Transistor optical tweezers with symmetric leakage current and microfluidic device comprising the same

Abstract

The present application provides an optical tweezer device, comprising a first electrode; a second electrode; a transistor array between the first and second electrodes, the transistor array being composed of arrayed transistors, each transistor being physically isolated from each other by an insulating layer and an insulating barrier, each transistor comprising a collector region, a base region and an emitter region on a substrate; and a microfluidic channel formed between the first electrode and the transistor array; when an alternating current is applied between the first electrode and the second electrode, in an inactivated state, the transistor has a positive drain current and a negative drain current in the positive half cycle and the negative half cycle of the alternating current respectively, the collector region and the emitter region have substantially equal conductivity or resistivity, so that the transistor has substantially symmetrical positive drain current and negative drain current. The present application also provides a microfluidic device comprising the optical tweezer device.

Description

Technical Field

[0001] This invention relates to an optical tweezers device based on a phototransistor, and more particularly to an optical tweezers device capable of generating symmetrical leakage current under alternating current operating conditions, and a microfluidic device comprising the device. Background Technology

[0002] Transistor-based optical tweezers have been applied to manipulate (e.g., select or move) micro-objects such as cells and microspheres. A typical structure of this type of optical tweezers device consists of a microfluidic channel between two electrodes. The upper electrode is usually a glass plate coated with indium tin oxide (ITO), and the lower electrode is a metal electrode with a phototransistor array instead of a conventional photoelectric layer. When patterned light shines on a specific area of ​​the phototransistor array, the activated transistors allow current to flow, creating a non-uniform electric field in the microfluidic channel and generating a dielectrophoretic (DEP) force capable of manipulating the micro-object. A bias voltage, typically alternating current (AC), is applied between the two electrodes.

[0003] CN 107223074 B discloses a transistor optical tweezers and its microfluidic device. Each transistor structure includes a lateral transistor and a vertical transistor. In each transistor structure, a P-type base region surrounds an N-type emitter region, and an N-type collector region surrounds a P-type base region. Both the base region and the collector region include lateral and vertical portions. Compared to optical tweezers with only a vertical transistor, both lateral and vertical currents are generated simultaneously under the same light intensity. The additional lateral transistor is said to increase the intensity of the generated current, thereby allowing for more robust control of micro-objects.

[0004] CN 107250344 A discloses a self-locking optical tweezers, in which the DEP force generated by a ring-shaped lateral phototransistor is used to lock single particles or cells in the dark. The locked particles or cells can be selectively released by optically deactivating these locking sites. The transistor in this optical tweezers uses a P-type silicon substrate, with ring-patterned electrodes formed by photolithography, and N-type ions implanted between the large electrode and the island electrode to generate an NPN-type phototransistor. In this structure, the P-type silicon substrate constitutes the majority of the phototransistor.

[0005] Cells or microparticles contained in physiological fluids or culture media are injected through the inlet of a microfluidic channel, flow through the microfluidic channel, and exit from the outlet of the microfluidic channel. The physiological fluid or culture medium environment in which the cells or microparticles reside contains a large amount of electrolytes, such as various amino acids and inorganic ions (such as calcium ions). 2+ Na + Cl - K + Mg 2+ PO4 3-(e.g., etc.), thus possessing high conductivity, for example, 1 to 10 mS / cm or higher. Transistor optical tweezers use the base region of the transistor to receive light, generating a current, which is amplified by the transistor to conduct the upper and lower electrodes. When alternating current is applied between the two electrodes, the unlit transistor, although in the off state, still generates leakage current. Due to the periodic positive and negative changes in the voltage of the alternating current, the leakage current also changes positive and negative. The inventors discovered that in the transistor structures provided by the prior art, the positive and negative leakage currents lack symmetry, manifested as a significant difference in intensity at equal absolute voltage values. For example, when the absolute values ​​of the positive and negative voltages are equal, the positive leakage current intensity is significantly higher than the negative leakage current intensity. Therefore, at any given time, a potential difference is always applied to the high-conductivity sample in the microfluidic channel. Consequently, the organisms and conductive materials in the sample are constantly subjected to voltage stress, which on the one hand may cause potential damage to cells and other organisms, affecting experimental results, and on the other hand may exacerbate electrochemical reactions in the solution.

[0006] Taking the array-type phototransistor optical tweezers disclosed in CN 107223074 B as an example, its structure is shown in Figure 5. Each phototransistor 526 is physically isolated by an insulating layer 512 and an insulating barrier 520 extending to a support layer 510, and includes a base region 504, an emitter region 502, and a collector region 506. The support layer 510, collector region 506, and emitter region 502 can be doped with N-type dopant, and the base region 504 is doped with P-type dopant. The support layer 510 and emitter region 502 are heavily doped N+ regions with a resistivity of about 0.025 to 0.050 ohm·cm, and the collector region 506 is a lightly doped N- region with a resistivity of about 5 to 10 ohm·cm. The ratio of the emitter region resistivity to the collector region resistivity is 1:100 to 1:400. The doping concentration of the N+ region can be about 10. 18 cm -3 Up to 10 21 cm -3 The doping concentration in the N region can be 10. 16 cm -3 Up to 10 18 cm -3As shown in the figure, the lateral width Wn of the collector region 506 is approximately 600 nm to approximately 750 nm, and the lateral width Wp of the base region 504 is approximately 200 nm to approximately 300 nm. The thickness He of the emitter region 502 is approximately 50 nm to approximately 150 nm. The thickness Hb of the longitudinal portion of the base region 504 is 1 to 4 times that of Wp, i.e., approximately 10 nm to approximately 1,600 nm. The thickness Hc of the longitudinal portion of the collector region 506 is 1 to 8 times that of Wn, i.e., approximately 100 nm to approximately 8,000 nm. The thickness Hc is approximately 3 to 6 times greater than the thickness Hb. The thickness Hc is approximately 10 to 16 times greater than the thickness He, meaning that the thickness difference between the emitter region 502 and the collector region 506 on both sides of the base region 504 is 10 to 16 times.

[0007] Figure 6A shows the current-voltage characteristic curves of the transistor based on the above structure, with alternating current (AC) applied to the two electrodes of the optical tweezers device. When patterned light illuminates the transistor, it is turned on, and its current-voltage characteristic curve is shown as curve A in the figure. At this time, the current intensity at the positive voltage is comparable to the current intensity at the corresponding negative voltage. When there is no light illumination, the transistor is in the off state, but leakage current still flows, and the leakage current current-voltage characteristic curve is shown as curve B in the figure. During the positive voltage period, the leakage current intensity is significantly greater than the current intensity at the same voltage absolute value during the negative voltage period. For example, at +10 μV, the leakage current intensity is approximately +5 μA, corresponding to the intercept S1 on the ordinate axis; when at -10 μV, the leakage current intensity is approximately -2 μA, corresponding to the intercept S2 on the ordinate axis. It can be clearly seen that S1 is significantly larger than S2, that is, at the same voltage with different directions, the leakage current not only has different directions but also shows significant differences in intensity. It can be seen that a potential difference always exists on the microfluidic over a certain period of time, inducing or intensifying the electrochemical reaction.

[0008] Electrochemical reactions are often accompanied by hydrogen or oxygen evolution at the electrode surface. These evolved gases are adsorbed onto the electrode surface as bubbles, resulting in a reduction in the active area of ​​the electrode, uneven microscopic distribution of surface potential and current density, and electrode polarization. When a large number of bubbles are adsorbed on the electrode surface, a gas film forms, causing electrode passivation and deactivation. The evolved gases also disperse in the solution as bubbles, making the solution a gas-liquid mixture, which affects the generation of non-uniform electric fields and is detrimental to DEP force manipulation of micro-objects such as cells.

[0009] In view of this, there is a need in the art for an improved optical tweezers device and a corresponding microfluidic device to overcome the above-mentioned deficiencies in the prior art. Summary of the Invention

[0010] One aspect of the present invention provides an optical tweezers device, comprising a first electrode; a second electrode; a phototransistor array located between the first and second electrodes, the phototransistor array being composed of arrayed transistors, each phototransistor being physically isolated from each other by an insulating layer and an insulating barrier, each transistor including a collector region, a base region, and an emitter region on a substrate, the collector region and the emitter region having a first doping type, the base region having a second doping type; and a microfluidic channel formed between the first electrode and the transistor array; when an alternating current is applied between the first electrode and the second electrode, the phototransistor, in an inactive state, has a positive leakage current and a negative leakage current, respectively, during the positive and negative half-cycles of the alternating current, the collector region and the emitter region having substantially equal conductivity or resistivity, thereby the transistor having substantially symmetrical positive and negative leakage currents.

[0011] In some embodiments, the emitter region includes a first doped region and a second doped region, wherein the doping concentration of the first doped region is higher than that of the second doped region. In some embodiments, the doping concentration of the first doped region is approximately 10. 18 To about 10 21 cm -3 In some embodiments, the doping concentration of the second doped region is approximately 10. 15 To about 10 18 cm -3 .

[0012] In some embodiments, the collector region and the second doped region have substantially the same doping concentration. In some embodiments, the doping concentration of the collector region and the second doped region is approximately 10. 15 To about 10 18 cm -3 .

[0013] In some embodiments, the first doped region has a first thickness, the second doped region has a second thickness, and the ratio of the first thickness to the second thickness is about 1:1 to about 1:30, preferably about 1:5.

[0014] In some embodiments, the collector region has a third thickness and the emitter region has a fourth thickness, the ratio of the third thickness to the fourth thickness being about 1:5 to about 5:1, preferably about 1:1.

[0015] In some embodiments, the current collector region has a third thickness, the ratio of which to the second thickness is about 1:5 to about 5:1, preferably about 1:1.

[0016] In some embodiments, the base region, the first doped region, and the second doped region extend laterally to the insulating barrier.

[0017] In some embodiments, the first doped region and the second doped region extend laterally, and the second doped region at least partially surrounds the first doped region. In some embodiments, the second doped region surrounds the first doped region with a first lateral width of about 100 nm to about 2,000 nm.

[0018] In some embodiments, the base region, the first doped region, and the second doped region extend laterally, and the base region at least partially surrounds the first doped region and the second doped region. In some embodiments, the base region surrounds the first doped region and the second doped region with a second lateral width of about 100 nm to about 2,000 nm.

[0019] In some embodiments, the base region, the first doped region, and the second doped region extend laterally, with the base region at least partially surrounding the first doped region and the second doped region, and the second doped region at least partially surrounding the first doped region. In some embodiments, the base region surrounds the first doped region and the second doped region with a second lateral width of about 100 nm to about 2,000 nm, and the second doped region surrounds the first doped region with a first lateral width of about 100 nm to about 2,000 nm.

[0020] In some embodiments, the first thickness is about 100 to about 1,000 nm. In some embodiments, the second thickness is about 500 to about 3,000 nm. In some embodiments, the thickness of the base region is about 100 to about 5,000 nm.

[0021] In some embodiments, the ratio of the conductivity of the emitting region to the conductivity of the collecting region is about 1:10 to about 10:1. In some embodiments, the resistivity of the collecting region is about 0.05 to about 10 ohm-cm. In some embodiments, the resistivity of the emitting region is about 0.05 to about 10 ohm-cm.

[0022] In some embodiments, the substrate has the same doping concentration as the first doped region. In some embodiments, the resistivity of the substrate is about 0.001 to about 0.05 ohm-cm.

[0023] In some embodiments, the first electrode is a glass plate coated with a conductive film. In some embodiments, the conductive film is an indium tin oxide (ITO) coating. In some embodiments, the second electrode is a metal electrode. In some embodiments, the metal electrode is a gold electrode.

[0024] In some embodiments, the first doping type is N-type doping, and the second doping type is P-type doping. In some embodiments, the first doping type is P-type doping, and the second doping type is N-type doping.

[0025] In some embodiments, the microfluidic channel is filled with a liquid sample having a conductivity of about 1 to about 10 mS / cm. In some embodiments, the liquid sample is a cell culture medium or a physiological solution. In some embodiments, the cell culture medium or physiological solution contains cells. In some embodiments, the cells are hybridoma cells.

[0026] In some implementations, the emission region is composed of a plurality of sub-emission regions.

[0027] In another aspect, the present invention provides a microfluidic device, including a control system, an optical pattern generation system, an image acquisition system, and an optical tweezers device, wherein the optical tweezers device is any of the optical tweezers devices described in the present invention.

[0028] The optical tweezers device and microfluidic apparatus provided by this invention, when an alternating current is applied to the two electrodes of the optical tweezers device, exhibit a symmetrical current-voltage characteristic curve of the leakage current on the unactivated transistor during the positive and negative cycles of the alternating current, thereby reducing or eliminating damage and / or electrochemical reactions to cells or other micro-objects in the microfluidic system. In some embodiments, the symmetrical leakage current-voltage characteristic curve is as follows: Figure 6B and 6C As shown.

[0029] Those skilled in the art will recognize that changes in the doping concentration and thickness of the collector and emitter regions on either side of the base region can affect the leakage current-voltage characteristic curve of the phototransistor. This invention anticipates maintaining leakage current symmetry by keeping the conductivity or resistivity (the reciprocal of conductivity) of the collector and emitter regions substantially equal. Generally, increasing the doping concentration leads to increased conductivity, thereby increasing the leakage current. Increasing the thickness leads to increased resistivity, thereby decreasing the leakage current. For example, while keeping the doping concentration and thickness of the emitter region constant, increasing the doping concentration of the collector region and / or decreasing its thickness can increase the leakage current. Alternatively, while keeping the doping concentration and thickness of the collector region constant, increasing the doping concentration of the emitter region and / or decreasing its thickness can increase the leakage current. The reverse is also true. Furthermore, the doping concentration and thickness of both the collector and emitter regions can be adjusted simultaneously to synergistically adjust their conductivity (or resistivity) to maintain symmetrical leakage current. When the emitter region contains multiple doped regions with different doping concentrations, the thickness and doping concentration of one, more, or all of the multiple doped regions can be changed individually or simultaneously to adjust the conductivity (or resistivity) of the emitter region. Attached Figure Description

[0030] This invention will be described in more detail with reference to the accompanying drawings. It should be noted that the illustrated schemes are merely representative examples of embodiments of the invention, and to more clearly illustrate the details of exemplary embodiments, the elements in the drawings are not drawn to scale; the number of actual elements may vary, the relative positions of the actual elements remain substantially consistent with the illustrations, and some elements are not shown. In cases where multiple embodiments exist, when one or more features described in previous embodiments are also applicable to another embodiment, for the sake of brevity, these reusable features will not be repeated in subsequent embodiments. These subsequent embodiments should be understood as having described these reusable features, unless otherwise stated. Those skilled in the art will recognize upon reading this invention that one or more features shown in one figure can be combined with one or more features in another figure to construct one or more alternative embodiments not specifically shown in the drawings, and these alternative embodiments also constitute a part of this invention.

[0031] Figure 1 shows an optical tweezers device according to an embodiment of the present invention, wherein... Figure 1A This shows a partial cross-sectional view of the optical tweezers device. Figure 1B This shows a partial top view of the transistor array of the optical tweezers device. Figure 1C This shows a partial perspective view of the transistor array. Figure 1D A schematic diagram of a microfluidic device containing this optical tweezers device is shown.

[0032] Figure 2 shows a transistor array included in an optical tweezers device according to another embodiment of the present invention, wherein Figure 2A This shows a partial cross-sectional view of the transistor array. Figure 2B This shows a partial top view of the transistor array.

[0033] Figure 3 shows the transistor array included in an optical tweezers device according to yet another embodiment of the present invention, wherein Figure 3A This shows a partial cross-sectional view of the transistor array. Figure 3B This shows a partial top view of the transistor array.

[0034] Figure 4 shows the transistor array included in an optical tweezers device according to another embodiment of the present invention, wherein Figure 4A This shows a partial cross-sectional view of the transistor array. Figure 4B This shows a partial top view of the transistor array.

[0035] Figure 5 shows a partial cross-sectional view of a transistor array contained in a prior art optical tweezers device.

[0036] Figure 6 shows the current-voltage characteristic curves of the phototransistor under light-activated and light-deprived conditions, wherein Figure 6A shows the current-voltage characteristic curve of the prior art transistor according to Figure 5. Figure 6B The current-voltage characteristic curves obtained by the transistors in Figures 1 and 2 according to the present invention are shown. Figure 6C The current-voltage characteristic curves of the transistors shown in Figures 3 and 4 of this invention are displayed.

[0037] Figure 7 This illustrates an exemplary manufacturing process for the phototransistor of the present invention.

[0038] The meanings of the reference numerals in the accompanying drawings are summarized as follows: Reference numerals with the same numbers represent the same elements. When applicable, a letter is added after the number to indicate repeated arrangements of the same element. For example, reference numerals 108a, 108b, 108c, and 108d represent four repetitions of element 108. 102, 202, 302, 402, 502 - First doped region; 104, 204, 304, 404, 504 - Second doped region; 105, 205, 305, 405 - Emitter region; 106, 206, 306, 406, 506 - Base region; 108, 208, 308, 408, 508 - Collector region; 110, 210, 310, 410, 510 - Substrate; 112 - Insulating layer; 114 - Conductive plating layer; 116 - Second electrode; 118 - Cell; 120 - Insulating barrier; 122 - Microfluidic channel; 124 - First electrode; 126 - Phototransistor; 128 - First electrode plate; 130 - Light pattern generating device; 132 - Image acquisition device; 134 - Computer system; 136 - Microfluidic devices; 138 - Control systems. H, W, L indicate dimensions. N+, N-, P indicate doping type and doping level. Detailed Implementation

[0039] The exemplary embodiments of the present invention are described in detail below with reference to the accompanying drawings. It should be understood that the scope of the present invention is not limited to the disclosed embodiments. Those skilled in the art, after reading the disclosure of this invention, can modify and vary these exemplary embodiments based on the teachings of the present invention, without any inventive effort. Such modifications and variations are intended to be included within the scope outlined in the appended claims.

[0040] refer to Figure 1AThe diagram schematically illustrates a partial cross-sectional view of an optical tweezers device according to an embodiment of the present invention. The optical tweezers device includes a first electrode 124 made of glass 128 coated with an indium tin oxide (ITO) conductive layer 114 and a second electrode 116 electrically connected to the first electrode 124, with an alternating current (AC) applied between the two electrodes. The peak voltage of the AC is between approximately 1 Vppk and approximately 50 Vppk, and the frequency is between approximately 100 kHz and approximately 10 MHz. The AC can be a square waveform, a sine waveform, or a triangular waveform. The first electrode 124 can also be other suitable ITO glass alternatives known in the art, such as AZO or GZO glass. In this embodiment, the second electrode 116 is a metal electrode. Suitable metal electrodes include precious metals such as gold, silver, platinum, palladium, and iridium; metals such as copper, tin, antimony, iron, cobalt, nickel, chromium, titanium, and manganese; or alloys such as platinum-barium, palladium-barium, iridium-tungsten-rhenium, and iridium-barium-osmium. In this embodiment, the second electrode 116 is a gold electrode.

[0041] An array of transistors is disposed on the second electrode 116 and electrically connected to the second electrode 116. The array of transistors includes a plurality of transistors 126 arranged in an array. An insulating assembly consisting of an insulating layer 112 and an insulating barrier 120 (e.g., SiO2) physically separates the individual transistors 126, thereby achieving electrical insulation between the individual transistors 126. The figure shows three transistors 126 physically separated by two identical insulating assemblies. Insulating layers 112a and 112b are located on the surface of transistors 126, and insulating barriers 120a and 120b extend downward from insulating layers 112a and 112b to the substrate layer 110 of transistors 126, respectively. Each transistor 126 can be a phototransistor 126. Transistor 126 includes a substrate layer 110, a collector region 108 disposed on the substrate layer, a base region 106 disposed on the collector region 108, and an emitter region 105 disposed on the base region 106. The upper surface of the emitter region 105 forms the upper surface of the transistor 126, and the lower surface of the substrate layer 110 forms the lower surface of the transistor 126. The upper surface of the emitter region 105 is exposed to the microfluidic channel 122 and is opposite to the ITO conductive plating layer 114 of the first electrode 124, and the lower surface of the substrate layer 110 is electrically connected to the second electrode 116.

[0042] The array of transistors 126 can be regular or irregular, but is preferably regular, for example, each transistor 126 is evenly spaced in the form of cubes or cuboids. When the array of transistors 126 is a regular arrangement of transistors 126, adjacent transistors 126 are spaced apart by a distance L4, also known as a pixel period, which is the distance between the longitudinal central axes of adjacent insulating barriers 120a and 120b. In this embodiment, L4 is about 5 to about 20 micrometers, for example, about 5 to about 15 micrometers, or about 5 to about 10 micrometers. The portion of transistor 126 not covered by insulating layer 112 is called a window, and the size L1 of this window depends on the distance L4 and the size of the portion of the transistor covered by insulating layer 112. Typically, this size L1 is about 20% to about 90% of the distance L4, for example, about 1 to about 18 micrometers, about 1 to about 12 micrometers, or about 1 to about 9 micrometers. The longitudinal depth L3 of the insulating barrier 120 is greater than the sum of the thicknesses H1+H2 of the emitter region 105, H3 of the base region 106, and H4 of the collector region of the transistor 126, for example, by about 10% to about 30% of the sum of the thicknesses. For example, L3 can be about 2 to about 10 micrometers, about 5 to about 10 micrometers, or about 8 to about 10 micrometers. The width L2 of the insulating barrier 120 can be about 100 nm to about 2,000 nm, for example, about 500 nm to about 1,500 nm, or about 800 nm to about 1,000 nm. Those skilled in the art will recognize that the aforementioned dimensions of L1 to L4 are merely examples, and the actual product dimensions can be larger or smaller as required.

[0043] The emitter region 105 includes a first doped region 102 and a second doped region 104, wherein the second doped region 104 is adjacent to the base region 106, the first doped region 102 is disposed above the second doped region 104, and at least a portion of the first doped region 102 directly faces the ITO conductive plating layer 114 of the first electrode 124. An insulating layer 112 at least partially covers the first doped region 102. The first doped region 102 and the second doped region 104 each extend laterally and parallel to adjacent insulating barriers 120a and 120b. The first doped region 102 and the second doped region 104 have the same doping type, and the first doped region 102 has a higher doping concentration than the second doped region 104. For example, both the first doped region 102 and the second doped region 104 contain an N-type dopant, with the first doped region 102 being a heavily doped N+ region and the second doped region 104 being a lightly doped N- region. When both the first doped region 102 and the second doped region 104 contain P-type dopant, the first doped region 102 is a heavily doped region (P+), and the second doped region 104 is a lightly doped region (P-). It should be noted that, unless otherwise stated, the terms "heavily doped region" and "lightly doped region" and their corresponding symbols are used in this invention only in their relative sense; that is, when the doping concentration of one doped region is higher than that of another, the region with the higher doping concentration is called the heavily doped region, and the region with the lower doping concentration is called the lightly doped region, and there is no necessary connection with the absolute value of their actual doping concentration. In other embodiments, the emitter region 105 may be composed of a plurality of (e.g., 2 or 4) sub-emitter regions 105, all of which share the base region 106 and the collector region 108. Each sub-emitter region 105 is separated by the base region 106, thereby increasing the illumination area of ​​the base region 106, which is beneficial for generating a larger DEP force, thus facilitating the manipulation of micro-objects in the microchannel.

[0044] The doping concentration of the first doped region 102 can be approximately 10 to approximately 10 of the doping concentration of the second doped region 104. 6 For example, the doping concentration of the first doped region 102 can be approximately 10 times that of the second doped region 104. 2 To about 10 5 times, or about 10 3 The doping concentration of the first doped region 102 can be approximately 10 times. 18 cm -3 To about 10 21 cm -3 The doping concentration of the second doped region 104 can be approximately 10. 15 cm -3 To about 10 18 cm -3 In this embodiment, the doping concentration of the first doped region 102 can be approximately 1 x 10⁻⁶. 18 cm -3The doping concentration of the second doped region 104 can be approximately 1 x 10⁴. 16 cm -3 N-type dopants can be from any source of electrons. Suitable examples of N or N+ dopants include phosphorus, arsenic, and antimony. P-type dopants can be from any source of holes. Suitable examples of P or P+ dopants include boron, aluminum, beryllium, zinc, cadmium, and indium.

[0045] The base region 106 extends laterally to adjacent insulating barriers 120a and 120b. In the illustrated embodiment, the base region 106 contains a p-type dopant. A suitable doping concentration can be approximately 10-1. 16 cm -3 To about 10 18 cm -3 In this embodiment, the doping concentration of the base region 106 is approximately 1 x 10⁶. 16 cm -3 The base region 106 has a suitable thickness H3, for example, about 100 nm to about 5,000 nm, or about 100 nm to about 2,500 nm, or about 100 nm to about 2,000 nm, or about 100 nm to about 1,500 nm, or about 100 nm to about 1,000 nm, or about 100 nm to about 500 nm, or about 100 nm to about 300 nm, or about 300 nm to about 3,000 nm, or about 300 nm to about 2,500 nm, or about 300 nm to about 2,000 nm, or about 300 nm to about 1,500 nm, or about 300 nm to about 1,000 nm, or about 300 nm to about 500 nm, or about 500 nm to about 3,000 nm, or about 500 nm to about 2,500 nm, or about 500 nm to about 2,000 nm, or about 500 nm to about 1,500 nm. nm, or about 500 nm to about 1,000 nm, or about 1,000 nm to about 3,000 nm, or about 1,000 nm to about 2,500 nm, or about 1,000 nm to about 2,000 nm, or about 1,000 nm to about 1,500 nm, or about 1,500 nm to about 3,000 nm, or about 1,500 nm to about 2,500 nm, or about 1,500 nm to about 2,000 nm, or about 2,000 nm to about 3,000 nm, or about 2,000 nm to about 2,500 nm. In this embodiment, the thickness H3 of the base region 106 is about 500 nm. When the patterned beam (see Figure 1D When the light beam shines on the transistor 126, it penetrates the emitter region 105 and reaches the base region 106, generating a photoelectric effect and turning on the transistor 126.

[0046] The collector region 108 and emitter region 105 are symmetrically distributed about the base region 106, extending laterally to adjacent insulating barriers 120a and 120b. The second doped region 104 of the emitter region 105 may have the same doping type as the collector region 108. For example, both the second doped region 104 and the collector region 108 contain N-type dopants. The doping concentrations of the second doped region 104 and the collector region 108 may be substantially the same. For example, the doping concentration of both the second doped region 104 and the collector region 108 is approximately 10. 15 cm -3 To about 10 18 cm -3 The term "substantially identical" doping concentration herein refers to a doping concentration ratio between the compared object and the reference object that is approximately 1:10 to approximately 10:1, for example, a doping concentration ratio of approximately 1:5 to approximately 5:1, or approximately 1:3 to approximately 3:1, or approximately 1:2 to approximately 2:1, or approximately 1:1.5 to approximately 1.5:1, or approximately 1:1.2 to approximately 1.2:1, or approximately 1:1.1 to approximately 1.1:1. In this embodiment, the doping concentration of the collector region 108 is 2 x 10⁻⁶. 15 cm -3 .

[0047] Substrate 110 is located at the bottom of transistor 126 and is directly electrically connected to the second electrode 116. In this embodiment, substrate 110 contains an N-type dopant. Substrate 110 can be a heavily doped region relative to collector region 108. Substrate 110 can have substantially the same doping concentration as the first doped region 102 of emitter region 105. For example, the doping concentration of substrate 110 is approximately 10⁻⁶. 18 cm -3 To about 10 21 cm -3 The thickness H5 of the substrate layer 110 can be a suitable thickness generally accepted in the art. For example, the thickness H5 of the substrate layer 110 is typically greater than 50 micrometers, such as about 50 to about 500 micrometers, or about 50 to about 450 micrometers, or about 50 to about 400 micrometers, or about 50 to about 350 micrometers, or about 50 to about 300 micrometers, or about 50 to about 250 micrometers, or about 50 to about 200 micrometers, or about 50 to about 150 micrometers, or about 50 to about 100 micrometers. In this embodiment, the thickness H5 of the substrate layer 110 is about 50 micrometers. The substrate layer 110 may have a resistivity of about 0.001 to about 0.05 ohm-cm.

[0048] In the emitter region 105, the thickness H1 of the first doped region 102 is preferably smaller than the thickness H2 of the second doped region 104. For example, the thickness H1 of the first doped region 102 is about 1 / 1 to about 1 / 30, or about 1 / 5 to about 1 / 30, or about 1 / 5 to about 1 / 20, or about 1 / 5 to about 1 / 15, or about 1 / 5 to about 1 / 10, or about 1 / 10 to about 1 / 30, or about 1 / 10 to about 1 / 20, or about 1 / 10 to about 1 / 15, or about 1 / 15 to about 1 / 30, or about 1 / 15 to about 1 / 25, or about 1 / 15 to about 1 / 20. Thus, the second doped region 104 constitutes the main part of the emitter region 105. For example, the thickness H1 of the first doped region 102 is about 100 nm to about 1,000 nm, such as about 100 nm to about 800 nm, or about 100 nm to about 500 nm, or about 100 nm to about 300 nm, or about 100 nm to about 200 nm, or about 500 nm to about 1,000 nm, or about 500 nm to about 800 nm, or about 800 nm to about 1,000 nm. The thickness H2 of the second doped region 104 can be from about 500 nm to about 3,000 nm, for example, from about 500 nm to about 2,500 nm, or from about 500 nm to about 2,000 nm, or from about 500 nm to about 1,500 nm, or from about 500 nm to about 1,000 nm, or from about 1,000 nm to about 3,000 nm, or from about 1,000 nm to about 2,500 nm, or from about 1,000 nm to about 2,000 nm, or from about 1,000 nm to about 1,500 nm, or from about 1,500 nm to about 3,000 nm, or from about 1,500 nm to about 2,500 nm, or from about 1,500 nm to about 2,000 nm. In this embodiment, the thickness H1 of the first doped region 102 is about 500 nm, and the thickness H2 of the second doped region 105 is about 2,000 nm.

[0049] The emitter region 105 and collector region 108 located on either side of the base region 106 can have substantially the same thickness, that is, the sum of the thickness H1 of the first doped region 102 and the thickness H2 of the second doped region 104 of the emitter region 105 is substantially the same as the thickness H4 of the collector region 108. The thickness H1 of the first doped region 102 can be increased or decreased within a certain range, and the thickness H2 of the second doped region 104 can be decreased or increased accordingly, such that the total thickness H1+H2 of the first doped region 102 and the second doped region 104 is substantially the same as the thickness H4 of the collector region 108. For example, the ratio of the total thickness H1+H2 to the thickness H4 is approximately 1:5 to approximately 5:1, such as approximately 1:4 to approximately 4:1, approximately 1:3 to approximately 3:1, approximately 1:2 to approximately 2:1, approximately 1:1.5 to approximately 1.5:1, approximately 1:1.2 to approximately 1.2:1, approximately 1:1.1 to approximately 1.1:1, or approximately 1:1. In one embodiment, the total thickness H1+H2 is greater than the thickness H4. In another embodiment, the total thickness H1+H2 is less than the thickness H4. In yet another embodiment, the total thickness H1+H2 is equal to the thickness H4.

[0050] In some embodiments, only the thickness H2 of the second doped region 104 and the thickness H4 of the collector region 108 are kept substantially the same. For example, the ratio of thickness H2 to thickness H4 is about 1:5 to about 5:1, such as about 1:4 to about 4:1, about 1:3 to about 3:1, about 1:2 to about 2:1, about 1:1.5 to about 1.5:1, about 1:1.2 to about 1.2:1, about 1:1.1 to about 1.1:1, or about 1:1. In one embodiment, thickness H2 is greater than thickness H4. In another embodiment, thickness H2 is less than thickness H4. In yet another embodiment, thickness H2 is equal to thickness H4.

[0051] In some embodiments, the thickness and doping concentration of the first doped region 102, the second doped region 104, and the collector region 108 exemplarily described above can be changed while always maintaining substantially the same conductivity (e.g., simultaneously increasing or simultaneously decreasing by the same amount). For example, the conductivity of the emitter region 105 and the collector region 108 can be increased simultaneously, for example, by decreasing the thickness of the first doped region 102 and / or the second doped region 104 and the thickness of the collector region 108, or by increasing the doping concentration of the first doped region 102 and / or the second doped region 104 and the doping concentration of the collector region 108. Alternatively, the conductivity of the emitter region 105 and the collector region 108 can also be increased simultaneously by decreasing the thickness of the emitter region 105 and increasing the doping concentration of the collector region 108, or by increasing the doping concentration of the emitter region and decreasing the thickness of the collector region 108. Optionally, the conductivity of both the emitter region 105 and the collector region 108 can be reduced simultaneously by increasing the thickness of the emitter region 105 and decreasing the doping concentration of the collector region 108, or by decreasing the doping concentration of the emitter region 105 and increasing the thickness of the collector region 108.

[0052] It is anticipated that the thickness and doping concentration of emitter region 105 can be changed simultaneously (e.g., decreased or increased), and the thickness and doping concentration of collector region 108 can also be changed simultaneously to achieve a consistent increase or decrease in conductivity. For example, the thickness of emitter region 105 can be decreased (by decreasing the thickness of at least one of the first doped region 102 and the second doped region 104) and the doping concentration of emitter region 105 can be increased (by increasing the doping concentration of at least one of the first doped region 102 and the second doped region 104) to jointly increase conductivity. Alternatively, the thickness of emitter region 105 can be increased and the doping concentration of emitter region 105 can be decreased to jointly decrease conductivity. The above description of emitter region 105 also applies to collector region 108, but for brevity, it will not be elaborated further.

[0053] It is anticipated that the increase in conductivity due to reduced thickness and / or increased doping concentration, or the decrease in conductivity due to increased thickness and / or decreased doping concentration, should be substantially the same in magnitude between the emitter region 105 and the collector region 108, in order to maintain the conductivity of the emitter region 105 and the collector region 108 at all times substantially equal. For example, the ratio of the conductivity of the emitter region 105 to the collector region 108 is about 1:10 to about 10:1, such as about 1:8 to about 8:1, or about 1:6 to about 6:1, or about 1:5 to about 5:1, or about 1:3 to about 3:1, or about 1:2 to about 2:1, or about 1:1.2 to about 1.2:1, about 1:1.1 to about 1.1:1, or about 1:1. In this embodiment, the conductivity of the emitter region 105 is about 12 S / cm, and the conductivity of the collector region 108 is about 2 S / cm.

[0054] In all the above embodiments, the thickness H4 can be from about 100 nm to about 15,000 nm, for example, from about 500 nm to about 15,000 nm, or from about 500 nm to about 15,000 nm, or from about 1,000 nm to about 15,000 nm, or from about 1,000 nm to about 12,000 nm, or from about 1,000 nm to about 10,000 nm, or from about 1,000 nm to about 8,000 nm, or from about 1,000 nm to about 6,000 nm, or from about 1,000 nm to about 4,000 nm, or from about 1,000 nm to about 3,000 nm, or from about 1,000 nm to about 2,000 nm, or from about 1,000 nm to about 1,500 nm, or from about 500 nm to about 1,000 nm, or from about 500 nm to about 1,5 ... The thickness H4 is approximately 5,000 nm to about 2,000 nm, or approximately 500 nm to about 2,500 nm, or approximately 500 nm to about 3,000 nm, or approximately 500 nm to about 3,500 nm, or approximately 500 nm to about 4,000 nm, or approximately 500 nm to about 4,500 nm, or approximately 500 nm to about 5,000 nm, or approximately 500 nm to about 5,500 nm, or approximately 500 nm to about 6,000 nm, or approximately 500 nm to about 6,500 nm, or approximately 500 nm to about 7,000 nm, or approximately 500 nm to about 7,500 nm, or approximately 500 nm to about 8,000 nm. In this embodiment, the thickness H4 is approximately 5,000 nm.

[0055] In this embodiment, the optical tweezers device further includes a microfluidic channel 122 located between the upper surface of the transistor array and the lower surface of the conductive plating layer 114 of the first electrode 124. The microfluidic channel 122 is generally composed of multiple microchannels connected in series or parallel, each microchannel containing multiple addressable micropores in which cells or other micro-objects can reside. The microfluidic channel 122 includes fluid inlets and outlets (not shown) for fluid communication with the external environment. Microfluidics (such as cell culture medium or physiological fluid) containing cells 118 (illustrated as cells 118a, 118b, 118c, and 118d, such as antibody-secreting hybridoma cells) flow into the microfluidic channel 122 through the inlet, flow through the microfluidic channel 122 in the direction indicated by arrow A, undergo processing and manipulation (including photoelectric detection, culture, screening, movement, etc.), and finally flow out from the outlet, realizing the operation program of the microfluidic chip. The microfluidic channel 122 is typically made of polymeric materials, such as PMMA, PC, PS, PP, PE, PDMS, etc., or is made using a photocurable agent. The height of the microfluidic channel 122 is typically in the micrometer range, for example, 20 to 50 micrometers.

[0056] Figure 1CShowing Figure 1A A partial cross-sectional view of an array of phototransistors 126 as shown. Figure 1D Displayed contains Figure 1A This is a schematic diagram of a portion of a microfluidic device 136 comprising an optical tweezers device with a structure shown in the diagram. The microfluidic device 136 includes an optical tweezers device and a control system 138. The control system 138 typically includes a computer system 134 and an image acquisition device 132 and a light pattern generation device 130 communicatively connected to the computer system 134. The image acquisition device 132 is used to acquire images of the microfluidic channel and / or micropores, such as a camera with a CCD chip. The light pattern generation device 130 is used to generate a patterned light beam to excite the transistor. The intensity of the light beam can be approximately 0.1 W / cm². 2 Up to approximately 1000 W / cm 2 The computer system 134 is communicatively connected to the optical tweezers device and controls the interaction between the image acquisition device 132, the optical pattern generation device 130, and the optical tweezers device according to preset instructions to complete microfluidic operations.

[0057] Figure 6B The current-voltage characteristic curve of the transistor according to this embodiment is shown, with alternating current (AC) applied to the two electrodes of the optical tweezers device. When patterned light illuminates the transistor, the transistor is turned on, and its current-voltage characteristic curve is shown as curve A in the figure. At this time, the current intensity at a specific positive voltage is comparable to the current intensity at the corresponding negative voltage. When there is no light illumination, the transistor is in the off state, but leakage current still flows, and the leakage current current-voltage characteristic curve is shown as curve B in the figure. The leakage current intensity during the positive voltage cycle is almost indistinguishable from the current intensity at the same voltage during the negative voltage cycle (i.e., "symmetrical"). For example, at +10 μV, the leakage current intensity is approximately +2.5 μA, corresponding to the intercept S3 on the ordinate axis, and at -10 μV, the leakage current intensity is approximately -2.5 μA, corresponding to the intercept S4 on the ordinate axis. Compared with the prior art in Figure 6A, the intensity of the positive leakage current is significantly reduced, the intensity of the positive and negative leakage currents is essentially equivalent, and the current-voltage characteristic curve is essentially symmetrical in both positive and negative cycles, thus significantly reducing or eliminating the possibility of electrochemical reactions.

[0058] As previously mentioned, the doping concentration and thickness of the collector region 108 and emitter region 105 can be adjusted, provided that the leakage current-voltage characteristic curve of transistor 126 shows substantially equal variation in the positive and negative leakage currents. That is, during the positive and negative voltage variation cycle of alternating current, when transistor 126 is not activated by light, the leakage current-voltage characteristic curve is substantially symmetrical in the positive and negative cycles. Therefore, the leakage current difference between the microfluidic fluid flowing through the microfluidic channel corresponding to transistor 126 and the micro-objects such as cells 118 therein is zero or substantially zero. In this document, the term "substantially zero" means that the difference in leakage current is small enough not to be considered to cause damage to the cells or other micro-objects of the microfluidic fluid, or to induce or exacerbate electrochemical reactions. For example, the difference could be about 1% to about 10% of the peak leakage current, or about 1% to about 5%, or about 1% to about 3%, or higher, or lower.

[0059] Figure 2 shows a phototransistor array according to another embodiment of the present invention, which can be used to form an optical tweezers device and a microfluidic device incorporating the optical tweezers device. As shown, the phototransistor array comprises an array of transistors 226, each transistor 226 being physically separated by an insulating layer 212 and an insulating barrier 220. The transistors 226 have a similar structure to transistor 126, except that the emitter region 205 differs from the emitter region 105 of transistor 126. In this embodiment, the emitter region 205 includes a first doped region 202 and a second doped region 204. The first doped region 202 and the second doped region 204 have the same doping type, and the first doped region 202 has a higher doping concentration than the second doped region 204. For example, both the first doped region 202 and the second doped region 204 contain N-type dopant, with the first doped region 202 being a heavily doped region N+ and the second doped region 204 being a lightly doped region N-.

[0060] The second doped region 204 extends laterally to adjacent insulating barriers 220a and 220b, and extends upward to insulating layers 212a and 212b adjacent to insulating barriers 220, surrounding the first doped region 202. The first doped region 202 extends laterally and abuts against the upward extension of the second doped region 204. Therefore, the first doped region 202 does not contact the insulating barriers 220a and 220b. Similarly, in this embodiment, the thickness of the emitter region 205 (or the thickness of the second doped region 204) is substantially the same as the thickness of the collector region 208. The relationship between the thickness of the first doped region 202 and the thickness of the second doped region 204 is described with reference to the description of the thickness relationship between the first doped region 102 and the second doped region 104, and will not be repeated here. The relationship between the thickness of the emitter region 205 and the thickness of the collector region 208 is described with reference to the description of the relationship between the thickness H1+H2 of the emitter region 105 and the thickness H4 of the collector region 108, and will not be repeated here. The relationship between the thickness of the second doped region 204 and the thickness of the collector region 208 is described in the same way as the relationship between the thickness H2 of the second doped region 104 and the thickness H4 of the collector region 108, and will not be repeated here. The doping concentrations and their relationships of the first doped region 202, the second doped region 204, and the collector region 208 are similar to those of the first doped region 102, the second doped region 104, and the collector region 108, and will not be repeated here.

[0061] The conductivity of emitter region 205 is substantially equal to that of collector region 208. Similarly, the thickness and doping concentration of emitter region 205 (including first doped region 202 and / or second doped region 204) and the thickness and doping concentration of collector region 208 can be adjusted as described above to coordinately increase or decrease the conductivity of emitter region 205 and collector region 208.

[0062] In this embodiment, the thickness of the first doped region 202 is approximately 150 nm, the thickness of the second doped region 204 is approximately 1,000 nm, the thickness of the base region 206 is approximately 5,000 nm, and the thickness of the collector region 208 is approximately 2,000 nm. In this embodiment, the doping concentration of the first doped region 202 is approximately 2 x 10⁻⁶. 17 cm -3 The doping concentration of the second doped region 204 is approximately 1 x 10⁻⁶. 17 cm -3 The doping concentration of base region 206 is approximately 1 x 10⁻⁶. 16 cm -3 The doping concentration of collector region 208 is approximately 2 x 10⁻⁶. 15 cm -3 .

[0063] The second doped region 204 extends upward to form a lateral width W1 on one side of the insulating layer 212a and a lateral width W2 on one side of the insulating layer 212b. The insulating layers 212a and 212b completely cover the lateral widths W1 and W2, and cover at least a portion of the first doped region 202. In this embodiment, the lateral widths W1 and W2 are substantially the same. The lateral widths W1 and W2 can be, for example, 100 nm to about 2,000 nm, or 100 nm to about 1,500 nm, or 100 nm to about 1,000 nm, or 100 nm to about 800 nm, or 100 nm to about 500 nm, or 100 nm to about 300 nm, or 100 nm to about 200 nm, or 100 nm to about 150 nm, or 300 nm to about 2,000 nm, or 300 nm to about 1,500 nm, or 300 nm to about 1,000 nm, or 300 nm to about 800 nm, or 300 nm to about 500 nm, or 500 nm to about 2,000 nm, or 500 nm to about 1,500 nm, or 500 nm to about 1,000 nm, or 500 nm to about 800 nm, or 1,000 nm to about 2,000 nm, or 1,000 nm to about 1,500 nm. nm, or 1,500 nm to about 2,000 nm. In this embodiment, both the lateral width W1 and the lateral width W2 are 500 nm.

[0064] The current-voltage characteristic curve of the phototransistor 226 provided in this embodiment is basically the same as that of the phototransistor 126 provided in the embodiment shown in Figure 1. For the sake of brevity, its current-voltage characteristic curve will not be repeated.

[0065] Figure 3 shows a phototransistor 326 according to another embodiment of the present invention, which can be used to form an optical tweezers device and a microfluidic device incorporating the optical tweezers device. As shown, the phototransistor array comprises an array of transistors 326, each transistor 326 being physically separated by an insulating layer 312 and an insulating barrier 320. The transistor 326 includes an emitter region 305, a base region 306, a collector region 308, and a substrate 310. The emitter region 305 includes a first doped region 302 and a second doped region 304. The first doped region 302 and the second doped region 304 have the same doping type, and the first doped region 302 has a higher doping concentration than the second doped region 304. For example, both the first doped region 302 and the second doped region 304 contain N-type dopant, the first doped region 302 being a heavily doped region N+, and the second doped region 304 being a lightly doped region N-.

[0066] The base region 306 extends laterally to adjacent insulating barriers 320a and 320b, and extends upward to insulating layers 312a and 312b adjacent to insulating barriers 320a and 320b, surrounding the first doped region 302 and the second doped region 304. The first doped region 302 and the second doped region 304 extend laterally and parallel to each other and abut against the upward extension of the base region 306. Therefore, the first doped region 302 and the second doped region 304 do not contact the insulating barriers 320a and 320b. The base region 306 contacts both the first doped region 302 and the second doped region 304.

[0067] Similarly, in this embodiment, the thickness of the emitter region 305 is substantially the same as the thickness of the collector region 308, or the thickness of the second doped region 304 is substantially the same as the thickness of the collector region 308. The relationship between the thickness of the first doped region 302 and the thickness of the second doped region 304 is described with reference to the description of the thickness relationship between the first doped region 102 and the second doped region 104, and will not be repeated here. The relationship between the thickness of the emitter region 205 and the thickness of the collector region 308 is described with reference to the description of the relationship between the thickness H1+H2 of the emitter region 105 and the thickness H4 of the collector region 108, and will not be repeated here. The relationship between the thickness of the second doped region 304 and the thickness of the collector region 308 is described with reference to the description of the relationship between the thickness H2 of the second doped region 104 and the thickness H4 of the collector region 108, and will not be repeated here. The doping concentrations and their relationships of the first doped region 302, the second doped region 304, and the collector region 308 are similar to those of the first doped region 102, the second doped region 104, and the collector region 108, and will not be repeated here.

[0068] The conductivity of emitter region 305 is substantially equal to that of collector region 308. Similarly, the thickness and doping concentration of emitter region 305 (including first doped region 302 and / or second doped region 304) and the thickness and doping concentration of collector region 308 can be adjusted as described above to coordinately increase or decrease the conductivity of emitter region 305 and collector region 308.

[0069] In this embodiment, the thickness of the first doped region 302 is approximately 500 nm, the thickness of the second doped region 304 is approximately 1,500 nm, the thickness of the base region 306 is approximately 1,000 nm, and the thickness of the collector region 308 is approximately 2,000 nm. In this embodiment, the doping concentration of the first doped region 302 is approximately 1 x 10⁻⁶. 18 cm -3 The doping concentration of the second doped region 304 is approximately 1 x 10⁻⁶. 17 cm -3 The doping concentration of base region 306 is approximately 1 x 10⁻⁶. 16 cm -3 The doping concentration of collector region 308 is approximately 2 x 10⁻⁶. 15 cm-3 .

[0070] The base region 306 extends upward and surrounds the first doped region 302 and the second doped region 304, forming a lateral width W3 on one side of the insulating layer 312a and a lateral width W4 on the other side of the insulating layer 312b. The insulating layers 312a and 312b completely cover the lateral widths W3 and W4, and cover at least a portion of the first doped region 302. In this embodiment, the lateral widths W3 and W4 are substantially the same size. The lateral widths W3 and W4 can be, for example, 100 nm to about 2,000 nm, or 100 nm to about 1,500 nm, or 100 nm to about 1,000 nm, or 100 nm to about 800 nm, or 100 nm to about 500 nm, or 100 nm to about 300 nm, or 100 nm to about 200 nm, or 100 nm to about 150 nm, or 300 nm to about 2,000 nm, or 300 nm to about 1,500 nm, or 300 nm to about 1,000 nm, or 300 nm to about 800 nm, or 300 nm to about 500 nm, or 500 nm to about 2,000 nm, or 500 nm to about 1,500 nm, or 500 nm to about 1,000 nm, or 500 nm to about 800 nm, or 1,000 nm to about 2,000 nm, or 1,000 nm to about 1,500 nm. nm, or 1,500 nm to about 2,000 nm. In this embodiment, both the lateral width W3 and the lateral width W4 are 500 nm. In other embodiments, the lateral width W3 and the lateral width W4 may have different dimensions.

[0071] In this embodiment, the base region 306 surrounding the emitter region 305 helps solve the leakage problem in the transistor that may be caused by manufacturing defects, i.e., the transistor's current-voltage characteristic curves are indistinguishable between the activated (e.g., under light) and inactive (e.g., in the absence of light) states. For example, one possible process defect is that during the ion implantation of dopant (e.g., P-type dopant) to form the base region 306, the P-type dopant (e.g., boron) may over-diffuse into the insulating barrier 320 (e.g., made of SiO2 material) at a location immediately adjacent to the insulating barrier 320, resulting in uneven doping concentrations or even no doping at the location adjacent to the insulating barrier 320 in the base region 306. This, in turn, leads to the formation of carrier channels from the emitter region to the aforementioned unevenly doped / undoped region to the collector region, bypassing the base region 306, resulting in the aforementioned leakage problem after voltage is applied.

[0072] In this embodiment, the base region 306 surrounds the emitter region 305, resulting in a larger contact area between the base region 306 and the insulating barrier 320. This facilitates more complete ion implantation, thereby reducing the likelihood of the aforementioned uneven doping and lowering or eliminating the risk of leakage. Furthermore, the base region 306 surrounds the emitter region 305, increasing the illumination area of ​​the base region 306 (the portion surrounding the emitter region 305), thus generating stronger current and DEP force, which is beneficial for manipulating micro-objects within the microfluidic channel.

[0073] Figure 6C The current-voltage characteristic curve of the transistor according to this embodiment is shown, with alternating current (AC) applied to the two electrodes of the optical tweezers device. When patterned light illuminates the transistor, the transistor is turned on, and its current-voltage characteristic curve is shown as curve A in the figure. At this time, the current intensity at the positive voltage is comparable to the current intensity at the corresponding negative voltage. When there is no light illumination, the transistor is in the off state, but leakage current still flows, and the leakage current current-voltage characteristic curve is shown as curve B in the figure. The leakage current intensity during the positive voltage cycle is almost the same as the current intensity at the same voltage during the negative voltage cycle. For example, at +10 μV, the leakage current intensity is approximately +1.5 μA, corresponding to the intercept S5 on the ordinate axis, and at -10 μV, the leakage current intensity is approximately -1.5 μA, corresponding to the intercept S6 on the ordinate axis. Compared with the prior art in Figure 6A, the intensity of the positive leakage current is significantly reduced, and the intensity of the positive and negative leakage currents is essentially equivalent, thus significantly reducing or eliminating the possibility of electrochemical reactions.

[0074] Figure 4 shows a phototransistor 426 according to another embodiment of the present invention, which can be used to form an optical tweezers device and a microfluidic device incorporating the optical tweezers device. As shown, the phototransistor array comprises an array of transistors 426, each transistor 426 being physically separated by an insulating layer 412 and an insulating barrier 420. The transistor 426 includes an emitter region 405, a base region 406, a collector region 408, and a substrate 410. The emitter region 405 includes a first doped region 402 and a second doped region 404. The first doped region 402 and the second doped region 404 have the same doping type, and the first doped region 402 has a higher doping concentration than the second doped region 404. For example, both the first doped region 402 and the second doped region 404 contain N-type dopant, the first doped region 402 being a heavily doped region N+, and the second doped region 404 being a lightly doped region N-.

[0075] The base region 406 extends laterally to adjacent insulating barriers 420a and 420b, and extends upward to insulating layers 412a and 412b adjacent to insulating barriers 420, surrounding the emitter region 405. The second doped region 404 extends laterally to the base region 406, and extends upward to insulating layers 412a and 412b adjacent to the base region 406, surrounding the first doped region 402. The first doped region 402 extends laterally and abuts against the upward extension of the second doped region 404. Therefore, neither the first doped region 402 nor the second doped region 404 contacts the insulating barriers 220a and 220b.

[0076] The base region 406 surrounds the second doped region 404 and its upward extension, and thus also surrounds the first doped region 402. The second doped region 404 is transverse and parallel to the first doped region 402, and the base region 406 extends and abuts against the upward extension of the base region 406. The base region 406 contacts the second doped region 404, but does not contact the first doped region 402.

[0077] The base region 406 extends upward and surrounds the first doped region 402 and the second doped region 404, forming a lateral width W5 adjacent to the insulating barriers 420a and 420b. The second doped region 404 extends upward and surrounds the first doped region 402, forming a lateral width W6 away from the insulating barriers 420a and 420b. The insulating layers 412a and 412b completely cover the lateral widths W5 and W6, and cover at least a portion of the first doped region 402.

[0078] The lateral widths W5 and W6 can be, for example, 100 nm to about 2,000 nm, or 100 nm to about 1,500 nm, or 100 nm to about 1,000 nm, or 100 nm to about 800 nm, or 100 nm to about 500 nm, or 100 nm to about 300 nm, or 100 nm to about 200 nm, or 100 nm to about 150 nm, or 300 nm to about 2,000 nm, or 300 nm to about 1,500 nm, or 300 nm to about 1,000 nm, or 300 nm to about 800 nm, or 300 nm to about 500 nm, or 500 nm to about 2,000 nm, or 500 nm to about 1,500 nm, or 500 nm to about 1,000 nm, or 500 nm to about 800 nm, or 1,000 nm to about 2,000 nm, or 1,000 nm to about 1,500 nm. nm, or 1,500 nm to about 2,000 nm. In this embodiment, both the lateral width W5 and the lateral width W4 are 500 nm. In other embodiments, the lateral widths W5 and W6 may have different dimensions.

[0079] Similarly, in this embodiment, the thickness of the emitter region 405 is substantially the same as the thickness of the collector region 408, or the thickness of the second doped region 404 is substantially the same as the thickness of the collector region 408. The relationship between the thickness of the first doped region 402 and the thickness of the second doped region 404 is described with reference to the description of the thickness relationship between the first doped region 102 and the second doped region 104, and will not be repeated here. The relationship between the thickness of the emitter region 405 and the thickness of the collector region 408 is described with reference to the description of the relationship between the thickness H1+H2 of the emitter region 105 and the thickness H4 of the collector region 108, and will not be repeated here. The relationship between the thickness of the second doped region 404 and the thickness of the collector region 408 is described with reference to the description of the relationship between the thickness H2 of the second doped region 104 and the thickness H4 of the collector region 108, and will not be repeated here. The doping concentrations of the first doped region 402, the second doped region 404, and the collector region 408 and their relationships are similar to those of the first doped region 102, the second doped region 104, and the collector region 108, and will not be repeated here.

[0080] The conductivity of emitter region 405 is substantially equal to that of collector region 408. Similarly, the thickness and doping concentration of emitter region 405 (including first doped region 402 and / or second doped region 404) and the thickness and doping concentration of collector region 408 can be adjusted as described above to coordinately increase or decrease the conductivity of emitter region 405 and collector region 408.

[0081] In this embodiment, the thickness of the first doped region 402 is approximately 500 nm, the thickness of the second doped region 404 is approximately 1,500 nm, the thickness of the base region 406 is approximately 500 nm, and the thickness of the collector region 408 is approximately 2,000 nm. In this embodiment, the doping concentration of the first doped region 302 is approximately 1 x 10⁻⁶. 18 cm -3 The doping concentration of the second doped region 404 is approximately 1 x 10⁻⁶. 17 cm -3 The doping concentration of base region 406 is approximately 1 x 10⁻⁶. 16 cm -3 The doping concentration of collector region 408 is approximately 2 x 10⁻⁶. 15 cm -3 .

[0082] The current-voltage characteristic curve of the phototransistor 426 provided in this embodiment is basically the same as that of the phototransistor 326 provided in the embodiment shown in Figure 3. For the sake of brevity, the current-voltage characteristic curve will not be repeated.

[0083] The transistor, optical tweezers device, and microfluidic device provided by this invention can be fabricated using conventional techniques in the art. Those skilled in the art, based on the current level of semiconductor manufacturing processes and in conjunction with the illustrations and descriptions in this specification, can fabricate the transistor of this invention without further explanation. This is merely an example. Figure 7 The schematic illustration shows a method 700 for manufacturing the phototransistor of the present invention.

[0084] Method 700 includes step 702, which provides a semiconductor substrate (e.g., silicon) comprising a doped substrate layer and an undoped layer thereon, the doped substrate layer being used to form the substrate in the embodiments of the present invention, and the undoped layer being used to form the collector region, base region, and emitter region in the embodiments of the present invention.

[0085] In step 704, a collector doped layer is formed adjacent to the doped substrate layer on the undoped layer. The collector doped layer forms the collector region in this embodiment of the invention. The collector doped layer and the doped substrate layer may have the same doping type (e.g., both are N-type doped), but may have different doping concentrations. For example, the collector doped layer may be a lightly doped layer, and the doped substrate layer may be a heavily doped layer. The semiconductor material obtained after step 704 includes the doped substrate layer and the collector doped layer.

[0086] Step 706 involves forming trenches in the obtained semiconductor material and filling the trenches with an electrically insulating material. The trenches penetrate the collector doped layer and extend into the doped substrate layer, thereby forming the insulating barrier in the embodiments of the present invention.

[0087] Furthermore, in step 708, a base doped layer is formed in the collector doped layer by ion implantation. The base doped layer has a different doping type (e.g., P-type doping) than the collector doped layer and the doped substrate layer. By controlling parameters such as the ion implantation time, speed, and implantation amount, the thickness of the formed base doped layer and collector doped layer can be controlled to meet the thickness requirements of the present invention.

[0088] In step 710, an emitter doped layer is formed in the base doped layer by ion implantation. The emitter doped layer has a different doping type (e.g., N-type doping) than the base doped layer. The emitter doped layer can be formed by separate ion implantation steps to form a first doped layer and a second doped layer with different doping concentrations. For example, the doping concentration of the first doped layer is higher than that of the second doped layer, to form the first doped region and the second doped region of the emitter region in this embodiment of the invention. Similarly, by controlling parameters such as the ion implantation time, speed, and implantation amount, the thickness of the formed first doped layer, second doped layer, and base doped layer can be controlled to meet the requirements of this invention for the thickness of each layer.

[0089] It is worth noting that although the doping type and doping level are shown in the figure, those skilled in the art will know that the NPN transistor shown can be replaced by a PNP transistor structure without affecting the achievement of the objectives of the various embodiments of the present invention.

[0090] The above descriptions are representative examples of embodiments of the present invention and are provided for illustrative purposes only. The present invention contemplates that one or more technical features used in one embodiment can be added to another embodiment to form improved or alternative embodiments without departing from the purpose of the embodiment. Similarly, one or more technical features used in one embodiment can be omitted or replaced without departing from the purpose of the embodiment to form alternative or simplified embodiments. Furthermore, one or more technical features used in one embodiment can be combined with one or more technical features in another embodiment without departing from the purpose of the embodiment to form improved or alternative embodiments. The present invention is intended to include all of the above-mentioned improved, alternative, and simplified technical solutions.

Claims

1. An optical tweezers device, comprising: First electrode; Second electrode; A phototransistor array located between a first electrode and a second electrode, the phototransistor array being composed of an array of phototransistors, each phototransistor being physically isolated from each other by an insulating layer and an insulating barrier, each phototransistor including a collector region, a base region and an emitter region on a substrate, the collector region and the emitter region having a first doping type, and the base region having a second doping type; as well as A microfluidic channel is formed between the first electrode and the phototransistor array; When an alternating current is applied between the first electrode and the second electrode, the phototransistor, in the absence of light, exhibits positive leakage current and negative leakage current during the positive and negative half-cycles of the alternating current, respectively. Its characteristic is that... The collector region and the emitter region have substantially equal conductivity, thereby the phototransistor has symmetrical positive and negative leakage currents, wherein the substantially equal conductivity means that the ratio of the conductivity of the emitter region to the conductivity of the collector region is 1:6 to 6:

1.

2. The optical tweezers device according to claim 1, characterized in that, The emission region includes a first doped region and a second doped region, wherein the doping concentration of the first doped region is higher than that of the second doped region.

3. The optical tweezers device according to claim 2, characterized in that, The first doped region has a first thickness, and the second doped region has a second thickness, wherein the ratio of the first thickness to the second thickness is 1:1 to 1:

30.

4. The optical tweezers device according to claim 3, characterized in that, The current collecting region has a third thickness, the emitting region has a fourth thickness, the fourth thickness is the sum of the first thickness and the second thickness, and the ratio of the third thickness to the fourth thickness is 1:5 to 5:

1.

5. The optical tweezers device according to claim 3, characterized in that, The current collecting region has a third thickness, and the ratio of the third thickness to the second thickness is 1:5 to 5:

1.

6. The optical tweezers device according to claim 2, characterized in that, The base region, the first doped region, and the second doped region extend laterally to the insulating barrier.

7. The optical tweezers device according to claim 2, characterized in that, The first doped region and the second doped region extend laterally, and the second doped region at least partially surrounds the first doped region.

8. The optical tweezers device according to claim 7, characterized in that, The second doped region surrounds the first doped region with a first lateral width of 100 nm to 2,000 nm.

9. The optical tweezers device according to claim 2, characterized in that, The base region, the first doped region, and the second doped region extend laterally, and the base region at least partially surrounds the first doped region and the second doped region.

10. The optical tweezers device according to claim 9, characterized in that, The base region surrounds the first doped region and the second doped region with a second lateral width of 100 nm to 2,000 nm.

11. The optical tweezers device according to claim 2, characterized in that, The base region, the first doped region, and the second doped region extend laterally, with the base region at least partially surrounding the first doped region and the second doped region, and the second doped region at least partially surrounding the first doped region.

12. The optical tweezers device according to claim 11, characterized in that, The base region surrounds the first doped region and the second doped region with a second lateral width of 100 nm to 2,000 nm, and the second doped region surrounds the first doped region with a first lateral width of 100 nm to 2,000 nm.

13. The optical tweezers apparatus according to any one of claims 2 to 12, characterized in that, The current collector region and the second doped region have substantially the same doping concentration, wherein the substantially the same doping concentration means a doping concentration ratio of 1:10 to 10:

1.

14. The optical tweezers device according to claim 13, characterized in that, The doping concentration of the current collector region and the second doped region is 10. 15 Up to 10 18 cm -3 .

15. The optical tweezers apparatus according to any one of claims 2 to 12, characterized in that, The doping concentration of the first doped region is 10. 18 Up to 10 21 cm -3 .

16. The optical tweezers device according to claim 3, characterized in that, The first thickness is 100 to 1,000 nm.

17. The optical tweezers device according to claim 3, characterized in that, The second thickness is 500 to 3,000 nm.

18. The optical tweezers apparatus according to any one of claims 1 to 12, characterized in that, The thickness of the base region is 100 to 5,000 nm.

19. The optical tweezers apparatus according to any one of claims 1 to 12, characterized in that, The ratio of the conductivity of the transmitting region to the conductivity of the collecting region is 1:5 to 5:1, 1:3 to 3:1, 1:2 to 2:1, 1:1.2 to 1.2:1, 1:1.1 to 1.1:1, or 1:

1.

20. The optical tweezers apparatus according to any one of claims 2 to 12, characterized in that, The substrate has the same doping concentration as the first doped region.

21. The optical tweezers apparatus according to any one of claims 1 to 12, characterized in that, The resistivity of the substrate is from 0.001 to 0.05 ohm-cm.

22. The optical tweezers apparatus according to any one of claims 1 to 12, characterized in that, The first doping type is N-type doping, and the second doping type is P-type doping.

23. The optical tweezers apparatus according to any one of claims 1 to 12, characterized in that, The microfluidic channel is filled with a liquid sample having an electrical conductivity of 1 to 10 mS / cm.

24. The optical tweezers device according to claim 23, characterized in that, The liquid sample is a cell culture medium or a physiological solution.

25. The optical tweezers device according to claim 24, characterized in that, The cell culture medium or physiological solution contains cells.

26. The optical tweezers apparatus according to any one of claims 1 to 12, characterized in that, The launch area consists of a plurality of sub-launch areas.

27. A microfluidic device, comprising a control system, an optical pattern generation system, an image acquisition system, and an optical tweezers device, characterized in that, The optical tweezers device is the optical tweezers device according to any one of claims 1 to 26.

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