JPH04336434A - Manufacture of solid state imaging element - Google Patents

Abstract

PURPOSE:To provide a method of manufacturing a solid state imaging element which can reduce fluctuation in amount of ion implantation by ion beam scanning performed using an ion implantation apparatus of an electrostatic scanning system. CONSTITUTION:A photoresist pattern 5 is formed on a P-type diffused layer 2 and an oxide film 4 on a silicon substrate 1 and an N-type diffused layer 3 is then formed by the ion implantation using such photoresist pattern 5 as a mask. In this case, an ion beam spot is given a diameter ranging from 10mm to 20mm and has a circular shape to attain uniform current density. Ion implantation is performed by scanning ion beam scanning lines with such ion beam.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a solid-state image sensor in which variations in ion implantation are 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 essential to use ion implantation to form diffusion layers in pixel sections and transfer sections of solid-state imaging devices. When forming a diffusion layer of a solid-state imaging device using an ion implantation method, it has become necessary to reduce variations in the amount of ion implantation in order to obtain uniform characteristics of each pixel cell.

[0003] The mainstream of ion implantation equipment used in the manufacture of solid-state image sensing devices is a medium current type, and most of them employ an electrostatic scanning method.

The process of forming a diffusion layer of a conventional solid-state image sensing device will be explained below. FIG. 2 shows a cross-sectional configuration in the process of forming a diffusion layer in a pixel portion of a solid-state image sensor. The solid-state image sensor shown in FIG. 2 is manufactured by the manufacturing method shown below. First, a P-type diffusion layer 2 and an oxide film 4 are sequentially formed on a silicon substrate 1, and then 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 where the N-type diffusion layer 3 will be formed later.
The photoresist 5 above the portion is partially removed.

Next, using the photoresist 5 patterned as described above as a mask, ion beam 6 is irradiated to selectively implant phosphorus ions. As a result, an N-type diffusion layer 3 is formed. In an electrostatic scanning 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 conventional manufacturing method described above, the number of ion beam scanning lines is determined by the electrostatic deflection frequency, so the ion beam is always scanned at intervals of several tens of microns to several hundred microns. It is being done. On the other hand, the shape of the ion beam spot that performs ion implantation while moving on this scanning line varies in size, so if the ion beam spot becomes small, uniform ion implantation will not be performed, and pixel cells will be spread vertically and horizontally over several thousand microns. In a solid-state imaging device in which several hundred pieces are arranged, the amount of ions implanted in the diffusion layer of each pixel cell becomes non-uniform. Further, even if the ion beam spot becomes large, if the current density is non-uniform, uniform ion implantation will not be performed, and the amount of ion implantation in the diffusion layer of each pixel will become non-uniform. In particular, in solid-state imaging devices, variations in the amount of ions implanted into pixels are a major problem because they are largely reflected in image characteristics.

The present invention solves the above-mentioned conventional problems, and aims to provide a method for manufacturing a solid-state imaging device that can reduce variations in the amount of ion implantation in the diffusion layer in each pixel cell of the solid-state imaging device. purpose.

[0008]

[Means for Solving the Problems] In order to achieve the above object, the invention of claim 1 makes the diameter of the ion beam spot larger than the interval between the scanning lines to perform uniform ion implantation over a wide area. It is something to do.

Specifically, the solution taken by the invention of claim 1 is directed to a method of manufacturing a solid-state imaging device in which a diffusion layer is formed by ion implantation, and the diameter of the ion beam spot during ion implantation is 10 mm to 20 mm. The configured configuration will be used.

[0010] Furthermore, according to the second aspect of the invention, ion implantation is performed by adjusting the shape of the ion beam spot so that a uniform current density can be obtained within the ion beam spot.

Specifically, the solution taken by the invention of claim 2 is to add to the structure of the invention of claim 1 a configuration in which ion implantation is performed using a circular ion beam spot having a uniform current density. It is something to do.

0012

[Operation] According to the structure of the invention as claimed in claim 1, since ion implantation is performed with the ion beam spot size set to 10 mm to 20 mm, the diffusion layer of each pixel cell covers an area wider than the interval between the scanning lines of the ion beam. The amount of ion implantation can be made uniform.

Furthermore, according to the configuration of the second aspect of the invention, since the shape of the ion beam spot is circular, the current density within the ion beam spot can be made constant.

[0014]

Embodiments Hereinafter, embodiments of the present invention will be explained based on the drawings.

FIG. 1 shows a step of forming a diffusion layer in a pixel portion of a solid-state image sensor in the method of manufacturing a solid-state image sensor according to this embodiment. The solid-state image sensor shown in FIG. 1 is manufactured by the manufacturing method shown below. First, P is placed on the silicon substrate 1.
A shaped diffusion layer 2 and an oxide film 4 are sequentially formed, and a photoresist 5 is further formed on the entire surface of the oxide film 4. Next, the photoresist 5 is patterned, and the photoresist 5 is formed above the portion of the P-type diffusion layer 2 where the N-type diffusion layer 3 will be formed later.
Partially remove.

Next, phosphorus ions are selectively implanted by irradiating the ion beam 6 using the photoresist 5 patterned as described above as a mask. As a result, an N-type diffusion layer 3 is formed. For ion implantation, an electrostatic scan type medium current ion implanter was used. The shape of the ion beam spot is circular to obtain a uniform current density, and the diameter is 10 mm to 20 mm.
adjusted to the size of. The diameter of the spot of the ion beam 5 is adjusted by specifying 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 for manufacturing a solid-state image pickup 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 be at least 50 times the distance between the scanning lines. Therefore, even if the spacing between the ion beam scanning lines is several hundred microns, while the center of the ion beam spot is scanning on one scanning line, ions will spread over the area of multiple other scanning lines. Since the implantation is performed, uniform ion implantation can be performed onto the silicon substrate 1. Therefore, uniform ion implantation is performed also in the N-type diffusion layer 3 of the pixel cell located between the ion beam scanning lines. Further, by making the shape of the ion beam spot circular, the current density within the ion beam spot can be made uniform, so that ion implantation can be performed more uniformly.

In this embodiment, the N-type diffusion layer 3 formed in the P-type diffusion layer 2 on the silicon substrate 1 has been described as a diffusion region of a pixel portion of a solid-state image sensor. It goes without saying that the same explanation can be given by referring to 3 as the diffusion region of the transfer section of the solid-state image sensor.

[0019]

As explained above, the method for manufacturing a solid-state imaging device according to the invention of claim 1 is such that ion implantation is performed with the ion beam spot size set at 10 mm to 20 mm during ion implantation. The amount of ion implantation into the diffusion layer of the pixel cell can be made uniform over an area wider than the interval between the scanning lines of the beam. This makes it possible to reduce non-uniform ion implantation regions caused by ion beam scanning using an electrostatic scanning ion implantation device, thereby making it possible to improve the image characteristics of the solid-state imaging device.

Furthermore, according to the method for manufacturing a solid-state image sensor according to the second aspect of the invention, the current density of the ion beam can be made constant by adjusting the shape of the ion beam spot into a uniform circle. Therefore, variations in the amount of ion implantation between pixel cells caused by ion beam scanning can be further reduced, and a more uniform diffusion layer can be formed.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view showing a method of manufacturing a solid-state image sensor according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view showing a conventional method for manufacturing a solid-state image sensor.

[Explanation 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)

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