JP3563880B2 - Semiconductor device and method of manufacturing semiconductor device - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a semiconductor device, and more particularly to a semiconductor device in which an electronic circuit and various microdevices are mounted at a high density, and a method of manufacturing the semiconductor device.
[0002]
[Prior art]
With the development of micromachine technology in recent years, mechanical devices such as physical sensors such as acceleration and angular velocity and microactuators have become as small as microelectronic devices typified by very large scale integrated circuits (VLSIs; Very Large Scale Integrated circuits). Is becoming more common.
[0003]
Along with this, attempts are being made to increase the functionality of, for example, an endoscope by mounting a micro mechanical device and a VLSI at a high density. As such a mounting technique, a technique similar to a mounting technique of a general electronic circuit such as a flexible board or a COB (Chip on Board) technique has been applied.
[0004]
Further, as a technique for disposing an electronic device in which a mechanical device is mounted in a narrow place, for example, a technique disclosed in Japanese Patent Application Laid-Open No. 7-86551 is known. That is, in the technology, a plurality of pressure sensors are mounted on electrodes of a flexible thin film integrally formed with a thinned electronic circuit. In this technique, since the entire module has flexibility, it is effective in assembling the apparatus having a complicated shape.
[0005]
[Problems to be solved by the invention]
However, in the mounting technology of a general electronic circuit such as the flexible substrate and the COB technology, a base for interconnecting an electronic device such as a VLSI and a micro mechanical device such as a microsensor or a microactuator is required separately. Therefore, miniaturization and thinning are limited due to device handling problems and space required for mounting on a board, which hinders miniaturization of the entire mounted device unit. For this reason, it is difficult to incorporate such a device unit into, for example, a distal end portion of an endoscope having a very small diameter, and it is desired to develop a technology for mounting higher-density mechanical devices and electronic devices.
[0006]
In addition, in the technique disclosed in Japanese Patent Application Laid-Open No. 7-86551, the rigidity and mechanical strength of the entire module are extremely low, so that when the module is mounted on a high-strength device surface such as an outer peripheral portion of an endoscope, for example, Although effective, when arranging the module in a narrow tube, it is necessary to fix the module on a high-rigidity base and then assemble it, which increases the number of assembly steps and the size of the entire module. . In addition, this technique has a problem that the manufacturing process of an electronic circuit becomes extremely complicated particularly when applied to a bipolar device suitable for analog processing due to a limitation on a manufacturing method of a thinned electronic device.
[0007]
SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has as its object to provide a semiconductor device and a semiconductor in which an electronic circuit and a miniaturized mechanical device are mounted at a high density, which can be assembled in a narrow tube. An object of the present invention is to provide a method for manufacturing a device.
[0008]
[Means for Solving the Problems]
In order to achieve the above object, a semiconductor device according to the present invention includes a semiconductor substrate having at least an electronic circuit formed on one principal surface, a flexible thin film integrally formed on the semiconductor substrate, and a flexible thin film. An electrode formed on and electrically connected to the electronic circuit, and a component that is electrically connected to the electrode and is separate from the semiconductor substrate disposed on the other main surface of the semiconductor substrate. It is characterized by having.
[0009]
In the method of manufacturing a semiconductor device, the island-shaped semiconductor region thinner than the semiconductor substrate is formed by forming an island-shaped reverse-conductivity-type diffusion layer on one main surface of the one-conductivity-type semiconductor substrate. And a step of etching the other main surface of the semiconductor substrate with an alkaline solution while applying a bias to the diffusion layer.
[0010]
That is, in the semiconductor device of the present invention, a flexible thin film is integrally formed on a semiconductor substrate on which at least an electronic circuit is formed on one main surface, and an electrode electrically connected to the electronic circuit on the flexible thin film. Is formed, and a component separate from the semiconductor substrate is electrically connected to the electrode and provided on another main surface of the semiconductor substrate.
[0011]
In the method of manufacturing a semiconductor device, an island-shaped diffusion layer of the opposite conductivity type is formed on one main surface of the semiconductor substrate of the one conductivity type, and the semiconductor substrate is formed with an alkaline solution while applying a bias to the diffusion layer. By etching from the other main surface, an island-shaped semiconductor region thinner than the semiconductor substrate is integrally formed.
[0012]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
First, FIG. 1 shows a configuration of a semiconductor device according to an embodiment of the present invention before mounting a separate component such as a mechanical device.
[0013]
In FIG. 1, a CMOS (Complementary MOS) electronic circuit 2 and electrodes 3 for external leads are formed on the surface of a P-type low-concentration silicon substrate 1 having a thickness of 500 μm and a plane orientation of <100>. A first port 4 and a second port 5 made of a polyimide thin film extend from one side of the P-type low-concentration silicon substrate 1.
[0014]
The first port 4 is composed of a polyimide film 6, an electrode 7 formed on the front surface of the polyimide film 6, and a single-crystal silicon thin film 8, 9 integrally formed on the back surface. The second port 5 includes a polyimide film 10, an electrode 11 formed on the surface of the polyimide film 10, and a thin-film single-crystal silicon 12 integrally formed on the back surface side. In addition, a CMOS electronic circuit 13 is formed on the single crystal silicon 8 of the thin film, and a polyimide film (not shown) (not shown in FIG. 2) is formed on the surface of the silicon substrate 1 here. I have.
[0015]
In this embodiment, the thickness of the thin film single crystal silicon 8, 12 is about 15 μm, and the thickness of the polyimide films 6, 10, 14 is about 10 μm. The surfaces of the electrodes 3, 7, and 11 are subjected to solder plating. However, it is a matter of course that the present invention is not limited to these.
[0016]
Here, FIGS. 2 and 3 show cross-sectional views of AA ′ and BB ′ in FIG. 1, respectively, and will be described. The polyimide films 6, 10, and 14 are two-layer films of an upper layer and a lower layer, and an Al wiring pattern 15 is formed between the upper layer and the lower layer. The wiring pattern 15 is connected to the electronic circuits 2 and 13 at predetermined positions via contact holes 16 opened in lower films of the polyimide films 10 and 14. Further, the wiring pattern 15 is connected to the electrodes 7 and 11 via contact holes 17 opened in the upper layers of the polyimide films 6 and 10.
[0017]
FIG. 4 shows a state in which the first port 4 and the second port 5 are deformed in order to mount another micro device.
In the figure, the polyimide films 6 and 10 are deformed into the shapes shown in the regions where the thin single crystal silicon 8, 9 and 12 are not formed. Since the polyimide films 6 and 10 are thin, the polyimide film itself and the internal wiring pattern 15 are not broken even if the polyimide films 6 and 10 are curved with a large curvature as shown.
[0018]
FIG. 5 shows a state in which the first micro mechanical device 18 is mounted on the first port 4 and the second micro mechanical device 19 is mounted on the second port 5.
In the figure, micromechanical devices 18 and 19 mounted on each port are manufactured by applying a semiconductor manufacturing technology, and for example, a micro optical scanner, a micro angular velocity sensor, a micro actuator, and the like are employed. . An electrode (not shown) for electrical connection of the micromechanical device 18 is soldered to the electrode 7 of the first port 4. Further, an electrode (not shown) for electrical connection of the micromechanical device 19 is soldered to the electrode 11 of the second port 5. The micromechanical devices 18 and 19 are fixed to the back surface of the silicon substrate 1 by bonding.
[0019]
Since thin-film single-crystal silicon 9 and 12 are formed on the back surface of the region where the electrodes 7 and 11 of the first port 4 and the second port 5 are formed, the region partially has high rigidity. I have. Therefore, when the electrodes 7 and 11 of the first port 4 or the second port 5 are joined to the electrode portion of the mechanical device by, for example, a method such as soldering, it is necessary to perform an operation such as pressing and further heating. Is easier to handle.
[0020]
The micro-mechanical device 19 is connected to the electronic circuit 2 formed on the surface of the silicon substrate 1 via the wiring pattern 15 in the second port, receives driving power from the electronic circuit 2, and further drives Sends and receives signals and measurement output signals. This is the same for the micromechanical device 18 connected to the first port 4, but between the micromechanical device 18 and the electronic circuit 2 on the silicon substrate, the electronic circuit formed on the thin single crystal silicon 8 is formed. 13 intervenes.
[0021]
An analog circuit for performing signal amplification and the like is formed in the electronic circuit 13. The analog circuit is separated from the electronic circuit 2 on the silicon substrate 1 and is arranged close to the mechanical device 18. Therefore, particularly when the mechanical device 18 is a sensor or the like that requires high-precision analog signal processing, it is difficult to be affected by noise generated from a digital circuit or the like of the electronic circuit 2. it can.
[0022]
The electronic circuit 2 is provided with a circuit for driving and controlling the mechanical devices 18 and 19. For example, a plurality of mechanical devices are arranged by a method such as time-division control of each mechanical device. In this case, it is needless to say that the number of wires required for connection with the external controller can be reduced, and as a result, the number of external lead electrodes 3 can be reduced.
[0023]
As described above, in the semiconductor device according to the present embodiment, the connection portion (port) for connecting the plurality of micromechanical devices to the electronic circuit for driving / control has flexibility and forms the electronic circuit. Because it is integrally formed on a silicon substrate, a general method such as wire bonding or solder ball that connects a connection part (port) for connecting to a micromechanical device and an electronic circuit is applied. There is an advantage that a required area is not required.
[0024]
Also, by arranging the micromechanical device on the back surface of the silicon substrate, there is no need for a separate substrate for electrically interconnecting the electronic circuit and the plurality of micromechanical devices. Substantial miniaturization is possible.
[0025]
Such a mounting method using a semiconductor device is effective when a plurality of electronic devices and mechanical devices are arranged in a narrow place. In addition, since the mechanical device is disposed on the back surface of the silicon substrate, unlike the case where the electronic device is disposed on the surface of the silicon substrate, an area such as an electrode pad for electrically connecting the mechanical device is provided. Therefore, the circuit area does not substantially decrease, and the circuit characteristics do not fluctuate due to the stress of the silicon substrate accompanying the fixing of the mechanical device.
[0026]
Furthermore, in an electronic circuit (corresponding to the reference numeral 2 in FIG. 1) other than the electronic circuit (corresponding to the reference numeral 13 in FIG. 1), a special structure (described later) necessary for electrochemical etching for normal thinning is used. (Corresponding to the reference numeral 102 in FIG. 8), various semiconductor devices including a bipolar device can be realized without requiring a significant additional manufacturing process.
[0027]
Next, a method of manufacturing the semiconductor device of the present embodiment will be described with reference to FIGS.
First, as shown in FIGS. 6A and 6B, CMOS electronic circuits 2 and 13 are formed on a low-concentration P-type silicon substrate 101 having a thickness of 500 μm. Further, a low-concentration deep N-type diffusion layer 102 is formed in a region corresponding to the single-crystal silicon 8, 9, 12 of the thin film in FIG. Here, in a region corresponding to the thin-film single crystal silicon 8, an N-type diffusion layer 102 is formed so as to cover the electronic circuit 13.
[0028]
For simplification of the drawing, detailed illustration of the electronic circuit portion is omitted here. However, as in the case of a normal CMOS integrated circuit, the surface thereof has an interlayer insulating film of a silicon oxide film and a multilayer Al wiring. Is formed.
[0029]
Next, as shown in FIGS. 6C and 6D, a lower polyimide film 103, an Al wiring pattern 15, and an upper polyimide film 104 are formed on the substrate surface. Here, the polyimide films 6, 10, and 14 in FIGS. 1 to 3 are configured by combining the lower polyimide film 103 and the upper polyimide film 104. Further, the Al wiring pattern 15 is mutually connected to the electronic circuits 2 and 13 and the electrodes 7 and 11 through contact holes 16 and 17 formed in predetermined portions of the upper polyimide film 103 and the lower polyimide film 104. Although not particularly shown, the electrode 3 is also electrically connected to the electronic circuit 2 by the Al wiring pattern 15.
[0030]
Next, as shown in FIGS. 7, 8A and 8B, patterns 105 and 106 of a silicon nitride film are formed on the back surface of the silicon substrate 101. Here, the silicon nitride film 105 is formed in a region corresponding to the silicon substrate 1 in FIG. 1, and the silicon nitride film 106 is formed in a region corresponding to the outer periphery of the semiconductor device in FIG.
[0031]
Next, the silicon substrate 101 is etched from the back side in an alkaline solution while a positive voltage is applied to the deep N-type diffusion layer 102 with the front side of the silicon substrate 101 protected. By this etching, etching proceeds in a region where the silicon nitride films 105 and 106 are not formed, and in a region where the deep N-type diffusion layer 102 is not formed, etching is performed up to a silicon oxide film (not shown) on the surface of the silicon substrate 1. Although progressing, in the region where the deep N-type diffusion layer 102 is formed, it stops near the junction between this diffusion layer and the substrate. Strictly, it stops near the end of the depletion layer of the PN junction on the substrate side.
[0032]
Therefore, the deep N-type diffusion layer 102 can be selectively left by this electrochemical etching. In this method, the thickness of the remaining single-crystal silicon is determined by the junction depth of the diffusion layer and the potential distribution when a bias is applied to the PN junction, which is controlled with high precision by using a normal semiconductor manufacturing technique. be able to. Therefore, very thin single-crystal silicon 8, 9, and 12 can be formed only by adding a step of forming the deep N-type diffusion layer 102 to a normal CMOS circuit manufacturing step.
[0033]
In this way, the shapes shown in FIGS. 8C and 8D are obtained. Thereafter, the silicon oxide film (not shown) exposed in the region from which silicon has been removed is selectively removed by reactive ion etching from the back surface, and the lower polyimide film 103 is exposed in this region. Thereafter, the semiconductor device shown in FIG. 1 is obtained by cutting out the shape of the broken line 107 in FIG. 9 (top view) by excimer laser ablation.
[0034]
As described above, in the method for manufacturing a semiconductor device according to the present embodiment, since the photolithography technique used for semiconductor manufacturing can be applied to all processing steps except cutting, there is an advantage that a very fine semiconductor device can be obtained. Also, since the thin-film single-crystal silicon 8 on which the electronic circuit 13 is formed and the thin-film single-crystal silicon 9 and 12 for increasing the rigidity of the electrode regions 7 and 11 are formed by electrochemical etching, a very thin single-crystal silicon Silicon can be manufactured easily and with high precision.
[0035]
Although the embodiment of the present invention has been described above, the present invention is not limited to this, and it is needless to say that various improvements and modifications can be made without departing from the gist of the present invention. For example, in describing the method of manufacturing a semiconductor device according to the above-described embodiment, only one semiconductor device is illustrated. However, it goes without saying that a large number of semiconductor devices can be manufactured from one silicon wafer.
[0036]
The summary of the semiconductor device and the method of manufacturing the semiconductor device of the present invention is as follows.
(1) a semiconductor substrate having at least an electronic circuit formed on one principal surface;
A flexible thin film formed integrally with the semiconductor substrate,
An electrode formed on the flexible thin film and electrically connected to the electronic circuit,
A part that is electrically connected to the electrode and is separate from the semiconductor substrate disposed on the other main surface of the semiconductor substrate;
It is characterized by having.
[0037]
In this aspect, another component such as a mechanical device is mounted on the back surface of the semiconductor substrate on which the electronic circuit is formed, and the connection between the component and the electronic circuit is formed in a flexible thin film integrally formed on the semiconductor substrate. Are formed by the wiring arranged in the first position. This eliminates the need for a substrate for separately arranging the electronic circuit and other components, and allows the wiring for electrically connecting the electronic circuit and other components to be formed integrally with the electronic device. The area required for wiring connection in the circuit is significantly reduced, so that the entire mounted module can be reduced in size.
(2) The semiconductor device according to (1), wherein an island-shaped semiconductor region thinner than the semiconductor substrate is formed integrally with a region where the electrode of the flexible thin film is formed.
[0038]
In this aspect, the thinned island-shaped semiconductor region is integrally formed in the electrode region of the flexible thin film on which the internal wiring is formed, to which another component such as a mechanical device is electrically connected. Therefore, the rigidity of this portion is increased, and the workability when connecting the electrode region of the flexible thin film to the electrode of another component is greatly improved.
(3) An island-shaped semiconductor region thinner than the substrate is integrally formed on the flexible thin film, an electronic circuit is formed on the island-shaped semiconductor region, and the electronic circuit is formed on the semiconductor substrate. The semiconductor device according to the above (1) or (2), wherein the semiconductor device is electrically connected to the formed electronic circuit and the electrode by a wiring formed in the flexible thin film.
[0039]
In this embodiment, a thin electronic circuit integrated with the thin film is arranged on a flexible thin film on which an electrode for electrically connecting the semiconductor device and another component such as a mechanical device is formed. it can. Since the thinned electronic circuit is thin and is formed integrally with the flexible thin film, an area necessary for electrical connection with the electronic circuit formed on the substrate of the semiconductor device is provided. Because it can be greatly reduced, the required size of the entire module is hardly increased. Further, since the thinned electronic circuit can be arranged very close to the mechanical device, the electronic circuit formed on the semiconductor substrate by processing the output signal of the mechanical device in this portion. Thus, it is possible to transmit a high-accuracy analog signal.
(4) In the method for manufacturing a semiconductor device according to (2) or (3), the island-shaped semiconductor region thinner than the semiconductor substrate is formed on one principal surface of a semiconductor substrate of one conductivity type. Forming an island-shaped reverse-conductivity-type diffusion layer on the semiconductor substrate, and etching from the other main surface of the semiconductor substrate with an alkaline solution while applying a bias to the diffusion layer. Device manufacturing method.
[0040]
In this embodiment, the thinned island-shaped semiconductor region is etched by using an alkaline solution in a state where a bias is applied to the substrate and the diffusion layer of the opposite conductivity type, thereby forming the diffusion layer and the diffusion layer therefrom. The extended depletion layer region can be selectively left in an island shape. In this method, since the etching of the silicon substrate itself can also serve as a process for forming a flexible thin film having wiring formed therein, an island-like thinned thin film does not require an additional process. A semiconductor region can be formed with high precision.
[0041]
【The invention's effect】
As described above in detail, according to the present invention, it is possible to provide a semiconductor device in which an electronic circuit and a miniaturized mechanical device are mounted at a high density, which can be assembled in a narrow tube, and a method of manufacturing the semiconductor device. Can be.
[Brief description of the drawings]
FIG. 1 is a diagram showing a configuration of a semiconductor device according to an embodiment of the present invention.
FIG. 2 is a sectional view of AA ′ in FIG. 1;
FIG. 3 is a sectional view of BB ′ in FIG. 1;
FIG. 4 is a diagram showing a state in which a first port 4 and a second port 5 are deformed in order to mount another micro device on the semiconductor device according to the embodiment.
FIG. 5 is a view showing a state in which a first micro mechanical device 18 is mounted on a first port 4 and a second micro mechanical device 19 is mounted on a second port 5;
FIG. 6 is a view illustrating a method of manufacturing the semiconductor device according to the embodiment;
FIG. 7 is a view illustrating a method of manufacturing the semiconductor device according to the embodiment;
FIG. 8 is a view illustrating a method of manufacturing the semiconductor device according to the embodiment;
FIG. 9 is a view illustrating a method of manufacturing the semiconductor device according to the embodiment;
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... P type low concentration silicon substrate 2, 13 ... Electronic circuit 3, 7, 11 ... Electrode 4 ... 1st port 5 ... 2nd port 6, 10 ... Polyimide thin film 8, 9, 12 ... Single crystal silicon

Claims (4)

A semiconductor substrate having at least an electronic circuit formed on one principal surface,
A flexible thin film formed integrally with the semiconductor substrate,
An electrode formed on the flexible thin film and electrically connected to the electronic circuit,
A part that is electrically connected to the electrode and is separate from the semiconductor substrate disposed on the other main surface of the semiconductor substrate;
A semiconductor device comprising: 2. The semiconductor device according to claim 1, wherein an island-shaped semiconductor region thinner than the semiconductor substrate is integrally formed with the region where the electrode of the flexible thin film is formed. An island-shaped semiconductor region thinner than the substrate is integrally formed on the flexible thin film, an electronic circuit is formed in the island-shaped semiconductor region, and the electronic circuit is formed on the semiconductor substrate. The semiconductor device according to claim 1, wherein the semiconductor device is electrically connected to a circuit and the electrode by a wiring formed in the flexible thin film. 4. The method for manufacturing a semiconductor device according to claim 2, wherein the island-shaped semiconductor region thinner than the semiconductor substrate is formed on one main surface of the one-conductivity-type semiconductor substrate. A method of manufacturing a semiconductor device, comprising: forming a diffusion layer of a mold type; and etching from the other main surface of the semiconductor substrate with an alkaline solution while applying a bias to the diffusion layer.

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