JPS6066857A - Manufacture of solid-state image pickup element - Google Patents

Abstract

PURPOSE:To obtain the titled element of a vertical type overflow drain structure without fixed pattern noises during operation and the generation of white damages by a method wherein an N type epitaxial layer of nearly the same specific resistance as that of the following substrate is grown on an N type pull-up single crystal substrate treated by intrinsic gettering, where a P type well region is provided. CONSTITUTION:The N type pull-up single crystal substrate 31 having the specific resistance of 1-several 10OMEGAcm is heat-treated in the atmosphere of a rare gas at a temperature of over 1,050 deg.C for 10hr or more. First, oxygen is diffused outward from the surface, and next cores of defects 36 are generated in the inside of the substrate 31 by heat treatment at 600-800 deg.C in the atmosphere of a rare gas or oxygen for 10-several 10hr. Thereafter, cores of defects 36 are grown by medium temperature heat treatment at 1,000 deg.C in the atmosphere of a rare gas or oxygen, and non-defect regions 37 are formed on both of the back and front surfaces of the substrate 31. Then, oxide films produced by these heat treatments are removed, and an N type layer 35 is epitaxially grown on the surface of the substrate 31, where a P type well region 32 is then formed by ion implantation and the succeeding drive-in treatment into an active region.

Description

[Detailed description of the invention] gff The present invention relates to a method of manufacturing an image sensor.

i+7-Problems with the previous configuration Vertical overflow drain (hereinafter referred to as 1" V-OFD) structure solid-state image sensor 1-J: Solid-state image sensor 1-i, anti-blooming, which is a remaining problem In terms of suppression ability, the 11-groove structure is becoming the standard for solid-state imaging collectors because it is effective in reducing smear and is suitable for miniaturization or high density.

With reference to the drawings below, the conventional V-OF D477
The 7-Series solid-state image sensor will be explained. Figure 1 υ: J2
1 is a schematic cross-sectional view of a conventional V-OFD structure solid-state imaging device. In the figure, 1 is an N-type Si substrate which is the starting material 1, 2 is a P-type well which is the active region of the solid-state sensor 5 formed by ion implantation and drive-in into the N-type Si substrate 1, and v( d N J<+2 S L substrate 1 k (2 positive voltages applied. The above structure;:'Htt2'',・
Therefore, the blooming suppression operation of the V-OF D structure solid-state imaging device is performed by applying V to the N-type Si substrate 1. A schematic diagram of the light receiving section l: at that time is shown in FIG. d is the photo-coated N1 diffusion layer, e is the P-type well portion. , q k−J,
Represents a potential profile. As is clear from the figure, N7! i1. ! 81 Due to the difference in resistivity of substrate 1, 1
: The height of the peak P of the potential in the figure differs depending on the impurity concentration profile of the P-type well. V
-, In the OFD solid-state image sensor, the height of the peak P is directly related to the ability to suppress blooming.

) When 11P is low, the ability to suppress blooming increases.

In addition, there is no variation in the height of IIIP, and there is also variation in blooming suppression ability. Generally, it is known that the Si substrate manufacturing method using the CZ method has a concentric periodic variation of 10 to 15% within the same substrate. Since the ion implantation is performed with less in-plane variation than the P-type well formation Q, the impurity concentration profile of the P-type well has variations in formation corresponding to the substrate resistivity.

As a result, when the V-OFD is operated, the substrate resistivity
The concentric fixed pattern noise that corresponds to the sound is very noticeable. Due to this, the current situation is that the V-OFD structure solid-state image sensor-r is not able to fully utilize its inherent ability to suppress blooming. Due to the high-temperature heat treatment during the formation of the P-type well, the oxygen contained in the CZ Si plate diffuses near the surface, causing defects. This is one of the causes of white scratches, which are image defects in solid-state imaging devices3.
Therefore, the performance of the V-OFD structure solid-state image sensor can be sufficiently improved by C.
(I was really looking forward to the elements that could be drawn out.

OBJECTS OF THE INVENTION The present invention prevents the occurrence of white flaws by preventing the occurrence of "national pattern inspection" during OFD operation with a V OFD 4G; The present invention provides a method for manufacturing a solid-state image sensor that also aims to prevent the above problems.

Structure of the Invention In order to achieve this object, the method for manufacturing a solid-state image sensor of the present invention uses an intrinsic getter (hereinafter referred to as IG).
The processed CZN type base substrate is constructed by forming an epitaxial layer having a resistivity comparable to that of the above substrate, and forming a P-type well within the epitaxial layer.

DESCRIPTION OF EMBODIMENTS An embodiment of the present invention will be described below with reference to its four aspects. FIG. 3 shows a schematic cross-sectional view formed by a method for manufacturing a semiconductor device according to an embodiment of the present invention. In the figure, 31 is a starting 4A substrate, 35 is an N-type epitaxial layer formed on the N-type substrate 31, 3AJ, 1N-type epitaxial layer 35'' is ion implanted into the second layer, and J is formed in the drive-in layer. Shida solid-state imaging device, P-type well serving as the active region of R, 36 and N-type substrate 31
37 is a defect-free region formed by the heat treatment described above.

Next, a method for manufacturing a solid-state image sensor according to the present invention will be explained.

J, Z ratio (1 (N-type Si with resistance of 1 to several 10Ωcm)), high n1□ of 1060°C or higher in the first step
t, in a flower gas atmosphere for 1 to several tens of hours, in the second step, e o o "C, in a low-temperature rare gas or acid wood atmosphere at ~800 ° C. for 1 to several tens of hours, in the third step, Heat treatment is performed for several hours at a medium temperature of 1000° C. in a rare gas 4 humid oxygen atmosphere. The third step is performed to allow the defects 36 formed in the second step to grow as nuclei.Next, after removing the oxide film formed by the above steps, the substrate is removed. Form an epitaxial layer with the same resistivity as 31,
Next, a P-type well 32, which is an active region of the solid-state imaging device, is formed by ion implantation and drive-in.

According to this embodiment, since a GZN type substrate having the same resistivity as the epitaxial layer 11+'+: which satisfies the characteristics required for a peripheral image sensor is used, the following advantages occur. First, since there is no autodoping during epitaxial growth, the resistivity of the epitaxial layer can be easily controlled without any special treatment. Second n/n”
- There is no need to take into account the reduction in the effective epitaxial layer width that occurs during the epitaxial wafer due to the diffusion of high concentration substrate impurities into the epitaxial layer due to heat treatment during the manufacturing process.

Therefore, the epitaxial layer? i9: <Since it is possible to shorten the heat treatment time during shrimp growth, it is possible to reduce the heat treatment time during shrimp growth.
:4 induced defects can be suppressed, and it is also advantageous in terms of cost. Thirdly, the heat treatment of the first, second, and 303rd steps described above is carried out in order to prevent defects caused by the high 7114 treatment necessary for P-type well formation J11, the so-called rG treatment. It has been experimentally confirmed that when a substrate with a high concentration of N-type impurities is used in the process, it is difficult to form defects inside the substrate. However, the specific resistance according to the present invention (1 to several 10Ω
By using a substrate of (on), internal defects can be reliably formed, and oxygen inside the substrate caused by drive-in during later P-type well formation will spread to the surface and generate near the surface of the F&L layer. It has been experimentally confirmed that defects can be reliably prevented. The resistivity of the fourth V epitaxial layer and the substrate are the same, and there is no potential gradient in the depth direction of the substrate. As a result, pseudo-magnetic mold generated inside the substrate will not be mixed into the active layer due to the potential difference. Note that the method of the present invention can naturally be applied to VC when an N-type well is formed on a P-type substrate.

1 for practical use” The specific resistance of one substrate and epitaxial layer is 111.
11mm 1''?-ze is not a problem in the range of 1m to several tens of Ωm.

Effects of the Invention As described above, according to the method of manufacturing a solid-state imaging collector of the present invention, by performing the so-called IG treatment, defects can be generated inside the substrate and oxygen can be bound to the defects.

As a result, the surface diffused oxygen concentration by the -, H"':f!+A treatment can be reduced to 1.- below the defect generation critical value.

This can prevent the occurrence of surface defects that cause white scratches on solid-state imaging devices. By forming a P-type well in the epitaxial layer, the substrate ratio 4')'C distribution unevenness Vζ causes a fixed pattern during vertical overflow drain operation.

Vertical overflow can be prevented.
The performance of the solid-state image sensor can be maximized.

[Brief explanation of the drawing]

Figure 1 is a schematic cross-sectional view of a solid-state imaging device with a vertical overflow drain structure, Figure 2 is a schematic cross-sectional view of a solid-state imaging device with a vertical overflow drain structure, Figure 2 is a potential profile of the P-type well under the photodiode during V-OFD operation, and Figure 3
The figure is manufactured by JVCJ knee) 7° solid-state imaging, +
, is a schematic cross-sectional view of the child. 31... N-type silicon substrate, 32... P-type Tsuenope 35... N-type Evita Gisharno 1〈. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
figure

Claims (1)

[Claims] CZ method: A step of heat treating a conductivity type substrate with a specific resistance of 1 to several tens of Ωcm at a temperature of 1060°C or higher in a rare gas atmosphere for 1 hour or more, and a process of 600°C to SOO°0 of 11
A process of heat treatment for 10 hours or more in a box gas or oxygen atmosphere at a temperature of 1000℃, a process of heat treatment in a rare gas or oxygen atmosphere at a temperature of 1000℃, and l'l! Step of removing the oxide film on the surface of the I ite substrate, and 1) No. 11 substrate-1-
(j) forming an evitagital layer with a resistivity comparable to that of the substrate;
'To form a well of type l! 1. Solid-state imaging with characteristics 2. Manufacturing method.