Semiconductor device manufacturing: process – Chemical etching
Reexamination Certificate
1999-06-18
2002-07-09
Dang, Trung (Department: 2823)
Semiconductor device manufacturing: process
Chemical etching
C438S694000
Reexamination Certificate
active
06417107
ABSTRACT:
BACKGROUND
1. Field of the Invention
The present invention relates to a method for manufacturing a functional device, more particularly, to a method for manufacturing a functional device preferably having a substantially flat reflective surface or a V-shaped groove at an angle of 45 degrees relative to a (100)-plane of a silicon substrate on the substrate by utilizing a wet etching.
2. Description of the Related Art
Optical disk devices represented by CD-ROMs (Compact Disk-Read Only Memory), MOs Magneto-Optical disk) and DVDs (Digital Versatile Disk) which reproduce information by the use of laser beams having a predetermined wavelength are widely used. An optical head which forms a major component of an optical head apparatus includes a laser diode and a photodiode integrated thereon.
FIG. 1
is a perspective view showing a schematic configuration of an IOU (Integrated Optical Unit)
20
, which is a type of functional device, a main portion of the optical head. The IOU
20
integrates a light-receiving element
24
that receives reflected light beam, a laser diode
25
that deflects the reflected light beam by 90 degrees by using a 45-degree-mirror
26
to emit an irradiated light beam
22
, and the like on a silicon substrate
20
.
FIG. 2
is a sectional view showing the laser diode
25
and the 45-degree-mirror
26
. The irradiated light beam
22
emitted by the laser diode
25
mounted on the silicon substrate
21
is reflected by the 45-degree-mirror
26
to be deflected upward and is guided to an optical disk through a lens system (not shown). The 45-degree-mirror
26
that reflects the irradiated light beam
22
is fabricated by etching on a silicon substrate
21
and depositing a reflective film made of Al, Au or the like on a surface of the 45-degree-mirror
26
.
Although the IOU
20
can be obtained in compact integrated form as a result, it has a serious problem in that a high cost is required for processing the silicon substrate
21
used therefor. The reason is that a (111)-plane is generally employed as the reflective surface of the 45-degree-mirror
26
and this requires a wafer having special specifications that are well known in the art by chemical companies that fabricate wafers.
A cut surface of a wafer sold as a “(100) silicon wafer” sliced from a silicon ingot is normally referred to as “(100)-plane”.
As described, for example, by Kurt E. Peterson, Proceedings of the IEEE, vol. 70, No. 5, pp. 424 (1982) (which is incorporated herein by reference in its entirety), it is known that when the (100)-plane of the silicon substrate
21
is etched, a (111)-plane appears at an angle of exactly 54.74 degrees to the (100)-plane on the section of the silicon substrate
21
as shown in FIG.
3
A. Because such a plane cannot be used as a 45-degree-mirror as it is, as shown in
FIG. 3B
, a silicon ingot
31
is sliced at an angle to obtain the (100) silicon wafer which is 9.74 degrees off, that is to make the angle exactly 45 degrees. The wafer is then etched to obtain a 45-degree-surface. It is difficult to control the inclination at the angle of 9.74 degrees accurately when the silicon ingot
31
is sliced. For example, when a round-bar ingot is sliced at an angle, the sliced part will have a elliptic configuration. Because the sliced wafer is difficult to process using a normal exposure apparatus if it remains in the elliptic configuration, a shaping operation is generally required to shape it into a circular configuration. Such a shaping operation involves much time and labor, resulting in a high cost. Further, the number of wafers available from one ingot
31
is small when they are obtained by slicing the wafers at an angle, and this also leads to a high cost. Presently, the cost of the 45 degree (100) wafer is at a level three or four times higher than that of normal (100) silicon wafers.
Attempts have been made to form the 45-degree-surface using a (100) silicon wafer which is less expensive. Specifically, a silicon substrate is patterned in a <100> direction as shown in FIG.
4
and is etched using an anisotropic etchant to form a surface at an angle of 45 degrees to the (100)plane of the silicon substrate, ie., the 45-degree-surface constituted by a (110)-plane.
In practice, however, the section becomes vertical instead of being at 45 degrees, as shown in
FIG. 5
, depending on the etchant used. Even when a 45-degree-surface is obtained, the surface has significant irregularities thereon such that it is difficult to achieve the desired RMS (Root Mean Square) of such a 45-degree-surface (i.e., 30 nm or less). Under such circumstances, there has been no report on successful formation of a smooth surface which can be used as a reflective surface Under some circumstances, a RMS of 30 nm or less is very important, for example, to read information on particular types of optical disks, such as DVD disks.
Backlund et al, Optical Planes and Reflectors, Anisotropically Etched in Silicon. 7th Int. Conf. On Solid-State Sensors and Actuator (Transducers 93) Yokohama, Japan, 1993, pp. 1031-1033 (which is incorporated herein by reference in its entirety) also describes chemical etching of silicon.
As described above, conventional functional devices and methods for manufacturing thereof have had a problem in that a 45-degree-surface has required a very high cost. Further, efforts toward the use of wafers at low cost have been unsuccessful in achieving desired configurations and operations.
SUMMARY OF THE INVENTION
The present invention has been made in view of the above-mentioned circumstances and intended to solve the above-mentioned problems. In particular, one object of the invention to provide a method for manufacturing a functional device with a 45-degree-surface formed by a (110)-plane using a (100) silicon wafer which is at a low cost.
The present invention provides a method for manufacturing a functional device including preparing a substrate made of a (100) silicon forming a pattern along a <100> direction of the (100) silicon, and etching with an anisotropic etchant using the pattern while applying an ultrasonic wave.
The present invention also provides a method for manufacturing a semiconductor device including preparing a substrate made of a (100) silicon, forming a pattern along a <100> direction of the (100) silicon and etching with an anisotropic etchant and a surface active agent.
Here, the surface formed by the etching step preferably has an angle of 45 degrees against the surface of the (100) silicon. The anisotropic etchant may include a surface active agent. The method may further comprise a step for coating a reflective material on the surface formed by the etching step.
Furthermore, the present invention provides a functional device including a (100) silicon, a pattern formed on the (100) silicon having a slanted surface along a <100> direction, wherein an RMS (Root Mean Square) of the slanted surface is 50 nm or less.
The present invention yet further provides an optical head apparatus, comprising, a light source that irradiates a light beam along a first direction, a reflector that reflects the light beam to a second direction, and an objective lens that receives the light beam from the reflector and condenses the light beam onto an optical recording medium, wherein the reflector is formed on a slanted surface along a <100> direction of a (100) silicon, and a RMS (Root Mean Square) of the slanted surface is 50 nm or less.
Further objects features and advantages of the invention will become apparent from the detailed description of preferred embodiments that follows.
REFERENCES:
patent: 5793153 (1998-08-01), Itoh et al.
patent: 5898167 (1999-04-01), Musha et al.
patent: 6132294 (2000-10-01), Lin
patent: 9-246254 (1997-09-01), None
Bäckuland et al. (Optical Planes and Reflectors, Anisotropically Etched in Silicon, 7the Int. Conf. on Solid-State Sensors and Actuators, Yokohama, Japan, 1993, pp. 1031-1033).*
Ohwada et al. (Groove Depth Uniformization in (110) Si Anisotropic etching by Ultrasonic Wave and Application to Accel
Dang Trung
Foley & Lardner
Kabushiki Kaisha Toshiba
Kebede Brook
LandOfFree
Method for manufacturing a functional device by forming... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method for manufacturing a functional device by forming..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method for manufacturing a functional device by forming... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2871150