JP2011038887A - Sample, sample preparing method, and sample preparing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a sample enabling the clearer observation or analysis, a sample preparing method, and a sample preparing device. <P>SOLUTION: The sample preparing method includes a rotation process for changing the direction of the sample 20 which keeps the first surface 10a directed upward and has a contact so that the first surface 10a may be directed laterally or downward and an irradiation process for irradiating the sample 20 with a converged ion beam from the short direction of the contact. In the irradiation process, the second surface 10b upward directed by the rotation process of the sample 20 is irradiated with the converged ion beam, and a membrane region 20a is formed at the sample 20 in the extending direction of the contact. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a sample for observation or analysis with various apparatuses, a method for producing the sample, and an apparatus for producing the sample. In particular, the present invention relates to a sample, a sample preparation method, and a sample preparation device for observing or analyzing a part of a semiconductor element using, for example, a transmission electron microscope or an energy dispersive X-ray spectrometer.

  A defective portion or a defect in the semiconductor element is observed using, for example, a transmission electron microscope (TEM). Therefore, a sample of a semiconductor element to be observed with a TEM can be manufactured using a focused ion beam (FIB).

  FIG. 7 is a schematic process diagram for explaining a sample manufacturing method according to the background art for manufacturing a TEM observation sample of a semiconductor element. FIG. 8 shows a schematic partial cross-sectional view of the semiconductor element or the sample in the state of FIG. 7 (a) or FIG. 7 (b). The semiconductor element 50 to be observed has a semiconductor substrate 54, an insulating layer 55 formed on the semiconductor substrate 54, and a contact 56 formed on the semiconductor substrate 54. The contact 56 extends toward the first surface 50a, which is the upper surface.

  A sample preparation method according to the background art will be described. First, the semiconductor element 50 is cut along the cutting line 52 (FIG. 7A), and the sample 60 is cut out so as to include the target region 51 (FIG. 7B). In FIG. 7, the target region 51 is illustrated with a check pattern on the surfaces of the semiconductor element 50 and the sample 60. Next, the sample 60 is cut along a dotted line 62 to thin the target region 51 (FIG. 7C) .Next, the sample 60 is placed on a holding mechanism (carrier) 72 such as a C-ring and the first element of the semiconductor element 50. Next, the target region 51 is thinned or thinned to about 0.1 μm to 0.2 μm by FIB so that the target region 51 can be observed by TEM. (FIG. 7E) In the background art, the cross-sectional structure of the target region 51 is observed by TEM using the sample 60 manufactured in this way.

  Patent Document 1 discloses a sample preparation method for TEM observation. The sample preparation method described in Patent Document 1 is observed by scraping a region excluding a predetermined region including an observation target portion in a thickness direction in a portion on one side in a thickness direction of a semiconductor substrate in a thickness direction. A first step of forming a convex portion including the target portion on one side in the thickness direction of the semiconductor substrate, and transmitting the portion of the convex portion including the observation target portion by etching the semiconductor substrate in the thickness direction A second step of thinning the film to an extent that can be observed with an electron microscope.

JP 2002-39926 A

  The following analysis is given from the perspective of the present invention.

  In the process shown in FIG. 7, the sample 60 is etched by FIB from the upper surface 50 a side of the semiconductor element 50 in the same manner as the sample manufacturing method described in Patent Document 1. That is, the etching by FIB is performed along the extending direction (arrow direction) of the contact 56 from the contact 56 side. FIG. 9 shows a TEM photograph of a sample manufactured by the sample manufacturing method according to the background art. The arrows shown in FIG. 9 indicate the FIB processing direction. When the contact 56 is made of a metal harder than the insulating layer 55 such as tungsten (W), the etching rate is slow at the portion where the contact 56 exists, and therefore, the cutting 57 occurs in the semiconductor substrate 54 below the contact 56. . Here, “curing” (also referred to as a processing line) means that a portion below the contact 57 remains thick without being sufficiently etched. In FIG. 9, the streak-like black region present in the semiconductor substrate 54 is the cartoning 57, indicating that the region is thicker than the other regions. That is, FIG. 9 shows that the thickness of the semiconductor substrate 54 in the target region 51 varies. When the curtaining 57 occurs, the TEM image becomes black, which causes a problem that it is difficult to observe the target region 51. Further, in energy-dispersive X-ray spectroscopy (EDS), the concentration depends on the thickness of the target region 51. Therefore, when the concentration profile is measured, it becomes thicker by the curtaining 57. The area appears darker than it actually is.

  Further, when the semiconductor element has an MIM (Metal-Insulator-Metal) structure, even if FIB etching is performed from the metal in the direction of the insulating film, the observation image of the insulating film is blurred. FIG. 10 shows a schematic partial cross-sectional view of the MIM structure. FIG. 11 shows a TEM photograph of a MIM structure in which a sample manufactured by the sample manufacturing method according to the background art is subjected to FIB etching from a metal toward an insulating film. The MIM structure shown in FIG. 10 includes a contact 56 as a lower electrode made of, for example, tungsten, a capacitor insulating film 59 formed on the contact 56, and a metal film 58 as an upper electrode formed on the capacitor insulating film 59. Have. At this time, if FIB etching is performed from the metal film 58 in the direction of the capacitive insulating film 59 (in the direction of the arrow), the etching rate of the metal film 58 is slow, so that the capacitive insulating film 59 is observed by TEM as shown in FIG. Will not be able to.

  Further, in the target region thinned by FIB etching, the thickness of the target region increases from the beam upstream side to the downstream side. That is, in the form shown in FIGS. 7 and 8, the target region 51 is tapered so as to become thicker from the upper surface 50 a of the semiconductor element 50 toward the semiconductor substrate 54. For this reason, even if an attempt is made to compare concentration profiles at different points from the insulating layer 55 toward the semiconductor substrate 54 (in the direction in which the contacts 56 extend) by EDS, the thicknesses are different, so that accurate comparison cannot be performed.

  According to a first aspect of the present invention, there is provided a sample preparation method including an irradiation step of irradiating a sample having a contact with a focused ion beam from a short direction of the contact.

  According to the second aspect of the present invention, a cutting mechanism for cutting an object or a sample, a rotating mechanism for rotating a sample cut from the object by a cutting mechanism in a predetermined direction, and a rotating mechanism for rotating the sample. And a holding mechanism for holding the sample.

  According to the second aspect of the present invention, the first cutting step of cutting the semiconductor element and cutting the sample, the sample with the first surface facing upward, the sample with the first surface facing sideways or downward. A rotating step of changing the orientation of the sample, a bonding step of bonding the dummy substrate to the sample, a second cutting step of cutting the sample so as to thin at least a part of the sample, and separating the sample from the dummy substrate; There is provided a sample preparation apparatus that automatically performs a process including an attaching process for attaching to a holding mechanism.

  According to a third aspect of the present invention, there is provided a sample including an insulating layer, a contact penetrating the insulating layer, and a thin film region that is at least partially thinned and includes the insulating layer and the contact. The contact extends along the thin film region and faces sideways when the thin film region is on the upper side.

  The present invention has at least one of the following effects.

  According to the present invention, the etching rate can be made constant by etching from the short direction of the contact (for example, the direction perpendicular to the extending direction). Thereby, generation | occurrence | production of curtaining can be suppressed. In addition, a sample capable of more clearly observing or analyzing the structure under or between metals can be obtained. Further, the concentration profiles in the contact extending direction can be compared more accurately.

The schematic process drawing for demonstrating one Embodiment of the sample preparation method of this invention. FIG. 2 is a schematic partial cross-sectional view of a semiconductor element or a sample in the state of FIG. FIG. 2 is a schematic partial cross-sectional view of a sample in the state of FIG. Schematic partial cross-sectional view of the MIM structure in the semiconductor element or sample in the state of FIG. 1A or FIG. FIG. 2 is a schematic cross-sectional view of an MIM structure when performing FIB processing in the state of FIG. 1F or FIG. The TEM photograph of the sample created by the sample preparation method of this invention. The schematic process drawing for demonstrating the sample preparation method based on the background art which produces the sample for TEM observation of a semiconductor element. FIG. 8 is a schematic partial cross-sectional view of a semiconductor element or a sample in the state of FIG. 7A or FIG. The TEM photograph of the sample produced by the sample preparation method concerning background art. FIG. 3 is a schematic partial cross-sectional view of an MIM structure. 4 is a TEM photograph of a MIM structure in which a sample manufactured by a sample manufacturing method according to the background art is FIB etched from a metal in an insulating film direction.

  The preferable form of each said viewpoint is described below.

  According to a preferred embodiment of the first aspect, the sample preparation method is such that, prior to the irradiation step, the sample is oriented so that the first surface faces upward, and the first surface faces sideward or downward. It further includes a rotating step of changing. In the irradiation step, the focused ion beam is irradiated to the second surface facing the upper surface by the rotation step, and a thin film region is formed on the sample along the contact extending direction.

  According to a preferred embodiment of the first aspect, the sample preparation method cuts a semiconductor element having an insulating layer and a contact penetrating the insulating layer and extending in the first surface direction before the rotating step. And a first cutting step of cutting the sample. The sample preparation method includes a bonding step of bonding a dummy substrate to a sample after the rotation step and before the irradiation step, cutting the sample so as to thin at least a portion where a thin film region is formed, It further includes a second cutting step of separating from the substrate and an attaching step of attaching the sample to the holding mechanism.

  According to a preferred form of the first aspect, the semiconductor element further includes a substrate formed on the opposite side of the first surface with respect to the insulating layer.

  According to a preferred embodiment of the first aspect, the semiconductor element further includes: an insulating film formed on the first surface side with respect to the contact; and a metal film formed on the first surface side with respect to the insulating film. Have.

  According to a preferred embodiment of the second aspect, the sample preparation device further includes a bonding mechanism that bonds the dummy substrate to the sample on the sample rotated by the rotation mechanism. The cutting mechanism cuts the sample so that at least a part of the sample bonded to the dummy substrate is thinned.

  According to the preferable form of the second viewpoint, the rotation mechanism rotates the sample so that the upper surface of the sample faces sideward or downward.

  According to the preferable form of the second aspect, the sample preparation device automatically performs the process from cutting the object to be observed until the sample is held by the holding mechanism based on a predetermined condition.

  According to a preferred form of the third aspect, the thin film region further includes a substrate formed on one side of the contact extending direction adjacent to the insulating layer.

  According to a preferred embodiment of the third aspect, the thin film region includes an insulating film formed in contact with the contact, a metal film formed in contact with the insulating film on a side opposite to the contact with respect to the insulating film, Further included. The contacts, the insulating film, and the metal film are arranged sideways.

  According to a preferred embodiment of the third aspect, the thin film region is formed by irradiating the focused ion beam from the short direction of the contact.

  One mode of the sample preparation method of the present invention will be described. FIG. 1 shows a schematic process diagram for explaining one embodiment of the sample preparation method of the present invention. In the form shown in FIG. 1, the observed object 10 is a semiconductor element. FIG. 2 shows a schematic partial cross-sectional view of the semiconductor element or sample in the state of FIG. 1 (a) or FIG. 1 (b). The semiconductor element 10 includes a semiconductor substrate 14, an insulating layer 15 formed on the semiconductor substrate 14, and a contact 16 formed on the semiconductor substrate 14 and penetrating the insulating layer 15. The contact 16 extends from the semiconductor substrate 14 toward the first surface 10a that is the upper surface.

  First, the semiconductor element 10 is cut by a cutting mechanism (for example, a dicer) along the cutting line 12 (FIG. 1A), and the sample 20 is cut out to include the target region 11 (FIG. 1B; first cutting step). . In FIG. 1, the target region 11 is illustrated with a check pattern on the surfaces of the semiconductor element 10 and the sample 20. At this time, the first surface 10a of the sample 20 faces upward (upper surface). Further, the position of the target region 11 in the sample 20 is close to the second surface 10b, which is one of the cut surfaces facing in the side surface direction of the sample 20, so that the observation location can be TEM-observed by subsequent FIB processing. To be.

  Next, the sample 20 is rotated so that at least the first surface 10a does not become the upper surface, and preferably at least the second surface 10b becomes the upper surface (FIG. 1 (c); rotation process). Thereby, the target region 11 is disposed on the upper side of the sample 20. Moreover, the 1st surface 10a turns sideways (side surface). In FIG. 1B to FIG. 1C, the sample 20 is rotated by 90 °. For example, the sample 20 is, for example, 90 ° from the state of FIG. 1B with the first surface 10a facing upward. The orientation may be rotated by 270 °. In this case, in the subsequent irradiation step, the etching rate is not affected by the contact, and the occurrence of the curtaining can be suppressed.

  Next, in order to cut the sample 20, the sample 20 is bonded to the side surface of the dummy substrate 31 (FIG. 1 (d); bonding step). In the embodiment shown in FIG. 1D, the dummy substrate 31 is attached to the surface opposite to the first surface 10a, that is, the surface on the semiconductor substrate 14 side. As the dummy substrate 31, for example, the same material (for example, Si) as that of the semiconductor substrate 14 can be used.

  Next, the sample 20 is thinned by a cutting mechanism (for example, a dicer) along the cutting line 22 indicated by a dotted line, for example, so that the thin film processing for TEM observation can be performed on the target region 11 by FIB processing. For example, the sample 20 is cut by the cutting mechanism so that the portion including the target region 11 has a thickness of, for example, 20 μm to 30 μm with respect to the electron transmission direction of the TEM. Next, the sample 20 is cut out from the dummy substrate 31 (FIG. 1E; second cutting step). Next, the sample 20 is attached to a holding mechanism (carrier) 32 such as a C-ring (FIG. 1 (f); attachment process). At this time, the second surface 10b faces upward, and the electron transmission direction of the TEM and the extending direction of the first surface 10a are the same direction (parallel). The contact 16 extends laterally with respect to the carrier 32. Further, the sample 20 is arranged at a position where the target region 11 can be subjected to the FIB processing.

  FIG. 3 shows a schematic partial cross-sectional view of the sample 20 in the state of FIG. Next, FIB treatment is performed from the second surface 10b (from the arrow direction shown in FIG. 3) so that the target region 11 can be observed by TEM, and a thin film region 20a having a thickness of, for example, 0.1 μm to 0.2 μm is formed in the target region 11. It forms (FIG. 1 (g); irradiation process). At this time, the FIB process is performed from the side surface direction of the semiconductor element 10 shown in FIG. That is, the FIB is irradiated from the short direction of the contact 16. In the present invention, the dimensions can be measured by, for example, a TEM or a scanning electron microscope (SEM) if the dimensions are in units, and measured by using an ellipsometer if the units are in nm or μm. can do.

  As a result, the thin film region 20 a of the sample 20 includes the thinned semiconductor substrate 14, the insulating layer 15, and the contact 16, and is formed along the contact 16. The contact 16 extends so as to face sideways when the thin film region 20a is turned upward.

  In the sample manufacturing method of the present invention, the FIB treatment is performed from the side surface direction of the semiconductor element 10. Thereby, the etching rate in the insulating layer 15 and the contact 16 can be made constant. Further, it is possible to prevent the occurrence of curtaining in the semiconductor substrate 14 in the thin film region 20a.

  Moreover, according to the sample preparation method of the present invention, the thickness of the thin film region 20a along the extending direction of the contact 16 can be made constant. Thereby, for example, concentration profile comparisons at several different points along the extending direction of the contact 16 in the thin film region 20a can be more accurately performed.

  The semiconductor element 10 may have an MIM structure. FIG. 4 shows a schematic partial cross-sectional view of the MIM structure in the semiconductor element 10 or the sample 20 in the state of FIG. 1A or FIG. For example, in the direction shown in FIG. 1A, the semiconductor element 10 includes a contact 16 as a lower electrode, a metal film 18 as an upper electrode above the contact 16, and a contact 16 and a metal film, as shown in FIG. 18 may be included. FIG. 5 shows a schematic cross-sectional view of the MIM structure when performing the FIB processing in the state of FIG. 1 (f) or FIG. 1 (g). In this case, in the state shown in FIG. 1 (f) or FIG. 1 (g), as shown in FIG. 5, in the MIM structure, the contact 16, the insulating film 19 and the metal film 18 are lateral (first surface 10a). ) In order. Therefore, since the FIB process is performed from the direction of the arrow shown in FIG. 5, the insulating film 19 is etched without being affected by the etching rate of the metal film 18. As a result, the insulating film 19 can be observed or analyzed more clearly.

  Next, an embodiment of the sample preparation apparatus of the present invention will be described. The sample preparation apparatus includes a cutting mechanism (for example, a dicer) that cuts the semiconductor element 10 or the sample 20 that is an object to be observed in the steps shown in FIGS. 1 (a) and 1 (d), and FIG. 1 (b). In the process, a rotation mechanism that rotates the sample 20 in a predetermined direction by a predetermined amount (for example, 90 ° to 270 °), a bonding mechanism that bonds the dummy substrate 31 to the sample 20 in the process shown in FIG. 1 (f) and FIG. 1 (g), a holding mechanism (carrier) 32 that holds the sample 20 is provided. It is preferable that the sample preparation apparatus can automatically perform the steps shown in FIGS. 1A to 1F based on predetermined conditions.

  As the rotation mechanism, for example, a mechanism that sandwiches the sample 20 and rotates the sample 20 in a predetermined direction by a predetermined angle can be applied.

  By each of the above mechanisms, the sample preparation device automatically performs a process including a first cutting process, a rotating process, a joining process, a second cutting process, and an attaching process.

  The sample obtained by the sample preparation method of the present invention does not have a semiconductor substrate. The insulating film in the MIM structure is etched without being affected by the slow metal etching rate. Thereby, according to the sample of the present invention, clearer observation or analysis can be performed.

  In the present invention, the contact may be a metal wiring penetrating the insulating layer, and includes, for example, what are called vias and through holes. In addition, the material of the contact in the present invention is not particularly limited, but the present invention is useful when the contact is a material harder than the insulating layer, and particularly when a harder metal such as tungsten is used. Useful.

  FIG. 6 shows a TEM photograph of a sample prepared by the sample preparation method of the present invention. The sample 20 includes the semiconductor substrate 14, the insulating layer 15, and the contacts 16 as in the above embodiment. The arrows shown in FIG. 6 indicate the direction of FIB processing. According to the sample manufacturing method according to the background art, as shown in FIG. 9, the semiconductor substrate 54 is cartened. However, according to the sample manufacturing method of the present invention, as shown in FIG. No curtaining was confirmed in 14. Thereby, according to this invention, it becomes possible to observe or analyze a sample more clearly.

  The sample, the sample preparation method, and the sample preparation apparatus of the present invention have been described based on the above embodiment, but are not limited to the above embodiment, and are within the scope of the present invention and the basic technology of the present invention. It goes without saying that various modifications, changes and improvements can be included in the above embodiment based on the idea. Further, various combinations, substitutions, or selections of various disclosed elements are possible within the scope of the claims of the present invention.

  Further problems, objects, and developments of the present invention will become apparent from the entire disclosure of the present invention including the claims.

10 Object to be observed (semiconductor element)
10a First surface 10b Second surface 11 Target region 12 Cutting line 14 Semiconductor substrate 15 Insulating layer 16 Contact 18 Metal film 19 Insulating film 20 Sample 20a Thin film region 22 Cutting line 31 Dummy substrate 32 Holding mechanism 50 Object to be observed (semiconductor element)
50a First surface 50b Second surface 51 Target region 52 Cutting line 54 Semiconductor substrate 55 Insulating layer 56 Contact 57 Curing 58 Metal film 59 Capacitor insulating film 60 Sample 62 Cutting line 72 Holding mechanism

Claims (14)

  A sample preparation method comprising an irradiation step of irradiating a sample having a contact with a focused ion beam from a short direction of the contact. Before the irradiation step,
A rotating step of changing the orientation of the sample such that the first surface faces upward, the first surface facing sideways or downward;
In the irradiation step, the focused ion beam is irradiated to the second surface facing the upper surface in the rotation step, and a thin film region is formed in the sample along the extending direction of the contact. The sample preparation method according to claim 1. Before the rotation process,
A first cutting step of cutting a semiconductor element having an insulating layer and the contact penetrating the insulating layer and extending in the first surface direction, and cutting out the sample;
After the rotation step and before the irradiation step,
A bonding step of bonding a dummy substrate to the sample;
Cutting the sample so as to thin at least the portion forming the thin film region, and cutting the sample from the dummy substrate;
The sample preparation method according to claim 2, further comprising an attaching step of attaching the sample to a holding mechanism.   The sample manufacturing method according to claim 3, wherein the semiconductor element further includes a substrate formed on a side opposite to the first surface with respect to the insulating layer.   The semiconductor element further includes an insulating film formed on the first surface side with respect to the contact, and a metal film formed on the first surface side with respect to the insulating film. The sample preparation method according to claim 3 or 4. A cutting mechanism for cutting an object or sample;
A rotation mechanism that rotates a sample cut out from the object to be observed by a predetermined amount in a predetermined direction by the cutting mechanism;
And a holding mechanism for holding the sample rotated by the rotating mechanism. A bonding mechanism for bonding a dummy substrate to the sample, the sample rotated by the rotation mechanism; and
The sample preparation apparatus according to claim 6, wherein the cutting mechanism cuts the sample so as to thin at least a part of the sample bonded to the dummy substrate.   The sample preparation apparatus according to claim 6 or 7, wherein the rotation mechanism rotates the sample so that an upper surface of the sample faces sideward or downward.   The sample preparation according to any one of claims 6 to 8, wherein from the cutting of the object to be observed until the sample is held by the holding mechanism is automatically performed based on a predetermined condition. apparatus. A first cutting step of cutting a semiconductor element and cutting a sample;
Rotating the sample with the first surface facing upward, and changing the orientation of the sample so that the first surface faces sideways or downward;
A bonding step of bonding a dummy substrate to the sample;
Cutting the sample so as to thin at least a part of the sample, and cutting the sample from the dummy substrate;
An attaching step of attaching the sample to the holding mechanism;
A sample preparation apparatus that automatically performs a process including: An insulating layer;
A contact penetrating the insulating layer;
A thin film region that is at least partially thinned and includes the insulating layer and the contact,
The sample according to claim 1, wherein the contact extends along the thin film region and faces sideways when the thin film region is turned upward.   The sample according to claim 11, wherein the thin film region further includes a substrate formed on one side in the extending direction of the contact adjacent to the insulating layer. The thin film region further includes an insulating film formed in contact with the contact, and a metal film formed in contact with the insulating film on a side opposite to the contact with respect to the insulating film,
The sample according to claim 11 or 12, wherein the contact, the insulating film, and the metal film are arranged in a lateral direction.   The sample according to any one of claims 11 to 13, wherein the thin film region is formed by irradiating a focused ion beam from a short direction of the contact.

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