JP3553889B2 - Manufacturing method of sensor for surface shape recognition - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method for manufacturing a surface shape recognition sensor that senses a surface shape having minute unevenness such as a human fingerprint or an animal nose pattern.
[0002]
[Prior art]
With the progress of the information society and the environment of the modern society, interest in security technology is increasing. For example, in the information-oriented society, personal authentication technology for system construction such as electronic cash has become an important key. In addition, research and development of authentication technology for protection against theft and unauthorized use of cards are being actively conducted (for example, Yoshimasa Shimizu et al., "A study on IC cards with functions with personal authentication". ", IEICE Technical Report of IEICE, OFS 92-32, p25 30 (1992)). There are various authentication methods such as fingerprints and voice prints. Among them, many techniques have been developed for the fingerprint authentication technique. Fingerprint authentication methods are broadly classified into an optical reading method, a method of detecting unevenness of a fingerprint and replacing it with an electric signal, and a method of utilizing human electrical characteristics.
[0003]
The optical reading method is a method in which a fingerprint is read mainly using light reflection and a CCD sensor, and the read fingerprint data is collated with pre-registered fingerprint data (for example, Seigo Igaki et al., “Personal collation method” And apparatus ", JP-A-61-221883). As a method of detecting the unevenness of a fingerprint, a method using a piezoelectric thin film to read the pressure difference of the fingerprint has been developed (for example, Masanori Sahara et al., "Fingerprint Sensor", JP-A-5-61965). As a method of detecting a fingerprint by replacing a change in electrical characteristics caused by contact with the skin with a distribution of electric signals, an authentication method using a resistance change amount or a capacitance change amount using a pressure-sensitive sheet has been proposed (for example, Kazuhiro Hemi, "Surface shape sensor, individual authentication device and activated system using the same," JP-A-7-168930).
[0004]
However, in the above techniques, first, the optical reading method has a problem that it is difficult to reduce the size and general use, and the application is limited. Next, it is considered that the method of detecting the unevenness of the fingerprint using a pressure-sensitive sheet or the like is difficult to be put into practical use due to the specialty of the material and the difficulty in workability, and the reliability is poor.
[0005]
In order to solve such a problem, Marco Tartagni et al. Have developed a capacitive fingerprint sensor by using LSI manufacturing technology (Marco Tartagni and Roberto Guerrieri, A390 dpi Liverberg Fedgerbinder Fedgerprint Image Finder Image Finder, Germany). Capacitive Sensing Scheme, 1997 IEEE International Solid-State Circuits Conference, p200 201 (1997)). This capacitive sensor detects a feedback capacitance of a small sensor element arranged two-dimensionally on an LSI chip, and detects an uneven pattern of the skin.
[0006]
Here, this capacitive fingerprint sensor will be described with reference to the drawings. FIG. 4 is a sectional view showing a conventional capacitive fingerprint sensor. As shown in FIG. 1, the capacitive fingerprint sensor has a sensor electrode 22 formed on a semiconductor substrate 21 on which an LSI or the like is formed, and an interlayer film 23 serving as a passivation film formed on the sensor electrode 22. is there. That is, the skin in contact with the interlayer film 23 immediately above the sensor electrode 22 functions as an electrode, and is configured to detect the unevenness of the fine structure by detecting the capacitance between the skin and the sensor electrode 22. This structure is characterized in that a special interface is not required and the size can be reduced as compared with the conventional optical type. However, in the capacitive sensor, since the skin is used as an electrode, there is a problem that an LSI or the like mounted on the semiconductor substrate 21 is easily damaged by static electricity generated at the time of contact.
[0007]
[Problems to be solved by the invention]
As described above, the optical sensor has a problem that it is difficult to reduce the size and general use, and the pressure-sensitive sensor has a problem that it is difficult to put it to practical use and has poor reliability. In addition, the capacitive sensor has a problem that the semiconductor circuit is easily damaged by electrostatic discharge. Therefore, there is provided a surface shape recognition sensor that is small and versatile and can detect minute irregularities such as human fingerprints and animal nose prints in a stable and highly reliable state with high sensitivity, and a method of manufacturing the same. Development has long been desired.
An object of the present invention is to provide a surface shape recognition sensor capable of performing stable and highly sensitive detection in a highly reliable state, for example, without being damaged by static electricity generated during sensing. It is in.
[0008]
[Means for Solving the Problems]
The method for manufacturing a sensor for recognizing a surface shape according to the present invention includes a step of forming a first electrode (3) on a semiconductor substrate (1), and a step of forming a second electrode on the semiconductor substrate around the first electrode. Forming (4), forming a third electrode (6) on the second electrode so as to be spaced apart from the first electrode, and forming a third electrode on the third electrode. A step of transferring the first insulator (9) by the STP method, a step of forming a second insulator (10) on the first insulator, and processing the second insulator into a projection shape. And a process.
Further, in the method of manufacturing a sensor for recognizing a surface shape according to the present invention, a step of forming a first electrode (3) on a semiconductor substrate (1) and a step of forming a second electrode around the first electrode on the semiconductor substrate. Forming the third electrode (4) on the second electrode, forming the third electrode (6) on the second electrode so as to be spaced apart from the first electrode, and forming the third electrode (6) on the third electrode. And a step of processing the insulator (11) into an upwardly convex shape by an STP method .
[0009]
Further, as one configuration example of a method of manufacturing a surface shape recognition sensor of the present invention, the step of forming the first electrode includes the steps of: forming a first metal film (2) on the semiconductor substrate; Forming a patterned first resist on a first metal film, forming the first electrode in an opening of the first resist, and removing the first resist; The step of forming the second electrode includes the step of forming a second resist patterned on the first metal film, and the step of forming the second electrode in an opening of the second resist. Forming a third electrode, comprising: forming the second resist; removing the second resist; and etching the first metal film using the first and second electrodes as a mask. Is a sacrificial film (on the first and second electrodes) ), Removing the sacrificial film on the second electrode to expose the second electrode, and forming a second metal film (7) on the second electrode and the sacrificial film. Forming a third resist patterned on the second metal film; forming the third electrode in an opening of the third resist; A step of removing the resist, a step of etching the second metal film using the third electrode as a mask, and a step of removing the sacrificial film, wherein the step of transferring the first insulator comprises: Transferring the first insulator onto the third electrode by the STP method; and forming the second insulator includes applying a photosensitive insulator onto the first insulator. And processing the second insulator into a protruding shape. A step of exposing a part of the serial second insulator is made of a step of developing after the exposure.
Further, as one configuration example of a method of manufacturing a surface shape recognition sensor according to the present invention, the step of forming the first electrode includes the steps of forming a first metal film on the semiconductor substrate; Forming a first resist patterned on a metal film, forming the first electrode in an opening of the first resist, and removing the first resist; The step of forming the second electrode includes a step of forming a patterned second resist on the first metal film, and a step of forming the second electrode in an opening of the second resist. Removing the second resist; and etching the first metal film using the first and second electrodes as a mask. The step of forming the third electrode comprises: Forming a sacrificial film on the first and second electrodes; Removing the sacrifice film on the second electrode to expose the second electrode; forming a second metal film on the second electrode and the sacrifice film; Forming a third resist patterned on the second metal film, forming the third electrode in an opening of the third resist, and removing the third resist; A step of etching the second metal film using the third electrode as a mask; and a step of removing the sacrificial film. In the step of transferring the insulator, a photosensitive insulator is formed by an STP method. The step of transferring the insulator onto a third electrode, and the step of processing the insulator into an upwardly convex shape includes exposing a part of the insulator and developing after exposure, thereby forming an exposed portion of the insulator. The thickness of the unexposed portion of the insulator and the film of the exposed portion It is made of the step of generating a difference.

[0010]
BEST MODE FOR CARRYING OUT THE INVENTION
[First Embodiment]
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. 1 and 2 are process cross-sectional views showing a method for manufacturing a surface shape recognition sensor according to a first embodiment of the present invention. The semiconductor substrate 1 in the present embodiment includes a semiconductor integrated circuit such as a sensor circuit for detecting the capacitance of the surface shape recognition sensor, and a wiring layer for connecting the semiconductor integrated circuit and the surface shape recognition sensor. An interlayer insulating film covering the semiconductor integrated circuit and the wiring layer has already been formed, and the interlayer insulating film has a through hole connected to the wiring layer. In the present embodiment, a method for manufacturing a surface shape recognition sensor will be described on the assumption that the above structure is already formed.
[0011]
First, a seed layer 2 made of metal is formed on the entire surface of an interlayer insulating film on a semiconductor substrate 1, and then a first resist (not shown) for plating is formed on the seed layer 2. For example, patterning is performed to form a square opening in a portion (a region where the first electrode 3 is formed), and the first electrode 3 made of metal is formed in the opening by plating (FIG. 1A). ). As a result, the first electrode 3 and the first through hole (not shown) provided in the interlayer insulating film are electrically connected via the seed layer 2, so that the first electrode 3 is connected to the semiconductor integrated circuit. Are electrically connected via the seed layer 2, the first through hole, and the first wiring layer (not shown).
[0012]
In this embodiment, Ti / Au is formed as a seed layer 2 by a vapor deposition method in a thickness of 0.1 μm, and a first resist for plating is formed in a thickness of 5.0 μm. In the plating step, an Au film was formed to a thickness of 1.0 μm as the first electrode 3 using electrolytic plating.
[0013]
Next, after the first resist for plating is peeled off, a second resist for plating (not shown) is formed on the seed layer 2 and a part of this resist (the second electrode 4 is formed). Patterning is performed to form an opening in the opening), and a second electrode 4 having a larger film thickness than the first electrode 3 is formed in the opening. Then, after the second resist for plating is removed, the seed layer 2 other than immediately below the electrodes 3 and 4 is removed by etching (FIG. 1B). As a result, the second electrode 4 and the second through hole (not shown) provided in the interlayer insulating film are electrically connected via the seed layer 2, so that the second electrode 4 is connected to the semiconductor integrated circuit. Are electrically connected via the seed layer 2, the second through hole, and the second wiring layer (not shown).
[0014]
In the present embodiment, a second resist for plating is formed with a thickness of 5.0 μm, and in the plating step, an Au film is formed as the second electrode 4 with a thickness of 3.0 μm using electrolytic plating. The seed layer 2 was removed by wet etching using the first and second electrodes 3 and 4 as a mask.
[0015]
Subsequently, a sacrificial film 5 is formed so as to cover the first and second electrodes 3 and 4 (FIG. 1C). In the present embodiment, the sacrificial film 5 made of photosensitive polyimide is formed to be thicker than the second electrode 4 by using the spin method. The sacrificial film 5 is not limited to photosensitive polyimide, but may be another material as long as the material can be a sacrificial film, that is, a material that can be removed by isotropic etching described later.
After the formation of the sacrificial film 5, the sacrificial film 5 on the second electrode 4 is exposed and developed to remove the sacrificial film 5 and expose the second electrode 4. After the exposure and development, annealing at 310 ° C. is performed (FIG. 1D).
[0016]
After the annealing, etching is performed using chemical polishing to flatten the surfaces of the second electrode 4 and the sacrificial film 5, and a third electrode made of metal is formed on the flattened second electrode 4 and the sacrificial film 5. 6 is formed by patterning (FIG. 1E). In the present embodiment, a seed layer 7 made of metal is formed so as to cover the entire surface of the second electrode 4 and the sacrificial film 5, and a third resist (not shown) for plating is formed on the seed layer 7. Then, patterning for forming an opening in a part of the resist (the region where the third electrode 6 is formed) was performed, and the third electrode 6 made of metal was formed by plating. Thus, the third electrode 6 and the second electrode 4 are electrically connected via the seed layer 7.
[0017]
Here, Ti / Au was formed as a seed layer 7 by a thickness of 0.1 μm by vapor deposition, and a third resist for plating was formed to a thickness of 5.0 μm. Then, the third resist is patterned so that the shape of the third electrode 6 becomes a mesh shape. In the plating step, an Au film was formed as the third electrode 6 to a thickness of 0.4 μm using electrolytic plating. After the formation of the third electrode 6, the third resist for plating is peeled off, and the seed layer 7 other than immediately below the electrode 6 is removed by wet etching using the third electrode 6 as a mask.
[0018]
Next, the sacrificial film 5 is removed by isotropic dry etching (FIG. 1F). In the present embodiment, since the third electrode 6 is processed into a mesh shape, the opening 8 for removing the sacrificial film is provided in the third electrode 6 and the seed layer 7, and the etching of the sacrificial film 5 is performed. It can be done easily.
[0019]
After removing the sacrificial film 5, the first insulator 9 is formed as a sealing film on the third electrode 6 (FIG. 2A). In the present embodiment, the first insulator 9 is formed using the STP (Spin Coating Film Transfer and Hot Pressing) method. In the STP method, an insulator is applied in advance on a film, and the insulator on the film is heated and pressed against the surface of the third electrode 6 in a vacuum, and then the film is peeled off, thereby separating the insulator. This is a method of transferring to the surface of the third electrode 6.
[0020]
In this embodiment, a polyimide film having a thickness of 1 μm is formed as the first insulator 9. As for the conditions of the STP, the transfer of the insulator was performed at a load of 5 kg, a degree of vacuum of 10 Torr, a heating temperature of 150 ° C., and a transfer time of 1 minute. After forming the first insulator 9, annealing at 300 ° C. was performed for 30 minutes.
[0021]
Then, a projecting second insulator 10 was formed on the first insulator 9 (FIG. 2B). In the present embodiment, a photosensitive polyimide film is formed as the second insulator 10 by a coating method of about 5 μm to 10 μm, and then light is exposed except for a central portion of the sensor (a portion located directly above the first electrode 3). After development, the film was removed. After the development, annealing at 300 ° C. was performed for 30 minutes. The first and second insulators 9 and 10 function as protective films. The reason why the second insulator 10 is formed in the shape of a protrusion is to improve the detection sensitivity.
[0022]
Thus, the manufacture of the surface shape recognition sensor is completed. When the second insulator 10 comes into contact with the object, the third electrode 6 is deformed. As a result, the capacitance between the first electrode 3 and the third electrode 6 changes. By detecting the change in the capacitance as an electric signal by the sensor circuit, the unevenness of the object can be detected. In the present embodiment, the second electrode 4 and the third electrode 6 are formed so as to surround the periphery of the first electrode 3. Grounding can prevent the semiconductor integrated circuit in the semiconductor substrate 1 from being electrostatically damaged.
[0023]
[Second Embodiment]
FIG. 3 is a process sectional view showing a method of manufacturing a sensor for recognizing a surface shape according to a second embodiment of the present invention, and the same components as those in FIG. Also in the present embodiment, the steps from FIG. 1A to FIG. 1F are completely the same as those in the first embodiment, and therefore the description is omitted.
[0024]
After removing the sacrificial film 5 in FIG. 1F, in the present embodiment, the photosensitive insulator 11 is formed as a sealing film on the third electrode 6 (FIG. 3A). The photosensitive insulator 11 is formed by using the STP method described in Embodiment 1. In this embodiment, a photosensitive polyimide film having a thickness of 10 μm is formed as the photosensitive insulator 11. As for the conditions of STP, the insulator was transferred at a load of 5 kg, a degree of vacuum of 10 Torr, a heating temperature of 150 ° C., and a transfer time of 1 minute.
[0025]
Next, the photosensitive insulator 11 was removed by exposing and developing a portion other than the center of the sensor, and the photosensitive insulator 11 was processed into an upwardly convex shape (FIG. 3B). After the development, annealing at 300 ° C. was performed for 30 minutes.
As described above, a surface shape recognition sensor having the same structure and operation principle as those of the first embodiment can be realized.
[0026]
As described above, in the first and second embodiments, by sealing the movable space of the sensor using the STP method, it is possible to manufacture the surface shape recognition sensor more easily than in the past.
In the first and second embodiments, the number of sensors for surface shape recognition is one, but a plurality of sensors may be arranged two-dimensionally.
[0027]
【The invention's effect】
According to the present invention, since the second electrode and the third electrode are formed so as to surround the periphery of the first electrode, if the second electrode and the third electrode are grounded, the inside of the semiconductor substrate can be formed. Of the semiconductor integrated circuit can be prevented from being electrostatically damaged. As a result, it is possible to suppress the occurrence of electrostatic destruction as with conventional capacitive sensors, and it is smaller and more versatile than optical or pressure-sensitive sensors, and can be used to reduce the fineness of human fingerprints and animal nose prints. It is possible to realize a surface shape recognizing sensor capable of detecting irregularities stably with high sensitivity in a highly reliable state. In addition, by using transfer as a method for forming an insulator on the third electrode, the manufacture of the sensor for surface shape recognition can be simplified.
[Brief description of the drawings]
FIG. 1 is a process sectional view showing a method for manufacturing a surface shape recognition sensor according to a first embodiment of the present invention.
FIG. 2 is a process sectional view illustrating a method for manufacturing the surface shape recognition sensor according to the first embodiment of the present invention.
FIG. 3 is a process sectional view illustrating a method for manufacturing a surface shape recognition sensor according to a second embodiment of the present invention.
FIG. 4 is a cross-sectional view of a conventional capacitive fingerprint sensor.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Semiconductor substrate, 2 ... seed layer, 3 ... 1st electrode, 4 ... 2nd electrode, 5 ... sacrifice film, 6 ... 3rd electrode, 7 ... seed layer, 8 ... Opening, 9 ... 1st Insulator 10; second insulator 11; photosensitive insulator.

Claims (4)

Forming a first electrode on a semiconductor substrate;
Forming a second electrode around the first electrode on the semiconductor substrate;
Forming a third electrode on the second electrode so as to face the first electrode at a distance;
Transferring the first insulator onto the third electrode by the STP method ;
Forming a second insulator on the first insulator;
Processing the second insulator into a projection shape. Forming a first electrode on a semiconductor substrate;
Forming a second electrode around the first electrode on the semiconductor substrate;
Forming a third electrode on the second electrode so as to face the first electrode at a distance;
Transferring an insulator onto the third electrode by an STP method ;
Processing the insulator into an upwardly convex shape. The method for manufacturing a sensor for surface shape recognition according to claim 1 ,
Forming a first metal film on the semiconductor substrate; forming a patterned first resist on the first metal film; and forming the first electrode on the first metal film. Forming a first electrode in an opening of one of the resists, and removing the first resist;
The step of forming the second electrode includes a step of forming a patterned second resist on the first metal film, and a step of forming the second electrode in an opening of the second resist. Removing the second resist; and etching the first metal film using the first and second electrodes as a mask.
The step of forming the third electrode includes forming a sacrificial film on the first and second electrodes and removing the sacrificial film on the second electrode to expose the second electrode. A step of forming a second metal film on the second electrode and the sacrificial film; a step of forming a patterned third resist on the second metal film; and a step of forming the third resist Forming the third electrode in the opening, removing the third resist, etching the second metal film using the third electrode as a mask, and removing the sacrificial film. Removal process,
The step of transferring the first insulator includes a step of transferring the first insulator onto the third electrode by an STP method;
Forming the second insulator comprises applying a photosensitive insulator on the first insulator;
Manufacturing the surface shape recognition sensor , wherein the step of processing the second insulator into a projection shape includes a step of exposing a part of the second insulator and a step of developing after exposure. Method. The method for manufacturing a sensor for surface shape recognition according to claim 2 ,
Forming a first metal film on the semiconductor substrate; forming a patterned first resist on the first metal film; and forming the first electrode on the first metal film. Forming a first electrode in an opening of one of the resists, and removing the first resist;
The step of forming the second electrode includes a step of forming a patterned second resist on the first metal film, and a step of forming the second electrode in an opening of the second resist. Removing the second resist; and etching the first metal film using the first and second electrodes as a mask.
The step of forming the third electrode includes forming a sacrificial film on the first and second electrodes and removing the sacrificial film on the second electrode to expose the second electrode. A step of forming a second metal film on the second electrode and the sacrificial film; a step of forming a patterned third resist on the second metal film; and a step of forming the third resist Forming the third electrode in the opening, removing the third resist, etching the second metal film using the third electrode as a mask, and removing the sacrificial film. Removal process,
The step of transferring the insulator includes a step of transferring a photosensitive insulator onto the third electrode by an STP method;
The step of processing the insulator into an upwardly convex shape includes exposing a part of the insulator and developing after exposure, thereby reducing a film thickness of an exposed portion of the insulator, and forming the non-insulator. A method for producing a sensor for recognizing a surface shape, comprising a step of causing a film thickness difference between an exposed portion and the exposed portion .

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