JPS6015915A - Manufacture of semiconductor substrate - Google Patents

Abstract

PURPOSE:To check condensation of an Si layer and dissolution of an Si substrate, and to obtain the SOI substrate having the still larger area and the flat surface by a method wherein a heat-resistant radiation heat absorbing film W is provided to intercept radiation to the Si layer, and at the same time, radiation heat from a strip heater is absorbed to be transmitted to the Si layer according to conduction. CONSTITUTION:An oxide film 2 is formed on an Si single crystal substrate 1 according to thermal oxidation, then a polycrystalline Si film 3 and an SiO2 film 4 are adhered in order according to the CVD method, and a metal tungsten film 5 is evaporated moreover according to the sputtering method to be annealed in N2 gas. Then the substrate thereof is put on a lamellar graphite heater 7, and the inside of a quartz tube 9 is filled with high pure N2 gas. Then the prescribed voltage is applied to the heater 6 to perform heating according to turning on electricity. After then, the strip heater 6 is transferred at a constant speed, and the polycrystalline Si layer in the sample is recrystallized.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a method of manufacturing a substrate for a high-speed, highly integrated semiconductor integrated circuit in which an active region is a Si layer on an insulator.

[Background of the invention]

J, EC8, '82.December, P2812"zone
-melting recnystulliz3tio
n of 8i films with amovabl
e-strip -heater oven'MW,G
According to e1s, MIT, S 13 N4 /S i
02 /S i/s joz /s j A sample having a layered structure of a substrate is heated to 1100 to 1300C, and when further radiant heating is performed using a strip heater installed above the sample, the Si film in the layered structure melts in a band shape. do. When the strip heater is moved along the sample surface, S
The melting zone of the i-layer also moves, resulting in the so-called zone melting method (zOne
-melting method) crystal growth occurs.

The disadvantages of this method are that the molten S1 itself tends to aggregate due to its large surface tension, and that the Si substrate itself is also easily melted because it is heated close to its melting point. In addition,
In this method, a S 1 3 N 4 film is further adhered and reinforced on the SiO 2 to prevent the above-mentioned agglomeration, but this method is not very effective as it causes cranking and deterioration.

[Purpose of the invention]

The present invention prevents the agglomeration of the Si layer and the melting of the Si substrate, which are the drawbacks of the conventional method, and enables a larger area and flat SQ process (
The purpose of the present invention is to provide a silicon on insulator substrate.

[Summary of the invention]

The disadvantages of the conventional method become more apparent due to the following circumstances. In other words, molten Si has a much higher radiant heat absorption rate than solid Si, so once melting starts from the welding point, the molten part absorbs more radiant heat. As a result, the temperature rises, and the Si in the vicinity melts. Due to this melting, the amount of heat absorbed further increases, and the melting progresses at an accelerated pace. In particular, in the SOI structure using the 3i substrate, the Si substrate and the Si layer are usually 8102 μm thick.
Since they are only partitioned by a film, the temperature difference is extremely small (~06llr), making it even more difficult to melt and recrystallize only the 54th layer without melting the 81st substrate. Moreover, since the 5jOzjii itself for fixing the Si layer is greatly softened by this temperature rise, the Si melt coagulates into droplets due to its own large surface tension. The above matters are the background of the present invention, which was confirmed through experiments.

As described above, since the initial melting phenomenon caused by ordinary radiation heating essentially has positive feedback instability, it is desirable to heat the 54 layers by thermal conduction in order to achieve stable melting. Therefore, the following heating methods can be considered to reduce heat radiation and increase heat conduction. In other words, (1) use a gas with high thermal conductivity (N2, He) as the heating atmosphere, (2) moving strike 1) move the tube heater as close to the sample surface as possible (N
(3) A heat-resistant radiant heat absorbing film (W, MO, etc.) is provided on the sample surface to block radiation to the 3i layer, and at the same time, the radiant heat from the strip heater 75 is first absorbed by this film. 3i layer by conduction.

The present invention is applicable to three of these examples, which are considered to be the most effective.
The present invention will be explained by the following seven examples, which are the method using the second example.

[Embodiments of the invention]

FIG. 1 shows a cross section of the layer structure of an SOI substrate according to the present invention, in which 1 is a 3i substrate, 2 and 4 are 5i02 films, 3 is a polycrystalline SL film, and 5 is a tungsten film.

FIG. 2 is a schematic diagram of an SOI substrate manufacturing apparatus using the band melting method used in the present invention. 6 in the figure is a graphite strike 1-knob heater, and the size of the heat generating part is 1 ran x 2 rtrrn x
120 temples.

7 is a plate-shaped graphite heater on which the 80I substrate sample 8 is placed and heated. 9 is a transparent quartz tube, 10 is a linear head motor for moving the strip heater, and the moving speed is 0.30 ~
4. Otm/11ec continuously variable.

Below, using FIG. 1 and FIG. 2, the SO according to the present invention will be described.
An example of a disaster in the I-board manufacturing process will be explained.

First, 75φX0.4n+mt, P type, (1oo), 1
An oxide film (sin) with a thickness of 0.6 μm is formed on a mirror-finished Si single crystal substrate of a 0Ω saw by thermal oxidation in wet Q2. Next, the usual CVD method (Chemical Vapo
A polycrystalline Bs film of Q, 5 p In, and 81 Q2 films were successively deposited to a thickness of 1.2 µm using a 3-layer deposition method, and a metallic tungsten film was further deposited to a thickness of 0.1 µm using an ordinary sputtering method. Vapor deposited in N2 gas for 10
00C - Neal for 30 minutes. Through the above steps, a sample having the cross-sectional structure shown in FIG. 1 is obtained.

Divide the sample into 8 mm x 16 mm pieces, place one of them on the plate graphite heater 7 as shown in Fig. 2, and fill the inside of the quartz tube 9 with high-purity N2 gas (99 mm). ,999%
). Next, when a predetermined voltage is applied to the heater and the heater is energized and heated, the predetermined constant temperature is reached after about 4 minutes. At this time, the temperature of the strip heater 6 was 1950 C, and the temperature of the plate heater was 1300 tl: the gap between the 1-stroke 1-knop heater and the sample was 0.6 m.

Thereafter, the strip heater 6 is moved at a constant speed (1 fin/8) to recrystallize the polycrystalline Si layer in the sample. An 80I substrate is obtained through the above steps.

Next, the characteristics of the SOI substrate obtained through the above steps are as follows:
When compared with a sample obtained by a similar process without using a W layer, Figures 3 (a) and (b) and the following Figure 1.
It will look like a table.

Table 1 □ No. 31t (a) and (b) show representative examples of recrystallization distribution of samples without W film and with W film, respectively.
11 in the figure is a part where recrystallization is formed homogeneously, 12
13 is a region where the Si layer has disappeared due to the aggregation, 14 is a region where the substrate Si has melted and recrystallized, and 15 is an unmelted region of the Si layer.

As is clear from this figure, the area of the truncated recrystallized layer is wider in the sample with the W film, and the good one is approximately 7 mm x 10 W.
For example, the area of 1 chip is 5n.
It is fully applicable to o++X5m LSI.

Table 1 shows the results of a comprehensive evaluation of 10 samples without the W film and 14 samples with the W film, which were melted and recrystallized under approximately the same conditions. It can be seen that there is a marked improvement.

〔Effect of the invention〕

According to the present invention, by providing the W film, it is possible to heat the Si layer without directly irradiating the Si layer with radiant heat from the strip heater, which has the effect of preventing aggregation of the Si layer and melting of the SL substrate.

The above effect can be improved by approximately 40 times in the area of the homogeneous recrystallized layer and approximately 2 times in the case of not melting the Si substrate, compared to the case without the W film, making it possible to improve practical large-area SOI.
This is an effective method for obtaining substrates.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of an 80I substrate according to the present invention, FIG. 2 is a schematic diagram of an SOI substrate manufacturing apparatus used in the present invention, and FIG.
) and (b) are recrystallization distribution diagrams of the SOI substrate viewed from the top.

Claims (1)

[Claims] 1. In the zone melting method in which a polycrystalline i9i layer formed on an insulator is heated and melted and recrystallized, the structure including the polycrystalline Si layer is changed to w/SiO2/polycrystalline Si/5in2.
/ A method for manufacturing a semiconductor substrate, characterized in that it has a multilayer structure of an Si substrate.