JP2553556B2 - Impurity doping method and apparatus - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a doping apparatus for doping a surface of a silicon substrate with a desired impurity, and more particularly to an impurity doping for automatically measuring an impurity doping amount and accurately controlling the doping amount. The present invention relates to a method and an apparatus thereof.

2. Description of the Related Art In recent years, shallow junction formation has been required along with high integration of integrated circuits, and plasma doping has attracted attention as a new impurity doping method in place of conventional heat dissipation and ion implantation.

An example of the above plasma doping will be described below with reference to the drawings. FIG. 4 shows a schematic view of the plasma doping apparatus. In FIG. 4, 1 is a vacuum container. 2 is a piezo-electrode for plasma generation. 3 is a power source of the plasma generation source (either a high frequency power source or a DC power source may be used). Reference numeral 4 is a gas containing impurities as a doping source. An exhaust port 5 is connected to an exhaust system (not shown). 6 is an object to be processed on a silicon substrate.

The operation of the plasma doping apparatus configured as above will be described below.

First, the inside of the vacuum container 1 is evacuated through an exhaust port 5 connected to an exhaust system (not shown). Next, the inside of the vacuum container 1 is set to a constant pressure while flowing a constant amount of the gas 4 containing impurities as a doping source. Next, power is supplied to the plasma generation electrode 2 from the power source 3 of the plasma generation source to generate plasma between the plasma generation electrodes 2 and the silicon substrate 6 is doped with impurities. (For example, Semiconductor World, "Semiconductor World" Vol. 6, No. 2, pp. 90-92) Problems to be Solved by the Invention However, in the above-mentioned configuration, there is no means for measuring the doping concentration of impurities, so that the doping process is performed. After that, the process conditions were determined from the results of sheet resistance measurement and SIMS analysis measurement on the surface of the silicon substrate, and the plasma doping process was performed by time control. Therefore, there is a problem that the doping concentration of impurities cannot be monitored in-process, and a certain amount of impurities cannot be doped with good reproducibility.

In view of the above-mentioned conventional problems, the present invention provides an impurity doping method and an apparatus for performing the in-process measurement of the impurity doping concentration and accurately controlling the doping concentration.

Means for Solving the Problems In order to solve the above problems, the impurity doping method according to the first invention of the present invention measures the amount of ions in a gas plasma with a probe having a negative potential to dope a silicon substrate. The amount monitored is monitored.

In the impurity doping apparatus of the second invention of the present invention, a probe having a negative potential is arranged in the plasma of the doping apparatus, a means for detecting an ion current flowing through the probe and a detection output required to obtain a desired doping amount. A means for calculating the processing time and outputting a doping end signal is provided.

According to the first aspect of the present invention, the doping concentration of impurities is monitored in-process by correlating the saturated ion current collected in the probe having a negative potential and the concentration of impurities doped on the surface of the silicon substrate. However, it is possible to dope a certain amount of impurities with good reproducibility.

Further, according to the second invention, by arranging the probe of negative potential in the plasma, it is possible to detect the saturated ion current in the plasma, calculate the processing time accordingly, and output the doping end signal, By stopping the impurity doping by this signal, desired doping can be performed with good reproducibility.

Example An example of the present invention will be described below with reference to the drawings.

FIG. 1 is a schematic diagram of a plasma doping apparatus according to an embodiment of the present invention. 1 to 6 in FIG.
Is similar to the conventional example of FIG. 7a is a probe that collects positive ions. 7b is an insulating tube that protects the probe 7a. Reference numeral 8 is a DC power supply that gives a negative potential to the probe 7a.
9 is an ammeter. 10 is a voltmeter. 11 is probe 7a
It is an arithmetic processing unit that calculates the concentration of impurities to be doped on the surface of the silicon substrate 6 from the saturated ion current value collected in the above and stops the power supply 3 of the plasma generation source.

The operation of the plasma doping apparatus configured as described above will be described below with reference to FIGS. 1, 2, and 3.

First, FIG. 2 shows a change in current value when the potential applied from the DC power source 8 to the probe 7a in plasma is changed, and Ii in FIG. 2 is a saturated ion current in plasma. This Ii can be measured by applying a constant negative potential to the probe 7a shown in FIG.

FIG. 3 shows the relationship between the above Ii and the concentration of impurities doped on the surface of the silicon substrate 6.

The gas containing impurities used was B ₂ H ₆ / He, and Ii was changed by changing the gas pressure in the vacuum chamber 1 and the high-frequency power (13.56 MHz) used as the power supply 3 of the plasma generation source. It was The doping time was fixed at 10 minutes.

As described above, according to the present embodiment, a probe having a negative potential is inserted into the plasma generation region of the conventional plasma doping apparatus, and the saturated ion current (Ii) in the plasma is measured, thereby doping the surface of the silicon substrate. While monitoring the in-process impurity concentration,
It is possible to dope a certain amount of impurities with good reproducibility. Further, since the impurity doping concentration is proportional to the product of the saturated ion current and the doping time, even if the saturated ion current fluctuates, the doping by the arithmetic processor 11 of FIG. It can be controlled by performing integration of. (A is a proportional constant).

That is, when the desired doping concentration is reached, a doping end signal is output and the device can be stopped. Although the high frequency power source is used as the power source 3 of the plasma generation source in the embodiment, the power source 3 of the plasma generation source may be a DC power source or an AC power source. In the embodiment, the probe 7a is Pt.
Although a single probe made of is used, the probe 7a may be made of any material as long as it can measure a saturated ion current in plasma.

As described above, according to the impurity doping method of the present invention, by measuring the saturated ion current in plasma, the concentration of impurities doped on the surface of a silicon substrate is monitored in-process, and the impurity concentration is constant with good reproducibility. An amount of impurities can be doped.

Further, according to the impurity doping apparatus of the present invention, since the processing time required to reach a predetermined doping amount is calculated and the doping end signal is output, the impurity doping is stopped by the signal and desired doping can be performed with good reproducibility. It can be carried out.

[Brief description of drawings]

FIG. 1 is a schematic diagram of a plasma doping apparatus according to an embodiment of the present invention, FIG. 2 is a diagram showing voltage-current characteristics with respect to a probe in plasma, and FIG. 3 is a saturated ion current in plasma and the surface of a silicon substrate. FIG. 4 is a schematic diagram of a conventional plasma doping apparatus, which shows a relationship between doped impurity concentrations. 1 ... vacuum container, 2 ... electrodes for plasma generation, 3 ...
Power supply for plasma generation, 4 ... Gas containing impurities to be doped, 5 ... Exhaust port, 6 ... Silicon substrate, 7a ...
… A probe with a negative potential, 11… A processor.

Claims (2)

(57) [Claims] 1. A method of doping impurities on a surface of a silicon substrate using gas plasma, comprising measuring the amount of ions in the gas plasma with a probe having a negative potential and monitoring the amount of doping in the silicon substrate. Characteristic impurity doping method. 2. A plasma doping apparatus comprising a vacuum container, an electrode for generating plasma, a power source, a gas introduction system for introducing and exhausting a gas containing impurities to be doped into the vacuum container, and an exhaust system. A negative potential probe is disposed in the probe, means for detecting an ion current flowing through the probe and means for calculating a processing time required for a desired doping amount by this detection output and outputting a doping end signal are characterized by Impurity doping apparatus.