JP2006138741A - Method of measuring wafer film strength - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To stably applying damage to the film formed on a semiconductor wafer in measuring the strength of a wafer film while measuring the strength of the wafer film corresponding to the shape of an end part. <P>SOLUTION: Dicing processing, laser processing, etching processing, or the like is adapted to the semiconductor wafer 2 having the film 1 formed to its surface part to form a groove 5 for cutting the film 1. Subsequently, a flattened resin layer 6 is formed on the semiconductor wafer 2 while filling the groove 5 and the semiconductor wafer 2 is cleaved across the groove 5. Thereafter, the cleaved semiconductor wafer (test piece 7) is cooled and the strength of the film 1 calculated from the temperature in which a peeling occurs from the end part of the film 1. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a method for measuring the strength of a film formed on a semiconductor wafer.

  In manufacturing a semiconductor device, various films are formed on a semiconductor wafer. In order to evaluate the reliability and practicality of such a film, the film strength is measured. As a method for measuring the strength of a film formed on a semiconductor wafer (a method for measuring the strength of a wafer film), a tape peeling method, a scratch method, a stud pull method, a peel method, and the like are known (for example, Patent Documents 1 to 3). 2). However, with these methods, it is difficult to quantitatively measure the strength of a film having particularly low adhesion. Therefore, the m-ELT (modified Edge Liftoff Test) method has been applied.

  For example, in order to cope with finer pitches and higher speeds of semiconductor devices, Cu wiring that lowers the wiring and low dielectric constant (low-k) insulating film (low-k film) that reduces inter-wiring capacitance ) Is being applied. Examples of the low dielectric constant insulating film (low-k film) include a silicon oxide (SiOF) film doped with fluorine, a silicon oxide (SiOC) film doped with carbon, an organic-silica film, and a porous film. A silica film or the like is used. Low-k films are very fragile and have the disadvantages of low adhesion. For this reason, the film strength of the low-k film is quantitatively measured by applying the m-ELT method.

The m-ELT method is performed as follows. First, the film formed on the semiconductor wafer is inscribed using an inscription pen or the like. Next, a resin called m-ELT resin (generally an epoxy resin) is dropped onto the injured film and cured after being made to have a substantially uniform thickness. After this, the semiconductor wafer is cleaved at the marked part as a boundary to make a test piece (recommended: 12.5 x 12.5 mm). Such a test piece is exposed to a low-temperature environment, and the temperature at which the film is peeled off from the end of the test piece together with the m-ELT resin is measured. The film strength is determined from the temperature at which the film peeling occurred and the physical property value of the resin.
JP 2002-122533 A JP2003-068847

  In the conventional m-ELT method described above, there is a problem that the film is not uniformly damaged by the marking with a marking pen or the like, and the cleavage yield of the semiconductor wafer is also poor. Moreover, even if the cleavage can be achieved, the measured film strength tends to vary. Furthermore, although the conventional m-ELT method is an index of film strength itself, it has a problem that the film strength in an actual semiconductor device cannot be accurately evaluated.

  That is, when manufacturing an actual semiconductor device, dicing processing, laser processing, RIE processing, etc. are performed in order to reduce damage to the film at the chip end as much as possible when the semiconductor wafer is divided into chips. It is necessary to make evaluations by changing various conditions such as the shape and distance from the guard ring. However, the conventional m-ELT method cannot measure the film strength corresponding to the shape of the chip end, and this is the most practical problem.

  The present invention has been made to cope with such problems, and can stably damage a film formed on a semiconductor wafer and measure the film strength corresponding to the end shape. An object of the present invention is to provide a method for measuring the strength of the wafer film.

  The method for measuring the strength of a wafer film according to an aspect of the present invention includes a step of forming a groove for cutting the film by applying a semiconductor processing method to a semiconductor wafer having a film formed on a surface portion; Forming a flattened resin layer while filling the groove, cleaving the semiconductor wafer across the groove, cooling the cleaved semiconductor wafer, and positioning in the groove And a step of measuring the film strength from the temperature at which peeling occurs from the end of the film.

  In the wafer film strength measuring method according to an aspect of the present invention, a semiconductor processing method used in an actual manufacturing process is applied to a semiconductor wafer having a film formed on a surface portion, and a groove is formed. Since the semiconductor wafer is cleaved, the film can be stably damaged, and an end shape corresponding to an actual semiconductor device can be obtained. Therefore, it is possible to accurately measure the film strength corresponding to the end shape.

  Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings. In addition, although embodiment of this invention is described based on drawing below, those drawings are provided for illustration and this invention is not limited to those drawings.

  FIG. 1 is a cross-sectional view illustrating a wafer film strength measurement process according to an embodiment of the present invention. First, a semiconductor wafer (for example, Si wafer) 2 having a film 1 formed on the surface portion is prepared. The type, material, and the like of the film 1 are not particularly limited, and various films that are applied when a semiconductor device is manufactured can be targeted. The method for measuring the wafer film strength of this embodiment is particularly suitable for measuring the film strength of a low dielectric constant insulating film having a low adhesion strength. The low dielectric constant insulating film is used, for example, in a circuit portion having Cu wiring. FIG. 2 shows an example of such a circuit portion, which has a Cu wiring 4 that is interlayer-insulated by a low dielectric constant insulating film 3 formed on a semiconductor wafer 2.

The low dielectric constant insulating film 3 is a film having a relative dielectric constant of 3.5 or less, for example. Examples of such a low dielectric constant insulating film 3 include a silicon oxide film doped with fluorine (SiOF film), a silicon oxide film doped with carbon (SiOC film), an organic silica film, an HSQ (hydrogen Examples include silsesquioxane) films, MSQ films (methyl silsesquioxane films), BCB (benzocyclobutene) films, PAE (polyarylether) films, PTFE (polytetrafluoroethylene) films, and porous films thereof. Such low dielectric constant insulating films 3 have low adhesion strength to each other, the semiconductor wafer 2 and the like, and have adhesion strength of, for example, 15 J / m ² or less.

  Grooves 5 are formed in the semiconductor wafer 2 having the film 1 as described above (FIG. 1A). The groove 5 is formed so that at least the film 1 is cut. The formation process of the groove 5 is performed by applying a semiconductor processing method used in the manufacturing process of the semiconductor device, for example, an etching process such as a dicing process, a laser process, or an RIE process. The shape and number of the grooves 5 are not particularly limited as long as they have at least the grooves 5 serving as cleavage boundaries. Moreover, the processing method of the groove | channel 5 should just apply semiconductor processing methods, such as a dicing process, a laser processing, and an etching process, and may form the groove | channel 5 combining these. In any case, the groove 5 is formed corresponding to the end shape of the semiconductor device to be evaluated.

  FIG. 1 shows a groove 5 formed by half dicing a semiconductor wafer 2 by dicing. 3 to 6 show other groove shapes. That is, FIG. 3 shows a groove 5A formed by half dicing the semiconductor wafer 2 by laser processing. FIG. 4 shows a groove 5B obtained by half-dicing the semiconductor wafer 2 and then deeply dicing the center part, that is, a stepped groove 5B. The stepped groove 5B can be formed by half dicing by laser processing and then deep half dicing by dicing processing, or by performing wide half dicing and deep half dicing by dicing processing. It is also possible to combine RIE processing.

  FIG. 5 shows a state in which two grooves 5C are formed with an interval, which is laser processing, and the grooves 5D are formed by half dicing near the center between them. FIG. 6 shows a state in which two grooves 5E are formed at an interval, which is an RIE process, and the groove 5F is formed by half dicing near the center between them. In FIG. 5 and FIG. 6, the grooves 5D and 5F near the center are boundaries for cleavage. 5 and 6 show the case where three grooves 5 are formed, the number of grooves 5 may be larger than this.

  As described above, the shape and number of the grooves 5 can be set as appropriate, and the processing method can also be selected as appropriate. Thus, it is possible to obtain the groove 5 corresponding to the end shape of the semiconductor device to be actually evaluated, the distance from the guard ring, and the like. A transparent resin layer 6 is formed by dripping a transparent resin onto the semiconductor wafer 2 having such grooves 5 and curing the resin after filling it into the grooves 5 to adjust to a substantially uniform thickness. (FIG. 1 (b)). For the resin layer 6, a resin (generally an epoxy resin) called m-ELT resin is used. The thickness of the resin layer 6 is, for example, 150 μm. The uniform resin layer 6 is formed with such a thickness.

  Next, as shown in FIG. 1C, the semiconductor wafer 2 is cleaved with the groove 5 as a boundary to produce a test piece (recommended: 12.5 × 12.5 mm) 7. Thus, by cleaving the semiconductor wafer 2 with the groove 5 as a boundary, the end shape of the test piece 7 corresponds to the shape of the groove 5. Therefore, by forming the groove 5 according to the end shape or the like of the actual semiconductor device, the test piece 7 having the end shape corresponding to the semiconductor device to be evaluated can be obtained. In other words, when manufacturing an actual semiconductor device, it is necessary to select an end shape or the like that minimizes film damage applied when a semiconductor wafer is singulated. It becomes possible to obtain the test piece 7 which can be performed.

  The cleaving of the semiconductor wafer 2 may be performed manually using the corners of the table, or may be performed using a braking device or the like. At this time, since the groove 5 is formed by dicing processing, laser processing, RIE processing, or the like capable of stably damaging the film 1, the measurement accuracy of the film strength can be improved. Furthermore, the cleavage yield of the semiconductor wafer 2 is also improved. In addition, as shown in FIG. 7, a groove 8 that triggers cleavage may be formed in the resin layer 6 in advance. By forming such grooves 8, the semiconductor wafer 2 can be cleaved more easily. The groove 8 may be a V-shaped groove, a U-shaped groove, or a bevel cut.

  Next, as shown in FIG. 1 (d), the test piece 7 produced by cleaving the semiconductor wafer 2 is placed on the cooling stage 9. The cooling stage 9 is a temperature controller (not shown) and can be controlled from room temperature to low temperature (for example, about -160 ° C.). Using such a cooling stage 9, the test piece 7 is gradually cooled from room temperature. The temperature change rate is, for example, about −2 to −8 ° C./min. The resin layer 6 constituting the test piece 7 contracts by being cooled, and a peeling force is applied to the end of the film 1 (the end of the film 1 located in the cleaved groove 5).

  Then, as shown in FIG. 1 (e), when the peeling force by the resin layer 6 exceeds the film strength, peeling occurs at the end of the film 1, so the temperature at which the film 1 is peeled is recorded. The temperature at which the film 1 is peeled off can be easily detected by, for example, continuously observing the test piece 7 with a camera. Here, the peeling force of the resin layer 6 that causes the film 1 to peel off is equal to the residual stress of the resin layer 6, and this residual stress value is obtained from the temperature at which the film 1 peeled off. Therefore, if the resin layer 6 is sufficiently thicker than the film 1, the film strength (peeling strength) of the film 1 can be obtained from the residual stress value and the thickness of the resin layer 6.

  As described above, according to the method of measuring the wafer film strength of this embodiment, the film strength of the film 1 is obtained using the test piece 7 in which the end shape corresponding to the actual shape of the semiconductor device to be evaluated is realized by the groove 5. Since (peel strength) can be measured, the film strength corresponding to an actual semiconductor device can be evaluated. Further, since damage to the film 1 is stabilized by the groove 5, the measurement accuracy of the film strength can be improved. By these, it becomes possible to evaluate the reliability, manufacturing yield, etc. of a semiconductor device having a film with low adhesion strength such as a low dielectric constant insulating film with high accuracy and practically.

It is sectional drawing which shows the measurement process of the wafer film | membrane intensity | strength by one Embodiment of this invention. It is sectional drawing which shows one structural example of the film | membrane with which this invention is applied. It is sectional drawing which shows the structural example of the groove | channel formed in the semiconductor wafer. It is sectional drawing which shows the other structural example of the groove | channel formed in the semiconductor wafer. It is sectional drawing which shows the structural example which formed the several groove | channel in the semiconductor wafer. It is sectional drawing which shows the other structural example which formed the several groove | channel in the semiconductor wafer. It is sectional drawing which shows the state which formed the groove | channel which becomes a trigger of cleavage in the resin layer in one Embodiment of this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Film | membrane, 2 ... Semiconductor wafer, 3 ... Low-dielectric-constant insulating film, 5 ... Groove, 6 ... Resin layer, 7 ... Test piece, 8 ... Groove used as a trigger of cleavage, 9 ... Cooling stage.

Claims (4)

Forming a groove for cutting the film by applying a semiconductor processing method to a semiconductor wafer having a film formed on a surface portion;
Forming a planarized resin layer on the semiconductor wafer while filling the groove;
Cleaving the semiconductor wafer across the groove;
Cooling the cleaved semiconductor wafer, and measuring the film strength from the temperature at which the film is peeled off from the end of the film located in the groove. The method for measuring wafer film strength according to claim 1,
The method for measuring wafer film strength, wherein the semiconductor processing method is at least one selected from dicing processing, laser processing, and etching processing. In the measuring method of the wafer film | membrane intensity | strength of Claim 1 or Claim 2,
The method for measuring wafer film strength, wherein the film includes a low dielectric constant insulating film. In the wafer film strength measuring method according to any one of claims 1 to 3,
The method for measuring the strength of the wafer film further comprises a step of forming a groove that is a cleave trigger in a portion of the resin layer located above the groove.

Images