CN114222080B - High dynamic pixel structure - Google Patents

Abstract

The present invention discloses a high dynamic pixel structure, which at least includes a photodiode (PD), a transmission tube (TX), a suspension node (FD), a reset tube (RESET), a source follower (SF), a row selection tube (SELECT), a power supply (VDD) and a pixel output (VOUT) placed in a semiconductor substrate. FD includes three regions with different areas and different ion implantation concentrations. By controlling the FD area, a variable FD capacitance and FD conversion gain are formed, and a potential gradient is formed by controlling the doping concentration. Under weak light, the high potential FD1 works, and FD1 corresponds to a high conversion gain, which can convert a small amount of electrons into a stronger voltage signal, thereby avoiding the problem of being unable to quantify the photoelectric signal due to weak light. Under strong light, FD1, FD2 and FD3 work at the same time, and their conversion gain is small. FD can collect a lot of photoelectrons, avoiding the problem of premature saturation of FD under strong light, effectively expanding the light intensity range, and thus expanding the dynamic range of the pixel.

Description

A high dynamic pixel structure

Technical Field

The invention relates to an image sensor, and in particular to a high dynamic pixel structure.

Background technique

Image sensors are currently commonly used devices. The pixel structure of image sensors in the prior art has at least the following disadvantages:

In weak light, the photoelectric signal cannot be quantified because of the weak light; in strong light, the FD tends to saturate prematurely. Therefore, the light intensity range is narrow.

In view of this, the present invention is proposed.

Summary of the invention

The purpose of the present invention is to provide a high dynamic pixel structure to solve the above technical problems existing in the prior art.

The objective of the present invention is achieved through the following technical solutions:

The high dynamic pixel structure of the present invention comprises a photodiode 102, a transmission tube 103, a suspension node, a reset tube 110, a source follower 112, a row gate tube 113, a power supply 111 and a pixel output 114 disposed in a semiconductor substrate 101;

There are three suspension nodes, and the three suspension nodes use regions with different areas and different ion implantation concentrations;

The three suspension nodes are suspension node 1 105, suspension node 2 107 and suspension node 3 109 from near to far from the transmission pipe 103;

By controlling the areas of the three suspension nodes, variable suspension node capacitance and suspension node conversion gain are formed, and by controlling the doping concentration, a potential gradient is formed.

Compared with the prior art, the high dynamic pixel structure provided by the present invention, the FD includes three regions of different areas and different ion implantation concentrations. By controlling the FD area, a variable FD capacitance and FD conversion gain are formed, and a potential gradient is formed by controlling the doping concentration. Under weak light, the high potential FD1 works, and FD1 corresponds to a high conversion gain, which can convert a small amount of electrons into a stronger voltage signal, avoiding the problem of being unable to quantify the photoelectric signal due to weak light. Under strong light, FD1, FD2 and FD3 work at the same time, and their conversion gain is small. FD can collect a lot of photoelectrons, avoiding the problem of premature saturation of FD under strong light. Therefore, the pixel structure of the present invention effectively expands the light intensity range, thereby expanding the dynamic range of the pixel.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG1 is a high dynamic pixel plane layout provided by an embodiment of the present invention;

Fig. 2 is a cross-sectional view taken along the line A-A' of Fig. 1 .

In the figure:

101:Semiconductor substrate (Silicon)

102: Photodiode PD (photodiode)

103: Transmission tube (TX)

104: Suspended node injection layer 1 (FD imp1): As, 10KeV～50KeV, 1E15～5E15

105: Suspended node 1 (FD1)

106: Floating node injection layer 2 (FD imp2): As, 10KeV～50KeV, 5E13～5E14

107: Suspended node 2 (FD2)

108: Floating node injection layer 3 (FD imp3): As, 10KeV～50KeV, 5E12～5E13

109: Suspended node three (FD3)

110: Reset tube (RESET)

111: Power supply (VDD)

112: Source Follower (SF)

113: Row strobe (SELECT)

114:Pixel out

115: Source-drain injection

Detailed ways

The following is a clear and complete description of the technical solutions in the embodiments of the present invention in conjunction with the drawings in the embodiments of the present invention; it is obvious that the described embodiments are only part of the embodiments of the present invention, not all of the embodiments, which does not constitute a limitation of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the protection scope of the present invention.

First, the terms that may be used in this article are explained as follows:

The term “and/or” means that either or both of them can be realized at the same time. For example, X and/or Y means both “X” or “Y” and “X and Y”.

The terms "include", "comprises", "contains", "has" or other descriptions with similar semantics should be interpreted as non-exclusive inclusion. For example, "including certain technical feature elements (such as raw materials, components, ingredients, carriers, dosage forms, materials, dimensions, parts, components, mechanisms, devices, steps, procedures, methods, reaction conditions, processing conditions, parameters, algorithms, signals, data, products or products, etc.) should be interpreted as including not only certain technical feature elements explicitly listed, but also other technical feature elements known in the art that are not explicitly listed.

The term "consisting of..." means excluding any technical feature elements not explicitly listed. If this term is used in a claim, it will make the claim closed, so that it does not contain technical feature elements other than the technical feature elements explicitly listed, except for the conventional impurities related to them. If this term only appears in a clause of a claim, it only limits the elements explicitly listed in the clause, and the elements recorded in other clauses are not excluded from the overall claim.

Unless otherwise specified or limited, the terms "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense, for example: it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be an indirect connection through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in this article can be understood according to specific circumstances.

The orientation or position relationship indicated by terms such as "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", etc. are based on the orientation or position relationship shown in the drawings and are only for the convenience and simplification of description, and do not explicitly or implicitly indicate that the device or element referred to must have a specific orientation, be constructed and operate in a specific orientation, and therefore should not be understood as a limitation of this document.

The contents not described in detail in the examples of the present invention belong to the prior art known to professionals in the field. If no specific conditions are specified in the examples of the present invention, the conditions are carried out according to the conventional conditions in the field or the conditions recommended by the manufacturer. If the manufacturers of the reagents or instruments used in the examples of the present invention are not specified, they are all conventional products that can be purchased commercially.

The high dynamic pixel structure of the present invention comprises a photodiode 102, a transmission tube 103, a suspension node, a reset tube 110, a source follower 112, a row gate tube 113, a power supply 111 and a pixel output 114 disposed in a semiconductor substrate 101;

There are three suspension nodes, and the three suspension nodes use regions with different areas and different ion implantation concentrations;

The three suspension nodes are suspension node 1 105, suspension node 2 107 and suspension node 3 109 from near to far from the transmission pipe 103;

By controlling the areas of the three suspension nodes, variable suspension node capacitance and suspension node conversion gain are formed, and by controlling the doping concentration, a potential gradient is formed.

Under weak light, the high potential suspension node 105 works. The suspension node 105 corresponds to a high conversion gain and can convert a small amount of electrons into a strong voltage signal, thus avoiding the inability to quantify the photoelectric signal due to weak light.

Under strong light, the suspension node 105, the suspension node 2 107 and the suspension node 3 109 work simultaneously, and the conversion gain thereof is small. The suspension nodes can collect a lot of photoelectrons, thus avoiding premature saturation of the suspension nodes under strong light.

The suspension node 105 is small in area and high in N-type ion implantation, and the adjacent suspension node 2 107 is larger in area than the suspension node 105 and has a lower N-type ion implantation concentration than the suspension node 105;

The area of the third suspension node 109 adjacent to the second suspension node 107 is larger than that of the second suspension node 107 and the N-type ion implantation concentration is lower than that of the second suspension node 107 .

When the reset tube 110 is turned on, the suspension node 1 105 , the suspension node 2 107 and the suspension node 3 109 are reset at the same time, and a potential gradient is formed on the reset suspension nodes. The potential of the suspension node 105 is higher than that of the suspension node 2 107 , and the potential of the suspension node 2 107 is higher than that of the suspension node 3 109 .

Under weak light, the number of photogenerated electrons in the photodiode 102 is small. When the transmission tube 103 is turned on, the electrons in the photodiode 102 are preferentially transferred to the suspension node 1 105 with a higher potential. As the light intensity continues to increase, the suspension node 1 105 is not enough to accommodate it, and the photogenerated electrons in the photodiode 102 will occupy the suspension node 2 107 and the suspension node 3 109 in turn.

From the above, it can be seen that the high dynamic pixel structure of the embodiment of the present invention, since the FD includes three regions of different areas and different ion implantation concentrations. By controlling the FD area, a variable FD capacitance and FD conversion gain are formed, and a potential gradient is formed by controlling the doping concentration. Under weak light, the high potential FD1 works, and FD1 corresponds to a high conversion gain, which can convert a small amount of electrons into a stronger voltage signal, avoiding the problem of being unable to quantify the photoelectric signal due to weak light. Under strong light, FD1, FD2 and FD3 work at the same time, and their conversion gain is small. FD can collect a lot of photoelectrons, avoiding the problem of premature saturation of FD under strong light. Therefore, the pixel structure of the present invention effectively expands the light intensity range, thereby expanding the dynamic range of the pixel.

In order to more clearly demonstrate the technical solution and technical effects provided by the present invention, the embodiments of the present invention are described in detail with specific embodiments below.

Example 1

As shown in Figures 1 and 2, the FD of the pixel structure is separated from the TX tube to form FD1, FD2 and FD3 in sequence. FD1 adopts a small area and high N-type ion implantation, and the adjacent FD2 has an area larger than FD1 and a lower N-type ion implantation concentration than FD1. The adjacent FD3 has an area larger than FD2 and a lower N-type ion implantation concentration than FD2.

The principle of the embodiment is:

The FD contains three regions with different areas and different ion implantation concentrations. By controlling the FD area, a variable FD capacitance and FD conversion gain are formed, and by controlling the doping concentration, a potential gradient is formed;

Under weak light, the high potential FD1 works. FD1 corresponds to high conversion gain and can convert a small amount of electrons into a stronger voltage signal, thus avoiding the problem of being unable to quantify the photoelectric signal due to weak light.

Under strong light, FD1, FD2 and FD3 work at the same time, and their conversion gain is small. FD can collect a lot of photoelectrons, avoiding the problem of premature saturation of FD under strong light;

It effectively expands the light intensity range, thereby expanding the dynamic range of pixels.

The specific adjustment process is:

When RESET is turned on, FD1, FD2 and FD3 are reset at the same time. After reset, the FD forms a potential gradient. The potential of FD1 is higher than that of FD2, and the potential of FD2 is higher than that of FD3. In weak light, the number of photogenerated electrons in PD is small. When TX is turned on, the electrons of PD are preferentially transferred to FD1 with higher potential. As the light intensity continues to increase, FD1 is not enough to accommodate it, and the photogenerated electrons of PD will occupy FD2 and FD3 in turn.

In the pixel structure, the area of FD1 is smaller than that of FD2, and the area of FD2 is smaller than that of FD3. In weak light, only FD1 is effective, and its conversion gain is the highest, which can effectively quantify the small amount of electrons generated by weak light. As the light intensity continues to increase, FD1, FD2 and FD3 are effective, and the conversion gain becomes smaller, avoiding premature saturation of FD.

Therefore, the image sensor of the present invention can effectively expand the dynamic range.

The above is only a preferred specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by any technician familiar with the technical field within the technical scope disclosed in the present invention should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims. The information disclosed in the background technology section of this article is only intended to deepen the understanding of the overall background technology of the present invention, and should not be regarded as an admission or in any form that the information constitutes prior art known to those skilled in the art.

Claims (1)

1. The high dynamic pixel structure is characterized by comprising a photodiode (102), a transmission tube (103), a suspension node, a reset tube (110), a source follower (112), a row gate tube (113), a power supply (111) and a pixel output (114) which are arranged in a semiconductor substrate (101);

the number of the suspension nodes is three, and the three suspension nodes adopt areas with different areas and different ion implantation concentrations;

The three suspension nodes are sequentially a suspension node one (105), a suspension node two (107) and a suspension node three (109) from near to far from the transmission pipe (103);

The variable floating node capacitance and the floating node conversion gain are formed by controlling the areas of the three floating nodes, and the potential gradient is formed by controlling the doping concentration;

under weak light, the high-potential suspension node I (105) acts, and the suspension node I (105) corresponds to high conversion gain, so that a small amount of electrons can be converted into a stronger voltage signal, and the situation that photoelectric signals cannot be quantized due to weak illumination is avoided;

Under strong light, the first suspension node (105), the second suspension node (107) and the third suspension node (109) act simultaneously, the conversion gain is smaller, and the suspension nodes can collect a lot of photoelectrons, so that the suspension nodes are prevented from being saturated prematurely under strong light;

the first suspension node (105) adopts small-area and high-N-type ion implantation, the area of the second suspension node (107) adjacent to the first suspension node is larger than that of the first suspension node (105), and the concentration of the N-type ion implantation is lower than that of the first suspension node (105);

The area of a suspension node III (109) adjacent to the suspension node II (107) is larger than that of the suspension node II (107), and the N-type ion implantation concentration is lower than that of the suspension node II (107);

When the reset tube (110) is conducted, the first suspension node (105), the second suspension node (107) and the third suspension node (109) are reset at the same time, the reset suspension nodes form a potential gradient, the potential of the first suspension node (105) is higher than that of the second suspension node (107), and the potential of the second suspension node (107) is higher than that of the third suspension node (109);

under weak light, the photo-generated electrons of the photodiode (102) are fewer, when the transmission tube (103) is turned on, the electrons of the photodiode (102) are preferentially transferred to the first suspension node (105) with higher potential, and with the increasing of the light intensity, the first suspension node (105) is insufficient to accommodate, and the photo-generated electrons of the photodiode (102) sequentially occupy the second suspension node (107) and the third suspension node (109).