CN110941153A

CN110941153A - Wavelength tunable exposure machine alignment system and alignment method thereof

Info

Publication number: CN110941153A
Application number: CN201811110447.9A
Authority: CN
Inventors: 不公告发明人
Original assignee: Changxin Memory Technologies Inc
Current assignee: Changxin Memory Technologies Inc
Priority date: 2018-09-21
Filing date: 2018-09-21
Publication date: 2020-03-31

Abstract

The invention provides a wavelength tunable exposure machine alignment system and a method, wherein the alignment system comprises: the light source component comprises a first wavelength tunable laser, a second wavelength tunable laser and a wavelength signal controller, wherein the first wavelength tunable laser and the second wavelength tunable laser can provide laser with tunable wavelengths, and the wavelength signal controller controls the first wavelength tunable laser and the second wavelength tunable laser to emit laser with specified wave bands. The alignment system of the wavelength tunable exposure machine can select or optimize the light source for aligning the pattern by adjusting the wavelength of the light source, thereby obtaining better or more stable product alignment performance; in addition, a remedy can be provided to deal with the abnormal condition of the alignment pattern caused by unstable process.

Description

Wavelength tunable exposure machine alignment system and alignment method thereof

Technical Field

The invention relates to a system and a method for manufacturing an IC device or other micro devices, in particular to an exposure machine alignment system and a method, which can be applied to a semiconductor laser alignment system and post-laser alignment pattern signal detection.

Background

In the prior art, exposure machines generally use either dual light sources (red/green) or four light sources (red/green/far-infrared/near-infrared), the specific choice of light source depending on the hardware applied. For the four-light-source exposure machine, as shown in fig. 1 and 2, four light sources of green light (532 nm)/red light (635 nm)/near infrared light (780 nm)/far infrared light (850nm) are used, each light source is a single-wavelength light source, and the alignment is determined by interference of light reflected by the light sources at the protrusions and the depressions of the mark, but because of the use of a single wavelength, in order to make the received signal coherent in a specific area, the wavelength of the single light source must be considered when designing the mark depth, which may limit the design of the mark depth D.

In addition, referring to fig. 3 and 4, the prior art light source has a limitation on the pitch size d of the alignment pattern that can be read. The numerical aperture NA is nsin theta and sin theta is m lambda/d, where n is 1 for air and m is the number of coherent orders of the two reflected lights on the upper and lower surfaces of the mark, and d is greater than or equal to m lambda/NA by combining the above two equations. It can be seen that the prior art alignment systems and methods for fixed wavelength light sources have limitations on the minimum value of the mark pitch size.

In summary, the prior art alignment system and method for an exposure machine have the following disadvantages: the pitch size and depth of the alignment pattern are limited. In addition, there is no back-up for a single wavelength exposure alignment system in case of abnormal alignment patterns due to unstable processes such as etching or Chemical Mechanical Polishing (CMP).

Disclosure of Invention

The present invention has been made to solve one or more of the above-mentioned problems. The invention provides a wavelength tunable exposure machine alignment system and method.

According to a first aspect, an embodiment of the present invention provides a wavelength tunable exposure machine alignment system, including: the light source component is characterized by comprising a first wavelength tunable laser, a second wavelength tunable laser and a wavelength signal controller, wherein the first wavelength tunable laser and the second wavelength tunable laser can provide laser with tunable wavelengths, and the wavelength signal controller controls the first wavelength tunable laser and the second wavelength tunable laser to emit laser with specified wave bands.

By providing a wavelength tunable laser for exposure alignment, the fixed two or four single wavelength light source options may be not limited, avoiding the limitations on alignment pattern pitch size and depth.

Optionally, the first tunable laser and the second wavelength tunable laser are designed to: one of the lasers emits laser light at a high waveband, and the other laser emits laser light at a low waveband, specifically, the high waveband is 650-950nm, and the low waveband is 189-650 nm; or the first tunable laser and the second tunable laser both use laser light of a full-amplitude band, specifically, the full-amplitude band is 189-950 nm.

By limiting the wavelength region of the light emitted by the laser, the selectable wavelength range is improved, which further contributes to the realization of the purpose of the invention.

Optionally, the wavelength tunable exposure machine alignment system further includes a first reflection element, a pupil plate, a level film, a second reflection element, an imaging lens, a reference grating, a detection portion and a polarization beam splitter, wherein light is emitted from the light source component, reflected to the polarization beam splitter by the first reflection element, and then enters the alignment mark, and a light beam diffracted by the alignment mark passes through the polarization beam splitter and then sequentially passes through the pupil plate, the level film, the second reflection element, the imaging lens and the reference grating and then is received by the detection portion, and the detection portion includes a photoelectric conversion plate for converting an optical signal into an electrical signal.

Optionally, the wavelength tunable exposure machine alignment system further comprises a CCD camera, and a part of light output through the pupil plate and the stage film is converted in direction by a reflection element and imaged on the CCD camera through a condensing lens and an imaging lens in order.

Coarse adjustment can be achieved by setting up a CCD camera and analyzing the image imaged thereby.

According to a second aspect, an embodiment of the present invention provides a wavelength tunable exposure machine alignment method, which is characterized by at least comprising the following steps:

s1: the first wavelength tunable laser and/or the second wavelength tunable laser of the light source component emit light of a specified waveband under the control of the wavelength signal controller;

s2: the alignment mark is subjected to interference imaging on the reference grating after diffracting modulated light beams emitted by the first wavelength tunable laser and/or the second wavelength tunable laser;

s3: the detection unit receives the light beam diffracted by the alignment mark and detects the alignment mark.

In a preferred embodiment, the first wavelength tunable laser and the second wavelength tunable laser are titanium sapphire lasers.

It is preferable that a photoelectric conversion panel for converting an optical signal into an electric signal is included in the detection section.

Preferably, a part of the light beams diffracted by the alignment marks may be changed in direction by a reflecting element after being output through the pupil plate and the level film, and imaged on the CCD camera through the condensing lens and the imaging lens in order to assist in the rough alignment.

By adopting the alignment system and the method of the dynamically adjustable wavelength exposure machine, compared with the double light sources or the four light sources in the prior art, the light sources for aligning patterns can be selected or optimized by adjusting the wavelength of the light sources through the application of different wavelengths of the multiple light sources, so that better or more stable product alignment production line performance can be obtained; in addition, a remedy can be provided to deal with the abnormal condition of the alignment pattern caused by the unstable process.

Drawings

The features and advantages of the present invention will be more clearly understood by reference to the accompanying drawings, which are illustrative and not to be construed as limiting the invention in any way, and in which:

FIG. 1-2 is a schematic illustration of an alignment laser of a prior art four-source exposure machine;

FIG. 3 is a schematic view of an alignment laser of a prior art exposure machine;

FIG. 4 is an enlarged fragmentary view of the circled area in FIG. 3;

FIG. 5 is a schematic diagram of a wavelength tunable exposure machine alignment system according to an embodiment of the present invention;

FIG. 6 is a schematic diagram of a light source section of a first design of a wavelength tunable exposure machine alignment system according to an embodiment of the invention;

fig. 7 is a schematic diagram of a light source section of a second design of a wavelength tunable exposure machine alignment system according to an embodiment of the invention.

Reference numerals

1 light source component

3-stage membrane

4 polarization beam splitter

5 alignment mark

6 CCD camera

11 first wavelength tunable laser

12 second wave light tunable laser

13 wavelength signal controller

14 first modulator

15 second modulator

21 first reflecting element

22 pupil plate

23-stage membrane

24 second reflective element

25 imaging lens

26 reference grating

27 detection part

Detailed Description

In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are some, but not all, embodiments of the present invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

Referring to fig. 5, the present invention provides a wavelength tunable exposure machine alignment system and method, wherein a first wavelength tunable laser 11 and a second wavelength tunable laser 12 are used for a light source portion, and the first and second wavelength tunable lasers can provide light sources with different wavelengths for the exposure machine alignment system and method of the present invention.

The embodiment of the invention provides an alignment system of a wavelength tunable exposure machine, which comprises: the light source component 1, the light source component 1 may include a first wavelength tunable laser 11 and a second wavelength tunable laser 12, wherein the first wavelength tunable laser and the second wavelength tunable laser are capable of providing laser light with tunable wavelength, and a wavelength signal controller 13, wherein the wavelength signal controller 13 controls the first and second wavelength

tunable lasers

11 and 12 to emit light with specified wavelength band. With the above structure, in the alignment process, the wavelength signal controller 13 can control the laser to scan the alignment mark using the continuous wavelength light source, thereby finding out the strongest signal wavelength in the wavelength interval and setting the wavelength as the optimal wavelength for subsequent alignment. The alignment system of the invention can remove the limitation on the depth and the pitch size of the alignment pattern due to the tunable wavelength, improves the tolerance of the abnormal marking pattern caused by other processes, and can realize accurate detection on various abnormal conditions in the process.

In a preferred manner, the first and second wavelength

tunable lasers

11 and 12 may be connected to a first modulator 14 and a second modulator 15, respectively, for modulating the light emitted by the first and second wavelength tunable lasers. In actual production, the alignment mark may cause changes in depth, width, symmetry and the like due to the influence of the production process, and a preset single wavelength may not be accurately aligned to find a preset position, so that the alignment system of the present invention can control the first and second wavelength

tunable lasers

11 and 12 to emit light of a specified waveband through the wavelength signal controller 13.

In a preferred manner, the first wavelength tunable laser 11 and the second wavelength tunable laser 12 may be designed to: one of the lasers emits laser light in the high band and the other wavelength tunable laser emits laser light in the low band, so that the two can support mutual use, referring to the structure shown in fig. 6. Thus, only two sets of lasers need be used.

In a more preferred embodiment, the high band region is set to 650-950nm, and the low band region is set to 189-650 nm. Thereby realizing the mutual supporting interactive use of the two lasers.

In another preferred mode, both lasers are full-waveband lasers in the range of 189 and 950nm, which provides a wider range of wavelength selection for lithography alignment.

In operation, one of the first wavelength tunable laser 11 and the second wavelength tunable laser 12 is set to a fixed wavelength for use according to the optimum wavelength set above.

The wavelength tunable exposure machine alignment system of the present invention may further include a first reflection element 21, a pupil plate 22, a stage membrane (order diaphragm)23, a second reflection element 24, an imaging lens 25, a reference grating 26, and a detection section 27. The dynamically adjustable wavelength exposure machine alignment system of the present invention may further comprise a polarizing beam splitter 4. The position of the mark 5 is detected by the wavelength tunable exposure machine alignment system of the present invention. Light is emitted from the light source part 1, reflected by the first reflecting element to the polarization beam splitter 4, and then enters the alignment mark 5, and a light beam diffracted by the alignment mark 5 passes through the polarization beam splitter 4, and then sequentially passes through the pupil plate 22, the order film (order diaphragm)23, the second reflecting element 24, the imaging lens 25, and the reference grating 26, and then is received by the detection part 27, and the detection part 27 includes a photoelectric conversion plate for converting an optical signal into an electrical signal, thereby realizing detection of the alignment mark.

Compared with the foregoing embodiments, the alignment system of the dynamically adjustable wavelength exposure machine according to the present embodiment may further include a CCD camera 6, and the same parts as those in the foregoing embodiments are not described again. A part of the light beam output through the pupil plate and the stage film 3 is converted in direction by a reflecting element and is imaged on the CCD camera 6 sequentially through a condenser lens and an imaging lens. The alignment system of the present invention can be assisted in coarse alignment by providing a CCD camera and analyzing the image formed on the CCD camera.

The first tunable laser 11 and the second tunable laser 12 adopted by the alignment system of the dynamically adjustable wavelength exposure machine can adopt a titanium sapphire laser, and the wavelength in the range of 189-950nm can be realized. By selecting the laser, the wavelength of the light source can be adjusted to select or optimize the light source for aligning the pattern, so that better or more stable product overlay production line performance is obtained; in addition, for the abnormal condition of the alignment pattern caused by the unstable manufacturing process such as etching or CMP, the alignment of the pattern can be realized by adjusting the wavelength of the light source used for alignment. In this regard, the system of the present invention overcomes the problem of the prior art that the dual light source or the four light source may not be able to read the alignment pattern when encountering the above-mentioned abnormal situation, and furthermore, the present invention has a larger tolerance range for the alignment pattern process.

As described above, the wavelength tunable exposure machine alignment system of the present invention can remove the limitation of the pitch size d of the alignment mark by removing the limitation of the wavelength range and d ≧ m λ/NA, as shown in Table 1 below, where Table 1 shows the range of the mark pitch size d that can be implemented when receiving the same level of light.

TABLE 1 ranges of marking pitch size d that can be implemented when receiving the same level of light

m	λ(189nm)	λ(650nm)	λ(950nm)	Range (nm)
					1	315	1083	1583	315～1583
2	630	2167	3167	630～3167
					3	945	3250	4750	945～4750
4	1260	4333	6333	1260～6333
					5	1575	5417	7917	1575～7917
6	1890	6500	9500	1890～9500
					7	2205	7583	11083	2205～11083
……	……	……	……	……

The invention also provides an alignment method of the wavelength tunable exposure machine, which comprises the following steps:

step S1: the first wavelength tunable laser 11 and/or the second wavelength tunable laser 12 of the light source component emit light of a specified waveband under the control of the wavelength signal controller;

step S2: the alignment mark 5 is subjected to interference imaging on the reference grating 26 after diffracting the light beams emitted by the first wavelength tunable laser 11 and/or the second wavelength tunable laser 12;

step S3: the detection unit 27 receives the light beam diffracted by the alignment mark 5 and detects the alignment mark.

When a new product is evaluated or the process is abnormal, in order to increase the process stability, in the alignment process, the alignment mark is scanned by the continuous wavelength light source, and the strongest signal wavelength is found out in the wavelength interval, so as to set the subsequent alignment optimal wavelength.

In a preferred embodiment, the first wavelength tunable laser 11 and the second wavelength tunable laser 12 are titanium sapphire lasers.

Preferably, both the first wavelength tunable laser 11 and the second wavelength tunable laser 12 can emit light in the range of 189-.

The light beam diffracted by the alignment mark 5 passes through the pupil plate 22, the stage film 23, the second reflecting element 24, the imaging lens 25, and the reference grating 26 in this order, and is received by the detection section 27. In a preferred embodiment, the detection unit 27 is provided with a photoelectric conversion plate for converting an optical signal into an electrical signal, and the detection unit is configured to detect the alignment mark.

Further, it is preferable that a part of the light beams diffracted by the alignment mark 5 may be changed in direction by a reflecting element after being output through the pupil plate and the stage film and be imaged on the CCD camera 6 through a condensing lens and an imaging lens in order, and the rough alignment may be assisted by providing the CCD camera and using the image imaged on the CCD camera.

The advantages and effects of the alignment method according to the present invention correspond to the solution of the product, and are not described herein again.

The foregoing embodiments are merely illustrative of the principles of this invention and its efficacy, rather than limiting it, and various modifications and variations can be made by those skilled in the art without departing from the spirit and scope of the invention, which is defined in the appended claims.

Claims

1. A wavelength tunable exposure machine alignment system, comprising:

a light source component comprising a first wavelength tunable laser and a second wavelength tunable laser;

the first modulator and the second modulator are respectively used for modulating laser emitted by the first wavelength tunable laser and the second wavelength tunable laser; and

and the wavelength signal controller controls the first wavelength tunable laser and the second wavelength tunable laser to emit laser in specified wave bands.

2. The wavelength tunable exposure machine alignment system of claim 1, wherein the first and second wavelength tunable lasers are designed to: one of the lasers emits laser light with a high waveband, wherein the high waveband is 650-950 nm; the other laser emits laser light with a low waveband of 189-650 nm.

3. The wavelength tunable exposure machine alignment system of claim 1, wherein the first and second wavelength tunable lasers both use a full-width band of 189 and 950nm, and the lasers used are titanium sapphire type lasers.

4. The wavelength tunable exposure machine alignment system of claim 1, further comprising:

a first reflecting element, a pupil plate, a stage film, a second reflecting element, an imaging lens, a reference grating, a detection part and a polarization beam splitter,

the laser beam emitted from the light source component is reflected to the polarization beam splitter by the first reflecting element and then enters the alignment mark, the light beam diffracted by the alignment mark passes through the polarization beam splitter and then sequentially passes through the pupil plate, the level film, the second reflecting element, the imaging lens and the reference grating and then is received by the detection part, and the detection part comprises a photoelectric conversion plate used for converting an optical signal into an electric signal.

5. The wavelength tunable exposure machine alignment system of claim 1, further comprising:

and the CCD camera converts the direction of a part of light output by the pupil plate and the stage film through a reflecting element, and images on the CCD camera through the converging lens and the imaging lens in sequence.

6. A method for aligning a wavelength tunable exposure machine, the method comprising at least the steps of:

the first wavelength tunable laser and/or the second wavelength tunable laser of the light source component emit light of a specified waveband under the control of the wavelength signal controller;

the alignment mark is subjected to interference imaging on the reference grating after diffraction is carried out on modulated light beams emitted by the first wavelength tunable laser and/or the second wavelength tunable laser;

the detection section receives the light beam diffracted by the alignment mark and detects the alignment mark.

7. The wavelength tunable exposure machine alignment method of claim 6, wherein: the first wavelength tunable laser and the second wavelength tunable laser are titanium sapphire lasers.

8. The wavelength tunable exposure machine alignment method of claim 6, wherein: the first wavelength tunable laser and the second wavelength tunable laser can both emit laser within 189-950nm, or one of the lasers can be used for emitting high-band laser, the high-band is 650-950nm, the other laser can be used for emitting low-band light, and the low-band is 189-650nm, so as to realize interactive use.

9. The wavelength tunable exposure machine alignment method of claim 6, wherein: the light beams diffracted by the alignment marks sequentially pass through a pupil plate, a level film, a second reflecting element, an imaging lens and a reference grating and are then received by a detection part.

10. The wavelength tunable exposure machine alignment method according to claim 6, characterized in that: a photoelectric conversion panel for converting an optical signal into an electrical signal is provided in the detection section.