JPS62144169A - Mask structure body for lithograph - Google Patents

Abstract

PURPOSE:To perform alignment and gap setting with a high precision by irradiating energy rays through a through hole provided in a mask material holding thin film to detect reflection from material to be worked in the state of less scattering and absorption. CONSTITUTION:Plural perforations 5 piercing a holding this film 2 from the front face to the rear face are provided in positions where mask materials 1 are not given. An electron beam is irradiated to perforations 5 from above while moving a mask structure body 13 right and left relatively to a semiconductor wafer 10, and secondary electrons generated from the semiconductor wafer 10 are detected. In this case, the detection value of secondary electrons is different between the presence and the absence of an alignment mark, and this detected value is an 3extreme value when perforations 5 of the mask structure body 13 are arrangned accurately with respect to a scribe line 12 of the semiconductor wafer. Similar detection is performed for plural perforations 5 to position relatively the semiconductor wafer 10 and the mask structure body 13 accurately.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to mask structures used in lithography. Such mask structures are used, for example, in the manufacture of semiconductor devices.

[Prior Art] It is widely used in industry, particularly in the electronics industry, to manufacture various products by partially altering the surface of a workpiece using lithography technology. Products with the same surface deterioration can be manufactured in large quantities. The surface of the workpiece is altered by irradiation with various types of energy rays, and in this case, a mask partially disposed with an energy ray absorbing material is used to form a pattern. When the irradiated energy beam is visible light, such a mask may be made by partially applying black paint to a transparent substrate such as glass or quartz, or by coating Ni, C, etc.
A metal plate or film partially coated with a visible light absorbing metal such as R was used.

However, in recent years, as finer pattern formation and lithographic processing techniques are required in a shorter time, X-rays and particle beams such as ion beams have come to be used as irradiation energy beams. In the case of visible light, most of these energy rays are absorbed when they pass through a glass plate or quartz plate used as a mask forming member. For this reason, when using these energy rays, it is not preferable to form a mask using a glass plate or quartz plate.Therefore, in the phosphor beam processing technology that uses X-rays or particle beams as irradiation energy rays, various types of Inorganic thin films such as silicon nitride, boron nitride, silicon oxide, titanium, etc., various organic thin films such as polyimide, polyamide, or polyester thin films, and laminated films of these are used as energy transmitters. A mask is formed by partially applying a metal such as gold, platinum, nickel, tungsten, palladium, rhodium, or indium as an energy ray absorber onto the surface. Since this mask does not have self-retaining properties, it is supported by a suitable holder. A mask structure constructed in this manner has conventionally been used as shown in the cross-sectional view of FIG. 11. This is done by attaching the energy ray absorbing mask material 1 in a desired pattern to one side of the energy ray transparent holding thin film I8!2 on one end surface (the upper end surface in the figure) of the annular holding substrate 3. It was formed by pasting using adhesive 4. Note that FIG. 12 is a top view of the holding substrate 3.

By the way, when performing photolithography processing using the above mask structure, the mask pattern of the mask structure must be accurately set on the workpiece, such as a silicon wafer (the surface of which is coated with photoresist). It is necessary to accurately set the alignment and the distance (gap) between the surface of the workpiece and the mask material holding Vj film of the mask structure.

Therefore, in lithography processing using a conventional mask structure, alignment marks are attached to the surface of the workpiece and the holding thin film of the mask structure, and after arranging these marks almost upward, the holding thin film is Alignment is performed by irradiating a visible light beam from the side and detecting the degree of matching between both marks, and gap setting is performed by detecting the light reflected from the holding thin film surface and the light reflected from the workpiece surface. Ta.

However, since this kind of detection involves detecting visible light that has passed through the holding thin film, the detection accuracy decreases due to scattering and/or absorption in the holding thin film, and photodetection on the submicron order or smaller order is detected. It is not possible to obtain sufficient alignment and gap setting accuracy in lithography.

Furthermore, in order to improve the detection accuracy of alignment marks, it is possible to use electron beams, ion beams, X-rays, ultraviolet rays, and vacuum ultraviolet rays instead of visible light, but these are subject to significant scattering and scattering due to the holding 6N film. It is practically unusable because it is absorbed.

[Object of the Invention] In view of the above-mentioned prior art, it is an object of the present invention to provide a lithography mask structure that can perform alignment with a workpiece and gap setting with high precision.

[Summary of the Invention] According to the present invention, the above object is to pass an energy beam through a mask material holding thin film made of a laminate of an organic thin film and a metal thin film in order to detect the alignment state with a workpiece. This is achieved by a lithography mask structure characterized by being provided with a plurality of through-holes that can be used to perform the process.

[Example] FIG. 1 shows a top view of a specific example of a lithography mask structure according to the present invention. Figure 2 is ■-H in Figure 1.
(However, FIG. 1 and FIG. 2 do not completely match). A concrete example of wood is a mask structure for X-ray photolithography.

The mask material 1 is applied to one side of the holding thin film 2 in a desired pattern. As the mask material 1, for example, gold, platinum, nickel, tungsten, tantalum, copper, molybdenum, palladium, rhodium, etc. 0.5 to 0.7. By using a thin film of about

The peripheral portion of the holding thin film 2 is bonded to the annular holding substrate 3 with an adhesive 4. The holding thin film 2 is an organic thin film and a metal 18I.
Consists of a laminate with a membrane.

As the organic thin film, a thin film of polyester, polyamide, polyimide, parylene, etc. can be used. The thickness of the organic thin film is, for example, about 2 to 20 pLm. It is preferable to use this organic thin film in a state in which it is isotropically stretched at a stretching ratio of, for example, about 5 to 20% (area printing ratio) in order to maintain good flatness.

Further, as the metal thin film, a thin film of titanium, copper, gold, platinum, chromium, tin, nickel, aluminum, etc. can be used. The thickness of the metal thin film is, for example, 0.01 to 1
．． It is about oJLm. Such a metal thin film can be formed by a thin film deposition method such as vapor deposition.

The holding thin film 2 may be composed of one layer of an organic thin film and one layer of a metal thin film, or may be composed of two or more layers of an organic thin film and a metal thin film, respectively. Since it is made of a laminate with a metal thin film, it has various properties such as mechanical strength, thermal conductivity, and electrical conductivity.

As the holding substrate 3, silicon, glass, quartz, phosphor bronze, brass, iron, nickel, stainless steel, etc. are used, for example.

As the adhesive 4, for example, epoxy type, rubber type, or other suitable adhesives are used, such as solvent type, thermosetting type, or photocuring type.

The holding FJ film 2 is provided with a plurality of small holes 5 (four in the figure) that can penetrate from the front surface to the back surface at a portion t where the mask material 1 is not applied.

The shape of the small hole 5 is not particularly limited, and may be any of rectangles such as squares and rectangles, squares such as triangles, hexagons, and hexagons, round shapes such as circles and ovals, and combinations thereof. However, it is particularly preferable to make the small hole 5 circular.
The size is not particularly limited, and may be set as appropriate depending on the alignment with the target workpiece, the state of the gap, the type of energy beam used for detection, and the required detection accuracy. be able to. Examples of energy rays used for detection include electron beams, ion beams, X-rays, ultraviolet rays, and vacuum ultraviolet rays, and furthermore, visible rays and infrared rays can also be used. - For example, in the case of detection using an electron beam, the diameter of the small hole 5 is about lθ~30
Bm, and two or four small holes 5 are provided axially symmetrically with respect to the symmetry axis of the annular holding substrate 3. However, the position where the small hole 5 is provided is appropriately set according to the pattern of the mask material 1 in the mask structure.

FIGS. 3(a) and 3(b) are enlarged views of the small hole 5 in FIGS. 1 and 2, respectively, and FIG.
) corresponds to the BB sectional view in FIG. 3(a). As shown, hold F! iII! 2 consists of a laminate of an organic thin film 2a and a metal thin film 2b. Since the organic thin film and the metal thin film are generally subjected to different treatments when forming the small holes 5, their diameters are different, and the metal thin film 2b has a smaller diameter.

Figure 4 (a), (b), Figure 5 (a), (b)
) and FIGS. 6(a) and (b) respectively.
), another example of the same part as (b) is shown. In these embodiments, the small hole 5 is not just an opening, but the bridge has a portion 5a. The bridge is partially formed of a metal thin film 2b, and the organic thin film 2a has the same structure as in the case of FIG. 3 above. In FIGS. 4 to 6, the planar shape of the portion 5a of the bridge is different, and thus the small hole 5
The pattern is different.

In photolithography processing, for example, in the manufacturing process of semiconductor elements, a large number of semiconductor elements 11 having the same pattern are formed on a semiconductor wafer 1o, which is a workpiece, as shown in FIG. After pattern formation, these semiconductor elements 11 are cut along boundary lines (scribe lines) 12 to form individual semiconductor element chips.

In such photolithography processing, a pattern formed by arranging a plurality of unit patterns of the above-mentioned semiconductor elements in parallel is used as a pattern of the mask material 1 of the mask structure. In FIG. 1, four unit patterns 7 of semiconductor elements are arranged. These unit patterns 7 are divided by lines 8 corresponding to the scribe lines 12 of the semiconductor wafer 10, and in photolithography, they are divided by lines 8 corresponding to the scribe lines 12 of the semiconductor wafer 10 and the mask structure 13 determined in advance. 8 and perform alignment with high accuracy (see Figure 8).
, and then irradiation with energy rays such as X-rays is performed.

Then, the relative position between the semiconductor wafer IO and the mask structure 13 is further changed, and the unirradiated semiconductor elements are aligned and irradiated with energy beams in the same manner as described above, and are turned green.

For example, a scribe line 12 is provided on the semiconductor wafer 10.
An alignment mark formed, for example, as a recess is provided at an appropriate position by etching or the like. In this way, when an alignment mark is formed on the scribe line 12 of the semiconductor wafer 10, the small hole 5 in the mask structure corresponds to the alignment mark, as shown in FIG. It is formed on the line 8 corresponding to the scribe line. The scribe line 12 of the semiconductor wafer 10 has a width of, for example, about 30 gm, and the alignment mark is formed to have a smaller width. In this case, the diameter of the small hole 5 is preferably about 15 μm.

Hold thin II! The method for forming the small holes 5 in the holding thin film 2
For example, a method using a laser beam (excimer laser, argon laser, etc.),
Dry etching (R, I.

Examples include a method using chemical etching (hydrazine etchant, etc.), and a method using mechanical means (milling': 4). Of course, two or more of these methods may be used in combination.As mentioned above, different methods may be adopted for forming the small holes 5 for the Ja-containing thin film 2a and the metal thin film 2b. Since the small holes can be formed in the organic thin film 2b with relatively high precision in shape and size, the small holes may be formed in the organic thin film 2a with relatively low precision.

It is preferable to form the small holes 5 in a process close to the final step of creating the mask structure, thereby preventing a decrease in the accuracy of the small holes due to post-processing. Good positional accuracy can be achieved by forming a pattern for forming small holes simultaneously with the step of forming the holes.

As shown in FIG. 9, the mask structure 13 as described above is used in close proximity to the semiconductor wafer 10 during use. A resist layer 14 is formed on the surface of the semiconductor wafer IO. While moving the mask structure 13 in the left-right direction relative to the semiconductor wafer io, the small hole 5 is irradiated with an electron beam from above, and secondary electrons generated from the semiconductor wafer 10 are detected. At this time, the alignment mark (
For example, the detected value of secondary electrons differs depending on the presence or absence of the four parts shown in the figure, and when this detected value takes an extreme value, the small hole 5 of the mask structure 13 is accurately positioned relative to the scribe line 12 of the semiconductor wafer. It is placed in the . By similarly detecting a plurality of small holes 5, the relative positional relationship between the semiconductor wafer 10 and the mask structure 13 can be made accurate. Similarly, when measuring the gap, the electron beam passing through the small hole 5 is measured.

Of course, a method of detecting out-of-focus using an optical lens can also be used.

During the electron beam irradiation, the detection accuracy is further improved when the small hole 5 has a pattern of bridge portions 5a as shown in FIGS. 4 to 6.

In addition to the above-mentioned electron beams, energy beams used for alignment or gap detection when using the mask structure of the present invention include ion beams,
Rays, ultraviolet rays, vacuum ultraviolet rays, and even visible light and infrared rays can be used.As alignment marks on the workpiece side, it is possible to form alignment marks that exhibit different behavior from the surroundings in response to these energy rays. good.

Below, '3! : The present invention will be explained in more detail with reference to Examples.

Example 1: A mask structure as shown in the vertical cross-sectional view in FIG. 10 was created. In FIG. 10, parts similar to those in FIG. 2 are labeled with the same symbols. In the wooden embodiment, no adhesive is applied to the upper flat end surface 3a of the annular holding substrate 3, and adhesive 4 is applied to the upper outer slope 3b.
As a result, the holding thin film 2 and the holding substrate 3 are bonded together. The angle θ of the slope is suitably about 5 to 15 degrees, and in this embodiment, it is set to 10 degrees.

According to the mask structure of this embodiment, the mask material holding plane of the holding thin film 2 is not affected by the adhesive 4 and achieves good flatness that is the same as the flatness of the upper flat end surface of the holding substrate 3. This improves the accuracy of lithography processing.

First, about 10% of the original state-preserving substrate 3 is applied using adhesive 4.
A polyimide membrane (approximately 7.5 m thick, trade name: Kapton membrane) was adhered by isotropically stretching at a stretching rate of .

Next, approximately 0.1p of
A nickel (Nt) film with a thickness of m was formed, thus forming a holding thin film consisting of a laminate of a polyimide film and a nickel film.

Next, a photoresist (AZ-13) is placed on the surface of the nickel film.
50 (manufactured by Sibley) under specified conditions to a thickness of 0.5 lumen, and a resist pattern of four small holes with a diameter of about 20 gm was formed with a quartz mask using a deep ultraviolet printing machine.

Next, the nickel film at the position of the small hole pattern was chemically etched using a nitric acid etchant to form four small holes in the nickel film.

Next, using the nickel film as a mask, the polyimide film at the position of the small hole pattern was etched away using a hydrazine etchant to form small holes.

In this way, four small holes 5 penetrating the holding thin film 2 as shown in FIG. 3 were formed.

Using the four small holes 5 as a reference, approximately 0.0.
An X-ray absorption pattern made of a gold film with a thickness of 5 JLm was formed.

Example 2: Similar to Example 1, titanium (T) was used instead of the nickel film.
i) (approximately 0.2ILrn thickness) - gold (Au) (approximately 0.05
A mask structure was prepared using a polyester film (approximately 6 m thick, manufactured by Toshi Co., Ltd., trade name: Lumirror) in place of the polyimide film.

In this example, a small hole with a diameter of about 25 m was formed in the titanium-gold film, and an iodine-based etchant was used to etch the gold film, and a nitric acid-based etchant was used to etch the titanium film. In addition, the polyester film has a diameter of approximately 30 μm.
Pulse A by excimer laser when forming a small hole in
Light'it was used.

Note that in this example, no X-ray absorption pattern was formed.

Example 3: In the same manner as in Example 1, a mask structure having a holding thin film in which a nickel film with a thickness of about 0.05 gm was formed on both sides of a polyimide film was created.

In this example, two small holes of nickel 11!2 were formed at corresponding positions, and the small holes of the polyimide film were formed using the nickel film as a mask.

Example 4: In the same manner as in Example 1, a mask structure having small holes 5 in a pattern as shown in FIG. 4 was produced.

In this example, Example 1 was used when forming small holes in the nickel film.
A mask different from that used in the above case was used to form a bridge portion 5a with a nickel film in the small hole portion. Incidentally, the formation of small holes in the polyimide film was carried out in the same manner as in Example 1.

Example 5: In the same manner as in Example 4, a mask structure having small holes 5 in a pattern as shown in FIG. 5 was produced.

[Effects of the Invention] As described above ξAccording to the present invention, in lithography processing, when aligning the mask structure and the workpiece and setting the gear 2, energy is transmitted through the through hole provided in the mask material holding thin film. By performing radiation irradiation, it is possible to detect the reflection from the workpiece material in a state with little scattering and absorption, so alignment and gap setting can be performed with high accuracy, thereby enabling high-precision lithography processing. You can get used to it.

Furthermore, according to the present invention, since the mask material holding thin film is made of a laminate of an organic thin film and a metal thin film, the end face of the through-hole of the organic thin film, which has high strength but is relatively flexible and easily deforms, can be moved over time. It is possible to maintain a good condition without changing it, thus allowing accurate alignment.

Further, since the holding thin film has a metal thin film, for example, during alignment using an electron beam or the like, by grounding the metal thin film, charging of the holding thin film is prevented, and more accurate alignment can be performed. This effect is further enhanced by forming the holding thin film into a laminate consisting of three layers: a metal thin film, an organic thin film, and a metal thin film.

In addition, since the holding thin film includes a metal thin film, the through holes can be patterned, which allows for more accurate alignment and also has the effect of preventing the shape of one through hole from changing over time.

[Brief explanation of drawings]

FIG. 1 is a plan view of the mask structure of the present invention, and FIG. 2 is a cross-sectional view taken along the line -■. 3 to 6 are enlarged views of the through hole portion. FIG. 7 is a partial plan view of the workpiece, and FIG. 8 is a partial cross-sectional view showing the relationship between the workpiece and the mask structure. FIG. 9 is a partial sectional view showing how the mask structure of the present invention is used. FIG. 10 is a sectional view of the mask structure of the present invention. FIG. 11 is a sectional view of a conventional mask structure, and FIG. 12 is a plan view of its holding substrate. 1: Mask material 2: Holding thin film 2a: Organic thin film 2b: Metal thin film 3: Holding substrate 4: Adhesive 5: Small hole 8 varnish scribe line corresponding line 10: Workpiece material 12 varnish scribe line 13: Mask structure 14 Ni resist Layered Agent Patent Attorney Yamashita
Figure 7, Figure 8, Figure 1O, Figure 11, Figure 12

Claims (1)

[Claims] (1) In a lithography mask structure in which the periphery of a mask material holding thin film on which a mask material is to be applied in a desired pattern is held by a holding substrate, the mask material is made of a laminate of an organic thin film and a metal thin film. A mask structure for lithography, characterized in that a holding thin film is provided with a plurality of through holes through which energy beams for detecting an alignment state with a workpiece can pass.