JPS6016460A - Manufacture of semiconductor image pickup device - Google Patents

Abstract

PURPOSE:To obtain the titled device easily manufactured at high yield and low cost by providing a photosensor array composed of SIT. CONSTITUTION:The surface of a high resistant Si substrate 21 at 50OMEGAcm or more is covered with an SiO2 film of about 1mum, an n<+> layer 22 being formed by As diffusion from the back surface, and the film 20 being then removed. An n<+> layer 25 is formed by As ion implantation from the side of the substrate 21, thus compensating the terminal part 23 of the previously formed layer 22 for diffusion sag and impurity concentration and then accurately controlling the thickness b of a channel region 24. Next, after crystal defects are annealed, the region is covered with an SiO2 film 26 about 1mum long, and with the film 26 as a mask a control gate region 26, a p<+> type shielding gate 27, and a p<+> drain 28 are formed by successive diffusion. Thereafter, when wiring is carried out by providing an electrode window, the image pickup element is completed. The n<-> channel layer can be formed with accurate uniformity by the use of the high resistant n<-> substrate and diffusion and ion implantation in such a manner, and then fine working at a high cost in SIT manufacture becomes unnecessitated, resulting in obtaining the titled device consisting of excellent SIT picture element cells at a low cost.

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field of the Invention) The present invention relates to a method for manufacturing a semiconductor imaging device in which one pixel cell is constructed using electrostatic induction transistors as photodetection and switching elements, and a large number of these are arranged. .

(Prior Art and Problems) Semiconductor imaging devices that perform light detection using diodes are known.

In contrast, an electrostatic induction transistor with high photosensitivity is used for photodetection, and an optical signal is multiplied in the gate region, and the current between the teeth and the drain is controlled according to the potential of this gate region to generate a video signal. Semiconductor imaging device that can obtain high signal output by taking out
No. 56, Japanese Patent Application No. 57-157693) has been proposed.

As a method for manufacturing a semiconductor imaging device using the electrostatic induction transistor, the thickness of the high-resistance semiconductor is approximately 2.
A high-quality, high-resistance epitaxial growth process has been introduced to form an extremely flat channel region parallel to the surface (μm ~ 1 (lcrm). In addition, there was a problem in the reproducibility of the high resistance value of the formed layer.Usually, the limit of the resistance value that can be expected from high-quality, high-resistance epitaxial growth is approximately several hundred Ωcm, and the resistance value is 1ooΩCm. In this case, the resistance values of the high resistance regions grown on each substrate vary significantly from one substrate to another.

Therefore, high yields of semiconductor imaging devices cannot be expected;
This is a contributing factor to the high manufacturing cost of semiconductor imaging devices using electrostatic induction transistors.

(Objective of the Invention) An object of the present invention is to provide a method for manufacturing a semiconductor imaging device that is easy to manufacture, has a high yield, and is low in cost, by configuring a photosensor gamma array made of electrostatic induction transistors.

(Structure of the Invention) In order to achieve the above object, a method for manufacturing a semiconductor imaging device according to the present invention provides a method for manufacturing a semiconductor imaging device in which a living electrode region and a different living electrode region of one conductivity type face each other across a channel region formed of a high-resistance semiconductor. and a control gate region of a different conductivity type provided in contact with the channel region in order to control the current flowing between the amphibodielectrode regions. In a method for manufacturing a semiconductor imaging device comprising a plurality of pixel cells arranged in such a manner that one of the pixel cells is accumulated in a control gate region, thereby controlling the current between the two electrodes, the light incident side surface of the semiconductor substrate and a step of diffusing an impurity of the same conductivity type as the semiconductor substrate only from a second surface opposite to the first surface of the semiconductor substrate; a step of implanting ions so that a portion thereof overlaps with a diffusion layer formed by diffusion from the second surface, and a shallow portion thereof is in a substrate where impurities diffused from the second surface are not diffused; and a control gate. The method includes a first diffusion step for forming a region and a shielding gate region, and a second diffusion step for forming a drain region.

(Embodiments of the Invention) The present invention will be described in more detail below with reference to the drawings and the like.

FIG. 1 is a cross-sectional view of a pixel cell of a semiconductor imaging device manufactured by the manufacturing method of the present invention. In the same figure,
2 is an n+ substrate of St, and 2 is a high-resistance n-layer (or an intrinsic semiconductor layer).

One main electrode (drain) 3 is formed from an n+ region with high impurity density. The first gate (control gate) 4 is formed from a p+ region with high impurity density, and the second gate (shielding gate) 5 is also formed from a p+ region with high impurity density.

The control gate electrode 6 is a SnO2 film, 8 is a drain electrode, 9 is 5i0215ii, and 10 is a source electrode.

Referring to FIG. 2, an embodiment of a method for manufacturing the static induction transistor imaging device shown in FIG. 1 will be described.

High resistance semiconductor substrate 21 of approximately 50 Ωc, m or more
(usually thickness is 200 to 500 μm)
A thermally oxidized film (Si02 film) 20 of approximately 100% is formed.

Next, by a step of diffusing arsenic or phosphorus from the back surface of the semiconductor 21, an impurity concentration of n +
A region 22 is formed (FIG. 2a).

After that, the thermal oxide film 20 is removed.

Next, an arsenic or phosphorus ion implantation process is performed from the surface opposite to the surface on which the diffusion process has been performed to form a lag region 25 having an impurity concentration of 1018 cm-3 or more (FIG. 2b).

From this, diffusion sagging and impurity concentration compensation of the termination portion 23 of the region 22 formed earlier, as well as channel region 2
4. Accurately control the thickness β.

Next, after annealing the crystal defects in the ion-implanted region, a thermal oxide film (Si02 film) is formed to a thickness of approximately 1 μm using a thermal oxidation method.
A field oxide film 26 having a thickness of about m is formed (FIG. 2C).

Next, by masking this field oxide film 26, a first diffusion process is performed to form a control gate region and a shielding region, and then a second diffusion process is performed to form a drain region. Figure 2 d).

In the figure, 21 is a StO high resistance n-substrate, 24 is a channel region, 26 is a control gate, 27 is a shielding gate, and 28 is a drain.

Thereafter, contact windows and electrode wiring are provided to complete the semiconductor image sensor (not shown).

Note that an ion implantation process may be used instead of the above-mentioned diffusion process from the back side, but considering the thickness of the semiconductor substrate, an ion implantation device with considerably high energy is required, and crystal defects and It has disadvantages such as increased manufacturing cost.

Further, the thickness β of the channel region 24 made of a single high-resistance n layer is approximately 2 μm to 10 μm.

(Effects of the Invention) As explained above, according to the present invention, in the method of manufacturing a semiconductor imaging device in which each pixel cell is composed of a static induction transistor consisting of a drain or source region, a control gate, and a shielding gate, resistance n
-By using a substrate and using a diffusion process and an ion implantation process, high quality, which was previously difficult to control and expensive,
A channel region made of a single high-resistance n layer, which was formed by a high-resistance epitaxial growth process, can be formed accurately and uniformly.

Furthermore, since a high resistance n-substrate is used, a high resistance value of approximately 10
One with a diameter of about 0 cm can be obtained.

This eliminates the need for sophisticated and expensive microfabrication processes in the manufacture of static induction transistors, resulting in significant benefits in terms of manufacturing yield and manufacturing costs.

Therefore, according to the method of the present invention, a semiconductor imaging device comprising an excellent electrostatic induction transistor pixel cell can be manufactured at high yield and at low cost.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view of a conventional pixel cell. FIGS. 2(a), 2(b), 2(c) and 2(d) are cross-sectional views showing the manufacturing process of an embodiment of the method of the present invention. 1... St n+ substrate 2... n''' consisting of a high resistance epitaxial growth process
Layer 3...Drain 4...Control cable +-5.
... Shielding gate 6 ... Control electrode 21 ... Si high resistance n-substrate 24 ... Channel region 26 ... Control gate 27 ... Shielding gate 28 ... Drain Patent applicant Hamamatsu Photonics Co., Ltd. Agent Patent Attorney Jusai 1, 2 (0) (b)

Claims (1)

[Claims] A main electrode region and a main electrode region of one conductivity type, which face each other via a channel region formed from a high-resistance semiconductor, are provided in contact with the channel region in order to control the current flowing between the two bidirectional electrode regions. The transistor is formed such that one of the electron-hole pairs generated by photoexcitation is accumulated in the control gate region, thereby controlling the current between the two electrodes. In a method of manufacturing a semiconductor imaging device in which a plurality of pixel cells are arranged, a first surface of a semiconductor substrate that is a light incident side surface and a second surface of the semiconductor substrate that is opposite to the light incident side surface of the semiconductor substrate.
a step of diffusing an impurity of the same conductivity type as the semiconductor substrate only from the first surface, and then diffusing an impurity of the same conductivity type as the semiconductor substrate from the first surface, the deeper part of which is more diffused than the second surface. a first step for forming a control gate region and a shielding gate region; 1. A method of manufacturing a semiconductor imaging device comprising a diffusion step and a second diffusion step for forming a drain region.