JPS61159741A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To reduce the number of processes by providing a process, in which an insulating film formed on the back side of a semiconductor substrate is removed, after a process in which the insulating film is formed to the substrate. CONSTITUTION:Insulating films 2 are shaped onto a semiconductor such as a silicon substrate 1. The insulating film 2 on the back side of the substrate 1 in the insulating films 2 is removed to expose the substrate 1, and polysilicon is grown. Consequently, a film 3 for a gate consisting of polysilicon is wired onto the insulating film 2. A polysilicon film 4 directly grows on the back side of the substrate 1, and applied stress to the substrate 1. A process in which an impurity is diffused is conducted in order to give the film 3 conductivity. Heavy metals, such as molybdenum, tungsten, etc. made to be contained in the substrate 1 are captured to a defective region formed on the basis of stress and strain generated due to the formation of SiP, etc. in the substrate 1 through heat treatment. As a result, double gettering effects are acquired through the growth of the polycrystalline semiconductor and the diffusion of the impurity. Accordingly, a gettering exclusive process is unnecessitated only by adding one process in which the insulating film on the back side of the semiconductor substrate is removed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for manufacturing a semiconductor device, and particularly to a method for manufacturing a semiconductor device that does not require a step dedicated to gettering.

[Prior Art] Semiconductor devices such as large-scale integrated circuits, especially memory devices such as dynamic RAMs and charge-coupled devices (CODs) that use electric field effects such as MOS type, have small leakage current at the junction surface and are free of charge. A long retention time is required as an essential requirement. Therefore, in manufacturing semiconductor devices, a gettering process is often provided in order to protect circuit elements from the adverse effects of heavy metal contamination, which is the main cause of deterioration of these circuit characteristics.

FIG. 2 shows an example of a conventional manufacturing method for silicon (St) gate MOS devices. In this manufacturing method, first, the semiconductor substrate l is oxidized to form the insulating film 2. Usually, in this step, the surface of the substrate l (
Polysilicon is grown by, for example, vapor phase growth, in which an insulating layer M2 is formed on both sides (the side on which a circuit element is formed) and the back side. Through this step, polysilicon 3 and 4 are formed on both the insulating film 2 on the front side and the insulating film 2 on the back side, respectively. And polysilicon 3.4
The polysilicon 3.4 is made conductive by diffusing phosphorus into the polysilicon 3.4 to form a gate. After that, although not shown, a step of forming a source and a drain on the surface side, a gettering step,
A normal MOS device manufacturing process such as a heat treatment process is performed.

Examples of the gettering process include the following.

! Phosphorus is diffused on the back side by pre-deposition of POCl, etc. to form SiP to generate strain, and heavy metals contained in the substrate are captured by the strain through subsequent heat treatment.

・Ri) Polysilicon is grown on an uneven surface, the stress of which forms a lattice defect region in the substrate, and the heavy metals contained in the substrate are trapped in this defect region by subsequent heat treatment.

In all of these gettering processes, it is necessary to selectively process the back side, so a series of dedicated processes are required after the formation of the circuit elements on the front side. In order to prevent phosphorus from being diffused on the surface side where phosphorus is formed, at least a step of forming a mask such as a silicon oxide film on the surface side and a step of removing this mask after pre-deposition are required. In addition, in order to prevent polysilicon from being formed on the surface side where one circuit element is formed, at least the step of forming a coating film on the surface and removing the coating film after forming the polysilicon. process is required.

As described above, a gettering process is essential in the manufacture of semiconductor devices, particularly in the manufacture of field-effect semiconductor devices. Moreover, the conventional manufacturing method requires a series of dedicated steps for gettering, which increases the number of semiconductor manufacturing steps, which causes an increase in the manufacturing cost of semiconductor devices.

[Object of the Invention] An object of the present invention is to provide a semiconductor device that eliminates a process dedicated to gettering and simultaneously performs gettering in other manufacturing processes, thereby reducing the number of manufacturing processes and reducing manufacturing costs. The purpose of this invention is to provide a method for manufacturing the same.

[Structure of the Invention] In order to achieve the above object, the method for manufacturing a semiconductor device of the present invention includes a step of removing an insulating film formed on the back side of the semiconductor substrate after a step of forming an insulating film on a semiconductor substrate. Configure the system to be set up.

[Operation of the Invention] As described above, in the method for manufacturing a semiconductor device of the present invention, the insulating film on the back side of the semiconductor substrate is removed at an early stage of the manufacturing process, so that it is not removed in the subsequent normal manufacturing process. Stress can be applied to the semiconductor substrate by the growth of the polycrystalline semiconductor. In other words, since there is no insulating film on the back side of the substrate that acts as a buffer, gettering is performed simultaneously during the polycrystalline semiconductor growth process and the subsequent heat treatment process. In addition, since there is no insulating film on the back side of the substrate that acts as a stopper for impurity diffusion, impurities diffuse into the substrate from the back side of the substrate through the polycrystalline semiconductor during the impurity diffusion process after the polycrystalline semiconductor growth process. Gettering is performed by the subsequent heat treatment process.

Therefore, a dedicated process for gettering becomes unnecessary.

Note that if the polycrystalline semiconductor does not grow on the back side, there will be no gettering effect due to the attachment of the polycrystalline semiconductor, but only the gettering effect due to impurities.If the impurity cannot be diffused to the back side, there will be no gettering effect due to the impurities. It is natural that the only gettering effect due to the attachment of the polycrystalline semiconductor will be obtained without it. However, in a general semiconductor device manufacturing method, polycrystalline semiconductor growth and impurity diffusion are performed on both sides of the substrate, so both gettering effects can be obtained.

[Embodiments of the Invention] An embodiment of the semiconductor device manufacturing method of the present invention will be described below with reference to FIG.

First, in the insulating film formation step, a semiconductor such as silicon (
An insulation film 2 is formed on a substrate 1 made of Si). The insulating film 2 is formed by, for example, oxidizing the substrate 1, so that silicon oxide (SfO) is formed on both sides of the substrate 1.
l) A film is formed.

Next, a back insulating film removal step according to the present invention is performed. In this step, of the insulating film 2 formed in the previous step, the insulating film 2 on the back side of the substrate l is removed to expose the semiconductor substrate 1. .

Next, a polycrystalline semiconductor growth step performed in a normal semiconductor device manufacturing method is performed, which involves growing polysilicon by, for example, a vapor phase growth method. As a result, the insulating film 2
A gate film 3 made of polysilicon, for example, is wired thereon. Further, polysilicon film 4 is directly grown on the back side of substrate 1, and this polysilicon film 4 gives stress to substrate 1.

Furthermore, in order to impart conductivity to 1l13 for the gate, a process of diffusing impurities is performed, for example, by F
This diffusion of impurities such as phosphorus, which is performed by pre-deposition of oxidation silicon or by diffusion from the phosphorus glass (psc) film, is also carried out on the back side, and the impurities such as phosphorus are
It also diffuses into the substrate l.

After that, when heat treatment, which is a normal semiconductor device manufacturing process, is performed, defective areas generated based on the stress,
Due to the distortion caused by the formation of SiP etc. in the substrate l,
Heavy metals such as molybdenum (Mo) and tungsten (W) contained in the substrate 1 are captured.

In this way, in this embodiment, a double gettering effect can be obtained by polycrystalline semiconductor growth and impurity diffusion.

It should be noted that, as a matter of course, the present invention is not limited to the illustrated embodiment.

[Effects of the Invention] As described above, in the semiconductor device manufacturing method of the present invention, only one step of removing the insulating film on the back side of the semiconductor substrate is added at the initial stage of the manufacturing process, and a gettering-dedicated step is eliminated. This has the excellent effect of making it unnecessary. For this reason,
The number of manufacturing steps for semiconductor devices is reduced, and manufacturing costs can be reduced.

2... Insulating film, 3.4... Polycrystalline semiconductor film.

Patent applicant Nisoni Co., Ltd. Chief brewer Manager: Patent attorney Toru Takatsuki 1
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Claims (1)

[Scope of Claims] 1. A method comprising the steps of forming an insulating film on a semiconductor substrate, growing a polycrystalline semiconductor on the semiconductor substrate on which the insulating film is formed, and diffusing impurities into the polycrystalline semiconductor. In the method for manufacturing a semiconductor device, after the step of forming the insulating film, a step of removing the insulating film formed on the back side of the semiconductor substrate is provided, and after the step, the polycrystalline semiconductor growing step or the impurity diffusion step is performed. A method for manufacturing a semiconductor device, characterized in that: 2. The method of manufacturing a semiconductor device according to claim 1, wherein the polycrystalline semiconductor is polysilicon. 3. The method of manufacturing a semiconductor device according to claim 1, wherein the impurity is phosphorus. ,