Patent Application
20090068784
The present application claims the benefit under 35 U.S.C. §119 of Korean Patent Application No. 10-2007-0091338, filed Sep. 10, 2007, which is hereby incorporated by reference in its entirety.
An image sensor is a semiconductor device that converts an optical image into an electrical signal. Image sensors are typically classified as charge coupled devices (CCD) or complementary metal oxide semiconductor (CMOS) image sensors (CIS).
A CMOS image sensor generally includes a photodiode and a MOS transistor in each unit pixel to sequentially detect an electrical signal in a switching manner, thereby forming an image.
Embodiments of the present invention provide improved methods for manufacturing an image sensor.
In an embodiment, a method for manufacturing an image sensor can comprise: preparing a semiconductor substrate comprising a transistor; forming a proton layer on the semiconductor substrate; forming a hydrogen gas layer by performing a heat treatment process on the semiconductor substrate including the proton layer; and removing a bottom portion of the semiconductor substrate. The bottom portion of the semiconductor substrate can include the hydrogen gas layer.
When the terms “on” or “over” or “above” are used herein, when referring to layers, regions, patterns, or structures, it is understood that the layer, region, pattern, or structure can be directly on another layer or structure, or intervening layers, regions, patterns, or structures may also be present, When the terms “under” or “below” are used herein, when referring to layers, regions, patterns, or structures, it is understood that the layer, region, pattern, or structure can be directly under the other layer or structure, or intervening layers, regions, patterns, or structures may also be present.
Hereinafter, methods for manufacturing an image sensor according to embodiments of the present invention will be described in detail with reference to the accompanying drawings.
The description of the present invention includes reference to a complementary metal oxide semiconductor (CMOS) image sensor (CIS). However, embodiments of the present invention are not limited thereto. For example, methods of the present invention can be applied to any suitable image sensor known in the art, such as a charge coupled device (CCD) image sensor.
Referring to
In an embodiment, a low-concentration p-type epi layer (not shown) can be formed on the semiconductor substrate 10 with the device isolating layer 12 formed in the epi layer. The p-type epi layer (not shown) can help make a depletion region of a photodiode large and deep so that the ability of the photodiode for collecting photo charges can be enhanced. Also, if a p-type epi layer is formed in a p++ semiconductor substrate, charges can recombine before diffusing to neighboring unit pixel, thereby r educing random diffusion of photo charges and making it possible to reduce a change in a transfer function of photo charges.
The device isolating layer 12 can be formed by any suitable method known in the art. In an embodiment, forming the device isolating layer 12 can include forming a trench in the semiconductor substrate 10, forming a channel stop ion implantation region 13 around the trench by implanting ions into the trench, and forming an insulating material in the trench.
The channel stop ion implantation region 13 can help inhibit cross talk or leakage current between adjacent pixels.
Referring to
The gate oxide film 22 can be formed of any suitable material known in the art, for example, an oxide film. Additionally, the gate electrode 24 can be formed of any suitable material known in the art, for example, a polysilicon layer or a metal silicide layer.
Referring to
In an embodiment, the first ion implantation layer 14 can be formed by implanting n-type impurities.
Referring to
In an embodiment, the second ion implantation layer 16 can be formed by implanting p-type impurities. Accordingly, a P-N junction region 17 can be formed by the first ion implantation layer 14 and the second ion implantation layer 16.
In certain embodiments, a PNP photodiode can be provided by the P-N junction region 17 and the semiconductor substrate 10. In these embodiments, the semiconductor substrate 10 can be a p-type substrate.
Referring to
In an embodiment, the third ion implantation layer 18 can be formed by implanting n-type impurities at a high concentration.
During operation of the image sensor photo charges generated in the P-N junction region 17 can be transferred to the third ion implantation layer 18, and photo charges transferred to the third ion implantation layer 18 can be transferred to a circuitry unit (not shown).
Referring to
The spacer 28 can be formed by any suitable process known in the art. In an embodiment, an oxide layer, a nitride layer, and an oxide layer can be sequentially formed on the semiconductor substrate 10 to form an oxide-nitride-oxide (ONO) layer. An etching process can be performed on the ONO layer to form the spacer 28. In an alternative embodiment, an oxide-nitride (ON) layer can be formed and etched to form the spacer 28.
Referring to
The fourth ion implantation process can be performed using protons (H+).
The depth of the proton layer 30 can be controlled by the ion implantation energy used during the fourth ion implantation process.
Referring to
Referring to
The proton layer 30 can be converted into the hydrogen gas layer 35 by performing the heat treatment process on the semiconductor substrate 10.
At this time, the proton layer 30 can be converted into the hydrogen gas layer 35, thereby making it possible to separate a bottom portion of the semiconductor substrate 10. The bottom portion of the semiconductor substrate 10 can include at least a portion of the hydrogen gas layer 35. In an embodiment, the bottom portion of the semiconductor substrate 10 can include at least a majority of the hydrogen gas layer 35. In a further embodiment, the bottom portion of the semiconductor substrate 10 can include approximately all of the hydrogen gas layer 35. In yet a further embodiment, the bottom portion of the semiconductor substrate can include the entire hydrogen gas layer 35.
The thickness of the separated portion of the semiconductor substrate 10 can be controlled according to the formation depth of the proton layer 30, which can be controlled by the ion implantation energy used during the fourth ion implantation process.
That is, the thickness of the bottom portion of the semiconductor substrate 10 that can be separated can be controlled by the ion implantation energy used during the fourth ion implantation process.
Referring
The color filter array 52 can be formed in a region corresponding to a unit pixel of a light-receiving area. The color filter array 52 can be formed by forming a color filter layer (not shown) and patterning the color filter layer.
Since the color filter array 52 can be formed on the backside of the semiconductor substrate 10 light can enter from below the photodiode 17 in the semiconductor substrate 10.
Although not shown, in an embodiment, a mircolens and a microlens protective layer for protecting the microlens can be formed on or under the color filter array 52.
According to embodiments of the present invention, a bottom, or backside, portion of the semiconductor substrate 10 can be separated and removed, making it possible to improve the sensitivity of the image sensor.
Any reference in this specification to “one embodiment,” “an embodiment,” “example embodiment,” etc., means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the invention. The appearances of such phrases in various places in the specification are not necessarily all referring to the same embodiment. Further, when a particular feature, structure, or characteristic is described in connection with any embodiment, it is submitted that it is within the purview of one skilled in the art to effect such feature, structure, or characteristic in connection with other ones of the embodiments.
Although embodiments have been described with reference to a number of illustrative embodiments thereof, it should be understood that numerous other modifications and embodiments can be devised by those skilled in the art that will fall within the spirit and scope of the principles of this disclosure. More particularly, various variations and modifications are possible in the component parts and/or arrangements of the subject combination arrangement within the scope of the disclosure, the drawings and the appended claims. In addition to variations and modifications in the component parts and/or arrangements, alternative uses will also be apparent to those skilled in the art.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10-2007-0091338 | Sep 2007 | KR | national |
