JPS60216540A - Introducing method of impurity to semiconductor substrate - Google Patents

Abstract

PURPOSE:To prevent the contamination of a substrate and the positional change of an existing junction by optically scanning a gas containing an impurity to be introduced to a semiconductor only on an introducing region and ionizing the gas, accelerating ions and driving in the ions and annealing the substrate through beam projection. CONSTITUTION:An N type Si substrate 1 is heated at 100 deg.C in a chamber 2 at 0.01Torr or lower, and a fixed quantity of BCl3 7 is flowed to keep the inside of the chamber at approximately 50Torr. ArF laser beams 8 having a 1,930Angstrom wavelength are focussed onto the substrate 1, and the upper section of a region, in which B must be introduced, is scanned by beams having a 2mum diameter and in 2MW/cm<2>. B ions are generated from BCl3 and accelerated by the DC bias of a negative plate 12, and B ions are driven only into the region scanning by beams 8. The inside of the chamber 2 is replaced with N2 13, an implantation region or the whole surface is scanned in approximately 10MW/cm<2> by CO2 laser beams 14 having a 9.6mum wavelength, and crystal defects are annealed. Since only a B implanting region in the vicinity of the surface is heated in said chamber in the substrate 1 and other sections are kept at a low temperature, the positional changes of other junctions previously formed are not brought about, and no contamination is generated.

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. [Prior art and its problems] A well-known method for forming a layer with 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 heat the inside of the substrate. However, this method is difficult to form shallow junctions, and requires the entire substrate to be
Since it is heated to around 000° C., there are drawbacks such as movement and deformation of the bonding surface previously formed in the substrate. On the other hand, an ion implantation method has recently become widely used, in which impurities are ionized by high-frequency discharge, electron bombardment, etc., and then accelerated with garbage and implanted into the semiconductor substrate. However, since crystal defects occur in the substrate due to the high energy during ion implantation, it is necessary to take the substrate out of the implanter after ion implantation and anneal it in a heating device at a temperature of around 900°C. Therefore, there is a risk of contamination from the external feces when the IC is removed.
There is a problem that the bond previously formed in the substrate may be displaced due to heating.

[Purpose of the invention]

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

[Key points of the invention]

According to the present invention, a gas containing an impurity is brought into contact with the surface of a semiconductor substrate, and light giving energy to ionize the impurity element is scanned directly above the region of the substrate surface where the impurity is to be introduced, and the generated ions are driven by an electric field. The above object is achieved by implanting ions into a semiconductor substrate at accelerated speed, and then annealing by irradiating at least the region of the semiconductor substrate into which the ions have been implanted with light that imparts thermal energy. The light used for ionization has a shorter wavelength than the wavelength corresponding to the energy required for ionization, but it is not so short that absorption is significant; therefore, the wavelength is 1000 to 4000.
Ultraviolet light of A is preferable〇 [Embodiment of the invention] Hereinafter, referring to FIG. 1 showing an apparatus for carrying out the present invention, an embodiment of implanting # and annealing the silicon substrate with # ions will be described. do. An n-type silicon substrate 1 is placed on a cathode plate 4 heated to 100° C. (in some cases, heating may not be necessary) by a heater 3 at the bottom of the reaction chamber 2. to the vacuum pump 5)
After creating a vacuum below 0.01 Tc)rr, mass 70
- The flow rate is controlled to 100 m1/- by meter 6.
C, gas was introduced into the reaction chamber from cylinder 7 at 50 T.
Ar with a wavelength of O order 1930X maintained at a pressure of about orr.
The oscillation light 8 of the F excimer laser is passed through a mirror 9 to a lens 10.
The beam is focused directly above the substrate 1, and is scanned as a beam with a diameter of 2 μm and a power density of 2 W over the region of the substrate 1 where boron is to be introduced using a mirror 9, a grating, and a shutter (not shown). This light generates #1 boron ions from the pxi3 gas, and these positive ions are stimulated by the DC bias applied by the power supply 12 between the cathode plate 4 and the anode plate 110 facing above with a distance of 105I. The O-implanted boron ions that are accelerated and implanted into the substrate IK exist only in the region scanned by the laser beam 8. Next, the ambient air in the reaction chamber 2 is converted into N2 gas from the cylinder 13, and then the mirror 9 is rotated to change the wavelength of the CO2 gas laser to 9.6.
The B ion implantation region or the entire surface of the substrate 1 is scanned as a beam with a power density of 1 o MW/aA using the oscillation light 14 of μm. As a result, crystal defects generated during B ion implantation are annealed, a healthy p-type region is formed, and a pn junction is completed. Since the silicon substrate 1 is heated by the laser beam 14 only in the vicinity of the ion-implanted region near the surface, the temperature of the other parts remains low. It does not cause a change in the position of the bond. [Effects of the Invention] The present invention scans light to ionize a gas containing impurities to be introduced into a semiconductor substrate only directly above the region to be introduced, and applies an electric field to the gas. The resulting ions are accelerated and implanted into the substrate, and the resulting crystal defects are annealed using light irradiation. Because the process can be performed in consecutive steps in the same reaction chamber, there is no risk of contaminating the substrate. In addition, since the entire substrate is not heated to a high temperature, the positions of the bonds already formed within the substrate will not change, making it extremely effective for manufacturing semiconductor devices, especially semiconductor integrated circuits.

[Brief explanation of drawings]

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

Claims (1)

[Claims] 1) In a method of introducing impurities into a predetermined region near the surface of a semiconductor substrate, a gas containing an impurity is brought into contact with the surface of the semiconductor substrate to ionize an impurity element directly above the predetermined region on the surface of the substrate. The method involves scanning light that gives energy, accelerating the generated ions using 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. Characteristic method of introducing impurities into semiconductor substrates. 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.