JP2002164331A - Method for analyzing polymer film in inside of contact hole - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for analyzing an evaporated film which is stuck to the inner face of a contact hole in a deep-submicron-order diameter. SOLUTION: When primary ions 18 are made incident on the surface 12a of an insulation film 12, in which the contact hole 14 is formed, and secondary ions 20 are generated. The primary ions are made to be incident from the same oblique direction with reference to the surface of the insulation film. When the mass of the generated secondary ions is analyzed, the composition of the evaporated film 16 formed on the inner surface of the contact hole is detected. Consequently, the composition distribution of the evaporated film is found along the depth direction of the contact hole.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for determining a depth distribution of a composition of an inner surface of a contact hole after the formation of the contact hole in order to establish a contact hole forming process in a manufacturing process of a semiconductor integrated circuit.

[0002]

2. Description of the Related Art Large-scale semiconductor integrated circuit devices (hereinafter, LS)
Called I. In (2), the number of elements is increasing due to recent high integration, and the number of contact holes for forming wiring is increasing. The diameter of the contact hole tends to gradually decrease. For this reason, formation of a contact hole is becoming more and more difficult. The contact hole is formed by etching. On the inner surface of the contact hole formed by etching, a deposition film is formed by an etching gas or the like. This deposited film is basically formed by depositing residues generated by etching. In order to establish a process for forming a contact hole, it is necessary to examine the composition distribution of the deposited film and optimize the etching process.

[0003] A conventional method for examining the composition distribution of the inner surface of a hole is described in the literature "Technical Research Report of IEICE, Vol.
3, No. 369 pp. 47-52 ". According to the method disclosed in this document, the multilayer wiring sample is cleaved to expose the inner surface of the through hole. Then, the deposited film formed on the inner surface of the through hole is analyzed by Auger electron spectroscopy.

[0004]

However, conventionally,
Deep submicron or tens of nanometers (n
A method for analyzing the composition distribution on the inner surface of a contact hole having a diameter (diameter) of m) and a depth of 1 μm or more has not been reported. For this reason, it was not possible to optimize the contact hole etching process, and it was difficult to form a contact hole having an aspect ratio of, for example, about 20 times.

Therefore, there has been a demand for a method for analyzing the composition distribution of a deposited film adhered to the inner surface of a contact hole having a diameter of the order of deep submicrons.

[0006]

The inventors of the present application have conducted intensive studies, and as a result, have found that the composition distribution of the inner surface (side wall) of the contact hole can be improved by using SIMS (secondary ion mass spectrometry). It has been found that analysis is possible.

According to the method of analyzing a polymer film in a contact hole according to the present invention, anisotropic etching is performed by a process of forming an insulating film on a silicon substrate and an etching gas containing carbon (C) and fluorine (F). Forming a plurality of contact holes in the insulating film, wherein, on the inner surface of the plurality of contact holes, forming a contact hole in which a polymer film containing carbon and fluorine is formed; and This is a step of generating secondary ions by irradiating the primary ions from obliquely above. The primary ions are also applied to the polymer film above the contact hole, and the irradiation causes the carbon and fluorine atoms of the polymer film to be generated. A step of generating secondary ions that simultaneously generate secondary ions; and a step of generating secondary ions of carbon and fluorine by secondary ion mass spectrometry (SIMS).
Performing a mass spectrometry of the secondary ions, the insulating film is gradually cut by continuously irradiating the primary ions, whereby the polymer film formed from the upper portion to the lower portion of the contact hole is continuously converted into the primary film. The method is characterized in that the distribution of the polymer film on the inner surface of the contact hole is analyzed by performing mass spectrometry of carbon and fluorine secondary ions of the polymer film generated by the irradiation with the ions.

That is, the surface of the insulating film to be inspected in which the contact hole is formed is irradiated with primary ions. 1
The secondary ions are preferably incident on the surface of the test insulating film from the same oblique direction. This makes it easier for primary ions to enter the inner surface of the contact hole.
For example, the incident angle of primary ions with respect to the surface of the insulating film is θ
And the diameter of the contact hole is Φ. At this time,
Φ × tan along the depth direction from the surface of the insulating film to be inspected
The inner surface area of the hole over a distance of θ is irradiated with the primary ions.

When the primary ions are irradiated, foreign substances adhering to the surface of the insulating film and the inner surface of the hole, that is, constituent substances on the surface of the deposited film are sputtered to generate secondary ions and the like. Then, by performing mass analysis of the generated secondary ions, it is possible to detect a desired amount of secondary ions. Therefore, the component ratio of the constituent elements of the deposited film is determined.

In addition, since the surface of the insulating film is sputtered by the primary ions, the surface is gradually etched. Therefore, the inner surface of the contact hole can be sequentially irradiated with the primary ions along the depth direction. Therefore, the inner surface of the contact hole can be gradually scanned in the depth direction by the primary ions. Therefore, the composition distribution of the deposited film over the depth direction of the contact hole is required.

Furthermore, by comparing the obtained depth distribution of the composition with the previously measured depth distribution of the composition of the reference insulating film, a contact hole is formed in the insulating film to be inspected. Make sure that.

As described above, the composition distribution in the depth direction of the deposited film deposited on the inner surface of the contact hole can be examined. Based on this information, it can be expected that various phenomena in the etching process will be elucidated. And
Etching conditions for forming a contact hole, such as the composition of an etching gas and various settings of an etching apparatus, can be optimized. Therefore, it is effective for forming a contact hole having a smaller diameter and a deeper hole.

Further, according to the method of the present invention, there is no need to perform a work of cleaving the sample as in the prior art. Therefore, it is possible to perform the inspection in a shorter time and more easily than in the conventional case.

In the method of the present invention, preferably, the inside of the contact hole is filled with a material of the same quality as the insulating film to be inspected.

In this way, the above-mentioned deviation of Φ × tan θ from the surface of the insulating film does not occur. Therefore, the depth position of the inner surface of the hole to be irradiated with the primary ions at a certain time coincides with the height position of the surface of the insulating film at that time. Therefore, the depth in the composition distribution of the deposited film is accurately obtained.

According to the method for inspecting a semiconductor device, the method for inspecting a semiconductor device for inspecting whether or not a contact hole is formed in an insulating film is the same as that for the surface of the insulating film in which the contact hole is formed. Secondary ions are generated by injecting primary ions from the oblique direction of the above, and the secondary ions are subjected to mass spectrometry to determine the depth distribution of the composition of the insulating film. It is characterized in that it is determined whether or not the contact hole is formed by comparing the measured depth distribution of the composition of the reference insulating film.

For example, a contact hole is formed in an insulating film formed on the upper surface of the substrate. When a contact hole is formed by etching, the etching stops at a position on the upper surface of the substrate. Therefore, a relatively thick deposited film is formed at the bottom of the contact hole. The thickness of the deposited film deposited on the bottom portion is thicker than other portions. Therefore, when the composition distribution is examined by the above-described method for detecting the composition distribution of the inner surface of the hole, the position of the bottom of the contact hole can be detected. Accordingly, it is possible to inspect whether or not the opening of the contact hole is good, that is, whether or not the etching reaches the upper surface of the substrate.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. It should be noted that the drawings only schematically show the configuration, size, and arrangement relationship so that the present invention can be understood. Further, the conditions and materials such as numerical values described below are merely examples. Therefore, the present invention is not limited to this embodiment.

[First Embodiment] A method of detecting a composition distribution on the inner surface of a hole according to this embodiment will be described with reference to FIG. FIG. 1 is a diagram for explaining a composition distribution detecting method. FIG. 1 shows a cross section of a cut surface of a region including the contact hole 14.

In this embodiment, a contact hole 14 is formed in an insulating film 12 formed on the upper surface of a silicon substrate 10. As the insulating film 12 of the test insulating film,
For example, a BPSG (silicate glass containing boron (B) and phosphorus (P)) film is formed. The contact hole 14 is formed by, for example, magnetron plasma etching. As an etching gas, a CF-based gas containing carbon (C) or fluorine (F), for example, a CHF ₃ gas is used.

The etching process will be briefly described. When high frequency power is applied by introducing an etching gas into a vacuum, plasma is generated, and ions and radicals are generated. The generated positive ions are accelerated by the internal electric field and collide with the surface of the insulating film 12. Due to this collision, an altered layer (defect layer) is formed on the surface of the insulating film 12. This altered layer easily reacts with radicals. The radical reacts with the altered layer to form a volatile gas as a reaction product. Therefore, the surface portion of the insulating film 12 is shaved. Since an impact is always applied to the surface of the insulating film 12 from almost the same direction, the anisotropic etching proceeds.

During the progress of the etching, a deposition film 16 is deposited on the side wall formed by the etching. The deposited film 16 is mainly formed by attaching a residue (foreign matter) generated during etching. As in this case, when a CF-based etching gas is used, a polymer film of C or F, that is, a fluorocarbon polymer film is formed as the deposition film 16. Since the side etching is suppressed by the deposited film 16, the tendency of anisotropy is strengthened. Examining the composition distribution of the deposited film 16 is important for optimizing the etching conditions such as the mixing ratio of the etching gas, the etching time, and the substrate temperature.

In this embodiment, the above-described deposited film 16 is used.
SIMS (Secondary Ion Mass Spectroscopy) is used to examine the composition distribution of. That is, the primary ions 1 are formed on the surface 12a of the insulating film 12 where the contact holes 14 are formed.
The secondary ions 20 are generated by making 8 incident. Then, mass analysis of the secondary ions 20 is performed,
Evaporated film 16 formed on inner surface of contact hole 14
Is detected. With this method, the composition of the deposited film 16 can be obtained in the depth direction of the contact hole 14.

First, the primary ions 18 are made into a beam and incident on the surface 12a of the insulating film 12 from the same oblique direction, as in the case of performing ordinary SIMS. The incident angle θ of the primary ions 18 to the surface 12a of the insulating film 12 is preferably set in a range from 7 ° to 70 °. In ordinary SIMS, the incident angle is often set to about 30 °. For the reason described later, the smaller the incident angle θ, the higher the detection accuracy. However, 1
Since the area of the deposited film 16 irradiated by the next ion 18 is narrowed, the detection sensitivity is reduced. Therefore,
The value of the incident angle θ is set in consideration of the balance between the accuracy and the sensitivity.

The primary ions 18 are, for example, oxygen ions. The primary ions 18 are incident as a beam having a beam diameter of about 0.1 μm. As described above, primary ion 1
Numeral 8 is incident on the surface 12a of the insulating film 12 from an oblique direction, that is, obliquely from above. Therefore, the primary ions 18
Is incident not only on the surface 12a of the insulating film 12, but also on the inner surface of the contact hole 14 near the surface 12a. Therefore, a part of the surface of the deposition film 16 is irradiated with the primary ions 18.

Here, the diameter of the contact hole 14 is Φ
And At this time, the deepest incident position of the primary ion 18 is a position lowered from the surface 12a of the insulating film 12 by a distance of △ = Φ × tan θ in the depth direction. Therefore, this △
The primary ions 18 are incident on the side wall surface in the range over the distance of. Since the surface 12a of the insulating film 12 is sputtered by the primary ions 18 and is shaved as the secondary ions 20, the height of the surface 12a gradually decreases with time. As the height of the surface 12a decreases, the irradiation area of the primary ions 18 moves downward along the depth direction of the contact hole 14 (the direction indicated by the arrow a in FIG. 1). Accordingly, the surface of the deposited film 16 formed on the inner surface of the contact hole 14 can be scanned by the primary ions 18 in the depth direction of the hole.

FIG. 2 is a diagram showing a state of composition analysis by SIMS. (A), (B) and (C) of FIG.
FIG. 2 is a sectional view of a cut surface of the sample structure corresponding to the position shown in FIG. 1. Over time, the structure of the sample
As shown in (A), (B) and (C), they are sequentially deformed. That is, by irradiating the primary ions 18, the height of the surface 12a of the insulating film 12 gradually decreases. Therefore, the irradiation position of the deposition film 16 by the primary ions 18 gradually decreases, and the secondary ions 20 can be generated along the inner surface of the contact hole 14.

At the initial point in time when the irradiation of the primary ions 18 is started, the deposition film 1 in the range of the above-mentioned distance △
Six areas are illuminated at one time. So, at this point,
The average composition of the region over the distance of Δ is detected, and is not detected as a distribution in the depth direction. However, at a position deeper than the distance of △, a composition distribution (profile) in the depth direction is detected at a high resolution matching the resolution of the SIMS.

Further, for example, the diameter Φ of the contact hole 14 is set to 0.06 μm, and the incident angle θ of the primary ion 18 is set.
Is 7 °, △ = Φ × tan θ, △
Is about 7 nm. Since the depth of the contact hole 14 to be analyzed is, for example, about 50 μm, such a value of △ can be ignored.

As described above, the smaller the distance △, the higher the accuracy of the analysis. Since the distance △ is expressed by Φ × tan θ, the smaller the incident angle θ, the smaller the value of 小 さ い. Therefore, as described above, the smaller the incident angle θ is, the higher the detection accuracy is, and a more true composition distribution can be obtained.

FIG. 3 is a graph showing profiles of C and F obtained by SIMS. FIG. 3A schematically shows a detection result of the composition distribution of the deposited film 16 obtained by the analysis method described with reference to FIGS. The horizontal axis of the graph in the figure indicates the initial surface 1 of the insulating film 12.
The depth (in μm) for 2a is shown. The vertical axis of the graph in FIG.
The numbers of ions or F ions are shown. The depth with respect to the surface 12a is obtained from the sputtering rate, and is detected as an amount proportional to the irradiation time of the primary ions 18.

FIG. 3B is a diagram showing the depth distribution of the composition of the reference insulating film. The reference insulating film is formed of the same material as the insulating film 12 described above. However, no contact hole is formed. The depth distribution of the composition of the reference insulating film is obtained by the analysis method described with reference to FIGS. By comparing the depth distribution of the composition of the reference insulating film with the composition distribution obtained for the insulating film 12, the contact hole 14 is formed in the insulating film 12.
Is formed.

As described above, when irradiation with the primary ions 18 is performed, atoms and ions such as C, F, Cl, and H, which are components of the vapor deposition film 16, together with the components Si and O of the insulating film 12. Occurs. The generated ions (secondary ions 20) are accelerated by an electric field and are bent in a direction corresponding to the mass by a magnetic field. Then, the ion intensity is detected for each mass by a detection device installed at a predetermined position. Therefore, the composition of the deposited film 16 can be determined. Further, the position where the primary ions 18 are incident on the deposition film 16 gradually moves downward (deep side) along the depth direction of the contact hole 14. Therefore, the depth distribution of the composition of the deposited film 16 is examined. For example, a curve a shown in FIG.
Represents the composition distribution of C, which is a component of the deposited film 16. A curve b shown in FIG. 3A represents a composition distribution of F, which is a component of the deposited film 16. FIG. 3 (A)
As shown in the figure, the secondary ion intensities of C and F are not constant with respect to the depth.

On the other hand, a curve a shown in FIG. 3B represents a composition distribution of C. Also, a curve b shown in FIG.
Represents the composition distribution of F. As described above, in the case of the reference insulating film in which the contact hole is not formed, the secondary ion intensities of C and F, which are the components of the deposited film 16, are substantially constant with respect to the depth. These secondary ion intensities respectively correspond to the background of the corresponding composition distribution shown in FIG. Therefore, by comparing the composition distribution shown in FIG. 3A with the composition distribution shown in FIG. 3B, it can be confirmed that the contact hole 14 is formed in the insulating film 12. Then, it is confirmed that the composition distribution shown in FIG. 3A is the depth distribution of the constituent elements of the deposited film 16 formed on the inner surface of the contact hole 14.

As described above, when the SIMS is used, the deposition film 1 formed on the inner surface of the contact hole 14 is formed.
The composition distribution over the depth direction of No. 6 can be analyzed. In the SIMS, since the secondary ions 20 are generated by performing the sputtering using the primary ions 18, there is a concern that the contact holes 14 may be crushed and a desired result may not be obtained. However, according to the experiments by the inventors, the contact hole 14 is not crushed,
It has been confirmed that the surface 12a of the insulating film 12 is gradually removed.

As described above, according to SIMS, the composition distribution of the deposited film formed in the contact hole having a relatively small size can be detected with high accuracy. For example,
With respect to a contact hole having a diameter of about 0.05 μm to 0.5 μm, the composition distribution of a deposited film can be analyzed. Conventionally, it has not been possible to analyze the composition distribution of a deposited film for a contact hole having such a size. According to the present invention, by using SIMS, the composition distribution of a deposited film can be analyzed for a contact hole having a relatively small size as described above.
Therefore, the etching process can be optimized, and a contact hole having a smaller size can be formed.

[Second Embodiment] Next, a second embodiment will be described with reference to FIG. FIG. 4 is a diagram showing a sample structure for detecting a composition distribution. FIG. 4A is a perspective view of a main part of the sample structure including the inspection area 22 cut out. The hatching of the cross section is omitted. FIG. 4B is a main part plan view showing the surface 12a side of the insulating film 12 constituting the sample structure. In FIG. 4, the deposited film is omitted. In addition, description of points overlapping with the first embodiment may be omitted.

In the second embodiment, an inspection area 22 is defined on the surface 12a of the insulating film 12, and the inspection area 2
A plurality of contact holes 14 are formed in 2.
Then, the inspection area 22 is scanned with the primary ions 18.

The sample structure shown in FIG.
An insulating film 12 such as BPSG is formed on the upper surface of the substrate. The inspection area 2 is formed on the surface 12a of the insulating film 12.
2 is defined. Inspection area 22 shown in FIG.
Is, for example, a rectangular area having a side of about 100 μm. In the inspection area 22, for example, 1000 or more contact holes 14 having the same diameter are formed.

As shown in FIG. 4A, primary ions 18
Is made into a beam and is incident on a partial region in the inspection area 22. The irradiation area of the primary ions 18 is the inspection area 22
Within a certain rule. Therefore, the region of the surface 12 a of the insulating film 12 included in the inspection area 22 is scanned by the primary ions 18. This scanning is preferably performed based on, for example, a raster method.

As described above, a large number of contact holes 14
In the sample structure provided with the primary ions 1
8 for irradiation. However, as described above, if the scanning is performed based on a certain rule, the composition distribution of the deposited film can be detected in the depth direction of the contact hole 14 as described in the first embodiment. Can be.

According to the above-described method, it is substantially equivalent to performing simultaneous analysis on a large number of contact holes 14. Therefore, since the amount of the deposited film to be analyzed increases, the intensity of the detected secondary ions 20 also becomes relatively large. Therefore, the composition distribution is detected with higher sensitivity. For this reason, it can be expected that various phenomena in the etching process will be clarified with higher accuracy.

[Third Embodiment] Next, a third embodiment will be described with reference to FIG. FIG. 5 is a plan view showing a sample structure having a plurality of inspection areas.

In the third embodiment, at least two inspection areas are defined on the surface 12a of the insulating film 12.
The surface 12a shown in FIG. 5 has four inspection areas 22a,
22b, 22c and 22d are defined. A plurality of contact holes 14a, 14b, 14c and 14d are provided in each of these inspection areas 22a to 22d.
Are formed respectively. Furthermore, these inspection areas 2
Contact holes 14a to 14d every 2a to 22d
The caliber is different.

In the case of this sample structure, the inspection area 22
Each of a to 22d is a region having the same square shape and the same area. Each inspection area 22a to 22d
Is a square region having an area of, for example, 100 μm × 100 μm. In each of the inspection areas 22a to 22d, for example, 100
Zero or more contact holes are formed.

As described above, the inspection areas 22a, 22a
b, 22c and 22d have a plurality of contact holes 14a, 14b, 14c and 14d, respectively.
Are formed. Contact holes 14a, 14b,
The apertures of 14c and 14d are designed to increase in this order. Therefore, a sample having contact holes of different diameters is formed by one sample preparation.

When the sample structure is analyzed, the second
As described in the embodiment, each of the inspection areas 22a to 22a
Scanning by primary ions is performed every 22d. By doing so, the composition distribution of the deposited film formed on the inner surface of each of the contact holes 14a to 14d can be obtained. Therefore, the dependence of the etching conditions on the diameter of the contact hole can be examined. Moreover, as described in the second embodiment, since a large number of contact holes are analyzed simultaneously, high-sensitivity detection is possible.

[Fourth Embodiment] Next, a fourth embodiment will be described. The sample structure of this embodiment includes:
As the insulating film, a film containing an element that does not hinder the detection of the composition distribution is used. For example, when it is desired to detect the composition components of C and F, a contact hole is formed in an insulating film not containing these C and F.

FIG. 6 is a view showing a sample structure on which an insulating film 12b containing no B, F, C and H is formed. FIG.
FIG. 3 is a cross-sectional view of a cutout at a position including a contact hole 14. The insulating film 12b is formed on the upper surface of the silicon substrate 10. A contact hole 14 is formed in the insulating film 12b. As described in the first embodiment,
The primary ions 18 are incident on the surface 12a of the insulating film 12b from the same oblique direction (incident angle θ). Then, by performing mass analysis of the generated secondary ions 20, the deposited film 1 formed on the inner surface of the contact hole 14 is formed.
The composition distribution of No. 6 is analyzed.

As described above, when the primary ions 18 are incident on the surface 12a of the insulating film 12b and the surface of the deposited film 16,
These films are sputtered to generate secondary ions 20. Therefore, if the insulating film 12b contains C, F, Cl, or H which is a constituent element of the deposited film 16, the insulating film 12b
Is added as a background to the profile of the deposited film. Therefore, a true composition distribution of the deposited film 16 cannot be obtained. On the other hand, in this embodiment, since the contact hole 14 is formed in the insulating film 12b, for example,
And the composition distribution of F can be accurately measured.

When B and H are contained as impurities in the insulating film, ¹¹ B ¹ H ⁺ ions are generated. The ¹¹ B
^{Since 1} H ⁺ ions have the same mass as C ⁺ ions, mass spectrometry cannot distinguish them. However, the background does not increase because the above-described insulating film 12b does not contain B and H.

In this embodiment, B, F,
As the insulating film 12b not containing C and H, for example, an NSG film (silicate glass containing no impurities) or a SiO ₂ film formed by CVD is used.

FIG. 7 is a graph showing profiles of C and F obtained when the contact hole 14 is formed in the insulating film 12b containing no B, F, C and H. FIG.
The depth of the contact hole 14 (in μm) is shown on the horizontal axis of the graph shown in FIG. The vertical axis of the graph shown in FIG. 7 shows the intensity of the detected secondary ions. The curve a in the graph indicates the profile of C, and the curve b indicates the profile of F. In order to show what effect can be obtained by the difference of the insulating film, the profile and the shape shown in FIG. 3 are made the same. The position of the arrow c shown in FIG. 7 represents the height of the background. It can be seen that the background is lower than the profile shown in FIG.

As described above, according to this embodiment, since the contact holes 14 are formed in the insulating film 12b containing no B, F, C, and H, the influence of these impurities is eliminated. . Therefore, it can be expected that the composition distribution is measured with higher sensitivity.

[Fifth Embodiment] Next, a fifth embodiment will be described. In this embodiment, the insulating film 12
In b, at least one marker layer for use in calibrating the depth in the composition distribution is formed. FIG. 8 is a diagram showing a configuration of a sample structure on which a marker layer is formed. FIG. 8 shows a cross section of a cut surface at a position including the contact hole 14.

The insulating film 12b shown in FIG. 8 is an insulating film not containing B and F. For example, as the insulating film 12b, N
SG is used. The insulating film 12b is formed on the upper surface of the silicon substrate 10. In this embodiment, the first insulating film 12c and the second insulating film 12d are laminated in this order to form the insulating film 12b. Then, three marker layers 24a, 24b and 24c are formed in the insulating film 12b.

The marker layer 24c is formed on the upper surface of the silicon substrate 10. The first insulating film 12c is formed on the upper surface of the marker layer 24c. Also, the marker layer 24b
Is formed on the upper surface of the first insulating film 12c. The second insulating film 12d is formed on the upper surface of the marker layer 24b. Further, a marker layer 24a is formed on the upper surface of the second insulating film 12d. An etching mask 26 is formed on the upper surface of the marker layer 24a. Etching mask 26
Is formed of, for example, polysilicon. Etching is performed using the etching mask 26 to form the contact holes 14. By this etching, a deposition film 16 to be analyzed is formed on the inner surface of the contact hole 14.

The above-mentioned marker layers 24a to 24c are formed of impurity layers containing elements which do not hinder the detection of the composition distribution. When NSG is used as the insulating film 12b, the marker layers 24a to 24c are formed of, for example, P or As. Since these elements are not included in the deposited film 16, there is no problem in detecting C and F constituting the deposited film 16.

The marker layers 24a to 24c are formed by, for example, ordinary ion implantation. In this case, the energy for implantation is set relatively low so that ions are implanted into the surface portions of the silicon substrate 10, the first insulating film 12c, and the second insulating film 12d. Alternatively, the marker layers 24a to 24c may be formed by exposing the surfaces of the silicon substrate 10, the first insulating film 12c, and the second insulating film 12d to the atmosphere to intentionally contaminate them.

The composition of the sample structure described above is analyzed by SIMS. For this reason, the primary ions 18 are incident on the surface 12a of the insulating film 12b from the same oblique direction (incident angle θ). Then, mass analysis of the generated secondary ions 20 is performed.

FIG. 9 is a graph showing a profile when the marker layers 24a to 24c are formed. The horizontal axis of the graph in the figure represents the depth (in μm) with respect to the surface 12a, and the vertical axis of the graph represents the intensity of the detected secondary ions 20. Curves a and b shown in the graph schematically show profiles of C and F, ie, composition distributions, respectively. Further, a curve c shown in the graph shows a profile of an element, for example, P or As which constitutes the marker layers 24a to 24c.

Curve c shows three peaks d, e and f,
It has in this order over the depth direction. The peak d standing at the shallowest position represents the intensity of the secondary ion generated from the first marker layer 24a. Further, a peak e standing at the next deeper position represents the intensity of the secondary ion generated from the second marker layer 24b. The peak f standing at the deepest position indicates the intensity of the secondary ion generated from the third marker layer 24c.

As described above, the peaks d, e and f corresponding to the respective marker layers 24a to 24c are respectively detected at the predetermined depth positions. First insulating film 12c or second insulating film 12d
The depth position where the marker layers 24a to 24c are formed can be known from the film thickness of. Therefore, by detecting the depth positions where the peaks d, e, and f stand, calibration regarding the depth of the profile a of C and the profile b of F can be performed.

As described in the first embodiment, the depth position of the vapor deposition film 16 on which the primary ions 18 are incident and the position of the surface 12a of the insulating film 12b (12) are different from each other by a distance of △. There is. For this reason, it may be unclear which depth the detected secondary ion 20 corresponds to the portion of the deposited film 16. However, in this embodiment, at the same time as detecting secondary ions generated from the deposited film 16, the marker layer 24 is detected.
Since secondary ions generated from a to 24c are also detected, it is possible to accurately know the depth of the location where the secondary ions are generated. Therefore, when the sample structure described in this embodiment is used, the composition depth distribution of the deposited film 16 can be detected more accurately.

[Sixth Embodiment] Next, a sixth embodiment will be described. FIG. 10 is a diagram showing a configuration of a sample structure in which holes are buried. FIG. 10 shows a cross section of a cut surface at a position including the contact hole 14.

As shown in FIG. 10, in the sample structure used in this embodiment, the inside of the contact hole 14 is buried with a burying layer 28 of the same material as the insulating film 12. For example, when the insulating film 12 is formed of BPSG, the buried layer 28 is formed of BPSG having the same quality as the insulating film 12. The height of the upper surface of the embedded layer 28 is
2 and the height of the upper surface.

When the buried layer 28 is formed in this manner, 1
The next ion 18 does not enter the hole deeper than the surface 12a of the insulating film 12. For this reason, the difference in the distance 距離 described above does not occur. In other words, the secondary ions 2 are always generated from the vapor deposition film 16 located at the same height as the surface 12a of the insulating film 12.
0 occurs. Therefore, the composition distribution in the depth direction of the deposition film 16 can be accurately and easily obtained.

[Seventh Embodiment] Next, a seventh embodiment will be described. This embodiment shows that the quality of the opening of the contact hole can be determined using the analysis method described in each of the above embodiments. And
The fact that the yield can be improved by incorporating this inspection process into the semiconductor device manufacturing process will be described.

As described above, when a contact hole is formed in an insulating film, a deposition film is deposited on the side wall of the hole as the etching proceeds. The etching is stopped by the selectivity of the etching when the etching reaches the surface of the silicon substrate on which the insulating film is formed. That is, when the surface of the silicon substrate appears, the etching does not proceed any further. Therefore, a relatively thick deposited film is deposited on the bottom of the formed contact hole. By examining the presence or absence of the deposited film deposited on the bottom, the quality of the opening of the contact hole can be determined.

The presence or absence of the deposited film is determined by the above-mentioned S
This can be performed by a composition distribution detection method using IMS. That is, according to SIMS, the composition distribution of the deposited film can be detected in the depth direction of the contact hole. When the contact hole is open, a relatively large peak corresponding to the deposited film deposited on the bottom appears in the profile showing the composition distribution. On the other hand, when the contact hole is not opened, such a peak does not appear.

FIG. 11 is a graph showing a profile when the aperture is good. The sample structure used for this measurement is such that an SiO ₂ film as an insulating film is formed on the upper surface of a silicon substrate, and a contact hole is formed in the insulating film. In forming this contact hole, an etching mask formed of polysilicon is used. On the horizontal axis of the graph of FIG. 11, the depth with respect to the surface of the etching mask is shown in units of μm, and the range from 0 μm to 5 μm is graduated every 0.2 μm. Further, the vertical axis of the graph in FIG. 11 shows the count number of the detected secondary ions, and the range of 0 to 10 ⁴ is shown in logarithmic scale. The profile measurement results were obtained using a SIMS device (trade name: IMS-wf) manufactured by Cameca.

The curve a shown in the graph indicates the composition distribution of F. A region c having a depth of 0 μm to 0.3 μm corresponds to a region of polysilicon as an etching mask. A region d having a depth of 0.3 μm to 2.3 μm corresponds to a region of SiO ₂ as an insulating film. Also,
The region e deeper than 2.3 μm corresponds to the region of the silicon substrate. Then, the boundary position b between the region d and the region e
, A peak occurs in the curve a. This peak is due to the constituent elements of the deposited film deposited on the bottom of the contact hole. As described above, since the deposited film is thicker at the bottom of the contact hole than at other portions,
Appears as a peak in the profile.

FIG. 12 is a graph showing a profile in the case of a defective opening. The results shown in FIG.
This was obtained under the same measurement conditions as in Example 1. However, a sample whose contact hole was not completely opened and whose etching did not reach the surface of the silicon substrate was measured. The axes, scales, and symbols shown in the figure are the same as those in FIG.

As shown in FIG. 12, the F profile shown by the curve a does not have a peak as shown in FIG. If the contact hole is opened, the region d
A peak should occur at the boundary position b between and e. Therefore, as is clear from the comparison between FIGS. 11 and 12, the quality of the contact hole opening is determined by SIMS.
Can be determined by the composition distribution detection method according to the above.

Next, the point where the above-described inspection step is incorporated into the semiconductor device manufacturing process will be described. In a semiconductor device manufacturing process, a circuit is formed on a wafer. The sample structure described in each of the above embodiments is formed in the inspection area on the wafer. For example, a region corresponding to one chip of an actual device may be assigned as the inspection area. Then, it is assumed that a contact hole is formed on this wafer in a manufacturing process of a certain semiconductor device. Subsequent to the step of forming the contact hole, a step of inspecting the quality of the opening of the contact hole is performed.

In the inspection process of the quality of the opening of the contact hole, the contact hole formed in the above-described inspection area is to be inspected. As described in the second embodiment, when a plurality of contact holes are formed in the inspection area, the detection sensitivity can be improved.

The quality of the opening of the contact hole is determined by the composition distribution detecting method by SIMS described above. For this reason, the wafer in which the contact holes are formed is introduced into an analysis room of a wafer-type SIMS device. The wafer type is preferable because the sample stage and the analysis chamber have a size corresponding to the wafer.

Therefore, it is possible to perform in-line inspection for the quality of the contact hole opening. As a result, when the contact hole is not opened, the process can be returned to the step of forming the contact hole again. Also,
When the hole is opened, the next manufacturing process may be performed on the wafer. Further, not only the determination of the quality of the opening of the contact hole but also the analysis of the residue deposited in the contact hole can be performed at the same time. In this way, a manufacturing process that is quicker, more accurate, and less wasteful than the conventional offline method using SEM or TEM is realized.

[Eighth Embodiment] Next, an eighth embodiment will be described. In this embodiment, as in the seventh embodiment, the quality of an opening of a contact hole formed in a wafer by a semiconductor device manufacturing process is determined by SI
Inspection is performed by a composition distribution detection method using MS. But,
The inspection process is performed separately from the manufacturing process. That is, in this embodiment, this inspection step is not incorporated in the manufacturing process, but is set as an off-line method. Therefore, it is not necessary to place a SIMS device for performing an inspection in a clean room.

In this embodiment, the inspection is performed by cutting out the inspection area of the wafer. That is, a portion of the inspection area defined on the wafer is cut out, and the cutout portion is inspected for the quality of the opening described above. This eliminates the need for a wafer-type SIMS device.

Therefore, the off-line method has an advantage that the equipment can be simplified. Further, as described above, the residues deposited in the contact holes can be analyzed at the same time. As described above, the SIMS inspection method has an advantage that cannot be obtained by the conventional SEM or TEM method.

[0082]

According to the method of the present invention, secondary ions are generated by making primary ions incident on the surface of the insulating film in which the contact holes are formed. Then, the composition distribution of the deposited film formed on the inner surface of the contact hole is detected by performing mass analysis of the secondary ions. According to this method, the composition distribution of the deposited film over the depth direction of the contact hole can be obtained. Various phenomena in the etching process can be elucidated based on the obtained information. Further, it is possible to optimize etching conditions for forming a contact hole, for example, the composition of an etching gas and various settings of an etching apparatus.
Therefore, it is effective for forming a contact hole having a smaller diameter and a deeper hole.

[Brief description of the drawings]

FIG. 1 is a diagram provided for explanation of a composition distribution detection method.

FIG. 2 is a diagram showing a state of a composition analysis by SIMS.

FIG. 3 is a diagram showing C and F profiles obtained by SIMS.

FIG. 4 is a diagram showing a sample structure for detecting a composition distribution.

FIG. 5 is a diagram showing a sample structure including a plurality of inspection areas.

FIG. 6 is a diagram showing a sample structure in which an insulating film containing no B, F, C, and H is formed.

FIG. 7 is a diagram illustrating a profile when B, F, C, and H are not included.

FIG. 8 is a diagram showing a sample structure on which a marker layer is formed.

FIG. 9 is a diagram showing a profile when a marker layer is formed.

FIG. 10 is a diagram showing a sample structure in which holes are buried.

FIG. 11 is a diagram showing a profile when an opening is good.

FIG. 12 is a diagram showing a profile when an opening is defective.

[Explanation of symbols]

 10: Silicon substrate 12: Insulating film 12a: Surface 14: Contact hole 16: Evaporated film 18: Primary ion 20: Secondary ion 22: Inspection area 14a to 14d: Contact hole 22a to 22d: Inspection area 12b: B, F , C, and H-free insulating films 24a to 24c: marker layer 12c: first insulating film 12d: second insulating film 26: etching mask 28: buried layer

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Izumi Aikawa 1-7-12 Toranomon, Minato-ku, Tokyo Oki Electric Industry Co., Ltd. (72) Naokazu Ikegami 1-7-12 Toranomon, Minato-ku, Tokyo Oki Electric Industry Co., Ltd. (72) Inventor Norio Hirashi 1-7-12 Toranomon, Minato-ku, Tokyo Oki Electric Industry Co., Ltd. F-term (reference) 4M104 DD08 DD19 HH20 5F004 AA09 AA16 BA13 BB13 CA09 CB04 DA16 DB03 DB06 EA03 EB01 5F033 QQ09 QQ37 RR15 WW00

Claims (7)

[Claims] A step of forming an insulating film on a silicon substrate; and performing anisotropic etching with an etching gas containing carbon (C) and fluorine (F) to form a plurality of contact holes in the insulating film. Forming a contact hole in which a polymer film containing carbon and fluorine is formed on inner surfaces of the plurality of contact holes; and irradiating primary ions from obliquely above the insulating film. This is a step of generating secondary ions, wherein the primary ions are also applied to the polymer film above the contact hole, and the irradiation simultaneously causes secondary ions of the carbon and fluorine of the polymer film. A step of generating the secondary ions to be generated; and a step of performing mass analysis of the carbon and fluorine secondary ions by secondary ion mass spectrometry (SIMS). By continuously irradiating the primary ions, the insulating film is gradually shaved, whereby the polymer film formed from the upper part to the lower part of the contact hole is continuously irradiated with the primary ions. The mass distribution of the carbon and fluorine secondary ions of the polymer film generated by the irradiation is performed, and the distribution of the polymer film on the inner surface of the contact hole is analyzed. Analysis method for polymer film. 2. A reference insulating film, which is made of a material having the same quality as that of the insulating film and has no contact hole, is irradiated with primary ions from obliquely above the surface of the reference insulating film. The method according to claim 1, wherein ions are generated, and a reference distribution created by performing mass spectrometry of the secondary ions is compared with a distribution of the polymer film obtained by a contact hole to be measured. Analysis method. 3. The analysis method according to claim 1, wherein the primary ions are applied to the surface of the insulating film in a range of 7 ° to 70 °. 4. A plurality of contact holes having the same diameter as the contact holes are formed in the insulating film.
2. The contact hole according to claim 1, wherein said contact holes are arranged at predetermined intervals in a first region in said insulating film.
The analysis method according to any one of claims 1 to 3. 5. A plurality of second contact holes having a second diameter larger than the diameter of the contact hole are arranged at desired intervals in a second region adjacent to the first region. The analysis method according to claim 4, characterized in that: 6. The analysis method according to claim 1, wherein the insulating film is formed of a material that does not contain an element constituting the polymerized film. 7. The method according to claim 6, wherein the insulating film is formed of a material that does not contain the carbon (C), the fluorine (F), the boron (B), and the hydrogen (H). Analysis method.