KR100954928B1 - Image sensor and manufacturing method of image sensor - Google Patents

Abstract

In another embodiment, a method of manufacturing an image sensor includes implanting impurity ions to form an ion implantation layer in an intermediate portion of a first substrate; Inverting and bonding the first substrate onto the second substrate; Separating the first substrate portion below the ion implantation layer with the ion implantation layer as a boundary; And forming a gate electrode by patterning the first substrate having a portion removed.

According to the embodiment, by forming the gate electrode using single crystal silicon instead of the conventional polysilicon, it is possible to minimize the resistance of the gate electrode, it is possible to lower the operating voltage.

Image sensor, transmitter gate, photodiode region, single crystal layer, ion implantation

Description

Image sensor and manufacturing method of image sensor

Embodiments relate to a method of manufacturing an image sensor.

An image sensor is a semiconductor device that converts an optical image into an electrical signal. The image sensor is largely a charge coupled device (CCD) and a complementary metal oxide silicon (CMOS) image sensor. Sensor).

The CMOS image sensor uses CMOS technology using a control circuit, a signal processing circuit, and the like as peripheral circuits 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.

The semiconductor region of the CMOS image sensor is largely divided into a photodiode region and a transistor region. The photodiode region converts light into electrons, and the transistor region constitutes a circuit for driving the image sensor.

The transfer transistor formed in the transistor region accumulates an electrical signal generated from the photodiode. The gate electrode of the transfer transistor may include: first depositing a polysilicon layer by a low pressure chemical vapor deposition (LPCVD) method; Second, implanting and annealing impurities by an implant to lower the resistance of the polysilicon layer, and third, patterning the polysilicon layer to form a gate electrode.

Thus, the gate electrode formed of the polysilicon layer has a capacitance due to its own resistive component, the operation speed of the transistor is lowered by the influence of the resistance and the capacitance, and high power is consumed.

That is, the resistance component and capacitance of the transfer transistor affect the time and amount of passage of electrons generated in the photodiode through the channel formed by the gate of the transfer transistor, which is a limiting factor in improving the operation characteristics of the image sensor. Function.

Therefore, a new method for lowering the resistance of the gate electrode of the transfer transistor is required.

The embodiment provides a method of manufacturing an image sensor capable of lowering an operating voltage by minimizing a resistance of a gate electrode of a transfer transistor and improving an operating speed by increasing a moving efficiency of electrons generated in a photodiode.

In another embodiment, a method of manufacturing an image sensor includes implanting impurity ions to form an ion implantation layer in an intermediate portion of a first substrate; Inverting and bonding the first substrate onto the second substrate; Separating the first substrate portion below the ion implantation layer with the ion implantation layer as a boundary; And forming a gate electrode by patterning the first substrate having a portion removed.

According to the embodiment, the following effects are obtained.

First, by forming the gate electrode using single crystal silicon instead of the conventional polysilicon, it is possible to minimize the resistance of the gate electrode, and to lower the operating voltage.

Second, since the electrons generated in the photodiode can shorten the time to pass through the channel formed by the gate of the transfer transistor and increase the amount of passage, it is possible to improve the operation speed and the operation reliability of the image sensor.

With reference to the accompanying drawings, it will be described in detail with respect to the image sensor and the manufacturing method of the image sensor according to the embodiment.

Hereinafter, in describing the embodiments, detailed descriptions of related well-known functions or configurations are deemed to unnecessarily obscure the subject matter of the present invention, and thus only the essential components directly related to the technical spirit of the present invention will be referred to. .

In the description of an embodiment according to the present invention, each layer (film), region, pattern or structure may be "on" or "under" the substrate, each layer (film), region, pad or pattern. "On" and "under" include both "directly" or "indirectly" formed through another layer, as described in do. Also, the criteria for top, bottom, or bottom of each layer will be described with reference to the drawings.

1 is a side cross-sectional view showing the shape of the donor substrate 100 after the ion implantation layer 120 is formed according to the embodiment.

In the embodiment, a single crystal layer to be used as the transfer gate electrode is separately manufactured in order to lower the resistance and capacitance characteristics of the gate electrode of the transfer transistor of the image sensor (hereinafter referred to as a "transfer gate electrode").

The first substrate 100 shown in FIG. 1 may be provided as a silicon substrate as a substrate for forming the single crystal layer. Hereinafter, the first substrate 100 is referred to as a "donor substrate".

A sacrificial oxide film 110 is formed on the donor substrate 100 in a bare wafer state.

The sacrificial oxide film 110 may be formed by a rapid thermal oxidation (RTO) process, and may be formed to a thickness of 70 kPa to 90 kPa.

The sacrificial oxide film 110 then performs a function of preventing lattice defects from occurring on the surface of the donor substrate 100 when the implant process is performed to form the ion implantation layer 120.

Subsequently, impurity ions such as hydrogen ions are implanted into the donor substrate 100 to form the ion implantation layer 120.

The ion implantation layer 120 may be formed in the middle portion of the donor substrate 100, and may be formed at a depth of 1000 μs to 3000 μm from the surface of the donor substrate 100.

The ion-implanted layer 120 is positioned to be formed may be adjusted by varying the implantation energy, dose of hydrogen ions, for example, the hydrogen ions of 10keV to 40keV energy and 1E16dose / cm ² To 1E18 dose / cm ² .

The donor substrate 100 having a portion above the ion implantation layer 120 is a portion corresponding to a transfer gate electrode (see FIG. 4) 130 to be formed later.

2 is a side cross-sectional view illustrating a form in which a semiconductor substrate 200 and a donor substrate 100 in which an image sensor is to be formed are coupled, according to an embodiment.

Thereafter, the sacrificial oxide film 110 of the donor substrate 100 is removed through a planarization process or an etching process, and the donor substrate 100 is inverted to be bonded on the second substrate 200 on which the photoresist and the transistor are to be formed. .

Hereinafter, the second substrate 200 is referred to as a "semiconductor substrate."

The gate oxide layer 210 and the device isolation region 220 are formed before the semiconductor substrate 200 is bonded to the donor substrate 100.

The donor substrate 100 may be pressed / coupled to the semiconductor substrate 200 by applying a force of a predetermined pressure to the bottom surface of the donor substrate 100.

3 is a side cross-sectional view showing a form after a part of the donor substrate 100 is separated according to the embodiment.

When the donor substrate 100 and the semiconductor substrate 200 are bonded to each other, the donor substrate 100 is heat-treated at a temperature of about 800 ° C. to 1000 ° C. for 30 seconds to 60 seconds.

The heat treatment may be performed through a rapid thermal annealing (RTA) process.

Thereafter, as shown in FIG. 3, a portion of the donor substrate 100 under the ion implantation layer 120 is separated by providing a simple physical force around the ion implantation layer 120 (usually, "smart cut"). (smart-cut) ".

For reference, the donor substrate 100 illustrated in FIGS. 2 and 3 is in a state in which the donor substrate 100 illustrated in FIG. 1 is inverted, and an area of the donor substrate 100 is represented based on FIG. 1. do.

Thus, the silicon single crystal layer to be used to form the transfer gate electrode is completed. The single crystal layer thus completed may be formed to a thickness of 1000 kPa to 3000 kPa as described above.

4 is a side cross-sectional view illustrating a form after the gate electrode 130 of the image sensor according to the embodiment is formed.

Thereafter, the donor substrate 100 completed with the single crystal layer is patterned to form a transfer gate electrode 130.

The transfer gate electrode may be patterned by applying a photoresist, forming a photoresist pattern, etching, or removing a photoresist pattern.

When the transfer gate electrode 130 is formed, a photoresist pattern is formed from the region where the transistor is to be formed to the transfer gate electrode 130, and ion implanted with low concentration of N-type impurities. Thereafter, the photoresist pattern is removed.

Accordingly, the photodiode 230 is formed in the region between the device isolation region 220 and the transfer gate electrode 130.

When the photodiode 230 is formed, spacers 240 are formed on both sides of the transfer gate electrode 130, and from the photodiode 230 region to one spacer 240 of the transfer gate electrode 130. The photoresist pattern 10 is formed.

Using the photoresist pattern 10 as an ion implantation mask, source / drain regions 250 are formed by ion implanting impurities into a region where the transistor is to be formed.

In this case, the implanted ions are implanted into the transfer gate electrode 130, and the annealing of the transfer gate electrode 130 into which the ions are implanted is completed to complete the silicon single crystal transfer gate electrode 130 having low resistance.

As described above, when the transfer gate electrode 130 is completed, a subsequent process may be further performed to transfer an electric signal generated from the photodiode 230 to the transistor region including the transfer gate electrode 130. An electrical signal is stored in a floating diffusion layer (FD) for storing the electrical signals stored in the transfer transistor (Tx), a reset transistor (Rx) for applying power to the floating diffusion layer (FD), and a floating diffusion layer (FD). As the gate potential changes, the access transistor Ax for applying the electric signal and the selector transistor for outputting the electric signal applied by the access transistor Ax are formed.

In addition, when the photodiode 230 and the transistors are formed on the semiconductor substrate 200, a plurality of insulating layers, color filter layers, protective layers, micro lenses, etc. including contact plugs and metal wires may be formed thereon. have.

The present invention has been described above with reference to the preferred embodiments, which are merely examples and are not intended to limit the present invention, and those skilled in the art to which the present invention pertains do not depart from the essential characteristics of the present invention. It will be appreciated that various modifications and applications are not possible that are not illustrated above. For example, each component specifically shown in the embodiments of the present invention can be modified and implemented. And differences relating to such modifications and applications will have to be construed as being included in the scope of the invention defined in the appended claims.

1 is a side cross-sectional view showing the form of the donor substrate after the ion implantation layer according to the embodiment is formed.

2 is a side cross-sectional view illustrating a form in which a semiconductor substrate and a donor substrate on which an image sensor is to be formed are coupled according to an embodiment;

3 is a side sectional view showing a form after a part of the donor substrate is separated according to the embodiment;

4 is a side sectional view showing a form after a gate of the image sensor is formed according to the embodiment;

Claims (9)

Implanting impurity ions to form an ion implantation layer in an intermediate portion of the first substrate; Inverting and bonding the first substrate onto the second substrate; Separating the first substrate portion below the ion implantation layer with the ion implantation layer as a boundary; And And forming a gate electrode by patterning the partially removed first substrate. The method of claim 1, wherein the ion implantation layer Conditions for implanting hydrogen ions into the impurity ions, conditions for supplying ion implantation energy of 10keV to 40keV, 1E16dose / cm ² To 1E18 dose / cm ² ion implantation conditions are formed to satisfy one or more of the conditions of the manufacturing method of the image sensor. The method of claim 1, wherein the ion implantation layer And a depth of 1000 mV to 3000 mV from the surface of the first substrate. The method of claim 1, further comprising: bonding the first substrate onto a second substrate And the second substrate has a device isolation region and a gate oxide layer formed thereon. The method of claim 1, The forming of the ion implantation layer may include forming a sacrificial oxide film on the first substrate before forming the ion implantation layer, Bonding the first substrate onto a second substrate comprises removing the sacrificial oxide film of the first substrate before being bonded onto the second substrate. The method of claim 5, wherein the sacrificial oxide film A method of manufacturing an image sensor, characterized in that formed in a thickness of 70 kHz to 90 kHz. The method of claim 1, wherein the bonding of the first substrate to the second substrate is performed. And heat-treating the first substrate for 30 seconds to 60 seconds at a temperature of 1000 ° C. to 1100 ° C. in the bonded state on the second substrate. The method of claim 1, Forming a photodiode in the second substrate region on one side of the gate electrode; And Forming a source / drain junction and simultaneously implanting ions into the gate electrode to reduce the resistance of the gate electrode. The method of claim 8, And annealing the low resistance gate electrode.

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