JPS60216541A - Introducing method of impurity to semiconductor substrate - Google Patents

Abstract

PURPOSE:To introduce an impurity to a predetermined region in the vicinity of the surface of an Si substrate by a method wherein a gas containing the impurity is brought into contact with the substrate, ultraviolet beams are projected through a mask to ionize the impurity, the ions are driven into the substrate by an electric field and a defect generated is annealed by beams. CONSTITUTION:An N type Si substrate 1 is placed on a negative plate 4 in a reaction chamber 2 and heated 3 at 100 deg.C, and the inside of the chamber is evacuated and BCl3 7 is introduced at a predetermined flow rate to keep the inside of the chamber at approximately 50Torr. ArF laser beams 9 having 1,930Angstrom are projected from a window for a mask 8 and focussed just above the substrate 1, and changed into beams in 2MW/ cm<2> energy and having a 2mum diameter and the upper section of the substrate is scanned. Ionized B is accelerated by a DC bias between an anode 12 and a cathode 4, and driven to a mask-window facing section in the substrate 1. The inside of the chamber is changed over to N2, an implantation region 4 is supplied with CO2 gas laser beams 16 in the energy of 10MW/cm<2>, and crystal defects are annealed. According to the constitution, only a surface section in an irradiation region is heated in the substrate 1, an existing junction is not displaced, and the substrate can be doped without being brought into contact with the outside air during processes.

Description

[Detailed description of the invention] [Technical field to which the invention pertains] The present invention relates to a method of introducing impurities into a predetermined region near the surface of a semiconductor substrate in order to form a layer having a predetermined conductivity type and impurity concentration on the semiconductor substrate. Related 0 [Prior art and its problems] A well-known method for forming a layer having a predetermined conductivity type and impurity concentration on a semiconductor substrate is to deposit an impurity source on the surface of the semiconductor substrate and thermally diffuse it into the substrate. There is a method, but this method is difficult to form shallow junctions, and requires the entire substrate to be
Recently, an ion implantation method in which the bonding surface previously formed in the substrate is implanted by heating to around 000° C. has become widely used. However, the high energy during ion implantation causes crystal defects in the substrate, so after ion implantation, the substrate is taken out of the implanter and heated to 9900 m
It is necessary to anneal the board at a temperature of around 30°F.For this reason, there is a small risk of contaminating the external environment when the board is taken out, and the bond previously formed in the board may be displaced due to heating. The problem still exists.

[Purpose of the invention]

The present invention aims to eliminate the above-mentioned drawbacks and provide a method that allows impurities to be introduced into a predetermined region of a substrate without increasing the substrate temperature and without exposing it to the outside air during the molding process. .

[Key points of the invention]

According to the present invention, a gas containing impurities is brought into contact with the surface of a semiconductor substrate, and light is irradiated to give energy to ionize impurity elements through a mask having a transparent pattern that is the same as the pattern of a region where impurities are to be introduced. The above purpose is achieved by accelerating the ions in an electric field and implanting them into a semiconductor substrate, and then annealing by irradiating at least the region of the semiconductor substrate into which the ions have been implanted with light that gives thermal energy. The light used for ionization has a wavelength shorter than the wavelength corresponding to the energy required for ionization, and is not so short that absorption becomes significant. Therefore, ultraviolet light with a wavelength of 1000 to 4000X is preferable.

[Embodiments of the invention]

An example of implanting boron ions into an NFI silicon substrate and annealing will be described below with reference to FIG. The inside of the reaction chamber 2 is placed on the cathode plate 4 which is heated to 100°C by the heater 3 (heating may not be necessary depending on the case).
After creating a vacuum of 0.01 Torr or less, the gloss 13 was controlled to a flow rate of 100 m1/- through a mass 70 meter 6.
A gas is introduced into the reaction chamber from a cylinder 7 and kept at a pressure of about 50 Torr, and a mask 8 is opposed to the substrate 1 at a position about 1 inch directly above it. The mask 8 has a transparent part with the same pattern as the region where impurities are to be implanted, and 193
The oscillation light 9 of the ArF excimer laser with a wavelength of 0 A is reflected by the mirror 10.
, is irradiated through the lens 11 so as to be focused directly above the substrate l. The irradiation light is scanned over the substrate as a beam with a power density of 2 MW/cd and a diameter of 2 μm to ionize the BCA 3 gas, and the generated boron cations are transferred to the cathode plate 4 and the anode plate located 1Ocfn above it. 12 and is accelerated by a DC bias applied by a power source 13 and is implanted into the substrate 1. The implanted ions 14 exist only in a predetermined area facing the transparent part of the mask.Next, the atmosphere in the reaction chamber is changed to N2 gas from the cylinder 15, and the mirror lO is rotated, cO□ Oscillation light 16 of a gas laser with a wavelength of 9.6 μm is passed through a mask 8 to ions 14.
The implanted area is irradiated with a power density of 10 MW/+d. As a result, crystal defects generated during B ion implantation are annealed, and a healthy p-type region is formed. The substrate 1 is only heated by the laser beam in the vicinity of the surface of the light irradiation area, and the temperature in other areas hardly increases, so the positions of other pre-formed junctions do not change. Depending on the position of other bonding, the mask 8 may be removed from the top of the substrate l by an operation from outside the reaction chamber during irradiation with the CO2 laser beam 16, and the entire surface of the substrate l may be irradiated with laser light to 7 times the entire surface. .

〔Effect of the invention〕

In the present invention, a gas containing impurities to be introduced into a semiconductor substrate is ionized by irradiating light only directly above the region to be introduced, and the ions are accelerated by an electric field and implanted into the substrate. Annealing is also performed using light irradiation, and since it can be performed in consecutive steps in the same reaction chamber, there is no risk of contaminating the substrate.Also, since the entire substrate is not heated to high temperatures, The effect is extremely large, as it does not affect the position of the bonded joint.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of an apparatus for one embodiment of the invention.

Claims (1)

[Scope of Claims] 1) A method for introducing impurities into a predetermined region near the surface of a semiconductor substrate, in which a gas containing an impurity is also brought into contact with the surface of the semiconductor substrate, and a mask having a light-transmitting pattern identical to the pattern of the predetermined region is provided. The impurity element ions produced are accelerated by an electric field and implanted into the semiconductor substrate, and then the semiconductor substrate is irradiated with light that imparts thermal energy to at least the region where the ions are implanted. A method for introducing impurities into a semiconductor substrate, the method comprising annealing. 2. In the method according to claim 1, the light providing ionization energy has a wavelength of 1000 to 4000.
A method for introducing impurities into a semiconductor substrate, characterized by using ultraviolet light of X.