JPH05251380A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To make it possible to carry out more enhanced alloy heat treatment for a semiconductor portion of an electrode metal layer clad on the semiconductor portion which forms a shallow junction without penetrating the shallow junction. CONSTITUTION:An electrode metal layer 6 clad on a semiconductor portion 3 which forms a shallow junction is alloy-treated based on pulse laser light irradiation. Prior to the pulse laser light irradiation, an optical absorption layer 7, which has an optical absorption with the waves of laser light, is clad and formed on the electrode metal layer 6.

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 depth of 0.1 .mu.m or less of about 0.2 .mu.m.
The present invention relates to a method of manufacturing a semiconductor device including a step of alloying an electrode on a surface of a semiconductor region forming a shallow junction of μm or less.

[0002]

2. Description of the Related Art In various single semiconductor devices, semiconductor integrated circuits, etc., an ohmic electrode is formed on a predetermined portion of the surface of a semiconductor substrate for connecting itself or other elements. In order to make a good ohmic contact, sintering is performed by so-called heat treatment for alloying the electrode such as Al with a semiconductor such as Si.

On the other hand, in recent years, for example, in semiconductor integrated circuits, with the demand for higher density and smaller size, the area of semiconductor elements as circuit elements has been reduced, and accordingly, these elements are configured. Junctions formed by diffusion of impurities, introduction of impurities such as ion implantation, for example, pn junctions are becoming shallower. That is, the semiconductor portion or the semiconductor region including the semiconductor region in which the impurity is introduced that forms the shallow junction becomes thin.

For this reason, when sintering the above-mentioned electrode, there is a problem that the alloying is performed through a shallow junction.

Usually, in this sintering, a semiconductor substrate (wafer) on which the above-mentioned electrode is formed is inserted into a heating furnace such as an electric furnace and, for example, its Al electrode is alloyed with a Si semiconductor. The sintering in this case is 400 to 450.
Heat treatment is performed at 30 ° C. for 30 minutes.

However, in such a method, as described above, in a thin semiconductor portion forming a shallow junction having a depth of 0.2 μm or less, for example, 0.1 μm, the alloy may penetrate through the junction. Junction leak,
Therefore, the yield is reduced due to the generation of defective products.

In order to avoid such an inconvenience, a method of irradiating infrared rays using a halogen lamp can be considered. In this case, the temperature measurement is performed by a pyrometer. Fifty
Since the measurement error at 0 ° C. is extremely large, accurate temperature control is difficult as a result, and it is difficult to apply the above-mentioned electrode sintering in the shallow junction.

[0008]

In order to solve the above-mentioned problems, sintering by laser light irradiation is also conceivable. In this case, there are great expectations for sintering, but local rapid From where heating and cooling are performed, the electrode metal, such as Al,
Since the coefficient of thermal expansion differs from that of a semiconductor such as Si by an order of magnitude, thermal strain is large and peeling of electrodes, disconnection, and influence on the characteristics of bonding also pose a problem.

In order to avoid such inconvenience, a barrier metal such as TiON or TiN is provided between the semiconductor and the electrode metal.
However, in this case, it is difficult to control the film thickness of the barrier metal, which causes a problem of peeling, and there is a problem that the ohmic contact resistance increases.

According to the present invention, when an electrode is formed on the surface of a thin semiconductor region such as a semiconductor layer or a semiconductor layer forming a shallow junction and sintering is performed, the sintering penetrates the shallow junction and leaks to the junction. It is possible to surely avoid the inconvenience of causing the deterioration of the characteristics or the generation of defective products, and moreover, the electrodes are reliably alloyed with the semiconductor so that the ohmic contact is made with a low resistance.

[0011]

According to a first aspect of the present invention, there is provided a method of manufacturing a semiconductor device, which comprises an alloying heat treatment step for a surface of the semiconductor portion of an electrode deposited on the semiconductor portion forming a shallow junction. The alloying heat treatment is performed particularly by irradiation with pulsed laser light, and further, prior to this irradiation with pulsed laser light, a light absorbing layer having a light absorbing property with respect to the wavelength of the laser light is deposited on the electrode metal layer.

Further, in the second aspect of the present invention, the light absorption layer is made of amorphous silicon or polycrystalline silicon.

In the third aspect of the present invention, an antireflection film is deposited on the light absorption layer, and pulsed laser light irradiation is performed on the antireflection film.

Further, in the present invention, preferably, the above-mentioned heat treatment process by pulsed laser light irradiation is performed on the electrode metal layer formed on the entire surface before patterning as an electrode, and then the electrode metal layer is patterned. Then, an electrode having a desired pattern is formed.

[0015]

In the present invention described above, the light absorption layer having the light absorption property for the laser light is provided on the electrode metal layer to be subjected to the sintering treatment, so that the laser light is efficiently absorbed in this light absorption layer. Is converted into heat, and the heat is efficiently supplied to the electrode metal layer, and the heating applied to the junction between the electrode metal layer and the semiconductor part by making the laser light irradiation pulsed laser light. Can be effectively prevented from penetrating the shallow junction due to its instantaneous heating to high temperature and rapid cooling.

Further, a light absorbing layer is formed on the electrode metal layer, and by virtue of this, the electrode metal layer is in a mechanically restrained state, so that the deformation and peeling of the electrode metal layer can be effectively avoided. It

Further, when the electrode metal layer is patterned after sintering, it is possible to more effectively avoid deformation, peeling and disconnection of the electrode.

Further, when the antireflection film is provided on the light absorption layer, the irradiation of pulsed laser light can be more effectively absorbed, and more effective sintering can be performed.

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An example of a method of manufacturing a semiconductor device according to the present invention will be described in detail with reference to the manufacturing process diagrams shown in FIGS.

In this case, for example, an insulating layer 2 for element isolation, which is formed of SiO ₂ film so-called LOCOS formed between circuit elements on a so-called field portion by thermal oxidation or the like on the semiconductor substrate 1 made of silicon or the like, is, for example, 2000 to 30.
It is formed by, for example, selective diffusion, implantation or the like so as to form a shallow junction J, for example, a shallow junction having a depth of 0.1 μm or less, in a so-called active region where the insulating layer 2 is not formed. Alternatively, a thin semiconductor region formed by epitaxy or the like, or a semiconductor portion 3 made of a semiconductor layer is formed, and a metal electrode is in ohmic contact with the semiconductor portion 3.

Further, in this case, when a structure in which two or more electrodes, wiring layers, etc. are laminated on the semiconductor substrate 1, the thickness is, for example, 1000 to 2000 Å, and the interlayer insulation is made of, for example, phosphosilicate glass (PSG). The case where the layer 4 is deposited is shown.

In this case, as shown in FIG. 1A, the interlayer insulating layer 4
By the well-known selective etching by photolithography, an electrode contact window is formed on the portion of the semiconductor portion 3 where ohmic contact of the electrode is to be made.

Then, as shown in FIG. 1B, the electrode metal layer 6 including the inside of the contact window 5 such as Al, Ti, W, C is formed.
O, Au, Cu or the like is entirely deposited by vapor deposition, sputtering or the like. Then, a light absorbing layer, for example, polycrystalline silicon is provided on the above in a range of 10 to 50 nm, preferably 10 to 20
nm, plasma CVD at a film forming temperature of 450 ° C. or less
(Plasma Chemical Vapor Deposition) or photo-CVD method for deposition. In this case, it is desirable that the film formation temperature is set to, for example, 450 ° C. or lower at which the alloy reaction with the electrode metal layer does not occur.

For the electrode metal layer 6, 1% of Si is used.
It is preferable to use contained Al-Si, and by doing so, mutual diffusion of Si and Al can be prevented.

Further, as the light absorption layer 5, it is desirable to use the above-mentioned polycrystalline silicon having a small thermal expansion coefficient.

Further, for example, SiO is formed on the light absorption layer 5.
_An antireflection film composed of ₂ is formed in a thickness of 70 to 100 nm, for example 50
The thickness is nm and the entire surface is deposited by CVD or the like.

Further, the antireflection film 8 is selected to have a thickness that effectively removes antireflection due to its interference effect according to the wavelength of the laser light to be irradiated, and is 70 to 100 nm at a short wavelength. Is selected.

Thereafter, a pulse laser is irradiated from above the antireflection film 8. This pulsed laser has an energy density of 400 to 1500 mJ / cm ² , preferably 50.
0 to 700 mJ / cm ² and beam area is 4 m, for example
As a rectangular spot of m × 4 mm to 15 mm × 15 mm, this is moved stepwise so that the pulsed light is irradiated once at one place so that at least the portion of the electrode metal layer 6 to be contacted with at least the semiconductor portion 3 is formed. Scan including. The pulse width of this pulse laser is 20 to 100.
nsec, preferably 40 nsec to 50 nsec is selected.

Further, as the laser, an excimer laser such as a XeF laser (wavelength λ = 351 nm), XeCl is used.
Laser (λ = 308 nm), KrF laser (λ = 249)
nm), ArF laser (λ = 193 nm), and ruby laser (λ = 694 nm).

The light absorption layer 7 is preferably made of the above-mentioned polycrystalline silicon or amorphous silicon, and in this case, it has a large absorption coefficient for short wavelengths. For example, XeCl laser light (λ = 308n
m) is about 1.4 × 10 ⁶ cm ⁻¹ .

FIG. 3 shows the relationship of the light absorption coefficient α of silicon with respect to the photon energy (wavelength of light). The solid curve represents crystalline silicon, and the broken curve 22 represents silicon amorphized by implantation of silicon. This is the case (Semiconductor and Semimetals Vo
1.23 Academic Press). In the case of polycrystalline silicon, it is presumed that the characteristics between these curves are exhibited. As is clear from this, silicon has a high light absorption coefficient α for short wavelengths and over a high range.

The light absorption coefficient α is given by equation 1.

[0033]

## EQU1 ## I = I ₀ exp (−αx)

Since I is the light intensity, I ₀ is the incident light intensity, and x is the junction depth, the light absorption coefficient of α = 1.4 × 10 ⁶ cm ^-1 for XeCl laser light is now obtained. , It is 2/3 of the energy of light at a depth of 70Å from the surface.
Will be absorbed and converted into almost heat.

Since the thermal conductivity of the electrode metal layer 6 is 50 times that of the interlayer insulating layer 4 at room temperature, the heat converted by the light absorption layer 7 immediately has a high thermal conductivity. To heat the contact portion with the semiconductor portion 3 through the contact window 5, and sintering is instantaneously performed.

After that, as shown in FIG. 2A, the antireflection film 8 and the light absorption layer 7 thereunder are removed as necessary by, for example, RIE (reactive ion etching).

Thereafter, as shown in FIG. 2B, the electrode metal layer 6 is pattern-etched into an electrode pattern by selective etching using well-known photolithography. When the electrode metal layer 6 is sintered to the semiconductor portion 3 by the above-described method of the present invention, the finally obtained electrode 9 is
Good ohmic contact was made with the semiconductor portion 3.

In the above-described method of the present invention, the light absorption layer 7 is provided on the electrode metal layer 6 and the laser light is efficiently absorbed therein. Therefore, the electrode metal layer 6 is efficiently given heat for sintering. You can

Since the laser light irradiation is pulse irradiation, sintering is performed by instantaneous heating / cooling. Therefore, it is effectively shallow, and the sintering of the electrode metal layer with respect to the semiconductor portion 3 can be performed. Further, when the light absorption layer 3 is present on the electrode metal layer 6 and is made of amorphous or polycrystalline silicon, the coefficient of thermal expansion of the light absorption layer 3 is, for example, Al being 2.9 × 10 ^−5. Since that of silicon is 2.4 × 10 ⁻⁶ , the thermal expansion of the light absorption layer is small even by heating due to this light absorption, so that deformation and peeling of Al are suppressed.

When the electrode metal layer 6 is sintered with respect to the semiconductor portion 3 as described above, that is, after the heat treatment, the electrodes are formed, that is, the electrode metal layer 6 is patterned. Since the heating is performed while the electrode metal layer 6 is formed, the electrode metal layer 6 is less likely to be deformed, and the ohmic contact of the electrode in the finally obtained semiconductor device is better, and peeling and disconnection are better. And the like, the influence of distortion on the bonding is improved, the characteristics are stable, the reliability is improved, and the defective product generation rate is suppressed.

[0041]

As described above, according to the method of the present invention, stable formation of an electrode and ohmic contact of this electrode to a semiconductor portion having a shallow junction can be favorably carried out, so that the yield is high. A highly reliable semiconductor device can be obtained, and its industrial profit is great.

[Brief description of drawings]

FIG. 1 is a manufacturing process diagram (1) of an example of a method for manufacturing a semiconductor device according to the present invention.

FIG. 2 is a manufacturing process diagram (2) of the example of the method for manufacturing the semiconductor device according to the present invention.

FIG. 3 is a curve diagram of the relationship between photon energy and the absorption coefficient of Si used for explaining the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Semiconductor substrate 2 Insulating layer 3 Semiconductor part 4 Interlayer insulating film 5 Electrode contact window 6 Electrode metal layer 7 Light absorption layer 8 Antireflection film 9 Electrode

Claims (3)

[Claims] 1. A method of manufacturing a semiconductor device, which comprises a step of alloying heat treatment on a surface of the semiconductor portion of an electrode deposited on a semiconductor portion forming a shallow junction, wherein the alloying heat treatment is performed by pulse laser light irradiation. A method for manufacturing a semiconductor device, which comprises depositing a light absorbing layer having a light absorbing property for the laser light on the electrode metal layer prior to the irradiation of the pulsed laser light. 2. The method for manufacturing a semiconductor device according to claim 1, wherein the light absorption layer is made of amorphous silicon or polycrystalline silicon. 3. The method for manufacturing a semiconductor device according to claim 1, wherein an antireflection film is deposited on the light absorption layer, and pulsed laser light irradiation is performed on the antireflection film. Method.