Electrical testing method for memory threshold voltage uniformity

Abstract

The present invention provides an electrical test method for the uniformity of a memory threshold voltage, comprising: applying a first voltage to a selection tube to keep the selection tube turned on; connecting source lines of all memory cells, connecting bit lines of all memory cells, and connecting base regions of all memory cells; applying a second voltage to the memory tube, the second voltage being a scanning voltage; applying a pulse voltage to the memory tube each time the second voltage changes; measuring the current in the base region; making a threshold voltage table of the current in the base region and the value of the second voltage; keeping the current in the base region constant, the smaller the amplitude of the second voltage change, the more uniform the memory threshold voltage. The present invention does not need to use an additional test structure, can test the threshold voltages of all memory cells at the same time to determine whether the threshold voltages of the memory are uniform, the test is simple, and there is no need to write a test program, the test time is short, and the memory development time is reduced.

Description

Technical Field

[0001] The present invention relates to the field of semiconductor technology, and in particular to an electrical property testing method for uniformity of memory threshold voltage. Background Art

[0002] In memory development, the uniformity of the threshold voltage of each memory cell is an important indicator of memory cell technology. In the existing technology, taking the 2T memory cell as an example, the memory cells are arranged in an array, and the main connection terminals between the memory cells include the word line of the selection tube (SG word line), the storage tube word line (word line), the source line (source line) and the drain area (drain line), as well as the base area.

[0003] After the storage unit is manufactured, it needs to be electrically tested. In the electrical test (WAT) stage after the storage unit is tape-out, the method used in the prior art is to set up a test structure around the test unit, and the pins on each test structure are connected to each storage unit, and each test unit requires a pin. However, this test structure can only test the threshold voltage of a limited number of storage units in the array. For example, the test of 4 storage units requires a test structure with more than 5 pins. If a lot of pins are required to test the threshold voltage of all storage units in the array, it is impossible to achieve it under the limited area of ​​the test structure. Therefore, it is impossible to test the threshold voltage and distribution of the entire array through the testkey (test structure), and it is impossible to know the threshold voltage uniformity of the entire array. In addition, the prior art also needs to design a complete test circuit to evaluate the uniformity of the threshold voltage of the storage unit, including the peripheral erase and write operation circuit and the read circuit, and it is necessary to establish a special test program, which requires a relatively long time and investment, and prolongs the time of memory development. Summary of the invention

[0004] The object of the present invention is to provide an electrical test method for uniformity of threshold voltage of a memory, which can test uniformity of threshold voltages of a plurality of memory cells in the memory, and the test is simple and the test time is short.

[0005] In order to achieve the above-mentioned object, the present invention provides an electrical testing method for uniformity of threshold voltage of a memory, which is used to test whether the threshold voltages of multiple memory cells in the memory are uniform. The memory cell comprises: a substrate, a base region located in the substrate, a selection tube and a storage tube located on the surface of the substrate and having a certain distance therebetween, a source line located on one side of the selection tube, and a bit line located on one side of the storage tube, wherein the selection tube and the storage tube are both located between the source line and the bit line. The electrical testing method comprises:

[0006] Applying a first voltage to the selection tube so that the selection tube is always kept in an on state;

[0007] connecting the source lines of all memory cells, connecting the bit lines of all memory cells and connecting the base regions of all memory cells;

[0008] Applying a second voltage to the storage tube, wherein the second voltage provides a scan voltage;

[0009] Each time the second voltage changes, a pulse voltage is applied to the storage tube;

[0010] measuring the current in the base region;

[0011] The current in the base region and the value of the second voltage are used to form a threshold voltage table;

[0012] The current in the base region is kept constant, and the smaller the amplitude of the second voltage change is, the more uniform the memory threshold voltage is.

[0013] Optionally, in the electrical testing method for memory threshold voltage uniformity, the first voltage is a constant voltage.

[0014] Optionally, in the electrical testing method for memory threshold voltage uniformity, the second voltage ranges from -4V to 4V.

[0015] Optionally, in the electrical test method for memory threshold voltage uniformity, the second voltage change step is 0.1V.

[0016] Optionally, in the electrical testing method for uniformity of memory threshold voltage, the voltage of the pulse voltage is 2V and the frequency is 1MHz.

[0017] Optionally, in the electrical test method for memory threshold voltage uniformity, the method of applying the first voltage to the selection tube includes: applying the first voltage to the word line of the selection tube.

[0018] Optionally, in the electrical test method for uniformity of memory threshold voltage, the method of applying the second voltage to the memory tube includes: applying the second voltage to the word line of the memory tube.

[0019] Optionally, in the electrical test method for uniformity of memory threshold voltage, a pulse voltage is applied to the gate of the memory tube.

[0020] Optionally, in the electrical test method for uniformity of memory threshold voltage, the horizontal coordinate of the threshold voltage table is the value of the second voltage, and the vertical coordinate of the threshold voltage table is the value of the base region current.

[0021] Optionally, in the electrical test method for memory threshold voltage uniformity, as the second voltage increases, the current in the base region first increases and then decreases.

[0022] The present invention also provides an electrical testing method for uniformity of threshold voltage of a memory, which is used to test whether the threshold voltages of a plurality of memory cells in the memory are uniform, wherein the memory cell comprises: a substrate, a base region located in the substrate, a memory tube located on the surface of the substrate, a source line located on one side of the memory tube, and a bit line located on the other side of the memory tube, wherein the memory tube is located between the source line and the bit line, and the electrical testing method comprises:

[0023] connecting the source lines of all memory cells, connecting the bit lines of all memory cells and connecting the base regions of all memory cells;

[0024] Applying a scan voltage to the storage tube;

[0025] Each time the scanning voltage changes, a pulse voltage is applied to the storage tube;

[0026] measuring the current in the base region;

[0027] The current and the scan voltage value of the base region are used to form a threshold voltage table;

[0028] The current in the base region is kept constant, and the smaller the amplitude of the scan voltage change is, the more uniform the memory threshold voltage is.

[0029] Optionally, in the electrical test method for uniformity of memory threshold voltage, the method of applying a scan voltage to a memory tube includes: applying a scan voltage to a word line of the memory tube.

[0030] Optionally, in the electrical test method for uniformity of memory threshold voltage, a pulse voltage is applied to the gate of the memory tube.

[0031] In the electrical test method for the uniformity of the threshold voltage of the memory provided by the present invention, firstly, a first voltage is applied to the selection tube to keep the selection tube turned on; then, the source line, the bit line and the base region of all the memory cells are connected; then, a second voltage is applied to the memory tube, and the second voltage is a scanning voltage; then, each time the second voltage changes, a pulse voltage is applied to the memory tube; then, the current of the base region is measured; then, the current of the base region and the value of the second voltage are made into a threshold voltage table; finally, the current of the base region is kept constant, and the smaller the amplitude of the second voltage change, the more uniform the threshold voltage of the memory. Compared with the prior art, the present invention can test the threshold voltage of all memory cells at the same time without using an additional test structure to determine whether the threshold voltage of the memory is uniform, the test is simple, and there is no need to write a test program, the test time is short, and the time of memory development is reduced. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 is a schematic structural diagram of a storage unit according to a first embodiment of the present invention;

[0033] Figure 2 is a flow chart of a method for electrical testing of memory threshold voltage uniformity according to a first embodiment of the present invention;

[0034] Figure 3 is a schematic diagram of a threshold voltage table according to Embodiment 1 of the present invention;

[0035] Figure 4 is a schematic structural diagram of a storage unit according to a second embodiment of the present invention;

[0036] Figure 5 is a flow chart of a method for electrical testing of memory threshold voltage uniformity according to a second embodiment of the present invention;

[0037] Figure 6 is a schematic diagram of a threshold voltage table according to a second embodiment of the present invention;

[0038] In the figure: 110-base region, 120-selection tube, 121-selection tube word line, 130-storage tube, 131-storage tube word line, 132-first ONO layer, 133-second ONO layer, 140-source line, 150-bit line, 210-base region, 230-storage tube, 231-storage tube word line, 240-source line, 250-bit line. DETAILED DESCRIPTION

[0039] The specific implementation of the present invention will be described in more detail below in conjunction with the schematic diagram. The advantages and features of the present invention will become clearer based on the following description. It should be noted that the drawings are all in a very simplified form and are not in exact proportions, and are only used to facilitate and clearly assist in explaining the purpose of the embodiments of the present invention.

[0040] Hereinafter, the terms "first", "second", etc. are used to distinguish between similar elements and are not necessarily used to describe a particular order or chronological sequence. It is to be understood that these terms used in this manner are interchangeable where appropriate. Similarly, if the method described herein includes a series of steps, the order of these steps presented herein is not necessarily the only order in which these steps can be performed, and some of the steps described may be omitted and / or some other steps not described herein may be added to the method.

[0041] Embodiment 1

[0042] Please refer to Figure 1 The present invention provides a memory cell, comprising: a substrate, a base region 110 located in the substrate, a selection tube 120 and a memory tube 130 located on the surface of the substrate and at a certain distance, a source line 140 located on one side of the selection tube 120, a bit line 150 located on one side of the memory tube 130, the selection tube 120 and the memory tube 130 are both located between the source line 140 and the bit line 150, the selection tube 120 is composed of a selection tube word line 121 located on the surface of the substrate, and oxide layers located on both sides of the selection tube word line 121. The memory tube 130 comprises: a memory tube word line 131, a first ONO layer 132 located on both sides of the memory tube word line 131, and a second ONO layer 133 between the memory tube word line 131 and the substrate. The structure of the memory cell is a prior art, and will not be described in detail here. Here, there are multiple memory cells arranged in an array, and the word lines and bit lines of the multiple memory cells are connected. The threshold voltage (opening voltage) of each memory cell is different. Based on this, the present invention wants to verify the uniformity of the threshold voltages of multiple memory cells. In the prior art, multiple memory cells are made on the periphery of the memory cells.

[0043] Therefore, please refer to Figure 2 The embodiment of the present invention provides an electrical testing method for uniformity of a memory threshold voltage, which is used to test whether the threshold voltages of a plurality of memory cells are uniform, and includes:

[0044] S11: applying a first voltage to the selection tube 120 so that the selection tube 120 remains in an on state;

[0045] S12: connecting the source lines 140 of all memory cells, connecting the bit lines 150 of all memory cells, and connecting the base regions 110 of all memory cells;

[0046] S13: applying a second voltage to the storage tube 130, where the second voltage is a scan voltage;

[0047] S14: applying a pulse voltage to the storage tube every time the second voltage changes;

[0048] S15: measuring the current of the base region 110;

[0049] S16: The current of the base region 110 and the value of the second voltage are used to form a threshold voltage table;

[0050] S17: Keeping the current in the base region 110 constant, the smaller the amplitude of the second voltage change is, the more uniform the memory threshold voltage is.

[0051] Preferably, the first voltage is a constant voltage, so as to keep the selection tube 120 always in an on state.

[0052] Preferably, the second voltage is in the range of -4 V to 4 V. The range of the second voltage is determined according to the range of the threshold voltage of the memory cell. The larger the range of the threshold voltage is, the larger the range of the second voltage is.

[0053] Preferably, the second voltage changes in a voltage step of 0.1v. That is, the second voltage ranges from -4v to 4v, and the second voltage is a scanning voltage, which is a sawtooth wave voltage. The voltage changes, and the amplitude of each change is 0.1v. For example, the second voltage is -4v at the beginning, then the second voltage changes to -3.9v, and then the second voltage changes to -3.8v, and so on, until the second voltage changes to 4v.

[0054] Preferably, the voltage of the pulse voltage is 2v and the frequency is 1MHz. That is, when the second voltage is -4v, in the process of changing to -3.9v, a pulse voltage is applied to the storage tube 130, the voltage of the pulse voltage is 2v, and the frequency is 1MHz, that is, the voltage applied to the storage tube 130 becomes the sum of -3.9v and 2v voltage, and finally becomes -1.9v. Then the second voltage changes to -3.8v, and after the pulse voltage is applied to the storage tube 130, it becomes -1.8v. Next, the second voltage changes to -3.7v, and after the pulse voltage is applied to the storage tube 130, it becomes -1.7v, and so on, until the second voltage changes to 4v.

[0055] Preferably, the method of applying the first voltage to the selection tube includes: applying the first voltage to the word line of the selection tube. That is, applying the first voltage to the selection tube word line 121. The source line of the memory cell is already connected, the bit line of the memory cell is already connected, and the base regions of all memory cells are already connected. Therefore, the current of the base region 110 can be tested to determine the uniformity of the threshold voltages of all memory cells.

[0056] Preferably, the method of applying the second voltage to the storage tube includes: applying the second voltage to the word line of the storage tube, that is, applying the second voltage to the word line 131 of the storage tube.

[0057] Preferably, a pulse voltage is applied to the gate of the storage tube 130 .

[0058] Preferably, the abscissa of the threshold voltage table is the value of the second voltage, and the ordinate of the threshold voltage table is the value of the base region current.

[0059] Preferably, as the second voltage increases, the current in the base region increases first and then decreases. In this way, when the current in the base region is kept constant, there are two corresponding second voltage values, and the smaller the difference between the two second voltages, the more uniform the memory threshold voltage. Figure 3 , is a threshold voltage table, the horizontal axis is the value of the second voltage, here only takes the second voltage value in the range of -4v to 0v as an example, in other embodiments of the present invention, the second voltage value in other ranges can be taken, for example, the second voltage value in the range of -4v to 4v can be taken as an example. Figure 3 It can be seen that keeping the current in the base region constant, corresponding to the horizontal axis, the second voltage has two values, namely X1 and X2. The smaller the difference between X1 and X2, the more uniform the memory threshold voltage.

[0060] Embodiment 2

[0061] Reference Figure 4 If the memory cell includes: a base region 210, a memory tube 230 located on the surface of the substrate, a source line 240 located on one side of the memory tube 230, and a bit line 250 located on the other side of the memory tube 230, and the memory tube 230 is located between the source line 240 and the bit line 250, the memory tube 230 includes: a memory tube word line 231, a first ONO layer 232 located on both sides of the memory tube word line 231, and a second ONO layer 233 between the memory tube word line 231 and the substrate.

[0062] Therefore, please refer to Figure 5 In view of the situation where there is only a storage tube, the present invention also provides an electrical test method for the uniformity of the memory threshold voltage, the electrical test method comprising:

[0063] S21: connecting the source lines of all memory cells, connecting the bit lines of all memory cells and connecting the base regions 210 of all memory cells;

[0064] S22: applying a scan voltage to the storage tube;

[0065] S23: applying a pulse voltage to the storage tube 230 every time the scanning voltage changes;

[0066] S24: measuring the current of the base region 210;

[0067] S25: creating a threshold voltage table with the current and scan voltage values ​​of the base region 210;

[0068] S26: Keeping the current of the base region 210 constant, the smaller the amplitude of the scan voltage change is, the more uniform the memory threshold voltage is.

[0069] Preferably, the method of applying a scan voltage to a storage tube includes: applying a scan voltage to a word line 231 of the storage tube.

[0070] Preferably, a pulse voltage is applied to the gate of the storage tube 230 .

[0071] Preferably, the range of the scan voltage is -4V to 4V. The range of the scan voltage is determined according to the range of the threshold voltage of the memory cell. The larger the range of the threshold voltage is, the larger the range of the scan voltage is.

[0072] Preferably, the step of the scanning voltage change voltage is 0.1v. That is, the scanning voltage ranges from -4v to 4v, and the scanning voltage is a sawtooth wave voltage. When the voltage changes, the amplitude of each change is 0.1v. For example, at the beginning, the second voltage is -4v, then the second voltage changes to -3.9v, and then the second voltage changes to -3.8v, and so on, until the second voltage changes to 4v.

[0073] Preferably, the voltage of the pulse voltage is 2v and the frequency is 1MHz. That is, when the scanning voltage is -4v, in the process of changing to -3.9v, a pulse voltage is applied to the storage tube 230, the voltage of the pulse voltage is 2v, and the frequency is 1MHz, that is, the voltage applied to the storage tube 230 becomes the sum of -3.9v and 2v voltage, and finally becomes -1.9v. Then the scanning voltage changes to -3.8v, and after the pulse voltage is applied to the storage tube 230, it becomes -1.8v, and the next scanning voltage changes to -3.7v, and after the pulse voltage is applied to the storage tube 230, it becomes -1.7v, and so on, until the scanning voltage changes to 4v.

[0074] Preferably, the abscissa of the threshold voltage table is the value of the scan voltage, and the ordinate of the threshold voltage table is the value of the base region current.

[0075] Preferably, as the scan voltage increases, the current in the base region increases first and then decreases. In this way, when the current in the base region is kept constant, there are two corresponding scan voltage values, and the smaller the difference between the two scan voltages, the more uniform the memory threshold voltage. Figure 6, is a threshold voltage table, the horizontal axis is the scan voltage value, here only takes the scan voltage value in the range of -4v to 0v as an example, in other embodiments of the present invention, other ranges of scan voltage values ​​can be taken, for example, the scan voltage value in the range of -4v to 4v can be taken as an example. Figure 6 It can be seen that keeping the current in the base region constant, corresponding to the horizontal axis, the scanning voltage has two values, namely X1 and X2. The smaller the difference between X1 and X2, the more uniform the memory threshold voltage is.

[0076] In summary, in the electrical test method for the uniformity of the threshold voltage of the memory provided by the embodiment of the present invention, firstly, a first voltage is applied to the selection tube to keep the selection tube turned on; then, the source line, the bit line and the base region of all the memory cells are connected; then, a second voltage is applied to the memory tube, and the second voltage is a scanning voltage; then, each time the second voltage changes, a pulse voltage is applied to the memory tube; then, the current of the base region is measured; then, the current of the base region and the value of the second voltage are made into a threshold voltage table; finally, the current of the base region is kept constant, and the smaller the amplitude of the second voltage change, the more uniform the threshold voltage of the memory. Compared with the prior art, the present invention can test the threshold voltage of all memory cells at the same time without using an additional test structure to determine whether the threshold voltage of the memory is uniform, the test is simple, and there is no need to write a test program, the test time is short, and the time of memory development is reduced.

[0077] The above is only a preferred embodiment of the present invention and does not limit the present invention in any way. Any technician in the relevant technical field, without departing from the scope of the technical solution of the present invention, makes any form of equivalent replacement or modification to the technical solution and technical content disclosed in the present invention, which does not depart from the content of the technical solution of the present invention and still falls within the protection scope of the present invention.

Claims

1. A method for testing the uniformity of a memory threshold voltage, for testing whether the threshold voltages of a plurality of memory cells in the memory are uniform, wherein the memory cells include: A substrate, a base region located in the substrate, a selection tube and a storage tube located on the surface of the substrate and at a certain distance, a source line located on one side of the selection tube, and a bit line located on one side of the storage tube, wherein the selection tube and the storage tube are both located between the source line and the bit line, wherein the electrical testing method comprises: Applying a first voltage to the selection tube so that the selection tube is always kept in an on state; connecting source lines of all memory cells, connecting bit lines of all memory cells, and connecting base regions of all memory cells; Applying a second voltage to the storage tube, wherein the second voltage provides a scan voltage; Each time the second voltage changes, a pulse voltage is applied to the storage tube; measuring the current in the base region; The current in the base region and the value of the second voltage are used to form a threshold voltage table; The current in the base region is kept constant, and the smaller the amplitude of the second voltage change is, the more uniform the memory threshold voltage is.

2. The electrical property testing method of memory threshold voltage uniformity according to claim 1, characterized in that: The first voltage is a constant voltage.

3. The electrical property testing method of memory threshold voltage uniformity according to claim 1, characterized in that: The second voltage ranges from -4V to 4V.

4. The electrical property testing method of memory threshold voltage uniformity according to claim 1, characterized in that: The step size of the second voltage change is 0.1V.

5. The electrical property testing method of memory threshold voltage uniformity according to claim 1, characterized in that: The voltage of the pulse voltage is 2V and the frequency is 1MHz.

6. The electrical property testing method of memory threshold voltage uniformity according to claim 1, characterized in that: The method of applying a first voltage to a selection tube includes: applying the first voltage to a word line of the selection tube.

7. The electrical property testing method of memory threshold voltage uniformity according to claim 1, characterized in that: The method of applying a second voltage to a storage tube includes: applying the second voltage to a word line of the storage tube.

8. The electrical property testing method of memory threshold voltage uniformity according to claim 1, characterized in that: A pulse voltage is applied to the gate of the storage tube.

9. The electrical property testing method of memory threshold voltage uniformity according to claim 1, characterized in that: The horizontal axis of the threshold voltage table is the value of the second voltage, and the vertical axis of the threshold voltage table is the value of the base region current.

10. The electrical property testing method of memory threshold voltage uniformity according to claim 1, characterized in that: As the second voltage increases, the current in the base region first increases and then decreases.

11. A method for testing the uniformity of a memory threshold voltage, for testing whether the threshold voltages of a plurality of memory cells in the memory are uniform, wherein the memory cells comprise: A substrate, a base region located in the substrate, a storage tube located on a surface of the substrate, a source line located on one side of the storage tube, and a bit line located on the other side of the storage tube, wherein the storage tube is located between the source line and the bit line, wherein the electrical testing method comprises: connecting source lines of all memory cells, connecting bit lines of all memory cells, and connecting base regions of all memory cells; Applying a scan voltage to the storage tube; Each time the scanning voltage changes, a pulse voltage is applied to the storage tube; measuring the current in the base region; The current and the scan voltage value of the base region are used to form a threshold voltage table; The current in the base region is kept constant, and the smaller the amplitude of the scan voltage change is, the more uniform the memory threshold voltage is.

12. The electrical property testing method of memory threshold voltage uniformity according to claim 11, characterized in that: The method of applying a scan voltage to a storage tube includes: applying a scan voltage to a word line of the storage tube.

13. The electrical property testing method of memory threshold voltage uniformity according to claim 11, characterized in that: A pulse voltage is applied to the gate of the storage tube.

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