JPH01215071A - Manufacture of photogeneration element - Google Patents

Abstract

PURPOSE:To prevent generation of pattern slippage of photomechanical process while reducing the number of processes by selectively forming a metal film on a cap layer and selectively etching only the cap layer self-matchingly having this metal film as a mask and selectively forming a reflection preventing film on an active layer. CONSTITUTION:An active layer 4 consisting of an n-type GaAs layer 2 and a p-type GaAs layer 3 are formed on an n-type GaAs substrate 1 by an MOCVD method and an MBE method and a window 5 and a cap layer 6 are formed on this active layer 4. Next, a metal film 10 is formed on the cap layer 6 by a vacuum evaporation method and a sputtering method. Next, an electrode pattern 7 is formed by selectively etching the metal film 10 while using a phototype process. Next, the cap layer 6 is selectively etched self-matchingly having the metal film 10 as a mask. Finally, a reflection preventive film 8 is formed by a CVD method and a sputtering method, while selectively forming a contact hole 11 for an interconnector by the photomechanical process and the etching method so as to finish an element.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method for manufacturing a photovoltaic device, and particularly to a method for forming a surface electrode having a structure with a cap layer.

(Prior art) Figure 2 (a) to (61) show the main manufacturing method of a GaAs solar cell in order of process as an example of the main manufacturing method of a photovoltaic device having a conventional surface electrode structure with a cap layer. It is a diagram.

In these figures, 1 is an n-type GaAs substrate, 2 is an n-type GaAs layer, 3 is a p-type GaAs layer, 4 is an active layer, and 5 is a p-type GaAs layer.
Type AJ! A window layer made of a GaAs layer, 6 a cap layer made of p-type GaAs, 7 an electrode pattern, 8 an antireflection film made of, for example, a silicon nitride film, 9 a contact hole, and 10 made of, for example, Ti/Ag, AuZn, etc. It is a metal film.

The conventional method will be explained below using FIGS. 2(a) to 2(6).

First, as shown in FIG. 2(a), an n-type GaAs substrate 1
An active layer 4 consisting of an n-type GaAs layer 2 and a p-type GaAs layer 3 is formed thereon by metal organic chemical vapor deposition (MOCVD), molecular beam epitaxy (MBE), or the like.
Next, a window layer 5 is formed on this active layer 4, and a cap layer 6 is formed on this window layer 5.

Next, as shown in FIG. 2(b), the cap layer 6 is selectively etched using photolithography to form an electrode pattern 7.

Next, as shown in FIG. 2(C), chemical vapor deposition (CV)
After forming the antireflection film 8 by the method D), sputtering method, etc., contact holes 9 are selectively formed on the cap layer 6 by photolithography and etching methods.

Next, as shown in FIG. 2(d), a metal film 10 is formed by vapor deposition, sputtering, or the like.

Then, as shown in FIG. 2(e), the metal film 10 is selectively etched using photolithography to form the electrode pattern 7, thereby completing the device.

In this device, the metal film 10 and the cap layer 6 function as one-sided electrodes that make electrical contact with the active layer 4, and the cap layer 6 separates the metal film 10 from the active layer 4 and
It has a function of suppressing the influence of the metal film 10 on the interface between the As layer 2 and the p-type GaAs layer 3.

[Problem to be solved by the invention]

In the conventional method for manufacturing a photovoltaic device as described above, photolithography must be performed three times: etching the cap layer 6, forming the contact hole 9, and etching the metal/film 10. and cap layer 6. There was a problem in that pattern deviation occurred in the contact hole 9 and the metal film 10.

The present invention was made to solve this problem, and aims to provide a method for manufacturing a photovoltaic device that does not cause photolithography pattern shift and that requires a small number of steps.

(Means for Solving the Problems) Manufacturing a photovoltaic device according to the present invention includes a step of sequentially forming an active layer having a pn junction, a cap layer, and a metal film on the main surface of a semiconductor substrate, and a step of forming an active layer having a pn junction, a cap layer, and a metal film, and A process of selectively forming a metal film on the active layer, a process of selectively etching only the cap layer using the metal film as a mask, and a process of selectively forming an antireflection film on the active layer. It includes.

(Function) In this invention, since the cap layer is selectively etched in a self-aligned manner using the metal film selectively formed on the cap layer as a mask, photolithography for forming the electrode is performed in one step.
Just do it once.

(Example) FIGS. 1(a) to 1(e) are diagrams showing in order of steps a method for manufacturing a GaAs solar cell as an example of the method for manufacturing a photovoltaic device of the present invention.

In this figure, the same reference numerals as in FIGS. 2(a) to (et) indicate the same parts, and 11 is a contact hole.

The manufacturing method of this invention will be explained below.

First, as shown in FIG. 1(a), an active layer 4 consisting of an n-type GaAs layer 2 and a p-type GaAs layer 3 is formed on an n-type GaAs substrate 1 by MOCVD, MBE, or the like. 4. Window layer on top 5. Form the character and bu layer 6. The state shown in FIG. 1 (II) is the same as the state shown in FIG. 2 (a).

Next, as shown in FIG. 1(b), a metal film 10 is formed on the cap layer 6 by a vapor deposition method, a sputtering method, or the like.

Next, as shown in FIG. 1(e), the metal film 10 is selectively etched using photolithography to form an electrode pattern 7.

Next, as shown in FIG. 1(d), the cap layer 6 is selectively etched in a self-aligned manner using the metal film 10 as a mask.

Finally, as shown in Figure 1(e), the CVD method,
The device is completed by forming an antireflection film 8 by a scattering method or the like, and selectively forming contact holes 11 for interconnectors by photolithography or etching.

That is, in this invention, after the metal film 10 previously formed on the cap layer 6 is selectively etched onto the electrode pattern 7, the cap layer 6 is selectively etched in a self-aligned manner using the metal film 10 as a mask. The electrodes of the cap layer material can be formed by plate making, and pattern misalignment between the cap layer 6 and the metal film 10 can be avoided.

Furthermore, since the anti-reflection film 8 is formed after the electrode shape is old, the alignment for forming the contact hole 11 is easy, and the alignment required to form the contact hole 11 is easy, unlike the conventional method, which is complicated to make electrical contact between the metal film 10 and the gap layer 6. There is no need to form the contact hole 9, which has such a shape that alignment is difficult. Therefore, pattern deviation of contact holes 9 that occurs in the conventional method can also be avoided. - In the above embodiment, a p-type GaAs layer is used for the cap layer 6, but a p-type Ge layer or another semiconductor layer lattice-matched to GaAs may be used. However, cap layer 6
As such, it is preferable to use a semiconductor layer having a coefficient of thermal expansion equal to or close to that of GaAs.

(Effects of the Invention) As explained above, the present invention includes a step of sequentially forming an active layer having a pn junction, a cap layer, and a metal film on the main surface of a semiconductor substrate, and selectively forming a metal film on the cap layer. , selectively etching only the cap layer in a self-aligned manner using this metal film as a mask, and selectively forming an antireflection film on the active layer.
Electrodes can be formed in one photolithography process, a photovoltaic device can be obtained without pattern deviation, and the process can be simplified.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing an embodiment of the method for manufacturing a photovoltaic device according to the present invention, and FIG. 2 is a diagram showing a conventional method for manufacturing a photovoltaic device. In the figure, 1 is an n-type GaAs substrate, 2 is an n-type GaAs substrate
3 is a P-type GaAs layer, 4 is an active layer, 6 is a cap layer, 8 is an antireflection film, 1o is a metal film, and 11 is a contact hole. Note that the same reference numerals in each figure indicate the same or corresponding parts. Agent Masuo Oiwa (2 others) Procedural amendment (voluntary)

Claims (1)

[Claims] A step of sequentially forming an active layer having a pn junction, a cap layer, and a metal film on the main surface of a semiconductor substrate, a step of selectively forming a metal film on the cap layer, and a step of forming the metal film as a mask. A method for manufacturing a photovoltaic device, comprising the steps of selectively etching only the cap layer in a self-aligned manner, and selectively forming an antireflection film on the active layer.