Wafer surface quality inspection method after copper CMP

Abstract

The invention provides a method for inspecting the surface quality of a wafer after copper CMP (chemical mechanical polishing), which comprises the following steps of: providing a wafer which is subjected to a copper CMP process; a transparent film is provided, the surface of the wafer is covered with the transparent film, and the refractive index of the transparent film ranges from 1.9 to 2.1; detecting the wafer through an optical microscope, and judging whether the wafer has defects or not by observing chromatic aberration in the hole; and after detection, taking down the covered transparent film. Before OM detection, the surface of a wafer is covered with a layer of organic polymer transparent film, whether chromatic aberration exists on the copper surface in the hole or not is observed through the refraction effect of the organic polymer transparent film, and then whether defects exist on the copper surface in the hole or not is determined; if defects exist, reworking and remedying can be carried out after the thin film is taken down. Through the method, the abnormality of the copper surface in the hole can be found in time, and meanwhile, the problem that reworking cannot be carried out due to the fact that defects are found after subsequent processes are completed is avoided.

Description

Technical Field

[0001] The invention belongs to the field of semiconductor manufacturing, and in particular relates to a method for inspecting the surface quality of a wafer after copper CMP. Background Art

[0002] Some semiconductor devices, such as infrared emitters, require copper filling and copper CMP processes because they need to pass large currents. After the CMP process, defects such as dishing and erosion are prone to occur on the copper structure. The commonly used optical microscope (OM) defect detection method cannot completely detect surface defects after copper CMP. The presence of defects will lead to subsequent abnormally low resistance quality defects, especially if the surface defects that could not be detected during the previous OM detection are detected after the subsequent process is completed, and rework and remediation are impossible. At present, surface defect detection can also be carried out through a scanning electron microscope (SEM). SEM detection can observe defects that cannot be observed by OM, but using SEM to detect defects consumes a long time.

[0003] Based on the above problems, a method for inspecting the surface quality of copper wafers after CMP is required to detect surface defects in a timely manner and enable rework. Summary of the invention

[0004] The present invention is to solve all or part of the problems of the above-mentioned prior art, and provides a method for inspecting the surface quality of wafers after copper CMP. Before the wafers after copper filling and copper CMP are subjected to OM inspection, a layer of a specially prepared organic polymer transparent film is covered on the surface, and then OM inspection is performed. The refraction effect of the organic polymer transparent film is used to observe whether there is color difference on the copper surface in the hole, and then confirm whether there is a defect on the copper surface in the hole after copper CMP; if a defect is detected, the wafer can be reworked after the organic polymer transparent film is removed after the inspection. Through the above method, the abnormality of the copper surface in the hole can be discovered in time, and the problem of being unable to rework after defects are discovered after the subsequent process is completed is avoided.

[0005] The present invention provides a method for inspecting the surface quality of a wafer after copper CMP, comprising the following steps: providing a wafer, the wafer having undergone a copper CMP process; providing a transparent film, covering the transparent film on the surface of the wafer, the refractive index of the transparent film being between 1.9 and 2.1; inspecting the wafer through an optical microscope, and judging whether the wafer has defects by observing the color difference in the hole; after the inspection, removing the covering transparent film. Before OM inspection, a layer of the organic polymer transparent film is covered on the surface of the wafer, and the refractive effect of the organic polymer transparent film is used to observe whether there is color difference on the copper surface in the hole, and confirm whether there is a defect on the copper surface in the hole after copper CMP. If defects are detected, rework and remediation can be performed after removing the organic polymer transparent film. Through the above method, abnormalities on the copper surface in the hole can be discovered in time, and the problem of being unable to rework after defects are discovered after the subsequent process is completed is avoided.

[0006] The transparent film is an organic polymer transparent film, has good flexibility, and can better fit the surface of the wafer.

[0007] Before using the organic polymer transparent film, it is confirmed that the surface of the film is free of damage or contamination to ensure that the optical properties of the organic polymer transparent film are uniform and consistent to avoid affecting the test results.

[0008] The size of the organic polymer transparent film is not less than the size of the wafer, ensuring that the organic polymer transparent film can completely cover the surface of the wafer, providing a uniform interface, and ensuring the reliability of the detection result.

[0009] Before covering the organic polymer transparent film, the surface of the wafer is cleaned to remove pollutants and particles on the surface of the wafer, which helps the organic polymer transparent film to be more evenly attached to the surface of the wafer to avoid affecting the detection results.

[0010] When covering, the organic polymer transparent film is closely attached to the surface of the wafer, reducing the formation of wrinkles and bubbles in the organic polymer transparent film, ensuring a clearer and more accurate image, and improving the ability to identify surface defects.

[0011] Under normal circumstances, the hole appears copper-red. When there is a defect, a dot-like purple color difference appears in the hole area. The refraction effect of the organic polymer transparent film is used to judge whether there is a defect on the wafer surface by the color difference.

[0012] After removing the organic polymer transparent film, the wafer after inspection is cleaned to remove the residues or pollutants on the surface of the wafer to ensure the quality of subsequent processes.

[0013] The organic polymer transparent film is placed in a protection box when not in use, and the protection box is kept clean to prevent the organic polymer transparent film from being exposed to the outside and contaminated or damaged.

[0014] If defects are detected, the organic polymer transparent film is removed and the wafer is reworked. The organic polymer transparent film can be removed after the detection, which is convenient for remediation after defects are found.

[0015] Compared with the prior art, the beneficial effects of the present invention mainly include the following: providing a method for inspecting the surface quality of wafers after copper CMP, before performing OM inspection on wafers after copper filling and copper CMP, covering the surface of the wafer with a layer of organic polymer transparent film, using the refraction effect of the organic polymer transparent film, by observing whether there is color difference on the copper surface in the hole, confirm whether there is a defect; if there is a defect, rework and remediation can be performed after removing the organic polymer transparent film. Through the above method, not only can the abnormality of the copper surface in the hole be discovered in time, with high detection efficiency, but also after the defect is discovered, it can be remedied in time, avoiding the problem of discovering defects after completing the subsequent process and being unable to rework. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0017] Figure 1 A flow chart of a method for inspecting wafer surface quality after copper CMP provided by the present invention.

[0018] Figure 2 This is a normal wafer OM inspection image.

[0019] Figure 3 This is a wafer OM inspection image with defects. DETAILED DESCRIPTION

[0020] The following description and accompanying drawings fully demonstrate specific embodiments of the present invention so that those skilled in the art can practice them. Other embodiments may include structural, logical, electrical, process and other changes. The embodiments represent possible variations only. Unless clearly required, separate components and functions are optional, and the order of operation may vary. The parts and features of some embodiments may be included in or replace the parts and features of other embodiments.

[0021] This embodiment provides a method for inspecting the surface quality of a copper wafer after CMP. The specific steps are as follows: Figure 1 As shown:

[0022] A wafer is provided, and copper filling and copper CMP processes are completed on the wafer. After the copper filling and copper CMP processes are completed on the wafer, dishing and erosion defects are likely to exist on the copper structure, so it is necessary to perform surface quality inspection on the wafer.

[0023] A transparent film is provided and covered on the surface of the wafer, wherein the refractive index of the transparent film is between 1.9 and 2.1; the refractive effect of the transparent film is utilized to observe the surface color difference phenomenon during the OM detection process, and the color difference is used to determine whether the wafer is abnormal. The transparent film uses an organic polymer transparent film, which has good flexibility and can better fit the surface of the wafer; before use, the surface of the organic polymer transparent film is confirmed to be free of damage or contamination, ensuring that the optical properties of the organic polymer transparent film are uniform and consistent, thereby avoiding affecting the detection results; the size of the organic polymer transparent film is not less than the size of the wafer; the organic polymer transparent film can completely cover the surface of the wafer, providing a uniform interface, and ensuring the reliability of the detection results. Before covering the organic polymer transparent film, the surface of the wafer is cleaned to remove pollutants and particles on the surface of the wafer, thereby avoiding affecting the detection results, and at the same time, helping the organic polymer transparent film to achieve a more uniform fit with the surface of the wafer, and the detection results are more reliable. The particle size of the organic polymer transparent film meets the standard of the mask cover film, better maintaining the consistency of the refractive index between it and the surface of the wafer, ensuring that the actual defects on the surface of the wafer can be clearly observed. When covering the film, ensure that the organic polymer transparent film is in close contact with the wafer surface, reduce the formation of wrinkles and bubbles on the organic polymer transparent film, ensure that a clearer and more accurate image can be obtained, and improve the ability to identify defects on the wafer surface.

[0024] The wafer is inspected by an optical microscope, and the color difference in the hole is observed to determine whether the wafer has defects. Figure 2-3 As shown, under normal circumstances, the hole appears copper-red. When there is a defect, the hole appears dotted purple-like color difference, which is used to determine whether the wafer has defects.

[0025] After the test, remove the covering transparent film. After removing the organic polymer transparent film, clean the wafer after the test to remove the residues or contaminants that may be brought into the wafer surface to ensure the quality of the subsequent process; when the organic polymer transparent film is not in use, place it in a protective box, and keep the protective box clean to prevent the organic polymer transparent film from being exposed to the outside and contaminated or damaged; if the test finds defects, the wafer can be reworked after the organic polymer transparent film is removed after the test is completed. The organic polymer transparent film can be removed after the test, which is convenient for remediation after defects are found.

[0026] After the wafer completes the copper filling and copper CMP process, before the OM test, the wafer to be tested is covered with an organic polymer transparent film in advance, and then the OM test is performed. The refraction effect of the organic polymer transparent film is used to observe whether there is a color difference on the copper surface in the hole to confirm whether there is an abnormality in the copper performance in the hole after the copper CMP. The present invention can not only detect the abnormality of the copper surface in the hole in time, but also has a high detection efficiency. At the same time, after the defect is found, it can be remedied in time, avoiding the problem of discovering defects after completing the subsequent process and being unable to rework.

[0027] It will be apparent to those skilled in the art that the invention is not limited to the details of the exemplary embodiments described above and that the invention can be implemented in other specific forms without departing from the spirit or essential features of the invention. Therefore, the embodiments should be considered exemplary and non-limiting in all respects, and the scope of the invention is defined by the appended claims rather than the foregoing description, and it is intended that all variations falling within the meaning and scope of the equivalent elements of the claims be included in the invention. Any reference numeral in a claim should not be considered as limiting the claim to which it relates.

Claims

1. A method for inspecting the surface quality of a copper wafer after CMP, characterized in that: The steps include: Providing a wafer, wherein the wafer has been subjected to a copper CMP process; Providing a transparent film, and covering the surface of the wafer with the transparent film, wherein the refractive index of the transparent film is between 1.9 and 2.1; Inspecting the wafer through an optical microscope, and judging whether the wafer has defects by observing the color difference in the hole; After the detection, the covering transparent film is removed.

2. The method for judging the surface quality of a wafer after copper CMP according to claim 1, characterized in that: The transparent film is an organic polymer transparent film.

3. The method for inspecting the surface quality of a copper wafer after CMP according to claim 2, characterized in that: Before using the organic polymer transparent film, confirm that the surface thereof is free of damage or contamination.

4. The method for inspecting the surface quality of a copper wafer after CMP according to claim 2, characterized in that: The size of the organic polymer transparent film is not less than that of the wafer.

5. The method for inspecting the surface quality of a copper wafer after CMP according to claim 2, characterized in that: Before covering the organic polymer transparent film, the surface of the wafer is cleaned.

6. The method for inspecting the surface quality of a copper wafer after CMP according to claim 2, characterized in that: During covering, the organic polymer transparent film is closely attached to the surface of the wafer.

7. The method for inspecting the surface quality of a copper wafer after CMP according to claim 1, characterized in that: Under normal circumstances, the inside of the hole appears copper-red; in the event of a defect, the hole area appears dotted purple-like color difference.

8. The method for inspecting the surface quality of a copper wafer after CMP according to claim 2, characterized in that: After removing the organic polymer transparent film, the wafer after inspection is cleaned.

9. The method for inspecting the surface quality of a copper wafer after CMP according to claim 2, characterized in that: The organic polymer transparent film is placed in a protective box when not in use.

10. The method for judging the quality of the copper CMP surface after the infrared emitter according to claim 2, characterized in that: If defects are detected, the organic polymer transparent film is removed and the wafer is reworked.

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