JPH11168097A - Manufacture of semiconductor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing a semiconductor device through which the surface of silicon is nitride at low temperatures. SOLUTION: By eliminating parts of hydrogen atoms and fluorine atoms from an inactive surface which is made by terminating a part of a dangling bond 2 on a cleans surface of silicon using atoms and molecules which react with the dangling bond 2, the reactivity for exciting nitrogen in an interface between the inactive surface and an active surface is increased. In order to efficiently introduce into the surface such an interface with high reactive to excited nitrogen, a region of one active region need to be as small as possible, while at the same time, to have their number as large as possible. The maximum size of the active region is nearly the same as that of the dangling bond of silicon.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a semiconductor device, and more particularly to a method of manufacturing a semiconductor device suitable for nitriding a silicon surface at a low temperature by utilizing the activity of dangling bonds on the silicon surface.

[0002]

2. Description of the Related Art As a conventional silicon nitriding technique, a thermal nitriding method and a plasma nitriding method are known. The details of the thermal nitriding method are detailed in Kazuo Maeda: Latest LSI Process Technology, Industrial Research Committee. According to this, thermal nitridation of silicon requires a temperature of 1200 ° C. or more in a pure nitrogen atmosphere. Also, HCl
Alternatively, nitriding in a nitrogen atmosphere to which a halogen such as Cl ₂ is added has been widely put to practical use. The temperature of nitriding varies depending on the type of nitriding, but is 700 to 1300 ° C., and the partial pressure of nitrogen is 0.3.
2 to 1.0 atm. On the other hand, the plasma nitriding method is described in Applied Physics Letters, Vol. 36, pp. 999-1001, (1980) (Appl. Phys. Lett. 36, 99).
9 (1980)). According to this, nitriding at 600 ° C. is realized by plasma nitriding using ammonia gas to which a trace amount of fluorine is added.

[0003]

The silicon nitride is 700 to 1300 ° C. in the thermal nitridation method, and 600 to
At a high temperature of ℃, it is generally formed uniformly on the silicon surface. For this reason, it has been difficult to use silicon nitride as an insulating material for an electronic device having a size on the order of nanometers formed on a silicon surface. For this reason, it has been desired to control the place to be nitrided at the atomic level and to perform nitriding at a lower temperature. However,
There is a problem that the reactivity between the clean silicon surface and nitrogen decreases as the temperature decreases, and hardly reacts at room temperature.

An object of the present invention is to provide a semiconductor manufacturing method for nitriding a silicon surface at a low temperature.

[0005]

In order to achieve the above object, the present invention utilizes a dangling bond on a silicon surface. There are dangling bonds remaining unbonded on the outermost surface of clean silicon. This dangling bond is chemically active. The present invention uses excited nitrogen as a nitrogen species and terminates a part of a dangling bond on a clean silicon surface with an atom or molecule that reacts with the dangling bond in order to increase the reactivity between the excited nitrogen and the silicon surface. To make it inactive.

A dangling bond is generally terminated by a hydrogen atom or a fluorine atom. The silicon surface terminated with a hydrogen atom or a fluorine atom is chemically stable, and is inactive to excited nitrogen at room temperature. When hydrogen and fluorine atoms are partially removed from such an inactive surface to make them active, the electronic state changes greatly at the boundary between the inactive surface and the active surface, and the reactivity with nitrogen increases. .

In order to efficiently introduce such highly reactive boundaries into the surface, it is necessary to increase the number of active regions while increasing the number of active regions. The minimum size of the active region is on the order of the size of dangling bonds in silicon. The surface thus increased in reactivity reacts with the excited nitrogen even at room temperature.

By utilizing this principle, the nitriding site can be controlled by forming a dangling bond in an arbitrary shape on the silicon surface inactivated by the terminal using a scanning tunneling microscope at an arbitrary position on the surface. It is also possible. Further, by irradiating an electron beam or a particle beam or heating the silicon surface, the terminated atomic molecules can be gradually desorbed. By irradiating with excited nitrogen under such conditions, it is possible to uniformly nitride the entire silicon surface.

[0009]

(Embodiment 1) An embodiment of the present invention will be described. The STM device used in this embodiment is a ST
M. The ultimate degree of vacuum in the vacuum chamber is 6 × 10 ⁻⁹ Pa. Si (100) (n-type, 0.003 to 0.025Ωc)
m) After degassing the sample at 710 ° C. overnight, the temperature was gradually increased while repeating annealing for about 10 seconds by applying current while maintaining the degree of vacuum at 3 × 10 ⁻⁸ Pa or less. Specifically, annealing was performed several times at 1260 ° C. for about 10 seconds to obtain a clean Si (100) −2 × 1 surface, which was confirmed by STM.

The passivation treatment of the silicon surface was performed by irradiating the surface of the clean silicon with atomic hydrogen. Atomic hydrogen is
Hydrogen molecules were dissociated by a coil-shaped tungsten filament heated to 1700 ° C., and the sample was irradiated. In this embodiment, hydrogen gas of 2 × 10 ⁻⁶ Pa is introduced as a degree of vacuum in the sample preparation tank, and 3 × 10 ⁻² ML / s (1 ML is defined by the number of Si atoms on the ideal bulk termination surface) Si
6.78 × 10 ¹⁴ atoms / cm ² on the (100) plane).

The clean surface is irradiated with atomic hydrogen for 5 to 10 minutes while maintaining a constant temperature of 650 K by electric heating to adjust the hydrogen-terminated Si (100) -2 × 1 surface, and the tungsten filament is heated by electric heating. The surface condition at that temperature was quenched by turning off the power supply at the same time.

The nitridation of the hydrogen-terminated Si (100) -2 × 1 surface was performed at room temperature. Nitrogen molecules are stored in a 3 mm diameter stainless steel tube directly connected to the variable leak valve.
A nitrogen gas of 0 ^-6 Pa is introduced, and about 5
Irradiated for 1800 seconds from cm. Although it is difficult to calculate the nitrogen dose, it is estimated to be approximately 1000 to 1500 L. The silicon surface was observed by STM before and after irradiation.

FIG. 1 shows a hydrogen-terminated silicon surface before irradiation with excited nitrogen. Dangling bonds 2 are observed in some of the hydrogen-terminated dimer bond rows 1. FIG.
Shows an STM image of the silicon surface after irradiation with excited nitrogen.
Due to the irradiation of the excited nitrogen, a place different from the dangling bond 2 is observed in some parts of the dimer row 1. This is a nitride site formed by a part of dangling bond 2 reacting with excited nitrogen. The nitridation sites are found on one side of the dimer row 1 because the dangling bonds 2 are present on one side of the dimer row 2.

(Embodiment 2) The STM apparatus used in this embodiment is an STM compatible with ultra-high vacuum. The ultimate degree of vacuum in the vacuum chamber is 6 × 10 ⁻⁹ Pa. The sample used was Si (100)
(p-type, 0.015 to 0.056 Ωcm). For the sample, a Si (100) -2 × 1 clean surface was obtained in the same procedure as in Example 1, and confirmed by STM. Inactivation treatment of the silicon surface was performed in the same manner as in Example 1.

Observation of the hydrogen-terminated Si (100) -2 × 1 surface by STM revealed that dangling bonds were almost completely terminated. Next, an electron beam was irradiated under ultra-high vacuum to partially desorb the terminating hydrogen atoms. The electron beam irradiation has a current value of 0.2 mA and an irradiation time of 23.
It was 0 seconds. Electron beam irradiation was performed at a fixed spot at the center of the sample. The spot diameter is unknown. When the surface after electron beam irradiation was observed by STM, dangling bonds were formed at a density of about 10%. Subsequently, the surface at room temperature was irradiated with excited nitrogen. Irradiation with excited nitrogen was performed in the same manner as in Example 1. Irradiation amount is 1000-1300L
It is estimated to be. STM observation was performed under the same conditions as in Example 1.
As a result, almost half of the dangling bonds were nitrided by the irradiation of the excited nitrogen.

(Embodiment 3) The STM apparatus used in this embodiment is an STM compatible with ultra-high vacuum. The ultimate vacuum of the STM tank and the sample preparation tank is 6 × 10 ⁻⁹ Pa. The sample used was Si (100) (p-type, 0.15 to 0.25 Ωcm). In the same procedure as in the sample example 1, Si (100) -2 was used.
× 1 clean surface was obtained and confirmed by STM. Inactivation treatment of the silicon surface was performed in the same manner as in Example 1.

Using a scanning tunneling microscope, hydrogen atoms were linearly desorbed over a length of 50 nm along a dimer array on the hydrogen-terminated Si (100) -2 × 1 surface. S
Observation of this dangling bond wire with TM revealed that dangling bonds and dangling bond pairs were mixed. Next, the sample was irradiated with excited nitrogen while being heated to 70 ° C. The irradiation amount is estimated to be 10 to 15 L. Irradiation with excited nitrogen was performed in the same manner as in Example 1. As a result of observing the place where the dangling bond row was located by STM, almost the same place was linearly nitrided.

[0018]

According to the present invention, it is possible to provide a semiconductor manufacturing method for nitriding a silicon surface at a low temperature. Further, according to the method of the present invention, a dangling bond is formed in an arbitrary shape on an arbitrary position on the surface of the silicon surface inactivated by the terminal using a scanning tunneling microscope,
It is also possible to control the nitriding sites. In addition, irradiation of electron beam and particle beam, heating of silicon surface, etc.
By irradiating with excited nitrogen under such conditions that the terminated atomic molecules are gradually desorbed, it is also possible to uniformly nitride the entire silicon surface.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing an STM image of a hydrogen-terminated silicon surface.

FIG. 2 is a schematic view showing an STM image of a silicon surface irradiated with excited nitrogen.

[Explanation of symbols]

Reference numeral 1 denotes a hydrogen-terminated dimer bond row, 2 denotes a dangling bond, and 3 denotes a nitrided dangling bond.

Claims (4)

[Claims] An excitable nitrogen is irradiated on the silicon surface in a state where a part of the dangling bond on the silicon surface is terminated by a molecule or atom that reacts with the dangling bond, so that a dangling bond on the silicon surface is formed. A method for manufacturing a semiconductor device, wherein a position of a ring bond is selectively nitrided. 2. The method according to claim 1, wherein the nitrogen on the silicon surface is irradiated with nitrogen in an excited state while maintaining the temperature of the silicon surface within a temperature range in which the dangling bond and the atomic molecules can be stably bonded. A method for manufacturing a semiconductor device, wherein a position of a ring bond is selectively nitrided. 3. An excited state while gradually removing atomic molecules terminating dangling bonds by means of electron beam, particle beam, light irradiation, substrate heating and the like. A method for manufacturing a semiconductor device, comprising: irradiating a certain nitrogen to selectively nitride a dangling bond on a silicon surface. 4. The method of claim 1, wherein (100)
A method for manufacturing a semiconductor device, wherein a dangling bond on a surface is terminated with any of a hydrogen atom, a deuterium atom, a fluorine atom, and a chlorine atom.