Patent Application
20150155323
The present invention relates to a chip-stacked image sensor and a manufacturing method thereof, and more particularly to a chip-stacked image sensor having a heterojunction structure and a manufacturing method thereof, in which the chip-stacked image sensor is manufactured by manufacturing a first semiconductor chip and a second semiconductor chip using substrate materials suitable for the characteristics of sensors formed on the semiconductor chips, respectively, and then stacking the semiconductor chips on each other.
In the semiconductor industry, packaging technology for integrated circuits has continued to develop in order to satisfy the demand for miniaturization and mounting reliability. Also, with the recent demand for high performance of electric and electronic products together with the miniaturization thereof, various three-dimensional (3D) wafer stacking technologies for vertically stacking two or more semiconductor chips or semiconductor packages have been developed.
In such wafer stacking technologies, a three-dimensional (3D) device is manufactured by stacking wafers, subjecting the stack to a thinning process of grinding the backside of the wafers to reduce the thickness, and subjecting the thinned stack to subsequent processes, followed by sawing and packaging.
In such wafer stacking technologies, a chip-stacked image sensor having a three-dimensional (3D) structure is manufactured by subjecting a first semiconductor chip and a second semiconductor chip to the respective processes, and then putting bonding pads, formed on the two semiconductor chips, respectively, on each other so as to come into contact with each other.
In this conventional chip-stacked image sensor, the first semiconductor chip and the second semiconductor chip have all been manufactured using a silicon (Si)-based substrate for high-speed and high-capacity data processing without taking into consideration the characteristics of a sensor formed in each of the semiconductor chips. For this reason, there is a problem in that the characteristics required for each sensor are not properly exhibited.
It is an object of the present invention to provide a chip-stacked image sensor having a heterojunction structure, in which the chip-stacked image sensor is manufactured by manufacturing a first semiconductor chip and a second semiconductor chip using substrate materials suitable for the characteristics of sensors formed in the semiconductor chips, respectively, and then stacking the semiconductor chips on each other, so that the characteristics of the sensor formed in each of the semiconductor chips can be properly exhibited.
Another object of the present invention is to provide a method for manufacturing a chip-stacked image sensor having a heterojunction structure, in which the chip-stacked image sensor is manufactured by manufacturing a first semiconductor chip and a second semiconductor chip using substrate materials suitable for the characteristics of sensors formed in the semiconductor chips, respectively, and then stacking the semiconductor chips on each other, so that the characteristics of the sensor formed on each of the semiconductor chips can be properly exhibited.
To achieve the above objects, an embodiment of the present invention provides a chip-stacked image sensor having a heterojunction structure, the chip-stacked image sensor including: a first semiconductor chip having, formed on a first semiconductor substrate, a photodiode and a first pad configured to transfer an image charge, which corresponds to an image signal sensed by the photodiode, to the outside of the first semiconductor substrate; and a second semiconductor chip having, formed on a second semiconductor substrate, a second pad that is bonded to the first pad, and a circuit region configured to output the image signal, transferred from the first semiconductor chip, to the outside of the second semiconductor chip, wherein the first semiconductor substrate and the second semiconductor substrate are made of different materials.
Another embodiment of the present invention provides a chip-stacked image sensor having a heterojunction structure, the chip-stacked image sensor including: a first semiconductor chip having, formed on a first semiconductor substrate, a photodiode, a transmission transistor configured to transmit an image charge, which corresponds to an image signal sensed by the photodiode, to a floating diffusion region, and a first pad configured to transfer the image charge, which corresponds to the image signal sensed by the photodiode, to the outside of the first semiconductor substrate; and a second semiconductor chip having, formed on a second semiconductor substrate, a second pad that is bonded to the first pad, and a circuit region configured to output the image signal, transferred from the first semiconductor chip, to the outside of the second semiconductor chip, wherein the first semiconductor substrate and the second semiconductor substrate are made of different materials.
Still another embodiment of the present invention provides a method for manufacturing a chip-stacked image sensor having a heterojunction structure, the method including the steps of: forming a first semiconductor chip having, formed on a first semiconductor substrate, a photodiode and a first pad configured to transfer an image charge, which corresponds to an image signal sensed by the photodiode, to the outside of the first semiconductor substrate; forming a second semiconductor chip having, formed on a second semiconductor substrate, a second pad that is bonded to the first pad, and a circuit region configured to output the image signal, transferred from the first semiconductor chip, to the outside of the second semiconductor chip; pretreating the first semiconductor chip and the second semiconductor chip before bonding; and bringing the first pad of the pretreated first semiconductor chip and the second pad of the pretreated second semiconductor chip into contact with each other so as to face each other, thereby bonding the first semiconductor chip and the second semiconductor chip to each other, wherein the first semiconductor substrate and the second semiconductor substrate are made of different materials.
Yet another embodiment of the present invention provides a method for manufacturing a chip-stacked image sensor having a heterojunction structure, the method including the steps of: forming a first semiconductor chip having, formed on a first semiconductor substrate, a photodiode, a transmission transistor configured to transmit an image charge, which corresponds to an image signal sensed by the photodiode, to a floating diffusion region, and a first pad configured to transfer the image charge, which corresponds to the image signal sensed by the photodiode, to the outside of the first semiconductor substrate; forming a second semiconductor chip having, formed on a second semiconductor substrate, a second pad that is bonded to the first pad, and a circuit region configured to output the image signal, transferred from the first semiconductor chip, to the outside of the second semiconductor chip; pretreating the first semiconductor chip and the second semiconductor chip before bonding; and bringing the first pad of the pretreated first semiconductor chip and the second pad of the pretreated second semiconductor chip into contact with each other so as to face each other, thereby bonding the first semiconductor chip and the second semiconductor chip to each other, wherein the first semiconductor substrate and the second semiconductor substrate are made of different materials.
A chip-stacked image sensor having a heterojunction structure according to the present invention and a manufacturing method thereof have an advantage in that, because a first semiconductor substrate that is used in a first semiconductor chip, and a second semiconductor substrate that is used in a second semiconductor chip, are made of different materials, the characteristics of a sensor formed in each of the semiconductor chips can be properly exhibited.
Hereinafter, the present invention will be described in further detail with reference to the accompanying drawings.
As shown in
On the first semiconductor substrate of the first semiconductor chip 10, there are formed a photodiode 14 and a first pad 17 configured to transfer an image charge, which corresponds to an image signal sensed by the photodiode, to the outside of the first semiconductor chip 10.
A first buffer layer 18, a color filter 12, a second buffer layer 19 and a micro-lens 11, which are formed above the photodiode 14 on the first semiconductor substrate, are known, and thus the detailed description thereof is omitted.
On the second semiconductor substrate of the second semiconductor chip 20, there are formed a second pad 21 bonded to the first pad 17, and a circuit region configured to output the image charge, transferred from the first semiconductor chip 10, to the outside of the second semiconductor chip 20.
In the circuit region located on the second semiconductor chip 20, there are formed a transmission transistor 22, a reset transistor 23, a source follower transistor 24, a blocking switch transistor 25, a read-out circuit, a vertical/horizontal decoder, a correlated double sampling (CDS) circuit which is involved in a sensor operation and image quality, an analog circuit, an analog-digital converter (ADC), and a digital circuit.
The first semiconductor substrate forming the first semiconductor chip 10 is preferably a substrate made of Ge, SiGe, GaAs, GaN, InP, InGaAs or InGaZnO in view of the characteristics of the sensor unit that is formed in the first semiconductor chip 10. In addition, the first semiconductor substrate may also be an epitaxial substrate obtained by allowing Ge, SiGe, GaAs, GaN, InP, InGaAs to InGaZnO to grow into a single crystal on a silicon (Si) substrate. Alternatively, it may be a GeOI, SiGeOI, GaAsOI, GaNOI, InPOI, InGaAsOI or InGaZnOOI substrate obtained by forming an insulating film on each substrate material so as to have silicon-on-insulator (SOI) characteristics.
Meanwhile, the second semiconductor substrate forming the second semiconductor chip 20 is preferably a silicon (Si) substrate.
The second semiconductor substrate forming the second semiconductor chip 20 may be a non-silicon substrate such as sapphire or SiGe, depending on the characteristics thereof. In other words, the first substrate and the second substrate are made of different materials regardless of the kind of material of the second substrate, and the first semiconductor chip 10 and the second semiconductor chip 20 are stacked by bonding so as to form a single circuit.
Preferably, the second substrate is a silicon (Si) substrate, and the first substrate is a non-silicon (non-Si) substrate.
For example, when a sensor that is formed in the first semiconductor chip 10 is an infrared ray sensor, the first semiconductor chip is formed using a first semiconductor substrate made of a germanium (Ge)-based material that is highly sensitive to infrared rays, and the second semiconductor chip is formed using a second semiconductor substrate made of a silicon (Si) material that enables high-speed data processing, so that infrared ray sensitization and high-speed data processing can all be performed.
Meanwhile, a sensor that is formed in the first semiconductor chip 10 can be fabricated using a Micro-Electro-Mechanical System (MEMS) or other methods, and the first semiconductor chip can be formed using a substrate made of a material that enables the characteristics of this sensor to be properly exhibited.
In the prior art, sensor elements in a sensor having a chip-stacked structure were uniformly formed on a silicon substrate. On the contrary, the present invention is characterized in that a substrate made of a material that enables the characteristics of each sensor element to be properly exhibited is selected and used.
As shown in
On the first semiconductor substrate of the first semiconductor chip 10, there are formed a photodiode 14, a transmission transistor 6 configured to transmit an image charge, which corresponds to an image signal sensed by the photodiode 14, to a floating diffusion region 15, and a first pad 17 configured to transfer the image charge, which corresponds to the image signal sensed by the photodiode 14, to the outside of the first semiconductor chip 10.
The chip-stacked image sensor having a heterojunction structure according to another embodiment of the present invention as shown in
As shown in
In the first semiconductor chip-forming step (S310), a first semiconductor chip is formed, which has, formed on a first semiconductor substrate, a photodiode and a first pad configured to transfer an image charge, which corresponds to an image signal sensed by the photodiode, to the outside of the first semiconductor chip.
In the second semiconductor chip-forming step (S320), a second semiconductor chip is formed, which has, formed on a second semiconductor substrate, a second pad that is bonded to the first pad, and a circuit region configured to output the image charge, transferred from the first semiconductor chip, to the outside of the second semiconductor chip.
Specifically, in the second semiconductor chip-forming step (S320), a circuit region is formed, which has formed therein a transmission transistor, a reset transistor, a source follower transistor, a blocking switch transistor, a read-out circuit, a vertical/horizontal decoder, a correlated double sampling (CDS) circuit which is involved in a sensor operation and image quality, an analog circuit, an analog-digital converter (ADC) and a digital circuit.
The first semiconductor chip-forming step (S310) and the second semiconductor chip-forming step (S320) may be performed simultaneously or in any order. In addition, the first semiconductor chip-forming step (S310) and the second semiconductor chip-forming step (S320) may be performed separately using different process technologies.
In the pre-bonding treatment step (S330), the surface of the first semiconductor chip and the surface of the second semiconductor chip, which are to be bonded to each other, are pretreated using a process such as plasma treatment, cleaning operation or surface treatment.
Next, in the semiconductor chip-bonding step (S340), the first pad of the pretreated first semiconductor chip 10 and the second pad of the pretreated second semiconductor chip are brought into contact with each other in such a manner as to face each other, thereby bonding the first semiconductor chip and the second semiconductor chip to each other.
Herein, the first semiconductor substrate that is used in the first semiconductor chip-forming step (S310), and the second semiconductor substrate that is used in the second semiconductor chip-forming step (S320), are made of different materials.
Specifically, in the first semiconductor chip-forming step (S310), the first semiconductor chip is preferably formed using a first semiconductor substrate made of Ge, SiGe, GaAs, GaN, InP, InGaAs or InGaZnO depending on the characteristics of a sensor unit to be formed in the first semiconductor chip.
Meanwhile, in the first semiconductor chip-forming step (S310), a first semiconductor substrate obtained by allowing Ge, SiGe, GaAs, GaN, InP, InGaAs or InGaZnO to epitaxially grow into a single crystal on a silicon (Si) substrate may be used. In addition, the first semiconductor substrate may also be a GeOI, SiGeOI, GaAsOI, GaNOI, InPOI, InGaAsOI or InGaZnOOI substrate obtained by forming an insulating film on each substrate material so as to have silicon-on-insulator (SOI) characteristics.
In this case, in the second semiconductor chip-forming step (S320), the second semiconductor chip is preferably formed using a second semiconductor chip made of silicon (Si).
Meanwhile, in a subsequent process step (S350) following the semiconductor chip-bonding step (S340), a color filter or a micro-lens is formed.
As shown in
In the first semiconductor chip-forming step (S410), a first semiconductor chip is formed, which has, formed on a first semiconductor substrate, a photodiode, a transmission transistor configured to transmit an image charge, which corresponds to an image signal sensed by the photodiode, to a floating diffusion region, and a first pad configured to transfer the image charge, which corresponds to the image signal sensed by the photodiode, to the outside of the first semiconductor chip.
Meanwhile, the method for manufacturing the chip-stacked image sensor having the heterojunction structure according to the embodiment of the present invention as shown in
As described above, a chip-stacked image sensor having a heterojunction structure according to the present invention and a manufacturing method thereof have an advantage in that, because a first semiconductor substrate that is used in a first semiconductor chip, and a second semiconductor substrate that is used in a second semiconductor chip, are made of different materials, the characteristics of a sensor formed in each of the semiconductor chips can be properly exhibited.
Although the preferred embodiments of the present invention have been disclosed for illustrative purposes, those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the invention as disclosed in the accompanying claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10-2012-0047946 | May 2012 | KR | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/KR2012/003680 | 5/10/2012 | WO | 00 | 11/7/2014 |
