JP2007173610A - Method for measuring film characteristic and sample for film characteristic measurement - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a technology capable of accurately obtaining physical properties, specifically an elastic modulus acting as a benchmark for an exfoliation and damage of a Low-k film having a thickness of tens to hundreds nm, and of obtaining quantitative information regarding a rate of occurrence (the exfoliation and damage of the film) of defects in a CMP process and a wirebonding process. <P>SOLUTION: A method for measuring the film characteristic comprises the steps of film forming a composite film in providing a film B that is harder than the film A on the film A, and after the film forming step, measuring the characteristic of the composite film from over the film B. The method for measuring the film characteristic calculates the characteristics of the film A at the time of zero thickness of the film B in conducting the same steps for several thickness of the film B. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention is for measuring film characteristics and film breakdown of a semiconductor wafer, particularly in a low dielectric constant insulating film, so-called low-k film, for example in a CMP (chemical / mechanical polishing) process or wire bonding process of a semiconductor wafer. Related to technology.

  In order to increase the calculation processing speed in a semiconductor device, it is important to reduce the signal delay in the device. This signal delay is represented by the sum of the signal delay and the wiring delay in the semiconductor element. By the way, in recent years, miniaturization of the wiring pitch is rapidly progressing. For this reason, the influence of wiring delay has exceeded the signal delay. This wiring delay is proportional to the product of the wiring resistance R and the inter-wiring capacitance C, so-called RC. Therefore, in order to reduce wiring delay, it is necessary to reduce wiring resistance and wiring capacity. For this reason, low resistance Cu has been selected as a wiring material. Further, a low dielectric constant insulating material (Low-k material) has been studied as an insulating material that fills between the wirings.

  In order to reduce the dielectric constant, it has been considered to introduce pores (holes) inside the film or introduce fluorine having a large polarity. In particular, methods for introducing pores have been actively studied, and a dielectric constant of 2.5 or less has been realized.

  However, the pore structure film has a low mechanical strength. Along with this, it has been found that the adhesion between the pore structure film and the upper and lower films of the pore structure film is lowered.

  However, this is a big problem. That is, when the film is as described above, that is, when the pore structure film having the above characteristics is adopted as the inter-wiring insulating film, for example, in the wiring film forming process, particularly in the CMP process and the packaging process, It has been found that film damage is likely to occur, and in particular, film peeling is likely to occur in the wire bonding process.

  Therefore, although the mechanical strength of the pore structure film (Low-k film) has to be sufficiently studied, it has not been established how to evaluate the mechanical structure.

For example, Japanese Patent Application Laid-Open No. 2001-349815 proposes a method for measuring physical properties (elastic modulus) of a single material thin film. That is, it has been proposed to measure the elastic modulus using the nanoindentation method. According to this proposal, there seems to be a certain effect for the purpose of increasing the accuracy of the elastic modulus of the thin film.
JP 2001-349815 A

  However, when the elastic modulus of a low-k film having a relative dielectric constant of 3 or less is to be obtained, the elastic modulus of the low-k film in a thin film such as an actual inter-wiring insulating film is obtained. In such a case, the mechanical strength is very weak. Therefore, the film itself deforms due to the pressing of the contact terminal when measuring hardness and elastic modulus by the nanoindentation method. As a result, it becomes difficult to detect the surface position at the time of pressing, and the measurement data becomes unclear. I have come to understand.

  In addition, the low-k film having a relative dielectric constant of 3 or less has a thin film thickness of 300 nm or less used in an actual device. Therefore, when a thin film with such a thickness is deposited on a silicon substrate and evaluated by the nanoindentation method, it is actually strongly influenced by the hard silicon substrate that is the base, and the numerical value is true. It has also been found that it seems to be far from the value of. In other words, it has been found that the numerical values are not reliable.

  Therefore, the problem to be solved by the present invention is to provide a technique capable of obtaining correct physical property values. In particular, it is to provide a technique capable of accurately obtaining physical properties, in particular, elastic modulus, which are evaluation criteria for peelability and damage degree of a low-k film as an inter-wiring insulating film. Among other things, it is to provide a technique that can accurately determine physical properties, in particular, elastic modulus, which are evaluation criteria for peelability and damage degree of a Low-k film having a thickness of several tens to several hundreds nm. Information that is very useful in the development of materials for inter-wiring insulating films in semiconductor devices can be easily obtained. In particular, quantitative information on the rate of defective products (film peeling and damage) in the CMP process and wire bonding process can be obtained. It is to provide the technology that becomes available.

  While the inventor has eagerly pursued the study on the above-mentioned problem, a high-hardness film (B) is laminated on the Low-k film (A) having a thickness of several tens to several hundreds of nm, and In the case of evaluation by the nanoindentation method, the elastic modulus of the composite film (A + B) is obtained in this case, and the measurement object is the composite film (A + B), so the Low-k film (A) is a thin film. There is no problem because of this, and there is a certain functional relationship between the elastic modulus obtained when the thickness of the B film in such a composite film is changed and the thickness of the B film. If so, if the B film is zero by extrapolation, that is, the elastic modulus of the Low-k film (A), which is a thin film of several tens to several hundreds of nm, It came to think that it might be obtained.

  That is, when measuring the strength of the low-k thin film provided on the Si substrate and measuring a laminated cap film having sufficient hardness and elastic modulus, the upper cap film of the low-k thin film is The measurement start point is clear, and the influence of hardness and elastic modulus due to the cap film changes the degree of influence as the measuring terminal enters the material as an indenter, and the amount of influence It came to a revelation that would be minimized.

  Based on this idea, the elastic modulus of the low-k film (A) having a thickness of several tens to several hundreds of nanometers (A) is obtained, and when the elastic modulus is verified, the above technical idea is correct. The support of was obtained.

The present invention has been achieved based on the above findings.
That is, the above-mentioned problem is a method for measuring the characteristics of the film A,
This is solved by a film characteristic measuring method characterized in that the film strength is measured from above the film B having a higher hardness than the film A provided on the film A.

Also, a method for measuring the characteristics of the film A,
A film forming step in which a film B having a hardness higher than that of the film A is provided on the film A to form a composite film;
After the film forming step, the method is solved by a film characteristic measuring method comprising a measuring step of measuring the characteristic of the composite film from the film B.

Also, a method for measuring the characteristics of the film A,
A film forming step for forming a composite film by providing a film B having a higher hardness than the film A on the film A, and a measuring step for measuring the characteristics of the composite film from the film B after the film forming step. Comprising
This is solved by a film characteristic measuring method characterized by calculating the characteristics of the film A when the thickness of the film B is 0 when the thickness of the film B is several.

  The above-mentioned film characteristic measurement method is a film characteristic measurement method in which measurement is performed particularly when an indenter is pushed into the film. Furthermore, it is a film | membrane characteristic measurement method in which a measurement is performed when an indenter is pushed into the film by a depth of 10 nm to 200 nm. Especially, it is a film | membrane characteristic measuring method in which a measurement is performed by the nanoindentation method.

  In the present invention, the film B laminated on the film A may be one having a hardness higher than the hardness of the film A, and in particular, one having an elastic modulus of 10 GPa or more is preferable. Of these, those of 20 GPa or more are preferable. Although there is no particular restriction on the upper limit value, it is practically about 70 GPa.

  In the present invention, the film A may be basically any type. However, if the hardness is high, accurate physical properties can be obtained without using the method of the present invention. If the method of the present invention is not employed, correct physical property values cannot be obtained in the case of a film having a pore structure. That is, the relative dielectric constant is 3 or less. In particular, the relative dielectric constant is 2.5 or less. Although there is no particular restriction on the lower limit value, the relative dielectric constant is larger than 1. Furthermore, the thickness is 10 to 1000 nm (particularly, 30 nm or more and 200 nm or less).

  In the present invention, the composite film of the film A and the film B preferably has a thickness of about 0.1 to 1 μm.

The above-mentioned problem is a measurement sample used for measuring the characteristics of the film A,
This is solved by a film characteristic measurement sample characterized in that a film B having a hardness higher than that of the film A is provided on the film A.

In particular, a measurement sample used in the above-described method for measuring film characteristics,
This is solved by a film characteristic measurement sample characterized in that a film B having a hardness higher than that of the film A is provided on the film A.

  In particular, the film B laminated on the film A is required to have a hardness higher than the hardness of the film A. In particular, the elastic modulus is preferably 10 GPa or more, and particularly preferably 20 GPa or more. . Although there is no particular restriction on the upper limit value, it is practically about 70 GPa.

  In particular, the film A has a relative dielectric constant of 3 or less. In particular, the relative dielectric constant is 2.5 or less. Although there is no particular restriction on the lower limit value, the relative dielectric constant is larger than 1. Furthermore, the thing whose thickness is 10-1000 nm is preferable. In particular, a thickness of 30 nm or more and 200 nm or less is preferable.

  The composite film of film A and film B preferably has a thickness of about 0.1 to 1 μm. Especially, the thing of 200 nm or more and 500 nm or less is preferable.

  According to the present invention, the elastic modulus of the low-k thin film can be obtained accurately. In particular, an elastic modulus that is an evaluation standard for the peelability and damage degree of the Low-k film as the inter-wiring insulating film is accurately obtained.

  In other words, information that is very useful in the development of materials for inter-wiring insulating films in semiconductor devices can be easily obtained. In particular, quantitative information on the incidence of defective products (film peeling and damage) in the CMP process and wire bonding process can be obtained. can get.

  The film (inter-wiring insulating film in a semiconductor device) characteristic (elastic modulus) measuring method according to the present invention is a method for measuring the characteristics of a film (inter-wiring insulating film having a thickness of 10 to 1000 nm) A. The film strength (elastic modulus) is measured from above a film (for example, a cap film) B having a higher hardness than the film A provided on the film A. In particular, a film forming step in which a film (for example, a cap film) B having a higher hardness than the film (inter-wiring insulating film) A is provided on the film A to form a composite film, and after the film forming step, A measurement step of measuring the characteristics of the composite membrane from above the membrane B. Further, a film forming step of forming a composite film by providing a film (for example, a cap film) B having a higher hardness than the film (inter-wiring insulating film) A on the film A, and after the film forming step A measurement step of measuring the characteristics of the composite film from above the film B, and the same process is performed in the case where the thickness of the film B is several, and the characteristics of the film A when the thickness of the film B is 0 This is a calculation method. The film characteristic measurement method is a method in which measurement is performed particularly when an indenter is pushed into the film. Furthermore, the measurement is performed by pressing the indenter into the film to a depth of 10 nm to 200 nm. Among them, the measurement is performed by the nanoindentation method. The film B laminated on the film A may be one having a hardness higher than that of the film A, but particularly has an elastic modulus of 10 GPa or more. Among them, it is 20 GPa or more. Although there is no particular restriction on the upper limit value, it is practically about 70 GPa. The thickness of the laminated film B is such that the laminated composite film has a thickness of about 0.1 to 1 μm. Especially, it is 30 nm or more and 500 nm or less.

  The measurement sample according to the present invention is a measurement sample used for measuring the characteristics (elastic modulus) of the film (inter-wiring insulating film having a thickness of 10 to 1000 nm) A. In particular, it is a measurement sample used in the above-described method for measuring film characteristics. A film B having a higher hardness than the film A is provided on the film A. The film B is a film having the above characteristics.

This will be described in more detail below.
FIG. 1 is a schematic view of the nanoindentation method used in the present invention.

  As a measurement sample to be used, a predetermined film, that is, a low-k film on a Si substrate and a cap film stacked thereon are used. In particular, a sample having a structure similar to that of a semiconductor element obtained through a CMP process or a wire bonding process is prepared as a measurement sample. This is from the viewpoint that more accurate information can be obtained if it is performed in a form as close as possible to the actual manufacturing of a semiconductor device. Therefore, as the cap film on the low-k film to be tested (measured: evaluated), the cap film employed in the semiconductor element is used. An example of the cap film stacked on the low-k film is a SiO film. In addition to the SiO film, for example, a SiC film, a SiN film, a SiCN film, a SiON film, a SiOC film, or the like can be used. In addition, the thickness of the target Low-k film is preferably a thickness as an inter-wiring insulating film. Furthermore, it is preferable that the processes performed before and after the film formation are performed in the same manner as in the case of actually performing CMP or wire bonding. Examples of such treatment include plasma treatment, use of an adhesion aid, and roughening of the film surface by reverse sputtering.

FIG. 2 is a graph showing the elastic modulus when indentation is performed.
As shown in FIG. 1, the measurement sample is pushed with an indenter. A minute vibration is applied to the measurement terminal of the indentation, and the measurement terminal reaches the surface of the measurement sample to start measurement. Conventionally, there is only a Low-k film to be measured on the Si substrate. For this reason, since the starting point was not clear, there was a tendency for the measurement to vary greatly. Furthermore, it is not certain which part of the obtained curve should be adopted as the measurement value. Also in FIG. 2, in the region where the amount of pushing is relatively small, there is a region where the indenter is sufficiently inserted and the measured value is in the horizontal direction, but it is not easy to quantitatively determine these.

  Therefore, as shown in FIG. 3, when a cap film made of SiO is laminated by CVD on a 150-nm-thick low-k film (insulating film) provided on a Si substrate, a nanoindentation method is used. Was used to measure the elastic modulus (measured using Nanoindenter DCM-SA2 manufactured by MTS), and the results are shown in FIG. That is, as shown in FIG. 4, the value gradually decreases at the beginning of pressing. It is presumed that the initial value is the value of the Cap film, and when the Cap film is broken and reaches the Low-k film, which is a measurement target in the lower layer, the influence of the mechanical strength comes out and falls. As the terminal is further pushed in, the value rises and eventually a quadratic curve with a minimum value is obtained. This minimum value is the elastic modulus of the composite film. The minimum value can be easily obtained by differentiating the curve.

  And the measurement sample which changed the thickness of the Cap film | membrane was prepared, and the same measurement was performed.

  FIG. 5 shows the relationship between the elastic modulus of the composite film thus obtained and the thickness of the Cap film. In FIG. 5, if the thickness of the Cap film is extrapolated to a position of 0, the elastic modulus without the Cap film, that is, the elastic modulus of the Low-k film having a predetermined thickness can be obtained.

And when the elasticity modulus of the bulk Low-k film calculated | required by this method and the elasticity modulus calculated | required by the other method were compared, it was equivalent. Therefore, it can be seen that the value obtained by this method is correct.
The same applies when the low-k film has two or more layers.

  Next, four types of measurement samples having the above-described laminated structure (Low-k film + Cap film) were prepared. The relative dielectric constant of the low-k material in sample A is 3.0, the relative dielectric constant of the low-k material in sample B is 2.4, and the relative dielectric constant of the low-k material in sample C is 2.3. The relative dielectric constant of the Low-k material in Sample D was 2.3. And the composite elastic modulus was measured like the above. Each sample was subjected to a tensile test in wire bonding. Based on the results thus obtained, FIG. 6 shows the relationship between the composite elastic modulus and the tensile test results (breaking strength). This shows that the correlation between the two is high. That is, samples A and B with high composite elastic modulus showed strong values in the wire bonding tensile test, while samples C and D with low composite elastic modulus showed low values in the wire bonding tensile test. ing.

Schematic diagram of nanoindentation method Elastic modulus-indentation depth graph Schematic diagram of the sample for measuring membrane properties of the present invention Graph of composite elastic modulus-indentation depth according to the present invention Composite elastic modulus-Cap film thickness graph Wire Bonding Test-Composite Elastic Modulus Graph Katsumi Utaka

Claims (12)

A method for measuring the characteristics of membrane A, comprising:
A method for measuring film properties, comprising measuring film strength from a film B having a higher hardness than the film A provided on the film A. A method for measuring the characteristics of membrane A, comprising:
A film forming step in which a film B having a hardness higher than that of the film A is provided on the film A to form a composite film;
A film characteristic measuring method comprising: measuring a characteristic of the composite film from above the film B after the film forming process. A method for measuring the characteristics of membrane A, comprising:
A film forming step for forming a composite film by providing a film B having a higher hardness than the film A on the film A, and a measuring step for measuring the characteristics of the composite film from the film B after the film forming step. Comprising
The film characteristic measurement method is characterized in that the characteristic of the film A when the thickness of the film B is 0 is calculated in the same manner when the thickness of the film B is several.   4. The film characteristic measuring method according to claim 1, wherein the measurement is performed by pressing the indenter into the film.   5. The film property measuring method according to claim 1, wherein the indenter is pressed into the film to a depth of 10 nm to 200 nm.   6. The film property measuring method according to claim 1, wherein the measurement is performed by a nanoindentation method.   The film characteristic measuring method according to claim 1, wherein the film B has an elastic modulus of 10 GPa or more.   The film characteristic measuring method according to claim 1, wherein the film A has a relative dielectric constant of 3 or less.   9. The film characteristic measuring method according to claim 1, wherein the sum of the film A and the film B is 0.1 to 1 [mu] m.   The method for measuring film characteristics according to any one of claims 1 to 9, which is a method for measuring an elastic modulus of a film. A measurement sample used for measuring the characteristics of the film A,
A film characteristic measurement sample, wherein a film B having a higher hardness than the film A is provided on the film A. A measurement sample used in the film property measurement method according to any one of claims 1 to 10,
A film characteristic measurement sample, wherein a film B having a higher hardness than the film A is provided on the film A.

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