KR100295057B1 - Apparatus and method for contact failure inspection in semiconductor devices - Google Patents

Abstract

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a contact failure inspection method of a semiconductor device for inspecting contact defects such as not-open of a contact hole through an electronic signal value detected using a scanning electron microscope, and an inspection apparatus thereof. A method for determining whether a contact is defective by comparing an electronic signal value detected from a unit area including at least one contact hole by scanning an electron beam by a microscope with an electronic signal value corresponding to a normal contact, and an inspection device that realizes the contact. .

Therefore, it is possible to accurately determine whether a contact is defective by a digitalized value without visual inspection or microscopic examination of the contact image, and it is possible to accurately determine whether the contact is defective even with a contact having a very large aspect ratio. Further, there is an effect that it can be determined in a short time whether the contact failure over the entire wafer surface can be applied to the mass production line.

Description

Contact defect inspection device and method of semiconductor device {APPARATUS AND METHOD FOR CONTACT FAILURE INSPECTION IN SEMICONDUCTOR DEVICES}

The present invention relates to the field of inspection of semiconductor devices. More specifically, the present invention relates to the detection of contact defects such as not-open contact holes using a scanning electron microscope (SEM).

Semiconductor integrated circuits are generally fabricated by first forming discrete semiconductor devices on the surface of a silicon wafer. A multi-layered metallization layer is then formed thereon in contact with the active elements of these discontinuous semiconductor devices and wired together to form the desired circuit. Such connection layers typically form an insulating material layer on the discontinuous semiconductor devices, and then perform a predetermined patterning and etching process to form contact holes in the insulating material layers, and to form a conductive material layer in these contact holes. It is formed by vapor deposition.

Subsequently, the conductive material layer deposited on the insulating material layer is etched in a predetermined pattern to construct a circuit of a first level, followed by deposition of the insulating material layer, formation of a contact hole or via hole, and a conductive material layer. The same process as before of forming and patterning is repeated to continuously configure a multilevel circuit.

Depending on the complexity of the overall integrated circuit, typically two or more metallization layers are needed for the internal wiring and the pads that connect the finished chip to the outside.

High-density integrated circuits designed in sub-micron dimensions require highly precise dimension control, especially 64M DRAM or 256M DRAM, which requires 0.25 to 0.30 µm of circuit line width, into semiconductor production systems. As the design rule of the memory device becomes more competitive, a highly sensitive inspection process for the formed pattern or contact hole is required.

In particular, as the design rule of the semiconductor device decreases, the aspect ratio (A / R) of the contact hole continues to increase, thereby increasing the need to inspect the inside of the contact, such as checking whether the contact is open. . In order to inspect the inside of the contact, the resolution required to inspect the inside of the contact is required. According to an optical method using a visible light band having a wavelength of 488 nm, the beam spot size is less than 1 μm. Due to the technical limitations that it can't be taken, it was not enough to inspect the inside of a contact below 200 nm.

A first object of the present invention is to provide a contact failure inspection method of a semiconductor device capable of accurately determining whether or not a contact is defective by a digitalized value without visual inspection or microscopic examination of a contact image, and an inspection apparatus therefor. .

A second object of the present invention is to provide a contact failure inspection method and a inspection system for a semiconductor device, which can accurately determine whether a defect is made even for a contact having a very large aspect ratio (that is, a ratio of the depth of a contact hole to its diameter). There is.

It is a third object of the present invention to provide a contact failure inspection method and a inspection system of a semiconductor device which can be applied to a mass production line by judging whether or not a contact failure over the entire wafer surface is in a short time.

A fourth object of the present invention is to provide a contact failure inspection method of such a semiconductor device and a manufacturing method of a semiconductor device to which the inspection system is applied.

A fifth object of the present invention is to provide a contact failure inspection method and a inspection system of a semiconductor device, which can improve the yield of a semiconductor device by tracking and improving a contact failure occurrence position in a short time.

A sixth object of the present invention is to provide an inspection method and an inspection system capable of determining whether a photoresist pattern is defective after a developing process in a pattern defect or a photolithography process over a contact defect of a semiconductor device.

1 is a schematic diagram illustrating the principle of a scanning electron microscope (SEM).

FIG. 2 is a schematic graph showing energy spectra of electrons emitted when secondary electrons and backscattered electrons are emitted when a sample is irradiated with an electron beam. FIG.

3 is a schematic block diagram showing the configuration of an in-line SEM.

4 is a schematic block diagram illustrating a contact failure inspection system of a semiconductor device according to an embodiment of the present invention.

5 is a schematic block diagram illustrating a contact failure inspection system of a semiconductor device in accordance with another embodiment of the present invention.

6 is a schematic block diagram illustrating a contact failure inspection system of a semiconductor device according to another embodiment of the present invention.

7 is a schematic block diagram illustrating a contact failure inspection system of a semiconductor device according to another embodiment of the present invention.

8 is a schematic and functional block diagram illustrating a contact failure inspection method and inspection system of a semiconductor device according to an embodiment of the present invention.

9 is a schematic and functional block diagram illustrating a contact failure inspection method and inspection system of a semiconductor device according to another embodiment of the present invention.

10 is a schematic and functional block diagram illustrating a contact failure inspection method and inspection system of a semiconductor device according to another embodiment of the present invention.

11 is a flowchart showing a logical flow of a method for inspecting a failure in contacting a semiconductor device according to one embodiment of the present invention.

12 is a flowchart showing a logical flow of a method for inspecting a failure in contacting a semiconductor device according to another embodiment of the present invention.

13 is a flowchart illustrating a logical flow of a method for inspecting a failure in contacting a semiconductor device according to another embodiment of the present invention.

14 is a flowchart showing a logical flow of a method for inspecting a failure in contacting a semiconductor device according to another embodiment of the present invention.

15 is a diagram illustrating a chip sampling position on a unit wafer to which a contact failure inspection process according to an embodiment of the present invention is applied.

FIG. 16 is a diagram illustrating a specific sampling area of the # 2 chip of FIG. 15.

17 is a cross-sectional view of a semiconductor device in which a specific contact hole is applied to which a contact failure inspection process according to an embodiment of the present invention is applied.

18 illustrates SEM image data of contact holes after the mesh is set by the contact position recognition method according to an embodiment of the present invention.

19 is a diagram illustrating a mesh set for performing a contact location recognizing method according to another embodiment of the present invention.

20 is a diagram illustrating a mesh set for performing a contact location recognizing method according to another embodiment of the present invention.

FIG. 21 is a diagram illustrating a relationship between a unit contact and vertical and horizontal pixel units according to an exemplary embodiment of the present invention.

22 illustrates an intensity profile of a unit contact before performing background removal according to an embodiment of the present invention.

FIG. 23 illustrates an intensity profile of a unit contact after performing background removal in the intensity profile of FIG. 22.

24 illustrates an intensity profile for SEM images of unit contacts after performing background removal according to an embodiment of the present invention.

FIG. 25 is a result chart showing whether or not a contact is defective for a unit SEM contact image performed according to an embodiment of the present invention. FIG.

Figure 26 is a diagram showing a portion of a contact failure test result performed according to one embodiment of the present invention.

27 is a flowchart showing the manufacturing process of the semiconductor device performed according to one embodiment of the present invention.

Figure 28 is a schematic flowchart illustrating the logical flow of one embodiment of a contact inspection method according to the present invention.

FIG. 29 is a schematic flowchart showing the logical flow of the SEM image data reading operation according to the method of FIG.

30A to 30D are schematic flowcharts showing the logical flow of a contact hole position recognition operation according to the method of FIG.

31A-31D are schematic flowcharts illustrating the logical flow of a contact hole profile calculation operation in accordance with the method of FIG.

32A-32B are schematic flowcharts showing the logical flow of a contact hole inspection operation in accordance with the method of FIG.

※ Explanation of symbols for main parts of drawing

10, 20, 30, 40,: main computer 11: vacuum forming unit

12: sample transfer unit 13: sample alignment unit

14 electron beam generator 15 electron beam deflection

16: signal detection unit 18: automatic focus control unit

19: main display unit 21: main control unit

22: main storage unit 70: contact CD measurement unit

60: contact failure inspection unit 60a: SEM signal reading module

60b: Graphic file transfer network module 60c: Graphic file → SEM signal conversion module

60d: contact position recognition module

60e: Contact Profile Calculation and Background Removal Module

60e (1): Contact Profile Calculation Module 60e (2): Background Removal Module

60f: contact failure inspection module 60g: result display module

80: subcomputer 82: sub-control unit

84: sub display unit 86: sub storage unit

100 scanning electron microscope (SEM) 102 electron gun

104: focusing lens 106: objective lens aperture

108: objective lens 110: a sample

112: signal detector 114: signal amplifier

116: first deflection coil 118: cathode ray tube (CRT)

120: scanning circuit 122: second deflection coil

124: shutter 130: semiconductor substrate

131: field oxide film 132: gate electrode

133 spacer 134 first insulating film

135: bit line 136: second insulating film

137: first contact hole 138: second contact hole

150: horizontal mesh line 152: vertical mesh line

153: contact hole

In order to achieve the above objects, the present invention is directed to a method and apparatus for inspecting at least one region of a semiconductor wafer. In the present invention, SEM image data for the region of the semiconductor wafer is read. Image data for any feature on the wafer is identified within the SEM image data. Parameters related to the shape are computed and compared with a range of allowable values for the parameters. The type is classified based on a comparison between the parameter and the range of allowable values for the parameter.

In one embodiment, the calculated parameter is the dimension or size of the shape. For example, when the shape is a contact hole in an integrated circuit, the parameter may be a diameter of a hole measured in the image data pixels. For example, a particular contact hole may be determined to be 20 pixels wide. In another embodiment, the parameter may be the average pixel intensity for pixels present in the shape. For example, when the shape is a contact hole, the parameter may be an average of pixel intensities for pixels associated with the contact hole. If the measured parameter is within the range of acceptable values for the parameter, the form may be classified as acceptable. If the parameter is outside the range of allowable values for the parameter, the shape may be classified as a failure. For example, if the shape is a contact hole, the hole may be concluded as defective because it is not opened, for example.

In one embodiment of the invention, two parameters are calculated for this form. The two parameters can be, for example, dimensions of a shape such as a contact hole, measured in pixels associated with the shape. The second parameter may be the average of pixel intensities for the pixels associated with the shape. Both parameters are compared with a set range of allowable values for the parameters. In one embodiment, the shape, for example a contact hole, is classified as passed if both parameters are simultaneously present within their respective tolerance values. For example, contact holes in this state may be classified as being open and of appropriate size and shape. The relationship between the parameters and the range of their respective allowable values can be used to classify the form as belonging to one of several types or categories. For example, each of the parameters may be used to classify the form based on whether the parameter is below, within, or above a range of its acceptable values.

In one embodiment, the SEM image data is obtained from both secondary electrons and high energy backscattered electrons in the SEM. The data values may be digitized and in the form of digitized gray scale pixel levels or color code values of the pixels.

In one embodiment of the invention, a grid or mesh structure is used for the characterization of the shapes to be inspected, such as determining the location and / or size of the shapes to be inspected. The grid or mesh structure typically includes a pair of mutually orthogonal axes superimposed over an image for the region on the wafer to be analyzed. Alternatively, the axis of the mesh may form other suitable geometric relationships such as triangles, trapezoids, and the like. As an embodiment, the positioning procedure by the mesh may be performed by analyzing the pixel values along a line parallel to one of the orthogonal axes that are continuously positioned at each pixel position along one orthogonal axis, Determine shape and / or periodic pattern. For example, the meshing approach involves placing vertical lines at multiple horizontal pixel positions and summing vertical pixel intensity values at each horizontal position. These summed intensities can be compared at each horizontal position to confirm the increase in intensity that can be used to indicate the presence of such a form of contact hole. This process is repeated for multiple pixel locations along a single dimension. The process is then repeated for the orthogonal dimensions so that all the patterns, shapes and sizes of all the shapes can be determined.

This approach can be used to determine the appropriate size of the subgrid or mesh unit containing the shapes to be analyzed. For example, the mesh procedure may be used to select an appropriate size of the mesh unit of a pixel including 100 contact holes to be analyzed at a time. This approach makes the process of the present invention more efficient for inspecting forms in that unnecessary processes can be omitted by optimizing the area of each region to be inspected.

In one embodiment, the SEM image pixel data is used to calculate an intensity profile for each shape, such as the contact hole being inspected. In one embodiment, the intensity profile is first generated by summing pixel intensity values for one shape along one orthogonal axis at a plurality of pixel positions disposed along a rectangular orthogonal coordinate axis. For example, the pixel intensity values in the vertical direction at each horizontal pixel position are summed, averaged, and the result is shown for the horizontal pixel position. Thus the pixel intensity profile can be used to classify the shape according to the invention.

In one embodiment, in order to normalize the intensity profile for all shapes, the background intensity value is subtracted from all intensity values in each mesh unit. This has the effect of lowering the background value of each intensity profile to zero. Next, a threshold is set in the normalized profile, and it is determined that it relates to the form in which pixel intensities above the threshold are checked. Next, the first and second parameters defined above can be calculated from the profile.

For example, the dimension of the shape can be obtained by calculating the number of pixel positions beyond the threshold along the first dimension where the intensity values are summed in the orthogonal dimension. Since the sum of pixel intensities exceeding the threshold can be assumed to be related to the shape, the number of pixel positions with the sum exceeding the threshold is measured for the dimension of the shape measured in the pixels. Provide a value. The second parameter is calculated by summing the average of the intensity values above the threshold. These two parameters may be compared with a setting range of their respective allowable values in order to classify a specific type as belonging to one of the classifications of the type of the type set in advance.

The inspection method and apparatus of the present invention provide numerous advantages over conventional approaches. For example, conventional approaches use optical methods such as optical microscopy or visual inspection to check for contact failure. However, these conventional systems cannot analyze small irregularities in shape that cause a bad circuit. Scanning electron microscopes used in conjunction with the present invention provide improved resolution so that even small irregularities can be detected. Thus, the present invention can be applied to realize a circuit form whose size is in the submicron range. In addition, the pixel data processing of the present invention can be made very effective due to the meshed approach of the present invention. Since the processing and defect checking can be performed very effectively and quickly, the inspection method and inspection apparatus of the present invention are very usefully applied to the mass production equipment of wafers and circuits.

In another aspect, the present invention provides a method for manufacturing a process cassette comprising: setting a process cassette on which wafers having a plurality of contact holes formed on a surface thereof are mounted; Selecting a particular wafer from the cassette and loading it onto a stage in a reference chamber of a scanning electron microscope; Aligning the loaded wafer for electron beam scanning; moving the wafer-mounted stage to a specific position relative to an incident direction of the electron beam of the SEM; Opening a shutter to scan an electron beam onto a particular location of the wafer; An automatic addressing step for detecting an inspection position by recognizing a pre-made reference image formed on the wafer; Scanning an electron beam of the SEM onto the inspection position; An automatic focusing step to secure a clearer image by repeating the electron beam scanning; Closing the shutter to separate the auto focused wafer from the electron beam; Investigating contact failure by comparing an electronic signal value detected from a unit surface including at least one contact hole after the electron beam scanning with an electronic signal value defining a normal contact; Further investigating and repeating contact failures at different locations on the wafer by moving the stage to another location; And repeatedly irradiating all the wafers in the cassette further by unloading the completed wafer and loading other wafers into the reference chamber.

According to another aspect of the invention, a method of manufacturing a semiconductor device of the present invention, forming a contact hole in a specific insulating material layer formed on a semiconductor substrate; Irradiating contacts of each contact hole by comparing an electronic signal value detected from a surface including at least one contact hole and an electronic signal value corresponding to a normal contact; And charging the conductive material layer in the contact holes after the irradiation and performing a subsequent process for manufacturing a semiconductor device.

The contact failure investigation step may be performed at a specific sampling position of the semiconductor substrate. For example, the contact failure investigation step may be applied to a mass production line. After performing the developing process for forming the photoresist pattern, the defect irradiation step may be further performed on the bottom of the photoresist pattern for forming the contact hole.

According to another aspect, the present invention provides a method of forming a photoresist contact hole pattern for forming a contact hole on an insulating material layer formed on a semiconductor substrate; And irradiating a contact of each contact hole by comparing an electronic signal value detected from a unit area including at least one contact hole pattern with an electronic signal value corresponding to a normal contact pattern.

Hereinafter, with reference to the accompanying drawings, a specific embodiment of the present invention will be described in detail.

1 is a schematic block diagram of a scanning electron microscope system 100 that may be used for contact hole irradiation in a semiconductor device in accordance with the present invention.

Referring to FIG. 1, the electron gun 102 projects an electron beam through the focusing lens 104. The beam passes through the deflection coil 122, the objective lens 108, and the aperture 106 of the shutter 124. The focused electron beam is projected and scanned on the sample surface 110, which can be the surface of the semiconductor wafer to be irradiated. Secondary electrons and backscattered electrons emitted from the sample are detected in the signal detector 112, which generates a signal indicative of the received electrons. This detected electronic signal is amplified by the signal amplifier 114. The amplified signal is scanned on the fluorescent surface inside the cathode ray tube 118 to form a visible image of the sample surface. The scan of the cathode ray tube 118 is controlled by a deflection coil 116 that correlates to the scan of the sample surface controlled by the deflection coil 122. In the scanning electron microscope, the scanning surface of the sample is divided into fine pixels, and the electronic signals detected in each pixel unit are transmitted in time series to form an SEM image. In order to realize this, the electronic signal passing through the signal amplifier 114 is transmitted to the scanning circuit 120 to control the deflection angle of the electron beam in the second deflection coil 122.

In addition, the amplified electronic signal data for each pixel may be transmitted to a processing unit 115 capable of performing various signal conditioning and processing functions. The processing unit 115 may convert an electronic signal for each pixel into a discrete gray scale value or color code value used to form an image. The gray scale value can be assumed to be one of 256 possible levels digitally coded by a binary value between 0 and 256. A memory device can be used to store the grayscale value for each pixel. In addition, a computer that is part of the processing unit may process a desired image value. In one form, the computer may be programmed to analyze the grayscale data to perform the contact inspection of the present invention described in detail below.

3 is a schematic block diagram showing the configuration of an in-line SEM system in which contact inspection can be performed inline. In conventional processes, SEM image data was analyzed off-line, ie, separated from the manufacturing process and collected. Since the inline approach of the present invention has very improved efficiency, the SEM image data can be collected and analyzed during the manufacturing process. Thus, additional inspection steps that have been used in conventional approaches can be omitted. The inline SEM system includes an electro-optical system, a sample section, an exhaust system and an electric system. The electron optical system includes an electron beam generator 14, an electron beam deflector 15, a signal detector 16, and the like. The sample unit includes a sample transfer unit 12 and a sample alignment unit 13 for transferring the sample from the cassette to the sample chamber together with the sample chamber, and the exhaust system includes a vacuum forming unit 11 for maintaining the vacuum in the sample chamber. The electric system includes a main controller 21 for controlling these electro-optical systems, a sample chamber, an exhaust system and other components, a memory or main storage 22 for storing signals detected from the signal detector 16, and detected electrons. And a main computer 10 having a main display portion 19 for displaying an image generated from a signal. Auto focusing unit 18 for performing auto focusing for a clear image may be included.

On the other hand, the scanning electron microscope detects secondary electrons (SE) emitted from the surface of the sample by the scanned primary electrons, and FIG. 2 shows the back of the sample when the primary electrons are irradiated onto the sample. It is a figure which shows the energy spectrum of the electron which emits or scatters.

As can be seen in Figure 2, the secondary electron has the largest number of emission electrons in the emission electron energy band of less than 50 eV, Backscattered Electron (BSE) occurs mainly in the energy band of thousands to tens of thousands of eV. Able to know. In general, in-line SEMs, which are widely used, mainly use secondary electrons generated in a low energy band of about 20 eV, so images at the surface or edge are clear, but have a very high aspect ratio. In the case of using the inspection of the contact, the secondary electrons generated inside the contact have a problem that the image of the contact is not clear because the secondary electrons generated through the contact hole are likely to disappear while reaching the signal detector. Since these forms were typically optically inspected by the naked eye, a clear image was essential for contact defect inspection.

4 to 7 are schematic block diagrams illustrating various embodiments of a contact failure inspection system of a semiconductor device according to the present invention.

The system of FIG. 4 is similar to the basic configuration of the inline scanning electron microscope as shown in FIG. 3, but has a feature in that the contact failure inspection module 60 is built in the main computer 20. That is, as described above, the basic configuration of the in-line SEM is basically composed of the electron beam generating unit 14, the electron beam deflecting unit 15, the signal detecting unit 16, and the like from the generation of the electron beam to the signal detection. Electro-optical systems. Signal detection preferably uses a detector capable of detecting both secondary electrons and backscattered electrons emitted after irradiation of an electron beam on a sample. The system also includes a sample chamber provided with a sample aligning unit 13 for rotating and tilting the stage on which the test sample wafer is placed on the X, Y, and Z axes, respectively. The vacuum forming unit 11 maintains the sample chamber at a desired vacuum. In addition, there is a sample transfer unit 12 for transferring a sample to the sample chamber, and the electric system is detected by the main control unit 21 and the signal detection unit 16 that control these electron optical system, the sample chamber, the vacuum forming unit 11 and the like. A main computer 20 including a main storage unit 22 for storing signals, a main display unit 19 for displaying the detected electronic signals as an image, and an autofocus controller for performing autofocusing for clear images ( 18) and the like. In addition, the present embodiment includes a contact failure inspection module 60 for inspecting whether each contact of the sample is defective by analyzing the information of the electronic signal transmitted and stored in the main computer 20 from the signal detection unit 16. do.

5 shows another embodiment of a contact failure inspection system for a semiconductor device according to the present invention. Referring to FIG. 5, the contact failure inspection module 60 and the contact CD measurement module 70 are included in the main computer 20, although they include a part of a component such as an inline scanning electron microscope as shown in FIG. The difference is that it is built. CD (Critical Dimension) is a specific type of dimension to be examined. For example, in the case of round holes, CD may be the diameter of the hole. In one embodiment, the contact CD measurement module 70 measures the contact diameter by comparing the reference value built into the computer with the contact image generated by the SEM.

6 is a block diagram illustrating a contact failure inline inspection system of a semiconductor device according to another embodiment of the present invention.

Referring to FIG. 6, the basic configuration of the inline scanning electron microscope as shown in FIG. 3 is partially the same, but the subcomputer 80 is interfaced with the main computer 10, and the contact failure inspection module 60 is provided. The feature is that it is built in the subcomputer 80. A general personal computer is used for the subcomputer 80, and a sub display unit 84 and a sub storage unit 86 are provided therein, and are stored in the main storage unit 22 of the main computer 10. It is configured to check whether the contact is defective by receiving the electronic signal of the contact.

7 is a block diagram illustrating a contact failure inspection system of a semiconductor device according to another embodiment of the present invention.

Referring to FIG. 7, a subcomputer 80, which is interfaced with the main computer 10, is provided, similar to the basic configuration of the inline scanning electron microscope as shown in FIG. It is built in the subcomputer 80, and at the same time has a feature that the contact CD measuring module 70 is built in the main computer 40.

8 to 10 are block diagrams illustrating various forms of a contact failure inspection module 60 for explaining a method and inspection apparatus for a contact failure inspection of a semiconductor device according to various embodiments of the present disclosure. Referring to Fig. 8, the contact failure inspection module 60 includes an SEM signal reading module 60a for receiving an SEM signal representing electrons received from a wafer while being irradiated by an electron beam. The contact position recognition module 60d analyzes the SEM signal to determine the position of the contact hole and / or another type to be inspected. The contact profile calculation module and the background value removal module 60e generate intensity profiles for the contact holes using the SEM signal data. The intensity profile is typically normalized by removing the data caused by the background intensity effect so that the shape of the intensity profile can be detected irrespective of the background value. The contact failure inspection module 60f analyzes the intensity profile of the contact hole in order to confirm the contact failure. As one example, as detailed below, the average intensity value for a contact is compared to a threshold (threshold) set to identify a failure. The result display module 60g can display the result of the failure analysis.

In another embodiment, the SEM signal reading module 60a reads information of a digitized electronic signal for a contact stored in a memory built in the main computer 20 or a main storage 22. )

In the in-line scanning electron microscope, the intensity of the electronic signal detected by scanning of the electron beam is digitized and stored at a gray scale or color code level. In one system, the grayscale value assigned to each pixel is one of 256 values ranging from '0' to '255'. The largest intensity is defined as '256' and the lowest intensity is defined as '0'. The digitized intensity values are color coded, ie grayscale, for each pixel. Contact images are obtained by reading the grayscale values for each pixel in time series and displaying them on a cathode ray tube, monitor, and / or printer. The grayscale may be converted to color for color display.

Referring to FIG. 9, the embodiment of the described contact failure inspection module is a modification to the embodiment of FIG. In FIG. 9, the contact profile calculation module 60e (1) and the background value removal module 60e (2) are separated modules as opposed to the combined contact profile calculation and background value removal module 60e shown in FIG. Is provided.

10 is a schematic and functional block diagram showing another embodiment of the contact failure inspection module 60 according to the present invention. Referring to FIG. 10, the contact failure inspection module 60 includes a graphic file transmission network module 60b, a graphic file → SEM signal conversion module 60c, a contact location recognition module 60d, a contact profile calculation and a background value removal. Module 60e, contact failure inspection module 60f, and result display module 60g.

As shown in FIG. 6, the graphic file transfer network module 60b shows a method of signal transmission between the main computer 10, 40 and the subcomputer 80. The main computer 10, 40 After converting the information of the digitized electronic signal for the contacts stored in the main storage unit 22 embedded in the graphic file into a graphic file, it is transmitted to the subcomputer 80 that is interfaced.

The graphic file to SEM signal conversion module 60c interprets the color code, ie, grayscale, of the graphic file transmitted to the subcomputer 80 and inversely converts it into a digitalized SEM signal. Meanwhile, the contact location recognition module 60d, the contact profile calculation and background value removal module 60e, the contact failure inspection module 60f, and the result display module 60g are the same as described with reference to FIGS. 8 and 9.

11 to 14 are flowcharts of various embodiments illustrating a process of in-line inspection of contact failure of a semiconductor device by a contact failure inspection system of a semiconductor device according to the present invention. Referring to FIG. 11, in FIG. 4, the contact failure inspection unit 60 uses a in-line scanning electron microscope (SEM) built in the main computer 40 to check a contact failure inspection method of a wafer in which a plurality of contact holes are arranged on a surface thereof. It is shown. First, a process performing cassette equipped with wafers having a plurality of contact holes arranged on a surface thereof is set to a predetermined position of an inline scanning electron microscope (S10). Subsequently, a specific wafer to be examined is removed from the cassette and loaded onto the stage in the sample chamber of the scanning electron microscope (S12). At this time, the flat zone of the wafer may be aligned. Next, the loaded wafer is aligned for electron beam scanning (S14), and the stage on which the wafer is mounted is moved to have a specific position with respect to the electron beam incident direction of the scanning electron microscope (S16).

Subsequently, the shutter positioned below the objective lens is opened (S18) so that the electron beam can be incident on a specific position on the wafer, and auto addressing is performed (S20). The auto-addressing recognizes a reference image pre-patterned at a specific position on which the inspection is to be performed, thereby recognizing a specific position on which the inspection is to be performed based on the reference image.

Subsequently, the electron beam of the scanning electron microscope is scanned to an inspection position (S22), and the electron beam scanning is repeatedly repeated by auto focusing by an autofocus controller to obtain a clear contact image (S24) and auto focusing. The shutter is closed to block the incident of the electron beam on the completed wafer (S26).

Subsequently, the profile of the electronic signal value detected by the electron beam scanning is analyzed according to the process of the present invention to perform the defect inspection of each contact (S28), and subsequently determine whether the contact inspection is performed on another position on the wafer. After moving the stage to another inspection position on the wafer (S30), the same steps are repeated to perform contact failure inspection on the entire inspection position of the wafer. Subsequently, after unloading the wafer in which the contact failure inspection is finished (S32), after determining whether a wafer to be inspected exists (S34), loading another wafer in the cassette into the sample chamber and repeatedly performing the same steps. Contact defect inspection is performed on all wafers in the cassette. Subsequently, when the inspection is completed for all wafers, the cassette is removed (S36) to end the process.

Referring to FIG. 12, in FIG. 5, a plurality of contact holes are formed on a surface by using an inline scanning electron microscope (SEM) built in the main computer 30 together with the contact failure inspection unit 60 and the contact CD measuring unit 70. A contact failure inline inspection method of an arrayed wafer is shown.

The defect inspection of the contact proceeds as shown in FIG. 11, and after closing the shutter (S26), unlike in FIG. 11, it is determined whether or not the contact failure inspection is performed (S27). CD measurement is performed (S29).

Referring to FIG. 13, in FIG. 6, a plurality of contacts are formed on the surface by using an inline scanning electron microscope (SEM) when the contact failure inspection unit 60 is not embedded in the main computer 10 but in the subcomputer 80. A contact failure inline inspection method of a wafer with holes arranged is shown. As shown in Fig. 13, after closing the shutter (S26), it is determined whether the SEM signal stored in the main storage of the main computer is transmitted to the subcomputer and whether or not contact inspection is performed at another position (S31). The subcomputer receives the signal to perform a contact failure test (S37).

Referring to FIG. 14, when the contact failure inspection unit 60 is not embedded in the main computer but is embedded in the subcomputer, the subcomputer and the main computer may exchange commands with each other. As shown in FIG. 11, after closing the shutter by the same process (S26), it is determined whether the SEM signal stored in the main storage of the main computer is transmitted to the subcomputer (S31-1), and then the contact of the subcomputer. The defect inspection is performed (S31-2), or it is determined whether the contact inspection of the other position (S31-3, S31-4).

15 shows the area numbers (# 2-# 37) of each inspection target in the wafer 110 to be subjected to the contact failure inspection of the present invention, and the portion marked 'AP' indicates an alignment point, and '# 1' 'Represents a chip at the prefocusing position. Several sampling positions can be defined within each area indicated by the numerals in FIG. For example, FIG. 16 shows an Upper Left (2, 1), Upper Right (2, 2), Lower Right (2, 2) chip with respect to the # 2 chip or region of FIG. 3) shows the sampling points of five points in the order of Lower Left (2,4), Center (C) (2,5). Of course, the sampling position or the number of sampling in each sampled unit chip can be variously selected. In the present embodiment, as shown in FIG. 15, 175 points of 5 points were sampled for each of 35 chips or regions, and different contact images were obtained. In case of using an 12.5 k magnification inline scanning electron microscope, 98 contacts may be included in 480 x 480 pixels. Thus, all 17,150 contacts were examined for each of the 35 chips or regions at five point sampling positions.

Fig. 17 is a schematic cross sectional view of a semiconductor device in which contact holes are to be inspected according to the present invention, showing a step of forming a buried contact of 64M DRAM. In other words, the field oxide film 131 is formed to define the active region of the semiconductor substrate 130. The gate electrode 132 is formed to be surrounded by the spacer 133 on the active region, and the first insulating film is formed of a high temperature oxide film on the entire surface of the semiconductor substrate 130. After the 134 is formed, the first contact hole 137 is formed as a direct contact for the bit line 135. After the bit line 135 is formed, a second insulating layer 136 of BPSG (Borophosphosilicate glass) is formed on the entire surface, and a second contact hole 138 for the word line is formed.

As an example of the inspection of the present invention, the inspection was performed for the buried contact (B.C) for word line formation in the manufacturing process of 64M DRAM. However, the present invention is not limited to this, but may be made even after the direct contact 137 shown in FIG. 17 or the developing process of the photoresist pattern for forming these contacts.

In the contact failure inspection method of the present invention, first, an appropriate image size for each position to be inspected is selected based on a dimension of a form to be inspected such as a diameter of a round contact hole. In one embodiment, a typical SEM image includes 480 X 480 pixels. This image can be taken from the numbered angular positions of FIG. The size of the contact hole and the distance between the contact holes determines the appropriate image size for each individual contact. 18 shows an example of a contact image of an inline SEM at 12.5 K magnification with respect to one sampling position of a semiconductor device. It is composed of 480 x 480 pixels, and the number of contacts represented in the image is 98, i.e., 14 in the horizontal direction and 7 in the vertical direction.

The appropriate resolution is determined based on the contact hole to be inspected, ie the size of the shape and the distance between the contact holes. For example, in one system each pixel is capable of obtaining a resolution of nearly 12 nm in the SEM. It is now known that contact holes have a diameter of 200 nm. The number of pixels covering one shape is selected so that irregularities of the shape can be detected in the image. For example, if the area to be inspected has 100 contact holes in one grid at regular intervals, in order to cover all the contact holes including the spaces between the contact holes, each corresponds to one contact hole. A set of 100 sub-grids with 48 x 48 pixels can be used. A rectangular grid or mesh consisting of vertical and horizontal lines can be superimposed over a 480 x 480 pixel array forming 100 48 x 48 pixel sub-grids used to inspect each contact hole.

In accordance with the present invention, it has been determined that a grid of 48 x 48 pixels is sufficient to analyze the irregularities in the contact holes to be inspected. The dimension of the contact hole is compared with the amount of space in each sub-grid to determine if the number of pixels covering the contact hole itself is sufficient to analyze the contact hole. The resolution is determined by dividing the threshold dimension, that is, the diameter of the hole, by the number of pixels covering the contact hole. The resolution is compared with a threshold such as 12 nm / pixel source threshold to determine whether the resolution is appropriate.

After the resolution of the pixel is determined, the mesh structure can be used to locate the contact holes and determine their dimensions. In one embodiment horizontal and vertical lines in the mesh or grid structure may be used to locate the contact holes.

Referring to FIG. 18 showing the process of the contact position recognition module 60d, the pitch of the horizontal and vertical axes may be positioned in each mesh after the mesh or grid is positioned over the contact images arranged in a matrix. It is adjusted within a certain irradiation range. In this case, the pitches may be controlled by increasing or decreasing the number of pixels forming the contact image. The irradiation range of the mesh line is preferably set to include an area where contact holes of the same pattern are repeated.

Referring to Fig. 18, in the contact position recognition process using the mesh irradiation, each unit mesh or sub-grid is composed of at least 32 pixels horizontally and at least 62 pixels vertically, and the irradiation range is at least 32 pixels horizontally and vertical axis. Is determined by moving the virtual horizontal mesh line 150 and the virtual vertical mesh line 152 within a range including at least 62 pixels, so that each contact is not disturbed by the mesh lines in the contact image. The position having the lowest digitalized electronic signal value is detected.

In one embodiment, the mesh irradiation is performed by placing either a vertical line or a horizontal line in the first position. Intensities along the line add up to determine the overall intensity for the line. The line is then moved to the next position. For example, the vertical line moves along the horizontal axis to the next position and the intensity values are summed again along the vertical line. The total intensity value at each position is compared with a preset threshold and the sum before it. If we assume that the holes have an intensity greater than the background value, the increase in intensity may indicate that the hole has reached the edge. In other embodiments, the holes may have an intensity less than the background value. The process can continue through the entire grid structure to specify and / or define the location, size and shape of each contact hole. After all the sums have been calculated in one direction, the process is repeated for other dimensions to fully characterize the size, shape and location of the holes. This information may be used during the procedure for various purposes. By knowing the position and shape of the contact holes, unnecessary processes for pixels not related to the holes are omitted. In addition, if a defect is defined during subsequent processing, the exact location of the defective contact hole is immediately determined.

After performing contact position recognition, the origin of the first unit mesh is, for example, pixel number XO = 13 on the horizontal axis and pixel number YO = 23 on the vertical axis. Unit meshes having the same size are subject to comparison, which is why the contact location recognition should be performed as above.

The unit mesh may be set in various ways. As shown in FIG. 19, the contact hole 153 is located in one unit mesh while crossing one unit mesh between two unit meshes, or as shown in FIG. 20. As described above, at least two contact holes 153 may be located in one unit mesh. Furthermore, the position recognition by the mesh method as described above may be applied to patterns of various shapes as long as the image pattern is repeated in each unit mesh as well as the circular contact image as described above.

18 is a SEM image of a contact unit (480 X 480 pixels) for a mesh set for performing a contact position recognition process according to the present invention. As described above, the unit mesh of this test is set to 32 X 62 pixels, and the pixel numbers of the origin XO and YO are (13, 23). The unit mesh setting is determined while moving the horizontal mesh line 150 and the vertical mesh line 152 within the irradiation range defined by each mesh line described above, and the irradiation range corresponds to each pitch of the unit mesh. About 60 pixels and about 30 pixels. In another embodiment, each mesh line may be used to determine the lowest intensity value corresponding to each mesh line in order to determine a hole position.

19 and 20 are diagrams illustrating another type of mesh setting relationship as described above, and FIG. 21 is a diagram illustrating unit contacts in pixel units for explaining the contact profile calculation module as described above. The first intensity profile in the unit mesh before performing the background removal module is shown, and FIG. 23 illustrates the intensity profile of the unit contact for explaining a method of setting the boundary of the normal contact after performing the background removal module.

In this test, the threshold electronic signal value is set to '5', and the number of threshold pixels corresponds to '20' in FIG. 23. The contact holes to be examined span 20 to 40 pixels along the vertical axis.

FIG. 24 illustrates the intensity profile of the unit SEM contact image of FIG. 18 after performing the background removal module in this test, and FIG. 25 shows the contact defect coded for the unit SEM contact image of FIG. 18 in this test. The result plot. It can be seen that the portion indicated by a circle in Fig. 24 is in good agreement with the position (code 4) indicated by a bad code in Fig. 25.

FIG. 26 is a table showing some results of a contact failure inline test performed for each sampling position shown in FIG. 15 in this test, wherein the total contact corresponding to the criteria for classifying a contact according to the present invention for each sampling position of each chip; FIG. The number is displayed. That is, the number according to the classification of the contact holes at each position is recorded for each 5 points in each chip or test area. For example, at position (1,3), there are 87 contact holes classified as D, 3 contact holes classified as E, 5 contact holes classified as G, and H shaped. There are three classified contact holes. In this test, as described above, all 175 points were sampled by 5 points for each of 35 inspection areas for the entire front surface of one wafer, and different contact images were obtained. 17 contacts were examined, all 17,150 contacts were examined. In one embodiment, such a test could be performed in less than an hour by reducing the processing time according to the present invention, indicating that it can be applied in-line sufficiently in production lines.

On the other hand, the contact profile calculation module 60e (1) generates a first intensity profile of the detected electronic signal value for each unit mesh of the specified mesh, and the background value removal module 60e (2). )) Creates a second intensity profile by removing a background value in each unit mesh from the first intensity profile.

Referring to FIG. 8, the contact profile calculation module 60e (1) and the background value removal module 60e (2) are replaced with a single module, the contact profile calculation and background value removal module 60e. This method will be used.

The first intensity profile and the second intensity profile are both calculated by digitalized electronic signal values corresponding to each pixel included in each unit mesh of the mesh. On the other hand, since each unit mesh includes both the electronic signal value at the contact and the electronic signal value generated at the outside of the contact, the electronic signal value at the outside of the contact is calculated in order to calculate the accurate electronic signal value only inside the contact within each unit mesh. In other words, by removing the background values collectively, a normalized second intensity profile is obtained. This is also known as removing the discolor effect.

In one embodiment of the present invention, the contact profile calculation and the background value removal are performed by the module 60e according to Equation 1 below.

Calculation 1

X: Sum of electronic signal values above a certain threshold in unit mesh (unit: level)

B: Sum of electronic signal values below a certain threshold in unit mesh (unit: level)

Bc: Number of electronic signals below a certain threshold in electronic signal values in unit mesh

Xc: number of electronic signals above a certain threshold in electronic signal values in unit mesh

Y: Electronic signal value whose background value is compensated in unit mesh

In Formula 1, the specific threshold may be set to '100', for example, to remove the background value and to measure the accuracy, but is not limited thereto.

The 'Y' value, which is the result of Equation 1, is the sum of the compensated electronic signal values in each unit mesh. As one embodiment, the upper limit and the lower limit for the Y value in the formula 1 are set. If the Y value calculated for a particular contact is less than or equal to the lower limit, the contact is determined to be bad. As an example, it may be pointed out that the above set lower limit becomes less than an open contact hole failure.

Equation 1 is typically used for the inspection of contact holes having irregular shapes. For example, Formula 1 can be used to inspect the photoresist layer used to form the contact holes prior to the formation of the holes.

In another embodiment, contact profile calculation and background removal are performed according to the following equations (2) to (4).

Calculation 2

Calculation 3

Calculation 4

n: horizontal axis number

k: pixel number in the vertical axis direction

P _nk : Digitized signal value for the pixel at horizontal position n and vertical position k

N: Mesh number to be analyzed

h _i ^N : Initial pixel number of horizontal axis in unit mesh

h _f ^N : Last pixel number of horizontal axis in unit mesh

The meanings of Formulas 2, 3, and 4 will be described with reference to FIGS. 21 and 22. FIG. FIG. 21 is a view showing pixel units within a unit mesh for a contact used to calculate a contact intensity profile according to an embodiment of the present invention, and FIG. 22 is calculated before removing a background value for the contact image of FIG. A first intensity profile in the unit mesh is shown schematically.

In one embodiment, the intensity profile is obtained by summing the intensity values in the orthogonal direction at each position while moving to discontinuous positions along one of the axes, and plotting the sum of the intensity of the pixels versus the pixel number along the pixel axis. . For example, the profile of Fig. 22 is obtained by summing pixel intensities in the horizontal direction while moving through pixel positions along the vertical axis. In the profile of Figure 22, the results indicate the presence of contact holes in the particular unit mesh.

An intensity profile with a peak near the center is shown. The contact hole extends from about 16 pixel positions to 44 pixel positions, thus occupying about 28 pixels in the vertical direction. The profile includes a drop in intensity at the peak of the peak in the center of the hole, indicating a drop in intensity detected at the bottom of the hole. The shape of this intensity profile represents a normal contact hole.

In Formula 3, (P _k ^N ) 'represents an average electronic signal value for each pixel in the vertical pixel number k. This is the sum (level) of the digitized electronic signal values corresponding to each pixel in the vertical pixel number k line (K = 20 in Fig. 21), that is, the height of the curve in Fig. 22, h _f ^N − h _i ^N. It is obtained by dividing by the number of horizontal axis pixels at a given vertical axis position k. Figure 22 shows the profile of the result obtained from equation (3). In addition, P _m ^N represents a minimum value of (P _k ^N ) ', that is, a background value or a reference value. Therefore, P _k ^N represents the average electronic signal value per pixel from which the background value is removed.

FIG. 23 is a diagram illustrating a second intensity profile from which a background value is removed according to Formula 2, and FIG. 24 is a diagram illustrating a second intensity profile normalized for each contact with respect to the contact image of FIG. 18.

In one embodiment, the contact failure inspection process of the present invention further analyzes Equations 2 to 4 to classify the contacts according to whether the contact holes are defective, and if so, what type of failure. The second intensity profile of each contact hole (Figure 24) is analyzed to define and classify the defects.

In one embodiment, as shown in Fig. 23, a threshold, for example '5', is applied to the second intensity profile (average electronic signal value per pixel after removing the threshold). The critical dimension CD ^N representing the threshold pixel number of the contact is defined as the length (or width) of the peak of the profile. As shown in Fig. 23, the threshold dimension CD ^N for a contact at a threshold set to 5 is CD ^N = 40-20 = 20 pixels. For example, the critical dimension CD ^N , which may be the diameter of the contact hole, may be calculated from Equation 5 below.

Calculation 5

v _i ^N : Initial pixel number of vertical axis in unit mesh

v _f ^N : Last pixel number of vertical axis in unit mesh

P _K ^N = (P _K ^N ) '-P _m ^N ,

W _K ^N indicates whether the pixel intensity exceeds the threshold, in particular

If P _K ^N ≥ threshold, W _K ^N is 1, P _K ^N <threshold and W _K ^N is 0.

Next, the average pixel intensity BSE ^N is calculated for the pixels above the threshold value according to Equation 6 below.

Calculation 6

Equations 5 and 6 show an inspection method that is selective from that in Equation 1 above. The average pixel intensity BSE ^N mentioned in Equation 6 corresponds to the Y value calculated in Equation 1 above. In addition, the CD ^N value in Equations 5 and 6 replaces the X _C value in Equation 1.

After the threshold pixel number CD ^N and the average pixel intensity value BSE ^N are calculated for the contacts to be examined, they can be used to classify the conditions of the contacts. In one embodiment, an upper limit value NOC2 and a lower limit value NOC1 may be set for the pixel number CD ^N. These limits can be used to define the range of acceptable pixels for normal contacts. A limit on the average pixel intensity BSE ^N may also be set. The upper limit value NOT2 and the lower limit value NOT1 may be used to define a range of acceptable average pixel values for the normal contact.

The values CD ^N and BSE ^N for each contact to be examined are compared with their respective range for classifying the contact. In one embodiment, each contact is classified as one of nine possible forms depending on the comparison of the values CD ^N and BSE ^N for their respective ranges. An example of the nine possible conditions and their corresponding classification forms and code numbers is shown in Table 1.

Contact taxonomy Classification (BSE ^N ) ≤ (NOT1) (NOT1) ≤ (BSE ^N ) ≤ (NOT2) (BSE ^N ) ≥ (NOT2) (CD ^N ) ≤ (NOC1) A type (code 1) B type (cord 2) C type (code 3) (NOC1) ≤ (CD ^N ) ≤ (NOC2) D type (cord 4) E type (code 5) F type (cord 6) (CD ^N ) ≥ (NOC2) G type (code 7) H type (code 8) Type I (code 9)

The three vertical rows of Table 1 define three conditions of contact hole depth. They are arranged in order of decreasing depth. That is, the first vertical row defines three conditions of A type, D type and G type which are relatively deep contact holes. The second longitudinal row includes three conditions of type B, E and H which are normal contact depths. The third vertical row defines three conditions, type C, type F and type I, which are insufficient contact depths. The form of such contact holes typically defines partially open contact holes or non-uniform contact holes. The rows in Table 1 are arranged in increasing order of the contact hole diameters. The first row, including the contact hole shapes of type A, type B and type C, has an insufficiently small diameter. The second row, including the D, E and F shapes, defines the contact holes having normal diameters. The third row, including G, H and I, defines contact holes with excessively large diameters.

As shown in Table 1, both CD ^N and BSE ^N are classified as normal contacts, which are within the range of normal contacts. It can be used to indicate branch shape or degree.

Next, the result display module 60g displays the normal contact or the poor contact result of each contact hole classified by the contact failure inspection module 60f. The display method of these results can be expressed by numerical coding for each contact position.

FIG. 25 is a table showing an example of pixel position and classification for the contact holes in FIG. Whether or not each contact is normal or bad is represented by numerical coding for each contact position corresponding to the second intensity profile.

In Fig. 25, code '5' represents a normal contact as type E, code '4' represents a bad contact as type D, and as an example, type D represents a better open contact. In Fig. 25, X represents the first horizontal axis pixel number for each unit mesh, and Y represents the first vertical axis pixel number for each unit mesh, respectively. Fig. 26 is a table showing inspection results of the present invention for five positions in each of seven regions on a semiconductor wafer. The table shows the number of contacts corresponding to each classification type within each location.

The CD ^N and BSE ^N values may be used to classify contacts in other ways. That is, the classification type to which a particular contact corresponds may characterize a particular type of contact failure. For example, if the BSE ^N for a contact is less than or equal to the minimum value NOT1, it typically represents a more open contact hole and will be classified as one of type A, type D and type G. If BSE ^N is greater than or equal to the maximum value NOT2, the contact hole may be considered open but still not suitable for some reason. For example, such a hole may have an irregular shape, such as when it is widened or narrowed toward the bottom of the hole. In this case, the contact holes will be classified as one of type C, type F and type I.

Similarly, if CD ^N is less than or equal to the minimum value NOC1, the displayed defect may be a hole that is too narrow or has a slightly irregular shape such as an ellipse. If CD ^N is greater than the maximum value NOC2, irregularly shaped holes are indicated.

27 is a process diagram showing the logic flow for the process of manufacturing the semiconductor device performed in accordance with one embodiment of the present invention. First, a photoresist is applied on a specific insulating structure such as a nitride film or an oxide film to form a contact hole at a specific step in the manufacturing process of a semiconductor device, and then a photolithography process is performed to form a photoresist pattern corresponding to a target contact hole. (S40). At this time, the photoresist pattern is performed by an exposure and development process.

Subsequently, a predetermined contact hole is formed by etching the insulating structure formed under the photoresist pattern as an etching mask (S42). Subsequently, after cleaning the inside of the contact hole, the wafers are transferred to an inline scanning electron microscope according to the present invention, and the defect of the contact hole according to the present invention is performed as described above (S44). Subsequently, a conductive material is filled in the contact hole to proceed a subsequent process for manufacturing a semiconductor device (S46).

Figure 28 is a schematic flowchart showing the logic flow of one embodiment of a contact inspection method of the present invention. In step 500 the parameters used by the process are read. In one embodiment, the parameters used by the process are as follows.

N: Pixel number in Y axis direction of SEM image

M: Pixel number in the X-axis direction of the SEM image

VP (Vertical Pitch): Y-axis contact pitch in the Y-axis direction of the mesh

HP (Horizontal Pitch): X-axis contact pitch along X-axis direction of mesh

MX: X-axis mesh irradiation pixel range

MY: Y-axis mesh irradiation pixel range

bse: reference threshold of the contact characteristic profile in unit mesh

NO1: Lower limit of normal contact characteristic profile intensity

NO2: Upper limit of normal contact characteristic profile intensity

CD1: Lower limit of normal contact characteristic profile pixel count

CD2: Upper limit of normal contact characteristic profile pixel count

XN: Total number of scanned SEM images calculated in chip or shut units in one wafer

YN: total number of scanned SEM images on one chip or shot

X: Sequence of SEM images inspected by chip or shut in one wafer

Y: Sequence of SEM images examined on one chip or shut

cdata [j] [i]: SEM image signal value per unit pixel

Next, in step 502, the X-axis value is initialized to zero, and in step 504, the Y-axis value is initialized to zero. The inspection system continues along the Y axis by the inner loop formed by steps 506 to 520 until the maximum Y value is reached. The X axis value is then incremented and the inner loop is repeated for all of the Y axes again. Finally, the outer loop terminates when the last X and Y values are reached. The SEM image data in the inner loop of FIG. 28 is read in (X, Y) and cdata [j] [i] in step 506, which is detailed in FIG. The mesh approach detailed herein uses a rectangular mesh structure with orthogonal X and Y axes. In addition to the rectangular mesh structure, other shapes of mesh may be used. For example, a triangle or trapezoidal mesh can be used. The mesh structure is selected such that a pattern of any periodically repeated contact can be detected.

Next, at step 508 of Figure 28, the contact hole location is determined. Step 508 is detailed in Figures 30A-30D. The contact hole location includes the selection of the shape and pattern of the mesh to be used to inspect the contact holes. The process described above in Figs. 30A to 30D sums the intensity values of all the pixels in the orthogonal second dimension (vertical) while moving pixel by pixel along the selected first dimension (horizontal). If a sharp deviation (jump) of intensity is detected, the edge of the contact hole is defined. The process continues until a sharp drop in intensity is detected which defines the opposite edge of the contact hole. This approach is used until all the holes have been positioned. It can be seen that the absolute value of the intensity difference is used in step 550 of FIGS. 30A-30D. This is because this is the difference in intensity or the magnitude of the contrast, which is important for defining the contact location. This approach is different from the conventional practice of defining holes as high or low intensity.

In step 514 of Figure 28, the contact hole profile is calculated. This process is shown in detail in the flowcharts of Figures 31A-31D. The profile is calculated by analyzing each contact hole identified in accordance with the process described above with respect to FIGS. 30A-30D. One profile is calculated for each hole. In one embodiment, the profile is obtained by summing the intensity values at each position in one dimension, along another orthogonal dimension. The intensity value at each location is averaged and plotted to obtain the profile. It can be seen that general variables F and F2 are used in the flowcharts of Figs. 31A to 31D. These variables may be compatible with the variables BSE ^N and CD ^N defined in Equations 5 and 6, respectively, according to a preferred embodiment of the present invention.

In step 516 of Figure 28, the contact holes are examined in accordance with the present invention. This process is shown in detail in Figures 32A-32B. As mentioned above, the values determined according to FIGS. 31A-31D are analyzed to classify each hole according to one of the nine contact types. As described above, the variables F and F2 may be compatible with the variables BSE ^N and CD ^N in FIGS. 32A to 32B.

Referring to Fig. 28, the Y axis value is incremented at step 518, and it is determined at step 520 whether the maximum Y axis value has been reached. If not, the flow returns to the top of the inner loop. If so, the X axis value is incremented at step 522 and the flow returns to the top of the outer loop at step 504 where the Y value has been initialized via block 524. If the outer loop terminates, the results of the inspection process are displayed in step 526.

As described above, FIG. 29 is a schematic flowchart showing details of the SEM image data reading step 506 shown in FIG. In step 528, the exponent j is initialized to zero, and the exponent i is initialized to zero in step 530. The cdata [j] [i] is read in step 532 and the index i is incremented in step 534. In step 536 it is determined whether the index i has reached its maximum value M. If not, the flow returns to step 532 where the data is read back. If so, the index j is incremented at step 538, and it is determined at step 540 whether the index j has reached the maximum value N. If so, the process terminates, otherwise flow returns to step 530 where the exponent i is initialized back to zero and the process repeats.

In one embodiment, the contact failure inspection according to the present invention may be performed after cleaning the inside of the contact hole after the contact hole is formed (After Cleaning Inspection; ACI), the process of forming a photoresist pattern for forming the contact hole In the case of performing the development process in the lower insulating structure is exposed, the above-described failure inspection according to the present invention can be applied (After Development Inspection; ADI).

As described above, although the contact hole to which the present invention is applied is not specified, the present invention may be applied to the via holes of all the steps for connecting the contact layers and the conductive layers in direct contact with the semiconductor substrate. In addition, it can be widely useful for inspecting whether a pattern is defective after completing a developing process during a photo process for forming a contact hole.

In addition, the present invention may be widely applied to detecting and inspecting images of various patterns repeatedly formed at regular intervals in addition to circular contact holes.

According to the present invention, it is possible to accurately determine the presence of contact defects by counting numerical values without visual inspection or microscopic examination of contact images. In addition, even a contact having a very large aspect ratio could be accurately judged whether or not the defect was present. Furthermore, by inspecting the contact defects over the entire wafer surface in a short time, it is possible to apply them to the mass production line with high efficiency and productivity with the inspection result of such contact defects.

In the above, the present invention has been described in detail with reference to the above detailed description and accompanying drawings, but it should not be construed as limiting the scope of the present invention, but variously defined within the technical scope of the present invention. Modifications and variations are apparent to those skilled in the art, and such variations and modifications are within the scope of the appended claims.

Claims (60)

A method of inspecting at least one region of a semiconductor wafer, Reading Scanning Electron Microscope (SEM) image data for the region of the semiconductor wafer; Identifying image data for a feature on the semiconductor wafer in the data for the region of the semiconductor wafer; Computing a first parameter associated with the shape from the image data for the shape; Comparing the first parameter with a range of tolerances for the first parameter; And Classifying the form according to a comparison with a range of tolerance values for the first parameter; Semiconductor wafer inspection method comprising a. The method of claim 1, And wherein the form is a contact hole in an integrated circuit. The method of claim 2, And the contact hole may be classified as not open if the first parameter is out of a range of an allowable value for the first parameter. The method of claim 1, And wherein the shape can be classified as a failure if the first parameter is outside the range of the allowable value for the first parameter. The method of claim 1, And wherein the form can be classified as acceptable if the first parameter is within a range of tolerance for the first parameter. The method of claim 1, And the SEM image data is obtained from secondary electrons and backscattered electrons. The method of claim 1, Wherein said first parameter comprises a dimension of said shape. The method of claim 1, And wherein the first parameter comprises the number of pixels of SEM image data associated with the shape. The method of claim 1, And wherein said first parameter comprises an average intensity of pixels associated with said shape. The method of claim 1, And estimating an image pixel intensity profile for the shape. The method of claim 10, And calculating the image pixel intensity profile comprises subtracting a background intensity value from an intensity value for pixels in a region including the shape. The method of claim 1, Calculating a second parameter associated with the shape from the image data for the shape; Comparing the second parameter with a range of tolerances for the second parameter; And Classifying the form according to a comparison with a range of tolerance values for the second parameter; The semiconductor wafer inspection method characterized in that it further comprises. The method of claim 12, And wherein said second parameter comprises a dimension of said shape. The method of claim 12, And wherein said second parameter comprises the number of SEM image data pixels associated with said shape. The method of claim 12, And wherein said second parameter comprises an average intensity of pixels associated with said shape. The method of claim 12, The form can be classified as acceptable only when the first parameter is within a range of tolerance for the first parameter and the second parameter is within a range of tolerance for the second parameter. The semiconductor wafer inspection method. The method of claim 1, further comprising characterizing the shape using a coordinate system, wherein the characterizing step comprises: Superimposing a coordinate system over an image of the area of the semiconductor wafer and analyzing the intensity values of pixels arranged in association with a second axis of the coordinate system at a plurality of locations that are contiguous to the first axis of the coordinate system. The semiconductor wafer inspection method characterized in that. The method of claim 17, And the analyzing step includes adding up intensity values of pixels arranged in association with the second axis. The method of claim 18, And said analyzing step further comprises detecting a change in the summed intensity value at a plurality of positions softer on said first axis to detect said shape. The method of claim 17, And said analyzing step comprises averaging the intensity values of pixels arranged adjacent to said second axis. The method of claim 20, And said analyzing step further comprises detecting a change in an average intensity value at a plurality of positions softer on said first axis to detect said shape. The method of claim 17, Wherein said characterizing step comprises determining a size of said shape. The method of claim 17, Wherein said characterizing step comprises determining a position of said shape. The method of claim 17, Wherein said characterizing step comprises identifying a plurality of patterns of said shapes. The method of claim 24, And said pattern is a periodic pattern. The method of claim 17, And said coordinate system is a rectangular coordinate system. The method of claim 17, And said coordinate system is a triangular coordinate system. The method of claim 17, And said coordinate system is a trapezoidal coordinate system. The method of claim 1, And the SEM image data is in the form of a gray scale value of a digitized pixel. The method of claim 1, And said SEM image data is in the form of pixel values of digitalized color codes. An apparatus for inspecting at least one region of a semiconductor wafer, Reading means for reading SEM (Scanning Electron Microscope) image data for the region of the semiconductor wafer; Identification means for identifying image data for a shape on the semiconductor wafer in data for the region of the semiconductor wafer; Calculating means for calculating a first parameter associated with the shape from the image data for the shape; Comparing means for comparing the first parameter with a range of tolerances for the first parameter; And Classification means for classifying the form according to a comparison with a range of allowable values for the first parameter; Semiconductor wafer inspection apparatus comprising a. The method of claim 31, wherein Wherein said form is a contact hole in an integrated circuit. 33. The method of claim 32, And said sorting means is configured to classify the contact hole as not open if the first parameter is out of a range of an allowable value for the first parameter. The method of claim 31, wherein And said sorting means can classify the form as defective if said first parameter is outside the range of an allowable value for said first parameter. The method of claim 31, wherein And said sorting means can be classified as acceptable if said first parameter is within a range of an allowable value for said first parameter. The method of claim 31, wherein And said SEM image data is obtained from secondary electrons and backscattered electrons. The method of claim 31, wherein And said first parameter comprises a dimension of said shape. The method of claim 31, wherein And said first parameter comprises the number of SEM image data pixels associated with said shape. The method of claim 31, wherein Wherein said first parameter comprises an average intensity of pixels associated with said shape. The method of claim 31, wherein And means for calculating an image pixel intensity profile for the shape. The method of claim 40, And means for estimating the image pixel intensity profile comprises means for subtracting a background intensity value from an intensity value for pixels in a region including the shape. 42. The method of claim 41 wherein Means for calculating a second parameter associated with the shape from the image data for the shape; Means for comparing the second parameter with a range of tolerance for the second parameter; And Means for classifying the form according to a comparison with a range of tolerance values for the second parameter; The semiconductor wafer inspection apparatus further comprises. The method of claim 42, wherein And said second parameter comprises a dimension of said shape. The method of claim 42, wherein And said second parameter comprises the number of SEM image data pixels associated with said shape. The method of claim 42, wherein And wherein the second parameter comprises an average intensity of pixels associated with the shape. The method of claim 42, wherein The form may be classified as pass only if the first parameter is within a range of tolerance for the first parameter and the second parameter is within a range of tolerance for the second parameter. Semiconductor wafer inspection device. 42. The apparatus of claim 41, further comprising means for characterizing the form using a coordinate system, wherein the characterization means is Means for superimposing a coordinate system over an image of the semiconductor wafer region and means for analyzing the intensity values of pixels arranged in association with a second axis of the coordinate system at a plurality of locations that are contiguous to the first axis of the coordinate system. The semiconductor wafer inspection apparatus. The method of claim 47, And said analyzing means comprises means for summing up intensity values of pixels arranged adjacent to said second axis. 49. The method of claim 48 wherein And said analyzing means further comprises means for detecting a change in the summed intensity value at a plurality of positions softer to said first axis to detect said shape. The method of claim 47, And said analyzing means comprises means for averaging the intensity values of pixels arranged adjacent to said second axis. 51. The method of claim 50 wherein And said analyzing means further comprises means for detecting a change in average intensity value at a plurality of positions softer on said first axis to detect said shape. The method of claim 47, And said characterization means comprises means for determining the size of said shape. The method of claim 47, And said characterization means comprises means for determining the position of said shape. The method of claim 47, And said characterizing means comprises a plurality of means for identifying said pattern of said shapes. The method of claim 54, wherein And said pattern is a periodic pattern. The method of claim 47, The coordinate system is the semiconductor wafer inspection apparatus, characterized in that the rectangular coordinate system. The method of claim 47, And said coordinate system is a triangular coordinate system. The method of claim 47, And said coordinate system is a trapezoidal coordinate system. The method of claim 31, wherein And said SEM image data is in the form of a grayscale value of a digitized pixel. The method of claim 31, wherein And said SEM image data is in the form of pixel values of digitized color coding.