JP2001351956A - Method for measuring by scanning electrostatic capacity microscope - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable relative comparison of the states of depletion layers of a diffused region, at each different sample structure for each observation of a semiconductor sample by making a voltage condition which is actually applied to a region of the surface of the sample constant, when observing the state of the depletion layer of the diffused region of the sample using an SCM. SOLUTION: The method for measuring with a scanning electrostatic capacity microscope comprises the steps of exposing the sections of a silicon substrate 101, a wall region 102 and a diffused region 103, forming an insulating film 105 on the exposed surface, and forming the sample 10 formed with a contact electrode 104 on a rear surface of the substrate. The method further comprises the steps of contacting a conductive probe 11 to the insulating film of the sample, applying a DC bias between the probe and the contact electrode, detecting dc/dv when the DC bias is applied between the probe and the electrode and an AC voltage is applied, and feedback controlling, so that voltage condition actually applied between the probe and the electrode is made constant, based on a result measured at the voltage between the probe and the electrode in the case of observing the state of the depletion layer of the diffused region based on the detected result.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a scanning probe microscope (SPM), and more particularly, to a scanning capacitance microscope (SCM).
And a method for measuring a semiconductor sample using the method described above.

[0002]

2. Description of the Related Art As one of the powerful means for observing and analyzing the inside of a semiconductor device with high spatial resolution, an SCM for measuring a local capacitance of a diffusion region on a sample surface portion is used. Is attracting attention.

FIG. 7A shows an example of a basic structure of an SCM and a sample represented by a gate transfer section of a semiconductor device.

In FIG. 7A, a sample 10 has a well region 102 selectively formed on a surface layer of a silicon substrate 101, a diffusion region 103 formed selectively on a surface layer of the well region, and a back surface of the substrate. For example, a contact electrode 104 is formed using a conductive paste or a conductive tape. Then, the cross section of the diffusion region 103, the well region 102, and the silicon substrate 101 is processed so as to be exposed. During this processing, an insulating film 105 made of, for example, a natural oxide film is formed on the exposed surface.

A tip 11 of a conductive cantilever 110 is brought into contact with the insulating film 105 of the sample 10, and a DC bias is applied between the probe 11 and the contact electrode 104 from a variable DC power supply 12. Is applied, the diffusion region 103
Inside, a depletion layer having a thickness depending on the carrier concentration is generated in a local region immediately below the probe. Then, FIG.
As shown in FIG. 5, a MOS capacitor C1 composed of the probe 11, the insulating film 105, and the diffusion region 103, a capacitance C2 of the diffusion region 103 and the well region 102, and a capacitance C3 of the silicon substrate 101 are connected in series. A circuit equivalent to the state is formed. In this case, the capacitances C2 and C3 differ depending on the structure of the sample 10. In this state, an AC voltage is applied between the probe 11 and the contact electrode 104 from the modulation power supply (AC power supply) 13.

When a DC bias and an AC voltage are applied as described above, a contact electrode with respect to the probe 11 at the ground potential is provided.
When the voltage at 104 changes alternately in the positive or negative direction and the voltage amplitude changes, the width of the depletion layer increases or decreases following this voltage change, and the silicon layer between the probe and the contact electrode is changed. The capacitance of the (impurity diffusion layer in a broad sense) changes.

Therefore, in order to detect a change in capacitance (dC / dV) with respect to the change in amplitude of the AC voltage, a known capacitance sensor (Capacitance sensor) 14 is connected to the probe 11, and the output is connected to a lock-in amplifier (Lock-in amplifier). -in amp.) 15 to detect a change in capacitance by amplifying, thereby indirectly observing the state of the local depletion layer in the diffusion region. At this time, the DC bias supplied from the variable DC power supply 12 is set to an appropriate value so that dC / dV can be easily detected. Then, in order to change the observation position of the diffusion region 103 in a scanning manner, the position of at least one of the probe 11 and the sample 10 is changed, for example, a piezo scanner.
(Piezoelectric tube scanner) 16 is configured to finely change the position of the sample 10 in a horizontal plane, and by scanning the detection position, the result can be displayed as an image. In order to detect the contact position of the probe 11, a pair of a laser beam irradiation device 17 and a reflected beam detection device 18 is provided.

[0008]

However, the conventional measuring method using the SCM has the following problems.

(1) At the time of measurement by SCM, a constant voltage is applied from the variable DC power source between the probe and the contact electrode, but how much voltage is actually applied to the diffusion region on the surface of the sample to be observed. It is unknown whether the voltage is applied. In other words, if the state of contact with the probe and the contact electrode differs for each observation, or the impedance of the well region 102 / silicon substrate 101 varies due to the difference in the sample structure, the voltage actually applied to the diffusion region 103 varies. As a result, the detection result (data) is affected, so that it is impossible to relatively compare the state of the depletion layer in the diffusion region for each observation of the sample or for each different sample structure.

(2) Since the voltage applied between the probe and the contact electrode acts three-dimensionally (also in the depth direction) on the diffusion region on the surface of the sample to be observed, the observation image is formed in the diffusion region. The information contains not only the state of the depletion layer but also three-dimensional elements including the depth direction of the diffusion region, and it was impossible to observe only the diffusion region accurately.

(3) Since the voltage applied to the diffusion region is not directly applied to the diffusion region but is applied from the silicon substrate, how much voltage is actually applied to the diffusion region to be observed is determined. It was unknown, and the extent of the diffusion region looked different depending on the sample structure, and it was impossible to measure quantitatively.

(4) The sample is processed so that the cross section of the diffusion region is exposed, and the probe is brought into contact with a natural oxide film formed on the surface to perform measurement from the cross section of the diffusion region. When the depth in the substrate direction is 0.1 μm or less, when the contact position of the probe is not opposed to the substantially center position of the diffusion region in the substrate direction (at the time of occurrence of contact displacement), it is directly below the probe. The extent of the depletion layer from the diffusion region exceeds the depth range of the diffusion region in the direction of the substrate, and it is difficult to measure the state of the depletion layer in the diffusion region.

(5) Since the main purpose is to observe the state of the depletion layer in the diffusion region, in order to know the active state of the impurity implanted in the diffusion region, a gate electrode is provided on the gate insulating film on the diffusion region. It was necessary to separately configure a sample and electrically measure the relationship between the voltage applied to the gate electrode and the current in the diffusion region.

The present invention has been made in order to solve the above-mentioned problems, and can stabilize a voltage condition actually applied to a diffusion region on a surface of a sample to be observed. It is a first object of the present invention to provide a measurement method using a scanning capacitance microscope, which makes it possible to relatively compare the state of a depletion layer in a diffusion region for each structure.

A second object of the present invention is to observe the diffusion region accurately by observing the state of the depletion layer in the thin film state of the diffusion region on the sample surface to be observed. An object of the present invention is to provide a measuring method using a scanning capacitance microscope.

A third object of the present invention is to apply a voltage directly to a diffusion region of a sample to be observed, to stabilize a voltage actually applied to the diffusion region, It is an object of the present invention to provide a measurement method using a scanning capacitance microscope that enables unified observation of voltage conditions in a diffusion region regardless of the measurement conditions.

A fourth object of the present invention is to measure by applying a voltage change from the upper surface side of the diffusion region on the surface of the sample to be observed so that the depth of the diffusion region in the substrate direction becomes zero. In the case of .ltoreq.1 .mu.m or less, it is possible to measure the state of the depletion layer in the diffusion region immediately below the probe, and also to use a measuring method using a scanning capacitance microscope that can simplify the sample preparation operation. To provide.

A fifth object of the present invention is to provide a scanning capacitance microscope capable of easily observing the two-dimensional distribution of the active state and carrier density of an impurity implanted in a diffusion region on the surface of a sample. It is to provide a measuring method.

[0019]

According to a first aspect of the present invention, there is provided a measuring method using a scanning capacitance microscope, wherein a semiconductor device having a well region and a diffusion region formed on a surface layer of a semiconductor substrate is processed, and the diffusion region and the diffusion region are processed. A first step of exposing the well region and the cross section of the semiconductor substrate, forming an insulating film on the exposed surface, and forming a sample in which a contact electrode is formed on the back surface of the semiconductor substrate; A constant voltage DC bias is applied between the probe and the contact electrode, and a change in the capacitance between the probe and the contact electrode with respect to a change in the voltage amplitude when an AC voltage is applied. And a second step of observing a state of a depletion layer in a diffusion region of a sample surface portion to be observed based on a detection result of the capacitance change. In step, a voltage between said probe and the contact electrodes is measured, based on this measurement result,
The present invention is characterized in that feedback control is performed so as to stabilize a voltage condition actually applied between the probe and the contact electrode.

According to a second aspect of the present invention, there is provided a measuring method using a scanning capacitance microscope, wherein a semiconductor device having a well region and a diffusion region formed in a surface layer of a semiconductor substrate is processed, and the diffusion region, the well region and the semiconductor substrate are measured. Expose the cross section,
An insulating film is formed on the exposed surface, and a groove is formed at the bottom of the diffusion region on the sample surface so that the thickness of the diffusion region, the well region, and the semiconductor substrate is constant when viewed from the sample surface. A first step of preparing a sample in which a contact electrode is formed on the back surface of the semiconductor substrate;
A conductive probe is brought into contact with the insulating film of the sample, and a constant DC bias is applied between the probe and the contact electrode, and the probe responds to a change in voltage amplitude when an AC voltage is applied. A second method of detecting a change in capacitance between the contact electrodes and observing a state of a depletion layer in a diffusion region of a sample surface to be observed based on the detection result;
And the following steps.

According to a third aspect of the present invention, there is provided a measuring method using a scanning capacitance microscope, wherein a semiconductor device having a well region and a diffusion region formed in a surface layer of a semiconductor substrate is processed, and the diffusion region, the well region and the semiconductor substrate are processed. Expose the cross section,
An insulating film is formed on the exposed surface, and a groove is formed at the bottom of the diffusion region on the sample surface so that the thickness of the diffusion region, the well region, and the semiconductor substrate is constant when viewed from the sample surface. A first step of forming a sample formed so as to embed a conductive member in contact with each of the diffusion region, the well region, and the semiconductor substrate in the groove; and a conductive probe in an insulating film of the sample. A contact is made, a constant DC bias is applied between the probe and the conductive member, and a change in the capacitance between the probe and the conductive member with respect to a change in the voltage amplitude when an AC voltage is applied is detected. And a second step of observing the state of the depletion layer in the diffusion region on the sample surface based on the detection result.

According to a fourth aspect of the present invention, there is provided a measuring method using a scanning capacitance microscope, wherein a semiconductor device having a diffusion region formed in a surface layer of a semiconductor substrate is processed, an upper surface of the diffusion region is exposed, and the surface is exposed. A first step of forming an insulating film and forming a sample in which a contact electrode is formed on the back surface of the semiconductor substrate, and contacting a conductive probe with the insulating film of the sample; A DC bias of a constant voltage is applied during the detection, and a change in the capacitance between the probe and the contact electrode with respect to a change in the voltage amplitude when the AC voltage is applied is detected. Based on the detection result of the change in the capacitance, the sample surface portion is detected. Observing the state of the depletion layer in the diffusion region.

According to a fifth aspect of the present invention, there is provided a measuring method using a scanning capacitance microscope, wherein a semiconductor device having a diffusion region formed in a surface layer of a semiconductor substrate is processed to expose a cross section or an upper surface of the diffusion region. A first step of forming a sample in which an insulating film is formed on the front surface and forming a contact electrode on the back surface of the semiconductor substrate; and contacting a conductive probe with the insulating film of the sample. The probe and the probe for applying a constant DC bias between the electrodes and changing the voltage amplitude when an AC voltage is applied.
A second step of detecting a change in capacitance between the contact electrodes and observing the active state of the implanted impurity in the diffusion region on the sample surface based on the detection result of the change in capacitance.

In the second step of the second to fifth aspects, the voltage between the probe and the contact electrode is measured in the same manner as in the second step of the first aspect. Based on this, it is possible to stabilize the voltage condition actually applied to the diffusion region of the sample surface portion by performing feedback control so as to stabilize the voltage condition actually applied between the probe and the contact electrode. is there.

[0025]

Embodiments of the present invention will be described below in detail with reference to the drawings.

<First Embodiment> FIG. 1A shows a method of measuring a semiconductor sample by using an SCM according to a first embodiment of the present invention.

In FIG. 1A, a sample 10 typified by a gate transfer portion of a semiconductor device has a well region 102 selectively formed in a surface layer portion of a semiconductor substrate (silicon substrate in this example) 101. Diffusion area selectively on the surface of the area
A semiconductor device having 103 formed thereon is processed, and a contact electrode 104 using a conductive paste or a conductive tape is formed on the back surface of the substrate. In the above processing,
Diffusion region 103 and well region 102 and silicon substrate
When exposing the cross section of 101, an insulating film 105 made of, for example, a natural oxide film is formed on the exposed surface.

When the probe 11 at the tip of the conductive cantilever 110 is brought into contact with the insulating film 105 of the sample 10 and a DC bias is applied between the probe 11 and the contact electrode 104 from the variable DC power supply 12, A depletion layer having a thickness depending on the carrier concentration is generated in the local region 103 immediately below the probe. Then, as shown in FIG. 1B, the probe 11 and the insulating film
MOS capacitor C1 composed of 105 and diffusion region 103, and capacitance C2 of diffusion region 103 and well region 102
Thus, a circuit equivalent to a state in which the capacitance C3 of the silicon substrate 101 is connected in series is formed. In this case, the capacitances C2 and C3 are
It depends on the structure of the sample 10. In this state, an AC voltage is applied between the probe 11 and the contact electrode 104 from the modulation power supply (AC power supply) 13.

When a DC bias and an AC voltage are applied as described above, the contact electrode with respect to the probe 11 at the ground potential
When the voltage at 104 changes alternately in the positive or negative direction and the voltage amplitude changes, the width of the depletion layer increases or decreases following this voltage change, and the silicon layer between the probe and the contact electrode is changed. The capacitance of the (impurity diffusion layer in a broad sense) changes.

In order to detect a change in capacitance (dC / dV) with respect to a change in the amplitude of the AC voltage, a known capacitance sensor 14 is connected to the probe 11, and the output is amplified by a lock-in amplifier 15. By detecting the change in capacitance, the state of the local depletion layer in the diffusion region 103 can be indirectly observed. At this time, dC / d
The DC bias supplied from the variable DC power supply 12 is set to an appropriate value so that V can be easily detected. Then, in order to change the observation position of the diffusion region 103 in a scanning manner, the probe 11 is used.
And at least one of the positions of the sample 10 is changed, for example, the position of the sample 10 is finely changed in a horizontal plane by a piezo scanner 16, and the diffusion region 103 is provided.
It is possible to display the result as an image by scanning the observation position. In order to detect the contact position of the probe 11, a pair of a laser beam irradiation device 17 and a reflected beam detection device 18 is provided.

Further, the voltage between the probe and the contact electrode is measured by the voltage measuring circuit 19, and the variable DC power supply 12 and / or the AC power supply 13 is controlled in accordance with the measurement result, so that each time the sample is observed or a different sample structure is used. A feedback control circuit 20 is provided for stabilizing the voltage condition actually applied between the probe and the contact electrode every time.

That is, the SC according to the first embodiment described above
According to the method of measuring a semiconductor sample by M, the voltage condition actually applied between the probe and the contact electrode is made constant.
Therefore, the probe 11 and the contact electrode 104
Even if the contact state with respect to the sample is different or the sample structure is different, the voltage condition actually applied to the diffusion region on the sample surface can be kept constant, so that the diffusion region 103 for each observation of the sample 10 or for each different sample structure can be obtained. Can be relatively compared with each other.

If the observation position of the sample is changed to the well region 102, the state of the depletion layer in the well region 102 can be observed.

<Second Embodiment> FIG. 2A shows a method of measuring a semiconductor sample by using an SCM according to a second embodiment of the present invention.

The sample 10a shown in FIG.
As shown in (b), a groove is formed on the bottom of the diffusion region 103 on the surface of the sample (opposite to the observation surface) by, for example, a known focused ion beam (FIB) process from the side of the sample.
By forming 106, each of the diffusion region 103, the well region 102, and the silicon substrate 101 is processed so that the thickness d as viewed from the sample surface side becomes a constant thin film portion. Other parts are the samples shown in FIG.
10, the same reference numerals as those in FIG. 1A are assigned. Since the measurement system shown in FIG. 2A is the same as the conventional measurement system shown in FIG.
The same reference numerals as in FIG.

A DC bias and an AC voltage are applied to the sample 10a as described above in the same manner as in the first embodiment.
/ DV is detected, the detection position is scanned, and the result is displayed as an image, whereby the diffusion region 103 (or the well region 10) is displayed.
2. The state of the depletion layer of the silicon substrate 101) can be indirectly observed. In this case, the equivalent circuit of sample 10a is
This is the same as the equivalent circuit of the sample 10 shown in FIG.

That is, the SC according to the second embodiment described above
According to the method of measuring a semiconductor sample by M, the applied voltage between the probe and the contact electrode is applied two-dimensionally to the thin film portion of the diffusion region (or well region) on the surface of the sample to be observed. , Suppress the effects of three-dimensional elements including the depth direction of the diffusion region (or well region),
It is possible to accurately observe the state of the depletion layer in the diffusion region (or well region) in the thin film state.

In the measurement system according to the second embodiment, the probe and the probe are used similarly to the measurement system according to the first embodiment.
If the voltage between the contact electrodes is measured and the variable DC power supply 12 and / or the AC power supply 13 is feedback-controlled based on the measurement result, the same effect as in the first embodiment described above can be obtained.

<Third Embodiment> FIG. 3A shows a method of measuring a semiconductor sample by using an SCM according to a third embodiment of the present invention.

The sample 10b shown in FIG.
As shown in FIG. 3B, the diffusion region 10 is formed inside the groove 106.
A conductive member 107 is embedded in the thin film portion of the silicon substrate 101, the well region 102, and the well region 102, respectively. The conductive member 107 is connected to a contact portion.
108 is drawn out and further connected, for example, to the contact electrode 104. Thus, a desired bias voltage can be directly applied to each of the diffusion region 103, the well region 102, and the silicon substrate 101 via the contact electrode 104 and the conductive member 107. The other parts are the same as those of the sample 10a shown in FIG. 2B, and thus are denoted by the same reference numerals as those in FIG. 2B. The measurement system shown in FIG. 3A is a conventional system shown in FIG.
7A, the same reference numerals as those in FIG. 7A are used.

A DC bias and an AC voltage are applied to the sample 10b as in the second embodiment, and dC
/ DV is detected, the detection position is scanned, and the result is displayed as an image, whereby the diffusion region 103 (or the well region 10) is displayed.
2) The state of the depletion layer can be observed indirectly.
In this case, the equivalent circuit of the sample 10b is different from the equivalent circuit of the sample 10 shown in FIG. 1B in that the variable DC power supply 12 is connected to the connection node between the capacitors C1 and C2 and the connection node between the capacitors C2 and C3. And the other is the same.

That is, the SC according to the third embodiment described above
According to the method of measuring a semiconductor sample by M, a voltage applied between a probe and a contact electrode is applied two-dimensionally to a thin film portion of a diffusion region 103 (or a well region 102) on a surface of a sample to be observed. Thus, the state of the depletion layer in the diffusion region 103 (or the well region 102) in a thin film state can be accurately observed.

In addition, a voltage can be directly applied to each of the diffusion regions (diffusion region 103 and well region 102 in a narrow sense) on the sample surface, and the voltage actually applied to each diffusion region can be made constant. Irrespective of the sample structure, it becomes possible to unify and observe the voltage conditions of each diffusion region.

In the measuring system according to the third embodiment, the probe and the probe are used similarly to the measuring system according to the first embodiment.
If the voltage between the contact electrodes is measured and the variable DC power supply 12 and / or the AC power supply 13 is feedback-controlled based on the measurement result, the same effect as in the first embodiment described above can be obtained.

<Fourth Embodiment> FIG. 4A shows a method for measuring a semiconductor sample by using an SCM according to a fourth embodiment of the present invention.

The sample 10d shown in FIG.
As shown in FIG. 1B, as compared with the sample 10 shown in FIG. 1A, the diffusion region 103 and the well region 10 are used as the sample surface.
2 and the upper surface of the silicon substrate 101 are exposed, and an insulating film 105 made of, for example, a natural oxide film is formed on the exposed surface.
The same reference numerals as in the figure are used. Further, the measurement system shown in FIG. 4A has the same configuration as the conventional measurement system shown in FIG. 7A, and thus is given the same reference numerals as those in FIG. 7A. .

The insulating film on the upper surface side of the sample 10c as described above
The probe 11 is brought into contact with the probe 105, and a DC bias and an AC voltage are applied thereto in the same manner as in the first embodiment to apply dC / dV
Is detected, the detected position is scanned, and the result is displayed as an image, whereby the state of the depletion layer in the diffusion region 103 can be indirectly observed.

At this time, since the measurement is performed by applying a voltage change from the upper surface side of the diffusion region 103, even if the correspondence between the contact position of the probe 11 and the substantially center position of the diffusion region 103 is slightly shifted, FIG. As shown in (a), the lateral extent of the depletion layer from immediately below the probe does not exceed the range of the diffusion region 103, so that the depth of the diffusion region 103 in the substrate direction is 0.1 μm.
Even in the case of m or less, the state of the depletion layer in the diffusion region 103 immediately below the probe can be measured by detecting dC / dV.

On the other hand, in the conventional measuring method, the probe
When the correspondence between the contact position of FIG. 11 and the substantially center position of the diffusion region 103 is slightly shifted, as shown in FIG.
Therefore, even when the depth of the diffusion region 103 in the direction of the substrate is 0.1 μm or less, the state of the depletion layer in the diffusion region 103 immediately below the probe is measured by detecting dC / dV. It was impossible.

That is, the SC according to the fourth embodiment described above.
According to the method of measuring a semiconductor sample by M, the probe 11 is brought into contact with the insulating film 105 on the upper surface side of the diffusion region 103 on the surface of the sample to be observed, and a voltage change is applied from the upper surface side of the diffusion region 103. By performing the measurement, the state of the depletion layer in the diffusion region 103 can be observed. Moreover, the work of preparing the sample can be simplified as compared with the conventional processing such as cross-section polishing required to expose the cross section of the diffusion region 103 as the sample surface.

When the observation position is changed to the well region 102 or the silicon substrate 101, the state of the well region 102 or the silicon substrate 101 can be observed.

In the measuring system according to the fourth embodiment, the probe and the probe are used similarly to the measuring system according to the first embodiment.
If the voltage between the contact electrodes is measured and the variable DC power supply 12 and / or the AC power supply 13 is feedback-controlled based on the measurement result, the above-described effects similar to those of the first embodiment can be obtained.

<Fifth Embodiment> FIG. 6A shows a method of measuring a semiconductor sample by an SCM according to a fifth embodiment of the present invention.

Since the method of measuring a semiconductor sample by the SCM shown in FIG. 6A is the same as that of the conventional measuring method shown in FIG.
(A) Although the same reference numerals as those in the figure are attached, the observation purpose (target) is not the state of the depletion layer in the diffusion region on the sample surface,
The difference lies in the active state (two-dimensional distribution of carrier density) of the implanted impurity in the diffusion region.

That is, when impurity ions are implanted and introduced into the silicon substrate 101 as shown in FIG. 6B, the activation of the impurity ions is insufficient and no carriers are present, so that the depletion layer elongates. The amount of change in the depletion layer with respect to the change in the amplitude of the AC voltage is extremely small, and dC / d
The V signal is very low. On the other hand, when the impurity ions are activated by sufficiently applying heat after the implantation of the impurity ions, the carriers are present as shown in FIG. The change amount of the depletion layer with respect to the change of the amplitude becomes large, and the dC / dV signal becomes large.

As described above, depending on the state of the carrier, dC /
Focusing on the principle that the dV signal is different, the method of measuring a semiconductor sample by the SCM according to the fifth embodiment employs dC / d
The carrier state is measured by measuring the V signal, and the active state of the impurity implanted in the diffusion region is detected. Therefore, conventionally, a sample (not shown) having a gate electrode (not shown) on a gate insulating film (not shown) on the diffusion region is separately provided in order to detect the active state of the implanted impurity in the diffusion region. In this embodiment, the relationship between the applied voltage of the gate electrode and the current in the diffusion region has to be measured electrically. The dimensional distribution can be easily observed.

In the measuring system according to the fifth embodiment, the probe and the probe are used similarly to the measuring system according to the first embodiment.
If the voltage between the contact electrodes is measured and the variable DC power supply 12 and / or the AC power supply 13 is feedback-controlled based on the measurement result, the above-described effects similar to those of the first embodiment can be obtained.

[0058]

As described above, according to the measuring method using the scanning capacitance microscope according to the first invention, the diffusion region (or well region, silicon substrate) on the surface of the sample to be observed is actually provided. The condition of the applied voltage can be made constant, and the state of the depletion layer in the diffusion region can be relatively compared for each observation of the sample or for each different sample structure.

According to the measuring method using the scanning capacitance microscope according to the second aspect of the present invention, the voltage applied between the probe and the contact electrode is measured by the diffusion region (or well region, By observing the state of the depletion layer in the thin film state of the silicon substrate, it becomes possible to accurately observe the diffusion region (or well region, silicon substrate).

Further, according to the measuring method using the scanning capacitance microscope according to the third invention, it is possible to directly apply a voltage to each diffusion region of the sample to be observed, and to apply a voltage to each diffusion region. The voltage actually applied can be kept constant,
Irrespective of the sample structure, it becomes possible to unify and observe the voltage conditions of each diffusion region.

According to the measuring method using the scanning capacitance microscope according to the fourth invention, the measurement is performed by applying a voltage change from the upper surface side of the diffusion region on the surface of the sample to be observed. The depth of the diffusion region in the substrate direction is 0.1 μm
Even in the following cases, the state of the depletion layer in the diffusion region immediately below the probe can be measured, and the work of preparing a sample can be simplified.

Further, according to the measuring method using the scanning capacitance microscope according to the fifth invention, the two-dimensional distribution of the active state and the carrier density of the implanted impurity in the diffusion region on the surface of the sample can be easily observed. Will be possible.

[Brief description of the drawings]

FIG. 1 is a view showing a method for measuring a semiconductor sample by SCM according to a first embodiment of the present invention.

FIG. 2 is a view showing a method for measuring a semiconductor sample by SCM according to a second embodiment of the present invention.

FIG. 3 is a view showing a method for measuring a semiconductor sample by SCM according to a third embodiment of the present invention.

FIG. 4 is a view showing a method for measuring a semiconductor sample by SCM according to a fourth embodiment of the present invention.

FIG. 5 is a diagram showing a relationship between the sample in FIG. 4 and an electric field from a contact position of a probe in comparison with a conventional example.

FIG. 6 is a diagram showing a method for measuring a semiconductor sample by SCM according to a fifth embodiment of the present invention.

FIG. 7 is a diagram showing a basic configuration of a conventional SCM and an example of a sample.

[Explanation of symbols]

 10 ... sample, 101 ... silicon substrate, 102 ... well region, 103 ... diffusion region, 104 ... contact electrode, 105 ... insulating film, 110 ... cantilever, 11 ... probe, C1 ... MOS capacitor, C2, C3 ... capacitance, 12 ... variable DC power supply, 13 ... modulation power supply (AC power supply), 14 ... capacitance sensor, 15 ... lock-in amplifier, 16 ... piezo scanner, 17 ... laser beam irradiation device, 18 ... reflected beam detection device, 19 ... voltage measurement circuit , 20 ... feedback control circuit.

Claims (6)

[Claims] A semiconductor device having a diffusion region formed in a surface layer of a semiconductor substrate is processed to expose a cross section of the diffusion region and the semiconductor substrate, an insulating film is formed on the exposed surface, and a back surface of the semiconductor substrate is formed. A first step of preparing a sample to which a contact electrode is added; and contacting a conductive probe with an insulating film of the sample, applying a constant voltage DC bias between the probe and the contact electrode. A change in capacitance between the probe and the contact electrode with respect to a change in voltage amplitude when an AC voltage is applied is detected, and a state of a depletion layer in a diffusion region of a sample surface portion is observed based on the detection result of the change in capacitance. 2) measuring the voltage between the probe and the contact electrode in the second step, and measuring the voltage between the probe and the contact electrode based on the measurement result. Measuring method using a scanning capacitance microscope voltage conditions applied, characterized in that the feedback control so as to made constant. 2. A semiconductor device having a diffusion region formed in a surface layer portion of a semiconductor substrate is processed to expose a cross section of the diffusion region.
An insulating film is formed on the exposed surface, a groove is formed at the bottom of the diffusion region on the surface of the sample so that the diffusion region becomes a thin film portion having a constant thickness as viewed from the surface of the sample, and a contact is made with the back surface of the semiconductor substrate. A first step of preparing a sample to which electrodes are added; contacting a conductive probe with the insulating film of the sample; applying a constant voltage DC bias between the probe and the contact electrode; A change in capacitance between the probe and the contact electrode with respect to a change in voltage amplitude when a voltage is applied is detected, and based on the detection result, a state of a depletion layer in a diffusion region of a sample surface to be observed is observed. Second
And a measuring method using a scanning capacitance microscope. 3. A semiconductor device in which a well region and a diffusion region are formed in a surface portion of a semiconductor substrate, a cross section of the diffusion region is exposed, an insulating film is formed on the cross section surface, and a diffusion region of a sample surface portion is formed. A groove is formed at the bottom of the substrate so that each of the diffusion region, the well region, and the semiconductor substrate becomes a thin film portion having a constant thickness as viewed from the sample surface. Further, the diffusion region, the well region, and the semiconductor substrate are formed within the groove. A first step of preparing a sample formed so as to embed a conductive member in contact therewith, and contacting a conductive probe with the insulating film of the sample, and applying a constant voltage between the probe and the conductive member. A change in the capacitance between the probe and the conductive member with respect to a change in the voltage amplitude when the DC bias is applied and the AC voltage is applied is detected. Measuring method using a scanning capacitance microscope, characterized by comprising a second step of observing the depletion of the state of the diffusion region parts. 4. A semiconductor device having a diffusion region formed in a surface layer portion of a semiconductor substrate is processed to expose an upper surface of the diffusion region.
A first step of forming an insulating film on the exposed surface and forming a sample with a contact electrode added to the back surface of the semiconductor substrate; and contacting a conductive probe with the insulating film of the sample. A constant DC bias is applied between the probe and the contact electrode, and a change in capacitance between the probe and the contact electrode with respect to a change in voltage amplitude when an AC voltage is applied is detected. A second step of observing a state of a depletion layer in a diffusion region on the surface of the sample by using a scanning capacitance microscope. 5. A semiconductor device in which a diffusion region is formed in a surface layer portion of a semiconductor substrate, a cross section or an upper surface of the diffusion region is exposed, an insulating film is formed on the exposed surface, and a contact is made on a back surface of the semiconductor substrate. A first step of preparing a sample to which electrodes are added; contacting a conductive probe with the insulating film of the sample; applying a constant voltage DC bias between the probe and the contact electrode; A change in the capacitance between the probe and the contact electrode with respect to a change in the voltage amplitude when a voltage is applied is detected, and based on the detection result of the change in the capacitance, the active state of the implanted impurity in the diffusion region on the sample surface is observed. 2. A measuring method using a scanning capacitance microscope, comprising: 6. In the second step, a voltage between the probe and the contact electrode is measured, and a voltage condition actually applied between the probe and the contact electrode is made constant based on the measurement result. The scanning capacitance microscope according to any one of claims 2 to 5, wherein feedback control is performed to stabilize a voltage condition actually applied to the diffusion region on the surface of the sample. Measuring method.