JPH0479215A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To obtain a semiconductor device where the degree of integration is further improved by activating the impurity atoms, which are introduced into a semiconductor substrate, while irradiating a semiconductor substrate with a supersoft X-ray and applying DC bias. CONSTITUTION:Ion implantation layer 2 is formed at the surface B of an Si substrate 1, and the surface of the implantation layer is coated with a metallic film 3, and the ion implantation layer is irradiated with a supersoft X ray 4 through a metallic film, while applying DC voltage to the board. At this time, the electromagnetic wave is one that the longest wavelength lambda in the effective wavelength region fulfils the relation of lambda>=lambda0, to the shortest wavelength lambda0 that the semiconductor material shows the atomic absorption section area equivalent to the maximum condition, when one has calculated the linear absorption coefficient which becomes the maximum at the depth position being set in the ion implantation layer region, and further heat treatment temperature is set to the temperature at which the element region determined by the concentration of impurity ions does not change, in excess of the allowable range. Further, the electromagnetic wave is synchrotron radiation, and includes the supersoft X-ray of the wavelength equivalent to the L absorbing band of Si.

Description

[Detailed Description of the Invention] [Summary] The present invention relates to activation processing of ion-implanted impurities, and aims to provide a lower temperature and faster activation processing method, The oxidation treatment is a process in which impurities related to conductivity are introduced into a semiconductor substrate, and then heat treatment is performed while irradiating the semiconductor substrate with electromagnetic waves to activate the introduced impurities. While applying a bias voltage, the energy of the electromagnetic wave is such that the longest wavelength λ in the effective wavelength range of the electromagnetic wave is absorbed in the minute depth width region of the semiconductor material, and the energy of the electromagnetic wave is absorbed at a depth set in the impurity introduction region. When calculating the maximum linear absorption coefficient at the position, the semiconductor material satisfies the relationship λ≧λo with respect to the shortest wavelength λo at which the semiconductor material exhibits an atomic absorption cross section that satisfies the maximum condition, and The heat treatment temperature is such that the element region determined by the concentration of the introduced impurity does not change beyond a permissible range due to the movement of the impurity atoms introduced into the semiconductor substrate.

The present invention is particularly effective in activating ion-implanted impurities, and also has the effect of improving the film quality of the implanted region.

[Industrial Application Field] The present invention relates to the activation of impurity atoms introduced into a semiconductor substrate, and in particular to a processing method for defining and forming an element region with a predetermined conductivity type and a predetermined carrier concentration by ion implantation. involved.

The manufacturing of integrated circuits involves the process of introducing impurities at a predetermined concentration into specific regions of a semiconductor substrate, but as integrated circuits become more highly integrated, the regions where impurities are limited and introduced become smaller, and ion implantation becomes more difficult. Non-thermal treatments such as these are increasingly being used.

When manufacturing devices on a single-crystal semiconductor substrate as usual, impurity atoms introduced into the substrate are located at lattice points of the semiconductor crystal, that is, become substitutional impurities, so that the impurity atoms are introduced into the base semiconductor in a predetermined manner. This will give an impurity unit.

The impurity atoms introduced into the substrate by ion implantation occupy only a few lattice positions as they are, and in order to form a device, it is necessary to convert them into substitutional impurities, that is, to perform an activation process. This activation treatment is usually performed by heating the substrate.

Since the processing temperature is as high as about 900° C., the distribution of impurities changes even if the processing time is only about 10 minutes. In particular, in the formation of active elements, ion implantation may be performed multiple times, and high-temperature heat treatment deforms the formed element region, so it is desirable to avoid it as much as possible.

[Prior art and problems to be solved by the invention] Activation of ion-implanted impurities is performed only by heat treatment, and no auxiliary means are used. The treatment temperature is approximately 900°C. If impurity redistribution becomes a problem due to the high temperatures involved, the implantation zone and depth are set in such a way that the desired impurity distribution is finally obtained, taking into account the heat treatment that will be applied in the subsequent process.

In the current situation, the required impurity distribution can be achieved by precisely controlling the heat treatment temperature and time, but as device miniaturization progresses, a method of activating impurities at lower temperatures will be needed. It is clear that this will happen.

Due to ion implantation, the host crystal becomes lighter and heavier, but
Becomes amorphous. Activation of impurity atoms by heat treatment is deeply related to their recrystallization.

Ion implantation severely damages the substrate crystal from the surface to the depth where the impurity concentration is maximum. In deeper regions, the impurity concentration decreases and the degree of damage is light. When this is heat-treated, recrystallization proceeds quickly in areas where the crystal is significantly destroyed, and the implanted impurity atoms also occupy lattice points, resulting in It becomes activated.

However, in areas where the crystal is lightly damaged, recrystallization progresses slowly, and therefore opportunities for impurity atoms to occupy lattice points do not increase, resulting in a situation where activation is difficult. In order to activate such impurity atoms, it is necessary to heat to a higher temperature, and a high temperature treatment such as the above-mentioned 900''C is performed.

Therefore, if a crystalline region with a low degree of damage can be recrystallized at a lower temperature by some method, it will also realize low-temperature activation of impurity atoms.

An object of the present invention is to provide a method of activating impurity atoms introduced into a semiconductor substrate by processing at a temperature significantly lower than the normal heat treatment temperature, thereby producing a semiconductor device with further improved integration. It is to provide.

[Means to solve the problem]

In order to achieve the above object, in the impurity atom activation treatment included in the semiconductor device manufacturing method of the present invention, impurities that are involved in the conductivity of the semiconductor substrate are introduced into the semiconductor substrate, and then electromagnetic waves are irradiated onto the semiconductor substrate. When performing the heat treatment, a DC bias voltage is applied to the semiconductor substrate, and the electromagnetic wave has the longest wavelength λ in its effective wavelength range, and the energy of the electromagnetic wave absorbed in the minute depth width region of the semiconductor material is , when calculating the maximum linear absorption coefficient at the depth position set in the impurity-introduced region, the atomic absorption cross section corresponding to the maximum condition is expressed as λ with respect to the shortest wavelength λo that the semiconductor material exhibits. ≧λo, and furthermore, the heat treatment temperature is set to prevent the element region determined by the concentration of the introduced impurity from changing beyond the allowable range due to the movement of the impurity atoms introduced into the semiconductor substrate. Not set to a temperature.

[For production]

It is known that vacancies and self-interstitial atoms are generated when a Si substrate is irradiated with X-rays, and that these interstitial Si atoms are extremely mobile.

This phenomenon is explained by a non-thermal diffusion mechanism called the Bourgouin-Corbett mechanism. In other words, the diffusion barrier disappears due to the interaction between a large amount of free carriers and units corresponding to interstitial atomic positions under X-ray irradiation.
Diffusion occurs even at low temperatures, such as in liquid helium.

The state in which vacancies and self-interstitials are generated is a thermally unbalanced state, and when a DC bias is applied to this state, the behavior of interstitials and free carriers is phenomenologically can be thought of roughly as follows.

Under X-ray irradiation as shown above, the St atoms in the host crystal are in an intermediate state between an ionized state and a neutral state, and appear to be in an upper plane.

The same applies to impurity atoms, for example, boron (B) is CB) = (B-) + (h”) ・−・・・
... can be considered to be in the equilibrium state shown in (1).

The fact that B atoms are activated as impurities means that (1
) formula, the number of interstitial B atoms (B) decreases and the number of ionized lattice B atoms [B-] increases, so (1)
Proceeding the reaction in the formula to the right will promote the activation of the B atom.

Therefore, when a DC bias is applied to the Si substrate and the holes [h] are absorbed in the region outside the injection region, the reaction (B)→[B-] progresses, and the B atoms are activated.

On the other hand, in the case of a donor impurity such as phosphorus (P), (P)=
CP')+ (e-) ------- (2) Therefore, the same effect can be obtained by reversing the polarity of the DC bias.

Although the above explanation focuses only on superficial phenomena and is not logically established, Bourgou in -Cor on the Si substrate by X-ray irradiation.
It has been confirmed that recrystallization of the Si substrate is promoted by creating a situation in which the Bett mechanism is established, and that activation of impurity atoms is promoted by applying a DC bias.

Next, the wavelength conditions of X-rays for creating a situation in which the Bourgouin-Corbett mechanism is established will be discussed.

The X-rays emitted from ordinary X-ray generators have relatively short wavelengths, and the probability of interaction with matter is very small.
Most of the irradiated X-rays pass through the vicinity of the surface, so in order to cause structural layer transitions such as solid-phase epitaxial recrystallization in the region close to the surface, or to activate impurity atoms, a certain amount of irradiation is required. Is required. Therefore, recrystallizing at low temperatures or activating impurities using amorphous b diffusion of several tens to hundreds of nanometers, which is involved in the LSI manufacturing process, is a problem that cannot be achieved with conventional technology. Met.

Here, the interaction between semiconductor materials such as St and electromagnetic waves such as X-rays will be considered.

The energy Δp of X-rays absorbed by a layer with a thickness Δt located at a depth t from the surface is calculated as Δp=Io exp by modifying the formula for the linear absorption coefficient α, assuming that the intensity at the surface is 10. (-αt)XαXΔt ・---
--(3) is indicated.

Here, in order to find α that maximizes Δp, equation (3) is changed to α
When differentiated by and set as d(Δp)/dα−〇, d(Δp
>ldα=I o exp(-αt)XΔt-Io
exp(-a t) XαXΔtxt=engine. exp(
−αt)XΔt× (1−α1 > = 0−−1・−−(4) In reality, I
. Since exp(-αt) XΔt≠0, equation (4) holds true when α=1/l. The linear absorption coefficient α is the product of the atomic absorption cross section σ and the atomic number density ρ (α = σ × ρ), and t = 100 to 1000.
When calculating the value of the atomic absorption cross section σ that maximizes Δp in the case of +v, σ = 2.3X10' ~ 2.3X10'b (1b
=10-"cm").

Ll of St! ! ! The absorption cross section at the convergence end is σζ6×1
0' b, so if t is larger than approximately 380 nm, the ultrasoft X of 99 to 200 eV, which corresponds to the L absorption band,
It can be seen that the lines interact effectively with St.

Such long-wavelength X-rays cannot be generated with effective intensity using ordinary X-ray tubes, but synchrotron radiation (SOR: 5 sync
Hrotron 0rbit Radiation) encompasses electromagnetic waves in a wide wavelength range from visible light to ultra-X-rays, and can be used as a white light source for ultra-soft X-rays in the above wavelength range.

Specifically, light with a bandwidth of 3 X l mrad is
5-, semi-monochromatic X-rays with a center energy of 120 eV and an energy width of 10 eV are transmitted at 10” photons/a.
It has been successfully extracted with a strength of m”·sec.

When St is irradiated with this, 1% of the irradiated light will be absorbed by one atomic layer located at a depth of several tens of nanometers from the surface. The atomic layer is irradiated with light of 10"photons/cm"-5ee.

It is also possible with current technology to further increase the intensity of this SOR light by 10 to 100 times, and in that case, the number density of photons absorbed by each atomic layer will be approximately the same as the atomic number density.

As mentioned above, by irradiating X-rays with appropriately selected wavelengths, the energy of the X-rays can be distributed and absorbed within the required range of depth, so it is possible to use a light source such as SOR. For example, by utilizing non-thermal diffusion by the Bourgouin Corbett mechanism, it becomes possible to rapidly convert an amorphous layer into a single crystal or to activate impurity atoms. In this case, the absorption of X-ray energy is limited to a necessary region near the surface, so that unnecessary temperature rise due to excessive energy injection does not occur.

That is, it is possible to realize a situation in which the Bourgouin-Corbett mechanism is established by irradiating X-rays in a selected wavelength range, and furthermore, by applying a DC bias to the substrate, impurity atoms with an interstitial character can be removed. It is also possible to encourage occupancy of grid points. Therefore, the means of the present invention can activate impurities introduced into a semiconductor substrate by a method such as ion implantation.

〔Example〕

FIG. 1 is a schematic diagram showing an example of activating p-type impurities. An ion implantation layer 2 is present on the surface of a Si substrate 1, and a metal thin film 3 is formed on the surface of the implantation layer to a thickness of 15 to 20n11. The implanted impurity is B, and the depth of the implanted layer is 10 to 20On11.

While applying a DC voltage of +IOV to the substrate, a voltage of 100 to 200 V was applied to the ion-implanted layer through the metal thin film.
e V ultra-soft X-ray 4 at 1013 photons/c@
The substrate is heated to 600"C, but there is no need to raise the temperature higher than that.

FIG. 2 is a schematic diagram showing an example of activating n-type impurities. Here again, 1 is a Si substrate, 2 is an ion-implanted layer, and 3 is a metal thin film, and only the polarity of the DC bias applied to this metal thin film differs from that in the case of FIG. Other than that, the ultrasoft X-ray irradiation conditions and substrate temperature are the same.

FIGS. 3 and 4 are diagrams schematically showing an optical system for irradiating a sample with SOR light.

Figure 3 shows an optical system using a bandpass mirror, which allows bending and
The SOR light 12 extracted by the magnet 11 is collected by a condensing band-pass mirror 13.
Light with a wavelength of 0 eV is selected and irradiated onto the sample 17. This condensing bandpass mirror is a quartz or SiC substrate coated with a PT film, and when incident at an oblique angle of incidence of 8.6°, the reflectance of 120 eV light exceeds 70%, and the reflectance of 600 eV or more Reflectance of high energy components is 1%
The following is true.

FIG. 4 shows an optical system using a multilayer mirror, in which SOR light 12 is transmitted from an electron storage ring 10 by a magnet 11.
The point in which is extracted is the same as in FIG. SOR
The light 12 first enters the front condensing mirror 15,
The reflected light enters the multilayer spectroscopic mirror 16.

The oblique incidence angle to the front focusing mirror 15 is 2'' to 10°.The multilayer spectroscopic mirror is a quartz substrate coated with 21 layers of Rh and C alternately, and by using this optical system, L absorption It is possible to selectively irradiate ultra-soft X-rays in the band and reduce damage to the irradiated area.
7 is a sample.

〔Effect of the invention〕

As explained above, in the present invention, impurities introduced into the semiconductor substrate by a non-thermal method such as ion implantation are removed by annealing the semiconductor substrate while irradiating the semiconductor substrate with ultra-soft X-rays and applying a DC bias. Atoms can be activated. At this time, it is not necessary to raise the substrate temperature to such an extent that redistribution of the introduced impurities occurs, so it is possible to arrange the step of introducing impurities by ion implantation at any time in the integrated circuit manufacturing process.

In addition, from the perspective of recrystallizing a semiconductor layer that has been made amorphous by intense ion implantation, the present invention is also effective for improving film quality in regions where it is difficult to restore film quality after recrystallization because the strain in the crystal structure is small. It is.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing an example of activating a p-type impurity of the present invention, and FIG. 2 is a schematic diagram showing an embodiment of activating an n-type impurity of the present invention, in which l is Si substrate, 2 is an ion implantation layer, 3 is a metal thin film, 4 is an ultra-soft X-ray, 10 is an electron storage ring, 11 is a bending magnet, 12 is an SOR light, 13 and 14 are a focusing-bandpass mirror 15 is The front focusing mirror 16 is a multilayer film, and the spectroscopic mirror 17 is a sample. A schematic diagram showing an optical system of an example using a mirror.A schematic diagram showing an optical system of an example using a multilayer mirror.

Claims (4)

[Claims] (1) A method for manufacturing a semiconductor device, which includes a process of introducing impurities related to conductivity into a semiconductor substrate, and then performing heat treatment while irradiating the semiconductor substrate with electromagnetic waves to activate the introduced impurities. In the activation process, a direct current bias voltage is applied to the semiconductor substrate, and the electromagnetic wave has an energy of the electromagnetic wave whose longest wavelength λ in its effective wavelength range is absorbed in a small depth width region of the semiconductor material. However, when calculating the maximum line absorption coefficient at the depth position set in the impurity-introduced region, the atomic absorption cross section corresponding to the maximum condition is calculated for the shortest wavelength λ_o exhibited by the semiconductor material. , λ≧λ_o, and the heat treatment temperature is set to prevent the element region determined by the concentration of the introduced impurity from changing beyond the allowable range due to the movement of the impurity atoms introduced into the semiconductor substrate. 1. A method for manufacturing a semiconductor device, characterized in that the temperature is low. (2) The method of manufacturing a semiconductor device according to claim 1, wherein the impurity introduced into the semiconductor substrate is by ion implantation. (3) The semiconductor material is Si, and the electromagnetic wave is L of Si.
2. The method of manufacturing a semiconductor device according to claim 1, further comprising ultrasoft X-rays having a wavelength corresponding to an absorption band. (4) The method for manufacturing a semiconductor device according to claim 1, wherein the electromagnetic wave is synchrotron radiation light using an electron storage ring as a light source.