WO2008031744A1

WO2008031744A1 - Method and system for adapting objects of a circuit layout

Info

Publication number: WO2008031744A1
Application number: PCT/EP2007/059225
Authority: WO
Inventors: Kuang-Hao Lay; Alexandre Anatolievich Arkhipov; Vadim Viktorovich Manuylov; Yefim Belenky; Linard Karklin; Jeroen Pieter Frank Willekens
Original assignee: Sagantec Israel Ltd
Current assignee: Sagantec Israel Ltd
Priority date: 2006-09-14
Filing date: 2007-09-04
Publication date: 2008-03-20
Anticipated expiration: 2009-03-14

Abstract

A method, a system and a computer program product of adapting objects of a circuit layout. The circuit layout comprises objects including a group of critical objects which are designed to comply with a critical layout restriction. In the method according to the invention a compliance value is generated to quantify a compliance of a printed image of the group of critical objects with the critical layout restriction. The printed image of the group of critical objects results from applying a manufacturing process to the group of critical objects of the circuit layout. If the compliance value deviates more than a predetermined value (PV) from perfect compliance, a proximity object is selected. The proximity object is a non-critical object located within a predetermined proximity of the group of critical objects. Finally, the proximity object is adapted for improving compliance of the printed image with the critical layout restriction.

Description

METHOD AND SYSTEM FOR ADAPTING OBJECTS OF A CIRCUIT LAYOUT

FIELD OF THE PRESENT SYSTEM: The invention relates to a method for adapting objects of a circuit layout.

The invention further relates to a system and to a computer program product.

BACKGROUND OF THE PRESENT SYSTEM: Integrated circuit layouts generally comprise objects wherein a set of objects is a representation of an integrated circuit. The objects in an integrated circuit layout typically must comply with a set of rules, so called design rules. Design rules are specific to a particular manufacturing process of integrated circuits. A set of design rules specifies certain geometric and connectivity restrictions between objects of the integrated circuit layout to account for variability in manufacturing processes of integrated circuits. Different manufacturing processes typically comprise different sets of design rules. Compliance of the objects to a specific set of design rules associated with a specific manufacturing process ensures that the integrated circuit layout can be manufactured using the specific manufacturing process.

Layout processing systems generally check compliance of an integrated circuit layout with a set of design rules. Subsequently, in a case of non-compliance, the layout processing system adapts the integrated circuit layout to substantially comply to the set of design rules. However, some critical objects may not be altered by the layout processing system. For example, an analog sub-circuit in the integrated circuit layout may be designed by hand such that, for example, some critical objects in the analog sub-circuit are arranged symmetrically with respect to a virtual line in the integrated circuit layout.

A drawback of the known layout processing methods is that the layout of the integrated circuit layout when manufactured using the specific manufacturing process may not function correctly. SUMMARY OF THE PRESENT SYSTEM:

It is an object of the present system to provide an improved method of adapting objects.

According to a first aspect of the present system, the object is achieved with a method of adapting objects of a circuit layout, the circuit layout comprising objects including a group of critical objects complying with a critical layout restriction, the objects being a representation of an integrated circuit, the method comprising the steps of: generating a compliance value quantifying a compliance of a printed image of the group of critical objects with the critical layout restriction, the printed image resulting from applying a manufacturing process to the group of critical objects of the circuit layout, determining a deviation of the compliance value from perfect compliance, if the deviation is more than a predetermined value, selecting a proximity object being a non-critical object located within a predetermined proximity of the group of critical objects, and adapting the selected proximity object of the circuit layout for improving compliance of the printed image with the critical layout restriction.

The effect of the method in accordance with the present system is that the compliance of the printed image of the group of critical objects with respect to the critical layout restriction is improved without altering the group of critical objects in the circuit layout. The method according to the present system checks whether the printed image complies with the critical layout restriction. If the printed image deviates more than a predetermined value from compliance with the critical layout restriction, a proximity object is selected. The selected proximity object is located in a predetermined proximity of the group of objects, and is a non-critical object, thus not belonging to the group of critical objects. The predetermined proximity is a distance away from the group of critical objects within which neighboring objects in the circuit layout have an effect on the printed image of the group of critical objects when the manufacturing process is applied to the circuit layout. The predetermined proximity typically varies for different manufacturing processes. By adapting the selected proximity object which is located in the predetermined proximity, the printed image of the group of critical objects is altered without altering the group of critical objects in the circuit layout.

The group of critical objects, for example, comprises objects within the circuit layout which may not be altered. For example, the group of critical objects may be an analog sub-circuit in which, for example, lines in a poly-layer of an integrated circuit must be arranged symmetrically with respect to an imaginary symmetry line, or, for example, the group of critical objects comprises objects in different layers of an integrated circuit, which must be aligned to each other, or must overlay according to specific requirements. Often, the group of critical objects is designed by hand to ensure compliance with the critical layout restriction.

Proximity effects are well known in manufacturing processes, especially in the so called low k-i chip manufacturing processes. For example, in optical lithography all objects in a circle of an optical halo around a specific object influence the quantity of light which reaches the specific object, and as such influence the imaging of the specific object. Also in electron beam lithography, elastically scattered electrons generally have sufficient energy to travel a certain distant where they can influence the imaging of neighboring objects. The printed image of the group of critical objects may not comply with the critical layout restriction associated with that group of critical objects. This non-compliance of the printed image may be caused, for example, by lens aberrations in the imaging tool of the optical lithography process, or, for example, caused by a resist used for imaging the printed image onto a silicon wafer, or caused by the processing of the resist, or, for example, caused by an etching process, or, for example, caused by the proximity effects present in the used manufacturing process. The inventors have realized that these proximity effects in the manufacturing process can be used to improve the compliance of a printed image of a group of critical objects with the critical layout restriction without altering the group of critical objects in the circuit layout. By adapting the selected proximity object located within the predetermined proximity, the printed image of the group of critical objects is altered. By selectively changing the proximity object, improved compliance of the printed image with the critical layout restrictions can be achieved. The objects of the circuit layout typically are depicted as polygons which may be defined by boundaries of the polygon, by a path having a specific width, and/or by the corners of the polygon. The adapting of the selected proximity object may result in moving the proximity object within the circuit layout and/or may result in reshaping the proximity objects within the circuit layout.

The method according to the present system can advantageously be combined with known layout processing methods performed by known layout processing tools. Typically the known layout processing tools must be adapted to be able to perform the method according to the present system. However, this combination of the method according to the present system and known layout processing methods enables a reduction of the processing time. During the known layout processing methods, the objects of the integrated circuit layout must be scanned after which compliance with the set of design-rules is checked. When combining the method according to the present system with the known layout processing methods, the scanning of objects can now both be used for checking compliance with the set of design rules and for selecting and adapting the proximity object, thus reducing the processing time.

The integrated circuit may be a representation of a miniaturized electrical circuit, also commonly known as a chip, or may be a representation of a part of the chip. Alternatively, the integrated circuit may be a representation of a miniaturized construction, also commonly known as nanostructures, comprising, for example, mechanical nanostructures, magnetic nanostructures, chemical nanostructures and biological nanostructures.

In an embodiment of the method, the circuit layout comprises an analog sub- circuit comprising the group of critical objects. The analog sub-circuit in the integrated circuit layout, for example, may be critical and, for example, may not be altered using a layout processing engine or tool. By altering the proximity of the analog sub-circuit, the compliance of the printed image of the analog sub-circuit with a critical layout restriction can be improved without altering the analog sub-circuit itself. In an embodiment of the method, the step of adapting the selected proximity object further comprises a step of: generating a proximity-constraint being a representation of a required adaptation of the selected proximity object for improving compliance of the printed image of the group of critical objects with the critical layout restriction, adding the proximity-constraint to a set of constraints associated with the circuit layout, the set of constraints comprising design-rule-constraints for applying a design rule to objects of the circuit layout, and adapting the objects of the circuit layout to substantially comply with the set of constraints. A benefit of this embodiment is that the adaptation of the selected proximity object is compliant with the design rules. Because the set of constraints in the method according to the present system comprises both the proximity-constraint and the design-rule-constraints, the step of adapting the objects of the circuit layout to substantially comply with the set of constraints results in the selected proximity object being adapted to improve compliance of the printed image of the group of critical objects with the critical layout restriction, while the adaptation of the selected proximity object and any adaptation of the remainder of the circuit layout substantially complies with the design rules.

In an embodiment of the method, the step of generating a compliance value further comprises comparing the printed image of the group of critical objects with the group of critical objects of the circuit layout. A benefit of this embodiment is that it provides a relatively simple method of quantifying compliance of the printed image with the critical layout restriction.

In an embodiment of the method, the step of adapting the selected proximity object is model based comprises a steps of: applying a predetermined adaptation of the selected proximity object, analyzing an effect of the predetermined adaptation on the compliance value of the printed image of the group of critical objects, and generating a function associating the effect of the predetermined adaptation on the compliance value with the predetermined adaptation of the selected proximity object. A benefit of this embodiment is that a relation between the predetermined adaptation and the effect of this predetermined adaptation is expressed in the function. The function may, for example, be used to determine whether the predetermined adaptation improves the compliance of the printed image of the group of critical objects with the critical layout restrictions, or may, for example, be used to determine whether the adaptation of the selected proximity object can be such that the compliance value of the printed image may deviate less than the predetermined value from perfect compliance.

In an embodiment of the method, the step of adapting the selected proximity object further comprises using the function for adapting the selected proximity object to improve compliance of the printed image with the critical layout restriction, in which the compliance value is deviating less than the predetermined value from perfect compliance. A benefit of this embodiment is that the function is used to determine a quantity of the required adaptation of the selected proximity object to improve the compliance value such that it deviates less than the predetermined value from perfect compliance.

In an embodiment of the method, the steps of the method are applied iteratively by in each iteration, selecting a further proximity object, and applying a further predetermined adaptation to generate a further function associating a further effect of the further predetermined adaptation on a further compliance value with the further predetermined adaptation, the model comprising the function and/or the further function for improving compliance of the printed image of the group of critical objects with the critical layout restriction. A benefit of this embodiment is that the iterative applying of a predetermined adaptation for adapting the proximity object enables to collect the effects of predetermined adaptations on the associated compliance values, resulting in a model providing information on what adaptation of which selected proximity object achieves which effect in the optical image of the group of critical objects. Using this model enables selection of a specific adaptation of a specific proximity object for substantially solving the non-compliance of the printed image, or selection of several adaptations of several proximity objects which must all be applied together for solving the non-compliance of the printed image of the group of critical objects with the critical layout restrictions. In an embodiment of the method, the steps of the method are applied iteratively by in each iteration, applying a further predetermined adaptation of the selected proximity object to generate a further function associating a further effect of the further predetermined adaptation on a further compliance value with the further predetermined adaptation, the model comprising the function and/or the further function for improving compliance of the printed image of the group of critical objects with the critical layout restriction. A benefit of this embodiment is that the iterative applying of a plurality of predetermined adaptations enables the method to find a specific predetermined adaptation which, for example, has an optimal effect on the improvement of the compliance of the printed image with the critical layout restriction.

In an embodiment of the method, the model comprises the function and/or the further function comprising the predetermined adaptation and/or the further predetermined adaptation, respectively, improving compliance of the printed image with the critical layout restriction. Functions associating a specific predetermined adaptation which does not result in an improvement of the compliance of the printed image with the critical layout restrictions are, for example, discarded and not included in the model.

In an embodiment of the method, the step of adapting the selected proximity object is rule based, the rules for adapting the selected proximity object being retrieved from a database. A specific set of rules, for example, belongs to a specific manufacturing process. The specific set of rules may, for example, provide information on the changes to be expected in the printed image of the group of critical objects when altering the proximity of the group of critical objects in the circuit layout in a prescribed way. Using a rule based method of adapting the selected proximity object typically results in relatively short processing time because a lengthy iteration process can be avoided.

In an embodiment of the method, the critical layout restriction is selected from a group comprising: symmetry between two critical objects from the group of critical objects, alignment of critical objects to a certain position in the circuit layout, minimum extension of one object with respect to another object, minimum area coverage between two critical objects, minimum dimensions of a critical object, and minimum space between two critical objects.

In an embodiment of the method, the steps of the method are applied iteratively by in each iteration, selecting and adapting a further proximity object for further improving compliance of the printed image of the group of critical objects with the critical layout restriction. A benefit of this embodiment is that a further proximity object may be used to further improve the compliance of the printed image with the critical layout restriction. The improvement of the printed image with the critical layout restriction by adapting the proximity object may be limited. By also adapting a further proximity object, the compliance of the printed image with the critical layout restriction may be improved.

In an embodiment of the method, the circuit layout including a plurality of groups of critical objects, wherein the steps of the method are applied iteratively by in each iteration, selecting a group of critical objects of the plurality of groups of critical objects for improving compliance of the printed image associated with the selected group of critical objects with the critical layout restriction.

According to an embodiment of the present system, the object is achieved with a system configured for adapting a circuit layout of objects including a group of critical objects complying with a critical layout restriction. The objects together represent an integrated circuit. The system may include a compliance generator, a comparator, an object selector, and a layout adapter. The compliance generator may generate a compliance value quantifying a compliance of a printed image of the group of critical objects with the critical layout restriction. The printed image of the group of critical objects results from applying a manufacturing process to the group of critical objects of the circuit layout. The comparator determines a deviation of the compliance value from perfect compliance. The object selector selects a proximity object that is a non-critical object located within a predetermined proximity of the group of critical objects if the deviation is more than a predetermined value. The layout adapter adapts the selected proximity object of the circuit layout for improving compliance of the printed image of the group of critical objects with the critical layout restriction.

According to a further embodiment of the present system, the object is achieved with a computer program product stored on a computer readable medium. The computer program product is arranged to adapt objects of a circuit layout including a group of critical objects complying with a critical layout restriction, wherein the objects are a representation of an integrated circuit. The computer program product may include program portions arranged for: generating a compliance value quantifying a compliance of a printed image of the group of critical objects with the critical layout restriction, the printed image resulting from applying a manufacturing process to the group of critical objects of the circuit layout; determining a deviation of the compliance value from perfect compliance; selecting a proximity object being a non-critical object located within a predetermined proximity of the group of critical objects if the deviation is more than a predetermined value; and adapting the selected proximity object of the circuit layout for improving compliance of the printed image with the critical layout restriction.

Accordingly to yet a further embodiment of the present system, the object is achieved with a computer program stored on a computer readable medium. The computer program may include: a program portion arranged to generate a compliance value quantifying a compliance of a printed image of a group of critical objects with a critical layout restriction, the printed image resulting from applying a manufacturing process to the group of critical objects of a circuit layout; a program portion arranged to determine a deviation of the compliance value from perfect compliance; a program portion arrange to select a proximity object that is a non-critical object located within a predetermined proximity of the group of critical objects if the deviation is more than a predetermined value; and a program portion arranged to adapt the selected proximity object of the circuit layout for improving compliance of the printed image with the critical layout restriction. In accordance with an embodiment, the computer program may be utilized to program a processor for operation in accordance with the computer program. BRIEF DESCRIPTION OF THE DRAWINGS:

These and other aspects of the present system are apparent from and will be elucidated with reference to the illustrative embodiments described hereinafter.

In the drawings: Fig. 1 shows a flowchart of a method according to the present system,

Fig. 2 shows a schematic representation of the system according to the present system,

Figs. 3A, 3B, 3C, 3D and 3E show several steps performed by the method according to the present system for improving the compliance of a printed image of a group of critical objects with a critical layout restriction being a symmetry restriction,

Figs. 4A, 4B, 4C and 4D show steps performed by the method according to the present system for improving the compliance of a printed image of a group of critical objects with a critical layout restriction, being a minimum area of overlap between the objects of the group of critical objects, and Figs. 5A, 5B, 5C, 5D, 5E and 5F show several steps performed by the method according to the present system for generating a function associating the effect of the predetermined adaptation of the proximity object on the compliance value with the predetermined adaptation of the proximity object.

The figures are purely diagrammatic and not drawn to scale. Particularly for clarity, some dimensions are exaggerated strongly. Similar components in the figures are denoted by the same reference numerals as much as possible.

DETAILED DESCRIPTION OF THE EMBODIMENTS: The following are descriptions of illustrative embodiments that when taken in conjunction with the drawings will demonstrate the above noted features and advantages, as well as further ones. In the following description, for purposes of explanation rather than limitation, specific details are set forth such as architecture, interfaces, techniques, etc., for illustration. However, it will be apparent to those of ordinary skill in the art that other embodiments that depart from these details would still be understood to be within the scope of the appended claims. Moreover, for the purpose of clarity, detailed descriptions of well-known devices, circuits, and methods are omitted so as not to obscure the description of the present system. It should be expressly understood that the drawings are included for illustrative purposes and do not represent the scope of the present system.

Fig. 1 shows a flowchart of a method according to an embodiment of the present system. The method according to the present system comprises a circuit layout 10 as input. In a step of "Groups of CO?" 12, the method checks if there are groups of critical objects GO1 , GO2 (e.g., see Figs. 3 and 4) which have to comply with a critical layout restriction. If no groups of critical objects GO1 , GO2 exist, the method ends with stop 38. Generally, a group of critical objects, by design, complies with the critical layout restriction; however, when applying a manufacturing process to the group of critical objects GO1 , GO2 to generate a printed image PM , PI2, PI3, PI4(e.g., see Figs. 3 and 4), the printed image may no longer comply with the critical layout restriction. If groups of critical objects GO1 , GO2 can be identified, the method selects a group of critical objects GO1 , GO2 in a step of "select GCO" 14 and selects an associated critical layout restriction in a step of "associate CLR" 18. The group of critical objects GO1 , GO2 may, for example, be an analog sub-circuit being part of the circuit layout 10, or, for example, may be mechanical nanostructures possibly combined on a miniaturized electrical circuit, or, for example, an optical structure possibly combined on a miniaturized electrical circuit. The associated critical layout restriction may, for example, be a symmetry requirement (e.g., see Figs. 3A to 3E) between two critical objects CO1 , CO2 from the group of critical objects GO1 , or an alignment of critical objects to a certain position in the circuit layout, or a minimum area A of overlap (e.g., see Figs. 4A to 4D) between two critical objects CL, CH, or minimum dimension of a critical object, or a minimum space between two critical objects. In parallel, the method according to the present system applies a chosen manufacturing process to the circuit layout 10 in a step of "Apply manufacturing process" 16 to obtain an image 60, 62 (e.g., see Figs. 3 and 4) of the circuit layout 10, including a printed image PM , PI2, PI3, PI4 (e.g., see Figs. 3 and 4) of the group of critical objects GO1 , GO2. The manufacturing process may be applied to the circuit layout 10 by actually patterning the circuit layout 10, for example, on a silicon wafer, or the manufacturing process may be applied to the circuit layout 10 by simulating the manufacturing process using a patterning model (not shown) of the manufacturing process. Examples of manufacturing processes are, for example, optical lithography processes, or, for example, electron-beam lithography processes, or, for example, imprint lithography, or, for example, contact printing, or, for example, a manufacturing process using techniques similar to inkjet printing. Next, the method according to the present system generates a compliance value CV1 , CV2, CV3, CV4, CV5, CV6, CV7, CV8 (e.g., see equations (1 ) to (6)) quantifying a compliance of the printed image PU , PI2, PI3, PI4 of the selected group of critical objects GO1 , GO2. The compliance value CV1 , CV2, CV3, CV4, CV5, CV6, CV7, CV8, for example, quantifies a symmetry between the two critical objects CO1 , CO2, or, for example, quantifies an area of overlap between two further critical objects CL, CH. Using the generated compliance value CV1 , CV2, CV3, CV4, CV5, CV6, CV7, CV8 and the selected group of critical objects GO1 , GO2 and the associated critical layout restriction, the method determines the difference Δ between the compliance value CV1 , CV2, CV3, CV4, CV5, CV6, CV7, CV8 and perfect compliance in a step of "determine Δ of CV and perfect compliance" 22. The term "perfect compliance" as utilized herein is intended to indicate an ideal level of compliance with the circuit layout, such as exact compliance with the circuit layout, although as may be readily appreciated, variations on the compliance level are intended to be encompassed when interpreting the phrase "perfect compliance" herein. Subsequently, the method compares the difference Δ with a predetermined value PV in a step "Δ > PV?" 24. If the deviation between the difference Δ is more than the predetermined value PV (so: "Δ >PV?" = Yes), the method continues by checking if there are proximity objects PO available to improve the compliance in a step "PO available?" 26. If there are proximity objects PO available (so: "PO available?" = Yes), proximity object PO1 , PO2, PO3, APO is selected from the circuit layout 10 in a step "select PO" 28 and, subsequently adapted for improving compliance of the printed image PH , PI2, PI3, PI4 with the critical layout restriction in a step "adapt PO in circuit layout" 30. The selected proximity object PO1 , PO2, PO3, APO is located in a predetermined proximity of the group of critical objects GO1 , GO2. The predetermined proximity is a distance away from the group of critical object GO1 , GO2 within which neighboring objects in the circuit layout 10 have an effect on the printed image PM , PI2, PI3, PI4 of the group of critical objects GO1 , GO2 when the manufacturing process is applied to the circuit layout 10.

If the deviation between the compliance value CV and perfect compliance is less than the predetermined value PV (so: "Δ >PV? = No), or if there are no proximity objects PO1 , PO2, PO3, APO available (so: "PO available?" = No), the method according to the present system, for example, disregards the selected group of critical objects GO1 , GO2 and searches the circuit layout 10 for other groups of critical objects which comply with a critical layout restriction. The method according to the present system may, for example, label the disregarded group of critical objects, for example, to enable review of the disregarded groups of critical objects by an operator.

In an embodiment of the method according to the present system, the method re-applies the manufacturing process to the circuit layout which includes the adapted proximity object PO1 , PO2, PO3, APO in the step of "applying manufacturing process" 16, from which a further compliance value is generated in the step of "Generate CV" 20 which is subsequently used to determined the difference between the further compliance value and perfect compliance. This further compliance value may, for example, be used to see whether the adaptation of the selected proximity object PO1 , PO2, PO3, APO has improved compliance of the printed image with the critical layout restriction. If the compliance of the printed image with the critical layout restriction is improved, the method according to the present system may, for example, link the adaptation of the selected proximity object PO1 , PO2, PO3, APO to the selected group of critical objects GO1 , GO2 and store this in a database as a successful adaptation for later reference. If a printed image of a similar group of critical objects must comply with a similar critical layout restriction, the database may be consulted and the successful adaptation may be applied to the similar group of critical objects. This typically results in a reduction of the processing time to obtain improved compliance of the printed image PU , PI2, PI3, PI4 of a group of critical objects GO1 , GO2 with the critical layout restriction.

In an embodiment of the method according to the present system, the process step of "adapt PO in circuit layout" 30 comprises a step of "generate proximity- constraint" 32, a step of "add proximity-constraint to set of constraints" 34, and a step of "adapt circuit layout to comply with set constraints" 36. In the step of "generate proximity-constraint" 32 a proximity-constraint is generated associated with the selected proximity object PO1 , PO2, PO3, APO. The proximity-constraint is a representation of a required adaptation of the selected proximity object for improving compliance of the printed image PU , PI2, PI3, PI4 of the group of critical objects GO1 , GO2 with the critical layout restriction. Subsequently the proximity-constraint is added to a set of constraints 160 (see Fig. 2) associated with the circuit layout 10 in a step of "Add proximity-constraint to set constraints" 34. The set of constraints 160 comprises design- rule-constraints for applying a design rule to the objects of the circuit layout 10. Subsequently, the circuit layout 10 is adapted to substantially comply with the set of constraints 160 including the proximity-constraint in the step of "adapt circuit layout to comply with set constraints" 36. Compliance of the objects of the circuit layout 10 to a specific set of design rules associated with a specific manufacturing process ensures that the circuit layout 10 can be manufactured using the specific manufacturing process. This embodiment enables the adaptation of the selected proximity object PO1 , PO2, PO3, APO such that the resulting adapted circuit layout substantially complies with the set of design rules and as such can be manufactured using the specific manufacturing process, while compliance of the printed image PM , PI2, PI3, PI4 with the critical layout restriction is improved.

Fig. 2 shows a schematic representation of an embodiment of a system 100 according to the present system. The system 100 comprises a scanner module 1 10 and a process simulator 120. The scanner module 1 10 receives the circuit layout 10 and scans the circuit layout 10 to identify objects, critical objects CO1 , CO2, CL, CH (e.g., see Figs. 3 and 4) and proximity objects PO1 , PO2, PO3, APO (e.g., see Figs. 3 and 4) from the circuit layout 10. The process simulator 120 receives the circuit layout 10 and simulates an image 60, 62 (see Fig. 3 and 4) of the circuit layout 10 resulting from simulating the applying of the manufacturing process to the circuit layout 10. Alternatively, the system 100 may receive the image 60, 62 of the circuit layout 10 as input, wherein the image 60, 62, for example, is produced by a simulator separate from the system (not shown), or, for example, is produced on silicon and subsequently digitized (not shown). The system 100 according to the present system comprises a CO selector 1 12 for selecting a group of critical objects GO1 , GO2 which comply with a critical layout restriction, and comprises a PO selector 1 14 for selecting proximity objects PO1 , PO2, PO3, APO located in the predetermined proximity of the of the group of critical objects GO1 , GO2. The system 100 according to the present system comprises a compliance generator 130 for generating a compliance value CV1 , CV2, CV3, CV4, CV5 quantifying a compliance of a printed image PH , PI2, PI3, PI4 of the group of critical objects GO1 , GO2 with the critical layout restriction. The compliance generator 130, for example, receives the printed image PM , PI2, PI3, PI4 from the process simulator 120, the group of critical objects from the CO selector 1 12 and the associated critical layout restriction associated with the group of critical objects GO1 , GO2 from, for example, an input "list of CO and associated CLR" 40. The printed image PM , PI2, PI3, PI4 is part of the image of the circuit layout 10 or the output layout 50 produced by the process simulator 120. The compliance value CV1 , CV2, for example, quantifies a symmetry between the two critical objects CO1 , CO2 (e.g., see Fig. 3), or, for example, the compliance values CV3, CV4, CV5 quantifies an area of overlap between two further critical objects CL, CH (e.g., see Fig. 4). A comparator 140 receives the compliance value CV1 , CV2, CV3, CV4, CV5 and a predetermined value PV 42 representing a maximum deviation of the compliance value CV1 , CV2, CV3, CV4, CV5 from perfect compliance. The comparator 140 determines the difference Δ between the compliance value CV1 , CV2, CV3, CV4, CV5 and perfect compliance, and if the difference Δ deviates more than the predetermined value PV 42, the system 100 according to an embodiment of the present system generates a proximity-constraint in the constraint generator 150, and adds the proximity-constraint to the set of constraints 160 associated with the circuit layout 10. The set of constraints 160 comprises design- rule-constraints for applying a design rule to the objects of the circuit layout 10. Subsequently, the system 100 according to the present system comprises a layout adapter 170 for adapting the objects of the circuit layout 10 to obtain an output layout 50 being a circuit layout 10 substantially complying with the set of constraints 160. Because the set of constraints 160 comprises the proximity-constraint and the design- rule-constraints, the selected proximity object PO1 , PO2, PO3, APO has been moved to improve compliance of the printed image PH , PI2, PI3, PI4 of the group of critical objects GO1 , GO2 with the critical layout restriction, and simultaneously the output layout 50 of the system 100 according to the present system substantially complies with the set of design rules which ensures that the output layout 50 can be manufactured using the manufacturing process associated with the design rules of the set of constraints 160. In an embodiment of the system 100, the system 100 comprises a database 180. The database 180, for example, stores rules for adapting the selected proximity object PO1 , PO2, PO3, APO to obtain improved compliance of the printed image PM , PI2, PI3, PI4 with the critical layout restriction.

In an embodiment of the layout adapter 170, the layout adapter 170 may include a solver module 175 for solving the set of constraints 160 and generating instructions for adapting the circuit layout 10 such that the circuit layout 10 adapted according to the instruction, substantially complies with the set of constraints 160. The solver module 175 may use well known methods for solving the set of constraints 160, for example, simplex algorithm or, for example, constraint graph longest path algorithm. Alternatively, the solver module 175 is a separate module of the system 100 which provides the instructions for adapting the circuit layout 10 to the layout adapter module 170 which subsequently adapts the circuit layout 10 according to the instructions.

In an embodiment of the system 100 according to the present system, the system 100 is integrated in a known layout processing system. In this embodiment, the system may, for example, share the scanner module 1 10, the solver module 175 and the layout adapter module 170 with the known layout processing system.

Figs. 3A, 3B, 3C, 3D and 3E show several steps performed by the method according to the present system for improving the compliance of a printed image PU , PI2 of a group of critical objects GO1 with a critical layout restriction. The critical layout restriction of Figs. 3A to 3E is a symmetry restriction which requires a first critical object CO1 and a second critical object CO2 to be symmetrically arranged with respect to a imaginary symmetry line S. The group of critical objects GO1 shown in Figs. 3A to 3E are illustratively located on different layers of the circuit layout 10, in which the first critical object CO1 and the second critical object CO2 are located in the so called Poly layer of the circuit layout 10, and a further object Ad is located in the so called Active layer of the circuit layout 10. The group of critical objects GO1 , for example may represent a pair of analog transistors in which the first and the second critical object CO1 , CO2 must be arranged symmetrically with respect to the symmetry line S. Fig. 3A represents the circuit layout 10 as originally designed and shows the objects, depicted as polygons of the poly layer and of the active layer. The objects of the poly layer are indicated with Pd1 , Pd2, Pd3, Pd4, Pd5, and the object in the active layer is indicated with Ad. The group of critical objects GO comprises a first critical object CO1 , which is the polygon of the poly layer indicated with Pd3, a second critical object CO2 which is the polygon of the poly layer indicated with Pd4, and a third critical object Ad which is the polygon of the active layer. As can be seen from Fig. 3A, the group of critical objects GO1 have been designed symmetrically with respect to the symmetry line S and thus comply with the symmetry restriction.

Fig. 3B represents an image 60 of the circuit layout 10 shown in Fig. 3A when a manufacturing process is applied to the circuit layout 10 of Fig. 3A. The manufacturing process, for example, is simulated to produce the image 60 of the circuit layout 10. In the printed image, the designed polygons Pd1 , Pd2, Pd3, Pd4, Pd5 of the poly layer now are processed to become the processed polygons Pp1 , Pp2, Pp3, Pp4, Pp5 of the poly layer, including the first critical object CO1 and the second critical object CO2. The designed polygon Ad of the active layer now is processed to become the processed polygon Ap of the active layer. It is clear that the printed image PU of the group of critical objects GO does not comply with the symmetry restriction. The reason for the non-compliance of the printed image PU with the symmetry restriction is that a distance between the polygon indicated with Pp2 and the first critical object CO1 is larger than the distance between the polygon indicated with Pp5 and the second critical object CO2. When applying the manufacturing process to the group of critical objects GO1 , the proximity of the first critical object CO1 is different compared to the proximity of the second critical object CO2, which results in a difference of the processing of the critical objects CO1 , CO2, resulting in a reduction of the designed symmetry between the first and second critical objects CO1 , CO2.

Fig. 3C shows the image 60 of the circuit layout 10 and indicates an embodiment of determining a compliance value CV1 , CV2 from the printed image Pl for quantifying a compliance of a printed image PU with the symmetry restriction. In the embodiment shown in Fig. 3C two additional symmetry-check lines Lsc1 and Lsc2 have been added, substantially perpendicular to the symmetry line S. The intersections between each additional symmetry-check line Lsc1 , Lsc2 and the boundaries of the processed critical objects CO1 , CO2 provide additional checkpoints Xi,i, Xi,₂, xi,3, xi,₄. X2,i, X2,2, X2,3, X2,4 from which, together with a coordinate x_s of the symmetry line S along the symmetry-check lines, for example, an equation can be generated for determining a first and a second compliance value CV1 , CV2:

CV1 = I Ix_{1 1} - XsI - |xi,4 - XsI I + I |xi,2 - XsI - |xi,s - x_s| I (1 )

CV2 = I |x₂, 1 - XsI - |x₂,4 - XsI I + I |X2,2 - XsI - |X2,3 - XsI I (2)

where | x_n,_m - x_s I indicates an absolute value of a distance between the checkpoint x_n,_m and the symmetry line S. If the processed first critical objects CO1 and the processed second critical objects CO2 are symmetrical with respect to the symmetry line S both the first and the second compliance value CV1 , CV2 will be zero. In the embodiment shown in Fig. 3C the second compliance value CV2, for example, deviates less than 5% from perfect compliance, while the first compliance value CV1 , for example, deviates more than 15% from perfect compliance. If, for example, a predetermined value PV of 10% is acceptable, the method according to the present system will select a proximity object PO1 (see Fig. 3D) and will adapt the selected proximity object PO1 to improve compliance of the first compliance value CV1 and, for example, will disregard the second compliance value CV2.

Fig. 3D shows an embodiment of an output layout 50 comprising an adapted proximity object PO1. The polygons shown in Fig. 3D again represent the circuit layout as originally designed. In the current example, the increased distance between the polygon indicated with Pd2 and the first critical object CO1 illustratively caused the non- compliance of the printed image PM with the symmetry restriction. Accordingly, the polygon indicated with Pd2 is selected as the proximity object PO1 and will be adapted to reduce the distance between the selected proximity object PO1 and the first critical object CO1. This is indicated with the dashed arrow in the selected proximity object PO1. Fig. 3E subsequently shows the image 62 of the output layout 50 comprising the adapted proximity object. As can clearly be seen from Fig. 3E, the symmetry between the processed critical objects CO1 , CO2 has improved. And again, the compliance of the printed image PI2 with the symmetry restriction can be quantified using the additional symmetry-check line Lsc1 , Lsc2 calculating the first and the second compliance values CV1 , CV2, as previously done at Fig. 3C. Due to the adaptation of the selected proximity object PO1 , both compliance values CV1 , CV2 have been improved. If, for example, the improvement of both compliance values CV1 , CV2 is such that they both deviate less than the predetermined value PV of, for example, 10% from perfect compliance, the method searches the circuit layout for further groups of critical objects which comply with a critical layout restriction and checks compliance of the printed image of the further groups of critical objects with the critical layout restriction. However, if, for example, the first compliance value CV1 still deviates more than the predetermined value PV from perfect compliance, the method according to the present system will either adapt the polygon indicated with Pd2 further to achieve further improved compliance of the printed image PI2 with the symmetry restriction, or, for example, selects a further polygon as a new proximity object PO1 which subsequently is adapted to improve compliance of the printed image PI2 with the symmetry restriction.

Alternative methods to determine a compliance value may be apparent to the person skilled in the art, for example, by determining a center of gravity for each of the processed critical objects CO1 , CO2 in the printed image PM and comparing the results with the center of gravity of the designed critical objects CO1 , CO2 of the group of critical objects GO1.

Figs. 4A, 4B, 4C and 4D show steps performed by the method according to the present system for improving the compliance of a group of critical objects GO2 with layout restriction, being a minimum extension of a critical object being a critical line CL over the edges of a critical object being a critical contact CH. In the manufacturing process of the circuit layout 10, the critical contact CH is located in a "via layer" of the circuit layout 10 and the critical line CL is located in a metal layer of the circuit layout 10 which is generally applied on top of the via layer. The critical contact CH and the critical line CL together form a group of critical objects GO2 which are designed to comply with the critical layout restriction in which the critical line CL must extend a predefined dimension over the critical contact CH.

In the embodiment shown in Fig. 4A the metal layer consist of an array of parallel objects M1 , M2, M3, M4 and the critical line CL, and the via layer consist of the critical contact CH (drawn as a dashed square in the critical line CL, indicating that the critical contact CH is underneath the critical line CL and fully covered by the critical line CL). The extension of the critical line CL over the critical contact CH is designed to be larger than a minimum extension. To achieve full compliance, the extension of the critical line CL in the printed image PI3 of the group of critical objects GO2 must not be less than the predetermined value d_m. This critical layout restriction can be described in three equations for calculating three compliance values:

CV3 = (y_m,i - y_c,i) - d_m (3)

CV4 = (y_c,2 - y_m,2) - d_m (4)

CV5 = (x_c - x_m) - d_m (5)

where y_{m n} is the y-coordinate of an edge of the line in the metal layer, y_{c n} is the y- coordinate of the contact in the via layer, x_m, x_c are the x-coordinate of an edge of the line in the metal layer and the contact in the via layer, respectively, and d_m is the minimum extension for complying with the critical layout restriction. Perfect compliance of the compliance values CV3, CV4, CV5 is achieved if all compliance values CV3, CV4, CV5 are larger or equal to zero.

Fig. 4B shows the image 60 of the circuit layout 10 of Fig. 4A when applying the manufacturing process. As can clearly be seen from Fig. 4B, the critical line CL does not overlap the critical contact CH. The compliance values CV3 and CV4 will probably be close to zero, as there is a remaining extension. However the compliance value CV5 will definitely be less than zero because the critical line CL no longer overlaps the critical contact CH. A possible reason for the non-compliance of the printed image PI3 of the group of critical objects GO2 with the critical layout restriction is that the array of parallel metal lines M1 , M2, M3, M4 (see Fig. 4A) is located relatively far away from the critical line CL.

Fig. 4C shows an output layout 50 indicating a possible adaptation of the circuit layout 10 in which the array of parallel metal lines M1 , M2, M3, M4 have been selected as an array of proximity objects APO. By extending the parallel metal lines M1 , M2, M3, M4 as indicated with the dashed arrows, the distance between the array of metal lines M1 , M2, M3, M4 and the critical line CL has been reduced, which will improve compliance of the printed image PI4 with the critical layout restriction.

Fig. 4D shows an image 62 of the output layout 50 when applying the manufacturing process, including a printed image PI4 of the group of critical objects GO2 when the array of selected proximity objects APO has been adapted. As clearly can be seen, the critical line CL extends over the critical contact CH in all directions. Whether or not this adaptation of the selected proximity objects results in an acceptable extension of the critical line CL depends on the actual calculated compliance values CV3, CV4, CV5 which may not deviate more than a predetermined value PV from perfect compliance.

Figs. 5A, 5B, 5C, 5D, 5E and 5F show several steps performed by the method according to the present system for generating a function F1 , F2 associating the effect of the predetermined adaptation Δ1 , Δ2 of the proximity object PO2, PO3 on the compliance value CV6, CV7, CV8 with the predetermined adaptation Δ1 , Δ2 of the proximity object PO2, PO3. The critical layout restriction of Figs. 5A to 5F again is a symmetry restriction which requires the third critical object CO3 and the fourth critical object CO4 to be symmetrically arranged with respect to the imaginary symmetry line S. The group of critical objects GO3 shown in Figs. 5A to 5F are located on different layers of the circuit layout 10, in which the third critical object CO3 and the fourth critical object CO4 are located in the so called Poly layer of the circuit layout 10, and the further critical object Ad is located in the so called Active layer of the circuit layout 10. The group of critical objects GO3 represent a pair of analog transistors in which the third and the fourth critical object CO3, CO4 must be arranged symmetrically with respect to the imaginary symmetry line S, similar to the arrangements and restrictions shown in Fig. 3A.

Fig. 5A represents the circuit layout 10 as originally designed and shows the objects being represented as polygons of the poly layer and of the active layer. The objects of the poly layer are indicated with Pd6, Pd7, Pd8, Pd9, and the object in the active layer is indicated with Ad. The group of critical objects GO3 comprises a third critical object CO3, which is the polygon of the poly layer indicated with Pd7, a fourth critical object CO4 which is represented as a polygon of the poly layer indicated with Pd8, and the further critical object Ad which is represented as the polygon of the active layer. As can be seen from Fig. 5A, the group of critical objects GO3 has been designed symmetrically with respect to the imaginary symmetry line S and thus comply with the symmetry restriction.

Fig. 5B represents an image 60 of the circuit layout 10 shown in Fig. 5A when a manufacturing process is applied to the circuit layout 10 of Fig. 5A. The manufacturing process, for example, is simulated to produce the image 60 of the circuit layout 10. In the printed image, the designed polygons Pd6, Pd7, Pd8, Pd9 of the poly layer now are processed to become the processed polygons Pp6, Pp7, Pp8, Pp9 of the poly layer, including the third critical object CO3 and the fourth critical object CO4. The designed polygon Ad of the active layer now is processed to become the processed polygon Ap of the active layer. It is clear that the printed image PI5 of the group of critical objects GO3 does not comply with the symmetry restriction. One of the reasons for the non-compliance of the printed image PI5 with the symmetry restriction is that the fourth critical object CO4 is deformed due to the presence of the polygon Pd9. Using a symmetry-check line similar to the one used in Fig. 3C a sixth compliance value CV6 can be determined for the printed image PI5 of Fig. 5B. Using checkpoints x1 , x2, x3 and x4, the sixth critical value CV6 becomes:

CV6 = Hx₁ - XsI - |x₄ - XsI I + I N - Xs| - |xs - x_s| I (6)

where | x_n - x_s | indicates an absolute value of a distance between the checkpoint x_n and the imaginary symmetry line S. If the processed third critical object CO3 and the processed fourth critical object CO4 are symmetrical with respect to the symmetry line S, the sixth compliance value CV6 will be zero.

Fig. 5C shows an output layout 52 in which a first predetermined adaptation Δ1 is applied. The polygon indicated with Pd9 has been assigned as a second proximity object PO2. The first predetermined adaptation Δ1 is applied to the second proximity object PO2 as indicated with the dashed arrow. Subsequently the effect of this first predetermined adaptation Δ1 is determined by simulating the output layout 52 of Fig. 5C and determining a seventh compliance value CV7 of the printed image PI6 of this adapted circuit layout 10. This is shown in Fig. 5D in which an image 62 is shown as a result of the first predetermined adaptation. An improved compliance with the symmetry restriction can be observed as the deformation due to the presence of the polygon Pd9 has been reduced. The seventh compliance value CV7 is determined using equation (6) and compared with the sixth compliance value CV6 to see whether the first predetermined adaptation Δ1 actually provided an improvement on the symmetry restriction of the circuit layout 10. For this, for example, a first critical value difference Δ_Cvi is calculated using:

Δ_Cvi = CV7 - CV6 (7)

In Fig. 5E a further output layout 54 is shown in which a second predetermined adaptation Δ2 is applied. The polygon indicated with Pd6 has been assigned as a third proximity object PO3. The second predetermined adaptation Δ2 is applied to the third proximity object PO3 as indicated with the dashed arrow. The dashed arrow indicates the movement of the whole proximity third proximity object PO3. Subsequently the effect of this second predetermined adaptation Δ2 is determined by simulating the further adapted circuit layout 54 of Fig. 5E and determining an eighth compliance value CV8 of the printed image PI7 of this further adapted circuit layout 10. This is shown in Fig. 5F in which an image 64 is shown as a result of the second predetermined adaptation. A reduced compliance with the symmetry restriction can be observed because a width of the third critical object CO3 has been reduced. The eighth compliance value CV8 is determined using equation (6) and compared with the sixth compliance value CV6 to see whether the second predetermined adaptation Δ2 actually provided an improvement on the symmetry restriction of the circuit layout 10. For this, for example, a second critical value difference Δ_Cv₂ is calculated using:

Δ_CV2 = CV8 - CV6 (8)

From each of these predetermined adaptations a first and a second function F1 , F2 can be generated. The first function F1 associates the effect of the first predetermined adaptation on the seventh compliance value CV7, with the first predetermined adaptation. The second function F2 associates the effect of the second predetermined adaptation on the eighth compliance value CV8, with the second predetermined adaptation. An example of the first and second functions are, for example, shown in equations 9 and 10.

F1 (Δ_Cvi , Δ1 ) = ( (Δcvi/Δ1 ) ^* Δ_POi + C1 (9)

F2 (Δ_CV2 , Δ2) = ( (Δ_CV2/Δ2) ^* Δ_PO2 + C2 (10)

in which Δ_POi and Δ_POi represent a specific variation of the first and second proximity object, respectively, and C1 and C2 represent a constant. The result of the exemplified functions F1 and F2 provide a first order estimation of the compliance value obtained when adapting the associated proximity objects PO1 , PO2. The skilled person can easily improve this first order estimation to a higher order estimation without departing from the scope of the present system.

The first and second functions F1 , F2 may be part of a model describing the effect of predetermined adaptations Δ1 , Δ2 on compliance values CV1 , CV2. This model may be used to determine what adaptation Δ_POi, Δ_PO2 would be effective to obtain improved compliance of the printed image PI5, PI6, PI7 with the critical layout restriction. As can be seen from the Figs. 5D and 5F, the first predetermined Δ1 adaptation results in an improvement of the compliance value CV7, while the second predetermined adaptation Δ2 results in a reduction of the compliance value CV8. From the information gained so far, it seems logical to use the first function F1 to calculate the specific adaptation Δ_POi of the second proximity object PO2 required to obtain a compliance value which deviates less than the predetermined value from perfect compliance. Generally the model would contain functions for predetermined adaptations of substantially all proximity objects to judge what specific adaptations can be taken to improve the compliance value CV6. In addition, the model may comprise combined functions providing a relation between effects on the compliance value CV6 when specific adaptations of a combination of proximity objects is applied. From these combined functions, an estimation of a combination of specific adaptations can be selected which will result in an improvement of the compliance value CV6.

The methods of the present system are suited to be carried out by a computer program, such program containing modules corresponding to one or more of the individual steps or acts described and/or envisioned by the present system. Such program may of course be embodied in a computer-readable medium 102, such as an integrated chip, a peripheral device, magnetic medium, optical medium and/or other storage device that may be suitably applied. For example, one or more portions of the system 100 shown in Fig. 2 may be arranged as a processor suitably programmed, for example, by such a computer program.

It should be noted that the above-mentioned embodiments illustrate rather than limit the present system, and that those skilled in the art will be able to design many alternative embodiments without departing from the scope of the appended claims. In addition, the section headings included herein are intended to facilitate a review but are not intended to limit the scope of the present system. Accordingly, the specification and drawings are to be regarded in an illustrative manner and are not intended to limit the scope of the appended claims.

Any reference to objects in layouts such as in the integrated circuit or the circuit layout may refer to polygons being defined by boundaries, paths, corners, and/or other layout features.

In the claims, any reference signs placed between parentheses shall not be construed as limiting the claim. Use of the verb "comprise" and its conjugations does not exclude the presence of elements, steps, or acts other than those stated in a claim. The article "a" or "an" preceding an element does not exclude the presence of a plurality of such elements. The present system may be implemented by means of hardware comprising several distinct elements, by means of a suitably programmed computer and any combinations thereof. In the device claim enumerating several means, several of these means may be embodied by one and the same item of hardware. No specific sequence of acts or steps is intended to be required unless specifically indicated. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage.

Claims

1. A method of adapting objects of a circuit layout, the circuit layout comprising objects including a group of critical objects complying with a critical layout restriction, the objects being a representation of an integrated circuit, the method comprising the acts of: generating a compliance value quantifying a compliance of a printed image of the group of critical objects with the critical layout restriction, the printed image resulting from applying a manufacturing process to the group of critical objects of the circuit layout, determining a deviation of the compliance value from perfect compliance, if the deviation is more than a predetermined value, selecting a proximity object being a non-critical object located within a predetermined proximity of the group of critical objects, and adapting the selected proximity object of the circuit layout for improving compliance of the printed image with the critical layout restriction.

2. The method as claimed in claim 1 , wherein the circuit layout comprises an analog sub-circuit comprising the group of critical objects.

3. The method as claimed in claim 1 or 2, wherein the act of adapting the selected proximity object further comprises acts of: generating a proximity-constraint being a representation of a required adaptation of the selected proximity object for improving compliance of the printed image of the group of critical objects with the critical layout restriction, adding the proximity-constraint to a set of constraints associated with the circuit layout, the set of constraints comprising design-rule-constraints for applying a design rule to the objects of the circuit layout, and adapting the objects of the circuit layout to substantially comply with the set of constraints.

4. The method as claimed in claim 1 or 2, wherein the act of generating a compliance value further comprises comparing the printed image of the group of critical objects with the group of critical objects of the circuit layout.

5. The method as claimed in claim 1 or 2, wherein the act of adapting the selected proximity object is model based comprising a step of: applying a predetermined adaptation of the selected proximity object, analyzing an effect of the predetermined adaptation on the compliance value of the printed image of the group of critical objects, and generating a function associating the effect of the predetermined adaptation on the compliance value with the predetermined adaptation of the selected proximity object.

6. The method as claimed in claim 5, wherein the act of adapting the selected proximity object further comprises the act of using the function for adapting the selected proximity object to improve compliance of the printed image with the critical layout restriction, in which the compliance value is deviating less than a predetermined value from perfect compliance.

7. The method as claimed in claim 5, wherein the acts of the method are applied iteratively by in each iteration, selecting a further proximity object, and applying a further predetermined adaptation to generate a further function associating a further effect of the further predetermined adaptation on a further compliance value with the further predetermined adaptation, the model comprising at least one of the function and a further function for improving compliance of the printed image of the group of critical objects with the critical layout restriction.

8. The method as claimed in claim 5, wherein the acts of the method are applied iteratively by in each iteration, applying a further predetermined adaptation of the selected proximity object to generate a further function associating a further effect of the further predetermined adaptation on a further compliance value with the further predetermined adaptation, the model comprising at least one of the function and the further function for improving compliance of the printed image of the group of critical objects with the critical layout restriction.

9. The method as claimed in claim 7, wherein the model comprises at least one of the predetermined adaptation and the further predetermined adaptation, respectively, improving compliance of the printed image with the critical layout restriction.

10. The method as claimed in claim 1 or 2, wherein the act of adapting the selected proximity object is rule based, the rules for adapting the selected proximity object being retrieved from a database.

1 1. The method as claimed in claim 1 or 2, wherein the critical layout restriction is selected from a group comprising: - symmetry between two critical objects from the group of critical objects, alignment of critical objects to a certain position in the circuit layout, minimum extension of one object with respect to another object, minimum area coverage between two critical objects, minimum dimensions of a critical object, and - minimum space between two critical objects.

12. The method as claimed in claim 1 or 2, wherein the acts of the method are applied iteratively by in each iteration, selecting and adapting a further proximity object for further improving compliance of the printed image of the group of critical objects with the critical layout restriction.

13. The method as claimed in claim 1 or 2, the circuit layout including a plurality of groups of critical objects, wherein the acts of the method are applied iteratively by in each iteration, selecting a group of critical objects of the plurality of groups of critical objects for improving compliance of the printed image associated with the selected group of critical objects with the critical layout restriction.

14. A system configured for adapting a circuit layout, the circuit layout comprising objects including a group of critical objects complying with a critical layout restriction, the objects being a representation of an integrated circuit, the system comprising: a compliance generator configured for generating a compliance value quantifying a compliance of a printed image of the group of critical objects with the critical layout restriction, the printed image of the group of critical objects resulting from applying a manufacturing process to the group of critical objects of the circuit layout, a comparator configured for determining a deviation of the compliance value from perfect compliance, an object selector configured for selecting, if the deviation is more than a predetermined value, a proximity object being a non-critical object located within a predetermined proximity of the group of critical objects, and a layout adapter configured for adapting the selected proximity object of the circuit layout for improving compliance of the printed image of the group of critical objects with the critical layout restriction.

15. A computer program product stored on a computer readable medium, the computer program product being arranged to perform the method as claimed in claim 1.

16. A computer program stored on a computer readable medium, the computer program comprising: a program portion arranged to generate a compliance value quantifying a compliance of a printed image of a group of critical objects with a critical layout restriction, the printed image resulting from applying a manufacturing process to the group of critical objects of a circuit layout, a program portion arranged to determine a deviation of the compliance value from perfect compliance, a program portion arrange to select a proximity object being a non-critical object located within a predetermined proximity of the group of critical objects if the deviation is more than a predetermined value, and a program portion arranged to adapt the selected proximity object of the circuit layout for improving compliance of the printed image with the critical layout restriction.