JP2009079948A - Semiconductor acceleration sensor and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a semiconductor acceleration sensor and its manufacturing method contributing to miniaturization, and a semiconductor acceleration sensor and its manufacturing method contributing to cost reduction by simplification of a structure and simplification of a loading process. <P>SOLUTION: This semiconductor acceleration sensor manufactured by using a semiconductor substrate includes a planar weight displaced by generation of an acceleration; a weight post projecting from the semiconductor substrate, for connecting the weight to the semiconductor substrate; a detection element formed on the semiconductor substrate, and connected to the weight post, for detecting an acceleration corresponding to movement of the weight; the first wiring formed on the semiconductor substrate, and connected to the detection element; and an external terminal projecting from the semiconductor substrate to the same direction as the weight post, and connected electrically to the first wiring. The external terminal is mounted directly on the mounting substrate. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a semiconductor acceleration sensor, and more particularly to a semiconductor acceleration sensor that contributes to downsizing and cost reduction by devising a structure and a manufacturing process, and a manufacturing method thereof.

  In recent years, a method of manufacturing a very minute structure of about several hundred microns using a micromachine technology applying a semiconductor microfabrication technology has attracted attention. Such microstructures are being studied for application to various sensors, optical switches, high-frequency components and the like in the field of optical communication. In general, such a micromachine application component is manufactured using a semiconductor process, and thus can be integrated on a signal processing LSI and a chip. As a result, a system having a certain function can be constructed on the chip. An element having such a function is called MEMS (Micro Electrical Mechanical System) in the United States, and MIST (Micro System Technology) in Europe.

One of widely used application parts of MEMS (MIST) is an acceleration sensor. Accelerometers are widely used in underground environment information measurement systems such as automobile airbags and seismic activities, and IT component earthquake resistance systems. Japanese Examined Patent Publication No. 8-7228 discloses a piezo-type acceleration sensor employing a MEMS structure.
Japanese Patent Publication No. 8-7228

  FIG. 1 is a top view (perspective view) of the semiconductor acceleration sensor disclosed in Patent Document 1. FIG. 2 shows a cross-sectional structure in the AA direction of FIG. This acceleration sensor is hermetically sealed by a thin plate material 11 such as ceramics, metal, or organic material. A wiring portion 12 is provided inside the thin plate material 11. A sensor chip 15 is mounted on the wiring part 12 via an adhesive 16. The sensor chip 15 includes a weight 13 that is displaced by the generation of acceleration and a glass plate 14 that controls the amplitude of the weight 13. The aluminum electrode 17 formed on the sensor chip 15 and the post 20 are connected via a metal wire 18. The post 20 is electrically connected to the external terminal 19.

In the conventional semiconductor acceleration sensor as described above, the wire from the chip electrode 17 connected to the acceleration detecting element (piezoresistive element) to the external terminal 19 (20) is wired by the metal wire 18, and the sensor is sealed. Therefore, the height and area of the entire sensor are increased. As a result, it has been difficult to use in small portable devices such as a mobile phone and an operation unit of a game machine. Moreover, since there are many constituent materials, a manufacturing process became complicated and the apparatus cost was high as a result.

  The present invention has been made in view of the above situation, and an object thereof is to provide a semiconductor acceleration sensor that contributes to downsizing and a method of manufacturing the same.

  Another object of the present invention is to provide a semiconductor acceleration sensor that contributes to cost reduction by simplifying the structure or simplifying the mounting process and a method for manufacturing the same.

  In order to achieve the above object, according to a first aspect of the present invention, there is provided a semiconductor acceleration sensor manufactured using a semiconductor substrate; a flat weight that is displaced by the generation of acceleration; A weight post that connects the semiconductor substrate and the semiconductor substrate; a sensing element that is formed on the semiconductor substrate and that is coupled to the weight post and detects acceleration according to the movement of the weight; and is formed on the semiconductor substrate and the detection A first wiring connected to the element; and an external terminal protruding from the semiconductor substrate in the same direction as the weight post and electrically connected to the first wiring. The external terminals are directly mounted on the mounting board.

  In the semiconductor acceleration sensor as described above, preferably, a predetermined space is formed between the weight and the mounting substrate, and the weight is not sealed with respect to the mounting substrate.

  The weight post is preferably a single post connected to the center of gravity of the weight.

  Furthermore, it is preferable that the detection elements are at least three elements arranged at equal intervals on a virtual circle centered on the position of the center of gravity of the weight.

  The weight can be formed by copper plating.

  According to a second aspect of the present invention, in the method for manufacturing a semiconductor acceleration sensor manufactured using a semiconductor substrate, a step of forming a detection element that detects acceleration according to the movement of a weight on the semiconductor substrate; Forming a first wiring connected to the sensing element on the substrate; forming a second wiring connected to the sensing element on the semiconductor substrate; and forming the second wiring on the semiconductor substrate. Forming a weight post connected and protruding from the semiconductor substrate; forming an external terminal protruding from the semiconductor substrate in the same direction as the weight post and electrically connected to the first wiring; Forming a flat plate-shaped weight connected to the weight post and substantially parallel to the semiconductor substrate. The stress applied to the weight post by the second wiring is transmitted to the sensing element. The external terminals are directly mounted on the mounting board.

  In the method of manufacturing a semiconductor acceleration sensor as described above, preferably, a predetermined space is formed between the weight and the mounting substrate, and the weight is not sealed with respect to the mounting substrate.

  The weight post is preferably a single post connected to the center of gravity of the weight.

  Furthermore, it is preferable that the detection elements are at least three elements arranged at equal intervals on a virtual circle centered on the position of the center of gravity of the weight.

The weight can be formed by copper plating.

  According to the present invention configured as described above, the height and area of the entire semiconductor sensor can be reduced because the external terminals are directly mounted on the mounting substrate without using metal wires for the connection between the sensor chip and the mounting substrate. Get smaller. The semiconductor acceleration sensor according to the present invention can be a WCSP (wafer level chip size package). Further, by not using a metal wire, the structure and the manufacturing process are simplified, and the cost can be reduced. Furthermore, the adoption of a weight having a novel structure completely different from the conventional one and its supporting structure also contributes to downsizing of the apparatus and simplification of the manufacturing process.

  By directly mounting the external terminals on the mounting substrate, the weight (sensor chip) can be prevented from being sealed with respect to the mounting substrate, and the apparatus can be thinned. Further, since the process of sealing the sensor chip is not required, the manufacturing process is simplified.

  If a structure in which one weight post is connected to the center of gravity of the weight is employed, the structure and the manufacturing process can be simplified.

  By arranging at least three detection elements at equal intervals on a virtual circle centered on the center of gravity of the weight, it becomes possible to accurately measure three-dimensional acceleration based on the output of each detection element.

In the weight and its supporting structure according to the present invention, the weight can be easily formed by copper plating, which contributes to simplification of the manufacturing process and reduction of manufacturing cost.

  FIG. 3 is a top view (perspective view) showing the structure of the semiconductor acceleration sensor according to the present invention. FIG. 4 is a cross-sectional view in the AA direction of FIG. FIG. 5 is an enlarged cross-sectional view showing the structure of region A in FIG. 6 is an enlarged cross-sectional view showing the structure of region B in FIG. FIG. 7 is an explanatory diagram (plane) showing the positional relationship between the weight, the weight post, the acceleration sensing element, and the stress transmission wiring of the semiconductor acceleration sensor according to the present invention.

  The semiconductor acceleration sensor 100 according to the embodiment of the present invention includes a flat plate-like weight 101 that is displaced by the generation of acceleration; a weight post 102 that protrudes from the semiconductor substrate 131 and connects the weight 101 and the semiconductor substrate 131; A sensing element 103 formed on the semiconductor substrate 131 to detect acceleration according to the movement of the weight 101; and connected to the weight post 102 and the sensing element 103 to detect stress applied to the weight post 102; A second wiring (stress transmission wiring) 118 for transmitting to the element 103; a first wiring 106 formed on the semiconductor substrate 131 and connected to the sensing element 103; and from the semiconductor substrate 131 in the same direction as the weight post 102 The external terminal (105, 108) which protrudes and is electrically connected with the 1st wiring 106 is provided. The external terminals (105, 108) are directly mounted on the mounting board.

  The “semiconductor acceleration sensor” according to the present invention can be applied to relatively large devices such as an air bag for automobiles, an underground environment information measuring system such as seismic activity, and an earthquake resistant system for IT parts, as well as mobile phones and game machines. It can also be used for small portable devices such as the operation unit.

  The weight 101 is formed into a rectangle having a thickness of about 100 micrometers and a side of about 1.5 mm by copper plating. The planar shape of the weight may be other than a rectangle, such as a circle or a regular polygon. As shown in FIG. 4, the difference (distance) d between the upper surface of the weight 101 and the upper surface of the external terminal 108 can be about 100 micrometers. This gap d allows the weight 101 to move freely away from the mounting substrate (not shown), while preventing excessive movement in the direction of the mounting substrate. That is, the mounting substrate itself serves as a stopper.

  As with the weight 101, the weight post 102 is formed of copper into a diameter of about 150 micrometers and a height (thickness) of about 90 micrometers. As can be seen from FIGS. 3 and 7, the weight post 102 is connected to the center of gravity (center) of the weight 101. A plurality of weight posts can be arranged.

  As the sensing element 103, a piezoresistive element that is common in acceleration sensors can be used. In the present embodiment, four detection elements 103 are arranged at equal intervals on a virtual circle centered on the position of the center of gravity of the weight 101. Note that the number of sensing elements 103 may be three or four or more.

  The stress transmission wiring 118 is formed of copper having a thickness of about 5 micrometers to 10 micrometers. If a plurality of weight posts (102) are provided, the weight posts (102) can be directly connected to the piezoresistive element (103), and the stress transmission wiring 118 can be omitted. However, the use of the stress transmission wiring 118 increases the degree of freedom of arrangement of the piezoresistive element 103. That is, the piezoresistive element 103 can be arranged at a position away from the weight 101.

  Similar to the weight post 102, the terminal post 105 is formed of copper to have a diameter of about 150 micrometers and a height (thickness) of about 90 micrometers. A solder terminal (solder ball) 108 is provided on the terminal post 105. The solder terminal 108 is formed to have a diameter of about 200 micrometers, and as described above, the solder terminal 108 protrudes upward from the weight 101 in the figure. As the solder terminal 108, a so-called “resin core” type solder including a resin at the center can be used in addition to the normal solder. In this case, the height (thickness) is higher than that of the normal solder. It becomes easy to enlarge and adjust the height.

  The terminal post 105 and the detection element 103 are connected by metal wirings 106 and 115. Here, the metal wiring 115 and the detection element 103 are formed in the first layer on the semiconductor substrate 131 and are covered with the insulating film 132. On the other hand, the wirings 106 and 108 are formed in the second layer and are covered with the insulating film 133.

  In the semiconductor acceleration device according to the embodiment of the present invention as described above, when acceleration is generated in the device, the metal post 102 that supports the weight 101 is deformed. When the post 102 is deformed, stress is transmitted to the detection element 103 via the stress transmission wiring 118, and the electrical characteristics of the detection element 103 change. This change is transmitted as an output signal of the detection element 103 to the mounting substrate 150 (see FIG. 11) via the wirings 115 and 106, the terminal posts 105, and the solder terminals 108.

  8A to 8D, FIG. 9E to FIG. 9G, FIG. 10H to FIG. 10J, FIG. 11K, and FIG. It is sectional drawing which shows the manufacturing process of the semiconductor acceleration sensor 100 which concerns on invention. In manufacturing the semiconductor acceleration sensor 100, first, as shown in FIG. 8A, the piezoresistive element 103 and the metal wiring 115 are formed on the surface of the semiconductor substrate (wafer) 131, and the insulating film 132 is further formed.

  Next, as shown in FIG. 8B, an insulating film 133 is formed on the entire surface of the wafer. Thereafter, as shown in FIG. 8C, the stress transmission wiring 118 and the metal wiring 106 are formed on the insulating film 133 and on the surface thereof. Next, as shown in FIG. 8D, an insulating film 134 that protects the metal wirings 106 and 118 is formed.

  Subsequently, an insulating film 135 is formed on the insulating layer 134. Thereafter, as shown in FIG. 9E, a cylindrical hole 136 that reaches the wirings 118 and 106 through the insulating layer 134 and the insulating film 135 is formed by a general photolithographic process and etching process.

  Next, as shown in FIG. 9F, a metal such as copper that will later become the weight post 102 and the terminal post 105 is filled into the cylindrical hole 136 by an electrolytic plating process. After that, as shown in FIG. 9G, another insulating film 140 is formed on the insulating film 135, and a portion corresponding to the weight 101 in the insulating film 140 is formed by a general photolithography process and an etching process. A hole 142 is formed.

  Subsequently, as shown in FIG. 10H, copper is formed in the hole 142 by plating. Next, the insulating films 135 and 140 are removed by a film removing step, thereby forming the weight posts 102, the weight 101, and the terminal posts 105 as shown in FIG. Thereafter, as shown in FIG. 10J, solder 108 is formed on the tip of the terminal post 105 by a solder printing process and a reflow process.

  Next, as shown in FIG. 11 (K), the wafer 131 is cut by a cutting blade or a laser and separated into individual chips 100. Thereafter, the chip 100 is turned over and mounted on the mounting substrate 150. At this time, the solder 108 is directly connected to the pad of the mounting substrate 150.

  As described above, in this embodiment, the device configuration is only the chip, the metal wiring, and the insulating film, and further, the processing cost can be reduced because batch processing can be performed on the wafer. Since the metal chip is not used for connection between the sensor chip 100 and the mounting substrate 150 and the external terminals 105 and 108 are directly mounted on the mounting substrate 150, the height and area of the entire semiconductor sensor 100 are reduced. The semiconductor acceleration sensor 100 according to the present embodiment can be a WCSP (wafer level chip size package). Further, by not using a metal wire, the structure and the manufacturing process are simplified, and the cost can be reduced. Furthermore, the adoption of a weight having a novel structure completely different from the conventional one and its supporting structure also contributes to downsizing of the apparatus and simplification of the manufacturing process.

  By directly mounting the external terminals 105 and 108 on the mounting substrate, the weight (sensor chip) can be prevented from being sealed with respect to the mounting substrate 150 (see FIG. 11L), and the device can be thinned. be able to. Moreover, since the process of sealing the sensor chip 100 is not required, the manufacturing process is simplified.

As mentioned above, although the Example of this invention was described, this invention is not limited to these Examples at all, It can change in the category of the technical idea shown by the claim. In the above-described embodiments, the order of the process for forming the insulating film after the formation of the wiring is used. However, the order of the process for forming the insulating film after the formation of the post may be used. Further, although the weight 101 is made of metal (copper), an insulator such as a resin or a semiconductor such as silicon can be used.

FIG. 1 is a top view (perspective view) showing the structure of a conventional semiconductor acceleration sensor. FIG. 2 is a cross-sectional view in the AA direction of FIG. FIG. 3 is a top view (perspective view) showing the structure of the semiconductor acceleration sensor according to the present invention. FIG. 4 is a cross-sectional view in the AA direction of FIG. FIG. 5 is an enlarged cross-sectional view showing the structure of region A in FIG. 6 is an enlarged cross-sectional view showing the structure of region B in FIG. FIG. 7 is an explanatory diagram (plane) showing the positional relationship between the weight, the weight post, the acceleration sensing element, and the stress transmission wiring of the semiconductor acceleration sensor according to the present invention. 8 (A) to 8 (D) are cross-sectional views showing the manufacturing process of the semiconductor acceleration sensor according to the present invention. FIGS. 9E to 9G are cross-sectional views showing the manufacturing process of the semiconductor acceleration sensor according to the present invention. 10 (H) to 10 (J) are cross-sectional views showing the manufacturing process of the semiconductor acceleration sensor according to the present invention. 11 (K) and 11 (L) are cross-sectional views showing the manufacturing process of the semiconductor acceleration sensor according to the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 100 Semiconductor acceleration sensor 101 Weight 102 Weight post 103 Piezoresistive element (acceleration detection element)
105 Terminal post 108 Solder terminal 115 Metal wiring (first wiring)
118 Stress transmission wiring (second wiring)
131 Semiconductor substrate (wafer)

Claims (11)

In a semiconductor acceleration sensor manufactured using a semiconductor substrate,
A flat weight that is displaced by the generation of acceleration;
A weight post protruding from the semiconductor substrate and connecting the weight and the semiconductor substrate;
A sensing element formed on the semiconductor substrate, coupled to the weight post, and sensing acceleration according to displacement of the weight;
A first wiring formed on the semiconductor substrate and connected to the sensing element;
An external terminal protruding from the semiconductor substrate in the same direction as the weight post and electrically connected to the first wiring;
The semiconductor acceleration sensor, wherein the external terminal is directly mounted on a mounting substrate.   2. The apparatus according to claim 1, further comprising: a second wiring formed on the semiconductor substrate, connected between the weight post and the sensing element, and transmitting stress applied to the weight post to the sensing element. 2. The semiconductor acceleration sensor according to 1.   The semiconductor acceleration sensor according to claim 1, wherein a predetermined space is formed between the weight and the mounting substrate, and the weight is not sealed with respect to the mounting substrate.   4. The semiconductor acceleration sensor according to claim 1, wherein the weight post is a single post connected to a center of gravity of the weight.   5. The semiconductor acceleration sensor according to claim 1, wherein the detection elements are at least three elements arranged at equal intervals on a virtual circle centered on the position of the center of gravity of the weight. .   The semiconductor acceleration sensor according to claim 1, 2, 3, 4, or 5, wherein the weight is formed by copper plating. In a method for manufacturing a semiconductor acceleration sensor manufactured using a semiconductor substrate,
Forming a sensing element on the semiconductor substrate for sensing acceleration according to the displacement of the weight;
Forming a first wiring connected to the sensing element on the semiconductor substrate;
Forming a second wiring connected to the sensing element on the semiconductor substrate;
Forming a weight post connected to the second wiring and protruding from the semiconductor substrate;
Forming an external terminal protruding from the semiconductor substrate in the same direction as the weight post and electrically connected to the first wiring;
Forming a flat plate weight connected to the weight post and substantially parallel to the semiconductor substrate,
A structure in which stress applied to the weight post by the second wiring is transmitted to the sensing element;
A method of manufacturing a semiconductor acceleration sensor, wherein the external terminal is directly mounted on a mounting substrate.   8. The method of manufacturing a semiconductor acceleration sensor according to claim 7, wherein a predetermined space is formed between the weight and the mounting substrate, and the weight is not sealed with respect to the mounting substrate.   9. The method of manufacturing a semiconductor acceleration sensor according to claim 7, wherein the weight post is a single post connected to the center of gravity of the weight.   10. The semiconductor acceleration sensor according to claim 7, 8 or 9, wherein the sensing elements are at least three elements arranged at equal intervals on a virtual circle centered on the position of the center of gravity of the weight. Method.   The method of manufacturing a semiconductor acceleration sensor according to claim 7, 8, 9, or 10, wherein the weight is formed by copper plating.

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