KR100673152B1 - A method for forming a pattern of a semiconductor device - Google Patents

Abstract

According to the present invention, since the exposure process is performed by inserting an incident copper filter having an inverse function of the Gaussian function, the pattern of the photoresist film is canceled by canceling the acid diffusion effect generated in the photoresist film during the post-exposure heat treatment process. (Pattern) relates to a method of forming a pattern of a semiconductor device for preventing distortion.

Since the pattern forming method of the semiconductor device of the present invention performs an exposure process using an exposure apparatus in which an incident copper filter having a light shielding region is inserted into a portion of the center portion, which is a low frequency region, to have a light intensity of the inverse function form of the Gaussian function, The light blocking layer in the center portion of the incident copper filter lowers the light intensity in the low frequency region, while the light intensity in the constant high frequency region is relatively increased, thereby improving image contrast, resolution and process margin of the pattern, and exposing the light. In the post-heat treatment process, the acid diffusion effect generated in the photosensitive film is canceled to suppress the pattern distortion of the photosensitive film, thereby improving yield and economic efficiency of the device.

Description

A method for forming a pattern of a semiconductor device

1 is a schematic view showing a general exposure apparatus

2 is a plan view illustrating an incident copper filter used in a conventional method for forming a pattern of a semiconductor device;

3 is a plan view illustrating an incident copper filter used in a method of forming a pattern of a semiconductor device according to an exemplary embodiment of the present disclosure.

4 is a view showing the light intensity of the incident copper filter of the present invention

<Description of Symbols for Major Parts of Drawings>

1: photosensitive film 2: projection lens

3: entrance pupil 4: mask

5: condenser lens 21, 31: incident copper filter

32: shading area

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of forming a pattern of a semiconductor device. In particular, in a lithography process, an incident copper filter having a light intensity of an inverse function of a Gaussian function is inserted into an exposure apparatus in a lithography process. It relates to a method for forming a pattern of a semiconductor device to improve the.

1 is a schematic diagram showing a general exposure apparatus, and FIG. 2 is a plan view showing an incident copper filter used in a conventional method for forming a pattern of a semiconductor element.

All optical lithography or non-photolithography processes using projection printing or reflective printing rather than contact printing use a lens system depending on the reduction magnification.

In general, an exposure apparatus such as a stepper or a scanner includes a projection lens 2 and an entrance pupil 3 which are sequentially spaced with each other on the photoresist film 1 and the photoresist film 1 as shown in FIG. 1. ), A mask (4) and a condenser lens (5) to transfer the pattern of the mask (4) to the photosensitive film (1) by using a lens system of the projection lens (2) and the condenser lens (5).轉 寫)

Here, the entrance pupil 3 is an empty space as a virtual entrance to which light enters the projection lens 2.

The center of the incident pupil 3 is a low frequency region, and the outer periphery of the incident pupil 3 is a fine pattern region, that is, a high frequency region, than the pattern of the low frequency region.

That is, in the pattern on the mask 4, the pattern with low periodicity enters light near the center of the incident pupil 3, and the fine pattern with high periodicity enters light around the incident pupil 3.

In addition, an incident pupil filter for changing light intensity or phase of light may be provided in the incident pupil 3 which is an empty space.

In the conventional method for forming a pattern of a semiconductor device, in the general exposure apparatus, as shown in FIG. 2, an incident copper filter 21 including holes is provided in the incident pupil 3 of FIG. 1.

Then, light is irradiated from above the exposure apparatus to transfer the mask 4 pattern of the exposure apparatus to the photosensitive film 1.

Subsequently, the exposed photosensitive film 1 is selectively etched to form a pattern.

However, since the pattern formation method of the conventional semiconductor device uses an incidence copper filter composed of holes, since the light intensity of the low frequency region and the high frequency region is the same, it is difficult to form a fine pattern due to image contrast and resolution of the high frequency region and the limitation of the process margin. There was a problem that the pattern of the photosensitive film is distorted by the acid diffusion effect generated in the.

The present invention has been made to solve the above problems by inserting an incident copper filter having a light intensity of the inverse function of the Gaussian function to perform the exposure process to cancel the acid diffusion effect generated in the photosensitive film in the post-exposure heat treatment process It is an object of the present invention to provide a method of forming a pattern of a semiconductor device for preventing pattern distortion of the photosensitive film.

The pattern forming method of the semiconductor device of the present invention comprises the steps of forming a photoresist film on the semiconductor substrate, and a concentric incidence copper filter having a light shielding area at a portion of the edge portion and the center portion to have a light intensity of the inverse function of the Gaussian function And exposing the photosensitive film with incoherent light by using an exposure apparatus having an interposed therebetween, and developing the exposed photosensitive film to form a pattern.

Referring to the accompanying drawings, a preferred embodiment of the method for forming a pattern of a semiconductor device according to the present invention as described above in detail as follows.

3 is a plan view illustrating an incident copper filter used in a method of forming a pattern of a semiconductor device according to an exemplary embodiment of the present invention, and FIG. 4 is a diagram illustrating light intensity of the incident copper filter of the present invention.

 In the method of forming a pattern of a semiconductor device according to an embodiment of the present invention, as shown in FIG. 3, the light shielding region 32 is formed in a part of the center portion, which is a low frequency region, to have the intensity of light in the inverse function of the Gaussian function. An incident copper filter 31 having a structure is installed in the incident pupil.

Then, light is irradiated from above the exposure apparatus to transfer the mask pattern of the exposure apparatus to the photosensitive film.

Subsequently, the exposed photosensitive film is developed to form a pattern.

Here, the formation conditions of the incident copper filter 31 having the intensity of light in the inverse function form of the Gaussian function are as follows.

When acid is generated in the exposed photosensitive film, an acid diffusion effect is generated by thermal energy in a post-exposure heat treatment process.

Among the theories used in the simulation of the acid diffusion effect, in the DIFfused Aerial Image Model (DAIM), when the intensity of light distribution immediately before being incident on the photosensitive film 1 is I, I _d after the diffusion effect is represented by Equation 1.

<Equation 1>

Here, ε and η are coordinates corresponding to x and y of the spatial frequency domain, respectively, and F and F ⁻¹ mean a Fourier transform and an Inverse Fourier transform, respectively.

And sigma _B is the diffusion length of the acid.

As described above, the acid diffusion effect is closely related to the spatial frequency of the mask pattern, and the lens is also closely related to the spatial frequency.

That is, if the mask pattern is M, I is represented by Equation 2.

<Equation 2>

I = | F ^-1 [LF (M)] | ² Full Coherence

= F ^-1 [LF (M)] Fully Incoherent

Here, L is a function representing the incident pupil of the lens. When there is no incident pupil filter, L is a function up to NA, which is the size of the lens, and a value greater than NA is 0.

M is a function representing the phase magnitude through the mask in the case of full coherence, and a function indicating the intensity of light passing through the mask in the case of completely incoherence.

In the case of complete incoherence, the acid diffusion effect generated in the photosensitive film is canceled by selecting L from Equations 1 and 2 to prevent the pattern distortion of the photosensitive film.

That is, in the case of optical lithography, the selection condition of L should use incoherent light in the first step and an incident copper filter capable of removing the pattern distortion of the photosensitive film in the second step.

In addition, in the case of non-light lithography, there is no concept of coherence, so only the second stage, that is, the incident pupil filter, is used.

The incoherent light is produced by making the line width of a laser used as a light source in optical lithography very small.

That is, the line width of the laser is 10 fsec (3 μm) or less so that the interference distance is sufficiently small, thus making the coherent light less coherent.

In the case of fully incoherent light, the lens becomes a light intensity conversion function expressed by Equation (3).

<Equation 3>

I = F ^-1 [LF (M)]

Equation 4, which is a function multiplied in the Fourier region of Equation 1, is referred to as a photosensitive film function.                     

〈Equation 4〉

The photoresist function varies according to the type of the photoresist 1, and the photoresist function represented by Equation 4 is a chemically amplified photoresist, and the photoresist function in the case of a Novolac type like an I-line photoresist is As shown in Equation 5, there is a diffusion effect but no amplification effect.

<Equation 5>

As described above, in the case of incoherent light, since both the photoresist film and the lens act as a light intensity conversion function, the equation (3) is substituted into the equation (1) in consideration of the photoresist film and the lens at the same time. .

<Equation 6>

I _d = F ^-1 [RF (I)]

= F ^-1 [RF (F ^-1 [LF (M)])]

= F ^-1 [RLF (M)]

Here, R is a photosensitive film function represented by Equation 3 or Equation 4.                     

The relationship between the pattern I _d of the photosensitive film and the pattern M of the mask from Equation 6 is as follows.

First, in the case of incoherent light, a function represented by the product of the photoresist function R and the lens function L in the Fourier region serves as a light intensity conversion function.

As a result, the pattern distortion of the photoresist film is blocked by the lens, the distortion by the photoresist function, and the like act as a product in the Fourier region.

The spatial frequency coordinates ε and η have a size of [m ⁻¹ ], so that ε → ε ＇· (2π / P), η → η＇ · (2π / P) (P (Pitch) is a pattern When the incident pupil filter is not installed, the lens function L is generally expressed as in Equation (7).

<Equation 7>

That is, it means that the light that enters the inside of the lens passes but the light that passes outside does not pass.

As shown in Equation 8, when the inverse dynamic filter of the inverse of the photosensitive film function, that is, the incident copper filter having the light intensity of the inverse function of the Gaussian function, the pattern distortion by the photosensitive film function is removed.

<Equation 8>

In the case of Equation 8, since the pattern image is I _d = M from Equation 6, a pattern without distortion is implemented.

In the case of the incident copper filter satisfying Equation 8, Equation 9 is obtained when the photosensitive film is chemically amplified, and Equation 10 when the photosensitive film is novolak-type.

<Equation 9>

〈Equation 10〉

Where P _D is Angular Diffusion Length at 2πσ _B.

P is a period of a pattern to be defined, and when the pattern to be defined is composed of several different periods, P is defined as the most frequent, average, or highest frequency.

라 할 때, ρ = 1의 값으로 상기 수학식 9와 수학식 10을 각각 규격화하면 수학식 11과 같다.The radius of the spatial frequency domain

In the case of Equation (9) and Equation (10), respectively, with the value of ρ = 1, Equation 11 is obtained.

<Equation 11>

Here, β is P _D / P and has a range of 0.1 to 10.

As shown in FIG. 4, which shows a result when β = 1.5 in Equation 11, when the light intensity outside the incident pupil is 1, the intensity of the central light is 60% (chemically amplified photosensitive film) or 32. An incident copper filter was produced so as to be% (novolak-type photosensitive film).

When the angular diffusion parameter P _D is 0.45 μm and the period P of the pattern is 0.3 μm, β = 0.15, thereby eliminating the pattern distortion caused by the photosensitive film 1 when the incident copper filter is patterned with incoherent light.

As described above, when the incident pupil filter 31 having the light intensity of the inverse function of the Gaussian function is mounted, part of the center portion of the incident pupil is blocked, so that information on the low frequency pattern is lost, but vice versa. Image contrast forms a good pattern without distortion because the image contrast increases relatively and also counteracts the diffusion effect of acid generated in the photosensitive film.

In addition, the present invention is a design method of the light intensity incident copper filter when the non-coherent light as a light source, but non-light such as E-Beam, X-Ray, and Ion beam that do not use light. Lithography can also design light intensity incident copper filters.

Since the pattern forming method of the semiconductor device of the present invention performs an exposure process using an exposure apparatus in which an incident copper filter having a light shielding region is inserted into a portion of the center portion, which is a low frequency region, to have a light intensity of the inverse function form of the Gaussian function, The light blocking layer in the center portion of the incident copper filter lowers the light intensity in the low frequency region, while the light intensity in the constant high frequency region is relatively increased, thereby improving image contrast, resolution and process margin of the pattern, and exposing the light. In the post-heat treatment process, the acid diffusion effect generated in the photosensitive film is canceled to suppress the pattern distortion of the photosensitive film, thereby improving the yield and economy of the device.

Claims (3)

Forming a photoresist film on the semiconductor substrate; Exposing the photosensitive film with incoherent light using an exposure apparatus having a concentric incidence pupil filter having a light shielding area at a portion of an edge portion and a central portion so as to have a light intensity in an inverse function form of a Gaussian function; And And developing the exposed photoresist to form a pattern. The method of claim 1, When defined as the intensity L of the light incident on the incident copper filter, the normalized radius p of the lens of the exposure apparatus, σ _B which is the diffusion length of the acid generated in the photosensitive film, and P which is the period of the pattern to be defined, And the incident copper filter is formed to satisfy the above equation. The method of claim 1, The pattern forming method of a semiconductor device, characterized in that the non-coherent light is made with a laser having a line width of 1 to 10 fsec.

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