JPS6364324A - Heating method and heating equipment therefor - Google Patents

Abstract

PURPOSE:To form a semiconductor device without exposing a substrate to a high temperature, by generating thermal elastic wave near the surface of a body to be heated, and making the surface chemically active at a low temperature. CONSTITUTION:A local part is irradiated by a beam 2, or a wide range is irradiated with a lamp and the like in the manner in which the intensity distribution of a radiating light is made ununiform. Temperature irregularity generates on a semiconductor substrate 1, thermal distortion is introduced into the vicinity of surface, and thermal elastic wave 3 generates near the surface of the substrate 1. Therecore the combination of atoms constituting the substrate 1 is subjected to expanding and contracting, and chemical bonding of atoms is apt to be cut. Then chemical reaction is liable to occur, and the reaction is promoted. Thereby, semiconductor device can be formed without exposing the substrate 1 to a high temperature.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a heating method and a heating device used therefor, and particularly to a heating method for heating near the surface of a semiconductor substrate in a manufacturing process of a semiconductor device. The present invention relates to a suitable heating method and apparatus.

[Conventional technology]

Conventionally used heating devices for heated objects include electric furnaces that heat the heated object using heating wires from around a quartz tube that houses the heated object, and electric furnaces that heat the heated object using an induced current generated within the heated object by high frequency waves. There are high-frequency induction heating devices that heat objects, devices that heat objects by irradiating microwaves, and the like. In particular, electric furnaces and high-frequency induction heating devices have played an important role as heating devices used in the manufacture of semiconductor devices. These heating devices basically heat the inner body of an object to be heated.

However, in recent years, as semiconductor devices have become more complex and miniaturized, a technique for heating only the vicinity of the surface of a semiconductor substrate has become necessary. An example of a semiconductor device that requires heating only near the surface of a semiconductor substrate is a three-dimensional ( Lamination) semiconductor integrated r5
There is a J road.

Laser annealing and lamp annealing have emerged as heating technologies to meet this demand. Literature related to laser annealing includes Applied Physics Letters, Vol. 9
1982) pp. 1089-1090 (Apρ1ic+1P
dynamics Letters, VoL, 41.
NaH (IC12) p(+, 1(Bii, 3-
1090), and I.E.I., 1-Transaction Electron Devices, E.D. Volume 32, Number 7 (1985) No. 1347-
1352 pages (IEEE, Trans, El
ectron DavicC8゜Vol, ED-3
2, Na 7 (1985) pp, 1347-13
52).

With these techniques, it is possible to intensively inject energy only in the very vicinity of the surface, which is about 0.1 to 1 - the penetration depth of light, and therefore it is possible to heat the semiconductor substrate particularly near the surface. can. Electron beam annealing has also been developed as a similar heating method that can heat only the vicinity of the surface of a semiconductor substrate. By utilizing these surface heating techniques, prototype examples of three-dimensional semiconductor integrated circuits have also been reported.

[Problem that the invention seeks to solve]

In the conventional surface heating technology described above, energy can be injected only near the surface, but the heat generated there diffuses toward the deep part of the semiconductor substrate.
As a result, all three parts were heated to some extent. Of course, if the energy to be injected is reduced, the extent to which deep parts are heated can be reduced. However, in that case, the surface of the semiconductor substrate is insufficiently heated, and the surface of the semiconductor substrate cannot be brought to a temperature (about 600° C.) necessary for crystal growth, for example, and crystal growth cannot be performed.

In the future, the miniaturization of semiconductor elements will progress, and as a result,
Considering the need for higher precision in manufacturing technology for semiconductor devices, it is desirable to develop a more precise surface heating technology as a future heating method for semiconductor substrates.

An object of the present invention is to provide a highly accurate surface heating method and apparatus for manufacturing semiconductor devices that can heat only the vicinity of the surface of a semiconductor substrate, which can meet the above requirements.

[Means for solving problems]

In the heating method of the present invention, first, the surface of the object to be heated is irradiated with light locally or over a wide range so that the intensity distribution is uneven, thereby causing temperature unevenness on the surface of the object to be heated. As a result, stress (thermal strain) based on the difference in the amount of thermal expansion is introduced near the surface of the heated object. By performing this heating intermittently (that is, modulating the intensity of the light), compression waves (hereinafter referred to as thermoelastic waves) of the constituent atoms of the heated object are generated near the surface of the heated object. , is characterized by supplying a large amount of atomic vacancies to the surface to activate chemical reactions near the surface.

The frequency at which the above-mentioned heating (i.e., light irradiation) is performed intermittently is determined by the lattice frequency (approximately 10
``I(z) or less, and in order to sufficiently supply the above atomic vacancies, it is necessary to have at least the reciprocal (1 to 10) IZ, ) of the atomic vacancy lifetime (1 second to 0.1 seconds). It is thought that.

In the method of the present invention, auxiliary heating is not required when performing crystal growth in the solid phase, for example, but when it is desired to complete a process that requires large activation energy such as oxidation or nitridation in a short time. Supplementary heating is also carried out. (By performing auxiliary heating, the generation of atomic vacancies on the surface of the semiconductor substrate is promoted, and the reaction is promoted.) For example, when oxidizing or nitriding a silicon layer,
It is desirable to perform auxiliary heating to about ℃. However, since the auxiliary heating used in the method of the present invention requires only low-temperature heating, the semiconductor substrate is not heated to the deep part, so this is not a problem.

The heating device of the present invention used in the heating method of the present invention includes at least one light source, means for making the intensity distribution of the light emitted from the light source non-uniform, and means for modulating the intensity of the light. (It is characterized by a.

[Effect]

FIG. 1 is a diagram showing the concept of the present invention. Here, a case where the method is used for manufacturing a semiconductor device will be described as an example.

In the figure, 1 is a semiconductor substrate (object to be heated).

2 is an intensity-modulated beam, 3 is a thermoelastic wave generated near the surface of the semiconductor substrate 1, and 4 is a large amount of atomic vacancies supplied near the surface of the semiconductor substrate 1.

As shown in the figure, local irradiation using beam 2 or
Alternatively, use a lamp etc. to spread light over a wide area,
If the irradiation light is irradiated with a non-uniform intensity distribution (not shown here), temperature unevenness will occur on the surface of the semiconductor w-board 10, and thermal strain will be introduced near the surface. Further, the irradiation of the beam 2 is intermittently turned on and off, and the intensity is modulated, thereby generating the above-mentioned thermoelastic wave 3 near the surface of the semiconductor substrate Fi1. Therefore, the bonds between atoms constituting the semiconductor substrate 1 are stretched.

The chemical bonds between atoms are more likely to be broken. Furthermore, the thermoelastic waves 3 supply a large amount of atomic vacancies 4 into the semiconductor. A high concentration of atomic vacancies is equivalent to a high temperature for chemical reactions, and the semiconductor substrate surface becomes chemically active. As a result, chemical reactions are more likely to occur in the area irradiated with light, and one reaction is promoted.

Therefore, there is no need to make the temperature of the surface of the semiconductor substrate Fil very high, and the thermal energy injected into the surface of the semiconductor substrate 1 can be small. As a result, the thermal energy flowing into the deep part of the semiconductor substrate 1 is small, and the diameter is small so that temperature rise in the deep part does not become a problem.

That is, in the manufacturing process of semiconductor devices, the steps are necessary for manufacturing semiconductor devices even at relatively low temperatures.

For example, oxidation, nitridation, impurity diffusion, and damaged layer recovery.

It is possible to realize electrical activation of impurities, solid-phase epitaxial growth, etc., prevent heating deep into the semiconductor substrate, and manufacture semiconductor devices without adversely affecting other devices that have already been manufactured. be able to. Therefore, it becomes possible to manufacture three-dimensional integrated circuits and the like using minute elements.

〔Example〕

Example 1 An example in which solid phase epitaxial growth was performed using the heating method of the present invention will be described with reference to FIG.

First, a single-crystal Si (silicon) substrate 21 with a 1-direction orientation (100) and an acceleration energy of 140 k eV t' S
Implant i ions into 6X1015■-2,
The surface of the Si substrate 210 was made amorphous, and an amorphous Si layer 25 having a thickness of about 2000 wafers was formed.

Next, as shown in FIG. 2, an Ar (argon) laser beam 22 of 5.5 mW and a wavelength of 488 nm was applied to the surface of this sample in an inert gas by turning it on and off at a period of IMHz. - The beam 22 was irradiated while modulating the intensity. The irradiation time is 2.5 seconds and the diameter of the laser beam at the sample surface is 11 m.

The crystallinity of the surface of this sample was determined by reflection high-speed electron diffraction (μmRHEED) using an electron beam with a beam diameter of 500 mm.
Microblow Reflective High Energy Electron Diffraction (μ-probe Refle
active High Energy Eiectro
As a result, a diffraction pattern with the same crystal orientation as the 5ijA plate 21 was obtained only in the region 26 irradiated with the laser, while a halo pattern was observed in other regions not irradiated with the laser. For this reason, the method of this embodiment is used.

It was confirmed that solid phase epitaxial growth occurred in the region 26 irradiated with the laser, and amorphous Si became single crystallized. By the way, while solid-phase epitaxial growth using a normal electric furnace requires a high temperature of about 600°C or higher, the method according to the present invention increases the surface temperature by only 150°C.
It's less than that.

In this way, in this example, Si could be grown by solid phase epitaxial growth at a low temperature of 150°C.

Note that epitaxial growth in this example.

Comparing conventional epitaxial growth using a pulsed laser, in this example, the laser is continuously turned on and off at a predetermined period for a predetermined time to achieve solid phase growth, whereas in the conventional method In the case of using a pulsed laser, a laser having a higher output than that of this embodiment is used and is turned on only one time to cause liquid phase growth of the semiconductor.

Example 2 Next, using the heating method and apparatus of the present invention.

An example will be described in which impurities introduced by ion implantation are electrically activated.

First, an example of the heating device according to the present invention is shown in No. 3x.

In the figure, 27 is a high-output light source, for example a 500W halogen lamp in the rare case of 14-\'Uni, and 28 is a lamp.
'C, 29 is an optical system for collimating the lamp light 28, 30, 30' is a half mirror, 3], 31' are total reflection mirrors, 32 is a device for creating light interference fringes (light intensity In this embodiment, for example, a half mirror 30.30' and a total reflection mirror 31.31 are used.
′. 33 is a device that intermittently irradiates light (light intensity modulation means); for example, a shutter (chopper) having a window in a rotatable disk; 34 is a sample to be heated; 35 is a surface of the sample 34; These are interference fringes formed in

In the heating device having such a configuration, the halogen lamp 2
The light irradiated from 7 is converted into parallel light by an optical system 29 and divided into two by a half mirror 30. The other half passes through the half mirror 30 and goes straight. The other half takes a longer journey than the other half. That is, it is reflected by the half mirror 30 and its course is bent at a right angle. Next, it is totally reflected by total reflection mirrors 31 and 31', and its course is bent at right angles.

after that.

The light is reflected by the half mirror 30' and returns to its original path, and is mixed with the other light that has passed through the half mirror 30 and 30'. Next, the shutter 33 having 2
By rotating the sample 34, light is intermittently irradiated onto the surface of the sample 34, and interference fringes are formed. That is, interference fringes of light are created by the half mirror 30.30' and the total reflection mirror 31.31', and light is intermittently irradiated by the shutter 33. Therefore, the surface of the sample 34 is irradiated over a wide range and with the intensity modulated so that the intensity distribution is non-uniform.

First, P (phosphorus) ions were injected into a single-crystal Si substrate with an orientation of (100) at an acceleration energy of 100 keV to 8XIO”+
An-” ions were implanted.

After that, the shutter 3 is heated using the heating device shown in FIG.
When this sample was irradiated with light from a halogen lamp 27 in an inert gas while being turned on and off at an IMHz cycle, approximately 9 of the implanted P ions were removed.
3% was activated as a donor-type impurity of Si.

In this example as well, the substrate surface temperature was approximately ψ, 2 (temperature), and therefore the inside of the substrate could be substantially prevented from being heated.

In the case of this embodiment, the supply of atomic vacancies tends to be insufficient in the dark areas of the interference fringes compared to the bright areas. Therefore, depending on the light irradiation conditions, the chemical reaction rate may vary depending on the location. To solve this problem, it is sufficient to repeatedly scan the irradiation light in a direction orthogonal to the interference fringes.

Furthermore, in this embodiment, the irradiation light is fixed.

Although thermoelastic waves were created by turning it on and off, thermoelastic waves can also be created by using continuous light as the irradiation light and scanning it at a sufficient speed. In other words, if we focus on one point on the second substrate, when the bright part of the interference fringes passes,
Equivalent to irradiation "on".

When the dark area passes, it corresponds to the irradiation being "off".

Example 3 In Example 1.2 above, the sample was treated in an inert gas. Here, an example will be described in which the inert gas was replaced with acid J-cogas to oxidize the sample surface. As a sample, 1 position orientation (1
The single-crystal Si substrate of 11) was used, and the heating device shown in FIG. 3 was used. When irradiation was performed for 10 minutes in an oxygen atmosphere, a silicon oxide desert (SiC2 film) with a thickness of approximately 100 mm was formed on the surface of the Si substrate.

In this example as well, the substrate surface temperature was relatively low, and therefore the inside of the substrate could be substantially prevented from being heated.

Example 4 In Example 3, the irradiation light passes through the silicon oxide that is being formed and is absorbed only by the Si substrate.

Therefore, heating according to the present invention is effective on the Si surface, but not on silicon oxide.

The formation of an oxide film occurs when oxygen in the atmospheric gas passes through silicon oxide using wave numbers, and when Em reaches f(J) on the Si substrate, a chemical reaction occurs with the Si substrate, forming silicon oxide.
You can proceed by following these steps.

In Example 3, since St is chemically activated by the heating of the present invention, the bond between oxygen and Si:, I-l''1
is active, but the oxygen diffusion process is inactive because the activation of silicon oxide is not sufficient. the result.

It is difficult to obtain a large oxide film in which the oxygen diffusion rate determines the oxidation rate.

Therefore, in order to make silicon oxide chemically active by heating according to the present invention and to obtain a large oxide film thickness, auxiliary heating using CO and pulsed laser was also performed simultaneously with the heating performed in Example 3. The wavelength of CO2 laser is about 10 folds, and it is well absorbed by silicon oxide, so it is effective for heating silicon oxide. the result.

The same 10 minute irradiation was successful in forming silicon oxide of about 500 H.

Note that in order to achieve an even higher oxidation rate, the entire sample should be heated to about 200 to 580°C.

It is best to perform the heating described above. In this case, although the entire sample is heated, the heating process used in the conventional semiconductor device manufacturing process (
(approximately 1100°C), and most chemical reactions do not proceed at this low temperature, so there is no problem.

Example 5 An example in which a single crystal Si film was formed on an insulating film by solid phase epitaxial growth using the method and apparatus of the present invention will be described.

First, as shown in FIG. 4, a silicon oxide purple film 47 with a thickness of 500 wafers was formed on a single crystal Si substrate 41 with 100 orientations (100 directions), and this was pattern-cut using ordinary photolithography technology. . The shape of the pattern at this time may be a rectangle, a triangle and a circle, or any other shape.

Next, an amorphous Si film 48 having a thickness of about 2,500 layers was deposited thereon by electron beam heating vapor deposition in an ultra-high vacuum.

FIG. 4 shows the state of the sample thus produced.

This sample was heated using the heating device shown in FIG. However, in this example, the irradiation light with interference fringes is
It was scanned over the sample surface at a speed of m/min (the means for scanning the irradiation light is not shown in FIG. 3). As a result, the amorphous Si film 48 directly deposited on the single crystal Si substrate 41 is
A single crystal was formed by solid phase epitaxial growth using the i-substrate 41 as a seed crystal, and then, using this as a seed crystal, the amorphous Si film deposited on the silicon oxide film 47 was formed into a single crystal by solid phase epitaxial growth.

Note that although the above embodiments use intensity-modulated beam annealing or intensity-modulated full-surface non-uniform annealing, either of the annealing methods may be used in any of the embodiments. The two are essentially the same, the only advantage being that the latter has better throughput. Furthermore, it goes without saying that a laser beam may be used as a light source for irradiating interference fringes. It is not necessarily necessary that the brightness and darkness of the interference fringes be parallel; they may be distorted or island-like, and it is effective as long as the intensity distribution of the irradiated light is non-uniform. Therefore, speckles of laser light can also be used. It is not necessary to use only one light source, and a plurality of light sources may be used. The means for creating the interference fringes is also not limited to the present embodiment, such as the use of speckles.

〔Effect of the invention〕

As described above, the present invention can bring the surface of a heated object into a chemically active state at low temperatures by generating thermoelastic waves near the surface. Therefore, in the manufacturing process of semiconductor devices, the substrate is not exposed to high temperatures.
A semiconductor device can be formed. As a result, it becomes possible to fabricate three-dimensional integrated circuits and the like using minute elements.

[Brief explanation of the drawing]

Fig. 1 is a diagram explaining the present invention in detail, Fig. 2 is a diagram showing an embodiment of the heating method of the invention, Fig. 3 is a diagram showing an embodiment of the heating device of the invention, and Fig. 4 is a diagram showing an embodiment of the heating device of the invention. FIG. 3 is a diagram showing another embodiment of the present invention. 1... Semiconductor substrate 2... Intensity modulated beam 3... Thermoelastic wave 4... Atomic vacancy 21.41... Single crystal SL substrate 22... Ar laser beam 25... -Amorphous Si layer 26...Laser irradiated area 27...Light source 28...Lamp light 29...Optical system 30.30'...Half mirror 31. 31'... Total reflection mirror 32... Device for creating interference fringes (means for making the intensity distribution of light non-uniform) 33... Shutter (means for modulating the intensity of light) 34.
...Sample 35...Interference fringes 47...Silicon oxide film 48/Amorphous Si film

Claims (1)

[Claims] 1. By irradiating the surface of the object to be heated with light locally or over a wide range so that the intensity distribution is non-uniform, and by modulating the intensity of the light. ,
A heating method characterized by generating thermoelastic waves near the surface to activate a chemical reaction near the surface. 2. A heating device comprising at least one light source, means for making the intensity distribution of the light emitted from the light source non-uniform, and means for modulating the intensity of the light.