JPS6244847B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of heating a semiconductor wafer by light irradiation.

Recently, as a method for introducing impurities into semiconductor wafers (hereinafter referred to as wafers), ion implantation has been used, in which the impurities are ionized and accelerated and implanted into the wafer because the impurity concentration and junction depth can be precisely controlled. It's coming. However, in this ion implantation method, it is necessary to heat the wafer to about 1000° C. or higher after implantation. In this case, the heat treatment must be performed in a short time so that the concentration distribution of the implanted impurity in the depth direction does not change due to thermal diffusion. Furthermore, rapid heating and cooling of wafers is required to improve productivity.

In response to the above request, a method has recently been developed to heat wafers by irradiating light, and according to this method, it can be heated within a few seconds.
It is possible to raise the temperature from 1000℃ to 1400℃ for a short period of time.

However, when a wafer, such as single-crystal silicon, is heated to over 1000 degrees Celsius within a few seconds, damage called "slip line" occurs due to the difference in temperature rise between the outer periphery and the center of the wafer, that is, uneven temperature rise. I understood. In other words, the thickness of the wafer is usually very thin, around 0.5 mm, and the temperature distribution in the thickness direction is relaxed in the order of 10 ^-3 seconds, so in practical terms, the temperature distribution on the wafer surface is Damage such as slip lines can be prevented if the temperature distribution of
Inevitably, heat dissipation from the vicinity of the wafer's outer periphery is
Since the heat dissipation is larger than that in the center, the temperature near the outer periphery becomes lower than the temperature in the center, and a slip line occurs.

From this point of view, the present invention has been made with the object of providing a method of heating semiconductor wafers by light irradiation that does not cause damage such as slip lines. An auxiliary heating source that generates heat from an external power source, such as a molybdenum heater, is arranged so as to surround the outer periphery of the semiconductor wafer, and the auxiliary heating source is used to supplementally heat the vicinity of the outer periphery of the semiconductor wafer, or the auxiliary heating source is preheated. The purpose is to heat a semiconductor wafer by irradiating it with light.

An embodiment of the present invention will be described below with reference to the drawings.

Figure 1 is an explanatory diagram of the heating method as seen from above the wafer placed in the light irradiation furnace, and Figure 2 is the
This is an explanatory drawing when the figure is viewed from the side, and from the top and bottom, 12 bar-shaped halogen bulbs each with a power consumption of 1.5KW are arranged close to each other on one plane to form a surface light source, and this surface light source and the wafer The wafer 1 is irradiated with light so that the surface temperature of the wafer 1 reaches about 1250° C. at the center portion 1a by setting the interval between the wafers 1 to about 40 mm and applying electricity for about 10 seconds. The total power consumption of the surface light source for light irradiation is approximately 35 KW, and the wafer is a single crystal silicon implanted with borax ions with a diameter of 4 inches.

Reference numeral 2 denotes a circular halogen bulb or infrared bulb made of quartz glass, which is equipped with a filament 5b, and is arranged so as to surround the outer periphery 1c of the wafer 1, with quartz claws 2a here and there supporting the wafer 1. It is equipped with Since the inner diameter d of the ring is approximately 11 cm, the gap t with respect to the wafer 1 is approximately 4 mm. When the wafer is heated by light irradiation, the light bulb is turned on with a power consumption of about 920W to supplementally heat the wafer's outer periphery 1b, and the outer periphery 1b is 1250°C compared to the 1250°C in the center 1a. It is about 1255℃, near the outer periphery 1b
Although the temperature is rather high, the wafer can be heat-treated without any damage such as slip lines. In the above case, when light irradiation heating was performed without auxiliary heating, the temperature near the outer periphery 1b became a fairly low value of about 1120° C., and damage like a slip line was observed.

Note that the energization of the auxiliary heating source may precede the light irradiation by about 5 seconds. The amount of heat from the auxiliary heating source is smaller than the amount of heat from light irradiation, so even if the auxiliary heating source is used in advance for about 5 seconds, the temperature difference within the wafer surface is small and no damage will occur, and the periphery of the wafer can be efficiently heated during light irradiation. The temperature can be raised to

As can be understood from the above embodiments, the present invention uses an auxiliary heating source to heat the outer periphery of the wafer so as to offset the temperature drop caused by heat dissipation from the outer periphery 1b.
By heating the area 1b near the outer periphery auxiliary so as to surround c, the temperature difference between the central part and the area near the outer periphery is reduced, and the temperature over the entire surface of the wafer is made uniform, thereby preventing the occurrence of slip lines. It is something.

Note that wafer heating by light irradiation is generally performed in an inert gas atmosphere such as argon or in a vacuum, so auxiliary heating sources are not limited to light bulbs, but also metal resistance heating sources such as molybdenum heaters. The body may be used, and the output of the auxiliary heating source may be one that generates heat from an external power source according to its power consumption.

As described above, the present invention is a method of heating a semiconductor wafer by light irradiation, in which an auxiliary heating source that generates heat from an external power source, such as a halogen bulb or a molybdenum heater, is arranged so as to surround the outer periphery of the semiconductor wafer, and the auxiliary heating source is used to heat the semiconductor wafer. By heating the semiconductor wafer with light irradiation while supplementally heating the vicinity of the wafer's outer circumference, or by pre-heating the wafer in advance, the uniformity of the temperature distribution on the wafer surface can be improved and the slip line can be improved. It suppresses such damage and has extremely great practical value.

[Brief explanation of the drawing]

FIGS. 1 and 2 are explanatory diagrams of a wafer placed in a light irradiation furnace, where 1 indicates the wafer and 2 indicates an auxiliary heating source.

Claims (1)

[Claims] 1 In a method of heating a semiconductor wafer by light irradiation, an auxiliary heating source that generates heat from an external power source, such as a halogen bulb or a molybdenum heater, is arranged so as to surround the outer periphery of the semiconductor wafer, and the auxiliary heating source is used to auxiliary the area near the outer periphery of the semiconductor wafer. A method in which a semiconductor wafer is heated by light irradiation while being heated primarily or supplementally.