JP2823853B2 - Manufacturing method of image reading device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for manufacturing an image reading device. An image reading apparatus according to the present invention has, for example, a line sensor in which optical sensors are arranged one-dimensionally, and reads image information while relatively moving a document related to image reading in a state where the line sensor is in close contact with the line sensor. It is suitably applied to a facsimile machine, an image reader, and the like. [Prior art and its problems] Conventionally, as an image reading apparatus using a line sensor,
2. Description of the Related Art There is known an image forming apparatus that forms an image of a document on a line sensor using a line sensor having a length of about several cm and a reduction optical system to read image information. This type of image reading apparatus has a drawback in that it requires a large optical path length because it uses a reduction optical system, and it is difficult to reduce the size of the apparatus because the volume of the imaging optical system is large. In addition, using a long line sensor having the same length as the document width, an image of the document is formed on the line sensor using an equal-magnification imaging optical system composed of a converging optical fiber assembly, and image reading is performed. What is done is also known. According to this, the volume of the optical system can be significantly reduced, and the size of the device can be reduced. FIG. 9 is a schematic configuration diagram showing an example of such an image reading apparatus of the unit-size imaging system. In the figure, reference numeral 102 denotes an apparatus frame, on which a reading unit 104, an irradiation light source 106, and a 1: 1 imaging optical system 108 are mounted. Also, a document conveying roller 110 is attached to the frame 102. Reference numeral 112 denotes a read original. The reading unit 104 includes a line sensor in which a plurality of optical sensors are arranged one-dimensionally in a direction perpendicular to the paper surface. The illumination light source 106 is an LED array, and the unit-magnification imaging optical system 108 is a converging optical fiber bundle.
Each of these, including the line sensor 10, has a longitudinal direction in a direction perpendicular to the paper surface, like the line sensor in the reading unit 104. A predetermined portion of the document 112 illuminated by the light source 106 is rotated by the driving means (not shown) to rotate a predetermined portion of the document 112 by the driving means (not shown). An image is read by forming an image on the sensor. The line sensor in the reading unit 104 has a length equal to the width of the document 112. As the sensor, conventionally, several line sensor units formed using an Si wafer having a length of about several inches are used. A single long sensor using a spliced or thin film semiconductor is used. However, those using the above-mentioned Si wafer line sensor unit can realize a high reading speed by forming the read signal transfer portion using the single crystal because the single crystal of Si is used. However, there is a problem in that a high level of technology is required for mounting for correctly connecting and arranging the units, and the unit becomes expensive. In addition, the use of the above-mentioned thin film semiconductor is advantageous in that the mounting is simple because it is integrated, but when the read signal transfer portion is formed using the thin film semiconductor such as the amorphous silicon, the charge mobility is low. As a result, the transfer capability is extremely low, and the reading speed is low. Therefore, an object of the present invention is to provide an inexpensive image reading apparatus that has a sufficiently high reading speed, is easy to mount, and is easy to mount. Another object of the present invention is to provide a method suitable for manufacturing such an image reading device. [Means for Solving the Problems] According to the present invention, as a means for achieving the above object, a sensor unit and a transfer unit for an output signal of the sensor unit are provided on a substrate having at least a surface portion having an insulating property. In the method for manufacturing an image reading apparatus, a nucleation surface having a nucleation density sufficiently higher than that of the material on the surface of the base and having a sufficiently small size such that only a single nucleus grows. Is formed of a dissimilar material, and then, by depositing a semiconductor material, a crystal based on the nucleus formed on the nucleation surface is grown to form a single crystal semiconductor layer on the substrate surface, and a signal including the semiconductor layer is formed. A method for manufacturing an image reading device is provided, wherein a transfer unit is formed and a sensor unit is formed on the semiconductor layer. [Operation] In the present invention, the formation of the single crystal semiconductor layer on the surface of the base is performed by selectively generating a single crystal nucleus on a desired position on the surface of the base, and depositing a crystal based on the nucleus. A selective nucleation crystal growth method for forming a film is used. First, the selective deposition method will be described to make the selective nucleation crystal growth method easier to understand. Selective deposition is a method of selectively depositing a thin film on a substrate by utilizing the differences between the materials, such as surface energy, adhesion coefficient, desorption coefficient, and surface diffusion rate, that affect nucleation during the film formation process. It is a method of forming. FIGS. 10A and 10B are explanatory diagrams of the selective deposition method. First, as shown in FIG.
And a thin film 2 made of a material having the above factors different from each other is formed at a desired portion. When a thin film made of an appropriate material is deposited under an appropriate deposition condition, a phenomenon that the thin film 3 grows only on the thin film 2 but not on the substrate 1 can be caused. By utilizing this phenomenon, the thin film 3 formed in a self-aligned manner can be grown, and a conventional lithography process using a resist can be omitted. Here, during deposition, the surface of the substrate 1 is used as a non-nucleation surface, and the surface of the thin film 2 is used as a nucleation surface. Materials that can be deposited by such a selective deposition method include, for example, SiO ₂ as the substrate 1, Si, GaAs, silicon nitride as the thin film 2, and Si, W, GaAs, InP as the thin film 3 to be deposited. . FIG. 11 is a graph showing the change over time of the nucleation density between the deposition surface of SiO _{2 and} the deposition surface of silicon nitride. As the graph shows, shortly after the start of deposition, SiO ₂
The nucleation density above is saturated below 10 ³ cm ^-2 , and its value hardly changes after 20 minutes. On the other hand, on silicon nitride (Si ₃ N ₄ ),
Once saturated at 0 ⁵ cm ^-2 , then it does not change for about 10 minutes,
After that, it increases rapidly. In this measurement example, Si
This shows a case in which Cl ₄ gas is diluted with H ₂ gas and deposited by the CVD method under the conditions of a pressure of 175 Torr and a temperature of 1000 ° C. S
iH ₄ , SiH ₂ Cl ₂ , SiHCl ₃ , SiF ₄ etc. are used as reaction gases,
A similar effect can be obtained by adjusting the pressure, temperature, and the like. Also, vacuum deposition is possible. In this case, nucleation on SiO ₂ is not a problem, but by adding HCl gas to the reaction gas, nucleation on SiO ₂ is further suppressed, and deposition of Si on SiO ₂ is completely eliminated. Can be Such a phenomenon is largely due to the difference in the adsorption coefficient, desorption coefficient, surface diffusion coefficient, etc. of the material surface of SiO ₂ and silicon nitride with respect to Si, but SiO ₂ reacts by the Si atoms themselves and the vapor pressure is high. The generation of silicon oxide etches SiO ₂ itself, and the fact that such an etching phenomenon does not occur on silicon nitride is also considered to be a cause of selective deposition (T. Yoneha).
ra, S.Yoshioka, S.Miyazawa Journal of Applied Physic
s 53,6839,1982). If SiO ₂ and silicon nitride are selected as the material for forming the deposition surface and silicon is selected as the deposition material, a sufficiently large nucleation density difference can be obtained as shown in the graph. Note that, here, SiO ₂ is desirable as a material for forming the deposition surface. However, the material is not limited to this, and a difference in nucleation density can be obtained even with SiOx. Of course, the invention is not limited to these materials, even a material such as 10 times or more at a density of nuclei preferably sufficient if 10 ³ times or more, exemplified later as shown by the same graph the difference in nucleation density Sufficient selective formation of a deposited film can be performed. As another method of obtaining the difference in nucleation density, a region having excessive Si, N, or the like may be formed by locally implanting ions of Si, N, or the like on SiO ₂ . Utilizing such a difference in nucleation density, a nucleation surface made of a dissimilar material having a nucleation density sufficiently higher than that of the deposition surface (non-nucleation surface) is made sufficiently fine so that only a single nucleus grows. By forming the nucleus, a single nucleus can be formed only at a portion where a nucleus forming surface made of a heterogeneous material having a small area exists, and a single crystal can be selectively grown from the nucleus. Since the selective growth of a single crystal is determined by the electronic state of the surface of the deposition surface, particularly the state of dangling bonds, a material having a low nucleation density (for example, SiO ₂ ) does not need to be a bulk material. What is necessary is just to form the above-mentioned deposition surface by being formed only on the surface of any material or substrate. Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. 1 (A) to 1 (E) are views showing a part of steps in an embodiment of a method for manufacturing an image reading device according to the present invention, and show steps of forming a single crystal semiconductor layer on a base. It is. First, as shown in FIG. 1 (A), an insulating layer 5 having a low nucleation density is formed on a substrate 4, and a heterogeneous material having a high nucleation density is thinly deposited thereon, and patterned by lithography or the like. By doing so, the nucleation surface 6 made of dissimilar material is formed sufficiently fine at a distance l. However, the material, size, crystal structure, and composition of the substrate 4 may be arbitrary, and may be a substrate on which a functional element is formed. The nucleation surface 6 made of a dissimilar material also includes an altered region having excessive Si, N, etc. formed by ion-implanting Si, N, etc. into the insulating layer 5 as described above. In this embodiment, silicon can be used as the substrate 4 and an amorphous silicon oxide thin film formed by thermally oxidizing the surface of the silicon can be used as the insulating layer 5. The substrate 1 according to the present invention comprises the substrate 4 and the insulating layer 5.
Is configured. Next, a single nucleus made of the deposited material is formed only on the nucleation surface 6 made of the dissimilar material by appropriate deposition conditions.
That is, the nucleation surface 6 needs to be formed fine enough to form only a single nucleus. The size of the nucleation surface 6 depends on the type of material, but may be several microns or less. As the deposition is continued, the nuclei grow while maintaining the single crystal structure, and become island-like single crystal grains 7 as shown in FIG. 1 (B). In order to form the island-shaped single crystal grains 7, it is necessary to determine conditions so that nucleation does not occur on the surface of the insulating layer 5 as described above. In this embodiment, amorphous Si ₃ N ₄ can be used as the dissimilar material. The island-shaped single crystal grains 7 grow further around the nucleation surface 6 while maintaining the single crystal structure, and come into contact with the adjacent single crystal grains 7 as shown in FIG. Since the orientation is not constant, a grain boundary 14 is formed at an intermediate position of the nucleation surface 6. Subsequently, the single crystal grain 7 grows three-dimensionally, but since the crystal face with a low growth rate appears as a facet, the surface is flattened by etching or polishing, as shown in FIG. 1 (D). A single crystal semiconductor layer 8 of a predetermined size is continuously arranged via a grain boundary 14. The size of each single crystal semiconductor layer 8 is determined by the interval 1 between the nucleation surfaces 6 as described above. That is, the position of the grain boundary can be controlled by appropriately determining the formation pattern of the nucleation surface 6, and the single crystal semiconductor layer 8 having a desired size can be controlled.
Can be formed in a desired arrangement. FIG. 1 (E) is a plan view of the state shown in FIG. 1 (D). In the present invention, as the substrate 1, in addition to the substrate described in the above embodiment, a substrate obtained by attaching a layer made of an insulating material such as SiO ₂ or silicon nitride on the surface of an appropriate substrate can be used. When the insulating layer 5 as a deposition surface (non-nucleation surface) is formed on the substrate 4 as described above, the substrate 4 serving as a support can be made of any material. The single crystal semiconductor layer 8 can be easily formed thereon even if such a structure is formed. In the above embodiment, the non-nucleation surface 5 is formed of a silicon oxide thin film, but, of course, an insulating material having a low nucleation density enabling selective nucleation, such as ceramics such as glass, quartz glass or alumina, is used as the base 1 as it is. make use of,
A single crystal semiconductor layer 8 may be formed on the surface of the base in a similar manner. 2 (A) to 2 (D) are views showing a part of the steps in one embodiment of the method for manufacturing the surface image reading device according to the present invention, and show the single crystal semiconductor layer 8 formed as described above. 2 shows a process of forming a sensor section and a signal transfer section by performing processes such as impurity diffusion, formation of a thermal oxide film, photolithography, and thin film deposition which are performed in a normal wafer process. As shown in FIG. 2A, the single-crystal semiconductor layer 8 is formed as described above, and is doped with a p-type impurity (for example, B-doping using a B ₂ H ₆ gas) during nucleation.
To be p-type. By diffusing an n-type impurity (for example, phosphorus or arsenic) into the single crystal semiconductor layer 8,
Form n ⁺ regions 22, 24, 26. Then, the single crystal semiconductor layer 8
The thermal oxide film 28 is formed on the surface of, the oxide film n ⁺ regions 22, 24
A contact hole is formed at a position corresponding to. Also,
A conductive layer 30 is formed on oxide film 8. As a result, a MOS type switching element 32 is formed in which the conductive layer 30 is used as a gate electrode, and the n ⁺ regions 22 and 24 are used as a source region and a drain region. Next, as shown in FIG. 2B, a photoconductive layer 3 made of amorphous silicon is formed on the thermal oxide film 28 by a plasma CVD method.
4 is formed, and n is further formed thereon for ohmic contact.
^{The +} layer 36 is formed. Next, as shown in FIG. 2 (C), A1 is deposited by sputtering and patterned into a desired shape to form a conductor layer for electrodes and wiring. The conductor layer is formed by a pair of electrodes 38, 40 at the photoconductive layer 34.
Constituting an electrode 42 in the portion of the n ⁺ layer 26,
The electrodes 44, 46, and 48 are configured in the signal transfer unit 32. A photoconductive sensor unit 50 is formed by the pair of electrodes 38 and 40 and the photoconductive layer 34, and the electrode 42, the thermal oxide film 28 and the n ⁺ layer 26 are formed.
Thus, the charge storage capacitor 52 of the signal transfer unit is formed. FIG. 2 (D) is a plan view of the state of FIG. 2 (C). In the device of the present embodiment as described above, the electron mobility of the switch element 32 is several hundred cm ² / Vs, and the electron mobility of the switch element formed using amorphous silicon is about 0.5 cm ² / V・
It is 1000 times larger than s. FIG. 3 is a diagram showing another embodiment of the image reading apparatus according to the present invention. In this figure, the same members as those in FIG. 2 are denoted by the same reference numerals. This embodiment is an example in which a diode type sensor is used for the sensor unit. In the figure, reference numeral 54 denotes a photoelectric conversion layer, which is sandwiched between the transparent electrode layer 56 and the electrode 40. The transparent electrode layer 56 is connected to the electrode 38, and these constitute a sensor unit 50 '. In this embodiment, the sensor is of the Schottky type,
Similarly, pin type and MIS type can be used,
These can all be formed by a well-known technique. FIG. 4 is a diagram showing another embodiment of the image reading apparatus according to the present invention. In this figure, the same members as those in FIG. 2 are denoted by the same reference numerals. This embodiment is an example in which a photoconductive sensor is used for the sensor unit and an auxiliary electrode is used. In the figure, 58 is an auxiliary electrode, 60 is an insulating layer, and the sensor section 50 ″ is configured to include these.
Reference numeral 62 denotes a wiring portion for driving the switch element 32, and reference numeral 64 denotes a wiring portion for signal reading, all of which are wired in a matrix. In the present embodiment, the auxiliary electrode 58 is for applying a desired potential to perform good reading, and an image reading apparatus using such an auxiliary electrode has already been applied for a patent by the present applicant. No.61-237064, Japanese Patent Application No.61
No.-237065, Japanese Patent Application No. 61-237066, Japanese Patent Application No. 61-237067
issue). FIG. 5 is a diagram showing another embodiment of the image reading apparatus according to the present invention. In this figure, the same members as those in FIG. 4 are denoted by the same reference numerals. This embodiment is an example in which a photoconductive sensor is used in the sensor section, an auxiliary electrode is used, and a CMOS transistor is used as a switch element. In the drawing, reference numeral 32 denotes a similar channel MOS in the embodiment of FIG. 4, and reference numeral 33 denotes a p-channel MOS. In the p-channel MOS, 66 is an n-well formed by phosphorus doping, and 68 and 70 are p ⁺ -type source and drain regions formed by boron diffusion. FIG. 6 is a diagram showing another embodiment of the image reading apparatus according to the present invention. In this figure, the same members as those in FIG. 4 are denoted by the same reference numerals. This embodiment is an example in which a photoconductive sensor is used for the sensor unit, an auxiliary electrode is used, and a bipolar transistor is used as a switch element. In the figure, 72 is an n ⁻ region formed by phosphorus diffusion, 74 is a p ⁺ type base region formed by boron diffusion, 76 is an n ⁺ type emitter region formed by phosphorus diffusion, Reference numeral 78 denotes an n-type collector region formed by phosphorus diffusion, and the impurity concentration near the interface with the wiring electrode is further increased to be n ⁺ -type. The switch element 80 is formed including these. FIG. 7 is an equivalent circuit diagram of the image reading apparatus of the embodiment of FIG. In the figure, Si1, Si2,... Sin (hereinafter, referred to as Si, where i is the block number and 1 to n are the number of bits in each block) are light in the sensor unit 50 ″. .., Cin (hereinafter, referred to as Ci) indicate charge storage capacitors 52, which store the photocurrent of each photosensor Si. STi1, STi2,. ... STin
(Hereinafter referred to as STi) indicates a transfer switch 32 for transferring the charge of the charge storage capacitor Ci to the load capacitors CX1, CX2,..., CXn, and SRi1, SRi2,.
(Hereinafter referred to as SRi) indicates a discharging switch for resetting the charge of the charge storage capacitor Ci. Each of the sensor section Si, the charge storage capacitor Ci, the transfer switch STi, and the discharge switch SRi are arranged in an array in a row, and each block constitutes one block of n pieces. Become. For example,
Assuming that there are 1728 sensors, n = 32, m
= 54. The gate electrodes of the transfer switch STi and the discharge switch SRi provided in an array are connected to the gate wiring unit 100. The gate electrode of the transfer switch STi is commonly connected in the i-th block, and the gate electrode of the discharge switch SRi is circulated and connected to the gate electrode of the transfer switch of the next block. Common lines of the matrix wiring section 100 (gate drive lines G1, G2
... Gm) are driven by the gate drive unit 94.
On the other hand, the signal outputs are connected to the signal processing unit 92 in block units via lead lines 98 (signal output lines D1, D2,..., Dn) having a matrix configuration. Also, the optical sensor S11,
The auxiliary electrodes 58 of S12,..., S1n, S21,..., Smn are connected to the drive section 96 and are appropriately biased. , Gm are sequentially supplied from the gate drive unit 94 to the gate drive units G1, G2,..., Gm. First, when the gate drive line G1 is selected, the transfer switch ST1 is turned on, and the charge stored in the charge storage capacitor C1 is transferred to the load capacitors CX1 to CXn. . Next, when the gate drive line G2 is selected, the transfer switch ST2 is turned on, and the charge stored in the storage capacitor C2 is transferred to the load capacitors CX1 to CXn,
At the same time, the charge of the storage capacitor C1 is reset by the discharging switch SR1. Hereinafter, similarly, G3, G4, ...
The reading operation is also performed with Gm selected. These operations are performed for each block, and the signal outputs VX1, VX2,... VXm of each block are input D1, D2,
... Sent to Dn, converted to a serial signal and output. FIG. 8 is a diagram showing an embodiment of the image reading apparatus of the present invention. In this figure, the same members as those in FIG. 4 are denoted by the same reference numerals. In this embodiment, the configurations of the sensor unit and the signal transfer unit are the same as those in the embodiment of FIG. The arrangement of the light source and the document is different from the case of FIG. That is, the light source 10
Reference numeral 7 is disposed on the base 1 side, and the illumination light flux from the light source passes through the base 1 and the single-crystal semiconductor layer 8, further passes through the transparent spacer 111 covering the sensor section and the signal transfer section, and The light is reflected by the original 112 which is disposed in close contact with the original, and the reflected light is incident on the sensor unit 50 ″, and reading is performed. The spacer 111 is used to maintain a constant distance between the sensor unit 50 ″ and the original 112. And a transparent body such as glass or quartz is used. The spacer may have a multilayer structure, for example, a layer adjacent to the sensor unit may be a passivation layer and a layer adjacent to the document 112 may be a wear-resistant layer. In the present embodiment, the auxiliary electrode 58 of the sensor unit 50 "also has a function of preventing direct light from the light source 107 from entering the photoconductive layer 34. [Effect of the Invention] The present invention as described above. According to this, since the sensor unit and the signal transfer unit are formed on the same base and the signal transfer unit is formed using the single crystal semiconductor layer, the signal transfer capability is extremely large and the reading speed is sufficient. In addition, the present invention provides an image reading device that is high in cost, easy to mount, and inexpensive.In addition, since the signal transfer portion is formed using a single crystal semiconductor layer, the variation in transfer capability is small, Since the current is suppressed and the SN ratio is high, a multi-gradation image reading device can be realized.

BRIEF DESCRIPTION OF THE DRAWINGS FIGS. 1 (A) to 1 (E) and 2 (A) to 2 (D) are views showing a part of the steps of a method of manufacturing an image reading apparatus according to the present invention. 3 to 6 and 8 are views showing an image reading apparatus according to the present invention. FIG. 7 is an equivalent circuit diagram of the image reading apparatus according to the present invention. FIG. 9 is a schematic configuration diagram showing an image reading apparatus of the unit-size imaging system. FIGS. 10A and 10B are explanatory diagrams of the selective deposition method.
FIG. 11 is a graph showing the change over time of the nucleation density in the selective deposition method. 1: base, 5: insulating layer, 6: nucleation surface, 8: single crystal semiconductor layer, 32, 33, 80: switch element, 50, 50 ′, 50 ″: sensor section.

Claims (1)

(57) [Claims] In a method for manufacturing an image reading apparatus in which a pair of a sensor unit and a transfer unit of an output signal of the sensor unit are formed on a substrate having at least a surface portion having an insulating property, the nucleation density of the substrate surface portion is higher than that of the material. A nucleation surface is formed of a dissimilar material that is sufficiently large and large enough to grow only a single nucleus, and then a crystal based on the nuclei formed on the nucleation surface is formed by depositing a semiconductor material. Forming a single-crystal semiconductor layer on the surface of the base, forming a signal transfer section including the semiconductor layer, and forming a sensor section on the semiconductor layer. Production method. 2. 2. The method according to claim 1, further comprising a step of forming a switch element in the signal transfer unit. 3. 3. The method according to claim 2, wherein the switch element is one of a MOS transistor, a CMOS transistor, and a bipolar transistor. 4. 2. The method according to claim 1, wherein the sensor unit is one of a photoconductive sensor and a diode sensor.