JPH07167903A - Charge amount measuring device - Google Patents

Abstract

PURPOSE:To simplify the construction of a test wafer so as to shorten manufacturing time, and also enable evaluation of highly sensitive charge-up amount, by forming an insulating protective film on an insulating film formed on a substrate, removing a part of protective film to expose the insulating film and forming a surface to be measured. CONSTITUTION:A silicon oxide film 12 serving as an insulating film is formed on a silicon wafer 11, and a silicon nitride film 13 serving as an insulating protective film is formed on the oxide film 12. Next the nitride film 13 is patterned by a photolithography and etching to expose the oxide film 12 for forming a surface to be measured 14. Also the diameter of the electrode part 21 of an electrode to be measured 2 is less than that of the part to be measured 14 of a test wafer 1, the diameter of the inner periphery of an insulating part 22 is less than that of the surface to be measured 14, and the diameter of the outer periphery of the insulating part 22 id larger than that of the surface to be measured 14. Thus, when the electrode part 21 is moved closely to the surface to be measured 14, a desired minute gap is formed between the electrode part 21 and the surface to be measured 14.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a charge amount measuring device for evaluating the charge-up amount of an object to be processed which is processed by a processing device using a plasma processing method such as ion implantation, etching or plasma CVD. .

[0002]

2. Description of the Related Art In the manufacture of semiconductor devices, various plasma processing methods such as ion implantation, etching and plasma CVD are used. Electric charges are deposited on an insulating layer such as a silicon oxide film formed on the surface of a semiconductor device processed by the above plasma processing method, and when the electric field strength is exceeded, a discharge is generated and the device circuit is destroyed. A so-called charge-up phenomenon occurs. In particular, today, due to the increase in the beam amount of ion implanters due to the miniaturization and mass production of devices, the yield of device manufacturing tends to deteriorate further due to the increase in insulation breakdown and leakage current due to charge-up. .

Therefore, for example, in an ion implantation apparatus, neutralization using electrons is used to deal with the problem, but in order to verify the effect, an actual device or test wafer group, so-called TEG (test element group) is used. ) Should be used to evaluate the charge-up amount.

Conventionally, as shown in FIG. 5, a silicon oxide film 52 is formed on a silicon wafer 51, and a protective film 53 such as a silicon nitride film and a patterned electrode 54 are further formed on the silicon oxide film 52. The charge-up amount is evaluated using the test wafer 50.

[0005]

However, it takes time to create the conventional test wafer 50 described above. This is because it is necessary to form the electrodes 54 on the surface of the test wafer 50, which complicates the process for producing the test wafer 50. That is, the following steps are required to create the test wafer 50.

First, as shown in FIG. 6A, after forming a silicon oxide film 52 on a silicon wafer 51,
As shown in FIG. 7B, a nitride film 55 is formed on the silicon oxide film 52. Next, as shown in FIG. 3C, the nitride film 55 is patterned by photolithography and etching, and then, as shown in FIG. 3D, a field oxide film 56 is grown by wet oxidation. Next, as shown in FIG. 6E, the nitride film 55 is removed by etching, and then a protective film 53 such as a nitride film is formed on the surface as shown in FIG. Next, as shown in FIG. 3G, the protective film 53 is patterned,
After that, an electrode layer is formed on the surface as shown in FIG. 3H, and the electrode layer is patterned to form an electrode 54 as shown in FIG.

As described above, the conventional test wafer 5 described above is used.
Since the process for creating 0 is very complicated, it usually takes more than one month to create TEG.

When the charge-up amount is evaluated using the above-described test wafer 50, which has a CV characteristic and an IV characteristic as semiconductor parameters, they are roughly divided into CV and CV characteristics.
It is difficult to live the law. This is the test wafer 50
Since the electrode 54 is formed on the surface of the
This is because the capacitance C cannot be measured when the measurement electrode for applying a bias is connected to the surface of the test wafer 50 because the charged charges escape through the electrode 54 and the measurement electrode.

Therefore, the IV method is used to evaluate the charge-up amount using the test wafer 50. In the IV method, the electrode 54 of the plasma-treated test wafer 50 is placed on the metal stage so that the electrode 54 faces upward, and a bias is applied between the metal stage and the electrode 54 of the test wafer 50. Is applied to examine the IV characteristics as shown in FIG. 7, and the withstand voltage is determined by the applied voltage when a current of 10 ⁻⁶ A flows, which is a so-called dielectric breakdown test. When the silicon oxide film 52 is damaged due to the charge-up caused by the plasma processing, the withstand voltage is lowered depending on the degree of the damage, so that the charge-up amount can be evaluated from the withstand voltage after the plasma processing.

When the charge-up amount is evaluated by using the IV method, the state of the silicon oxide film 52 is not necessarily uniform depending on the patterning accuracy, so there are some places where dielectric breakdown occurs and others where it is difficult to occur. However, a statistical interpretation is required, the measurement takes time, and the evaluation is difficult in terms of reproducibility.

As described above, in the related art, it takes a long time to create a TEG and perform measurement using the TEG, and it is difficult to evaluate the charge-up amount in terms of reproducibility. It is difficult to acquire data for improving the charge-up prevention function, which is one of the factors that hinder the development of the device.

For this reason, today, there is a strong demand for a method of evaluating the charge-up amount, which is simpler than the withstand voltage evaluation by the IV method using the above-mentioned conventional TEG which is generally performed. It is also fully expected that neutralization control based on more detailed data will be required in the future.

The present invention has been made in view of the above circumstances, and an object thereof is to simplify the structure of a test wafer, shorten the time required for producing the test wafer, and to make it simpler and higher than the conventional charge-up amount evaluation. An object of the present invention is to provide a charge amount measuring device capable of performing a sensitive charge-up amount evaluation.

[0014]

A charge amount measuring device of the present invention is a substrate having conductivity, an insulating film having a predetermined thickness formed on the substrate, and a predetermined film formed on the insulating film. An insulating protective film having a film thickness of, and a test wafer formed by removing a part of the protective film to expose the insulating film to form a portion to be measured. An electrode portion whose surface facing the portion is formed in a size that does not protrude from the measured portion, and is provided on the outer peripheral portion of the electrode portion,
When the electrode portion and the measured portion are brought close to each other so that the electrode portion does not protrude from the measured portion of the test wafer, a predetermined minute gap is formed between the electrode portion and the insulating film of the measured portion. As described above, the measuring electrode having an insulating contact portion that contacts the protective film of the test wafer is provided.

[0015]

According to the above structure, since the test wafer does not need to have electrodes formed on its surface, the structure is simpler than that of the conventional test wafer, and the number of steps for producing the test wafer is significantly increased. Since this can be reduced, the time required to create a test wafer can be significantly reduced.

Further, an insulating contact portion is provided on the outer peripheral portion of the electrode portion of the measuring electrode, and the electrode portion and the measured portion are arranged so that the electrode portion does not protrude from the measured portion of the test wafer. So that the insulating contact portion comes into contact with the protective film of the test wafer and a predetermined minute gap is formed between the insulating film and the electrode portion of the measured portion of the test wafer. Has become.

As described above, since the insulating film of the measured portion of the test wafer and the electrode portion are not in contact with each other, the electric charges accumulated on the insulating film by the plasma treatment are not released to the outside.
Therefore, if a bias voltage is applied between the electrode portion of the measurement electrode and the conductive substrate of the test wafer, the capacitance including the capacitance of the air and the capacitance of the insulating film existing in the minute gap is measured. can do. Since the capacity of air can be calculated from the gap, the capacity of the insulating film can be calculated. Therefore, if the above bias voltage is continuously changed in the positive direction or the negative direction, C
The -V characteristic can be measured.

Therefore, the charge amount can be measured with high sensitivity by using the CV method, which is simpler than the withstand voltage evaluation by the conventional IV method (specifically, the CV characteristic measured before the plasma treatment). For the curve, C measured after plasma treatment
Since the −V characteristic curve shifts according to the charge amount, the charge amount can be obtained from the difference (shift amount) of the flat band voltage before and after the plasma treatment), and the charge-up amount can be evaluated quickly and accurately. it can.

[0019]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The following will describe one embodiment of the present invention with reference to FIGS.

As shown in FIG. 2, the charge amount measuring apparatus according to this embodiment is an information processing apparatus such as a test wafer 1, a measuring electrode 2, a measuring prober 3, a shield box 4, an LCR meter 5, and a personal computer. It is composed of 6.

As shown in FIG. 1, the test wafer 1 has a silicon wafer 11 as a substrate and a film thickness of about 50 as an insulating film formed on the silicon wafer 11.
The silicon nitride film (SiO ₂ ) 12 having a thickness of 00 Å and the silicon nitride film (Si ₃ N ₄ ) 13 having a thickness of about 1000 Å as a protective film formed on the silicon oxide film 12 are provided. A substantially circular measured portion 14 in which a part of 13 is removed to expose the silicon oxide film 12 is patterned on the surface.

An example of a method for producing the test wafer 1 will be described below with reference to FIG. First, as shown in FIG. 3A, a silicon oxide film 12 is formed on a silicon wafer 11 by dry oxidation or wet oxidation. In the case of dry oxidation, an annealing furnace is used for the silicon wafer 11
Is heated in a range of 900 ° C. to 1200 ° C. in an N ₂ atmosphere, and after reaching a predetermined temperature, O ₂ gas is introduced and oxidation treatment is performed for a predetermined time. In the case of wet oxidation, the above-mentioned O ₂ gas is passed through warm pure water to carry out the oxidation treatment while introducing steam together with O ₂ gas. In wet oxidation, oxidation progresses rapidly, and a thick oxide film can be formed in a short time.

Next, as shown in FIG.
A silicon nitride film 13 is formed on the silicon oxide film 12 by using D (Low Pressure Chemical Vapor Deposition). That is, the inside of the furnace is decompressed and the silicon wafer 11 having the silicon oxide film 12 formed on the surface thereof is heated to about 600 ° C. to 1000 ° C. in an N ₂ atmosphere to obtain a mixed gas of NH ₃ OH gas and H ₂ gas. Is introduced into a furnace and treated for a predetermined time to form a silicon nitride film 13 on the silicon oxide film 12.

After that, the silicon nitride film 13 is patterned by photolithography and etching to form a measured portion 14 with the silicon oxide film 12 exposed as shown in FIG. In this case, wet etching is used instead of plasma etching in order to remove the influence of plasma processing.

The test wafer 1 of this embodiment can be produced by the above steps. The test wafer 1 of the present embodiment has a simpler structure than the conventional test wafer, has a small number of manufacturing steps, and can be manufactured in a short time.

As shown in FIG. 1, the measuring electrode 2 has a disk-shaped electrode portion 21 made of tungsten carbide,
It is composed of a ring-shaped insulating portion 22 as an insulating contact portion provided on the outer peripheral portion of the electrode portion 21, and an electrode support portion 23 made of tungsten carbide attached to the center of the upper surface of the electrode portion 21. ing.

The diameter (area) of the electrode portion 21 is less than or equal to the diameter (area) of the measured portion 14 of the test wafer 1. The diameter of the inner circumference of the insulating portion 22 is the same as the test wafer 1
Smaller than the diameter of the measured portion 14 of the
The diameter of the outer circumference is larger than the diameter of the measured portion 14 of the test wafer 1.

As shown in FIG. 2, the measuring prober 3 holds the measuring electrode 2 and drives the measuring electrode 2 in the vertical direction (vertical direction), and the measuring electrode 2 It is the opposite of the test wafer 1
Stage 32 made of metal (for example, made of stainless steel) for mounting the stage, a stage drive unit 33 for driving the stage 32 in the horizontal direction (X-Y direction), and the stage 3 described above.
The test wafer 1 mounted on the stage 32 is moved in the vertical direction, and the measurement electrode 2 is moved in the vertical direction to perform probeing. is there.

As shown in FIG. 1, the measuring prober 3 includes the stage 32 and the insulator 34.
A vacuum chuck 35 having an exhaust path 35a and a vacuum pump 35b formed in the above is provided, and the test wafer 1 can be closely attached to the stage 32 for chucking.

The measuring prober 3 is provided in the shield box 4 in order to eliminate the influence of noise such as electromagnetic waves.

The LCR meter 5 is a tester for measuring CV characteristics, and enables high frequency measurement of about 1 MHz in order to enable measurement in accordance with semiconductor characteristics. A sweep voltage of ± 100 V or more is used so that the capacitance including the capacitance can be measured.

The information processing device 6 evaluates the amount of charge-up based on the CV characteristics measured by the LCR meter 5.

The procedure for measuring the charge amount using the charge amount measuring device having the above structure will be described below.

First, the test wafer 1 which has not been subjected to the plasma treatment is placed on the stage 32 of the measuring prober 3 so that the measured portion 14 faces upward, and the back surface of the test wafer 1 (silicon wafer 11 ) Is in close contact with the stage 32. Further, the measurement electrode 2 is set in the measurement electrode driving unit 31 of the measurement prober 3.

Next, the High terminal side of the LCR meter 5 is connected to the measurement electrode 2, and the Low terminal side thereof is connected to the stage 32 which is the counter electrode.

Next, the test wafer 1 mounted on the stage 32 by the stage driving unit 33 of the measuring prober 3.
Are moved in the X-Y directions and set so that the measured portion 14 of the test wafer 1 is located below the measurement electrode 2.

Next, the measurement electrode driving section 31 is driven to move the measurement electrode 2 downward, and the insulation section 22 of the measurement electrode 2 is moved.
And the silicon nitride film 13 of the test wafer 1 are set in contact with each other.

At the time of probing, the electrode portion 21 of the measuring electrode 2 is set so as not to protrude from the measured portion 14 of the test wafer 1.

In the state set as described above, a minute gap (silicon nitride film of the test wafer 1) is formed between the electrode portion 21 of the measuring electrode 2 and the silicon oxide film 12 of the measured portion 14 of the test wafer 1. 13 film thickness (about 10
A gap of 00Å) will be formed. With this minute gap, it is possible to measure the capacitance of the silicon oxide film 12 without letting the charged charges of the silicon oxide film 12 on the surface of the test wafer 1 escape to the outside.

After that, the CV characteristic is measured by the LCR meter 5. That is, a bias voltage is applied between the measurement electrode 2 and the stage 32 which is the counter electrode thereof, and the capacitance C including the capacitance C _{air of air} and the capacitance C _in of the silicon oxide film 12 present in the above-mentioned minute gap. measure _all . Since the above-mentioned air capacity C _air can be calculated from the above-mentioned gap, the capacity C _in of the silicon oxide film 12 can be calculated by the following equation: 1 / C _in = (1 / C _all ) − (1 / C _air ) Can be calculated by This arithmetic processing is performed in the information processing device.

The silicon wafer 11 of the test wafer 1 of this embodiment is an n-type. In this case, if the above bias voltage is swept to the positive side and the CV characteristic is measured,
For example, a CV profile as shown by the solid line in FIG. 4 is obtained. In the case of the p-type semiconductor test wafer 1,
The bias voltage is swept to the negative side, and the CV characteristic is measured. And from the obtained C-V profile,
The flat band voltage V _fb of the test wafer 1 before plasma processing is obtained. That is, the flat band voltage V _fb is a voltage corresponding to the capacitance in the flat band state (flat band capacitance C _fb ), and the flat band capacitance C _fb can be calculated from the film thickness of the silicon oxide film 12, and therefore corresponds to it. The flat band voltage V _fb is _calculated from the CV profile.

Thereafter, the test wafer 1 is removed from the measurement prober 3 and the test wafer 1 is removed.
Using a device that tries to evaluate the charge-up amount,
Plasma processing such as ion implantation is performed.

The above-mentioned test wafer 1 which has been plasma-treated
Is again set on the measurement prober 3, and the CV characteristic is measured in the same manner as the above-described procedure performed before the plasma treatment. The C-V profile obtained at this time is shifted from the C-V profile before the process shown by the solid line by the amount of the silicon oxide film 12 charged by the plasma process, as shown by the chain line in FIG. 4, for example. To do. Then, the flat band voltage V _fb ′ (the voltage corresponding to the flat band capacitance C _fb ) of the test wafer 1 after the plasma processing is obtained from the obtained CV profile.

The difference ΔV _fb in the flat band voltage of the test wafer 1 before and after the plasma processing, which is obtained as described above, is
It is calculated by the following equation, ΔV _fb = | V _fb −V _fb ′ |. This ΔV _fb has a correlation with the charge amount, and enables highly sensitive measurement (evaluation) of the charge-up amount.

The charge amount (surface fixed charge amount) Q can be obtained by the following equation: Q = ΔV _fb × C _in In addition, C in the above formula
_in is the total capacity of the silicon oxide film 12. The above arithmetic processing is performed in the information processing device 6.

If the plasma treatment is used when the test wafer 1 is formed, the surface of the test wafer 1 is charged before the measurement is started, and an accurate charge amount cannot be measured. , Plasma processing such as plasma etching must be avoided.

As described above, the charge amount measuring apparatus of this embodiment is used for evaluating the charge-up amount of the object to be processed which is processed by the processing apparatus using the plasma processing method. 1, a silicon wafer 11 as a substrate having conductivity, a silicon oxide film 12 as an insulating film having a predetermined film thickness (about 5000 Å) formed on the silicon wafer 11, and the silicon oxide film. A silicon nitride film 13 as an insulating protective film having a predetermined film thickness (about 1000 Å) formed on 12 and removing a part of the silicon nitride film 13 to expose the silicon oxide film 12. And a surface of the test wafer 1 facing the measured portion 14 is formed in such a size that it does not protrude from the measured portion 14. When the electrode portion 21 and the outer peripheral portion of the electrode portion 21 are provided so that the electrode portion 21 does not protrude from the measured portion 14 of the test wafer 1 and the electrode portion 21 and the measured portion 14 are brought close to each other, Electrode part 21 and measured part 1
No. 4 silicon oxide film 12 and a predetermined minute gap (about 1000 Å in this embodiment) are formed so as to contact the silicon nitride film 13 of the test wafer 1 as an insulating contact portion. It is the structure provided with the measurement electrode 2 which has 22.

As a result, it is possible to form a minute gap between the electrode portion 21 and the silicon oxide film 12 of the measured portion 14 which is indispensable for the measurement of the charge amount by the CV method.
The charge-up amount can be evaluated using the C-V method, which is simpler than the conventional IV method and is capable of highly sensitive measurement.

Further, since the test wafer 1 of this embodiment does not need to have electrodes formed on its surface, it has a simpler structure than the conventional test wafer, and the number of steps for producing the test wafer is also large. It is possible to significantly reduce the number, and the test wafer 1 can be created in a short time.

As described above, by using the charge amount measuring device of this embodiment, the time required for producing the TEG and the measurement using the TEG can be significantly shortened as compared with the conventional technique, and the charge-up amount can be evaluated. Since it is possible with high accuracy, development of a processing apparatus using a plasma processing method can be smoothly proceeded.

In the above embodiment, the silicon wafer 11 is used as the substrate of the test wafer 1, but the present invention is not limited to this, and other semiconductors or conductors such as metals may be used. The insulating film of the test wafer 1 is not limited to the silicon oxide film 12, and the protective film is not limited to the silicon nitride film 13. For example, a phosphorus glass film or the like can be used as the protective film.
However, as the protective film, a film that is easily wet-etched is desirable.

In the above embodiment, the LCR meter 5 is used for measuring the CV characteristic, but a CV meter may be used. The above embodiments are merely for clarifying the technical contents of the present invention, and should not be construed in a narrow sense by limiting only to such specific examples. The spirit of the present invention and the scope of the claims It can be implemented with various modifications.

[0053]

As described above, the charge amount measuring apparatus of the present invention is formed of a conductive substrate, an insulating film having a predetermined thickness formed on the substrate, and an insulating film formed on the insulating film. A test wafer having an insulating protective film having a predetermined film thickness, which is formed by removing a part of the protective film to expose the insulating film to form a portion to be measured. The electrode portion whose surface facing the measured portion is formed so as not to protrude from the measured portion, and is provided on the outer peripheral portion of the electrode portion, and the electrode portion protrudes from the measured portion of the test wafer. Insulation that contacts the protective film of the test wafer so that a predetermined minute gap is formed between the electrode part and the insulating film of the measured part when the electrode part and the measured part are brought close to each other And a measuring electrode having a sex contact portion.

Therefore, if the electrode section and the measured section are brought close to each other so that the electrode section does not protrude from the measured section of the test wafer, the insulating contact section contacts the protective film of the test wafer. Thus, it is possible to form a minute gap, which is indispensable for the measurement of the charge amount by the CV method, between the insulating film of the measured portion of the test wafer and the electrode portion, and the withstand voltage evaluation by the conventional IV method is performed. The charge amount can be measured with high sensitivity using a simpler CV method, and the charge-up amount can be evaluated quickly and accurately. In addition, since the test wafer does not need to have electrodes formed on its surface, its structure is simpler than that of conventional test wafers, and the number of steps when creating test wafers can be greatly reduced. There is an effect that the time required can be greatly reduced.

[Brief description of drawings]

FIG. 1 is a schematic vertical sectional view showing an embodiment of the present invention and mainly showing the configurations of a test wafer and a measurement electrode of a charge amount measuring device.

FIG. 2 is a schematic configuration diagram showing an overall configuration of the charge amount measuring device.

FIG. 3 is an explanatory diagram showing a procedure for creating the test wafer.

FIG. 4 is a graph showing CV characteristics of test wafers before and after plasma processing.

FIG. 5 is a schematic vertical sectional view showing the configuration of a conventional test wafer.

FIG. 6 is an explanatory diagram showing a procedure for creating the conventional test wafer.

FIG. 7 shows I- measured using the conventional test wafer.
6 is a graph showing V characteristics.

[Explanation of symbols]

 1 Test Wafer 11 Silicon Wafer (Substrate) 12 Silicon Oxide Film (Insulating Film) 13 Silicon Nitride Film (Protective Film) 14 Measured Part 2 Measuring Electrode 21 Electrode Part 22 Insulating Part (Insulating Contact Part) 3 Prober for Measurement 4 Shield box 5 LCR meter 6 Information processing device

Claims (1)

[Claims] 1. A conductive substrate, an insulating film having a predetermined film thickness formed on the substrate, and an insulating protective film having a predetermined film thickness formed on the insulating film. A test wafer in which a portion to be measured is formed by removing a part of the protective film to expose the insulating film, and a surface of the test wafer facing the portion to be measured does not protrude from the portion to be measured. When the electrode portion and the measured portion are brought close to each other so that the electrode portion is provided on the outer peripheral portion of the electrode portion and the electrode portion does not protrude from the measured portion of the test wafer, And a measuring electrode having an insulating abutting portion that abuts the protective film of the test wafer so that a predetermined minute gap is formed between the insulating film and the insulating film of the measured portion. Charge amount measuring device.