JPS63151029A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To suppress the expansion of the volume of formed silicon oxide, by immersing Si in oxidizing liquid comprising ethylenediamine or hydrazine, water and alcohol, and oxidizing the Si. CONSTITUTION:Silicon (Si) is immersed in oxidizing liquid comprising ethylenediamine or hidrazine, water and alcohol having a specified mixing ratio so that oxidizing property is higher than etching property. Thus the Si is oxidized. The oxidizing liquid 11 comprising, e.g., 60% ethylenediamine, 20% water and 20% isopropyl alcohol, is injected in a reaction container 12. The liquid is heated by a heater 13 up to the boiling point (80-90 deg.C) of the oxidizing liquid 11. Silicon wafers 7 aligned on a wafer boat 14 are immersed in the liquid. Thus the silicon wafers 7 are oxidized. Since a silicon nitride (Si3N4) film 6 is formed as an oxidation resisting film, step parts due to the expansion of the volume of a silicon oxide film 15 are not yielded at a part where selective oxidation is performed. A bird's beak phenomenon due to lateral expansion does not occur.

Description

[Detailed Description of the Invention] [Summary] In order to perform silicon fermentation without causing volume expansion, the present invention uses ethylenediamine in a predetermined mixing ratio, which is mixed so that the oxidizing property is greater than the oxidizing property. Alternatively, silicon (St
) is oxidized by immersing it.

[Industrial application field]

The present invention relates to a method of manufacturing a semiconductor device, and particularly to a method of oxidizing silicon.

[Conventional technology]

An example of a conventional silicon oxidation method is shown in FIG.

The illustrated method is called a high-temperature oxidation method, and for example, nitrogen (N) and oxygen (0) gases that have passed through a dryer 1 and a filter 2 are heated to 1000 to 1200
The silicon wafer 5 placed inside the reaction tube 4 is oxidized by being introduced into the reaction tube 4 heated to (C).

[Problem that the invention seeks to solve]

In the conventional silicon oxidation method described above, silicon (St)
Silicon nonaoxide (Sloz) is formed by the reaction of decaoxygen (01) to complete its oxidation.
In particular, a silicon nitride (SisN+) film 6 is formed as an oxidation-resistant film on the silicon wafer 5 as shown in FIG. If silicon oxidation is performed in the third
As shown in Figure (B), due to the increase in film thickness due to the volume expansion of the silicon oxide (StO) film 8, a step 9 is created on the surface, and in particular, in a later process, a tile line made of aluminum <AI) etc. is applied to the upper part of the step 9. In this case, there was a problem that wire breakage occurred at the corner of the step 9. In addition, the silicon oxide film 8 formed in this case has a rounded bird's beak (Bird'5-Beak) 1 that spreads in the horizontal direction as shown in FIG.
0 occurs, and there is a problem in that the integration density of the rounded elements is reduced because the element cannot be shaped at this location.

Furthermore, the high-temperature oxidation method described above is used to reduce silicon wafer S5 to 100%.
Since the oxidation is carried out at a high temperature of 0 to 1200 DEG C., defects such as cracks and pores occur on the silicon wafer 5, resulting in a reduction in product yield.

[Means for solving problems]

In view of the above-mentioned problems, the present invention aims to oxidize silicon without volume expansion by adding 5 ift of ethylenediamine or hydrazine to an oxidizing solution consisting of water and alcohol at a predetermined mixing ratio, which has greater oxidizing properties than etching properties. The oxidation process is carried out by immersion.

[Effect]

The silicon oxidation method of the present invention produces silicon oxide (SlOt) by a reaction between silicon and OH ions in the above-mentioned mixed solution.
At the same time as the shadow is formed, part of the silicon oxide formed on the surface is removed by the etching properties of the mixed solution, so that the volumetric expansion of the formed silicon oxide is suppressed.

[Metal practice]

Hereinafter, one embodiment of the present invention will be described in detail with reference to FIG. In this embodiment, as shown in FIG. 1 (4), an oxidizing liquid 11 consisting of, for example, 60 ethylenediamine, Φ20% water and 20% isopropyl alcohol is injected into a reaction vessel 12, and a heater 13 is used to raise the boiling point of the oxidizing liquid 11. The silicon wafers 17 are oxidized by immersing the silicon wafers 7 arranged in a wafer boat 14 in the wafer boat 14 while heating the wafer to a temperature of 80 to 90°C. As a result of experiments, it was found that in an oxidizing solution with the above mixing ratio, oxidation of Sl at a rate of 600 to 1000 (X/min) resulted in color change, and silicon nitride was used as an oxidation-resistant film as shown in Figure 1 (6). (Sis
At the location where selective oxidation is performed by forming the N+) film 6, no difference occurs due to the volume expansion of the silicon oxide film 15, and furthermore, there is no bird's beak (Blrd'5- Beak) phenomenon did not occur. In addition, the oxidizing liquid 11 with the above mixing ratio
It was confirmed that when polysilicon (Poly-al) was oxidized, the oxidation was performed at a rate of 3000 to 5000 (X/min).

All examples of mixing ratios of ethylenediamine or hydrazine/water/alcohol that result in greater oxidizing properties than those in Table IK are shown below.

Table 1 Mixing ratio of oxidizing liquid As a result of the experiment, the oxidizing liquid with each of the above mixing ratios was mixed at boiling point (80 to 90
℃) and place polysilicon (Polysilicon) in it.
-81) Example 1
The oxidation rate is 300 to 500 (X/
minutes), 500-600 (also 7 minutes) in Example 2, Example 3
It was confirmed that oxidation was carried out at 400 to 600 (7 minutes).

[Results of the invention]

As described above, according to the silicon oxidation method of the present invention, an increase in film thickness due to volume expansion and a bird's beak (bird's beak)
s-B@ak) does not occur. Therefore, if a semiconductor device is manufactured according to the present invention, a highly reliable semiconductor device can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a diagram for explaining an example of the silicon oxidation method of the present invention, FIG. 2 is a diagram for explaining a conventional silicon oxidation method, and FIG.
The figure is a diagram illustrating problems caused by the conventional silicon oxidation method. In the figure, 1 is a dryer, 2 is a filter, 3 and 13 are heaters, 4 is a reaction tube, 5 and 7 are silicon wafers, 6 is a silicon nitride film, 8 and 15 are silicon oxide films, and 9 is due to volume expansion of silicon oxide Step, 10 is Bird's Beak (Blrd'5-Beak), 11 is oxidizing liquid,
12 is a reaction vessel, and 14 is a wafer boat. Above (A) Actual fabric example of book B Metrics 2I3 Figure 1 Z-9 difference Conventional oxidation method problem 1 turn Figure 3

Claims (1)

[Claims] A method for manufacturing a semiconductor device characterized by oxidizing silicon in an oxidizing solution consisting of water and alcohol, ethylenediamine or hydrazine mixed in a predetermined ratio so that the oxidizing property is greater than the etching property. .