JP2626275B2 - Ion implantation monitoring method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for managing an ion implantation apparatus. In recent years, ion implantation techniques are indispensable for the semiconductor device manufacturing process, and for that purpose, fast and accurate dose monitoring technology is required.

[0002]

2. Description of the Related Art The conventional dose monitoring technique is based on a method of measuring the sheet resistance of an ion-implanted measurement sample (TP) in a high dose region (dose amount of 1 × 10 ¹⁴ cm ⁻² or more). Low dose area (dose is 1x10 ¹⁴
(cm ^-2 or less), the measured value was large, and there was a drawback that the dose could not be followed.

[0003] Recently, the results of TP have been found in a short time of about 10 minutes for a low dose region since the advent of the therma probe method. Therma probe method is therma probe (trade name DTHERMA-PROBE 300, manufacturer THER
MA-WAVE Inc.) is a method of optically measuring the crystal defects based on the ion-implanted impurities and converting them into doses. Therefore, there is no need to perform TP annealing, and nondestructive It is a measuring method and simple.

On the other hand, in the conventional measurement of the sheet resistance performed for a high dose region, the ion-implanted TP is annealed, and then an oxide film (in the case of silicon, SiO _{2 is used).}
It takes 3 to 4 hours for the results to be determined, after removal of the film, to measure with a four-point needle meter.
Moreover, this is a destructive method and TP cannot be reused.

[0005]

Therefore, the thermistor probe method should be applied to a high dose region. However, the measurable impurity concentration range in the therma-probe method was about 1 × 10 ¹⁴ cm ^-2 or less, and therma-probe method could not be used for monitoring high dose regions.

Accordingly, an object of the present invention is to provide a method for improving the efficiency of dose monitoring by applying therma probe method even to a high dose region.
It also contributes to cost reduction by reusing TP.

[0007]

SUMMARY OF THE INVENTION The above object is achieved by an ion
The oxide film formed on the substrate (TP) for injecting, the oxide film
The output of the thermal probe is proportional to the dose.
And sea urchin set, ions are implanted into the substrate through the oxide film, Sa - Mapuro - injected into the substrate by using the blanking method Io
Emissions of de - How to measure the amount's and, de ions - the amount's
After the measurement, the oxide film formed on the substrate was further removed, and the substrate from which the oxide film had been removed was heat-treated .
Thereafter, an oxide film is formed again on the substrate, and the thickness of the oxide film is
Is set so that the output of the thermal probe is proportional to the dose.
Constant, and is solved again, by a method utilizing as a TP.

FIG. 1 is a diagram illustrating the principle of the present invention. In the figure,
The solid line shows the impurity concentration distribution when a high dose impurity ion implantation is performed on a silicon substrate on which a silicon oxide film (SiO2 film) is formed. The dotted line shows the impurity concentration distribution when a high dose of impurity ions is implanted into a silicon substrate having no SiO2 film under the same conditions. If there is a SiO ₂ film, the impurity implanted into the silicon substrate is Si
Compared to the case without the O ₂ film, the number is reduced by one digit or more. Therefore,
Since this state is within the range that can be measured by therma probe, monitoring by therma probe can be performed.

[0009]

It is known that the diffusion coefficient of impurities in a SiO ₂ film is smaller than that in a silicon substrate. Therefore, Si
The O ₂ film has the property of a dose trap that traps the implanted ions, and most of the ions are trapped by the SiO ₂ film and injected into the silicon substrate in a small amount.

[0010] The amount of impurities trapped in the SiO ₂ film, implantation energy - depends on the thickness of the SiO ₂ film.
Therefore, the thickness of the SiO ₂ film is set so that a low dose is implanted into the silicon substrate with the usual implantation energy. To set the thickness of the SiO ₂ film in this way
I, the high de - de injected into practice silicon substrate even in the case of FIG injection -'s weight low de - becomes's. Therefore, in this case, measurement by the thermal probe method becomes possible.

FIG. 2 is an explanatory diagram in the case where the thickness of the SiO ₂ film is inappropriate for the implantation energy. FIG. 2 (a) shows an impurity concentration distribution in a case where a high dose impurity is entirely implanted into a silicon substrate. Fig. 2 (b) shows that when the impurity concentration distribution is as shown in Fig. 2 (a), the output (TW) of the thermistor becomes unstable when it exceeds a certain dose, and becomes in proportion to the dose. Is shown.

FIG. 3 is an explanatory diagram in the case where the thickness of the SiO ₂ film is appropriate for the implantation energy. FIG. 3 (a) shows the impurity concentration distribution when most of the high-dose impurities are trapped in the SiO ₂ film and a small amount of impurities is implanted into the silicon substrate. FIG. 3 (b) shows how the output (TW) of the therma probe is proportional to the dose when the impurity concentration distribution is as shown in FIG. 3 (a). Such a case is the case of the present invention in which high dose monitoring is performed by therma probe method. In general, since the diffusion coefficient of impurities is smaller in the oxide film of the substrate than in the substrate, the above-mentioned matter also applies to a combination of a substrate other than silicon and its oxide film.

[0013]

An embodiment of the present invention will be described. After performing normal surface cleaning on a silicon wafer having a p-type resistivity of 15 Ωcm, an SiO ₂ film having a thickness of about 100 nm is formed on the surface of the silicon wafer by a normal thermal oxidation method.

This wafer is used as a TP for high dose ion implantation. Boron ions (B ⁺ ) are implanted into the TP at an energy of ¹⁵ KeV and a dose of 2 × 10 ¹⁵ . Then, this TP is measured by therma probe method. Since the output of the therma probe is previously calibrated to the dose of the injection, the dose can be obtained immediately from the output of the therma probe. After ion implantation, the time until the dose value is obtained is 20 minutes to 40 minutes.
Thus, high dose monitoring is performed by measuring TP by therma probe method.

The SiO ₂ film of the TP is removed with hydrofluoric acid.
900 ° C in a vacuum or inert gas atmosphere
Annealing at ~ 1000 ° for about 30 minutes to remove crystal defects caused by ion implantation and forming an oxide film similar to the above can be reused as a new TP. Further, the same annealing can be performed in an inert gas atmosphere, leaving the SiO ₂ film of the TP without removing it, and this can be reused as a new TP.

[0016]

According to the present invention, the time until the measurement result of TP becomes clear is reduced to 1/5 of the conventional case, and the efficiency of high dose ion implantation monitoring is remarkably improved. In addition, TP can be reused, which greatly contributes to cost reduction.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating the principle of the present invention.

FIG. 2 is an explanatory diagram in a case where the thickness of an SiO ₂ film is inappropriate for implantation energy.

FIG. 3 is an explanatory diagram in a case where the thickness of an SiO ₂ film is appropriate for implantation energy.

Claims (2)

(57) [Claims] 1. A high de - Zuion injection de - in's monitoring method, to form an oxide film on the substrate implanting ions, the oxide film
Adjust the thickness so that the output of the thermal probe is proportional to the dose.
And ion implantation into the substrate through the oxide film, and measuring the dose of the ions implanted into the substrate by using a thermal probe method. A dose monitoring method comprising the steps of: 2. A high de - Zuion injection de - in's monitoring process, de ions - after the step of measuring's weight, further, removing the oxide film formed on the substrate, wherein after heat treatment the substrate when the oxide film is removed again, an oxide film is formed on the substrate, support the thickness of the oxide film - Mapuro
Setting the output of the probe so as to be proportional to the dose .