Extended resistance test method
By calculating and extending the starting point of the test surface to increase the effective length of the small pattern, the resistivity and doping concentration of the small pattern were tested using existing dual-probe SRP testing equipment. This solved the problem that the small pattern could not meet the junction depth requirements in the existing technology, reduced costs, and improved the accuracy of the test results.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- SHANGHAI HUAHONG GRACE SEMICON MFG CORP
- Filing Date
- 2026-03-31
- Publication Date
- 2026-06-19
AI Technical Summary
In existing SRP dual-probe testing methods, the length of small patterns cannot meet the junction depth requirements of parabolic surfaces under conventional testing angles, and even after adjusting the testing angle to its limit, depth testing still cannot be achieved. As a result, small patterns cannot complete SRP depth testing for resistivity and doping concentration.
A dual-probe SRP testing device was used. Based on the spatial coordinate system of width X, length Y, and depth Z and the angle α of the test base, the starting point of the test surface was extended by calculation to increase the effective test length of the small pattern, so that the parabolic surface could pass through the bottom of the small pattern. Resistivity and doping concentration were then tested using a conventional dual-probe SRP testing device.
It enables accurate measurement of resistivity and doping concentration of small patterns, reduces testing costs, and improves the accuracy and stability of test results. It is suitable for SRP testing of various small-sized semiconductor patterns.
Smart Images
Figure CN122238809A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of semiconductor testing, and in particular to a method for testing extended resistance. Background Technology
[0002] Spreading resistance profile (SRP) testing is an important method for characterizing the resistivity and doping concentration of semiconductor materials. Existing SRP testing equipment all employ the dual-probe method. This method has specific requirements for the size of the test pattern; a typical test pattern must meet the size requirement of 200µm x 500µm, with a minimum test junction depth of 0.5µm. During testing, the width of the test pattern must be greater than the probe spacing, and the pattern length must be determined based on the test junction depth and the number of test points to meet the parabolic junction depth requirements formed by the test angle.
[0003] In actual semiconductor device fabrication and testing, there are numerous small-sized test patterns (such as etched areas). While the width of a single side of these small patterns may meet the requirements for the spacing between dual probes, their length cannot meet the junction depth requirements of the parabolic surface formed under conventional testing angles. In such cases, conventional SRP testing methods cannot achieve effective measurements. If the testing depth is increased simply by adjusting the angle of the test base, even when the angle is adjusted to the equipment's limit, the junction depth testing requirements for small patterns still cannot be met. This makes resistivity and doping concentration testing of small patterns a technical challenge, limiting the performance characterization and development of small-sized semiconductor devices. Summary of the Invention
[0004] The summary of this invention introduces a series of simplified concepts, all of which are simplifications of existing technologies in the field, and will be further explained in detail in the detailed description section. This summary is not intended to limit the key features and essential technical features of the claimed technical solution, nor is it intended to determine the scope of protection of the claimed technical solution.
[0005] To address the shortcomings of existing technologies, the technical problem solved by this invention is that in existing SRP dual-probe testing methods, the length of small patterns cannot meet the junction depth requirements of parabolic surfaces under conventional testing angles, and even after adjusting the testing angle to its limit, depth testing still cannot be achieved, resulting in the inability of small patterns to complete SRP depth testing for resistivity and doping concentration.
[0006] To address the aforementioned technical problems, this invention provides an extended resistance testing method for measuring the resistivity and doping concentration of small patterns in semiconductor devices. It employs a dual-probe SRP testing device and performs the test based on a spatial coordinate system of width X, length Y, and depth Z, and a test base angle α. The method includes the following steps: (1)Measurement of small graphic parameters: Measure the actual length Y of the area to be tested under a focused ion beam microscope; (2)Determination of test parameters: Select the parabolic angle 𝜕 of the spreading resistance test base. According to the target test junction depth Z, determine the reference range Y1~Y2 of the surface starting length that meets the junction depth requirement through the starting point extension calculation range formula; The starting point extension calculation range formula is: ∆Y1 = cot𝜕 * Z - Y, ∆Y2 = cot𝜕 * Z, Y1 < starting point extension < Y2, where ∆Y1 is the minimum extension of the surface starting point and ∆Y2 is the maximum extension of the surface starting point; (3)Marking of starting point position: Under the focused ion beam, select a position within the reference range Y1~Y2 of the surface starting length for laser marking positioning as the new surface starting point; (4)Parabolic sample preparation: Fix the marked sample on the base, grind and polish the inclined plane along the direction parallel to the long side of the graphic to be tested on the grinding and sample preparation table until it is polished to the position of the laser - marked surface starting point to complete the sample preparation; (5)Spreading resistance test: Put the sample with completed sample preparation into the spreading resistance test equipment, set the probe test parameters, and conduct a two - probe test based on the marked surface starting point to complete the depth measurement of the small graphic.
[0007] Preferably, further improve the spreading resistance test method. Before step (1), it further includes: sample pretreatment, intercepting the semiconductor small graphic sample to be tested, and cleaning and drying the sample; Preferably, further improve the spreading resistance test method. In step (2), use a focused ion beam microscope to accurately measure the actual length of the test area of the small graphic to be tested.
[0008] Preferably, further improve the spreading resistance test method. In step (3), determine the extended test surface starting point at the middle position of the extended reference range (Y1~Y2) and conduct marking positioning.
[0009] Preferably, further improve the spreading resistance test method. In step (3), use laser marking to position the extended test surface starting point.
[0010] Preferably, further improve the spreading resistance test method. Before step (1), it further includes a sample pretreatment step: intercept the sample to be tested from the semiconductor substrate, soak the sample in HF, rinse it with DIW, and then dry it for standby.
[0011] Preferably, further improve the spreading resistance test method. The soaking time range of the HF is 1 minute to 10 minutes, and the sample drying is completed by blowing dry with inert gas.
[0012] Preferably, the extended resistance test method is further improved by including: The steps for preparing and testing the verification sample are as follows: After moving the starting point forward by a preset distance along the Y-axis (the direction of the graphic length), re-mark and prepare the sample to form a verification sample. The verification sample is then tested according to step (5) to verify the accuracy of the test results.
[0013] Preferably, in a further improvement to the extended resistance testing method, the preset distance range is 1µm to 50µm, and more preferably 20µm.
[0014] Preferably, the extended resistance test method is further improved, and the probe test parameters in step (5) include: probe test step range of 1um~5um, preferably 2.5um, maximum cutoff depth range of 5um~15um, preferably 10um, and the test starting point is horizontally aligned with the starting point of the extended surface.
[0015] Preferably, in a further improvement to the extended resistance test method, the SRP test equipment is the SEMILABS spreading resistance profiler system-2100 system.
[0016] Based on the above technical solution, the working principle of the present invention is explained as follows; This invention abandons the existing approach of simply adjusting the test angle to achieve knot depth testing. Instead, it artificially increases the effective test length of the small pattern by calculating and extending the starting point of the test surface. This extended effective length matches the knot depth requirements of the parabolic surface under the selected test base angle, allowing the test parabolic surface to penetrate the bottom of the small pattern. This enables the depth testing of the small pattern using conventional dual-probe SRP testing equipment. Furthermore, by setting verification samples and marking the middle section of the extended range, the accuracy and stability of the test results are further improved.
[0017] Based on the above technical solution and working principle, the present invention can achieve at least the following technical effects compared with the prior art; 1) Existing technologies rely solely on adjusting the test angle or conventional sample preparation methods. The length of the small graphic itself cannot meet the depth requirements of the parabolic surface, and there are equipment limitations in angle adjustment, making it impossible to allow the parabolic surface to pass through the bottom of the small graphic, thus making it impossible to complete the depth measurement.
[0018] This invention increases the effective testing length by extending the starting point, overcoming the size limitations of small patterns and satisfying the requirements for parabolic junction depth. This invention enables SRP depth testing of small patterns whose length does not meet conventional requirements, filling a technological gap in characterizing the resistivity and doping concentration of small-pattern semiconductor materials.
[0019] 2) To achieve small pattern testing using existing technologies, it is necessary to develop or modify dedicated testing equipment, which increases equipment investment and testing costs. Furthermore, dedicated equipment has poor compatibility with conventional testing systems.
[0020] This invention is based on the hardware foundation of existing dual-probe SRP testing equipment. It only optimizes the sample preparation and test point selection methods, without requiring structural modifications to the existing SRP testing equipment. Testing can be achieved simply by calculating the test points and extending the sample preparation stage, which reduces testing costs and has strong compatibility.
[0021] 3) Existing technologies lack effective methods for small-scale test sample preparation and point selection, making it impossible to form a test surface that meets the requirements and obtain accurate knot depth test data.
[0022] This invention determines the extension range of the starting point through precise calculation and selects the middle position for marking to ensure the matching degree between the test parabolic surface and the small pattern. The actual test knot depth can be close to the predicted knot depth. At the same time, the setting of the verification sample can cross-validate the test results, resulting in high accuracy and improved data reliability.
[0023] 4) Existing technologies lack a unified testing and sample preparation method for small patterns, and only involve scattered, trial-and-error operations that cannot be standardized for reproduction.
[0024] This invention clarifies the complete steps and parameter selection methods for point measurement, calculation, marking, sample preparation, and testing. The steps are clear, the parameters are well-defined, and the sample preparation and testing steps are standardized. It can be directly reproduced by those skilled in the art and is applicable to SRP testing of various small-sized semiconductor patterns, making it highly practical. Attached Figure Description
[0025] The accompanying drawings are intended to illustrate the general characteristics of the methods, structures, and / or materials used in specific exemplary embodiments of the invention, supplementing the description in the specification. However, the drawings are schematic diagrams not drawn to scale and may not accurately reflect the precise structural or performance characteristics of any of the given embodiments. The drawings should not be construed as limiting or restricting the range of numerical values or properties covered by exemplary embodiments of the invention. The invention will now be described in further detail with reference to the accompanying drawings and specific embodiments.
[0026] Figure 1 The diagram illustrates that when the length of the small graphic to be tested is insufficient, the parabolic surface formed at the conventional test points cannot meet the target knot depth requirements, thus making it impossible to complete the test. Figure 2 A schematic diagram for normal testing of large graphics: This shows that when a typical large graphic is placed at a standard test point, the resulting parabolic surface meets the depth requirements and can be tested normally. Figure 3This is a schematic diagram showing a situation where the graphic length meets the requirements but the depth is not measured: It illustrates the state where the parabolic surface cannot reach the target test depth when the graphic length meets the requirements but the starting point is not optimized. Figure 4 A schematic diagram showing that when the graphic length meets the requirements and the starting point is moved forward to meet the depth requirements, the diagram illustrates that when the graphic length meets the requirements, moving the starting point forward can make the parabolic surface meet the target depth requirements. Figure 5 A schematic diagram illustrating the situation where the graphic length is reduced and the existing angle test depth is insufficient: This shows that when the length of the small graphic is insufficient, the parabolic test depth cannot reach the target value under the conventional test angle. Figure 6 A schematic diagram illustrating how adjusting the angle can increase the test depth when the graphic length remains constant to meet the requirements: This shows that when the graphic length meets the standard, adjusting the angle of the test base can increase the test depth. Figure 7 The diagram illustrates the situation where the test depth is insufficient even after the test base angle is adjusted to its limit when the length of the small graphic is insufficient. Figure 8 A schematic diagram of a small graphic: This diagram illustrates the basic shape and size characteristics of the small graphic to be tested in the XYZ coordinate system. Figure 9 Schematic diagram of sample preparation for extending a small graphic: This shows the sample preparation shape after extending the starting point of the surface of the small graphic in this invention, and the positional relationship between the extended parabolic surface and the small graphic; Figure 10 Schematic diagram of extending the calculation range of the starting point. Figure 1 This demonstrates a situation where the graphic length is reduced, the angle is increased to its limit, and the test depth is insufficient. Figure 11 Schematic diagram of extending the calculation range of the starting point. Figure 2 This shows the starting point of the calculation, which meets the length requirement and passes through the bottom of the figure. Figure 12 Schematic diagram of extending the calculation range of the starting point. Figure 3 This shows the reference range of the starting point of the extended surface of the calculated graphic's long side. Detailed Implementation
[0027] The following specific embodiments illustrate the implementation of the present invention. Those skilled in the art can fully understand other advantages and technical effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through different specific embodiments, and various details in this specification can also be applied based on different viewpoints, with various modifications or changes made without departing from the overall design concept of the invention. It should be noted that, in the absence of conflict, the following embodiments and features in the embodiments can be combined with each other. The following exemplary embodiments of the present invention can be implemented in many different forms and should not be construed as being limited to the specific embodiments set forth herein. It should be understood that these embodiments are provided to make the disclosure of the present invention thorough and complete, and to fully convey the technical solutions of these exemplary embodiments to those skilled in the art. It should be understood that when an element is referred to as "connected" or "combined" to another element, the element can be directly connected or combined to the other element, or there may be intermediate elements. The difference is that when an element is referred to as "directly connected" or "directly combined" to another element, there are no intermediate elements. Throughout the drawings, the same reference numerals always denote the same elements. Example
[0028] This embodiment uses a small scribe line pattern (width meets the pin pitch requirement, length 120μm) of an 8-inch IGBT uncut silicon wafer as the test sample to perform SRP testing to obtain junction depth data of resistivity and doping concentration. The equipment and parameters used in this embodiment are actual test values, and the data source is the test record of the SEMILAB Spreadingresistance profiler system-2100 system.
[0029] Test materials and equipment specifications: The sample to be tested is an 8-inch IGBT uncut silicon wafer. The actual length of the scribeline in its scribeline area is 120um. The width of the scribeline meets the pin pitch requirement for SRP dual probe testing, but the length does not meet the requirements for conventional junction depth testing. Test equipment: SEMILABS spreading resistance profiler system—2100 SRP test system (dual probe test method); Auxiliary equipment: Focused ion beam microscope (for measuring graphic length and marking positioning), grinding and sample preparation stage (for testing the grinding and polishing of the surface). Auxiliary reagents: hydrofluoric acid (HF), deionized water (DIW).
[0030] Take a 3 cm * 3 cm silicon wafer sample to be tested, immerse the sample in hydrofluoric acid for 5 minutes to remove the oxide layer on the sample surface, then repeatedly rinse the sample surface with deionized water until there is no reagent residue, and place the cleaned sample in a drying oven for drying for standby.
[0031] Measurement of the actual length of the small pattern: Place the dried sample under a focused ion beam microscope, accurately measure the test area of the small pattern in the scribed area, and determine that the actual length of the small pattern to be measured is 120 μm; Select the polishing angle 𝜕 = 2 degrees 52 minutes of the SRP test base, set the target test junction depth Z = 7 μm, and calculate the reference range of the surface starting length that meets the junction depth requirement through the starting point extension calculation range formula. The starting point extension calculation range formula is: ∆Y1 = cot𝜕 * Z - Y, ∆Y2 = cot𝜕 * Z, Y1 < starting point extension < Y2; where, ∆Y1 is the minimum extension of the surface starting point, and ∆Y2 is the maximum extension of the surface starting point.
[0032] After calculation, the reference range of the surface starting length in this embodiment is obtained as: 138.6 μm < starting length < 258.6 μm.
[0033] Under the focused ion beam microscope, select the middle position of the reference range of the surface starting length calculated above as the new surface starting point, and use a laser marking device to mark and position at this position to complete the marking of the starting point position.
[0034] Fix the sample completed with laser marking on the SRP test base, place the base on the grinding and sample preparation table, and grind and polish the sample along the direction parallel to the long side of the scribe line (Y-axis direction). The angle between the inclined plane formed by grinding and polishing and the horizontal plane is the preset 2 degrees 52 minutes. Continue grinding until the polished surface reaches the position of the new surface starting point marked by laser, and stop grinding to complete the SRP test polishing sample preparation of the small pattern.
[0035] To verify the reliability of the test results, prepare a parallel verification sample: Move the marked position of the surface starting point of the original sample forward by 20 μm, and repeat the above steps 4 - 5 to complete the polishing sample preparation of the verification sample.
[0036] Place the prepared test sample and the verification sample into the SEMILAB Spreading resistance profiler system—2100 SRP testing system. Set the test parameters: probe test step 2.5μm, maximum cutoff depth 10μm. Align the probe test starting point of the testing equipment with the starting point of the new laser-marked surface on the sample. Start the testing equipment to complete the dual-probe SRP depth test.
[0037] In this embodiment, the actual test knot depth of the sample to be tested is about 6.5 μm, which is close to the preset target knot depth of 7 μm. This verifies that the deviation between the test knot depth of the sample and the test knot depth of the sample to be tested is within a reasonable range, proving that the test method of the present invention is accurate in sample preparation and reliable in test results, and successfully realizes the SRP depth measurement of a small pattern with a length of 120 μm.
[0038] Optionally, the above embodiments can be further improved. The following improvements can be combined or added individually to the above embodiments. 1. If the actual length of the small graphic to be tested is 80um and the predicted target knot depth is 5um, the test base angle α can be selected as 2 degrees. After calculating the corresponding extension starting point reference range, the sample can be marked. 2. If no additional verification test results are required, the sample preparation step can be omitted, and the sample preparation and testing can be completed directly. 3. The marking method can be selected according to the actual equipment conditions, such as laser marking or ion beam marking, as long as the precise positioning of the extended starting point can be achieved.
[0039] Unless otherwise defined, all terms used herein (including technical and scientific terms) shall have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. It will also be understood that, unless explicitly defined herein, terms such as those defined in a general dictionary shall be interpreted as having the meaning consistent with their meaning in the relevant field context, and not as having an idealized or overly formal meaning.
[0040] The present invention has been described in detail above through specific embodiments and examples, but these are not intended to limit the invention. Many modifications and improvements can be made by those skilled in the art without departing from the principles of the invention, and these should also be considered within the scope of protection of the present invention.
Claims
1. A method for measuring the resistivity and doping concentration of small patterns in semiconductor devices, characterized in that, It includes the following steps: (1) Measure the actual length Y of the area to be tested under a focused ion beam microscope; (2) Select the parabolic angle 𝜕 of the spreading resistance test base, and determine the reference range of the surface starting length that meets the junction depth requirement through the starting point extension calculation range formula according to the target test junction depth Z; The starting point extension calculation range formula is: ∆Y1 = cot𝜕 * Z - Y, ∆Y2 = cot𝜕 * Z, Y1 < starting point extension < Y2, where ∆Y1 is the minimum extension of the surface starting point, and ∆Y2 is the maximum extension of the surface starting point; (3) Under the focused ion beam, select a position within the reference range of the surface starting length for laser marking positioning as the new surface starting point; (4) Fix the marked sample on the base, and polish the inclined plane along the direction parallel to the long side of the test pattern on the grinding sample preparation table until it is polished to the position of the laser-marked surface starting point to complete sample preparation; (5) Put the sample with completed sample preparation into the spreading resistance test equipment, set the probe test parameters, and perform double-probe test based on the marked surface starting point to complete the depth measurement of the small pattern.
2. The extended resistance testing method according to claim 1, characterized in that, Before step (1), it also includes: sample pretreatment, intercept the semiconductor small pattern sample to be tested, and clean and dry the sample.
3. The extended resistance testing method according to claim 1, characterized in that: In step (3), determine the extended test surface starting point at the middle position of the extended reference range (Y1~Y2) and perform marking positioning.
4. The extended resistance testing method according to claim 1, characterized in that: In step (3), use laser marking to position the extended test surface starting point.
5. The extended resistance testing method according to claim 1, characterized in that: Before step (1), it also includes a sample pretreatment step: intercept the sample to be tested from the semiconductor substrate, soak the sample in HF, rinse it with DIW, and then dry it for standby.
6. The extended resistance testing method according to claim 5, characterized in that: The soaking time range of the HF is 1 minute to 10 minutes, and the sample drying is completed by blowing dry with inert gas.
7. The extended resistance testing method according to claim 1, characterized in that, It also includes: Verification sample preparation and test steps: Move the extended starting point forward a preset distance along the Y-axis (graphic length direction), re-mark and prepare the sample to form a verification sample, and test the verification sample according to step (5) to verify the accuracy of the test results.
8. The extended resistance testing method according to claim 7, characterized in that: The preset distance range is 1um to 50um.
9. The extended resistance testing method according to claim 1, characterized in that: The probe test parameters in step (5) include: the probe test step range is 1um to 5um, the maximum cut-off depth range is 5um to 15um, and the test starting point is horizontally aligned with the extended surface starting point.
10. The method for testing extended resistance according to any one of claims 1-9, characterized in that: The SRP test equipment is the SEMILAB Spreading resistance profiler system - 2100 system.