CN110335882B - Pixel structure capable of improving frame transfer CCD (Charge coupled device) responsivity - Google Patents
Pixel structure capable of improving frame transfer CCD (Charge coupled device) responsivity Download PDFInfo
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- 238000002513 implantation Methods 0.000 claims description 6
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- 239000000243 solution Substances 0.000 description 3
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 2
- 238000013461 design Methods 0.000 description 2
- 230000005684 electric field Effects 0.000 description 2
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- H01L27/14—Devices consisting of a plurality of semiconductor or other solid-state components formed in or on a common substrate including semiconductor components sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation
- H01L27/144—Devices controlled by radiation
- H01L27/146—Imager structures
- H01L27/148—Charge coupled imagers
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- H04N25/00—Circuitry of solid-state image sensors [SSIS]; Control thereof
- H04N25/70—SSIS architectures; Circuits associated therewith
- H04N25/71—Charge-coupled device [CCD] sensors; Charge-transfer registers specially adapted for CCD sensors
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Abstract
The invention belongs to the field of photoelectric detection and imaging, and particularly relates to a pixel structure capable of improving frame transfer CCD (charge coupled device) responsivity; the device comprises a substrate, a plurality of parallel vertical transfer electrodes, a CCD (charge coupled device) buried channel region, a protection ring and a channel resistor; a p-type signal amplification region and an n-type signal amplification region are sequentially arranged between the substrate and the CCD buried channel region; the upper part of the CCD buried channel region is connected with a vertical transfer electrode, and one side of each vertical transfer electrode is connected with a signal amplification control electrode through a dielectric layer; and respectively arranging a protection ring and a trench resistor from the left side and the right side of the top of the substrate to the CCD buried channel region. The invention can change the photosensitive responsivity of the CCD pixel in real time by changing the injection concentration of the signal amplification structure and the applied voltage thereof, thereby enabling the CCD to more flexibly select the signal amplification capability when facing different incident light intensities and improving the imaging detection adaptability of the CCD to different light intensity environments.
Description
Technical Field
The invention belongs to the field of photoelectric detection and imaging, and particularly relates to a pixel structure capable of improving frame transfer CCD (charge coupled device) responsivity.
Background
A CCD, which is a charge coupled device operating in a Frame Transfer (FT) mode, is the most simple in structure and easy to manufacture. Frame transfer CCDs have been considered a very good CCD structure since a year, and although twice as large as its photosensitive area, have many improvements in performance over photoelectric pickup tubes.
At present, the main means for improving the responsivity of the frame transfer CCD is to reduce the noise of the device and improve the quantum efficiency of the device. In terms of noise reduction, the existing noise level of the CCD is reduced to be within 5 electrons at the lowest under the condition of specific operating frequency and operating temperature, and the noise level is basically limited. In the aspect of improving the quantum efficiency, the quantum efficiency of the back-illuminated frame transfer CCD reaches over 90 percent at most and also basically reaches the theoretical limit.
Therefore, the existing device structure and technology has reached the response sensitivity limit of the frame transfer CCD, and if the responsivity of the device is further improved, a new technology or/and device structure must be adopted.
Disclosure of Invention
Based on the problems in the prior art, the invention provides a method for improving the responsivity of a frame transfer CCD, which is mainly realized by improving the photosensitivity of a CCD pixel. A structure for enhancing the photosensitive sensitivity is designed in the pixel, so that the photosensitive capability of the CCD pixel is improved, and the responsiveness of the CCD is further improved.
The invention relates to a pixel structure capable of improving frame transfer CCD (charge coupled device) responsivity, which comprises a substrate, a plurality of parallel vertical transfer electrodes, a CCD (charge coupled device) buried channel region, a protection ring and a channel resistor, wherein the substrate is provided with a plurality of parallel vertical transfer electrodes; a p-type signal amplification region and an n-type signal amplification region are sequentially arranged between the substrate and the CCD buried channel region; the upper part of the CCD buried channel region is connected with a vertical transfer electrode, and one side of each vertical transfer electrode is connected with a signal amplification control electrode through a dielectric layer; respectively arranging a protection ring and a channel resistor from the left side and the right side of the top of the substrate to the CCD buried channel region; one of p-type and n-type is p-type and the other is n-type.
Furthermore, the substrate is a p-type substrate, the guard ring is doped in an n-type mode, and the channel resistor is doped in a p-type mode.
Preferably, the p-type signal amplification region has an implantation concentration of 0.8 × 1012/cm2～1.2×1012/cm2(ii) a The implantation concentration of the n-type amplification region is 0.8 × 1015/cm2～1.2×1015/cm2。
Further, a pn junction diode is formed in the p-type signal amplification region and the n-type signal amplification region, when a positive voltage less than or equal to a threshold voltage is applied to the signal amplification control electrode, the pn junction diode is in a reverse bias state, and signal electrons are collected to the CCD buried channel region below the vertical transfer electrode; when a positive voltage larger than a threshold voltage is applied to the signal amplification control electrode, the pn junction diode is broken down, and the number of signal electrons collected in a CCD (charge coupled device) buried channel region below the vertical transfer electrode is multiplied; when the positive voltage applied to the signal amplification control electrode is turned off, the amplified signal electrons are sequentially transferred by applying a CCD transfer clock pulse to the vertical transfer electrode.
Wherein, the threshold voltage can be determined by adjusting the injection concentration of the p-type signal amplification region, the higher the injection concentration is, the lower the threshold voltage (breakdown voltage) is, and vice versa.
Preferably, the high voltage required for the vertical transfer electrode is 5V to 10V, and the low voltage is-5V to 0V.
The invention has the beneficial effects that:
the image element of the frame transfer CCD is internally provided with a photosensitive sensitivity enhancing structure, and the photosensitive sensitivity enhancing structure is mainly characterized in that a signal amplifying region and a control electrode are designed at corresponding positions of a buried channel and a substrate of the CCD image element and are controlled by an external voltage, so that the amplification of an incident light signal can be realized, and the photosensitive responsivity of the CCD image element is greatly improved. The photosensitive responsivity of the CCD pixel can be changed by changing the injection concentration of the signal amplification structure and the voltage applied by the signal amplification structure. The larger the implantation concentration is, the stronger the signal amplification capability (i.e. the higher the photoresponse of the device) is obtained when the same voltage is applied, and the higher the applied voltage is, the stronger the signal amplification capability is under the same implantation concentration condition. Therefore, when the CCD imaging detection device is used, different voltages can be applied to enable the CCD to flexibly select the signal amplification capacity when facing different incident light intensities, and the imaging detection adaptability of the CCD to environments with different light intensities is improved. Through tests, the light sensitivity responsivity of the CCD is improved by more than 10 times compared with that of the traditional frame transfer CCD through reasonable structure and voltage design. In addition, the pixel structure in the invention can directly amplify the signal charge generated by the CCD, and under the technical situation that the quantum efficiency reaches the limit, the responsivity of the device can be further improved, thereby providing a new technical scheme for the development of the high-responsivity CCD.
Drawings
FIG. 1 is a top view of a pixel structure of the present invention that improves frame transfer CCD responsivity;
FIG. 2 is a cut-away view of a pixel structure of the present invention for improving the responsivity of a frame transfer CCD;
FIG. 3 is a perspective view of a pixel structure of the present invention for improving the responsivity of a frame transfer CCD;
in the figure, 1,2,3 and 4 vertical transfer electrodes, 5, a signal amplification control electrode, 6, a guard ring, 7, a channel resistor, 8, a dielectric layer, 9, a CCD buried channel, 10, an n-type signal amplification region, 11, a p-type signal amplification region, 12 and a substrate.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more clearly and completely apparent, the technical solutions in the embodiments of the present invention are described below with reference to the accompanying drawings, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments.
The invention designs a signal amplification area and a control electrode structure in the frame transfer CCD pixel, can amplify the incident light signal in the CCD pixel, and the signal amplification capability can be controlled by changing the voltage of the control electrode, thereby realizing the real-time control of the signal amplification capability and further realizing the real-time promotion of the CCD responsivity.
A pixel structure capable of improving the responsivity of a frame transfer CCD is shown in figures 1-3:
the pixel structure comprises a substrate 12, a plurality of parallel vertical transfer electrodes 1,2,3 and 4, a CCD (charge coupled device) buried channel region 9, a protection ring 6 and a channel resistor 7; a p-type signal amplification region 11 and an n-type signal amplification region 10 are sequentially arranged between the substrate 12 and the CCD buried channel region 9; vertical transfer electrodes 1,2,3 and 4 are connected above the CCD buried channel region 9, and one side of each vertical transfer electrode is connected with a signal amplification control electrode 5 through a dielectric layer 8; guard ring 6 and trench resistor 7 are provided from both left and right sides of the top of substrate 12 up to CCD buried channel region 9, respectively.
It is understood that four parallel vertical transfer electrodes are provided in the present invention, but the present invention is not limited to 4, and may be 3, 5, 6, and so on.
The working principle of the CCD pixel structure in this embodiment may be as follows:
the frame transfer CCD of this embodiment structurally adds an n-type signal amplification region 10, a p-type signal amplification region 11, and a signal amplification control electrode 5, as compared with a conventional frame transfer CCD pixel.
During the light integration period, incident photons of the CCD pixel enter the pixel, are absorbed and then are converted into electron-hole pairs, the holes are guided away through the substrate, and the rest electrons are signal electrons. By applying high and low voltages to the vertical transfer electrodes 1,2,3,4, signal electrons can be collected in the pixel.
In this embodiment, a high voltage (typically, a voltage in the range of 5V to 10V) is applied to the vertical transfer electrode 2, and a low voltage (typically, a voltage in the range of-5V to 0V) is applied to the electrodes 1, 3, and 4. The signal electrons will be collected to the CCD buried channel region 9 below the vertical transfer electrode 2.
The n-type signal amplification region 10 and the p-type signal amplification region 11 form a pn junction diode, when a positive voltage is applied to the signal amplification control electrode 5, the pn junction diode is in a reverse bias state, if the positive voltage applied to the signal amplification control electrode 5 is large enough, the pn junction diode can be broken down, a high electric field is generated in a CCD pixel, and the high electric field can multiply the number of signal electrons which are collected in the CCD buried channel region 9 below the vertical transfer electrode 2, so that the effect of improving the responsivity of the device is achieved.
After the amplification of the signal electrons is achieved, the positive voltage on the signal amplification control electrode 5 is switched off. And applying normal CCD transfer clock pulses on the vertical transfer electrodes 1-4 to sequentially transfer the amplified signal electrons, wherein the subsequent working process is consistent with that of a conventional frame transfer CCD. And finally, a peripheral processing circuit displays the formed image to finish the process of one-time imaging.
As shown in fig. 2 and 3, the trench 7 is used for isolating each pixel of the CCD, and the guard ring 6 is used for protecting other areas of the pixel from being affected when breakdown occurs in the pixel, and controlling the breakdown occurring area within the range of the CCD buried trench 9, the n-type signal amplification area 10, and the p-type signal amplification area 11. The vertical transfer electrodes 1-4 and the signal amplification control electrode 5 are isolated by a silicon dioxide dielectric layer so as to avoid mutual influence among the electrodes during working.
The amplification capability of the structure for signal electrons can be controlled by changing the injection concentrations of the n-type signal amplification region 10 and the p-type signal amplification region 11 and the voltage on the signal amplification control electrode 5. Typical values: the n-type signal amplification region 10 has an implantation concentration of 1015/cm2P-type signal amplification region 11 with an injection concentration of 1012/cm2The signal amplification factor obtained by applying a voltage of 20V-30V to the signal amplification control electrode 5 is 10-20 times. If a larger signal amplification capability is to be obtained, this can be achieved by increasing the injection concentration of the n-type signal amplification region 10 and the p-type signal amplification region 11 or increasing the voltage of the signal amplification control electrode 5.
According to the invention, the signal amplification structure is designed in the CCD pixel, and meanwhile, the photosensitive responsivity of the CCD pixel can be changed in real time by changing the injection concentration of the signal amplification structure and the voltage applied by the signal amplification structure, so that the signal amplification capability of the CCD can be more flexibly selected when the CCD faces different incident light intensities, and the imaging detection adaptability of the CCD to environments with different light intensities is improved.
The above-mentioned embodiments, which further illustrate the objects, technical solutions and advantages of the present invention, should be understood that the above-mentioned embodiments are only preferred embodiments of the present invention, and should not be construed as limiting the present invention, and any modifications, equivalents, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (5)
1. A pixel structure capable of improving the responsivity of a frame transfer CCD (charge coupled device) comprises a substrate, a plurality of parallel vertical transfer electrodes, a CCD (charge coupled device) buried channel region, a protection ring and a channel resistor; the CCD buried channel structure is characterized in that a p-type signal amplification region and an n-type signal amplification region are sequentially arranged between a substrate and a CCD buried channel region; the upper part of the CCD buried channel region is connected with a vertical transfer electrode, and one side of each vertical transfer electrode is connected with a signal amplification control electrode through a dielectric layer; and respectively arranging a protection ring and a trench resistor from the left side and the right side of the top of the substrate to the CCD buried channel region.
2. A pixel structure according to claim 1, wherein the substrate is p-type, the guard rings are n-type doped, and the channel stop is p-type doped.
3. A pixel structure according to claim 1, wherein the p-type signal amplifying region has an injection concentration of 0.8 x 1012/cm2～1.2×1012/cm2(ii) a The implantation concentration of the n-type amplification region is 0.8 × 1015/cm2～1.2×1015/cm2。
4. A pixel structure according to claim 1, wherein the p-type signal amplification region and the n-type signal amplification region are formed with a pn-junction diode which is in a reverse-biased state when a positive voltage equal to or less than a threshold voltage is applied to the signal amplification control electrode, and signal electrons are collected in a CCD buried channel region below the vertical transfer electrode; when a positive voltage larger than a threshold voltage is applied to the signal amplification control electrode, the pn junction diode is broken down, and the number of signal electrons collected in a CCD (charge coupled device) buried channel region below the vertical transfer electrode is multiplied; when the positive voltage applied to the signal amplification control electrode is turned off, the amplified signal electrons are sequentially transferred by applying a CCD transfer clock pulse to the vertical transfer electrode.
5. A picture element structure for improving the responsivity of a frame transfer CCD according to claim 1, wherein the high voltage required for the vertical transfer electrodes is 5V to 10V, and the low voltage is-5V to 0V.
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| CN101960597A (en) * | 2009-01-30 | 2011-01-26 | 浜松光子学株式会社 | Solid-state imaging device |
| CN106981496A (en) * | 2017-04-05 | 2017-07-25 | 中国电子科技集团公司第四十四研究所 | Output amplifier and preparation method for frame transfer Visible-light CCD |
| CN107046046A (en) * | 2017-04-14 | 2017-08-15 | 中国电子科技集团公司第四十四研究所 | CCD pixel structures |
| CN107946389A (en) * | 2017-11-14 | 2018-04-20 | 重庆邮电大学 | A kind of CMOS single-photon avalanche diodes for long-wave band faint light |
| JP2018067615A (en) * | 2016-10-19 | 2018-04-26 | セイコーエプソン株式会社 | Solid-state imaging device, method of manufacturing the same, and electronic device |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN101960597A (en) * | 2009-01-30 | 2011-01-26 | 浜松光子学株式会社 | Solid-state imaging device |
| JP2010278086A (en) * | 2009-05-26 | 2010-12-09 | Panasonic Corp | Solid-state imaging device |
| JP2018067615A (en) * | 2016-10-19 | 2018-04-26 | セイコーエプソン株式会社 | Solid-state imaging device, method of manufacturing the same, and electronic device |
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