KR100866253B1 - Method for manufacturing of the image sensor - Google Patents

Abstract

A method for manufacturing am image sensor is provided to prevent the deterioration of device caused by etch damages and to obtain the reliability of device. A method for manufacturing am image sensor comprises a step for forming a salicide prevention layer(121) in a photodiode formation region on the semiconductor substrate; a step for forming a gate electrode(141) and a gate insulating layer by patterning and depositing an oxide layer and polysilicon on the semiconductor substrate; a step for forming a spacer at a sidewall of the gate electrode; a step for forming a photodiode(160) at one side of the gate electrode; a step for forming a floating diffusion layer(170) at the other side of the gate electrode; a step for forming a salicide layer on the upper surface of the gate electrode and floating diffusion layer.

Description

Method for Manufacturing of the Image Sensor

1 to 6 are diagrams illustrating a manufacturing process of a conventional image sensor.

7 to 11 are diagrams illustrating a manufacturing process of the image sensor of the embodiment.

In an embodiment, a method of manufacturing an image sensor is disclosed.

An image sensor is a semiconductor device that converts an optical image into an electrical signal, and is classified into a charge coupled device (CCD) image sensor and a complementary metal oxide silicon (CMOS) image sensor (CIS). do.

CCD image sensor has complex driving method, high power consumption, multi-stage photo process, and manufacturing process has complicated disadvantage. Therefore, as a next generation image sensor to overcome the disadvantage of the charge coupling device, Morse image sensor is attracting attention.

CMOS image sensor uses CMOS technology that uses a control circuit and a signal processing circuit as peripheral circuits to make MOS transistors by the number of pixels and sequentially detects the output using them. The device adopts the switching method.

The pixel of the CMOS image sensor includes one photodiode and four MOS transistors that receive light to generate photoelectric charges.

The four MOS transistors include a transfer transistor that transfers the photocharges collected by the photodiode to the floating diffusion, a reset transistor that sets the potential of the floating diffusion to a desired value and discharges charge to reset the floating diffusion, and a voltage of the floating diffusion. The gate transistor includes a drive transistor applied to the gate and serving as a source follower buffer amplifier, and a select transistor serving as a switching role.

In the CMOS image sensor manufacturing process, a salicide process is adopted to lower the resistance of the active region and the polysilicon gate. Since the metal films used in the salicide process have high reflectance to light, the salicide should be applied only to the gate in the pixel structure in which the photodiode and the gate are adjacent to each other.

A manufacturing process of a conventional image sensor will be described with reference to FIGS. 1 and 6.

Referring to FIG. 1, a sacrificial oxide film 20 is formed on a semiconductor substrate 10 on which an isolation layer 11 is formed. The sacrificial oxide film 20 is to prevent the surface of the semiconductor substrate 10 from being damaged during ion implantation for well formation of a circuit region (not shown).

After completion of ion implantation for well formation on the semiconductor substrate 10 on which the sacrificial oxide film 20 is formed, all of the sacrificial oxide film 20 is removed by a wet etching process.

2 and 3, after the oxide film 30 and the polysilicon film 40 are formed on the semiconductor substrate 10, the gate oxide film 31 and the gate electrode 41 are formed through an etching process. . The gate electrode 41 is a gate electrode 141 of a transfer transistor adjacent to the photodiode.

Here, the gate oxide layer 31 is also patterned when the gate electrode 41 is formed, but all of the oxide layer 32 on the surface of the semiconductor substrate is not removed but remains in a thin state.

The photodiode 60 is formed by implanting impurity ions using the gate electrode 41 and a separate photoresist pattern as a mask.

After the spacers 51 are formed in contact with both sidewalls of the gate electrode 41, the spacers 51 on the other side of the gate electrode 41 are formed using the gate electrode 41 and the spacer 51 as an ion implantation mask. A floating diffusion region 70 is formed that is aligned with.

Referring to FIG. 4, after the TEOS material is deposited on the semiconductor substrate 10, a photoresist pattern is formed to form the passivation layer 80 only on the photodiode 60.

5 and 6, the oxide film 32 remaining in the region other than the photodiode 60 is removed through a cleaning process and then the salicide layer 90 is formed in the gate electrode 141 and the source / drain regions. Is formed.

In the conventional image sensor as described above, a wet etching process is used to remove the sacrificial oxide layer. In the wet etching, the photodiode surface region is damaged by the etchant to cause dark current.

In addition, when the gate electrode 141 is formed, the surface of the photodiode is damaged by a dry etching process to cause dark current.

In addition, when the protective layer is formed on the photodiode, a reactive ion etching process is used. The ion etching damages the surface of the semiconductor substrate and the gate oxide layer, causing a threshold voltage delay of the peripheral circuit region, thereby improving the quality. There is a problem of deterioration.

The embodiment provides an image sensor and a method of manufacturing the same, which can secure device reliability by preventing deterioration of device characteristics due to etching damage.

In another embodiment, a method of manufacturing an image sensor includes: forming a salicide prevention layer on a photodiode formation region on a semiconductor substrate; Depositing and patterning an oxide film and polysilicon on the semiconductor substrate to form a gate electrode and a gate insulating film; Forming a spacer on sidewalls of the gate electrode; Forming a photodiode in the semiconductor substrate on one side of the gate electrode; Forming a floating diffusion on the other side of the gate electrode; And forming a salicide layer on an upper surface of the gate electrode and an upper surface of the floating diffusion.

Hereinafter, a method of manufacturing an image sensor according to an embodiment will be described in detail with reference to the accompanying drawings.

In the description of the embodiments, where described as being formed "on / over" of each layer, the on / over may be directly or through another layer ( indirectly) includes everything formed.

In the drawings, the thickness or size of each layer is exaggerated, omitted, or schematically illustrated for convenience and clarity of description. In addition, the size of each component does not necessarily reflect the actual size.

A method of manufacturing the image sensor of the embodiment will be described with reference to FIGS. 7 to 11.

Referring to FIG. 7, a sacrificial insulating layer 120 is formed on the semiconductor substrate 100.

The semiconductor substrate 100 may be a high concentration P ++ semiconductor substrate 100, and a low concentration p-type epi layer (not shown) may be formed by performing an epitaxial process on the semiconductor substrate.

In the exemplary embodiment, the semiconductor substrate 100 and the epi layer are used as p-types, but the present invention is not limited thereto.

An isolation layer 110 is formed in a predetermined region of the semiconductor substrate 100 on which the p-type epitaxial layer is formed to define an active region and a field region and separate unit pixels.

The sacrificial insulating layer 120 is formed to protect the surface of the semiconductor substrate 100 during ion implantation for well formation of a peripheral circuit region (not shown). For example, the sacrificial insulating layer 120 may be formed of an oxide film and may be formed to a thickness of about 100 to about 200 Å.

When a well region (not shown) is formed by implanting ions onto the semiconductor substrate 100 on which the sacrificial insulating film 120 is formed, a photoresist pattern 200 is formed on the sacrificial insulating film 120 to form the sacrificial insulating film ( Etch 120).

The photoresist pattern 200 is formed by coating and patterning a photoresist layer on the sacrificial insulating layer 120. The photoresist pattern 200 is formed only on a photodiode formation region.

Referring to FIG. 8, a salicide prevention layer 121 is formed on a region on which a photodiode is to be formed of the semiconductor substrate 100.

The salicide preventing layer 121 is to prevent salicide of the photodiode in a later step, and the sacrificial insulating layer 120 is etched by using the photoresist pattern 200 as an etching mask to form the photodiode formation region. Only the sacrificial insulating layer 120 remains so that the salicide barrier layer 121 is formed. .

Etching of the sacrificial insulating layer 120 for forming the salicide barrier layer 121 is performed by a wet etching process, so that the sacrificial insulating layer 120 remains only in a region where the photodiode is to be formed and all of the sacrificial insulating layers 120 in the remaining region are formed. The surface of the semiconductor substrate 100 that is etched to form the CMOS circuit and the peripheral circuit region is exposed.

Since the salicide preventing layer 121 is formed in the photodiode formation region, the surface of the semiconductor substrate 100 of the photodiode formation region may be protected by an etching process of the sacrificial insulating layer 120.

9 and 10, a gate insulating layer 131 and a gate electrode 141 are formed on the semiconductor substrate 100.

The gate insulating layer 131 and the gate electrode 141 are stacked with an oxide film 130 and a polysilicon film 140 on the semiconductor substrate 100, and then a gate photoresist pattern on the polysilicon film 140. (Not shown) is formed. The gate electrode 141 is formed by etching the lower polysilicon layer 140 using the photoresist pattern as an etching mask.

When the gate electrode 141 is formed, the lower oxide layer 130 is also etched to form a gate insulating layer 131 under the gate electrode 141.

In this case, since the oxide film 130 formed on the semiconductor substrate 100 is etched when the gate electrode 141 is formed, but not all of them are removed, the oxide film 132 having a thin thickness remains on the semiconductor substrate 100. do.

In addition, since the oxide film 132 is formed on the salicide barrier 121, the thickness of the salicide barrier 121 is increased.

As described above, since the salicide barrier layer 121 is formed in the photodiode formation region, the surface of the semiconductor substrate 100 in the photodiode formation region is prevented from being damaged during etching to form the gate electrode 141. Can be.

The n-region is formed in the photodiode formation region on one side of the gate electrode 141 through impurity implantation using the gate electrode 141 and a separate photoresist pattern as a mask. In addition, a photodiode 160 is formed by forming a p0 region having a shallow depth in an n− region of the photodiode formation region through an impurity implantation process using the gate electrode 141 and a separate photosensitive light pattern as a mask. .

Next, a spacer 151 is formed to contact both sidewalls of the gate electrode 141, and a gate electrode 141 is formed through an ion implantation process of impurities using the gate electrode 141 and the spacer 151 as an ion implantation mask. Floating diffusion region 170 is formed on the other side of the substrate.

9, an oxide film 132 remaining on the surface of the semiconductor substrate 100 is removed by performing a surface cleaning process on the semiconductor substrate 100. Then, as shown in FIG. 10, the salicide barrier layer 121, the gate electrode 141, and the spacer 151 remain on the semiconductor substrate 100.

For example, HF is used as the cleaning liquid used in the cleaning process for removing the oxide film 132, and the oxide film 132 is removed about 100 to 125 kPa.

In particular, since the thickness of the salicide barrier 121 is formed to a thickness of 100 μm or more greater than that of the oxide layer 132 formed in the region other than the salicide barrier 121, the salicide barrier may be removed even if all of the oxide layer 132 is removed. The 121 may remain without being removed to protect the surface of the photodiode 160.

Referring to FIG. 11, a salicide layer 190 is formed on an upper surface of the gate electrode 141 and the floating diffusion region 170.

The salicide layer 190 is formed on the gate electrode 141 and the floating diffusion region 170 by depositing a metal material on the semiconductor substrate 100.

For example, the salicide layer 190 deposits one metal film selected from the group consisting of titanium, cobalt nickel, molybdenum, and nickel alloy onto the semiconductor substrate 100. In addition, a salicide layer 190 may be formed on the gate electrode 141 and the floating diffusion region 170 by inducing a silicide reaction between the metal layer and the silicon.

In this case, since the salicide prevention layer 121 is formed on the photodiode 160, the photodiode 160 is not salicided.

Therefore, the upper portion of the gate electrode 141 and the floating diffusion region 170 is salicided, and the upper portion of the photodiode 160 is nonsalicided by the salicide barrier layer 121, The condensing rate can be improved.

In addition, since the salicide preventing layer 121 is formed by a deposition process for forming the sacrificial insulating film 120 and the gate insulating film 131, the etching process that is performed when the protective film is formed on the conventional photodiode 160 may be omitted. Since the process can be simplified, and the etching process can be omitted, the threshold voltage delay defect of the peripheral circuit region can be prevented.

The embodiments described above are not limited to the above-described embodiments and drawings, and it is to be understood that various changes, modifications, and changes can be made without departing from the technical spirit of the present embodiments. It will be obvious to those who have it.

In the image sensor and the method of manufacturing the same, the sacrificial oxide is left on the surface of the photodiode so that the sacrificial oxide becomes a silicide prevention layer, thereby preventing the surface damage of the photodiode in the etching process, thereby preventing the occurrence of dark current in advance. It has an effect.

In addition, since the upper portion of the photodiode is protected on the silicide prevention layer during the etching process according to the gate formation, it is possible to prevent surface damage of the photodiode according to the etching process to improve the reliability of the device.

Claims (6)

Forming a salicide barrier layer on a region in which a photodiode is to be formed on the semiconductor substrate; Forming a gate electrode and a gate insulating film on the semiconductor substrate on one side of the salicide preventing layer; Forming a photodiode in the semiconductor substrate under the salicide barrier layer so as to be aligned with one side of the gate electrode; Forming a spacer on sidewalls of the gate electrode; Forming a floating diffusion in the semiconductor substrate on the other side of the gate electrode; And Forming a salicide layer on an upper surface of the gate electrode and an upper surface of the floating diffusion. The method of claim 1, Forming the salicide prevention layer, Forming a sacrificial insulating film on the semiconductor substrate; Implanting ions into the semiconductor substrate on which the sacrificial insulating film is formed to form a well region; Forming a photoresist pattern only on a region in which the photodiode is to be formed on the sacrificial insulating film; And And etching the sacrificial oxide layer using the photoresist pattern. The method of claim 1, The salicide blocking layer is formed of an oxide film. The method of claim 1, And performing a cleaning process such that an oxide film remains only on the photodiode before forming the salicide layer. The method of claim 2, And the sacrificial insulating layer is etched by a wet etching process. The method of claim 1, And the photodiode is formed by ion implantation into the semiconductor substrate on which the salicide prevention layer is formed.

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