CN103163728A - OPC correction method based on photoetching process window - Google Patents

Abstract

The invention discloses an OPC correction method based on a photoetching process window. When the margin position error of a pattern is calculated, the method uses different photoetching model weights for different patterns in a photoetching layout according to a photomask error reinforcement factor, a light intensity maximum value, a light intensity minimum value and slope of a pattern measuring point. The method sets variable weights to patterns by determining the pattern characteristics and the pattern environment in the layout, and prevents the OPC correction error caused by the changes of the photoetching pattern.

Description

OPC modification method based on lithographic process window

Technical field

The present invention relates to SIC (semiconductor integrated circuit) and make the field, particularly relate to a kind of OPC modification method based on lithographic process window.

Background technology

Present optical approach effect correction (OPC, Optical Proximity Correction) technology, as a kind of resolution enhance technology (RET, Resolution Enhancement Technology), be widely used in the above key stratum technique of 0.13 μ m technology node.But along with day by day dwindling of semiconductor technology size, (design rule) is more and more less for the design rule of figure, also becomes increasingly complex simultaneously, how to coordinate photoetching process, carries out the expansion of process window, also more and more becomes the research direction of OPC technique.

At present, common OPC modification method is based on the OPC (Model Based OPC) of model, this model is the lithography model that is based upon on the raw data of the OPC model that obtains when photoetching process obtains top condition, is generally optimum exposure energy pinpointed focus lithography model (being called for short best etching condition model here).Except best etching condition model, also have optimum exposure energy off-target focal length lithography model, and off-target energy pinpointed focus lithography model etc., these models are called for short non-best etching condition model.

In the OPC modification method based on single best model, objective function generally is made as the difference of the revised analogue value of figure and desired value, and namely the expression formula of EPE (edge placement error, marginal position error) is:

EPE＝CD _targ?et-CD _sim

In formula, CD _{Targ et}Be the desired value of figure correction, CD _simBe the revised analogue value of figure.

And in the OPC modification method based on lithographic process window, except best etching condition model, also must use one or more non-best etching condition models, the non-best etching condition model here refers to that etching condition is the lithography model, pinpointed focus of optimum exposure energy and focus offset pinpointed focus and the lithography model of exposure energy off-target energy or the lithography model of exposure energy off-target energy and focus offset pinpointed focus.Its objective function EPE _FinalComputing method be:

${\mathrm{EPE}}_{\mathrm{final}}=W_{\mathrm{best}}\×{\mathrm{EPE}}_{\mathrm{best}}+\underset{i=1}{\overset{n}{\mathrm{\Σ}}}{W}_i\×{\mathrm{EPE}}_i$

$W_{\mathrm{best}}+\underset{i=1}{\overset{n}{\mathrm{\Σ}}}{W}_i=1$

Wherein, W _BestThe weight of best etching condition model, EPE _BestThe EPE value of best etching condition model, W _iThe weight of other non-best etching condition models, EPE _iThe EPE value of other non-best etching condition models, EPE _FinalIt is the objective function after aforementioned EPE value is merged according to weight.For each figure that OPC revises, this objective function EPE _FinalIn the value of weight of each lithography model all identical, be namely a specific constant, this has caused larger puzzlement for value of weight.Because on the one hand, when the edge of lithographic process window, the stability performance of litho pattern is poor, critical size CD (Critical Dimension, critical dimension) variation is larger, from the statistical significance, is exactly that 3Sigma is larger, the variation range of the raw data of the OPC model of namely collecting is larger, thereby need to reduce the numerical value of weight; But, on the other hand, in order to judge more exactly EPE _FinalScope, need to increase weighted value as far as possible, brought difficulty for thus the value of weight, the confidence level of the OPC model of so setting up also can be lower, thereby when causing revising based on the OPC of lithographic process window, introduce larger error in the correction of some figures, cause revised figure serious distortion.

Summary of the invention

The technical problem to be solved in the present invention is to provide a kind of OPC modification method based on lithographic process window, and it can reduce the OPC round-off error.

For solving the problems of the technologies described above, the OPC modification method based on lithographic process window of the present invention to the different graphic in lithography layout, when calculating the marginal position error of figure, is set different lithography model weights.

Described weight can be strengthened the factor, light intensity maximal value, light intensity minimum value and slope according to the light shield error of graphical measurement point and set.

The present invention sets variable weight to the figure in domain, thereby has avoided when the edge of lithographic process window by judging graphic characteristics in domain and the surrounding environment of figure, the OPC round-off error that causes because of the variation of litho pattern.

Embodiment

Understand for technology contents of the present invention, characteristics and effect being had more specifically, existing details are as follows in conjunction with illustrated embodiment:

OPC modification method based on lithographic process window of the present invention, its objective function EPE _FinalIn the value of weight of each lithography model, be not changeless for the different graphic in domain, but set according to the surrounding environment of the characteristics of different graphic and figure.The establishing method of weight is by certain functional form W _i=f (x ₁, x ₂...) control, wherein, x _iCan be MEEF (Mask Error Enhancement Factor, the light shield error is strengthened the factor), the I of graphical measurement point _max(light intensity maximal value), I _minAlso can there be x in (light intensity minimum value) or Slope (slope) etc. in function _iWith x _jA product term.

Specifically, can set weight by following steps:

At first step 1, uses best etching condition modeling test pattern, measures the I of test pattern _max, I _minWith the scope of Slope value, obtain the photoetching raw data of test pattern.

Step 2, the photoetching raw data of the test pattern that obtains according to step 1 calculates the scope of the MEEF value of these test patterns.

Step 3 is with the I at design rule place _max, I _min, Slope and the value of MEEF and the I of test pattern _max, I _min, Slope and MEEF the scope of value compare, determine parameters (I _max, I _min, Slope and MEEF) factor of influence.

The design rule here refers to minimum feature (minimum Line) and the minimum aperture (minimum Space) of current layer, minimum period (Pitch)=minimum feature+minimum aperture.

Step 4 builds the weight equation of non-best etching condition model:

W _i＝f(I _max，I _min，Slope，MEEF)

Above-mentioned weighting function W _iCan be about I _max, I _min, Slope and MEEF piecewise function, function of first order or other function, can be also the combination of many kinds of function.

For example, when only considering MEEF, the MEEF value that the calculation Design rule is located is 2, and the MEEF scope of test pattern is 1.5～3.5, weighting function W _iCan be the piecewise function of following form:

$W_1=\left\{\begin{array}{cc}0.5& \mathrm{MEEF}>2.5\\ 1& \mathrm{MEEF}\≤2.5\end{array}\right.$

As weight function W _iAbout I _max, I _min, Slope and MEEF function of first order the time, the weight equation can for:

W ₁＝c ₁×MEEF+c ₂×I _max+c ₃×I _min+c ₄×Slope

Wherein, c1, c2, c3, c4 are the constant parameter.

Step 5 is used best etching condition modeling lithography layout, obtains the I at lithography layout place _max, I _min, Slope and MEEF, the weight equation of the non-best etching condition model of substitution step 4 calculates the weight at this lithography layout place.

Claims (5)

1. the OPC modification method based on lithographic process window, is characterized in that, to the different graphic in lithography layout, when calculating the marginal position error of figure, sets different lithography model weights.

2. method according to claim 1, is characterized in that, strengthens the factor, light intensity maximal value, light intensity minimum value and slope according to the light shield error of graphical measurement point and set described weight.

3. method according to claim 2, is characterized in that, the step of setting weight comprises:

1) use best etching condition modeling test pattern, measure the light intensity maximal value I of test pattern _max, light intensity minimum value I _minWith the scope of slope S lope value, obtain the photoetching raw data of test pattern;

The photoetching raw data of the test pattern that 2) obtains according to step 1, the light shield error that calculates test pattern is strengthened the scope of factor M EEF value;

3) with the I at design rule place _max, I _min, Slope and the value of MEEF and the I of test pattern _max, I _min, Slope and MEEF the scope of value compare, determine the factor of influence of parameters;

4) build the weight equation W of non-best etching condition model _i=f (I _max, I _min, Slope, MEEF);

5) use best etching condition modeling lithography layout, obtain the I at lithography layout place _max, I _min, Slope and MEEF, substitution step 4) the weight equation, calculate the weight at this lithography layout place.

4. method according to claim 3, is characterized in that step 3) in, described design rule refers to minimum feature, minimum aperture and the minimum period of current layer, the described minimum period is minimum feature and minimum aperture sum.

5. method according to claim 3, is characterized in that step 4) in, W _iI _max, I _min, Slope and MEEF piecewise function or function of first order.