JP2005246580A - Method for cutting substrate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for efficiently manufacturing a chip, in which the accuracy of its cut end part is excellent, by cutting a substrate composed of an aluminum nitride sintered body with a rotary grinding wheel. <P>SOLUTION: When the substrate composed of an aluminum nitride sintered body is cut, (a) the substrate 1 composed of an aluminum nitride sintered body is prepared, (b) a groove 2 is formed in partial depth H from the surface at the cutting position of the substrate 1 with a rotary grinding wheel α having an average abrasive particle size of less than three times the average crystal particle size of the aluminum nitride sintered body, and (c) the substrate is cut by grinding the remaining part 3 with the rotary grinding wheel β having a smaller grinding width C than the width B of the groove and an average abrasive particle size of three times or more the average crystal particle size of the aluminum nitride sintered body. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a novel method for cutting a substrate made of an aluminum nitride sintered body. Specifically, the present invention provides a cutting method for efficiently producing a chip having a good cutting edge accuracy by cutting the substrate.

  Ceramic materials represented by aluminum nitride, alumina, boron nitride and the like are widely used because they have excellent characteristics such as electrical characteristics, optical characteristics, and thermal characteristics. Among these ceramic materials, aluminum nitride, in particular, has not only thermal conductivity, but also has excellent properties in terms of insulation, dielectric properties, and thermal expansion characteristics, so it has rapidly spread as a highly functional heat dissipation substrate for semiconductor mounting. It's getting on.

  Such a heat dissipation board is usually manufactured by the following method. That is, the surface of the aluminum nitride sintered body is ground or polished as necessary to finish it to a certain surface roughness, and a metal thin film layer is formed on the surface. Such a metal layer includes a first thin film layer such as Ti, Cr, Ni—Cr, TaN, Al, Mo, W, and Zr, a second thin film layer such as Ni and Pt, Co, Cu, Au, Ag, and Pd. It is generally formed by forming the third thin film layer in this order.

  After the metal thin film layer is formed on the surface in this way, patterning is performed as necessary, and then the substrate is cut and divided to finish the final product in size and shape, and then the electronic device is formed on the metal thin film layer. (For example, a laser diode) is mounted using a thin film solder or the like.

  In the cutting of the substrate, as the electronic elements are miniaturized and densified, the processing accuracy has been required to be significantly improved in recent years.

  Conventionally, a rotary grinding wheel is generally used for cutting a substrate made of the aluminum nitride sintered body. The cutting device using this rotary grinding wheel is characterized by good economic efficiency because the device itself is simple and the processing speed is high. Various improved methods for cutting a workpiece with high accuracy using the grinding wheel have been proposed. (See Patent Documents 1 and 2).

  However, when a hard material such as an aluminum nitride sintered body is used by using a rotary grinding wheel, the substrate made of the aluminum nitride sintered body is a relatively fragile member. In the case of cutting, there is a problem that it is impossible to avoid the occurrence of chipping at the processing end during processing. In addition, the above-mentioned problem of chipping is greatly affected by the yield of semiconductor products obtained in recent years because the positional accuracy at the time of cutting has increased and the distance between the cutting end and the mounting position of the electronic element has become shorter. It came to influence.

  On the other hand, since a substrate made of an aluminum nitride sintered body is also a relatively hard material, wear of the grinding wheel is great, which adversely affects the economy.

JP-A-4-13552 Japanese Patent No. 3223421

  Accordingly, an object of the present invention is to provide an industrially advantageous cutting method in which chipping at the cutting edge on the substrate surface is reduced in cutting a substrate made of an aluminum nitride sintered body, particularly a substrate having a metal thin film layer on the surface. Is to provide.

  The present inventors have intensively studied to solve the above problems. As a result, a part of the substrate is ground with a rotating grinding wheel having a specific average abrasive grain size smaller than that of a rotating grinding wheel that has been industrially used for cutting a substrate made of an aluminum nitride sintered body. By forming a groove, it is possible to form a cut end portion that suppresses chipping of the cut end portion, and then by cutting the remaining portion with a rotating grinding wheel having a grinding width smaller than this groove and a faster grinding speed, While having a surface portion in which cutting end portion chipping, which is a feature of processing with a rotating grinding wheel of minute diameter abrasive grains, has been suppressed, a great amount of cutting time is not required, and further, the wear amount of the wheel can be reduced. The inventors have found that the object of the present invention can be achieved, and have completed the present invention.

  That is, according to the present invention, when cutting a substrate made of an aluminum nitride sintered body, the depth from the surface of the substrate to a part of the depth at the cutting position of the substrate with respect to the average crystal grain size of the aluminum nitride sintered body. A groove is formed by grinding with a rotary grinding wheel (α) having an average abrasive grain size of less than 3 times, and the grinding width is smaller than the width of the groove and is 3 to the average crystal grain size of the aluminum nitride sintered body. A substrate cutting method characterized in that the remaining portion is ground and cut by a rotary grinding wheel (β) having an average abrasive grain size of twice or more.

  According to the substrate cutting method of the present invention, by performing initial grinding with a rotary grinding wheel (α) to form a groove, a highly accurate cutting end can be secured on the surface layer portion and obtained by cutting. Electronic components can be mounted on the chip surface with high accuracy. In addition, after that, the remaining portion is ground and cut with a rotary grinding wheel (β), so that it is possible to industrially advantageously perform cutting while maintaining the precision of the cut end portion. In other words, the rotary grinding wheel (α) can be ground with high precision, but the grinding wheel is extremely worn. However, since a part of the substrate is ground, such wear can be prevented. Further, after that, since a grindstone having a high grinding speed and a slow grindstone wear speed is used, the cutting speed can be sufficiently shortened and the wear amount of the entire grindstone can be effectively reduced.

  In the cutting method of the present invention, a known substrate made of an aluminum nitride sintered body is used without particular limitation. Among them, the cutting method of the present invention is particularly effective particularly for crystals having an average particle diameter of about 1 to 10 μm constituting the aluminum nitride sintered body. Also, those having such a crystal grain size are suitable in the present invention because the accuracy by polishing the substrate surface can be increased.

  The shape of the substrate is not particularly limited, but from the viewpoint of easy processing, the thickness is preferably 50 μm to 5 cm, particularly 100 μm to 2 cm.

  The substrate made of the aluminum nitride sintered body that is the object of the cutting method of the present invention is not particularly limited. For example, the aluminum nitride sintered body substrate in an unprocessed state, those subjected to various honing processes, and lapping are performed. Or a mirror-finished product, or a sintered body of aluminum nitride in which a metal thin film layer is formed on a substrate surface as a substrate for mounting a semiconductor element by vapor deposition, sputtering, chemical vapor deposition (CVD), etc. Examples include substrates.

  FIG. 1 is a process diagram showing a typical embodiment of the cutting method of the present invention. As shown in FIG. 1, in the cutting method of the present invention, (a) a substrate 1 made of the aluminum nitride sintered body is prepared, and (b) a partial depth (H) from the surface at the cutting position of the substrate 1. ) To form a groove 2 by grinding with a rotating grinding wheel (α), and (c) grinding the remaining portion 3 with a rotating grinding wheel (β) having a grinding width (C) smaller than the width (B) of the groove. It is important to achieve the above-mentioned purpose to cut the substrate.

  That is, if the entire layer of the substrate made of the aluminum nitride sintered body is cut by the rotary grinding wheel (β) without forming the groove by the rotary grinding wheel (α), the chip generated at the cut end portion becomes large. The quality is deteriorated and the object of the present invention cannot be achieved. Moreover, when the whole is cut | disconnected only with a rotational grinding grindstone ((beta)), while a long time is required for a cutting | disconnection, the abrasion loss of this grindstone is large, and has a problem in industrial implementation.

Further, according to the study by the present inventors, the occurrence of chipping at the cut end is due to the separation of crystal grains of the aluminum nitride sintered body during grinding, in order to prevent such chipping from occurring. Rotating grinding having abrasive grains having an average abrasive grain size less than 3 times the grain size at which the separation of the crystal grains is difficult to proceed, that is, the average crystal grain size of the aluminum nitride sintered body constituting the substrate It has been found that it is effective to use a grindstone.

  In the present invention, the width (B) of the groove formed by the rotating grinding wheel (α) is not particularly limited as long as it is relatively larger than the cutting width (C) by the rotating grinding wheel (β) described later. If the width of the groove is too large, the cutting allowance increases and the economy may be impaired. Therefore, the groove formed by the rotary grinding wheel (α) is generally set to 400 μm or less, preferably 150 μm or less. It is preferable.

  The depth of the groove by the rotary grinding wheel (α) is 2 to 10 times the average crystal grain size of the aluminum nitride sintered body and 50% or less of the thickness of the substrate made of the aluminum nitride sintered body. The average crystal grain size (d; μm) of the aluminum nitride sintered body is preferably 2 to 5 times, and more preferably 30% or less of the thickness of the substrate made of the aluminum nitride sintered body.

  That is, when the present inventors cut a polycrystalline material such as an aluminum nitride sintered body with a rotating grinding wheel, the depth of the groove when forming the groove with the rotating grinding wheel (α) is the size of the crystal grains. By setting the depth to be twice or more of the average crystal grain size on the basis of the thickness, as described above, the grinding can be performed without dropping of the crystal grains, and the cutting end portion having excellent accuracy can be obtained. Can be formed.

  However, when the depth (B) of the groove is deeper than the preferred range, the substrate made of the aluminum nitride sintered body is likely to warp, and the subsequent grinding accuracy of the rotating grinding wheel (β) is improved. If the lowered or warped substrate is fixed to the apparatus at the time of cutting with a rotating grinding wheel, the substrate may be broken.

  As the rotary cutting grindstone used for the cutting of the present invention, known ones are used without particular limitation, but those using a grinding grindstone using diamond abrasive grains are suitable. The diamond abrasive is a grinding wheel to which diamond abrasive is fixed using a binder. Natural or synthetic industrial diamond powder is used for the diamond abrasive grains, and the binder may be any method such as resin bond, metal resin bond, metal bond, vitrified bond, electrodeposition bond, and electroformed metal bond. Moreover, the whole grinding wheel may be comprised with the abrasive grain and the binder, and the part which does not relate to a cutting | disconnection may be comprised with other materials, such as a metal.

  In the present invention, the cutting width (C) by the rotating grinding wheel (β) is not particularly limited as long as it is set relatively thinner than the width (B) of the groove formed by the rotating grinding wheel (α). It is preferable that the thickness be as thin as possible within a range where no adverse effects such as meandering of the groove and increase in the wear amount of the grindstone occur. Specifically, it is preferably in the range of 50 to 95% with respect to the width (B) of the groove formed by the rotary grinding wheel (α).

  Further, the shape of the tip of a general grinding wheel is a square shape, but it may be R or tapered. Further, a method generally called multi-blade dicing, in which a large number of grindstones of the same shape are arranged in parallel on the same axis and rotated to cut a large number of cuts at a time, is particularly preferable because the economy is improved. is there.

  The method for fixing the substrate to the grinding machine when using the rotary grinding wheel is not particularly limited, and any known method can be used without limitation. For example, vacuum suction, sticking with an adhesive sheet, sticking with a solid wax, sticking with an adhesive, etc. are applicable, and these may be used in combination. Moreover, what is marketed can be used conveniently for the grinding machine which cut | disconnects.

  As the grooving and cutting method using the rotary grinding wheel targeted in the present invention, known methods can be used without limitation. For example, up cut, down cut, creep feed grinding, high speed stroke grinding and the like can be mentioned.

  Moreover, although the grindstone rotation speed should just be 5000 rpm or more, Preferably it is 20000 rpm or more. The upper limit of the rotational speed is not particularly limited, but is about 100,000 rpm, particularly about 60000 rpm.

  The substrate feed rate may be 300 mm / s or less, but is preferably 30 mm / s or less. There are no restrictions due to other processing conditions.

  Furthermore, the outer diameter of the grinding wheel used in the present invention is not particularly limited, and may be appropriately determined according to the substrate to be cut.

  As a preferred embodiment of the present invention, an embodiment using an adhesive sheet can be mentioned. That is, for example, polyester, polyethylene, polypropylene, polybutene, polybutadiene, vinyl chloride, vinyl chloride copolymer, ionomer resin, ethylene- (meth) acrylic acid copolymer, A known pressure-sensitive adhesive sheet having a structure in which a silicone pressure-sensitive adhesive, an acrylic pressure-sensitive adhesive, or the like is applied on a resin base material such as coalescence, ethylene- (meth) acrylic acid ester copolymer, polystyrene, polycarbonate, By cutting the substrate while leaving the pressure-sensitive adhesive sheet, it is possible to improve the handleability of the substrate after chip formation.

  Further, as another aspect of the cutting method of the present invention, after the groove is formed by the rotary grinding wheel (α) from both sides of the substrate at the cutting position, the remaining part is cut by the rotary grinding wheel (β). Can be adopted. In this case, the said range is applied suitably for the depth of a groove | channel.

  In the cutting method using the pressure sensitive adhesive sheet in the above embodiment, after forming a groove by a rotating grinding wheel (α) on one surface of the substrate, the pressure sensitive adhesive sheet is pasted on the surface having the groove, and then the other side of the substrate. Grooves are formed on the surface of the rotary grinding wheel (α), and finally, cutting is performed by grinding with the rotary grinding wheel (β) to form chips.

  In order to describe the present invention more specifically, examples and comparative examples will be described below, but the present invention is not limited to these examples.

Examples 1-3
Average grain size of abrasive grains on aluminum nitride sintered body substrate (50.8 mm × 50.8 mm × 0.3 mm) subjected to mirror finishing (Ra <0.03 μm) with an average crystal grain size of 6.7 μm Is 12 μm (Disco, B1A803SD1200N50M51, 52D × 0.12T × 40H), 120 μm thick rotating grinding wheel (α), with a cutting machine (Disco, DAD522), grinding wheel rotation speed is 30000 rpm 50 grooves were formed at intervals of 1 mm under the conditions of a speed of 20 mm / s and down cut. The aluminum nitride sintered body substrate was attached to a UV sheet (UDV-100A) and vacuum-adsorbed with a porous chuck and fixed to a cutting machine.

  Then, the rotating grindstone (β) having an average grain size of 25 μm (B1A803SD600N50M51, 52D × 0.1T × 40H, manufactured by Disco Corporation) and a thickness of 100 μm with respect to the aluminum nitride sintered body substrate having the grooves formed therein. With a cutting machine (Disco 522, manufactured by Disco Corporation), all 50 grooves are cut by down-cutting according to the formed grooves under the conditions of a grinding wheel speed of 30000 rpm and a feed rate of 20 mm / s. did.

  The aluminum nitride sintered body substrate was attached to a UV sheet (UDV-100A) and vacuum-adsorbed and fixed with a porous chuck. In order to completely cut the substrate, the UV sheet was cut by 50 μm. Further, the amount of reduction in the radius of the grindstone before and after groove formation and cutting was defined as the amount of wear of the grindstone, and was measured by a cutting machine setup function.

  Observe the processed end after cutting with a 200x measuring microscope, measure the maximum chip width of the cut end within one cut (50.8 mm), and perform this for all cuts. It was set as the cutting edge chip width. The above results are shown in Table 2. As is clear from these results, the cutting method of the present invention is an industrially effective cutting method with a small cutting width at the cutting end and a short cutting time. Is understood.

  Moreover, in each Example, the curvature of the board | substrate after formation of the groove | channel by the rotary grinding wheel ((alpha)) is measured by the surface roughness shape measuring device (The Tokyo Seimitsu make, Surfcom 470A; brand name) in the edge and center of a board | substrate. The results of the difference as the amount of warpage are also shown in Table 2.

Comparative Example 1
The aluminum nitride sintered body substrate (50.8 mm × 50.8 mm × 0.3 mm) subjected to mirror finishing (Ra <0.03 μm) with an average crystal grain size of 6.7 μm is used, and in Comparative Example 1, the groove formation of the example is performed. Only the cutting was performed without performing. In Comparative Example 1, the wear amount of the grindstone is less than that in the example, but the chip width at the cut end of the substrate is large. The cutting conditions are shown in Table 1, and the results are shown in Table 2.

Comparative Example 2
An aluminum nitride sintered body substrate (50.8 mm × 50.8 mm × 0.3 mm) subjected to mirror finishing (Ra <0.03 μm) with an average crystal grain size of 6.7 μm is compared with the rotation of Example 1 in Comparative Example 2. Cutting was performed using only the grinding wheel (α).

  The cutting conditions are shown in Table 1, and the results are shown in Table 2. In Comparative Example 2, the chip width at the cut end of the substrate is smaller than in the example, but the wear amount of the grindstone is large.

Comparative Example 3
An aluminum nitride sintered body substrate (50.8 mm × 50.8 mm × 0.3 mm) subjected to mirror finishing (Ra <0.03 μm) with an average crystal grain size of 6.7 μm was used, and in Comparative Example 3, abrasive grains were formed when grooves were formed. A rotating grinding wheel having an average particle size of 12 μm (B1A803SD1200N50M51, 52D × 0.12T × 40H, manufactured by Disco Corporation) and a thickness of 100 μm was used. Others were cut in the same manner as in the examples.

  The cutting conditions are shown in Table 1, and the results are shown in Table 2. In Comparative Example 3 in which the width of the formed groove and the cutting width are the same, the wear amount of the grindstone is the same as that of the example, but the chip width at the cut end of the substrate is large.

Process drawing which shows the typical aspect of the manufacturing method of the board | substrate of this invention

Explanation of symbols

1 Substrate 2 Groove 3 Remainder

Claims (3)

  When cutting a substrate made of an aluminum nitride sintered body, an average grinding less than 3 times the average crystal grain size of the aluminum nitride sintered body from the surface of the substrate to a partial depth at the cutting position of the substrate. Grooves are formed by grinding with a rotary grindstone (α) having a grain size, the grinding width is smaller than the width of the groove, and the average abrasive grain is 3 times or more the average crystal grain size of the aluminum nitride sintered body A method for cutting a substrate, characterized in that the remaining portion is ground and cut by a rotary grinding wheel (β) having a diameter.   In the cutting method, the depth of the groove formed by the rotating grinding wheel (α) is 2 to 10 times the average crystal grain size of the aluminum nitride sintered body and the thickness of the substrate made of the aluminum nitride sintered body is A method for cutting a substrate, characterized by being less than 50%. The substrate cutting method according to claim 1 or 2, wherein the substrate made of the aluminum nitride sintered body has a metal layer laminated on the surface thereof.

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