JPH04154143A - Method of measuring charged-up amount - Google Patents

Abstract

PURPOSE:To measure a charged-up amount accurately by measuring an electrical change amount corresponding to the accumulated amount of charged particles of a MOS capacitor in which a film having a polarization-holding property has been formed between an oxide film and a gate electrode for the capacitor. CONSTITUTION:A capacitor having the following structure is formed: a field oxide film 2 and a gate oxide film 3 are formed on an N-type Si substrate 1; and a phosphosilicate glass(PSG) film 4 is provided between the film 3 and a gate electrode 5. A charged-up amount corresponding to the accumulated amount of charged particles by an implantation operation is measured.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for optimizing a manufacturing process of a semiconductor device, and particularly to a method for measuring a charge-up amount.

[Conventional technology]

Conventionally, as a method for measuring the amount of charge-up, for example,
Monthly Semiconductor World (Se+n1konduc)
tor%1orld), 1987.11. P31-37
MNOS (Metal, N1
Using a capacitor with a trideOxideSil 1con) structure as a measurement means,
There is a method that measures the amount of charge-up during plasma processing.

FIG. 6 is a cross-sectional view showing the structure of a semiconductor device for explaining a conventional method for measuring the amount of charge-up. The method for measuring the charge-up amount is, for example, as shown in FIG. When the potential is positive, due to the electric field caused by charge-up, electrons in the Si substrate 1 tunnel through the gate oxide film 3 as thin as 2 nm and form the gate oxide film 3 and the nitride film 7.
trapped at the interface. Therefore, when measuring the C-■ characteristics of the MNOS capacitor before and after plasma treatment,
After plasma treatment, characteristics that are positively shifted compared to before treatment are obtained. Therefore, by determining the shift amount (ΔVpe) of the flat band voltage of this MNOS capacitor, charge-up during plasma processing can be evaluated. That is, in the case of positive charge-up, it is measured as Δ■FB>0, and in the case of negative charge-up, it is measured as ΔVpa<O.

FIG. 7 is a schematic cross-sectional view of a memory element for explaining another example of the conventional method for measuring the amount of charge-up. FIG. 8 is a diagram showing the control gate voltage dependence of Δvth in the memory element of FIG. . A method for measuring the charge-up amount other than the one described above is, for example, a method using an electrically writable memory element shown in FIG. 7, as disclosed in Japanese Patent Laid-Open No. 1-69025. Another method for this method is to perform a manufacturing process on a semiconductor substrate and then measure the amount of electrical change depending on the amount of accumulated charged particles to measure the amount of charge-up.

That is, in the memory element shown in FIG. 7, if the control game 12 is 10 V and the drain region 8 is ○■, then
An electric field is applied to tunnel oxide film 9 and a tunnel current flows. As a result, electrons are injected from the train region 8 into the floating gate 10. At this time, the threshold voltage vth of the n-channel MOS transistor 11 shifts positively depending on the amount of injected electrons. Conversely, when the control gate 12 is set to 1 and the drain region 8 is set to 0, electrons are emitted from the floating gate 10, and vth of the n-channel transistor 11 shifts to the negative side. That is,
The amount of charge-up is measured by the amount of shift of this vth (Δvth>).

[Problem to be solved by the invention]

However, the conventional charge-up amount measuring method described above has the following problems. First, the former MNO3
In the method of using a structured capacitor in a measurement device, electrons in the Si substrate tunnel through a thin tunnel oxide film and become trapped at the interface between the oxide film and nitride film due to the electric field generated by the gate electrode where charge-up occurs. Therefore, that ΔVPB
is measured, but if the potential difference between the charged-up gate electrode and the Si substrate increases beyond a certain value, the thin tunnel oxide film will be destroyed, making it impossible to monitor the amount of charge-up using ΔvpB. . In addition, in the latter method using a nonvolatile memory element having a floating gate, the relationship between the control gate voltage and Δvth is as shown in FIG. The problem was that it was not observed.

An object of the present invention is to provide a method for measuring the amount of charge-up that solves this problem.

[Means to solve the problem]

The charge-up amount measurement method of the present invention uses a capacitor having a structure in which a polarization retaining film is formed between an oxide film of a MOS capacitor formed on a silicon substrate and a gate electrode in a semiconductor device manufacturing process. After application, the amount of charge-up is measured by measuring the amount of electrical change depending on the amount of accumulated charged particles.

〔Example〕

Next, the present invention will be explained with reference to the drawings.

FIG. 1 is a cross-sectional view of a semiconductor device for explaining an embodiment of the charge-up amount measuring method of the present invention. As shown in FIG. 1, the semiconductor device used in this charge-up measurement method has a field oxide film 2 and a gate oxide film 3 formed on an N-type silicon substrate 1. The capacitor has a structure in which a phosphosilicate glass (hereinafter abbreviated as PSG) film 4 is provided between the gate electrode 5 and the gate electrode 5.

FIG. 2 is a diagram showing the results of optimization evaluation of ion implantation conditions using the semiconductor device of FIG. 1. When the optimization evaluation of ion implantation conditions, which is one process, was performed using the semiconductor device having the capacitor structure described above, the results shown in FIG. 2 were obtained. The implanted ions at this time were arsenic (As) acceleration energy of 70 keV and dose of 5.
E15''-''The beam current was kept constant, and the electron Java current was used as a parameter. Also, M shown in Figure 6
When ions were implanted into a NO8 structure capacitor under the same conditions, the tunnel oxide film was destroyed.

From the results shown in Figure 2, the electro Java current is
For example, if the beam current is set to less than twice the beam current, a charge-up will occur due to the positive charge of the ion beam, and
If it is about 25 times or more the electro Java current, charge-up due to negative charges of electrons will occur. Furthermore, it can be seen that setting the electron Java current to about twice the beam current is the optimum condition where the positive ions and negative electrons are electrically neutralized, resulting in less charge-up.

FIG. 3 is a diagram showing the No dependence of VFR in the semiconductor device of FIG. 1. Furthermore, as shown in Fig. 3, ΔvFB gate voltage (■0) dependence of this capacitor is shown.
■FB and V. It can be seen that there is a proportional relationship and that if charge-up occurs, it can be measured by ΔVFB.

FIG. 4 is a sectional view of a semiconductor device for explaining another embodiment of the charge-up amount measuring method of the present invention. As shown in the figure, the capacitor structure of the semiconductor device used in this method of measuring the charge-up amount is such that an electrode 6 having an area several orders of magnitude larger than the gate area is connected to the gate electrode 5. Therefore, the electric field due to the charges collected on the electrode 6 is
Since the membrane 4 is polarized, the sensitivity to charge-up can be increased compared to the previous embodiment.

Figure 5(a) is a plan view of the semiconductor substrate as the object to be measured, and Figure 5(b) is the measurement of each point from the center of the semiconductor substrate in Figure 5(a) using the semiconductor device in Figure 6. 5 is a diagram showing the results and the measurement results using the semiconductor device of FIG. 4. FIG. Therefore, an experiment was conducted to compare charge-up evaluation during plasma processing, which has less charge-up than ion implantation, between the semiconductor device of this embodiment and the case where a conventional non-volatile memory element is used. Here, the horizontal axis X in FIG. 5(b) represents the distance from the center of the semiconductor substrate to the measurement point shown in FIG. 5(a).As can be seen from this result, in the past, electrical changes Even points that cannot be observed as quantities can be observed in this example. In the embodiments described above, the film formed between the gate oxide film and the gate electrode of the capacitor is a PSG film, but other materials with polarization retention properties such as boron glass, arsenic glass, boron-phosphorous glass, etc. It is clear that similar effects can be obtained if the substrate used in the present invention is a semiconductor substrate such as a P-type silicon substrate, gallium, arsenic substrate, etc. in addition to an N-type silicon substrate. It is.

〔Effect of the invention〕

As explained above, the present invention has a capacitor structure in a semiconductor device for measuring the amount of charge-up so that the polarization-retaining film is polarized by the electric field received from the charged-up gate electrode, and when the electric field is removed. Since it is possible to maintain the polarized state of the capacitor, the C-■ characteristic of the capacitor can be shifted according to the amount of charge-up, so by determining the amount of shift ΔVFB, the charge-up in the manufacturing process of semiconductor devices can be reduced. This has the effect of providing a method for measuring the charge-up amount that can accurately measure the charge-up amount.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of a semiconductor device for explaining an embodiment of the charge-up amount measuring method of the present invention, and FIG. 2 is a cross-sectional view of a semiconductor device for explaining an embodiment of the charge-up measurement method of the present invention. FIG. FIG. 3 is a diagram showing the dependence of ΔVPB on G in the semiconductor device of FIG. 1, and FIG. Figure 6 shows the measurement results of each point from the center of the semiconductor substrate in a) using the semiconductor device in Figure 6 and the semiconductor device in Figure 4. Figure 6 shows the conventional method for measuring the amount of charge-up. A cross-sectional view of a semiconductor device for explaining an example of
FIG. 7 is a schematic cross-sectional view of a memory element for explaining another example of the conventional method for measuring the amount of charge build-up, and FIG. 8 is a diagram showing the control gate voltage dependence of Δvth in the memory element of FIG. 7. . DESCRIPTION OF SYMBOLS 1... N-type silicon substrate, 2... Field oxide film, 3... Gate oxide film, 4... PSG film, 5...
Gate electrode, 6... Nitride film, 7... Electrode, 8...
Drain region, 9... tunnel oxide film, 10... floating gate, 11... n channel transistor, 12... control gate.

Claims (1)

[Claims] After a capacitor with a structure in which a polarization-retaining film is formed between the oxide film of a MOS capacitor formed on a silicon substrate and a gate electrode is applied to a semiconductor device manufacturing process, it is A method for measuring a charge-up amount, characterized in that the charge-up amount is measured by measuring the amount of electrical change.