JPH0329295B2 - - Google Patents

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention is utilized in the field of manufacturing semiconductor devices, and particularly relates to an insulating film forming method for forming an insulating film on a silicon substrate by chemical vapor deposition. It is about improvement.

<Prior Art> In recent years, thin film forming methods using photochemical vapor phase reactions using light energy have been attracting attention because damage-free films can be formed at low temperatures. Compared to chemical vapor deposition using plasma, this thin film formation method using photochemical vapor phase reaction does not cause irradiation damage to the underlying substrate or deposited film due to charged particles such as ions and electrons during the film deposition process. This is a characteristic.

<Problems to be Solved by the Invention> However, in the thin film formation process by photochemical vapor phase reaction, the processing method before film formation and the effect of the processing on film properties are unknown.
The search was urgent.

The present invention was devised in view of these points, and provides an insulating film forming method that can form a high quality insulating film on a silicon substrate and contribute to improving electrical properties such as improving withstand voltage and reducing leakage current. is intended to provide.

<Means for Solving the Problems> The present invention involves irradiating the silicon substrate with ultraviolet light using a mercury lamp in an oxidizing gas atmosphere immediately before forming an insulating film on the silicon substrate by photochemical vapor deposition, and then continuously The structure is such that an insulating film is formed by photochemical vapor deposition.

<Function> With the above configuration, it was possible to obtain an insulating film with improved dielectric strength compared to an insulating film formed by photochemical vapor deposition without pretreatment with ultraviolet light irradiation. .

<Example> Hereinafter, an example of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a schematic diagram showing an example of a thin film forming apparatus used to carry out the insulating film forming method of the present invention. In FIG. 1, 1 is a reaction chamber (sample chamber);
is the wafer susceptor, 3 is the silicon wafer, and 4 is the wafer susceptor.
IR lamp, 5 is synthetic quartz, 6 is a mercury lamp (Hg lamp), 7 is a gas inlet, 8 is a gate valve, 9 is a mechanical booster pump, and 10 is an oil rotary pump.

First, a P-type (100) silicon (Si) substrate (15-20Ω cm) 3 is placed on the wafer susceptor 2 in the sample chamber 1 of the apparatus configured as described above, and then the rotary pump 10 is activated. After roughly evacuation of the pressure inside the sample chamber 1, the mechanical booster pump 9
The inside of the sample chamber 1 was evacuated to 10 ^-3 [Torr] using a vacuum cleaner. During this evacuation operation, the temperature of the substrate 3 was raised to 150 [° C.] and maintained using the IR lamp 4.
After evacuation to 10 ^-3 [Torr] or less using the pump 9 described above, while introducing N ₂ O gas as an oxidizing gas from the gas inlet 7 at a rate of, for example, 200 (SCCM), the automatic pressure control device (APC, not shown)
to increase the pressure in the sample chamber to 1.9 to 2.0 [Torr].
to hold.

Next, under these conditions, a mercury lamp (Hg lamp) 6 is used to apply ultraviolet light (for example,
185 nm) for 60 minutes. Next, in this state, disilane (Si ₂ H ₆ ) gas is introduced at, for example, 3.2 (SCCM),
Maintain at 1.9 to 2.0 [Torr] and use a mercury lamp (Hg lamp)
6 to emit ultraviolet light onto the surface of the silicon substrate 3.
A silicon oxide film was formed by irradiation for 60 minutes.

Next, close the gas inlet 7, use the mechanical booster pump 9 to exhaust the atmosphere to below 10 ^-3 {Torr], introduce N ₂ gas into the sample chamber 1 to return it to atmospheric pressure, and open the sample chamber 1. Sample 3 was taken out.

In addition, a sample in which a silicon oxide film was formed after irradiation with ultraviolet light in N ₂ O gas for 480 minutes in the same manner as above, and a silicon oxide film that was not irradiated with ultraviolet light in N ₂ O gas for comparison. For each sample with a silicon oxide film formed on a substrate,
When we fabricated a MIS capacitor and investigated the dielectric strength distribution, we found that although the reason is not clear, Figure 2 a~
As shown in Fig. c, as the ultraviolet light irradiation time in N ₂ O gas increased, the dielectric strength improved and a high quality silicon oxide film was obtained.

In Fig. 2, a is when no UV light is irradiated, b is when UV light is irradiated for 60 minutes, and c is when UV light is irradiated for 60 minutes.
shows the dielectric strength distribution when UV light is irradiated for 480 minutes.

It should be noted that the present invention is not limited to the above-mentioned embodiments, and can be implemented in various modifications without departing from the gist thereof. For example, the energy beam source for irradiating onto the silicon substrate is limited to a mercury lamp. Instead, for example, an excimer laser may be used, and the atmospheric gas as an oxidizing gas may be N ₂ O.
It goes without saying that the material is not limited to gas, and for example, O ₂ may be used.

Furthermore, it goes without saying that the conditions such as the gas pressure in the sample chamber and the substrate heating temperature described above may be determined as appropriate according to specifications and the like.

<Effects of the Invention> As described above, according to the present invention, it is possible to form a high-quality insulating film that improves breakdown voltage and reduces leakage current, and as a result, it can be applied to interlayer insulating films and memory capacitor parts. It is extremely effective.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing a configuration example of a thin film forming apparatus used to carry out the insulating film forming method of the present invention, and FIGS. 2 a to 2 c each show the dielectric breakdown voltage distribution of the silicon oxide film according to the present invention. FIG. 1...Sample chamber, 2...Wafer susceptor, 3...Silicon wafer, 6...Mercury lamp, 7...Gas inlet.

Claims (1)

[Claims] 1. A step of irradiating a silicon substrate with an energy beam in an oxidizing gas, and subsequently introducing a source gas after the step,
An insulating film forming method comprising the step of forming an insulating film on the silicon substrate by photochemical vapor deposition. 2. The insulating film forming method according to claim 1, wherein the energy beam is ultraviolet light from a mercury lamp, and the oxidizing gas is _N2O or _O2 .