JP2006216639A - Method for designing light source intensity distribution, aligner, exposure method, and method for manufatcuring semiconductor device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for setting light intensity distribution by which the optimized intensity distribution of exposure light is set to demonstrate the maximum performance even at a through pitch. <P>SOLUTION: The method for setting light intensity distribution is comprised of the steps to diffract lights emitted from an exposure light source that are supposed to be emitted from four point light sources located at the specified positions, by a pattern having Q kinds of specified pitches P<SB>q</SB>formed on an exposure mask, to obtain light intensity distribution by calculation when the images are formed, to calculate a value S<SB>q</SB>as an NILS value from the obtained light intensity distribution, to calculate a map of an average value S<SB>OPT</SB>of a sum of products of weight rates WT<SB>q</SB>and values S<SB>q</SB>set at the respective pitches P<SB>q</SB>, and to design the light source intensity distribution to the angle of lights which are emitted from the exposure light sources so that the map of the average value S<SB>OPT</SB>can be obtained and enter the exposure mask. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention is used in a lithography process in the manufacturing process of a semiconductor device, and is emitted from an exposure light source for transferring a pattern formed on an exposure mask to a photoresist layer formed on a substrate, and enters the exposure mask. The present invention relates to a light source intensity distribution design method for an angle of light to be emitted, an exposure apparatus to which the light source intensity distribution design method is applied, an exposure method, and a method for manufacturing a semiconductor device.

  In the lithography process in the manufacturing process of a semiconductor device, with the miniaturization of a semiconductor device pattern, high resolution exceeding the resolution limit determined from the wavelength of exposure light is required. In the following description, the light emitted from the exposure light source and incident on the exposure mask is referred to as illumination light, passes through the exposure mask, enters the photoresist layer applied and formed on the substrate, and the photoresist layer is The exposure light may be referred to as exposure light. In recent years, as a super-resolution technique for forming a fine pattern below the wavelength of exposure light, a Shibuya-Levenson type phase shift mask (Shibuya Masato: JP 57-62052, MD Levenson et al: IEEE Trans. Application of Electron Device, ED-29, p1828 (1982), oblique incidence illumination (for example, K. Matsumoto and T. Tsuruta: Optical Engineering, 31, p2657 (1992)) and the like are being studied. Here, the former is resolved by controlling not only the light intensity of the exposure light that has passed through the pattern to be transferred formed on the exposure mask but also the phase information of the exposure light by a special exposure mask. This is a technique for improving the property and depth of focus (DOF). In the latter case, an ordinary binary mask or a halftone phase shift mask is used as an exposure mask to be used. However, illumination light emitted from an exposure light source and incident on the exposure mask (hereinafter referred to as such) Illumination light intensity distribution with respect to the angle of the illumination light (sometimes referred to as an effective light source) (hereinafter, such light source intensity distribution may be referred to as the effective light source shape) To form a quadrupole illumination with locally intensified, quadrupole illumination (also called cross-pole illumination) having locally intensities in the directions of 0, 90, 180, and 270 degrees. This is a technique for improving resolution and depth of focus (DOF) by illuminating the mask for oblique incidence and bringing the image formation on the photoresist layer close to two-beam interference. Some of these super-resolution techniques are applied as mass production processes for semiconductor devices.

  By the way, the Shibuya-Levenson type phase shift mask is a special exposure mask, and has a problem that it is expensive in addition to technical difficulties in manufacturing the exposure mask. On the other hand, in oblique incidence illumination, it is not necessary to use a special exposure mask, but it is basically effective only for patterns having a specific pitch, and patterns having other pitches, such as isolated patterns, etc. For this, resolution and depth of focus may be inferior to those of ordinary circular illumination. For this reason, there is almost no improvement effect with respect to the common process margin when viewed from the entire pattern in the exposure mask, or conversely, it results in deterioration, especially in logic devices. The current situation is not applied to the mass production process.

  Incidentally, as presented in Japanese Patent No. 3458549, the intensity of light emitted from the central portion of the effective light source is reduced by a predetermined amount with respect to the intensity of light emitted from the peripheral portion of the effective light source. Based on the shape of the effective light source, it is possible to reduce the pitch dependency of the pattern.

JP-A 57-62052 Japanese Patent No. 3458549 JP 2001-242414 A JP 2001-230180 A M.M. D. Levenson et al: IEEE Trans. Electron Device, ED-29, p1828 (1982). K. Matsumoto and T.M. Tsuruta: Optical Engineering, 31, p2657 (1992).

  In the technique disclosed in Japanese Patent No. 3458549, it is possible to obtain imaging characteristics compatible with a pattern having a dense pitch (dense pitch) and an isolated pattern. As a specific effective light source shape, a quadrupole illumination of 45 degrees orientation as shown in FIG. 12, and an effective light source shape having an attenuated light source intensity distribution at the center and the periphery is proposed. ing.

  As shown in FIG. 13, the shape of an effective light source in Japanese Patent No. 3458549 is obtained by dividing an excimer laser beam emitted from an exposure light source into four beams B1, B2, B3, and B4, and fly eyes (fly eyes). It is an effective light source that can be easily formed with an illumination optical system that is superposed on the entrance surface of the lens. However, the shape of the effective light source shown in FIG. 12 is such that an exposure mask having a certain pitch still has unnecessary intensity in the imaging performance, and an exposure mask having a through pitch (dense pitch). The light intensity distribution of the effective light source (the shape of the effective light source) that draws the maximum performance in the exposure mask having various pitches from to the isolated pattern is not obtained. In addition, a quantitative design method relating to the light intensity distribution (effective light source shape) of the effective light source is not disclosed specifically and in detail.

  Accordingly, an object of the present invention is to provide a light source intensity distribution design method for designing a light intensity distribution (effective light source shape) of an optimized effective light source that can draw out the maximum performance even at a through pitch, and the light source intensity concerned. An object of the present invention is to provide an exposure apparatus, an exposure method, and a semiconductor device manufacturing method to which a distribution design method is applied.

The light source intensity distribution design method of the present invention for achieving the above object is used in a lithography process in a manufacturing process of a semiconductor device, and a pattern formed on an exposure mask is transferred to a photoresist layer formed on a substrate. A light source intensity distribution design method for an angle of light emitted from an exposure light source and incident on an exposure mask,
(A) In light emitted from the exposure light source, four points (i · ΔX, j · ΔY), (−i · ΔX, j · ΔY), (−i · ΔX, −j) in the pupil coordinates of the equivalent light source surface ΔY), (i · ΔX, −j · ΔY) [where i = 0, 1, 2,... I, j = 0, 1, 2,... J, ΔX · I = σ, ΔY · J = σ, where σ indicates the size of the light source, and light that is assumed to be emitted from each of the point light sources located at 1 or less is formed on the exposure mask. A light intensity distribution is calculated for each pitch when diffracted by a pattern having Q kinds of predetermined pitches P _q (q = 1, 2,... Q) and imaged on the photoresist layer. normalized image intensity log slope value from the distribution (NILS value, normalized image Log slope value) or a value S _q (i · ΔX is the contrast value, j · [Delta] Y To calculate the i = 0~I, for j = 0~J,
(B) Based on the weight ratio WT _q set at each pitch P _q , the weight average value S _OPT (i · ΔX, j · ΔY) is calculated from the following equation (1):
(C) Design a light source intensity distribution with respect to the angle of light emitted from the exposure light source and incident on the exposure mask so that a relative light intensity distribution of value S _OPT (i · ΔX, j · ΔY) is obtained.
It consists of a process.

In order to achieve the above object, an exposure apparatus of the present invention is used in a lithography process in a manufacturing process of a semiconductor device, and transfers a pattern formed on an exposure mask to a photoresist layer formed on a substrate. An exposure apparatus having an exposure light source and a diffractive optical element,
(A) In light emitted from the exposure light source, four points (i · ΔX, j · ΔY), (−i · ΔX, j · ΔY), (−i · ΔX, −j) in the pupil coordinates of the equivalent light source surface ΔY), (i · ΔX, −j · ΔY) [where i = 0, 1, 2,... I, j = 0, 1, 2,... J, ΔX · I = σ, ΔY · J = σ, where σ indicates the size of the light source, and light that is assumed to be emitted from each of the point light sources located at 1 or less is formed on the exposure mask. A light intensity distribution is calculated for each pitch when diffracted by a pattern having Q kinds of predetermined pitches P _q (q = 1, 2,... Q) and imaged on the photoresist layer. normalized image intensity log slope value from the distribution (NILS value) or a value _{S q (i · ΔX, j} · ΔY) is the contrast value i = 0~I, j = 0 Calculated for J,
(B) Based on the weight ratio WT _q set at each pitch P _q , the weight average value S _OPT (i · ΔX, j · ΔY) is calculated from the following equation (1):
(C) Design a light source intensity distribution with respect to the angle of light emitted from the exposure light source and incident on the exposure mask so that a relative light intensity distribution of value S _OPT (i · ΔX, j · ΔY) is obtained.
Diffraction optics arranged between the exposure light source and the exposure mask, the light source intensity distribution with respect to the angle of the light emitted from the exposure light source and incident on the exposure mask, which is set based on the light source intensity distribution design method comprising the steps It can be based on an element.

An exposure method of the present invention for achieving the above object is used in a lithography process in a manufacturing process of a semiconductor device, and is formed on the exposure mask by irradiating the exposure mask with light emitted from an exposure light source. An exposure method for transferring a pattern to a photoresist layer formed on a substrate,
The light source intensity distribution with respect to the angle of light emitted from the exposure light source and incident on the exposure mask,
(A) In light emitted from the exposure light source, four points (i · ΔX, j · ΔY), (−i · ΔX, j · ΔY), (−i · ΔX, −j) in the pupil coordinates of the equivalent light source surface ΔY), (i · ΔX, −j · ΔY) [where i = 0, 1, 2,... I, j = 0, 1, 2,... J, ΔX · I = σ, ΔY · J = σ, where σ indicates the size of the light source, and light that is assumed to be emitted from each of the point light sources located at 1 or less is formed on the exposure mask. A light intensity distribution is calculated for each pitch when diffracted by a pattern having Q kinds of predetermined pitches P _q (q = 1, 2,... Q) and imaged on the photoresist layer. normalized image intensity log slope value from the distribution (NILS value) or a value _{S q (i · ΔX, j} · ΔY) is the contrast value i = 0~I, j = 0 Calculated for J,
(B) Based on the weight ratio WT _q set at each pitch P _q , the weight average value S _OPT (i · ΔX, j · ΔY) is calculated from the following equation (1):
(C) Design a light source intensity distribution with respect to the angle of light emitted from the exposure light source and incident on the exposure mask so that a relative light intensity distribution of value S _OPT (i · ΔX, j · ΔY) is obtained.
It is set based on the light source intensity distribution design method which consists of a process.

In order to achieve the above object, a method of manufacturing a semiconductor device according to the present invention comprises: irradiating an exposure mask with light emitted from an exposure light source; and applying a pattern formed on the exposure mask to a substrate. A method of manufacturing a semiconductor device, including a step of etching a substrate using an etching mask obtained by transferring to a resist layer and developing the photoresist layer,
The light source intensity distribution with respect to the angle of light emitted from the exposure light source and incident on the exposure mask,
(A) In light emitted from the exposure light source, four points (i · ΔX, j · ΔY), (−i · ΔX, j · ΔY), (−i · ΔX, −j) in the pupil coordinates of the equivalent light source surface ΔY), (i · ΔX, −j · ΔY) [where i = 0, 1, 2,... I, j = 0, 1, 2,... J, ΔX · I = σ, ΔY · J = σ, where σ indicates the size of the light source, and light that is assumed to be emitted from each of the point light sources located at 1 or less is formed on the exposure mask. A light intensity distribution is calculated for each pitch when diffracted by a pattern having Q kinds of predetermined pitches P _q (q = 1, 2,... Q) and imaged on the photoresist layer. normalized image intensity log slope value from the distribution (NILS value) or a value _{S q (i · ΔX, j} · ΔY) is the contrast value i = 0~I, j = 0 Calculated for J,
(B) Based on the weight ratio WT _q set at each pitch P _q , the weight average value S _OPT (i · ΔX, j · ΔY) is calculated from the following equation (1):
(C) Design a light source intensity distribution with respect to the angle of light emitted from the exposure light source and incident on the exposure mask so that a relative light intensity distribution of value S _OPT (i · ΔX, j · ΔY) is obtained.
It is set based on the light source intensity distribution design method which consists of a process.

  In the light source intensity distribution design method, exposure apparatus, or exposure method of the present invention, light emitted from the exposure light source and incident on the exposure mask (hereinafter, such light is referred to as illumination light, or alternatively The light source intensity distribution with respect to the angle of the illumination light source (which may be referred to as an effective light source) (hereinafter, the light source intensity distribution with respect to the angle of the illumination light may be referred to as the shape of the effective light source) It is preferable to be able to obtain it based on the diffractive optical element disposed between them from the viewpoints of simplifying the configuration and minimizing the light loss.

Further, in the light source intensity distribution design method, exposure apparatus, exposure method, or semiconductor device manufacturing method of the present invention (hereinafter, these may be collectively referred to as the present invention), the above steps Following (C),
(D) Based on the light source intensity distribution with respect to the set light angle, a pattern having Q types of predetermined pitches P _q (q = 1, 2... Q) formed on the exposure mask is applied and formed on the substrate. Calculate the process margin when transferred to the photoresist layer
(E) Evaluating whether or not the calculated process margin satisfies a predetermined process margin at all pitches P _q (q = 1, 2,... Q)
Further comprising a step,
When the calculated process margin does not satisfy the predetermined process margin at all the pitches P _q (q = 1, 2,... Q), the weight ratio WT at the pitch P _q in the step (B). _q is changed, and the process (B), the process (C), the process (D), and the process (E) are performed at all the pitches P _q (q = 1, 2,... Q). It is desirable to repeat until the calculated process margin satisfies a predetermined process margin.

In the present invention, when the maximum value of the values S _OPT (i · ΔX, j · ΔY) indicating the relative light intensity distribution in the optimized light source is Max (S _OPT ), _{Dividing the} value S _OPT (i · ΔX, j · ΔY) by Max (S _OPT ) and normalizing the value S _OPT (i · ΔX, j · ΔY) is the relative in the optimized light source. This is preferable from the viewpoint of simplifying the evaluation of the value S _OPT (i · ΔX, j · ΔY) indicating the light intensity distribution.

  In the present invention, the normalized image light intensity logarithmic gradient value is obtained when each point light source of the four point light sources illuminates a pattern (called a mask pattern) formed on the exposure mask and forms an image on the photoresist layer. The logarithmic gradient value of the light intensity at the portion corresponding to the edge portion (X = ± WD / 2) of the target transfer dimension of the calculated optical image (hereinafter referred to as a transfer optical image by a point light source) is calculated. , Given by the following equation (2) multiplied by the target transfer dimension width WD of the optical image. In formula (2), “I” is the light intensity. Details of the NILS value are described in, for example, the document C.A. Mack, Optical Engineering, Vol. 32, No 10, pp2350-2362 (Oct 1993). The NILS value represents the steepness of the transferred optical image. The higher the numerical value, the wider the exposure tolerance.

NILS = WD · ∂ [ln (I)] / ∂x (2)

Further, the contrast value (C) can be obtained from the following general formula (3), where the maximum light intensity and the minimum light intensity of the transfer optical image are I _MAX and I _MIN , respectively.

C = (I _MAX -I _MIN ) / (I _MAX + I _MIN ) (3)

The setting of the weight ratio WT _q at each pitch P _q may be determined from the accumulation of a large number of data based on the execution of a large number of light source intensity distribution design methods. Here, the weight ratio WT _q at the pitch P _q may be set independently depending on the importance of the pattern in the semiconductor device and whether or not the process margin is insufficient. Step (B), step (C), step (D), and step (E) are performed for all pitches P _q (q = 1, 2. until satisfying process margins, if repeated, but changing the weight ratio WT _q in the pitch P _q in step (B), the in the change of the heavy rate WT _q, calculated process margin of a predetermined It is preferable to change the weight ratio WT _q regarding the pitch P _q not satisfying the process margin.

  In the present invention, the shape of the optimized effective light source can be based on, for example, a diffractive optical element (DOE, Diffractive Optical Element) disposed between the exposure light source and the exposure mask. The element may be designed based on, for example, a technique disclosed in Japanese Patent Laid-Open No. 2001-242414. By using the diffractive optical element in this manner, an effective light source having an arbitrary light intensity distribution, that is, a gray gradation can be formed. More specifically, the diffractive optical element is disposed between the exposure light source and the exposure mask so that an optimum effective light source shape can be obtained on the pupil plane (equivalent light source surface) of the illumination optical system of the exposure apparatus. Thus, an exposure apparatus having an effective light source shape having an essentially arbitrary light source intensity distribution can be realized.

In the present invention, in the step (A), four points (i · ΔX, j · ΔY), (−i · ΔX, j · ΔY), (−i · The light that is assumed to be emitted from each of the point light sources located at (ΔX, −j · ΔY) and (i · ΔX, −j · ΔY) has Q types of predetermined pitches P _q formed on the exposure mask. The light intensity distribution formed on the defocused surface that is diffracted by the pattern having, and defocused from the best focus surface by a predetermined amount based on the depth of focus (DOF) required for the process is calculated for each pitch. It is preferable. That is, the equivalent light source formed on the equivalent light source surface by the light emitted from the exposure light source is divided into a finite number of point light sources in a matrix form, and a predetermined defocus surface determined from the required depth of focus (DOF) It is desirable that four point light sources positioned at the position illuminate the mask and obtain a light intensity distribution of a transfer optical image to be formed by calculation. Thus, by obtaining the light intensity distribution of the transfer optical image on a predetermined defocus surface, a process margin having a desired exposure dose tolerance and depth of focus can be realized.

In the present invention, the Q types of predetermined pitches P _q formed on the exposure mask have, for example, a pattern having the closest density (dense pitch), a pattern having an isolated pattern, and a medium pitch (semi-dense pitch). A typical pitch such as a pattern or a pitch important for the operation of the semiconductor device may be used.

  The mask for exposure is, for example, a light-shielding thin layer or semi-light-shielding thin layer made of metal or metal oxide (such as low-expansion glass transparent to exposure light or synthetic quartz glass). The thin layer may be a single layer or a multilayer. In the present invention, as an exposure mask, a normal exposure mask (binary mask) in which a pattern made of a light shielding thin layer is formed, a phase shift mask, and a halftone phase in which a pattern made of a semi-light shielding thin layer is formed. A shift mask can be exemplified.

Examples of the substrate in the exposure method or the semiconductor device manufacturing method include a semiconductor substrate, a semi-insulating substrate, an insulating substrate, or a layer to be processed formed on these substrates. Specifically, the layer to be treated is a polycrystalline silicon layer doped with impurities; a metal layer such as aluminum alloy, tungsten, copper, or silver; a metal compound layer such as tungsten silicide or titanium silicide; A laminated structure of a polycrystalline silicon layer and a metal compound layer such as tungsten silicide or titanium silicide, a laminated structure of a polycrystalline silicon layer doped with impurities, a metal compound layer such as tungsten silicide or titanium silicide, and an insulating film; It can be illustrated. Here, as an insulating film or an insulating _{layer, SiO 2, BPSG, PSG,} BSG, AsSG, SbSG, NSG, SOG, LTO (Low Temperature Oxide, low temperature CVD-SiO _2), SiN, known insulating material such as SiON, Or what laminated | stacked these insulating materials can be mentioned.

In the present invention, the normalized image light intensity obtained on the basis of the weight ratio WT _q and the light intensity distribution of the transfer optical image formed by the four point light sources located at predetermined positions for each of a plurality of pitches of interest. By adding the logarithmic gradient value (NILS value) and the like, the light source intensity distribution (the shape of the effective light source) with respect to the angle of the illumination light, which is summed, averaged, normalized, and comprehensively optimized with a through pitch, is obtained. Obtainable. Here, the light intensity in the optimized effective light source shape is analog having an intermediate value of 0 or more and 1 or less, that is, light intensity having a gray gradation. Then, based on the optimized shape of the effective light source, the pattern formed on the exposure mask is transferred to the photoresist layer formed on the substrate, so that steep optical images of patterns having various pitches are transferred. A profile can be obtained in the photoresist layer.

  If the optimum effective light source shape is finally determined based on the defocused transfer optical image, a process margin having a desired depth of focus and exposure tolerance can be realized. Furthermore, if the weight ratio is changed depending on the importance of the pattern in the semiconductor device, it is possible to finely adjust the shape of the optimized effective light source. In addition, if a diffractive optical element (DOE) is used as a means for realizing an optimized effective light source shape, the energy utilization efficiency is ideally 100%, and no light loss occurs or the minimum light quantity is achieved. It is possible to realize an optimized effective light source shape that requires no loss.

  Hereinafter, the present invention will be described based on examples with reference to the drawings.

  Example 1 relates to a light source intensity distribution design method and an exposure apparatus of the present invention. That is, the light source intensity distribution design method of Example 1 is used in a lithography process in the manufacturing process of a semiconductor device, and an exposure light source for transferring a pattern formed on an exposure mask to a photoresist layer formed on a substrate. Is a light source intensity distribution design method with respect to the angle of light (illumination light) emitted from the light and incident on the exposure mask. The exposure apparatus of Example 1 is used in a lithography process in the manufacturing process of a semiconductor device, and an exposure light source for transferring a pattern formed on an exposure mask to a photoresist layer formed on a substrate, and An exposure apparatus having a diffractive optical element.

  The first embodiment relates to a lithography process for forming a buried wiring made of copper (Cu) of 65 nm node (closest pitch 180 nm, line width 90 nm, space width 90 nm). That is, in order to bury copper (Cu), it is an object to form a groove (trench) in the photoresist layer by a lithography process. Here, as patterns formed on the exposure mask, two types of patterns extending in two directions of the exposure mask in the x direction and the y direction are assumed, and the minimum pitch of the pattern is 180 nm and the maximum pitch is an isolated pattern. Further, it is assumed that a halftone phase shift mask having a transmittance of 6% is used as an exposure mask. Further, the specifications of the exposure apparatus are shown in Table 1 below. After development of the photoresist layer, an opening or groove (trench) is formed in the portion of the photoresist layer corresponding to the pattern of the exposure mask (this pattern is “space”). ) Is embedded with copper (Cu) by a plating method to form a wiring.

[Table 1]
Wavelength of exposure light (λ): 193 nm
Numerical aperture (NA) of projection lens: 0.85
Coherence factor (σ) [maximum illumination σ]: 0.90

  Here, when a pattern is formed by exposure light on a photoresist layer coated and formed on a semiconductor substrate, a pattern used for reduction projection is called a reticle, and a pattern used for one-to-one projection is called a mask. However, in this specification, such reticles and masks in various meanings are collectively referred to as exposure masks. In the following embodiments, the design size of the pattern formed on the exposure mask is 4 when the exposure mask of 4 times, that is, the design size of the pattern formed on the photoresist layer is 1. An exposure mask is used. In the following description, the length and size related to the pattern are the length and size converted into the photoresist layer unless otherwise specified. When obtaining the length and size of the pattern formed on the exposure mask, the length and size of the photoresist layer may be quadrupled. Further, unless otherwise specified, the unit of length and width is “nm”.

  Hereinafter, the light source intensity distribution designing method of the first embodiment will be described with reference to the flowchart shown in FIG.

[Step-1]
First, the defocus amount (d) is set. The defocus amount is determined based on the required process margin. In general, the depth of focus (DOF) is given by the following equation (4) when the wavelength of exposure light is λ. Note that the value of K ₂ that is a process factor is typically assumed to be approximately 0.6, for example. At this time, when λ = 193 nm and NA = 0.85, the defocus amount (d) is 160 nm. In the following description, the defocus amount (d) is 150 nm for convenience.

d = K ₂ (λ / NA ² ) (4)

Further, predetermined pitches P _q (q = 1, 2,..., Q) of Q types (Q = 3 in the first embodiment) formed on the exposure mask are as shown in Table 2 below. To do.

[Table 2]
q = 1 Line and space pattern (Space width: 90 nm, Line width: 90 nm)
q = 2 Line and space pattern (Space width: 90 nm, Line width: 270 nm)
q = 3 isolated pattern (space width: 90 nm)

  In the following description, a pattern corresponding to q = 1 [line and space pattern (space width: 90 nm, line width: 90 nm)] is called a dense pattern (q = 1), and q = 2 [line and space pattern]. A pattern corresponding to a space pattern (space width: 90 nm, line width: 270 nm) is called a semi-dense pattern (q = 2), and a pattern corresponding to q = 3 [isolated pattern (space width: 90 nm)] Sometimes referred to as an isolated pattern (q = 3).

[Step-2]
Then, as shown in FIG. 2A, the grid sizes ΔX (= 0.1) and ΔY (= 0) normalized from the illumination light (effective light source) emitted from the exposure light source and incident on the exposure mask. .1) is divided into a grid and is divided into four points (i · ΔX, j · ΔY), (−i · ΔX, j · ΔY), (−i · ΔX, −j · ΔY) in the pupil coordinates of the equivalent light source surface , (I · ΔX, −j · ΔY) [where i = 0, 1, 2... I, j = 0, 1, 2,... J, and in the first embodiment, ΔX = ΔY = 0.05, I = J = 18, ΔX · I = σ, ΔY · J = σ, where σ indicates the size of the light source and is a positive real number of 1 or less] A predetermined pitch P _q (q = 1, 2... Q) of Q types (Q = 3 in the first embodiment) formed on the exposure mask is assumed to be emitted from each of the point light sources. ) The light intensity distribution (light intensity distribution of the transferred optical image by a four-point light source) when diffracted by the pattern and imaged on the photoresist layer is calculated for each pitch, and the normalized image light intensity is calculated from this light intensity distribution. A value S _q (i · ΔX, j · ΔY) that is a logarithmic gradient value [NILS value, see equation (2)] is calculated for i = 0 to I and j = 0 to J.

  Since the pattern formed on the exposure mask extends in the x direction and the y direction, the shape of the effective light source finally obtained is also symmetric with respect to the x axis and is related to the y axis. It is necessary to consider four point light sources that are symmetrical.

In FIG. 2A, point A ₁ [(i, j) = (5,2)], point A ₂ [(i, j) = (− 5,2)], point A ₃ [(i, j) = (− 5, −2)], point A ₄ [(i, j) = (5, −2)]. Four point light sources are shown. FIG. The light intensity distribution calculation result of the transfer optical image of the 150 nm defocused surface in the semi-dense pattern (q = 2) based on the point light source is schematically shown by a solid line. Further, in FIG. 2A, a point B ₁ [(i, j) = (1,6)], a point B ₂ [(i, j) = (− 1,6)], a point B ₃ [ (I, j) = (− 1, −6)] and point B ₄ [(i, j) = (1, −6)] are shown as four point light sources, and FIG. A light intensity distribution calculation result of the transfer optical image on the 150 nm defocused surface in the semi-dense pattern (q = 2) based on the four point light sources is schematically shown by a dotted line. Note that the horizontal axis σ _X and the vertical axis σ _Y in FIG. 2A are normalized by the numerical aperture NA of the projection lens. In FIG. 2B, the horizontal axis represents position coordinates in the photoresist layer, and the vertical axis represents light intensity (unit is arbitrary).

  Here, the calculation of the light intensity distribution of the transferred optical image is basically based on the method described in paragraph Nos. [0017] to [0039] of Japanese Patent No. 3458549.

  That is, in the projection optical system in the exposure apparatus, the entire diaphragm is disposed on the focal planes of the first group lens group and the second group lens group, which is a bi-telecentric imaging system. Suppose that it is an afocal system. That is, the exposure mask and the pupil plane (substantially equal to the stop), and the pupil plane and the photoresist plane are in a Fourier transform relationship. All of the exposure light from the illumination optical system that illuminates the exposure mask can be expressed by developing a plane wave. Because of the afocal characteristics, each plane wave corresponds to each point light source in the exposure light. For the above description, see FIG. 6 of Japanese Patent No. 3458549.

Because of such characteristics, the coordinate system on the exposure mask, pupil surface, and photoresist surface is (x, y), (ξ, η), (α, β), and the first lens group. If the focal lengths of the lens group and the second lens group are f ₁ and f ₂ , the amplitude distribution f (ξ, η, θ ₁ , θ ₂ ) can be expressed by the following equation (5). Here, θ ₁ and θ ₂ are incident angles of the plane wave incident on the exposure mask in the x and y directions.

When the amplitude distribution on the photoresist surface is g (α, β, θ ₁ , θ ₂ ) and the pupil function is p (ξ, η), the following equation (6) is established.

Further, the light intensity distribution I (α, β, θ ₁ , θ ₂ ) on the photoresist surface of the plane wave incident at the incident angles θ ₁ and θ ₂ can be expressed by the following number (7).

Since the entire light intensity distribution I (α, β) is a superposition of the plane waves, if the weight function is w (θ ₁ , θ ₂ ), the following equation (8) is established.

  Here, assuming that the pattern formed on the exposure mask is a lattice pattern equidistantly parallel to the y direction, the transmission function o (x, y) of the pattern that mathematically expresses the pattern pitch is the pattern frequency. Can be expressed by the following equation (9).

Therefore, the amplitude distribution f (ξ, η, θ ₁ , θ ₂ ) on the pupil plane can be expressed by the following equation (10).

If the wavefront aberration on the pupil plane is W (ξ, η), the amplitude distribution g (α, β, θ ₁ , θ ₂ ) on the wafer surface can be expressed by the following equation (11). The defocus amount is handled as wavefront aberration W (ξ, η).

  Here, as is clear from Equation (11), the spectral distribution of the object on the pupil plane is the sum of the δ function. Therefore, the determination of whether the nth diffracted light enters or does not enter the pupil plane is clear. Therefore, a vignetting factor “Pn” is used to determine whether the diffracted light enters or does not enter the pupil plane in equation (8). That is, when the diffracted light enters the pupil plane, the formula (12-1) is used, and when the diffracted light does not enter the pupil plane, the formula (12-2) is set.

Pn (θ ₁ , θ ₂ ) = 1 (12-1)
Pn (θ ₁ , θ ₂ ) = 0 (12-2)

From the above, the intensity distribution I (α, β, θ ₁ , θ ₂ ) of each plane wave on the photoresist surface can be expressed by the following equation (13).

In the case of ideal imaging that ignores aberrations and the like, W (ξ, η) = 0. Therefore, the intensity distribution I (α, β, θ ₁ , θ ₂ ) of each plane wave can be expressed by the following equation (14).

A value S _q (i · ΔX, j · ΔY), which is a NILS value, is calculated from the light intensity distribution calculation result of the defocused optical image obtained in this manner, based on Expression (2). The above operations are performed for all point light sources within the maximum σ.

  Here, the reason why the calculation of the light intensity distribution of the optical image and the calculation of the NILS value is not performed in the best focus state but in the defocus plane is that the shape of the effective light source is optimized in the best focus state. However, the CD (Critical Dimension) value variation of the pattern formed in the photoresist layer against defocus cannot be suppressed, and a desired depth of focus (DOF), in other words, a desired process margin cannot be obtained. Because.

  The NILS value calculation result in the first quadrant for the point light source within the effective light source within the coherence factor (σ) = 0.9 in the dense pattern (q = 1) is shown in FIG. The figure is shown in FIG.

  Moreover, the NILS value calculation result in the first quadrant regarding the point light source within the effective light source within the coherence factor (σ) = 0.9 in the semi-dense pattern (q = 2) is shown in FIG. The resulting contour diagram is shown in FIG. In this case, the width WD of the optical image for obtaining the NILS value is set to 110 nm in consideration of the omission of the actual photoresist material.

  Furthermore, in the isolated pattern (q = 3), the NILS value calculation result in the first quadrant for the point light source within the effective light source within the coherence factor (σ) = 0.9 is shown in FIG. The resulting contour diagram is shown in FIG. In this case as well, the width WD of the optical image for obtaining the NILS value is set to 110 nm in consideration of the omission of the actual photoresist material.

  As is clear from FIGS. 3B, 4B, and 5B, the NILS value distribution varies greatly depending on each pitch. For this reason, even if these NILS values are simply added and averaged, in most cases, an optimal effective light source shape cannot be obtained comprehensively.

[Step-3]
Next, based on the weight ratio WT _q set at each pitch P _q , a weight average value S _OPT (i · ΔX, j · ΔY) is calculated from the following equation (1). Here, the value of the weight ratio WT _q is set as shown in Table 3 below. However, the setting of the weight ratio WT _q at each pitch P _q is a stack of a large number of data based on the execution of a large number of light source intensity distribution design methods. It can be determined from Here, since the distributions of FIGS. 4B and 5B have relatively similar distributions, the weight ratio WT _q as shown in Table 3 is used.

[Table 3]
q = 1 WT ₁ = 2
q = 2 WT ₂ = 1
q = 3 WT ₃ = 1

The calculation results of the value S _OPT (i · ΔX, j · ΔY) are shown in Table 4 below, and a contour diagram of the calculation results is shown in FIG. When the maximum value of these values S _OPT (i · ΔX, j · ΔY) is Max (S _OPT ), each value S _OPT (i · ΔX, j · ΔY) is Max (S _OPT ). The value S _OPT (i · ΔX, j · ΔY) is normalized.

[Table 4]

[Step-4]
In the first embodiment, the relative light intensity distribution of the value S _OPT (i · ΔX, j · ΔY) is obtained in this way with respect to the angle of the illumination light emitted from the exposure light source and incident on the exposure mask. The light source intensity distribution (effective light source shape) is once determined. Specifically, the calculation results are shown in Table 4, and a contour diagram of the results of the normalization calculation is shown in FIG. The normalized distribution of this value S _OPT (i · ΔX, j · ΔY) is taken as the shape of the effective light source. Then, based on the determined shape of the effective light source (see FIG. 6), a predetermined pitch P _q (q = 1, Q) of Q types (Q = 3 in the first embodiment) formed on the exposure mask. 2... Process margin when the mask pattern having Q) is transferred to the photoresist layer formed on the substrate is calculated. Then, it is evaluated whether or not the calculated process margin satisfies a predetermined process margin at all pitches P _q (q = 1, 2... Q).

More specifically, the mask bias value (mask space dimension value) at each pitch P _q is calculated. Here, a reference pattern for determining an exposure amount is fixed to a pattern corresponding to a dense pattern (q = 1), optical proximity effect correction (OPC) is performed, and an exposure amount at which a space width of 90 nm is obtained. Is determined as a reference exposure amount. Furthermore, with this reference exposure amount, a pattern corresponding to a semi-dense pattern (q = 2) and a pattern corresponding to an isolated pattern (q = 3) are transferred to the photoresist layer, and a space width of 110 nm is transferred to the photoresist layer. The mask space width CD value is obtained such that The calculation results of the mask space width CD value are shown in Table 5 below.

[Table 5]
Space width CD value dense pattern (q = 1) 90nm
Semi-dense pattern (q = 2) 115 nm
Isolated pattern (q = 3) 125nm

  The reference exposure amount, the mask space width CD value for each pitch, and the space width CD value after transfer to the photoresist layer when the exposure amount and defocus are changed as process error factors using the above-mentioned optimum illumination. Calculate for each pitch and calculate the process margin. In Example 1, in consideration of the removal property of the actual photoresist material, the target space width CD value is set to 90 nm in the pattern corresponding to the dense pattern (q = 1), and the semi-dense pattern (q = In the pattern corresponding to 2) and the isolated pattern (q = 3), the target space value CD value is 110 nm.

  In Example 1, the tolerance of the transfer resist space width CD value was ± 10%, and the depth of focus (DOF) when the exposure margin was 7% with respect to the required process margin was 0.25 μm.

As a result of the evaluation, if the calculated process margin does not satisfy the predetermined process margin at all pitches P _q (q = 1, 2,... Q), [Step-3] Return to, change the weight ratio WT _q at each pitch P _q , and specifically increase the weight ratio WT _{q of the} pitch with insufficient process margin and execute [Step-4]. This procedure is repeated until the calculated process margin satisfies the predetermined process margin at all pitches P _q (q = 1, 2,..., Q).

FIG. 7A shows the process margin (exposure amount) for each pitch calculated using the optimized effective light source shown in FIG. 6, the weight ratio WT _q shown in Table 3, and the mask space CD value shown in Table 5. (Example of tolerance and depth of focus). As Comparative Example 1, FIG. 7B shows a simulation example of a process margin for each pitch using σ = 0.9 and the 2/3 ring zone as an exposure light source. Here, in FIGS. 7A and 7B, curves “A”, “B”, and “C” have dense patterns (q = 1), semi-dense patterns (q = 2), and isolated patterns (q = Exposure tolerance in 3). Furthermore, the depth of focus (DOF) value (unit: μm) when the exposure tolerance is 7% is shown in Table 6 below.

  As shown in FIG. 7A, compared with Comparative Example 1 shown in FIG. 7B, particularly in patterns corresponding to a semi-dense pattern (q = 2) and an isolated pattern (q = 3). It can be seen that the process margin has been improved. This is because the light intensity distribution in the light source is optimized for each pitch so that a high NILS value is obtained for each pitch, and the effective light sources optimized for each pitch are multiplied and averaged by an appropriate weighting factor. It is.

[Table 6]
Target space width Example 1 Comparative example 1
Dense pattern (q = 1) 90 nm 0.4915 0.6172
Semi-dense pattern (q = 2) 110 nm 0.2559 0.1721
Isolated pattern (q = 3) 110 nm 0.3194 0.1727

Table 4 shows the calculation results. The normalized distribution (contour diagram in FIG. 6) of the calculation result values S _OPT (i · ΔX, j · ΔY) is defined as the optimum effective light source shape, and the mask space width and The target space width WD is fixed at 90 nm, and the NILS values on the best focus and 150 nm defocus surfaces at all pitches are shown by curves “dotted line A” and “solid line B” in FIG. 8, respectively. In FIG. 8, as Comparative Example 1, σ = 0.9, which is a typical illumination condition, the best focus in the 2/3 annular zone, and the NILS value on the 150 nm defocus plane are also shown by the curve “dotted line a”. And “solid line b”. In Example 1, the NILS value exceeds the annular illumination of Comparative Example 1 at all pitches, and it can be seen that the steepness of the optical image formed on the photoresist layer is improved. Further, in FIG. 8, when Example 1 and Comparative Example 1 are compared, the NILS value undulation with respect to the pitch is smaller in Example 1 at both the best focus and the defocus. This is due to the fact that the effective light source has a gray gradation. This produces an effect that the required range of the pattern correction value of the exposure mask based on the optical proximity effect correction can be reduced.

  As described above, from the dense pattern (q = 1) to the isolated pattern (q = 3), the process margin is improved as compared with the annular illumination which is a typical example of the prior art, and the light source intensity distribution design of the present invention is performed. It turns out that the method is effective.

In the first embodiment, as a result of the evaluation, as shown in FIG. 7A, the calculated process margin is predetermined at all pitches P _q (q = 1, 2,... Q). Since the process margin (specifically, the depth of focus (DOF) of 0.25 μm when the exposure tolerance is 7%) was satisfied, it was emitted from the exposure light source without returning to [Step-3], The process ends when an optimum light source intensity distribution (optimized effective light source shape) with respect to the angle of the illumination light incident on the exposure mask is obtained.

  An example for realizing an optimum light source intensity distribution with respect to the angle of the illumination light thus obtained in the exposure apparatus is shown in FIG. 9 as a conceptual diagram. This exposure apparatus includes a diffractive optical element (DOE) on which exposure light (laser light) that is emitted from an exposure light generation unit 11 and an exposure light generation unit 11 that are laser devices and passes through a beam shaping optical system (not shown) is incident. ) 12, Uniformer 14 including a fly's eye (fly eye) lens on which exposure light (laser light) emitted from a diffractive optical element (DOE) 12 and passed through a collimating lens system 13 is incident, condenser lens 15, and projection It is composed of a system lens group 16. An exposure mask 20 is disposed between the condenser lens 15 and the projection system lens group 16. In FIG. 9, reference numeral 30 denotes a photoresist layer applied and formed on a substrate (not shown). The equivalent light source surface 15A in the illumination light that illuminates the exposure mask 20 has a conjugate relationship with the pupil surface 16A of the projection system lens group 16. Therefore, the light source intensity distribution with respect to the angle of the optimized illumination light may be formed on the equivalent light source surface 15A. In addition, the schematic diagram which expanded the part which the exposure light (laser light) inject | emitted from the diffractive optical element (DOE) 12 and passed through the collimating lens system 13 injected into the uniform 14 consisting of a fly's eye (fly eye) lens. Is shown in FIG.

  Here, the diffractive optical element (DOE) 12 is based on, for example, the technique disclosed in Japanese Patent Application Laid-Open No. 2001-242414, that is, the step of generating an initial solution of the phase function of the diffractive optical element and the initial solution of the phase function. Using the step of calculating the point spread function and the distribution of this point spread function and the target function determined from this point spread function as an evaluation function, the optimization function is What is necessary is just to design based on the design method of the beam shaping element which has the process of converging a solution.

  Whether or not the shape of the effective light source is obtained based on the diffractive optical element (DOE) 12 thus obtained is determined by, for example, the technique disclosed in Japanese Patent Laid-Open No. 2001-230180, that is, the light emitted from the illumination optical system. An optical system including a light transmission pattern in which a light transmitting part and a light shielding part are repeated at a finite period, and a diffraction grating pattern having a plurality of ratios of the light transmitting part and the light shielding part is provided and the periphery is shielded by a light shielding region Based on the pattern image of the 0th-order diffracted light transferred to the photomask on which the pattern is formed by the member, the 0th-order diffracted light generated through the photomask is transferred onto the wafer through the projection optical system. An exposure apparatus for measuring a light intensity distribution in a secondary light source viewed from an illumination optical system from a photomask, wherein the photomask and the wafer are transferred in a non-conjugated state with respect to the projection optical system Based on the test method, it should be verified.

  Example 2 relates to an exposure method of the present invention and a method of manufacturing a semiconductor device of the present invention. In other words, the exposure method is used in a lithography process in the manufacturing process of a semiconductor device. Light (illumination light) emitted from an exposure light source is irradiated onto an exposure mask, and a pattern formed on the exposure mask is applied to a substrate. This is an exposure method for transferring to a coated photoresist layer. In addition, regarding a method for manufacturing a semiconductor device, light (illumination light) emitted from an exposure light source is irradiated onto an exposure mask, and a pattern formed on the exposure mask is transferred to a photoresist layer formed on a substrate. And a method of manufacturing a semiconductor device including a step of etching a substrate using an etching mask obtained by developing the photoresist layer. Then, an optimized light source intensity distribution (optimized effective light source shape) with respect to the angle of illumination light emitted from the exposure light source and incident on the exposure mask is set based on the first embodiment.

  In the second embodiment, specifically, as shown in the schematic partial cross-sectional view of FIG. 11A, the base is composed of an interlayer insulating layer 41 formed above the semiconductor substrate 40. However, it is not limited to this. Then, for example, a positive photoresist layer 42 is applied and formed on the interlayer insulating layer 41. The optimized light source intensity distribution with respect to the angle of illumination light emitted from the exposure light source and incident on the exposure mask, determined by the same method as in the first embodiment, is defined between the exposure light source and the exposure mask. Using the exposure apparatus obtained based on the diffractive optical element arranged in the above, the exposure mask 50 is irradiated with illumination light, and the mask pattern formed on the exposure mask 50 is formed on the interlayer insulating layer 41 which is the substrate. The transferred photoresist layer 42 is transferred. This state is shown in FIG. 11B, and the hatched portion of the photoresist layer 42 is a pattern transfer portion. Reference numerals 51 and 52 are a glass substrate and a light-shielding thin layer constituting the exposure mask 50, respectively. Next, after developing the photoresist layer 42, the trench 43 is formed in the interlayer insulating layer 41 by etching the substrate, more specifically the interlayer insulating layer 41, using the patterned photoresist layer 42 as an etching mask. (See FIG. 11C). Thereafter, the photoresist layer 42 is removed by ashing (see FIG. 11D), and a copper layer is formed on the interlayer insulating layer 41 including the inside of the trench 43 by a plating method. The copper wiring 44 can be formed in the trench 43 by removing the copper layer based on, for example, a chemical / mechanical polishing method (CMP method). Thus, a semiconductor device having the structure shown in FIG. 11E can be manufactured.

  As mentioned above, although this invention was demonstrated based on the preferable Example, this invention is not limited to these Examples. The materials and various conditions used in the examples are examples and can be changed as appropriate. Moreover, each process in Example 1 or Example 2 can also be changed.

FIG. 1 is a flowchart for explaining a light source intensity distribution designing method according to the first embodiment. 2A shows a point light source in which the exposure light source is divided into a matrix, and FIG. 2B shows four point light sources (point A ₁ to point A ₄ and point B ₁ to point B). is a graph showing the calculation result of the defocus optical image based on the B _4). 3A and 3B are a NILS value calculation result in the first quadrant in the dense pattern (q = 1) of Example 1, and a contour diagram of the calculation result, respectively. 4A and 4B are a NILS value calculation result in the first quadrant in the semi-dense pattern (q = 2) of Example 1, and a contour diagram of the calculation result, respectively. 5A and 5B are NILS value calculation results in the first quadrant in the isolated pattern (q = 3) of Example 1, and contour diagrams of the calculation results, respectively. FIG. 6 is a contour diagram of the calculation result of the value S _OPT (i · ΔX, j · ΔY) in the first embodiment. 7A is a diagram showing a simulation example of the process margin for each pitch calculated with the weight ratio WT _q in the first embodiment, and FIG. 7B is a process for each pitch in the first comparative example. -It is a figure which shows the simulation example of a margin. FIG. 8 is a diagram showing NILS values on the best focus and 150 nm defocus planes at all pitches with the space width fixed at 90 nm in Example 1 and Comparative Example 2. FIG. 9 is a conceptual diagram of the exposure apparatus according to the first embodiment. FIG. 10 is an enlarged schematic view of a portion where illumination light (laser light) emitted from a diffractive optical element (DOE) and passed through a collimating lens system is incident on a uniform formed of fly-eye lenses. is there. 11A to 11E are schematic partial cross-sectional views of a semiconductor substrate and the like for explaining the second embodiment. FIG. 12 is a diagram showing the quadrupole illumination of 45 degrees orientation disclosed in Japanese Patent No. 3458549. FIG. 13 is a diagram showing a light source shape (light intensity distribution) in Japanese Patent No. 3458549.

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 ... Exposure light generation part, 12 ... Diffractive optical element (DOE), 13 ... Collimating lens system, 14 ... Uniformer, 15 ... Condenser lens, 15A ... Illumination optical system Pupil plane (equivalent light source plane), 16 ... projection system lens group, 16A ... pupil plane of projection system lens group, 20 ... exposure mask, 30 ... photoresist layer, 40 ... semiconductor Substrate, 41 ... interlayer insulating layer, 42 ... photoresist layer, 43 ... trench, 44 ... copper wiring, 50 ... exposure mask, 51 ... glass substrate, 52 ... Light shielding thin layer

Claims (8)

Angle of light used in a lithography process in the manufacturing process of a semiconductor device and emitted from an exposure light source for transferring a pattern formed on an exposure mask to a photoresist layer formed on a substrate and entering the exposure mask A light source intensity distribution design method for
(A) In light emitted from the exposure light source, four points (i · ΔX, j · ΔY), (−i · ΔX, j · ΔY), (−i · ΔX, −j) in the pupil coordinates of the equivalent light source surface ΔY), (i · ΔX, −j · ΔY) [where i = 0, 1, 2,... I, j = 0, 1, 2,... J, ΔX · I = σ, ΔY · J = σ, where σ indicates the size of the light source, and light assumed to be emitted from each of the point light sources positioned at a positive real number of 1 or less was formed on the exposure mask. A light intensity distribution is obtained by calculation for each pitch when diffracted by a pattern having Q kinds of predetermined pitches P _q (q = 1, 2,... Q) and imaged on the photoresist layer. a normalized image intensity log slope values or contrast values from the distribution value _{S q (i · ΔX, j} · ΔY) of i = 0 to i, for j = 0~J calculated And,
(B) Based on the weight ratio WT _q set at each pitch P _q , the weight average value S _OPT (i · ΔX, j · ΔY) is calculated from the following equation (1):
(C) Design a light source intensity distribution with respect to an angle of light emitted from the exposure light source and incident on the exposure mask so that a relative light intensity distribution of value S _OPT (i · ΔX, j · ΔY) is obtained.
A light source intensity distribution design method characterized by comprising steps.

  The light source intensity distribution with respect to the angle of the light emitted from the exposure light source and incident on the exposure mask can be obtained based on a diffractive optical element disposed between the exposure light source and the exposure mask. Light source intensity distribution design method. Following the step (C),
(D) Based on the light source intensity distribution with respect to the set light angle, a pattern having Q types of predetermined pitches P _q (q = 1, 2... Q) formed on the exposure mask is applied and formed on the substrate. Calculate the process margin when transferred to the photoresist layer
(E) Evaluating whether or not the calculated process margin satisfies a predetermined process margin at all pitches P _q (q = 1, 2,... Q)
Further comprising a step,
When the calculated process margin does not satisfy the predetermined process margin at all the pitches P _q (q = 1, 2,... Q), the weight ratio WT at the pitch P _q in the step (B). _q is changed, and the process (B), the process (C), the process (D), and the process (E) are performed at all the pitches P _q (q = 1, 2,... Q). 2. The light source intensity distribution design method according to claim 1, wherein the calculation is repeated until the calculated process margin satisfies a predetermined process margin. In the change of the heavy rate WT _q, calculated process margin of claim 3, wherein the changing the weight ratio WT _q with respect to the pitch P _q which does not satisfy the predetermined process margin Light source intensity distribution design method. In the step (A), four points (i · ΔX, j · ΔY), (−i · ΔX, j · ΔY), (−i · ΔX, −j · ΔY), ( The light that is assumed to be emitted from each of the point light sources located at i · ΔX, -j · ΔY) is diffracted by a pattern having a predetermined pitch P _q of Q types formed on the exposure mask. 2. The light source according to claim 1, wherein a light intensity distribution formed on the defocus surface defocused by a predetermined amount defined based on a depth of focus required in the process from the focus surface is calculated for each pitch. Intensity distribution design method. An exposure apparatus having an exposure light source and a diffractive optical element for use in a lithography process in a manufacturing process of a semiconductor device and for transferring a pattern formed on an exposure mask to a photoresist layer coated on a substrate. ,
(A) In light emitted from the exposure light source, four points (i · ΔX, j · ΔY), (−i · ΔX, j · ΔY), (−i · ΔX, −j) in the pupil coordinates of the equivalent light source surface ΔY), (i · ΔX, −j · ΔY) [where i = 0, 1, 2,... I, j = 0, 1, 2,... J, ΔX · I = σ, ΔY · J = σ, where σ indicates the size of the light source, and light that is assumed to be emitted from each of the point light sources located at 1 or less is formed on the exposure mask. A light intensity distribution is calculated for each pitch when diffracted by a pattern having Q kinds of predetermined pitches P _q (q = 1, 2,... Q) and imaged on the photoresist layer. a normalized image intensity log slope values or contrast values from the distribution value _{S q (i · ΔX, j} · ΔY) of i = 0 to i, for j = 0~J calculated And,
(B) Based on the weight ratio WT _q set at each pitch P _q , the weight average value S _OPT (i · ΔX, j · ΔY) is calculated from the following equation (1):
(C) Design a light source intensity distribution with respect to the angle of light emitted from the exposure light source and incident on the exposure mask so that a relative light intensity distribution of value S _OPT (i · ΔX, j · ΔY) is obtained.
Diffraction optics arranged between the exposure light source and the exposure mask, the light source intensity distribution with respect to the angle of the light emitted from the exposure light source and incident on the exposure mask, which is set based on the light source intensity distribution design method comprising the steps An exposure apparatus characterized in that it can be based on an element.

An exposure that is used in a lithography process in the manufacturing process of a semiconductor device, irradiates an exposure mask with light emitted from an exposure light source, and transfers a pattern formed on the exposure mask onto a photoresist layer formed on a substrate. A method,
The light source intensity distribution with respect to the angle of light emitted from the exposure light source and incident on the exposure mask,
(A) In light emitted from the exposure light source, four points (i · ΔX, j · ΔY), (−i · ΔX, j · ΔY), (−i · ΔX, −j) in the pupil coordinates of the equivalent light source surface ΔY), (i · ΔX, −j · ΔY) [where i = 0, 1, 2,... I, j = 0, 1, 2,... J, ΔX · I = σ, ΔY · J = σ, where σ indicates the size of the light source, and light that is assumed to be emitted from each of the point light sources located at 1 or less is formed on the exposure mask. A light intensity distribution is calculated for each pitch when diffracted by a pattern having Q kinds of predetermined pitches P _q (q = 1, 2,... Q) and imaged on the photoresist layer. a normalized image intensity log slope values or contrast values from the distribution value _{S q (i · ΔX, j} · ΔY) of i = 0 to i, for j = 0~J calculated And,
(B) Based on the weight ratio WT _q set at each pitch P _q , the weight average value S _OPT (i · ΔX, j · ΔY) is calculated from the following equation (1):
(C) Design a light source intensity distribution with respect to the angle of light emitted from the exposure light source and incident on the exposure mask so that a relative light intensity distribution of value S _OPT (i · ΔX, j · ΔY) is obtained.
An exposure method comprising: setting based on a light source intensity distribution design method comprising steps.

Etching obtained by irradiating an exposure mask with light emitted from an exposure light source, transferring a pattern formed on the exposure mask to a photoresist layer formed on a substrate, and developing the photoresist layer A method of manufacturing a semiconductor device including a step of etching a substrate using a mask for manufacturing,
The light source intensity distribution with respect to the angle of light emitted from the exposure light source and incident on the exposure mask,
(A) In light emitted from the exposure light source, four points (i · ΔX, j · ΔY), (−i · ΔX, j · ΔY), (−i · ΔX, −j) in the pupil coordinates of the equivalent light source surface ΔY), (i · ΔX, −j · ΔY) [where i = 0, 1, 2,... I, j = 0, 1, 2,... J, ΔX · I = σ, ΔY · J = σ, where σ indicates the size of the light source, and light assumed to be emitted from each of the point light sources positioned at a positive real number of 1 or less was formed on the exposure mask. A light intensity distribution is calculated for each pitch when diffracted by a pattern having Q kinds of predetermined pitches P _q (q = 1, 2,... Q) and imaged on the photoresist layer. a normalized image intensity log slope values or contrast values from the distribution value _{S q (i · ΔX, j} · ΔY) of i = 0 to i, for j = 0~J calculated And,
(B) Based on the weight ratio WT _q set at each pitch P _q , the weight average value S _OPT (i · ΔX, j · ΔY) is calculated from the following equation (1):
(C) Design a light source intensity distribution with respect to the angle of light emitted from the exposure light source and incident on the exposure mask so that a relative light intensity distribution of value S _OPT (i · ΔX, j · ΔY) is obtained.
A method of manufacturing a semiconductor device, wherein the method is set based on a light source intensity distribution design method comprising steps.

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