JPH05285935A - Dividing method for semiconductor base - Google Patents

Abstract

PURPOSE:To provide the dividing method for a semiconductor base without generating chippings and cracks, also without affecting adversely to element characteristics and with a cut face in the good state. CONSTITUTION:A semiconductor base 21 is provided with a zincblende crystal structure with a main surface (100). A separating channel 27 is formed by wet anisotropic etching in the direction of forming a section into the regular mesa shape on the rear face of said semiconductor base 21. Also another separating channel is formed by dicing in the direction crossing perpendicularly above-said direction on the surface of the semiconductor base 21.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor substrate dividing method for dividing a semiconductor substrate into a plurality of small pieces in a manufacturing process of a semiconductor integrated circuit device or the like.

[0002]

2. Description of the Related Art When an integrated circuit is formed on the main surface of a semiconductor substrate and formation of a passivation film for surface protection is completed, usually the back surface processing of the substrate is started. In the back surface processing step of the substrate, the thickness of the substrate is reduced, the via (VIA) hole is formed, and the back surface metal thin film is formed according to the application of the integrated circuit and the package form. Further, in order to improve the adhesion of the back surface metal, the back surface may be surface-treated before forming the back surface metal. Then, the process of dividing the semiconductor substrate into chips is performed, and the semiconductor chips are divided into unit pieces.

Conventional methods of dividing a substrate include a method of breaking and dividing after scribing, a method of dividing by breaking after half-cut dicing, a method of dividing by full-cut dicing, and a method of dividing by etching. It is roughly divided into. Here, the method of is to divide the substrate along the marking line with a roller or the like after being scribed with a diamond point tool, and the method of is to cut a part of the substrate thickness with a blade,
The rest is broken and divided by braking. Also,
In the method (1), the entire thickness of the substrate is cut by a blade to divide the substrate, and in the method (2), the separation boundary region is melted with an etching solution and divided.

The dicing with a blade has a feature that the cutting speed is fast and mass productivity is excellent. Since the breaking of the substrate crystal is used in breaking, the cutting direction is restricted. Etching has the drawback that as the substrate thickness increases, the time taken to dissolve the isolation region becomes longer. Among the above methods (1) to (3), the mass productivity is excellent in the order of >>, and the method (2) is considered to be applicable to the division of an ultrathin substrate (about 100 μm).

In recent years, III-V group compound semiconductor substrates such as GaAs and InP have been used as materials for realizing high-speed electronic circuits and high-performance light emitting / receiving elements, and GaAs and InP are most commonly used. It is a semiconductor substrate whose main surface is the (100) plane of a zinc blende crystal such as InP. This semiconductor substrate is shown in FIG. It is known that the semiconductor substrate having the (100) plane as the main surface has an easy-cutting direction and a difficult-cutting direction due to the crystal structure. That is, the ease of cutting depends on the direction. Specifically, when cutting from the surface side by dicing or the like, chipping (cracks) and cracks (breaks) are likely to occur in the direction perpendicular to the orientation flat (OF), the kerf loss is large, and the cross-sectional shape is difficult. There is. That is, this direction corresponds to the difficult-to-cut direction. Further, the kerf loss is small in the direction parallel to the OF, and the cross-sectional shape is also good. That is, this direction corresponds to the easy cutting direction. Therefore, conventionally, there has been a problem that two orthogonal directions cannot be cut / separated under the same condition.

In order to solve such a problem, conventionally, for example, the following three measures have been taken.

This is a method of extremely slowing the cutting / cutting speed in cutting in the direction difficult to cut during dicing. It is a method to increase the separation area width in the difficult cutting direction,
This is the method disclosed in JP-A-2-25053. This is a method of performing a special treatment such as forming a metal thin film on the separation region in the difficult-to-cut direction, and is the method disclosed in Japanese Patent Laid-Open No. 2-65154. Further, as a countermeasure against chipping, conventionally, for example, the following countermeasures have been adopted. This is a method disclosed in Japanese Examined Patent Publication No. 3-42508, which is a method in which the cutting direction orthogonal to each other is not parallel or perpendicular to the OF but is shifted by 45 °.

[0008]

However, each of the conventional cutting methods described above has the following problems.

First, in the above-mentioned conventional method, since the cutting / cutting speed is extremely slow, mass productivity (cutting throughput) is deteriorated, and the cross-sectional shape of the cut chip is not necessarily improved.

Further, in the above-mentioned conventional method, since the width of the isolation region is made large, the utilization efficiency of the semiconductor substrate is deteriorated and the cost is increased.

Further, in the above-mentioned conventional method, the number of steps for special processing is increased, and although the extra steps are increased, the sectional shape of the cut chip is not improved as in the method.

Further, the above-mentioned conventional method cannot be applied to the case where it is desired to divide in two directions parallel and perpendicular to the OF, instead of dividing the direction shifted by 45 ° from the characteristics required for the element. From such a background, a cutting method capable of performing good division in two directions parallel and perpendicular to OF has been desired.

Incidentally, such a problem does not occur in a silicon semiconductor substrate, and the above-mentioned properties are peculiar to many III-V group compound semiconductors having a zinc blende crystal structure, and the cause thereof is the crystal structure. Is derived from. In particular, GaA
Since the material itself of s, InP, etc. is more brittle than Si, the effect of chipping and cracks becomes more prominent when dividing in the difficult-to-cut direction, and sometimes even the element performance is affected, which may lead to product defects. There were many.

In GaAsIC and the like, via holes penetrating the front and back surfaces may be provided in the IC pellet in order to improve the heat dissipation of the IC pellet (= chip) or because of the need for high frequency grounding. In that case, the substrate is 100 μm
It is often thinned to a thickness or less. The problem of chipping cracks is more sensitive in dividing thinned substrates than in thick substrates. For this reason,
There has been a demand for a chip dividing method that does not damage the IC.

[0015]

The present invention has been made to solve such a problem, and a semiconductor substrate having a zincblende crystal structure having a (100) plane as a main surface is formed into a plurality of small pieces. In the method of dividing a semiconductor substrate to be divided, from one surface of the semiconductor substrate, a step of forming a separation groove by etching in a direction in which the cross section is in a forward mesa shape by anisotropic etching, and from the other surface of the semiconductor substrate, The step of forming a separation groove by dicing in the direction orthogonal to the above direction is used to divide the semiconductor substrate.

[0016]

The surface etching characteristics of a semiconductor substrate having a zincblende crystal structure whose main surface is the (100) plane are shown in FIGS. 6 and 7. That is, as shown in FIG. 6, when the patterns 16a and 16b are formed by the protective films 15a and 15b on the front and back surfaces 14a and 14b of the semiconductor substrate 14 and the etching is performed, an etching cross section as shown in FIG. It is known that a shape is obtained. As shown in FIG. 7, a groove 17 having a forward mesa etching cross-sectional shape is formed.
c and 17d, and a groove 17 having an inverted mesa etching sectional shape
a and 17b are formed on the front and back surfaces of the semiconductor substrate 14.

That is, on one surface (front surface) of the (100) semiconductor substrate, a forward mesa is formed in a direction parallel to the OF, and the direction parallel to the OF is a direction in which cutting / division is easy. In addition, an inverted mesa is formed in a direction perpendicular to the OF, and a direction perpendicular to the OF becomes a direction in which cutting / division is difficult. On the other hand, on the other surface (back surface) of the semiconductor substrate, the above relationship is reversed, and an inverse mesa is formed in a direction parallel to the OF, and a direction parallel to the OF becomes difficult to cut and divide. Further, a forward mesa is formed in the direction perpendicular to the OF, and the direction perpendicular to the OF is a direction in which cutting / division is easy. That is, the difficult cutting / dividing direction when viewed from the front side of the (100) semiconductor substrate is equivalent to the easy cutting / dividing direction when viewed from the front side when viewed from the back side.

Therefore, in the present invention, the OF is formed from one substrate surface on which the forward mesa is formed in the direction parallel to the OF.
A separation groove is formed by etching or dicing in a direction parallel to the. Further, a separation groove is formed by dicing or etching in the direction perpendicular to the OF from the other substrate surface where the forward mesa is formed in the direction perpendicular to the OF. Further, the step of forming the separation groove by etching can be used together with the via hole forming step. If this etching process is performed after the semiconductor substrate is thinned, the process time is shortened.

[0019]

1 and 2 are sectional views showing a method of dividing a semiconductor substrate according to an embodiment of the present invention. This manufacturing process corresponds to the back surface forming process performed at the final stage of manufacturing the MMIC (monolithic microwave IC).

When the integrated circuit forming process on the front side of the semiconductor substrate 21 is completed, a resist 22 is applied to the front side of the semiconductor substrate 21 to protect the surface (see FIG. 1A). Here, the semiconductor substrate 21 is made of a GaAs material having a zinc blende crystal structure. The surface seen in the front of the drawing is an OF surface, which is a surface parallel to the paper surface, and the left-right direction of the paper surface is the direction parallel to the OF. The direction from the front to the back of the paper is the direction perpendicular to the OF. The surface of the substrate on which the resist 22 is applied is (1
The (00) plane corresponds to the front side of the substrate and the opposite side corresponds to the back side of the substrate. After the resist 22 is hardened, wax is applied to this surface, and a quartz plate 23, for example, is attached to the surface of the resist 22 using the wax as an adhesive (see FIG. 2B). At this point the substrate thickness is 600μ
Since the thickness is about m, the wafer is thinned from the back side by grinding, polishing, etc., and is formed to a thickness of about 100 μm or less (see (c) of the same figure). This thinning of the substrate is due to Ga
Since a semiconductor substrate such as As or InP has poor thermal conductivity, it is performed to improve the heat dissipation of the integrated circuit.

Next, SiO ₂ is formed on the back surface of the thinned substrate 21.
The film 24 is formed (see FIG. 7D). Then Si
A resist 25 is applied to the surface of the O ₂ film 24 and patterned. Normally, in this patterning, a via hole pattern 25a is formed.
In this embodiment, the isolation region pattern 25b is simultaneously formed in the direction perpendicular to the OF (see FIG. 8E). Therefore, the via hole pattern 25a and the OF vertical separation region pattern 25b can be formed in the same mask, and only one patterning mask is required. Next, the via hole 26 and the separation groove 27 are formed by wet etching using this pattern as a mask (see (f) of the same). This separation groove 27, as shown in FIG.
The direction is perpendicular to the OF when viewed from the back side of the semiconductor substrate 21, and is the direction in which a forward mesa is formed by anisotropic etching.

In this via hole forming step, wet etching is usually performed until the hole penetrates, so the processing time is determined by the via hole forming condition. Therefore, by appropriately adjusting the pattern width of the OF vertical separation region pattern 25b, a strip-shaped pellet aggregate in which the OF vertical direction is completely separated can be obtained as in this embodiment, and the separation region can be obtained. It is also possible to cut a groove of any depth. When the groove is simply cut, the OF vertical direction is not completely separated.

Next, after wet-etching, the via holes are penetrated and the OF vertical direction is separated (or grooved).
The SiO ₂ film 24 and the resist 25 on the back surface side are removed (see FIG. 2G), and subsequently the back surface metal 28 is vapor-deposited (see FIG. 2H). At this time, a metal film is also deposited on the via hole 26. Further, if necessary, masking may be performed so that the metal film does not adhere to the OF vertical separation region (or groove). The illustrated state shows the case of masking.

Next, wax is applied to the back surface side of the semiconductor substrate 21 this time, and the semiconductor substrate 21 is fixed by being attached to the fixing base 29 (see FIG. 9 (i)). Further, instead of being fixed to the flat plate in this way, it may be fixed by being attached to an adhesive sheet. Then, the wax adhering to the quartz plate 23 that has fixed the front side of the substrate 21 until now is peeled off, and the quartz plate 23 is not removed. Further, the resist 22 on the front side is removed. Finally, dicing is performed from the front side of the semiconductor substrate 21 fixed to the fixed table 29 by a rotary grindstone (dicing blade) 30. The dicing direction from the substrate surface side is a direction parallel to OF as shown in FIG. 3B, and is a direction in which a forward mesa is formed by anisotropic etching.

The above-mentioned etching process (see FIG. 1 (f))
If the OF vertical direction on the back surface of the substrate is not completely separated, or if the OF parallel direction on the substrate surface is not fully cut in the above dicing process, the braking method is performed after the above dicing process is completed. Using substrate 21
Is completely divided. As a result, the semiconductor substrate 21 is divided into a plurality of substantially rectangular parallelepiped pellets.

As described above, in the semiconductor dividing method according to the present embodiment, the separation groove is formed by dicing in the direction parallel to the OF from the surface of the semiconductor substrate 21 where the forward mesa is formed in the direction parallel to the OF. To be done. Further, the semiconductor substrate 21 in which the forward mesa is formed in the direction perpendicular to the OF
A separation groove is formed from the back surface of the substrate by wet etching in a direction perpendicular to the OF. That is, dicing is not performed in the reverse mesa direction, which is a difficult direction to cut on the substrate surface. Further, since this direction is a forward mesa direction in which cutting is easy when viewed from the back surface of the substrate, wet etching is performed from the back surface in this easy cutting direction. Therefore, on the front surface and the back surface of the semiconductor substrate 21, the separation groove is extremely easily formed in a direction that is easy to cut and divide with good productivity, and chipping (cracking) or cracking (breaking) unlike the conventional case does not occur. Moreover, the chip cutting shape is good,
It does not damage the device performance.

Further, the step of forming the OF vertical separation groove on the back surface of the substrate by etching can be used in combination with the via hole forming step, so that the number of steps is reduced. Of course, the via hole forming step and the separation groove forming step may be performed as independent steps. If this etching process is performed after the semiconductor substrate 21 is thinned, the process time is shortened. In particular, this effect is effective when the semiconductor substrate is thinned to about 100 μm or less as in this embodiment.

In the description of the above embodiment, the separation groove is formed from the back surface of the substrate in the direction perpendicular to the OF by etching, and then the separation groove is formed from the surface of the substrate in the direction parallel to the OF by dicing. The order of may be changed. Further, each of the separation grooves on the front surface and the back surface of the substrate may not be a groove that completely separates the substrate. For example, a cutting separation groove may be formed from the front surface of the substrate in a direction parallel to the OF by half-cut dicing, the front side is fixed with wax, and then the separation groove may be formed from the back surface of the substrate by etching in the vertical direction of the OF. Also in this case, it is possible to divide the semiconductor substrate into pellets in a good state as in the above-mentioned embodiment.

Further, in the above-mentioned embodiment, the formation of the separation groove by etching from the back surface of the substrate is the single line pattern shown in FIG. 3A, but it is not always necessary to have this pattern shape. For example, as shown in FIG.
An intermittent line pattern 31 may be formed from the back surface of the semiconductor substrate 21 in the forward mesa direction perpendicular to the OF. Even in this case, if the braking method is used, the same effect as that of the above embodiment can be obtained.

Further, the etching used for forming the separation groove in the vertical direction of OF is not necessarily wet etching as in the above embodiment, and other etching method may be used.

Further, in the above embodiment, the semiconductor substrate 21 is
Although described as aAs, a III-V group compound semiconductor substrate having another zinc blende crystal structure such as InP may be used. Further, in the above embodiment, the case where the present invention is applied to the manufacture of the MMIC has been described, but a light emitting element, a light receiving element or the like may be used. In each of these cases, the same effect as that of the above-described embodiment can be obtained.

[0032]

As described above, according to the present invention, O
Separation grooves are formed by etching or dicing in the direction parallel to the OF from one substrate surface where the forward mesa is formed in the direction parallel to F. Further, a separation groove is formed by dicing or etching in the direction perpendicular to the OF from the other substrate surface where the forward mesa is formed in the direction perpendicular to the OF. Therefore, the direction of forming the separation groove on each surface of the substrate is such that cutting / division is easy, chipping or cracking does not occur, the element characteristics are not adversely affected, and the state of the cutting surface is A good method for dividing a semiconductor substrate is provided. Furthermore, this dividing method does not impair the utilization efficiency of the semiconductor substrate.

Further, the step of forming the separation groove by etching can be used in combination with the via hole forming step, and in this case, the number of manufacturing steps is reduced. Further, if this etching process is performed after the semiconductor substrate is thinned, the process time is shortened. Therefore, a method of dividing a semiconductor substrate suitable for mass production is provided.

[Brief description of drawings]

FIG. 1 is a process sectional view of the first half of a semiconductor manufacturing process according to an embodiment in which the present invention is applied to an MMIC manufacturing process.

FIG. 2 is a process cross-sectional view of the latter half of the semiconductor manufacturing process according to the present embodiment.

FIG. 3 is a diagram showing a separation groove forming direction of a semiconductor substrate in the present embodiment.

FIG. 4 is a view showing another example of the separation groove other than the separation groove shown in FIG.

[FIG. 5] (10 of a semiconductor substrate having a zinc blende crystal structure)
It is a perspective view explaining a 0) plane, an OF plane, and other crystal axes.

FIG. 6 is a process sectional view explaining the surface etching characteristics of a (100) semiconductor substrate.

FIG. 7 is a perspective view illustrating surface etching characteristics of a (100) semiconductor substrate.

[Explanation of symbols]

21 ... Semiconductor substrate having a zinc blende crystal structure, 22 ... Front resist, 23 ... Quartz plate, 24 ... SiO ₂ film, 25 ... Back resist, 25a ... Via hole pattern, 25b ...
OF vertical separation area pattern, 26 ... Via hole, 27
… OF vertical separation groove, 28… Back metal, 29… Fixing stand, 3
0 ... Rotating whetstone (dicing blade).

Claims (2)

[Claims] 1. A method of dividing a semiconductor substrate having a zincblende crystal structure having a (100) plane as a main surface into a plurality of small pieces, wherein one surface of the semiconductor substrate is anisotropic. A step of forming a separation groove by etching in a direction in which the cross section has a forward mesa shape, and a step of forming a separation groove by dicing from the other surface of the semiconductor substrate in a direction orthogonal to the direction. A method for dividing a semiconductor substrate, comprising: 2. The method for dividing a semiconductor substrate according to claim 1, wherein in the step of forming the separation groove by etching, the etching is solution etching.