JPH04234172A - Solid-state image sensing element for x-ray - Google Patents

Abstract

PURPOSE:To enable an X-ray solid-state image sensing element improved in sensitivity to be offered when a conventional CCD solid-state image sensing element is used. CONSTITUTION:A photodiode 4 of a photodetective section is composed of a second conductivity type signal charge storage region 2 formed on a first conductivity type semiconductor substrate 1 and a first conductivity type diffusion region which forms a stripe-like joint surface 3a in the second conductivity type signal charge storage region 2, whereby holes and electrons generated through incident X-ray are enhanced in quantity to enable a solid-state image sensing element of this design to be improved in sensitivity.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an X-ray solid-state imaging device, and more particularly to an X-ray solid-state imaging device with improved sensitivity.

0002

2. Description of the Related Art Conventionally, X-only cameras using X-ray film have been mainly used. In addition, as an example of a conventional solid-state imaging device for X-rays, for example, Japanese Patent Laid-Open No. 1-16199
As described in Japanese Patent No. 76, it is known that an X-ray image is converted into an optical image by an image intensifier, and this optical image is captured by a CCD solid-state image sensor and displayed on a monitor.

0003

[Problems to be Solved by the Invention] However, an X-ray camera using an X-ray film is not suitable for emergency situations, and an X-ray image is converted into an optical image by an image intensifier. However, it has the disadvantage that it is more expensive than a so-called normal CCD solid-state image sensor.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide an X-ray solid-state image pickup device that improves sensitivity when a normal CCD solid-state image pickup device is used.

[0005]

[Means for Solving the Problems] In order to achieve the above object, the X-ray solid-state imaging device of the present invention includes a signal charge storage region 2 of a second conductivity type formed on a semiconductor substrate 1 of a first conductivity type.
and a first conductivity type diffusion region forming a vertically elongated junction surface 3a within the second conductivity type signal charge storage region 2, forming a photodiode 4 as a light receiving section.

[0006]

[Operation] In the solid-state imaging device for X-rays according to the present invention, since the photodiode in the light receiving section has a vertically long junction surface, the amount of holes and electrons generated in response to the incident X-rays increases, and the output signal level is increased. The sensitivity is improved accordingly.

[0007]

Embodiments Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIGS. 1A to 1C each show a cross-sectional view of an X-ray solid-state imaging device showing an embodiment of the present invention. That is, in this example, the P-type silicon substrate 1 is
An N-type signal charge accumulation region 2 as shown in FIG.
Relatively deep, more than a micron (previously 0.3 micron)
A groove 3 is formed, and this groove 3 is filled with P-type highly doped polysilicon 8 as shown in FIG. 1C. In this case, the P-type is diffused into the signal charge storage region 2 on the outer periphery of the high-topped polysilicon 8 filled in the groove 3, a junction surface 3a is formed in this portion, and a photodiode of the light receiving section 4 is formed. In addition,
A P-type region is formed in a part of the signal charge storage region 2, and a transfer gate 5 is provided on this P-type region. Furthermore, an N-type channel region, for example, is formed on the side surface of the P-type region and on the front surface side, and a vertical transfer electrode 6a is formed on this channel region. In this case, if the junction surface 3a of the photodiode of the light receiving section 4 is set to 10 microns or more in the depth direction, the amount of holes and electrons generated for X-rays will increase as the depth of this junction surface increases, as shown in FIG. As the output signal level increases, the output signal level of the light receiving section 4 increases,
Sensitivity to X-rays is improved.

FIG. 2 shows a plan view of an IT (interline) type X-ray solid-state imaging device using a CCD. In FIG. A predetermined number of photodiodes 4 are arranged in a matrix, and a transfer gate electrode 5 and a vertical resistor 6 are arranged along the vertical arrangement of the photodiodes 4.
The signal charge of the photodiode 4 is read out to the vertical register 6 via the transfer gate electrode 5, and the signal charge of this vertical register 6 is read out to the FD via the horizontal register 7.
(floating diffusion) and supplied to an amplifier (not shown). Then, after discharging the signal charges of the vertical register 6 to, for example, the semiconductor substrate 1, the signal charges received by the photodiode 4 for a predetermined period of time are read out to the vertical register 6 via the transfer gate electrode 5, and the signal charges of the vertical register 6 are read out. Detected via horizontal register 7. Note that the present invention is not limited to the above embodiments, and is applicable to IT
The present invention is not limited to the (interline) type, and can be applied to, for example, an FT (frame transfer) type X-ray solid-state imaging device.

[0009]

As explained above, in the solid-state imaging device for X-rays according to the present invention, the signal charge accumulation region of the second conductivity type formed on the semiconductor substrate of the first conductivity type;
The photodiode of the light receiving section is formed by the diffusion region of the first conductivity type forming a vertically elongated junction surface in the signal charge accumulation region of the conductivity type, so that the photodiode of the light receiving section has a longitudinally elongated junction surface, and the photodiode of the light receiving section has a longitudinally elongated junction surface. As a result, the amount of holes and electrons generated in response to incident X-rays increases, the output signal level can be increased, and the sensitivity is improved accordingly.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of an X-ray solid-state imaging device showing an embodiment of the present invention.

FIG. 2 is a plan view of an X-ray solid-state imaging device to which the present invention is applied in an IT (interline) system.

FIG. 3 is an explanatory diagram showing the depth versus the number of electrons and holes used to explain the present invention.

[Explanation of symbols]

1 Semiconductor substrate 2 Signal charge accumulation region 3 groove 3a　Joint surface 4 Light receiving section 5 Transfer gate electrode 6 Vertical register 7 Horizontal register 8 Highly doped polysilicon

Claims (1)

[Claims] 1. A signal charge storage region of a second conductivity type formed on a semiconductor substrate of a first conductivity type, and the first conductive conductor forming a vertically elongated bonding surface within the signal charge storage region of the second conductivity type. 1. A solid-state imaging device for X-rays, characterized in that a photodiode of a light receiving section is formed by a diffusion region of a mold.