Image sensor and method for manufacturing the same

Embodiments relate to an image sensor and a method of manufacturing an image sensor. According to embodiments, an image sensor may include a first substrate, a photodiode, and an ion implantation isolation layer. According to embodiments, circuitry including a metal interconnection may be disposed over the first substrate. A photodiode may be provided in a crystalline semiconductor layer bonded to the first substrate, and electrically connected to the metal interconnection. The ion implantation isolation layer may be provided in the photodiode.

The present application claims priority under 35 U.S.C. 119 to Korean Patent Application No. 10-2007-0139749 (filed on Dec. 28, 2007), which is hereby incorporated by reference in its entirety.

BACKGROUND

An image sensor may be a semiconductor device that converts an optical image into an electrical signal. Image sensors may be classified into categories, such as a charge coupled device (CCD) image sensor and a complementary metal oxide silicon (CMOS) image sensor (CIS).

A CIS may include a photo diode and a MOS transistor formed in a unit pixel. A CIS may obtain an image by sequentially detecting electrical signals of unit pixels in a switching manner. In a CIS structure, a photo diode region may convert a light signal to an electrical signal, and a transistor may process the electrical signal. A CMOS image sensor may include a photodiode and a MOS transistor within a unit pixel to sequentially detect electrical signals of each unit pixel, implementing an image. A photo diode region and a transistor may be horizontally arranged in a semiconductor substrate.

In a horizontal type CIS according to the related art, a photo diode and a transistor may be horizontally formed adjacent to each other on and/or over a substrate. Therefore, an additional region for forming a photo diode may be required.

Also, in a related art horizontal type CIS, it may be difficult to achieve an optimized process of concurrently forming a photodiode and a transistor. That is, a shallow junction may be required to meet low sheet resistance in a rapid transistor process, but such a shallow junction may not be suitable for a photodiode.

Further, in a related art horizontal type CIS, extra on-chip functions may be added to an image sensor. Thus, a unit pixel size may need to be increased to maintain a sensitivity of an image sensor or an area for a photodiode may need to be decreased to maintain a pixel size. However, if a pixel size increases, a resolution of an image sensor may decreases. If an area of a photodiode decreases, a sensitivity of an image sensor may become poor.

SUMMARY

Embodiments relate to an image sensor and a manufacturing method thereof that may provide a vertical integration of circuitry and a photodiode. Embodiments relate to an image sensor and a manufacturing method thereof that may prevent a dark current in a vertical type photodiode having a crystalline structure.

Embodiments relate to an image sensor and a manufacturing method thereof that may implement a vertical type photodiode, which may improve bondability and an alignment margin between substrates. Embodiments relate to an image sensor and a manufacturing method thereof that may enhance resolution and sensitivity.

Embodiments relate to an image sensor and a manufacturing method thereof that may implement a vertical type photodiode, which may prevent generation of defects in the photodiode.

According to embodiments, an image sensor may include at least one of the following. A first substrate on and/or over which circuitry including a metal interconnection may be formed. A photodiode in a crystalline semiconductor layer bonded to the first substrate, where the photodiode may be electrically connected to the metal interconnection. An ion implantation isolation layer in the photodiode.

According to embodiments, a method for manufacturing an image sensor may include at least one of the following. Forming circuitry including a metal interconnection on and/or over a first substrate. Forming a photodiode in a crystalline semiconductor layer of a second substrate. Forming an ion implantation isolation layer in the photodiode. Bonding the first and second substrates to each other, which may connect the photodiode to the metal interconnection. Removing a lower portion of the second substrate to expose the photodiode.

DESCRIPTION

An image sensor and a method for manufacturing an image sensor according to embodiments will be described with reference to the accompanying drawings.

ExampleFIG. 1is a sectional view of an image sensor, according to embodiments. Referring to exampleFIG. 1, an image sensor may include first substrate100on and/or over which circuitry including a metal interconnection may be formed. According to embodiments, photodiode210may be disposed in a crystalline semiconductor layer, which may be bonded to first substrate100, and may be electrically connected to the metal interconnection. Ion implantation isolation layer220may be provided in photodiode210.

According to embodiments, photodiode210may include second conduction type conduction layer212in the crystalline semiconductor layer and first conduction type conduction layer214on and/or over second conduction type conduction layer212. According to embodiments, defects in a photodiode may be minimized or prevented by implementing a vertical type photodiode in which a photodiode may be positioned over circuitry. According to embodiments, photodiode210may be formed in a crystalline semiconductor layer.

According to embodiments, ion implantation layer220may include second conduction type second ion implantation isolation layer220b, which may be disposed at an interface between pixels of photodiode210. According to embodiments, ion implantation isolation layer220may include second conduction type first ion implantation isolation layer220a, which may be disposed under and/or below first conduction type conduction layer214.

According to embodiments, a side and/or the bottom of photodiode210, which may be lightly doped with n-type impurities, may be insulated using an ion implantation isolation layer. This may achieve pixel-to-pixel isolation. According to embodiments, an ion implantation isolation layer may be P0 layer220. According to embodiments, ion implantation isolation layer220may be used instead of using a related art shallow trench isolation (STI) process. According to embodiments, dark current that may be caused by crystal defects that may be generated during an etching process may be minimized.

According to embodiments, an image sensor may further include second dielectric260under photodiode210and metal pad270in second dielectric260. According to embodiments, in manufacturing an image sensor implementing a vertical type photodiode, substrates may be bonded after forming dielectric260and metal pad270. This may improve a bondability and an alignment margin between substrates.

A method for manufacturing an image sensor according to embodiments will be described with reference to exampleFIGS. 2 through 8. Referring to exampleFIG. 2, photodiode210may be formed in a crystalline semiconductor layer of second substrate200. According to embodiments, since photodiode210may be formed in a crystalline semiconductor layer, defects inside a photodiode may be minimized or prevented.

According to embodiments, second substrate200may be formed by an epitaxial growth method. According to embodiments, hydrogen ions may be implanted into an interface between second substrate200and a crystalline semiconductor layer. This may form a hydrogen ion implantation layer. According to embodiments, hydrogen ions may be implanted after implanting impurity ions for formation of photodiode210.

According to embodiments, impurity ions may be implanted into a crystalline semiconductor layer. This may form photodiode210. According to embodiments, second conduction type conduction layer212may be formed in a lower portion of a crystalline semiconductor layer. Second conduction type conduction layer212may be a high concentration P-type conduction layer. According to embodiments, high concentration P-type conduction layer212may be formed in a lower portion of a crystalline semiconductor layer. According to embodiments, this may be done by performing a first blanket-ion implantation on and/or over an entire surface of second substrate200without a mask. According to embodiments, second conduction type conduction layer212may be formed at a junction depth of less than approximately 0.5 μm.

According to embodiments, first conduction type conduction layer214may be formed on and/or over second conduction type conduction layer212, for example by performing a second blanket-ion implantation on and/or over an entire surface of second substrate200without a mask. According to embodiments, first conduction type conduction layer214may be a low concentration N-type conduction layer. According to embodiments, low concentration first conduction type conduction layer214may be formed at a junction depth ranging from approximately 1.0 μm to approximately 2.0 μm.

According to embodiments, a method for manufacturing an image sensor may also include forming second conduction type first ion implantation isolation layer220aon and/or over first conduction type conduction layer214. According to embodiments, ion implantation may be performed without a mask, which may form second conduction type first ion implantation isolation layer220a. According to embodiments, this may be first P0 layer220a.

Referring to exampleFIG. 3, second conduction type second ion implantation isolation layer220bmay be formed at an interface between pixels of photodiode210. According to embodiments, second P0 layer220bmay be formed at an interface between pixels using a photolithographic process and an ion implantation process. Second P0 layer220bmay be used for pixel-to-pixel isolation of N− layer214, which may be first conduction type conduction layer214, used as the photodiode, and may also be used for a ground line connection.

Referring to exampleFIG. 4, high concentration first conduction type ion implantation region230may be selectively formed. According to embodiments, first conduction type conduction layer214may be connected to second conduction type first ion implantation isolation layer220a. According to embodiments, N+ layer230may be formed using a photolithographic process and an ion implantation process. N− layer214may act as photodiode210. According to embodiments, first P0 layer220aand second P0 layer220bmay serve as a pixel-to-pixel isolator and a ground line. According to embodiments, N+ layer230may serve as an electron movement path of electrons generated from pixels, and may contribute to ohmic contact.

Referring to exampleFIG. 5, first dielectric240may be formed on and/or over second substrate200. According to embodiments, metal plug250may then be formed. According to embodiments, an oxide layer may be formed on and/or over second substrate200. According to embodiments, metal plug250may be formed of tungsten, but may not be limited thereto.

Referring to exampleFIG. 6, second dielectric260may be formed on and/or over photodiode210of second substrate200. According to embodiments, metal pad270may be formed in second dielectric260. According to embodiments, in manufacturing an image sensor implementing a vertical type photodiode, substrates may be bonded after forming dielectric260and metal pad270. This may improve a bondability and an alignment margin between the substrates. According to embodiments, metal pad270may be formed of tungsten (W), aluminum (Al), copper (Cu), or the like.

Referring to exampleFIG. 7, first substrate100, which may include a metal interconnection and circuitry, may be prepared. According to embodiments, first substrate100may be bonded to second substrate200through a wafer-level bonding. A metal interconnection of first substrate100may include metal110and plug120.

According to embodiments, bonding may be performed by contacting first substrate100and second substrate200with each other and then performing activation by plasma. According to embodiments, this may increase a surface energy in a bonding surface.

Referring to exampleFIG. 8, hydrogen ion implantation layer, which may be formed in second substrate200, may be changed into a hydrogen gas layer. According to embodiments, this may be done by performing heat treatment to second substrate200. According to embodiments, a portion of second substrate200may then be removed. According to embodiments, photodiode210may remain under a hydrogen gas layer. This may expose photodiode210. According to embodiments, second substrate200may be removed using a cutting apparatus, such as a blade.

According to embodiments, P-Epitaxial layer, which may be at an upper portion of second substrate200, may be removed by performing a cleaving or backside thinning process after bonding the first and second substrates. According to embodiments, an uppermost layer of photodiode210, which may be P+ layer212, may be connected to a ground line during a subsequent process.

According to embodiments, an image sensor and method for manufacturing the same may provide vertical integration of circuitry and a photodiode. According to embodiments, to achieve pixel-to-pixel isolation, portions of a photodiode lightly doped with n-type impurities may be insulated from each other using a P0 layer instead of implementing a related art STI process. According to embodiments, it may be possible to minimize a dark current that may be caused by crystal defects that may be generated during an etching process.

According to embodiments, in manufacturing an image sensor implementing a vertical type photodiode, substrates may be bonded after forming a dielectric and a metal pad. This may improve a bondability and an alignment margin between the substrates.

According to embodiments, vertical integration of circuitry and a photodiode may make it possible to obtain a fill factor close to 100%, and may make it possible to maximize a sensitivity.

Although embodiments may be described with respect to a complementary metal oxide semiconductor (CMOS) image sensor (CIS), embodiments may not be limited to a CIS. According to embodiments, any image sensor requiring a photodiode may be used.

It will be obvious and apparent to those skilled in the art that various modifications and variations can be made in the embodiments disclosed. Thus, it is intended that the disclosed embodiments cover the obvious and apparent modifications and variations, provided that they are within the scope of the appended claims and their equivalents.