Sheet resistance measuring unit and method in magnetic tunnel junction fabrication process

Abstract

The application provides a sheet resistance measuring unit and method in a magnetic tunnel junction preparation process. The measuring unit comprises three or more electrode blocks, and the electrode blocks are connected in series by interconnection lines with different aspect ratios. The method comprises using the aforementioned sheet resistance measuring unit in the magnetic tunnel junction preparation process, measuring the resistance value between adjacent electrode blocks, and calculating the sheet resistance value using a preset formula. The application connects three or more electrode blocks in the magnetic tunnel junction preparation layout in series by interconnection lines with different aspect ratios to form a sheet resistance measuring unit in the magnetic tunnel junction preparation process. Using this structure, the probe can be used to contact and measure each adjacent electrode block in turn, and the resistance value between adjacent electrode blocks can be measured. Since the same product prepared by the same process can be considered as having no process difference, the sheet resistance value can be calculated according to the different resistance values measured between different groups of adjacent electrode blocks and the numerical relationship between the resistance value, the sheet resistance and the contact resistance.

Description

Technical Field

[0001] This invention relates to the field of magnetic electronic devices for memory (MRAM), and particularly to a sheet resistance measurement unit and method in the fabrication process of a magnetic tunnel junction. Background Technology

[0002] Magnetic random access memory (MRAM) based on the magnetic tunnel junction (MTJ) principle has the potential to become the next generation of low-power general-purpose memory due to its advantages such as non-volatility, infinite erasure and write capability, and fast writing speed. The core memory cell (bitcell) of an MRAM chip is a hybrid device combining a transistor and a magnetic tunnel junction. Low power consumption is a major advantage of MRAM chips. The resistance of the device's electrode blocks has a significant impact on power consumption; excessively high resistance leads to increased power consumption, increased heat generation, and reduced MRAM chip performance. Therefore, monitoring the resistance of the device's electrode blocks is extremely important.

[0003] Sheet resistance (SRT) is used to calibrate the resistance of electrode blocks in a device. SRT refers to the resistance between edges of a square thin-film conductive material. A key characteristic of SRT is that the edge-to-edge resistance is the same for any square of any size, regardless of whether the side length is 1 meter or 0.1 meters. This means that SRT is only related to factors such as the thickness of the conductive film. In the core memory cell layout of an MRAM chip, electrode blocks (squares) with various aspect ratios are designed. Since the SRT of these electrode blocks is identical, monitoring the electrode blocks directly translates to monitoring their SRT. During the patterning process of magnetic tunnel junctions, etching has the most direct impact on the SRT of the electrode blocks. The remaining thickness of the heavy metal layer after etching directly determines the magnitude of the SRT. Monitoring the SRT of the heavy metal layer after the etching process is crucial for device performance.

[0004] In the MRAM process flow, the etching process uses endpoint monitoring (EPD) to detect the degree of etching completion. This is achieved by collecting optical emission spectra (OES) curves generated by the chemical changes in different dielectric layers during plasma etching, which determine the extent of the etching process. However, a significant portion of current etching equipment still relies on human judgment of the OES signal to determine the etching stop time, resulting in substantial errors. Since the film thickness is typically on the nanometer scale, even extremely short etching times can lead to the etching of a layer through or missing the desired location, causing the entire wafer fabrication process to fail. Summary of the Invention

[0005] To address the aforementioned technical problems, this invention provides a sheet resistance measurement unit in the fabrication process of a magnetic tunnel junction, comprising three or more electrode blocks, wherein the electrode blocks are connected in series using interconnects with different aspect ratios.

[0006] Optionally, the resistance value can be obtained by sequentially contacting each adjacent electrode block with a probe, and the sheet resistance value can be calculated using the following formula:

[0007]

[0008] In the above formula, R S The sheet resistance value is represented in the fabrication process of the magnetic tunnel junction; M represents the serial number of the series electrode block; R M(M+1) τ represents the measured resistance value between the Mth electrode block and the adjacent (M+1)th electrode block; M(M+1) W represents the aspect ratio of the interconnect line between the Mth electrode block and the adjacent (M+1)th electrode block; M(M+1) L represents the width of the interconnect line between the Mth electrode block and its adjacent (M+1)th electrode block; M(M+1) This represents the length of the interconnect line between the Mth electrode block and the adjacent (M+1)th electrode block.

[0009] Optionally, each of the electrode blocks has the same contact area with the interconnect.

[0010] Optionally, the resistance value can be obtained by sequentially contacting each adjacent electrode block with a probe, and the sheet resistance value can be calculated using the following formula:

[0011]

[0012] In the above formula, R S The sheet resistance value represents the magnetic tunnel junction fabrication process; M and N represent the serial numbers of the series electrode blocks, and M≠N; R M(M+1) R represents the measured resistance value between the Mth electrode block and the adjacent (M+1)th electrode block; N(N+1) τ represents the measured resistance value between the Nth electrode block and the (N+1)th adjacent electrode block; M(M+1) τ represents the aspect ratio of the interconnect line between the Mth electrode block and the adjacent (M+1)th electrode block; N(N+1) L represents the aspect ratio of the interconnect line between the Nth electrode block and the (N+1)th adjacent electrode block; M(M+1) W represents the length of the interconnect between the Mth electrode block and the adjacent (M+1)th electrode block. M(M+1) L represents the width of the interconnect line between the Mth electrode block and its adjacent (M+1)th electrode block; N(N+1) W represents the length of the interconnect between the Nth electrode block and its adjacent (N+1)th electrode block. N(N+1) This represents the width of the interconnect line between the Nth electrode block and its adjacent (N+1)th electrode block.

[0013] Optionally, the electrode blocks are connected in series using interconnecting lines with increasing aspect ratios.

[0014] Optionally, the electrode blocks are sequentially selected with the same width and length L. n = nL1 interconnects in series; or

[0015] Using the same length and width in sequence The interconnects are connected in series;

[0016] Among them, L n L1 represents the length of the nth interconnect; L1 represents the length of the 1st interconnect; n represents the interconnect number, i.e., n = 1, 2, 3, ..., n; W n W1 represents the width of the nth interconnect; W1 represents the width of the 1st interconnect.

[0017] Optionally, the electrode blocks are all the same size and have the same spacing between adjacent blocks.

[0018] Optionally, the resistance value is measured using the resistance measurement mode of a digital multimeter.

[0019] Optionally, a probe is used to sequentially contact each adjacent electrode block to measure the corresponding resistance value. A Cartesian coordinate system is constructed with aspect ratio and resistance value as the abscissa and ordinate, respectively. Based on the aspect ratio of the interconnection line between adjacent electrode blocks measured each time, the resistance value of each measurement is marked with data points in the Cartesian coordinate system. The data points are connected to form a fitted straight line. The slope of the fitted straight line is the sheet resistance value. The resistance value corresponding to the intersection of the fitted straight line and the ordinate is twice the contact resistance.

[0020] This invention also provides a method for measuring sheet resistance in the fabrication process of a magnetic tunnel junction. Using the sheet resistance measurement unit described above in the magnetic tunnel junction fabrication process, each electrode block has the same contact area with the interconnect. The resistance values ​​between different adjacent electrode blocks are obtained by measurement, and the sheet resistance value is calculated using the following formula:

[0021]

[0022] In the above formula, R S The sheet resistance value represents the magnetic tunnel junction fabrication process; M and N represent the serial numbers of the series electrode blocks, and M≠N; R M(M+1) R represents the measured resistance value between the Mth electrode block and the adjacent (M+1)th electrode block; N(N+1) τ represents the measured resistance value between the Nth electrode block and the (N+1)th adjacent electrode block; M(M+1) τ represents the aspect ratio of the interconnect line between the Mth electrode block and the adjacent (M+1)th electrode block; N(N+1) L represents the aspect ratio of the interconnect line between the Nth electrode block and the (N+1)th adjacent electrode block; M(M+1) W represents the length of the interconnect between the Mth electrode block and the adjacent (M+1)th electrode block.M(M+1) L represents the width of the interconnect line between the Mth electrode block and its adjacent (M+1)th electrode block; N(N+1) W represents the length of the interconnect between the Nth electrode block and its adjacent (N+1)th electrode block. N(N+1) This represents the width of the interconnect line between the Nth electrode block and its adjacent (N+1)th electrode block.

[0023] Optionally, the resistance value is measured using the resistance measurement mode of a digital multimeter.

[0024] Optionally, the calculated sheet resistance value can be compared with the designed sheet resistance value. If the calculated sheet resistance value is greater than the designed sheet resistance value, it means that the actual etching depth is greater than the designed etching depth, and the etching time or etching rate needs to be reduced.

[0025] This invention constructs a sheet resistance measurement unit in the magnetic tunnel junction (MRAM) fabrication process by sequentially connecting three or more electrode blocks in the layout using interconnects with different aspect ratios. Using this structure, a probe can be used to sequentially contact adjacent electrode blocks for measurement, obtaining the resistance values ​​between them. Since products fabricated using the same MRAM fabrication process are essentially considered to have no process differences (i.e., sheet resistance and contact resistance remain constant), the sheet resistance value of the MRAM fabrication process can be calculated using the relationship between resistance and sheet resistance / contact resistance. This invention tests sheet resistance by adding the aforementioned measurement unit structure to the heavy metal layer. The measured sheet resistance is compared with the known design value of the heavy metal layer's sheet resistance. If the measured sheet resistance value is larger than the design value, it indicates that the etching depth is deeper than designed, and the etching time or rate needs to be adjusted promptly, either by reducing the etching time or keeping the time constant while reducing the etching rate. This invention can quantitatively monitor the etching process in MRAM fabrication with higher accuracy than human observation of OES signals.

[0026] 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.

[0027] 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

[0028] 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:

[0029] Figure 1This is a schematic diagram of a sheet resistance measurement unit in a magnetic tunnel junction fabrication process according to an embodiment of the present invention;

[0030] Figure 2 This is a schematic diagram of an embodiment of the sheet resistance measurement unit in the magnetic tunnel junction fabrication process of the present invention, which includes four electrode blocks and whose interconnection lines have an aspect ratio that increases by the same amount.

[0031] Figure 3 This is a schematic diagram of an embodiment of the sheet resistance measurement unit in the magnetic tunnel junction fabrication process of the present invention, which includes four electrode blocks and the aspect ratio of the interconnects increases in multiples.

[0032] Figure 4 This is a schematic diagram of the fitting lines of the resistance measurement results, plotted with aspect ratio and resistance value as the abscissa and ordinate respectively, in an embodiment of the sheet resistance measurement method in the magnetic tunnel junction fabrication process of the present invention. Detailed Implementation

[0033] 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.

[0034] like Figure 1-3 As shown, an embodiment of the present invention provides a sheet resistance measurement unit in the fabrication process of a magnetic tunnel junction, comprising three or more electrode blocks 2, wherein the electrode blocks 2 are connected in series using interconnecting lines 1 with different aspect ratios.

[0035] The working principle and beneficial effects of the above technical solution are as follows: This solution connects three or more electrode blocks in the magnetic tunnel junction fabrication layout in series with interconnects of different aspect ratios to form a sheet resistance measurement unit in the magnetic tunnel junction fabrication process. With this structure, a probe can be used to contact each adjacent electrode block in sequence to measure the resistance value between adjacent electrode blocks. Since the same product prepared by the same magnetic tunnel junction fabrication process can be regarded as having no process difference, that is, the sheet resistance and contact resistance are constant, the sheet resistance value of the magnetic tunnel junction fabrication process can be calculated by the relationship between the resistance and the sheet resistance and contact resistance.

[0036] In one embodiment, the resistance value is obtained by contacting each adjacent electrode block 2 with a probe, and the sheet resistance is calculated using the following formula:

[0037]

[0038] In the above formula, R S The sheet resistance value is represented in the fabrication process of the magnetic tunnel junction; M represents the serial number of the series electrode block; R M(M+1) τ represents the measured resistance value between the Mth electrode block and the adjacent (M+1)th electrode block; M(M+1)W represents the aspect ratio of the interconnect line between the Mth electrode block and the adjacent (M+1)th electrode block; M(M+1) L represents the width of the interconnect line between the Mth electrode block and its adjacent (M+1)th electrode block; M(M+1) This represents the length of the interconnect line between the Mth electrode block and the adjacent (M+1)th electrode block.

[0039] The working principle and beneficial effects of the above technical solution are as follows: This solution obtains the corresponding resistance value by measuring the contact of probes with each adjacent electrode block. The resistance value can be measured using the resistance measurement mode of a digital multimeter. The sheet resistance value is calculated using the above formula, which is derived from the resistance formula. The formula S = w * d is derived by reverse calculation, which shows that it reflects the relationship between sheet resistance and length and width. In the resistance formula, R represents the measured resistance value, ρ represents the resistivity of the material, s represents the cross-sectional area in the width direction, d represents the film thickness, l represents the length, and w represents the width.

[0040] In one embodiment, the resistance value is obtained by contacting each adjacent electrode block 2 with a probe. The resistance value can be measured using the resistance measurement mode of a digital multimeter, and the sheet resistance value is calculated using the following formula:

[0041]

[0042] In the above formula, R S The sheet resistance value represents the magnetic tunnel junction fabrication process; M and N represent the serial numbers of the series electrode blocks, and M≠N; R M(M+1) R represents the measured resistance value between the Mth electrode block and the adjacent (M+1)th electrode block; N(N+1) τ represents the measured resistance value between the Nth electrode block and the (N+1)th adjacent electrode block; M(M+1) τ represents the aspect ratio of the interconnect line between the Mth electrode block and the adjacent (M+1)th electrode block; N(N+1) L represents the aspect ratio of the interconnect line between the Nth electrode block and the (N+1)th adjacent electrode block; M(M+1) W represents the length of the interconnect between the Mth electrode block and the adjacent (M+1)th electrode block. M(M+1) L represents the width of the interconnect line between the Mth electrode block and its adjacent (M+1)th electrode block; N(N+1) W represents the length of the interconnect between the Nth electrode block and its adjacent (N+1)th electrode block. N(N+1) This represents the width of the interconnect line between the Nth electrode block and its adjacent (N+1)th electrode block.

[0043] The working principle and beneficial effects of the above technical solution are as follows: This solution obtains the corresponding resistance value by measuring the contact between the probe and each adjacent electrode block. The resistance value can be measured using the resistance measurement mode of a digital multimeter. The sheet resistance value is calculated using the above formula. Due to the contact resistance between the lead wire and the adjacent electrode block, the resistance formula is modified as follows: In the revised resistance formula, R represents the measured resistance value, l represents the length, w represents the width, and Rc represents the contact resistance. The formula in this scheme takes into account the numerical relationship between the resistance value, sheet resistance, and contact resistance. It is derived by means of the revised resistance formula, thus the sheet resistance value obtained is more accurate.

[0044] In one embodiment, the electrode blocks 2 are connected in series using interconnecting lines 1 with increasing aspect ratios; the electrode blocks 2 have the same size and the same spacing between adjacent ones.

[0045] The working principle and beneficial effects of the above technical solution are as follows: The aspect ratio of the interconnecting lines used in this solution increases sequentially, so that the corresponding resistance values ​​show a certain increasing characteristic. The increasing regularity is conducive to calculation and also facilitates the plotting of the fitting straight line using the coordinates of aspect ratio and resistance value, so as to express the measurement results graphically. The electrode blocks use the same size and the same adjacent spacing, which makes the layout more reasonable and beautiful, and simplifies the process and facilitates the formulation of unified process standards.

[0046] In one embodiment, the electrode blocks 2 are sequentially selected with the same width and length L. n = nL1 interconnect line 1 in series; or

[0047] Using the same length and width in sequence The interconnects are connected in series;

[0048] Among them, L n L1 represents the length of the nth interconnect; L1 represents the length of the 1st interconnect; n represents the interconnect number, i.e., n = 1, 2, 3, ..., n; W n W1 represents the width of the nth interconnect; W1 represents the width of the 1st interconnect.

[0049] The working principle and beneficial effects of the above technical solution are as follows: The aspect ratio of the interconnecting lines used in this solution increases sequentially by the same amount, which further reflects the regularity and makes the corresponding resistance value show a certain increasing regularity. The increasing regularity can simplify the calculation formula and facilitate calculation; it is also beneficial to use the coordinates of aspect ratio and resistance value to draw a fitted straight line and represent the measurement results graphically.

[0050] In one embodiment, such as Figure 4As shown, the corresponding resistance values ​​are obtained by sequentially contacting each adjacent electrode block with a probe. A Cartesian coordinate system is constructed with aspect ratio and resistance value as the abscissa and ordinate, respectively. Based on the aspect ratio of the interconnection line between adjacent electrode blocks in each measurement, the resistance values ​​of each measurement are marked with data points in the Cartesian coordinate system. The data points are connected to form a fitted straight line. The slope of the fitted straight line is the sheet resistance value. The resistance value corresponding to the intersection of the fitted straight line and the ordinate is twice the contact resistance.

[0051] The working principle and beneficial effects of the above technical solution are as follows: This solution constructs a plane rectangular coordinate system with aspect ratio and resistance value as the abscissa and ordinate, respectively. The aspect ratio and resistance value between adjacent electrode blocks measured each time are marked in the plane rectangular coordinate system. The marks are connected to form a fitting straight line. The slope of the fitting straight line reflects the sheet resistance value. The resistance value corresponding to the intersection of the fitting straight line and the ordinate is twice the contact resistance. Therefore, this solution can obtain two parameters, sheet resistance value and contact resistance, at the same time and intuitively, which can more comprehensively reflect the state of the preparation process.

[0052] This invention also provides a method for measuring sheet resistance in the fabrication process of a magnetic tunnel junction. Using the sheet resistance measurement unit in the above-mentioned magnetic tunnel junction fabrication process, each electrode block has the same contact area with the interconnect. The resistance value between different adjacent electrode blocks is obtained by measurement. The resistance value can be measured using the resistance measurement mode of a digital multimeter. The sheet resistance value is calculated using the following formula:

[0053]

[0054] In the above formula, R S The sheet resistance value represents the magnetic tunnel junction fabrication process; M and N represent the serial numbers of the series electrode blocks, and M≠N; R M(M+1) R represents the measured resistance value between the Mth electrode block and the adjacent (M+1)th electrode block; N(N+1) τ represents the measured resistance value between the Nth electrode block and the (N+1)th adjacent electrode block; M(M+1) τ represents the aspect ratio of the interconnect line between the Mth electrode block and the adjacent (M+1)th electrode block; N(N+1) L represents the aspect ratio of the interconnect line between the Nth electrode block and the (N+1)th adjacent electrode block; M(M+1) W represents the length of the interconnect between the Mth electrode block and the adjacent (M+1)th electrode block. M(M+1) L represents the width of the interconnect line between the Mth electrode block and its adjacent (M+1)th electrode block; N(N+1) W represents the length of the interconnect between the Nth electrode block and its adjacent (N+1)th electrode block. N(N+1) This represents the width of the interconnect line between the Nth electrode block and its adjacent (N+1)th electrode block.

[0055] The working principle and beneficial effects of the above technical solution are as follows: This solution connects three or more electrode blocks in the magnetic tunnel junction fabrication layout in series with interconnects of different aspect ratios to form a sheet resistance measurement unit in the magnetic tunnel junction fabrication process. Using this structure, a probe can be used to contact each adjacent electrode block in sequence to measure the resistance value between adjacent electrode blocks. The sheet resistance value of the magnetic tunnel junction fabrication process can be calculated using the above formula. The formula of this solution considers the numerical relationship between the resistance value, sheet resistance, and contact resistance. It is derived by using a modified resistance formula, so the obtained sheet resistance value is more accurate. Since the same product fabricated by the same magnetic tunnel junction fabrication process can be regarded as having no process difference, that is, the sheet resistance and contact resistance remain constant.

[0056] In one embodiment, the method further includes comparing the calculated sheet resistance value with the designed sheet resistance value. If the calculated sheet resistance value is greater than the designed sheet resistance value, it indicates that the actual depth of the etching process is greater than the designed etching depth, and the etching time or etching rate needs to be reduced.

[0057] The working principle and beneficial effects of the above technical solution are as follows: This solution tests the sheet resistance by adding the aforementioned measurement unit structure to the heavy metal layer. The measured sheet resistance is compared with the known design value of the sheet resistance of the heavy metal layer. If the measured sheet resistance value is larger than the design value, it indicates that the etching depth is deeper than the design value, and the material of the heavy metal layer may have been etched through. Under the premise that the process conditions have not changed, this indicates that the etching rate of the equipment has fluctuated, and relevant parameters need to be calibrated in a timely manner, such as adjusting the etching time or rate in a timely manner, reducing the etching time or keeping the time constant to reduce the etching rate. This invention can quantitatively monitor the etching process in MRAM fabrication, and its accuracy is higher than that of human observation of OES signals.

[0058] The following example uses the etching monitoring of a W 5nm (heavy metal layer) / CoFeB (free layer) / MgO (barrier layer) / CoFeB (reference layer) magnetic tunnel junction. During the MTJ pattern etching process, etching must stop at the heavy metal layer W. To monitor the etching of the heavy metal layer W, a sheet resistance measurement unit is added to the MTJ board, such as... Figure 2 or Figure 3 As shown.

[0059] by Figure 3Taking the example shown, pad is an electrode block, and the interconnect line width is 2μm. Pad1 and pad2, pad2 and pad3, and pad3 and pad4 are connected by serpentine curves with aspect ratios (L:w) of 50, 150, and 200 respectively using interconnect line 11. For example, the spacing between pads is 50μm if interconnect lines of the same width are used; the length of the interconnect line L1 between pad1 and pad2 is 50μm; the interconnect line between pad2 and pad3 includes the first interconnect line segment 12, the second interconnect line segment 13, the third interconnect line segment 14, the fourth interconnect line segment 15, and the fifth interconnect line segment 16, and its total interconnect line length is the sum of the lengths of the first interconnect line segment 12, the second interconnect line segment 13, the third interconnect line segment 14, the fourth interconnect line segment 15, and the fifth interconnect line segment 16, i.e., L2+L3+L4+L5+L6=150um; the length of the interconnect line between pad3 and pad4 is 200um. Using Keithley's resistance measurement mode, probes were inserted onto pad1 and pad2 respectively to obtain R. 12 Plug into pad2 and pad3 to get R 23 R was measured by stabbing pad3 and pad4. 34 Substituting the values ​​into the formula R = L / w Rs + 2Rc, we obtain the following equations for each measurement:

[0060] R 12 =50*Rs+2Rc

[0061] R 23 =150*Rs+2Rc

[0062] R 34 =200*Rs+2Rc

[0063] The sheet resistance and contact resistance can be calculated using the above equations.

[0064] Furthermore, based on the data from the three measurements mentioned above, a Cartesian coordinate system was constructed with aspect ratio and resistance value as the x and y axes, and the marks were connected to form a fitted straight line, resulting in the following: Figure 4 The fitting graph shown has a resistance value of 2Rc at the intersection of the fitted line and the vertical axis, and a slope of Rs. The values ​​of Rs and Rc can be intuitively read from the graph.

[0065] Comparing the sheet resistance (Rs') of 5nm W with the design value, if Rs >> Rs', it indicates that the etched heavy metal layer W has been etched through. Given that the etching process remains unchanged, this suggests fluctuations in the etching rate and other parameters. In such cases, it's necessary to check the relevant etching parameters as soon as possible. Process optimization can be achieved by reducing the etching time or decreasing the etching rate. If Rs ≈ Rs', the measured sheet resistance is comparable to the design value, indicating that the etched thickness meets the design thickness.

[0066] 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 sheet resistance measurement unit in the fabrication process of a magnetic tunnel junction, characterized in that, It includes three or more electrode blocks, and the electrode blocks are connected in series using interconnecting lines with different aspect ratios; the electrode blocks are of the same size and their adjacent spacing is the same; the contact area between each electrode block and the interconnecting line is the same; The sheet resistance measurement unit is formed in the heavy metal layer of the magnetic tunnel junction fabrication layout; Each adjacent electrode block is configured to be contacted by a probe in sequence to measure the resistance value between each adjacent electrode block; each resistance value is equal to the product of the sheet resistance of the heavy metal layer and the aspect ratio of the corresponding interconnect line plus twice the contact resistance, and each measurement has the same contact resistance.

2. The sheet resistance measurement unit in the magnetic tunnel junction fabrication process according to claim 1, characterized in that, The resistance values ​​are obtained by sequentially contacting each adjacent electrode block with a probe, and the sheet resistance is calculated using the following formula: ； In the above formula, This represents the sheet resistance value in the fabrication process of a magnetic tunnel junction. Indicates the serial number of the series electrode blocks; Indicates the first The first electrode block and the adjacent first The resistance value measured between the electrode blocks; Indicates the first The first electrode block and the adjacent first The aspect ratio of the interconnect lines between the electrode blocks; Indicates the first The first electrode block and its adjacent first electrode block The width of the interconnecting lines between the electrode blocks; Indicates the first The first electrode block and the adjacent first The length of the interconnecting lines between the electrode blocks.

3. The sheet resistance measurement unit in the magnetic tunnel junction fabrication process according to claim 1, characterized in that, The resistance values ​​are obtained by sequentially contacting each adjacent electrode block with a probe, and the sheet resistance is calculated using the following formula: ； In the above formula, This represents the sheet resistance value in the fabrication process of a magnetic tunnel junction. and Indicates the serial number of the series electrode blocks, and ; Indicates the first The first electrode block and the adjacent first The resistance value measured between the electrode blocks; Indicates the first The first electrode block and the adjacent first The resistance value measured between the electrode blocks; Indicates the first The first electrode block and the adjacent first The aspect ratio of the interconnect lines between the electrode blocks; Indicates the first The first electrode block and the adjacent first The aspect ratio of the interconnect lines between the electrode blocks; Indicates the first The first electrode block and the adjacent first The length of the interconnecting lines between the electrode blocks; Indicates the first The first electrode block and its adjacent first electrode block The width of the interconnecting lines between the electrode blocks; Indicates the first The first electrode block and its adjacent first electrode block The length of the interconnecting lines between the electrode blocks; Indicates the first The first electrode block and its adjacent first electrode block The width of the interconnect lines between the electrode blocks.

4. The sheet resistance measurement unit in the magnetic tunnel junction fabrication process according to claim 1, characterized in that, The electrode blocks are connected in series using interconnecting lines with increasing aspect ratios.

5. The sheet resistance measurement unit in the magnetic tunnel junction fabrication process according to claim 1, characterized in that, The electrode blocks are sequentially selected with the same width and length. The interconnects are connected in series; or Using the same length and width in sequence The interconnects are connected in series; in, Indicates the first The length of each interconnect; Indicates the first The length of each interconnect; Indicates the serial number of the interconnect, i.e. , Indicates the total number of interconnects; Indicates the first The width of each interconnect line; Indicates the first The width of each interconnect line.

6. The sheet resistance measurement unit in the magnetic tunnel junction fabrication process according to claim 1, characterized in that, The resistance values ​​are measured by sequentially contacting each adjacent electrode block with a probe. A Cartesian coordinate system is constructed with aspect ratio and resistance value as the abscissa and ordinate, respectively. Based on the aspect ratio of the interconnection line between adjacent electrode blocks measured each time, the resistance values ​​of each measurement are marked with data points in the Cartesian coordinate system. The data points are linearly fitted to obtain a fitted straight line. The slope of the fitted straight line is the sheet resistance value. The resistance value corresponding to the intersection of the fitted straight line and the ordinate is twice the contact resistance.

7. A method for measuring sheet resistance in the fabrication process of a magnetic tunnel junction, characterized in that, Using the sheet resistance measurement unit in the magnetic tunnel junction fabrication process described in claim 1, a probe is used to sequentially contact each pair of adjacent electrode blocks to obtain the resistance values ​​between different pairs of adjacent electrode blocks, and the sheet resistance value is calculated using the following formula: ； In the above formula, This represents the sheet resistance value in the fabrication process of a magnetic tunnel junction. and Indicates the serial number of the series electrode blocks, and ; Indicates the first The first electrode block and the adjacent first The resistance value measured between the electrode blocks; Indicates the first The first electrode block and the adjacent first The resistance value measured between the electrode blocks; Indicates the first The first electrode block and the adjacent first The aspect ratio of the interconnect lines between the electrode blocks; Indicates the first The first electrode block and the adjacent first The aspect ratio of the interconnect lines between the electrode blocks; Indicates the first The first electrode block and the adjacent first The length of the interconnecting lines between the electrode blocks; Indicates the first The first electrode block and its adjacent first electrode block The width of the interconnecting lines between the electrode blocks; Indicates the first The first electrode block and its adjacent first electrode block The length of the interconnecting lines between the electrode blocks; Indicates the first The first electrode block and its adjacent first electrode block The width of the interconnecting lines between the electrode blocks; The calculated sheet resistance is compared with the designed sheet resistance. If the calculated sheet resistance is greater than the designed sheet resistance, it means that the actual etching depth is greater than the designed etching depth, and the etching time or etching rate needs to be reduced.

8. The sheet resistance measurement method in the magnetic tunnel junction fabrication process according to claim 7, characterized in that, The resistance value was measured using the resistance measurement mode of a digital multimeter.

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