JPH0420253B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field) The present invention relates to an apparatus that rapidly heats a semiconductor substrate using infrared rays or visible light to perform heat treatment in the manufacturing process of a semiconductor device. Such heat treatment is particularly effective in microfabrication manufacturing processes. For example, in ion-implanted semiconductor substrates, it is used for electrical activation to minimize distribution changes of implanted ions, and for PSG (phosphosilicate glass), etc. It is effective for flattening interlayer insulating films by short-time reflow, forming silicides, and forming shallow oxide films, and has a wide range of uses.

(Prior Art) Various heat treatment apparatuses for semiconductor substrates have been proposed in the past, and the present inventors have also proposed Japanese Patent Application No. 58-89139, Japanese Patent Application No. 217835-1983, and Utility Application No. 1983.
-We are making proposals such as No. 178820.

First, the heating system will be explained. It is well known that wafers are heated by irradiation with photothermal rays such as infrared rays, but in the past, wafers were heated using a support plate (called a susceptor).
A method was used in which infrared rays were irradiated from above the wafer surface. However, with this method, the temperature of the top surface of the wafer increases rapidly, while the temperature of the bottom surface of the wafer, which is in contact with the susceptor with a large heat capacity, rises slowly, creating a large temperature gradient between the top and bottom surfaces of the wafer, which can cause various defects. Become. As a countermeasure to this, the temperature gradient can be significantly reduced by making the susceptor from an infrared transmitting material such as quartz, by irradiating infrared rays from the bottom of the susceptor, and by providing about three protrusions on the susceptor and placing the wafer on these protrusions. However, it is known that it is not possible to eliminate the temperature gradient on the wafer surface due to variations in the arrangement interval of the infrared sources and the amount of radiation from the infrared sources. This temperature gradient on the wafer surface can be removed by rotating the susceptor, but this has the disadvantage of complicating the apparatus. The wafer was rotated in a floating state by irradiating the wafer with a susceptor and injecting inert gas from the bottom surface without using a susceptor, and it was shown that uniform heat treatment could be obtained. It became clear that there was a problem.

FIG. 1 shows a cross-sectional view A, a top view B, and a sheet resistance characteristic diagram C of the semiconductor substrate surface of a substrate floating and holding portion of an example of a conventional semiconductor substrate heat treatment apparatus. In these figures, 1 is a semiconductor substrate, and 2 is a structure made using a near-infrared and visible light transmitting material such as quartz.The substrate 1 is heated by heat sources (not shown) installed above and below the structure. Heat. The surface of this structure (hereinafter referred to as the stand) is provided with a plurality of small holes for injecting inert gas toward the substrate 1, and 3 is for levitating or rotating the semiconductor substrate (hereinafter referred to as the wafer). The small hole 3' is a small hole for floating and holding the wafer in a fixed position, and the arrow indicates the direction of gas jetting. Reference numeral 4 denotes a groove for carrying the wafer onto the table 2 from one side thereof and carrying it out to the same side or the opposite side.

The wafer carried onto the table 2 is heated from above and below while being floated by gas jets from below or in a floating rotation state. FIG. 1C is an example of the results of measuring the sheet resistance of the wafer surface after heat-treating the ion-implanted wafer. As shown in this figure, since the table 2 has grooves, the sheet resistance (area resistivity) is non-uniform. In other words, this indicates that an uneven temperature distribution occurred in the radial direction of the wafer. Also, compared to the case of using a table without grooves, which will be described later, if the gas flow rate for levitation and rotation is the same, the wafer levitation and rotation state will be more unstable, and it is necessary to increase the gas flow rate to increase stability. It turns out that there is. Furthermore, the structure of this table has grooves, making it complicated and expensive, and depending on the manufacturing method, there are drawbacks such as cracks may occur due to thermal strain during heating.

Next, the above-mentioned patent application filed in 1983 proposed by the present inventor
In No. 89139, the cross-sectional view is shown in Figure 2A,
In this figure, 11 is a wafer, 12 is a wafer holding plate, 13 is a gas outlet, 14 is a wafer floating positioning gas outlet, 15 is a levitation gas outlet, 16 is a rotating gas outlet, 17 is an upper lid, and 18 is a The infrared irradiation device with a reflector, 19, is an infrared transparent gas conduit. FIG. 2B is a layout diagram of the gas discharge ports and jet ports on the holding plate 12.

The apparatus shown in FIG. 2 does not have grooves as in the apparatus shown in FIG. 1, so the temperature distribution of the wafer can be improved, but there is a problem when transporting the wafer to this heating position. That is, it is quite difficult to carry the wafer into and out of a narrow space as shown in the figure without touching anything with the upper surface of the wafer. The distance between the upper surface of 12 and the lower surface of the levitated wafer is, for example, 0.2 to 0.3.
It is about mm.

Next, the method of heating the wafer while floating and rotating it has the following drawbacks.

a Since gas is ejected, there is generally a cooling effect on the wafer, and there is a power loss of approximately 5% compared to the case where the wafer is supported at three points and heated without ejecting gas.

b When _N2 gas is used as the gas, a link-shaped film (which was found to be a SiN film by analysis) is formed at the gas ejection site on the back side when the back surface of the wafer is silicon, and it also forms a link-like film (which was found to be a SiN film by analysis), as well as formation of a link-like film at the gas ejection port on the holding plate or the table. There may be deposits in the vicinity. This deposit is probably caused by the cooling effect of the gas from the evaporated Si.

c Since wafers generally have an orientation flat (an example is shown at 32 in Figure 5),
Wafer rotation tends to be rather unstable.

d) The positions of the positioning holes vary depending on the diameter of the wafer, and it is necessary to change the structure of the holding plate and stand for floating and rotating the wafer.

(Objective of the Invention) The present invention has been carried out to eliminate the above-mentioned drawbacks, and specifically uses a uniform quartz holding plate surface without grooves, and has a simple structure with good temperature distribution.

b The wafer can rotate, but the rotation is stable.

c Wafer transport is easy.

d No contamination occurs on the wafer or quartz plate surface due to gas cooling.

e There is no cooling effect on the wafer due to floating gas.

f Can be used for wafers with different diameters or non-circular wafers without replacing the quartz stand or plate.

The objective is to provide a device that satisfies the following requirements.

(Structure of the Invention) FIGS. 3 to 5 are diagrams for explaining an apparatus according to an embodiment of the present invention, and FIG. 3 is a sectional view of an example of the structure of the apparatus. In this figure, 26 and 27 are a number of rod-shaped tungsten halogen lamps arranged above and below each other at right angles to each other, and 24 and 25 are reflectors for efficiently reflecting the light emitted from the lamps. It is not particularly necessary to arrange the upper and lower lamp groups 27 and 26 orthogonally to each other if the wafer 1 is rotated at a sufficiently fast speed during heat treatment, but it is not necessary to arrange the upper and lower lamp groups 27 and 26 at right angles to each other if the wafer 1 is rotated at a sufficiently high speed during heat treatment. Approximately 5
If the heat treatment is performed at a speed of less than 2 seconds), there is an effect of compensating for the rotation speed. 23 is a reflector on the side, 21 is a quartz chamber (heat treatment chamber) through which heating light is transmitted, and isolates the processing atmosphere from the surroundings. 28
29 is a quartz disk which is a feature of the present invention, and wafer 1.
These are protrusions or quartz pins for holding the quartz disk on the quartz disk 28, and the fact that three of them are attached concentrically on the quartz disk 28 can be seen in Figure 4A, which is an enlarged view of a part of Figure 3. This is shown in FIG. 4B, which is a top view.

Further, FIG. 4 30 is a fork for carrying the wafer into and out of the heat treatment chamber 21, and is generally made of quartz. 31, the quartz disk 28 is attached to the wafer 1
This is an inlet for introducing gas into the quartz structure (quartz stand or base) 22 for floating and circularly rotating the quartz structure (quartz stand or base). is provided. It should be noted that it is possible to divide the upper and lower lamp groups into multiple zones and control the power supply to each zone to control the illumination distribution, as described in the inventor's previous application (Utility Application No. 1983-
178820).

(Explanation of operation) FIG. 5 is an explanatory diagram of a method for uniformly heating the wafer 1. When the origin of polar coordinates is set at the center of the wafer and the wafer is rotated, uniform heating in the rotational direction θ is achieved.
By performing zone control of the light sources 26 and 27, uniformity in the radial direction of the wafer can be achieved, but these are extremely effective because ions implanted that are not sufficiently activated in the initial stage of heating can be made uniform. This has been experimentally confirmed by measuring sheet resistance after heating the wafer.

The present invention focuses on how to rotate a wafer while eliminating the drawbacks of the conventional levitation and rotation method. In Figure 3, quartz chamber 2
A quartz stand 22, which can be called a quartz jig for constant levitation and one rotation, and a quartz disk 28 to which a quartz pin 29 is attached are disposed inside the quartz holder 1. After placing the wafer 1 on the quartz fork 30 outside the chamber 21,
By moving the fork 30 horizontally to place the wafer 1 into the chamber, and lowering the fork slightly just above the quartz disk 28, the wafer 1 is placed in the chamber as shown in FIG.
The fork 30 rests on the quartz pin 29 in contact with it, and the fork 30 is not in contact with the wafer or the quartz disk 28. The fork 30 is moved horizontally again and moved to the outside of the chamber 21. Alternatively, a sufficiently thin fork may be used to park within the chamber 21 without significantly affecting the heating results of the wafer.

Next, when gas is supplied from the gas inlet 31,
The quartz disk 28 levitates and rotates as in the conventional device due to the flow of gas from the gas outlets 3 and 3'.
In this state, a predetermined power is applied to the lamps 26 and 27. (Concerning power settings, a certain amount of power is sometimes applied even when wafers are loaded and unloaded, in order to avoid the influence of the thermal history of the structure around the wafer, and to extend the life of the lamp group. )
The unloading of the wafer 1 is performed in the reverse sequence of the loading process described above.

To give an example of actual numerical values, in the device of the present invention, the quartz disk 28 has a thickness of 0.7 to 1 mm and a diameter of 175 to 200 mm. This diameter is necessary to process wafers with a diameter of 150 mm, but it is clear that smaller wafers can also be used. The quartz pin 29 has a length of about 3 mm, the lower part is welded to the quartz disk, and its diameter is about 2 mm, and the upper end is rounded to approximate point contact in order to prevent heat conduction with the wafer.

The arrangement and direction of gas ejection ports for floating and rotating the wafer are, for example, the same as in FIG. 2B. In order to simplify the structure, in this embodiment there is only one gas inlet 31, and the gas injection hole is used for both levitation and rotation. Further, a barrier 32 is provided to prevent the quartz disk 28 from deviating from a predetermined position when the rotation of the quartz disk 28 starts and stops.

Compared to the conventional device using one rotation of levitation, the device of the present invention has a quartz disk 28, which seems to cause problems with lower light transmittance and heat conduction through the quartz pin, but according to actual measurements, the wafer No significant differences were found in terms of temperature rise or heating unevenness. However, it has been found that if the quartz pin 29 is not in close to point contact, crystal defects may occur due to heating.

It was also confirmed through experiments that the gas did not have a cooling effect on the wafer or cause contamination, and it was found that each of the objectives of the invention had been achieved.

(Effects of the invention) The effects of the invention are a) to f) shown in the purpose of the invention.
The goal is to be able to achieve each of the following items. Furthermore, the object to be heated is not limited to semiconductor substrates, and it is clear that the present invention can be used to levitate, levitate, and rotate relatively light thin plate-like objects.

[Brief explanation of drawings]

FIG. 1 shows a cross-sectional view A and a top view B of a substrate floating and holding portion of an example of a conventional semiconductor substrate heat treatment apparatus, and a sheet resistance distribution diagram C of a semiconductor substrate heat-treated after ion implantation. Figure 2 shows a cross-sectional view A of another conventional device and a layout diagram B of gas jets and exhaust ports, and Figures 3 to 5 relate to a device embodying the present invention, and Figure 3 is a cross-sectional view of a structural example. Figure 4 is an enlarged view of the main parts in Figure 3, A is a sectional view, B is a top view,
FIG. 5 is an explanatory diagram of a method for uniformly heating a semiconductor substrate. DESCRIPTION OF SYMBOLS 1... Semiconductor substrate (wafer), 3... Levitating rotating gas outlet, 3'... Positioning gas outlet, 21... Heat treatment chamber (chamber), 22... Quartz base, 23... Side reflector, 24, 25... Reflector ,2
6, 27... Infrared lamp (round bar shape), 28... Quartz disk, 29... Quartz projection (quartz pin), 30... Fork, 31... Gas inlet, 32... Wafer removal prevention wall.

Claims (1)

[Scope of Claims] 1. The device is sealed from the external atmosphere, and the upper and lower surfaces are made of a material that is substantially transparent to infrared rays or visible light, and the object to be heated is heated from the outside through the lower surface. a heat treatment chamber, an infrared or visible light transparent base provided inside the heat treatment chamber and having a gas inlet and a plurality of gas ejection holes; 1. A heat treatment apparatus for semiconductor substrates, comprising: an infrared or visible light transparent disk that levitates and rotates; and a plurality of protrusions attached to the disk and on which semiconductor substrates to be heat treated are placed. . 2. The semiconductor substrate according to claim 1, characterized in that a wall is provided on the periphery of the upper surface of the base to prevent the floating and rotating disk on which the semiconductor substrate is mounted from moving out of a fixed position. Heat treatment equipment.