Leakage detection unit and method in magnetic tunnel junction fabrication process

Abstract

The application provides a leakage detection unit and method in a magnetic tunnel junction preparation process. The leakage detection unit comprises a capacitance matrix arranged on the same metal layer; the capacitance matrix comprises multiple columns of spaced-apart capacitance poles, each two adjacent columns of the capacitance poles form a group, the number of the capacitance poles in different columns in the same group is the same and the capacitance poles in the different columns are arranged in pairs; the capacitance poles in the same column are connected in series, and the series capacitance poles in different columns in the same group are respectively connected with different electrode blocks. The method comprises the following steps: using the leakage detection unit in the magnetic tunnel junction preparation process, measuring the resistance value by contacting the two electrode blocks connected with the different column capacitance poles through a probe; if the measured resistance value is infinite, it indicates that there is no leakage and the distance between the adjacent lines is sufficient; otherwise, it indicates that there is contact between the lines or the distance between the adjacent lines is insufficient, resulting in device breakdown, and the distance needs to be adjusted. The application can detect the leakage by detecting the resistance value, and test the process.

Description

Technical Field

[0001] This invention relates to the field of magnetic electronic device detection technology in integrated circuits, and particularly to a leakage current detection unit and method in the fabrication process of a magnetic tunnel junction. Background Technology

[0002] Research has found that when current is passed through a material exhibiting the spin-orbit torque effect (SOT), a spin-polarized spin current is generated at the material's interface. This spin current can be used to flip the free layer of nanomagnets, such as in a magnetic tunnel junction (MTJ). This technique requires adding a thin film of heavy metal (platinum, tantalum, tungsten) beneath the free layer of the MTJ. The current flowing through the heavy metal film can induce a torque sufficient to drive the magnetization reversal of the free layer. MRAM write operations are achieved through the magnetization reversal of the free layer in the MTJ. The lower the critical reversal current, the higher the efficiency of the spin-orbit torque reversal, and the smaller the required write current. The write current can be reduced as the process size shrinks. In the MRAM in-line integrated circuit fabrication process, the precision of the lithography machine determines the upper limit of the chip size. From small-scale integrated circuits to today's million-chip chips, the reduction in the feature size of individual components has played a crucial role. This is thanks to significant improvements in patterning processes called photolithography and multilayer interconnect technology. Even with achievable lithography precision, if the distance between lines is too close, charge accumulation during current flow can lead to breakdown, ultimately causing MRAM performance failure. This invention designs a leakage current detection unit for monitoring the magnetic tunnel junction fabrication process in MRAM fabrication. This simple leakage current detection unit tests for leakage current in the metal lines. If no leakage current is detected, it indicates that the design meets the precision requirements of the lithography machine and avoids breakdown due to insufficient line spacing, indirectly providing feedback on the lithography process.

[0003] MRAM write operations are achieved through magnetization reversal of the free layer in the magnetic tunnel junction. A lower critical reversal current results in higher self-selected orbital moment reversal efficiency and requires less write current. Reducing the write current can be achieved by decreasing the device size. In integrated circuit fabrication, the precision of photolithography plays a decisive role in the device size. During layout design, based on the precision of the photolithography machine, and with a certain degree of redundancy in equipment precision, the width of the lines and the spacing between lines are made as close as possible to the equipment limits to reduce the device size, thereby reducing chip power consumption and improving performance. However, the photolithography process is complex. Feature pattern size, alignment tolerance, wafer surface condition, and the number of photolithography layers all affect the difficulty of the photolithography process and the process at each step, causing fluctuations in photolithography stability. Once a photolithography process is established, it is rarely changed. Therefore, monitoring photolithography, especially monitoring the photolithography precision limits, is particularly important. Even with achievable photolithography precision, insufficient distance between adjacent lines can lead to charge accumulation and breakdown, causing the entire device to fail and the entire fabrication process to fail. Summary of the Invention

[0004] To address the aforementioned technical problems, this invention provides a leakage current detection unit in the fabrication process of a magnetic tunnel junction, comprising a capacitor matrix disposed on the same metal layer; the capacitor matrix comprises multiple rows of capacitor electrodes spaced apart, each pair of adjacent columns of capacitor electrodes forming a group, the number of capacitor electrodes in different columns within the same group being the same and arranged in pairs; the capacitor electrodes in the same column are connected in series, and the series-connected capacitor electrodes in different columns within the same group are respectively connected to different electrode blocks.

[0005] Optionally, the multiple columns of capacitors in the capacitor matrix are arranged in a square matrix with spacing.

[0006] Optionally, the capacitor blocks are square and all capacitor blocks are the same size; the electrode blocks are the same size.

[0007] Optionally, the capacitor electrode is square and its size ranges from 1μm to 20μm.

[0008] Optionally, the size of the electrode block ranges from 1μm to 200μm.

[0009] Optionally, the spacing between different columns of the capacitor electrode block is 1μm-90μm.

[0010] Optionally, the series connection of the capacitor blocks in the same column adopts interconnecting lines with a size range of 1μm-10μm.

[0011] Optionally, the resistance value can be measured by contacting two electrode blocks connected to different columns of capacitors with a probe; if the measured resistance value is infinite, it indicates that there is no leakage and the distance between adjacent lines is sufficient; otherwise, it indicates that there is contact between the lines or that the distance between adjacent lines is insufficient, causing the device to break down, and the distance needs to be adjusted.

[0012] Optionally, the resistance value is measured using the resistance measurement mode of a digital multimeter.

[0013] This invention also provides a leakage current detection method in the fabrication process of a magnetic tunnel junction, including using the leakage current detection unit in the above-mentioned magnetic tunnel junction fabrication process, measuring the resistance value by contacting two electrode blocks connected to different columns of capacitors with a probe; if the measured resistance value is infinite, it indicates that there is no leakage current and the distance between adjacent lines is sufficient; otherwise, it indicates that there is contact between the lines or that the distance between adjacent lines is insufficient, causing the device to break down, and the distance needs to be adjusted.

[0014] The capacitor matrix in this invention comprises multiple rows of spaced capacitor electrodes. Each capacitor electrode is a single-pole module, i.e., an anode or cathode plate. Electrodes in the same column have the same polarity, while those in different columns within the same group have different polarities. Electrodes in all columns connected to the same electrode block have the same polarity, while those connected to different electrode blocks have different polarities. Two capacitor electrodes forming the same capacitor are connected to different electrode blocks, meaning that two capacitor electrodes of the same capacitor cannot be short-circuited; conversely, they must be open-circuited. During testing, a multimeter, such as a digital multimeter in resistance mode, is used. Two probes are placed on electrode blocks pad1 and pad2 respectively to measure the resistance. An infinite open-circuit resistance is normal. If a short circuit or breakdown occurs, the measured resistance will be zero or show a certain resistance value, indicating that the product is unqualified and its manufacturing process has problems. This invention allows the above-mentioned leakage current detection unit graphic structure to be added to any layout position in any metal layer that needs monitoring. Leakage current testing is performed by measuring resistance. If the measured resistance is infinite, it indicates that there is no leakage and the product is qualified, and the process is correct. Furthermore, the photolithography lines and the processes between the lines are all satisfactory, indicating that the leakage current detection unit is manufactured reliably.

[0015] Other features and advantages of the invention will be set forth in the description which follows, and will be apparent in part from the description, or may be learned by practicing the invention. The objects and other advantages of the invention may be realized and obtained by means of the structures particularly pointed out in the written description, claims, and drawings.

[0016] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0017] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used in conjunction with embodiments of the invention to explain the invention and do not constitute a limitation thereof. In the drawings:

[0018] Figure 1 This is a schematic diagram of a leakage current detection unit in a magnetic tunnel junction fabrication process according to an embodiment of the present invention;

[0019] Figure 2 This is a schematic diagram of the arrangement and connection of capacitor blocks in an embodiment of the leakage current detection unit in the magnetic tunnel junction fabrication process of the present invention.

[0020] Figure 3 This is a schematic cross-sectional view of the MTJ film layer in an embodiment of the leakage current detection unit in the magnetic tunnel junction fabrication process of the present invention.

[0021] In the diagram: 1-capacitor electrode block, 2-first electrode block, 3-second electrode block, 4-interconnection line. Detailed Implementation

[0022] The preferred embodiments of the present invention will be described below with reference to the accompanying drawings. It should be understood that the preferred embodiments described herein are for illustration and explanation only and are not intended to limit the present invention.

[0023] like Figure 1-2 As shown, this embodiment of the invention provides a leakage current detection unit in the fabrication process of a magnetic tunnel junction, including a capacitor matrix disposed on the same metal layer; the capacitor matrix includes multiple rows of spaced capacitor plates 1, with each pair of adjacent columns of capacitor plates 1 forming a group, for example... Figure 1 As shown, columns 1 and 2 form the first group, columns 3 and 4 form the second group, columns 5 and 6 form the third group, columns 7 and 8 form the fourth group, and columns 9 and 10 form the fifth group. Within each group, different columns have the same number of capacitor blocks, and these blocks are arranged in pairs. Figure 1 Each group shown consists of two columns containing seven capacitors each. Within the same group, for example, the seven capacitors in the first column of the first group are arranged correspondingly to each other, and the seven capacitors in the third column of the second group are arranged correspondingly to each other, and so on. Capacitors in the same column are connected in series; that is, the seven capacitors in the first column of the first group are connected in series, the seven capacitors in the second column are connected in series, and the capacitors in the first and second columns are not connected to each other. In different columns within the same group, the series-connected capacitors are connected to different electrode blocks, such as... Figure 1 The odd-numbered capacitor blocks are connected to the first electrode block 2, and the even-numbered capacitor blocks are connected to the second electrode block 3.

[0024] The working principle of the above technical solution is as follows: The capacitor matrix in this solution includes multiple rows of capacitor electrodes spaced apart. Each capacitor electrode is a single-pole module, i.e., anode or cathode plate. The capacitor electrodes in the same column have the same polarity, while the capacitor electrodes in different columns in the same group have different polarities. All columns of capacitor electrodes connected to the same electrode block have the same polarity, while columns of capacitor electrodes connected to different electrode blocks have different polarities. The two capacitor electrodes that make up the same capacitor are connected to different electrode blocks respectively. That is, the two capacitor electrodes of the same capacitor cannot be short-circuited. On the contrary, the two capacitor electrodes of the same capacitor are in an open-circuit state. During testing, a multimeter, such as a digital multimeter, is used in resistance measurement mode. The two probes are placed on electrode blocks pad1 and pad2 respectively to measure the resistance. An open-circuit resistance of infinite is normal. If a short circuit or breakdown occurs, the measured resistance will be zero or there will be a certain resistance value, indicating that the product is unqualified and there is a problem with its manufacturing process.

[0025] The beneficial effects of the above technical solution are: the present invention can add the above-mentioned leakage current detection unit graphic structure (e.g., ...) to any layout position in any metal layer that needs to be monitored. Figure 1 (As shown). Leakage testing is performed by detecting the resistance value. If the measured resistance value is infinite, it indicates that there is no leakage and the product is qualified, and the process is correct. Furthermore, the photolithography lines and the processes between the lines are all satisfactory, indicating that the leakage detection unit is reliable.

[0026] In one embodiment, such as Figure 1 As shown, the multiple columns of capacitor plates 1 of the capacitor matrix are arranged in a square matrix with intervals.

[0027] The working principle and beneficial effects of the above technical solution are as follows: In this solution, the capacitor blocks of the capacitor matrix are arranged in a square matrix with multiple columns spaced apart. That is, the number of capacitor blocks in each column is equal, and the capacitor blocks in each column are arranged in parallel relative to each other. There is no misalignment between the capacitor blocks in adjacent columns. The arrangement of the capacitor blocks in the square matrix graphic method can enhance the compactness of the structure, save the metal space occupied, and improve the integration.

[0028] In one embodiment, such as Figure 2 As shown, the capacitor electrode 1 is square, and all capacitor electrodes are the same size, ranging from 1μm to 20μm, for example, an 8μm*4μm size is selected; the spacing between different columns of the capacitor electrode 1 is 1μm to 90μm, for example, a 2μm spacing can be selected; the connection of capacitor electrodes 1 in the same column is made of interconnecting lines 4 with a size ranging from 1μm to 10μm, for example, an interconnecting line with a width of 1μm and a length of 2μm can be used; the electrode blocks are the same size, ranging from 1μm to 200μm, for example, a 100μm*100μm electrode block can be used.

[0029] The working principle and beneficial effects of the above technical solution are as follows: The capacitor electrodes in this solution are made into squares of the same size, which makes the process uniform, reduces the difficulty of the process, and facilitates processing; the capacitor electrodes in different columns maintain a certain distance, which can enhance safety and prevent short circuits caused by breakdown; the interconnecting wires connecting the capacitor electrodes are of the same specification, which can also make the process uniform, reduce the difficulty of the process, and facilitate processing; the electrode blocks are of the same size, which reduces the space occupied by the metal layer while ensuring the probe contact effect during measurement; adopting this solution can make the layout of the leakage current detection unit more reasonable and aesthetically pleasing.

[0030] In one embodiment, the resistance value is measured by contacting two electrode blocks connected to different columns of capacitors with a probe; the resistance value is measured using the resistance measurement mode of a digital multimeter; if the measured resistance value is infinite, it indicates that there is no leakage and the distance between adjacent lines is sufficient; otherwise, it indicates that there is contact between the lines or that the distance between adjacent lines is insufficient, causing the device to break down, and the distance needs to be adjusted.

[0031] The working principle and beneficial effects of the above technical solution are as follows: This solution uses the resistance measurement mode of a digital multimeter for measurement. By contacting the probes with two electrode blocks connected to different columns of capacitors, the resistance value can be measured. If the measured resistance value is infinite, it indicates that there is no leakage and the distance between adjacent lines is sufficient. Conversely, it indicates that there is contact between the lines or that the distance between adjacent lines is insufficient, causing the device to break down, and the distance needs to be adjusted. In other words, by using the above-mentioned leakage detection unit to measure the resistance value, the accuracy of the photolithography process can be evaluated, preventing product defects caused by process problems. This solution is simple to operate, easy to implement, and low in cost.

[0032] In one embodiment, the present invention also provides a leakage current detection method in the fabrication process of a magnetic tunnel junction, including using the leakage current detection unit in the above-mentioned magnetic tunnel junction fabrication process, measuring the resistance value by contacting two electrode blocks connected to different columns of capacitor blocks with a probe; if the measured resistance value is infinite, it indicates that there is no leakage current and the distance between adjacent lines is sufficient; otherwise, it indicates that there is contact between the lines or the distance between adjacent lines is insufficient, causing the device to break down, and the distance needs to be adjusted.

[0033] The working principle and beneficial effects of the above technical solution are as follows: This solution provides a leakage current detection method in the magnetic tunnel junction fabrication process. Using the leakage current detection unit in the aforementioned magnetic tunnel junction fabrication process, a probe contacts two electrode blocks connected to different columns of capacitors to measure the resistance value. If the measured resistance value is infinite, it indicates that there is no leakage current and the distance between adjacent lines is sufficient; conversely, it indicates that there is contact between lines or insufficient distance between adjacent lines leading to device breakdown, requiring adjustment of the distance. Using the above leakage current detection unit to measure the resistance value allows for the evaluation of the precision of the photolithography process, preventing product defects caused by process problems. This solution is simple to operate, easy to implement, and low in cost.

[0034] Multiple leakage current detection units can be set on the same metal layer. By setting multiple leakage current detection units at different positions on the metal layer, the resistance value of each leakage current detection unit can be measured. This can help to understand whether the processing technology at different positions on the same metal layer is consistent, and to evaluate the stability of the process. Multiple leakage current detection units can be evenly set at a certain distance at the edge of the metal layer, which can avoid interfering with the design layout of other parts.

[0035] Taking MTJ film as an example, such as Figure 3 As shown, W is the heavy metal layer, the first layer below is CoFeB, which is the free layer, the second layer is the reference layer, and MgO is the tunneling layer. The three layers CoFeB / MgO / CoFeB constitute the MTJ tunnel junction structure. To monitor the photolithography process of the heavy metal layer W, a leakage detection unit of this invention is added to this layer. The size of a single capacitor electrode is 8μm*4μm. The capacitor electrodes are first repeated 7 times to form a 1*7 small unit column. The small unit column is repeated 10 times to form a 7*10 capacitor matrix. The spacing between the small unit columns is 2μm. The 7 capacitor electrodes in each small unit column are connected in series with interconnects that are 1μm wide and 2μm long. The capacitor electrodes in the odd-numbered columns are connected to electrode pad1 with interconnects, and the capacitor electrodes in the even-numbered columns are connected to electrode pad2. Electrode pad1 and electrode pad2 have the same size, both being 100μm*100μm. After the chip fabrication process is completed, the resistance measurement mode of a digital multimeter is used to attach two probes to electrode blocks pad1 and pad2 respectively to measure the resistance value. If the measured resistance value is infinite, it indicates that there is no leakage; otherwise, it indicates that leakage has occurred. The leakage may be due to contact between lines or insufficient spacing leading to breakdown. Feedback to the process department is needed to locate and eliminate the problem, thereby improving leakage detection and production efficiency. The leakage detection unit of this invention has a simple graphic structure, low process requirements, and does not require SEM or other observation methods to obtain accurate process monitoring feedback through leakage testing, resulting in higher efficiency. The test is simple, and leakage results can be obtained with just a simple multimeter test, which can save detection costs.

[0036] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this invention and their equivalents, this invention also intends to include these modifications and variations.

Claims

1. A leakage current detection unit in the fabrication process of a magnetic tunnel junction, characterized in that, The leakage current detection unit is installed in the heavy metal layer of the tunnel structure, including a capacitor matrix installed in the same metal layer. The capacitor matrix includes multiple rows of capacitor electrodes spaced apart. Each pair of adjacent columns of capacitor electrodes forms a group. The number of capacitor electrodes in different columns within the same group is the same and they are arranged in pairs, so that the capacitor electrodes in the same column have the same polarity, while the capacitor electrodes in different columns within the same group have different polarities. The capacitor electrodes in the same column are connected in series, and the series-connected capacitor electrodes in different columns within the same group are connected to different electrode blocks. The capacitor electrodes in all columns connected to the same electrode block have the same polarity, while the capacitor electrodes in columns connected to different electrode blocks have different polarities.

2. The leakage current detection unit in the magnetic tunnel junction fabrication process according to claim 1, characterized in that, The capacitor matrix has multiple columns of capacitors arranged in a square matrix with intervals.

3. The leakage current detection unit in the magnetic tunnel junction fabrication process according to claim 1, characterized in that, The capacitor blocks are square and all capacitor blocks are the same size; the electrode blocks are the same size.

4. The leakage current detection unit in the magnetic tunnel junction fabrication process according to claim 1, characterized in that, The capacitor electrode is square and its size ranges from 1μm to 20μm.

5. The leakage current detection unit in the magnetic tunnel junction fabrication process according to claim 1, characterized in that, The size of the electrode block ranges from 1μm to 200μm.

6. The leakage current detection unit in the magnetic tunnel junction fabrication process according to claim 1, characterized in that, The spacing between different columns of the capacitor electrode is 1μm-90μm.

7. The leakage current detection unit in the magnetic tunnel junction fabrication process according to claim 1, characterized in that, The capacitor electrodes are connected in series in the same column using interconnecting lines with a size range of 1μm-10μm.

8. The leakage current detection unit in the magnetic tunnel junction fabrication process according to claim 1, characterized in that, The resistance value is measured by contacting two electrode blocks connected to different columns of capacitors with a probe. If the measured resistance value is infinite, it means that there is no leakage and the distance between adjacent lines is sufficient. Otherwise, it means that there is contact between the lines or the distance between adjacent lines is insufficient, causing the device to break down, and the distance needs to be adjusted.

9. The leakage current detection unit in the magnetic tunnel junction fabrication process according to claim 8, characterized in that, The resistance value was measured using the resistance measurement mode of a digital multimeter.

10. A leakage current detection method in the fabrication process of a magnetic tunnel junction, characterized in that, The method includes a leakage detection unit in the magnetic tunnel junction fabrication process described in claim 1, which measures the resistance value by contacting two electrode blocks connected to different columns of capacitors with a probe; if the measured resistance value is infinite, it indicates that there is no leakage and the distance between adjacent lines is sufficient; otherwise, it indicates that there is contact between the lines or that the distance between adjacent lines is insufficient, causing the device to break down, and the distance needs to be adjusted.

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