KR20090077587A - Method for forming photo mask - Google Patents

Abstract

A method for manufacturing an exposure mask is provided to perform stably optical proximity correction(OPC) convergence by dividing multiple edges of polygonal pattern into some groups and performing OPC as to the groups. A layout of a polygonal pattern is designed(S10). A primary OPC is performed as to each edge of the polygonal pattern(S18). The adjacent edges of the polygonal pattern are divided into some groups and a secondary OPC is performed as to every group(S22). An exposure mask is manufactured by using the result of the secondary OPC(S26).

Description

Exposure mask manufacturing method {Method for forming photo mask}

The present invention relates to a method of fabricating an exposure mask, and more particularly, to perform OPC by dividing a plurality of edges of a polygonal pattern into groups to stably perform OPC convergence and to reduce process margin by lowering EPE after performing OPC. The present invention relates to a method for producing an exposure mask that can sufficiently secure the.

In general, a lithography process is a process of performing exposure and development after applying a photoresist on a wafer, and is performed before an etching process or an ion implantation process requiring a mask.

As the degree of integration of semiconductor devices increases, the size and pitch of the patterns that make up the circuits are decreasing, so that during processing, the photolithography technology refines the mask design to adequately control the amount of light emitted through the mask. Overcoming the technical limitations of semiconductor device manufacturing devices by adjusting, developing new photosensitizers, developing scanners using high numerical aperture lenses, and developing modified masks. Doing.

On the other hand, the most widely used UV lasers use KrF light sources with a wavelength of 248 nm, but light sources have evolved to shorter wavelengths, EUV, including ArF with a wavelength of 193 nm and F2 laser with a wavelength of 157 nm. It is becoming.

However, as the degree of integration of semiconductor devices increases, the size of the pattern formed on the mask approaches the wavelength of the light source, and as a result, the influence of light diffraction and interference increases in lithography technology.

Since the optical system of the exposure apparatus acts as a low pass filter, the pattern formed on the wafer appears in a distorted form in the pattern defined in the mask pattern.

In particular, an optical proximity effect (OPE) in which a corner portion of the pattern is distorted in a round shape is generated.

As a technique for overcoming the optical proximity effect, optical proximity correction (hereinafter referred to as OPC) that intentionally deforms the shape of the mask pattern and corrects the pattern distortion is used. Such OPC uses methods of adding or removing small patterns of less than resolution to a mask pattern formed on a mask. For example, line end treatment is a method of adding a corner serif pattern or a hammer pattern to overcome the problem that the line end becomes round in shape, and insertion of scattering bars Bars are a method of adding sub-resolution scattering bars around the target pattern in order to minimize the line width variation of the pattern according to the pattern density.

In addition, the OPC program is based on a rule-based method that refines the layout of the lithography engineer's experience into several rules according to the approach and model-based correction of the layout using a mathematical model of the lithography system. It is divided into model based methods.

The general OPC method designs the target pattern layout of a desired circuit, checks for abnormalities of the layout through Design Rule Check (DRC), and performs OPC if there is no abnormality in the layout. After improving the pattern transfer fidelity, a large number of biases are obtained based on the Layer Versus Layer (LVL) and at least two space widths according to the line threshold size, and the optimum bias amount is obtained from these bias amounts. OPC checks for abnormalities through the Optical Rule Check (ORC) step that checks the pattern shape. Next, the expected weak point is detected through MBV (Model Based Verification) and the mask is finally manufactured.

As the degree of integration of semiconductor devices increases and design rules become smaller, sufficient resolution and process margins are required. Exposure Latitude (EL) or Depth of Focus (DOF) margins are determined by process variation, which is particularly affected by Mask Error Enhancement Factor (MEEF).

For example, the contact pattern has many adjacent edges, so as the size of the pattern decreases, the MEEF is considerably larger and the uniformity is poorer than that of other normal patterns. Therefore, if the OPC of the contact pattern is performed by the conventional method, stable OPC convergence is very difficult, and as a result of the OPC, the value of Edge Placement Error (EPE) increases. Here, the larger the EPE value, the lower the process margin. Figure 1 is a graph showing the EL according to the DOF, it can be seen that the process margin (DOF) is reduced by about 30% as the EPE value increases from 0nm to 1nm.

When OPC is performed in a general manner for a general contact pattern with a large MEEF, one edge is affected by adjacent edges, and thus OPC convergence becomes unstable. 2 is a graph showing the EPE value according to the number of iterations, and it can be seen that the EPE values do not converge even if the number of iterations is increased.

An object of the present invention is to provide a method of manufacturing an exposure mask that can stably perform OPC convergence and lower the EPE value after performing OPC to sufficiently secure process margins.

The exposure mask manufacturing method according to the present invention

Designing a layout of the polygonal pattern;

Performing a first order OPC on each side of the polygonal pattern;

Dividing adjacent edges of the polygonal pattern into groups and performing second optical proximity correction (OPC) for each group; And

Fabricating an exposure mask using the secondary OPC results.

The method may further include simulating the first OPC result.

In the simulation result, if the edge placement error (EPE) is larger than the first set value, the first OPC is repeatedly performed.

Simulating each of the group-specific secondary OPC results;

In the simulation result, if the EPE is larger than the second set value smaller than the first set value, the first OPC is repeatedly performed.

The polygonal pattern may be a contact pattern or an island pattern.

According to the present invention, OPC is performed by dividing a plurality of edges of a polygonal pattern into groups, thereby stably performing OPC convergence and lowering the EPE value after performing OPC, thereby sufficiently securing the process margin.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. However, the present invention is not limited to the embodiments described herein and may be embodied in other forms. Rather, the embodiments introduced herein are provided so that the spirit of the present invention is thoroughly and completely disclosed, and the spirit of the present invention to those skilled in the art will be fully delivered. Also, like reference numerals denote like elements throughout the specification.

3 is a flowchart illustrating a method of manufacturing an exposure mask according to the present invention. Here, an example of a hexagonal contact pattern is described, but it can be applied to all polygonal patterns.

Referring to FIG. 3, the layout of the contact pattern is designed (S10), and general OPC (Optical Proximity Correction) is performed on all edges (A, B, C, and D), respectively (S12). Lower the value to a preset value (PV). That is, a margin for defects such as bridge or thinning of a pattern is secured primarily by performing general OPC.

After simulating using the OPC results (S14), the EPE value is calculated and the EPE value is larger than the preset value (PV) (S16) until the EPE value becomes smaller by the preset value (PV). The general OPC (S12) is repeated.

Next, when the EPE value is smaller than the preset value PV (S16), the four sides A, B, C, and D of the contact pattern are divided into two groups M (A, D) and N (B, C)), first performing OPC for one group (M) (S18), and then simulating the primary OPC for the result (S20) and performing a second OPC for the other group (N). (S22).

If the EPE value is larger than the desired value (DV) by calculating the EPE value using the result of the second OPC (S24), the process is repeated again from the step of performing the general OPC (S12), and the EPE value is the desired value ( If smaller than DV (S24), a final exposure mask is produced using the second OPC result (S26). Here, the desired value DV of the EPE is set to a value smaller than the preset value PV.

As described above, according to the present invention, since the variation of the EPE is smaller than that of the OPC method considering the general OPC or MEEF, the number of OPC iterations can be reduced, thereby reducing the TAT (Turn Around Time).

Although not described in the above embodiments, after designing the layout in general (S10), a design rule check (DRC) checks whether the layout is abnormal.

In addition, after performing OPC, a plurality of bias amounts are obtained based on the layer width of at least two layers according to the Layer Versus Layer (LVL) and each line threshold size, and the pattern shape having the optimum bias amount is examined from these bias amounts. Perform OC (Optical Rule Check) to check for OPC abnormalities.

Next, MBV (Model Based Verification) is performed using the OPC results, and finally an exposure mask is manufactured using the MBV results.

In the above embodiment, the contact pattern has been described as an example, but the present invention is also applicable to a two-dimensional independent pattern.

In addition, a preferred embodiment of the present invention is for the purpose of illustration, those skilled in the art will be able to various modifications, changes, substitutions and additions through the spirit and scope of the appended claims, such modifications and changes are the following claims It should be seen as being in scope.

1 is a graph illustrating an exposure latitude (EL) according to DOF.

2 is a graph showing EPE values according to the number of iterations.

3 is a flowchart illustrating a method of manufacturing an exposure mask according to the present invention.

<Description of the symbols for the main parts of the drawings>

S10: Layout Design of Contact Patterns

S12: OPC on all edges

S14: simulation

S16: EPE <PV (predetermined value)

S18: Perform primary OPC on any pair of edges

S20: simulation

S22: Second OPC for different pairs of edges

S24: EPE <desired value

S26: making an exposure mask

Claims (6)

Designing a layout of the polygonal pattern; Performing a first order OPC on each side of the polygonal pattern; Dividing adjacent edges of the polygonal pattern into groups and performing second optical proximity correction (OPC) for each group; And Manufacturing an exposure mask using the second OPC result. The method of claim 1, And simulating the first OPC result. The method of claim 2, And if the edge placement error (EPE) is greater than the first set value in the simulation result, repeating the first OPC. The method of claim 3, wherein And simulating the second OPC results for each group. The method of claim 4, wherein And the primary OPC is repeated when the EPE is larger than the second set value smaller than the first set value in the simulation result. The method of claim 1, Wherein said polygonal pattern is a contact pattern or an island pattern.

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