JPH03254117A - Thin-film elimination method - Google Patents

Abstract

PURPOSE:To prevent smear of a thin-film surface due to thin-film fine particles which scatters when a beam is projected by forming a smear-preventing film on the thin film previously and then eliminating this smear-preventing film after machining by the beam. CONSTITUTION:A smear-preventing film 1 is formed on a surface of a thin film 2 previously, an energy beam 5 is projected onto this smear-preventing film 1 to allow a desired part of the smear-preventing film 1 and a thin film 2 to be eliminated, and then the smear-preventing film 1 on the thin film 2 which has not been eliminated is eliminated. Thus, the thin films which scattered due to pumping phenomenon etc., attach onto the smear-preventing film 1, and the thin films which attach onto the smear-preventing film 1 are eliminated along with the smear-preventing film 1 after irradiation with the energy beam 5. Thus preventing thin pieces of the thin film which scattered onto the surface of the thin film 2 from remaining, thus preventing the surface of the thin film 2 from being smeared and enabling the desired part of the thin film 2 to be eliminated.

Description

Detailed Description of the Invention [Industrial Field of Application] The present invention provides a method for forming a thin film as desired by selectively irradiating an energy beam onto a thin film deposited on a supporting substrate such as a semiconductor substrate (wafer). Concerning how to remove the part.

[Prior Art] In the photoresist process of manufacturing semiconductor devices, a wafer coated with a photoresist is generally irradiated with ultraviolet light through a photomask to print a mask pattern. There are two types of photoresists: positive type and negative type.
For positive type, the area exposed to ultraviolet rays becomes soluble after 7 days of development, while for negative type, the area exposed to ultraviolet rays becomes insoluble during development.

In recent years, with the large-scale integration of semiconductor devices, it has become necessary to respond to further miniaturization of the semiconductor device manufacturing process to the level of light sockeye. In optical lithography technology for achieving high integration, ultra-high pressure mercury lamps are used as ultraviolet light sources, and have played a central role in forming fine patterns. Furthermore, in order to form fine patterns in the submicron range that will be required for future integrated circuits, the use of light sources with shorter wavelengths is being regulated. We are waiting for the development of a photoresist that can achieve high resolution.

On the other hand, photo-etching methods that do not require a subsequent development step are being considered. This one? In the past, high-energy ultraviolet light such as an excimer laser was passed through a photomask, or
By scanning the beam two-dimensionally, unnecessary portions of the resist on the wafer are selectively irradiated. When the resist is irradiated with high-energy ultraviolet light, its molecular bonds are broken, and the scattered molecules are oxidized and become volatile molecules (H2O, (
:02 etc.) to form the desired pattern.

[Problems to be Solved by the Invention] However, in the conventional techniques as described above, the photoetching method does not depend on the characteristics of the resist such as photosensitivity and resolution, so it is difficult to form a fine pattern in the submicron region. Although it has the advantage of being able to use a resist, it has the disadvantage that its removal speed is slow and impractical. In order to increase the removal rate, it is necessary to irradiate the resist with high energy ultraviolet light. However, when such a high-energy beam is irradiated onto the resist surface, a rapid rise occurs in the surface area, and due to the stress caused by the difference in the degree of thermal expansion with the lower layer, the surface area increases. A phenomenon in which the resist becomes small pieces and flies away (also known as bombing) may occur. The blown resist adheres to the periphery of the beam irradiation area and contaminates the surface of the resist layer, thereby interfering with the next manufacturing process.

In addition, in the conventional optical solenoid printing process, the reticle or mask to be overlaid and exposed is aligned with the wafer by charging and detecting optical information from alignment marks attached to the wafer tip area. (alignment). Typically, wafer alignment is performed by irradiating an alignment mark with light and photoelectrically detecting reflected light, scattered light, diffracted light, etc. from the mark.

However, since a resist is thermally applied to the wafer before exposure, detection of the alignment mark is performed through the resist layer (1 to 2 μm thick). When alignment is performed via the projection optical system of the exposure device (TTL Through The Lens),
Since the projection optical system has strong chromatic aberration, is it necessary to use exposure light during alignment? Naturally, exposure light is absorbed by the resist, so it is difficult to determine whether the optical information generated from the alignment mark is affected by the resist layer. This results in the inconvenience of being weakened.

Furthermore, since the alignment mark has a minute step structure, it is inevitable that the resist film thickness will be non-uniform around the mark. For this reason, the alignment accuracy decreases because the interference effect inherent to the thin film becomes noticeable in the vicinity of the mark, or because the unevenness of the resist film thickness becomes asymmetrical at both ends of the mark.

Furthermore, when using a multilayer resist to achieve finer patterns, the alignment mark itself may become optically invisible under the illumination wavelength, making it difficult to ensure alignment accuracy. It has become.

Therefore, is it possible to partially remove the resist by irradiating the resist layer above the mark with a high-energy beam such as an excimer laser prior to the alignment operation? For these reasons, the resist surface may become contaminated, which may interfere with the next manufacturing process.

This invention was made in view of these points, and W.
# Aims to provide a thin film removal force that can remove a desired portion of the thin film without contaminating the film surface.

[Means for Solving the Problems] In the present invention, a thin rA varnish deposited on a support substrate is used.
- When removing a desired portion of a thin film by selectively irradiating an energy beam, a contamination prevention film is applied on the surface of the thin film in advance, and the energy beam is irradiated from above this contamination prevention film. The above object is achieved by removing both the anti-contamination film and the desired portion of the thin film, and then removing the anti-contamination film on the thin film that was not removed.

[Function] In the present invention, a contamination prevention film is applied to the surface of the thin film prior to energy beam irradiation, so that all of the thin film blown away by the bombing phenomenon etc. will adhere to the contamination prevention film. Become. The thin film attached to the pollution prevention film is
Since it is removed along with the anti-contamination film after irradiation with the energy beam, no scattered pieces of the thin film remain on the surface of the thin film.

As the anti-contamination film, one that satisfies the following conditions can be used.

■Can be dissolved and removed using a solvent that does not dissolve the thin film.

■Absorbs the irradiated energy beam. If the contamination prevention film itself hardly absorbs the beam, even if the lower layer thin film absorbs well, the upper layer will remain stretched, making it impossible to remove the desired portion of the thin film.

■When depositing on thin M, do not place the groove film on a stand. Isn't it true that the thin film and anti-contamination film should not be mixed together at all?When separating and removing the anti-staining film later, there should be no unevenness on the surface of the thin film that could interfere with subsequent processes. No.

[Example] Hereinafter, the present invention will be described in detail with reference to the drawings.

First, the outline of the thin film removal old note process according to the embodiment of the present invention will be explained with reference to FIGS. 1(a) to (C). In this method, as shown in FIG. 1(a), a contamination prevention film 1 is further coated on the surface of the resist layer 2 (thin film) on the support substrate 4 (wafer) prior to irradiation with the high-energy beam 5. do. At this time, the contamination prevention film 1 may be applied uniformly over the entire surface of the resist layer 2, or in some cases, it may be applied only to a certain area centered on the removal area where contamination is expected. good.

Next, as shown in FIG. 1(b), the high energy beam 5
is applied to a desired area of the resist layer 2, and both the resist layer 2 and the anti-contamination film 1 are removed. At this time, the irradiated resist layer 2 and contamination prevention film 1 are cut by their molecular bonds or by photon energy and scattered into fine particles, and some are further oxidized and become volatile substances such as CO2, 820. ,
Most of the particles remain in the form of fine particles (fine particles 3) and are scattered around and adhere to the pollution prevention film 1.

Thereafter, as shown in FIG. 1C, the contamination prevention film 1 is physically peeled off from the surface as a resist layer 2 or dissolved and removed using an etching solution to complete this process.

In dissolving and removing the contamination prevention film 1, for example, if a positive resist is used as the resist layer 2 in which the light-exposed part becomes soluble, the light-exposed part of the contamination prevention film 1 undergoes a crosslinking reaction and dissolves in the solvent. If a negative resist is used, only the negative resist is dissolved in the developer before exposure, so it is possible to remove only the contamination prevention film 1 by immersion in the developer.

In addition, as a contamination prevention film for positive resist N2, ARC (product name: BRE), which has a high absorption of g-rays and is generally used for the purpose of reducing the occurrence of standing branching, is recommended.
(manufactured by WER5CIENCE) and interlayer parts for Al-Ihacell! BC5 (product name +
(manufactured by General Electric), etc. can be used. ARC can be removed by dissolving in pure water after 7 nights of resist development if bri-hake is carried out, and BC5 can be dissolved and removed in an alkaline developer when bri-hake is not carried out. When systemizing using a coater/developer, which will be described later, in order to reduce running costs, it is necessary to use a contamination prevention film that can be dissolved and removed using the conventional resist development process or resist coating pre-process (especially cleaning process). (That is, it is preferable to use a contamination prevention film that can be peeled off using a resist developer or pure water).

When a negative resist, especially an organic solvent-developed negative resist, is used as the resist layer 2, if BC5 is used as the anti-contamination film, only the BC5 can be removed by an alkaline developer. Alternatively, it is preferable to use an alkaline development type XP8843 (trade name, manufactured by Sibley) as the anti-contamination layer, and use the above-mentioned ARC as the anti-contamination film without briking. If ARC is not washed, rinse with purified water (spin wash) for 2 minutes + ffl degree.
It is best to dissolve it and remove it, and then dry it by what is called a spin try. In addition, if a material with a higher etching rate than the resist of the resist layer 2 is used as the contamination prevention film 1, it is possible to completely remove only the contamination prevention film 1 by setting the etching time appropriately. It remains on the support substrate 4 as shown in FIG. 1(C).

Next, a system suitable for carrying out the method according to this embodiment will be specifically explained with reference to FIG.

Figure 2 shows the main body 1 of a projection reduction exposure apparatus (hereinafter referred to as stepper) used in the process of manufacturing semiconductor devices.
0. It is a schematic plan view showing how a coater/deheroper (a device having a resist coating section and a developing section integrated, hereinafter referred to as CD) 15 and a resist removing device 20 are coupled in-line, and C, D, +5 Improvements have been made in this embodiment to efficiently carry out the process.

The wafers to be exposed are C, D, 15.
After being placed at position P1, a resist (positive type resist in this embodiment) is applied in a resist coating/drying section 11, and then a contamination prevention film is applied on the resist in a contamination prevention film application section 12. Applied (and dried if necessary). The wafer waits in this state at buffer position P2.

In accordance with the operation of the resist removing device 20 (details will be described later),
The wafer is transported from the buffer position P2 to the processing position P3 on the stage of the resist removing device 20. Here, the wafer from which the resist and anti-contamination film in predetermined areas including alignment marks (described later) etc. have been removed is C, D, 1
Return to position P2 of 5. And branch position P
4. P7 and the developing section 13 through position P8.
sent to. For example, when using a negative resist as a contamination prevention film, the resist development process
The stain-preventing film is dissolved and removed.

Here, C, D, and 15 in this embodiment are particularly improved in that a linear kite rail 14 is disposed between the resist coating section 11 and the developing section 13, and along this kite rail 14, A transfer arm 16 that holds the wafer and moves in one dimension is also provided. Arm 16
is configured to be able to move up and down and rotate, and the developing section 1
The wafer that has come out from position P9 is lifted up by a predetermined amount while being held at position P9, and is moved to the right in FIG. 2 along the kite rail 14 to convey the wafer to branch position P7. The wafer moves from position P7 to buffer position P.
The uke is passed to the 4th and waits here.

Note that the wafer that has been taken out of the resist removing device 20 and is waiting at the buffer position P2 may be directly transported to the developing section 13 by the arm 16.

When the stepper main body 10 starts the exposure operation, the wafer is transferred from position P4 to the funnel position P5 of the stepper 10, and the wafer is transferred onto the wafer stage where exposure is performed. After exposure, the wafer is taken out from the stage, passes through unload position P6, and is reloaded to C, D, +
5, the receiver is passed to branch position P7, and position P8
The image is sent to the developing section 13 through the. The wafer on which resist development has been completed is stored in the tick-out position PIO via positions C, D, and 15 P9.

As described above, by assembling in-line using guide rails 14 and C and D15 equipped with transport arms 16 that can move up and down and rotate, a contamination prevention film can be efficiently formed using a conventional resist development section. It is possible to remove the resist in a desired area without significantly reducing throughput.

Furthermore, in the apparatus shown in FIG. 2, processing cannot be carried out in the order described above; for example, the wafer after development must be immediately returned to the stepper main body 1o to observe the resist image and perform various measurements on the stepper. This may be done using an alignment system. Of course, if there is no need to remove the resist, the wafer coated with the resist and dried can be directly transported to the stepper 10 for exposure in the conventional manner.

Next, FIG. 3 is a block diagram showing an example of an exposure apparatus (stepper 10) used in the system shown in FIG. As the exposure apparatus used in this embodiment, a conventional apparatus (the exposure apparatus disclosed in Japanese Patent Application Laid-open No. 63-283129) can be used as is.

In the figure, an illumination light source 21 such as an ultra-high pressure mercury lamp generates illumination light of a wavelength (exposure wavelength) that sensitizes the resist layer, such as G-line and 1-line, and this illumination light is passed through a mirror 22 to a variable blind. 24, the light enters an illumination optical system 23 including an optical integrator (fly's eye lens), etc. (not shown). The illumination light whose luminous flux has been made uniform by the illumination optical system 23 passes through the condenser lens 25, is vertically reflected by the dichroic mirror 26, and then illuminates the pattern area PA of the reticle R with uniform illuminance.

A reticle mark RM for alignment consisting of a rectangular transparent window and a diffraction grating mark is formed on the reticle R in association with the pattern area PA. variable blinds 2
Since the surface 4 has an image forming relationship with the reticle R, by opening and closing the movable plate constituting the variable blind 24 to change the opening position and shape, the observation of the reticle R and the field of view (
During exposure, the illumination field of view can be arbitrarily selected. The illumination light transmitted through the pattern area PA of the reticle R is incident on the telecentric projection lens PL on both sides (or on one side), and the projection lens PL projects the circuit pattern and the reticle mark RMO image onto the wafer W. A diffraction grating-like wafer mark WM (alignment mark) is provided to determine the position of the fresh coal on the wafer W, and a resist layer (single layer resist, multilayer resist, pigmented resist, etc.) is provided on the surface.
or is formed. The wafer W is placed on a wafer stage 27 that moves two-dimensionally in a step-and-repeat manner.

In addition, the exposure device simultaneously irradiates the diffraction grating mark with parallel laser beams from two directions to create one-dimensional interference fringes. j) TTR (Through The Reticle) that performs alignment using M
) type alignment system, especially an alignment system that adopts the heterotine method that gives a certain frequency difference between the laser beams irradiated from two directions (hereinafter referred to as La5er Int).
Erferomatric Alignment;L
It is provided above the dichroic mirror 26 via a bifocal optical system 28 (referred to as an IA system) or a bifocal optical system 28.

Since the LIA system is a well-known alignment system, a detailed explanation will be omitted, but the reticle mark RM and wafer mark WM are irradiated with two beams of different polarization, and two beams of light are generated on the marks RM and WM, respectively. A beat signal is detected by photoelectrically converting the second-order diffracted light due to the movement of interference fringes (corresponding to the frequency difference between two beams), and the relative position of reticle R and wafer W is determined from the phase difference between this beat signal and the reference beat signal. This is to find the deviation.

Second, FIG. 4 is a block diagram showing an example of the resist removing apparatus 20 used in the system shown in FIG. 2.

This resist removal apparatus is provided with an excimer laser light source 31 for resist removal and an illumination system 41 for alignment. (
(variable aperture) 35 is uniformly irradiated. The aperture image of the variable aperture 35 is set on the wafer W by the processing objective lens 37.
A reduced image is formed on the surface of. A transparent protection plate 39 is removably disposed between the objective lens 37 and the wafer W to prevent the objective lens 37 from getting dirty during processing.

A resist layer and a dyeing support film are coated on the surface of the wafer W, and the position of the wafer W is measured using an interferometer or the like, and the wafer W is placed on a two-dimensionally moving stage 4o. Further, the alignment illumination light from the illumination system 41 is reflected by the beam splitter 42, enters the alignment objective lens 43, and illuminates the surface of the wafer W uniformly. The reflected light from the mark WM on the wafer W is guided to the observation system through the objective lens 43 and the beam fritter 42, and through the relay system 44. This objective lens 43, beam flitter 4
2 and the relay system 44 constitute an off-axis wafer alignment system.

Further, in order to directly observe the processing point (resist removed portion) through the processing objective lens 37, a beam fritter 36 that can move forward and backward is arranged in the optical path between the objective lens 37 and the variable aperture 35. This beam splitter 36
When the wafer W is in the optical path, the illumination light from the illumination system 41 is guided to the objective lens 37 and uniformly illuminates the processed portion on the wafer W.

The reflected light from the surface of the wafer W passes through an objective lens 37, a beam splitter 36, and a variable aperture 35, and then enters a relay system 38 via a lens system 34 and a beam splitter 33, and is guided to an observation system. Here, since the wafer W and the variable aperture 35 are conjugate, the relay system 3
8, the aperture image of the variable aperture 35 and the processed portion on the wafer W are simultaneously observed. That is, variable aperture 3
The stage 40 is positioned so that the mark WM is located within the opening of 5.
After locating the wafer mark WM, the beam splitter 36 is retracted and the excimer laser light source 31 emits excimer laser light (pulsed light), thereby removing only the resist layer in a local area including the wafer mark WM. become. In the above configuration, it is preferable that the beam fritter 33 is wavelength selective, such as a tichroic mirror, and that the wavelength of the illumination light from the illumination system 41 is in the visible range.

By the way, in order to accurately align the pattern image of the reticle R and the shot area on the wafer W, for example, Japanese Patent Application Laid-Open No. 61-44429 or Japanese Patent Application Laid-Open No. 62-8451 has been proposed.
As disclosed in Japanese Patent No. 6, it is considered promising to employ an extended wafer global alignment (hereinafter referred to as enhanced global alignment-EGA) method. Here, the EGA method is 1
To expose a single wafer W, first, the positions of marks attached to multiple shot areas on the wafer W are measured (sample alignment), and then the offset of the wafer center position (X, Y direction), ＼Expansion and contraction of W (X, Y directions), remaining rotation amount of wafer W, and wafer stage orthogonality (
A total of six parameters (orthogonality of the arrangement of the point areas) are determined by a statistical method based on the difference between the designed position of the mark and the measured position of the mark. Then, the position of the second (2nd) shot for overlapping exposure is corrected from the designed position based on legally established parameter values, and the wafer stage is sequentially stepped. The advantages of this method are that throughput can be improved compared to alignment for each shot, and when a sufficient number of marks are sampled and aligned, individual mark detection errors can be reduced by statistical calculation. This means that alignment accuracy equivalent to or higher than alignment for each shot can be expected for all shot areas on the entire surface of the wafer. Therefore, in this embodiment, alignment is performed using the EGA method using the LIA system, and the resist layer is removed using the resist removing device 20 only in the wafer mask WM attached to the shot area where sample alignment is to be performed. Therefore, it is possible to perform alignment with sufficient accuracy, and it is possible to minimize the decrease in throughput caused by the removal of the resist layer.

FIG. 5 is a plan view showing the arrangement of shot areas SA and wafer marks WM on wafer W, and FIG. 6 is a sectional view showing the resist removal process on wafer marks WM.

In FIG. 5, each shot area SA is divided by a narrow band-shaped scribe area CL extending downward in the X direction. Furthermore, each shot area SA corresponds to the size of the circuit pattern area of the reticle R that is projected and exposed once in the exposure apparatus 10. In this embodiment, wafer marks WM are provided separately for the X direction and the Y direction at two locations attached to one shot area SA, and the mark for the X direction is WMx, and the mark for the Y direction is WMy. . The wafer marks WMx and WMy are a plurality of long lattice elements (haver turns) or each X.

Diffraction grating marks arranged in the Y direction (duty is 1.
1).

In the wood embodiment, L is
When performing alignment using the EGA method using the IA system, shot areas SAI to SA5 shown in FIG.
All that is required is to remove the resist layer 2 in the area including the wafer marks WMx and WMy attached to the wafer marks WMx and WMy, respectively.

Here, the size of the resist layer 2 to be removed (removal area D
A, see FIG. 6) is smaller than the width of the scribe area CL, and larger than the exclusive area of the wafer mark WM, for example, the minimum area where no pattern other than the wafer mark must be provided (so-called mark forming area). It is determined that it will become. Similarly, the irradiation area of the excimer laser beam LB in the resist removal device 20 (aperture image of the variable aperture 35)
The size of is also uniquely determined. In addition, variable aperture 3
Since the opening size 7L and the shape of the opening 5 can be changed arbitrarily, the shape and size 7 of the opening 7L can be made to suit the shape and size of the mark forming area (removal area DA) including the wafer mark WM.

In order to remove the resist on the wafer mark WM for sample alignment and expose the mark WM, the wafer W coated with the stain prevention film 1 on the resist layer 2 is c.
D, +5 (Fig. +2), the wafer is transported to the resist removing apparatus 20, and the wafer mark WM forming area is irradiated with a laser beam LB as shown in FIG. 6A. Then, a resist layer 2 made of an organic material and a contamination prevention film 1 are formed.
molecules are cut off by the photon energy of the heel and scattered, and some of them are further oxidized by oxygen in the atmosphere,
Co2. ) 120, and the wafer mark WM is exposed as shown in FIG. 6B. At this time, part of the resist layer 2 and the anti-contamination film 1 becomes fine particles 3 and scatters around, but the fine particles 3 adhere to the anti-contamination film 1, so that the underlying resist layer 2 is not contaminated. do not have. Next, the wafer W is transported from the resist removing device 20 to the developing sections C, D, +5, and the contamination prevention film 1 on the resist layer 2 is dissolved using pure water or a developer as shown in FIG. 6C. At this time, the fine particles 3 are also removed together with the anti-contamination film 1.

By transporting the wafer W with the mark WM for sample alignment exposed in this way to the exposure apparatus 10 and aligning it using the EGA method, the deterioration of alignment accuracy due to the resist layer is avoided, and it is possible to achieve very accurate alignment. It is.

Further, unlike the conventional method, pattern defects and short circuits caused by scattered resist particles do not occur.

In addition, in the above, the case where the resist layer in the wafer mark WM formation area is removed has been specifically explained.
It goes without saying that the method of the present invention can be similarly applied to the case where a resist is directly processed into a desired pattern shape by photo-etching.

[Effects of the Invention] As described above, in the present invention, when removing a desired portion of a thin film with a high-energy beam, a contamination prevention film is applied on the thin film in advance, and this Z5 stain prevention film is applied after processing with a heel. Since the film thickness is removed, it is possible to prevent the thin film surface from being contaminated by F'l film fine particles scattered during beam irradiation. When applying this method to the manufacturing of semiconductor devices, it is possible to remove a desired portion of the resist without causing problems as much as Rick Rough due to Q% staining on the resist surface. By removing the resist on the mark, alignment accuracy can be improved.

[Brief explanation of drawings]

FIGS. 1(a), (b), and (c) are cross-sectional views showing the basic steps of the thin film removal method of the present invention, FIG. 2 is a schematic plan view of a system suitable for the method according to an embodiment of the present invention, and FIG. The figure is a block diagram showing an example of the exposure apparatus of the system shown in Fig. 2, Fig. 4 is a block diagram showing an example of the resist removing apparatus of the system shown in Fig. 2, and Fig. 5 is a block diagram showing an example of the resist removal apparatus of the system shown in Plan view showing shot area and wafer mark arrangement, FIG. 6(A)
, (B) and (C) are cross-sectional views showing the process of removing the resist on the wafer. [Explanation of symbols of main parts] 1... Contamination prevention film 2... Resist layer (thin film) 3... Resist fine particles 4... Support substrate W... Wafer WM... Wafer mark 10...・Exposure device 11...Resist coating/drying section 12...Contamination prevention film coating section 13...Developing section 14...Guide rail 15...Coater/developer 16...Transport arm 20...Resist Removal device No.

Claims (2)

[Claims] (1) In a thin film removal method in which a desired portion of the thin film is removed by selectively irradiating the thin film deposited on a support substrate with an energy beam, a contamination prevention film is deposited on the surface of the thin film, A thin film removal method characterized by irradiating an energy beam from above the contamination prevention film to remove both the contamination prevention film and a desired portion of the thin film, and then removing the contamination prevention film on the thin film that was not removed. . (2) The thin film removing method according to claim 1, wherein alignment marks are provided on the support substrate, and the thin film is removed so as to expose at least the alignment marks.