KR100538071B1 - Image sensor having new salicide mask - Google Patents

Abstract

The present invention provides an image sensor that can prevent the degradation of the optical characteristics of the photodiode while minimizing the possibility of time delay in the reset and select gates regardless of the mask shift by using the new salicide mask.

The present invention provides a display device comprising: a pixel region including a photodiode, a reset gate spaced apart from the photodiode on one side of the photodiode, and a selection gate disposed in parallel with the reset gate adjacent to the photodiode on the other side of the photodiode; And a salicide mask disposed to mask the photodiode of the pixel region and the select gate of the portion adjacent to the photodiode. Preferably, the reset gate is made of polysilicon lines and the select gate is made of polysilicon lines or metal lines.

Description

Image sensor with new salicide mask {IMAGE SENSOR HAVING NEW SALICIDE MASK}

The present invention relates to an image sensor, and more particularly to an image sensor having a new salicide mask.

In general, an image sensor is a semiconductor device that converts an optical image into an electrical signal. The image sensor is composed of an optical sensing part that senses light and a logic circuit part that processes the sensed light into an electrical signal to make data. (Complementary Metal Oxide Semiconductor) In the case of image sensor, CMOS technology is used to make MOS transistors by the number of pixels, and the switching method is used to detect the output sequentially.

The unit pixel of the image sensor is composed of a photodiode, which is a light sensing part, and four NMOS transistors. Among the four NMOS transistors, a transfer transistor transports photocharges generated by the photodiode to a floating node, and is reset. The reset transistor serves to discharge the charge stored in the floating node for signal detection, the drive transistor serves as the source follower, and the selective transistor serves as the switching and It serves as addressing.

In addition, in the image sensor, in order to protect the photodiode, improve the operation speed and prevent leakage current characteristics deterioration, the time between the reset gate and the selection gate made of a polysilicon line of inevitable and relatively long length is inevitable. In order to suppress the delay phenomenon, a salicide (Self Aligned Silicid) layer is selectively formed.

In order to form such a selective salicide, conventionally, a salicide prevention film and a BARC (Bottom Anti-Reflective Coating) film are sequentially formed prior to the salicide process, and first, the BARC film is etched back to expose the salicide prevention film on the gate and then the salicide prevention film again. After etching back to expose the upper surface of the gate, a process of opening only the reset and select gate by a mask process is performed.

However, in this case, since two etch back processes and a mask process have to be performed, a problem arises in that the process becomes complicated and the manufacturing cost increases. In addition, since the mask process must be performed after the etch back of the BARC film, KrF exposure equipment other than the conventional I-Line is required, and the reliability of the device is remarkably degraded due to particle contamination caused by the etch back of the BARC film. Problems will arise.

On the other hand, using the recent I-Line exposure equipment, as shown in Fig. 1, the reset gate Rx and the select gate Sx, which are salicide forming regions S1 and S2, are opened and the active region A is opened. A method of selectively forming a salicide layer by applying a new salicide mask 100 masking all of the salicide non-forming regions NS1, NS2, and NS3 including the same has been proposed.

However, even if such a new salicide mask 100 is applied, mask alignment control is necessary because I-line exposure equipment typically has a high probability of about 0.1 μm of mask shift, for example, technology of 0.18 μm or less. In the CMOS image sensor, when a salicide mask shift occurs, a non-uniformly formed salicide layer is formed in the gates Rx and Sx, which increases the possibility of time delay, particularly in the selection gate portion adjacent to the photodiode. This causes a problem that the optical characteristics of the photodiode are significantly lowered.

The present invention has been proposed to solve the above problems of the prior art, by using a new salicide mask to reduce the optical characteristics of the photodiode while minimizing the possibility of time delay in the reset and select gates regardless of the mask shift. The purpose is to provide an image sensor that can be prevented.

According to an aspect of the present invention for achieving the above technical problem, a photodiode, a reset gate disposed spaced apart from the photodiode on one side of the photodiode, and the other side of the photodiode adjacent to the photodiode And a photodiode comprising a pixel region including a selection gate disposed in parallel with the reset gate, a photodiode of the pixel region, and a salicide layer on the selection gate in a portion adjacent to the photodiode. An image sensor including a salicide mask disposed to mask a portion of the selection gate is provided.

Preferably, the reset gate is made of polysilicon lines and the select gate is made of polysilicon lines or metal lines.

In addition, according to another aspect of the present invention for achieving the above technical problem, a photodiode, a reset gate disposed to be spaced apart from the photodiode on one side of the photodiode, and the photodiode on the other side of the photodiode A pixel region including a select gate adjacent to and parallel to the reset gate, a photodiode of the pixel region, and the select gate and the reset gate of a portion adjacent to the photodiode so that a salicide layer is not formed To provide an image sensor including the photodiode, and the salicide mask disposed to mask the selection gate and a portion of the selection gate.

Preferably, the reset gate is made of polysilicon lines or metal lines, and the select gate is made of polysilicon lines or metal lines.

Hereinafter, preferred embodiments of the present invention will be introduced in order to enable those skilled in the art to more easily carry out the present invention.

An image sensor according to an embodiment of the present invention will be described with reference to FIG. 2.

As shown in FIG. 2, a photodiode PD, a transfer gate, and a driving gate (not shown) are respectively disposed in the pixel region, and a relatively long reset gate Rx is disposed on one side of the photodiode PD. ) Is spaced apart from the photodiode PD, and a relatively long length select gate Sx is disposed on the other side of the photodiode PD in parallel with the reset gate Rx while adjacent to the photodiode PD. Unlike the prior art, the salicide mask pattern 200a is disposed to mask the photodiode PD and the selection gate Sx of a portion adjacent to the photodiode PD in the pixel region.

Accordingly, even if a slight mask shift occurs, the salicide layer can be stably formed in the reset gate Rx, and the formation of the salicide layer in the photodiode can be prevented, thereby preventing the possibility of time delay in the reset gate. It is possible to prevent the photodiode deterioration while minimizing.

On the other hand, since the select gate Sx of the portion adjacent to the photodiode PD is masked by the salicide mask 200a and no salicide is formed on the select gate Sx, time delay occurs in the select gate Sx. When the select gate Sx is formed of a metal line during the wiring process instead of a polysilicon line, this can be minimized.

In addition, as the salicide layer forming region becomes wider, a possibility of generating a junction leakage current in the active region is increased. In view of this, the mask pattern 200b may be formed as shown in FIG. 3 by using the photodiode PD and the select gate Sx adjacent thereto. In addition, the salicide layer forming region may be relatively reduced by disposing the reset gate Rx. In addition, the problem of time delay in the selection gate Sx and the reset gate Rx generated at this time may include the selection gate Sx or the reset gate Rx as a metal line during the wiring process instead of the polysilicon line, or both of them. It can be solved by forming a metal line.

The present invention described above is not limited to the above-described embodiments and the accompanying drawings, and various substitutions, modifications, and changes are possible in the art without departing from the technical spirit of the present invention. It will be clear to those of ordinary knowledge.

The present invention described above reduces the resistance of the reset gate and the select gate while using a new salicide mask having a relatively large salicide layer forming region, thereby minimizing the possibility of time delay in the reset gate and the select gate regardless of the mask shift. It is possible to prevent the degradation of the optical characteristics of the photodiode, and thus to improve the reliability of the image sensor.

1 is a layout plan view showing a salicide mask of a conventional image sensor.

2 is a layout plan view showing a salicide mask of an image sensor according to an exemplary embodiment of the present invention.

3 is a layout plan view showing a salicide mask of an image sensor according to another exemplary embodiment of the present invention.

※ Explanation of symbols for main parts of drawing

200a, 200b: salicide mask

Rx: reset gate

Sx: selection gate

PD: Photodiode

Claims (6)

A pixel region including a photodiode, a reset gate spaced apart from the photodiode on one side of the photodiode, and a selection gate adjacent to the photodiode on the other side of the photodiode and disposed in parallel with the reset gate ; And An image sensor including a photodiode in the pixel region and a salicide mask disposed to mask a portion of the photodiode and the select gate so that a salicide layer is not formed in the select gate in a portion adjacent to the photodiode . The method of claim 1, The reset gate is an image sensor, characterized in that consisting of a polysilicon line. The method according to claim 1 or 2, The selection gate is an image sensor comprising a polysilicon line or a metal line. A pixel region including a photodiode, a reset gate spaced apart from the photodiode on one side of the photodiode, and a selection gate adjacent to the photodiode on the other side of the photodiode and disposed in parallel with the reset gate ; And Masking the photodiode, the select gate and a part of the select gate so that a salicide layer is not formed from the photodiode of the pixel region and the select gate and the reset gate in a portion adjacent to the photodiode. An image sensor comprising a salicide mask. The method of claim 4, wherein The reset gate is an image sensor comprising a polysilicon line or a metal line. The method according to claim 4 or 5, The selection gate is an image sensor comprising a polysilicon line or a metal line.