JP6942943B2 - Manufacturing method of semiconductor element - Google Patents

Description

The present invention relates to a method for manufacturing a semiconductor device.

_{With the announcement of the InGaZnO 4} (a-IGZO) thin film transistor (TFT), which exhibits mobility of a-Si or higher in the amorphous state, research and development of oxide semiconductors are being energetically promoted all over the world. .. However, most of these oxide semiconductor materials are n-type oxide semiconductors having electrons as carriers.

Development of p-type oxide semiconductors has been promoted mainly on oxides containing monovalent Cu (see, for example, Patent Document 1) and oxides containing divalent Sn (see, for example, Non-Patent Document 1). ing. However, the characteristics of transistors using these p-type oxide semiconductors as active layers do not reach the same level as the transistor characteristics of n-type oxides, and therefore both n-type and p-type active layers are used. The development of semiconductor devices formed of oxides and having complementary operations has not progressed.

An object of the present invention is to provide a method for manufacturing a semiconductor device capable of manufacturing a semiconductor device having a p-type oxide semiconductor and an n-type oxide semiconductor with good controllability.

The means for solving the above-mentioned problems are as follows.
That is, the method for manufacturing a semiconductor device of the present invention is
A method for manufacturing a semiconductor device having a first active layer made of a p-type oxide semiconductor and a second active layer made of an n-type oxide semiconductor.
It has a first oxide layer for forming the first active layer, a second oxide layer for forming the second active layer, and an insulating layer covering the second oxide layer. Including a heating step of heating the semiconductor device precursor in a reducing atmosphere,
In the heating step, the first oxide layer is in contact with the reducing atmosphere, and the second oxide layer is not in contact with the reducing atmosphere.

According to the present invention, a semiconductor device having a p-type oxide semiconductor and an n-type oxide semiconductor can be manufactured with good controllability.

FIG. 1A is a schematic cross-sectional view for explaining an example of the method for manufacturing a semiconductor device of the present invention (No. 1). FIG. 1B is a schematic cross-sectional view for explaining an example of the method for manufacturing a semiconductor device of the present invention (No. 2). FIG. 1C is a schematic cross-sectional view for explaining an example of the method for manufacturing a semiconductor device of the present invention (No. 3). FIG. 1D is a schematic cross-sectional view for explaining an example of the method for manufacturing a semiconductor device of the present invention (No. 4). FIG. 1E is a schematic cross-sectional view for explaining an example of the method for manufacturing a semiconductor device of the present invention (No. 5). FIG. 2 is a circuit configuration diagram of the semiconductor element of FIG. 1E.

Prior to explaining embodiments of the present invention, techniques related to the present invention will be described.
In n-type oxide semiconductors such as ITO (Sn-doped In ₂ O ₃ ) used as a transparent conductive film and IGZO (In-Ga-Zn-O) used as an active layer of a thin film transistor, electrons are carriers. The lower end of the conduction band, which is the transport path of the metal element, is mainly composed of spatially expanded s orbitals of metal elements, which realizes high carrier mobility. On the other hand, in the case of the p-type, the transport path of the hole, which is a carrier, is the upper end of the valence band. Many oxides are composed of 2p orbitals of oxygen in which the upper end of this valence band is localized, and in this case, high mobility cannot be obtained.

Therefore, in the prior art, _{oxides containing monovalent Cu such as Cu 2} O, SrCu ₂ O ₂ , and CuAO ₂ (A = B, Al, Ga, In) have been targeted for development as p-type semiconductors. .. In these oxides, the upper end of the valence band is composed of a hybrid orbital of 2p of oxygen and 3d of Cu, and the mobility is expected to be improved by weakening the localization. Further, an oxide (SnO) containing divalent Sn is known as another p-type oxide, but in this case, the upper end of the valence band is composed of 5s orbitals of Sn having weak localization. In any p-type oxide, carrier holes are generated by oxygen-excessive non-stoichiometry. That is, in order to control the carrier density and obtain a p-type semiconductor having a desired conductivity, it is necessary to control the amount of oxygen in the oxide in the process of forming the oxide.

In Japanese Patent Application Laid-Open No. 2010-212285, an amorphous SnO film which is a film containing SnO is formed while controlling the amount of oxygen at room temperature (first step), and then insulation such as _{SiO 2 is formed on the amorphous SnO film.} A method of forming a p-type semiconductor by forming a film (second step) and then heat-treating these laminated films (third step) is disclosed. Further, by utilizing the fact that the region in which the insulating film is formed in the second step becomes a p-type semiconductor in the third step and the region in which the insulating film is not formed becomes an n-type semiconductor, a complementary semiconductor element is formed. The method of forming is disclosed. Regarding the formation of the p-type semiconductor, the second step eliminates the need to control the amount of oxygen in the third step, and has the effect of preventing the desorption of oxygen from the amorphous SnO film or the uptake of oxygen into the amorphous SnO. Therefore, it is stated that a SnO polycrystalline monophasic film can be easily obtained.
However, this method has a problem that it is difficult to control the conductivity of the p-type semiconductor. As described in JP-A-2010-212285, since the desorption and uptake of oxygen from the amorphous SnO film is suppressed by the presence of the insulating film in the third step, oxygen in the SnO film is suppressed in this step. The amount cannot be controlled. That is, there is no means to control the carrier density of the film obtained as a result of heating.

The present inventors form an active layer made of a p-type oxide semiconductor (first active layer) and an active layer made of an n-type oxide semiconductor (second active layer) on a substrate with good controllability. The method was examined.
As a result, the first oxide layer for forming the first active layer, the second oxide layer for forming the second active layer, and the insulating layer covering the second oxide layer. In the heating step, the first oxide layer is in contact with the reducing atmosphere, and the second oxide layer is brought into the reducing atmosphere. We found that it is effective not to touch.

(Manufacturing method of semiconductor element)
The method for producing a semiconductor device of the present invention includes at least a heating step, preferably includes an oxide layer forming step, and further includes other steps, if necessary.
The method for manufacturing a semiconductor device is a method for manufacturing a semiconductor device having a first active layer made of a p-type oxide semiconductor and a second active layer made of an n-type oxide semiconductor.

<Heating process>
The heating step covers the first oxide layer for forming the first active layer, the second oxide layer for forming the second active layer, and the second oxide layer. This is a step of heating a semiconductor device precursor having an insulating layer in a reducing atmosphere.
In the heating step, the first oxide layer is in contact with the reducing atmosphere, and the second oxide layer is not in contact with the reducing atmosphere.

In the heating step, the first oxide layer is brought into contact with the reducing atmosphere and reduced to exhibit p-type conductive properties, and the first oxide layer is converted into the first active layer.
On the other hand, the second oxide layer is in a state where it does not come into contact with the reducing atmosphere in the heating step. By doing so, the second oxide layer is reduced to prevent an increase in oxygen deficiency and an excess of carriers. That is, the second oxide layer becomes the second active layer without changing the degree of oxidation of itself.

As the reducing atmosphere, a mixed gas containing hydrogen gas can be used. For example, heating is performed while flowing nitrogen gas containing 1% to 5% of hydrogen through the heating chamber. The degree of reduction can also be controlled by the concentration of hydrogen gas.

As the reducing atmosphere, it is also effective to use an atmosphere containing an inert gas as a main component, the concentration of oxygen as an impurity is controlled, and the oxygen partial pressure is ^{10-5 Pa or less.} When the oxygen partial pressure is ^10-10 Pa or less, a sufficient reducing action can be obtained, and the degree of reduction can be controlled by the value. In this case, a method of flowing a predetermined amount of an inert gas having a controlled oxygen concentration through the heating chamber is a preferable form.

It is preferable to control the gas flow rate with a mass flow controller or the like and monitor the pressure in the chamber and the oxygen partial pressure at any time. Feedback control of the flow rate of the inert gas and the oxygen concentration in the inert gas so that the partial pressure of oxygen in the chamber is maintained at a predetermined value is effective in improving the controllability of the process.

When the pressure in the chamber is, for example, 10 kPa and the oxygen partial pressure is ^10-5 Pa, the oxygen concentration of the inert gas is 0.001 ppm. In order to obtain such an inert gas having an extremely low oxygen concentration, it is preferable to use an oxygen pump capable of removing oxygen. As the oxygen pump, for example, an oxygen pump having zirconium oxide as a solid electrolyte can be used. The inert gas is not particularly limited, but for example, Ar or N ₂ can be used.

The heating temperature in the heating step is preferably 100 ° C. or higher and 500 ° C. or lower as a condition for the reduction to proceed efficiently and with good controllability.

The first active layer and the second active layer contain the same metal oxide as a main component, and the degree of oxidation of the second active layer is higher than the degree of oxidation of the first active layer. Is preferable.
The same metal oxide is, for example, an oxide of either tin oxide or thallium oxide, or a mixture thereof. When the same metal oxide is tin oxide, the first active layer is SnO and the second active layer is SnO ₂ . When the same metal oxide is thallium oxide, the first active layer is Tl ₂ O and the second active layer is Tl ₂ O ₃ .
Here, the principal component means a component that expresses semiconductor characteristics.
Here, the degree of oxidation corresponds to the oxidation number of the metal in the metal oxide. That is, "the degree of oxidation of the second active layer is higher than the degree of oxidation of the first active layer" means that "the oxidation number of the metal of the metal oxide as the main component of the second active layer is the first. It means that it is larger than the oxidation number of the metal of the metal oxide which is the main component of the active layer. Further, in terms of the oxidation number, it is assumed that 0 is larger than a negative integer and a positive integer is larger than 0.

Further, for example, when tin oxide is used as the first active layer, the n-type SnO ₂ is much more stable than the p-type SnO. Therefore, it is easier and more stable to form the _{SnO 2} layer as the first oxide layer first. This is heated in a reducing atmosphere to obtain SnO, which is the first active layer. Further, by appropriately selecting the degree of reducing property of the atmosphere in the heating step, the temperature, and the heating time, the amount of oxygen in the SnO layer, which is the first active layer, is controlled to have a desired conductivity. An active layer can be obtained.

It is also a preferable form to use a substitution-doped n-type oxide semiconductor as the second active layer. In the substitution-doped n-type oxide semiconductor, the carrier density can be controlled by the doping amount instead of the oxygen deficiency amount. In the heating step, since the second oxide layer for forming the second active layer is heated in a state where it does not come into contact with the atmosphere, it is difficult to adjust the amount of oxygen in this step, but the second By adding a necessary amount of the substitution dopant in advance when forming the second oxide layer for forming the active layer, it becomes easy to form the second active layer having a desired conductivity.

The insulating layer is not particularly limited and may be appropriately selected depending on the intended purpose, but an oxide layer having an insulating property is preferable. Examples of the oxide layer having an insulating property include a SiO ₂ layer and the like.

The method for forming the first oxide layer and the second oxide layer is not particularly limited and may be appropriately selected depending on the intended purpose. For example, sputtering and chemical vapor deposition (CVD) ), Vacuum film formation method such as atomic layer deposition (ALD), and the like. Alternatively, the composition containing the metal compound and the solvent may be applied by a printing method such as spin coating, die coating, or inkjet, and then heat-treated such as drying or firing to form the composition.
The first oxide layer and the second oxide layer may be formed separately or at the same time.
The following oxide layer forming step is preferable as the method for forming the first oxide layer and the second oxide layer.

<Oxide layer formation process>
The oxide layer forming step is not particularly limited as long as it is a step of forming the first oxide layer and the second oxide layer at the same time using the same metal oxide material. It can be appropriately selected according to the above, and examples thereof include the following steps (i) and (ii).
Step (i) By forming a metal oxide material using a vacuum film forming method through a mask having a predetermined opening, the first oxide layer and the second oxide layer are simultaneously formed. Step of Forming Step (ii) After forming an oxide layer using a metal oxide material, the oxide layer is divided by etching to obtain the first oxide layer and the second oxide layer. Steps to form at the same time

In a semiconductor device manufactured through the oxide layer forming step using the method for manufacturing the semiconductor device of the present invention, the first active layer and the second active layer are the same metal oxide. Since the material is used as a raw material, the metal density, layer thickness, and the like in the first active layer and the second active layer are the same. Therefore, for example, in a certain semiconductor device, when the first active layer made of a p-type oxide semiconductor and the second active layer made of an n-type oxide semiconductor are the same in terms of metal density, layer thickness, and the like. Is highly likely that the method for manufacturing a semiconductor device of the present invention is used.
For example, the fact that the first active layer and the second active layer were produced through the oxide layer forming step can be confirmed by quantitative analysis such as EPMA and film thickness evaluation using a cross-sectional TEM. ..

The semiconductor device manufactured by the method for manufacturing a semiconductor device is not particularly limited and may be appropriately selected depending on the intended purpose. Examples thereof include CMOS. CMOS is an abbreviation for Complementary MOS (Metal Oxide Semiconductor).

Here, an example of the method for manufacturing the semiconductor device of the present invention will be described with reference to the drawings.
First, a structure having two gate electrodes 2A and 2B and a gate insulating layer 3 formed so as to cover the gate electrodes 2A and 2B is prepared on the substrate 1 (FIG. 1A). This structure can be formed by a known method.
Next, the first oxide layer 4A and the second oxide layer 4B are formed on the gate insulating layer 3 (FIG. 1B). The first oxide layer 4A and the second oxide layer 4B are formed at the same time, for example, by using the same metal oxide material.
Next, on the gate insulating layer 3, the source electrode 5A in contact with the first oxide layer 4A, the source electrode 5C in contact with the second oxide layer 4B, and the first oxide layer 4A and the second oxidation A drain electrode 5B in contact with the material layer 4B is formed (FIG. 1C). These electrodes can be formed, for example, by forming an Al film using a vacuum vapor deposition method and patterning it through a metal mask.
Next, the insulating layer 6 is formed on the second oxide layer 4B (FIG. 1D). By doing so, the second oxide layer 4B is covered with the gate insulating layer 3, the source electrode 5C, the drain electrode 5B, and the insulating layer 6 so as not to come into contact with the reducing atmosphere in the next heating step.
Next, the semiconductor device precursor produced by the above procedure is heated in a reducing atmosphere. At that time, the oxygen partial pressure ^{is preferably 10-5} Pa or less. The reducing atmosphere is in contact with the first oxide layer 4A but not with the second oxide layer 4B. Therefore, the first oxide layer 4A is reduced to become the first active layer 4p which is an n-type oxide semiconductor, and the second oxide layer 4B is the second active layer which is an n-type oxide semiconductor as it is. Layer 4n (FIG. 1E).
From the above, a CMOS type semiconductor element can be obtained.

Although not shown in the figure, it is also preferable to form a protective layer covering the first active layer 4p in order to prevent the first active layer 4p from coming into contact with oxygen or moisture in the atmosphere and changing its characteristics. Is. At that time, the protective layer may be laminated not only on the first active layer 4p but also on the insulating layer 6 to enhance the protective effect on the second active layer 4n. Further, when an interlayer insulating film is provided on the semiconductor element and another element such as a display element is formed on the interlayer insulating film, the interlayer insulating film covers the second active layer 4n and the insulating layer 6. It is also preferable to take a structure that is present.

(Example 1)
<Manufacturing of CMOS inverter>
-Formation of gate electrode-
A gate electrode was formed by depositing Al on a glass substrate so as to have a thickness of 100 nm, performing photolithography, and patterning in a line shape.

-Formation of gate insulating layer-
By plasma CVD, SiH ₄ gas and N ₂ O gas were used as raw materials, and a SiON film having a thickness of 200 nm was formed at a temperature of 200 ° C. This is used as a gate insulating layer.

-Formation of oxide layer to be the first and second active layers-
Argon (Ar) and oxygen (O ₂ ) gas were introduced into the _{chamber, and a SnO 2} film was formed by performing an RF sputtering method at room temperature using a _{SnO 2 sintered body target.} The oxygen ratio in the flow rate of the gas introduced into the chamber at the time of film formation was 10.0% of oxygen with respect to the total flow rate (sum of the flow rates of argon gas and oxygen gas). The patterning was performed by forming a film through a metal mask, and the first oxide layer for forming the first active layer and the second oxide layer for forming the second active layer were separated. I got a pattern.

-Formation of source and drain electrodes-
On the gate insulating layer, a source electrode and a drain electrode in contact with the first oxide layer for forming the first active layer were formed. At the same time, a source electrode and a drain electrode in contact with the second oxide layer for forming the second active layer were formed.
The electrodes were formed by forming an Al film having a thickness of 100 nm using a vacuum thin-film deposition method and patterning it through a metal mask. Here, the drain electrode connected to the first oxide layer for forming the first active layer and the drain electrode connected to the second oxide layer for forming the second active layer are electrically conductive. doing. The size of the channel region created by each source / drain electrode was 200 μm in width and 50 μm in channel length.

-Formation of an insulating layer on the second oxide layer to serve as the second active layer-
Argon (Ar) and oxygen (O ₂ ) gases were introduced into the _{chamber, and a SiO 2} insulating layer was formed by performing an RF sputtering method at room temperature using a _{SiO 2 target.} The oxygen ratio in the flow rate of the gas introduced into the chamber at the time of film formation was 25.0% oxygen with respect to the total flow rate. The patterning was performed by forming a film through a metal mask, and formed in a region covering a second oxide layer for forming a second active layer. As a result, the second oxide layer used as the second active layer was surrounded by the gate insulating layer, the source electrode, the drain electrode, and the SiO ₂ insulating layer, and was not exposed to the outside air.

-Heating process in reducing atmosphere-
The substrate was placed on a heating stage in a highly airtight chamber and heated at 300 ° C. for 4 hours. The temperature was measured with a thermocouple attached to the stage and kept constant by feedback control. During heating, G2 grade Ar gas whose oxygen concentration was reduced by an oxygen pump was introduced into the chamber furnace. The flow rate of Ar was controlled by a mass flow controller, and the pressure in the chamber furnace was set to 10 kPa. In addition, the output of the oxygen pump was controlled to maintain the ^{partial pressure of oxygen in the chamber furnace at 1 × 10 -10 Pa.}

Through the above process, a CMOS inverter similar to FIG. 1E, consisting of an n-type field-effect transistor having a second active layer and a p-type field-effect transistor having a first active layer, was produced. Although not shown in FIG. 1E, the gate electrode under the first active layer and the gate electrode under the second active layer are conductive, and an input voltage (Vin) is applied thereto. Further, the drain electrode connected to the first active layer and the drain electrode connected to the second active layer are conductive, and the circuit configuration as shown in FIG. 2 in which the voltage here is the output (Vout) is formed. There is.

<Measurement of characteristics>
The characteristics of the obtained CMOS inverter were evaluated. The V _dd and _10V, was to measure the _{V out} by changing the _{V in} from 0V to _{10V, V} in = In _{0V V out = 10V, V in} = 10V in the _V out = 0V, and the operation in which the output is inverted It could be confirmed.

Aspects of the present invention are, for example, as follows.
<1> A method for manufacturing a semiconductor device having a first active layer made of a p-type oxide semiconductor and a second active layer made of an n-type oxide semiconductor.
It has a first oxide layer for forming the first active layer, a second oxide layer for forming the second active layer, and an insulating layer covering the second oxide layer. Including a heating step of heating the semiconductor device precursor in a reducing atmosphere,
A method for manufacturing a semiconductor device, characterized in that, in the heating step, the first oxide layer is in contact with the reducing atmosphere and the second oxide layer is not in contact with the reducing atmosphere.
<2> The method for manufacturing a semiconductor device according to <1>, wherein the reducing atmosphere contains hydrogen gas.
<3> The method for manufacturing a semiconductor device according to any one of <1> to <2>, wherein the oxygen partial pressure in the reducing atmosphere is ^{10-5 Pa or less.}
<4> The method for manufacturing a semiconductor device according to any one of <1> to <3>, wherein the heating temperature in the heating step is 100 ° C. or higher and 500 ° C. or lower.
<5> The first active layer and the second active layer contain the same metal oxide as a main component, and the degree of oxidation of the second active layer is the degree of oxidation of the first active layer. The method for manufacturing a semiconductor device according to any one of <1> to <4>, which is higher than the above.
<6> The method for manufacturing a semiconductor device according to <5>, wherein the same metal oxide is a tin oxide, a thallium oxide, or an oxide obtained by mixing these.
<7> The steps <1> to <6> including an oxide layer forming step of simultaneously forming the first oxide layer and the second oxide layer using the same metal oxide material. The method for manufacturing a semiconductor element according to any one of the above.
<8> The method for manufacturing a semiconductor device according to any one of <1> to <6>, wherein the n-type oxide semiconductor contains a substitution dopant.
<9> The method for manufacturing a semiconductor device according to any one of <1> to <8>, wherein the insulating layer is an oxide layer having an insulating property.
<10> The method for manufacturing a semiconductor element according to any one of <1> to <9>, wherein the semiconductor element is CMOS.

According to the present invention, it is possible to provide a method for manufacturing a semiconductor device capable of solving the above-mentioned problems in the past and manufacturing a semiconductor device having a p-type oxide semiconductor and an n-type oxide semiconductor with good controllability.

1 Substrate 2A Gate electrode 2B Gate electrode 3 Gate insulating layer 4A First oxide layer 4B Second oxide layer 4p First active layer 4n Second active layer 5A Source electrode 5B Drain electrode 5C Source electrode 6 Insulation layer

Japanese Unexamined Patent Publication No. 2002-114515

Y. Ogo, 6 others, "p-channel thin-film transistor using p-type oxide semiconductor, SnO", APPLIED PHYSICS LETTERS 93, p. 032113 (2008)

Claims (8)

A method for manufacturing a semiconductor device having a first active layer made of a p-type oxide semiconductor and a second active layer made of an n-type oxide semiconductor.
By heating a semiconductor device precursor having a first oxide layer, a second oxide layer, and an insulating layer covering the second oxide layer in a reducing atmosphere, the first oxide Including a heating step in which the layer is the first active layer and the second oxide layer is the second active layer.
In the heating step, the first oxide layer is heated so as to be in contact with the reducing atmosphere, and the second oxide layer is heated so as not to be in contact with the reducing atmosphere.
The first oxide layer and the second oxide layer are the same metal oxide.
A method for producing a semiconductor device, wherein the same metal oxide is a tin oxide, a thallium oxide, or an oxide obtained by mixing these. The method for manufacturing a semiconductor device according to claim 1, wherein the reducing atmosphere contains hydrogen gas. The method for manufacturing a semiconductor device according to any one of claims 1 to 2, wherein the oxygen partial pressure in the reducing atmosphere is ^{10-5 Pa or less.} The method for manufacturing a semiconductor device according to any one of claims 1 to 3, wherein the heating temperature in the heating step is 100 ° C. or higher and 500 ° C. or lower. The semiconductor according to any one of claims 1 to 4, which includes an oxide layer forming step of simultaneously forming the first oxide layer and the second oxide layer using the same metal oxide material. Manufacturing method of the element. The method for manufacturing a semiconductor device according to any one of claims 1 to 5, wherein the n-type oxide semiconductor contains a substituted dopant. The method for manufacturing a semiconductor device according to any one of claims 1 to 6, wherein the insulating layer is an oxide layer having an insulating property. The method for manufacturing a semiconductor element according to any one of claims 1 to 7, wherein the semiconductor element is CMOS.

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