JP2005215588A - Method for manufacturing phase shift mask and phase shift mask - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To correct a phase shift mask to prevent the formation of a step shifter part, to easily layout a pad for correcting a narrowed part, and to improve symmetry in the distribution of light intensity. <P>SOLUTION: The phase shift mask has a light shielding pattern P1 to expose a predetermined pattern and shifters S11, S12 in both sides of the light shielding pattern P1 so as to transmit light in different phases from each other. When adjacent shifters in shifters S11, S12, S21, S22 corresponding to the respective light shielding patterns P1, P2 having different lengths are connected because the light shielding patterns approach nearer to each other, the connected shifters S21, S21 are corrected into a rectangular pattern, and a pad to correct light intensity is laid as required with respect to the corrected shifter S31 and to other shifters S11, S22. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a method for manufacturing a phase shift mask and a phase shift mask, each including a light shielding pattern corresponding to a pattern formed by exposure, and a shifter provided adjacent to the light shielding pattern and transmitting light having different phases.

  As the performance of semiconductor devices increases, miniaturization and higher density are required in the semiconductor manufacturing process, and even in the formation of resist patterns by photolithography, the resolution limit determined by the wavelength of light and the optical system Creation of fine patterns exceeding the following is required.

  When trying to resolve a pattern that is less than the resolution limit of the exposure device with high accuracy, a shifter is provided on one of the adjacent patterns using the modified illumination method or transfer mask, which is called super-resolution technology, and the phase of the exposure light is adjusted. A phase shift technique that reverses 180 degrees and improves the contrast of the pattern edge portion is used.

  Among the phase shift techniques, the spatial frequency modulation mask (Levenson type phase shift mask) is a type of phase shift mask in which shifters are arranged in every other pattern (see FIG. 8A), and has already been put into practical use. It is. In the Levenson type phase shift mask, the contrast of the light intensity distribution on the wafer can be increased as compared with the conventional Cr mask (see FIG. 8B).

  FIG. 9 shows the shifter height of the Levenson type phase shift mask and the light intensity distribution of the light transmitting portion. Normally, exposure with a Levenson-type phase shift mask increases the contrast of the pattern edge portion and suppresses the influence of lens aberration, so that the aperture (σ) of the light source is set to be small. As a result, as the shifter is lengthened, the light intensity distribution becomes discrete as shown in FIG. 9, and the resist line pattern is constricted near the end of the line, and the line width variation (swells) in the line length direction occurs. This necking and waviness causes problems such as line breakage and non-uniform line width, which causes transistor characteristics and process margin degradation. Here, this line shape is referred to as constriction and swell.

  For the above-described line shape constriction correction (OPC: Optical Proximity Correction), a method of arranging a pad t on a rule basis as shown in FIG. 10 has been proposed (see, for example, Patent Document 1 and Patent Document 2). ), Effective in correcting the line necking. Here, FIG. 10A is an example described in Patent Document 1, in which a pad t is provided at the even part of the shifters S51 to S53, and FIG. 10B is an example described in Patent Document 2. Yes, a pad t is provided near the even part of the sides of the shifters S51 to S53.

Japanese Patent No. 2001-155717 JP 2001-42545 A

  However, when the lines are close to each other to some extent, adjacent shifters overlap (generation of a step shifter) as shown in FIG. 11, and the light intensity distribution becomes asymmetric. That is, as shown in FIG. 11A, when the distance between the light shielding patterns P1 and P2 is somewhat apart, the shifters S61 and 62 and the shifters S71 and S72 provided corresponding to the light shielding patterns P1 and P2 are Although provided independently, as shown in FIG. 11B, when the distance between the light shielding patterns P1 and P2 approaches, the adjacent shifter S62 and shifter S71 become continuous. At this time, if the lengths of the light shielding patterns P1 and P2 are different, the lengths of the shifter S62 and the shifter S71 are also different, so that the continuous shifter becomes the step shifter S80.

  Since such a step shifter has an asymmetric shape in the vertical direction in the figure, the light intensity distribution is different between a location above the line and a location below the line. Therefore, a difference in the amount of constriction occurs in the exposure pattern, and a huge amount of man-hours for data acquisition is required for creating a rule-based table due to the difference in the size and position of the correction pads arranged on the exposure pattern.

  In addition, even when trying to make corrections based on the model (simulation) for line necking and waviness due to the above step shifter, the amount of data acquisition for creating an OPC model increases by the amount of the step shifter shape, and the accuracy It will be difficult to pursue.

  The present invention has been made to solve such problems. That is, the present invention provides a method of manufacturing a phase shift mask comprising a light shielding pattern for exposing a predetermined pattern and a shifter provided on both sides of the light shielding pattern and transmitting light having different phases, and the light shielding pattern is long. When adjacent shifters corresponding to the respective light-shielding patterns are consecutive by approaching two different thicknesses, a step of correcting the shape of the continuous shifter into a rectangle, a corrected continuous shifter, and other shifters And a step of arranging a pad for correcting light intensity as required with respect to the shifter.

  Further, the present invention provides a phase shift mask having a light shielding pattern for forming a predetermined exposure pattern and a shifter provided on both sides of the light shielding pattern, each of which transmits light having a different phase. When different first light-shielding patterns and second light-shielding patterns are arranged substantially in parallel, and adjacent shifters corresponding to the respective light-shielding patterns are continuously configured as one common shifter, this common shifter Is a rectangle.

  In the present invention, when adjacent ones of the shifters are continuous due to the approach of the light shielding pattern, the shape of the continuous shifters (common shifters) is corrected to a rectangle, so that There will be no steps. Therefore, the contrast of the light intensity distribution can be enhanced by arranging the light intensity correction pad with respect to the rectangular shifter.

  According to the present invention, there are the following effects. That is, it is possible to simplify and simplify the correction for the line non-uniformity when exposure is performed with a Levenson type phase shift mask. In addition, according to the present invention, the symmetry of the light intensity distribution of the light transmitting portion of the phase shift mask ringing from the Levenson type is improved, and the characteristics of the element formed by exposure can be stabilized.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a schematic diagram for explaining a method of manufacturing a phase shift mask according to this embodiment. The phase shift mask 1 is provided with a light shielding pattern (for example, light shielding patterns P1 and P2) provided as a light shielding portion 10 for forming a predetermined exposure pattern, and provided on both sides of each of the light shielding patterns P1 and P2. Shifters S11, S12 and S21, S22 that transmit different light.

  For example, the shifters S11 and S12 provided on both sides of the light shielding pattern P1 have a shifter S11 having a phase of 180 ° and a shifter S12 having a phase of 0 °, and the shifters S21 and S22 provided on both sides of the light shielding pattern P2 are The shifter S21 has a phase of 0 °, and the shifter S22 has a phase of 180 °. Each of the shifters S11, S12 and S21, S22 is sized in accordance with the length (vertical direction in the drawing) of the corresponding light shielding pattern P1, P2.

  The present embodiment is characterized in that the phase shift mask 1 is manufactured by using a mask design method suitable for such a case where two light shielding patterns P1 and P2 having different lengths and substantially parallel to each other approach each other. is there. Specifically, the mask design tool (program) is realized by a program that automatically corrects the shape of the shifter in the pattern design before placing the constriction correction pad.

  First, as shown in FIG. 1A, when light shielding patterns P1 and P2 having different lengths approach each other, shifters S11 and S12 and S21 and S22 provided corresponding to each of them are adjacent to each other (shifter S12 and S12). The shifter S21) continuously becomes one common shifter. Here, the shifter S12 and the shifter S21 have different sizes because the lengths of the corresponding light shielding patterns P1, P2 are different. Therefore, at the design stage of the phase shift mask, the continuous common shifter becomes the step shifter S30 which is not rectangular.

  Next, in the state where such a step shifter S30 is generated, the shifter (shifter S21) having the longer one of the corresponding light shielding patterns P1 and P2 among the two shifters S12 and S21 constituting the step shifter 30. Accordingly, the step shifter 30 is deformed into a rectangle to generate a corrected shifter S31 as shown in FIG. The corrected shifter 31 has a shape in which a step is eliminated by adding a correction unit S100 to the step shifter S30 shown in FIG.

  FIG. 2 is a schematic diagram showing an example of a light intensity distribution by a shifter, where (a) is a step shifter and (b) is a shifter corrected to a rectangle. In the figure, the thinner the dots, the stronger the light intensity.

  3 is a diagram showing the amount of constriction above and below the line when exposure is performed with the light intensity distribution shown in FIG. 2, and FIG. 3 (a) corresponds to the a1-b1 line arrow view of FIG. 2 (a). 3 (b) shows the amount of constriction corresponding to the a2-b2 line arrow view of FIG. 2 (b). In both figures, the a1 and a2 sides are 0 on the Y-Position (horizontal axis).

The amount of constriction is obtained by determining the line width in the line length direction by an intensive (resist) parameter model (LPM) simulation. The simulation conditions are as follows: light source wavelength 193 nm, lens numerical aperture NA 0.70, coherence factor σ 0.30, resist contrast (LPM parameter) 12, resist film thickness 200 nm, absorption coefficient (LPM parameter) 0.8um ^-1 , diffusion length (LPM parameter) was set to 30 nm.

  Thus, it can be seen that asymmetry occurs in the amount of constriction as a result of exposure using the step shifter. On the other hand, in the exposure using the shifter corrected to a rectangle, there is almost no asymmetry in the amount of line constriction.

  Next, a process for arranging a pad for correcting the constriction is performed on the shifter corrected to a rectangle. FIG. 4 is a diagram showing a specific example in which a pad is arranged on a rectangular shifter. In this example, two pads t are arranged at the upper and lower even portions of the side of the shifter S11 on the light shielding pattern P1, and the light is shielded by a rectangle at the lower even portion of the side of the shifter S31 on the light shielding pattern P1 side after correction. Two pads t are arranged at the upper and lower even portions of the side on the pattern P2 side, and two pads t are arranged at the upper and lower even portions of the side of the shifter S22 on the light shielding pattern P2 side.

  Here, as shown in the enlarged view of the pads corresponding to the portions shown in FIGS. 2B and 3B, the upper and lower pads t have the same length of 100 nm and the width of 25 nm. FIG. 5 shows the amount of constriction before and after correction by the pad t. As described above, the arrangement of the correction pad with respect to the rectangular shifter makes it possible to relax the amount of constriction by installing the pad in addition to the original good symmetry.

  FIG. 6 is a diagram showing a specific example in which a pad is arranged on the step shifter, and FIG. 7 is a diagram showing a constriction amount before and after arranging a correction pad for the step shifter. As in the case of the rectangular shifter shown above, two pads t are arranged at the upper and lower even portions of the side of the shifter S11 on the light shielding pattern P1 side, and the lower even portion of the side of the step shifter S30 on the light shielding pattern P1 side. In addition, two pads t are arranged at the upper and lower even portions of the side on the light shielding pattern P2 side, and two pads t are arranged at the upper and lower even portions of the side of the shifter S22 on the light shielding pattern P2 side.

  However, in the step shifter 30, the size of the pad corresponding to the portion shown in FIGS. 2 (a) and 3 (a) is 100 nm in length on the upper side and 25 nm in width while the length on the lower side is 100 nm. , The sizes are different, such as a width of 15 nm. That is, in the step shifter 30, since the light intensity distribution is asymmetrical, the size of the squeezing correction pad is also different in the vertical direction.

  Even if such a correction pad is arranged, the amount of constriction can be reduced as shown in FIG. 7, but the asymmetry is not improved much. Therefore, when exposure is performed using such a mask, asymmetry is also reflected in the formed pattern.

  In this embodiment, since the phase shift mask is corrected to a rectangular shifter without generating a step shifter, calculation can be simplified and simplified when a pad for constriction correction is arranged. In addition, by performing exposure using the phase shift mask after correction, it is possible to form a pattern with excellent symmetry and corrected necking.

  Further, since the step shifter becomes a rectangular shifter, the sizes of the pads for constriction correction are made uniform, and the creation of the rule-based table is greatly simplified. Furthermore, even when the correction pads are arranged on the model base, the amount of data can be reduced, and the calculation time can be shortened and high-precision tracking can be realized.

It is a schematic diagram explaining the manufacturing method of the phase shift mask which concerns on this embodiment. It is a schematic diagram which shows the example of the light intensity distribution by a shifter. It is a figure which shows the amount of constrictions of a line up and down. It is a figure which shows the specific example which has arrange | positioned the pad to the rectangular shifter. It is a figure which shows the amount of constrictions before and behind correction | amendment by a putt. It is a figure which shows the specific example which has arrange | positioned the pad to the level | step difference shifter. It is a figure which shows the amount of constrictions before and behind correction | amendment by a putt. It is a schematic diagram explaining a phase shift mask. It is a figure which shows the light intensity distribution of the light transmissive part by the height of a shifter. It is a schematic diagram which shows the example of the conventional correction | amendment pad. It is a schematic diagram explaining generation | occurrence | production of a level | step difference shifter.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Phase shift mask, 10 ... Light-shielding part, P1 ... Light-shielding pattern, P2 ... Light-shielding pattern, S11 ... Shifter, S12 ... Shifter, S21 ... Shifter, S30 ... Shifter, S31 ... Shifter after correction, t …Pat

Claims (5)

In a method of manufacturing a phase shift mask comprising a light shielding pattern for forming a predetermined exposure pattern, and a shifter that is provided on both sides of the light shielding pattern and transmits light having different phases,
When adjacent ones of shifters corresponding to each light shielding pattern are continuous by approaching two different lengths in the light shielding pattern, correcting the shape of the continuous shifter to a rectangle;
And a step of arranging a pad for correcting light intensity as necessary with respect to the continuous shifter and other shifters after correction, and a method of manufacturing a phase shift mask. In the light shielding pattern, when a shifter corresponding to a light shielding pattern having a shorter length and a shifter corresponding to a light shielding pattern having a longer length are continuous, the shape of the continuous shifter is changed to the longer length. The method of manufacturing a phase shift mask according to claim 1, wherein the correction is made to a rectangle matching the long side of the shifter corresponding to the light shielding pattern. In a phase shift mask comprising a light shielding pattern for forming a predetermined exposure pattern and shifters provided on both sides of the light shielding pattern and transmitting light having different phases,
The first light-shielding pattern and the second light-shielding pattern having different lengths in the light-shielding pattern are arranged substantially in parallel, and adjacent ones of shifters corresponding to the respective light-shielding patterns are continuously configured as one common shifter. If this is the case, the phase shift mask is characterized in that this common shifter is rectangular. 4. The phase shift mask according to claim 3, wherein the common shifter has a size that matches the longer one of the first light shielding pattern and the second light shielding pattern. 5. The phase shift mask according to claim 3, wherein a pad for correcting light intensity is disposed for the common shifter and the other shifters having a rectangular shape.

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