DE19860704A1 - Semiconductor wafer inspecting method using a scanning electron microscope (SEM) - Google Patents

Abstract

The method involves reading SEM image data and identifying image data for a feature such as a contact hole on a semiconductor wafer. A parameter is computed related to the feature from the image data and the parameter is compared to a range of acceptable values. The feature is then classified according to the comparison. An Independent claim is included for an apparatus for inspecting a portion of a semiconductor wafer.

Description

Related registrations

This application is based on that filed on June 22, 1998 American Provisional Application with the file number 60 / 090,137.

Field of the Invention

The present invention relates to the review of Semiconductor devices. In particular, it concerns the detection of incorrect data Using contacts, such as non-open contact openings of a scanning electron microscope.

Background of the Invention

Integrated circuits are manufactured in such a way that discrete at first Semiconductor components are formed in silicon wafers. In the Components now become metallic in several levels Connection network formed that to the active parts of the components establishes a contact and uses it to generate the desired circuits connects with each other. The connection layers are formed as follows: Depositing an insulating layer over the discrete components, Structuring and etching contact openings in this layer and Deposit conductive material in these openings. Above the insulating layer now typically becomes a conductive layer  upset. The conductive layer is now patterned and etched to the Formation of a first circuit level connections between the contacts to manufacture the components. By creating a circuit with The following process steps are repeated at several levels performed: deposition of an insulating layer, formation of Contact openings or vias, formation of conductive Material layers, structuring, etc.

Depending on the complexity of the overall integrated circuit typically several metallic levels, for example two to four Layers required to create the necessary connections and these Connections to connect with contact points that have an external connection to the completed circuit. A high density of integrated Circuits with dimensions in the submicrometer range make one extremely precise control of the dimensions required. It will very sensitive surveillance procedures to investigate the Connection structure and / or the contact openings required to the Accuracy of dimensions and flawless structure of the Ensure design. These requirements are increasing Density and miniaturization of the circuits stricter, such as at the mass production of semiconductor memory devices such as 64 M DRAMs or 256 M DRAMs, for the currently typically Circuit dimensions from 0.25 to 0.30 µm are required.

Checking contact openings for their condition, such as to a not open or not free state, is becoming increasingly important since the aspect ratio (A / R) of contact openings, i.e. H. The relationship their depth to their diameter, with increasing need for higher ones Densities in the components has increased. A conventional one Light microscopy method with a wavelength of 488 nm in the visible However, the area is in terms of reviewing the internal structure of the  Contact openings technically limited as it is used to check the inner Structure of the contact openings with a dimension of 200 nm or less, has too low a resolution. Leave with light microscopy no light spot sizes of 1 µm or less are generated.

Summary of the invention

An object of the present invention is to provide a Verification procedure for faulty contacts or contacting errors and in the creation of a device for semiconductor devices that exact checking of contacting or contact errors by means of digitized values on contact pictures and not by the naked eye or enable through the microscope and through which one or more of the due to the limitations and disadvantages of the prior art Let problems be solved.

Another object of the present invention is to provide a method for checking contacting or contact errors Semiconductor components and a contacting fault checking system to detect contacting errors in contacts with a large Aspect ratio, d. H. a great relationship between depth and that Diameter of a contact.

Another object of the present invention is to provide a review process for contact errors Semiconductor devices and in creating a contacting fault Checking system for recording contacting errors on the Surface of a wafer within a short period of time, which is suitable for the application at the Mass production are suitable.  

Another object of the present invention is to provide a manufacturing method for semiconductor devices using the mentioned verification procedure and the corresponding Checking system for contacting errors.

Another object of the present invention is to provide a review process and system for Contacting errors to record the position of contacting errors, so that in the manufacture of semiconductor devices a larger Yield yields.

Another object of the present invention is to provide a verification process and a verification system for registration of structuring errors in semiconductor components and for detection a faulty photoresist structure after a Development processing step in a photolithography process.

The present invention relates to a method and an apparatus for Checking at least a part of a semiconductor wafer that can be used have these and other tasks solved. According to the Image data from a scanning electron microscope (SEM = Scanning Electron Microscop) read for the part of the semiconductor laser. Of these SEM Image data becomes image data for a certain characteristic or a certain one Property of the wafer identified. One with this trait related parameter is calculated and with a range values still to be accepted for this parameter. Based on this comparison between the parameter and that too the characteristic can be classified in the accepting range of values.

In one embodiment according to the invention, as Computer parameters used the dimension or size of the feature.  

If the feature, for example, a contact opening in an integrated Circuit is, the parameter is for example the diameter of the opening measured in image data pixels. A certain contact opening can be determined, for example, by being 20 pixels wide owns. In another exemplary embodiment, a average pixel intensity for pixels within the Feature. If the feature is a contact opening, it is called Parameters, for example, the mean of the pixel intensities for the pixels used, which are assigned to the contact opening. If the measured Parameters within a range of acceptable values for this Parameter, the characteristic is classified as acceptable. If the Parameters outside this range of acceptable values for this parameter, the characteristic is classified as incorrect. If that Feature is a contact opening, the opening is detected as faulty if for example, it is not open.

In an embodiment according to the invention, the feature calculated two parameters. For example, the two parameters can be one Dimension of a feature, such as a contact opening, measured in pixels associated with the feature. The second parameter can be the average or average pixel intensity of the feature assigned pixels. Both parameters are predetermined Ranges of acceptable values for these parameters compared. If both parameters at the same time within their respective range accepting values, the characteristic, such as a Contact opening, classified as acceptable in one embodiment. Under these circumstances, a contact opening is considered to be open, correctly measured and can be classified correctly. The connection between the Parameters and their corresponding ranges can be used for this classify the characteristic into one of several category types. The Parameters can vary depending on whether they are below, inside or  are above a still acceptable range of values Classification of a characteristic can be used.

In one embodiment, the SEM image data is both from Secondary electrons as well as from higher energetic backscattered Electrons generated in the scanning electron microscope. The data values are digitized and can be digitized Grayscale pixel levels or levels or color-coded pixel values available.

In an exemplary embodiment according to the invention, characterization uses a lattice or mesh structure of the feature to be checked, where for characterization, for example, the position and / or the Dimensions of the feature to be checked is determined. The grids- or mesh structure typically comprises two orthogonal superimposed axes, the image of the part of the wafer to be analyzed be overlaid. Alternatively, the grid axes can be any have geometric interdependency, d. that is, they for example triangular, trapezoidal, etc. At a The position is determined by the grid localization method determines the shape and / or the periodic structure of the feature by the pixel values are analyzed along a line that is parallel to one of the runs orthogonal axes that successively at pixel positions along the other orthogonal axis is positioned. The grid method can for example, positioning a vertical line on multiple horizontal pixel positions and adding the vertical ones Include pixel intensity values at each horizontal location. The accumulated intensities can at the respective horizontal point compared to determine an increase in intensity that as an indication of the presence of a feature, such as one Contact opening, is used. This procedure can work for several  Pixel positions are repeated in a dimension or direction. It can then be repeated in the direction perpendicular thereto, so that the structure, shape and dimensions of the features can be determined.

This procedure can also be used to find the optimal one To determine the dimension of a sub-grid or sub-mesh unit includes the characteristics to be analyzed. The grid method can For example, the optimal dimension can be used To determine the grid unit in pixels, the 100 to be analyzed simultaneously Contact openings includes. This procedure does that Method according to the invention for checking features very much more efficient, since unnecessary processing steps can be achieved by optimizing the Have the area of the area to be checked eliminated.

In one embodiment, the SEM image data pixels become Calculation of an intensity profile of the characteristic to be checked in each case, d. H. a contact opening used. In one embodiment, this is Intensity profile first by summing the pixel intensity values of one Feature along an orthogonal axis on each of several Generates pixel positions that are arranged along the perpendicular axis are. For example, at each horizontal pixel position Summed up pixel intensity values in the perpendicular direction, averaged and as a function of the pixel position on the horizontal axis applied. The pixel intensity profile is related to the invention Classification of the characteristic can be used.

In one embodiment, the intensity profiles are standardized all features of all intensity values in the respective grating unit of the Background intensity value subtracted. This causes the Background value for the respective intensity profile reduced to zero. In which standardized profile can now next set a threshold like this  pixel intensities above the threshold value be assigned to the checking characteristic. From the profile you can now the above-mentioned first and the above-mentioned second parameters are calculated become. The dimensions of the feature can be, for example, by Counting the number of pixel positions in a first direction the accumulated intensity values in the perpendicular to it Have a direction that exceeds the threshold. Since assumed that a sum of the pixel intensity that exceeds the threshold assigned to the characteristic is the number of pixel positions with a Sum that exceeds the threshold, a measure of the characteristic in a direction, measured in pixels. The second parameter can be through Calculation of an average exceeding the threshold Intensity value can be calculated. You can use these two parameters with your compared the respective predetermined range of values to be accepted to the predetermined feature in one of the predetermined classes Classify characteristic types.

The checking method according to the invention and the one according to the invention Verification systems have numerous advantages compared to the state of the art Technology. In certain prior art processes for example optical methods, such as light microscopy or checking with the naked eye; to record contacting or Contact errors used. These systems are unsuitable for resolution minor feature errors that lead to circuit failure. The Use of a scanning electron microscope according to the invention ensures a much better resolution with which even minor errors can be detected to let. The present invention is therefore more up to date on the features Circuits applicable, their dimensions in the submicrometer range lie. The processing is due to the grid method according to the invention the pixel data according to the invention is also extremely efficient. The Processing and error detection can be very efficient and fast  take place, so that the verification process according to the invention and the inspection system according to the invention very good for mass production of wafers and integrated circuits.

Another aspect of the present invention relates to a Verification procedure for contacting errors in semiconductor components with the following procedural steps: setting up a processing cassette with Wafers, on the surface of which several contact openings are formed are; Removing a specific wafer from the cassette and loading one Tables in a reference chamber of an SEM with the wafer; Align the Electron beam scanning wafers; Moving the table with the wafer attached to it at a special location, the one Direction of incidence of the electron beam of the SEM is assigned; Opening one Aperture for the scanning electron beam at a specific point on the Wafers; Self-addressing or self-control to record the Verification position by detecting one formed on the wafer pre-structured reference image; Deflecting the electron beam of the SEM in the checking position; Self-focusing to create another clear image by repeating the electron beam deflection; Conclude the aperture to separate the self-focused wafer from the Electron beam; Check for a faulty contact or Contacting errors by comparing that of a unit area with at least one contact opening detected electron signal values after the Deflecting the electron beam with an electron signal value that corresponds to one corresponds to normal contact; further checking of a contacting error in a different position of the wafer by moving the table into the different position and repetition of the same procedural steps; and more Check all other wafers in the cassette for contact errors by removing the checked wafer and inserting the other wafers into the reference chamber and repetition of the same process steps.  

According to another aspect of the present invention, a Methods of manufacturing semiconductor devices the following Process steps: formation of contact openings for certain on one Semiconductor substrate formed insulating material layers; Review of the Contacts of the contact openings by comparing each one Surface with at least one contact opening detected electron signal values with the electron signal values corresponding to a normal contact and Carrying out the subsequent processing steps of the Manufacturing process for semiconductor devices according to the Verification of the introduction of conductive layers of material into the Contact openings.

The contact error checking step can be for a specific Scan position can be performed on the semiconductor substrate for example the checking step for contacting errors in a To be able to use the production line for mass production. After End of development processing to form the photoresist structure the contacting error check step can also be on the bottom the photoresist structure to form contact openings.

Another aspect of the present invention relates to a method for Manufacture of semiconductor components with the following process steps: Formation of a photoresist contact opening structure to form Contact openings for insulating formed on a semiconductor substrate Layers of material; and checking the respective contact of the Contact openings by comparing that of a unit area with at least a contact opening structure detected electron signal values with the one normal contact structure corresponding electron signal values.  

Brief description of the drawings

The above objects, features and advantages of the present Invention arise along with other objects, features and Advantages from the following detailed description are more preferred Embodiments that are shown in the accompanying drawings. In the drawings, the drawings are not necessarily drawn to scale are the same components with the same reference numerals. The Drawings serve to illustrate the invention underlying principles.

Show it:

FIG. 1 is a schematic illustration of a block diagram for illustrating the operation of a scanning electron microscope (SEM = Scanning Electron Microscope);

Fig. 2 is a schematic representation of the energy spectrum of the emitted electrons in a SEM, including secondary electrons and the backscattered electrons upon irradiation with an electron beam of a comparative sample;

Fig. 3 is a schematic illustration of a block diagram for illustrating the configuration of an in-line SEMs;

Fig. 4 is a schematic illustration of a block diagram of an embodiment of an inspection system according to the invention for bonding failure in semiconductor devices;

Fig. 5 is a schematic illustration of a block diagram of an alternative embodiment of an inspection system according to the invention for bonding failure in semiconductor devices;

Fig. 6 is a schematic illustration of a block diagram of another alternative embodiment of an inspection system according to the invention for bonding failure in semiconductor devices;

Fig. 7 is a schematic illustration of a block diagram of another alternative embodiment of an inspection system according to the invention for bonding failure in semiconductor devices;

Fig. 8 is a schematic illustration of a functional block diagram of an embodiment of an inspection method of the invention for bonding failure and a corresponding system;

Fig. 9 is a schematic illustration of a functional block diagram of another embodiment of an inspection method of the invention for bonding failure and a corresponding system;

FIG. 10 is a schematic illustration of a functional block diagram of another embodiment of an inspection method of the invention for bonding failure and a corresponding system;

Figure 11 is a schematic representation of a flow chart illustrating the logical sequence in an embodiment of an inspection method of the invention for contacting errors in semiconductor devices.

Figure 12 is a schematic representation of a flow chart illustrating the logical sequence in an alternative embodiment of an inspection method of the invention for contacting errors in semiconductor devices.

FIG. 13 is a schematic representation of a flow chart illustrating the logical sequence with another alternative embodiment of an inspection method of the invention for bonding failure in semiconductor devices;

FIG. 14 is a schematic representation of a flow chart illustrating the logical sequence with another alternative embodiment of an inspection method of the invention for bonding failure in semiconductor devices;

Figure 15 is a schematic illustration of a diagram showing a pattern of Chipabtaststellen on a wafer according to the invention for checking Kontaktierungsfehlern.

FIG. 16 is a schematic illustration of a diagram for illustrating details of the scanning to the Chipabtaststellen of FIG. 15;

Figure 17 is a schematic representation of a cross-section through a semiconductor device having formed therein contact holes, in which the inspection method of the invention for bonding failure is applicable.

Fig. 18 SEM-image data for contact holes having been set by an inventive contact point recognition method, a grating;

Figure 19 is a schematic representation of a grid for implementing an embodiment of the contact detection method of the invention.

FIG. 20 is a schematic representation of a grid for implementing an alternative embodiment of the contact detection method according to the invention;

FIG. 21 is a schematic representation of the relationship between a contact unit, and horizontal and vertical pixel units of an inventive embodiment;

FIG. 22 is an intensity profile of a contact unit prior to performing a background value correction in an embodiment of the invention;

FIG. 23 shows an intensity profile of the contact unit according to FIG. 22 after a background value correction has been carried out;

FIG. 24 is an intensity profile of an SEM image of contact units after performing a background value correction;

Figure 25 is a table of codes for identifying results in an embodiment of the inspection method of the invention for bonding failure.

FIG. 26 is a table with a part of the results in the verification of Kontaktierungsfehlern according to an embodiment of the invention;

Figure 27 is a flow chart illustrating the logical sequence of a processing sequence according to the invention for semiconductor devices.

FIG. 28 is a schematic representation of a flow chart illustrating the logical sequence in one embodiment of the contact inspection method of the invention;

Figure 29 is a schematic representation of a flow chart illustrating the logic sequence when reading the image data of the scanning electron microscope according to the method shown in FIG. 28.;

FIG. 30A to 30D in a schematic diagram a flow chart illustrating the logical sequence in the detection of the contact opening positions in accordance with the method shown in Fig. 28;

FIG. 31A to 31D in a schematic diagram a flow chart illustrating the logical sequence in the calculation of contact opening profiles according to the method shown in Fig. 28;

FIG. 32A to 32B a schematic representation of a flow chart illustrating the logical sequence in the verification of contact openings according to the method shown in Fig. 28.

Detailed description of preferred embodiments

Fig. 1 is a schematic block diagram showing a scanning system 100 that is suitable for the inventive examination of contact holes in semiconductor devices.

Fig. 1 shows an electron gun 102 that shoots an electron beam through a condenser lens 104th The beam passes through a deflection coil 122 , an iris 106 , an object lens 108 and an aperture 124 . The focused electron beam strikes a reference or sample surface 110 which it sweeps or scans. The surface 110 can be the surface of a semiconductor wafer to be checked. Secondary electrons and backscattered electrons emitted from the reference surface are detected by a signal detector 112 that generates signals indicative of the received electrons. The detected electron beam is amplified by a signal amplifier 114 . The amplified signal is deflected across the fluorescent surface in a cathode ray tube (CRT) 118 , so that a visible image of the reference surface is formed.

Scanning of the surface of the CRT 118 by the beam is controlled by a deflection coil 116 , which is correlated with the scanning process of the reference surface controlled by the deflection coil 122 . In the SEM, the scanned surface of the reference surface is divided into fine pixels or picture elements. The electron signals detected by the pixel elements are transmitted one after the other in time to form the SEM image. The electron signal passing through the signal amplifier 114 is transmitted to a scanning circuit 120 , by means of which the deflection angle of the electron beam in the second deflection coil 122 is controlled.

In addition to this, the amplified electron signal data for the individual pixels can be transmitted to a processing unit 115 , which performs numerous signal processing and signal processing functions. The processing unit 115 can convert the electron signal for the individual pixels to form an image into a discrete gray scale value or a color-coded value. The gray scale value can take on one of 256 possible levels or states that are digitally encoded by a binary value between 0 and 255. A storage device can be used to store the gray scale values for the individual pixels. A computer, which is also part of the processing unit, can process the image values as desired. In one embodiment, the computer can be programmed to analyze the gray scale data to perform the inventive contact check described in detail below.

Fig. 3 shows a schematic representation of a block diagram with the characteristic components of an in-line-SEM system, in which the contact check can be done in-line. In methods according to the prior art, the SEM image data are collected and analyzed offline, ie apart from the production method. Since the inline method according to the invention is much more efficient, the SEM image data can be collected and analyzed during the manufacturing process, so that the additional checking steps customary in conventional methods are eliminated. The in-line SEM system includes an electron optical section, a reference section, a vacuum section and an electrical section. The electron optical section comprises an electron beam generator 14 , a deflection device 15 for the electron beam and a signal detector 16 . The reference section comprises a reference transport part 12 for transporting the reference sample, ie the wafer, from a cassette to a reference chamber and a reference alignment part 13 . The vacuum section comprises a vacuum generating part 11 for maintaining a negative pressure in the reference chamber. The electrical section comprises a main computer 10 with a main control device 21 for controlling the electron-optical section, the reference chamber, the vacuum section and the other system components. The electrical section includes a main storage unit or memory 22 for storing the detected signal data values of the signal detector 16 . The electrical section also includes a main display or screen 19 for displaying the images generated from the detected electronic signals. An automatic focus control device 18 provides automatic focusing to produce clear or sharp images.

In a typical scanning electron microscope, the reference surface is irradiated with the electron beam, secondary electrons being generated and emitted from the reference surface. The electrons of the beam can also be scattered through the surface. FIG. 2 shows an energy spectrum of the electrons emitted by the reference surface and the electrons scattered thereon when the reference surface is irradiated. As can be seen in Fig. 2, the largest number of secondary electrons (SE = Secondary Electrons) is in an electron energy band of less than 50 eV, while most backscattered electrons (BSE = Back Scattered Electrons) are in a much higher energy band are to be found. In commonly used in-line SEMs, the secondary electrons (SE) generated in the low energy band of about 20 eV are used, so that clear or sharp images of surfaces and edges result. When checking certain features, such as contact openings with a large aspect ratio, ie the ratio of the opening depth to the opening diameter, the secondary electrons generated in the contact openings can be dissipated as they pass through the contact openings, so that the contact openings are not clearly or sharply imaged. Since these features are typically checked visually with the naked eye, clear images are essential for detecting faulty contacts.

FIGS. 4 to 7 show a schematic illustration of block diagrams of various embodiments of the inspection system according to the invention for contacting errors in semiconductor devices. The system shown in FIG. 4 comprises some of the components of the in-line SEM according to FIG. 3. However, in a computer 20 it also includes a checking module 60 for contacting errors. As already described above, the in-line SEM comprises an electron-optical section with an electron beam generator 14 , a deflector 15 for the electron beam and a signal detector part 16 . A detector is preferably used as the signal detector, which can detect both secondary electrons (SE) and backscattered electrons (BSE) which are emitted by the electron beam after the reference surface has been irradiated. The system also includes a reference chamber with a reference alignment member 13 for rotating or tilting the table on which the reference wafer to be checked is placed while being moved along the X, Y or Z axis. A vacuum generating part 11 serves to maintain a desired negative pressure in the reference chamber. A reference transport part 12 serves to transport the reference sample into the reference chamber. The electrical section comprises a main computer 20 with a main control part 21 for controlling the electron optical section, the reference chamber, the vacuum generating part 11 and the other subsystems. A main memory unit or a main memory 22 stores the signals detected by the signal detector 16 . A main display device or a main display 19 displays the image derived from the detected electronic signal. An automatic focus control device 18 automatically focuses to produce a clear or sharp image on the display. This embodiment also includes a contacting error checking module 60 for analyzing the information contained in the electron beam, which is transmitted by the signal detector 16 and stored in the main computer 20 in order to be able to check the contacts according to the invention.

Fig. 5 illustrates another embodiment of an inspection system according to the invention for contacting errors in semiconductor devices. The system shown in FIG. 5 also includes some of the components of the in-line SEM of FIG. 3. One difference is that it also includes a contacting error check module 60 and a critical dimension (CD) module 70 Contacts that may be located in the main computer 20 . A critical dimension is the dimension of a certain feature to be checked. In the case of a round opening, the critical dimension can be, for example, the diameter of the opening. In one exemplary embodiment, the measurement is carried out by the measuring module 70 for critical contact dimensions (CD) by comparing the contact diameter determined from the contact images generated by the SEM with pre-stored standard values.

FIG. 6 illustrates another exemplary embodiment according to the invention of an in-line checking system for contacting errors in semiconductor components. The system of FIG. 6 also includes some of the components of the in-line SEM of FIG. 3. One difference is that it can also include a subcomputer 80 that interfaces with the main computer 10 . In the sub-computer 80 there is a checking module 60 for contacting errors. As the sub computer 80 , a conventional commercially available PC with a sub screen and a sub memory unit or a sub memory can be used. The occurrence of contacting errors is detected by analysis of the contact electron signal data stored in the main storage unit 22 by the contacting error checking module 60 in the subcomputer 80 .

Fig. 7 illustrates another embodiment of an inspection system according to the invention for contacting errors in semiconductor devices. The system according to FIG. 7, which also contains some components of the in-line SEM according to FIG. 6, comprises a subcomputer 80 connected to the main computer 40 via an interface. The system according to FIG. 7 also includes a contacting error checking module 60 in the subcomputer 80 and a measuring module 70 for critical contact dimensions in the main computer 40 .

Figs. 8 to 10 show a schematic illustration of functional block diagrams for various embodiments of the bonding failure-check module 60 of the invention. As can be seen in Fig. 8, a bonding failure-check module, a read module 60 may comprise a 60-SEM for signals that receives the SEM signals indicative of the signals received from an irradiated by an electron beam wafer electrons. The SEM signal is analyzed by a contact position detection module 60 d in order to determine the positions of the contact openings and / or of other features to be checked. A module 60 e for calculating contact profiles and for eliminating the background generates intensity profiles for the contact openings using the SEM signal data. The intensity profiles are typically standardized by eliminating the data generated by background intensity effects, so that the shape of the intensity profiles can be checked independently of background effects. A contacting error checking module 60 f analyzes the intensity profiles of the contact openings in order to identify contacting errors. As will be described in detail below, in one exemplary embodiment for identifying a faulty contact, the average intensity value of the contact is compared with a predetermined threshold value. A result display module 60 g serves to display the results of the error analysis.

In one embodiment, the reading module 60 a for the SEM signals reads the digitized electron signal information of the contacts that are stored in the main memory unit or the main memory 22 of the main computer 20 . The in-line SEM digitizes the intensity of the electron signals that are detected due to scanning by the electron beam and stores the intensities as a gray scale level or as a color-coded level. In a system, the gray scale value assigned to the pixels corresponds to one of 256 possible values between 0 and 255. The highest intensity is defined as 255, while the lowest intensity is defined as 0. The digitized intensity values are color-coded by the individual pixel elements, ie as a gray scale value. The contact images are generated by reading the gray scale values for the individual pixels one after the other and displaying the pixel images on a cathode ray tube, a screen and / or a printer. The gray scale values can also be converted to a color for a color screen.

In Fig. Embodiment of the Kontaktierungsfehler- check module illustrated 9 is a modification of the embodiment according to FIG. 8. In Fig. 9, the Kontaktierungsprofil calculation module are 60 e (1) and the background value-elimination or -Korrekturmodul 60 e (2) as separate modules, while they are shown in Fig. 8 as a common module 60 e.

Fig. 10 is a functional block diagram of another embodiment of the invention Kontaktierungsfehler- shows a schematic representation of checking module 60. The illustrated Kontaktierungsfehler- checking module 60 comprises a graphics file transmission network module 60 b, a conversion module 60 c for converting the graphics file in a SEM signal, a contact position detection module d 60, a combined contact profile calculating and background value correction module 60 e, a contact failure -Check module 60 f and a display module 60 g for the results.

The graphics file transmission network module 60 b is a device for signal transmission between the main computer 10 , 40 and the sub-computer 80 (see FIG. 6). The module 60 b converts the information of the digitized electron signals of a contact stored in the main storage unit 22 of the main computer 10 , 40 into a graphics file and transmits it to the subcomputer 80 .

The conversion module 60 c of the graphics file in an SEM signal reads the color-coded values, ie gray scale values, of the transmitted to the sub computer 80 graphics file and converts it into a digitized signal SEM. The contact position detection module d 60, Kontaktprofil- calculation and background value correction module 60 e, the Kontaktfehler- checking module 60 e, and the module 60 g to show the results have been described above already with reference to FIGS. 8 and 9..

Figs. 11 to 14 contain flow charts for different embodiments of the in-line contact failure verification process for semiconductor devices according to the invention by Kontaktfehler- verification systems. The contact failure checking part 60 shown in FIG. 4 performs the contact failure checking in a wafer having a plurality of contact openings by using the in-line SEM installed in the main computer 40 (see FIG. 11). First, a cassette with a plurality of wafers mounted thereon, each with a plurality of contact openings, is set up at a predetermined location of the in-line SEM (S10). After removing a wafer to be checked from the cassette, a table in the reference chamber of the SEM is now loaded with the wafer (S12). Now the bevel or the segment section of the wafer is aligned. Then the wafer is aligned for scanning by the electron beam (S14) and the table with the wafer mounted thereon is moved to a specific position in the direction of incidence of the electron beam of the SEM (S16).

The aperture located under the object lens is opened by one to irradiate a specific point of the wafer with the electron beam, whereby self-control or self-addressing takes place (S20). Through the Self-addressing is recognized by a specific location pre-structured standard image is applied to the specific location in such a way that a check can be made on the standard image.  

Now the point to be checked is with the electron beam of the SEM irradiated (S22) and scanning by the electron beam becomes Creation of a clear or sharp contact image by the Auto focus control part repeatedly performed (S24). Subsequently the shutter is closed to stop the wafer from scanning End electron beam (S26).

Now for all the contacts captured by the scanning electron beam checks the intensity profile of the electron signals according to the invention (S28). Then it is determined whether there is one at other locations on the wafer Checking for contacting errors should be made (S30). If so If necessary, the flowchart jumps back to the Step S16. The table is moved to other parts of the wafer and that The above steps are repeated. After completing the Contact error check is taken out of the wafer (S32). It will determines whether other wafers are also checked (S34). In this case the reference chamber is loaded with another wafer from the cassette and the above steps are repeated so that for all wafers in a contact error check is carried out on the cassette. After done Checking all wafers, the cassette is removed (S36) and that Procedure ended.

FIG. 12 shows the contacting error checking method for wafers with multiple contact openings using the in-line SEM according to FIG. 5, in whose main computer 30 the contacting error checking part 60 and the measuring part 70 for the critical contact dimensions are formed together. The check for contacting errors is carried out according to FIG. 11, however, in contrast to FIG. 11, the diaphragm is closed (S26), the contacting error check or detection is determined (S27) and the measurement of the critical contact dimensions takes place (S29) if the contacting error check (S28) is not carried out.

FIG. 13 shows an in-line contact failure check method for a multi-contact wafer using the in-line SEM of FIG. 6, in which the contact failure check part 60 is not housed in the main computer 10 but in the sub computer 80 is. As can be seen in FIG. 13, after the shutter (S26) is closed, the SEM signal stored in the main memory of the main computer is transmitted to the subcomputer and it is determined whether a contacting error check should also be carried out for other locations on the wafer (S31). The sub-computer receives the transmitted signal to perform the contact failure check (S37).

In the embodiment shown in FIG. 14, the arrangement or position of the sub-computer and the main computer is reversed if the contacting error checking part 60 is installed in the sub-computer and not in the main computer, as shown in FIG. 6. The shutter is closed (S26) by the same method steps as in FIG. 11, the transmission of the SEM signals stored in the main memory part of the main computer to the subcomputer is determined (S31-1) and the contactor is checked for contact errors (S31 -2). It is also determined whether a contact check is also required at other points (S31-3, S31-4).

Fig. 15 shows numbered shaded regions (# 2 to # 37) on a wafer 110 to be checked by the inventive Kontaktierungsfehler- verification procedures. An area labeled "AP" shows an alignment point, while "# 1" denotes the chip-free focusing point.

In the shaded areas in FIG. 15, several sampling points can be defined in each case. For example, for the chip or area # 2 in FIG. 15, FIG. 16 shows five sampling points, the top left ( 2 , 1 ), top right ( 2 , 2 ), bottom right ( 2 , 3 ), bottom left ( 2 , 4 ) and in the middle ( 2 , 5 ). The scanning points or the scanning numbers can be selected in different ways within a chip unit to be scanned. In the present exemplary embodiment, 175 locations from 35 chip or scanning regions are scanned, with five scanning locations being checked for each chip. In one embodiment in which an in-line SEM with a gain of 12.5 k is used, there can be 98 contacts for each sampling point in a 480 × 480 pixel image. With five sampling points for each of the 35 areas, 17 150 contacts are checked. Fig. 17 shows a schematic representation of a cross-section through a semiconductor device according to the invention to be tested contact openings. Fig. 17 shows the manufacturing process for a buried contact of a 64 M DRAM. An active region is defined by a field oxide layer 131 and is formed over a semiconductor substrate 130 . A gate electrode 132 is formed over the active region and is covered by a spacer layer 133 . After forming a first insulating layer 134 from a high-temperature oxide film on the surface, a first contact opening 137 is formed, which serves as a direct contact to a bit line 135 . After the bit line 135 has been formed , a second insulating layer 136 is formed on the surface as a BPSG. In addition, a second contact opening 138 is formed as a word line.

As an example of the checking method according to the invention, the buried contact for the formation of the word line is checked during the manufacturing process for the 64 M DRAM. As shown in FIG. 17, the direct contact 137 can also be checked. The check can also take place after the development process of the photoresist structure for the formation of these contacts.

In the checking method for contacting errors according to the invention is the optimal image size for the areas to be checked selected based on the dimension of the feature to be checked, such as for example based on the diameter of a round contact opening. At In one embodiment, a typical SEM image comprises 480 × 480 pixels.

Such an image can be created for each of the numbered digits in FIG. 16. Depending on the size and the distance between the contact openings, an optimal image size is determined for the individual contacts.

Fig. 18 shows an example of a contact image of an in-line SEMs with a gain of 12.5 K for a scanning of the semiconductor device. It consists of 480 × 480 pixels. The number of contacts shown in the picture is 98, ie 14 in the horizontal direction and 7 in the vertical direction.

The optimal resolution is determined and based on the dimensions the feature to be checked, d. H. the contact opening, and the distance checked between the openings. In a system, the pixels for example, each resolve 12 nm in the SEM. Contact openings are currently known to have diameters in the range of 200 nm. The number of pixels covering a feature is chosen to be ensure that irregularities or errors in the characteristic in the Image are clearly recognizable. If an area to be examined for example 100 openings in the form of a grid with a uniform Mesh size includes, a set of 100 sub-grids with 48 × 48 pixels used to cover all openings including the area between  to cover the openings, each opening having a sub-grid assigned. The 480 × 480 pixel field can be a right-angled grid or a right-angled mesh of horizontal and vertical lines be overlaid to check the openings respectively used to form 100 sub-grids with 48 × 48 pixels.

According to the invention, it is now determined whether a grid with 48 × 48 pixels is sufficient to detect irregularities or errors in the items to be checked Opening to dissolve. The dimension of the opening is the distance in compared to each sub-grid to determine whether the number of the pixel covering the opening is sufficient to analyze the opening. The Resolution is determined by the critical dimension, i. H. of the Diameter of the opening, by the number of those covering the opening Pixel is divided. The resolution is compared to a threshold, such as the 12 nm / pixel threshold to determine if the Resolution is adequate.

After determining the pixel resolution, the grid structure becomes this used to locate the contact openings and their dimensions too determine. In one embodiment, vertical and horizontal Lines of a grid or mesh structure to locate the openings used.

Fig. 18 illustrates the contact position detection process of the module 60 d, in which a grid or a mesh is placed over the contact images aligned in a matrix, the horizontal and vertical axis spacings being set within a specific search range so that the contacts are in one mesh of the Mesh network. At this point, the distances can be changed. Increase or decrease the number of pixels forming the image can be controlled. The search area of the mesh line is preferably set to include the area in which the same pattern or structure repeats at contact openings.

In the contact position detection method shown in FIG. 18 using the stitch search process, it is specified that the mesh units or sub-grids each consist of at least 32 pixels in the horizontal direction and at least 62 pixels in the vertical direction. The search area is determined by moving the imaginary horizontal axis grid line 150 and the imaginary vertical axis grid line 152 within the areas comprising at least 32 pixels on the horizontal axis and at least 62 pixels on the vertical axis. The position of the lowest or weakest digitized electron signal value is detected, so that the contacts in the contact images do not overlap the grid line.

In one embodiment, the stitch search method is like this performed that either the vertical line or the horizontal line is positioned in a first position. The intensity values along the line are summed up to determine the total intensity for the line. The Line is now gradually moved to the next position. The vertical line can, for example, step in along the horizontal axis next position, in which the intensity values along the vertical line can be added up again. In every position the Total intensity value with a predetermined threshold and that previous total compared. An increase in intensity can be seen as Indicate that the edge of the opening has been reached under the Assumption that the openings have a higher intensity than that Possess background intensity. In other embodiments, the Openings have a lower intensity than the background. This Process continues across the entire lattice structure to the openings to locate and / or determine their dimensions and shape.  

After calculating all the totals in one direction, the Process repeated for the other direction, resulting in a complete Characterization of the size, shape and position of the openings leads. This information may be used for subsequent processing different purposes can be used. By knowing the Positions and the shapes of the openings can be unnecessary Avoid processing pixels that are not assigned to an opening. If an irregularity or a Error is found, the exact position of the error or simply determine the faulty opening.

After performing the contact position detection method, the origin of the first grid unit is, for example, the pixel with the number XO = 13 on the horizontal axis and the pixel with the number YO = 23 on the vertical axis (see FIG. 18). Units of the same size can be compared. This is the reason that the contact position detection process is carried out in the manner described above.

The mesh or grid unit can be defined differently. As shown in FIG. 19, a contact opening 153 can be arranged in a mesh unit, a mesh unit being skipped between two such units. As shown in FIG. 20, at least two contact openings 153 can also be arranged in a mesh unit. The position detection method of the grid or mesh method described above can also be used for different image shapes if a pattern of images is repeated in the unit areas, such as square or oval-shaped contact patch or contact point images in contrast to the round contact images mentioned above.

Fig. 18 shows an SEM image of a contact unit (480 × 480 pixels) for the fixing of the grid or the mesh network for carrying out of a contact position detecting method of the invention. As already described above, in this example the grid unit of the present test is set to 32 × 62 pixels, while the number of pixels (XO, XY) of the origin is (13, 23). The determination of the grid unit described above is determined by the movement of the horizontal grid line 150 and the vertical grid line 152 within the search range, which are determined in the manner described above by the respective grid line and are approximately 60 pixels or respectively corresponding to the respective distance of the grid unit about 30 pixels are fixed. In another embodiment, the lines are each analyzed in order to identify the lowest intensity value corresponding to the respective grid line and to determine the position of the openings.

FIGS. 19 and 20 show different types of grid specifications of the type described above. Fig. 21 shows how the grid unit is occupied by pixel units, in order to explain the production of contact intensity profiles. Fig. 22 shows a first intensity profile in a lattice unit, wherein the intensity values of the vertical axis are represented by elimination of the background intensity values before normalization of the profile with respect to. FIG. 23 shows the intensity profile according to FIG. 22 after the background values have been eliminated with a fixed contact threshold value. In the present test, the electronic threshold signal is set at 5, while the number of pixels at the threshold according to FIG. 23 is 20. The checking contact opening spans pixels 20 to 40 along the vertical axis.

FIG. 24 shows the intensity profiles of the SEM images of the contacts according to FIG. 18 after normalization by eliminating the background value. FIG. 25 shows a table with coded results of the contact error checking method according to the invention for the contacts according to FIG. 18. The contacts with a circle in FIG. 24 correspond to the position which is indicated in FIG. 25 by code 4 as contact or contacting error is marked.

Fig. 26 is a table showing a part of the contact failure check results for the sampling points shown in Fig. 15 in the present test with respect to the sampling points of each chip, indicating the number of all contacts which correspond to the respective classification criteria for the contacts according to the present invention . At all five locations of the chips or test areas, the number of classifications for the individual types for the opening found at the location is listed. At point (1,3), for example, 87 contact openings were classified as belonging to type D, while three contact openings were classified as belonging to type E. Five contact openings were classified as type G, while three of the contact openings were classified as type H. It should be noted that 98 openings were checked and classified at each location, which corresponds to a total of 17,510 openings in the 35 regions examined. In one embodiment, this test can be carried out completely within one hour due to the saving in processing time according to the invention. The process is therefore suitable for mass production.

The contact profile calculation module 60 e (1) is used to generate a first intensity profile of the electronic signal values detected above for the individual grid units of the grids specified above. The background value elimination or correction module 60 e (2) is used to generate a second intensity profile from the first intensity profile by subtracting the background value from the first intensity profile for each grid unit.

The first intensity profile and the second intensity profile are under Use of electronic signal values calculated accordingly the pixels contained in the grid units are digitized. The from the Grid units obtained electron signal values, however, include both the electronic signal value of the corresponding contact as well as one electronic signal value from that surrounding the contact Outside area is generated. To get accurate electronic signal values, the only intensity values from the inside of the contact in one Grid unit, the electronic signal background value of outside the contact area, d. H. the one surrounding the contact Range, subtracted from the intensity profile according to the invention, around the to generate a second standardized intensity profile. This is called elimination of the Inscribed "Iscoloreffektes".

In one exemplary embodiment according to the invention, the contact intensity profiles are calculated and the background values are eliminated by the module 60 e in accordance with the following equation 1:

Where X is:
X is the sum of the electron signal values above a predetermined threshold within a mesh or grid unit;
B the sum of the electron signals below a predetermined threshold within a mesh or grid unit;
B _c the number of electron signals whose value is below a predetermined threshold value within a mesh or grid unit;
X _{c is} the number of electron signals whose value within a mesh or grid unit is above a predetermined value;
Y is the electron signal value with background elimination or background correction in a mesh or grid unit.

In equation 1, the predetermined value given above can be by Elimination of the background value to obtain accurate measurement results be determined. In one embodiment, the value is for example 100, but you are not limited to this value.

The Y value, i.e. H. the result of equation 1 is the sum of the terms of the background value corrected electron signals within the lattice or mesh units. In one embodiment, the value Y in Equation 1 sets an upper and a lower limit. If the value of Y is below the lower limit for a specific contact the contact is regarded as faulty. In one embodiment, a Value below the predetermined lower limit as an indication of a faulty contact opening not opened.

Equation 1 is typically used to check contact openings used with irregular shapes. Equation 1 can, for example the formation of openings used to check the photoresist layer be used to form the openings.

In another exemplary embodiment, the contact profiles are calculated and the background value is eliminated in accordance with the following equations 2 to 4:

P _k ^N = (P _k ^N ) '- P _m ^N (2)

P _m ^N = baseline [(P _k ^N ) '] (4)

Here is:
n the number of pixels on the horizontal axis;
k the number of pixels on the vertical axis;
P _{nk is} the digitized signal value of a pixel at position n on the horizontal axis and at position k on the vertical axis;
N the number of the grid or mesh unit checked;
h _i ^{N is} the initial number of pixels on the horizontal axis within a grid or mesh unit;
h _f ^{N are} the number of pixels on the horizontal axis within a mesh or grid unit.

Equations 2 through 4 are described with reference to FIGS. 21 and 22. Fig. 21 shows a graphical representation based pixel units in a mesh or grid unit of a contact used in the inventive calculation of the contact intensity profile. FIG. 22 shows a schematic representation of the first intensity profile within the mesh or grid unit, as calculated before the subtraction of the background value for a contact image according to FIG. 18. In one exemplary embodiment, the intensity profile is generated by stepwise change along an axis and by summing up the intensity values along the axis perpendicular thereto at the individual positions. The accumulated pixel intensities are shown as a function of the pixel number along the other axis. The profile according to FIG. 22 is determined, for example, by moving step by step over the pixel positions along the vertical axis and adding up the pixel intensities in the horizontal direction. In the profile shown in FIG. 22 is an intensity profile results with a spade in the vicinity of the center, which indicates the presence of a contact opening in the special grid or mesh unit. The opening extends approximately from pixel position 16 to pixel position 44 , so that the opening extends in the vertical direction over approximately 28 pixels. The profile has a small indentation in the center of the opening at the top of the spade, indicating a decrease in the detected intensity at the bottom of the opening. This form of the intensity profile is an indication of a normal contact opening.

The value (P _k ^N ) 'from equation 3 is the average electron signal value per pixel of pixel k on the vertical axis. It is obtained by taking the total (the total level of the digitized electron signal values) that corresponds to the respective pixel with the pixel line k on the vertical axis ( FIG. 21; k = 20), ie the height of the curve in FIG. 22, divided by the number of horizontal pixels at the vertical axis position k, which is given by h _f ^N - h _i ^N. Fig. 22 shows the also equation 3 resulting profile. P _m ^N is a minimum value of (P _k ^N ) ', that is, it corresponds to the intensity background or the value of the baseline. P _k ^N therefore corresponds to an average electron ^signal value per pixel when the background value is subtracted.

FIG. 23 shows a second intensity profile after subtracting the background value or the baseline P _m ^N according to equation 2. FIG. 24 shows the standardized second intensity profile for contacts of the contact image according to FIG. 18.

In one exemplary embodiment, the results of equations 2 to 4 are also analyzed by the contacting error checking method according to the invention, in order to classify the contacts as faulty and, if appropriate, to be able to recognize the types of the errors. The second intensity profile ( FIG. 24) of the openings is analyzed with regard to the identification and classification of irregularities or errors.

As shown in Fig. 23, in one embodiment, a threshold, for example 5, is used for the second intensity profile (the average electron signal value per pixel after subtracting the background value). The contact's critical dimension CD ^N is defined as the length (or width) of the peak in the profile at the threshold. As shown in FIG. 23, with a threshold value of 5, the critical dimension for the contact is CD ^N = 40-20 = 20 pixels. The critical dimension CD ^N , which can be, for example, the diameter of the contact opening, can be calculated according to equation 5 below:

Here is:
v _i ^{N is} the initial number of pixels on the vertical axis within the grid or mesh unit;
V _f ^{N is} the end number of pixels on the vertical axis within the grid or mesh unit;

P _k ^N = (P _k ^N ) '- P _m ^N ; and

W _k ^N indicates whether the pixel intensity is above the threshold, ie the following applies:
W _k ^N = 1 if P _k ^{N is} greater than or equal to the threshold
0 if P _k ^{N is} less than the threshold

An average pixel intensity BSE ^N is now calculated for the pixels above the threshold value according to the following equation 6.

It should be noted that Equations 5 and 6 represent an alternative verification method to Equation 1. The mean pixel intensity BSE ^N according to equation 6 corresponds to the value Y calculated in equation 1. The value CD ^N in equations 5 and 6 is replaced by the value X _c in equation 1.

After calculating the number of pixels for CD ^N and the mean pixel intensity BSE ^N for the contact to be checked, these values are used to classify the contact state. In one embodiment, an upper limit value NOC2 and a lower limit value NOC1 are set for the pixel number CD ^N. These limits are used to set a range of acceptable pixel counts for normal contacts. A limit for the mean pixel intensity BSE ^N can also be set. An upper limit NOT2 and a lower limit NOT1 can be used to determine a range of average pixel values to be accepted for normal contact.

The CD ^N and BSE ^N values of the checked contacts are compared to classify the contacts with their respective ranges. In one embodiment, the contacts are classified so that, according to the comparison of the values for CD ^N and BSE ^N with their corresponding ranges, they are divided into one of nine possible classes that correspond to the individual types. An example of the nine possible conditions and their corresponding type classification as well as the corresponding numerical codes are summarized in Table 1 below:

Table 1

The three columns in Table 1 determine the three conditions for depth of the contact openings. They are in the order of decreasing depth arranged. The first column defines three states, namely types A, D and G, from relatively deep contact openings. The second column has three Conditions for normal deep contact openings, namely types B, E and H. The third column defines three states of insufficient contact hole depth, namely types C, F and E. Through these contact opening types are  typically partially open contact openings or non-uniform Contact openings determined. The rows in Table 1 are after increasing contact hole diameter arranged. The first line includes the contact opening types A, B and C with insufficiently small diameters. The second category with types D, E and F are contact openings determined with a normal diameter. Through the third category with Types G, H and I are contact openings with an excessively large size Diameter determined.

As shown in Table 1, type E classification occurs when both CD ^N and BSE ^{N are} within their respective predetermined ranges, indicating normal contact. The other types, in which one of the values or both values lie outside the ranges, are classified in the remaining type classes, which serve as an indication of the different levels of error formation and of different types of contact errors.

The result screen or the result display 60 g serves to display the results of the classification of normal contacts and / or contact errors, which were classified by the contacting error checking module 60 f. The results can be displayed as digitized values for the position of the individual contacts.

FIG. 25 shows a table with examples for the classification and the pixel position of the contact openings according to FIG. 24. Whether a contact is normal or faulty is shown according to the second intensity profile as a numerical code for the position of the individual contacts. The code "5" represents the type E and corresponds to a normal contact, while the code "4" represents a contacting error of the type D. In one embodiment, type "D" represents a closed contact. The X values in Figure 25 represent the initial pixel number for the individual mesh or grid units on the horizontal axis, while the Y values represent the initial pixel number on the vertical axis. FIG. 26 is a table of results contains a review in five places according to the invention at each of the seven regions of the semiconductor wafer. The table shows the number of contacts for the individual classification types at the individual positions.

The values for CD ^N and BSE ^N can be used to classify the contacts in different ways. The type classification for a specific contact can thus serve to specify a specific type of contacting error. If the BSE ^N value for a contact is below a minimum value NOT1, which typically indicates an unopened contact opening, the opening is classified into one of the type classes A, D or G. If the BSE ^N value is greater than a maximum value NOT2, the opening is open, but for a certain reason it is not yet acceptable. The opening may, for example, be shaped irregularly, so that it has, for example, a widening or narrowing in the direction of its base or its underside. In this case, the opening is classified into one of the type classes C, F or I.

If the CD ^N value is below the minimum value NOC1, the detected error may indicate an opening that is too narrow or has an irregular shape, such as an oval. If the CD ^N value is above the maximum value NOC2, this is an indication of an irregularly shaped opening.

FIG. 27 contains a flowchart to illustrate the logical sequence of the processing steps in a manufacturing method for semiconductor components according to the invention. In a certain processing step in the production of semiconductor components, a photoresist structure corresponding to the contact openings is first formed after the photoresist has been applied to certain insulating layers, such as, for example, a nitride film or an oxide film. A photolithographic process is now used (S40). The photoresist structure is created by exposure and development steps.

Now the photoresist structure is used as an etching mask and the one under the Insulating layer lying photoresist structure is used to form the Contact openings etched (S42). Then the inside of the Contact openings cleaned and the wafers are inserted into the in- introduced line SEM facility, where in the manner described above and Way the checking method according to the invention in faulty Contact openings is carried out. Now the inside of the Provide contact openings with a conductive material and it will subsequent process steps for the production of semiconductor components carried out (S46).

FIG. 28 shows a schematic illustration of a flowchart with the logical sequence in one exemplary embodiment of the contact checking method according to the invention. In method step 500 , the parameters used are read in. In one embodiment, the following parameters are used for the method:
N = number of pixels of the SEM image in the direction of the Y axis;
M = number of pixels of the SEM image in the direction of the X axis;
VP (Vertical Pitch) = Y-axis contact distance in the direction of the Y-axis of the grid or mesh;
HP (Horizontal Pitch = horizontal distance) = X-axis contact distance in the direction of the X-axis of the grid or the mesh;
MX = X-axis pixel area for the grid method;
MY = Y-axis pixel area for the grid method;
bse = basic threshold value for a characteristic contact profile in a grid or mesh unit;
NO1 = lower limit for the characteristic profile intensity of normal contacts;
NO2 = upper limit for the characteristic profile intensity of normal contacts;
CD1 = lower limit for the number of pixels of a characteristic profile of normal contacts;
CD2 = upper limit for the number of pixels of a characteristic profile of normal contacts;
XN = total number of SEM images checked (final number or result) per chip or SHOT unit of a wafer;
YN = total number of SEM images checked (final number or result) in a chip or a SHOT unit;
X = checked SEM image order or order per chip or SHOT unit of a wafer;
Y = checked SEM image order or order in a chip or a SHOT unit;
cdata [j] [i] = SEM image signal level at (per) pixel unit.

Now the X-axis value is initialized to 0 in step 502 , while the Y-axis value is initialized to 0 in step 504 . The checking process is now continued along the Y axis in an inner loop formed from steps 506 to 520 until the maximum Y axis value is reached. Now the X-axis value is incremented and the inner loop is repeated again for all Y-axis values. Finally, the outer loop ends when the end values for the X and Y axis values are reached. In the inner loop of FIG. 28, the SEM image data at location (X, Y) and cdata [j] [i] are read in step 506 , which is shown in detail in FIG. 29. It should be noted that in the mesh or lattice method described here, a rectangular lattice structure with perpendicular X and Y axes is used. It should be noted that a right-angled grille is not required. Other grid or mesh shapes can also be used. For example, a triangular or a trapezoidal grid can be used. The grid or mesh structure is selected so that any periodically repeating structure of contacts is detected.

In step 508 in FIG. 28, the position of the contact opening is now determined. Step 508 is shown in detail in Figures 30A-30D. The detection of the contact opening position comprises the selection of the type and the structure of the grid or the mesh which is used to check the contact openings. In the method detailed in FIGS. 30A-30D, one moves pixel by pixel along a first selected direction (in the horizontal direction) and sums up all pixel intensity values in a second direction orthogonal thereto (the vertical direction). The edge of an opening is defined by detecting a noticeable change (a jump) in the intensity. The process continues until a significant drop in intensity is determined by which the opposite edge of the opening is defined. This procedure is used until all openings are located. It should be noted that in steps 550 and 582 in FIGS. 30A-30D, the absolute value of the intensity differences is used. This is due to the fact that the amount of the difference in intensity or the contrast is important for determining the contact points. This method uses different conventions to define the openings by a high or low intensity.

At step 514 in FIG. 28, the contact opening profiles are calculated. This process is illustrated in detail in the flow diagrams in Figs. 31A-31D. The profiles are calculated by analyzing the individual contact openings, which were identified according to the invention by the method described in connection with FIGS . 30A-30D. A profile is calculated for each opening. In one embodiment, the profile is generated by summing up the intensity values in one direction at each point along the other direction orthogonal thereto. The intensity values at the individual points are averaged and displayed to generate the profile. It should be noted that general variables F and F2 are used in the flowcharts of Figures 31A-31D. In a preferred exemplary embodiment according to the invention, these variables are interchangeable with the variables BSE ^N or CD ^N , which were defined in equations 5 and 6 above.

In step 516 in FIG. 28, the contact openings are checked according to the invention. This process is illustrated in detail in Figures 32A-32B. As already described above, the values determined according to FIGS . 31A-31D are analyzed in order to classify the individual contact openings into one of nine possible contact classes. As already mentioned in connection with FIGS. 32A-32B, the variables F and F2 are interchangeable with the variables BSE ^N and CD ^N.

In step 518 in Fig. 28, the Y axis value is incremented and in step 520 it is determined whether the maximum Y axis value has already been reached. If this is not the case, the flowchart returns to the beginning of the inner loop. Otherwise, the X-axis value is incremented in step 522 and the flowchart returns via block 524 to the beginning of the outer loop in step 504 where the Y-axis value is initialized. After the outer loop has ended, the results of the check can be displayed in step 526 .

As already mentioned above, FIG. 29 shows a schematic illustration of a flow chart for the detailed illustration of step 506 in FIG. 28 for reading in the SEM image data. In step 528 the index j is initialized with 0, in step 530 the index i is initialized with 0. In step 03308 00070 552 001000280000000200012000285910319700040 0002019860704 00004 03189tt 532 the data cdata [j] [i] is read, while in step 534 the index i is incremented. In step 536 it is determined whether the index i has already reached its maximum value M. If this is not the case, the flowchart returns to step 532 , in which the data is read in again. Otherwise, the index j is incremented in step 538 and it is determined in step 540 whether j has already reached its maximum value M. In this case the process ends. Otherwise, the flowchart returns to step 530 , in which the index i is reinitialized with 0. The process is then repeated.

In one embodiment, the check according to the invention is carried out faulty contacts after the formation of the contact openings and the Cleaning the inside of the contact openings (ACI = After Cleaning Inspection = check after the cleaning step has been carried out). The However, error checking can also be done on the exposed insulation layer over the wafers in the development process where the Photoresist structure is formed to form the contact openings (ADI = after Development Inspection = review after development has been carried out).

The present invention is not only for the manner described Contact openings applicable, but also for vias every step to directly connect all contact openings and to Contacting the semiconductor substrate and the conductive layers. The The present invention is also for checking structure formation defects after the development process during the Photo processing step to form contact openings suitable.  

In addition to this, the present invention is not only for checking of round contact openings, but also for checking Patterns or structures by capturing the different types of Structural images that repeat themselves regularly.

According to the invention, contact or contacting errors are caused by digitized values recorded exactly without the contact pictures with the naked eye or a microscope. With contacts with a larger one Aspect ratio, contact errors can be confirmed easily and very precisely. In addition, the check for faulty contacts is carried out for the whole Wafer surface within a short period of time in which the for the Proof of contact errors required results are generated. The Process has high efficiency and enables high productivity in mass production.

It is obvious to experts in this field that there are also numerous Modifications and changes to the present inventions can be performed, which is covered by the inventive concept become. The present invention therefore covers all modifications and Variations of the invention are included within the scope of protection Claims fall, as well as the corresponding equivalents.

Claims (60)

1. Method for checking at least part of a semiconductor wafer with the following method steps:

• 1. Reading in image data of a scanning electron microscope (SEM = Scanning Electron Miscroscop) for the part of the semiconductor wafer;
• 2. Identification of image data for a feature of the semiconductor wafer from the data for the part of the semiconductor wafer;
• 3. Calculation of a parameter assigned to the feature from the image data of the feature;
• 4. Comparison of the parameter with a range of parameter values to be accepted; and
• 5. Classification of the feature according to the comparison with the parameter values to be accepted.

2. The method of claim 1, wherein the feature a contact opening in an integrated circuit. 3. The method of claim 2, wherein the contact opening as not open is classified if the parameter is out of range accepting parameter values. 4. The method of claim 1, wherein the feature as faulty is classified if the parameter is out of range accepting parameter values. 5. The method of claim 1, wherein the feature is acceptable is classified if the parameter is within the range too accepting parameter values.   6. The method of claim 1, wherein the SEM image data by Secondary electrons and backscattered electrons are generated. 7. The method of claim 1, wherein the parameter is a dimension of the Feature includes. 8. The method of claim 1, wherein the parameter is a number of SEM Includes image data pixels associated with the feature. 9. The method of claim 1, wherein the parameter is an average Intensity of the pixels assigned to the feature comprises. 10. The method of claim 1, wherein in an additional Method step calculates an image pixel intensity profile of the feature becomes. 11. The method according to claim 10, wherein the calculation of the Image pixel intensity profile the subtraction of a Background intensity value from the intensity values of the pixels in an area comprising the feature. 12. The method according to claim 1 with the following additional method steps:

• 1. Calculation of a second parameter assigned to the feature from the image data of the feature;
• 2. Comparison of the second parameter with a range of values to be accepted for the second parameter;
• 3. Classification of the feature according to the comparison with the range of acceptable values for the second parameter.

13. The method of claim 12, wherein the second parameter is a Dimension of the feature includes. 14. The method of claim 12, wherein the second parameter is a number of SEM image data pixels associated with the feature. 15. The method of claim 12, wherein the second parameter is an average Intensity of the pixels assigned to the feature. 16. The method according to claim 12, wherein the feature only as is classified as acceptable if the first parameter within the Range of acceptable values for the first parameter and if the second parameter is within the range, too accepting values for the second parameter. 17. The method of claim 1 with additional characterization of the feature using a coordinate system, the characterization comprising the following steps:

• 1. superimposing an image of the part of the semiconductor wafer with the coordinate system; and
• 2. Analysis of the intensity values of the pixels arranged along a second axis of the coordinate system at several locations along a first axis of the coordinate system.

18. The method of claim 17, wherein the analysis is the summation of the Intensity values of the pixels arranged along the second axis includes. 19. The method of claim 18, wherein the analysis to detect the Characteristic also the detection of a change in the total Includes intensity values at several locations along the first axis.   20. The method of claim 17, wherein the analysis averages the Intensity values of the pixels requested along the second axis includes. 21. The method of claim 20, wherein the analysis to detect the Characteristic also the detection of a change in the averaged Includes intensity values at several locations along the first axis. 22. The method of claim 17, wherein the characterizing the Detection of a dimension of the feature includes. 23. The method of claim 17, wherein the characterizing the Determination of the position of the feature includes. 24. The method of claim 10, wherein the characterizing the Identification of a pattern or structure from several Features includes. 25. The method of claim 24, wherein the structure is periodic Structure is. 26. The method of claim 10, wherein the coordinate system is a rectangular coordinate system. 27. The method of claim 10, wherein the coordinate system is a triangular coordinate system. 28. The method of claim 17, wherein the coordinate system is a is a trapezoidal coordinate system.   29. The method of claim 1, wherein the SEM image data in the form of digitized gray scale pixel values are available. 30. The method of claim 1, wherein the SEM image data in the form of digitized color-coded pixel values are available. 31. Device for checking at least part of a semiconductor wafer with the following components:

• 1. A device for reading in the image data of a scanning electron microscope (SEM = Scanning Electron Microscop) for the part of the semiconductor wafer;
• 2. A device for identifying image data for a feature on the semiconductor wafer from the data for the part of the semiconductor wafer;
• 3. A device for calculating a parameter assigned to the feature from the image data of the feature;
• 4. means for comparing the parameter with a range of parameter values to be accepted; and
• 5. A device for classifying the feature according to the comparison with the range of parameter values to be accepted.

32. The apparatus of claim 31, wherein the feature is a Contact opening is in an integrated circuit. 33. The apparatus of claim 32, wherein the means for Classify the characteristic of the contact opening as not open classified if the parameter is outside of a range accepting parameter values.   34. The apparatus of claim 31, wherein the means for Classifying the characteristic classifies the characteristic as incorrect, if the parameter is outside the range to be accepted Parameter values. 35. The apparatus of claim 31, wherein the means for Classifying the characteristic classifying the characteristic as acceptable, if the parameter in the range to be accepted Parameter values. 36. The apparatus of claim 31, wherein the SEM image data Secondary electrons and backscattered electrons are generated. 37. The apparatus of claim 31, wherein the parameter is a dimension of the feature. 38. The apparatus of claim 31, wherein the parameter is a number Includes SEM image data pixels associated with the feature. 39. The apparatus of claim 31, wherein the parameter is an average Intensity of the pixels assigned to the feature. 40. Apparatus according to claim 31 with an additional device for Calculation of an image pixel intensity profile of the feature. 41. The apparatus of claim 40, wherein the means for calculation an image pixel intensity profile means for subtracting a Background intensity value from the intensity values of the pixels in the the feature encompassing area. 42. Device according to claim 31 with:

• 1. a device for calculating a second parameter assigned to the feature from the image data of the feature;
• 2. means for comparing the second parameter with a range of acceptable values for the second parameter; and
• 3. A device for classifying the feature according to the comparison with the range of values to be accepted for the second parameter.

43. The apparatus of claim 42, wherein the second parameter is a Dimension of the feature includes. 44. The apparatus of claim 42, wherein the second parameter is a number of SEM image data pixels associated with the feature. 45. The apparatus of claim 42, wherein the second parameter is a includes the average intensity of the pixels assigned to the feature. 46. Apparatus according to claim 42, wherein the feature only as is classified as acceptable if the first parameter within the Range of acceptable values for the first parameter and if the second parameter is within the range, too accepting values for the second parameter. 47. Apparatus according to claim 31 with a device for characterizing the feature using a coordinate system, comprising the following devices:

• 1. a device for superimposing the image of the part of the semiconductor wafer with a coordinate system; and
• 2. A device for analyzing the intensity values of the pixels arranged along a second axis of the coordinate system at several locations along a first axis of the coordinate system.

48. The apparatus of claim 47, wherein the analysis device Device for summing up the intensity values along the second axis arranged pixels. 49. Apparatus according to claim 48, wherein the analysis device for Detection of the feature a device for detecting a Change of the accumulated intensity values in several places along the first axis. 50. The apparatus of claim 47, wherein the analysis device a Means for averaging the intensity values along the second Axis arranged pixels includes. 51. The apparatus of claim 50, wherein the analysis device for Detection of the feature also a device for recording a Change in the averaged intensity values in several places along the first axis. 52. The apparatus of claim 47, wherein the characterization means a device for determining a dimension of the feature includes. 53. The apparatus of claim 47, wherein the characterization means includes means for determining the position of the feature.   54. The apparatus of claim 47, wherein the characterizing means a device for identifying a pattern or structure includes several features. 55. The apparatus of claim 54, wherein the structure is periodic Structure is. 56. The apparatus of claim 47, wherein the coordinate system is a is a rectangular coordinate system. 57. The apparatus of claim 47, wherein the coordinate system is a triangular coordinate system. 58. The apparatus of claim 47, wherein the coordinate system is a is a trapezoidal coordinate system. 59. The apparatus of claim 31, wherein the SEM image data is in the form of digitized gray scale pixel values are available. 60. The apparatus of claim 31, wherein the SEM image data is in the form of digitized color-coded pixel values are available.