JP2000146734A - Semiconductor pressure sensor and its junction surface inspection method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a semiconductor pressure sensor where inspection accuracy is improved without causing increase in inspection processes and costs, and its junction surface inspection method. SOLUTION: The important point of a silicon wafer 2 is etched and a plurality of recessed parts 3 are provided for forming a plurality of diaphragms 4, and boron or the like is diffused to each diaphragm 4, thus forming a gauge resistor 5. A glass pedestal 7 is subjected to anode junction to the silicon wafer 2. A site other than sites that oppose the junction site of the silicon wafer 2 is metallized by metal using sputtering or the like to form a metal film 8 within a surface at the opposite side of a junction surface 13 of the silicon wafer 2 in the glass pedestal 7, and a site that opposes the junction site is subjected to mirror surface finishing to form a mirror surface 9. When inspecting the state of the junction surface 13, the junction surface 13 is directly observed through the mirror surface 9 from the side of the mirror surface 9 of the glass pedestal 7, thus inspecting the release of the junction surface 13 and the presence or absence of void.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a silicon substrate in which a gauge resistor is formed on a diaphragm formed by forming a recess by etching a key point, and a silicon substrate so as to cover the recess. The present invention relates to a semiconductor pressure sensor having a glass pedestal formed with a through hole communicating with a recess, and a method for inspecting a joint surface thereof.

[0002]

2. Description of the Related Art Conventionally, as shown in FIG. 4, a sensor chip 1 in which a gauge resistor 5 is formed in a diaphragm 4 formed by etching a silicon substrate 10 to form a recess 3, Anodically bonded, recess 3
A through hole 6 communicating with the sensor chip 1 and a glass base 7 made of Pyrex glass having a metal film 8 formed by metalizing a surface opposite to the bonding surface 13 with the sensor chip 1 with metal by vapor deposition or sputtering. There was a semiconductor pressure sensor A having the following.

In such a semiconductor pressure sensor A, a metal pipe (not shown) having a pressure introduction hole is joined to the metal film 8 of the glass pedestal 7 by soldering, and the pressure introduction hole of the metal pipe and the penetration of the glass pedestal 7 are provided. The pressure is introduced into the diaphragm 4 through the hole 6, and the introduced pressure causes the diaphragm 4 to bend and the resistance value of the gauge resistor 5 to change, so that the pressure can be detected from the change in the resistance value of the gauge resistor 5. it can.

[0004] When a bonding defect such as peeling or voids occurs at the bonding surface 13 between the silicon substrate 10 and the glass pedestal 7, pressure leakage occurs and pressure cannot be detected accurately, or the silicon substrate 10 and the glass pedestal 7 are not detected. It is necessary to inspect the bonding quality of the bonding surface 13 because there is a possibility that the bonding strength with the bonding surface 7 is reduced. However, the metal film 8 is formed on the entire surface of the glass pedestal 7 opposite to the bonding surface 13. Therefore, the joint surface 13 could not be directly visually observed from the metal film 8 side.

Therefore, as shown in FIGS. 4 and 5, the semiconductor pressure sensor A was sunk with the glass pedestal 7 upward in a water tank 20 in which water 21 was stored to a depth at which the semiconductor pressure sensor A was sufficiently sunk. In this state, there is an inspection method for inspecting the quality of the bonding surface 13 by irradiating light from one side surface of the glass pedestal 7 and observing light reflected on the bonding surface 13 from the other side surface of the glass pedestal 7. (Japanese Unexamined Patent Publication No.
No. 9250). Arrows in FIGS. 4 and 5 indicate optical paths along which light travels, and hatched portions in FIG. 5 indicate bonding surfaces 13.

Light entering the water from the light source 22 enters the glass pedestal 7 from one side of the glass pedestal 7, is reflected by the joint surface 13, and proceeds to the water from the other side of the glass pedestal 7. . Here, the reflection state of the light differs between the normal part and the defective part of the bonding surface 13, and the brightness of the light reflected on the bonding surface 13 looks different, so that the microscope 23 is moved from the other side of the glass pedestal 7. By observing the reflection state of the bonding surface 13 by using this, it is possible to inspect the quality of the bonding surface 13. The inspection of the bonding surface 13 with the semiconductor pressure sensor A submerged in water is performed on the bonding surface 1
This is for increasing the brightness contrast between the normal part and the defective part of No. 3.

[0007]

The glass pedestal 7 is formed by cutting a sheet glass into a predetermined size.
Since the side surface of the glass pedestal 7 is rough and in a frosted glass state, the light refracted on the side surface of the glass pedestal 7 is scattered and travels in different directions. In the meantime, the water surface when entering the water from the air, one side surface of the glass pedestal 7, the joining surface 13,
Since the light is refracted at five points, that is, the other side surface of the glass pedestal 7 and the water surface when exiting from the water to the air, and the light is scattered on each refraction surface, images such as peeling of the bonding surface 13 and voids are clearly formed. Could not be observed. In addition, since the light from the light source 22 is obliquely incident on the bonding surface 13, images such as peeling and voids generated on the bonding surface 13 are distorted, and the size thereof cannot be determined. Further, the through hole 6 of the glass pedestal 7 is generally formed by an ultrasonic processing method of processing by vibrating a cutting needle. When the through hole 6 is formed by this method, the end face of the through hole 6 is rough, and the through hole 6 is formed into a ground glass shape. Therefore, when light passes through the end face of the through hole 6, the light is scattered. For this reason, it is necessary to enter light avoiding the through hole 6, and by adjusting the angle of the optical axis of the light source 22 or rotating the direction of the semiconductor pressure sensor A,
There is a problem that the work of inspecting the joint surface 13 is troublesome.

The present invention has been made in view of the above problems, and has as its object to provide a semiconductor pressure sensor and a semiconductor pressure sensor having improved inspection accuracy without increasing the number of inspection steps and the inspection cost. An object of the present invention is to provide a bonding surface inspection method.

[0009]

According to a first aspect of the present invention, there is provided a silicon substrate in which a gauge resistor is formed on a diaphragm formed by forming a recess by etching a key point. And a glass pedestal joined to the silicon substrate so as to cover the recess, and a through-hole formed in the through-hole communicating with the recess, the silicon pedestal in a surface opposite to the bonding surface with the silicon substrate in the glass pedestal. At least a mirror surface finish is applied to a portion facing the bonding portion where the substrate is bonded, and a portion of the glass base opposite to the bonding surface with the silicon substrate is mirror-finished in a surface opposite to the bonding surface. The joint surface can be directly observed through this mirror-finished part, and the surface on which light enters has been mirror-finished. Light is not scattered in the shaded area, and the mirror-finished area faces the joint area, so it can be observed from a direction substantially perpendicular to the joint plane. Further, it is possible to realize a semiconductor pressure sensor that can inspect the quality of the bonding surface with high accuracy without causing the image of the peeling or void generated on the bonding surface to be distorted.
In addition, since the mirror-finished part faces the joint part, the light incident on the glass pedestal from the mirror-finished part does not pass through the end face of the through-hole and is scattered. There is no need to rotate the semiconductor pressure sensor to avoid passing through the through-holes or adjust the optical axis of the incident light, reducing the number of inspection steps and realizing a semiconductor pressure sensor with reduced inspection costs. it can.

According to the second aspect of the present invention, a silicon substrate in which a gauge resistor is formed on a diaphragm formed by forming a recess by etching a key point is joined to the silicon substrate so as to cover the recess. A glass pedestal formed with a through hole communicating with the recess, and at least a mirror surface at a portion of the glass pedestal opposite to a bonding portion to which the silicon substrate is bonded, in a surface opposite to a bonding surface with the silicon substrate. A method for inspecting a bonding surface of a semiconductor pressure sensor having been subjected to finishing, wherein a mirror surface finish is applied from a surface of the glass pedestal opposite to a bonding surface with the silicon substrate in a state where the glass pedestal and the silicon substrate are bonded. It is characterized by directly observing the condition of the joint surface through the part that has been mirrored. Light is not scattered at the applied part, and images of peeling and voids generated at the joint surface can be clearly observed, and the mirror-finished part faces the joint part Since it can be observed from a direction substantially perpendicular to the joint surface, the image of peeling or voids generated on the joint surface is not distorted, and the quality of the joint surface can be inspected with high accuracy, and furthermore, the mirror surface Since the finished part is opposed to the joint part, the light incident on the glass pedestal from the mirror-finished part does not pass through the end face of the through hole and is scattered. This eliminates the need to rotate the semiconductor pressure sensor in order to avoid passing through, or to adjust the optical axis of the incident light, thereby reducing the number of inspection steps and the cost for inspection.

[0011]

Embodiments of the present invention will be described with reference to the drawings.

As shown in FIGS. 1A and 1B, a plurality of diaphragms 4 are formed in a matrix by etching a key portion of a silicon wafer (silicon substrate) 2 to provide a plurality of recesses 3. After diffusing boron or the like into each diaphragm 4 to form a gauge resistor 5 made of a piezoresistive element, a glass pedestal 7 made of, for example, Pyrex glass, in which a plurality of through holes 6 communicating with each recess 3 is formed, is made of silicon. Anodically bonded to the wafer 2, cut by a dicing saw in a cutting margin (dicing lane) 11 having a width of about 200 to 400 μm provided between adjacent chips, separated into individual chips, and separated as shown in FIG. A semiconductor pressure sensor A is formed. In the anodic bonding, for example, Pyrex glass having a thermal expansion coefficient close to that of silicon and silicon are heated to about 400 ° C. in a state where their bonding surfaces are in contact with each other, and a positive DC voltage (for example, 500 to 1000 V) is applied to the silicon side. )
Is applied so that glass and silicon are brought into close contact with each other by electrostatic attraction consisting of Coulomb force.

Here, the bonding surface 13 of the glass pedestal 7
In the surface on the side opposite to the above, a part other than a part facing the bonding part to which the silicon wafer 2 is bonded is metallized with metal by vapor deposition or sputtering, for example, Ti / Ni / A
A metal film 8 such as u, Ti / Pt / Au, or Cr / Pt / Au (Au is the uppermost layer) is formed. On the other hand, a portion of the glass pedestal 7 opposite to the bonding surface in a surface opposite to the bonding surface 13 is mirror-finished, and a transparent mirror surface 9 is formed. Note that a hatched portion in FIG. 1B indicates a portion where the mirror surface 9 is formed.

A metal pipe (not shown) having a pressure introducing hole is joined to the metal film 8 by soldering, and pressure is introduced into the diaphragm 4 through the pressure introducing hole of the metal pipe and the through hole 6 of the glass pedestal 7. You. Thus, the diaphragm 4 bends due to the introduced pressure, and the resistance of the gauge resistor 5 changes according to the amount of deflection of the diaphragm 4, so that the pressure can be detected from the change in the resistance of the gauge resistor 5.

Here, a process of forming the metal film 8 and the mirror surface 9 on the surface of the glass pedestal 7 will be described with reference to FIGS. First, the bonding surface 1 on the glass pedestal 7
The surface opposite to 3 is mirror-finished to form a mirror surface 9. Thereafter, as shown in FIG. 3A, the silicon wafer 2 is formed in a surface of the glass pedestal 7 opposite to the bonding surface 13.
Site 15 other than the site facing the bonding site to be bonded to
Is roughened by a sand blast method using a mask 14 made of a metal plate, a resist, or the like. Next, FIG.
As shown in (b), the roughened portion 15 is metallized with a metal by a sputtering method using a mask 14 ′ made of a metal plate, a resistor, etc., to form a metal film 8.

As described above, in the surface of the glass pedestal 7 opposite to the bonding surface 13, the metal film 8 is not formed on the portion facing the bonding portion with the silicon wafer 2, and the mirror surface 9 is formed. Therefore, when inspecting the quality of the bonding surface 13, when the silicon wafer 2 is bonded to the glass pedestal 7, the state of the bonding surface 13 is passed through the mirror surface 9 from the mirror surface 9 side of the glass pedestal 7 using, for example, a microscope (FIG. (Not shown) to observe the peeling of the bonding surface 13 and the presence or absence of voids. As described above, since the state of the bonding surface 13 is directly observed through the mirror surface 9, no light is scattered by the mirror surface 9, and the mirror surface 9 is formed at a portion facing the bonding portion with the silicon wafer 2. Since the state of the bonding surface 13 can be observed from a direction substantially perpendicular to the bonding surface 13, the image of the separation or void is not distorted, and a clear image of the separation or void generated on the bonding surface 13 is obtained. Can be obtained, and the joining surface 1
3 can be inspected with high accuracy. Furthermore, since the state of the joint surface 13 can be observed from a direction substantially perpendicular to the joint surface 13, light incident from the mirror surface 9 does not pass through the end surface of the through hole 6 and is scattered. In order to prevent light incident from one side surface of the glass pedestal 7 from passing through the through hole 6 as described above, the position is adjusted on the silicon wafer 2 and the glass pedestal 7 or the optical axis of the incident light is adjusted. There is no need to reduce the inspection process,
The labor required for the inspection can be reduced, and the cost for the inspection can be reduced.

In the present embodiment, before the silicon wafer 2 and the glass pedestal 7 that have been anodically bonded are cut by a dicing saw and separated into individual chips, the bonding surfaces 13 are separated.
Since the quality of the bonding surface 13 is inspected, the bonding surface 13 can be inspected at a time by inspecting the bonding surface 13 in units of wafers. However, as shown in FIG. May be inspected. In addition, the bonding surface 13 may be inspected in a state where the semiconductor pressure sensor A is submerged in water having a refractive index close to that of the glass. Is hardly scattered, and it is possible to prevent the light from being difficult to see due to the scattering of light. Note that the inspection of the bonding surface 13 may be performed in a state where the semiconductor pressure sensor A is immersed in a liquid (for example, silicon oil) having a refractive index close to that of glass instead of water, and the same effect can be obtained. .

[0018]

[Table 1]

[0019]

As described above, according to the first aspect of the present invention, a silicon substrate in which a gauge resistor is formed on a diaphragm formed by forming a recess by etching a key point, and the recess is closed. And a glass pedestal formed with a through hole communicating with the recess,
In a surface opposite to a bonding surface with the silicon substrate in the glass pedestal, at least a mirror finish is applied to a portion other than a portion opposed to a bonding portion to which the silicon substrate is bonded, and a bonding surface in the glass pedestal On the opposite side of the surface, the part facing the bonding part with the silicon substrate is mirror-finished, so that the bonding surface can be directly observed through this mirror-finished part, and the light Since the incident surface is mirror-finished, light is not scattered at the mirror-finished part, and the mirror-finished part faces the joint part, so the joint surface A semiconductor pressure sensor that can inspect the quality of the bonded surface with high accuracy without observing peeling or void images generated on the bonded surface because it can be observed from a direction substantially perpendicular to the surface There is an effect that kill. In addition, since the mirror-finished part faces the joint part, light incident on the glass pedestal from the mirror-finished part does not pass through the end surface of the through hole and is scattered,
A semiconductor pressure sensor that eliminates the need to rotate the semiconductor pressure sensor to prevent light from passing through the through-hole and adjust the optical axis of the incident light, reducing the number of inspection steps and reducing the cost of inspection. There is an effect that can be realized.

According to a second aspect of the present invention, a silicon substrate in which a gauge resistor is formed on a diaphragm formed by providing a recess by etching a key point is joined to the silicon substrate so as to cover the recess. A glass pedestal formed with a through hole communicating with the recess, and at least a mirror surface at a portion of the glass pedestal opposite to a bonding portion to which the silicon substrate is bonded, in a surface opposite to a bonding surface with the silicon substrate. A method for inspecting a bonding surface of a semiconductor pressure sensor having been subjected to finishing, wherein a mirror surface finish is applied from a surface of the glass pedestal opposite to a bonding surface with the silicon substrate in a state where the glass pedestal and the silicon substrate are bonded. It is characterized by directly observing the condition of the joint surface through the part that has been mirrored, and because the condition of the joint surface is directly observed through the part with the mirror finish, the mirror finish is Light is not scattered at the part that was made, the image of peeling and voids generated on the joint surface can be clearly observed, and the part with mirror finish is facing the joint part, Since the image can be observed from a direction substantially perpendicular to the bonding surface, the image of the peeling or void generated on the bonding surface is not distorted, and the quality of the bonding surface can be inspected with high accuracy. In addition, since the mirror-finished part is opposed to the joint part, light incident on the glass pedestal from the mirror-finished part does not pass through the end face of the through hole and is scattered,
There is no need to rotate the semiconductor pressure sensor to prevent light from passing through the through-hole or adjust the optical axis of the incident light. This reduces the number of inspection steps and reduces the cost of inspection. is there.

[Brief description of the drawings]

FIG. 1 shows a semiconductor pressure sensor according to an embodiment of the present invention;
Is a sectional view, and (b) is a top view.

FIG. 2 is a sectional view showing a state where the semiconductor pressure sensor is divided into individual chips.

FIGS. 3 (a) and 3 (b) are explanatory views illustrating a manufacturing process of a glass pedestal used for the semiconductor pressure sensor according to the embodiment.

FIG. 4 is a schematic configuration diagram showing a conventional method for inspecting a bonding surface of a semiconductor pressure sensor.

FIG. 5 is an explanatory diagram showing a bonding surface inspection method according to the first embodiment;

[Explanation of symbols]

 2 Silicon wafer 3 Concave part 4 Diaphragm 5 Gauge resistance 7 Glass pedestal 8 Metal film 9 Mirror surface 13 Joining surface

Continued on front page F term (reference) 2F055 AA40 BB20 CC02 DD05 EE14 FF43 GG01 GG12 2G051 AA90 AB20 AC22 CA11 4M112 AA01 BA01 CA15 DA02 DA16 DA17 DA18 EA02 EA13

Claims (2)

[Claims] 1. A silicon substrate in which a gauge resistor is formed on a diaphragm formed by forming a recess by etching a key point, and a silicon substrate is joined so as to cover the recess, and communicates with the recess. A glass pedestal having a through hole formed therein, and at least a mirror-finished portion is applied to a portion of the glass pedestal opposite to a bonding portion to which the silicon substrate is bonded in a surface opposite to a bonding surface with the silicon substrate. A semiconductor pressure sensor characterized by the above-mentioned. 2. A silicon substrate in which a gauge resistor is formed on a diaphragm formed by providing a concave portion by etching a key portion, and a silicon substrate is joined so as to cover the concave portion, and communicates with the concave portion. A glass pedestal having a through hole formed therein, and at least a mirror-finished portion is applied to a portion of the glass pedestal opposite to a bonding portion to which the silicon substrate is bonded in a surface opposite to a bonding surface with the silicon substrate. A method for inspecting a bonding surface of a semiconductor pressure sensor, wherein a glass pedestal and a silicon substrate are bonded together, and a bonding surface is passed through a mirror-finished portion from a surface of the glass pedestal opposite to a bonding surface with the silicon substrate. A method for inspecting a bonding surface of a semiconductor pressure sensor, wherein a state of the semiconductor pressure sensor is directly observed.