JPH04273142A - Ion implantation monitoring method - Google Patents

Abstract

PURPOSE:To provide a method which can enhance a dose monitoring efficiency in a high dose region and reduce production cost by enabling the reapplication of TP. CONSTITUTION:This monitoring method comprises a step to form an oxide film on an implantation board, a step to implant ions on the board by way of the oxide film, a step to measure the amount of dose using a thermal probe process, a step to eliminate the oxide film formed on the board after the measurement of the amount of dose, a step to heat-treat the board from which the oxide film is removed, and a step to form an oxide film again on the board.

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 implanter. In recent years, ion implantation techniques have become essential to semiconductor device manufacturing processes;
Moreover, accurate dose monitoring technology is becoming necessary.

0002

[Prior Art] Conventional dose monitoring technology relies on a method of measuring the sheet resistance of an ion-implanted measurement sample (TP) for high-dose regions (dose of 1x1014 cm-2 or more); The measurement value is large in the dose region (dose amount is 1 x 1014 cm -2 or less), and there is a problem in that it cannot follow changes in the dose.

[0003]Recently, since the appearance of the thermal probe method, TP can be completed in a short time of about 10 minutes for low dose regions.
The results are now known. The thermaprobe method is the thermaprobe (product name DTHERMA-PRO).
BE 300, Manufacturer THERMA-WAVE I
nc. ) is used to optically measure crystal defects based on ion-implanted impurities and convert this into a dose, so there is no need to TP annealing, and it is a non-destructive measurement method. It's simple.

On the other hand, conventional sheet resistance measurements performed on high-dose regions are based on ion-implanted T
Because the P is annealed, the oxide film (SiO2 film in the case of silicon) is removed, and the measurement is performed using a four-point needle measuring device, it takes 3 to 4 hours before the results are known.
It takes time. Moreover, this is a destructive method and the TP cannot be reused.

[0005]

[Problem to be Solved by the Invention] For this reason, the thermaprobe method should naturally be applied to high-dose regions as well. However, the impurity concentration range that can be measured using the thermaprobe method is approximately 1x1014 cm in dose.
-2 or less, making it impossible to use the thermaprobe method for monitoring high-dose regions.

[0006] Therefore, the purpose of the present invention is to provide a method that improves the efficiency of dose monitoring by applying the thermal probe method even to high dose regions, and further reduces costs by reusing TP. It is also a contribution.

[0007]

[Means for solving the problem] The above problem is solved by forming an oxide film on an implanted substrate (TP), implanting ions into the substrate through the oxide film, and controlling the dose using the therma probe method. How to measure and after measuring the dose,
Remove the oxide film on the substrate, then heat treat it,
The problem can be solved by forming an oxide film on the substrate again and using it as TP again.

FIG. 1 is a diagram explaining the principle of the present invention. In the figure, the solid line indicates the impurity concentration distribution when a high dose of impurity ions is implanted into a silicon substrate on which a silicon oxide film (SiO2 film) is formed. Also, the dotted line is S
It shows the impurity concentration distribution when high-dose impurity ions are implanted into a silicon substrate without an iO2 film under similar conditions. When there is a SiO2 film, the amount of impurities implanted into the silicon substrate is reduced by more than an order of magnitude compared to when there is no SiO2 film. Therefore, since this condition is within the range that can be measured by the therm probe, monitoring using the therm probe can be carried out.

[0009]

[Operation] It is known that the diffusion coefficient of impurities in a SiO2 film is smaller than that in a silicon substrate. Therefore, the SiO2 film has the property of a dose trap that traps the implanted ions, and most of the ions are trapped in the SiO2 film, reducing the amount implanted into the silicon substrate.

[0010] The amount of impurities trapped in the SiO2 film depends on the implantation energy and the thickness of the SiO2 film.
Therefore, the thickness of the SiO2 film is set so that a low dose is implanted into the silicon substrate using conventional implantation energy. By setting the thickness of the SiO2 film in this manner, even in the case of high-dose implantation, the actual dose implanted into the silicon substrate becomes low. Therefore, in this case, measurement using the thermaprobe method becomes possible.

[0011] Figure 2 shows the Si
FIG. 4 is an explanatory diagram of a case where the thickness of the O2 film is inappropriate. Figure 2
(a) shows the impurity concentration distribution when all high-dose impurities are implanted into the silicon substrate. Figure 2(b) shows how when the impurity concentration distribution is as shown in Figure 2(a), the output (TW) of the thermal probe becomes unstable and is no longer proportional to the dose when it exceeds a certain dose. It shows.

[0012] Figure 3 shows the Si
FIG. 4 is an explanatory diagram when the thickness of the O2 film is appropriate. Figure 3(a)
shows the impurity concentration distribution when most of the high-dose impurities are trapped in the SiO2 film and a small amount of impurities are implanted into the silicon substrate. Figure 3 (
Figure 3b) shows how the output (TW) of the thermal probe is proportional to the dose when the impurity concentration distribution is as shown in Figure 3(a). Such a case is the case of the present invention, in which high dose monitoring is performed by the thermaprobe method. Generally, the diffusion coefficient of impurities is smaller in the oxide film of the substrate than in the substrate, so the above also applies to combinations of substrates other than silicon and their oxide films.

[0013]

[Embodiment] An embodiment of the present invention will be explained. p type,
After performing normal surface cleaning on a silicon wafer with a specific resistance of 15 Ωcm, SiO2 with a thickness of approximately 100 nm is deposited on the surface of this silicon wafer using a normal thermal oxidation method.
Forms a film.

This wafer was subjected to high-dose ion implantation TP.
Use as. For this TP, boron ion (B
+) with an energy of 15KeV and a dose of 2x1
Injection is performed at 015. Thereafter, this TP is measured by the thermaprobe method. Since the output of the therma probe is calibrated in advance to the implantation dose, the dose can be obtained immediately from the output of the therma probe. After ion implantation, it takes 20 to 40 minutes to obtain a dose value. In this way, high dose monitoring is performed by measuring TP using the thermaprobe method.

[0015] This TP SiO2 film was removed with hydrofluoric acid,
This is then annealed at 900°C to 1000° for about 30 minutes in a vacuum or inert gas atmosphere to remove crystal defects caused by ion implantation.
If an oxide film similar to the above is formed again, this will become a new T.
It can be reused as P. Furthermore, TP's S
It is also possible to leave the iO2 film without removing it, perform similar annealing in an inert gas atmosphere, and reuse it as a new TP.

[0016]

[Effects of the Invention] According to the present invention, the time required to obtain TP measurement results is shortened to 1/5 of the conventional method, and the efficiency of high-dose ion implantation monitoring is greatly improved. Additionally, since TP can be reused, it greatly contributes to cost reduction.

[Brief explanation of the drawing]

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

FIG. 2 is an explanatory diagram when the thickness of the SiO2 film is inappropriate for the implantation energy.

FIG. 3 is an explanatory diagram when the thickness of the SiO2 film is appropriate for the implantation energy.

Claims (2)

[Claims] Claim 1. A dose monitoring method for high-dose ion implantation, which comprises: forming an oxide film on an implantation substrate; implanting ions into the substrate through the oxide film; and controlling the dose using a thermaprobe method. A dose monitoring method comprising the step of measuring the amount. 2. A dose monitoring method for high-dose ion implantation, further comprising: after measuring the dose, removing an oxide film formed on the substrate; and heat-treating the substrate from which the oxide film has been removed. 2. The dose monitoring method according to claim 1, further comprising the steps of: forming an oxide film on the substrate again.