KR20100030812A

KR20100030812A - Method for fabricating of cmos image sensor

Info

Publication number: KR20100030812A
Application number: KR1020080089711A
Authority: KR
Inventors: 황상일
Original assignee: 주식회사 동부하이텍
Priority date: 2008-09-11
Filing date: 2008-09-11
Publication date: 2010-03-19

Abstract

PURPOSE: A method for manufacturing a CMOS image sensor is provided to improve sensitivity by differently forming the thickness of a silicon film according to each color filter. CONSTITUTION: A first interlayer insulation layer(20a) is selectively etched on a photo diode area. A silicon layer(24) is formed by gap-filling the etched part of the first interlayer dielectric layer. A plurality of interlayer dielectric layers, metal wirings(26a,26b), and contact plugs(22a,22b) are formed on the firs interlayer dielectric layer. The silicon layers with different thickness are left on blue, green, and red regions by selectively etching the first interlayer dielectric layer, the silicon layer, and the plurality of interlayer dielectric layer.

Description

Method for fabricating CMOS image sensor

The present invention relates to a method for manufacturing a CMOS image sensor, and more particularly, to a method for manufacturing a CMOS image sensor capable of improving sensitivity.

In general, an image sensor is a semiconductor device that converts an optical image into an electrical signal, and is generally classified into a charge coupled device (CCD) and a CMOS image sensor. A charge coupled device (CCD) has a structure in which MOS capacitors are disposed adjacent to each other, and a charge carrier is stored in an arbitrary MOS capacitor and then transferred to a later MOS capacitor. . The charge coupling device has disadvantages such as a complicated driving method, a large power consumption, and a complicated manufacturing process due to many photoprocess steps. In addition, the charge coupling device has a disadvantage in that it is difficult to integrate a control circuit, a signal processing circuit, an analog-to-digital conversion circuit (A / D converter), and the like into a charge coupling device chip, which makes it difficult to miniaturize a product.

Recently, CMOS image sensors have attracted attention as next-generation image sensors to overcome the disadvantages of charge-coupled devices. The CMOS image sensor uses CMOS technology that uses a control circuit and a signal processing circuit as a peripheral circuit to form MOS transistors corresponding to the number of unit pixels on a semiconductor substrate, thereby outputting each unit pixel by the MOS transistors. It is a device that employs a switching method that detects sequentially. That is, the CMOS image sensor implements an image by sequentially detecting an electrical signal of each unit pixel by a switching method by forming a photodiode and a MOS transistor in the unit pixel. CMOS image sensor has advantages such as low power consumption, simple manufacturing process according to few photo process steps because of CMOS technology. In addition, since the CMOS image sensor can integrate a control circuit, a signal processing circuit, an analog / digital conversion circuit, and the like into the CMOS image sensor chip, the CMOS image sensor has an advantage of easy miniaturization.

The CMOS image sensor determines the color of each spot by combining neighboring pixels using a three primary color filter on the photodiode for each pixel in order to realize the color of light.

A semiconductor device that converts light from an image sensor into an electron is a photodiode in a pixel. When a photodiode is applied in a reverse direction to a junction portion formed of a PN junction formed on a silicon substrate, a charge depletion region is formed around the junction. In this case, photons called photons generate a pair of electrons and holes in this region, and the holes move to the P type region by the applied voltage, and the electrons move to the N type region. At this time, the N-type region is used as the charge accumulation region, and the electrons accumulated therein are read as voltages through the circuit.

These photodiodes vary the light absorption in the silicon substrate of the photon depending on the wavelength of the light. The shorter the wavelength of the light, the more the light is absorbed from the surface of the silicon. That is, for example, the blue color of the visible light region having a short wavelength is the highest within about 0.1 μm from the surface of the silicon substrate, and the green color, which is the middle region of the visible light, penetrates to a slightly deeper region, and the red color The case penetrates deep into the silicon substrate.

In the conventional CMOS image sensor including a photodiode, as shown in FIG. 1, the interlayer insulating film 9 is removed and a film having a high refractive index is embedded in the photodiode 6 to improve sensitivity. The diode 6 has a structure for concentrating light. Here, the CMOS image sensor of the related art includes a semiconductor substrate 1, a gate insulating film 2, a gate electrode 4, a spacer 5, and a source region 8 in an unexplained configuration.

However, as described above, the light incident on the photodiode has a different depth to penetrate into the silicon depending on the wavelength of each color, but the blue light is used because the single diode photodiode structure is used for the light having the different wavelengths of the three primary colors. There is a problem in that optimal light absorption for green and red cannot be obtained.

Accordingly, in order to solve the above problems, an object of the present invention is to provide a method for manufacturing a CMOS image sensor that can improve the sensitivity.

The method for manufacturing a CMOS image sensor according to the present invention is a method for manufacturing a CMOS image sensor including a semiconductor substrate, a photodiode region, a source region, a gate insulating film, a gate electrode, a spacer, a first interlayer insulating film, and a first contact plug. Selectively etching a first interlayer dielectric layer on the photodiode region, forming a silicon film by gap-filling an etched portion of the first interlayer dielectric layer, a plurality of interlayer dielectric layers on the first interlayer dielectric layer, Forming a plurality of metal wirings and a plurality of contact plugs, and selectively etching the first interlayer insulating film, the silicon film, and the plurality of interlayer insulating films on the photodiode region to form a silicon film having a different thickness for each blue, green, and red region. Characterized in that it comprises a step of leaving.

As described above, the manufacturing method of the CMOS image sensor according to the present invention may improve the sensitivity by optimizing the optimum sensitivity by leaving the thickness of the silicon film differently according to each color filter.

Hereinafter, a method of manufacturing the CMOS image sensor according to the present invention will be described with reference to the accompanying drawings.

2A to 2E are cross-sectional views illustrating a manufacturing process of the CMOS image sensor according to the present invention.

First, as shown in FIG. 2A, an epitaxial process is performed on the semiconductor substrate 10 to form an epitaxial layer (not shown). In this case, the epitaxial layer is formed to form a depletion region large and deep in the photodiode PD to increase the ability of the low voltage photodiode PD to collect the optical charge and further improve the optical sensitivity.

Subsequently, an element isolation layer STI (not shown) is formed in a portion for the element isolation region of the semiconductor substrate 110 to define the active region and the element isolation region of the semiconductor substrate 10.

Subsequently, a gate insulating film and a gate metal layer are sequentially formed on the active region of the semiconductor substrate 10, and the gate insulating film 12 and the gate electrode 14 are patterned by patterning the gate insulating film and the gate metal layer by a photolithography process using a mask. To form.

Next, impurity ions are implanted into the surface of the semiconductor substrate 10 adjacent to the side surface of the gate electrode 14 by a predetermined distance from the photodiode region with the gate electrode 14 interposed therebetween. A drain region is formed.

Thereafter, an insulating film is formed on the entire surface of the semiconductor substrate 10 including the gate pattern composed of the gate insulating film 12 and the gate electrode 14, and then subjected to an etch back process to form gate spacers 15 on both sidewalls of the gate electrode 14. ).

Next, impurity ions are implanted into the semiconductor substrate 10 in the photodiode region PD to form the photodiode 16.

The first interlayer insulating film 20a is formed on the entire surface of the semiconductor substrate 10 including the gate electrode 12 and the gate spacer 15, and passes through the first interlayer insulating film 20a to form the gate electrode 14 and the source. A first contact plug 22a is formed which is connected with the region 18.

Next, as shown in FIG. 2B, the first interlayer insulating film 20a in the photodiode 16 region is etched to leave 100 to 200 Å of the first interlayer insulating film 20a on the photodiode 16 region.

Subsequently, as shown in FIG. 2C, silicon is deposited on the resultant to gap-fill the open portions of the first interlayer insulating film 20a to form the silicon film 24, and then planarize it.

As shown in FIG. 2D, the first metal wiring 26a is formed on the resultant to be connected to the first contact plug 22a. Then, the first metal wiring 26a is formed on the entire surface of the resultant. A two interlayer insulating film 20b is formed. Subsequently, a second contact plug 22b is formed through the second interlayer insulating film 20b to be connected to the first metal wiring 26a, and the second metal wiring 26b is connected to the second contact plug 22b. Form in turn.

Then, as shown in FIG. 2E, a portion of the second interlayer insulating film 20b is etched using the photoresist pattern 28 exposing the second interlayer insulating film 20b on the photodiode 16 region. .

Then, as shown in FIG. 2F, after the photoresist pattern 28 is removed, the silicon film 24 for each of the red, green, and blue regions is etched using a mask different for each of the red, green, and blue regions. Perform RIE etching of varying degrees. Here, the silicon film 24 in the blue region is etched, and the green region and the red region leave the silicon film 24, but leave the silicon film 24 in the red region thicker than the silicon film 24 in the green region.

At this time, in order not to damage the photodiode 16, the first interlayer insulating film 20a is left to a thickness of 50 to 100 Å.

Thereafter, the CMOS image sensor having improved sensitivity is completed by performing a known subsequent process.

Here, although the CMOS image sensor according to the present invention is described as the first and second interlayer insulating films, the interlayer insulating film may be formed in more multilayers, and the first and second metal wirings may also be formed in many more wirings. In addition, the first and second contact plugs may also be formed of more plugs.

Those skilled in the art will appreciate that various changes and modifications can be made without departing from the technical spirit of the present invention. Therefore, the technical scope of the present invention should not be limited to the contents described in the detailed description of the specification but should be defined by the claims.

1 is a cross-sectional view showing a conventional CMOS image sensor.

2A to 2F are cross-sectional views illustrating a manufacturing process of the CMOS image sensor according to the present invention.

10 semiconductor substrate 12 gate insulating film

14 gate electrode 15 spacer

16: photodiode 18: source region

20a: first interlayer insulating film 20b: second interlayer insulating film

22a: first contact plug 22b: second contact plug

24: silicon film 26a: first metal wiring

26b: second metal wiring 28: photoresist pattern

Claims

In the method of manufacturing a CMOS image sensor comprising a semiconductor substrate, a photodiode region, a source region, a gate insulating film, a gate electrode, a spacer, a first interlayer insulating film and a first contact plug,

Selectively etching a first interlayer dielectric layer on the photodiode region;

Gap-filling the etched portion of the first interlayer insulating film to form a silicon film;

Forming a plurality of interlayer insulating films, a plurality of metal wirings, and a plurality of contact plugs on the first interlayer insulating film;

And selectively etching the first interlayer insulating film, the silicon film, and the plurality of interlayer insulating films on the photodiode region to leave a silicon film having a different thickness for each of the blue, green, and red regions. Way.

The method of claim 1,

Forming a plurality of interlayer insulating films, a plurality of metal wirings and a plurality of contact plugs on the first interlayer insulating film

Forming a first metal wire connected to the first contact plug on the first interlayer insulating film;

Forming a second interlayer insulating film on the entire surface of the first interlayer insulating film including the first metal wiring;

Forming a second contact plug penetrating the second interlayer insulating film and connected to the first metal wiring;

And forming a second metal wire connected to the second contact plug on the second interlayer insulating film.

The method of claim 1,

Selectively etching the first interlayer dielectric layer on the photodiode region

The method of manufacturing a CMOS image sensor, characterized in that the first interlayer insulating film to leave a thickness of 100 ~ 200Å.

The method of claim 1,

Selectively etching the first interlayer dielectric layer, the silicon layer, and the plurality of interlayer dielectric layers on the photodiode region to leave a silicon layer having a different thickness for each of the blue, green, and red regions;

And etching using different etching masks for each of the blue, green, and red regions.

The method of claim 1,

Selectively etching the first interlayer dielectric layer, the silicon layer, and the plurality of interlayer dielectric layers on the photodiode region to leave a silicon layer having a different thickness for each of the blue, green, and red regions using a RIE etching process Method of manufacturing the sensor.

The method of claim 1,

And the blue region etches all of the silicon layer, and the red region leaves a silicon layer thicker than the green region.

The method of claim 1,

The method of manufacturing a CMOS image sensor, characterized in that the first interlayer insulating film to leave a thickness of 50 ~ 100Å.