The method of smoothing regulation type optical approach correcting light mask pattern
Technical field
The present invention relates to a kind of method of regulation type optical approach correcting light mask pattern.
Background technology
From first integrated circuit in 1958 since TIX's invention, IC industry has obtained swift and violent development, has only several components and parts to develop into present chip piece from initial chip piece (integrated circuit) and surpasses 1,000,000 even ten million devices.Its performance has had huge raising accordingly, is used in the every field in the life.Integrated circuit becomes the core of advanced information society.Photoetching technique is the driving force of integrated circuit fabrication process development, also is a wherein the most complicated technology.With respect to other single manufacturing technology, photoetching has revolutionary contribution to the raising of chip performance.Before photoetching process begins, the structure of integrated circuit can be earlier by specific device replication to a piece on the quartz glass plate of big (with respect to the silicon chip of production usefulness) mask by name, the light (as 248 microns ultraviolet ray) that produces specific wavelength by lithographic equipment copies to the structure of integrated circuit on the mask on the used silicon chip of production chip then.Duplicate from mask the silicon chip process at this, can produce the distortion of circuit structure.Especially present 180 microns and following manufacturing process stage have been arrived, if this distortion does not go correction can cause the failure of whole manufacturing technology.This distortion is owing to optical approximate effect (Optical ProximityEffect) causes.Correct this distortion, the common practice of semiconductor industry is to utilize to be selected in the method for carrying out structure compensation on the mask in advance, this technology is called the correction of optical approximate effect again, be called for short OPC (Optical ProximityEffect Correction), it is undertaken in advance circuit structure on the mask being compensated by calculating some data that photoetching process produces in the integrated circuit production, thereby reach the distortion of chip circuit structure minimum degree on silicon chip, the yield rate that this has improved in the chip production process has guaranteed the normal function of integrated circuit.The rule-based OPC of optical proximity correction (rule based OPC) adds the enhanced features pattern at last handling process for the pattern that all satisfy given standard.Fig. 1 is a light mask pattern for revising, close on the requirement of modification method through regulation type optical in conjunction with lithographic process window, the correction of isolation pattern district and intensive graph area in the last light mask pattern (being the exposure figure comparatively dense) can differ greatly, and therefore a very big step (see figure 2) can occur in isolation pattern district and intensive graph area junction.Carry out photoetching with so adjacent two mask blanks of revising the difference of the correction that existence is bigger between segment, figure after the exposure can take place near big step than great fluctuation process, usually make step place size decreases, size than isolation pattern is little, (see figure 3) brings difficulty for the control of photoetching process dimension of picture and process window.The scope of the deviation of the exposure figure that the equipment that lithographic process window refers to fix can be controlled, the basic law of process window: the litho pattern size is big more, and process window is big more.Also have by reducing optics correction fragment length, with this step effect that weakens, but this method can make the correction segment increase several times, so also need to handle with several times computer running time, causes waste of time.
Summary of the invention
The technical problem to be solved in the present invention provides a kind of method of smoothing regulation type optical approach correcting light mask pattern, and it can make the figure after the exposure present mild gradual change in isolation pattern district and intensive graph area junction, and saves computing time.
For solving the problems of the technologies described above, the method of smoothing regulation type optical approach correcting light mask pattern of the present invention, this method is after carrying out conventional regulation type optical approach correcting light mask pattern, further comprising the steps of: the correction segment at intensive graph area and step place, junction, isolation pattern district is the benchmark segment, the correction of at least two continuous correction segments being adjacent is adjusted between the correction of its previous correction segment and the value between correction of revising segment thereafter, to reduce adjacent two differences of revising correction between segments.
After above-mentioned correction operation, a big step of original isolation pattern district and intensive graph area is become a plurality of small stairs, adjacent two differences of revising correction between segment have been reduced, under the situation that need not increase too many computer running time, light mask pattern is revised, make the figure after the exposure present mild gradual change, the dimension of picture of junction is increased, so increased lithographic process window in isolation pattern district and intensive graph area junction.
Description of drawings
The present invention is further detailed explanation below in conjunction with accompanying drawing and embodiment:
Fig. 1 is uncorrected light mask pattern synoptic diagram;
Fig. 2 is through the revised light mask pattern synoptic diagram of formal style;
Fig. 3 is the litho pattern emulation that obtains with after the exposure of Fig. 2 light mask pattern;
Fig. 4 is a correction segment synoptic diagram of the present invention;
Fig. 5 is a light mask pattern synoptic diagram of the present invention;
Fig. 6 is the litho pattern emulation that obtains with after the exposure of Fig. 4 light mask pattern.
Embodiment
Regulation type optical closes on correction, by light mask pattern is divided into a segment by certain-length, according to the optics modification rule, the requirement of combined process draws correction correction to each segment, this makeover process can be finished by fixed software automatically by setting main parameter at present.The segment number should select then a suitable scope, if establish very little, then figure can not get basic correction, if the segment choosing is too many, has then increased the time of computer run greatly.
The present invention can finish correction automatically by writing a specific computer program.A concrete example promptly utilizes the following formula written program to move: new X
n=(C
1* X
n+ C
2* X
N-1+ C
3* X
N+1)/(C
1+ C
2+ C
3); X in the formula
n, X
N-1, X
N+1Be respectively correction current and correction segment before and after it, be vector; C
1, C
2, C
3All, be respectively stack the scale-up factor current and correction of correction segment before and after it, C greater than 0
1/ (C
1+ C
2+ C
3) characterize the size that level and smooth degree is adjusted.After the regulation type optical of finishing routine closed on correction, the operation said procedure was handled all the correction segments in the light mask pattern, in two kinds of situation: X
n, X
N-1, X
N+1Value when equating, handle back X
nBe worth constant; X
N-1, X
N+1Value when unequal, new X
nValue falls between.The segment number that obtains actual correction in a process also is to pass through C
1, C
2, C
3Ratio regulate.Fig. 4 revises synoptic diagram for the step place, and the correction of the correction segment of the step position of intensive graph area and the sudden change of junction, isolation pattern district generation correction is X
n, the correction X of its last segment of while
N-1Thereafter the correction X of a segment
N+1, at this moment pass through C
1, C
2, C
3Choose and adjust X
nValue, make new correction between above-mentioned last segment X
N-1Correction and a segment X thereafter
N+1Correction between, to reduce adjacent two differences of revising the correction between segments.As can be seen from the above equation, work as C
2Proportion when big, new X
nJust near X
N-1Numerical value, work as C
3Proportion when big, new X
nJust near X
N+1Numerical value.Those skilled in the art can be by regulating C
1, C
2, C
3Value, promptly get through the revised level and smooth light mask pattern (see figure 5) of method of the present invention.