JPH0244717A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To diffuse and activate an impurity and to form a shallow impurity layer by implanting the impurity to the shallow region on a semiconductor substrate, and then heating only the shallow region of the surface by an excimer laser. CONSTITUTION:An impurity is implanted to one main face of a semiconductor substrate by an ECR plasma excitation, it is irradiated with a predetermined dose of excimer laser to uniformly diffuse the impurity shallowly. For example, an SiO2 for interelement isolation is formed as the substrate, As is shallowly implanted to the substrate in which an N<+> type polysilicon gate 23 and a sidewall oxide film 25 are formed by an ECR plasma doping, it is wholly irradiated with the laser to activate the As, thereby obtaining N<+> type source 26, drain 27. In this case, since the laser is used and the temperature of only the shallow region irradiated with the laser is raised, the As is activated to form the N<+> type layer, but its depthwise and lateral diffusions can be reduced. Thus, a very shallow impurity layer can be formed.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a shallow impurity diffusion method in the fabrication of semiconductor devices.

BACKGROUND OF THE INVENTION In recent years, there has been a trend toward miniaturization and higher speed in MOS transistors, etc., and therefore it is necessary to introduce impurities shallowly.

Conventionally, in forming an impurity layer, the mainstream method has been to introduce the impurity by ion implantation and then perform heat treatment to activate the impurity to form the impurity layer. Furthermore, a shallow impurity layer is formed by a technique that uses low acceleration energy during ion implantation or by ion implantation such as BF Mori. In addition, other techniques have been developed for forming impurity layers by plasma doping or laser doping.

Problems that the invention aims to solve However, the conventional technology has the following problems.

■ If heat treatment is performed after implanting impurities by ion implantation, even if shallow implantation is performed using low acceleration energy or BF2, the temperature must be raised to the point at which the impurities are activated during the heat treatment, and at this temperature, the impurities The spread of is inevitable. In other words, the impurity layer spreads and becomes deeper.

■ In normal plasma doping, impurities cannot be introduced unless the temperature of the semiconductor substrate is increased, the acceleration energy of impurity ions during doping is non-uniform, and activation by heat treatment is required. As mentioned above, the impurity layer becomes deep.

■ Laser doping heats the semiconductor substrate surface to high temperatures and melts it, so crystal defects are likely to occur during the melting and recrystallization of the surface. Furthermore, it is not practical to thermally decompose impurity gas in the gas phase on the surface of the semiconductor substrate and diffuse it into the substrate because the efficiency of impurity doping is poor. Furthermore, when an impurity thin film is formed on the surface of a semiconductor substrate and then diffused by laser heating the surface, crystal defects are likely to occur between the impurity thin film and the semiconductor substrate, and it is difficult to remove only the impurity thin film. There was an issue.

Means for Solving the Problems The present invention provides a step of introducing impurities into one principal surface of a semiconductor substrate by ECR plasma excitation;
By irradiating the surface of the semiconductor substrate with a desired amount of excimer laser, the impurities are uniformly and shallowly diffused.

After an impurity layer is formed in a very shallow region of the surface of the semiconductor substrate by ECR plasma excitation, excimer laser irradiation is performed. Excimer lasers have short wavelengths that are absorbed by shallow layers on the surface of semiconductor substrates, and can obtain high laser power, so that the heat of the substrate heated by the laser is absorbed before it is diffused deeply. The surface temperature can be increased, and only the surface of the semiconductor substrate can be heated, and impurities are diffused only into this heated region, which is extremely shallow. In addition, since the absorption depth differs depending on the wavelength of the excimer laser, it is possible to heat in the range of several tens of nanometers to several hundred nanometers, thereby creating an impurity layer with a depth of several tens of nanometers to several hundred nanometers. formation and activation of impurities.

Example Examples of the present invention are described below.

First Embodiment FIG. 1 is a diagram showing an impurity concentration profile in the depth direction for explaining the first embodiment of the present invention. First, after installing a (100) P-type Si substrate 1 as a semiconductor substrate in an ECR plasma generator as shown in FIG.
s H3 gas is introduced to generate EC,R plasma under ECR conditions.

Ru. As+ ions excited by the ECR plasma are guided by a divergent magnetic field and introduced into the surface of the Si substrate 1. In Figure 1, the horizontal axis is the depth from the surface of the Si substrate 1, and the vertical axis is the As
The arsenic concentration is shown, and FIG. 1a shows the state when As is introduced by ECR plasma. As can be seen in FIG. 1a, As is introduced into a shallow region of about 0.1 μm from the surface, and the surface concentration is extremely high. Next, when the Si substrate 1 into which As has been introduced is irradiated with an appropriate amount of ArF excimer laser (193nl11) in an N2 atmosphere or vacuum, the surface of the Si substrate 1 is irradiated by several tens of nanometers to several hundred nanometers.
heated only. At this time, the As introduced into the Si substrate 1 diffuses, resulting in a --like concentration distribution as shown in Figure 1, and because the region where As diffuses is near the surface heated by the laser. , the spread of As is limited,
As can also be uniformly diffused into the shallow region. Moreover, since As is activated, a shallow N-type region can be formed.

Furthermore, although As was used as the impurity in the first embodiment, other impurities such as B (boron) and P (phosphorus) can be used to form a shallow diffusion layer in the same way.

Second Embodiment FIG. 2 is a process sectional view for explaining the second embodiment of the present invention, in which 5iO222 for isolation between elements is formed as a semiconductor substrate as shown in FIG. 2(A). , n+ polysilicon gate 23. After shallowly introducing As into the substrate on which the sidewall oxide film 25 is formed by ECR plasma doping, the entire surface is irradiated with an excimer laser to form As.
Activate the n-type source 26. Obtain drain 27. At this time, an excimer laser is used to raise the temperature only in the shallow area irradiated with the laser, so As can be activated and form an n-soil layer, or diffusion in the depth direction or in the direction of the slope can be reduced. .

Third Embodiment FIG. 3 is a diagram showing an impurity concentration profile in the depth direction for explaining the third embodiment of the present invention. After doping B (boron) into a very shallow layer on the surface of the Si substrate 1, it is oxidized at a temperature of 850° C. or lower (a temperature at which B hardly diffuses). FIG. 3C shows the B concentration profile after oxidation. Next, after removing the oxide film, the surface layer is heated by irradiation with an excimer laser to activate B. The B concentration profile after laser irradiation is shown in FIG. 3d. As described above, by removing the oxide film after oxidation, the high concentration layer of B near the surface created by ECR plasma doping is removed, and then the excimer laser
By diffusing through heating, a layer with a constant concentration can be formed in a shallow region.

Fourth Embodiment FIG. 4 is a diagram showing an impurity concentration profile in the depth direction for explaining the fourth embodiment of the present invention.
After oxidizing the i-substrate 1, it is doped with B by ECR plasma doping. FIG. 4e shows the B concentration profile after doping. Thereafter, after removing the oxide film, the surface layer is heated by irradiation with an excimer laser to activate B, thereby forming a shallow B layer having a uniform concentration as shown in FIG. 4f.

As described above in the fourth embodiment] to the fourth embodiment, the explanation has been made using ECR plasma doping as the impurity doping, but this is less than 20 KeV (
For example, ion implantation may be performed in the B layer using an acceleration energy of 10 K e V). For example, Figure 6g
As shown in FIG. 2, the impurity profile when implanted at 10 KeV is almost the same as that performed by ECR plasma doping. However, as shown in Figure 6, when implanted at 30 KeV, a peak of impurity appears in the semiconductor substrate.

Therefore, if implantation is performed at approximately 20 K e V or less, a very shallow impurity layer can be formed even with impurity doping using ion implantation instead of ECR plasma doping. In addition, although an ArF excimer laser (193r+m) was used as an example of heating a Si substrate with an excimer laser, it may also be of other wavelengths (the laser power and irradiation amount may be adjusted depending on the purpose (for example, impurity layer Similar results can be obtained by irradiating an appropriate amount with a wavelength suited to the R
A device of the type that applies a direct current bias voltage using an F application type device may be used.

Effects of the Invention According to the present invention, after impurities are introduced into a very shallow region of the surface of a semiconductor substrate, an excimer laser is used to heat only the shallow region of the surface to diffuse and activate the impurities. It can form layers and can be applied to high-speed, miniaturized transistors.

[Brief explanation of the drawing]

FIG. 1 is an impurity concentration profile diagram in the depth direction for explaining the first embodiment of the present invention, FIG. 2 is a sectional view of the manufacturing process for explaining the second embodiment of the present invention, and FIG. 3 is an impurity concentration profile diagram in the depth direction for explaining the third embodiment of the present invention, and FIG. 4 is an impurity concentration profile diagram in the depth direction for explaining the fourth embodiment of the present invention. , FIG. 5 is a schematic diagram of the ECR plasma generator used in the embodiment of the present invention, and FIG. 6 is a diagram for explaining that the profile differs due to the difference in acceleration energy when introducing impurities by ion implantation. It is an explanatory diagram. 21...Si substrate, 26...source,
27...Drain. Name of agent: Patent attorney Shigetaka Awano and one other person 3 Bossilicate so ttyo tso wD Imposition (11) 9 Fu 15θ Uri depth (normal → depth (de sail) 5tt rtro tso mθ depth (le 9) Fig. 5tl 106 Bu Vθ depth (nfyL) Shakuhachi room - osoiθθ pu turbidity oath (sa (ri tw) fig.,, t8L ::2 [ so ttv tso zt lira shimisa (gan〃t) ,,:B1

Claims (3)

[Claims] (1) The impurities are uniformly and shallowly diffused by a step of introducing impurities into the surface of the semiconductor substrate by ECR plasma excitation on one main surface of the semiconductor substrate, and a step of irradiating the surface of the semiconductor substrate with a desired amount of excimer laser. A method for manufacturing a semiconductor device, characterized in that: (2) A step of introducing an impurity into the surface of the semiconductor substrate by ECR plasma excitation into one main surface of the semiconductor substrate, a step of oxidizing the semiconductor substrate at a temperature at which the impurity hardly diffuses, and a step of A method of manufacturing a semiconductor device, characterized in that the impurity is uniformly and shallowly diffused by a step of removing an oxide film and a step of irradiating the surface of the semiconductor substrate with a desired amount of excimer laser. (3) On one main surface of the semiconductor substrate, a step of oxidizing the surface, a step of introducing impurities into the surface of the semiconductor substrate by ECR plasma excitation, a step of removing an oxide film on the surface of the semiconductor substrate, and a step of oxidizing the surface of the semiconductor substrate. A method of manufacturing a semiconductor device, characterized in that the impurity is uniformly and shallowly diffused by a step of irradiating a substrate surface with a desired amount of excimer laser.