Method for removing microparticles on surface of failure analysis sample

Abstract

The invention provides a method for removing microparticles on the surface of a failure analysis sample, the failure sample is treated to a failure defect generation layer through layer-by-layer grinding, microparticles of grinding liquid are left on the failure defect generation layer, and exposed contact holes exist on the failure defect generation layer; fixing the failure sample on a sample table in a vacuum chamber, and then vacuumizing the vacuum chamber; using inert gas as an ion source, ionizing the inert gas by using a machine table to form an ion beam, adjusting setting parameters of the ion beam and an angle between the ion beam and the surface of the failure sample, and removing microparticles; and continuously adjusting the setting parameters of the ion beam and the angle between the ion beam and the surface of the failure sample, and removing residual microparticles. Under the condition that the surface state of the sample is not affected, the microparticles on the surface of the failure analysis sample can be removed.

Description

Technical Field

[0001] The invention relates to the field of semiconductor technology, in particular to a method for removing microparticles on the surface of a failure analysis sample. Background Art

[0002] Integrated circuit failure analysis is an important means to improve product yield. Failure analysis engineers grind the failed samples layer by layer to the failure defect occurrence layer, and then use SEM (scanning electron microscope) and nanoprobe to locate design or production process defects. In the process of grinding samples, silicon dioxide microparticles in the grinding fluid will adhere to the surface of the sample, and these attached microparticles will have a serious impact on subsequent electron microscope observations and nanoprobe tests.

[0003] 1. First, these attached microparticles will contaminate the electron gun under SEM, causing irreversible damage to the electron microscope that requires high vacuum and high cleanliness;

[0004] 2. Secondly, these microparticles may adhere to the surface of the target location, hindering the precise positioning of the defect location;

[0005] 3. Finally, the microparticles on the surface will cause rapid carbon deposition on the sample surface during testing, making the nanoprobe test impossible.

[0006] Solution: Usually microparticles can be removed by grinding and cleaning, but for some samples of the CT (contact hole) layer, the tungsten in the contact hole will undergo a photocatalytic electrochemical reaction with the grinding fluid under light conditions, and the generated reactants will dissolve in water, forming a depression in the contact hole, making it impossible to test the nanoprobe, and the failure rate is high. Therefore, it is not suitable to use grinding and cleaning to remove surface microparticles for samples with contact holes.

[0007] In order to solve the above problems, a new method for removing microparticles on the surface of failure analysis samples needs to be proposed. Summary of the invention

[0008] In view of the above-mentioned shortcomings of the prior art, an object of the present invention is to provide a method for removing microparticles on the surface of failure analysis samples, so as to solve the problem that it is not suitable to use grinding and cleaning method to remove surface microparticles for samples with contact holes in the prior art.

[0009] To achieve the above-mentioned object and other related objects, the present invention provides a method for removing microparticles on the surface of a failure analysis sample, comprising:

[0010] Step 1: grinding the failed sample layer by layer to a failure defect occurrence layer, on which microparticles of the grinding liquid remain and exposed contact holes exist;

[0011] Step 2, fixing the failed sample on a sample table in a vacuum chamber, and then evacuating the vacuum chamber;

[0012] Step 3: using an inert gas as an ion source, using a machine to ionize the inert gas to form an ion beam, adjusting the setting parameters of the ion beam and the angle with the surface of the failed sample, and using the ion beam to remove the microparticles;

[0013] Step 4: Continue to adjust the setting parameters of the ion beam and the angle with the surface of the failed sample, and use the ion beam to remove the remaining microparticles.

[0014] Preferably, the failure defect occurrence layer in step 1 is a layer in the interconnect structure of the failed sample.

[0015] Preferably, the interconnection structure in step 1 includes various conductive components to connect various IC devices to an integrated circuit, and the interconnection structure also includes an interlayer dielectric layer to separate and isolate the various conductive components.

[0016] Preferably, the microparticles in step 1 are silicon dioxide microparticles.

[0017] Preferably, in step 2, a position controller is used to adjust the grinding target point, and the target point is moved to the cross center of the sample stage.

[0018] Preferably, the method for fixing the failed sample in step 2 includes: placing the failed sample in a fixer, adjusting the failed sample using a height controller so that it fits the surface, and then locking the sample stage to fix the failed sample.

[0019] Preferably, the inert gas in step three is argon.

[0020] Preferably, the machine in step three is an ion milling machine.

[0021] Preferably, the acceleration voltage of the ion milling instrument in step three is less than 3V, and the starting voltage is 1.5V.

[0022] Preferably, the sample stage in step three is selected as a rotation mode.

[0023] Preferably, in step three, the angle between the rotation axis of the sample stage and the ion beam is 90°, so that the ion beam hits the surface of the failed sample parallel to the failed sample.

[0024] Preferably, the acceleration voltage of the ion milling instrument in step three is less than 3V.

[0025] Preferably, the sample stage in step 4 is selected to be in rotation mode.

[0026] Preferably, in step 4, the angle between the sample stage rotation axis and the ion beam is 80°, so that there is an inclination angle between the ion beam and the failed sample and the ion beam hits the surface of the failed sample.

[0027] As described above, the method for removing microparticles from the surface of failure analysis samples of the present invention has the following beneficial effects:

[0028] The present invention can remove microparticles on the surface of failure analysis samples without affecting the surface state of the samples. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 Shown is a schematic diagram of the process flow of the present invention;

[0030] Figure 2 It is a schematic diagram showing the first use of an ion beam to remove most of the adhered microparticles according to the present invention;

[0031] Figure 3 It is a schematic diagram showing the second use of ion beam to remove the remaining microparticles according to the present invention;

[0032] Figure 4 Shown is a schematic diagram of the present invention before the removal of microparticles;

[0033] Figure 5 It is a schematic diagram showing the effect of using ion beam to remove most of the adhered microparticles for the first time according to the present invention;

[0034] Figure 6 It is a schematic diagram showing the effect of using an ion beam to remove the remaining microparticles for the second time according to the present invention;

[0035] Figure 7 Shown are SEM images of the sample surfaces after different treatment times according to the present invention. DETAILED DESCRIPTION

[0036] The following describes the embodiments of the present invention through specific examples, and those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present invention.

[0037] See also Figure 1 The present invention provides a method for removing microparticles on the surface of a failure analysis sample, comprising:

[0038] Step 1: grinding the failed sample layer by layer to a failure defect occurrence layer, where microparticles of the grinding fluid remain on the failure defect occurrence layer, and exposed contact holes exist on the failure defect occurrence layer;

[0039] In some embodiments, the failure defect occurrence layer in step 1 is a layer in an interconnect structure in the failed sample.

[0040] In some embodiments, the interconnection structure in step one includes various conductive components to connect various IC devices to the integrated circuit, and the interconnection structure also includes an interlayer dielectric layer to separate and isolate various conductive components. For example, the interconnection structure includes contact holes; metal lines; and through holes. The metal lines are distributed in multiple metal layers. The contact holes provide vertical electrical wiring from the semiconductor substrate to the metal lines. The through holes provide vertical electrical wiring between adjacent metal layers. Various conductive components are formed by one or more conductive materials such as metals, metal alloys, or silicides. For example, the metal lines may include copper, aluminum-copper alloys, other suitable conductive materials, or combinations thereof. The through holes may include copper, aluminum-copper alloys, other suitable conductive materials, or combinations thereof. The contact holes may include tungsten, silicide, nickel, cobalt, copper, other suitable conductive materials, or combinations thereof. In some instances, the various conductive components may further include barrier layers such as tantalum and tantalum nitride, titanium, and titanium nitride. In this embodiment, the material of the contact holes is tungsten.

[0041] In some embodiments, the microparticles in step 1 are silicon dioxide microparticles. In other embodiments, the microparticles may also be other particles in the polishing liquid.

[0042] Step 2: fix the failed sample on the sample stage in the vacuum chamber, and then evacuate the vacuum chamber;

[0043] In some embodiments, in step 2, a position controller is used to adjust the polishing target point and move the target point to the center of the sample stage cross.

[0044] In some embodiments, the method for fixing the failed sample in step 2 includes: placing the failed sample in a fixer, adjusting the failed sample using a height controller so that it fits the surface, and then locking the sample stage to fix the failed sample.

[0045] Step 3: Using an inert gas as an ion source, using a machine to ionize the inert gas to form an ion beam, adjusting the setting parameters of the ion beam and the angle with the surface of the failed sample, and using the ion beam to remove microparticles;

[0046] In some embodiments, the inert gas in step three is argon.

[0047] In some embodiments, the machine in step three is an ion milling instrument. An ion milling instrument (Ion miller) usually uses inert gas argon, and after ionizing the argon gas, bombards the sample surface at a certain angle under the action of electric field acceleration, and uses momentum transfer to finely polish the sample by physical sputtering bombardment under controllable rate conditions to meet the sample preparation requirements of surface sensitive analysis technologies such as scanning electron microscopes. In failure analysis laboratories, ion milling instruments are usually used for the processing of cross-sectional samples, and a uniformly cut cross-sectional sample is obtained by sputtering a part of the sample along the edge of the baffle. The present invention draws on the cutting function of the ion milling instrument, changes different voltages and angles, bombards the microparticles on the surface of the sample, but does not damage the surface state of the sample, and improves the success rate of sample analysis.

[0048] In some embodiments, the acceleration voltage of the ion milling instrument in step three is less than 3V, for example, the acceleration voltage is 2V. Using a smaller voltage can reduce the bombardment degree, and the starting voltage is 1.5V.

[0049] In some embodiments, the sample stage in step three is selected as a rotation mode.

[0050] In some embodiments, see Figure 2 In step 3, the angle between the sample stage rotation axis and the ion beam is 90°, so that the ion beam hits the surface of the failed sample parallel to the failed sample. Most of the adhered microparticles can be removed by physical sputtering of Ar ions above the failed sample surface through the accelerating electric field. Figure 4 and Figure 5 The clear effect of the microparticles is shown respectively.

[0051] In some embodiments, the acceleration voltage of the ion milling instrument in step three is less than 3V, for example, the acceleration voltage is 2V.

[0052] Step 4: Continue to adjust the setting parameters of the ion beam and the angle with the surface of the failed sample, and use the ion beam to remove the residual microparticles.

[0053] In some embodiments, the sample stage in step 4 is selected as a rotation mode.

[0054] In some embodiments, see Figure 3 In step 4, the angle between the sample stage rotation axis and the ion beam is 80°, so that there is an inclination angle between the ion beam and the failed sample and the ion beam hits the surface of the failed sample. Figure 6 Complete removal of microparticles is shown.

[0055] See also Figure 7, which shows an SRAM sample with microparticles on the surface. The microparticles cover the area to be tested, and the nanoprobe electrical test cannot be performed. Removing the microparticles by washing with water may cause the sample contact holes to sag and affect subsequent tests. The sample is treated by the method of the present invention. From the SEM image (SEL mode), it can be seen that as the treatment time increases, the microparticles on the sample surface gradually decrease. First, the small and dispersed microparticles are removed first, and then most of the microparticles that are piled together are gradually bombarded and become smaller until they are all cleaned and removed.

[0056] During the cleaning process, the roughness of the contact holes in other areas of the sample was not affected, meeting the test requirements for electrical verification.

[0057] It should be noted that the illustrations provided in this embodiment are only used to illustrate the basic concept of the present invention in a schematic manner. Therefore, the drawings only show components related to the present invention rather than being drawn according to the number, shape and size of components in actual implementation. In actual implementation, the type, quantity and proportion of each component may be changed arbitrarily, and the component layout may also be more complicated.

[0058] In summary, the present invention can remove microparticles on the surface of failure analysis samples without affecting the surface state of the samples. Therefore, the present invention effectively overcomes various shortcomings of the prior art and has high industrial utilization value.

[0059] 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 familiar with 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 a person of ordinary skill in the art without departing from the spirit and technical concept disclosed by the present invention shall still be covered by the claims of the present invention.

Claims

1. A method for removing microparticles from the surface of a failure analysis sample, characterized in that: At least: Step 1: grinding the failed sample layer by layer to a failure defect occurrence layer, on which microparticles of the grinding liquid remain and exposed contact holes exist; Step 2, fixing the failed sample on a sample table in a vacuum chamber, and then evacuating the vacuum chamber; Step 3: using an inert gas as an ion source, using a machine to ionize the inert gas to form an ion beam, adjusting the setting parameters of the ion beam and the angle with the surface of the failed sample, and using the ion beam to remove the microparticles; Step 4: Continue to adjust the setting parameters of the ion beam and the angle with the surface of the failed sample, and use the ion beam to remove the remaining microparticles.

2. The method for removing microparticles from the surface of a failure analysis sample according to claim 1, characterized in that: The failure defect occurrence layer in step 1 is a layer in the interconnect structure of the failed sample.

3. The method for removing microparticles from the surface of a failure analysis sample according to claim 2, characterized in that: The interconnect structure in step 1 includes various conductive components to connect various IC devices to the integrated circuit, and the interconnect structure also includes an interlayer dielectric layer to separate and isolate the various conductive components.

4. The method for removing microparticles from the surface of a failure analysis sample according to claim 1, characterized in that: The microparticles in step 1 are silicon dioxide microparticles.

5. The method for removing microparticles on the surface of a failure analysis sample according to claim 1, characterized in that: In step 2, the grinding target point is adjusted by using a position controller to move the target point to the cross center of the sample stage.

6. The method for removing microparticles from the surface of a failure analysis sample according to claim 1, characterized in that: The method for fixing the failed sample in step 2 includes: placing the failed sample in a fixer, adjusting the failed sample using a height controller so that it fits the surface, and then locking the sample stage to fix the failed sample.

7. The method for removing microparticles from the surface of a failure analysis sample according to claim 1, characterized in that: The inert gas in step three is argon.

8. The method for removing microparticles from the surface of a failure analysis sample according to claim 1, characterized in that: The machine in step three is an ion milling machine.

9. The method for removing microparticles from the surface of a failure analysis sample according to claim 8, characterized in that: The acceleration voltage of the ion milling instrument in step three is less than 3V, and the starting voltage is 1.5V.

10. The method for removing microparticles on the surface of a failure analysis sample according to claim 1, characterized in that: The sample stage in step three is selected as a rotation mode.

11. The method for removing microparticles on the surface of a failure analysis sample according to claim 10, characterized in that: In step three, the angle between the sample stage rotation axis and the ion beam is 90°, so that the ion beam hits the surface of the failed sample parallel to the failed sample.

12. The method for removing microparticles from the surface of a failure analysis sample according to claim 8, characterized in that: The acceleration voltage of the ion milling instrument in step 3 is less than 3V.

13. The method for removing microparticles on the surface of a failure analysis sample according to claim 1, characterized in that: The sample stage in step 4 is selected as a rotation mode.

14. The method for removing microparticles on the surface of a failure analysis sample according to claim 13, characterized in that: In step 4, the angle between the sample stage rotation axis and the ion beam is 80°, so that there is an inclination angle between the ion beam and the failed sample and the ion beam hits the surface of the failed sample.

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