Method for accurately measuring contact resistance of probe

Abstract

The invention provides a method for accurately measuring the contact resistance of a probe, which comprises the following steps of: providing a test structure with N test pads, connecting resistors of a tested device with the same resistance value between adjacent pads, and N is greater than or equal to 5; 0A current is continuously applied to the first bonding pad and the Nth bonding pad; a 0V voltage is applied to the Xth bonding pad, and a driving current Iforce (1lt) is applied to the (X + 1) th bonding pad; xlt; n-1; measuring a first pad voltage V1, an (X + 1) th pad voltage V (X + 1) and an Nth pad voltage VN; the contact resistance Rpad X of the Xth bonding pad is calculated according to the formula: Rpad X = V1 / Iforce, and the contact resistance Rpad (X + 1) of the (X + 1) th bonding pad is calculated according to the formula: Rpad (X + 1) = (V (X + 1)-VN) / Iforce; and progressively increasing the X value by stepping 2, and circularly executing the steps 3-5 to obtain the contact resistance value of each middle bonding pad. Under the condition that an existing testing structure is not changed, only the testing method is changed, the contact resistance of the probe is accurately measured, and therefore the state of the probe card is monitored.

Description

Technical Field

[0001] The present invention relates to the field of semiconductor technology, and in particular to a method for accurately measuring probe contact resistance. Background Art

[0002] In integrated circuit wafer testing, metal probes are used to contact the test pads on the surface of the wafer to measure the chip's electrical parameters. However, the existence and variation of the probe contact resistance will interfere with the testing process, so measuring the probe contact resistance is particularly important.

[0003] See also Figure 1 , the current probe contact resistance test method is as follows:

[0004] The pattern of pads 1 through N is used to test probe contact resistance. Between each pad is the resistance of the device under test (DUT), which is of the same size, such as polysilicon or active area resistance. The DUT resistance is measured using the two-terminal method to determine the probe's condition. To maintain test accuracy, the DUT resistance must be relatively high, typically several hundred ohms. However, the probe contact resistance is typically less than 1 ohm. If the contact is poor, it may be a few ohms, a small fraction of the total. Therefore, changes in contact resistance are less noticeable, making it difficult to determine the probe's condition.

[0005] Problems with current approaches include:

[0006] 1. Contact resistance changes cannot be effectively characterized;

[0007] 2. Insufficient measurement sensitivity makes it difficult to judge the needle insertion status;

[0008] 3. A special high-resistance test structure needs to be designed, which increases the complexity of the process.

[0009] In order to solve the above problems, a new method for accurately measuring the probe contact resistance needs to be proposed. Summary of the Invention

[0010] In view of the shortcomings of the prior art described above, the object of the present invention is to provide a method for accurately measuring probe contact resistance, which is used to solve the problem in the prior art that the probe contact resistance measurement adopts the two-terminal method to measure the DUT (device under test) resistance. When the DUT resistance value (hundreds of ohms) is much larger than the probe contact resistance (<1Ω), the change in contact resistance has little effect on the measurement result.

[0011] To achieve the above-mentioned and other related purposes, the present invention provides a method for accurately measuring probe contact resistance, comprising:

[0012] Step 1: Provide a test structure with N test pads, with DUT resistors of the same resistance value connected between adjacent pads, where N ≥ 5;

[0013] Step 2: continuously apply 0A current to the first pad and the Nth pad;

[0014] Step 3: Apply 0V voltage to the Xth pad and drive current I_force to the X+1th pad, where 1 <X<N-1;

[0015] Step 4: Measure the first pad voltage V1, the X+1 pad voltage V(X+1), and the N pad voltage VN;

[0016] Step 5: Calculate the Xth pad contact resistance Rpad_X=V1 / I_force, and the X+1th pad contact resistance Rpad_(X+1)=(V(X+1)-VN) / I_force;

[0017] Step 6: Increase the X value by 2, and repeat steps 3 to 5 to obtain the contact resistance value of each middle pad.

[0018] Preferably, the resistance of the device under test in step 1 is a polysilicon resistor or an active area resistor.

[0019] Preferably, the test pad in step 1 is arranged in a cutting path.

[0020] Preferably, the resistance of the device under test in step 1 is greater than 100Ω.

[0021] Preferably, the driving current in step three is greater than 0.001A.

[0022] Preferably, in step 4, the pads from the second pad to the (N-1)th pad except the Xth pad and the X+1th pad are in an electrically floating state.

[0023] Preferably, in step six, when the value of X increases to X+2≤N-2, the current application states of the first pad and the Nth pad are kept unchanged.

[0024] Preferably, the method uses a metal probe to contact the pads on the surface of the wafer to be measured to measure the electrical parameters of the chip.

[0025] Preferably, the resistance of the metal probe is less than 1Ω.

[0026] As described above, the method for accurately measuring probe contact resistance of the present invention has the following beneficial effects:

[0027] The present invention only changes the test method without changing the existing test structure, accurately measures the probe contact resistance, and thus monitors the needle stuck state. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1Shown is a schematic diagram of a test structure of the prior art;

[0029] Figure 2 Shown is a schematic diagram of the measurement method of the present invention;

[0030] Figure 3 Shown is a measurement schematic diagram of the second pad and the third pad of the present invention;

[0031] Figure 4 Shown is a schematic diagram of the measurement principle of the second pad and the third pad of the present invention;

[0032] Figure 5 It shows a measurement schematic diagram of the fourth pad and the fifth pad of the present invention. DETAILED DESCRIPTION

[0033] The following describes the embodiments of the present invention through specific examples. Those skilled in the art will readily understand the other advantages and benefits of the present invention from the disclosure herein. The present invention may also be implemented or applied through various other specific embodiments, and the details in this specification may be modified or altered based on different viewpoints and applications without departing from the spirit of the present invention.

[0034] See also Figure 2 The present invention provides a method for accurately measuring probe contact resistance, comprising:

[0035] Step 1: Provide a test structure with N test pads, with DUT resistors of the same resistance value connected between adjacent pads, where N ≥ 5;

[0036] In some embodiments, the resistance of the device under test in step 1 is a polysilicon resistor or an active area resistor.

[0037] In some embodiments, the test pads in step 1 are disposed in the dicing streets.

[0038] In some embodiments, the resistance of the device under test in step 1 is greater than 100Ω, such as several hundred Ω.

[0039] In some embodiments, the method uses a metal probe to contact a pad on the surface of the wafer to be measured to measure the electrical parameters of the chip.

[0040] In some embodiments, the resistance of the metal probe is less than 1Ω.

[0041] Step 2: continuously apply 0A current to the first pad and the Nth pad;

[0042] Step 3: Apply 0V voltage to the Xth pad and drive current I_force to the X+1th pad, where 1 <X<N-1;

[0043] In some embodiments, the driving current in step three is greater than 0.001A.

[0044] Step 4: Measure the first pad voltage V1, the X+1 pad voltage V(X+1), and the N pad voltage VN;

[0045] In some embodiments, in step 4, the pads from the second pad to the (N-1)th pad except the Xth pad and the X+1th pad are in an electrically floating state.

[0046] Step 5: Calculate the Xth pad contact resistance Rpad_X=V1 / I_force, and the X+1th pad contact resistance Rpad_(X+1)=(V(X+1)-VN) / I_force;

[0047] For example, see Figure 4 , which shows the measurement of the second and third pads, specifically, see Figure 4 , a current greater than 0.001A is stimulated on the excitation line. This current flows from probe 3 through pad 3 → a → b → pad 2 to probe 2, stimulating a current of 0A on the sensing line. Based on the Kelvin principle, since the current from probe N to node a is zero, the voltage at probe N equals the voltage at node a. Since there is current from probe 3 to node a, there is a voltage drop, which is the voltage drop caused by the contact resistance of probe 3. The measured voltage at probe 3 is V3, and the voltage on probe N is VN. Therefore, the contact resistance of probe 3 is Rpad 3 = (V3 - VN) / Iforce. Similarly, the voltage at probe 1 equals the voltage at node b. The measured voltage at probe 1 is V1, and the contact resistance of probe 2 is Rpad2 = (V1 - V2) / Iforce. Since V2 = 0, Rpad 2 = V1 / Iforce.

[0048] Step 6: Increase the X value by 2, and repeat steps 3 to 5 to obtain the contact resistance value of each middle pad.

[0049] In some embodiments, in step six, when the value of X increases to X+2≤N-2, the current application state of the first pad and the Nth pad is kept unchanged, and the terminal pads are kept at zero current input to reduce signal switching time.

[0050] For example, see Figure 5 , which shows the measurements of the fourth and fifth pads.

[0051] It should be noted that the illustrations provided in this embodiment are only used to schematically illustrate the basic concept of the present invention. Therefore, the illustrations only show components related to the present invention and are not drawn according to the number, shape and size of components in actual implementation. In actual implementation, the type, quantity and proportion of each component can be changed at will, and the component layout type may also be more complicated.

[0052] In summary, the present invention accurately measures probe contact resistance and thus monitors probe stuck status without changing the existing test structure, only the test method. Therefore, the present invention effectively overcomes the shortcomings of the existing technology and has high industrial application value.

[0053] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the present invention. Anyone skilled in the art may modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by one of ordinary skill in the art without departing from the spirit and technical principles disclosed herein are intended to be covered by the claims of the present invention.

Claims

1. A method for accurately measuring probe contact resistance, characterized in that: At least: Step 1: Provide a test structure with N test pads, with DUT resistors of the same resistance value connected between adjacent pads, where N ≥ 5; Step 2: continuously apply 0A current to the first pad and the Nth pad; Step 3: Apply 0V voltage to the Xth pad and drive current I_force to the X+1th pad, where 1 <X<N-1; Step 4: Measure the first pad voltage V1, the X+1 pad voltage V(X+1), and the N pad voltage VN; Step 5: Calculate the Xth pad contact resistance Rpad_X=V1 / I_force, and the X+1th pad contact resistance Rpad_(X+1)=(V(X+1)-VN) / I_force; Step 6: Increase the X value by 2, and repeat steps 3 to 5 to obtain the contact resistance value of each middle pad.

2. The method for accurately measuring probe contact resistance according to claim 1, wherein: The resistance of the device under test in step 1 is a polysilicon resistor or an active area resistor.

3. The method for accurately measuring probe contact resistance according to claim 1, wherein: The test pad in step 1 is set in the cutting path.

4. The method for accurately measuring probe contact resistance according to claim 1, wherein: The resistance of the device under test in step 1 is greater than 100Ω.

5. The method for accurately measuring probe contact resistance according to claim 1, wherein: The driving current in step three is greater than 0.001A.

6. The method for accurately measuring probe contact resistance according to claim 1, wherein: In step 4, the pads from the second pad to the N-1 pad except the X pad and the X+1 pad are in an electrically floating state.

7. The method for accurately measuring probe contact resistance according to claim 1, wherein: In step 6, when the value of X increases to X+2≤N-2, the current application state of the first pad and the Nth pad is kept unchanged.

8. The method for accurately measuring probe contact resistance according to claim 1, wherein: The method uses a metal probe to contact the pad on the surface of the wafer to be tested to measure the electrical parameters of the chip.

9. The method for accurately measuring probe contact resistance according to claim 8, characterized in that: The resistance of the metal probe is less than 1Ω.

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