Semiconductor device manufacturing: process – Semiconductor substrate dicing
Reexamination Certificate
2002-05-21
2003-11-25
Ghyka, Alexander (Department: 2812)
Semiconductor device manufacturing: process
Semiconductor substrate dicing
C438S463000, C219S121670, C219S121720
Reexamination Certificate
active
06653210
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method and apparatus for cutting a non-metallic substrate, by which the non-metallic substrate formed of a non-metal material such as glass and silicon is precisely separated into a plurality of small pieces, and more particularly, to a method and apparatus for cutting the non-metallic substrate, in which the non-metallic substrate formed of the glass and the silicon is completely cut using only a scribing laser beam and a breaking laser beam without a cooling device.
2. Description of the Related Art
In recent years, the semiconductor industry, which fabricates a highly-integrated and high-performance semiconductor product, has continued to develop along with a semiconductor thin film processing technique. The semiconductor product has anywhere from a few to a few tens of million semiconductor devices that are integrated on a high-purity substrate called a “wafer” that is made of single crystalline silicon, as one of a non-metal material, by the semiconductor thin film processing technique. The semiconductor product serves to store data in digital form or to quickly operate the stored data.
Further, as one of the semiconductor industry applications, a liquid crystal display (LCD) for displaying an analog video signal processed by a data processing unit into digital form has been rapidly developed. In the LCD, liquid crystal is injected between two transparent substrates. A voltage is applied to a certain molecular alignment of the liquid crystal to transform the molecular alignment into that of another. The optical property, such as double refractivity, optical rotary power, dichroism and light scattering, of a liquid crystal cell is changed by the molecular alignment.
The semiconductor product and the LCD have a common feature in that they are formed on a non-metallic substrate, i.e., a high-purity silicon substrate and a glass substrate. Unfortunately, the non-metallic substrate is subject to shock and quite fragile. However, a plurality of semiconductor chips or LCD unit cells are formed on a sheet of wafer or a large-sized glass substrate and then easily separated into each piece.
In the case of the semiconductor product, after forming anywhere from a few to a few hundred semiconductor chips on a sheet of wafer at the same time, and cutting into each chip through a separating process, the semiconductor chip is packaged to produce the semiconductor product.
In the case of the LCD, after forming at least two or more LCD unit cells on the large-sized glass substrate called a motherboard, the LCD unit cell is separated from the motherboard by a separating process, and then they are assembled. At this time, since the separating process occurs during a last step of a production process, a defect in the separating process negatively impacts the productivity and yield of the product. Particularly, the motherboard used for the LCD does not have a crystal structure having the property of glass, the brittleness of the motherboard is lower than that of a silicon wafer. A fine crack is formed at an edge portion of the motherboard during the separating process. The stress is amplified along the crack during a next process used to form the motherboard. Therefore, a defect is easily generated in which an undesired portion of the motherboard is cut.
In the conventional art, a diamond blade, in which a circular plate having a desired diameter is studded with fine diamonds at a circumferential surface thereof and rotated at a high speed, is contacted with a “cutting path” using friction to form a scribe line at a desired depth on a surface of the substrate along the cutting path. Then, a physical impact is applied to the substrate so that a crack is propagated along the scribe line to a lower face of the substrate, thereby separating the semiconductor chip or the LCD unit cell from the wafer or the glass motherboard.
When the wafer or the glass motherboard is separated using the diamond blade, it is necessary to use a cutting margin, which is a desired surface area for the cutting process. Therefore, if the cutting process is not precisely performed, the number of obtained semiconductor chips per a unit wafer decreases due to waste.
Particularly, in the case of the LCD, since a cut face by the diamond blade is roughly formed, many portions on which stresses are concentrated are formed on the cut face. The stress concentration portion of the cut face is easily broken by only a slight impact applied from the outside, so that a crack or a chipping is vertically generated to the cut face.
Further, since the diamond blade generates so many glass particles, an additional cleaning and drying process is required to remove the glass particles. This is disadvantageous to production efficiency.
Recently, to solve the problem, cutting methods using a laser beam have been suggested. For example, U.S. Pat. No. 4,467,168, entitled “Method of Cutting Glass with a Laser and an Article Made Therewith”, U.S. Pat. No. 4,682,003, entitled “Laser Beam Glass Cutting” and U.S. Pat. No. 5,622,540, entitled “Method of Breaking a Glass Sheet” disclose such methods. Since the cutting method using the laser beam is a non-contact type, the vertical crack formed perpendicularly to the cut face is not generated as compared with the cutting method of a contact type using friction with the diamond blade.
FIG. 1
is a view of a conventional laser cutting apparatus for cutting a glass substrate using a laser beam.
As shown in
FIG. 1
a scribing laser beam
13
, for example a CO
2
laser beam having an absorptivity of 95% or more with respect to the glass, is scanned along a cutting path
12
formed on a glass motherboard
10
so as to rapidly heat the cutting path
12
of the motherboard
10
.
Then, a cooling fluid beam
14
having a markedly lower temperature than the heating temperature of the glass motherboard
10
is applied onto the rapidly heated cutting path
12
. Accordingly, while the glass motherboard
10
is rapidly cooled, a crack is generated on a surface of the motherboard
10
to a desired depth to generate a scribe line
15
. Also, the cooling fluid beam
14
may be positioned to be apart from the scribing laser beam
13
at a desired distance or to be adjacent to the scribing laser beam
13
. Otherwise, the cooling fluid beam
14
may be positioned at an inner portion of the scribing laser beam
13
.
Subsequently, a breaking laser beam
16
, such as the CO
2
laser beam, is linearly scanned along the scribe line
15
so as to heat the scribe line
15
rapidly. Thus, a strong tensile force is generated at the scribe line
15
in the direction shown in
FIG. 1
, so that the glass motherboard
10
is completely cut off along the scribe line
15
. Meanwhile, the breaking laser beam
16
is symmetrically applied with respect to the scribe line
15
to heat both sides of the scribe line
15
rapidly.
The conventional laser cutting apparatus, as described above, is mainly comprised of a laser beam generating portion and a cooling portion so as to heat a non-metallic substrate, such as the glass having a low thermal conductivity, using the laser beam and then rapidly cool the heated portion of the non-metallic substrate. Therefore, a thermal stress is propagated to a heat moving direction, so that the substrate is cut.
However, in the conventional laser cutting apparatus, the substrate has to be cooled rapidly, using a cooling material in gaseous or liquid state, after being scanned by the scribing laser in order to induce sudden temperature changes. This limits the cutting speed of the substrate.
In order to out the glass such as Borosilicate glass (BSG) having a thermal conductivity of 0.26 kcal/mh° C. (the thermal conductivity of metal is 57 kcal/mh° C.), the laser beam should be condensed. However, since laser beam energy applied to each unit surface area is inversely proportional to the cutting speed, increasing the cutting speed causes the laser beam energy applied to each unit surface area to be lowered, even if the lase
Choo Dae-Ho
Jeon Baek-Kyun
Nam Hyung-Woo
Ghyka Alexander
McGuireWoods LLP
Samsung Electronics Co,. Ltd.
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