Optimization method for resisting emitter crowding effect of wide-working-interval photo-transistor

Abstract

The invention discloses an anti-emitter crowding effect optimization method for a wide-working-interval photo-transistor, which comprises the following steps of: forming non-uniform emitter metal contact on the upper surface of an emitter region of the transistor through non-uniform contact window distribution, and arranging a plurality of independent emitter units to form a multi-emitter structure so as to increase the total contact area; the emitter units follow the non-uniform design principle, the unit number density of the center area of the emitter region is higher than that of the edge area, and the area of a single unit can be adjusted according to the current crowding degree, so that the current density of the center area of the emitter contact is higher than that of the edge area. And the number of current injection channels in the central region and the single-channel bearing capacity are doubly improved, so that the bias voltage non-uniformity of the emitter junction caused by the resistance of the base region is compensated. According to the invention, the current distribution uniformity of the photo-transistor under a large-current working condition can be obviously improved, the linear working interval and the dynamic range of the photo-transistor are effectively widened, the maximum output current capability and the reliability are improved, and the current gain does not need to be sacrificed.

Description

Technical Field

[0001] This invention relates to the field of phototransistor optimization, and more specifically, to an optimization method for resisting emitter crowding effects in a phototransistor with a wide operating range. Background Technology

[0002] Phototransistors, as a common photodetector, are widely used in optical communication, sensing, and automatic control fields because they combine the amplification function of transistors with the photoelectric conversion function of photodiodes. Traditional phototransistors typically inject photogenerated carriers into the base region of the transistor, and through the current amplification of the transistor, achieve a photocurrent gain much higher than that of photodiodes.

[0003] However, with the development of application requirements, especially in scenarios requiring high brightness or high current output, the performance of traditional phototransistors has revealed significant limitations. The core problem lies in the "emitter crowding effect" (also known as the base resistance self-biasing effect). When the transistor operates at high current, the lateral current flowing through the base resistor generates a significant voltage drop, causing the bias voltage of the emitter junction to gradually decrease from the edge to the center. This results in a high concentration of emitter current density at the edge of the emitter region, while injection is almost impossible in the central region. This uneven current distribution is known as the emitter crowding effect.

[0004] Therefore, we have made improvements and proposed an optimization method for resisting emitter crowding effect in phototransistors with a wide operating range. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention aims to provide an optimization method for resisting emitter crowding effects in phototransistors with a wide operating range. This system achieves high-precision, low-latency, and personalized real-time early warning of myocardial infarction risk at home through a cloud-edge collaborative deployment approach, combined with light-heavy model collaboration and multimodal data fusion.

[0006] To achieve the above-mentioned objectives, this invention provides an optimization method for resisting emitter crowding effects in a wide-operating-range phototransistor, thereby solving the aforementioned problems.

[0007] The present invention is as follows: It includes a collector region, a base region, and an emitter region, characterized in that a non-uniform emitter metal contact is formed on the upper surface of the emitter region; the non-uniform contact is configured such that the current density flowing into the emitter contact is higher in the central region of the emitter region than in the edge region, in order to compensate for the non-uniformity of the emitter junction bias caused by the base region resistance. The upper surface of the emission region is provided with a plurality of independent emitter units, forming a multi-emitter structure to increase the total contact area of the emitter metal and the emission region; the distribution of the plurality of emitter units follows the principle of non-uniform design, that is, the number density of the emitter units in the central region of the emission region is higher than that in the edge region, and the area of a single emitter unit can be adaptively adjusted according to the current crowding degree, and the area of a single emitter unit in the central region can be greater than or equal to that in the edge region, further strengthening the central priority characteristic of current injection.

[0008] As a preferred technical solution of the present application, the non-uniform emitter metal contact is realized by a non-uniform contact window distribution, and the number of contact windows of the emitter units in the central region is more than that in the edge region. Combined with the increased total contact area of the multi-emitter, the number of current injection channels in the central region and the single channel carrying capacity are doubled, further compensating for the emission junction bias voltage caused by the base resistance.

[0009] As a preferred technical solution of the present application, the distribution density of the contact window continuously or stepwise increases from the edge to the center of the emission region.

[0010] As a preferred technical solution of the present application, the non-uniform emitter metal contact is realized by a gradient distribution of metal-semiconductor contact resistance; wherein the contact resistance in the central region of the emission region is lower than that in the edge region of the emission region.

[0011] As a preferred technical solution of the present application, the gradient distribution of the contact resistance is realized by selectively doping the surface layer of the emission region, so that the doping concentration in the central region is higher than that in the edge region.

[0012] As a preferred technical solution of the present application, the non-uniform emitter metal contact is realized by simultaneously using a non-uniform contact window distribution and a gradient distribution of the contact resistance.

[0013] As a preferred technical solution of the present application, a method for optimizing the anti-emitter crowding effect of a wide working interval photosensitive transistor is characterized in that it specifically comprises the following steps: Device structure modeling and analysis step: determine the emitter current crowding degree of the photosensitive transistor under the target working current through modeling and simulation; Non-uniform contact pattern design step: based on the simulation results, design a non-uniform emitter contact pattern for compensating the current crowding degree; Process implementation step: according to the designed pattern, form the non-uniform emitter contact structure through semiconductor manufacturing process.

[0014] As a preferred technical solution of the present application, the upper surface of the emission region of the photosensitive transistor has a non-uniform emitter metal contact structure.

[0015] As a preferred technical solution of the present application, an optoelectronic detection circuit comprises the photosensitive transistor as claimed in claim 8 Compared with the prior art, the present application has the following beneficial effects: 1. Significantly suppresses crowding effect: fundamentally improves the current density distribution under the emission region, so that the central region of the emission region can also be effectively utilized under large injection conditions.

[0016] 2. Widens the linear operating range: the output photocurrent of the device and the incident light intensity maintain a good linear relationship in a wider range, and the dynamic range is greatly improved.

[0017] 3. Increases the maximum output current capacity: due to uniform current distribution, premature saturation or thermal failure of the edge region is avoided, and the maximum safe operating current of the device is improved.

[0018] 4. Without sacrificing current gain: the method is mainly realized by changing the metal contact design, without significantly increasing the base region doping concentration, so that a high current gain can be maintained.

[0019] 5. Good process compatibility: the method can be realized by modifying the contact hole mask design without changing the core device process (such as ion implantation and diffusion), and is easy to integrate into the existing semiconductor manufacturing process. BRIEF DESCRIPTION OF DRAWINGS

[0020] Figure 1 A device structure modeling and current crowding analysis flowchart of the anti-emitter crowding effect optimization method of the wide operating range photosensitive transistor provided by the present application; Figure 2 A non-uniform contact pattern design flowchart of the anti-emitter crowding effect optimization method of the wide operating range photosensitive transistor provided by the present application; Figure 3 A process implementation and performance verification flowchart of the anti-emitter crowding effect optimization method of the wide operating range photosensitive transistor provided by the present application.

[0021] Indicated in the figure: DETAILED DESCRIPTION In order to enable those skilled in the art to better understand the present application, the technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, not all. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor should be within the scope of protection of the present application.

[0022] In order to better understand the technical scheme of the present application, the technical scheme in the embodiments of the present application will be clearly and completely described below with reference to the drawings.

[0023] It should be noted that the embodiments in the present application and the features and technical solutions in the embodiments can be combined with each other without conflict.

[0024] It should be noted that: similar reference numerals and letters represent similar items in the following drawings, so once an item is defined in one drawing, it does not need to be further defined and explained in subsequent drawings.

[0025] A method for optimizing the anti-emitter crowding effect of a wide operating range phototransistor, the phototransistor comprising a collector region, a base region and an emitter region, characterized in that a non-uniform emitter metal contact is formed on the upper surface of the emitter region; the non-uniform contact is configured so that the current density flowing from the emitter contact is higher in the central region of the emitter region than in the edge region, to compensate for the non-uniformity of the emitter junction bias caused by the base resistance; A plurality of independent emitter units are provided on the upper surface of the emitter region to form a multi-emitter structure to increase the total contact area of the emitter metal and the emitter region; the distribution of the plurality of emitter units follows the principle of non-uniform design, that is, the number density of the emitter units in the central region of the emitter region is higher than that in the edge region, and the area of a single emitter unit can be adaptively adjusted according to the degree of current crowding, and the area of a single emitter unit in the central region can be greater than or equal to that in the edge region, further strengthening the central priority characteristic of current injection.

[0026] The traditional uniform contact passively conforms to the non-uniformity of the high edge voltage and low central voltage of the emitter junction caused by the base resistance, thereby exacerbating the current crowding. The present scheme, on the contrary, artificially creates a lower contact impedance in the center of the emitter region by designing a non-uniform contact, and actively guides more current to flow from the central region. In this way, the "high central current density" effect introduced by the contact design can exactly offset the "high edge current density" crowding effect caused by the base resistance, thereby achieving uniform distribution of current as a whole.

[0027] The non-uniform emitter metal contact is realized by a non-uniform distribution of contact windows, and the number of contact windows of the emitter units in the central region is greater than that in the edge region, in combination with the increased total contact area of the multi-emitter, so that the number of current injection channels in the central region and the single-channel carrying capacity are both improved, further compensating for the non-uniformity of the emitter junction bias caused by the base resistance; The multi-emitter structure increases the total contact area, which, in combination with a higher window density or lower contact resistance in the central region, allows more current to be injected into the channel, further reducing the difference in current density between the center and the edge. The larger contact area reduces the current carrying pressure per unit area and reduces the energy loss caused by contact resistance, allowing more current to be effectively injected into the emitter region. In combination with the guiding effect of the non-uniform design, the injection efficiency is significantly improved. The increased contact area disperses the current load in the edge region, preventing local current over-concentration that can cause thermal failure or saturation. In combination with the optimization of the anti-crowding effect, the device can operate stably in a larger current range.

[0028] The contact window is regarded as a current channel from the metal to the semiconductor. More and denser contact windows are arranged in the central region, which is equivalent to providing more parallel low-resistance paths for current in the central region, resulting in a significant reduction in the total contact resistance of the region. According to the principle that current will prefer low-resistance paths, a larger proportion of current will naturally be "absorbed" from the central region, thereby balancing the current crowding in the edge.

[0029] The distribution density of the contact window increases continuously or stepwise from the edge of the emitter region to the center.

[0030] The lateral voltage drop and current density variation caused by the base resistance can be continuous or non-uniform. The use of continuous or stepwise increasing density design can better "match" the intensity distribution of the contact resistance compensation effect and the crowding effect. This can more finely and smoothly regulate the current density than the simple "dense center and sparse edge" two-zone division, achieving optimal uniformization under the entire emitter junction surface and avoiding the creation of new points of current non-uniformity.

[0031] The non-uniform emitter metal contact is achieved through a gradient distribution of the metal-semiconductor contact resistance, wherein the contact resistance in the central region of the emitter region is lower than the contact resistance in the edge region of the emitter region.

[0032] The size of the metal-semiconductor contact resistance directly determines the ease of current flow. By making the contact resistance in the central region lower than the edge, it is equivalent to directly reducing the "threshold" of current injection in the central region on a physical level. Current will instinctively flow to the area with a lower threshold, thereby achieving the same effect of guiding current to the center as the density gradient design.

[0033] The gradient distribution of the contact resistance is achieved by selectively doping the surface layer of the emitter region, so that the doping concentration in the central region is higher than that in the edge region.

[0034] In semiconductor process, metal and heavily doped semiconductor can form better ohmic contact, and the contact resistance is also lower. Therefore, by selectively doping the surface layer of the emitter region, the central region has a higher doping concentration than the edge region, which can directly and effectively achieve the design goal of lower contact resistance in the central region than in the edge region, and is a specific and reliable process means for realizing the scheme of claim 4.

[0035] The non-uniform emitter metal contact is realized by combining the non-uniform contact window distribution and the gradient distribution of the contact resistance.

[0036] Combining the two ways of contact window density gradient and contact resistance gradient is equivalent to optimizing the current injection capability of the central region from two dimensions of "quantity" (more parallel paths) and "quality" (low impedance of single path). The two effects are multiplied, which can produce a "1+1>2" synergistic effect, so as to cope with more severe crowding effect challenges, or obtain better current uniformity under the same process difficulty.

[0037] A method for optimizing the anti-emitter crowding effect of a wide working range photosensitive transistor, Specifically comprising the following steps: Device structure modeling and analysis step: through modeling and simulation, the degree of emitter current crowding of the photosensitive transistor under the target working current is determined; Non-uniform contact pattern design step: based on the simulation results, a non-uniform emitter contact pattern for compensating the degree of current crowding is designed; Process implementation step: according to the designed pattern, a non-uniform emitter contact structure is formed through semiconductor manufacturing process.

[0038] First, the problem (crowding degree) is quantified by modeling and simulation, then targeted and quantitative design (design compensation pattern) is carried out based on the simulation results, and finally it is realized through process. This ensures that the optimization scheme is not blind, but has a clear goal and predictable effect, greatly improving the success rate and optimization efficiency of the design.

[0039] A method for optimizing the anti-emitter crowding effect of a wide working range photosensitive transistor, The upper surface of the emitter region of the photosensitive transistor has a non-uniform emitter metal contact structure.

[0040] The physical structure (non-uniform contact) itself embeds the ability to resist crowding effect. When the device is working, without external circuit or control, its unique electrode structure can automatically and real-time adjust the internal current density distribution according to the total current, so that it can maintain a relatively uniform distribution in the entire working range (especially under large current), thereby playing the performance advantages of high linearity, large dynamic range and high voltage swing.

[0041] A photodetection circuit comprising the phototransistor of claim 8.

[0042] Since the phototransistor used itself has a wide linear working range and the ability to resist crowding effect, the entire circuit can output an electrical signal with less distortion and better linearity when processing large amplitude optical signals or requiring high fidelity conversion, thereby improving the performance and reliability of the entire circuit system.

[0043] Embodiment one: The metal contact on the emitter region of the traditional phototransistor structure is uniformly distributed. When the working current is large, the lateral current Ib in the base region produces a voltage drop on the base resistance Rb, so that the bias voltage Vbe1 at the edge of the emitter junction (such as position P1) is higher than the bias voltage Vbe2 at the center (such as position P2), resulting in a current density J1 much larger than J2, forming a serious current crowding.

[0044] Embodiment one of the present application provides an optimized phototransistor structure. It includes: The semiconductor substrate is usually N-type lightly doped as the collector region.

[0045] The base region is formed in the collector region by P-type doping.

[0046] The emitter region is formed in the base region by N-type heavy doping.

[0047] The emitter metal realizes ohmic contact with the emitter region through the contact window.

[0048] The key improvement of this embodiment is that the distribution of the contact window is non-uniform. In the central region (C) of the emitter region, the distribution density of the contact window is high (i.e. the number of windows is large and the spacing d1 is small); and from the center to the edge (E), the distribution density of the contact window gradually decreases (i.e. the number of windows decreases, the spacing d2 increases, and d2>d1). This density gradient design makes the current flowing from the emitter metal encounter a lower contact resistance path in the central region, so it is more inclined to inject from the central region. This "central injection" current offsets the "edge priority" injection trend caused by the base resistance, so that the current density distribution under the entire emitter junction becomes more uniform.

[0049] Embodiment two: Embodiment two of the present application provides another way to achieve non-uniform contact. In this embodiment, the distribution of the emitter contact windows can be uniform, but the contact resistance is made to have a gradient distribution in the semiconductor layer. Specifically, before forming the emitter contact, an additional mask and ion implantation step can be used to selectively dope the surface layer of the emitter region. The doping concentration of the center region (C') is made to be higher than that of the edge region (E'). Since the contact resistance is inversely proportional to the doping concentration, the metal-semiconductor contact resistance Rc1 of the center region (C') will be lower than the contact resistance Rc2 of the edge region (E'). This difference in contact resistance can also achieve the purpose of guiding the current to the center region, thereby suppressing the crowding effect.

[0050] A method for optimizing the anti-emitter crowding effect of a wide operating range photosensitive transistor, the photosensitive transistor comprising a collector region, a base region and an emitter region, characterized in that a non-uniform emitter metal contact is formed on the upper surface of the emitter region; the design of the non-uniform contact makes the current density flowing from the emitter contact higher in the center region of the emitter region than in the edge region, to compensate for the non-uniformity of the emitter junction bias caused by the base region resistance.

[0051] Working principle Specifically, the optimization method comprises the following steps: Device structure modeling and analysis step: establish a photosensitive transistor SPICE model or a two-dimensional / three-dimensional physical model containing the base region resistance and the emitter junction diode characteristics, analyze the lateral bias distribution and current density distribution of the emitter junction under different total emitter currents through simulation, and determine the severity of the crowding effect.

[0052] Non-uniform contact pattern design step: based on the analysis results of step 1, design the pattern of the emitter metal contact. The non-uniform contact is achieved by at least one of the following ways: Contact window density gradient distribution: in the layout design of the upper surface of the emitter region, the distribution density of the emitter contact windows (Contact Hole) is set to gradually increase from the edge to the center of the emitter region. That is, the center region has more contact windows and smaller spacing, while the edge region has fewer contact windows and larger spacing.

[0053] Contact resistance gradient distribution: on the upper surface of the emitter region, the metal-semiconductor contact resistance of the center region of the emitter region is made to be lower than that of the edge region by changing the doping concentration of the semiconductor surface or using different metallization processes.

[0054] Composite structure: combine the above two ways, and use both the contact window density gradient and the contact resistance gradient.

[0055] Process implementation step: according to the figure designed in step 2, the non-uniform emitter contact structure is formed by using semiconductor manufacturing process.

[0056] The core idea of the present application is to counteract the crowding effect itself by artificially creating an "unbalanced current distribution" that is opposite to the crowding effect. The traditional uniform contact aggravates the crowding effect because the edge contact points are more likely to draw current from the low resistance path. The non-uniform contact of the present application, by providing lower total contact resistance (or more parallel contact points) in the center region, guides more current to flow from the center region, thus forcing the current to be more evenly distributed under the emitter region. When properly designed, the compensation effect introduced by this non-uniform contact can reach a dynamic balance with the crowding effect caused by the base region resistance within a wide range of current In the present application, unless otherwise clearly specified and limited, the terms "mounting", "connecting", "connecting", "fixing" and the like should be understood broadly, for example, it can be fixed connection, or detachable connection, or integrated; it can be mechanical connection, or electrical connection or communication with each other; it can be directly connected, or indirectly connected through intermediate medium, it can be the internal communication of two elements or the interaction relationship between two elements, unless otherwise clearly limited. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances. Obviously, the above described embodiments are only a part of the embodiments of the present application, not all the embodiments, and the preferred embodiments of the present application are given in the drawings, but do not limit the patent scope of the present application. The present application can be realized in many different forms, and on the contrary, the purpose of providing these embodiments is to make the disclosure of the present application more thorough and comprehensive. Although the present application has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions recorded in the foregoing embodiments, or make equivalent replacement for part of the technical features. Any equivalent structure made by using the content of the present application specification and drawings, directly or indirectly used in other related technical fields, is also within the patent protection scope of the present application.

Claims

1. A method for optimizing the anti-emitter crowding effect of a phototransistor with a wide operating range, wherein the phototransistor comprises a collector region, a base region, and an emitter region, characterized in that, A non-uniform emitter metal contact is formed on the upper surface of the emitter region; the non-uniform contact is configured such that the current density flowing into the emitter contact is higher in the central region of the emitter region than in the edge region, in order to compensate for the non-uniformity of the emitter junction bias caused by the base region resistance. Multiple independent emitter units are arranged on the upper surface of the emitter region to form a multi-emitter structure, thereby increasing the total contact area between the emitter metal and the emitter region. The distribution of the multiple emitter units follows a non-uniform design principle, that is, the number density of emitter units in the central region of the emitter region is higher than that in the edge region, and the area of ​​a single emitter unit can be adaptively adjusted according to the degree of current congestion. The area of ​​a single emitter unit in the central region can be greater than or equal to that in the edge region, further enhancing the center-priority characteristic of current injection.

2. The optimization method for resisting emitter crowding effect of a wide operating range phototransistor according to claim 1, characterized in that, The non-uniform emitter metal contact is achieved through a non-uniform contact window distribution, and the number of contact windows of the emitter unit in the central region is greater than that in the edge region. Combined with the increased total contact area of ​​multiple emitters, the number of current injection channels and the single-channel carrying capacity in the central region are both improved, further compensating for the uneven emitter junction bias caused by the base resistance.

3. The optimization method for resisting emitter crowding effect of a wide operating range phototransistor according to claim 2, characterized in that, The distribution density of the contact windows increases continuously or in a stepped manner from the edge of the emission area towards the center.

4. The optimization method for resisting emitter crowding effect of a wide operating range phototransistor according to claim 1, characterized in that, The non-uniform emitter metal contact is achieved through a gradient distribution of metal-semiconductor contact resistance; wherein the contact resistance located in the central region of the emitter region is lower than the contact resistance located in the edge region of the emitter region.

5. The optimization method for resisting emitter crowding effect of a wide operating range phototransistor according to claim 4, characterized in that, The gradient-distributed contact resistance is achieved by selectively doping the surface layer of the emitter region, such that the doping concentration in the central region is higher than that in the edge region.

6. The optimization method for resisting emitter crowding effect of a wide operating range phototransistor according to claim 1, characterized in that, The non-uniform emitter metal contact is achieved by employing a combination of non-uniform contact window distribution and gradient distribution of contact resistance.

7. A method for optimizing the anti-emitter crowding effect of a wide operating range phototransistor according to any one of claims 1-6, characterized in that, Specifically, the following steps are included: Device structure modeling and analysis steps: Through modeling and simulation, determine the degree of emitter current congestion of the phototransistor under the target operating current; Non-uniform contact pattern design steps: Based on the simulation results, design a non-uniform emitter contact pattern to compensate for the degree of current congestion; Process implementation steps: Based on the designed pattern, the non-uniform emitter contact structure is formed through semiconductor manufacturing processes.

8. A phototransistor, optimized using the anti-emitter crowding effect optimization method for a wide operating range phototransistor as described in any one of claims 1-7, characterized in that, The phototransistor has a non-uniform emitter metal contact structure on the upper surface of its emitter region.

9. A photoelectric detection circuit, characterized in that, It includes the phototransistor as described in claim 8.

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