KR100824626B1 - Cmos image sensor and method for manufacturing having the same - Google Patents

Abstract

A CMOS image sensor and a method for manufacturing the same are provided to enhance transfer efficiency of electrons by reducing a contact resistance. A gate electrode(210) including a trench formed at a predetermined area of an upper part thereof is formed on an active region of a semiconductor substrate(200). An active contact(230) is electrically connected to the gate electrode by burying a conductive material into the trench formed at the upper part of the gate electrode. A metal contact(240) is formed on an upper surface of the active contact to be electrically connected to the active contact. The gate electrode includes a gate oxide layer(212) and polysilicon(214). The active contact having the thickness of 0.05-0.15 mum is formed on a partial region of an upper part of the polysilicon.

Description

CMOS Image Sensor and Method for Manufacturing Having the Same}

1A is a cross-sectional view of a CMOS image sensor according to the prior art,

1b is a plan view of a CMOS image sensor according to the prior art,

2 is a cross-sectional view showing the structure of a CMOS image sensor according to an embodiment of the present invention;

3A to 3D are cross-sectional views illustrating a method of manufacturing a CMOS image sensor according to an exemplary embodiment of the present invention.

<Description of Symbols for Main Parts of Drawings>

200: semiconductor substrate 210: gate electrode

212: gate oxide film 214: polysilicon

220: spacer 230: active contact

240: metal contact

The present invention relates to a CMOS image sensor and a method of manufacturing the same, and more particularly, to a CMOS image sensor and a method of manufacturing the same for preventing the leakage current and resistance generated when forming an active contact.

In general, an image sensor is a semiconductor device that converts an optical image into an electrical signal. A charge coupled device (CCD) is a device in which individual metal-oxide-silicon (MOS) capacitors are very close to each other. A device in which charge carriers are stored and transported in a capacitor while being positioned, and a CMOS (Complementary MOS) image sensor uses a CMOS technology that uses a control circuit and a signal processing circuit as peripheral circuits. It is a device that adopts switching method that makes as many MOS transistors and uses it to detect output sequentially.

In the manufacture of such various image sensors, efforts are being made to increase the photo sensitivity of the image sensor, one of which is a condensing technology. For example, a CMOS image sensor is composed of a photodiode for detecting light and a portion of a CMOS logic circuit for processing the detected light into an electrical signal to make data. In order to increase the light sensitivity, the area of the photodiode in the total image sensor area is greatly increased. Efforts are underway.

In addition, a high degree of integration of the CMOS image sensor is rapidly being achieved separately from the CCD. Also in the manufacture of image sensors in a technology having a line width of 0.25 mu m or less, a gate electrode and a source / drain region having a salicide such as Ti or Co have become indispensable, similar to existing standard logic.

Korean Patent Laid-Open Publication Nos. 2003-1108 and 2003-58276 describe a method of manufacturing an image sensor using salicide that can reduce leakage current, and US Patent No. 6,040,592 also uses a salicide process. It is described about a Morse image sensor.

The salicide forming process of the image sensor according to the prior art first forms a field insulating film locally on the semiconductor layer, and then forms a gate electrode in an area away from the field insulating film, and then the photodiode and the gate electrode contacting one side of the gate electrode. The source / drain in contact with the other side is formed, and is formed through an ion implantation process for forming a conventional photodiode. The semiconductor layer uses a stacked P ++ layer and a P-Epi layer of high concentration. Subsequently, a metal film such as Ti is formed along the entire structure surface so as to have a thickness of 300 kPa to 500 kPa by the sputtering method.

Next, a rapid thermal treatment (Rapid Thermal Process, hereinafter 'RTP') for about 20 seconds at a temperature of about 730 ℃ to form a silicide (Silicide). At this time, by heat treatment in a gas atmosphere such as N ₂ , metals such as Si and Ti on the substrate react to form silicide such as TiSi ₂ .

At this time, a salicide (Salicide: Self Align Silicide) process is applied. In the oxide film series, since Ti does not react and unreacted Ti remains, a washing process or the like is performed to remove such unreacted Ti, and then 850 ° C. By conducting RTP at a high temperature, silicides are formed that can reduce resistance to contact formation such as floating diffusion (FD).

Next, after the interlayer insulating film is formed to insulate the gate electrode and the first metal layer, the interlayer insulating film is selectively etched to form a metal layer contact portion, and then a metal pattern is formed on the contact portion.

However, in the prior art as described above, by forming contacts in the active region A and the gate region B as shown in FIGS. 1A and 1B, respectively, and simultaneously forming pixel active contacts in forming M1C contacts, As shown in A of FIG. 1A, when the active contact is formed, the active surface is excessively etched and overetched to the inside of the silicon, thereby increasing the leakage current or the contact resistance (Rc) and increasing the resistance value. This results in a loss of the voltage that must be applied to the channel at the applied voltage, resulting in a drop in the voltage delivered to the source stage, thus requiring a larger voltage during operation of the photodiode.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and provides a CMOS image sensor and a method of manufacturing the same for preventing leakage current and resistance generated when the active contact is formed in the active region and the gate region. There is a purpose.

Another object of the present invention is to provide a CMOS image sensor and a method of manufacturing the same for improving process margins when forming metal contacts.

The present invention for achieving the above object is a CMOS image sensor, the gate electrode formed on the active region on the semiconductor substrate; An active contact buried in an upper portion of the gate electrode and electrically connected to the gate electrode; And a metal contact formed on an upper surface of the active contact and electrically connected to the active contact.
The present invention provides a method for manufacturing a CMOS image sensor according to the present invention, comprising: (a) sequentially depositing a gate oxide film and polysilicon on an active region of a semiconductor substrate; (b) etching a portion of the upper portion of the polysilicon to a predetermined depth to form an active contact forming trench; (c) embedding and planarizing a conductive material in said trench to form an active contact electrically connected with said polysilicon; (d) forming a gate electrode by patterning the polysilicon in which the gate oxide layer and the active contact are formed; And (e) forming a metal contact electrically connected to an upper surface of the active contact.

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Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. In addition, in describing the present invention, when it is determined that the detailed description of the related well-known configuration or function may obscure the gist of the present invention, the detailed description thereof will be omitted.

2 is a cross-sectional view illustrating a structure of a CMOS image sensor according to an exemplary embodiment of the present invention.

Referring to FIG. 2, the CMOS image sensor may include a gate electrode 210 formed on an active region excluding a field region on a semiconductor substrate 200, a spacer 220 formed on sidewalls of the gate electrode 210, It includes an active contact 230 formed in the upper portion of the gate electrode 210, a metal contact 240 electrically connected to the upper surface of the active contact 230.
In detail, the gate electrode 210 may include a gate oxide film 212 and polysilicon 214, and the active contact 230 may be formed to a thickness of 0.05 μm to 0.15 μm on a portion of the upper portion of the polysilicon 214. . Here, the active contact 230 may be formed to have the same width as the metal contact 240 or may be formed to have a width equal to or less than 1.5 times the metal contact 240, and the same metal or gate electrode 210 as the metal contact 240. It may be made of a material forming the ohmic contact and may be aluminum (Al), copper (Cu) and aluminum-copper alloy.
In this case, the active region refers to a region in which each element (for example, a transistor and a capacitor) is formed on the semiconductor substrate 200, and a plurality of active regions are formed on the semiconductor substrate 200. A field region composed of an insulating film or device isolation film and a delamination is formed. The gate region described in the description of the present invention means a region in which the gate electrode 210 is formed among the active regions.
In addition, the active contact 230 formed in the upper portion of the gate electrode 210 and the metal contact 240 formed on the upper surface of the act contact 230 and electrically connected to each other are manufactured by the manufacturing process. Although described in different terms, the two contacts 230 and 240 described above electrically connect the gate electrode 210 to other regions not shown in the drawings.
The CMOS image sensor according to the present invention forms a trench in a portion of the upper portion of the polysilicon 214 of the gate electrode 210 and forms an active contact 230 by filling a conductive material in the trench to reduce electrical resistance. Can be. This configuration can reduce the drop in the voltage applied to the gate electrode 210 and the voltage transmitted to the source electrode, that is, leakage current and contact resistance generated in the CMOS image sensor, and due to the decrease in the contact resistance, The transmission efficiency can be improved. Through this, the operating voltage of the photodiode can be lowered, thereby reducing the power consumption of the device.
The CMOS supporting sensor according to the present invention can prevent an increase in leakage current and contact resistance generated when the active region other than the field region is formed on the semiconductor substrate as well as the gate region where the gate electrode 210 is formed. Through this, the operating voltage of the photodiode can be lowered, thereby reducing the power consumption of the device.

3A to 3D are cross-sectional views illustrating a method of manufacturing a CMOS image sensor according to an exemplary embodiment of the present invention.

As shown in FIG. 3A, a gate oxide film 212 is formed on the active region of the semiconductor substrate 200 by a thermal oxidation process, and a gate is formed on the gate oxide film 212 by a chemical vapor deposition process. Polysilicon 214 is deposited for electrode 210.

As shown in FIG. 3B, a portion of the upper portion of the polysilicon 214 is etched to a depth of 0.05 to 0.15 μm using a photoresist process to form the trench 230a for forming the active contact 230. Here, the trench 230a may be formed to have the same width as the metal contact 240 or may be formed to have a width equal to or less than 1.5 times the metal contact 240.

As shown in FIG. 3C, the conductive material is embedded in the trench 230a, and then planarized using a chemical mechanical polishing (CMP) process to form the active contact 230. Here, the conductive material may be made of the same metal as the metal contact 240 or a material forming ohmic contact with the gate electrode 210 or may be aluminum (Al), copper (Cu), an aluminum-copper alloy, or the like. Can be.

Subsequently, as shown in FIG. 3D, the polysilicon 214 having the gate oxide film 212 and the active contact 230 is patterned to form the gate electrode 210, and then the semiconductor substrate 200 and the gate electrode ( An insulating film for forming the spacer 220 on the entire surface of the 210 is deposited by a chemical vapor deposition process or the like, and the nitride film is etched through a dry etching process, which is an anisotropic etching, thereby forming spacers 220 on both sidewalls of the gate electrode 210. ), And the metal contact 240 is electrically connected to the upper surface of the active contact 230, thereby completing the manufacture of the CMOS image sensor.

Thereafter, a salicide prevention oxide layer may be additionally formed on the entire surface of the semiconductor substrate 200 except for the metal contact 240.

Although an embodiment of the present invention describes a method of forming the active contact 230 on the gate electrode 210, the present invention is not limited thereto, and a portion of the upper portion of the active region of the semiconductor substrate 200 may have a predetermined depth. Also, a method of forming the active contact 230 by etching the same may be proposed.

The above description is merely illustrative of the technical idea of the present invention, and those skilled in the art to which the present invention pertains may make various modifications and changes without departing from the essential characteristics of the present invention. Therefore, the embodiments disclosed in the present invention are not intended to limit the technical idea of the present invention but to describe the present invention, and the scope of the technical idea of the present invention is not limited by these embodiments. The protection scope of the present invention should be interpreted by the following claims, and all technical ideas within the equivalent scope should be interpreted as being included in the scope of the present invention.

As described above, according to the present invention, by providing a CMOS image sensor including a non-Salicide (NSAL :) contact made of a metal material including aluminum, copper and the like and a method of manufacturing the same, The leakage current and contact resistance generated can be reduced, the transmission efficiency of electrons can be increased due to the reduction of the contact resistance, and the operating voltage of the photodiode can be lowered, thereby reducing the power consumption of the device.

In addition, when the metal contact is formed, the point for forming the contact becomes wider, thereby increasing the process margin, and the metal component acts as an etching barrier during the etching process, thereby increasing the process margin of the etching process.

Claims (11)

CMOS image sensor, A gate electrode formed on the active region on the semiconductor substrate by including a trench in a portion of the upper portion; An active contact embedded in a trench formed on the gate electrode and electrically connected to the gate electrode;  And a metal contact formed on an upper surface of the active contact and electrically connected to the active contact. In claim 1, The gate electrode may include a gate oxide layer and polysilicon, and the active contact may be formed to a thickness of 0.05 to 0.15 μm on a portion of the upper portion of the polysilicon. In claim 1, And the active contact is formed to have the same width as the metal contact or is formed to be 1.5 times or less wider than the metal contact. In claim 1, And the active contact is made of the same metal as the metal contact. In claim 1, And the active contact is made of a material forming ohmic contact with the gate electrode. In claim 1, The active contact is a CMOS image sensor, characterized in that made of any one selected from aluminum (Al), copper (Cu) and aluminum-copper alloy. In the method of manufacturing the CMOS image sensor, (a) sequentially depositing a gate oxide film and polysilicon on the active region of the semiconductor substrate; (b) etching a portion of the upper portion of the polysilicon to a predetermined depth to form an active contact forming trench; (c) embedding and planarizing a conductive material in said trench to form an active contact electrically connected with said polysilicon; (d) forming a gate electrode by patterning the polysilicon in which the gate oxide layer and the active contact are formed; And (e) forming a metal contact electrically connected to an upper surface of the active contact. In claim 7, The active contact may be formed to have the same width as the metal contact or may be formed to be 1.5 times or less wider than the metal contact. In claim 7, And the active contact is made of the same metal as the metal contact. In claim 7, And the active contact is made of a material forming ohmic contact with the gate electrode. In claim 7, The active contact is made of any one selected from aluminum (Al), copper (Cu) and aluminum-copper alloy.

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