JP2006257500A - Dicing saw tape frame - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a dicing saw tape frame whose shape is not changed even after surface polishing, and capable of cutting chips from a wafer at a high yield. <P>SOLUTION: The dicing saw tape frame is produced from a subzero-treated type high strength stainless steel sheet in which the difference in surface residual stress between the front and rear is controlled to ±100 MPa. The stainless steel sheet comprises, by mass, 0.09 to 0.17% C, ≤1.0% Si, ≤1.5% Mn, 4.0 to 7.0% Ni, 14.0 to 17.0% Cr, ≤0.10% N and 0.001 to 0.010% B, and the components are also regulated in such a manner that AHV=985-135C-14Si-30Mn-43Ni-29Cr-265N≤250, and SHV=1882-255C-43Si-101Mn-70Ni-55Cr-921N≥350 are satisfied. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a dicing saw tape frame used when cutting a chip from a semiconductor wafer.

  The semiconductor wafer is diced into individual chips after an integrated circuit is formed in a predetermined area. In the dicing process, the semiconductor wafer 1 is fixed by attaching a dicing tape to the semiconductor wafer 1 and the dicing saw tape frame 2, and the semiconductor wafer 1 is cut by the dicing saw 3 (FIG. 1).

  A dicing saw tape frame is manufactured by laser-cutting a martensitic stainless steel plate such as SUS420J2 hardened to 400HV or higher by heat treatment of quenching and tempering, and then deburring by # 350 polishing of about 2 passes. ing.

  The dicing saw tape frame is required to have a flatness of 0.3 mm or less in order to cut the semiconductor wafer uniformly. However, even if the flatness after laser cutting is good, the flatness may fall below the required level if the shape changes due to stress or strain introduced during polishing. A dicing saw tape frame with inferior flatness is inferior in chip cutting accuracy, and tends to cause a decrease in yield.

  The inventors of the present invention conducted various investigations and examinations on the relationship between the flatness before and after surface polishing and the steel type, hardness, residual stress, and the like for a tape frame made of martensitic stainless steel subjected to a deep cooling process. As a result, it was clarified that when the stainless steel plate formed into a predetermined shape is hardened by a deep cooling process, the residual stress on the surface of the steel plate has a great influence on the flatness after polishing.

The stainless steel itself, which has been strengthened by deep cooling treatment, was introduced by the present inventors in Patent Document 1, but it has excellent flatness when the deep cooling treatment is performed in a restrained state, and there is little difference in surface residual stress. As a result, it was found that the deterioration of flatness after polishing was reduced.
JP 2002-155346 A

  In the present invention, the difference in surface residual stress is reduced by confining deep cooling treatment, so that good flatness is maintained without causing a shape change even after polishing, and chips can be cut out from a semiconductor wafer with high yield. An object is to provide a dicing saw tape frame.

  The dicing saw tape frame of the present invention is manufactured from a deep-cooling type high-strength stainless steel having a difference in surface residual stress within ± 100 MPa. The stainless steel has C: 0.09 to 0.17 mass%, Si: 1.0 mass% or less, Mn: 1.5 mass% or less, Ni: 4.0 to 7.0 mass%, Cr: 14 0.0-17.0% by mass, N: 0.10% by mass or less, B: 0.001 to 0.010% by mass, AHV value defined by formula (1) is 250 or less, formula (2) The component is adjusted so that the SHV value defined in (1) is 350 or more.

AHV = 985-135C-14Si-30Mn-43Ni-29Cr-265N (1)
SHV = 1882-255C-43Si-101Mn-70Ni-55Cr-921N (2)
Cold-rolled sheets that have been straightened after annealing and pickling and cut to the target size are deep-cooled, but flatness can be achieved by constraining the cold-rolled sheets between flat upper and lower surface plates during deep-cooling. And a stainless steel plate having a difference in surface residual stress within ± 100 MPa can be obtained.

  For the stainless steel used in the present invention, the content of each element is determined so as to sufficiently satisfy the component range of the metastable austenitic stainless steel, the AHV value indicating the hardness after annealing, and the hardness after the deep cooling treatment. The components are adjusted so that the expressed SHV values are AHV ≦ 250 and SHV ≧ 350, respectively. In other words, in the annealed state, the amount of martensite phase produced is small, a relatively soft material mainly composed of the austenite phase, and a component design that increases strength and hardness by increasing the amount of martensite produced by deep cooling treatment. Yes.

  The component design is relatively soft in the annealed state, and the shape is corrected when sandwiched between upper and lower surface plates. When the austenite phase is transformed into the martensite phase by a deep cooling process in a state where the plates are constrained between the platens, the residual stress before transformation is relaxed and the stress distribution is uniform in any direction. For this reason, the deep-cooled stainless steel plate is flat and has a small difference in surface residual stress, so that it does not change in shape even when polished and maintains a good flatness.

As an index indicating the stability of the metastable austenitic stainless steel, the martensite transformation start point M _s during quenching and the generation index Md ₃₀ of the processing induced martensite are usually used. M _s and Md ₃₀ are indicators for estimating the stability of the austenite phase and the amount of martensite generated, and are applied when, for example, the permeability after annealing or the difficulty of processing is a problem. On the other hand, in applications that require shape correction, the strength level at which shape correction is easier than the amount of martensite generated after annealing, in other words, hardness after annealing, becomes an important factor.

  As a result of experiments and data analysis on various components based on such premise, the inventors have found that the AHV value indicating the hardness after annealing and the SHV value indicating the hardness after deep cooling treatment are shapes in the annealed state. It has been found that a high quality dicing saw tape frame can be obtained by an alloy design satisfying AHV ≦ 250 and SHV ≧ 350, which is a factor governing the improvement of strength by modification and deep cooling.

  By appropriately controlling the stability of the austenite phase with the AHV value and SHV value, it is possible to adjust the amount of martensite that is effective for increasing the strength. If the austenite phase becomes too stable, the martensite phase is hardly generated even by the deep cooling treatment, and the strength and hardness cannot be increased. Conversely, if the austenite phase becomes too unstable, a large amount of martensite phase is generated in the annealed state, and flattening becomes difficult.

  The coefficient of each element in the definition formulas (1) and (2) of the AHV value and the SHV value is a negative value, and the hardness after annealing and after the deep cooling treatment decreases as the amount of each element increases. In addition, the coefficient of each element indicates that the larger the value, the greater the influence on hardness even with the same added amount, and it can be said that the influence of C and N is particularly large.

Hereinafter, alloy components and contents contained in stainless steel will be individually described.
C is an important component for increasing the strength of the martensite phase produced by the deep cooling treatment, and sufficient strength and hardness are imparted by the deep cooling treatment at 0.09% by mass or more. However, when an excessive amount of C exceeding 0.17% by mass is contained, carbides are formed during the cooling process during annealing, and surface defects are likely to occur during polishing.

Si is added as a deoxidizer in the steelmaking stage, and also works to increase the hardness of the martensite phase. The effect of adding Si becomes noticeable at 0.05% by mass or more, but if it exceeds 1.0% by mass, the strength becomes too high after annealing, making it difficult to correct the shape by sandwiching the annealed material with a surface plate. Become.
Mn is an austenite generating element and also functions as a deoxidizer. It is a component necessary for making the austenite phase in the annealed state, and the effect of adding Mn becomes remarkable at 0.05 mass% or more. However, when an excessive amount of Mn exceeding 1.5% by mass is contained, inclusions such as MnS increase and pit-like surface defects are likely to occur.

Ni is an austenite-forming element and is a component necessary for obtaining an austenite phase in the annealed state. In addition, it is an important component for adjusting the hardness after annealing and after deep cooling treatment, and the austenite phase is appropriately stabilized by regulating the Ni content in the range of 4.0 to 7.0% by mass. To do. When the Ni content is less than 4.0% by mass, the austenite phase becomes too unstable, and when the Ni content exceeds 7.0% by mass, the austenite phase becomes too stable.
Cr is a component necessary for maintaining the corrosion resistance of stainless steel, and a target corrosion resistance can be obtained at 14.0% by mass or more. However, an excessive amount of Cr exceeding 17.0% by mass impairs the stability of the structure and causes a decrease in the toughness of the martensite phase.

N is a component that increases the strength of the martensite phase in the same manner as C, and the effect of N becomes remarkable when it is 0.005% by mass or more. However, when an excessive amount of N exceeding 0.10% by mass is included, the amount of nitride generated increases and surface defects are likely to occur.
B is an effective component for improving hot workability and hardenability, and an effect of suppressing the occurrence of hot work cracks is observed at 0.001% by mass or more. However, when an excessive amount of B exceeding 0.010% by mass is contained, the amount of borides generated increases and surface defects are likely to occur.

  In addition to regulating the content of each component, adjust the components so that the AHV value defined by Equation (1) and the SHV value defined by Equation (2) are AHV ≦ 250 and SHV ≧ 350, respectively. Yes. AHV ≦ 250 and SHV ≧ 350 are conditions obtained from a number of experimental results. In the annealed state, the amount of martensite produced is kept small and tempered to a relatively soft material, and a large amount of martensite is obtained by deep cooling. A phase is formed to increase the strength. Therefore, it can be corrected to a flat shape in a relatively soft state after annealing, and the strength and hardness are increased by a deep cooling process after the flattening, so that the scratch resistance required for the dicing saw tape frame is also improved.

Next, a method for manufacturing a dicing saw tape frame from stainless steel will be briefly described.
Stainless steel adjusted to a predetermined composition is preferably melted in a vacuum melting furnace and then cast. Although there are no particular restrictions on the casting method, it is efficient to use the continuous casting method. The slab is hot-rolled through hot forging as necessary. Hot rolling conditions do not need to be particularly restricted, and normal hot rolling conditions during the production of metastable austenitic stainless steel are adopted.

  A hot-rolled steel sheet is cold-rolled after solution treatment and annealed to obtain a steel sheet having an annealed structure in which a small amount of martensite phase is formed in the austenite single phase or austenite phase. The annealing conditions are also sufficient within the normal range. Cold rolling and annealing are repeated until the cold-rolled steel sheet reaches a target plate thickness as a dicing saw tape frame. In addition, the pickling process is incorporated after annealing, and a scale is pickled and removed from the steel plate surface.

  The cold-rolled steel sheet rolled to the target thickness is straightened with a roll or the like and then cut into a shape and size necessary for manufacturing a dicing saw tape frame. The cut sheet is clamped between upper and lower surface plates and subjected to deep cooling. As the surface plate for restraining the cut plate, it is preferable to use a stainless steel plate having a plate thickness of about 1.0 to 5.0 mm and wider than the cut plate.

  The deep cooling treatment is preferably performed at a temperature of −50 ° C. or lower. In order to easily secure the condition of −50 ° C. or lower, the cutting plate is held in a cryogenic tank using vaporization of a dedicated refrigerant or liquid nitrogen, or is immersed in a dry ice / alcohol mixture. In order to completely transform the martensite by deep cooling treatment, it is preferably kept in an extremely low temperature atmosphere of −50 ° C. or lower for 1 hour or longer. The austenite phase is transformed into the martensite phase by the deep cooling treatment, and the residual stress before the transformation is relaxed because of the deep cooling treatment in the constrained state, resulting in a uniform stress distribution in any direction. That is, the steel sheet is tempered to have a uniform stress distribution and a high flatness. Incidentally, when shape correction is performed after deep cooling without load, the difference between the front and back of the surface residual stress increases, so that shape deterioration and flatness reduction are likely to occur after polishing.

  Next, the constrained deep-cooled cut plate is processed into a target frame shape. The processing method is preferably laser processing in order to minimize processing distortion introduced into the cut plate. FIG. 2 shows an example of a frame shape obtained from a cut plate. Since the generation of burrs and the like is unavoidable even by laser processing, the dicing saw tape frame is finished by removing the burrs by polishing after laser processing.

  After 80 tons of stainless steel having the composition shown in Table 1 was vacuum-melted, it was cast into a steel ingot having a thickness of 200 mm, and a hot rolled sheet having a thickness of 3.0 mm was manufactured by hot rolling. In the table, steel type A satisfies the component conditions defined in the present invention, steel type B corresponds to SUS420J2, steel type C corresponds to SUS304, and steel type D corresponds to SUS430.

  For steel type A, the hot-rolled sheet was annealed and pickled, then cold-rolled to a thickness of 1.5 mm, and further annealed and pickled. The obtained cold-annealed plate was restrained by being sandwiched between stainless steel plates and charged into a −70 ° C. cool box using a dedicated refrigerant for 6 hours. In the test No. 1, the plate thickness: 3 mm, and in the test No. 2, the cold-annealed plate was restrained with a stainless steel plate having a plate thickness of 1 mm. In test No. 3, the steel plate was not cooled with a stainless steel plate and was subjected to a deep cooling treatment with no load.

Regarding steel type B, the hot-rolled sheet was annealed for a long time and then pickled and cold-rolled to a thickness of 1.5 mm. Next, the cold-rolled sheet is annealed and pickled, and further solutionized: 1000 ° C. × 30 minutes → quenched by water cooling, and plate thickness: 400 ° C. × 30 minutes restrained by sandwiching between 5 mm stainless steel plates → air-cooled tempered Was given.
In steel type C, the hot-rolled sheet was annealed and pickled, and then cold-rolled to a thickness of 1.5 mm.
In steel type D, the hot-rolled sheet was annealed for a long time and then pickled and cold-rolled to a sheet thickness of 1.5 mm.

A 300 mm square test piece was cut out from each stainless steel plate, three locations around the center were determined as measurement points, and the results measured at each measurement point were averaged to calculate the surface residual stress.
In the hardness test, Vickers hardness was measured at a load of 98 N, and the measured values at five measurement points were averaged.
A surface grinder was used for polishing, and the target grinding amount was set to 50 μm per side.
Moreover, the test piece after surface residual stress measurement was mounted on the surface plate for shape measurement, and the flatness was measured using the clearance gauge. When the measured value is the required flatness of the dicing saw tape frame: 0.3 mm or less, the flatness was evaluated as good (◯), and when it exceeded 0.3 mm, the flatness was evaluated as defective (×).

  As can be seen from the investigation results in Table 2, in Test Nos. 1 and 2 using steel type A, the difference in surface residual stress is 8 MPa, 79 MPa, the hardness is 448 HV, the flatness after polishing is 0.15 mm, It was 0.25 mm and was a good result in any evaluation. Even in the case of using the same steel type A, in Test No. 3 in which the cryogenic treatment was performed with no load, the shape was deteriorated, so that the shape correction after the cryogenic treatment was necessary. In this case, the difference between the front and back of the surface residual stress was 121 MPa, and the flatness after polishing was 0.4 mm, and the required flatness of the dicing saw tape frame was not satisfied. The comparison between Test No. 1 and No. 2 and Test No. 3 confirms that it is necessary to obtain a dicing saw tape frame with good flatness so that the difference in surface residual stress is within ± 100 MPa. .

In Test No. 4, although good hardness is obtained, the flatness after polishing is worse than the flatness before polishing because the front and back difference in surface residual stress is large. The deterioration of the flatness due to the polishing is caused by the uneven distribution of the residual stress after the polishing.
In Test Nos. 5 and 6, the difference in surface residual stress is large and the hardness is low compared to steel types A and B. The difference between the front and back of the large surface residual stress is a manifestation that the steel types A and B are HT-finished (cold-rolled) to obtain hardness, and the surface residual stress varies greatly between the front and back. It means that it is difficult to obtain with.

  As described above, the dicing saw tape frame obtained by subjecting a stainless steel plate whose components have been adjusted to AHV ≦ 250 and SHV ≧ 350 to a target shape and then subjected to a deep cooling treatment has a surface residual stress of Since the difference between the front and back is small, the shape change accompanying polishing is small, and good flatness is maintained. For this reason, a sufficient restraining force is applied to the semiconductor wafer when cutting out the chips, so that dicing with high productivity becomes possible.

Explanatory drawing of dicing a semiconductor wafer restrained by a dicing saw tape frame Diagram showing the shape and dimensions of the dicing saw tape frame produced in the example

Explanation of symbols

1: Semiconductor wafer 2: Dicing saw tape frame 3: Dicing saw

Claims (1)

C: 0.09 to 0.17 mass%, Si: 1.0 mass% or less, Mn: 1.5 mass% or less, Ni: 4.0 to 7.0 mass%, Cr: 14.0 to 17. SHV including 0 mass%, N: 0.10 mass% or less, B: 0.001 to 0.010 mass%, AHV value defined by formula (1) is 250 or less, formula (2) A dicing saw tape frame produced from a deep-cooled high-strength stainless steel plate whose components have been adjusted to a value of 350 or more, and having a difference in surface residual stress within ± 100 MPa.
AHV = 985-135C-14Si-30Mn-43Ni-29Cr-265N (1)
SHV = 1882-255C-43Si-101Mn-70Ni-55Cr-921N (2)

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