JPH0677155A - Heat treatment method for semiconductor substrate - Google Patents

Abstract

PURPOSE:To provide a heat treatment method by which the defects in close proximity to the junction boundary of the shallow impurities diffusing area of a semiconductor substrate can be eliminated and besides the expansion of the junction. CONSTITUTION:After an LLD region 19, a source region 21 A and a drain region 21B are formed in a silicon substrate 11, a ruby laser beam of 600mJ/cm<2> is applied thereto and then an XeCl laser beam of 700mJ/cm<2> is applied, thereby repairing a point defect caused by ion implantation and at the same time activating ions.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a semiconductor device, and more particularly to a semiconductor manufacturing process provided with a unique annealing treatment for recovering crystallinity of a semiconductor substrate after ion implantation and activating carriers. Involve

[0002]

2. Description of the Related Art In the process of manufacturing various semiconductor devices,
A plurality of semiconductor elements are formed on the same semiconductor substrate, and various kinds of high temperature heat treatments are performed to separate or connect the semiconductor elements. In addition, LDD of semiconductor device
An ion implantation process is performed to form a (Lightly Doped Drain) structure and source / drain regions, and thereafter, to recover the crystallinity of the semiconductor substrate and electrically activate the implanted acceptor ions and donor ions, Activation annealing treatment is performed. Further, in order to reduce the contact resistance, refractory metal (W,
Mo, Ti, etc.) and Pt. High temperature heat treatment of a silicide layer, which is a compound layer of a metal such as Pd and Si, is required. Conventionally, a furnace annealing method or a rapid thermal annealing (abbreviated as RAT) method has been adopted as such activation annealing treatment or high-temperature heat treatment.

On the other hand, as the integration of semiconductor devices progresses, individual semiconductor elements are reduced in size, and shallow junctions are required in the source / drain regions, the emitter regions, the base regions and the like. When such a region is subjected to activation annealing treatment by a furnace annealing method or a RAT method, the diffusion layer becomes deep, and the source / drain junction is made shallow to miniaturize a semiconductor device to achieve high integration. Can't be satisfied. In addition, with miniaturization, for example, M
In the case of an OS transistor, the gate length is shortened, and the diffusion layer forming the source / drain regions is expanded not only in the depth direction but also in the lateral direction by the activation annealing treatment after the ion implantation, which easily causes punch-through. There is a point.
In order to suppress such expansion of the diffusion layer and make the source / drain junction shallow, the temperature of the activation annealing process must be lowered. In this case, the resistance becomes high and the current driving characteristic is deteriorated, so that This causes a problem that the switching characteristics are deteriorated.

Therefore, as a method of forming an impurity diffusion region of a shallow junction, an activation annealing method of performing pulse laser irradiation has been proposed.

Since the energy of this pulsed laser is absorbed by the very surface (about 20 nm) of the semiconductor substrate, the depth that can be annealed by the pulsed laser is about 100 nm or less even if thermal diffusion is taken into consideration. The temperature rise of the entire wafer is extremely small (about 1 to 2 ° C.). for that reason,
The annealing treatment by the pulse laser is suitable for the activation annealing treatment when forming the shallow LLD structure or the source / drain regions.

[0006]

However, when the bottom of the ion-implanted region is deeper than the annealed region, defects are not sufficiently annealed out and the junction leak increases. . In order to solve this problem, it is possible to increase the laser power and anneal to a deeper region, but there is a problem that the junction in the source / drain region becomes deep. When the laser power is low, only the very surface of the semiconductor substrate is melted, and then the surface of the semiconductor substrate is immediately flat. However, if the laser power is high,
There is also a problem that the flatness of the surface of the semiconductor substrate is significantly impaired because the semiconductor substrate melts to a considerably deep portion.

The present invention was made in view of such conventional problems, and by using the pulse laser method, a shallow junction is formed in a fine semiconductor device and a transistor junction is formed. Provided is a heat treatment method for a semiconductor substrate, which can reduce a leak current.

[0008]

The above problems are caused by the fact that the energy of the pulsed laser is absorbed by the very surface of the semiconductor substrate, so that the temperature distribution in the depth direction of the substrate becomes too steep. ing.

Therefore, according to the first aspect of the present invention, after forming an ion implantation layer having a shallow ion implantation depth on the semiconductor substrate, the surface of the semiconductor substrate is irradiated with two kinds of pulse lasers having different wavelengths. It is a solution.

The invention according to claim 2 is characterized in that the irradiation of the pulse laser is performed from a pulse laser having a long wavelength to a pulse laser having a short wavelength.

The invention according to claim 3 is characterized in that the pulse lasers having different wavelengths are a combination of a ruby laser and a XeCl laser.

According to a fourth aspect of the present invention, after forming an ion implantation layer having a shallow ion implantation depth on a semiconductor substrate, irradiation with a long wavelength pulse laser is performed to recover the crystallinity of the semiconductor substrate, and then a short wavelength irradiation is performed. It is characterized in that the impurities in the ion-implanted layer are activated by irradiation with a pulse laser.

[0013]

[Function] In pulse laser annealing, ruby laser (wavelength: 694 nm), XeF (wavelength: 351n)
m), XeCl (wavelength: 308 nm), KrF (wavelength:
249 nm), ArF (wavelength: 193 nm) and the like can be used, but among them, it is promising to use a combination of a ruby laser and a XeCl laser. The two types of lasers have different absorption depths in the Si substrate due to the difference in wavelength.

That is, the XeCl laser is absorbed on the very surface of the substrate, and the ruby laser reaches a part deeper than that (about 1 μm), so that it is heated to a deeper part. Therefore, it is possible to control the temperature distribution in the depth direction by optimizing the powers of these two types of lasers and irradiating the same portion simultaneously or continuously.
Note that FIG. 2 is a graph showing the relationship between the photoenergy of various pulse lasers and the absorption coefficient.

In practice, the XeCl laser requires sufficient power to activate the region in which high-concentration ions are implanted, and the irradiation energy during XeCl laser annealing is 650 to 1100 mJ / cm ² , and more preferably 700.
It is desirable to set it to ˜900 mJ / cm ² . The pulse width is preferably 20 to 100 nsec, and the irradiation interval may be arbitrary.

The ruby laser anneals to a deeper region, but the high-concentration region near the surface is activated and annealed by the XeCl laser, so that it is sufficient if the defects in the tail portion of the ion implantation having a relatively low concentration can be removed. A smaller amount can prevent redistribution of impurities.

In the method for heat treating a semiconductor substrate of the present invention, after forming the element isolation region and the gate electrode region,
LDD and source / drain regions are formed, and pulse laser processing is performed by a combination of a ruby laser and a XeCl laser. As a result, the temperature distribution in the depth direction can be made gentle and annealing is performed deeper than the junction boundary surface, so that the junction leakage current of the diffusion layer formed in these regions can be reduced. it can.

Since such a pulse laser treatment only affects the surface of the semiconductor substrate (for example, a depth of 100 nm or less), a shallow junction can be maintained in the source / drain regions, and a fine semiconductor device can be obtained. It becomes possible to manufacture.

An important point here is to optimize the power balance of the two types of pulse laser irradiation to activate the high-concentration layer near the surface and remove defects near the junction boundary surface. , To minimize the spread of the joint.

After the laser irradiation step, only heat treatment at 600 ° C. or lower is performed. That is, if heat treatment at 600 ° C. or higher is performed after the pulse laser irradiation step for activating the source / drain regions, the LDD structure or the junction in the source / drain regions becomes deep. As a case where a heat treatment is required in a later step, there is a sintering process when forming an aluminum wiring layer, and the temperature required in this process is about 450 to 600 ° C.

[0021]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The details of the heat treatment method for a semiconductor substrate according to the present invention will be described below with reference to the embodiments shown in the drawings.

(Embodiment) FIGS. 1 (A) to 1 (C) are cross-sectional views of essential parts showing the steps of an embodiment in which the present invention is applied to the manufacture of a MOS transistor.

First, the silicon substrate 1 is formed by using a well-known method.
1, an element isolation region 12 and a channel stop ion implantation layer 13 under the element isolation region 12 are formed. Next, after forming the gate oxide film 14, the threshold voltage adjusting ion implantation layer 15 is formed. Then, after covering the gate oxide film 14 with the gate polysilicon layer 16, the silicide layer 17 is formed.
To form the silicide layer 1 as shown in FIG.
7, the gate polysilicon layer 16 and the gate oxide film 14 are patterned to form a gate electrode region 18.

Next, as shown in FIG. 1 (B), LDD
(Lightly Doped Drain-source)
e) Region 19 is formed by ion implantation.

Thereafter, as shown in FIG. 1C, a side spacer 20 is formed on the side wall of the gate electrode by a known method, and then the source region 21A and the drain region 21B are formed.
Ion implantation process is performed. In the case of arsenic (As ⁺ ) ions, this ion implantation process is performed under the implantation condition of 5 to 20 ke.
V and the dose amount can be set to 1 × 10 ^{15 to} 3 × 10 ¹⁵ / cm ² . In the case of BF ₂ ⁺ ions, the implantation condition 5
〜20 keV, dose amount 1 × 10 ¹⁵ 〜3 × 10 ¹⁵ / c
It can be m ² .

Then, as shown in FIG. 1C, an oxide film 2 is formed as an antireflection film by chemical vapor deposition if necessary.
2 is formed to a film thickness of 50 nm, and thereafter the pulsed laser is applied to the silicon substrate 11 to form the LDD region 1
9 and the ions implanted in the source region 21A and the drain region 21B are activated. The activation annealing treatment by the pulse laser is performed by first irradiating a ruby laser which is a long wavelength (694 nm) pulse laser with an irradiation energy of 600 mJ / cm ² , and then 700 mJ / cm of a XeCl laser having a shorter wavelength (308 nm) than the ruby laser. cm ²
Irradiate with the irradiation energy of.

In the subsequent steps, the semiconductor device is completed according to the conventional method for manufacturing a semiconductor device. In the subsequent steps, it is important that the semiconductor substrate only be subjected to heat treatment at 600 ° C. or lower.

In this embodiment, the source region 21A,
Point defects generated when ions are implanted into the drain region 21B are effectively reduced by the ruby laser irradiation. Therefore, by performing the ruby laser irradiation, the point defects can be effectively reduced without deepening the junction. When such pulsed laser irradiation is performed, reverse leakage current can be suppressed. Since the source region 21A and the drain region 21B are activated by XeCl laser irradiation, a shallow junction can be maintained, and an ultrahigh-speed integrated circuit composed of minute transistors can be formed.

Although the embodiment has been described above, the present invention is not limited to this, and various design changes can be made accompanying the gist of the configuration, and the pulse laser can be combined other than the above. .

Further, although the present invention is applied to the MOS transistor in the above embodiment, it is of course possible to apply the present invention to a bipolar transistor.

[0031]

According to the present invention, by optimizing the power balance of the two types of pulse laser irradiation, the activation of the high-concentration layer near the surface and the removal of defects near the junction boundary surface are performed. However, it is possible to minimize the spread of the joint. Therefore, a diffusion layer with less junction leakage can be obtained, a low resistance and a shallow junction can be maintained, and an ultrahigh-speed integrated circuit composed of minute transistors can be formed.

[Brief description of drawings]

FIG. 1A to FIG. 1C are cross-sectional views of essential parts showing steps of an embodiment of the present invention.

FIG. 2 is a graph showing the relationship between the photo energy of a pulsed laser and the absorption coefficient.

[Explanation of symbols]

 11 ... Silicon substrate, 19 ... LDD region, 21A ... Source region, 21B ... Drain region.

Continuation of the front page (51) Int.Cl. ⁵ Identification code Office reference number FI technical display location H01L 29/784

Claims (4)

[Claims] 1. A heat treatment method for a semiconductor substrate, comprising forming an ion implantation layer having a shallow ion implantation depth on the semiconductor substrate and then irradiating the surface of the semiconductor substrate with two kinds of pulse lasers having different wavelengths. 2. The heat treatment method for a semiconductor substrate according to claim 1, wherein the irradiation of the pulse laser is performed from a pulse laser having a long wavelength to a pulse laser having a short wavelength. 3. The heat treatment method for a semiconductor substrate according to claim 1, wherein the pulse lasers having different wavelengths are a combination of a ruby laser and a XeCl laser. 4. After forming an ion implantation layer having a shallow ion implantation depth on a semiconductor substrate, a long wavelength pulse laser is irradiated to restore the crystallinity of the semiconductor substrate, and then a short wavelength pulse laser is irradiated. A method for heat treating a semiconductor substrate, which comprises activating impurities in the ion-implanted layer.