CN103928485B

CN103928485B - A kind of radioscopic image sensor of high output amplitude

Info

Publication number: CN103928485B
Application number: CN201410192257.1A
Authority: CN
Inventors: 孟丽娅; 王庆祥; 袁祥辉
Original assignee: Chongqing University
Current assignee: Chongqing University
Priority date: 2014-05-08
Filing date: 2014-05-08
Publication date: 2016-05-11
Anticipated expiration: 2034-05-08
Also published as: CN103928485A

Abstract

The radioscopic image sensor that the invention provides a kind of high output amplitude, comprises sequential control circuit, pixel unit circuit, sampling hold circuit and output buffer, and in described imageing sensor, the charge-trapping of pixel circuit unit unites two into one with reset switch pipe. Reset switch pipe adopts PMOS transistor arrangement, and the PMOS transistor of making on P type substrate is produced in N trap, and charge-trapping unit is and utilizes the diode (N trap/P substrate diode) forming between this N trap and P type substrate. In the improved pixel circuit of the present invention, change the reset transistor in pixel structure into PMOS transistor by common nmos pass transistor, PMOS reset transistor is structured in the N well structure that forms charge-trapping diode. PMOS transistor has played collection trap and two kinds of functions of reset transistor simultaneously like this, having avoided introducing unnecessary N trap affects the effect to radiation charge-trapping on the one hand, make the cathode voltage of charge-trapping unit can better reset to supply voltage because reset transistor changes PMOS transistor into by nmos pass transistor on the other hand, thereby improve signal voltage output amplitude.

Description

A kind of radioscopic image sensor of high output amplitude

Technical field:

The present invention relates to radiant image, high energy particle Detection Techniques field, be specifically related to a kind of radioscopic image sensor of high output amplitude.

Background technology:

In prior art, cmos image sensor mainly comprises sequential control circuit, pixel unit circuit, sampling hold circuit and output buffer, shown in Figure 1. Wherein pixel unit circuit is the elementary cell for detecting x-ray, and the quality of its output signal directly determines the final performance of imageing sensor.

And in existing radioscopic image sensor, the pixel circuit of the cmos image sensor of direct detection X ray generally adopts the mode that builds N trap on P type silicon substrate to form N trap/P substrate diode, for collecting the electric charge of radiation excitation; Because the transistorized making of PMOS also needs N trap, for avoiding affecting due to the unnecessary N trap that PMOS transistor is introduced the collection of the electric charge that pixel excites radiation, generally in the pixel circuit of X-radiation imaging CMOS active picture element image sensor, all select nmos pass transistor, be that MOS transistors all in pixel is NMOS pipe, collecting meta structure is N trap/P substrate diode, as shown in Figure 2. Reset owing to can only adopting nmos pass transistor to build in pixel, source is with structures such as, gatings, the existence of transistor threshold voltage can make amplitude output signal constantly reduce, the dynamic range of final institute picked up signal is little, and signal to noise ratio is little, is unfavorable for the imaging in signal later stage. Obviously,, although use nmos pass transistor structure pixel circuit to avoid the introducing of other N trap outside radiation electric charge collection trap, but greatly limited the amplitude of pixel output signal.

Summary of the invention:

For prior art above shortcomings, the object of the present invention is to provide a kind of output signal wide dynamic range, be conducive to the radioscopic image sensor of the high output amplitude of later stage imaging.

Realize above-mentioned purpose, the present invention adopts following technical scheme: a kind of radioscopic image sensor of high output amplitude, comprise sequential control circuit, M × N position pixel circuit, N position sampling hold circuit and output buffer, it is characterized in that, M × N position pixel circuit and N position sampling hold circuit and output buffer be common composition CMOS active picture element image sensor under the control of sequence circuit; The collection unit of described pixel circuit unites two into one with reset transistor, adopts PMOS transistor arrangement.

Further, described pixel circuit is made up of PMOS reset transistor, source tube, line EAC and radiation charge-trapping unit; PMOS reset transistor connects NMOS source tube, and the voltage of source tube output is exported by line EAC;

Described radiation charge-trapping unit be the N well structure that builds on P type substrate to form N trap/P substrate diode, as injecting formation source electrode and drain electrode by P+ in the N trap of charge-trapping unit, in this N well structure, be made into PMOS transistor; By transistorized PMOS substrate be N trap for charge-trapping, control the transistorized grid of this PMOS and to realize, the integration of charge-trapping unit resetted.

Compared to existing technology, the present invention has following beneficial effect:

The present invention, by by building PMOS reset transistor as collecting first N trap, unites two into one reset transistor with collecting meta structure, can not affect the collection of radiation electric charge, can increase substantially the amplitude of output signal simultaneously. In three pipe pixel structures of employing 5V--0.5um technique,, the output voltage of the pixel of this structure is promoted to 3.32V by the 2.04V of conventional structure, improves approximately 65%, and the amplitude of output signal is significantly improved, and dynamic range expands, and signal to noise ratio improves.

In invention, the improvement of pixel circuit is increased substantially the output voltage amplitude of pixel signal, made the performance of imageing sensor have significantly lifting.

Brief description of the drawings:

Fig. 1 is the circuit block diagram of X ray active picture element image sensor.

Fig. 2 is the schematic diagram of pixel circuit in X ray active picture element image sensor.

Fig. 3 is the schematic diagram of X ray active picture element image sensor pixel circuit of the present invention.

Detailed description of the invention:

Be illustrated in figure 1 exemplary x-ray imageing sensor, comprise sequential control circuit, M × N position pixel circuit, N position sampling hold circuit and output buffer, pixel circuit and sampling hold circuit and output buffer be common composition CMOS active picture element image sensor under the control of sequence circuit. The present invention improves mainly for the pixel circuit of radioscopic image sensor, and as shown in Figure 3, it is collected unit and unites two into one with multiple tube, adopts PMOS transistor arrangement.

As shown in Figure 3, described pixel circuit is made up of PMOS reset transistor, source tube, line EAC and radiation charge-trapping unit; PMOS reset transistor connects NMOS source tube, and the voltage of source tube output is exported by line EAC; Described radiation charge-trapping unit is the N trap/P substrate diode on P type substrate, as injecting formation source electrode and drain electrode by P+ in the N trap of charge-trapping unit, in this N trap, is made into PMOS transistor; By transistorized PMOS substrate be N trap for charge-trapping, control its grid and to realize, the integration of pixel circuit resetted. The radiation charge-trapping unit that in the present invention, pixel circuit adopts is the N trap/P substrate diode on P type substrate, and the transistorized making of PMOS need to build N trap equally on P type substrate, just played the function of charge-trapping unit with reset mos transistor by build PMOS transistor on P type substrate simultaneously, wherein thereby PMOS transistor itself replaces original NMOS reset transistor raising output voltage as reset transistor, thereby the transistorized N well structure of PMOS is realized charge-trapping as radiation electric charge collection trap on the other hand. This makes radiation electric charge collection trap that PMOS transistor plays simultaneously and the effect of reset transistor. Invention has increased substantially the output voltage amplitude of pixel signal to the improvement of pixel circuit, can make the performance of imageing sensor have significantly lifting.

Claims

1. the radioscopic image sensor of a high output amplitude, comprise sequential control circuit, M × N position pixel circuit, N position sampling hold circuit and output buffer, it is characterized in that, M × N position pixel circuit and N position sampling hold circuit and output buffer be common composition CMOS active picture element image sensor under the control of sequence circuit; The collection unit of described pixel circuit unites two into one with reset transistor, adopts PMOS transistor arrangement;

Described pixel circuit is made up of PMOS reset transistor, source tube, line EAC and radiation charge-trapping unit; PMOS reset transistor connects NMOS source tube, and the voltage of source tube output is exported by line EAC;

Described radiation charge-trapping unit is the N well structure building on P type substrate, as injecting formation source electrode and drain electrode by P+ in the N trap of charge-trapping unit, in this N well structure, makes PMOS transistor; By transistorized PMOS substrate be N trap for charge-trapping, control the transistorized grid of this PMOS and to realize, the integration of charge-trapping unit resetted.