JPH0720147A - Fabrication of semiconductor acceleration sensor - Google Patents

Abstract

PURPOSE:To prevent occurrence of insufficiently sealed chip due to deformation or breakage of an adhesive pattern caused by pressurization and heating in the step for bonding the upper and lower stopper wafers to a center wafer when a semiconductor acceleration sensor is fabricated. CONSTITUTION:A circular pattern 6 of adhesive for preventing the chipping is formed on the outer peripheral part of a stopper wafer. Since the grid pattern 7 of sealing adhesive applied to the inside of wafer and the circular pattern 6 do not form any enclosed space, the variation of the space between the stopper wafer and a center wafer and the expansion of air caused by the pressurization and heating of the wafer have no effect on the sealing adhesive which is not thereby deformed nor broken. The sealing adhesive may have a linear pattern extending in a predetermined direction.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a semiconductor acceleration sensor, and more particularly to a sensor section for detecting acceleration by vibration of a thick weight section obtained by processing a single crystal silicon substrate, and this weight section. The present invention relates to a method for manufacturing a semiconductor acceleration sensor in which upper and lower stoppers for providing an air damping effect against the vibration of the above are bonded with an adhesive.

[0002]

2. Description of the Related Art A semiconductor acceleration sensor has a sensor portion 1, an upper stopper portion 2 and a lower stopper portion as seen in a perspective view shown in FIG. 3A and an AA sectional view shown in FIG. 3B. 3 has a triple structure, and each outer peripheral portion is sealed with an adhesive portion 5. The sensor portion 1 has a thick-walled weight portion 4 and a thin-walled beam portion 13 formed by processing a single crystal silicon wafer, and the beam portion 13 is generated by vibration when acceleration is applied to the weight portion 4. The acceleration is detected by the strain. The gaps between the upper stopper 2 and the sensor portion 1 and between the lower stopper 3 and the sensor portion 1 are sealed by the adhesive portion 5, and the vibration of the weight portion 4 is damped by the air damping effect. It is a thing.

A method of manufacturing the semiconductor acceleration sensor having the above structure will be described below. First, an adhesive 10 having a lattice pattern over the entire surface as shown in FIG. 4A is applied to a silicon stopper wafer. A ventilation hole 8 penetrating the front and back of the wafer is provided in advance in a portion of the stopper wafer corresponding to the sensor portion. However, since the outer peripheral portion of the wafer is used as a region for handling the wafer by vacuum suction when processing the wafer during the manufacturing process, the vent hole is not provided in the outer peripheral portion of the wafer. On the other hand, a sensor wafer having a structure in which a thick weight portion and a thin beam portion are formed on a single crystal silicon wafer by anisotropic etching using, for example, an alkaline solution is prepared.

Next, the sensor wafer is sandwiched between the upper and lower stopper wafers to be superposed. The positioning at this time is performed by aligning the alignment marks formed on each wafer with a microscope.

Next, the stacked wafers are pressed and heated to bond the three wafers. Then, as shown in FIGS. 5 (a) and 5 (b), each sensor is obtained by cutting at the bonded portion with a dicing saw or the like.

Here, as shown in FIG. 4A, the pattern of the adhesive 10 applied to the stopper wafer extends to the end of the stopper wafer (that is, the outer peripheral portion of the stopper wafer, The lattice-like pattern is formed even in the region where the sensor is not formed.) The entire-face lattice-like pattern is as follows. That is, the semiconductor acceleration sensor having this structure can be obtained by bonding three wafers and then cutting them. Now, if the lattice pattern does not extend to the edge of the wafer, the wafers are not bonded to each other at the outer peripheral portion of the wafer, but simply overlap each other. So-called chipping occurs, in which each wafer is separated into individual chips. The reason why the adhesive application pattern is a grid pattern on the entire surface is to prevent this chipping.

As described above, the upper and lower stopper wafers are for providing the air damping effect against the vibration of the weight portion due to the gap between the sensor wafer and the stopper wafer, and therefore, on the flat plate having good flatness. The material is not limited to the silicon wafer, and other materials such as a quartz plate can be used as long as they are made of quartz. However, since it may be heated together with the sensor wafer during the manufacturing process,
A silicon wafer having a coefficient of thermal expansion equal to that of the sensor wafer is usually used. Furthermore, as the sensor wafer, a single crystal silicon wafer must be used because it is necessary to make the beam portion exhibit a piezoresistive effect, but the silicon wafer used as the stopper wafer does not necessarily have to be a single crystal silicon wafer. .

[0008]

The above-described conventional method of manufacturing a semiconductor acceleration sensor has a drawback that a sensor having a defective seal is likely to occur. The description will be given below.

In the conventional manufacturing method, the state of the adhesive on the stopper wafer is shown in FIG. 4 after applying the adhesive in the form of a lattice pattern on the entire surface, stacking three wafers, and applying heat and pressure to bond them. Shown in b). Referring to FIG. 4B, the disconnection portion 1 is formed in the adhesive pattern on the outer peripheral portion of the wafer (where the ventilation holes 8 are not formed) where the sensor is not formed.
1A has occurred. A similar disconnection portion 11B of the adhesive also occurs in the adhesive of the outermost sensor. This is for the following reason. That is, there is no vent hole 8 on the outer peripheral portion of the stopper wafer. Therefore, a sealed space surrounded by the adhesive, the sensor wafer, and the stopper wafer is formed in this portion. Then, the volume change of the sealed space due to the pressurization of the wafer or the expansion of the air due to the heating causes an imbalance in the pressure inside and outside the sealed space, which deforms the application pattern of the adhesive and causes a disconnection when it is serious.

When the three wafers integrated by the adhesive thus broken are cut along the grid pattern, as shown in the sectional view of FIG. Thus, the defective sealability portion 12 is generated.

Therefore, an object of the present invention is to provide a method for manufacturing a semiconductor acceleration sensor, which does not cause defective sealing due to the chipping prevention adhesive provided on the outer peripheral portion of the wafer.

[0012]

According to a method of manufacturing a semiconductor acceleration sensor of the present invention, a sensor array in which sensors including a thick weight portion for detecting acceleration are arranged in an array is formed on a silicon wafer. To obtain a wafer for a sensor, and an upper stopper array and a lower stopper array in which an upper stopper and a lower stopper for forming an air damping space against the vibration of the weight portion are arranged in an array, respectively. Forming on a wafer to obtain an upper stopper wafer and a lower stopper wafer, and an adhesive for applying a sealing adhesive for forming the air damping space to the upper stopper wafer and the lower stopper wafer Agent coating step, the upper stopper wafer and the sensor wafer A method of manufacturing a semiconductor acceleration sensor, the method comprising: stacking and adhering the lower stopper wafer on top of each other, and then cutting the lower stopper wafer into the sensor units. The chipping prevention adhesive is applied to the parts other than the lower part and the parts other than the lower stopper array forming part of the lower stopper wafer at the same arrangement pitch as the sensor array, and the chipping prevention adhesive application pattern. Is formed on the silicon wafer coated with the chipping prevention adhesive so that the sealing adhesive and the chipping prevention adhesive do not form a closed loop.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, preferred embodiments of the present invention will be described with reference to the drawings. FIG. 1A is a diagram showing a pattern of an adhesive applied to a stopper wafer in one embodiment of the present invention. In this embodiment, first, an adhesive having the pattern shown in FIG. 1A is applied to the upper and lower stopper wafers by screen printing. As shown in the figure, the application pattern of this adhesive has a grid pattern 7 at the portion where the sealing property of the sensor portion is required (the chip portion provided with the ventilation holes 8), while A portion of the outer peripheral portion of the stopper wafer which is not related to the sealing property of the sensor portion has a circular pattern 6. In the adhesive coating pattern, the grid pattern 7 has a width of 400 μm, and the round pattern 6 has a diameter of 800 μm. The size of the diameter of the circular pattern 6 is determined so that the area of each circular pattern 6 is equal to the area of one chip of the grid pattern 7. When the adhesive is applied by screen printing, the coating film thickness is generally related to the coating area. Therefore, by equalizing the area of the grid pattern 7 and the area of the round pattern 6, the film of the grid pattern 7 is formed. The thickness and the film thickness of the round pattern 6 can be made equal. As a result, when the upper and lower stopper wafers and the sensor wafer are bonded together in a later process, the air damping gap (gap between the stopper wafer and the sensor wafer) becomes uniform within the wafer, so that there is a special variation for each sensor. Can be more uniform. In this embodiment, the emulsion thickness of the printing screen is 10 μm, and the printing film pressure of the adhesive under this condition is 26 to 32 μm.

Next, the upper and lower stopper wafers and the sensor wafer are superposed on each other using the alignment marks. In addition, stacking the upper and lower stopper wafers and the sensor wafer
The square wafers are bonded together by pressurizing and heating under the conditions of pressurizing pressure: 50 kgf, heating temperature: 120 ° C., heating time: 2 hours. The state of the adhesive on the stopper wafer after this bonding step is shown in FIG. Referring to the figure, the adhesive has no pattern disorder or disconnection. This is because the adhesive pattern on the printed surface of the stopper wafer (outer peripheral portion of the stopper wafer) corresponding to the area where the sensor chip of the sensor wafer is not formed is a circular pattern that does not allow a sealed portion.・ Because it is not affected by the volume change of the gap between stoppers and the expansion of air. The width of the grid pattern after pressurization and heating was 850 to 950 μm, and the gap between the sensor and the stopper was 14.0 to 14.5 μm.

Next, the bonded wafer is cut into chips along the bonding portion 5 to obtain a semiconductor acceleration sensor, as shown in FIGS. 5 (a) and 5 (b). As shown in FIG. 3 (a), the sensor obtained in this manner has an adhesive portion 5
There is no part with poor sealing property, and it is surely sealed.

The operating principle of the semiconductor acceleration sensor is to detect the magnitude of the acceleration by vibrating the weight when the weight acts on the weight at the center of the sensor. The weight that vibrates once stops due to the air damping effect. The air damping effect is
Reliable sealing between the sensor and the stopper is important because it affects the characteristics of the sensor because it is greatly affected by the movement of air between the stoppers. In the case where the wafer is manufactured by the conventional technique, the adhesive pattern may be disturbed or broken, so that when the wafer is cut into chips, defective sealing may occur. On the other hand, according to the present embodiment,
The adhesive pattern after bonding the wafer is always stable,
Since the sensor chip obtained from this wafer is reliably sealed, stable characteristics can be obtained. In this example, the process yield could be doubled compared to the conventional one.

FIG. 2A shows another example of the adhesive application pattern. Referring to the figure, in the adhesive pattern of this example, the portion of the sensor portion that requires sealing property is the grid pattern 7, and the outer peripheral portion of the wafer not related to the sealing property is the wafer in one direction from the grid pattern. The linear pattern 9 extends to the outer peripheral portion. The line width of the grid pattern 7 is 400μ
m, the width of the linear pattern 9 is 800 μm, and the area per chip of the linear pattern 9 is equal to the area per chip of the grid pattern 7.

FIG. 2B shows the state of the adhesive after the upper and lower stopper wafers and the sensor wafer have been bonded.
As shown in the figure, the adhesive pattern has neither disorder nor disconnection. This is because the adhesive pattern on the outer peripheral portion of the wafer is a linear pattern in one direction, so that the lattice pattern 7 and the linear pattern 9 of the sensor section do not form a sealed portion. Since an air passage is always ensured between the outermost adhesive of the grid pattern 7 and the outer peripheral portion of the wafer, the adhesive pattern is not affected by pressurization and heating in the bonding process. .

[0019]

As described above, according to the method for manufacturing a semiconductor acceleration sensor of the present invention, the coating pattern of the chipping prevention adhesive applied to the outer peripheral portion of the stopper wafer is applied to the sensor chip portion. And the chipping prevention adhesive has a pattern that does not create a closed space.

As a result, according to the present invention, it is possible to provide a semiconductor acceleration sensor which does not have a defective sealing property due to the deformation and disconnection of the adhesive due to the pressurization / heating at the time of wafer bonding.

Further, by making the thickness of the chipping prevention welding adhesive equal to the thickness of the sealing adhesive, the air damping voids can be made uniform in the wafer surface, and variations in the characteristics of the acceleration sensor can be suppressed. it can.

[Brief description of drawings]

FIG. 1A is a diagram showing an adhesive application pattern in an embodiment of the present invention. FIG. 6B is a diagram showing the state of the adhesive after the wafer bonding step.

FIG. 2A is a diagram showing another example of an adhesive application pattern. Diagram (b) is a diagram showing the state of the adhesive after the wafer bonding step when the adhesive application pattern shown in diagram (a) is used.

FIG. 3A is a perspective view of a semiconductor acceleration sensor. Part (b) is a sectional view of the semiconductor acceleration sensor.

FIG. 4A is a diagram showing an adhesive application pattern in a conventional method of manufacturing a semiconductor acceleration sensor. Diagram (b) is a diagram showing the state of the adhesive after the wafer bonding step when the adhesive application pattern shown in diagram (b) is used.

FIG. 5 is a diagram showing a wafer cut state in the manufacturing process of the semiconductor acceleration sensor.

FIG. 6 is a perspective view of a semiconductor acceleration sensor manufactured by a conventional technique.

[Explanation of symbols]

 1 Sensor part 2 Upper stopper 3 Lower stopper 4 Weight part 5 Adhesive part 6 Round pattern 7 Lattice pattern 8 Vent hole 9 Linear pattern 10 Adhesive 11A, 11B Disconnection part 12 Sealing failure part 13 Beam part

Claims (3)

[Claims] 1. A step of forming a sensor array, in which sensors including a thick-walled weight portion that vibrate according to acceleration are arranged in an array, on a single-crystal silicon wafer to obtain a sensor wafer; and An upper stopper array and a lower stopper array, in which an upper stopper and a lower stopper for forming an air damping space against vibrations are arranged in an array, are formed on different silicon wafers to form an upper stopper wafer and a lower stopper. A step of obtaining a wafer for use, an adhesive applying step of applying a sealing adhesive for forming the air damping space to the upper stopper wafer and the lower stopper wafer, the upper stopper wafer and the sensor Wafer and the lower stopper wafer are overlapped and bonded After that, in the method for manufacturing a semiconductor acceleration sensor, including the step of cutting into sensor units, in the adhesive applying step, a portion other than the upper stopper array forming portion of the upper stopper wafer and a lower portion of the lower stopper wafer are formed. The chipping prevention adhesive was applied to the portions other than the stopper array forming portion at the same arrangement pitch as the sensor array, and the chipping prevention adhesive was applied with the chipping prevention adhesive coating pattern. A method for manufacturing a semiconductor acceleration sensor, characterized in that a seal adhesive and a chipping prevention adhesive are formed in a pattern in which a closed loop is not formed on a silicon wafer. 2. The method for manufacturing a semiconductor acceleration sensor according to claim 1, wherein the thickness of the chipping prevention adhesive is the same as the sealing adhesive applied to the silicon wafer coated with the chipping prevention adhesive. A method for manufacturing a semiconductor acceleration sensor, which has a thickness substantially the same as that of the semiconductor acceleration sensor. 3. The method for manufacturing a semiconductor acceleration sensor according to claim 2, wherein the chipping prevention adhesive has an area per unit of its arrangement applied to a silicon wafer coated with the chipping prevention adhesive. A method for manufacturing a semiconductor acceleration sensor, wherein the area of the adhesive for sealing is approximately equal to the area per unit.