Method for pn junction region detection

Abstract

The application discloses a PN junction area detection method, comprising the following steps: sequentially heating different areas of a semiconductor device, the semiconductor device comprising a conductive loop and P-type semiconductor and N-type semiconductor connected to the conductive loop; detecting the current in the conductive loop after each heating; based on the detected current in the conductive loop generated based on the heating, identifying a target area corresponding to the heated area in an optical image of the semiconductor device. Compared with the method of atomic force microscope detection, the application does not need to use a detection probe, is not affected by the number of uses and the degree of wear of the probe, helps to reduce errors, realizes stable detection, does not need to detect the topographic features of the semiconductor device, thus does not need to perform delayering treatment, can check steps, improves efficiency, can perform large-range defect positioning, also can improve detection efficiency, and can directly develop the PN junction area in the optical image, which is convenient for detection personnel to check.

Description

Technical Field

[0001] This invention relates to the field of integrated circuit testing, and in particular to a method for detecting PN junction regions. Background Technology

[0002] In some analytical scenarios, it is necessary to identify the location of PN junction regions on semiconductor devices. Atomic force microscopy (AFM) is commonly used for this purpose. The principle is that when the distance between atoms decreases to a certain extent, the interatomic force increases rapidly. The height of the sample surface can be calculated based on the force exerted on the microprobe, thus obtaining the morphological characteristics of the sample surface. Then, the PN junction region is identified based on these morphological characteristics. Specifically, one end of a microcantilever, which is extremely sensitive to weak forces, is fixed, and the tip of the other microprobe is brought close to the sample. The microcantilever deforms or changes its motion state under the influence of interatomic forces. Sensors detect these changes to obtain surface morphology and roughness information. However, this method has the following drawbacks:

[0003] 1. The quality of the obtained images is affected by probe wear and the number of times it is used, which can easily lead to errors;

[0004] 2. Atomic force microscopy detects morphological features, therefore it requires delamination of the sample down to the substrate layer before detection, which increases the number of process steps;

[0005] 3. It can only perform detection at the micrometer level and within a small area;

[0006] 4. Defects that do not involve changes in morphology (such as defects with abnormal semiconductor doping concentration) cannot be detected.

[0007] Therefore, there is an urgent need for a method for detecting PN junction regions that can at least solve one of the aforementioned problems. Summary of the Invention

[0008] This invention aims to at least solve one of the technical problems existing in the prior art. To this end, this invention proposes a method for detecting PN junction regions, which can ensure detection accuracy and improve detection efficiency.

[0009] The PN junction region detection method according to the first embodiment of the present invention includes the following steps:

[0010] Different regions of a semiconductor device are heated sequentially, the semiconductor device comprising a conductive loop and P-type and N-type semiconductors connected in the conductive loop;

[0011] Each heating cycle detects the current generated by heating within the conductive loop.

[0012] Based on the current detected in the conductive loop, the target region corresponding to the heating region in the optical image of the semiconductor device is identified.

[0013] The PN junction region detection method according to the first embodiment of the present invention has at least the following beneficial effects:

[0014] Compared with atomic force microscopy, this invention does not require the use of a detection probe, is not affected by the number of times the probe is used or its wear, helps to reduce errors and achieve stable detection; it does not require the detection of the morphological features of semiconductor devices, so delamination is not required, allowing for inspection steps and improving efficiency; it can perform large-scale defect localization, which also improves detection efficiency; and it can directly image the PN junction area in the optical image, making it convenient for inspection personnel to view.

[0015] In other embodiments of the present invention, the method for marking on the optical image includes one of the following:

[0016] The target area is identified by a set color;

[0017] The target area is marked with a set grayscale value.

[0018] In other embodiments of the present invention, the method for acquiring the optical image includes:

[0019] The semiconductor device is scanned sequentially to obtain multiple local images corresponding to each of the target regions;

[0020] The individual local images are aggregated to form an overall image of the semiconductor device.

[0021] In other embodiments of the present invention, the method for scanning the semiconductor device includes at least one of the following:

[0022] The scan time for a single local image is 4 μs to 8 μs;

[0023] The length and width of the local image range from 50 μm to 2750 μm.

[0024] In other embodiments of the present invention, the method for heating the semiconductor device includes:

[0025] The semiconductor device is heated by a laser light source.

[0026] In other embodiments of the present invention, the parameters of the laser source satisfy at least one of the following:

[0027] The power ranges from 48mW to 80mW;

[0028] The length of the laser spot ranges from 0.507 μm to 5.08 μm, and the width ranges from 0.507 μm to 5.08 μm.

[0029] In other embodiments of the present invention, the method for detecting the current in the conductive loop includes:

[0030] Select the corresponding pin on the semiconductor device according to the conductive loop;

[0031] Connect the pin to the corresponding interface of the detection device.

[0032] In other embodiments of the present invention, the PN junction region detection method further includes the following steps:

[0033] Identify the ground pin of the semiconductor device and the noise reduction interface of the detection equipment;

[0034] Connect the ground pin electrically to the noise reduction interface.

[0035] In other embodiments of the present invention, the parameters of the detection device satisfy at least one of the following:

[0036] The voltage applied to the conductive loop is 0V;

[0037] When the current detected by the detection device is greater than 20nA, the current value is limited to 20nA.

[0038] In other embodiments of the present invention, the following steps are included before heating the semiconductor device:

[0039] Remove the mold covering the outside of the semiconductor device;

[0040] The passivation layer on the semiconductor device is thinned.

[0041] The PN junction region detection method according to a second embodiment of the present invention includes the following steps:

[0042] Different regions of a semiconductor device are heated sequentially, the semiconductor device comprising a conductive loop and P-type and N-type semiconductors connected in the conductive loop;

[0043] Each heating cycle detects the current generated by heating within the conductive loop.

[0044] Based on the magnitude of the current value detected in the conductive loop, a target region corresponding to the heating region is marked in the optical image of the semiconductor device. The marked target region is a region with abnormal doping concentration.

[0045] In other embodiments of the present invention, the method for identifying the target area includes:

[0046] To obtain a reference range of current generated by the same semiconductor with normal doping concentration under the same detection conditions;

[0047] The actual measured current value in the loop is compared with the reference range. If the actual measured current value deviates from the reference range, the target area is marked.

[0048] Compared to atomic force microscopy (AFM) methods, this invention eliminates the need for a detection probe, is unaffected by probe usage frequency or wear, helps reduce errors, and achieves stable detection. It also eliminates the need to examine the morphological features of semiconductor devices, thus avoiding delamination and improving efficiency. Furthermore, it enables large-scale defect localization, further enhancing detection efficiency. The invention allows direct imaging of the PN junction region in optical images, facilitating inspection by personnel. In addition, this invention can detect abnormal ion doping concentrations within semiconductors.

[0049] In other embodiments of the present invention, the method for identifying the target area includes:

[0050] Whether the actual measured current value is greater than or less than the reference range, the target area will be marked in the same way.

[0051] Alternatively, if the actual measured current value is greater than the reference range, the target area is marked with a first identifier; if the actual measured current value is less than the reference range, the target area is marked with a second identifier.

[0052] Alternatively, when the actual measured current value is greater than the reference range, the target area is marked with a third identifier, which can change synchronously with the offset between the actual measured current value and the reference range. When the actual measured current value is less than the reference range, the target area is marked with a fourth identifier, which can change synchronously with the offset between the actual measured current value and the reference range.

[0053] Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0054] The present invention will be further described below with reference to the accompanying drawings and embodiments, wherein:

[0055] Figure 1 An optical image of a semiconductor device obtained based on the detection method of the first embodiment of the present invention;

[0056] Figure 2 The image is obtained by the detection device using standard parameters;

[0057] Figure 3 The image is obtained by the detection device when using the parameters in the embodiment;

[0058] Figure 4 This is an optical image of a semiconductor device obtained based on the detection method of the second embodiment of the present invention, showing areas with abnormal doping concentration.

[0059] Figure 5 The image shows an optical image of a semiconductor device obtained using the detection method of the second embodiment of the present invention. The semiconductor doping concentration in the image is normal.

[0060] Figure 6 for Figure 4 Image of a semiconductor device after etching;

[0061] Figure 7 for Figure 5 Image of a semiconductor device after etching.

[0062] Figure label:

[0063] P-type semiconductor 100;

[0064] N-type semiconductor 200. Detailed Implementation

[0065] Embodiments of the present invention are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention.

[0066] In the description of this invention, it should be understood that the orientation descriptions, such as up, down, front, back, left, right, etc., are based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limiting this invention.

[0067] In the description of this invention, "several" means one or more, "multiple" means two or more, "greater than," "less than," and "exceeding" are understood to exclude the stated number, while "above," "below," and "within" are understood to include the stated number. The use of "first" and "second" in the description is merely for distinguishing technical features and should not be construed as indicating or implying relative importance, or implicitly indicating the number of indicated technical features, or implicitly indicating the order of the indicated technical features.

[0068] In the description of this invention, unless otherwise explicitly defined, terms such as "set up," "install," and "connect" should be interpreted broadly, and those skilled in the art can reasonably determine the specific meaning of the above terms in this invention in conjunction with the specific content of the technical solution.

[0069] In the description of this invention, the terms "one embodiment," "some embodiments," "illustrative embodiment," "example," "specific example," or "some examples," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0070] Due to the inherent physical properties of PN junctions, conventional detection methods used for semiconductor device failure analysis cannot detect the location, shape, or ion doping type of the PN junction region, nor can they detect doping concentration defects. For example, since PN junctions do not emit photons before breakdown, they cannot be detected using emission microscopy (EMMI). Furthermore, since PN junctions do not cause significant changes in leakage current before breakdown, detection schemes based on optical beam-induced resistance change (OBIRCH) are also ineffective. As mentioned earlier, atomic force microscopy (AFM) is currently commonly used to inspect the surface morphology of semiconductor devices and then identify PN junctions based on these morphological features. However, this method is limited by the wear and tear of the probe and the number of uses, making it prone to errors. It also suffers from cumbersome procedures and low detection efficiency. Moreover, AFM cannot detect PN junction defects that do not involve morphological changes (such as excessively high or low doping concentrations). Based on the above problems, the present invention proposes a method for imaging the PN junction region and the doping defects of semiconductors within the PN junction region based on the first thermoelectric effect, which will be described below with reference to specific embodiments.

[0071] To facilitate understanding, the terminology of this invention is first defined. The PN junction region, as used in this invention, refers to the region including the semiconductor structure (including N-type semiconductor 200 and P-type semiconductor 100). The PN junction is formed at the interface between N-type semiconductor 200 and P-type semiconductor 100. The principle of this invention is as follows: The first thermoelectric effect, also known as the Seebeck effect, refers to the thermoelectric phenomenon caused by the temperature difference between two different conductors or semiconductors, resulting in a voltage difference between them. In semiconductor devices, the requirements for the two materials in the first thermoelectric effect are met between the P-type semiconductor 100 and the carrier structure (usually made of aluminum or copper) and between the N-type semiconductor 200 and the carrier structure. When a temperature difference exists between the P-type semiconductor 100 and the carrier structure (or between the N-type semiconductor 200 and the carrier structure) and is connected in a loop, a current will be generated in the loop due to the thermoelectric electromotive force. Simultaneously, combining the formula for the first thermoelectric effect: V = (S... A -S B )*(T2-T1), S A With S B These are the Seebeck coefficients of the two materials, respectively. The thermoelectric potential is proportional to the difference in Seebeck coefficients between the materials and the temperature difference. When the temperature difference is fixed, the larger the difference in Seebeck coefficients, the larger the thermoelectric potential, and the larger the corresponding current. Depending on the doping ions of the semiconductor, the absolute value of the Seebeck coefficient of common semiconductor materials is between 200 and 300, while the absolute value of the Seebeck coefficient of metal materials such as aluminum and copper is less than 10. Therefore, in the PN junction region, the difference in Seebeck coefficients between the semiconductor and the carrier structure is relatively large, and the generated current is also relatively large. In other areas of the semiconductor device, even if the Seebeck effect exists, it is usually generated between different metal materials. Since the difference in Seebeck coefficients is very small, the generated current is also very small. Thus, the PN junction region can be identified by detecting the current in the detection loop. Furthermore, the direction of the thermoelectric potential of the N-type semiconductor 200 is from the low temperature end to the high temperature end (i.e., the Seebeck coefficient is negative), while the direction of the thermoelectric potential of the P-type semiconductor 100 is from the high temperature end to the low temperature end (i.e., the Seebeck coefficient is positive). Therefore, the direction of the thermoelectric potential (i.e., the direction of the current) can be used to further determine whether the semiconductor is an N-type semiconductor 200 or a P-type semiconductor 100.

[0072] Based on the foregoing, the PN junction region detection method in the first embodiment of the present invention includes the following steps:

[0073] Different regions of a semiconductor device are heated sequentially. The semiconductor device includes a conductive loop and a P-type semiconductor 100 and an N-type semiconductor 200 connected to the conductive loop.

[0074] It should be noted that the conductive loop and the semiconductor structure connected to the conductive loop are already formed during the fabrication of the semiconductor device. Typically, no additional conductive loop components are needed. The conductive loop is electrically connected to the pins of the semiconductor device, so the current in the loop can be measured through the pins. Furthermore, semiconductor devices usually have multiple loops, with different loops electrically connected to different pins; therefore, selecting different pins allows for the detection of current in different loops.

[0075] Each heating cycle involves detecting the current within the conductive loop. For example, this can be achieved through an external detection device for automatic heating and measurement, as will be explained in subsequent specific embodiments.

[0076] Based on the current detected in the conductive loop, the target area corresponding to the heating area is marked in the optical image of the semiconductor device.

[0077] It should be noted that the current detection in this step actually detects one or more parameters related to the current, such as whether current is generated in the loop, the magnitude of the current, and the direction of the current. Different parameters can form different functions. For example, based on whether current is generated in the loop, the location and shape of the PN junction region can be identified. Specifically, when heating a certain area, if no current is generated in the loop, it is a non-PN junction region; when heating another area, if current is generated in the loop, it is a PN junction region. After the entire semiconductor device has completed one heating cycle, the PN junction region can be identified. As another example, when heating a certain area, if a relatively small current is generated in the loop, and this current value does not reach the set value, then this area is a non-PN junction region. When heating another area, if a larger current is generated in the loop, and this current value reaches the set value, then this area is a PN junction region. After the entire semiconductor device has completed one heating cycle, the PN junction region can be identified. For example, when a certain area is heated, a current is generated in the loop, and the direction of the current is the first direction. Then the semiconductor structure of that area is a P-type semiconductor 100. When another area is heated, a current is generated in the loop, and the direction of the current is the second direction. Then the semiconductor structure of that area is an N-type semiconductor 200. After the entire semiconductor device has completed one heating cycle, the positions and corresponding shapes of the P-type semiconductor 100 and the N-type semiconductor 200 on the semiconductor device can be identified.

[0078] Furthermore, even if the detection equipment detects a change in current, it is difficult for the inspection personnel to visually identify it. Therefore, this embodiment can also image the PN junction region, specifically by obtaining an optical image of the semiconductor device. Each heating area on the semiconductor device will have a corresponding target area in the optical image. When a certain area of ​​the semiconductor device is heated, and a corresponding current is generated in the loop, the target area corresponding to the heating area on the optical image is marked. The marked area is the PN junction region. The marked optical image can be displayed on a display device such as a screen, thereby facilitating the inspection personnel's visual inspection of the PN junction region. It is understood that the marking mentioned in this invention can also be understood as highlighting, thereby creating a more significant distinction from other areas. The specific marking method will be described in subsequent embodiments.

[0079] It should be noted that this embodiment does not limit the method or order in which the optical images of the semiconductor device are obtained.

[0080] As mentioned above, compared with atomic force microscopy in related technologies, the detection method of this embodiment has at least the following advantages:

[0081] 1. No detection probe is required, and it is not affected by the number of times the probe is used or the degree of wear, which helps to reduce errors and achieve stable detection;

[0082] 2. Since there is no need to inspect the morphological features of semiconductor devices, there is no need for delamination, which enables inspection steps and improves efficiency;

[0083] 3. By using a mobile heat source, defects can be located over a wide area, which can also improve detection efficiency;

[0084] 4. It can directly visualize the PN junction area in optical images, making it convenient for inspection personnel to view.

[0085] Based on the first embodiment, in some embodiments, the method for marking on an optical image includes marking the target area with a set color. For example, a corresponding mapping relationship is pre-set in the detection device, marking non-PN junction areas with a first color and PN junction areas with a second color, thus distinguishing different areas through color differentiation. Furthermore, the P-type semiconductor 100 can be marked with the second color and the N-type semiconductor 200 with a third color, which can also distinguish different semiconductor structures. (Refer to...) Figure 1 The image shows an optical image obtained by the detection method of this embodiment. The red area is the P-type semiconductor 100, the green area is the N-type semiconductor 200, and the black, white and gray areas are non-PN junction areas. The position and shape of the P-type semiconductor 100 and the N-type semiconductor 200 can be seen intuitively from the image.

[0086] It should be noted that the colors involved in this invention, such as red, green, black and white in this embodiment, are merely examples and do not represent a limitation on colors.

[0087] In other embodiments, the method of marking on an optical image includes marking the target area with a set gray level. Compared with the previous embodiments, this embodiment does not distinguish by different colors, but by different gray levels. Specifically, a corresponding mapping relationship is preset in the detection device, marking the non-PN junction area with a first gray level and the PN junction area with a second gray level. The difference in gray levels forms the distinction between different areas. Furthermore, the P-type semiconductor 100 can also be marked with a second gray level and the N-type semiconductor 200 with a third gray level, which can also distinguish different semiconductor structures.

[0088] Based on the first embodiment, in some embodiments, the method for acquiring an optical image includes the following steps:

[0089] The semiconductor device is scanned sequentially to obtain multiple local images corresponding to each target region;

[0090] The individual images are aggregated to form the overall image of the semiconductor device.

[0091] That is, in this embodiment, an optical image is formed in a manner similar to the pixels of a display device. The overall image of the semiconductor device is formed by merging multiple local images. It should be noted that the above image merging method can adopt known techniques.

[0092] Typically, the area of ​​the target region is much smaller than the size of the PN junction region. Combined with the aforementioned marking method, this embodiment can achieve accurate marking. For example, when a region of the semiconductor device is heated and a current that meets the first set condition is generated in the loop, the local image of the target region corresponding to the heated region on the optical image is marked in red. When a region of the semiconductor device is heated and a current that meets the second set condition is generated in the loop, the local image of the target region corresponding to the heated region on the optical image is marked in green. When a region of the semiconductor device is heated and no current is generated in the loop, or the generated current does not meet the set condition, the local image of the target region corresponding to the heated region on the optical image is marked in black. In the aggregated image formed after the entire semiconductor device is scanned, all the red local images together show the position and shape of the P-type semiconductor 100, all the green local images together show the position and shape of the N-type semiconductor 200, and all the black local images together show the position and shape of the non-PN junction region.

[0093] It should be noted that the detection accuracy of this invention is related to the area of ​​the single heating area and the target area. The smaller the area of ​​the single heating area and the target area, the higher the detection accuracy.

[0094] Based on obtaining optical images of semiconductor devices by scanning, in some embodiments the scanning time for a single local image is 4μs to 8μs, thereby enabling the region corresponding to the single local image to be heated to the required temperature.

[0095] Based on the acquisition of optical images of semiconductor devices by scanning, in some embodiments the length of the local image obtained by a single scan is 50μm to 2750μm and the width is 50μm to 2750μm. As mentioned above, the smaller the size of the local image, the more it helps to improve the accuracy. Within this size range, the imaging accuracy of the PN junction region can be guaranteed.

[0096] In some embodiments, the method for heating a semiconductor device involves heating the semiconductor device using a laser light source. The laser light source offers stable power, rapid heating, and the ability to focus the light spot, which helps to reduce the area to be heated. The laser light source can move the light spot using a laser galvanometer, thereby heating different areas of the semiconductor device.

[0097] Based on scanning heating, in some embodiments the power of the laser source is 48mW to 80mW to ensure the heating effect.

[0098] Based on scanning heating, in some embodiments the laser spot length of the laser source is 0.507μm to 5.08μm and the width is 0.507μm to 5.08μm. As mentioned above, the smaller the size of the heating area, the more it helps to improve accuracy. Within this size range, the imaging accuracy of the PN junction area can be guaranteed.

[0099] It should be noted that when performing inspections using the equipment, images are generated relying on the equipment's built-in programs. Therefore, the selection of the equipment's parameters directly affects the imaging results. For example, referring to... Figure 2 If the parameters of the detection equipment are not set properly, the PN junction region will not stand out in the image, affecting the detection effect. Therefore, in some embodiments, by properly setting various parameters, the imaging can be clearer. For example, the scanning time of a single local image is 4μs, the size of the local image is 400μm to 500μm, the power of the laser source is 48mW, and the size of the laser spot is 1.269μm to 1.269μm. The produced image is as follows: Figure 3 As shown, the PN junction region can be displayed relatively clearly.

[0100] Based on the first embodiment, in some embodiments, the method for detecting current in a conductive loop includes the following steps:

[0101] Select the corresponding pin on the semiconductor device based on the conductive loop;

[0102] Connect the pins electrically to the corresponding interface of the testing equipment.

[0103] As mentioned earlier, semiconductor devices have multiple conductive loops, and different loops are electrically connected to different pins. Therefore, before detection, the corresponding pins on the semiconductor device can be selected according to the corresponding conductive loops. After connecting the pins to the corresponding interfaces of the detection device through wires, the current can be detected by the detection device. In some embodiments, the detection device integrates multiple modules, including but not limited to a heating module, a scanning module, a current detection module, and a control module. The heating module can be the aforementioned laser heating module, which can sequentially heat different areas of the semiconductor device. The scanning module is used to scan the semiconductor device to obtain multiple local images. The current detection module is used to detect the current value in the loop. Since the current generated in this embodiment is small, the current detection module includes a sensitive galvanometer, which can detect the weak current in the loop. The control module is used to implement corresponding image processing, area marking, and other functions, and can also control the heating module, scanning module, and current detection module to perform corresponding operations.

[0104] In some embodiments, the PN junction region detection method further includes the following steps:

[0105] Identify the grounding pins of semiconductor devices and the noise reduction interface of the testing equipment;

[0106] Connect the ground pin electrically to the noise reduction interface.

[0107] By connecting the ground pin of the semiconductor device to the noise reduction interface of the detection equipment, the impact of interference signals on the detection results can be reduced, and the possibility of non-PN junction regions being incorrectly identified can be improved.

[0108] It should be noted that when testing is performed using a testing device, other methods can also be used to ensure testing accuracy. For example, in some embodiments, the voltage applied by the testing device to the conductive loop is 0V, meaning that the device does not need to directly apply current to the semiconductor device. In conventional OBIRCH testing methods, the testing device needs to apply current to the semiconductor device, and the applied current is significantly greater than the current generated by the thermoelectric potential. Therefore, even if the Seebeck effect exists, it is difficult to distinguish between the PN junction region and the non-PN junction region. However, by setting the voltage applied by the testing device to the conductive loop to 0V, the current in the loop is almost entirely generated by the thermoelectric potential, thus eliminating interference from external current and helping to ensure accuracy.

[0109] In other embodiments, when the current in the detection loop exceeds 20nA, the current value is limited to 20nA. That is, the maximum current value obtained by the detection device from the loop is 20nA. This is because, to highlight the PN junction region, a relatively large difference is needed between the current generated when the PN junction region is heated and the current generated when the non-PN junction region is heated. To reduce random errors, the detection device collects current values ​​over a period of time or at multiple time points and then takes the average. If a large interference current signal is generated in the loop, then... This will increase the average value, leading to a reduction in the current difference, thus making the PN junction region unable to be effectively identified. For example, if the average current generated when the PN junction region is heated is 15nA, while the average current generated when the non-PN junction region is heated is 2nA, then the current difference is 13nA. If there is a large value of interference signal in the loop, causing the average current generated when the PN junction region is heated to be 58nA, while the average current generated when the non-PN junction region is heated to be 55nA, then the current difference is reduced to 3nA, causing the current signals of the PN junction region and the non-PN junction region to be too close to be effectively identified.

[0110] In some embodiments, the following steps are included before heating the semiconductor device:

[0111] Remove the mold covering the outside of the semiconductor device;

[0112] The passivation layer on a semiconductor device is thinned.

[0113] In this embodiment, a laser is used as the heat source. The laser irradiates from the upper layer of the passivation layer, and the laser beam penetrates through the passivation layer to heat the structure below it. By thinning the passivation layer, the attenuation effect of the passivation layer on the laser energy can be reduced, ensuring that the laser can heat the local area of ​​the semiconductor device to a sufficient temperature within a set time, avoiding detection errors caused by insufficient temperature rise. It should be noted that in the method of detection using atomic force microscopy, in addition to removing the passivation layer, it is also necessary to remove other layers below the passivation layer. Therefore, this invention still simplifies the operation and improves efficiency compared with atomic force microscopy.

[0114] The second embodiment of the present invention also proposes a PN junction region detection method. The difference between the second and third embodiments is that the first embodiment mainly distinguishes between PN junction regions and non-PN junction regions, while the second embodiment can further determine whether there is an abnormality in the doping concentration of the semiconductor based on the identification of the PN junction region.

[0115] In this embodiment, the PN junction region detection method includes the following steps:

[0116] Different regions of a semiconductor device are heated sequentially. The semiconductor device includes a conductive loop and a P-type semiconductor 100 and an N-type semiconductor 200 connected to the conductive loop.

[0117] It should be noted that the conductive loop and the semiconductor structure connected to the conductive loop are already formed during the fabrication of the semiconductor device. Typically, no additional conductive loop components are needed. The conductive loop is electrically connected to the pins of the semiconductor device, so the current in the loop can be measured through the pins. Furthermore, semiconductor devices usually have multiple loops, with different loops electrically connected to different pins; therefore, selecting different pins allows for the detection of current in different loops.

[0118] Each heating cycle involves detecting the current in the conductive loop. For example, automatic heating and measurement can be performed using the detection device described in the first embodiment, which will be explained in subsequent specific embodiments.

[0119] Based on the magnitude of the current detected in the conductive loop, the target region corresponding to the heating region is marked in the optical image of the semiconductor device. The marked target region is a region with abnormal doping concentration.

[0120] Unlike the first embodiment, this step requires the ability to detect the current in the loop. This is because the ion doping concentration in the semiconductor will affect the thermoelectric potential. In other words, even for the same semiconductor, different ion doping concentrations will cause different currents under the same conditions. Therefore, by measuring the current value in the loop, it can be determined whether the ion doping concentration in the semiconductor is abnormal.

[0121] Furthermore, similar to the first embodiment, this embodiment can also image the PN junction region, specifically by obtaining an optical image of the semiconductor device. Each heated area on the semiconductor device will have a corresponding target area in the optical image. When a certain area of ​​the semiconductor device is heated, and a corresponding current is generated in the loop, the target area corresponding to the heated area on the optical image is marked differently based on the measured current value. The marked optical image can be displayed on a display device such as a screen, thereby facilitating intuitive viewing of the PN junction region by inspection personnel.

[0122] It should be noted that this embodiment does not limit the method or order in which the optical images of the semiconductor device are obtained.

[0123] As mentioned above, compared with atomic force microscopy in related technologies, the detection method of this embodiment has at least the following advantages:

[0124] 1. No detection probe is required, and it is not affected by the number of times the probe is used or the degree of wear, which helps to reduce errors and achieve stable detection;

[0125] 2. Since there is no need to inspect the morphological features of semiconductor devices, there is no need for delamination, which enables inspection steps and improves efficiency;

[0126] 3. By using a mobile heat source, defects can be located over a wide area, which can also improve detection efficiency;

[0127] 4. It can directly visualize the PN junction region in optical images, making it convenient for inspection personnel to view;

[0128] 5. It can detect abnormal ion doping concentrations within semiconductors.

[0129] In some embodiments, the current value generated by a semiconductor with normal ion doping concentration based on the Seebeck effect can be detected under the same conditions. Of course, to improve accuracy, multiple sets of data can be tested, and then a reference range can be formed based on the measured data. For example, for this type of normal semiconductor, the generated current values ​​will all be distributed between the first value and the second value. Then, the current value actually measured in the semiconductor device under test under the same conditions is compared with the reference range. If the actual measured current value is also within the reference range, it can be determined that the semiconductor doping concentration in the semiconductor device under test is normal. If the actual measured current value deviates from the reference range, it can be determined that the semiconductor doping concentration is abnormal.

[0130] In different embodiments, the present invention proposes different marking methods. For example, regardless of whether the actual measured current value is greater than or less than the reference range, the target area is marked in the same way. That is, this embodiment can determine that the semiconductor corresponding to the target area has an abnormal doping concentration, but cannot distinguish whether the doping concentration is too high or too low.

[0131] For example, when the actual measured current value is greater than the reference range, the target area is marked as a first mark; when the actual measured current value is less than the reference range, the target area is marked as a second mark. That is, in addition to determining that the semiconductor corresponding to the target area has an abnormal doping concentration, this embodiment can also distinguish whether the doping concentration is too high or too low.

[0132] For example, when the actual measured current value is greater than the reference range, a third mark is made on the target area. The third mark can change synchronously with the offset between the actual measured current value and the reference range. When the actual measured current value is less than the reference range, a fourth mark is made on the target area. The fourth mark can change synchronously with the offset between the actual measured current value and the reference range. That is, in addition to determining that there is an abnormal doping concentration in the semiconductor corresponding to the target area, this embodiment can distinguish between high or low doping concentration and can also intuitively show the degree of abnormality in doping concentration.

[0133] In some embodiments, the method for marking on an optical image includes marking target areas with a set color. For example, a corresponding mapping relationship is pre-set in the detection device, marking target areas with current values ​​greater than or less than a reference range with the same color, and marking target areas with current values ​​distributed within the reference range with a different color or keeping the original color. The color difference is used to distinguish between normal and abnormal doping areas. Figure 4 , Figure 5 ,in Figure 4 Images of samples with abnormally high (excessive) doping concentrations. Figure 5 Both images are of samples with normal doping concentrations and are optical images obtained based on the detection method of this embodiment. Figure 4 , Figure 5 The same areas (shown by the dashed boxes in the figure) are compared, as shown in the figure. Figure 4 The dashed box in the image shows an area that is darker than the background color (a black area). Figure 5 The dashed box contains an area lighter than the background color (white area), therefore, according to... Figure 4 or Figure 5 The shape and location of the P-junction region can be identified, and the color or grayscale of the P-junction region can be used to further identify whether the P-junction has an excessively high doping concentration. The aforementioned structure is verified experimentally, referring to... Figure 6 , Figure 7 , Figure 6 It is Figure 4 The image is formed after a portion of the sample is removed along a vertical plane within the P-junction region, and the cut surface is etched. Figure 7 It is Figure 5 The image is formed after a portion of the sample is removed along a vertical plane within the P-junction region and the cut surface is etched. Higher doping concentrations and faster etching rates result in the easier formation of three-dimensional structures on the etched surface, which manifests as shadowed areas in the optical image. Figure 6 As shown in the dashed box, there is an area that is darker than the background color, which means that the doping concentration in this area is too high, thus proving that the method of this embodiment can further identify defects in doping concentration.

[0134] For example, target areas with current values ​​greater than the reference range are marked with a first color (e.g., red), target areas with current values ​​less than the reference range are marked with a second color (e.g., green), and target areas with current values ​​within the reference range are marked with other colors or remain in their original colors. The difference in color is used to distinguish between areas with normal and abnormal doping, as well as areas with high and low doping.

[0135] For example, target areas with current values ​​greater than the reference range are marked with a third color (e.g., red), and the larger the current value, the darker the third color. Target areas with current values ​​less than the reference range are marked with a fourth color (e.g., green), and the smaller the current value, the lighter the fourth color. Target areas with current values ​​distributed within the reference range are marked with other colors or remain in their original colors. The color distinctions help to differentiate between normal and abnormal doping areas, between areas with high and low doping, and to identify the degree of deviation.

[0136] The embodiments of the present invention have been described in detail above with reference to the accompanying drawings. However, the present invention is not limited to the above embodiments, and various changes can be made within the scope of knowledge possessed by those skilled in the art without departing from the spirit of the present invention. Furthermore, the embodiments of the present invention and the features thereof can be combined with each other unless otherwise specified.

Claims

1. A method for detecting PN junction regions, characterized in that, Includes the following steps: Different regions of a semiconductor device are heated sequentially. The semiconductor device includes a conductive loop and a P-type semiconductor, an N-type semiconductor, and a support structure connected to the conductive loop. The support structure is made of aluminum or copper. When there is a temperature difference between the P-type semiconductor and the support structure or between the N-type semiconductor and the support structure, a current is generated in the loop. Each heating cycle detects the current generated by the heating within the conductive loop. Based on the current detected in the conductive loop, the target area corresponding to the heating area in the optical image of the semiconductor device is identified; The method for detecting the current within the conductive loop includes: Select the corresponding pin on the semiconductor device according to the conductive loop; The pin is electrically connected to the corresponding interface of the detection device, and the voltage applied by the detection device to the conductive loop is 0V; The method for acquiring the optical image includes: The semiconductor device is scanned sequentially to obtain multiple local images corresponding to each of the target regions; The individual local images are aggregated to form an overall image of the semiconductor device.

2. The PN junction region detection method according to claim 1, characterized in that, The method for marking on the optical image includes one of the following schemes: The target area is identified by a set color; The target area is marked with a set grayscale value.

3. The PN junction region detection method according to claim 1, characterized in that, The method for scanning the semiconductor device includes at least one of the following: The scan time for a single local image is 4 μs to 8 μs; The length and width of the local image range from 50 μm to 2750 μm.

4. The PN junction region detection method according to claim 1, characterized in that, The method for heating the semiconductor device includes: The semiconductor device is heated by a laser light source.

5. The PN junction region detection method according to claim 4, characterized in that, The parameters of the laser source satisfy at least one of the following: The power ranges from 48mW to 80mW; The length of the laser spot ranges from 0.507 μm to 5.08 μm, and the width ranges from 0.507 μm to 5.08 μm.

6. The PN junction region detection method according to claim 1, characterized in that, The PN junction region detection method further includes the following steps: Identify the ground pin of the semiconductor device and the noise reduction interface of the detection equipment; Connect the ground pin electrically to the noise reduction interface.

7. The PN junction region detection method according to claim 1, characterized in that, The parameters of the detection equipment satisfy: When the current detected by the detection device is greater than 20nA, the current value is limited to 20nA.

8. The PN junction region detection method according to claim 1, characterized in that, Before heating the semiconductor device, the following steps are also included: Remove the mold covering the outside of the semiconductor device; The passivation layer on the semiconductor device is thinned.

9. A method for detecting PN junction regions, characterized in that, Includes the following steps: Different regions of a semiconductor device are heated sequentially. The semiconductor device includes a conductive loop and a P-type semiconductor, an N-type semiconductor, and a support structure connected to the conductive loop. The support structure is made of aluminum or copper. When there is a temperature difference between the P-type semiconductor and the support structure or between the N-type semiconductor and the support structure, a current is generated in the loop. Each heating cycle detects the current generated by heating within the conductive loop. Based on the magnitude of the current value detected in the conductive loop, the target region corresponding to the heating region is marked in the optical image of the semiconductor device. The marked target region is a region with abnormal doping concentration. The method for detecting the current within the conductive loop includes: Select the corresponding pin on the semiconductor device according to the conductive loop; The pin is electrically connected to the corresponding interface of the detection device, and the voltage applied by the detection device to the conductive loop is 0V; The method for acquiring the optical image includes: The semiconductor device is scanned sequentially to obtain multiple local images corresponding to each of the target regions.

10. The PN junction region detection method according to claim 9, characterized in that, The method for identifying the target area includes: To obtain a reference range of current generated by the same semiconductor with normal doping concentration under the same detection conditions; The actual measured current value in the loop is compared with the reference range. If the actual measured current value deviates from the reference range, the target area is marked.

11. The PN junction region detection method according to claim 10, characterized in that, The method for identifying the target area includes: Whether the actual measured current value is greater than or less than the reference range, the target area will be marked in the same way. Alternatively, if the actual measured current value is greater than the reference range, the target area is marked with a first identifier; if the actual measured current value is less than the reference range, the target area is marked with a second identifier. Alternatively, when the actual measured current value is greater than the reference range, the target area is marked with a third identifier, which can change synchronously with the offset between the actual measured current value and the reference range. When the actual measured current value is less than the reference range, the target area is marked with a fourth identifier, which can change synchronously with the offset between the actual measured current value and the reference range.

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