TWI524079B - Inspection method for contact by die to database - Google Patents

Description

Contact window detection method for wafer pair database

The present invention relates to a wafer inspection method, and more particularly to a contact detection method for a wafer to database (D2DB).

As the line width of the IC process continues to shrink, the control and monitoring of the critical dimension (CD) of the process is also more important. In view of nanometer semiconductor technology, it is even more difficult to accurately detect defects in the surface structure of the wafer.

Taking the detection of the contact window as an example, there are two common ways. One method of detection is to examine the contact window after lithography etching through a matrix of exposure energy and focal length (FEM) under different conditions to define a FEM window. Another method of detection is to use an E-beam inspection tool to detect the contact window.

However, since the FEM window does not particularly indicate the contact window that is too small, this is caused by the fact that the disconnection of the opening is too small to be detected, and the reliability of the component interconnection is affected. And because the contact window size of the entire wafer is different, it also increases The difficulty of detection.

As for the electron beam detection method, only the blind defect is marked, and it is affected by the underlying structure (such as a metal wire), and the result is wrongly judged. In addition, the E-Beam test requires that the entire wafer image be acquired before it can be inspected one by one, so the wafer inspection time is often as long as several months. Therefore, this type of detection is not immediate enough.

The invention provides a contact detection method for a wafer to database (D2DB), which can obtain accurate contact window detection results in real time and can obtain accurate contact window detection results when off-line. .

The method for detecting a contact window of a wafer pair database of the present invention comprises obtaining an actual image of a plurality of contact windows in a wafer, and decoding the position thereof to obtain a decoded graphic file. Then, the graphic file is aligned with the design database of the wafer, and the actual image is image-extracted to obtain the image contour of the contact window, and then the image contour and the design database of the contact window are measured ( The difference in the key dimensions of the corresponding contact window in design database).

In an embodiment of the invention, the contact window further comprises a via or a polysilicon contact plug in the wafer.

In an embodiment of the invention, the difference includes a difference in at least one of a radius, a size, and a circular area of the contact window.

In an embodiment of the invention, the method may further comprise determining the type of defect of the contact window according to the difference, such as the opening being too small, bridging or hiding. Blind defects.

In an embodiment of the present invention, the method may further select an inspection area where the contact window to be inspected in the wafer is located before acquiring the actual image, and then reset coordinates of the inspection area to make each area The overlap is minimized.

In an embodiment of the invention, the method of selecting the inspection region includes setting an area of a critical dimension (CD) in the design database below a predetermined value as an inspection region.

In an embodiment of the invention, the method of selecting the inspection region includes setting an area of the contact window that exceeds or falls below a predetermined value as an inspection area according to a design rule.

In an embodiment of the invention, the method of selecting the inspection region includes selecting an inspection region from a defect detection result based on a previously performed wafer.

In an embodiment of the invention, the method of obtaining the actual image includes using an EBI inspection or an e beam SEM review tool (EBR).

In various embodiments of the present invention, an apparatus for performing the above-described electron beam detection includes an E-beam inspection tool, a bright field inspection device with a light source having a wavelength of 150 nm to 800 nm, and a matching Ray A laser light source with dark field inspection device or a scanning electron microscope review tool.

In an embodiment of the invention, the method for obtaining the actual image may also The method further includes decoding a defined graphic metafile in the actual image and marking the die position of the wafer and the relative corner of the scan wafer, or linking with the image according to the KLA Klarf file. The way to transfer the actual image to the wafer database.

In an embodiment of the invention, the method of obtaining the actual image further includes decoding a file name of the actual image and indicating the position of the wafer and the position of the defect coordinate relative to the scan wafer origin to display the actual image. Transfer to the wafer database.

In an embodiment of the invention, the method for obtaining the actual image includes performing only a shooting action according to a known die position and a relative coordinate position of a scanning die origin, thereby The wafer position and relative image are transferred to the wafer database.

In an embodiment of the invention, the design database includes a GDSII file of the original design database, a post-OPC GDSII file of the simulated post-OPC, or a design converted by a simulated tool. database.

In an embodiment of the invention, the method for obtaining an actual image of the contact window includes obtaining an actual image or a partial wafer of a plurality of contact windows in the selection area of all the chips or chips in the entire wafer ( Die or chip) Acquires the actual image of multiple contact windows in the selection area.

In an embodiment of the invention, before the actual image of the contact window is obtained, in order to enable the detecting device to accurately align the wafer on each die, a die register may be performed first. Ie align with some position in each Die), that is, aligning the same position (such as the origin) on each wafer; and placing the easy to identify position or the virtual die corner on the different wafers at the desired position or The Klarf file for photo detection improves its alignment.

Based on the above, the present invention can accurately or accurately obtain contact window defect information, such as an opening, a bridge, or a concealment, by displaying an actual image of a contact window in the entire wafer on a design database. (blind) a defect. Moreover, the present invention compares the actual image with the design database by means of image extraction, and can obtain accurate results. In addition, the present invention can obtain defect information more quickly if the actual image and design database are directly compared based on the physical coordinates. The invention is based on the wafer-to-database method of the contact window to determine the optimal condition and range of the process of the yellow light exposure energy and the focal length matrix (FEM), but the method is not limited to the range of the process conditions of the contact window, the method It can be applied to the matrix optimum conditions and ranges of exposure energy and focal length in various line width or line distance yellow etching processes or Process window qualification (PWQ).

The above described features and advantages of the invention will be apparent from the following description.

100~140‧‧‧Steps

1 is a flow chart of contact window detection of a wafer-to-bank according to an embodiment of the invention.

Figure 2 is a schematic illustration of the resulting contact window in accordance with current KLA detection.

3 is a schematic illustration of the range of contact windows detected in accordance with an embodiment of the present invention.

1 is a flow chart of contact window detection of a wafer-to-bank according to an embodiment of the invention.

In FIG. 1, step 100 is first performed to obtain a raw image of a contact window in a wafer, such as by electron beam detection or photographing from a scanning electron microscope. In the present embodiment, although the "contact" is taken as an example, the present invention is not limited thereto; the method of the present invention can be applied to an interconnect portion to be fabricated in a semiconductor process, such as a wafer. The aperture or circular image detection such as Via or poly plug, or the matrix of exposure energy and focal length for various line width or line yellow etch processes Condition and Range (FEM) Wafer or Process Window Qualification (PWQ). In one embodiment, an apparatus for performing the above-described electron beam detection, such as an E-beam inspection tool, a bright field inspection device with a wavelength of 150 nm to 800 nm, and a laser source. A laser light source with dark field inspection device, or a scanning electron microscope review tool or the like. When the actual image obtained by the above method is output, the defined graphic metafile in the actual image can be decoded and the location of the wafer is marked. And scanning the defect coordinate position of the die corner to transfer the actual image into the wafer database. In addition, the method of obtaining the actual image may further decode the file name of the actual image, and indicate the position of the wafer and the position of the defect coordinate relative to the scanning die origin or according to the KLA Klarf file and image connection, so as to The actual image is transferred to the wafer database. In addition, the method of obtaining the actual image may also be based on the known die position and the relative coordinate position of the scanning wafer origin, such as the Klarf file, and the known wafer. The position and relative image are transferred to the wafer database.

In addition, prior to step 100, a plurality of inspection regions in the wafer where the contact window to be inspected is located may be selected (step 102). The step 102 of selecting the inspection area can greatly shorten the time of the entire inspection process. There are many ways to reduce the inspection area to be tested in this embodiment, for example, according to risk analysis, pattern density, design rule, minimum critical size, uniform pattern. The pattern uniformity, or the result of detection by KLA bright field or dark field optical instrument, is used to select the area where the following steps are to be performed. If desired, all of the contact windows of the entire wafer can still be selected to perform the following steps.

In detail, the method of selecting an inspection area in this embodiment has the following types. The first is to set the critical dimension (CD) in the design database below a predetermined value as the inspection area. The design database is, for example, a graphic data system (GDSII) file of the original design database, a post-OPC GDSII file of the simulated post-OPC, or converted by a simulated tool. Design database, etc. The so-called "GDSII" is the design database. One of the formats, whose file format is not limited to GDSII, can be any format that can be transferred out of the design file, such as Oasis or other database format. The second option is to set a region that exceeds a predetermined value or below a predetermined value as an inspection region according to a design rule, such as lithographic rule checking (LRC) and design rule checking. , DRC), risk area, etc. can be directly transferred as the basis for selecting the inspection area. A third method of selecting is to select an inspection area according to a previously performed wafer defect detection result, wherein the wafer defect detection is, for example, a result detected by a KLA instrument, and the file form is called KLARF (ie, KLA result file), and The KLARF output may come from a variety of different light sources and resolution scans, optical scans, or single scans of a single condition. The above various selection methods may be used alone or in combination of two or more. In addition, the method in this embodiment still includes obtaining an actual image of multiple contact windows in a selected area of all the chips in the entire wafer; or a Die or chip is obtained in the selection area. Actual image of multiple contact windows.

The selection of the above risk area, for example, by risk analysis input (such as LRC, DRC, etc.), selects the inspection area. Alternatively, the inspection area can be selected by pattern search or similarity of risk pattern specification. In addition, the inspection area can be selected by risk reduction or by KLA BF or DF.

Further, step 100 may be performed directly after step 102; or the coordinates of the above-described inspection area may be reset to minimize the overlap of the areas (step 104). For example, if step 102 is based on a previously performed wafer defect inspection When the measurement result (such as KLA detection) selects the inspection area, it is possible to obtain an area in which parts overlap each other. If the same part of the wafer is subjected to multiple electron beam irradiation detection, the line structure may be destroyed. Therefore, in order to avoid overlapping of the inspection areas, the inspection area that overlaps each other by operation optimization may be used according to the rule. The coordinates exclude overlapping parts, and the inspection area is reset to an inspection area that does not overlap.

In addition, before step 100 is performed, in order to make the detecting device accurately align each die of a wafer, step 106 may be performed: die register, ie align with some position in each Die), that is, aligning the same position (such as the origin) on each wafer; or proceeding to step 108: placing the same mark (such as easy to identify position) or wafer origin on different wafers (virtual die) Corner) On the Klarf file to be photographed or to be photographed to enhance its alignment.

After step 100, step 110 is performed to decode the position of the actual image to obtain a decoded graphics file. This step can be output from the instrument used to obtain the electron beam detection of the actual image as in the previous step 100. That is to say, the above decoding is performed after the LRC or Care area and the risk area are detected by the electron beam and the photographing is completed (step 100).

Next, proceeding to step 120, aligning the graphic file with the design database of the wafer; that is, converting the detection position relative to the detection machine to the graphic file of the design base GDS coordinate, corresponding to the design On the layout (scale is 1:1).

Then, proceed to step 130 to perform image extraction on the actual image (image) Extraction) to obtain the image outline of the contact window. The above image extraction extracts the contour of a two-dimensional (2D) image. As for image extraction methods such as Edge contour extraction, Self-Affine mapping system, Self-Affine snake model, Active contour model, Expectation-maximisation algorithm, principal component analysis, level sets algorithm or Monte Carlo techniques. Moreover, the above image extraction can be on-line extraction, which can achieve immediate processing by fast calculation and can mark coordinates. Moreover, this step is not only for a single actual image, but for all the captured actual images for image extraction.

Then, step 140 is performed to measure the difference between the image contour of the contact window and the corresponding contact window in the design database on the critical dimension (CD) to obtain the result of the contact window defect detection, wherein each of the selected regions may be The unit is measured once, and the unit can be measured once from 0.0001 μm to 0.5 μm. The above difference is, for example, a difference in at least one of a radius, a size, and a circular area of the contact window. Moreover, after the difference is output, the defect can be classified according to the degree of the difference by setting a threshold condition. If the difference value is much larger than the standard target, the bridge is easily formed, and if the difference value is larger than the standard The target is much smaller (if the opening is too small) to form an open. Finally, the classification severity and its final defect analysis result are output. These defects can be found in the corresponding position according to the wafer database coordinate system. Since the image outline can be displayed on the graphic of the design database, the difference between the image outline and the design database can be accurately and accurately compared, and the defect type of the contact window is directly determined and Classification of differences in size and severity. In addition, this embodiment can also obtain repeated systematic defects or hot spots by the detection results of different chips in the wafer.

Also note that the above steps should exclude the use of an algorithm that avoids errors caused by the actual image interface.

The results of the above examples are enumerated below to verify the effects of the above examples, but are not intended to limit the scope of the invention.

First, the contact window detection is performed on the entire wafer using the current KLA detection method, and the contact window obtained by the detection together with the developed DCD window is shown in FIG.

As can be seen from Fig. 2, most of the defects of the KLA detection result (such as the dot area or the oblique line area in Fig. 2) are outside the DCD window.

However, when the same wafer is subjected to contact window detection using the method of the present invention, all contact windows in each wafer in the wafer can be observed by the CDU Map; in other words, up to thousands of contact windows can be detected in a single wafer. . Figure 3 shows the DCD window and the contact window obtained in accordance with an embodiment of the present invention, the result of which appears that most of the area within the DCD window has openings that are too small (as in the dot area of Figure 3) or concealed (Figure The slash area in 3) is defective, and a bridge (such as the cross area in FIG. 3) can be found, so that the detection method according to the present invention can more accurately measure the contact window range as compared with FIG.

In summary, the present invention can directly or offline the E-beam image of the contact window by directly placing it on the design database and having coordinates for alignment. All contact windows in the film or even the entire wafer get accurate defect information and quickly compare it with the database.

Although the present invention has been disclosed in the above embodiments, it is not intended to limit the present invention, and any one of ordinary skill in the art can make some changes and refinements without departing from the spirit and scope of the present invention. The scope of the invention is defined by the scope of the appended claims.

100~140‧‧‧Steps

Claims (19)

A method for detecting a contact window of a wafer to a database, comprising: obtaining an actual image of a plurality of contact windows in a wafer; and connecting the KLA Klarf file and the image to transfer the actual image into the wafer database; Decoding the position of the actual image of the contact window to obtain a decoded graphic file; aligning the graphic file with a design database of the wafer; performing image extraction on the actual image And obtaining a plurality of image contours of the contact window; and measuring a difference in a critical dimension (CD) between the image contour of the contact window and a plurality of corresponding contact windows in the design database. The method of detecting a contact window of a wafer-to-bank according to claim 1, wherein the contact window further comprises a via or a polysilicon contact plug in the wafer. The method of detecting a contact window of a wafer-to-bank according to claim 1, wherein the difference comprises a difference in at least one of a radius, a size, and a circular area of the contact window. The method for detecting a contact window of a wafer pair database according to claim 1, further comprising determining a defect type of the contact window according to the difference. Contact window detection of the wafer-to-database as described in claim 4 The method wherein the defect type comprises an opening that is too small, a bridge, or a blind defect. The method for detecting a contact window of a wafer pair database according to claim 1, wherein before the obtaining the actual image, the method further comprises: selecting a plurality of inspection regions of the wafer in which the contact window to be inspected is located. And resetting the coordinates of the inspection area to minimize the overlap of the areas. The method for detecting a contact window of a wafer-to-bank according to claim 6, wherein the method of selecting the inspection region comprises setting a region of the design database that is less than a predetermined value to a predetermined value. The inspection area. The method for detecting a contact window of a wafer pair database according to claim 6, wherein the method of selecting the inspection region comprises selecting a size of the contact window to exceed a predetermined value according to a design rule. The area is set as the inspection area. The method for detecting a contact window of a wafer pair database according to claim 6, wherein the method of selecting the inspection region comprises selecting the inspection region according to a previously performed wafer defect detection result. The method for detecting a contact window of a wafer-to-bank according to claim 1, wherein the method of obtaining the actual image comprises using an electron beam detection or a scanning electron microscope. Contact window inspection of the wafer-to-database as described in claim 10 The measuring method, wherein the apparatus for performing the electron beam detection comprises an E-beam inspection tool, a bright field inspection device with a light source having a wavelength of 150 nm to 800 nm, or a dark field with a laser light source A laser light source with dark field inspection device or a scanning electron microscope review tool. The method for detecting a contact window of a wafer pair database according to claim 1, wherein the method for obtaining the actual image further comprises: decoding and marking a defined graphic metafile in the actual image. The wafer position and the defect coordinate position relative to the scan die corner are derived. The method for detecting a contact window of a wafer pair database according to claim 1, wherein the method for obtaining the actual image further comprises: decoding a file name of the actual image and marking the wafer position and relative Scan the defect coordinate position of the die corner. The method for detecting a contact window of a wafer pair database according to claim 1, wherein the method for obtaining the actual image comprises: a defect to a known wafer position and a relative scan wafer defect (die corner) The coordinate position is taken as a shooting action; and the known wafer position and relative image are transferred to the wafer database. The method for detecting a contact window of a wafer pair database according to claim 1, wherein the design database comprises a GDSII file of the original design database, and a post-OPC GDSII file of the simulated post optical effect correction (post-OPC). Or a design library converted from a simulated tool. The method for detecting a contact window of a wafer pair database according to claim 1, wherein the method for obtaining the actual image of the contact window comprises: obtaining a majority of all in-wafer selection regions in the entire wafer. The actual image of the contact window. The method for detecting a contact window of a wafer pair database according to claim 1, wherein the method for obtaining the actual image of the contact window comprises: obtaining a plurality of wafers in the entire wafer to obtain a plurality of selected areas in the selection area. The actual image of the contact window. The method for detecting a contact window of a wafer pair database according to claim 1, wherein before the actual image of the contact window is obtained, a die register is further included to enhance alignment thereof. effect. The method for detecting a contact window of a wafer pair database according to claim 1, wherein before the actual image of the contact window is obtained, the method further comprises: placing the same mark on different wafers. (identify position) to enhance the alignment effect on the coordinate file to be photographed or to be photographed; and to place a virtual die corner on the different wafers at the desired position or to take a photo test The coordinate file enhances its alignment.