JP2005142399A - Dicing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a dicing method capable of preventing a wafer surface from being contaminated owing to the curling-up and exfoliation of a TEG film E for the wafer having a TEG formed on a street, and of preventing the occurrence of wafer rear surface tipping caused by an influence of the TEG film E. <P>SOLUTION: The wafer W is completely cut by forming a ground groove G1 in the wafer W from the surface side of the wafer using a first dicing blade 10 and hereby incompletely cutting the wafer W to completely remove the TEG (first processing), and then by forming a ground groove G2 in a part of the wafer left behind by the incomplete cutting using a second dicing blade 11 (second processing). <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a dicing method, and more particularly to a dicing method for dividing a wafer such as a semiconductor device or an electronic component into individual chips.

  In semiconductor manufacturing processes, etc., wafers with semiconductor devices or electronic parts formed on the surface are subjected to electrical tests in the probing process and then divided into individual chips (also called dies or pellets) in the dicing process. The individual chips are then die bonded to the component base in a die bonding process. After die bonding, wire bonding is performed, and after wire bonding, resin molding is performed to obtain a finished product such as a semiconductor device or an electronic component.

  After the probing process, as shown in FIG. 3, the back surface of the wafer is bonded to an adhesive sheet S (also called a dicing sheet or dicing tape) S having a thickness of about 100 μm with an adhesive layer formed on one side, and a rigid ring. Is mounted on a frame F. In this state, the wafer W is conveyed in the dicing process, between the dicing process and the die bonding process, and in the die bonding process.

  In the dicing process, a dicing apparatus that cuts the wafer by inserting grinding grooves into the wafer W with a thin grindstone called a dicing blade is used. The dicing blade is obtained by electrodepositing fine diamond abrasive grains with Ni, and an extremely thin one having a thickness of about 30 μm is used.

  The dicing blade is rotated at a high speed of 30,000 to 60,000 rpm and cut into the wafer W to completely cut the wafer W (full cut). At this time, since the adhesive sheet S stuck on the back surface of the wafer W is cut only about 10 μm from the front surface, the wafer W is cut into individual chips T, but the individual chips T are separated. In other words, since the arrangement of the chips T is not collapsed, the wafer state is maintained as a whole.

  However, in the case of grinding with this dicing blade, since the wafer W is a highly brittle material, it becomes brittle mode processing, and chipping occurs on the front and back surfaces of the wafer W, and this chipping is a factor that deteriorates the performance of the divided chips T. It was.

On the other hand, in order to improve the general function of the dicing blade, a dicing blade that has a plurality of grooves formed radially on both the front and back sides of the dicing blade to improve the supply of cutting water to the processing part and the removal of chips Has been proposed (see, for example, Patent Document 1).
JP-A-6-188308

  By the way, in recent years, for a wafer W having a large number of semiconductor devices formed on the surface, a process and a device called ТEG (test elementary group) are evaluated on a dicing area (called a street) between semiconductor chips. There are many cases where test patterns for management and management are formed.

  This ТEG is formed of a single-layer or multi-layer thin film on the street, and many of them are formed to fill the street width due to the recent trend of narrow streets.

  When such a wafer W with ТEG is diced, there is a problem that the ТEG film is turned over or peeled off, and the peeled fine ТEG film adheres to and contaminates the circuit pattern in the semiconductor chip.

  FIG. 7 is a plan view showing a state where the dicing groove G is processed on the street K of the wafer W. FIG. The ТEG film E formed on the street K is left uncut. This left uncut ТEG film E is partially turned or peeled off.

  Thus, the ТEG film E left uncut when the dicing groove is formed in one direction of the wafer W is peeled off and scattered when the dicing groove is formed in the direction perpendicular to the dicing direction, thereby contaminating the surface of the wafer W. There is a noticeable case.

  In addition, when the wafer W is completely cut together with the ТEG film E, there is a problem that the ТEG film E adheres to the cutting edge of the dicing blade and chipping generated on the back surface of the wafer W is increased.

  The turning and peeling of the ТEG film E generated during dicing and the chipping on the back surface of the wafer can be improved even by using the dicing blade described in the above-mentioned Patent Document 1, which should have been improved in function. could not.

  The present invention has been made in view of such circumstances, and the wafer surface with ТEG formed on the street is not contaminated by turning or peeling of the ТEG film E. An object of the present invention is to provide a dicing method that does not cause wafer backside chipping due to influence.

  In order to achieve the above object, the present invention provides a wafer dicing method in which a test pattern (referred to as ТEG) is formed in a dicing area on a surface, and is ground from the surface side of the wafer using a first dicing blade. A groove is formed and the wafer is cut incompletely to completely remove the ТEG (first processing), and then a second dicing blade is used to grind the portion left uncut by the incomplete cutting (first processing). 2), the wafer is completely cut.

  According to the present invention, the ТEG film formed in the dicing area (street) of the wafer by the first processing is removed by rooting, and then the wafer is completely cut by the second processing, so that the ТEG film is turned over or peeled off. Contamination of the wafer surface is prevented. Further, in the second processing, since the portion having no ТEG film is cut, chipping on the back surface of the wafer is reduced.

  Further, the present invention has an additional requirement that the thickness of the second dicing blade is thinner than the thickness of the first dicing blade. This prevents the second dicing blade from contacting the wall surface of the grinding groove formed by the first processing during the second processing.

  Furthermore, the present invention uses a dicing apparatus having two spindles, that is, a spindle to which the first dicing blade is attached and a spindle to which the second dicing blade is attached, and the second machining is used as the first machining. On the other hand, it is an additional requirement to carry out simultaneously with a slight time difference or with a delay of one line or a plurality of lines.

  According to this additional requirement, the ТEG film complete removal processing (first processing) by grinding groove processing on the front surface side of the wafer and the cutting processing (second processing) performed on the bottom of the grinding groove have a predetermined time difference. The dicing time is greatly shortened because the process proceeds simultaneously.

  As described above, according to the dicing method of the present invention, since the ТEG film is completely removed by grinding the groove on the surface side of the wafer, the wafer surface is prevented from being contaminated by turning or peeling of the ТEG film. The Further, the subsequent complete cutting process in the grinding groove grinds the portion where ТEG does not exist at all, so that the wafer back surface chipping due to the ТEG film adhering to the cutting edge of the dicing blade does not occur.

  Hereinafter, preferred embodiments of a dicing method according to the present invention will be described in detail with reference to the accompanying drawings. In each figure, the same number or symbol is attached to the same member.

  First, a dicing apparatus used in the dicing method according to the present invention will be described. FIG. 1 is a perspective view showing the appearance of the dicing apparatus. The dicing apparatus 100 includes a load port 60 that transfers a cassette containing a plurality of wafers W to / from an external apparatus, a transport unit 50 that has a suction unit 51 and transports the wafer W to each part of the apparatus, The imaging unit 81 for imaging the surface, the processing unit 20, a spinner 40 for cleaning and drying the processed wafer W, a controller 90 for controlling the operation of each unit of the apparatus, and the like.

  Two high-frequency motor built-in type air bearing spindles 22A and a second dicing blade 11 are mounted on the processing unit 20. Are both rotated at a high speed of 30,000 rpm to 60,000 rpm, and the index feed in the Y direction and the cut feed in the Z direction are performed independently of each other. . In addition, the work table 23 on which the wafer W is sucked and mounted is ground and fed in the X direction in the figure by the movement of the X table 30.

  As shown in FIG. 3, the wafer W is mounted on the frame F via the adhesive sheet S and supplied to the dicing apparatus 100.

  FIG. 2 is a side sectional view showing a first dicing blade used in the dicing method of the present invention. As shown in FIG. 2, the first dicing blade 10 comprises a flange 10B made of aluminum (Al) and a cutting blade 10A.

  The cutting blade 10A is obtained by fixing diamond abrasive grains on one end face of the flange 10B by electroforming using an electroplating technique using nickel (Ni) as a binder, and after fixing the diamond abrasive grains. The blade portion is formed by removing the flange portion 10C of the flange 10B (the portion indicated by the two-dot chain line in FIG. 2) by etching.

  By using a softer metal than nickel, for example, an alloy of nickel (Ni) and a softer metal than nickel such as copper (Cu) as the binder, the self-generated action of the abrasive grains is activated and sharpness is improved. It can have a lasting effect.

As the diamond abrasive grains, fine abrasive grains having a grain size of # 4000 to # 6000 are used to reduce chipping during wafer cutting. Further, the degree of concentration representing the ratio of the abrasive grains in the cutting blade 10A is based on the weight unit of diamond, and 4.4ct / cm ^{3 is set} to 100, so that the value is four times the volume%. However, in this embodiment, it is 60 to 90.

  When the degree of concentration is less than 60, the number of abrasive grains is insufficient and the sharpness is lowered, and when it is greater than 90, pockets formed between the abrasive grains are too small, and the supply of cutting water and the removal of chips are poor. The sharpness is also reduced. In the present embodiment, the degree of concentration is preferably 60 to 90, but more preferably 70 to 80.

  The outer diameter of the cutting blade 10A is about 50 mm, the thickness is about 60 μm to 90 μm, and the thickness minus about 10 μm from the width of the street K of the wafer W is used corresponding to the street width.

  The structure of the second dicing blade 11 is the same as that of the first dicing blade 10 shown in FIG. 2, and is composed of an aluminum (Al) flange and a cutting blade.

  The cutting blade of the second dicing blade 11 is obtained by fixing diamond abrasive grains on one end face of the flange by electroforming using an electroplating technique using nickel (Ni) as a binder. As with the dicing blade 10, after the diamond abrasive grains are fixed, the flange portion is removed by etching to form a blade portion.

  Moreover, a softer metal than normal nickel may be used for the binder, and the self-generating action of the abrasive grains may be activated to maintain the sharpness.

  Similar to the first dicing blade 10, diamond abrasive grains having fine grains # 4000 to # 6000 (preferably # 5000) are used to reduce chipping on the back surface during wafer cutting. If it is coarser than # 4000, the back surface chipping of the wafer W occurs more than the allowable value. Further, the degree of concentration representing the proportion of abrasive grains in the cutting blade was also set to 60-90.

  When the degree of concentration is less than 60, the number of abrasive grains is insufficient and the sharpness is lowered, and when it is greater than 90, pockets formed between the abrasive grains are too small, and the supply of cutting water and the removal of chips are poor. The sharpness is also reduced. In the present embodiment, the degree of concentration is 60 to 90, but 70 to 80 is more preferable.

  The outer diameter of the cutting blade of the second dicing blade 11 is about 50 mm, and the thickness is about 20 μm to 30 μm (preferably 15 μm to 20 μm). If the blade thickness is less than 20 μm, the rigidity is weak and breaks immediately, which is not practical. If the blade thickness is more than 30 μm, the grinding load is excessively applied and back surface chipping is likely to occur.

  FIG. 4 is a conceptual diagram illustrating an embodiment according to the dicing method of the present invention. The first dicing blade 10 is attached to the front side (left side in FIG. 4) of the two spindles 22A and 22B arranged opposite to each other in the dicing apparatus 100, and the rear side (right side in FIG. 4). A very thin second dicing blade 11 is attached to the spindle 22B.

  The first dicing blade 10 is rotated at 50,000 to 55,000 rpm. The ultra-thin second dicing blade 11 is also rotated at 50,000 rpm to 55,000 rpm.

  In the dicing method of the present invention, first, as shown in FIG. 4A, streets between a plurality of circuit pattern surfaces P formed on the main surface of the wafer W with the back surface of the wafer W attached to the adhesive sheet S. A grinding groove G1 is formed in K by the first dicing blade 10, and the ТEG film E of the test pattern (ТEG) formed in the street K is completely removed.

In grinding the grinding groove G1, incomplete cutting is performed by cutting from the surface side of the wafer W while supplying a grinding liquid from a nozzle (not shown) provided with the first dicing blade 10 interposed therebetween. As the grinding fluid, pure water bubbling CO ₂ is used.

  FIG. 5 is an enlarged plan view of a part of the front side of the wafer W, and the ТEG film E formed on the street K by the grinding groove G1 is completely removed not only in the depth direction but also in the width direction. Represents the state of being.

  That is, by using a thickness of the first dicing blade 10 that is about 10 μm smaller than the width of the street K, it is possible to completely remove it without cutting the ТEG film E.

  After several lines of the grinding groove G1 are formed, as shown in FIG. 4B, the bottom of the first grinding groove G1 is cut into the pressure-sensitive adhesive sheet S by using an extremely thin second dicing blade 11. The grinding groove G2 is formed in a shape, and full cut dicing (complete cutting) is performed.

  In the full cut dicing (complete cutting) by the formation of the grinding groove G2, it is formed in the street K by the half cut (formation of the grinding groove G1) by the first dicing blade 10 performed prior to the full cut dicing (complete cutting). Since the ТEG film E is completely removed, the ТEG film E does not adhere to the cutting edge of the second dicing blade 11, and chipping generated on the back surface of the wafer W can be suppressed as much as possible.

  In addition, when full-cut dicing is performed on the bottom of the grinding groove G1 using the ultra-thin second dicing blade 11, the grinding water easily flows into the grinding groove G1, so that the grinding water can be supplied to the grinding point. In addition, effects such as reduction of the back surface chipping of the wafer W and reduction of clogging due to adhesion of the adhesive sheet S to the tip of the second dicing blade 11 are brought about.

  The formed grinding grooves G1 and G2 are as shown in part A of FIG. FIG. 6 is an enlarged view of the A part. As shown in the figure, the ТEG film E formed on the street K is completely removed by the grinding groove G1, and the grinding groove G2 is formed in the bottom of the grinding groove G1 by cutting into the adhesive sheet S by about 10 μm. The wafer W is completely cut.

  As shown in FIG. 4C, half cut dicing by forming the grinding groove G1 and full cut dicing by forming the grinding groove G2 proceed at the same time, and when all the streets K are processed, the wafer W is finished. It is rotated by 90 °, and the grinding groove G1 of the street K perpendicular to the previous street K is formed and full cut dicing is performed by forming the grinding groove G2.

  At the time of forming the grinding groove G1 of the street K that is orthogonal, the ТEG film E formed on the street K is completely removed, so that a good half cut can be performed. In this way, a large number of chips T, T,... Are divided from the wafer W.

  In this way, the first dicing blade 10 is used to remove the ТEG film E formed on the street K (first processing), and then the second dicing blade 11 is used to completely cut the wafer ( Therefore, the wafer surface is prevented from being contaminated by turning or peeling of the ТEG film E. Further, in the second processing, since the portion where there is no ТEG film E is cut, chipping on the back surface of the wafer is reduced.

  Moreover, since full cut dicing is performed simultaneously with half cut dicing with a predetermined time delay, an increase in dicing time can be suppressed.

  In the above-described embodiment, the first dicing blade 10 and the second dicing blade 11 are described as the flanged type. However, the present invention is not limited to this, and the washer type blade is not integrated with the flange. It may be. Also, the abrasive grains used are not limited to diamond abrasive grains, CBN (cubic, boron, nitride) abrasive grains may be used, and not only electroformed blades, but also ordinary metal bond blades and resin bond blades are applied. May be.

Perspective view showing a dicing apparatus Side sectional view showing the first dicing blade Perspective view showing wafer mounted on frame The conceptual diagram showing the dicing method which concerns on embodiment of this invention Partial enlarged plan view of wafer surface Enlarged sectional view showing the processed grinding groove Partially enlarged plan view showing conventional machining

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... 1st dicing blade, 11 ... 2nd dicing blade, 10A ... Cutting blade, 10B ... Flange, 22A, 22B ... Spindle, 100 ... Dicing apparatus, E ... ТEG film, F ... Frame, G1, G2 ... Grinding Groove, P ... Circuit pattern surface, S ... Adhesive sheet, T ... Chip, W ... Wafer

Claims (3)

In a wafer dicing method in which a test pattern (referred to as ТEG) is formed in a dicing area on the surface,
A grinding groove is formed from the surface side of the wafer using a first dicing blade, the wafer is cut incompletely and the ТEG is completely removed (first processing),
Next, using a second dicing blade, the wafer is completely cut by grinding (second processing) a portion left uncut by the incomplete cutting.   The dicing method according to claim 1, wherein a thickness of the second dicing blade is thinner than a thickness of the first dicing blade. Using a dicing apparatus having two spindles, a spindle for attaching the first dicing blade and a spindle for attaching the second dicing blade,
3. The dicing method according to claim 1, wherein the second processing is performed simultaneously with a slight time difference with respect to the first processing or with a delay of one line or a plurality of lines. 4.

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