TWI900897B - Wafer inspection method - Google Patents

Abstract

A wafer inspection method includes: loading a first wafer to an optical inspection device; positioning the first wafer; inspecting the first wafer and generating a first wafer optical data; loading a second wafer to the optical inspection device; positioning the second wafer; inspecting the second wafer and generating a second wafer optical data; comparing the first wafer optical data and the second wafer optical data; determining whether the first wafer optical data and the second wafer optical data are the same; when the second wafer optical data is determined to be substantially different from the first wafer optical data, obtaining a minimum unit pattern on the second wafer; inspecting optical data of a first die unit and a second die unit based on the minimum unit pattern; and comparing optical data of the first die unit and the second die unit.

Description

Wafer inspection method

The present invention relates to a detection method, and in particular to a wafer detection method.

The manufacture of semiconductor devices typically involves processing semiconductor wafers through numerous processes to form the various features and multiple layers of a semiconductor device. Defects can form during any of these processes. Therefore, wafers must be inspected for defects after more than one process step.

Difference images have been used for defect detection. Typically, these images are obtained by comparing a target image with a reference image. However, some image differences are sometimes incorrectly labeled as defects. Therefore, accurately determining the defect status of wafers is a pressing issue.

The present invention provides a wafer inspection method that can accurately determine the defect status of a wafer.

The present invention provides a wafer inspection method comprising: loading a first wafer into an optical inspection device; positioning the first wafer; inspecting the first wafer and generating first wafer optical data; loading a second wafer into the optical inspection device; positioning the second wafer; inspecting the second wafer and generating second wafer optical data; comparing the first wafer optical data with the second wafer optical data; determining whether the first wafer optical data and the second wafer optical data are identical; when it is determined that the second wafer optical data is substantially different from the first wafer optical data, obtaining a minimum unit pattern on the second wafer; inspecting optical data of a first wafer unit and optical data of a second wafer unit based on the minimum unit pattern; and comparing the optical data of the first wafer unit with the optical data of the second wafer unit.

In some embodiments, the wafer inspection method further includes: determining whether optical data of a first wafer unit and optical data of a second wafer unit are the same; and determining that the second wafer is in a defective state when the optical data of the second wafer unit is determined to be substantially different from the optical data of the first wafer unit.

In some embodiments, obtaining the minimum unit pattern on the second wafer includes: reading a preset pattern data; obtaining a plurality of unit patterns based on the preset pattern data; and obtaining the minimum unit pattern based on the unit patterns.

In some embodiments, detecting optical data of a first chip unit and optical data of a second chip unit includes: restoring an arrangement of a plurality of chip units in a preset pattern data based on a minimum unit pattern; selecting adjacent first chip units and second chip units from the chip units; and detecting the optical data of the first chip unit and optical data of the second chip unit.

In some embodiments, inspecting a first wafer and generating first wafer optical data includes: illuminating a top surface of the first wafer with a mixed light; receiving reflected light from the top surface of the first wafer; and generating the first wafer optical data based on the reflected light.

In some embodiments, irradiating the upper surface of the first wafer with mixed light includes irradiating the upper surface of the first wafer with the mixed light at a predetermined incident angle. In some embodiments, the mixed light includes at least two light beams having different wavelengths.

In some embodiments, inspecting the first wafer and generating first wafer optical data includes storing the first wafer optical data as reference data.

In some embodiments, the first wafer and the second wafer are loaded into the optical inspection device at the same time.

In some embodiments, inspecting the second wafer and generating the second wafer optical data includes: rotating the second wafer by a predetermined angle; illuminating a top surface of the second wafer with a mixed light; receiving a reflected light from the top surface of the second wafer; and generating the second wafer optical data based on the reflected light.

As mentioned above, the wafer inspection method of the present invention is to load two wafers (for example, a first wafer and a second wafer) into an optical inspection device and generate wafer optical data respectively. By comparing the wafer optical data of the two wafers, it can be determined whether there is a difference between the two. If it is determined that there is a difference after inspection, the optical data of each chip on one of the wafers can be compared. In other words, after the wafer inspection method of the present invention has compared the wafer optical data of the first wafer (for example, as a reference wafer) and the second wafer (for example, as a test wafer), if there is a difference between the two, the multiple chips on the test wafer can be further inspected to determine whether the test wafer is actually defective. Thus, the wafer inspection method of the present invention can first inspect the wafer condition over a large area, and then conduct inspection on the wafer's finer details. This can eliminate the effects of slight optical property non-uniformities caused by the manufacturing process, thereby improving wafer inspection accuracy.

1, 3: Wafer

11, 31: Wafer optical data

311: Different parts

2: Optical detection device

4: Minimum unit graphic

5: Default pattern data

51:Unit Graphics

52: vertical line

53: Horizontal Line

54, 61, 62: Chip units

S01~S11: Steps

The following drawings and description set forth details of one or more embodiments of the subject matter described in this specification. Other features, aspects, and advantages of the subject matter of this specification will become apparent from the description, drawings, and claims, including:

Figure 1 is a diagram showing the steps of a wafer inspection method according to the present invention.

Figures 2A to 2E are schematic diagrams illustrating the process of the wafer inspection method of the present invention.

Figures 3A to 3E are schematic diagrams illustrating the process of the wafer inspection method of the present invention.

Figures 4A to 4D are schematic diagrams illustrating the process of the wafer inspection method of the present invention.

Figures 5A and 5B are schematic diagrams illustrating the process of the wafer inspection method of the present invention.

As used herein, terms such as "first," "second," etc. describe various elements, components, regions, layers, and/or parts, and these elements, components, regions, layers, and/or parts should not be limited by these terms. These terms are only used to distinguish one element, component, region, layer, or part from another. Unless the context clearly indicates otherwise, the use of terms such as "first," "second," etc. herein does not imply a sequence or order.

Figure 1 is a step diagram showing a wafer inspection method of the present invention. The wafer inspection method of the present invention includes steps S01 to S11. In step S01, a first wafer is loaded into an optical inspection device. In step S02, the first wafer is positioned. In step S03, the first wafer is inspected and first wafer optical data is generated. In step S04, a second wafer is loaded into the optical inspection device. In step S05, the second wafer is positioned. In step S06, the second wafer is inspected and second wafer optical data is generated. In step S07, the first wafer optical data and the second wafer optical data are compared. In step S08, it is determined whether the first wafer optical data and the second wafer optical data are the same. In step S09, when it is determined that the optical data of the second wafer is substantially different from the optical data of the first wafer, a minimum unit pattern is obtained on the second wafer. In step S10, the optical data of the first wafer unit and the optical data of the second wafer unit are detected based on the minimum unit pattern. In step S11, the optical data of the first wafer unit and the optical data of the second wafer unit are compared.

Figures 2A to 2E are schematic flow diagrams illustrating the wafer inspection method of the present invention. As shown in Figures 1 and 2A, in step S01, a wafer (e.g., a first wafer) 1 is loaded into an optical inspection device 2. Wafer 1 is, for example, a semiconductor wafer having a patterned chip film layer formed thereon. Optical inspection device 2 may include, for example, a light source, a carrier, an optical imaging module, a storage module, a computing module, and/or an interface module, without limitation. It is worth noting that the light source may be, for example, an epi-coaxial light source integrated with a light-emitting diode, an annular light source, an oblique light source, or other light-emitting device capable of defect detection. Alternatively, the light source may include a plurality of active light sources arranged in a one-dimensional or two-dimensional matrix to simultaneously output light to various portions of wafer 1. Furthermore, the optical imaging module is, for example, disposed above the carrier stage and may include a semiconductor photosensitive element, such as a charge-coupled device (CCD) lens, to receive light reflected from the wafer 1.

In some embodiments, the light source comprises LEDs of different wavelengths to produce mixed light. For example, mixed light can be produced by a red LED emitting red light with a wavelength of 620 nm to 750 nm and a green LED emitting green light with a wavelength of 495 nm to 570 nm. This is not intended to limit the present invention; mixed light with three or more wavelengths may also be used. Furthermore, the mixing ratio of the different wavelengths in the mixed light is not limiting; for example, a mixture of 70% to 90% red light and 10% to 30% green light may be used, and this is not intended to limit the present invention.

In some embodiments, the incident angle of the light source on the upper surface of the wafer 1 (the default incident angle), and the offset angle of the optical imaging module relative to the normal of the upper surface of the wafer 1 can be set differently depending on the design. For example, the light source and the optical imaging module can both be perpendicular to the upper surface of the wafer 1, but located at different heights. That is, the incident angle of the light source relative to the normal of the upper surface of the wafer 1 is 0 degrees (that is, the two are parallel), and the offset angle of the optical imaging module relative to the normal of the upper surface of the wafer 1 is also 0 degrees. For another example, the incident angle of the light source relative to the normal of the upper surface of the wafer 1 can be offset by 5 degrees to 10 degrees, and the offset angle of the optical imaging module relative to the normal of the upper surface of the wafer 1 can be -5 degrees to -10 degrees, and the two are set corresponding to each other. Note that positive and negative angles indicate different directions of deviation from the normal. For example, 5 degrees means a 5-degree deviation to the right from the normal, and -5 degrees means a 5-degree deviation to the left from the normal.

As shown in Figures 1, 2B, and 2C, in step S02, wafer 1 is positioned. As shown in Figure 2B, the carrier stage of optical inspection device 2 can rotate, and the optical imaging module of optical inspection device 2 can automatically detect the positioning notches of wafer 1 to perform positioning. In this embodiment, the optical imaging module of optical inspection device 2 automatically selects and inspects the four corners of wafer 1 as an example for illustration. However, this is not intended to limit the present invention; different designs can select and inspect different locations. As shown in Figure 2C, the optical imaging module of optical inspection device 2 can also capture images of the four corners of wafer 1 to record alignment information, which is not intended to limit the present invention.

As shown in Figures 1, 2D, and 2E, in step S03, the wafer 1 is inspected and wafer optical data 11 (for example, first wafer optical data) is generated. In some embodiments, the light source of the optical detection device 2 can utilize light of various wavelengths, angles, and/or brightness to illuminate the upper surface of the wafer 1. For example, the light source of the optical detection device 2 can utilize the mixed light as described above and illuminate the upper surface of the wafer 1 at the preset incident angle as described above. The optical imaging module of the optical detection device 2 can receive the reflected light from the upper surface of the wafer 1 to generate wafer optical data 11. In other words, the optical imaging module of the optical detection device 2 can receive the reflected light generated after the mixed light illuminates the upper surface of the wafer 1, and generate wafer optical data 11 based on the reflected light. Wafer optical data 11 may include, for example, the surface image of wafer 1, reflected brightness distribution, grayscale distribution, and/or other optical characteristic data. Notably, grayscale distribution can be used to eliminate uneven brightness caused by process issues. Furthermore, the carrier of the optical inspection device 2 can slightly rotate wafer 1, varying the angle by ±θ. The optical imaging module then captures wafer optical data 11 to provide an error range for slight angular errors, thus preventing misjudgments due to misalignment.

Figures 3A to 3E are schematic flow charts illustrating the wafer inspection method of the present invention. As shown in Figures 1 and 3A , in step S04, wafer 3 (e.g., a second wafer) is loaded into optical inspection apparatus 2. Wafer 3 is, for example, a semiconductor wafer identical to wafer 1, having formed thereon a patterned chip film layer identical to wafer 1.

As shown in Figures 1, 3B, and 3C, in step S05, wafer 3 is positioned. As shown in Figure 3B, the carrier stage of optical inspection device 2 can rotate, and the optical imaging module of optical inspection device 2 automatically detects the positioning notches of wafer 3 to perform positioning. In this embodiment, the optical imaging module of optical inspection device 2 automatically selects and inspects the four corners of wafer 3 for illustration. However, this is not intended to limit the present invention; different locations can be inspected in different designs. As shown in Figure 3C, the carrier stage of optical inspection device 2 can slightly rotate wafer 3, varying the preset angle ±θ. The optical imaging module then captures optical data from the wafer to provide an error range for slight angle errors, thus avoiding misjudgments due to alignment errors.

As shown in Figures 1, 3D, and 3E, in step S06, the wafer 3 is detected and wafer optical data 31 (for example, second wafer optical data) is generated. In some embodiments, the light source of the optical detection device 2 utilizes light with the same parameters as that used to illuminate the wafer 1 to illuminate the upper surface of the wafer 3. For example, the light source of the optical detection device 2 can utilize the mixed light as described above and illuminate the upper surface of the wafer 3 at the preset incident angle as described above. The optical imaging module of the optical detection device 2 can receive the reflected light from the upper surface of the wafer 3 to generate wafer optical data 31. In other words, the optical imaging module of the optical detection device 2 can receive the reflected light generated after the mixed light illuminates the upper surface of the wafer 3, and generate wafer optical data 31 based on the reflected light. Wafer optical data 31 may include, for example, the surface image, reflective brightness distribution, grayscale distribution, and/or other optical characteristics of wafer 3. As shown in Figure 3E , wafer optical data 31 of wafer 3 may have a portion 311 that differs from wafer optical data 11 of wafer 1. It is worth noting that, as mentioned above, the portion 311 referred to here does not include the error range caused by slight angular errors caused by slightly rotating the wafer 3 on the carrier of the optical inspection device 2.

Referring again to Figures 1, 2E, and 3E, in step S07, wafer optical data 11 and wafer optical data 31 are compared. In step S08, a determination is made as to whether wafer optical data 11 and wafer optical data 31 are identical. Note that in this embodiment, wafer 1 is used as the reference wafer and wafer 3 as the test wafer. Therefore, using wafer optical data 11 of wafer 1 as the default data, the differences between wafer optical data 31 and wafer optical data 11 are compared to determine whether the two are identical. It is worth noting that in step S06, the different light source characteristics of optical inspection device 2 can also be used to create a significant contrast between the reflected or absorbed brightness of defects on the surface of wafer 3 and the brightness of the normal state.

Note that wafer 1 and wafer 3 can be loaded into optical inspection apparatus 2 simultaneously or separately. In other words, in some embodiments, two wafers 1 and 3 can be placed simultaneously onto two loading platforms within optical inspection apparatus 2. The wafer on one loading platform serves as a reference wafer (master wafer), which is pre-set as a normal wafer, while the wafer on the other loading platform serves as a test wafer. In other embodiments, using a single loading platform, wafers can be placed one at a time onto the loading platform within optical inspection apparatus 2, and the middle wafer in the cassette can be removed as a reference wafer (master wafer), which is pre-set as a normal wafer.

In some embodiments, since wafer 1 serves as a reference wafer, wafer optical data 11 can also be stored as reference data. That is, after alignment, optical inspection device 2 is used to inspect and record the optical data of a normal wafer (such as, but not limited to, wafer 1) under a light source as a reference standard. Subsequent inspections can then be compared with wafer optical data 11.

Figures 4A to 4D are schematic flow diagrams illustrating the wafer inspection method of the present invention. As shown in Figures 1, 3E, and 4A to 4E, in step S09, when it is determined that wafer optical data 31 is substantially different from wafer optical data 11, a minimum unit pattern 4 on wafer 3 is obtained. In certain embodiments, obtaining the minimum unit pattern 4 on wafer 3 includes: reading preset pattern data 5; obtaining a plurality of unit patterns 51 based on the preset pattern data 5; and obtaining the minimum unit pattern 4 based on the unit patterns 51.

On the other hand, if wafer optical data 31 is determined to be substantially identical to wafer optical data 11, it indicates that wafer 3 meets the specification requirements and the next wafer can be tested.

Referring again to FIG. 4A , to obtain the minimum unit pattern on the wafer, the preset pattern data 5 can be read first. The preset pattern data 5 may be, for example, partial pattern data of a mask used to form the pattern on the wafer 3 , such as pattern data of the edge of the mask, and is not intended to limit the present invention.

Referring to Figures 4B and 4C , a plurality of unit patterns 51 are obtained based on the default pattern data 5. As described above, after obtaining the default pattern data 5 (e.g., pattern data of the edge of a mask), lines can be drawn along the corners of the default pattern data 5 to form a plurality of vertical lines 52 and horizontal lines 53. These vertical lines 52 and horizontal lines 53 can form a plurality of unit patterns 51. It should be noted that the unit patterns 51 do not necessarily have to be identical in shape; however, they are all composed of minimal unit patterns.

Referring to FIG. 4D , after obtaining the unit graphics 51, rotation and translation are used to overlap certain corner points. Furthermore, by overlapping the unit graphics 51, the minimum unit graphics 4 constituting the unit graphics 51 can be obtained.

Figures 5A and 5B are schematic flow diagrams illustrating the wafer inspection method of the present invention. As shown in Figures 1, 5A, and 5B, in step S10, optical data of a chip unit (e.g., a first chip unit) 61 and optical data of a chip unit (e.g., a second chip unit) 62 are inspected based on the minimum unit pattern 4. In step S11, the optical data of chip unit 61 and the optical data of chip unit 62 are compared. In some embodiments, inspecting the optical data of chip unit 61 and the optical data of chip unit 62 includes: restoring the arrangement of the plurality of chip units 54 in the preset pattern data 5 based on the minimum unit pattern 4; selecting adjacent chip units 61 and chip units 62 from the chip units 54; and inspecting the optical data of chip unit 61 and the optical data of chip unit 62.

Specifically, the minimum unit pattern 4 represents the pattern of each chip unit 54 in the default pattern data 5. Therefore, after obtaining the minimum unit pattern 4, the arrangement of the plurality of chip units 54 in the default pattern data 5 can be restored. After restoring the arrangement of the chip units 54, adjacent chip units 61 and 62 within these chip units 54 can be selected for regions of the wafer optical data 31 that are substantially different from the wafer optical data 11 on the wafer 3 to detect the optical data of the chip units 61 and 62.

In certain embodiments, the wafer inspection method of the present invention further includes determining whether the optical data of wafer unit 61 and the optical data of wafer unit 62 are identical; and determining that wafer 3 is defective when the optical data of wafer unit 62 is determined to be substantially different from the optical data of wafer unit 61. Therefore, if the optical data of adjacent wafer units 61 and 62 are substantially different, it may indicate that wafer 3 has experienced significant variation during the manufacturing process, and that there are also significant differences between the plurality of wafer units 54 within the wafer unit. Therefore, wafer 3 can be determined to be defective. Of course, the requirements for determining a defective state can be set differently depending on the needs.

On the other hand, if the optical data between adjacent chip units 61 and 62 are substantially identical, it indicates that there is not much difference between the multiple chip units 54 on wafer 3. Therefore, wafer 3 may be in a normal state. Its wafer optical data differs from that of the reference wafer due to some reason (e.g., different positioning angles). Therefore, wafer 3 can be determined to be in a normal state.

It should be noted that the inspection of adjacent chip units 61 and 62 is not limited to local inspection. All chip units 54 of the entire wafer 3 can also be inspected as needed.

It is worth mentioning that the wafer inspection method of this embodiment can also perform an automatic part number creation process after the above-mentioned inspection. After the process is established, the fully automatic part number creation mode can be executed for the same process status, saving time in part number creation.

In summary, the wafer inspection method of the present invention loads two wafers (e.g., a first wafer and a second wafer) into an optical inspection device and generates wafer optical data for each wafer. By comparing the wafer optical data of the two wafers, it is possible to determine whether there is a difference between the two. If a difference is determined after inspection, the optical data of each chip on one of the wafers can be further compared. In other words, after comparing the wafer optical data of the first wafer (e.g., a reference wafer) and the second wafer (e.g., a test wafer), if a difference is found between the two, the wafer inspection method of the present invention can further inspect multiple chips on the test wafer to determine whether the test wafer is truly defective. Thus, the wafer inspection method of the present invention can first inspect the wafer condition over a large area, and then conduct inspection on the wafer's finer details. This can eliminate the effects of slight optical property non-uniformities caused by the manufacturing process, thereby improving wafer inspection accuracy.

The above overview of several embodiments is intended to help those skilled in the art better understand the concepts of the embodiments of the present invention. Those skilled in the art will appreciate that the embodiments of the present invention can be used as a basis for designing or modifying other processes and structures to achieve the same objectives and/or benefits as the embodiments described herein. Those skilled in the art will also appreciate that these equivalent structures do not depart from the spirit and scope of the present invention, and that various modifications, substitutions, and other options are possible without departing from the spirit and scope of the present invention. Therefore, the scope of protection of the present invention shall be determined by the appended patent application.

S01~S11: Steps

Claims (7)

A wafer inspection method includes: loading a first wafer into an optical inspection device; positioning the first wafer; inspecting the first wafer and generating first wafer optical data; loading a second wafer into the optical inspection device; positioning the second wafer; inspecting the second wafer and generating second wafer optical data; comparing the first wafer optical data with the second wafer optical data; determining whether the first wafer optical data and the second wafer optical data are identical; when it is determined that the second wafer optical data is substantially different from the first wafer optical data, obtaining a minimum unit pattern on the second wafer; inspecting optical data of a first wafer unit and optical data of a second wafer unit based on the minimum unit pattern; and comparing the optical data of the first wafer unit with the optical data of the second wafer unit. Determining whether the optical data of the first chip unit and the optical data of the second chip unit are the same; and when it is determined that the optical data of the second chip unit is substantially different from the optical data of the first chip unit, determining that the second wafer is in a defective state, wherein obtaining the minimum unit pattern on the second wafer includes: reading a preset pattern data, wherein the preset pattern data is data related to a mask used to form a pattern on the second wafer; obtaining a plurality of unit patterns based on the preset pattern data; and obtaining the minimum unit pattern based on the unit patterns; wherein detecting the optical data of the first chip unit and the optical data of the second chip unit includes: After determining that the second wafer optical data is substantially different from the first wafer optical data, an arrangement of the plurality of chip units of the preset pattern data is restored based on the minimum unit pattern; the first chip unit and the second chip unit that are adjacent to each other are selected from the chip units; and the optical data of the first chip unit and the optical data of the second chip unit are detected. A wafer inspection method as described in claim 1, wherein inspecting the first wafer and generating the first wafer optical data includes: irradiating an upper surface of the first wafer with a mixed light; receiving a reflected light from the upper surface of the first wafer; and generating the first wafer optical data based on the reflected light. The wafer inspection method as described in claim 2, wherein irradiating the upper surface of the first wafer with the mixed light comprises: irradiating the upper surface of the first wafer with the mixed light at a preset incident angle. A wafer inspection method as described in claim 2, wherein the mixed light includes at least two lights with different wavelengths. The wafer inspection method as described in claim 1, wherein inspecting the first wafer and generating the first wafer optical data includes: storing the first wafer optical data as reference data. The wafer inspection method as described in claim 1, wherein the first wafer and the second wafer are loaded into the optical inspection device at the same time. A wafer inspection method as described in claim 1, wherein inspecting the second wafer and generating optical data of the second wafer includes: rotating the second wafer by a preset angle; irradiating an upper surface of the second wafer with a mixed light; receiving a reflected light from the upper surface of the second wafer; and generating optical data of the second wafer based on the reflected light.