JPH0142618B2 - - Google Patents

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention relates to a method for manufacturing a semiconductor crystal thin film,
In particular, the present invention relates to a method of manufacturing a semiconductor crystal thin film, in which a polycrystalline or amorphous semiconductor thin film deposited on a substrate is crystallized by irradiation with a high-energy beam.

[Technical background of the invention and its problems]

As is well known, miniaturization of the elements of two-dimensional semiconductor devices to increase their integration and speed is nearing its limit, and for this reason so-called three-dimensional semiconductor devices in which elements are formed in multiple layers have been proposed. There is. The most important question in realizing a three-dimensional semiconductor device is how to form a high quality semiconductor film on an insulating film. To solve this problem, a beam annealing method has been proposed in which a polycrystalline or amorphous semiconductor thin film on a substrate is scanned while being irradiated with a high-energy beam to obtain a polycrystalline or single-crystalline semiconductor thin film with large grains.

In conventional methods, the substrate is left at room temperature or kept at a high temperature by applying a certain amount of heat while being irradiated with a high-energy beam. When beam annealing is performed while the substrate is left at room temperature, the point irradiated with the beam reaches the melting temperature of the semiconductor, as shown in Figure 1, but the temperature of the end of the substrate far away from it is close to room temperature, and the temperature of the substrate is close to room temperature. There is a large temperature gradient above. For this reason, temperature non-uniformity is large near the point where the beam is irradiated, making it difficult to grow coarse crystal grains. As the beam is continuously irradiated, the temperature near the beam irradiation point gradually increases, leading to the risk that the semiconductor thin film will not only melt but also evaporate, and further damage the substrate.

As a solution to this problem, a method has recently been proposed in which beam annealing is performed by raising the temperature of the substrate to which the beam is irradiated to about 500 degrees Celsius. In this method, as shown in FIG. 2, since the temperature gradient on the substrate is reduced, it is possible to grow relatively coarse crystal grains. However, since the substrate is heated with a constant amount of heat even during beam irradiation, the temperature near the beam irradiation point gradually increases, making it difficult to uniformly anneal a wide area on the substrate.

[Purpose of the invention]

An object of the present invention is to provide a method for manufacturing a semiconductor crystal thin film that can perform uniform annealing over a wide area and can form high-quality polycrystals or single crystals on a substrate by beam annealing. be.

[Summary of the invention]

The gist of the present invention is to detect with high precision the temperature of a semiconductor thin film at a point irradiated with an energy beam, and to control the amount of heat applied to the thin film in accordance with the detected temperature.

There are various means for non-contact detection of semiconductor surface temperature, but in scanning beam annealing, the point to be detected constantly moves, so temperature detection that follows this is required. It is substantially difficult to set the detection range of the temperature detector to a minute area and to move this area in accordance with beam scanning. Furthermore, in beam annealing, the point to be detected is considered to be at the highest temperature (approximately the melting point of the semiconductor to be annealed).

Focusing on these points, the inventors of the present invention have conducted extensive research, and as a result have detected the black body radiation from the semiconductor to be annealed, and detected the light intensity at a wavelength shorter than the strongest wavelength of the black body radiation at the melting point temperature of the semiconductor. It was found that the temperature at the beam irradiation point can be detected with high accuracy by detecting the .

That is, the present invention provides a method for manufacturing a semiconductor crystal thin film in which the entire substrate is heated by a heater and an energy beam is scanned over the semiconductor thin film formed on the substrate to crystallize the thin film.
The amount of heat given to the thin film by detecting light shorter than the maximum intensity wavelength of black body radiation at the melting temperature of the thin film from the surface region of the semiconductor thin film, and controlling the heating temperature of the heater according to the detected signal intensity. This is a method that controls the

〔Effect of the invention〕

According to the present invention, since the temperature at the beam irradiation point can be detected with high precision, uniform beam annealing can be performed over a wide area at a constant temperature. Therefore, it is possible to form a high quality and uniform semiconductor crystal thin film having practically sufficient characteristics as an element formation substrate of a three-dimensional semiconductor device.

[Embodiments of the invention]

FIG. 3 is a schematic diagram showing the structure of an electron beam annealing apparatus used in a method according to an embodiment of the present invention. In the figure, 1 is a heater on a flat plate, and a sample 2 to be annealed is placed on this heater 1. Sample 2 is, for example, P-type (100) single crystal Si, as shown in Figure 4.
A 1 [μm] SiO ₂ film 22 is formed on the substrate 21,
A 5000 [Å] polycrystalline Si film (semiconductor thin film) 23 is deposited on the SiO ₂ film 22, and then a 2000 [Å] thick polycrystalline Si film (semiconductor thin film) 23 is deposited on top of that.
It is formed by depositing a SiO ₂ film 24 of.

An electron optical system including an electron gun, focusing lenses 3 and 4, a deflector 5, etc. (not shown) is provided above the heater 1. The electron beam emitted from the electron gun is focused by coils 3 and 4, and is scanned over the sample 2 by a deflector 5.

A light receiver 6 is arranged diagonally above the heater 1 . This light receiver 6 has its field of view set on the surface area of the front sample 2, and is designed to detect light having wavelengths λ ₁ and λ ₂ shorter than the maximum intensity wavelength of black body radiation at the melting point temperature of Si. The detection output of the photodetector 6, that is, the radiation intensities P ₁ and P ₂ at wavelengths λ ₁ and λ ₂ are supplied to a temperature detection circuit 7. The temperature detection circuit 7 calculates the ratio of the radiation intensities P ₁ and P ₂ and detects the temperature T from this ratio. Then, this detected temperature T is supplied to a heater temperature control circuit 8, and the current applied to the heater 1 is controlled so that the temperature T becomes a predetermined constant temperature.

By the way, when a semiconductor is irradiated with an energy beam, the temperature of the semiconductor is increased, and energy is radiated as expressed by the so-called Planck's radiation law: ρλ=C ₁ /λ ⁵ ·1/e×p(C ₂ /λT). This situation is shown in FIG. The temperature of the surface of the semiconductor is lower as the point of irradiation with the energy beam is further away, and energy is radiated according to each temperature. Therefore, in order to detect only the temperature at the energy beam irradiation point from the temperature distribution in the area near the energy beam irradiation point (Figure 6),
If the temperature at the energy beam irradiation point is the melting point of the semiconductor and the radiation intensities P ₁ and P ₂ at wavelengths λ ₁ and λ ₂ shorter than the maximum intensity wavelength of blackbody radiation at that temperature are measured, the temperature is lower than the melting point. Since radiation at low points can be almost ignored, the temperature T at the irradiation point of the energy beam can be calculated from the ratio of P ₁ and P ₂ (P ₁ /P ₂ ). Further, while irradiating the beam, the amount of heat applied to the substrate 21 is adjusted according to the rise and fall of the temperature of the point being irradiated with the beam, as shown in FIG. It is possible to keep the temperature at a certain point constant.

Thus, according to this embodiment, beam annealing can be performed at a constant temperature, so uniform annealing can be performed. According to experiments conducted by the present inventors, when annealing was performed using the apparatus shown in FIG. 3 and the sample 2 shown in FIG. 4, the following results were obtained. First, the acceleration voltage of the electron beam as a beam source is 10 [kV], the beam current reaching the Si substrate is 5 [mA], and the beam spot diameter is
300 [μmφ], and the area of 5 [cm] x 5 [cm] is 100
Annealing was performed while scanning at a pitch of [μm] at a speed of 1 [m/sec]. At this time, the field of view for detecting blackbody radiation is set to the same size as the area to be annealed, and the substrate temperature is adjusted to 500℃ before beam irradiation.
It was kept at [℃]. Simultaneously with the start of beam irradiation, the temperature at the beam irradiation point was controlled as described above. As a result, the entire region irradiated with the beam was annealed substantially uniformly, and crystal grain boundaries of substantially the same size could be grown in the polycrystalline Si film 23.

Note that the present invention is not limited to the embodiments described above. For example, the semiconductor thin film to be annealed is not limited to polycrystalline Si, and may be amorphous Si, a semiconductor other than Si, or a metal. Further, the effects of the present invention can be expected in areas other than crystal growth by annealing, and it is thought that it becomes possible to homogenize the annealed region for activation of the ion-implanted layer. Furthermore, the beam source may be a laser beam or an ion beam other than an electron beam. Furthermore, the wavelengths λ ₁ and λ ₂ for temperature detection may be appropriately determined within a range shorter than the maximum intensity wavelength at the melting point of the semiconductor to be annealed. Furthermore, a method of integrating wavelengths shorter than the maximum intensity of blackbody radiation at the melting point of the semiconductor may be considered for temperature detection. Also, as a means of temperature control, instead of varying the heater temperature,
It is also possible to vary the intensity of the beam. In addition, various modifications can be made without departing from the gist of the present invention.

[Brief explanation of drawings]

Figures 1 and 2 are for explaining the problems of the conventional technology, respectively. Figure 1 is a characteristic diagram showing the temperature distribution on a semiconductor substrate irradiated with a beam, and Figure 2 is a characteristic diagram showing the temperature distribution on a semiconductor substrate irradiated with a beam. ] Characteristic diagrams showing the temperature distribution when the beam is irradiated after heating, and FIGS. 3 to 6 are for explaining one embodiment of the present invention, and FIG. 3 is used for the same embodiment. Fig. 4 is a cross-sectional view showing the sample to be annealed, Fig. 5 is a characteristic diagram showing the radiation intensity distribution due to black body radiation, and Fig. 6 is a two-dimensional diagram of the vicinity of the beam irradiation point. FIG. 1... Heater, 2... Sample to be annealed, 3,
4... Focusing lens, 5... Deflector, 6... Light receiver, 7... Temperature detection circuit, 8... Heater temperature control circuit, 21... Single crystal Si substrate, 22, 24...
SiO ₂ film, 23...polycrystalline Si film (semiconductor thin film).

Claims (1)

[Scope of Claims] 1. A method for manufacturing a semiconductor crystal thin film in which the entire substrate is heated by a heater and an energy beam is scanned over a semiconductor thin film formed on the substrate to crystallize the thin film, wherein the semiconductor thin film is heated by a heater. Detecting light shorter than the maximum intensity wavelength of black body radiation at the melting temperature of the thin film from the surface region of the thin film, and controlling the amount of heat applied to the thin film according to the detected signal intensity. Method. 2. The method of manufacturing a semiconductor crystal thin film according to claim 1, wherein the means for controlling the amount of heat applied to the thin film controls the heating temperature of the heater in accordance with the intensity of the detection signal.