changes by 1 [K, and the temperature of the element Jf:I
The fI property deteriorates by 4iK. Moreover, as mentioned above, if the adhesive layer is made thinner in order to reduce the influence of the adhesive layer, the wafer itself has the disadvantage that it is likely to suffer from defects due to non-uniform thickness of the wafer itself.

Purpose of the Invention The present invention has been made in consideration of the above circumstances, and its purpose is to provide a practical method which is free from the influence of distortion due to &W stress during poor airtightness, and which is rich in quantitative properties. An object of the present invention is to provide a semiconductor pressure sensor having a diamond-shaped structure with high performance.

Summary of the Invention The present invention uses a filler as an adhesive for bonding a pressure-sensitive pellet and a pedestal made of a semiconductor material to glass, and has a thickness of 50# to 180 swr that is reversible to repeated heating and melting. It is characterized by the use of glass material.

Effects of the Invention Thus, if the base wafer and the wafer formed into pressure-sensitive pellets are bonded to each other using the glass material described above as an adhesive, even if the adhesive is cut into 11 pellets, the air in the glass bonding layer will be reduced. Problems such as IIB leakage and unbalanced strain due to residual stress will not occur, such as deterioration of element characteristics. Moreover, by stably bonding and fixing the pressure-sensitive pellet and the pedestal at zero, it becomes possible to fully exhibit the desired zero-zero characteristics of the pressure-sensitive pellet.

Further, by fully utilizing the above-mentioned mass production process rtao* characteristics, it is possible to mass produce semiconductor pressure sensors with high yield, and other great effects are achieved.

Example of invention ) DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

Semiconductor pressure sensors related to collective feeding are shown in Figure 2 ←) to (e)
It is manufactured according to the process shown in K and has a nine structure, but in particular, filler is mixed in the glass bonding between the pressure sensitive pellet 11 and the silicon pedestal 14, and the rhinoceros SOμ is reversible against repeated heating and melting. Ayano to 130#
ll O glass material, 8 electric solder glass (m name t
, s-0104) is used.

The effects achieved by using such a glass material as the glass adhesive 15 will be described below.

First, use a glass adhesive with a thickness of 30μSt - 1F at 9! In order to eliminate other problems during flipping, it is necessary to use a glass adhesive 15 that is close to the thermal a1 intensity of the silicon that composes the @p1 pressure-sensitive pellet 11. .

Therefore, the only way to lower the coefficient of thermal expansion of the required solder glass and make it almost equal to that of silicon is to mix filler. This is a comparison of the main characteristics of solder glass that does not contain any contaminants.

As shown in this table, in order to obtain solder glass that has a thermal expansion coefficient of 5Ox10°C @ 1 degree or less (81 = 30x1G/'C) and a single bonding operation of 560°C or less, , it is necessary to mix a filler.The size of the filler particles is 30 to 40 μm, and the specific gravity is very different from other components in the puffer glass. As such, Adhesive-15 cannot be formed by a precipitation method, and it is necessary to use, for example, a screen printing method or the like for its formation.

Therefore, solder glass mixed with a filler is cast in a casting medium, and a glass adhesive layer 15 is coated on the silicon pedestal I4 using a screen having mesh-like holes. At this time, unlike the conventional precipitation method, there is no risk that the glass adhesive @II will be partially separated into components due to the different specific gravity of tDK. Gang,
The thickness of the glass adhesive layer 15 can be precisely controlled by the thickness of the screen and the size of the mesh.
When bonding the silicon wafer 11 formed by forming the pressure-sensitive pellet 11 and the silicon pedestal 11 using the silicon pedestal 11, the following major conditions exist. One of them is 4, which is unique to solder glass with a lot of fill, and the other is O, which is blind to the pressure sensitive element (bellet 12) J11. The major condition that influences these is the thickness of the glass adhesive layer 15. The airtightness depends on this thickness.
The figure shows the airtightness after 111 was made according to the process described above and cut into individual element pellets.
Using a helium leak detector, those with a needle toothed quantity of 10-910-9 at/aec or less were considered good, and those with a helium leakage amount of less than 10-910-9 at/aec were considered defective, and the manufacturing yield was determined. It shows the characteristics with respect to the thickness.

Incidentally, what is shown in this third column is the characteristic when 8den glass L8-0104 and Toshiba No. SO3 are used as the glass adhesive 15. As shown by this characteristic, in Toshiba No. 503 solder glass, which has a larger coefficient of thermal expansion than silicon, the leakage yield is the highest when the thickness of the deposited layer 15 is 30-50 mm. Even if it is less than that,
Or even if it is more than that, the yield is reduced. 41, when the thickness of the plate 4115 is less than 30 seconds, it is considered that the yield rate decreases due to the flatness of the wafer.

If the tab is too thin, the glass adhesive layer 1j will collapse by 2m between the wafers 11.1a.
In the case of a thickness of 11 or more, the thermal expansion coefficient 1 is as described above.
This is thought to be due to glass adhesion-IIK tsutsugi occurring due to the 110 roof.

On the other hand, when using silicon and Nichiden Glass T, 5-0104 with a thermal expansion coefficient of a%/m, the
It is shown that by setting Oam or more, the data yield becomes constant and becomes very large. However, when the thickness of the adhesive layer 110 becomes as thin as 60 swr, the leakage yield rapidly decreases. This is mounted on the silicon pedestal 18.
Even if the glass adhesive layer is die-cut by pre-baking and then combined with the element wafer 1r to form the final product, it will take 70 hours to finish.
It is confirmed by K that NK is not done. This means that the filler particle O is extremely hot at sO ~ 40 sin 11 degrees, so this makes the i-las adhesion @1i
t) This is thought to be due to loss of adhesive strength. Taking these things together, it can be seen that if a filler is mixed in and nine-hender glass is used as the adhesive IJ, and the thickness is made to be .Oβ type or more, the leakage yield can be improved.

However, #Ik! Since there are conditions specific to pressure-sensitive elements as described above, even if we simply add glass adhesion (1it) to a thickness of 60mm or more as described above, it is expected that this alone will improve the manufacturing yield. It is not possible to do so, however, there are inherent limitations due to the chain construction of the device.

Figure jI4 shows glass adhesion @X that changes depending on the adhesion work.
The state of S is schematically shown, and the good state is also O.

In FIG. 4, numeral 12 indicates the diaphragm surface position before the bonding operation, and Ilb indicates the diaphragm surface position after the bonding operation. The column "1l=11" shows the glass adhesive layer before the bonding process, and the glass adhesive layer after the JJbti bonding process.

That is, now, 8-den glass L8-0104 mixed with filler is placed on the silicon pedestal 14 to a thickness of J (s=70J111
) K was applied, and this was temporarily heated at 400°C to bond the glass H.
Get the Xtt head. xzaK
The position of the diaphragm surface is as shown. After that, a pressure of about 20 t/aaM was applied to these O-separators, and N was added in this state.

When the solder glass adhesive layer is SS* heated to 460'C@ill in air, the thickness l/Ii of the glass adhesive 115b decreases as shown by tK in the figure. The glass adhesive extruded by this thickness reduction is I[, 4 holes 16
At the same time, some of it leaked out to 1 of 12 Hirodia 7 Rams.
Climb up along No. 11. The height T of this selvedge has the following relationship experimentally between the original thickness 11 of the glass-adhesive $IS turtle and the thickness t after adhesion.

r = il (J-s) + s 冨Ml- is written as follows *1ItWkO glass result 1llll
JbO size t needs to be 60s wealth or more.

However, because of this relationship, if the thickness l of the glass bonding t@SS* is increased before bonding, then
The amount T increases, which may destroy the diaphragm 11. Therefore, if the diameter of the diamond 7 is L, then in order to prevent the diamond 7 Tsumu I2 from being destroyed by the glass bonded steel, T: 2l-t(L). Must be praised.

Therefore, the diaphragm 12 is a silicon wafer J r
tHF, HNOs Oa combinationflK YoJ*strong 11+
, [formed by strong alkaline etching with OHK. In this case, in order to protect the silicone parts other than the diaphragm 12 from the above strong acid or strong alkali, the pressure is usually 81 mN.
+* is used as a mask, and even if this 811N4[ is used as %Alt, the depth L of the diaphragm 12 is at most 200 m1ali degree. Therefore, in order to prevent the diaphragm II from being destroyed, it is necessary to keep the thickness l of the glass adhesive layer 15 & to #<130 μm.

As described above, wafer J7 was mixed with filler and used with nine glass adhesives. When bonding JJ, what are the conditions to prevent the adhesive force from decreasing due to the size of filler particles, and what are the conditions for glass bonding @150cm? Diaphragm 1 by
10 Glass adhesion @II as a condition to avoid damage
It is necessary to set the thickness l to 50<1<, 13G (,5lift)O1.

Thus, by using a glass material with a limited thickness and a filler mixed in to keep the coefficient of thermal expansion low as a glass adhesive, P1 Q1! It becomes possible to mass-produce a semiconductor pressure sensor with good characteristics without causing damage to the device due to the application of the F-type adhesive on the surface, and with a high yield rate. Further, there is no unbalanced strain applied to the pellet from the glass adhesive layer, and the device characteristics can be fully exhibited. Thus here,
It is possible to provide a semiconductor pressure sensor with good characteristics and a practical structure.

It should be noted that the present invention is not limited to the above-mentioned actual implementation, and it is needless to say that it can be implemented with various modifications without departing from the gist of the invention.

[Brief explanation of the drawing]

Figure 1 is a schematic configuration diagram of a precision industrial pressure sensor 10, and Figures 2 (&) to (C) are diagrams for explaining the structure of a general-purpose expansion pressure sensor and its manufacturing process. FIG. 3 is a diagram showing the relationship between the leakage yield and the stiffness of the adhesive, and FIG. 4 is a diagram schematically showing the state of the glass adhesive layer. 11-Pellet, Jj-・Diamond 7 Tsum, 11-Piezo resistance gauge, 14-$/recon pedestal, 15-Glass adhesive layer, 16-Through hole. Client agent Patent attorney Takehiko Suzue 31plI!
I- Spear figure 3/I- Spear figure 4

Claims (1)

[Claims] A nine-thin diaphragm vi formed in the center of four semiconductor plates.
A pressure-sensitive pellet formed by forming a K diffusion resistance layer and a pressure-sensitive pellet having a through hole for introducing pressure in the center and cutting the zero strain. A base made of a semiconductor material bonded to glass with a peripheral wall thickness of s K, and a glass plate for bonding the base and the pressure-sensitive pellets contains a filler and is reversible against repeated heating. A semiconductor pressure sensor made of glass material with a thickness of s o sm to 180 mm.