Film for application to three-dimensional sample, method for manufacturing same, and method for transferring fine pattern using same

Abstract

Provided is a film for application to a 3D sample, the film including a photoresist layer that has alignment or direction marks thereon. After the fine pattern of the photoresist layer or coat is exposed, the photoresist layer is applied to a desired position of the 3D sample by aligning the alignment or direction marks of the film with alignment or direction marks on the 3D sample. This allows for transfer of an appropriate fine pattern. Part or all of the thickness or area of the photoresist layer is developed to form projections or depressions in the photoresist layer before the film is applied to the 3D sample.

Claims

1. A film for application to a 3D sample, the film comprising a photoresist layer that has alignment or direction marks or references for aligning the position or direction of the film with the 3D sample, wherein a latent image is generated in the photoresist layer by completing an exposure of a fine pattern before the film is applied to the 3D sample.

2. The film of claim 1, wherein part or all of an area of the photoresist layer is developed to form projections or depressions in the photoresist layer before the film is applied to the 3D sample.

3. The film of claim 1, wherein the photoresist layer is partially or fully developed in a thickness direction to form projections or depressions in the photoresist layer before the film is applied to the 3D sample.

4. The film of claim 1, wherein a width of the fine pattern is 2 μm or less.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) For a fuller understanding of the nature and objects of the present invention, reference should be made to the following detailed description and the accompanying drawings, in which:

(2) FIG. 1 is a process chart for applying a film to a 3D sample according to a first embodiment of the present invention;

(3) FIG. 2 is a process chart for applying a film to a 3D sample according to a second embodiment of the present invention;

(4) FIG. 3 is a process chart for applying a film to a 3D sample according to a third embodiment of the present invention;

(5) FIG. 4 is a process chart for applying a film to a 3D sample according to a fourth embodiment of the present invention; and

(6) FIG. 5 illustrates a line-and-space pattern of an example of the present invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

(7) Preferred embodiments of the present invention will be described hereinafter with specific reference to the attached drawings. The drawings are provided for the purpose of illustration only and the shapes, materials, and the sizes of the films and the 3D samples or items to be processed (“workpieces”) described therein are not limited to those depicted in the figures. In the following description, while examples of positive photoresist layers are illustrated, negative photoresist layers may also be used. In embodiments where a chemical amplification type photoresist is used, thermal processing may be additionally performed after exposure.

Embodiment 1

(8) The first embodiment of the present invention relates to a film 1 for application to a three-dimensional (3D) sample, the film 1 comprising a photoresist layer that has alignment or direction marks or references (“film references” hereinafter) 1A.

(9) The first embodiment additionally relates to a film on which a fine pattern is exposed before the film is affixed or applied to a 3D sample or workpiece.

(10) FIG. 1 illustrates a film 1 for application to a 3D sample having a photoresist layer 2 and a process of its application.

(11) The film 1 includes the photoresist layer 2, a support layer 3, and film references 1A. The film references 1A are disposed on the side of the film 1 that is not in contact with the photoresist layer 2. In other word, as shown in FIG. 1(1), the film 1 has the structure of the photoresist layer 2, the support layer 3, and the film references 1A in that order.

(12) In Step (1), a fine pattern is exposed. This creates both areas 2a where the photoresist is to be removed by the subsequent development and areas 2b where the photoresist is to remain after the development. In some applications, the width of the fine pattern may be 2 micrometers (μm) or less. A light-emitting diode or a laser diode having an emission wavelength shorter than that of i-line of a mercury lamp (365 nm in wavelength) is used to achieve high resolution in the exposure process. The film references 1A and the alignment marks 5A on a photomask 5 (referred to as “mask references” hereinafter) are used to align the film 1 with the fine pattern.

(13) In Step (2), the film 1 is applied to the 3D sample 7. To align the 3D sample 7 with the film 1, alignment marks (“sample references” hereinafter) 7A are prepared on the 3D sample 7 in advance. The photoresist layer 2 and the fine pattern transferred into it are placed in the desired position by aligning these marks.

(14) In Step (3), the support layer 3 is removed. If the support layer 3 is a multilayer film, a combination of different methods or processes are used to remove the layers of different materials in the film in a step-by-step manner.

(15) In Step (4), the photoresist layer 2 is brought into the grooves in the 3D sample.

(16) In Step (5), the photoresist layer 2 is developed to transfer the fine pattern onto the desired position of the 3D sample 7.

(17) It should be noted that the film references 1A may alternatively be embedded in the film 1. This will not require any change in Steps (1)-(5).

Embodiment 2

(18) The second embodiment of the present invention differs from the first embodiment in that part 3a of the support layer 3 remains on the 3D sample in Step (2) to subsequently conform to the shape of the sample. A more detailed description is provided below with reference to FIG. 2.

(19) As shown FIG. 2(1), in Step (1), film references 1A are provided on the side of the support layer 3 of a film 1 that is in contact with the photoresist layer 2. In other words, the film references 1A are in contact with the photoresist layer 2 on the support layers 3 (3a and 3b).

(20) Although the photoresist layer 2 is susceptible to variation in the film thickness around the film references 1A, the microscope image can more easily be focused during observation to achieve alignment.

(21) Although Step (1) of this embodiment is similar to Step (1) of the first embodiment, the support layer 3b is removed when the process advances to Step (2), and in Step (3), the support layer 3a is deformed together with the photoresist layer 2 and fitted into the V-shape grooves. If polyvinyl alcohol (PVA) and its modification product(s) are used for the support layer 3a, this layer can be removed as shown in Step (4) by immersing it in water as this material is water-soluble. This step does not affect the photoresist layer 2. Subsequently, in Step (5), the photoresist layer 2 is developed.

(22) It should be noted that if the support layer 3a is a PVA layer, Step (4) may be omitted as PVA can be dissolved in the aqueous developer of Step (5). That is, in this case, Steps (4) and (5) can be carried out simultaneously.

Embodiment 3

(23) In the third embodiment of the present invention, unlike in Step (1) of the first embodiment, no film references 1A are provided in advance on the film 1 for application to a 3D sample. Rather, they are formed simultaneously with the transfer of a fine pattern in this embodiment. A more detailed description is provided below with reference to FIG. 3.

(24) In Step (1), the film references 1A are transferred from the photomask together with the exposure of the fine pattern. In Step (2), part of the area of the photoresist layer 2 of the film 1 is developed to manifest the film references. Although partial development of an area is a special process, it has the advantage of providing the film references 1A at the accuracy of the photomask. Furthermore, as the alignment procedure can be omitted when transferring the fine pattern, this can minimize the risk of causing abrasion between the film 1 and the photomask 5 and mutual damage due to their relative movement. Step (3) and the subsequent steps are identical with those of the first and second embodiments illustrated in FIGS. 1 and 2, respectively.

Embodiment 4

(25) In the fourth embodiment of the present invention, unlike in Step (1) of the first embodiment, no film references 1A are provided in advance on the film 1 for application to a 3D sample. Rather, they are formed simultaneously with the transfer of a fine pattern in this alternate embodiment. A more detailed description is provided below with reference to FIG. 4.

(26) In Step (1), the film references 1A are transferred from the photomask together with the exposure of the fine pattern. In Step (2), the photoresist layer 2 of the film 1 is partially developed in the thickness direction to manifest the film references. Although partial development of the resist layer in the thickness direction is a special process, it has the advantage of providing the film references 1A at the accuracy of the photomask while confirming the pattern across the entire surface. Furthermore, as the alignment procedure can be omitted when transferring the fine pattern, this can minimize the risk of causing abrasion between the film 1 and the photomask 5 and mutual damage due to their relative movement. Methods for suppressing or stopping the development of the photoresist layer in the thickness direction halfway include diluting the developer and shortening the developing time. Step (3) and the subsequent steps are identical with those of the first and second embodiments illustrated in FIGS. 1 and 2, respectively.

(27) During the application procedure in Steps (3) and (4), as the areas 2a of the photoresist layer 2 where the layer is eventually removed by development have been reduced so as to provide gaps 4. As air can be vented (i.e., evacuated or removed) through these gaps, air bubbles are not trapped, facilitating close or intimate contact of the photoresist layer 2 with the 3D sample 7. As there is less of the photoresist that has to be removed in the final development, it is easier to develop photoresist with a higher aspect ratio using a thicker photoresist layer.

EXAMPLE

(28) One example of the present invention will be described hereinafter with reference to FIG. 5. The 3D sample in this example was made from a silicon (Si) substrate. V grooves were formed by thermal reflow of a polyimide film having a bottom width of 13 μm and an approximate height of 6.2 μm. The sidewall angle at around the bottom was about 50 degrees. A film/sheet 1 was prepared by spin coating a 1 μm-thick photoresist layer 2 on a support layer 3, which comprises a PVA layer 3a and a PET layer 3b, (using the SO Sheet available from AICELLO Corporation). The film/sheet 1 and the photomask 5 were brought into close contact with each other to carry out exposure with UV light so as to generate a latent image inside the photoresist layer. In this step, the film references 1A on the film/sheet 1 and the mask references 5A on the photomask 5 were used to align the direction of the film/sheet 1 with that of the V grooves in the 3D sample 7.

(29) The film/sheet 1A was applied to the 3D sample 7 with the film references 1A on the prepared film/sheet 1 aligned with the sample references 7A on the 3D sample 7 so that the obtained line-and-space fine pattern was along the transverse direction or ran across the V grooves.

(30) FIG. 2 depicts the fabrication process of the example. When applying the resist layer to the 3D sample 7, the supporting PET layer 3a was manually peeled off from the film/sheet 1. The PVA layer 3a, which remained on the 3D sample, was dissolved and removed by immersing it in water. Finally, the photoresist layer 2 was developed in the developer.

(31) FIG. 5 shows the line-and-space fine pattern formed by the above-described processes. The pattern width is 2 μm and the pitch is 4 μm in the mask design. The resist pattern across the V grooves closely followed the groove contour, reaching their bottom portions.

INDUSTRIAL APPLICABILITY

(32) There is a need for photolithography-based micromachining of 3D samples in a wide variety of applications that require 3D structures for achieving their functions, including, for example: MEMS devices, such as sensors, actuators (e.g., patterning of fragile microactuators released from substrates), and microfluidic devices based on the trench channels; optical devices or systems on which elements need to be aligned along the light path; 3D LSI circuits, which are implemented by stacking a plurality of conventional planer LSI devices and image sensors; and the functional surface texturing of precision machine elements having local flat and/or curved surfaces, which cannot be handled in the same manner as flat wafers.