JPH09145510A - Semiconductor mechanical quantity sensor and its manufacture - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a semiconductor mechanical quantity sensor having a sufficient bonding strength at an anodic bonded part and its manufacture. SOLUTION: The sensor has a semiconductor sensor substrate 3 where a sensitive part 31 is formed, a sensor base 1 of semiconductor, and a glass layer 2 interposed between the substrate 3 and the base 1 and bonded to the substrate 3 and the base 1. The glass layer 2 is formed of a glass thin plate anodically bonded to both the substrate 3 and the base 1. The glass thin plate 1 has a thickness of 20μm or larger. In order to obtain the sensor, the glass thin plate 2 is anodically bonded to the base 1, ground and reduced in thickness and then anodically bonded to the substrate 3. Since the sufficiently thick glass thin plate 2 is anodically bonded to the base 1 and the substrate 3 with a sufficient voltage applied, the bonded part is increased in reliability and a yield is improved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor type mechanical quantity sensor for measuring a pressure sensor, an acceleration sensor, an angular velocity sensor and the like and a manufacturing method thereof, and belongs to the technical field of semiconductor sensors.

[0002]

2. Description of the Related Art As a conventional technique relating to a semiconductor type mechanical quantity sensor, for example, there is an "integrated pressure sensor" disclosed in Japanese Patent Laid-Open No. 7-3380. This is manufactured by forming a thin film of borosilicate glass on one surface of a pedestal made of silicon by a sputtering method, and anodic bonding the pedestal and a silicon substrate having a pressure sensitive portion through this thin film.

[0003]

In the above-mentioned prior art,
Although sputtering is used as a means for forming a glass thin film, the thickness of the glass thin film that can be formed by sputtering is practically at most about several μm. Therefore, the dielectric breakdown voltage is 5 × even if the dielectric breakdown voltage is high.
Considering that it is about 10 ⁵ V / cm = 5 × 10 V / μm, it is about 200 to 300 V at most.

When the applied electric field exceeds the breakdown voltage of the material and a discharge phenomenon occurs, a hole is formed in the glass layer or the silicon bonded to the glass layer, and the chip becomes a defective product. This is inconvenient because the yield is poor. Therefore, if you consider the thickness of the glass thin film formed by sputtering and the dispersion of components, and when you consider the safety margin,
The voltage that can be applied during anodic bonding is at most about 50V.

Generally, when the anodic bonding between the glass and the silicon substrate is performed at a low applied voltage of about 50 V, the bonding takes a long time and good bonding is not desired. This is because the potential difference acting on the interface between the glass surface and the silicon surface does not become sufficiently large at a low applied voltage, so that the movement of oxygen ions from SiO ₂ in the glass layer into the Si crystal in the silicon substrate is not sufficient. is there. Therefore, the conventional technique has a disadvantage that the yield rate of the product is low due to incomplete airtightness or insufficient bonding strength at the anodic bonding portion.

Therefore, the inventors have noticed that the above-mentioned inconvenience occurs because the thickness of the glass layer (thin film) is thin, and the glass layer having a sufficient thickness (thus having a high dielectric breakdown voltage). The idea was to provide a (thin plate) between the substrate and the pedestal. That is, it is an object of the present invention to provide a semiconductor type mechanical quantity sensor in which the anodic bonding portion has a sufficient bonding strength, and a manufacturing method thereof in which complete anodic bonding is performed in a relatively short time. .

[0007]

Means for Solving the Problems and Their Functions and Effects In order to solve the above problems, the inventors have invented the following means. [Device Invention] (First Means) The first means of the present invention is the semiconductor mechanical quantity sensor according to claim 1.

Here, it is ideal that the substrate and the pedestal are formed of the same semiconductor material for the purpose of making the thermal expansion coefficients the same, and that the crystal planes of the two also have the same orientation. Yes, but this is not a mandatory requirement. That is, if the thermal expansion coefficients are substantially the same, the substrate and the pedestal do not necessarily have to be formed of the same semiconductor material.

Further, the mechanical quantity mentioned here indicates pressure, acceleration, angular velocity and the like. Therefore, the sensing unit corresponds to the diaphragm structure when the observed amount is pressure and the cantilever structure when the observed amount is acceleration or angular velocity. The substrate, the glass thin plate, and the pedestal may be in wafer units or chip units.

In the present means, the glass layer interposed between the semiconductor sensor substrate and the sensor pedestal and anodically bonded to them is not a thin film (thickness up to several μm) but a thickness of several tens μm or more. Is formed from a thin plate having. The thin glass plate is anodically bonded to both the substrate and the pedestal, and is interposed between the two for the purpose of indirectly bonding the substrate and the pedestal.

Since the dielectric breakdown voltage of a glass thin plate having a thickness of several tens of μm or more reaches several hundred V or 1,000 V or more, when the glass thin plate is anodically bonded to the pedestal or when it is anodically bonded to the substrate. Also, it becomes possible to apply a sufficiently high applied voltage. Therefore, a large potential difference is generated at the interface between the glass and the semiconductor during anodic bonding, and many oxygen ions move to firmly bond the glass and the semiconductor (substrate or pedestal).

Therefore, according to the present means, the anodic bonding between the substrate and the pedestal and the glass thin plate can be carried out quickly and completely. Therefore, there is an effect that the bonding strength at the anodic bonding portion becomes sufficiently strong and the airtightness is kept high. As a result, there is also an effect that the yield rate in the process of anodic bonding in manufacturing the semiconductor mechanical quantity sensor is improved.

In addition, since an expensive sputtering apparatus is not required for forming the glass layer and the glass layer can be produced by a small-scale and inexpensive manufacturing facility, the product price can be kept relatively low. (Second Means) A second means of the present invention is a semiconductor mechanical quantity sensor according to the second aspect.

According to this means, the thin glass plate has a thickness of 20 μm.
As described above, the withstand voltage is about 1000 V or higher, and the applied voltage of 400 V can be easily applied even with a safety margin. Therefore, a sufficient voltage can be applied at the time of anodic bonding to quickly and completely perform anodic bonding. Therefore, according to this means, in addition to the effect of the first means, the glass layer is sufficiently firmly anodically bonded to both the pedestal and the substrate, so that the robustness and airtightness are improved and the product This has the effect of improving the yield rate.

(Third Means) A third means of the present invention is a semiconductor dynamic quantity sensor according to a third aspect. In this means, an upper limit is set on the thickness of the glass thin plate. This is because when the sensor has a pressure introducing hole penetrating the pedestal and there is a possibility of submergence and freezing, even if the pressure introducing hole is blocked by freezing, a large amount of water Has a function of preventing the gap from being left between the closed portion and the sensor sensing portion. This is because, if a large amount of water remains, the volume expansion that occurs when the water freezes exceeds the elastic limit of the semiconductor sensor substrate, causing the insensitivity portion to burst.

For example, when a thick glass thin plate (for example, 300 μm) is used without the limitation of this means, the glass material has a lower thermal conductivity than the semiconductor material (Si), and therefore the vicinity of the glass thin plate during freezing. A large amount of water is left behind. When this blockage water freezes, its volume expansion exceeds the elastic limit of the semiconductor sensor substrate, and the sensing portion bursts. On the contrary, if the glass thin plate having a thickness of 150 μm, which is the limit of the present means, is sandwiched between the semiconductor sensor substrate and the semiconductor sensor pedestal and anodically bonded to the both, the effect of the glass having low thermal conductivity is exerted. There is little, and the area near the sensing area freezes relatively quickly. Therefore, the amount of blockage water remaining in the vicinity of the sensing portion after the pressure introducing hole is frozen is small, and the volume expansion that occurs during the freezing is also small, so that the sensor only deforms within the elastic limit, and the sensing portion Not destroyed. Of course, after thawing, the sensor of this means restores the sensor function.

Therefore, according to this means, in addition to the effect of the first means, it is possible to provide a semiconductor mechanical quantity sensor which recovers the sensor function after thawing even when used in an environment where it is submerged and freezes. There is an effect. (Fourth Means) A fourth means of the present invention is a semiconductor mechanical quantity sensor as set forth in claim 4.

In the present means, a thin glass plate having a difference in thermal expansion coefficient within 10% is anodically bonded to the semiconductor material forming the substrate and the pedestal. Therefore, the occurrence of thermal stress at the joint due to temperature changes during operation of the semiconductor mechanical quantity sensor is reduced to the extent that there are no problems such as cracks or peeling. Therefore, according to this means, the first
In addition to the effect of the means, there is an effect that it is possible to provide a semiconductor type mechanical quantity sensor that is more resistant to thermal stress.

[Invention of Manufacturing Method] (Fifth Means) A fifth means of the present invention is a method of manufacturing a semiconductor mechanical quantity sensor according to a fifth aspect. In this means, the first
In the anodic bonding step and the second anodic bonding step, the thin glass plate is anodically bonded to the substrate and the pedestal on both sides to manufacture a semiconductor mechanical quantity sensor.

Therefore, according to the present means, it is not necessary to use an expensive and large-scale sputtering device to form the glass layer sandwiched between the substrate and the pedestal, and the semiconductor type mechanical quantity sensor can be manufactured with relatively inexpensive equipment. The effect is that it will be possible. (Sixth Means) A sixth means of the present invention is a method for manufacturing a semiconductor mechanical quantity sensor according to claim 6.

In this means, the thin glass plate is first anodically bonded to the pedestal, and then anodically bonded to the substrate. When the semiconductor mechanical quantity sensor has a ventilation hole (pressure introduction hole) such as a pressure gauge or a differential pressure gauge, if the thin glass plate is joined to the pedestal, it communicates with the pressure sensitive portion of the sensor substrate. This is convenient because the vent holes can be easily opened at once.

On the contrary, if the glass thin plate is anodically bonded to the substrate first, a part of the glass thin plate which is not backed by the substrate is produced, which makes the handling difficult. Further, when the thin glass plate is anodically bonded to the pedestal, electric charges do not sufficiently flow to a portion of the substrate where there is no backing, which may cause a problem in the anodic bonding. Therefore, according to the present means, in addition to the effect of the fifth means, there is an effect that the above inconvenience can be avoided and the manufacturing of the semiconductor mechanical quantity sensor is facilitated.

(Seventh Means) A seventh means of the present invention is a method for manufacturing a semiconductor mechanical quantity sensor according to a seventh aspect. In this means, since there is a thinning step of reducing the thickness of the glass thin plate between the first anodic bonding step and the second anodic bonding step,
In the first anodic bonding process, a glass thin plate that is sufficiently thick and easy to handle is used. Then, in the second anodic bonding step, the thickness of the glass thin plate has already been sufficiently reduced in the thinning step, so in the semiconductor mechanical quantity sensor, the substrate and the pedestal are bonded by the sufficiently thin glass thin plate.

Supplementally, it is desirable that the glass layer sandwiched between the pedestal and the substrate is as thin as possible without impairing the dielectric breakdown voltage, because thermal stress is less likely to occur on the pedestal and the substrate. On the other hand, a thin glass sheet is too fragile and difficult to handle. Therefore, if a relatively thick glass thin plate is ground and thinned while being bonded to a pedestal, for example, it is backed by the pedestal and reinforced so that it is easy to handle. That is, a relatively thick glass thin plate that is easy to handle is used at the beginning of manufacturing, and thinning is performed in a state of being backed and reinforced by anodic bonding to reduce thermal stress.

Therefore, according to the present means, in addition to the effect of the fifth means, it is possible to use a relatively thin glass thin plate which is hard to break and easy to handle and is easy to manufacture, and is a thin glass layer with little thermal stress. It is possible to manufacture a semiconductor type mechanical quantity sensor in which a substrate and a pedestal are anodically bonded. (Eighth Means) An eighth means of the present invention is a method for manufacturing a semiconductor mechanical quantity sensor according to claim 8.

In this means, the applied voltage at the time of anodic bonding is 4
Since it is regulated to be not less than 00V, an extremely strong, airtight and highly reliable anodic bonding surface is formed. Therefore, according to this means, in addition to the effect of the fifth means, it is possible to manufacture a highly reliable semiconductor mechanical quantity sensor with a very low probability of occurrence of a failure due to a failure of the anodic bonding surface. There is.

(Ninth Means) A ninth means of the present invention is a method for manufacturing a semiconductor mechanical quantity sensor according to a ninth aspect. In this means, when the pedestal is joined to the stem (base) by soldering, the solder having a low melting point (220 ° C. or less) is used, so that the residual stress generated by the heat during the joining is small. Therefore, variations in the output voltage of the semiconductor type mechanical quantity sensor, which is a product, are reduced, and trimming and output adjustment are facilitated. As a result, a sensor with stable quality can be manufactured by reducing the number of steps in the adjustment process.

Therefore, according to this means, in addition to the effect of the fifth means, there is an effect that it is possible to provide a semiconductor dynamic quantity sensor with less variation in sensor output voltage at a lower cost. (Tenth Means) The tenth means of the present invention is a method for manufacturing a semiconductor mechanical quantity sensor according to claim 10.

According to the present means, the wettability of the solder is remarkably improved by metallizing the bonding surface of the pedestal made of a semiconductor having poor solder wettability. That is, titanium (Ti), nickel (Ni), and gold (Au) layers are formed by vapor deposition from the lower layer on the bonding surface of the semiconductor pedestal. Here, the Ti vapor deposition film has an action of improving the adhesion between the pedestal and the Ni vapor deposition film, and the Ni vapor deposition film has an action of improving the adhesion between the Ti vapor deposition film and the Au vapor deposition film. The Au vapor deposition film has a function of preventing oxidation of the Ni vapor deposition film and a function of improving solder wettability.

Therefore, according to this means, in addition to the effect of the ninth means, the pedestal is firmly joined to the stem and high airtightness is maintained even when soldering with a low melting point solder. is there.

[0031]

[Example 1]

(Semiconductor type mechanical quantity sensor of Embodiment 1) Embodiment 1 of the present invention
As shown in FIG. 1 in a state before dicing (separation), the semiconductor mechanical quantity sensor as described above is configured by bonding a sensor pedestal 1, a glass layer 2 and a semiconductor sensor wafer (substrate) 3 in layers.

The sensor pedestal 1 is made of a flat plate of silicon single crystal having a thickness of 2 mm, and is provided with through holes 10 having a cylindrical inner peripheral surface at predetermined intervals. On one flat surface (upper surface in the figure) of the sensor pedestal 1, a glass layer 2 made of a thin plate of borosilicate glass (trade name Pyrex) having a thickness of 150 μm.
However, it is airtightly and strongly anodically bonded. The glass layer 2 has a through hole continuous with the through hole 10 of the pedestal 1.

The semiconductor sensor wafer 3 is made of a flat plate of silicon single crystal made of the same material as the pedestal 1 (the thermal expansion coefficient is also the same), and the sensing portion 31 is formed coaxially with the through hole 10.
The sensing unit 31 is a diaphragm serving as a pressure sensor, and a strain gauge (not shown) or the like is attached thereto to function as a sensor. Thickness of sensor wafer 3 (thickness of thick portion 32)
Is 300 μm, and the thickness of the sensitive portion (thin portion) 31 is 1
2 μm. The sensitive portion 31 is formed by removing the material from one surface (lower surface in the figure) of the sensor wafer 3.

The sensor wafer 3 is hermetically and strongly anodically bonded to one surface (lower surface in the drawing) of the thick portion 32 and to one surface (upper surface in the drawing) of the glass layer 2 described above. That is, the thin glass plate 2 is anodically bonded to both the wafer 3 and the pedestal 1 on both sides. Therefore, the sensor wafer 3 and the sensor pedestal 1
Are indirectly bonded to each other via the glass layer 2 made of a thin glass plate, and the recessed portion of the sensitive portion 32 of the wafer 3 communicates with the through hole 10.

In the sensor having the above structure, the glass layer 2 is initially formed by anodically bonding a glass thin plate having a thickness of 500 μm to the pedestal 1. Thereafter, the thin glass plate is polished to reduce its thickness to 150 μm, and then anodically bonded to the wafer 3. The coefficient of thermal expansion of the thin glass plate 2 is approximately the same as the coefficient of thermal expansion of the silicon single crystal forming the wafer 3 and the pedestal 1, and the difference in coefficient of thermal expansion between them is within ± 10%. It has settled down.

(Manufacturing Method of Embodiment 1) The manufacturing method for manufacturing the above-mentioned semiconductor type mechanical quantity sensor of this embodiment is as shown in FIG.
As shown in (a) to (e), the manufacturing process includes two anodic bonding processes. That is, first, referring to FIG.
As shown in (a), a disk-shaped glass thin plate having the same diameter and a thickness of 0.5 mm is formed on one surface 11 of a disk-shaped semiconductor sensor base 1'made of a silicon single crystal having a diameter of 100 mm and a thickness of 2 mm. The one surface 21 of 2'is joined.

In this first anodic bonding step, as shown in FIG. 2B, the base 1'and the glass thin plate 1'are sandwiched between the carbon jigs 5 and 6, and the bonding surfaces 1 are bonded to each other with a predetermined pressing force.
1, 21 were crimped. In this state, 350-400 °
The temperature was raised to C, and a voltage of about 400 to 1000 V was applied from the DC power supply 9 for a predetermined time, so that the base 1'and the glass thin plate 1 'were firmly anodically bonded to each other. At that time, FIG.
As shown in (b), a relatively positive voltage was applied to the base 1'and a negative voltage was applied to the glass thin plate 1 '.

The base 1'and the glass thin plate 2'after the first anodic bonding step are integrally bonded to form a laminated plate 12, as shown in FIG. 2 (c). The plywood 12 has
The through hole 10 is punched and the thin glass plate 2'is thinned. In the boring process, a plurality of through holes 10 are opened in a grid pattern at predetermined intervals by ultrasonic honing.

In the thinning step, the glass thin plate 2'is ground in two steps and its thickness is reduced from 500 μm to 150 μm.
reduce to m. That is, the glass plate 2'is lapped to a thickness of 180 μm at one end and further polished to a thickness of 150 μm. The thickness of the glass thin plate 2 after the thinning process and its accuracy are 150 μm ± 20 μm
It is. By thinning the glass thin plate 2, it is not necessary to apply a high applied voltage (with a risk of vacuum discharge in the second anodic bonding process described later), and at the same time, generation of thermal stress can be suppressed. .

Through the above steps, as shown in FIG.
A laminated plate 12 having the thin glass plate 2 and the through hole 10 is formed. The sensor wafer 3 is placed on the surface of the laminated plate 12 on which the glass layer 2 is formed, in an aligned manner, and anodically bonded. That is, in the second anodic bonding process, as shown in FIG.
One surface of the laminated plate 12 is pressure-bonded to the bonding surface 22 of the glass layer 2 of the laminated plate 12 and is anodically bonded. Here, the pressing force and the applied voltage are applied by the carbon jig 7 and the stainless jig 8 that hold the laminated plate 12 and the wafer 3 therebetween. The temperature at this time is raised to 350 to 400 ° C., and the voltage applied by the DC power supply 9 is 400 to 1000V.

At this time, a relatively positive voltage was applied to the wafer 3 and a negative voltage was applied to the laminated plate 12 composed of the pedestal 1 and the glass thin plate 2. The stainless jig 8 is formed in such a shape that only the thick portion 32 is in contact with the thin portion 31, which is the sensitive portion of the wafer 3, so that the pressing force and the applied voltage are not applied. In the second anodic bonding process, when a high voltage is applied, a discharge is generated in the through hole 10 and the sensing unit 31
There is a problem that the material is damaged, but the inventors have already developed a technique for avoiding this inconvenience (Japanese Patent Application No.
-164169).

By the above manufacturing method, the above-mentioned semiconductor type mechanical quantity sensor (see FIG. 1) is manufactured, and if necessary, a strain gauge or the like is added and then cut out for each sensor unit to complete. To do. Depending on the case, it may be used as a one-dimensional sensor array or a two-dimensional sensor array having a plurality of through-holes 10 and sensing portions 31 without being separated into individual sensor units.

(Effects of Embodiment 1) As described above in detail, the following effects are exerted in the semiconductor mechanical quantity sensor of the present invention and the manufacturing method thereof. First, since the glass layers 2 ', 2 are sufficiently thick in the first anodic bonding step and the second anodic bonding step, the anodic bonding with the pedestal 1 and the wafer 3 is sufficiently strong, and the product yield is high. The effect is that the rate becomes extremely high.

Here, the dielectric breakdown voltage per unit thickness of quartz glass is 20 to 40 [kV / mm] (School of Science), and borosilicate glass is 3 × 10 ⁴ [V / m].
m]. Calculating on the basis of this, in the first anodic bonding step, the dielectric breakdown voltage of the glass thin plate 2 ′ having a thickness of 0.5 mm is 15000 V, and in the second anodic bonding step, the glass layer having a thickness of 150 μm = 0.15 mm. The dielectric breakdown voltage of No. 2 reaches 4500V. Therefore, 400-1
Since an applied voltage of about 000 V does not cause dielectric breakdown, unlike a glass thin film (thickness of about 4 μm) formed by conventional sputtering, a sufficiently high applied voltage is applied during anodic bonding to form an extremely strong bond. Done.

The bonding strength of anodic bonding is evaluated by a tensile fracture test. In the tensile fracture test, as shown in FIG. 3, the semiconductor mechanical quantity sensor 123 joined and held on the base surface G is pulled by the hook H with the metal fitting N joined and fixed to the surface of the wafer 3 by the adhesive A. The tensile force F increases until it is destroyed. The results of this test,
Wafer 3 forming one end of sensor 123 and pedestal 1 forming the other end
Somewhere in between, the sensor 123 breaks. Base surface G
Of the vertical projected area of the fracture surface with respect to
The ratio of 2 depends on the applied voltage during anodic bonding.

That is, as shown in FIG. 4, when the applied voltage is 200 V, 40% (area ratio) of the fracture surface is taken as the bonding surface 2.
1, 22 occupy, but at 300V, it drastically decreases to about 2%,
It is 0% at 400 V or higher. The number of samples in this test is about 10 for each voltage value. Therefore, in this embodiment, since 400 to 1000 V is applied in the first anodic bonding process and the second anodic bonding process, there is almost no defect in the anodic bonding portion, and the yield rate is extremely high.

Secondly, there is an advantage that the manufacturing facility is small and inexpensive. This is because unlike the prior art, a large-scale and expensive sputtering device is not required. Therefore, there is an effect that the product price can be kept low. Thirdly, there is an effect that a semiconductor-type mechanical quantity sensor that is easy to manufacture and resistant to temperature changes and highly reliable can be obtained.

That is, before the first anodic bonding step, the thickness of the glass thin plate 2 ′ alone is relatively large at 0.5 mm, and the glass thin plate 2 ′ is hard to break, so that it is easy to handle. The thin glass plate 2'is reduced in thickness to 150 μm in the thinning process after being bonded to the pedestal 1 in the first anodic bonding process and backed to eliminate the risk of cracking. Therefore, a large thermal stress does not occur between the thin glass plate 2 and the pedestal 1 and the sensor wafer 3 made of silicon, and there is an effect that the temperature becomes strong and the reliability is improved.

(Modification 1 of Example 1) In the above example, borosilicate glass was used as the material of the glass thin plate 2, but various glasses such as alumina / silicate glass may be used. At that time, in order to suppress the thermal stress generated between the glass thin plate 2 and the pedestal 1 and the wafer 3 to a low level,
The coefficient of thermal expansion of the material forming the thin glass plate 2 should be matched to the coefficient of thermal expansion of the silicon single crystal material forming the pedestal 1 and the wafer 3 as much as possible. It is desirable that the difference between the two thermal expansion coefficients be within ± 10%.

(Variation 2 of Embodiment 1) In the thinning step described above, the thickness of the glass thin plate 2 may be reduced by various other grinding and polishing methods. Alternatively, the thickness of the glass thin plate 2 may be reduced by etching with hydrofluoric acid or another method. Regarding these processing methods in the thinning process, it is desirable that the optimum selection be made in consideration of various evaluation items such as manufacturing cost and reliability.

(Modification 3 of Embodiment 1) In the above embodiment, the through hole 10 is provided on the assumption of a differential pressure gauge.
The through hole 10 is often not provided in a rate (angular velocity) sensor, an absolute pressure gauge, an acceleration sensor, or the like. Further, although the sensing unit 31 is a diaphragm for pressure measurement, in the case of a sensor that measures acceleration, angular velocity, etc.,
The sensitive portion is formed as a cantilever.

(Variation 4 of Embodiment 1) In the above embodiment, the semiconductor mechanical quantity sensor is formed using the wafer 3 as the substrate. However, the semiconductor-type mechanical quantity sensor of the present invention can be manufactured by a manufacturing method having the same processing steps as the above-described manufacturing method, using a substrate that has already been diced (separated) into a chip shape. That is, the semiconductor mechanical quantity sensor of the present invention can be manufactured not only on a wafer basis but also on a chip basis.

Second Embodiment (Pressure Sensor of Second Embodiment) As shown in FIG. 5, a semiconductor type mechanical quantity sensor according to a second embodiment of the present invention has a stem 6 ′.
And a sensor body 1234 joined to the stem 6 ′.

Here, the stem 6'is made of an iron-based 42 alloy, and the joint surface with the sensor body 1234 is plated with gold (thickness 1500 angstrom). The through hole 10 of the sensor body 1234 is provided at the center of the stem 6 ′.
A pressure introducing hole 60 communicating with
60 is filled with silicone oil 9'to prevent infiltration of water and the like. On the other hand, the thin portion 31 forms a diaphragm in the central portion of the semiconductor sensor wafer 3. A plurality of Al—Si wires 8 ′ extend from a sensor circuit (not shown) having a gauge resistance region formed on the diaphragm and are connected to the surrounding terminals 7 ′, respectively. The terminal 7'is a metal rod supported by the stem 6 ', and is fitted into a through hole (not shown) of the stem 6', and thereafter, a low melting point glass for sealing (not shown) Insulated and sealed.

The main characteristics of the pressure sensor of this embodiment are summarized in the following three points. That is, firstly, the stem 6 '
This is that the metal thin film 4 consisting of three layers is formed on the surface (joint surface) of the sensor body 1234 to be soldered to. Secondly, the melting point of the solder 5'used for joining to the stem 6'is low and is 220 ° C or lower. Thirdly, the thickness of the glass thin plate 2 interposed between the semiconductor sensor wafer 3 and the sensor pedestal 1 so as to be bonded to both is 1
It is limited to 50 μm or less. These features will be described in detail below.

The three-layer metal thin film 4 is formed on the end surface of the sensor pedestal 1 facing the semiconductor sensor wafer 3. The metal thin film 4 is formed on the surface of silicon forming the sensor pedestal 1 by vacuum vapor deposition of titanium, nickel, and gold in this order. The thickness of the vapor-deposited film is 3000 angstroms for the titanium layer, 6000 angstroms for the nickel layer, and 1500 angstroms for the gold layer, for a total of about 10500 angstroms.

Of the above layers, the thickest is the nickel layer, and the titanium layer has the function of improving the familiarity between the silicon of the pedestal 1 and the nickel layer. On the other hand, the outermost gold layer has the functions of preventing oxidation of the nickel layer and improving solder wettability. Therefore, since the above three layers are formed in an overlapping manner, the adhesion to the sensor base 1 made of silicon is good (it does not easily come off), and it is difficult to oxidize even if it is exposed to air, etc. The joint surface is formed by the metal thin film 4 on which the solder 5'for use in the soldering process is good.

The joint surface of the pedestal 1 formed as described above and the joint surface of the gold-plated stem 6'have good solder wettability and the low melting point solder 5 having a melting point of 220 ° C. or less. It is airtightly and firmly joined by. More specifically, a solder having a eutectic composition of Sn63-Pb37 is used as the solder 5 ', and its melting point is 183 °.
It is about C.

The glass thin plate 2 has a thickness of 1 as in the first embodiment.
It is made of borosilicate glass of 50 μm and is anodically bonded to both the semiconductor sensor wafer 3 and the sensor pedestal 1. (Manufacturing Method of Embodiment 2) In the manufacturing method of the pressure sensor of the present embodiment, as shown in FIG. 6, the pressure sensor is manufactured through a plurality of steps. The feature of this manufacturing method is that the metal thin film 4 consisting of three layers is formed on the lower surface of the sensor pedestal 1 made of silicon by vapor deposition, and the pedestal 1 is formed at a relatively low temperature by using the solder 5 ′ having a low melting point. And the point of joining to the stem 6 '.

In this manufacturing method, first, in the same manner as in Example 1, the sensor pedestal 1 made of silicon and the glass thin plate 2 are anodically bonded in the first anodic bonding step, and then the through holes 10 are punched and the glass is thinned. To reduce the wall thickness. The above processing is performed on a wafer-by-wafer basis, and as shown in FIG. 6A, a pedestal 1 made of silicon in which a glass thin plate 2 having a thickness of 150 μm is bonded to one end face is intermediately manufactured.

Here, the pedestal 1 is placed in a heat treatment furnace,
Perform an annealing process. That is, the internal stress due to residual strain from the pedestal 1 and the thin plate 2 is reduced by raising the temperature and maintaining the temperature in the furnace at 450 ° C. for 60 minutes and then gradually cooling. Next, a metallization process is performed. That is, a titanium vapor deposition film layer having a thickness of 3000 angstroms, a vapor deposition film layer of nickel having a thickness of 6000 angstroms, and a vapor deposition film layer of gold having a thickness of 1500 angstroms are uniformly formed on the other end surface of the pedestal 1 by vacuum vapor deposition. The above three-layer vacuum vapor deposition is sequentially performed without returning the pressure in the vacuum tank to atmospheric pressure on the way. After completing the metallization process,
As shown in (b), a Ti / Ni / Au thin metal film 4 is formed on the other end surface of the pedestal 1. In the sputtering, metal molecules and the like adhere to the inner peripheral surface of the through hole 10 and the like, which is inconvenient, but the vacuum vapor deposition as in the present embodiment is unlikely to cause such a problem.

Thereafter, a second anodic bonding process is performed to bond the sensor wafer 3 and the glass thin plate 2 of the pedestal 1 to each other as shown in FIG. 6 (c). Then, as shown in FIG. 6D, a half-cutting step is performed in which a groove H having a depth from the sensor wafer 3 to the middle of the pedestal 1 is carved vertically and horizontally. A wafer trim process is performed in a state of being half-cut (no distortion or stress is transmitted from the adjacent sensor). That is, FIG.
As shown in (e), a predetermined position of the sensor wafer 3 is irradiated with a laser to change the electric resistance in the material of the sensor circuit (not shown) to adjust the sensor characteristics.

After the wafer trim step, the pedestal 1 is separated along the above-mentioned groove H, and a dicing cut step for forming each independent sensor chip 1234 is performed as shown in FIG. 6 (f). Finally, a stem joining step of joining each sensor chip 1234 to the stem 6 ′ with the low melting point solder 5 ′ (Sn63-Pb37) is performed. At that time, as described above, Ti
A metal thin film 4 of / Ni / Au is formed on the joint surface of the pedestal 1, and the corresponding joint surface of the stem 6'is gold-plated (thickness 1500 angstrom).
Therefore, since the joint surface of the pedestal 1 and the joint surface of the stem 6 ′ are covered with a gold thin film that has excellent solder wettability and is hard to oxidize, extremely good joint can be achieved even with the low melting point solder 5 ′. . For the same reason, the airtightness of the joint between the pedestal 1 and the stem 6 ′ can be extremely high.

After the main steps are completed, wire bonding between the sensor circuit (not shown) and the terminal 7'and filling of the internal space such as the through hole 10 through the pressure introducing hole 60 with the silicone oil 9 ' The pressure sensor of this embodiment described above (see FIG. 5) is manufactured. It should be noted that the silicone oil 9'determines whether to be filled or not depending on the necessity. (Effects of Embodiment 2) The pressure sensor as the semiconductor mechanical quantity sensor of this embodiment has the above-mentioned configuration and is manufactured by the above manufacturing method. Therefore, in addition to the effects of Embodiment 1,
The following excellent effects are exhibited.

First, the glass thin plate 2 has a thickness of 150 μm.
Since it is limited to the above, even if the silicone oil 9 ′ is not used, it can withstand the freezing of water that has entered the internal space of the pressure introducing hole 60,
There is an effect that the function can be restored after the thaw. this is,
It was found out comprehensively from the results of thermal analysis (numerical simulation) of the pressure sensor shown below.

First, when the pedestal 1 is made of glass instead of silicon, the thermal conductivity of the glass pedestal is the stem 6 '.
Since the thermal conductivity of the alloy forming the alloy is much lower than that of the alloy forming the alloy, the pressure introducing hole 60 is first blocked by icing, and a large amount of water is absorbed in the through hole 1.
It is left in the internal space such as 0. After that, the thin portion (diaphragm) 31 of the sensor wafer 3 bursts due to volume expansion when the water freezes. As a result, the sensor portion is destroyed, and the function as the pressure sensor is lost and never recovered.

Next, the thickness of the glass thin plate 2 bonded to the silicon pedestal 1 exceeds 150 μm (for example, 30).
0 μm), the thin glass plate 2 is the silicon pedestal 1
Lower thermal conductivity. Therefore, when the through holes 10 are frozen and closed, an amount of water corresponding to the thickness of the thin glass plate 2 is left in the internal space of the sensor wafer 3 in excess of a predetermined amount. After that, the thin portion (diaphragm) 31 of the sensor wafer 3 bursts due to volume expansion when the water freezes. As a result, the sensor portion is destroyed, and the function as the pressure sensor is lost and is not recovered as in the case of the glass pedestal described above.

On the other hand, when the thickness of the glass thin plate 2 is 150 μm or less as in this embodiment, the glass thin plate 2 having a low thermal conductivity is sufficiently thin so that the through hole 10 is frozen and closed. At this time, almost no water is left in the internal space. Therefore, the volume expansion when the water freezes is absorbed by the elastic deformation of the thin portion (diaphragm) 31 of the sensor wafer 3 and the sensor portion is not destroyed. As a result, the pressure sensor of this embodiment can withstand freezing and recover its function after being thawed.

Secondly, the annealing step has the effect of reducing fluctuations in the output voltage due to temperature. That is, since the residual stress contained in the pedestal 1 and the glass thin plate 2 bonded in the first anodic bonding step is removed by the annealing, the residual stress generated during the first anodic bonding causes fluctuations and variations in the sensor output voltage. Reduce.

Thirdly, since the metal thin film 4 of Ti / Ni / Au is formed on the joint surface of the sensor pedestal 1 made of Si,
The joint with the stem 6'by the low melting point solder 5'is stronger. Therefore, not only the joint strength between the pedestal 1 and the stem 6 ′, but also the airtightness at the joint is improved. Fourth, since the low melting point solder 5'is used in the stem joining step, the pedestal 1 and the stem 6'can be joined without raising the temperature to a high temperature. Therefore, the use of the low-melting-point solder 5 ′ has an effect of reducing the variation (variation) in the sensor output voltage due to soldering.

This effect was found from the results of an experiment in which the pressure sensor was manufactured by changing the setting of the temperature inside the furnace during soldering in the stem joining step within the range of 183 ° C to 310 ° C. That is, as shown in FIG. 7, when the soldering is performed at a low temperature of 220 ° C. or lower, the fluctuation range (± 3σ) ΔV of the output voltage is dramatically smaller than that of 230 ° C. or higher. Become. It is presumed that this is because the thermal stress at the time of soldering remains after cooling, but the amount thereof changes drastically at 220 to 230 ° C.

Although there is a "non-heated" temperature display at the left end of the figure, this non-heated bonding is also possible if an adhesive is used. However, the adhesive agent is not always the optimum joining means because it is not only airtight but also unstable for long-term stability and reliability.
In addition, due to the low melting point solder 5 ', the temperature is relatively low (220 ° C
The advantages of the manufacturing method of the present embodiment in which the stem joining step is performed) will be described with reference to FIG. In the figure, comparison is made between a pressure sensor (left) having a glass pedestal (normal soldering) as a conventional technique and a silicon sensor pedestal 1 (normal soldering) corresponding to the first embodiment. Example 2 using the pressure sensor (middle) and the same solder
The low melting point solder 5 '(right). The pressure sensor having the silicon pedestal 1 joined to the stem 6'by ordinary solder has a slightly larger variation than the conventional glass pedestal, and in this respect, it can be said that it is rather a step back. On the other hand, the pressure sensor using the low-melting-point solder 5'of the present embodiment exhibits excellent characteristics with less variation than the conventional glass pedestal.

(Modification of Example 2) As the low melting point solder 5 ', if the melting point is 220 ° C or lower, Sn
-Pb system (for example, eutectic composition Pb37, Sn63% has a melting point of 183 ° C), as well as Sn-In system and Sn-A
A g-In-Bi system or the like can also be used. As for other modified modes, it is possible to implement modified modes corresponding to the modified modes of the first embodiment.

[Brief description of the drawings]

FIG. 1 is a side sectional view of a semiconductor type mechanical quantity sensor (semi-finished product state) of Example 1.

FIG. 2 is an assembly diagram showing a method for manufacturing a semiconductor mechanical quantity sensor of Example 1 (a) A side sectional view showing a glass thin plate and a sensor pedestal before joining (b) A side schematically showing a first anodic joining step Sectional view (c) Side sectional view showing glass thin plate and pedestal after anodic bonding (d) Side sectional view showing glass thin plate and pedestal after thinning step (e) Side sectional view schematically showing second anodic bonding step Figure

FIG. 3 is a schematic diagram showing a method of tensile fracture test of a semiconductor type mechanical quantity sensor.

FIG. 4 is a graph showing the relationship between the voltage applied during anodic bonding and the bonding failure rate.

FIG. 5 is a side sectional view showing a configuration of a pressure sensor of Example 2.

FIG. 6 is an assembly view showing a method for manufacturing a pressure sensor of Example 2 (a) an end view showing a state after a first anodic bonding step (b) an end view showing a state after a metallizing step (c) a second anode (D) End view showing the state after the half cutting process (e) End view showing the wafer trimming process (f) End view showing the state after the dicing cutting process (g) Low melting point solder End view showing the state after the stem joining process

FIG. 7 is a graph showing the relationship between temperature and output fluctuation in the stem joining process.

FIG. 8 is a graph showing the effect of low melting point solder.

[Explanation of symbols]

1, 1 ': Sensor pedestal (after formation / before formation of ventilation holes) 2, 2': Glass thin plate, glass layer (after thinning process / before thinning process) 10: Through holes 21, 22: Anode bonding surface 3: Semiconductor sensor wafer (substrate) 31: Sensitive portion (thin portion) 32: Thick portion 5, 6, 7: Carbon jig 8: Stainless jig
9: DC power supply 4 ': Metal thin film (three-layer deposited film of Ti, Ni, Au)
5 ': Low melting point solder 6': Stem 7 ': Terminal 8': Wire (Al-Si wire) 9 ': Silicone oil 60: Pressure introduction hole

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor, Yasutoshi, 1-1, Showa-cho, Kariya, Aichi Prefecture, Nihon Denso Co., Ltd. (72) Inventor, Masakazu, 1-1, Showa-cho, Kariya, Aichi Japan Denso Co., Ltd.

Claims (10)

[Claims] 1. A semiconductor sensor substrate on which at least one sensing portion is formed, a sensor pedestal made of a semiconductor material, and a substrate interposed between the substrate and the pedestal and joined to the substrate and the pedestal. In the semiconductor-type mechanical quantity sensor, the glass layer is made of a thin glass plate anodically bonded to both the substrate and the pedestal. 2. The semiconductor-type mechanical quantity sensor according to claim 1, wherein the thin glass plate has a thickness of 20 μm or more. 3. The semiconductor mechanical quantity sensor according to claim 1, wherein the glass thin plate has a thickness of 150 μm or less. 4. The semiconductor type mechanical quantity sensor according to claim 1, wherein the thermal expansion coefficient of the glass thin plate is within ± 10% with respect to the thermal expansion coefficient of the semiconductor material forming the substrate and the pedestal. 5. A first anodic bonding step of anodic bonding a thin glass plate to one of a bonding surface of a semiconductor sensor substrate on which at least one sensing portion is formed and a bonding surface of a sensor pedestal made of a semiconductor material. A second anodic bonding of the thin glass plate to the other of the two bonding surfaces
A method of manufacturing a semiconductor mechanical quantity sensor, comprising: an anodic bonding step. 6. The first anodic bonding step comprises a step of bonding the pedestal and the glass thin plate, and the second anodic bonding step comprises a step of bonding the substrate and the glass thin plate. 5. The method for manufacturing the semiconductor mechanical quantity sensor according to 5. 7. The semiconductor dynamics according to claim 5, wherein between the first anodic bonding step and the second anodic bonding step, a thinning step of reducing the thickness of the glass thin plate by grinding, polishing or etching is carried out. Method of manufacturing a quantity sensor. 8. The method for manufacturing a semiconductor mechanical quantity sensor according to claim 5, wherein the voltage applied in the first anodic bonding step and the second anodic bonding step is 400 V or more. 9. A stem joining step of joining the pedestal to a stem by soldering after the second anodic joining step, wherein the melting point of the solder used in the stem joining step is
The method for manufacturing a semiconductor mechanical quantity sensor according to claim 5, wherein the temperature is 220 ° C. or lower. 10. A metallizing step of forming, by vapor deposition, on the surface of the pedestal to be joined to the stem, a metal thin film in the order of titanium, nickel, and gold from the lower layer, before the stem joining step. The method for manufacturing a semiconductor mechanical quantity sensor according to claim 9, which comprises.