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Text File | 1994-01-14 | 18.6 KB | 442 lines

≡≡ Introduction Introduction The program LASIDRC.EXE is a design rule checking program that performs various layout design rule checks by making 2-dimensional bitmaps of drawing layers and then doing logical operations on the bitmaps. The program has some major changes and improvements over earlier versions of LASI design rule checkers: 1. The program reads a Check File which contains parameters and operators that perform one or more checks. You can write your own Check File, and devise any type of design rule checks that you may want, within the limits of the available operations. 2. The program now can find "near miss errors" where one area misses being to be connected to another area in a drawing by a single smallest drawing unit. 3. The program can be interrupted at any check within the processing of a Check File, the state will be saved, and checking will continue in the area where it was suspended if LASILL is started again. The program works on a cell drawing in the default directory (drawing directory), and scans the cell in small areas, performing its sequence of operations. The results may be displayed on a monitor, may be stored in a disk file, or may be printed on a line printer. Automatic or manual hardcopies of the display may be made using the same hardcopy programs that LASI.EXE uses. Running LASIDRC Running LASIDRC To run LASIDRC you first need to write a Check File as explained below. This file contains small "programs" that tell LASIDRC what to do. Make the drawing directory the default directory and type "LASIDRC". LASIDRC will come up in a setup display, providing it finds the drawing files: FORM.DBD, CELLS4.DBD and CONSTS4.DBD. It will also allocate memory for LASI objects and its bitmaps. If any of this fails, it will tell you so and will return to DOS. When the Setup Display comes up, you can enter or change any parameters by moving through the parameters using the up, down, left, right or ENTER keys and then typing in any value. The values will be changed if any characters are typed and the location is then moved. You can step around and around until you have the parameters as you want them. The parameters are as follows: 1. The "Name of Cell to DRC" is the main cell you want to check. Note that this also checks any lesser cells in the main cell. 2. The "Name of Check File" is the name of the Check File that LASIDRC will use. It will always have the extension ".CHK", which will automatically be added to the name. This may include a path. 3. The "Starting Check Number" is the test in the Check File where you want the checking to start. This allows you to skip over some tests. 4. The "Finishing Check Number is the last test you want to do. This allows some trailing tests to be omitted. 5. The Summary File switch. You may make a Summary File (always named LASIDRC.SUM). This is an appended file, which will keep information on all tests until it is erased. 6. The Summary Print switch. You may also print the summary information on a printer as the program runs. Alternately, you can just print the Summary File when it is done. 7. The Enable switches. There are two enables for the PAUSE and HCPY operators. You can turn these operators on and off as you please without editing the Check File. 8. The Resolution and Distance Parameters. The resolution and distance in the check file may be overridden if you want. These values stay in place until new RESOLUTION= or DISTANCE= parameters are encountered in the Check File in any of the following tests. Leaving these to blank (press the Delete key) causes them to default to the minimum scale unit and zero. 9. The Starting Point. You may start checking areas anywhere by writing the bottom-left coordinates in the setup. This allows you to go to an certain area in a cell without doing all the previous areas. Leaving these parameters blank causes them to be ignored at first and then be set to the coordinates of the last area being checked. The setup is slightly "smart"; it checks and adjusts parameters to conform to LASIDRC's checking rules. Units are automatically added to any dimensions. You will also notice that where "y" or "n" is wanted, anything but "y" will set "n". To start checking, press F10. Once you start checking, the parameters are saved in the LASIDRC.SET file and are returned when LASIDRC is run again. When LASIDRC runs a short status is displayed which moves up and down the screen as a screen saving feature. You may jump to the NEXT CHECK by pressing F10 again. You may abort checking by pressing ESC. You will go back to the Setup Display. When this is done, the last area position and the check number will be saved in the setup. If you start LASIDRC.EXE again this information will be restored. Press ESC to go from the Setup to DOS. Note: There may be a short delay if ESC is pressed, be patient. Pressing F2 in Setup will read the contents of the Check File as it is seen by LASIDRC. That is, the defaults for parameters will be listed and any operators that have been disabled by making them into comments will not be shown. Pressing F3 in Setup will shell to DOS. You can run your favorite editor to make changes to the Check File, for example. Once in a while there will not be enough contiguous memory available to run a program; in that case you need to exit LASIDRC and go back to DOS. You may check the available memory by pressing F4. If a Check File is read completely, the program will terminate normally and go back to DOS. Certain setup parameters will be set to their default values. The Check File Check File Format A Check File consists of one or more test sequences or checks arranged in blocks that contain parameters and operators. Each block starts with a TITLE parameter and is ended with an OPERATORS parameter. The OPERATORS parameter is always followed by a set of OPERATORS that are enclosed in brace characters "{" and "}". Characters may be upper or lowercase. The format is as follows: TITLE=aaaa<nl> (40 char. max.) []=optional [RESOLUTION=nnnn<nl>] (in physical units) <nl>=newline (CRLF) [DISTANCE=nnnn<nl>] (in physical units) [LOCATION=xxxx,yyyy<nl>] (in physical units) OPERATORS=<nl> {<nl> [OPERATOR<nl>] . . . }<nl> TITLE=bbbb<nl> etc. Check Parameters: TITLE= is the name of a particular test, and must be present. If no new title is read, the Check File is considered finished. RESOLUTION= is the physical size of each bit in a bitmap. This will be snapped to multiples of the basic units used in the drawing. Making this larger speeds up checking, but, details smaller than this number may be lost. This defaults to the previous setting if not present. DISTANCE= is the distance by which bitmaps will be expanded when spacing checks are being done. It also affect the position is the areas being checked. This defaults to the previous setting. LOCATION= sets the point on a cell of where to start scanning. This is the bottom-left corner of the area to be scanned. This does not default to any previous values. OPERATORS= begins the sequence of operator mnemonics that do the actual checking. The block of operators always starts with "{" and ends with "}". Each operator is written on a new line (CR-LF) and may contain arguments separated by a comma ",". Operators are read character by character starting after "=". The right brace "}" terminates the operations and the present check. There is space for a maximum of 50 operators in the sequence. The variables above are recognized by only their first two characters and may be upper or lower case. For example, "op=" is equivalent to "OPERATORS=". A semicolon may be added to an operator line, which has the effect of making everything to the right a comment. You may "turn off" and operator by putting a ";" as the first character in the line. This lets you leave temporary operators in place in the file while you are working out a test. Working Maps The program maintains several internal 640x640 bitmaps. Only two are available to the user. These are the R (results) and S (secondary) maps. All tests are done by making and moving layer maps into the R and S working maps, where the various operators can work on them. R and S maps are arranged in a 2-map "stack" as shown below: PUSH layer map ────┐ ┌─────────┐ │ │ R │<─┐<── R Operator Map Stack ├─│───────┤ │ │ S │──┴─── RS Operator └─────────┘ To do any operations on maps you first push a layer map onto the map stack. When a map is pushed into R, the contents of R are first pushed into S. Certain operators work with the R map and some work with both the R and S maps. The results are always placed in the R map. Operators MAP,layer This creates a layer map file on the hard disk, which may be retrieved by other operators. Layer is a number from 0 to 64. Layer 0 is a special layer, will store the R map for later use at any stage of a checking sequence. You must ALWAYS use the MAP operator to generate a layer map if you are going to use that layer map later. PUSH,layer Retrieves a layer map from the hard disk and pushes the map onto the map stack. The contents of the R map are moved to the S map. The contents of the S map are lost. PUSH,0 retrieves and pushes a MAP,0 that may have been previously stored. NOTR, ANDRS, ORRS, XORRS These are the logical operators that do just what they indicate. The results are placed in the R map and the S map remains unchanged. SETR,CLRR These are rarely used operators that set all bits of R to "1" or "0" respectively. DBLR This doubles the bits in X and Y directions so that single bits may be displayed better. This is used automatically by EXPR (below). EXPR[,offset] This is the single map expand operator. It performs an iterative octagonal (see below) expansion on the R map. Each iteration expands the pattern by ONE RESOLUTION UNIT. The results are placed in the R map and the original R map is lost. The results represent a pattern produced by single "0s" in the map as the "1s" merge with each expansion pass. The optional offset is a correction that may be used if found necessary. The offset is the number of iterations (or resolution units) to be subtracted from the expansion so that the distance parameter gives the correct results. EXPRS[,offset] This expands the R and S maps using an iterative octagonal expansion, and places the results in the R map. Each iteration is one resolution unit. The original R and S maps are lost. Since there are two separate maps, the result is the intersection of the maps as they expand. TESTR This is a conditional branching operator that tests if any bits are set to "1" in the R map. If there are any "1s" the sequence of operators continues. If there are no results, the rest of the operators are skipped and the sequence of operators starts over again in the next drawing area. This is used to determine is there is anything to print or display. DSPR,color index,sparse modulus This displays the R map as a rectangular pattern on the monitor screen. The color index is the usual integerr (0 to 15) used by the PC video to set a color: 0=black, 1= blue, 2=green, etc. The sparse modulus is a integer that allows only those pixels whose X and Y position divided by the modulus that leaves a remainder of 0 to be displayed. This "thins out" the filled patterns to give a better display or print. For all pixels, the modulus is 1; for every other pixel, the modulus is 2, etc. DSP,map,color index,sparse modulus This is the same as DSPR except it displays a stored map. Use this to display the layers as a background when displaying any results. PAUSE This produces a pause after a display so that you can examine the screen. Without it, LASIDRC would go on to the next area to be checked. This is enabled by the Setup switch. HCPY This calls the hardcopier automatically to produce a picture of the screen after any results are displayed. If the Print Summary Setup switch is set this does not work, since it would disrupt the summary printing. This must also be enabled by the Setup switch. An Example If included in the LASI files, the demonstration layout (compressed in DEMO.EXE) contains a sample Check File named DEMO.CHK. This has been written to work with the demonstration, but can serve as an example of how to write a file. Examining this file should make the preceding information much clearer. Octagonal Expansion Octagonal Expansion When an expansion is done, an iterative process is used to enlarge the map patterns. With each pass the pattern is enlarged by one bit by shifting it in each of the four orthogonal directions (+x,-x,+y,-y). It is also shifted diagonally, on the average, .707 of the time. This produces an octagonal pattern if the original pattern is a single point. * * * * * Octagonal single point expansion * * * * * * * after four passes * * * * * * * * * * * * * * * * * * * * * * X * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * Optimizing Parameters Optimizing Parameters Resolution can be made as small as 1 basic unit used in a drawing. Making the Resolution larger allows checking to be done much faster because larger pieces of a drawing can be checked at a time and less iterations are necessary when checking. The time required to check is roughly in inverse proportion to the 3rd power of the Resolution. That is, if you halve your Resolution it will run about 8 times faster. Unless you have a very fast computer, the highest Resolution is best used on small cells or for checks that involve small dimensions. For example, contact coverage or checking for small gaps in metal runs might run at the smallest Resolution. Making Resolution too large can cause errors to be missed because details cannot be resolved smaller than that size and roundoffs may occur. However, scanning for gross errors can quickly be done using a larger Resolution. The Distance parameter will affect the test time, since each iteration of an expansion takes about the same amount of time. Distance will also affect the size and position of the areas being checked. Distance can be set to 0, but a small correction, depending on the Resolution, will be made so that checked areas will overlap slightly. Missed and False Errors Missed and False Errors When checking distances, if programmed correctly, LASIDRC should always find an flag distances <= (Distance - Resolution). For example, a 10 um Distance and a Resolution of .5um should find anything less than or equal to 9.5um. Note that as the Resolution approaches zero, this distance approaches the Distance. This does not mean that all distances will be accepted if they are greater than (Distance - Resolution). For 45 deg. diagonal distances, there can be an uncertainty that is less than +/- half the Resolution, due partly to the way that LASIDRC works and due partly to numerical roundoff problems. For angles that are in a range centered around odd multiples of 22.5 deg. ( 22.5, 67.5, etc.) there is an exaggeration of the expansion distance. This may flag oddly shaped objects. Since LASIDRC expands areas using an octogonal pattern, these exaggerations correspond to the octogon vertex peaks or about an 8 percent exaggeration at most. Since LASIDRC looks for single bits when doing a single layer expansion, once in a while on odd shapes, the map can produce single bit extensions or notches. LASIDRC will find these and will flag them, even though they are an artifact. You should examine these and see if there really is anything wrong. In fact, the way that LASIDRC works often picks out patterns that are not good layout practice. LASIDRC works in such a way that sharp corners tend to be rounded, just as actual photomasking and etching might do. Keep this in mind when setting the Distance parameter. For example, the distance between two adjacent corners will be seen by LASIDRC as a little more than the actual tip to tip distance. The method by which LASIDRC works is sensitive to gross errors which are well beyond the actual flagging threshold. It is virtually impossible for LASIDRC to miss these. LASIDRC will find "near miss" errors in which there is a gap between filled areas that is greater than or equal to the value set as the Resolution. Set the Resolution to the smallest physical unit (1 basic drawing unit), and set the Distance to some value large enough to find all small gaps, but small enough to let LASIDRC run quickly. On strange shapes, LASIDRC will sometimes flag small notches. Ignore these if they cause no trouble. Disclaimer Disclaimer The LASIDRC.EXE program is furnished on an "as is" basis. LASIDRC will make a "best effort" to call to attention any possible layout errors. Experience should confirm that it doesn't miss much. However, the author or anyone distributing the program cannot assume responsibility for how the program is used, how it is programmed or for the results of its use. The program cannot be absolutely guaranteed to find all instances in a layout that may result in incorrect function of an integrated circuit or other device. LASIDRC is to be considered as a valuable aid to actual visual inspection and the users own knowledge.