JP2003229386A - Method for machining semiconductor device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for machining a semiconductor device in which a substantially flat cross-section can be attained at a position for observing the cross-section. <P>SOLUTION: In a semiconductor device formed on a semiconductor substrate, a wiring layer formed above a specified position for observing the cross-section is removed. Subsequently, a transparent resin 10 of such a thickness as the position for observing the cross-section is not subjected to rounding at the time of polishing the cross-section by chemical mechanical polishing is applied on the surface of the semiconductor device corresponding to the position for observing the cross-section and the resin is cured eventually. Consequently, the position for observing the cross-section is located outside the rounding region. Subsequently, the semiconductor device is polished from the side face to the position for observing the cross-section using a chemical mechanical polishing method. Structure at the position for observing the cross-section is then observed for the semiconductor device thus machined thus analyzing the failure thereof. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention polishes a cross section of a semiconductor device formed on a semiconductor substrate by using a chemical mechanical polishing method in order to observe a cross section structure at a predetermined cross section observation position. The present invention relates to a semiconductor device processing method.

[0002]

2. Description of the Related Art When conducting a failure analysis of a semiconductor device,
Observing the cross-sectional structure of a defective part is very important in terms of elucidating the defective mechanism.
Conventionally, there are the following two methods for obtaining a sample for observing a cross-sectional structure at a certain cross-section observation position. The first method is, for example, a method of irradiating a focused ion beam (FIB: Focused Ion Beam) onto a semiconductor device and etching a position corresponding to a cross-section observation position to obtain a cross-section at the cross-section observation position. is there.

The second method is chemical mechanical polishing (CMP).
This is a method of polishing a semiconductor device in cross section by using a chemical mechanical polishing method. Here, the CMP method is a chemical reaction (Chemic reaction) between the slurry solution and the material to be polished.
al) and the frictional reaction between the abrasive particles and the material to be polished (Mechanic
al) is a technique for polishing a material to be polished. Further, the cross-section polishing is to polish the semiconductor device with the surface of the semiconductor device standing upright with respect to the surface of the polishing plate while applying appropriate pressure and rotation conditions to the polishing plate. Further, a large number of holes are formed in the polishing plate. When the polishing plate is rotated, the polishing particles remain in the holes and rotate together with the polishing plate.

When applying the second method, it is necessary to remove the wiring layer of the semiconductor device existing above the cross-section observation position in advance. This is because the cross-section observation position is often obscured by the wiring layer and cannot be seen from the outside.
When the wiring layer is removed, only a few thousand Å passivation film remains on the surface where the cross section is observed. That is, the cross-section observation position is located very close to the surface from the silicon substrate.

[0005]

By the way, CMs are usually used.
When the P method is used for polishing, a phenomenon called rounding occurs. Rounding is a phenomenon in which the polishing rate at the edge of the polishing surface of the material to be polished becomes faster than the polishing rate at the center of the material, and the entire polishing surface cannot be ground flat, and the edges of the polishing surface are rounded. That is. This is believed to occur because during polishing, the abrasive particles move more actively at the edges of the polishing surface than at the edges. Such rounding also occurs in cross-section polishing. Therefore, when a sample for cross-section observation is produced by the above-mentioned second method, the cross-section observation position is located near the surface of the silicon substrate, so that it is affected by rounding. Therefore, at the cross-section observation position,
There is a problem that it is difficult to obtain a flat cross section due to the influence of rounding, and it is not possible to check the cross-sectional shape at the cross-section observation position in detail when performing failure analysis.

The present invention has been made in view of the above circumstances, and an object thereof is to provide a method of processing a semiconductor device capable of obtaining a substantially flat cross section at a cross section observation position.

[0007]

The invention according to claim 1 for achieving the above object is to observe a cross-sectional structure at a predetermined cross-sectional observation position for a semiconductor device formed on a semiconductor substrate. A method of processing a semiconductor device in which a cross-section of the semiconductor device is polished using a chemical mechanical polishing method, a step of removing a wiring layer formed above the cross-section observation position, and after removing the wiring layer, The surface of the semiconductor device corresponding to the cross-section observation position is made of a transparent resin having a thickness such that the cross-section observation position is not affected by the rounding that occurs when the cross-section is polished by the chemical mechanical polishing method. Cross-section polishing from the side surface to the cross-section observation position of the semiconductor device coated with the transparent resin by using the chemical mechanical polishing method. It is characterized in that it comprises that the step.

According to a second aspect of the present invention, in the method of processing a semiconductor device according to the first aspect, the transparent resin is cured after removing air bubbles remaining inside the transparent resin. It is a thing.

According to a third aspect of the present invention, in the method of processing a semiconductor device according to the first or second aspect, the transparent resin is a silicone resin.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram for explaining a semiconductor device processing method according to an embodiment of the present invention.

The semiconductor device processing method of this embodiment uses the CMP method in order to observe the cross-sectional structure of a semiconductor device formed on a silicon substrate (Si substrate) at a predetermined position (cross-section observation position). It is a method of polishing a cross section of a semiconductor device. Here, the CMP method is a technique for polishing the material to be polished by a chemical reaction between the slurry solution and the material to be polished (Chemical) and a frictional reaction between the abrasive particles and the material to be polished (Mechanical).
Further, the cross-section polishing means polishing the semiconductor device in a state where the surface of the semiconductor device stands upright with respect to the surface of the polishing plate.

Next, the method for processing the semiconductor device of this embodiment will be described in detail.

First, the cross-section observation position is specified in the semiconductor device. Usually, the cross-section observation position is often invisible from the surface of the semiconductor device because it is obstructed by the wiring layer arranged above it. Therefore, in such a case, the uppermost layer formed above the cross-section observation position to the wiring layer is removed. In order to remove the wiring layer and the like, for example, surface polishing treatment or corrosion treatment with a chemical solution is performed. As a result, the cross-section observation position becomes visible from the surface of the semiconductor device. In fact, this cross-section observation position can be easily confirmed with the naked eye or a microscope.

When the wiring layer and the like are removed, only a few thousand Å passivation film remains on the surface at the cross-section observation position. For example, in the case of a semiconductor device integrated on a silicon substrate, the thickness of the silicon substrate is 0.7 m.
If m, the cross-section observation position is at a position of 0.699 mm or more from the back surface of the silicon substrate. That is, FIG.
As shown in (a), the cross-section observation position is extremely close to the surface of the silicon substrate.

After that, a mark for indicating the cross-section observation position is provided near the cross-section observation position. When performing cross-section polishing, the semiconductor device is polished with this mark as a target.

Next, as shown in FIG. 1B, the transparent resin 10 is applied to the surface of the semiconductor device corresponding to the cross-section observation position. This coating operation is performed as follows, for example. First, a little resin 10 is attached to the surface of the semiconductor device corresponding to the cross-section observation position. next,
After the resin 10 is thinly spread on the surface of the semiconductor device by using a brush or the like, pressure gas (for example, nitrogen gas) is blown to the resin 10. Thereby, the resin 10 extends substantially uniformly. In this embodiment, a silicone resin is used as the resin 10. Further, the transparent resin 10 is used so that the above-mentioned marks and cross-section observation positions can be seen from the surface of the semiconductor device. The transparent resin 10
May be formed on the entire surface of the semiconductor device.

The thickness of the transparent resin 10 is set so that the observation position of the cross section is not affected by the rounding which occurs when the cross section is polished by the CMP method. In fact, by adjusting the polishing conditions, the occurrence of rounding can be considerably suppressed. In this situation,
For example, the transparent resin 10 may have a thickness of at least several microns to several tens of microns. By providing the transparent resin 10 having such a thickness, the cross-section observation position is located outside the region where the rounding occurs (rounding region). Specifically, in the semiconductor device of FIG. 1C, the outside of the area represented by the ellipse is the rounding area, and the cross-section observation position is located within the area of the ellipse.

By the way, when the resin 10 is applied, air may remain inside the resin 10 to form bubbles. In fact, the surface of the semiconductor device after the wiring layer is removed is not always flat and has an uneven state. Therefore, when the resin 10 is applied to the surface of such an uneven state, bubbles are generated at the foot of the convex portion. Cheap. In this way, when bubbles are left inside the resin 10 and the semiconductor device is cross-section polished by the CMP method, the abrasive particles enter the space due to the bubbles, and rounding occurs at the cross-section observation position. Therefore, such bubbles are removed (defoaming) before the applied resin 10 is cured.
However, it is necessary to adhere the resin 10 to the passivation film of the semiconductor device. As this defoaming method, for example, a method is used in which the semiconductor device coated with the resin 10 is put into a predetermined processing chamber and then the atmospheric pressure of the processing chamber is lowered. Thereby, the bubbles existing inside the resin 10 can be naturally discharged from the surface of the resin 10 to the outside. After that, the transparent resin 10 is cured. As described above, by performing the curing treatment after the defoaming treatment, the adhesion between the transparent resin 10 and the passivation film of the semiconductor device can be further enhanced.

As a matter of course, if no bubbles remain inside the resin 10, the defoaming process can be omitted.

After the transparent resin 10 is cured, the semiconductor device is subjected to cross-section polishing from its side surface to the cross-section observation position by the CMP method. When the cross-section is polished by the CMP method, as shown in FIG. 1C, the semiconductor device is placed above the polishing plate 30 with the surface of the semiconductor device standing upright with respect to the surface of the polishing plate 30. Will be placed. First, the slurry is applied to the surface of the polishing plate 30. Here, the slurry is, for example, a weak alkaline solution (slurry solution) containing a large number of colloidal silica (abrasive particles) having a diameter of about 0.1 μm. As the polishing plate 30, a cloth called buff or a multi-hole structure such as polyurethane foam is used. Therefore, when the polishing plate 30 is rotated, the polishing particles are rotated together with the polishing plate 30 while being kept in the holes formed on the surface of the polishing plate 30. Next, while rotating the polishing plate 30, the polishing plate 30 is brought into contact with the surface of the semiconductor device. As a result, the cross-section of the semiconductor device is polished by the frictional reaction between the abrasive particles and the material to be polished and the chemical reaction between the slurry solution and the material to be polished.

In the cross-section polishing by the CMP method, rounding occurs at the end of the polishing surface of the semiconductor device which is the material to be polished. However, in the present embodiment, the cross-sectional observation position is deviated from the rounding region by applying the transparent resin 10 having a predetermined thickness to the surface of the semiconductor device corresponding to the cross-sectional observation position. Therefore, when such cross-section polishing is performed up to the cross-section observation position, the cross-section observation position is not affected by rounding and a substantially flat cross section is obtained at the cross-section observation position, as shown in FIG. .

After that, the semiconductor device thus processed is subjected to defect analysis by observing the structure at the cross-section observation position.

In the method for processing a semiconductor device of this embodiment, the transparent resin having a thickness that does not affect the cross-section observation position when the cross-section observation position is affected by the rounding that occurs when the cross-section is polished by the CMP method is used. After being applied on the surface of the semiconductor device corresponding to and cured, the semiconductor device is subjected to cross-section polishing from the side surface to the cross-section observation position by the CMP method. As a result, the cross-section observation position is located outside the rounding region. Therefore, at the cross-section observation position, it is possible to prevent rounding from occurring and obtain a substantially flat cross section. Therefore, by applying the method of this embodiment to prepare a sample for cross-section observation, the cross-sectional shape at the cross-section observation position can be confirmed in detail.

The present invention is not limited to the above embodiment, and various modifications can be made within the scope of the gist thereof.

In this embodiment, the case where the silicone resin is used as the resin has been described, but any resin may be used as long as it is transparent.

[0026]

As described above, according to the semiconductor device processing method of the present invention, the cross-section observation position is not affected by the rounding that occurs during the cross-section polishing by the chemical mechanical polishing method. After applying a transparent resin having a thickness of 3 to the surface of the semiconductor device corresponding to the cross-section observation position and curing the cross-section, the cross-section of the semiconductor device is polished from the side surface to the cross-section observation position by using the chemical mechanical polishing method. As a result, the cross-section observation position is located outside the rounding region. Therefore, at the cross-section observation position, it is possible to prevent rounding from occurring and obtain a substantially flat cross section.

[Brief description of drawings]

FIG. 1 is a diagram illustrating a method for processing a semiconductor device according to an embodiment of the present invention.

[Explanation of symbols]

10 Transparent resin 30 polishing plate

Claims (3)

[Claims] 1. A method for processing a semiconductor device, wherein a cross-section of a semiconductor device formed on a semiconductor substrate is observed by a chemical mechanical polishing method in order to observe a cross-section structure at a predetermined cross-section observation position. The step of removing the wiring layer formed above the cross-section observation position, and the effect of rounding that occurs during cross-section polishing by the chemical mechanical polishing method after removing the wiring layer A step of applying a transparent resin having a thickness not to be received by the cross-section observation position to the surface of the semiconductor device corresponding to the cross-section observation position and curing the same, using the chemical mechanical polishing method, A method of processing a semiconductor device, comprising: a step of polishing the semiconductor device coated with the transparent resin from its side surface to the section observation position. . 2. The method for processing a semiconductor device according to claim 1, wherein the transparent resin is cured after removing air bubbles remaining inside the transparent resin. 3. The method for processing a semiconductor device according to claim 1, wherein the transparent resin is a silicone resin.