JPH0629205A - Method and apparatus for manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To protect an oxide semiconductor from corrosion by a method wherein, in a process wherein a semiconductor device is immersed in an ion-conductive liquid, the semiconductor device is connected electrically to an auxiliary metal whose potential is lower that the equilibrium potential of a metal layer and the semiconductor device is immersed in the ion-conductive liquid. CONSTITUTION:A sample 8 is immersed in a developing solution 6 inside an apparatus for 45 seconds. Mg is used as an auxiliary metal 9, and the area ratio of the sample 8 to the auxiliary metal 9 is adjusted so as to be 1:1. The auxiliary metal 9 and the sample 8 are connected by a copper wire 10. A Microposit Developer made by Shipley is used as the developing solution 6 for photolithography. When the degree of the corrosion of an oxide semiconductor layer on the sample 8 which has been immersed in the developing solution 6 in this manner is evaluated visually from an ITO face, the corrosion of an ITO layer is not recognized on the sample 8.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a semiconductor device and an apparatus therefor, and particularly in a liquid having a ionic conductivity such as a photolithography process when a semiconductor device such as a liquid crystal display is manufactured. TECHNICAL FIELD The present invention relates to a method for manufacturing a semiconductor device and a device therefor, which has a step of immersing in a semiconductor.

[0002]

2. Description of the Related Art Conventionally, in a semiconductor device, an oxide semiconductor has been widely used as a transparent electrode layer or an insulating layer in liquid crystal displays, solar cells and the like. As the transparent electrode layer, since it exhibits high light transmittance and high electrical conductivity, ITO (In ₂ O ₃ + SnO ₂ ), In ₂ O ₃ ,
SnO ₂ is used, and T is used as an insulating layer.
such as _{a 2 O 5, Al 2 O} 3 is used. On the other hand, as the electrode layer, low-resistance metallic aluminum is mainly used.

A semiconductor device is manufactured by repeating deposition of a thin film by a CVD method or a sputtering method and processing of the thin film by wet etching or dry etching, photolithography and the like. Here, for simplification, an amorphous silicon thin film transistor (TF) is used as a semiconductor device.
A manufacturing method of a liquid crystal display device incorporating T) will be described as an example.

An ITO layer is deposited on a glass substrate by a sputtering method, and a pattern is formed by wet etching. Next, as the ITO protective layer, SiOx is formed by the CVD method.
Form the layers. After that, a Cr layer is formed by a sputtering method and patterned to be a gate electrode. Then CV
Forming a SiNx / a-Si / SiNx layer by the D method,
After patterning, an n ⁺ a-Si layer is deposited. Next, a contact hole with ITO is opened by dry etching, and a Ti layer and an Al layer are sequentially deposited by a sputtering method. Finally, a two-layer source / drain made of Ti / Al is formed by photolithography.

[0005]

However, in the case of manufacturing a semiconductor device as described above, for example, in manufacturing a liquid crystal display, corrosion occurs in the step of forming source / drain Al layers by photolithography. The principle will be described with reference to FIG. As a semiconductor device, an ITO layer 2 is patterned on a glass substrate 1,
An Al layer 3 is deposited thereon, and a pattern of a photoresist 4 is further formed on the Al layer 3. A large number of local active parts exist on the surface of the Al layer 3, and when immersed in the alkaline developing solution 6, the Al dissolution reaction proceeds from the active parts. As a result, a large number of minute pinholes 5 reaching the ITO layer are generated inside the Al layer 3, and an Al / developer (electrolyte) / ITO-based local battery is formed. The chemical reaction formula of the local battery is considered as follows.

Anode side (1) Al + 4OH ⁻ → H ₂ AlO ₃ ⁻
+ H ₂ O + 3e ⁻ E ⁰ Al = −2.3 (V) Cathode side (2) In ₂ O ₃ + 3H ₂ O + 6e ^{−
→ 2In + 6OH -. E 0} ITO = -1 0 (V) (3) 2H 2 O + 2e - → 2OH -. + H 2 ↑ E 0 H 2 = -0 83 (V) E 0 is the equilibrium potential of each portion. As represented by the above reaction formula, the Al film is dissolved on the anode side (equation (1)),
At the same time, a hydrogen generation reaction occurs as a reduction reaction on the cathode side (equation (3)). When the electrolyte enters the ITO layer 2 through the pinhole 5, In ₂ O ₃ is reduced ((2)
Formula), as a result, the ITO layer 2 is corroded.

Even when two layers of Ti and Al are used for the source / drain, the electrolyte that has penetrated to the Ti layer through the pinholes of the Al layer is further penetrated to the ITO layer through the pinholes and crystal grain boundaries existing in the Ti layer. And a local battery of Al / developer (electrolyte) / ITO system is formed, and corrosion of ITO occurs.

The present invention solves the above problems, and provides a method of manufacturing a semiconductor device in which an oxide semiconductor is not corroded in the step of immersing the semiconductor device in a liquid having ionic conductivity, and a device therefor. It is intended.

[0009]

In order to solve the above problems, the present invention provides a method for manufacturing a semiconductor device having at least an oxide semiconductor layer and a metal layer, wherein the semiconductor device is immersed in a liquid having ionic conductivity. In the dipping step, the semiconductor device is electrically connected to an auxiliary metal having a potential lower than the equilibrium potential of the metal layer, and dipped in the liquid having ionic conductivity.

[0010]

According to the above, when the semiconductor device is immersed in the liquid having ionic conductivity, an auxiliary metal having a potential lower than the equilibrium potential of the metal layer of the semiconductor device is simultaneously immersed, and the semiconductor device and the auxiliary By electrically connecting the metal, the auxiliary metal becomes an anode, and the auxiliary metal ions are eluted. The metal layer of the semiconductor device serves as a cathode, no pinhole is generated due to the dissolution reaction, and the electrolyte solution does not soak into the oxide semiconductor layer. Therefore, the reduction reaction or corrosion of the oxide semiconductor is avoided.

When the liquid having ionic conductivity is alkaline, electrochemical oxidation of the metal such as Al and electrochemical reduction of the oxide semiconductor are likely to occur in the liquid, but the method of the present invention is used. This makes it possible to avoid this reaction or corrosion.

Further, the developer used for developing the resist in the photolithography step is alkaline, and in this step, a stacked structure of an oxide semiconductor and a metal is often formed in the semiconductor device. Corrosion of the oxide semiconductor is likely to occur due to a general reduction reaction, but it is possible to avoid the corrosion by using the method of the present invention.

[0013]

The present invention will be described in detail below with reference to examples, but the present invention is not limited thereto.

Example 1 In this example, in order to investigate the effect of the present invention, ITO was used as an oxide semiconductor, and a metal layer on which Ti and Al were sequentially laminated was used. A developer for photolithography was selected as a liquid having ionic conductivity, and corrosion of ITO when immersed in the developer was examined.

FIG. 1 shows a sample 8 used in this embodiment, in which an ITO layer 2, a Ti layer 7 and an Al layer are formed on a glass substrate 1.
Layer 3 is sequentially sputtered to 100 nm, 100 nm,
It is formed with a thickness of 700 nm.

This sample 8 was immersed in the developer 6 in the apparatus as shown in FIG. 2 for 45 seconds. Note that the auxiliary metal 9 has M
and the area ratio of the sample 8 and the auxiliary metal 9 is 1: 1.
Was adjusted so that the auxiliary metal and the sample were connected by a copper wire 10. SH is used as the developer 6 for photolithography.
A microposit developer made by IPLEY was used.

When the degree of corrosion of the oxide semiconductor layer of the sample 8 thus immersed in the developing solution 6 was visually evaluated from the ITO surface, no corrosion of the ITO layer was observed in the sample 8.

For comparison, a similar sample 8 was immersed in developer 6 for 45 seconds without connecting to auxiliary metal 9. When the degree of corrosion of the oxide semiconductor layer of this sample 8 was visually evaluated from the ITO surface in the same manner as above, corrosion of the ITO layer was observed at an average of 2 places per cm ² .

A similar experiment was carried out with the immersion time of 90 seconds, and it was found that 1 was not connected to the auxiliary metal 9.
Corrosion of the ITO layer was observed at an average of 9 places per cm ² , whereas no corrosion of the ITO layer was observed in the case of immersion in which the auxiliary metal 9 was connected according to the present invention.

From the above, according to the method of the present invention,
It was found that corrosion of the oxide semiconductor layer can be avoided in the manufacturing process of the semiconductor device. (Embodiment 2) In the present embodiment, the manufacturing method and the manufacturing apparatus according to the present invention were used in the photoresist process in the process of manufacturing a liquid crystal display device as a semiconductor device.

FIG. 3 is a sectional view for explaining the manufacturing process of the liquid crystal display device according to this embodiment. First, the ITO layer 2 is deposited on the glass substrate 1 by the sputtering method,
After forming the pattern by wet etching, the SiOx layer 11 was formed by the CVD method. After that, the Cr layer 12 was formed by the sputtering method and patterned to form a gate electrode. Next, the SiNx layer 13 and a-Si are formed by the CVD method.
After forming the layer 14 and the SiNx layer 15 and forming a pattern, n
⁺ a-Si layer 16 was deposited. Next, the contact hole 17 with ITO was opened by dry etching, and the Ti layer 7 and the Al layer 3 were sequentially deposited by the sputtering method. Then, the photoresist 4 was applied on the surface and exposed.

The principle of the photoresist developing device is shown in FIG. Reference numeral 20 in the drawing denotes a semiconductor device similar to that shown in FIG. 3, which was fixed by suction by a fixing jig 21. An auxiliary metal 9 is fixed in the developing device, which is used as the semiconductor device 2
It was electrically connected to 0. In this way, the semiconductor device 20 was fixed and the developer 6 was injected. When the development was completed, the developing solution was discharged, and the semiconductor device 20 was washed with water 22.

After that, a Ti / Al layer pattern was formed by etching to form a source and a drain, and the resist was peeled off to form a liquid crystal display device. For comparison, a liquid crystal display device was constructed in the same manner as above except that the auxiliary metal was not connected.

When a driving IC was mounted on the liquid crystal display device thus obtained and its characteristics were evaluated,
According to the present invention, the product developed by connecting the auxiliary metal worked normally, whereas the product not connected with the auxiliary metal showed malfunction. When the failure analysis was performed, corrosion of ITO was found in the part where the IC was mounted.

From the above, it was found that the present invention makes it possible to avoid corrosion of the oxide semiconductor layer in the manufacturing process of the semiconductor device. (Example 3) In this example, an amorphous silicon solar cell was manufactured as a semiconductor device.

FIG. 5 shows a sectional view of the manufacturing process of the amorphous silicon solar cell according to this embodiment. First, the ITO layer 31 was vapor-deposited on the glass substrate 30 by the sputtering method. Next, by the CVD method, p-a-Si / i-a-Si
The / na-Si layer 32 was formed into a film. After that, a pattern was formed by dry etching, and an Al layer 33 was formed as an electrode by a sputtering method. Next, a resist 34 for photolithography was applied to the surface and exposed.

The photoresist was developed in the same manner as in Example 2, and for comparison, the photoresist which was not connected to the auxiliary metal was similarly developed. When the amorphous silicon solar cell thus obtained was visually inspected, no abnormality was found in the product developed by connecting the auxiliary metal according to the present invention, whereas the auxiliary metal was not connected. Corrosion was observed in the ITO layer.

From the above, it was found that the present invention makes it possible to avoid corrosion of the oxide semiconductor layer in the manufacturing process of the semiconductor device. Further, in the embodiment of the present invention, ITO was used as the oxide semiconductor, but indium oxide (In ₂ O
₃ ), tin oxide (SnO ₂ ) and other oxide semiconductors have similar effects.

Further, in the embodiments of the present invention, the liquid crystal display device and the amorphous silicon solar cell have been described as the semiconductor device, but the same effect can be obtained with other semiconductor devices such as a photodiode and an electroluminescence element. Needless to say.

[0030]

As described above, according to the present invention, when a semiconductor device is immersed in a liquid having ionic conductivity, an auxiliary metal having a potential lower than the equilibrium potential of the metal layer of the semiconductor device is simultaneously immersed. By electrically connecting the semiconductor device and the auxiliary metal, reduction reaction of the oxide semiconductor, that is, corrosion, can be avoided.

When the liquid having ionic conductivity shows alkalinity, the method of the present invention is used to electrochemically oxidize a metal such as Al or electrochemically reduce an oxide semiconductor by using the method of the present invention. Can be avoided and therefore corrosion can be avoided.

Further, in the photolithography process in which the developing solution exhibits alkalinity and a stacked structure of an oxide semiconductor and a metal is often formed in the semiconductor device in the process, this process can be performed by using the method of the present invention. It is possible to avoid corrosion of the oxide semiconductor due to the electrochemical reduction reaction that tends to occur in.

Further, according to the apparatus of the present invention, since the auxiliary metal is held in the liquid having ionic conductivity, the manufacturing method of the present invention can be easily carried out.

[Brief description of drawings]

FIG. 1 is a diagram showing a measurement sample in one example of the present invention.

FIG. 2 is a diagram showing a developing device in one embodiment of the present invention.

FIG. 3 is a cross-sectional view for explaining a manufacturing process of a liquid crystal display device according to another embodiment of the present invention.

FIG. 4 is a diagram showing the principle of a developing device in another embodiment of the present invention.

FIG. 5 is a cross-sectional view for explaining a manufacturing process of an amorphous silicon solar cell according to still another embodiment of the present invention.

FIG. 6 is a diagram showing a conventional principle of occurrence of corrosion.

[Explanation of symbols]

 2 ITO layer (oxide semiconductor layer) 3 Al layer (metal layer) 6 Developer (solution having ion conductivity) 7 Ti layer (metal layer) 8 Sample (semiconductor device) 9 Auxiliary metal

Claims (8)

[Claims] 1. A method of manufacturing a semiconductor device having at least an oxide semiconductor layer and a metal layer, wherein the step of immersing the semiconductor device in a liquid having ionic conductivity is performed so that the semiconductor device has an equilibrium potential of the metal layer. A method for manufacturing a semiconductor device, which comprises electrically connecting to an auxiliary metal exhibiting a lower potential and immersing the auxiliary metal in the liquid having ionic conductivity. 2. The method of manufacturing a semiconductor device according to claim 1, wherein the auxiliary metal is composed of a component mainly containing magnesium. 3. The method of manufacturing a semiconductor device according to claim 1, wherein the metal layer is composed of a component mainly containing aluminum. 4. The method for manufacturing a semiconductor device according to claim 1, wherein the oxide semiconductor layer is a layer mainly containing indium oxide, tin oxide, or both. 5. A semiconductor device has an oxide semiconductor layer and one or a plurality of metal layers sequentially laminated thereon, and the oxide semiconductor layer is mainly composed of indium oxide, tin oxide, or both. 2. The method of manufacturing a semiconductor device according to claim 1, wherein the last metal layer is a layer containing aluminum as a main component. 6. The liquid having ionic conductivity is a liquid showing alkalinity at pH ≧ 10.
6. The method for manufacturing a semiconductor device according to claim 5. 7. The method for manufacturing a semiconductor device according to claim 6, wherein the liquid having ionic conductivity is a photoresist developing liquid. 8. An apparatus for manufacturing a semiconductor device according to claim 1, wherein an auxiliary metal is fixed in a liquid having ionic conductivity.