KR100266822B1 - Semiconductor acceleration sensor and method of fabricating the same - Google Patents

Abstract

PURPOSE: A semiconductor acceleration sensor and a method for manufacturing the same are provided to protect a vibration movement of a mass from the outside by forming a support plate as a silicon material. CONSTITUTION: A mass(16) is formed at a lower face of a silicon wafer(10). A piezoresistor(14) and an aluminium(15) are deposited on the silicon wafer(10). An upper support plate(20) and a lower support plate(30) are formed with a silicon material. Reception portions(24,34) are formed on a bottom face of the upper support plate(20) and an upper face of the lower support plate(30), respectively. A multitude of hole(13,23,33) is formed on edge portions of the silicon wafer(10), the upper support plate(20), and the lower support plate(30).

Description

Semiconductor Acceleration Sensor and Its Manufacturing Method

The present invention relates to a semiconductor acceleration sensor and a manufacturing method thereof, and more particularly, to a support plate provided on one surface of a silicon substrate to protect the vibration movement of the mass from the outside.

In general, a semiconductor acceleration sensor is used to measure the acceleration of an object by detecting a change in resistance of a piezoresistor, the structure of which is schematically illustrated in FIG. 1.

As shown in the figure, the semiconductor accelerometer includes a piezoresistor 3 whose resistance value is changed by acceleration through a predetermined semiconductor process on the upper surface of the silicon wafer 1, and again serves as an electrical conductor on the piezoresistor 3. The aluminum 4 to be carried out is deposited. In the central portion of the lower surface of the silicon wafer 1, a mass 2 that oscillates in the vertical direction is formed in a moving mass that converts the acceleration into a force and transmits it to the beam. The support plate 5 is bonded to the lower portion of the silicon wafer 1 so as to support it. The glass support plate 5 is made of the same size as the silicon wafer 1, and a recessed recess 5a is formed on the upper surface thereof so as not to disturb the vertical vibration of the mass 2. .

On the other hand, the silicon wafer 1 and the support plate 5 are joined by anodic bonding. That is, when the lower surface of the silicon wafer 1 and the upper surface of the support plate 5 are aligned so that the mass 2 is positioned above the receiving portion 5a formed on the support plate 5, the edge portions are in contact with each other. Then, a high voltage of DC 500 mA is applied thereto to generate an electrostatic power, and when heat is applied at about 500 ° C., the silicon wafer 1 and the edge of the support plate 5 made of glass are joined. As a result, the mass 2 vibrating according to the acceleration of the moving object is blocked from the outside by the support plate 5, so that the mass 2 does not interfere with its movement, and the air remaining in the accommodating part 5a is prevented. Perform a damping role.

When the semiconductor sensor is mounted on a moving object, the mass 2 oscillates in the vertical direction in proportion to the acceleration of the object, and the beam supporting the semiconductor sensor is bent. In addition, the stress is generated in the beam and the resistance value of the piezoresistor 3 therein is changed, and this is sensed through the aluminum 4 serving as the electrical conductor, thereby measuring the acceleration of the object.

However, in the conventional semiconductor acceleration sensor, since the silicon wafer 1 and the support plate 5 are bonded by the anodic bonding method and the high temperature, the aluminum 4 may be short-circuited and the thermal stress may reduce the sensitivity thereof. There is this.

That is, in order to bond the silicon wafer 1 and the support 5 made of glass material, as described above, a high voltage of DC 500 V and heat of about 500 ° C. are applied. In this process, the silicon wafer 1 is manufactured. A breakdown phenomenon occurs in the element wiring and circuit of the piezo resistor 3 and the aluminum 4 which functions as an electrical conductor. In addition, the reason why the support plate 5 is made of a glass material is that the silicon and the thermal expansion coefficients are almost similar, but due to the slight difference in the thermal expansion coefficient during cooling after the bonding is completed, the silicon wafer 1 and the support plate 5 This is twisted. The degree of distortion caused by thermal stress is very small, but this has a lot of negative effect on acceleration detection.

SUMMARY OF THE INVENTION The present invention has been made to solve such a problem, and an object of the present invention is to fabricate a support plate for supporting a silicon wafer made of a silicon material and joining them at a low temperature using an Au layer, thereby forming device wirings and circuits fabricated on the silicon wafer. Is to provide a semiconductor acceleration sensor and a method of manufacturing the same to prevent damage to the silicon wafer and to prevent distortion of the silicon wafer and the support plate during the cooling process.

1 is a schematic view showing a conventional semiconductor acceleration sensor.

2 illustrates a semiconductor acceleration sensor according to the present invention.

3 is a block diagram schematically illustrating a manufacturing process of a semiconductor acceleration sensor according to the present invention.

* Description of Signs of Main Parts of Drawings *

10. Silicon wafer 14. Resistive resistor 15 Aluminum

16. Mass 20. Upper support plate 30. Lower support plate

11,21,31..Cr layer 12,22,32..Au layer 13,23,33..hole

24, 34. Receptacle 41. Guide rod 50. Weighted object

The semiconductor acceleration sensor according to the present invention for achieving the above object, the upper surface is provided with aluminum to perform the electrical conductor function and the piezoresistor, the silicon wafer formed on the center of the lower surface, the support plate is provided to cover the upper and lower surfaces of the silicon wafer In the semiconductor acceleration sensor provided with, the receiving portion is provided on one surface of the support plate to vibrate in the vertical direction, the support plate is characterized in that made of silicon material.

In the method for manufacturing a semiconductor accelerometer according to the present invention, a piezo resistor and an aluminum conducting electrical conductor function are provided on an upper surface thereof, and a silicon wafer on which a mass is formed on a central portion of a lower surface of the semiconductor acceleration sensor is bonded to cover the upper and lower surfaces of the silicon wafer. In the method of manufacturing a semiconductor acceleration sensor having a silicon support upper and lower support plate formed in the receiving portion, the Au layer is formed on the upper and lower edges of the silicon wafer, and the upper and lower support plates to correspond to the Au layer of the silicon wafer. Forming an Au layer on the edge of the silicon wafer, and matching the upper and lower support plates to the upper and lower surfaces of the silicon wafer, and bonding the Au layer of the silicon wafer and the upper and lower support plates to the upper and lower surfaces of the silicon wafer. And applying heat and pressure to couple the lower support plate.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. 2 is a schematic view of a semiconductor acceleration sensor according to the present invention, Figure 3 is a block diagram showing a manufacturing process of the semiconductor acceleration sensor according to the present invention in the order of process.

As shown in the semiconductor acceleration sensor according to the present invention, the silicon wafer 10 formed with the piezoresistor 14, the aluminum 15, the mass 16 and the like, and upper and lower support plates provided to cover the upper and lower surfaces thereof. It consists of (20,30).

On the lower surface of the silicon wafer 10, a mass 16, which vibrates in the vertical direction, is formed on the center of the silicon wafer 10, and on the upper surface thereof, a piezo resistor 14 and aluminum 15, which functions as an electrical conductor, are deposited. The upper and lower support plates 20 and 30 are made of a silicon material, and the lower support plate 30 corresponding to the lower surface of the upper support plate 20 and the lower surface of the silicon wafer 10 correspond to the upper surface of the silicon wafer 10. Each of the receiving surfaces 24 and 34 is formed in the upper surface of the crest to form a free space so as not to interfere with each other in the vibration movement of the mass (16). Reference numerals 13, 23, and 33 are holes drilled in the edges of the silicon wafer 10 and the upper and lower support plates 20 and 30, which are inserted into the guide rods 41 to be described later. This will be described in detail.

The bonding structure of the silicon wafer 10 and the upper and lower support plates 20 and 30 is as follows. First, Cr / Au layers 11 and 12 are formed at the edge of the silicon wafer 10, which is formed along the upper and lower edges. Further, Cr / Au layers 11 and 12 are formed on the lower surface of the upper support plate 20 and the upper support plate 30 of the silicon material along the edges thereof. At this time, both of the Cr / Au layers formed on the silicon wafer 10 and the upper and lower support plates 20 and 30 are made to expose the Au layer to the outside.

Therefore, when the upper support plate 20 and the lower support plate 30 are bonded to the upper and lower surfaces of the silicon wafer 10, the respective Cr / Au layers coincide with each other, and when a predetermined heat and pressure are applied thereto, each Au layer 12 , 22,32 are joined. That is, the upper support plate 20 is bonded to the upper portion of the silicon wafer 10, and the lower support plate 30 is bonded to the lower portion of the silicon wafer 10, so that the free space is formed by the receiving portions 24 and 34. The vibration of the mass 16 is not interfered.

At this time, the heat applied during the bonding is about 375 ℃, the eutectic temperature of silicon and Au, that is, the eutectic temperature is preferably in the range of 350 ~ 400 ℃, and at the same time the upper support plate 20 Put the weighted object (50, see Fig. 3) on the upper side of the pressing firmly bonded. On the other hand, the silicon wafer 10 and the upper and lower support plates 20 and 30 bonded by applying a predetermined heat are required to be cooled, and both are made of silicon and have the same thermal expansion coefficient, so that the bonded state is not twisted during the cooling process. Will remain the same.

In other words, the upper and lower support plates 20 and 30 made of silicon are formed to cover the upper and lower surfaces of the silicon wafer 10 to enable vibration in the vertical direction of the mass 16. The eutectic eutectic of silicon and Au is performed by using an Au layer. It joins by applying pressure at the temperature of 375 degreeC. As a result, the piezoresistor 14 and aluminum 15 formed on the upper surface of the silicon wafer 10 are prevented from being damaged, and at the time of cooling thereof, they are not deformed by thermal stress.

Next, a method of manufacturing the semiconductor acceleration sensor will be described in detail with reference to FIGS. 2 and 3.

First, the piezo resistor 14 and the mass 16 are formed, and as described above on the upper and lower surfaces of the silicon wafer 10 on which the aluminum 15 is deposited on the piezo resistor 14, the Cr / Au layers 11 and 12. ) Is formed along the edge, which causes the Au layer 12 to be exposed to the outside (step a). Cr / Au layers (21,22,31,32) are formed along the edges of the upper and lower support plates (20,30) made of silicon material having the receiving portions (24,34) formed to enable the vibration of the mass (16). In this case, too, the Au layers 22 and 32 are exposed to the outside (step b). On the other hand, the holes 12, 23, 33 are drilled in the edges of the silicon wafer 10 and the upper and lower support plates 20, 30, and when they are overlapped, they communicate with each other. It is also possible to change the steps A and I.

Subsequently, a guide rod 41 having a predetermined length is installed on the holder 40, and the lower support plate 30 and the silicon wafer 10 are formed by using the holes 13, 23, and 33 in the guide rod 41. And, when installed in the order of the upper support plate 20, the Cr / Au layer formed on the surface adjacent to each other is in contact. In this state, the weighted object 50 weighing a predetermined weight on the upper support plate 20 is placed on the end of the guide rod 41, and then heat is applied to the eutectic temperature of Au and silicon at about 375 ° C. The Au layers 12, 22, and 32 are bonded to each other, and as a result, the upper and lower support plates 20 and 30 are bonded to the upper and lower surfaces of the silicon wafer 10 (step C). At this time, they are pressed by the weight of the weighted object 50, so that the bonding is securely performed.

After the bonding is completed, the silicon wafer 10 and the upper and lower support plates 20 and 30 need to be cooled, and since the material of the upper and lower support plates 20 and 30 is made of silicon as described above, It does not cause the phenomenon of deformation. After cooling, the weighted object 50 is removed, and the silicon wafer 10 to which the upper and lower support plates 20 and 30 are bonded is removed from the guide rod 41, and the acceleration sensor as shown in FIG. 2 is completed. do.

When the semiconductor acceleration sensor manufactured through this series of processes is mounted on a moving object, the acceleration of the object is transmitted to the sensor, and the mass 16 vibrates up and down in proportion to the sensor. At this time, the beam supporting the mass 16 is bent, so that stress is generated in the beam and the resistance value of the piezo resistor 14 on the top is changed. Therefore, the acceleration of the object is sensed by detecting the change in the resistance of the piezoresistor 14.

In the semiconductor accelerometer sensor according to the present invention having such a function, the upper and lower support plates 20 and 30 are made of a silicon material, and are bonded to the silicon wafer 10 at a low temperature by using an Au layer. The device wiring and circuit fabricated in) are not damaged, and the silicon wafer 10 and the support plates 20 and 30 are made of the same material, and thus do not receive thermal stress during cooling, so that no distortion occurs.

As described in detail above, the semiconductor acceleration sensor and its manufacturing method according to the present invention is composed of a silicon material of the upper and lower support plates for supporting the silicon wafer and bonded them at a low temperature using an Au layer. Therefore, damage to device wirings and circuits fabricated in the silicon wafer is prevented, and also, since there is no thermal stress during the cooling process, the silicon wafer and the support plate are prevented from being warped.

Claims (2)

The Au layer 12 is formed on the upper and lower edges of the silicon wafer 10 on which the piezoelectric body 14 and the electrical conductor 15 functioning as electrical conductors are formed on the upper surface, and the mass 16 is formed on the central portion of the lower surface. The upper and lower surfaces of the silicon wafer 10 are coupled to each other, but the upper and lower support plates 20 and 30 of the silicon material having the receiving portions 24 and 34 formed thereon to allow the mass 16 to vibrate. Forming an Au layer (22) (32) to correspond with the Au layer (12) of the silicon wafer (10); Temporarily assembling the upper and lower support plates (20, 30) so that the respective Au layers (12, 22, 32) correspond to the upper and lower surfaces of the silicon wafer (10); The silicon wafer 10 and the Au layers 12, 22, and 32 of the upper and lower support plates 20 and 30 are bonded to the silicon wafer 10 and the upper and lower support plates 20 and 30. In the method of manufacturing a semiconductor acceleration sensor comprising the step of applying by applying heat and pressure to be coupled (); Temporarily assembling the upper and lower support plates 20 and 30 on the upper and lower surfaces of the silicon wafer 10; Holes 13, 23 and 33 are drilled to communicate with each other at the edges of the silicon wafer 10 and the edges of the upper and lower support plates 20 and 30, respectively. The lower support plate 30, the silicon wafer 10, and the upper support plate 20 are sequentially formed by using the holes 13, 23, and 33 in the guide rod 41 that is erected to have a predetermined length. Method of manufacturing a semiconductor acceleration sensor comprising the step of fitting. The method of claim 1, Bonding by applying heat and pressure, the method of manufacturing a semiconductor acceleration sensor comprising the step of applying a pressure by placing a weighting object (50) on top of the upper support plate (20).

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