JPH01292343A - Pellicle - Google Patents

Abstract

PURPOSE:To transfer a high-accuracy mask pattern onto a wafer and to improve pattern accuracy by using a pellicle which does not spoil the flatness of a photomask substrate when mounting a frame part on the substrate. CONSTITUTION:A lower frame part 41 adhered to the photomask substrate 2 is small in rigidity, so even if the flatness of the adhesion surface for the substrate 2 is inferior, the frame part is adhered by deforming so that the reverse surface becomes flat profiling the substrate 2. Then an intermediate frame part 42 is in flexible structure, so even if an upper frame part 43 is inferior in flatness and high in rigidity and variation in height from the frame part 41 is caused, that is absorbed by the frame part 42. The frame part 41, therefore, deforms freely profiling the surface of the substrate 2 and the entire circumference is adhered, so the pellicle 3 can be adhered without straining the substrate 2 and the mask pattern can be transferred onto the wafer with high accuracy.

Description

[Detailed Description of the Invention] [Summary] Regarding a pellicle that prevents dust from adhering to a photomask used in a semiconductor manufacturing process, the pellicle prevents dust from adhering to the photomask and impairs the flatness of the photomask to be adhered. Our goal is to provide a pellicle frame that holds a pellicle film made of a transparent thin film on a photomask substrate with a predetermined space between them. is provided between an upper frame portion that holds the pellicle film in a substantially planar shape, a lower frame portion that is bonded to the photomask substrate, and both frame portions, and absorbs deformation of the lower frame portion. and an intermediate frame portion having a flexible structure that does not transmit the information to the upper frame portion.

[Industrial application field]

The present invention relates to a pellicle that prevents dust from adhering to a photomask used in a semiconductor manufacturing process, and particularly to a pellicle that does not impair the flatness of a mask substrate mounted thereon.

[Conventional technology]

A pellicle is used to prevent dust from adhering to a photomask during the semiconductor manufacturing process, and as shown in FIG. 3, it consists of a pellicle film 3 and a pellicle frame 12. The material is, for example, nitrocellulose or mylar with a thickness ranging from submicron to 172 mil.

The frame 12 is made of metal, such as aluminum or aluminum alloy, and has an inner diameter of 120 to 160 mm and a frame thickness of 2 to 3 mm.
a+m, a round or square frame-shaped member with a height of 4 to 6 mm, with a pellicle membrane 3 attached to the upper edge and a lower edge 1
Adhesive is applied to 2a.

When in use, the lower edge 12a of the photomask substrate 2 is fixed to the surface of the photomask substrate 2 with an adhesive to form a sealed space on the photomask that prevents dust from entering, keeping the photomask clean, and the pellicle film 3 Even if dust 13 adheres thereto, it will be defocused and will not be transferred to the exposed wafer. For this purpose, the frame needs to have a certain height.

[Problem to be solved by the invention]

In the conventional pellicle described above, the frame that supports the pellicle film and is bonded to the photomask is made of a hard material such as aluminum or its alloy and is integrally formed with a predetermined height.

However, since this frame is usually manufactured by mechanical processing, the processing accuracy is low, and as shown in FIG. 4(a), the flatness δ of the lower edge 12a bonded to the mask substrate is 50 to 100μ.
The flatness of the photomask substrate is extremely poor compared to the 1 to 5 μm flatness of the photomask substrate.

Therefore, when a highly rigid integral frame is bonded to a photomask substrate as described above, the mask substrate 2 deforms following the bonding surface of the frame 11, as shown in FIG. 4(b), and the flatness of the photomask is impaired. , which deteriorates the accuracy of the pattern exposed on the wafer. In other words, if a correctly formed mask pattern is transferred onto a mask substrate with good flatness and is distorted to a flatness of 10 μm, the lateral deviation of the pattern exposed on the wafer may reach 0.5 μm. This is an unacceptable value for fine patterns such as LSI.

In this way, even if the precision of the photomask is improved, the precision of the pattern formed on the wafer cannot be improved, and manufacturing yields may be lowered due to overlay defects or dimensional defects in the case of multiple exposures. There was a problem.

The present invention was created in view of the above problems, and it prevents dust from adhering to the photomask, does not impair the flatness of the photomask to be adhered, and prevents deterioration of the accuracy of the transferred pattern. The purpose of the present invention is to provide becryl for photomask protection that can be used to protect a photomask.

[Means to solve the problem]

The above problem is that the pellicle frame that holds the pellicle film made of a transparent thin film on the photomask substrate at a predetermined distance has an upper frame portion that holds the pellicle film in a substantially planar shape;
A lower frame part that is bonded to the photomask substrate, and an intermediate frame part that is provided between the two frame parts and has a flexible structure that absorbs deformation of the lower frame part and does not transmit it to the upper frame part. This problem is solved by the pellicle of the present invention, which is characterized by the following.

[Effect]

Since the lower frame portion to be bonded to the photomask substrate has low rigidity, even if the flatness of the surface to be bonded to the substrate is poor, the lower frame portion is deformed and bonded to follow the substrate so that the bottom surface becomes flat. Since the intermediate frame has a flexible structure, even if the upper frame has poor flatness and is highly rigid, even if there is a change in height between it and the lower frame, it will be absorbed by the intermediate frame. It will be done. Therefore, the lower frame part is freely deformed to follow the surface of the mask substrate and is bonded all around, so the pellicle can be attached without distorting the mask substrate, and the mask pattern can be transferred onto the wafer with high precision. It becomes possible.

〔Example〕

The present invention will be explained in detail below with reference to the accompanying drawings.

FIG. 1 is a perspective view showing a pellicle of the present invention, and FIG. 2 is a sectional view showing another embodiment.

The pellicle of the present invention has a structure in which a pellicle membrane 3 is attached to the upper surface of a pellicle frame 4 formed by laminating a lower frame part 41, an intermediate frame part 42, and an upper frame part 43.

The pellicle film 3 is a transparent thin film made of nitrocellulose, mylar, etc., and is the same as in the conventional example.

The lower frame portion 41 is an aluminum alloy frame member with a thickness of about 1 mm, and is made wide to ensure an adhesive margin to the mask substrate. Even if the rigidity in the plate thickness direction (frame height direction) is low and the flatness is somewhat poor, it can be bonded closely around the entire circumference, imitating the photomask substrate.

The intermediate frame portion 42 is made of a thin aluminum alloy plate having a thickness of, for example, about 0.05 mm and is formed into a bellows shape with a height of about 41 mm, and is formed to have a flexible structure in the height direction.

The upper frame portion 43 has a thickness of, for example, 1 m, which is sufficient to hold the pellicle membrane 3 stretched on its upper surface in a substantially flat shape.
This is a frame member made of an aluminum alloy with a diameter of about 1.5 m.

The above three frame parts are laminated by adhesive etc. to form a pellicle film 3.
is pasted on the upper surface of the upper frame portion 43 to complete the pellicle of the present invention.

As long as the lower frame 41 is flat, its flatness does not have to be a problem, and processing is easy.

The pellicle frame 4 having the above structure has a flexible bellows structure in most of the height of the side wall, so the rigidity against deformation in the height direction is extremely small compared to the rigidity against warp deformation of the mask substrate. Substrate adhesive surface 41
Even if the flatness of a is poor, it is adhered following the pattern of the mask substrate and does not deform the mask substrate as in the conventional example.

Fig. 2 shows another embodiment, in which a wide frame-shaped upper frame part 43' and a lower frame part 41' are connected by a thin intermediate frame part 42', which is integrally molded with resin or the like. The pellicle frame 4 has a pellicle frame 4, and the same effect can be obtained because the overall rigidity is small.

〔Effect of the invention〕

As described above, according to the present invention, it is possible to provide a pellicle that does not impair the planarity of the substrate when attached to a photomask substrate, and it is possible to provide a pellicle that does not impair the flatness of the substrate when attached to a photomask substrate, and can be used to print a high-precision mask pattern such as a reticle with a high-precision pattern. It can be transferred onto a wafer and greatly contributes to improving pattern accuracy and overlay accuracy.

[Brief explanation of the drawing]

Fig. 1 is a partially cutaway perspective view showing the pellicle of the present invention, Fig. 2 is a cross-sectional view showing another embodiment, Fig. 3 is a view showing a conventional pellicle, and Fig. 4 shows the problems of the conventional technology. FIG. In the figure, 2--Photomask substrate, 3--Pellicle film, 4.
4"--pellicle frame, 41.41'--lower frame section, 42, 42'--intermediate frame section 1, i3, 43'--upper frame section. Good - Honju B The moon n beso kuru is shown as a chisel and the other hands g'1 - twrt1 mouth confinement 2

Claims (1)

[Claims] A pellicle frame (4) that holds a pellicle film (3) made of a transparent thin film on a photomask substrate (2) at a predetermined distance, the pellicle frame (4) holds the pellicle film (3) in a substantially planar shape. an upper frame portion (43) held on the photomask substrate (2), a lower frame portion (41) adhered to the photomask substrate (2), and both frame portions (41).
, 43), and the lower frame part (41)
an intermediate frame part (42) having a flexible structure that absorbs deformation of the pellicle and does not transmit it to the upper frame part (43).