JPS6088431A - Heating method by photo irradiation - Google Patents

Abstract

PURPOSE:To enable the even heating of wafers by a method wherein the heat amount by auxiliary heating is determined in the optimum range according to the temperature of heat treatment of wafers. CONSTITUTION:The surface of a wafer 5 is heated by photo irradiation with main heaters 3, and the neighborhood of the outer periphery of the wafer is heated in an auxiliary manner by means of a ring-form auxiliary heater 6 provided in proximity to the neighborhood of the outer periphery of the wafer. When the temperature of heat treatment of the wafer is T deg.C and the power applied per unit length of the circumference of the wafer by means of the auxiliary heater is W watt/cm, it is contrived that a relation of 0.20T-212>=W>=0.14T- 152 is satisfied at T>=1,100 deg.C. In this case, for example, the main heaters 3 are arranged in the upper and lower parts in a device casing 1 via reflection member 2, and the density of irradiation energy on the wafer is made uniform within + or -2%. A transparent container 4 made of quartz glass is arranged at the center of the casing, and the wafer the object to be processed is placed and supported on the auxiliary heater used also as a supporter therein.

Description

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

Recently, semiconductor wafers (hereinafter simply referred to as ``wafers'') have become popular.

), the impurity concentration is 1. Since the junction depth t can be precisely controlled, ion implantation has been used in which impurities are ionized and accelerated and implanted into the wafer. In this ion implantation method, the crystal state of the wafer surface changes after the ions are implanted and becomes rough, so in order to eliminate this roughness and create a good surface condition, approximately 100
It is necessary to heat the wafer to a temperature of 0° C. or higher, and this 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 addition to such heat treatment, there are other processes that require heating in semiconductor manufacturing, such as impurity diffusion processes,
Chemical vapor phase IjM long process, thermal JI for electrical activation
I: There is a heat treatment process for fully nitriding or oxidizing the surface layer of the 7 recon wafer, and when performing these processes, rapid heating and cooling of the wafer is required as described above. .

Using MW, a light irradiation furnace has recently been developed that heats the wafer with light irradiation.This light irradiation furnace can heat the wafer from 1000℃ to 1400℃ in just a few seconds. It is.

By the way, when performing heat treatment on a wafer, for example, single crystal silicon, by simply irradiating it with light, the temperature is raised to a processing temperature of around 1150°C within a short period of several seconds, and then maintained at this processing temperature throughout the process. , a relatively large difference in temperature occurs between the outer periphery or the vicinity of the outer periphery and the center of the wafer at external temperature and processing temperature,
It has been found that this temperature difference causes large ``warps'' in the wafers that can interfere with subsequent processing steps, as well as damage called ``slip lines.'' This temperature difference also caused variations in the wafer's 7-t resistance value, which affected its performance.

This is because the thickness of the wafer is usually very thin, around 0.5 mm, and the temperature distribution in the thickness direction is approximately 10 mm thick over time.
- Since it is slowed down to the order of 5 seconds, it is essentially "ζ
However, the temperature distribution in the direction along the wafer surface is such that even if the wafer surface is irradiated with light at a uniform irradiation energy density, heat from the wafer periphery or near the wafer periphery Since the heat dissipation is larger than that from the center of the wafer, the wafer
- The temperature at or near the outer periphery of the wafer cannot follow the temperature at the center of the wafer, and even at processing temperatures, the temperature at or near the outer periphery of the wafer does not reach the temperature at the center of the wafer. This is because the temperature at or near the outer periphery of the wafer ends up being much lower than the temperature at the center of the wafer.

For this reason, a method has been proposed in which the outer periphery of the wafer or the vicinity of the outer periphery is additionally heated. The wafer is primarily heated by light irradiation, and the wafer is heated while the outer periphery or the vicinity of the wafer is auxiliary heated by a link-shaped auxiliary heater such as a lamp or heater.

However, even if this auxiliary heating is performed, if the amount of heat applied is too small or too large, the wafer temperature will not be uniform and the above-mentioned problem will occur. iM h=1 also varies depending on the heat treatment temperature of the wafer.

Therefore, the present invention addresses the above-mentioned problems +? The purpose of this method is to provide a wafer light irradiation heating method that enables uniform heating of the wafer by determining the optimal range of the amount of heat from auxiliary heating depending on the wafer heat treatment temperature. The present invention was completed as a result of intensive and detailed research. The structure of the present invention is such that a main heater heats the surface of the wafer by irradiating light, and a ring-shaped auxiliary heater disposed close to the wafer's outer periphery assists the entire wafer's outer periphery. It is a method of heating Ueno--〇 heat treatment temperature to T
(°C), and when the power applied per unit length of the circumference of Ueno- by the auxiliary heater is W ("tsu1/rrn), when T≧1100°C, 0.20T-212≧
It is characterized by satisfying the relationship W≧0.14T-152.

The implementation of the present invention will be specifically explained below with reference to the drawings.

FIG. 1 is a cross-sectional view schematically showing a light irradiation heating furnace used in an embodiment of the present invention, and a main heater 6 is disposed above and below inside the device box 1 via a reflecting member 2f. The main heater 6 is a planar light bulb made of bar-shaped halogen bulbs with a power consumption of 2150 W arranged closely in a plane.
The uniformity of the irradiation energy density on the wafer is within ±2%, and the temperature of the object to be processed can be raised to 1400°C. A transparent container 4 made of quartz glass is placed in the center of the apparatus box 1, and a wafer 5, which is an object to be processed, is placed and supported on an auxiliary heater 6 which also serves as a supporter. Wafer 5 has a diameter of 6 inches (circumference approximately 24 cr)
n), is a disk shape with a thickness of 0.4 m, and phosphorus ions are 5 x 10"5"/
It consists of monocrystalline silicon implanted with a proportion of cr4. The auxiliary heater 6 includes a link-shaped enclosure 61 as shown in FIG.
It is a halogen bulb with a filament 62 sealed inside, and its maximum power consumption is 1300W. Four supports 7 are hung on the seal 61, and the wafer 5 is placed on the protrusions of the supports 7. Therefore, sea urchin/
・The vicinity of the outer periphery 5a of -5 is located directly above the auxiliary heater 6.
, L, the distance is 10Inll. However, the auxiliary heater 6 needs to be located directly under the outer circumference 5a.
-f, it may be on the side or above the outer periphery, and the distance is selected within the range of 5 to 15 m from the outer periphery.

Thus, the surface of the wafer 5 is irradiated with light and heated by the main heater 6, and the vicinity of the outer periphery 5a is heated by the auxiliary heater 6.
This compensates for the large heat dissipation from the vicinity of the outer periphery and heats the entire area evenly, but as mentioned above, if the heating by the auxiliary heater B is too much or too little, The whole is not uniform, and there is still "warp"
Otherwise, slip lines will occur, and the variation in the resistance value will not be reduced.

Therefore, in the present invention, the heat treatment temperature T of the wafer 5 is set to 110
In the range of 0 to 1300℃, the power consumption of the auxiliary heater 6 per unit circular length of Moda Ueno-5 is up to 5077
-F7crn was heated to check for the occurrence of slip lines, and at the same time, the variation in the C)-Ut resistance value ρ was measured to find heating conditions that could keep this variation within the allowable range. Note that the allowable range of variation in the sheet resistance value ρ of the wafer 5 is 3 a /7. is within 5 inches. The measurement results are shown in Figure 4. The 0 mark in the figure indicates that 3a/- is 5.
The points within ρ are plotted, and the × marks are plotted for points with ρ of 5% or more. Here, the 0 mark is 1. ”W=0.20T-212 and W=
0.14T-152 two lI], is within the range of the wings, and therefore, in the area A indicated by the diagonal lines between the inner straight lines, the variation in sheet resistance value can be kept within the permissible range, and in practice At the 0 mark, no "warpage" or slip lines occurred. Add χ・1 to this and get W>0.20T-Q 1 'J-7
S! L IA own ITJ) Ding t 11 rr+ ktatami i lN+ 1llll lik 9'L A f?
n1rtJc is too large, and the temperature near the outer periphery 5a becomes too high than that at the center, and conversely, W<0. '14
In region C, which is T-152, the heating is too low and the temperature near the outer periphery 5a is low, and in any case, the purpose of uniform heating cannot be achieved.

As explained above, in the present invention, the wafer heat treatment temperature T
(°C) and the power W ('7t/cm) applied by the auxiliary heater per unit length of the wafer's circumference.
It has been found that the purpose of uniform heating can be achieved when the relationship 212≧W≧0.14T-152 is satisfied. According to the present invention, the appropriate range of auxiliary heating by the auxiliary heater at each heat treatment temperature can be easily determined. Can be bent and "warped"
It is possible to provide a light irradiation heating method that can heat wafers without generating slip lines or slip lines and with small variations in sheet resistance.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a heating furnace used in an embodiment of the present invention;
Figure 2 is a plan view of the auxiliary heater, Figure 5 is a cross-sectional view,
FIG. 4 shows explanatory diagrams of the data. 1... Equipment box 2... Reflective member 5... Main heater 4... Transparent container 5... Wafer 6... Auxiliary heater applicant Ushio Inc. agent Patent attorney Toranosuke Tahara 3

Claims (1)

[Claims] A main heater irradiates the surface of the semiconductor wafer with light to heat it, and a ring-shaped auxiliary heater disposed close to the outer periphery of the semiconductor wafer heats the surface of the semiconductor wafer. A method of auxiliary heating of a semiconductor wafer, comprising: a heat treatment temperature tT (°C) of a semiconductor wafer, a heat treatment temperature tT (°C) of a semiconductor wafer; When, T≧1100
At °C, α20T-212kW, Po, 14T-1
A method for heating a semiconductor wafer by light irradiation, characterized in that the following relationship is satisfied: