JPS6051058B2 - Manufacturing method of gas/humidity sensor - Google Patents

Description

Detailed Description of the Invention The present invention provides a gas/humidity sensor that combines an oxide ultrafine particle film that is sensitive to external factors such as gas and water vapor and a MOS field effect transistor (hereinafter referred to as MOS FET). This relates to a manufacturing method.

According to the present invention, a
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This is based on the discovery that when activated in a fluorine atmosphere, it becomes more sensitive to gases and water vapor.

The method of the present invention incorporates the plasma reaction activation treatment into the manufacturing process of a semiconductor detection device, so that it can be carried out efficiently.

As a result, most of the manufacturing processes are common to the manufacturing process of normal semiconductor devices and thin film integrated circuits, and are not only extremely easy to implement, but also highly reliable and have uniform characteristics. It is possible to mass produce high-quality equipment. The manufacturing method of the present invention will be described in detail below.

FIG. 1 is a process diagram for explaining one embodiment of this method. In the figure, 1 is, for example, a p-type silicon substrate having an orientation of <100>, and its resistivity is approximately 1Ω-α.

After forming an oxide film 2 with a thickness of about 3000 Å on the surface of the silicon substrate 1, a window 3 is formed by removing the oxide film in a predetermined area by a well-known photolithography method. An impurity for forming an n-type semiconductor, such as phosphorus, is diffused or implanted through this window by a well-known thermal diffusion method or ion implantation method, thereby forming a source region 4 and a drain region 5 (FIG. 1A).
Next, after the oxide film 2 is completely removed, the substrate 1i is subjected to heat treatment in a steam atmosphere at 1000° C., for example, to form a new thermal oxide film 6 with a thickness of about 3000 Å. A portion of this thermal oxide film 6 is selectively removed by ordinary photolithography to open a window for forming a gate insulating film.
Then, substrate 1 was replaced with Fl2O2-H2SO4, HF-N
After carefully washing in the order of H4F, HNO3, and ultrapure water, about 2 powders were heat-treated in a dry oxygen atmosphere at 900°C.
A gate thermal oxide film 7 having a thickness of about 100 Å is formed on the window (FIG. 1B). Thereafter, contact windows for source region 4 and drain region 5 are selectively formed in oxide film 6. Next, a metal thin film such as Ni is formed on the entire surface of the substrate 11 by vapor deposition or the like, and then selectively removed by a well-known photolithography method to form a predetermined source electrode 8 and drain electrode 9 (see FIG. C). After forming the electrodes 8 and 9, a commercially available photosensitive resin was placed on the substrate 1 at a spinner rotation speed of 3.5 rpm at 2000 rpm.
The resin film 10 is formed by spin coating to a thickness of approximately μm. Then, at least the photosensitive resin on the gate oxide film 7 is removed by a well-known photolithography method (FIG. 1D). After that, the surface of the substrate 1 is coated with, for example, SnO2, TiO2,
An oxide ultrafine particle film 11 is formed of ultrafine particles of ZnO, NlO, etc. with an average particle size of 10 to 120A (
Figure 1E). Taking the production of an ultrafine particle film of Sn oxide as an example, the method for forming the film will be explained in detail with reference to FIG.

The first
The substrate 1 shown in Figure D is attached with the resin film 10 facing downward in the drawing. After setting the evaporation material 24 such as Sn, snOl or SnO2 in the evaporation board 23, the vacuum port connected to the exhaust port 25 is opened. A pump (not shown) is operated to bring the inside of the device 21 to a degree of vacuum of about 5×10 −6 T0rr. Thereafter, the cock of the 02 gas inlet 26 is opened, the 02 gas is introduced into the device 21, and its pressure is maintained at, for example, about 0.5T0rr'. Next, the evaporation power source 27
By boat. 23 is energized to generate heat, and 0. The evaporation material 24 is evaporated in a gas atmosphere for several seconds to several minutes. For example, if Sn is selected as the evaporation material 24, 70~
When a power of 80AN4V is applied to the boat 23 for 1 minute,
Ultrafine particle film of Sn oxide with a thickness of about 1 μm1. −． 1 was formed on the substrate 1 as shown in FIG. 1E. Here, a method using resistance heating has been described as an example for evaporating the evaporation material, but it goes without saying that other methods such as induction heating or infrared heating may also be used.

The substrate 1 that has undergone the above steps is placed in an O2 gas plasma atmosphere at a flow rate of 1'/min to activate the ultrafine oxide particle film 11 by about 3 times.

During this activation process, the photosensitive resin film 10 and the oxide ultrafine particles 11 thereon are also removed together with the photosensitive resin film 10, leaving the oxide ultrafine particle film 11 only on the gate oxide film 7 (the first Figure F). 1 Ultrafine oxide particles are extremely sensitive to external agents such as gas and water vapor, but when they are subjected to the activation treatment described above, they become even more sensitive.

For example, as shown in Figure 3, the sensitivity of ultrafine Sn oxide particles to isobutane gas increases with the increase in the high-frequency applied power for forming 02 gas plasma, and becomes almost saturated when it exceeds a certain value. do. In addition, in the figure, the point where the high frequency applied power for 02 gas plasma formation is 0 indicates the state before the activation process is performed. Here, a method for measuring gas concentration using the sensor of the present invention will be described.

As shown in FIG. 4, the p-channel MOS type F of the present invention
In the ET sensor, the drain voltage ■. When is 20■, the gate voltage ■. When is 0V, drain current 1D is 1mA
It flows to a certain extent. When this sensor is installed in, for example, an isobutane gas atmosphere at an operating temperature of about 250 °C, the 0 ions adsorbed on the SnO2 surface and isobutane gas are
Perform a reaction like O+02C3H9OH+e to obtain SIl
Electrons are released into the O2 ultrafine particle film. These electrons diffuse to the surface of the gate oxide film, increasing the gate voltage of the MOS FET.
decrease. As a result, the drain current is 1. decreases. As shown in FIG. 5, the amount of decrease in ID is proportional to the amount of decrease in Vc, that is, the concentration of C4HlO gas. In the figure, a solid line indicates a sensor subjected to plasma activation treatment, and a broken line indicates an untreated sensor. The sensitivity of the sensor subjected to the 02 gas plasma treatment is approximately 1.8 times higher than that before the 02 gas plasma activation treatment is applied to the oxide particles.

As described above, according to the manufacturing method of the present invention, since the resin film is formed in advance on the other parts except on the gate insulating film, the 02 gas plasma reaction activation treatment of the ultrafine oxide particles and the gate oxidation are performed. Since ultrafine oxide particles other than those on the film can be removed at the same time, the manufacturing process can be carried out without complicating it.

In terms of manufacturing technology, it can be carried out using normal semiconductor manufacturing technology or thin film manufacturing technology, so highly sensitive semiconductor detection devices can be stably mass-produced.

[Brief Description of the Drawings] Figure 1 is a process diagram for explaining one embodiment of the method for manufacturing a semiconductor detection device according to the present invention, and Figure 2 is a process diagram for manufacturing an oxide ultrafine particle film in this embodiment. FIG. 3 is a diagram for explaining the effect of activation treatment of ultrafine oxide particle film. FIG. 4 is a diagram showing the relationship between drain current and gate voltage of a MOS FET. FIG. 5 is a diagram showing the relationship between gas concentration and drain current. 1...Substrate, 4...Source region, 5.
... Drain region, 7 ... Gate oxide film, 8 ... Source electrode, 9 ... Drain electrode, 10 ... Resin film, 11. ...Oxide ultrafine particle film.

Claims (1)

[Claims] 1. After forming a resin film on other parts of the semiconductor substrate having at least a source region, a drain region, and a gate insulating film except for the gate insulating film, the resin film is further coated with an average grain size of 10
After forming a metal oxide ultrafine particle film made of ultrafine particles of ~120 Å, the metal oxide ultrafine particle film is activated in oxygen or a plasma atmosphere containing it, and at the same time, the metal oxide ultrafine particle film is activated on the resin top film. A method for manufacturing a gas/humidity sensor, comprising removing the metal oxide ultrafine particle film together with the resin film. 2. The method of manufacturing a gas/humidity sensor according to claim 1, wherein the resin film is formed of a photosensitive resin. 3. The method of manufacturing a gas/humidity sensor according to claim 1, wherein the metal oxide ultrafine particle film is formed of a Sn oxide ultrafine particle film.