Optical: systems and elements – Lens – Including a nonspherical surface
Reexamination Certificate
2003-06-25
2004-10-26
Epps, Georgia (Department: 2873)
Optical: systems and elements
Lens
Including a nonspherical surface
C359S718000, C359S642000, C250S216000, C369S013330, C369S112230, C369S112240, C430S321000
Reexamination Certificate
active
06809886
ABSTRACT:
BACKGROUND
1. Field of the Invention
The invention relates a method for manufacturing a combined solid immersion lens (SIL) and submicron aperture, and device thereof and, more specially, to a batch process for manufacturing a combined solid immersion lens (SIL) and nanometer aperture, which utilizes two photo mask steps incoporated with electroplating to combine a microlens structure with a nanometer order of aperture in order to manufacture an optical read/write apparatus having solid immersion lens and nanometer aperture with high resolution so as to increase optical storage density, and device thereof.
2. Related Arts of the Invention
The high density of optical data storage technologies has been currently a rapidly development and increasingly mature technology. Nowadays, there are already some commercial products like CD-ROM, MO, DVD and so forth utilized in multimedia or data storage. At present, the highest density of data storage in these commercial products performs just nearly 2 to 4.7 Gb/in
2
in DVD technology. It means that there are still lots efforts to make the data storage density more advanced.
To get a higher storage density, the optical read/write apparatus (optical pick up head) must offer a small spot to reduce the size of data pits. In conventional optical pick up head, an objective lens is used to focus the light source such that the light source becomes a small spot to write or read data on the media. Among others, it is known that the numerical aperture (NA) and wavelength can dominate the spot size. Besides, it is also approved that a tiny aperture can restrict the spot size. For those reasons, the research here will put emphasis on the fabrications of lens and aperture to gain a smaller spot size.
In contrast with the conventional optical lens, the Solid Immersion Lens (SIL) using solid state technology gets the great performance in reducing spot size. The SIL was introduced by Mansfield and Kino in 1990 for use in high resolution microscopy (Appl. Phys. Lett.57(1990) 2615), and in 1994, Terris introduced the SIL for optical recording (Appl. Phys. Lett.65(1994) 388). As shown in
FIG. 1
, the
FIG. 1
is a schematic drawing showing a conventionally optical read/write apparatus having combined SIL and aperture. The configuration of
FIG. 1
can record the data in high density. The reference numerals of
FIG. 1
,
1
represents SIL,
2
indicates aperture,
3
is beam splitter,
4
is objective,
5
is laser beam, and
6
represents recording media. Typically, the diameter of the focused spot can be &lgr;/NA (where NA is the numerical aperture of the lens, i.e. NA=n×sin&thgr;, &lgr; is the wavelength, n is the refractive index of where the spot is located, and &thgr; is the incident angle.), the greatest efficacy of the SIL is to increase the NA. Therefore, by using a lens material with high n and a possibly round shaped lens curvature, as well as an arrangement of near field to increase &thgr; for the increase of the NA, is indeed capable of reducing the spot size. It was known that the photoresist AZ-P4620 (n≈1.65) meets this requirement. Moreover, the aperture below the SIL can further limit the spot size. However, in traditional etching methods to form the aperture, once over-etching occurs, the aperture size becomes larger than the expected. The etching process is hard to be recoverable. Therefore, in 2001, Lane has developed the over-electroplating methods (ISOM, 2001, pp.252-253) to make a tiny aperture in order to improve the disadvantages of the etching methods.
As described above, it is necessary to integrate the SIL with the aperture together to form an excellent optical read/write head so as to achieve a high density optical storage technology. Kate, et al, in 2001, reported a small-sized near-field optical head structure with high throughput. The device combined the SIL and aperture. However, the parts were fabricated separately. After that, the individual part should have to be precisely aligned and bonded. In addition, the planar microlens was far apart from the aperture. The refraction index of air between the microlens and aperture would influence the NA and quality of focused spot.
U.S. Pat. No. 6,335,522B1, entitled “Optical Probe Having a Refractive Index Micro-Lens and Method of Manufacturing The Same”, Asimada, et al, published on Jan. 1, 2002 disclosed an optical probe having a movable end arranged on an elastic body and a micro-lens with refractive index adaptive for focussing light in an aperture. The method of which is to fabricate aperture and SIL on two substrates individually, and then combine these two substrate together to accomplish the assembly of the element. The disadvantages include that the alignment exists error and the configuration is hard to be obtained in consecutive steps.
U.S. Pat. No. 6,154,326, entitled “Optical Head, Disk Apparatus, Method For Manufacturing Optical Head, and Optical Element”, Ueyanagi; et al, published on Nov. 11, 2000, and U.S. Pat. No. 6,055,220, entitled “Optical Disk Data Storage System With Improved Solid Immersion Lens”, Mamin, et al, published on Nov. 11, 2000, disclosed optical apparatus having aperture. The disclosed methods need to use a high resolution apparatus, such as Electron beam or FIB (Focus Ion Beam), to define the aperture size. Therefore, it needs expensive instrument to accomplish this manufacturing process. In addition, there have no further technology disclosed for the shrinkage of the finished aperture.
As shown in FIG.
2
and
FIGS. 3A
to
3
D which illustrate the conventional process for manufacturing SIL and metallic aperture. In these drawings,
FIG. 2
is a schematic drawing showing a combined SIL and aperture which are fabricated separately and then combined together, and
FIGS. 3A
to
3
D are cross section views showing manufacturing process steps of the device of the FIG.
2
. As shown in these figures, the reference numeral
17
represents silicon substrate,
18
indicates film such as SiN,
19
is Al layer which is deposited on the film. In these conventional process, a combined SIL and aperture is manufactured by using FIB technique to cut away the material to make a small square shaped aperture, and then attaching a SIL on the rear side of the film. As described above, besides the process utilizes the expensive instrument to define the aperture, it does not provide any technology for the shrinkage of the aperture. Moreover, the SIL and aperture are manufactured separately, and after that, they are combined together. Thus, the process is inconvenient and costly.
Therefore, a manufacturing process is developed here to combine SIL and aperture, which is much simpler than the current process for the fabrication of the aperture without any special instrument, and capable of making a complete element by using current available semiconductor manufacturing process in continuous process steps without assembling.
SUMMARY OF THE INVENTION
In view of the above described conventional problems, the object of the invention is to provide an integrated method for manufacturing a combined solid immersion lens (SIL) and submicron aperture, and device thereof, which incorporates photoresist reflow and electroplating to combine a microlens structure with a nanometer order of aperture in order to manufacture an optical read/write apparatus having solid immersion lens and nanometer aperture with high resolution so as to increase optical storage density, and device thereof. The method just uses two photomasks and can be processed in batch, such that the yield and accuracy can be promoted.
To achieve the above object, according to one aspect of the invention, an integrated method for manufacturing a combined solid immersion lens (SIL) and submicron aperture is provided, comprising the following steps: (i) providing a substrate; (ii) depositing a sacrificial layer on the substrate; (iii) coating a first photoresist layer on the sacrificial layer, and using photo—lithography to pattern the first photoresist layer to define an initial aperture; (iv) performin
Chou Hsueh Liang
Hsu Wensyang
Tien Chung Hao
Bucknam and Archer
Dinh Jack
Epps Georgia
National Chiao Tung University
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