Semiconductor device manufacturing: process – Semiconductor substrate dicing – Having specified scribe region structure
Reexamination Certificate
2001-03-28
2001-10-09
Niebling, John F. (Department: 2812)
Semiconductor device manufacturing: process
Semiconductor substrate dicing
Having specified scribe region structure
C438S460000, C438S465000, C438S008000, C438S014000, C438S016000, C257S048000, C257S797000
Reexamination Certificate
active
06300224
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a method for dicing a semiconductor wafer into chips, particularly to a method for dicing a semiconductor wafer provided with grooves in dicing areas. The present invention further relates to the structure of such grooves.
BACKGROUND ART
When a semiconductor wafer (or a semiconductor substrate) on which semiconductor elements are built in is diced into chips, if the surface of the semiconductor wafer is covered by an electrically insulating hard protective film such as oxide film and nitride film, the peeling-off of the protective film is caused in the edge part of a cut line.
With reference to
FIG. 1
, the protective film
4
provided on the substrate
2
is peeled off during a dicing step by a blade
6
. A reference numeral
8
denotes a part of the film peeled off.
In order to prevent the peeling-off of the protective film conventionally, a dicing step is conducted after the protective film is etched away along a dicing line as shown in
FIG. 2
, reference numeral
10
denoting the part of the protective film etched away.
According to the conventional dicing method in
FIG. 2
, the step for etching away the protective film is needed to be conducted other than the step for fabricating semiconductor elements, resulting in the problems of the increase of manufacturing steps and cost.
When the semiconductor wafer is diced after the protective film is peeled off along dicing lines, the substrate is laid bare in the edge part of each diced chip. Accordingly, in the case where a semiconductor element
12
is mounted on a printed circuit board
14
and the element
12
is connected to the board
14
through a lead wire
16
as shown in
FIG. 3
, there is a possibility that the substrate
12
and the wire
16
are electrically shorted around the position
18
, resulting in the malfunction of the semiconductor element
12
.
DISCLOSURE OF INVENTION
An object of the present invention is to provide a method for dicing a semiconductor wafer which is covered by an electrically insulating hard protective film such as oxide film or nitride film to protect the surface of the wafer.
Another object of the present invention is to provide a structure of grooves formed in dicing areas of the wafer.
Still another object of the present invention is to provide a structure of grooves for preventing the displacement of the dicing position from being caused during a dicing step by an full automatic dicing apparatus.
A further object of the present invention is to provide a method for detecting the edge of each cut line accurately.
According to the present invention, grooves are formed in dicing area around each chip by utilizing etching steps during the fabrication of semiconductor elements. Then, a hard protective film is deposited on the inner surface the groove and the surface of the substrate. An edge of a dicing blade is aligned in such a manner that the edge passes through the bottom of the groove. A stress is applied upward or downward to the portion of the protective film to which the edge of the dicing blade is contacted. This stress is propagated from the protective film on the groove to the protective film on the substrate. At this time, the stress is concentrated to the bending portion at the interface between the protective films on the inner surface of the groove and the surface of the substrate, so that the crack is caused along the bending portion. The bending portion where such stress is caused is herein referred to as a crack caused portion.
In order to cause such crack, it is required that the radius of the bending portion is substantially smaller than the thickness of the protective film. For example, if the radius of the bending portion is one-half the thickness of the protective film, a bending stress caused at the bending portion having a bending angle of 0°-120° is 1.5 times that caused at another part of the film. Also, if the radius of the bending portion is one-tenth the thickness of the protective film, the pending stress caused at the pending portion is increased by 2.5 times that of a peripheral part of the film. If the radius of the bending portion is one-twentieth the thickness of the protective film, the bending stress is increased by 3.4 times that of a peripheral part of the film. While an acute angle is preferable for a bending angle of the bending portion, the angle of 90° is comparable to an acute angle.
As a protective film is disrupted by a crack caused at the bending portion, the stress caused by the edge of the blade is not propagated to the area of a semiconductor element. Therefore, the peeling-off of the protective film is not caused at the area of a semiconductor element.
The width of a groove is preferably about 1-20 &mgr;m. While a groove is preferably formed at both-side edges of a dicing line, respectively, a groove may be formed only at one-side edge of a dicing line in the case where only the area neighboring said one-side edge is required to be protected by the film. Alternatively, only one groove which has a width larger than the that of a dicing line may be formed in place of providing groove in both-side edges of a dicing line, respectively.
When one or more etching steps are conducted in the fabricating process of semiconductor elements, an additional groove may be formed in the bottom of an already provided groove to increase the number of crack caused portions. In this case, if a stress has been propagated through a first crack caused portion, the propagation of the stress may be blocked at a second crack caused portion. As a result, the peeling-off of the protective film at the area of a semiconductor element may necessarily be avoided.
Furthermore, according to the present invention, a groove non-formed part may be provided for grooves to be formed at a dicing area. An accurate position of the edge of a cut line may be detected at the groove non-formed part by means of a CCD camera. In this manner, the position of the edge of the cut line may be accurately recognized, so that a next dicing position estimated based on the accurate position of the edge of the cut line may also precisely recognized, i.e. an erroneous recognition for a dicing position is not caused. AS a result, a misregistration of a dicing position may be avoided.
In the present invention, a groove non-formed part is needed to be provided at one or more positions for one dicing line which is required to have a more accurate dicing position. In most cases, as a plurality of chips each having the same configuration are arranged repeatedly on a wafer, it is easy to provide only one groove non-formed part at the peripheral part of each chip. As a result, a groove non-formed part may be easily searched by a CCD camera after dicing.
Where the length of a groove non-formed part is too long, a chipping or a peeling-off of a protective film is caused, and where is too short, it becomes difficult to detect a accurate position of a cut line. When monitoring a groove non-formed part on a CRT with a magnification of 400, the length of a groove non-formed part is preferably about 10-100 &mgr;m.
Also, a dicing method of the present invention comprising the steps of: a) detecting an edge of a cut line after cutting a first dicing area of the semiconductor wafer by picking up an image of an area of the cut line including the groove non-formed part by an image pick-up device; b) correcting a next dicing position stored in the full automatic dicing apparatus based on the edge of the cut line detected; c) cutting a next dicing area based on the next dicing position corrected; d) detecting an edge of a cut line after cutting the next dicing area in the step c) by picking up an image of an area of the cut line including the groove non-formed part by an image pick-up device; e) correcting a further next dicing position stored in the full automatic dicing apparatus based on the edge of the cut line detected in the step d); f) cutting a further next dicing area based on the further next dicing position corrected in the step e); and g) repeating the ste
Arima Takahisa
Kusuda Yukihisa
Niebling John F.
Nippon Sheet Glass Co. Ltd.
Ratner & Prestia
Zarneke David A
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