JP2612108B2 - Method for manufacturing solid-state imaging device - Google Patents

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 sensor in which a dispersion of ion implantation is reduced when forming a diffusion layer of the solid-state image sensor.

[0002]

2. Description of the Related Art In recent years, it has become indispensable to use an ion implantation method for forming diffusion layers in a pixel portion and a transfer portion of a solid-state image sensor. When a diffusion layer of a solid-state imaging device is formed by using an ion implantation method, it is necessary to reduce variations in the amount of ion implantation in order to obtain uniform characteristics of each pixel cell.

The mainstream type of ion implantation apparatus used for manufacturing a solid-state imaging device is a medium current type, and most of the ion implantation apparatuses employ an electrostatic scanning system.

[0004] A process for forming a diffusion layer of a conventional solid-state imaging device will be described below. FIG. 2 shows a cross-sectional configuration in a step of forming a diffusion layer in a pixel portion of the solid-state imaging device. The solid-state imaging device shown in FIG. 2 is manufactured by the following manufacturing method. First, a P-type diffusion layer 2 and an oxide film 4 are sequentially formed on a silicon substrate 1, and a photoresist 5 is formed on the entire surface of the oxide film 4. Next, the photoresist 5 is patterned, and the P-type diffusion layer 2 on which the N-type diffusion layer 3 is to be formed later is formed.
The photoresist 5 above the portion is partially removed.

Next, by using the photoresist 5 patterned as described above as a mask, an ion beam 6 is irradiated to selectively implant phosphorus ions.
Thereby, the N-type diffusion layer 3 is formed. In an electrostatic scan type ion implantation apparatus, phosphorus ion implantation is performed by moving an ion beam at a constant speed on an ion beam scanning line determined by a combination of vertical and horizontal electrostatic deflection frequencies.

[0006]

However, in the above-mentioned conventional manufacturing method, since the number of scanning lines of the ion beam is determined by the electrostatic deflection frequency, the scanning of the ion beam is always performed at intervals of several tens to several hundreds of microns. Is being done. On the other hand, the shape of the ion beam spot where the ion implantation is performed while moving on the scanning line varies in size, so that when the ion beam spot is small, uniform ion implantation is not performed, and the pixel cell extends vertically and horizontally over several thousand microns. With hundreds of solid-state imaging devices, the amount of ion implantation in the diffusion layer of each pixel cell becomes non-uniform. In addition, even if the ion beam spot becomes large, if the current density is non-uniform, uniform ion implantation will not be performed similarly, and the amount of ion implantation in the diffusion layer of each pixel will be non-uniform. In particular, in a solid-state imaging device, since the variation in the amount of ion implantation into pixels is greatly reflected in image characteristics,
It is a big problem.

SUMMARY OF THE INVENTION The present invention solves the above-mentioned conventional problems, and provides a method of manufacturing a solid-state imaging device capable of reducing variation in the amount of ion implantation in a diffusion layer in each pixel cell of the solid-state imaging device. Aim.

[0008]

In order to achieve the above object, according to the first aspect of the present invention, the diameter of an ion beam spot is made larger than the interval between scanning lines, and uniform ion implantation is performed over a wide area. Is what you do.

Specifically, a solution taken by the invention of claim 1 is directed to a method for manufacturing a solid-state imaging device in which a diffusion layer is formed by ion implantation, and the diameter of an ion beam spot at the time of ion implantation is 10 mm to 20 mm. This is the configuration that has been set.

Further, according to the invention of claim 2, ion implantation is performed by adjusting the shape of the ion beam spot so as to obtain a uniform current density in the ion beam spot.

Specifically, the solution taken by the invention of claim 2 is that the ion implantation is performed by using a circular ion beam spot having a uniform current density to the structure of the invention of claim 1. Is what you do.

[0012]

According to the first aspect of the present invention, since the ion implantation is performed with the ion beam spot size set to 10 mm to 20 mm, the diffusion layer of each pixel cell extends over a region wider than the interval between the scanning lines of the ion beam. The amount of ion implantation can be made uniform.

According to the second aspect of the present invention, the shape of the ion beam spot is circular, so that the current density in the ion beam spot can be made constant.

[0014]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows a process of forming a diffusion layer in a pixel portion of a solid-state imaging device in a method of manufacturing a solid-state imaging device according to this embodiment. The solid-state imaging device shown in FIG. 1 is manufactured by the following manufacturing method. First, P on the silicon substrate 1
Formed diffusion layer 2 and oxide film 4 are sequentially formed, and a photoresist 5 is formed on the entire surface of oxide film 4. Next, the photoresist 5 is patterned, and the photoresist 5 above the portion of the P-type diffusion layer 2 where the N-type diffusion layer 3 is to be formed later is formed.
Is partially removed.

Next, by using the photoresist 5 patterned as described above as a mask, an ion beam 6 is irradiated to selectively implant phosphorus ions.
Thereby, the N-type diffusion layer 3 is formed. For the ion implantation, a medium current ion implantation apparatus of an electrostatic scan type was used. The shape of the ion beam spot was circular so as to obtain a uniform current density, and the diameter was adjusted to a size of 10 mm to 20 mm. The diameter of the spot of the ion beam 5 is adjusted by defining the voltage of the beam focusing lens, and the shape of the spot of the ion beam 6 is adjusted while monitoring the beam waveform with an oscilloscope.

According to the method of manufacturing a solid-state imaging device of this embodiment, the diameter of the ion beam spot moving on the scanning line is set to 10 mm to 20 mm, and is set to at least 50 times or more the distance between the scanning lines. Therefore, even if the interval between the scanning lines of the ion beam becomes several hundred microns, while the center of the ion beam spot scans on one scanning line, the ion beam extends over the region of a plurality of other scanning lines. Since the implantation is performed, uniform ion implantation can be performed on the silicon substrate 1. Therefore, uniform ion implantation is also performed on the N-type diffusion layer 3 of the pixel cell located between the ion beam scanning lines. In addition, by making the shape of the ion beam spot circular, the current density in the ion beam spot can be made uniform, so that the ion implantation can be performed more uniformly.

In this embodiment, the N-type diffusion layer 3 formed on the P-type diffusion layer 2 on the silicon substrate 1 has been described as the diffusion region of the pixel portion of the solid-state imaging device. Needless to say, the same applies to the case where 3 is a diffusion region of the transfer section of the solid-state imaging device.

[0019]

As described above, the method for manufacturing a solid-state image pickup device according to the first aspect of the present invention is characterized in that the ion implantation is performed by setting the ion beam spot size at the time of ion implantation to 10 mm to 20 mm. It is possible to make the ion implantation amount of the diffusion layer of the pixel cell uniform over an area wider than the interval between the scanning lines of the beam. Thereby, since the non-uniform ion implantation region by the ion beam scanning using the ion implantation apparatus of the electrostatic scan method can be reduced,
The image characteristics of the solid-state imaging device can be improved.

According to the method of manufacturing a solid-state imaging device according to the second aspect of the present invention, the current density of the ion beam can be made constant by adjusting the shape of the ion beam spot to a uniform circular shape. Therefore, it is possible to further reduce the variation in the amount of ion implantation between the pixel cells generated by the ion beam scanning, and to form a more uniform diffusion layer.

[Brief description of the drawings]

FIG. 1 is a sectional view illustrating a method for manufacturing a solid-state imaging device according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view illustrating a method for manufacturing a conventional solid-state imaging device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Silicon substrate 2 P-type diffusion layer 3 N-type diffusion layer 4 Oxide film 5 Photoresist 6 Phosphorus ion beam

Claims (2)

(57) [Claims] 1. A method for manufacturing a solid-state imaging device in which a diffusion layer is formed by ion implantation, wherein a diameter of an ion beam spot at the time of ion implantation is set to 10 mm to 20 mm. Production method. 2. The method according to claim 1, wherein the ion implantation is performed using a circular ion beam spot having a uniform current density.