JP2006037173A - Martensitic stainless steel for dicing saw tape frame and production method therefor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide martensitic stainless steel for a dicing saw tape frame in which the precipitation of chromium carbide is suppressed by the addition of Nb and Ti and the content of solid solution Cr in a matrix is secured to a level required for corrosion resistance, and which has excellent hardness and toughness as well. <P>SOLUTION: The martensitic stainless steel comprises, by mass, 0.15 to 0.5% C, 11 to 16% Cr, ≤1.0% Si, ≤1.0% Mn, 0.1 to 1.0% Ti and/or Nb. The stainless steel is produced by the process of holding at 950 to 1,150°C, the subsequent quenching, and tempering at ≤500°C, has a Vickers hardness of ≥450 HV, and has no rusting caused by cooling water at the time of dicing even when Ni plating is obviated. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a martensitic stainless steel suitable as a dicing saw tape frame used when a chip is cut out from a semiconductor wafer and a method for manufacturing the same.

  The semiconductor wafer is diced into individual chips after various functions are formed. In dicing, the entire semiconductor wafer 1 is fixed to a dicing saw tape frame 2, and the semiconductor wafer 1 is cut with an ultra-thin and disk-shaped diamond blade (dicing saw) 3 (FIG. 1). The dicing saw tape frame 2 is made of ferritic or martensitic stainless steel.

  The dicing saw tape frame is required to have strength to prevent wrinkling due to contact with the diamond blade and toughness to prevent cracking due to impact. Considering the dicing work that prevents the seizure of the wafer due to processing heat by feeding the cooling water to the cutting point, it is also one of the required characteristics that it has excellent corrosion resistance to suppress the generation of heat caused by contact with the cooling water. One. However, if a SUS420J2 frame, which has been provided with strength and toughness by quenching and tempering, is used for dicing while quenching and tempering, it is easy to start up and induces wafer contamination.

  Ni plating is applied to the frame after quenching and tempering to improve corrosion resistance. However, since Ni plating is applied to each manufactured frame, the process load increases significantly and the product cost increases. Invite. In addition, when the Ni-plated frame is used for a long time, the Ni plating layer is peeled off from the base steel, and there is a concern about contamination of the wafer by the peeled piece, which causes a reduction in wafer yield and an increase in cost.

In addition to the martensite series, it is also known to use stainless steel having a ferrite + martensite structure for a dicing saw tape frame (Patent Document 1). However, the hardness required of the dicing saw tape frame is Vickers hardness: 450 HV or more, and the required hardness tends to be insufficient in ferrite + martensite stainless steel.
JP-A-9-263912

  The present invention is based on the knowledge that a large amount of Cr-based carbide precipitates cause corrosion of the quenching and tempering material, so that solid solution C is precipitated as Ti-based carbide and Nb-based carbide, thereby forming a solid solution in the matrix. Martensite that has the strength and toughness required for a dicing saw tape frame without generating Ni even if the Ni plating required for martensitic stainless steel is omitted to secure the Cr content and improve the corrosion resistance An object is to provide a stainless steel.

The martensitic stainless steel for dicing saw tape frame of the present invention is C: 0.15-0.5 mass%, Cr: 11-16 mass%, Si: 1.0 mass% or less, Mn: 1.0 mass % Or less, Ti and / or Nb: 0.1 to 1.0 mass%, Fe: substantially the remaining composition and exhibiting a martensite structure.
Stainless steel having a predetermined composition is manufactured by holding at 950 to 1150 ° C., quenching, and then tempering at a temperature of 500 ° C. or less.

Effects and embodiments of the invention

  The present inventors investigated the effects of steel composition, heat treatment conditions, etc. on the corrosion resistance, strength, toughness, etc. required for martensitic stainless steel for dicing saw tape frames. As a result, it was clarified that when martensitic stainless steel added with Nb and Ti is used as a material and the quenching and tempering conditions are controlled, corrosion resistance, strength and toughness satisfying the required characteristics can be imparted.

  First, the influence of Nb and Ti on corrosion resistance was investigated. The test steel types are SUS420J2 (conventional steel), 12% Cr-0.3% C-0.35% Nb steel (present invention steel A), 12% Cr-0.3% C-0.30% Ti steel. (Invention steel B) was used. Each steel type was subjected to a heat treatment of solution treatment (1050 ° C. × 1 hour) → quenching → tempering (300 ° C. × 30 minutes), and then a salt spray test based on JIS Z2371 was continued for 8 hours. When the appearance of each stainless steel was observed after spraying with salt water, the conventional steel had spawned, but the steels A and B of the present invention did not detect any spatter and maintained the same beautiful surface as before the salt spray test. It was.

In order to investigate the cause of the difference in generation depending on the addition of Nb and Ti, the cut surface of each test piece was mirror-polished, then electrolytically etched in an oxalic acid bath, and the cross-sectional structure was observed. As can be seen in FIG. 2, many precipitates are dispersed in the conventional steel, while the precipitates of the steels A and B of the present invention are greatly reduced. When the precipitates dispersed in the steel were analyzed by EPMA, all of the precipitates in the conventional steel were chromium carbide. In the steel A of the present invention, chromium carbide and niobium carbide, and in the steel B of the present invention, chromium carbide and titanium carbide. It was.
From the above results, it can be explained as follows that the corrosion resistance is improved by the addition of Nb and Ti.

  In the case of SUS420J2 (conventional steel) quenching and tempering material, the amount of solute Cr in the matrix decreases with the large amount of chromium carbide precipitation, and the corrosion resistance decreases. On the other hand, in the present invention steel A to which Nb is added and the present invention steel B to which Ti is added, the precipitation amount of chromium carbide is reduced by the amount of precipitation of niobium carbide or titanium carbide, and the reduction in the amount of solute Cr is suppressed. Corrosion resistance does not decrease.

Next, the influence of quenching / tempering conditions on strength and toughness was investigated. Plate thickness: When hardening and tempering 12% Cr-0.3% C-0.30% Ti steel (Invention Steel B) with 1.5mm, the solution temperature and tempering temperature are variously changed. The relationship between tempering temperature and hardness after heat treatment was investigated. The solution time and tempering time were both set to 10 minutes.
As can be seen from the investigation results of FIG. 3, the hardness decreased as the tempering temperature increased at any solution temperature, and the same tempering temperature tended to become harder as the solution temperature increased. It was also found that when the solution temperature was 950 ° C. or higher and the tempering temperature was 500 ° C. or lower, the Vickers hardness required for the dicing saw tape frame: 450 HV or higher was obtained.

  Further, a strip-shaped test piece 4 having a length of 80 mm and a width: 15 mm was cut out from the heat-treated steel material, and V-notch 5 having a depth of 2 mm and a radius of 0.25 mm was provided on both sides of the central portion in the length direction ( FIG. 4). Using a Charpy impact tester, the center between both V-notches 5 was hit with a hammer 6 to investigate whether the test piece 4 was broken. The toughness was evaluated by setting the test piece 4 broken by the hammer 6 to be X, and the test piece 4 bent without being broken as ○. As apparent from Table 1 showing the toughness evaluation results, all the tempered test pieces had good toughness. In the test piece as-quenched without tempering, only the 1020 ° C. hardened material had poor toughness.

  From the above results, it was found that the strength and toughness satisfying the required characteristics are imparted by setting the solution temperature to 950 ° C. or higher and the tempering temperature to 500 ° C. or lower. However, if the solution temperature is too high, not only the heat treatment cost increases but also the furnace life tends to decrease, so the upper limit was set to 1150 ° C. The tempering temperature is set to 200 ° C. or higher in order to avoid prolonged tempering treatment. Preferably, it is preferable to select a solution temperature in the range of 1000 to 1060 ° C and a tempering temperature in the range of 300 to 500 ° C.

The stainless steel targeted by the present invention is a martensitic stainless steel in which the amounts of C, Si, and Mn are regulated and the amount of Cr is adjusted to 11 to 16% by mass, and chromium carbide is added by adding Ti and / or Nb. Precipitation is suppressed.
C has a martensite structure by quenching, so 0.15% by mass is necessary. However, since an excessive amount of C deteriorates hot workability due to a large amount of precipitation of eutectic carbide, the upper limit of the C content is set to 0.5% by mass. Preferably, the C content is selected in the range of 0.2 to 0.4 mass%. Si and Mn are components added as a deoxidizer during steelmaking, but excessive addition causes an increase in production cost, so the upper limit was set to 1.0% by mass (preferably 0.8% by mass).

  Cr is an alloy component indispensable for improving corrosion resistance, and considering the usage environment of the dicing saw tape frame, 11 mass% or more of Cr is necessary. However, excessive addition causes the production cost to increase, so the upper limit was made 16% by mass. Preferably, the Cr content is selected in the range of 12 to 15% by mass.

  Nb and Ti are niobium carbide or titanium carbide and are dispersed in the matrix to suppress the precipitation of chromium carbide, and are effective components for maintaining the amount of solid solution Cr in the matrix at a level required for corrosion resistance. In order to precipitate and disperse niobium carbide and titanium carbide, which are effective for suppressing precipitation of chromium carbide, 0.1% by mass or more is required by single addition, and when Nb and Ti are added together, the total of 0.1% by mass or more is required. Addition amount is required. However, excessive addition increases the amount of intermetallic compound produced and decreases toughness, so the upper limit of the addition amount was set to 1.0% by mass. Preferably, the added amount of Nb alone, the added amount of Ti alone, or the total added amount of Nb and Ti is determined in the range of 0.2 to 0.5% by mass.

  The addition of Nb and Ti suppresses the precipitation of chromium carbide, but the effect of improving the corrosion resistance is significant by precipitating 0.25 volume% or more of niobium carbide and 0.4 volume% or more of titanium carbide. In this component system, the necessary precipitation amount of niobium carbide and titanium carbide is ensured by controlling the components, composition, and manufacturing process. The volume fraction of the precipitate is obtained by EPMA analysis of the mirror-polished sample, measuring the area ratio of the portion identified as niobium carbide and titanium carbide, and converting the measured value of the area ratio.

  The stainless steel is tempered to a martensite structure by quenching and tempering. The martensite structure is a high-strength steel material because it contains high-density dislocations and contains supersaturated carbon as a solid solution, and toughness is improved by tempering. Incidentally, in the ferrite or austenite series, it is difficult to obtain a Vickers hardness of 450 HV or higher by quenching.

  A steel material having the components and compositions shown in Table 2 was melted in a 30 kg vacuum melting furnace, and after casting, the steel sheet was hot-rolled to a thickness of 5.0 mm. In the table, A1 to A3 are steel materials that satisfy the component conditions defined in the present invention, and B1 to B3 are comparative steels. After heating steel types A1 to A3, B1 and B2 at 780 ° C. for 9 hours, furnace cooling, pickling, primary cold rolling, intermediate annealing, and secondary cold rolling, a sheet thickness of 1.5 mm was obtained, Furthermore, after maintaining at 780 ° C. for 1 minute, it was cooled and pickled. Steel type B3 was a cold-rolled annealed steel sheet having a thickness of 1.5 mm under the same conditions except that heat treatment was performed at 1050 ° C. for 1 minute after hot rolling and after cold rolling.

Each cold-rolled annealed plate was soaked at 900 ° C. or 1050 ° C. for 10 minutes, and then subjected to a quenching treatment with water cooling. Next, it was tempered by air cooling after holding at 250 ° C. for 1 minute or air cooling after holding at 450 ° C. for 1 minute. The samples that were quenched or quenched / tempered were subjected to hardness test, toughness test, and corrosion test.
In the hardness test, Vickers hardness was measured at a load of 98 N, and the measured values at five measurement points were averaged. Required hardness of dicing saw tape frame: Hardness was evaluated with a test piece exceeding 450 HV as ◯ and a test piece not reaching the required hardness as X.

In the toughness test, a V-notch test piece (FIG. 4) was set on a Charpy impact tester and examined for breakage due to hammering. Toughness was evaluated with a test piece broken by hammering as x and a test piece bent without breaking as ○.
In the corrosion test, a salt spray test according to JIS Z2371 was continued for 8 hours, and then the appearance of the test piece was observed. Corrosion resistance was evaluated with a test piece that had been spoiled as x and a test piece that had not been spoiled as ◯.

As can be seen from the investigation results in Table 3, in steel types A1 to A3, which were water-cooled after 1050 ° C. × 10 minutes soaking and tempered to 250 ° C. or 450 ° C., both the component conditions and the heat treatment conditions were specified in the present invention. Satisfied the conditions, high hardness and excellent toughness and corrosion resistance.
On the other hand, even when steel type A1 was used, if tempering was omitted, the toughness was poor, and when tempering was performed at a temperature that was too high, the hardness was insufficient and the corrosion resistance was also poor.
Steel type B1 had good hardness and toughness, but was inferior in corrosion resistance because Nb and Ti were not added. B2 having a ferrite structure and B3 having an austenite structure are not suitable for dicing saw tape frame applications because of insufficient hardness.

  As described above, the martensitic stainless steel of the present invention suppresses the dispersion and precipitation of chromium carbide by adding Nb and Ti, so that the amount of solid solution Cr in the matrix is maintained at a level necessary for ensuring corrosion resistance. Since it is a site structure, it has a Vickers hardness of 450 HV or more, and toughness is improved by tempering. Therefore, the characteristics required for the dicing saw tape frame are satisfied, the dicing saw tape frame is used for a long time for dicing a semiconductor wafer, and contamination of the semiconductor wafer is prevented even if Ni plating is omitted.

A perspective view showing a dicing saw tape frame used for dicing a semiconductor wafer A micrograph of a metal structure showing a matrix in which precipitates are dispersed in a matrix of Nb and Ti-free steel and precipitates in comparison with Nb and Ti-added steel. Graph showing the effect of quenching and tempering conditions on hardness Shape of specimen used for Charpy impact test

Explanation of symbols

1: Semiconductor wafer 2: Dicing saw tape frame 3: Dicing saw 4: Test piece 5: V notch

Claims (2)

  C: 0.15-0.5% by mass, Cr: 11-16% by mass, Si: 1.0% by mass or less, Mn: 1.0% by mass or less, Ti and / or Nb: 0.1-1. 0% by mass, Fe: Martensitic stainless steel for dicing saw tape frame characterized by having a substantially remaining composition and exhibiting a martensitic structure.   C: 0.15-0.5% by mass, Cr: 11-16% by mass, Si: 1.0% by mass or less, Mn: 1.0% by mass or less, Ti and / or Nb: 0.1-1. Martens for dicing saw tape frame, wherein 0% by mass, Fe: stainless steel having a substantially remaining composition is melted at 950 to 1150 ° C., then quenched and then tempered to a temperature of 500 ° C. or lower. Method for producing site-based stainless steel.

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