JP2003229558A - Method for manufacturing solid-state imaging device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing a solid-state imaging device capable of manufacturing a solid-state imaging device capable of reducing an interface state and stabilizing the interface state and having good characteristics. . When manufacturing a solid-state imaging device in which a surface protection film is formed so as to cover an imaging region including a sensor portion, after forming the sensor portion, a surface protection material layer is formed so as to cover the imaging region. Then, a heat treatment is performed on the surface protection material layer 14, and then the surface protection material layer 14 is processed into a predetermined thickness to form the surface protection film 13.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a solid-state image pickup device such as a CCD solid-state image pickup device.

[0002]

2. Description of the Related Art Charge coupled semiconductor devices (CCD: Charge)
Coupled Device) is a functional element that has both a function of accumulating photoelectrically converted electrons and a function of transferring accumulated electrons, and is used as an imaging device, a delay element, or the like.

CCDs are classified into surface channel type CCDs and embedded channel type CCDs according to the channel formation position, and are also classified into a single layer type and a two layer type according to the transfer driving method.

Of these, the embedded channel type CCD is
Since charges are transferred at a specific depth position in the silicon substrate, it is said that they are less affected by the interface between the silicon substrate and the oxide film on the surface, and the charge transfer efficiency and dark current are small.

[0005]

However, in a CCD solid-state image pickup device using a CCD as an image pickup device, even if an embedded channel type CCD is adopted due to the recent increase in the number of pixels and the unit cell size reduction, It is difficult to suppress the dark current to a sufficiently low level.

As measures against this, silicon substrate gettering (Intrinstic Gettering) by causing crystal defects in the silicon substrate, external gettering (Extrinstic Gettering) by heavy metal doping, plasma silicon oxide film containing N--H group, A method of forming a plasma silicon nitride film as a passivation film on a light receiving portion to reduce the interface state by supplying hydrogen ions, AlS
A method of forming a polyimide as an interlayer insulating film under a light-shielding film such as i or W to reduce the interface state by supplying hydrogen ions, a Zn _x Cd _1-x M (M is S or Se) thin film with H ₂ M
(M is S or Se) A method of annealing in a gas and reducing the interface state by supplying hydrogen ions (the annealing method is a method of irradiating a laser beam such as an RF plasma method, an ECR plasma method or an excimer laser, There is a method of heating by infrared lamp annealing, etc.), inert gas ions such as helium ions (He ⁺ ) or neutral gas ions and hydrogen ions (H ⁺ ) such as silane gas (SiH ₄ ) in plasma ions Attempts have been made to reduce the dark current by using a technique such as supplying hydrogen ions by applying a high frequency voltage to reduce the interface state.

However, none of the above-mentioned conventional methods is sufficient in the effect of reducing the interface state and stabilizing the interface state, and the dark current cannot be suppressed to a sufficiently low level.

In order to solve the above-mentioned problems, in the present invention, it is possible to manufacture a solid-state image pickup device having good characteristics, which can reduce the interface state and stabilize the interface state. A method for manufacturing an image sensor is provided.

[0009]

According to the method of manufacturing a solid-state image pickup device of the present invention, the sensor unit is formed when the solid-state image pickup device having the surface protection film formed to cover the image pickup region including the sensor unit is formed. After that, a step of forming a surface protective material layer covering the imaging region, a step of heat-treating the surface protective material layer, and then processing the surface protective material layer to a predetermined thickness to form a surface protective film. And a step of forming.

According to the above-described method for manufacturing a solid-state image pickup device of the present invention, after the sensor portion is formed, a step of forming a surface protective material layer to cover the image pickup region and a heat treatment to the surface protective material layer. By including the step of performing and the step of subsequently processing this surface protective material layer to a predetermined thickness to form a surface protective film, the surface protective material layer is sufficiently thicker than the film thickness of the surface protective film to be formed. Then, it is possible to supply hydrogen ions from this thick surface protection material layer by heat treatment to reduce the interface state and stabilize the interface state.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention is a method for manufacturing a solid-state image pickup device in which a surface protective film is formed so as to cover an image pickup area including a sensor section, and after the sensor section is formed, the image pickup area is covered. Solid having a step of forming a surface protective material layer, a step of heat-treating the surface protective material layer, and a step of subsequently processing the surface protective material layer to a predetermined thickness to form a surface protective film It is a manufacturing method of an image sensor.

Further, according to the present invention, in the method for manufacturing a solid-state image pickup device, the solid-state image pickup device has a charge transfer section for transferring a signal charge from the sensor section.

FIG. 1 is a schematic configuration diagram (cross-sectional view) of one embodiment of a solid-state image pickup device to which the present invention is applied. This solid-state image sensor is a vertical overflow type CCD solid-state image sensor (image sensor). First of n-type silicon substrate 1
N-type impurity diffusion region 6 in p-type semiconductor well region 2 of
And an n-type transfer channel region 4 and a p-type channel stop region 5 forming the vertical transfer register 16 are formed. Then, a p-type positive charge accumulation region 3 is formed on the surface of the n-type impurity diffusion region 6, and a second p-type semiconductor well region 7 is formed immediately below the n-type transfer channel region 4.

A sensor section (light receiving section) 15 is constituted by a photodiode having a pn junction between the n-type impurity diffusion region 6 and the first p-type semiconductor well region 2. The sensor unit 15 serves as a pixel, and although not shown, a plurality of sensor units 15 are arranged in a matrix to form an image pickup area of the solid-state image pickup device.

Further, the transfer by the polycrystalline silicon layer is performed on the transfer channel region 4, the channel stop region 5 and the read gate portion 17 which constitute the vertical transfer register 16 through the insulating film 8 and the gate insulating film 9 on the substrate surface. Electrode 1
0 is formed. However, the insulating film on the light receiving portion 15 is formed only by the insulating film 8 on the substrate surface. Transfer electrode 1
0, an interlayer insulating film 11 is formed on the interlayer insulating film 1.
A light shielding film 12 made of Al or W is formed on the surface 1. A portion of the light shielding film 12 on the sensor portion 15 is selectively removed by etching to form an opening 12A, and light is allowed to enter the light receiving portion 15 through the opening 12A.

Further, a surface protection film 13 is formed on the light-shielding film 12 so as to cover the entire image pickup area, and the surface protection film 13 as a whole is
One pixel is constructed. The surface protection film 13 is formed of, for example, a plasma nitride film or the like.

By being configured as described above,
The CCD solid-state imaging device shown in FIG. 1 can discharge excess signal charges generated in the sensor section 15 to the silicon substrate 1 side, that is, a vertical overflow type CCD solid-state imaging device.

Next, a manufacturing process of the solid-state image pickup device shown in FIG. 1 will be described as an embodiment of the method of manufacturing the solid-state image pickup device of the present invention.

First, in the first p-type semiconductor well region 2 in the silicon substrate 1, the sensor section 15 and the vertical transfer register 1 are provided.
6, each of the regions 3, 4 constituting the channel stop region 5
Form 5, 6, and 7. Further, the insulating film 8, the gate insulating film 9, the transfer electrode 10, the interlayer insulating film 11, and the light shielding film 12 made of Al or W on the surface of the silicon substrate 1 are sequentially formed by a known method.

Next, as shown in FIG. 2A, a surface protective material layer 14 made of, for example, a plasma nitride film is formed on the light shielding film 12 so as to cover the entire imaging region.

At this time, the film thickness of the surface protective material layer 14 is
It is desirable that the thickness is 1.5 times or more the thickness of the surface protective film 13 to be formed later. For example, the surface protection film 13
When forming with a film thickness of m, the film thickness of the surface protection material layer 14 is set to 1.5 μm or more. In addition, the surface protection material layer 14
The film thickness of is preferably 1 μm or more.

Next, as shown in FIG. 2A, the surface protection material layer 14 is heat-treated in a diffusion furnace or the like. As conditions for this heat treatment, it is desirable to use a nitrogen atmosphere at 380 ° C. or higher (an atmosphere in which most of nitrogen is 100%) or a 100% hydrogen atmosphere.

As a result, hydrogen ions can be supplied from the plasma nitride film of the thick surface protective material layer 14 to reduce or stabilize the interface state. Hydrogen ions existing in the nitride film have a film thickness dependence, and by being formed in a thick film, the supply of hydrogen ions increases, and the effect of reducing the interface state and stabilizing the interface state is promoted. .

After that, the surface protection material layer 14 made of a plasma nitride film is processed by using a method such as etch back. At this time, a flattening step is performed if necessary. As a result, as shown in FIG. 2B, the surface protective film 13 having a predetermined film thickness can be formed, and the CCD solid-state imaging device shown in FIG. 1 can be manufactured. After that, if necessary, an upper layer film, for example, a color filter, a microlens, a flattening film, or the like is formed.

After that, when forming the second layer and the third layer of the plasma nitride film, for example, the heat treatment is similarly performed on the plasma nitride film each time. This allows
Further, hydrogen ions can be supplied. As such a case, for example, when forming a microlens on the surface protection film 13, a plasma nitride film may be formed. It should be noted that the plasma nitride films of the second and subsequent layers do not necessarily have to be formed to a thickness 1.5 times or more the final film thickness.

According to the manufacturing process of this embodiment described above,
By heat-treating the plasma nitride film of the surface protective material layer 14 formed thick, a sufficient amount of hydrogen ions are supplied from the plasma nitride film formed thick to reduce the interface state and reduce the interface state. The effect for stabilization is obtained.

After the heat treatment, the surface protective material layer 14 is processed to obtain the surface protective film 1 having a predetermined thickness.
3 can be formed.

Actually, the surface protective film 13 having a thickness of 1 to 1.5 μm
When the CCD solid-state imaging device having the above is manufactured, the surface protection material layer 14 made of a plasma nitride film is formed to a film thickness of 2 μm or more, then heat treatment is performed, and then the surface protection film 13 is formed by etch back. The dark current was reduced by 20% or more.

In the above embodiment, the surface protective material layer 1
A plasma nitride film is used as the material for the protective layer 4 and the surface protection film 13. This is because the plasma nitride film has a high refractive index and a high transmittance for incident light.

In the present invention, it is possible to use other materials as the material for the surface protective material layer 14 and the surface protective film 13. For example, a nitride film formed by the low pressure CVD (chemical vapor deposition) method or an insulating film formed by the O ₃ -TEOS method can be used as the material of the surface protective material layer 14 and the surface protective film 13. In this case as well, the surface protective material layer 14 is similarly formed thick, and after the heat treatment, the surface protective material layer 14 is processed to form the surface protective film 13 having a predetermined film thickness.

The atmosphere for the heat treatment is not limited to the above-mentioned nitrogen atmosphere or 100% hydrogen atmosphere, but may be an inert gas atmosphere or the like. The above nitrogen atmosphere or 100%
The hydrogen atmosphere has the advantage of being cheaper than the inert gas atmosphere. It should be noted that the atmosphere of this heat treatment is set so as not to contain a gas having reactivity with hydrogen ions such as oxygen so as not to reduce the effect of supplying hydrogen ions.

Further, although the present invention is applied to the CCD solid-state image pickup device in the above-mentioned embodiments, the present invention can be applied to the solid-state image pickup device having other configurations. For example, the present invention can be similarly applied to a solid-state image pickup device having a configuration other than the CCD for transferring charges, a MOS type solid-state image pickup device, and a CMOS type solid-state image pickup device. Even in the solid-state imaging device having such a configuration, the signal amount becomes small due to the miniaturization of the pixel size. Therefore, the application of the present invention has an effect of reducing the interface state and stabilizing the interface state. For example, it is possible to suppress the occurrence of white defects and the like.

In particular, in a structure in which a charge transfer unit is provided to transfer charges, such as a CCD solid-state image pickup device, dark current due to an interface state cannot be corrected by another method such as a method of correcting by a circuit. Therefore, the effect of applying the manufacturing method of the present invention is great.

The present invention is not limited to the above-mentioned embodiments, and various other configurations can be adopted without departing from the gist of the present invention.

[0035]

According to the present invention described above, a sufficient amount of hydrogen ions are supplied from a thickly formed surface protection material layer,
A sufficient effect for reducing the interface state and stabilizing the interface state can be obtained. Therefore, according to the present invention, it is possible to suppress the occurrence of defects such as dark current and white defects, and manufacture a solid-state imaging device having good characteristics.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram (cross-sectional view) of one form of a solid-state image sensor to which the present invention is applied.

2A and 2B are process diagrams showing a manufacturing process of the solid-state imaging device of FIG. 1 according to the manufacturing method of the present invention.

[Explanation of symbols]

1 silicon substrate, 2 first p-type semiconductor well region,
3 positive charge storage region, 4 transfer channel region, 5 channel stop region, 6 n-type impurity diffusion region, 7 second p
Type semiconductor well region, 9 gate insulating film, 10 transfer electrode, 12 light-shielding film, 13 surface protective film, 14 surface protective material layer, 15 sensor section, 16 vertical transfer register, 1
7 Read gate section

Claims (2)

[Claims] 1. A method of manufacturing a solid-state imaging device having a surface protective film formed covering an imaging region including a sensor unit, the method comprising: forming the sensor unit and then covering the imaging region; And a step of performing a heat treatment on the surface protective material layer, and then processing the surface protective material layer to a predetermined thickness to form the surface protective film. And a method for manufacturing a solid-state image sensor. 2. The method of manufacturing a solid-state image sensor according to claim 1, wherein the solid-state image sensor has a charge transfer unit that transfers signal charges from the sensor unit.