JPH02235330A - Manufacture of semiconductor device - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Summary] The present invention relates to an improvement in a method of ion-implanting impurities into a semiconductor layer, particularly an improvement in preventing the semiconductor layer from being contaminated with heavy metals, alkali metals, etc. contained in a resist. An object of the present invention is to provide a method for implanting impurity ions, which can remove a resist film used as an ion implantation mask using an oxygen plasma etching method without contaminating a semiconductor layer even when ions are implanted. For the purpose, a silicon nitride film is formed on the semiconductor layer, a resist film is formed on this silicon nitride film, and this resist film is exposed and exposed.
After developing to form an opening in the impurity introduction region and implanting impurity ions, the resist film is removed using an oxygen plasma etching method, and then the silicon nitride film is removed. It consists of a method for manufacturing semiconductor devices. [Industrial Application Field] The present invention relates to an improvement in a method of ion-implanting impurities into a semiconductor layer, and particularly to an improvement in preventing the semiconductor layer from being contaminated by heavy metals, alkali metals, etc. contained in a resist. [Prior art] When implanting impurity ions into a semiconductor layer, a resist film is formed directly on the semiconductor layer, or a resist film is formed on a thin oxide film on the semiconductor layer, and then the ions are implanted. Using a mask with an opening in the implantation area, expose and develop to leave a resist film in the area excluding the ion implantation area,
After implanting impurity ions, the resist film is removed using a stripping solution. [Problems to be Solved by the Invention] By the way, when impurity ions are implanted at a dose of about 10"c1-" or more, the polymerization reaction of the resist progresses, so it is necessary to remove the resist film using a stripping solution or the like. It becomes difficult to remove, and can only be removed using oxygen plasma etching, which has strong oxidizing power. Resist contains large amounts of impurities such as heavy metals and alkali metals, so when the resist film is removed using oxygen plasma etching, the semiconductor layer will be contaminated by these impurities, resulting in the formation of The characteristics of semiconductor devices deteriorate. The purpose of the present invention is to eliminate this drawback, and even when impurity ions are implanted at a high dose, the resist film used as an ion implantation mask can be etched with oxygen plasma without contaminating the semiconductor layer. The object of the present invention is to provide a method for ion implantation of impurities, which can be removed using a method. [Means for solving the problem] The above purpose is to form silicon nitride M (3) on the semiconductor layer (1).
), a resist film (4) is formed on this silicon nitride film (3), this resist film (4) is exposed to haze light and developed to form an opening (5) in the impurity introduction region, and the impurity is ionized. This is achieved by a method of manufacturing a semiconductor device in which, after implantation, the resist film (4) is removed using an oxygen plasma etching method, and then the silicon nitride II (3) is removed. Note that an oxide film (2) is formed on the semiconductor layer (1).
), and silicon nitride H (3) is formed on this oxide B (2).
) may be formed. [Function] In the impurity ion implantation method according to the present invention, silicon nitride Wl! is deposited on the oxide H2 formed on the semiconductor layer 1 or the semiconductor mt. 3 is formed, and a resist lI*4 serving as an ion implantation mask is formed on it, so when the resist film 4 is removed using oxygen plasma etching after ion implantation of impurities, Heavy metals, alkali metals, etc. contained in the resist are prevented from reaching the semiconductor layer l by the silicon nitride film 3 and are removed together with the silicon nitride film 3, so the semiconductor layer l is not contaminated. ．． The experimental confirmation results are shown below. See Figure 7. Figure 7 shows a silicon substrate or
C-T characteristics (measurement of carrier generation rate based on time response) when a resist film is formed on a silicon dioxide film with a thickness of 0 to 800 mm and this resist film is removed using an oxygen plasma etching method. is shown. The horizontal axis shows the thickness of the silicon dioxide film formed on the silicon substrate, and the vertical axis shows the resist a formed on the silicon dioxide film with the thickness shown on the horizontal axis by the oxygen plasma etching method. This shows the lifetime time (ms) of minority carriers generated on a silicon substrate when used and removed. Note that O on the horizontal axis indicates the case where the resist film is directly formed on the silicon substrate, and the lifetime time corresponding to S on the horizontal axis indicates the case where the resist film is formed directly on the silicon substrate. The figure shows the lifetime of minority carriers generated on a silicon substrate from which the resist has not been removed, that is, an uncontaminated silicon substrate.

This figure shows that even if the silicon dioxide film is formed to a thickness of about 800 mm, contamination cannot be avoided. See Figure 8. Figure 8 shows a resist film on a 200-layer thick silicon dioxide film formed on a silicon substrate and on a 50-1,000-layer thick silicon nitride film formed on this silicon dioxide film. The CT characteristics are shown when a film is formed and the resist film is removed using an oxygen plasma etching method three times. The horizontal axis shows the film thickness (in thickness) of the silicon nitride film, and the vertical axis shows the generated minority carrier life time (ms). S on the horizontal axis
Similarly to FIG. 7, the lifetime time of generated minority carriers corresponding to is the lifetime time of generated minority carriers of an uncontaminated silicon substrate. From this figure, we can see that the silicon nitride film is
It can be seen that if the resist film is formed to a thickness equal to or thicker than that of a human being, the silicon substrate will not be contaminated even if the resist film is removed using an oxygen plasma etching method.

[Example] Hereinafter, an impurity ion implantation method according to the present invention will be described with reference to the drawings.

Refer to FIG. 2. For example, on a p-type silicon substrate 1, thermal oxidation or CVD is applied.
Using the method, the silicon dioxide film 2 is
Form it to be thick. Referring to FIG. 3, a silicon nitride film 3 having a thickness of about 100 people is formed on the silicon dioxide film 2 by a CVD method using silane and ammonia.

Referring to FIG. 4, a resist film 4 is formed, exposed and developed using a mask having an opening in the ion implantation region, and an opening 5 is formed in the ion implantation region. See Figure 1. For example, injection of n-type impurity arsenic into synthetic aluminum 60-70Ke.
The p-type region 6 is formed by ion implantation with a dose of I x 1014 cm or more. Using a parallel plate type oxygen plasma etching apparatus (not shown), see FIG. 15 at room temperature
The resist film 4 is removed by etching using oxygen plasma generated by providing oxygen at a rate of about 0 cc/min and applying a high frequency power of about 1Kw. Refer to FIG. 6. The silicon nitride film 3 is removed using hot phosphoric acid or the like, and then the silicon dioxide 11 is removed using hydrofluoric acid or the like. J2 is removed to complete a p-type silicon substrate l having a p-type region 6. Note that this ion implantation method is used to form channels in field effect transistors and emitters and emitters in bibolar transistors.
It can be used for base formation, diffusion resistance formation, etc. [Effects of the Invention] As explained above, in the method for manufacturing a semiconductor device according to the present invention, a silicon nitride film is formed on a semiconductor layer or an oxide film formed on the semiconductor layer, and a resist formed on the silicon nitride film is formed on the semiconductor layer or on the oxide film formed on the semiconductor layer. Since impurities are ion-implanted using the film as a mask, even if the resist film is removed using oxygen plasma etching, impurities such as heavy metals and alkali metals contained in the resist film will not be removed by being blocked by the silicon nitride film. Therefore, the semiconductor layer will not be contaminated. Furthermore, by using the oxygen plasma etching method, a resist film that has been degraded due to impurity ion implantation at a high dose can be effectively removed. As a result, deterioration of the characteristics of semiconductor devices is prevented and reliability and yield are improved.

[Brief explanation of the drawing]

1 to 6 are process diagrams of ion implantation according to an embodiment of the present invention. FIG. 7 shows that a resist film is formed on a silicon dioxide film,
This is a CT characteristic diagram when a resist film is removed using an oxygen plasma etching method. FIG. 8 is a C-TI characteristic diagram when a resist film is formed on a silicon nitride film and the resist film is removed using an oxygen plasma etching method. Semiconductor layer, oxide film, silicon nitride film, resist film, opening, p-type region.

Claims (1)

[Claims] [1] A silicon nitride film (3) is formed on the semiconductor layer (1), a resist film (4) is formed on the silicon nitride film (3), and the resist film (4) After exposing and developing the resist film (5) to form an opening (5) in the impurity introduction region and implanting impurity ions, the resist film (4) is etched using an oxygen plasma etching method.
A method for manufacturing a semiconductor device, comprising the steps of removing the silicon nitride film (3), and then removing the silicon nitride film (3). [2] Form an oxide film (2) on the semiconductor layer (1), form a silicon nitride film (3) on the oxide film (2), and form a resist film (4) on the silicon nitride film (3). ), the resist film (4) is exposed and developed to form an opening (5) in the impurity introduction region, and the impurity is ion-implanted, and then the resist film (4) is removed using an oxygen plasma etching method.
, and then removing the silicon nitride film (3) and the oxide film (2).