CN111508549A - SOT-MRAM test structure and test method thereof - Google Patents
SOT-MRAM test structure and test method thereof Download PDFInfo
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- CN111508549A CN111508549A CN202010315504.8A CN202010315504A CN111508549A CN 111508549 A CN111508549 A CN 111508549A CN 202010315504 A CN202010315504 A CN 202010315504A CN 111508549 A CN111508549 A CN 111508549A
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- G—PHYSICS
- G11—INFORMATION STORAGE
- G11C—STATIC STORES
- G11C29/00—Checking stores for correct operation ; Subsequent repair; Testing stores during standby or offline operation
- G11C29/04—Detection or location of defective memory elements, e.g. cell constructio details, timing of test signals
- G11C29/50—Marginal testing, e.g. race, voltage or current testing
- G11C29/50008—Marginal testing, e.g. race, voltage or current testing of impedance
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- G—PHYSICS
- G11—INFORMATION STORAGE
- G11C—STATIC STORES
- G11C29/00—Checking stores for correct operation ; Subsequent repair; Testing stores during standby or offline operation
- G11C29/04—Detection or location of defective memory elements, e.g. cell constructio details, timing of test signals
- G11C29/50—Marginal testing, e.g. race, voltage or current testing
- G11C2029/5004—Voltage
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- G—PHYSICS
- G11—INFORMATION STORAGE
- G11C—STATIC STORES
- G11C29/00—Checking stores for correct operation ; Subsequent repair; Testing stores during standby or offline operation
- G11C29/04—Detection or location of defective memory elements, e.g. cell constructio details, timing of test signals
- G11C29/50—Marginal testing, e.g. race, voltage or current testing
- G11C2029/5006—Current
Abstract
The invention provides a test structure of an SOT-MRAM and a test method thereof. Each spin orbit torque magnetic storage bit includes a spin orbit torque supply line, a magnetic tunnel junction disposed on the spin orbit torque supply line; between two adjacent spin orbit torque magnetic storage bits, a magnetic tunnel junction in one provides a line connection with spin orbit torque in the other. The magnetic tunnel junction device further comprises an excitation circuit used for exciting the n magnetic tunnel junctions and two first test electrodes, wherein the two first test electrodes are respectively connected with two spin orbit torque magnetic storage bit units positioned at the head end and the tail end of the n spin orbit torque magnetic storage bit units. The n spin orbit torque magnetic storage bit positions are sequentially connected in series end to end, the first test electrode and the excitation circuit, so that the test structure is simplified, and the total area of a test device is reduced. And meanwhile, a large number of devices are tested, and the testing efficiency is improved.
Description
Technical Field
The invention relates to the technical field of semiconductors, in particular to a SOT-MRAM test structure and a test method thereof.
Background
A recently developed Magnetic Random Access Memory SOT (Spin Orbit Torque) MRAM (a nonvolatile Magnetic Random Access Memory) has excellent characteristics. The defects of large SRAM (Static Random-Access Memory) area and large electric leakage after the size is reduced are overcome; the defect that DRAM (Dynamic Random Access Memory) needs to be refreshed all the time and has large power consumption is overcome. The magnetic random access memory SOT MRAM is superior to a Flash memory in terms of read/write time and read/write times by several orders of magnitude.
The core memory cell of the current MRAM memory generally adopts a magnetic tunnel junction with a vertical magnetization characteristic, and has the advantages of multiple layers, small thickness and very complex preparation process. Various electrical parameters need to be tested and monitored. In the research and development and mass production stages, in order to monitor electrical parameters such as a device Rp (parallel resistor), an Rap (anti-parallel resistor), a TMR (Tunnel Magnetoresistance), a Vc (voltage), an Ic (flip current), and the like, the functionality and stability of a product are ensured, and the selection amount of a test sample is large. At present, for electrical testing of multiple samples, the samples are generally tested one by one, and then statistical analysis is performed on the test data.
The main methods for testing the electrical parameters of the sotmj (Magnetic Tunnel Junction) device, such as Rp, Rap, TMR, Ic, and Vc distributions, are as follows: testing a large number of single devices, and obtaining parameter statistical distribution through data processing; and obtaining the statistical distribution of parameters by using a parallel test method through a parallel structure. The aforementioned test methods have the disadvantages that: the large area of test units (testkeys) required for testing a large number of single devices respectively, the long test time and the wafer level process uniformity information contained in statistical data create difficulties for further analysis. In the parallel test method, under the condition that the precision of a machine table is limited, the number of parallel devices is limited (when the number of parallel devices is high, the total resistance value of the devices is possibly equivalent to that of a lead wire, and the test error is large), the test efficiency cannot be greatly improved, and in addition, if the devices are short-circuited (short), the test structure cannot be used.
Disclosure of Invention
The invention provides a SOT-MRAM test structure and a test method thereof, which are used for simplifying the arrangement of a test structure, reducing the total area of a test device and simultaneously testing a large number of devices so as to improve the test efficiency.
In a first aspect, the present invention provides a test structure for an SOT-MRAM, the test structure comprising n spin-orbit torque magnetic storage bits connected end-to-end in series. Each spin orbit torque magnetic storage bit includes a spin orbit torque supply line, and a magnetic tunnel junction disposed on the spin orbit torque supply line; between two adjacent spin orbit torque magnetic storage bits, the magnetic tunnel junction in one of the spin orbit torque magnetic storage bits is in line connection with the spin orbit torque supply in the other spin orbit torque magnetic storage bit. The test structure also comprises an excitation circuit used for exciting the n magnetic tunnel junctions and two first test electrodes used for testing the resistance values of the n magnetic tunnel junctions, wherein the two first test electrodes are respectively connected with two spin orbit torque magnetic storage bit units positioned at the head end and the tail end in the n spin orbit torque magnetic storage bit units.
In the scheme, the n spin orbit torque magnetic storage bit elements are connected in series end to end in sequence, two first test electrodes are respectively connected in series on the two spin orbit torque magnetic storage bit elements positioned at the head end and the tail end in the n spin orbit torque magnetic storage bit elements, and an excitation circuit for exciting the n magnetic tunnel junctions is further arranged, so that the arrangement of a test structure is simplified, and the total area of a test device is reduced. When the device is applied, the resistance values of the n magnetic tunnel junctions which are sequentially connected in series can be conveniently tested, electrical parameters such as Rp, Rap, TMR, Vc and Ic distribution of the device can be obtained according to the tested resistance values through analysis and fitting, and a large number of devices can be tested, so that the testing efficiency is improved.
In one specific embodiment, the excitation circuit includes two second test electrodes, both ends of each spin orbit torque supply line are respectively connected in series with the two second test electrodes, and any two spin orbit torque supply lines are connected in parallel. The excitation circuit further includes two control switches connected in series across each spin orbit torque supply line for controlling whether the two second test electrodes are open or closed with respect to each spin orbit torque supply line. The n spin orbit torque supply lines are connected in parallel, and control switches are arranged at two ends of each spin orbit torque supply line. When n magnetic tunnel junctions need to be excited, the switch is controlled to be closed, so that the two second test electrodes can provide overturning current for the n spin orbit torque supply lines; when the resistance value between the two first test electrodes needs to be tested, the switch is controlled to be open-circuited so as to test the resistance values of the n magnetic tunnel junctions which are sequentially connected in series end to end.
In one particular embodiment, each control switch has two terminals, and a control terminal that controls the two terminals to be open or closed. One of the two terminals on each control switch is connected with the corresponding spin orbit torque supply line, and the other terminal is connected with the corresponding second test electrode; and the control terminals of the two control switches on the same spin orbit torque supply line are connected in series. The test structure further includes m third test electrodes, where m is an integer greater than 0 and less than or equal to n. Each third test electrode is connected with the control ends of at least two control switches on one spin orbit torque supply line so as to control the open circuit or the closed circuit of the control switches, and the control ends of the two control switches on each spin orbit torque supply line are connected with only one third test electrode. The control switch connected with the third testing electrode can be controlled by arranging m third testing electrodes, wherein one third testing electrode is at least connected with the control end of one control switch. When the test circuit is applied, different magnetic tunnel junctions can be isolated from the test circuit according to the requirements, so that the test of other magnetic tunnel junctions is prevented from being influenced due to short circuit of a single or a plurality of magnetic tunnel junctions.
In a specific embodiment, between any two adjacent spin orbit torque magnetic storage bits, the spin orbit torque supply line in one spin orbit torque magnetic storage bit is connected in series with the spin orbit torque supply line in the other spin orbit torque magnetic storage bit. The two first test electrodes are also respectively connected in series with two spin orbit torque supply lines positioned at the head end and the tail end of the n spin orbit torque supply lines so as to supply the n spin orbit torque supply lines with the overturning current. The excitation circuit includes a control switch disposed between any adjacent two spin orbit torque supply lines and for controlling whether the adjacent two spin orbit torque supply lines are open or closed. The spin orbit torque providing lines are connected in series, so that the number of the test electrodes and the number of the control switches are reduced, and the area occupied by the test structure is further reduced.
In one specific embodiment, the control switch has two terminals, and a control terminal that controls the two terminals to be opened or closed, wherein one of the two terminals of each control switch is connected to one of the adjacent two spin orbit torque supply lines, and the other terminal is connected to the other of the adjacent two spin orbit torque supply lines. The excitation circuit includes m third test electrodes, where m is an integer greater than 0 and less than or equal to n. Each third test electrode is connected to at least the control terminal of one control switch to turn on or off the two terminals of the control switch on the spin orbit torque supply line. And the control terminal of each control switch is connected to only one third test electrode. The control switch connected with the third testing electrode can be controlled by arranging m third testing electrodes, wherein one third testing electrode is at least connected with the control end of one control switch. When the test circuit is applied, different magnetic tunnel junctions can be isolated from the test circuit according to the requirements, so that the test of other magnetic tunnel junctions is prevented from being influenced due to short circuit of a single or a plurality of magnetic tunnel junctions.
In a specific embodiment, the control switch is an N/PMOS Transistor (an insulated gate field effect Transistor with three electrodes), a BJT (Bipolar Junction Transistor), or an IGBT (insulated gate Bipolar Transistor) so as to set the control switch and control the control switch to be closed or open.
In a specific embodiment, each magnetic tunnel junction includes a free layer disposed on the corresponding spin orbit torque supply line, a tunnel barrier layer disposed on the free layer, and a reference layer disposed on the tunnel barrier layer, and the free layer and the reference layer are separated by the tunnel barrier layer. Between two adjacent spin orbit torque magnetic storage bits, a reference layer on a magnetic tunnel junction in one of the spin orbit torque magnetic storage bits is in line connection with the spin orbit torque supply of the other spin orbit torque magnetic storage bit.
In one embodiment, the test structure further comprises a magnetic excitation assembly for providing excitation to the n magnetic tunnel junctions, such that the test structure may employ either an electrical excitation source or a magnetic excitation source.
In a second aspect, the present invention further provides a testing method corresponding to the testing structure of the SOT-MRAM, the testing method including: the excitation circuit provides excitation to the n magnetic tunnel junctions; measuring a resistance value between the two first test electrodes; repeating the steps, and testing the resistance values under different excitation voltages; and calculating and fitting by adopting a series test method to obtain Rp, Rap, TMR, Vc and Ic distribution parameters of the n magnetic tunnel junctions. N spin orbit torque magnetic storage bit elements are connected in series end to end in sequence, resistance values of the magnetic tunnel junctions after series connection under different excitation voltages are tested, and Rp, Rap, TMR, Vc and Ic distribution parameters of the n magnetic tunnel junctions are obtained through calculation and fitting by adopting a series connection testing method, so that a large number of devices can be tested simultaneously, and the testing efficiency is improved.
Drawings
FIG. 1 is a diagram illustrating a test structure of an SOT-MRAM according to an embodiment of the present invention;
FIG. 2 is a diagram illustrating another SOT-MRAM test structure according to an embodiment of the present invention;
FIG. 3 is a diagram illustrating another SOT-MRAM test structure according to an embodiment of the present invention;
FIG. 4 is a diagram illustrating another SOT-MRAM test structure according to an embodiment of the present invention;
FIG. 5 is a diagram illustrating another SOT-MRAM test structure according to an embodiment of the present invention;
FIG. 6 is a diagram illustrating another SOT-MRAM test structure according to an embodiment of the present invention.
Reference numerals:
10-magnetic tunnel junction 11-free layer 12-tunnel barrier layer 13-reference layer
20-spin orbit torque supply line 31-first test electrode 32-second test electrode
33-third test electrode 40-control switch 41-terminal 42-control terminal
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
To facilitate understanding of the test structure of the SOT-MRAM provided by the embodiment of the present invention, an application scenario of the test structure of the SOT-MRAM provided by the embodiment of the present invention is first described below, and the test structure of the SOT-MRAM is applied to an SOT-MRAM chip for testing Rp, Rap, TMR, Vc and Ic distribution parameters of the SOT-MRAM. The test structure of the SOT-MRAM will be described in detail with reference to the accompanying drawings.
Referring to FIG. 1, the test structure of the SOT-MRAM of the present invention includes n spin-orbit torque magnetic storage bits connected end-to-end in series. Each spin orbit torque magnetic memory bit includes a spin orbit torque providing line 20, and a magnetic tunnel junction 10 disposed on the spin orbit torque providing line 20. And between two adjacent spin orbit torque magnetic storage bits, the magnetic tunnel junction 10 in one of the spin orbit torque magnetic storage bits is connected to the spin orbit torque supply line 20 in the other spin orbit torque magnetic storage bit. The test structure further includes an excitation circuit for exciting the n magnetic tunnel junctions 10, and two first test electrodes 31 (electrodes A, C in fig. 1 represent the two first test electrodes 31) for testing the resistance values of the n magnetic tunnel junctions 10, the two first test electrodes 31 being respectively connected to two of the n spin-orbit torque magnetic storage bits located at the head and the tail ends.
In the above scheme, n spin orbit torque magnetic storage bit elements are connected in series end to end in sequence, two first test electrodes 31 are respectively connected in series on two spin orbit torque magnetic storage bit elements located at the end and the end in the n spin orbit torque magnetic storage bit elements as test circuits, and an excitation circuit for exciting n magnetic tunnel junctions is further provided, so that the arrangement of the test structure is simplified, and the total area of the test device is reduced. When the device is applied, the resistance values of the n magnetic tunnel junctions 10 which are sequentially connected in series can be conveniently tested, electrical parameters such as Rp, Rap, TMR, Vc and Ic distribution of the device can be obtained according to the tested resistance values through analysis and fitting, and a large number of devices can be tested, so that the testing efficiency is improved. The spin-orbit torque magnetic memory bit, the excitation circuit, and the arrangement and connection thereof will be described in detail with reference to the accompanying drawings.
In particular with each magnetic tunnel junction 10 and the corresponding spin orbit torque providing line 20, referring to fig. 1 and 4, each magnetic tunnel junction 10 includes a free layer 11 disposed on the corresponding spin orbit torque providing line 20, a tunnel barrier layer 12 disposed on the free layer 11, and a reference layer 13 disposed on the tunnel barrier layer 12, and the free layer 11 and the reference layer 13 are separated by the tunnel barrier layer 12.
In the specific determination of the number of the magnetic tunnel junctions 10, the number of the magnetic tunnel junctions 10 may be any value not less than two, such as 2, 4, 6, 8, 20, 50, and the like. The number of spin-orbit torque providing lines 20 is equal to the number of magnetic tunnel junctions 10, and each magnetic tunnel junction 10 is disposed on one spin-orbit torque providing line 20, thereby realizing that the spin-orbit torque providing line 20 provides excitation to the corresponding magnetic tunnel junction 10, causing the free layer 11 on the magnetic tunnel junction 10 to be flipped.
Specifically, when n spin orbit torque magnetic storage bits are connected end to end in series, the reference layer 13 on the magnetic tunnel junction 10 in one of the spin orbit torque magnetic storage bits is connected to the spin orbit torque supply line 20 in the other spin orbit torque magnetic storage bit between the adjacent two spin orbit torque magnetic storage bits. Specifically, referring to fig. 1 and 4, the free layer 11 in each magnetic tunnel junction 10 is electrically connected to a spin orbit torque providing line 20 on the magnetic tunnel junction 10; and between two adjacent magnetic tunnel junctions 10, the reference layer 13 on one magnetic tunnel junction 10 is connected with the corresponding spin orbit torque providing line 20 of the other magnetic tunnel junction 10. By using the spin orbit torque supply line 20 in connection with the free layer 11, the spin orbit torque supply line 20 is partially made to function as a conductor connecting between the adjacent two magnetic tunnel junctions 10, thereby facilitating the arrangement.
When the excitation circuit is specifically provided, the excitation circuit may adopt different modes depending on whether any two spin orbit torque supply lines 20 of the n spin orbit torque supply lines 20 are connected in parallel or in series. As described in detail below.
Example 1
Referring to fig. 1, 2 and 3, the excitation circuit includes two second test electrodes 32 (two second test electrodes 32 are denoted by electrode D and electrode E), and the two second test electrodes 32 are used to supply the inversion current to the n spin orbit torque supply lines 20. Both ends of each spin orbit torque supply line 20 are connected in series with two second test electrodes 32, respectively, and any two spin orbit torque supply lines 20 are connected in parallel. The excitation circuit further comprises two control switches 40 connected in series across each spin orbit torque supply line 20 and for controlling whether there is an open or closed circuit between the two second test electrodes 32 and each spin orbit torque supply line 20. The n spin orbit torque supply lines 20 are connected in parallel, and a control switch 40 is provided at both ends of each spin orbit torque supply line 20. So that when n magnetic tunnel junctions 10 need to be excited, the control switch 40 is closed, so that the two second test electrodes 32 can provide the flipping current to the n spin orbit torque providing lines 20, thereby causing the magnetic tunnel junctions 10 to flip; when it is required to test the resistance value between the two first test electrodes 31, the switch 40 is controlled to be opened to test the resistance values of the n magnetic tunnel junctions 10 connected end to end in series.
The connection of two adjacent spin orbit torque magnetic storage bits among the n spin orbit torque magnetic storage bits is the same as that shown above, and is not described herein again. In addition, referring to fig. 1, 2 and 3, two magnetic tunnel junctions 10 located at the head and tail ends are respectively connected to two first test electrodes 31. The magnetic tunnel junction 10 on the left (with reference to the structures shown in fig. 1, 2 and 3) is connected to an electrode a in such a way as to provide a portion of the line 20 for spin orbit torque corresponding to the magnetic tunnel junction 10 as a conductor for connection between the electrode a and the free layer 11 above the magnetic tunnel junction 10. The magnetic tunnel junction 10 on the right (with reference to the structures shown in fig. 1, 2 and 3) is connected to the electrode C in such a manner that the reference layer 13 on the magnetic tunnel junction 10 is connected to the electrode C via a conductor.
In the specific arrangement of the control switches 40 described above, with continued reference to fig. 1, each control switch 40 has two terminals 41, and a control terminal 42 that controls the two terminals 41 to open or close. One terminal 41 of the two terminals 41 on each control switch 40 is connected to the corresponding spin orbit torque supply line 20, and the other terminal 41 is connected to the corresponding second test electrode 32; and the control terminals 42 of the two control switches 40 on the same spin orbit torque supply line 20 are connected in series. The test structure further includes m third test electrodes 33 (electrodes B, B in fig. 1, 2, and 3)1、B2、…、Bm、…、BnRepresenting a third test electrode 33), where m is an integer greater than 0 and less than or equal to n. Each third test electrode 33 is connected to at least the control terminals 42 of the two control switches 40 on one spin orbit torque supply line 20 to control the control switches 40 to be opened or closed, and the control terminals 42 of the two control switches 40 on each spin orbit torque supply line 20 are connected to only one third test electrode 33. By providing m third test electrodes 33, and connecting one third test electrode 33 to at least one control terminal 42 of a control switch 40, the control switch 40 connected to the third test electrode 33 can be controlled. In application, different magnetic tunnel junctions 10 can be isolated from the test circuit as needed, so as to avoid affecting the test of other magnetic tunnel junctions 10 due to short circuit of a single or several magnetic tunnel junctions 10. Specifically, when the resistance value between the two first test electrodes 31 exceeds a set range, each third test electrode 33 of the m third test electrodes 33 is individually electrified to test the resistance value between the two first test electrodes 31 so as to determine a certain magnetic tunnel or tunnelsAn abnormality occurs in the road junction 10. After determining the magnetic tunnel 10 in which the abnormality occurs, applying a voltage to the third test electrode 33 corresponding to the one or more magnetic tunnel junctions 10 to short the one or more magnetic tunnel junctions 10 from the test circuit, so that the test circuit separates the one or more magnetic tunnel junctions 10; the resistance value between the two first test electrodes 31 is then tested.
When the control switch 40 is specifically determined, the control switch 40 may be an N/PMOS Transistor (an Insulated Gate field effect Transistor with three electrodes), a BJT (Bipolar Junction Transistor), or an IGBT (Insulated Gate Bipolar Transistor) so as to set the control switch 40 and control the control switch 40 to be closed or open.
In the specific determination of the number of the third test electrodes 33, referring to fig. 2, the number of the third test electrodes 33 may be n, that is, the number of the third test electrodes 33 is equal to the number of the magnetic tunnel junctions 10, one third test electrode 33 is connected to the control terminals 42 of the two control switches 40 on each spin orbit torque supply line 20, and each third test electrode 33 is connected to the control terminal 42 of the control switch 40 on only one spin orbit torque supply line 20. At this time, it is possible to control whether the magnetic tunnel junction 10 is isolated from the test circuit by controlling whether each third test electrode 33 is energized or not, at the time of application. If one or more of the n magnetic tunnel junctions 10 is shorted, the control switch 40 on the spin orbit torque supply line 20 may be closed so that the test circuit does not test the configuration in which the magnetic tunnel junctions 10 are shorted while testing. It should be understood that the number of the third test electrodes 33 is not limited to the n shown above, and other numbers may be used.
For example, the number of the third test electrodes 33 may also be 1, and in particular, referring to fig. 3, when the number of the third test electrodes 33 is 1, and the control terminals 42 of the control switches 40 on the n spin orbit torque supply lines 20 are all connected to the third test electrodes 33, the third test electrodes 33 control the open circuit or the closed circuit of the control switches 40. In use, all of the control switches 40 are first closed by applying current to the third test electrode 33; an excitation current is then supplied to all spin orbit torque supply lines 20 through the two second test electrodes 32, causing all of the magnetic tunnel junctions 10 to switch. Then, the third testing electrode 33 is powered off, so that all the control switches 40 are opened, and the resistance values of the n magnetic tunnel junctions 10 connected in series end to end can be tested by testing the resistance values between the two first testing electrodes 31.
It should be noted that the number of the third test electrodes 33 may be any value greater than 0 and less than or equal to n, such as 1, 2, 3, and the like. When the number of the third test electrodes 33 is specifically determined, if the n magnetic tunnel junctions 10 are reliable and stable, the number of the third test electrodes 33 can be set to be smaller, so that the space occupied by the third test electrodes 33 is reduced; if the reliability and stability of the n magnetic tunnel junctions 10 are poor, a plurality of third test electrodes 33 may be additionally provided, so that 1 or several magnetic tunnel junctions 10 may be isolated from the test circuit by controlling the open circuit or the closed circuit of the control switch 40 connected to each third test electrode 33, thereby preventing the test operation of the entire test structure from being affected by the short circuit of the individual magnetic tunnel junctions 10, and thus increasing the flexibility of the test structure in application. In application, more third test electrodes 33 may be used in the initial stage of development to reduce the influence of a failed device (open or short) on the test result, and improve the utilization rate of the test structure. More magnetic tunnel junctions 10 may be connected in series during the production run and fewer third test connections provided to improve test efficiency.
Example 2
Referring to fig. 4, 5 and 6, it is also possible to provide a series connection between the lines 20 using spin orbit torque. Specifically, as shown in fig. 4, between any two adjacent spin orbit torque magnetic storage bits, the spin orbit torque supply line 20 in one spin orbit torque magnetic storage bit is connected in series with the spin orbit torque supply line 20 in the other spin orbit torque magnetic storage bit. The two first test electrodes 31 (electrodes a and C in fig. 4, 5, and 6 denote two first test electrodes 31) are also connected in series with the two spin orbit torque supply lines 20 located at the head and the tail of the n spin orbit torque supply lines 20, respectively, to supply the n spin orbit torque supply lines 20 with the inversion current. The excitation circuit includes a control switch 40 provided between any adjacent two spin orbit torque supply lines 20 and used to control whether the adjacent two spin orbit torque supply lines 20 are open or closed. When n magnetic tunnel junctions 10 need to be excited, the control switch 40 is closed, so that the two first test electrodes 31 can provide the inversion current for the n spin orbit torque providing lines 20, thereby exciting the magnetic tunnel junctions 10 to invert; when it is required to test the resistance value between the two first test electrodes 31, the switch 40 is controlled to be opened to test the resistance values of the n magnetic tunnel junctions 10 connected end to end in series. And the spin orbit torque providing lines 20 are connected in series, thereby reducing the number of test electrodes and control switches 40, and further reducing the area occupied by the test structure.
The connection manner of two adjacent magnetic tunnel junctions 10 of the n magnetic tunnel junctions 10 is the same as that shown above, and is not described again here. In addition, referring to fig. 4, 5 and 6, the two magnetic tunnel junctions 10 located at the head and tail ends are respectively connected to the two first test electrodes 31. The magnetic tunnel junction 10 (with reference to the structures shown in fig. 4, 5 and 6) on the left is connected to the electrode a in such a manner that the spin orbit torque supply line 20 on the magnetic tunnel junction 10 partially serves as a conductor for connection between the electrode a and the free layer 11 on the magnetic tunnel junction 10, and one end of the spin orbit torque supply line 20 is connected to the electrode a, thereby preventing the spin orbit torque supply line 20 from being unable to supply a sufficient excitation current to the magnetic tunnel junction 10 corresponding to the spin orbit torque supply line 20. The magnetic tunnel junction 10 (with reference to the structure shown in fig. 1, 2 and 3) on the right is connected to the electrode C in such a manner that the reference layer 13 on the magnetic tunnel junction 10 is connected to the electrode C through a conductor, one end of the spin orbit torque supply line 20 corresponding to the magnetic tunnel junction 10 is also connected to the electrode C, and a control switch 40 is further disposed between the spin orbit torque supply line 20 and the electrode C to control whether the electrode C and the spin orbit torque supply line 20 are open or closed to prevent the spin orbit torque supply line 20 from affecting the test circuit test.
In the specific arrangement of the control switch 40, referring to fig. 4, the control switch 40 has two terminals 41, and a control terminal 42 that controls the two terminals 41 to be opened or closed, wherein one terminal 41 of the two terminals 41 of each control switch 40 is connected to one spin orbit torque supply line 20 of the adjacent two spin orbit torque supply lines 20, and the other terminal 41 is connected to the other spin orbit torque supply line 20 of the adjacent two spin orbit torque supply lines 20. The excitation circuit includes m third test electrodes 33 (electrodes B, B in fig. 4, 5, and 6)1、B2、…、Bm、…、BnRepresenting a third test electrode 33), where m is an integer greater than 0 and less than or equal to n. Each third test electrode 33 is connected to at least a control terminal 42 of one control switch 40 to open or close two terminals 41 of the control switch 40 on the spin orbit torque supply line 20. And the control terminal 42 of each control switch 40 is connected to only one third test electrode 33. By providing m third test electrodes 33, and connecting one third test electrode 33 to at least one control terminal 42 of a control switch 40, the control switch 40 connected to the third test electrode 33 can be controlled. In application, different magnetic tunnel junctions 10 can be isolated from the test circuit as needed, so as to avoid affecting the test of other magnetic tunnel junctions 10 due to short circuit of a single or several magnetic tunnel junctions 10. Specifically, when the resistance value between two first test electrodes 31 exceeds a set range, each third test electrode 33 in the m third test electrodes 33 is individually energized to test the resistance value between the two first test electrodes 31, so as to determine that one or some magnetic tunnel junctions 10 are abnormal. After determining the magnetic tunnel component with the abnormality, applying a voltage to the third test electrode 33 corresponding to the one or more magnetic tunnel junctions 10 to short the one or more magnetic tunnel junctions 10 from the test circuit, so that the test circuit separates the one or more magnetic tunnel junctions 10; the resistance value between the two first test electrodes 31 is then tested.
When the control switch 40 is specifically determined, the control switch 40 may also be an N/PMOS Transistor (an Insulated Gate field effect Transistor with three electrodes), a BJT (Bipolar Junction Transistor), or an IGBT (Insulated Gate Bipolar Transistor) so as to set the control switch 40 and control the control switch 40 to be closed or open.
When the number of the third test electrodes 33 is specifically determined, the number of the third test electrodes 33 may be n, that is, the number of the third test electrodes 33 is equal to the number of the magnetic tunnel junctions 10, the control end 42 of the control switch 40 between any two adjacent spin orbit torque supply lines 20 is connected with one third test electrode 33, and each third test electrode 33 is connected with the control end 42 of only one control switch 40; and a third test electrode 33 is also connected to the control switch 40 between the electrode C and the spin orbit torque supply line 20 on the right side. At this time, it is possible to control whether the magnetic tunnel junction 10 is isolated from the test circuit by controlling whether each third test electrode 33 is energized or not, at the time of application. If one or more of the n magnetic tunnel junctions 10 is shorted, both of the control switches 40 at both ends of the spin orbit torque supply line 20 may be closed, so that the test circuit does not test the structure in which the magnetic tunnel junctions 10 are shorted when testing. It should be understood that the number of the third test electrodes 33 is not limited to the n shown above, and other numbers may be used.
For example, the number of the third testing electrodes 33 may also be 1, and in particular, referring to fig. 3, in this case, the number of the third testing electrodes 33 is 1, and the control terminals 42 of the n control switches 40 are all connected to the third testing electrodes 33, that is, the third testing electrodes 33 control the open circuit or the closed circuit of the control switches 40. In use, all of the control switches 40 are first closed by applying current to the third test electrode 33; then, an excitation current is supplied to all spin orbit torque supply lines 20 through the two first test electrodes 31, and all the magnetic tunnel junctions 10 are excited to flip. Then, the third testing electrode 33 is powered off, so that all the control switches 40 are opened, and the resistance values of the n magnetic tunnel junctions 10 connected in series end to end can be tested by testing the resistance values between the two first testing electrodes 31.
It should be noted that the number of the third test electrodes 33 may be any value greater than 0 and less than or equal to n, such as 1, 2, 3, and the like. When the number of the third test electrodes 33 is specifically determined, if the n magnetic tunnel junctions 10 are reliable and stable, the number of the third test electrodes 33 can be set to be smaller, so that the space occupied by the third test electrodes 33 is reduced; if the reliability and stability of the n magnetic tunnel junctions 10 are poor, a plurality of third test electrodes 33 may be additionally provided, so that 1 or several magnetic tunnel junctions 10 may be isolated from the test circuit by controlling the open circuit or the closed circuit of the control switch 40 connected to each third test electrode 33, thereby preventing the test operation of the entire test structure from being affected by the short circuit of the individual magnetic tunnel junctions 10, and thus increasing the flexibility of the test structure in application. In application, more third test electrodes 33 may be used in the initial stage of development to reduce the influence of a failed device (open or short) on the test result, and improve the utilization rate of the test structure. More magnetic tunnel junctions 10 may be connected in series during the production run and fewer third test connections provided to improve test efficiency.
Example 3
It is also possible to adopt a mode in which some of the n spin orbit torque supply lines 20 are connected in parallel and some are connected in series. The specific arrangement manner of the multiple spin orbit torque providing lines 20 connected in parallel is the same as that in embodiment 1, and the specific arrangement manner of the multiple spin orbit torque providing lines 20 connected in series is the same as that in embodiment 2, and is not described herein again.
In addition, it should be noted that, when it is specifically determined whether the n spin orbit torque supply lines 20 are connected in series or in parallel, it may be determined according to the number of spin orbit torque supply lines 20, and when the number of spin orbit torque supply lines 20 is large, it may be determined according to the parallel connection, so as to ensure that the excitation voltages on each spin orbit torque supply line 20 are equal. When the number of spin orbit torque supply lines 20 is small, the serial connection may be adopted, thereby reducing the number of control switches 40 and test electrodes, and thus reducing the area occupied by the test structure.
It should be noted that the switching of the magnetic tunnel junction 10 may be actuated by other means than by an electrical actuation source. For example, a magnetic excitation source may be adopted, and the test structure further includes a magnetic excitation component for providing excitation to the n magnetic tunnel junctions 10, and the magnetic excitation component generates a variable magnetic field to excite the n magnetic tunnel junctions 10 to flip, and simultaneously tests the resistance value between the two first test electrodes 31, so as to obtain the Rp, Rap, TMR, Vc and Ic distribution parameters of the n magnetic tunnel junctions 10 by analytical fitting. The test structure can adopt an electric excitation source and a magnetic excitation source, and multi-dimensional analysis can be conveniently carried out on the same device.
The n spin orbit torque magnetic storage bit elements are connected in series end to end in sequence, two first test electrodes 31 are respectively connected in series on the two spin orbit torque magnetic storage bit elements positioned at the head end and the tail end in the n spin orbit torque magnetic storage bit elements, and an excitation circuit for exciting the n magnetic tunnel junctions 10 to overturn is further arranged, so that the arrangement of a test structure is simplified, and the total area of a test device is reduced. When the device is applied, the resistance values of the n magnetic tunnel junctions 10 which are sequentially connected in series can be conveniently tested, electrical parameters such as Rp, Rap, TMR, Vc and Ic distribution of the device can be obtained according to the tested resistance values through analysis and fitting, and a large number of devices can be tested, so that the testing efficiency is improved.
In addition, the embodiment of the invention also provides a test method corresponding to the test structure of the SOT-MRAM, and the test method comprises the following steps: the excitation circuit provides excitation to the n magnetic tunnel junctions 10; measuring the resistance value between the two first test electrodes 31; repeating the steps, and testing the resistance values under different excitation voltages; and calculating and fitting by adopting a series test method to obtain Rp, Rap, TMR, Vc and Ic distribution parameters of the n magnetic tunnel junctions 10. The n magnetic tunnel junctions 10 are connected in series, resistance values of the magnetic tunnel junctions 10 connected in series under different excitation voltages are tested, and Rp, Rap, TMR, Vc and Ic distribution parameters of the n magnetic tunnel junctions 10 are obtained by calculating and fitting through a series testing method, so that a large number of devices can be tested at the same time, and the testing efficiency is improved.
Wherein, repeating the above steps, the resistance value under different excitation voltages can be tested specifically as follows: the excitation source is scanned (shmoo) in a certain way (step) and the resulting R-S curve is then fitted with the parameter characteristic values.
In addition, before the test, the excitation circuit may be turned on to initialize the test structure, so that the n magnetic tunnel junctions 10 are all in the high resistance state or the low resistance state.
The above description is only for the specific embodiment of the present invention, but the scope of the present invention is not limited thereto, and any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope of the present invention are included in the scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the claims.
Claims (9)
1. A test structure for an SOT-MRAM, comprising:
n spin orbit torque magnetic storage bits connected end to end in series in sequence, each spin orbit torque magnetic storage bit comprising a spin orbit torque supply line and a magnetic tunnel junction disposed on the spin orbit torque supply line; between two adjacent spin orbit torque magnetic storage bit units, the magnetic tunnel junction in one spin orbit torque magnetic storage bit unit is connected with the spin orbit torque supply line in the other spin orbit torque magnetic storage bit unit;
an excitation circuit for exciting the n magnetic tunnel junctions;
and the two first test electrodes are used for testing the resistance values of the n magnetic tunnel junctions and are respectively connected with two spin orbit torque magnetic storage bit elements positioned at the head end and the tail end in the n spin orbit torque magnetic storage bit elements.
2. The test structure of SOT-MRAM of claim 1, wherein the stimulus circuit comprises:
two second test electrodes; two ends of each spin orbit torque providing line are respectively connected with the two second testing electrodes in series, and any two spin orbit torque providing lines are connected in parallel;
two control switches connected in series across each spin orbit torque supply line and used to control whether the two second test electrodes are open or closed with each spin orbit torque supply line.
3. The test structure of the SOT-MRAM of claim 2, wherein each control switch has two terminals, and a control terminal that controls the two terminals to be open or closed; one of the two terminals on each control switch is connected with the corresponding spin orbit torque supply line, and the other terminal is connected with the corresponding second test electrode; the control ends of the two control switches on the same spin orbit torque supply line are connected in series;
the test structure further comprises: m third test electrodes, wherein m is an integer greater than 0 and less than or equal to n; each third test electrode is connected with the control ends of at least two control switches on one spin orbit torque supply line so as to control the open circuit or the closed circuit of the control switches; and the control terminals of the two control switches on each spin orbit torque supply line are connected with only one third test electrode.
4. The test structure of the SOT-MRAM of claim 1, wherein between any adjacent two spin orbit torque magnetic storage bits, a spin orbit torque supply line in one spin orbit torque magnetic storage bit is connected in series with a spin orbit torque supply line in the other spin orbit torque magnetic storage bit;
the two first test electrodes are also respectively connected with two spin orbit torque supply lines positioned at the head end and the tail end of the n spin orbit torque supply lines in series;
the excitation circuit includes:
and a control switch disposed between any adjacent two spin orbit torque supply lines and used for controlling whether the adjacent two spin orbit torque supply lines are open or closed.
5. The SOT-MRAM test structure of claim 4,
the control switch is provided with two terminals and a control end for controlling the two terminals to be opened or closed; wherein one of the two terminals of each control switch is connected to one of the two spin orbit torque supply lines adjacent to each other, and the other terminal is connected to the other of the two spin orbit torque supply lines adjacent to each other;
the excitation circuit includes: m third test electrodes, wherein m is an integer greater than 0 and less than or equal to n; each third test electrode is connected with the control end of at least one control switch so as to open or close two terminals of the control switch on the spin orbit torque supply line; and the control terminal of each control switch is connected to only one third test electrode.
6. The SOT-MRAM test structure of any of claims 2-5, wherein the control switch is an N/PMOS transistor, a BJT, or an IGBT.
7. The test structure of SOT-MRAM of claim 1, wherein each magnetic tunnel junction comprises:
a free layer disposed on the corresponding spin orbit torque supply line;
a tunnel barrier layer disposed on the free layer;
and a reference layer disposed on the tunnel barrier layer, and the free layer and the reference layer are separated by the tunnel barrier layer;
between two adjacent spin orbit torque magnetic storage bits, the reference layer of the magnetic tunnel junction in one of the spin orbit torque magnetic storage bits is in line connection with the spin orbit torque supply of the other spin orbit torque magnetic storage bit.
8. The test structure of SOT-MRAM of claim 1, further comprising a magnetic excitation component for providing a magnetic excitation source to the n magnetic tunnel junctions.
9. A method for testing the SOT-MRAM test structure of claim 1, comprising:
the excitation circuit provides excitation to the n magnetic tunnel junctions;
measuring a resistance value between the two first test electrodes;
repeating the steps, and testing the resistance values under different excitation voltages;
calculating and fitting by adopting a series test method to obtain Rp, Rap, TMR, Vc and Ic distribution parameters of the n magnetic tunnel junctions.
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