JPS61281523A - Formation of contact - Google Patents

Abstract

PURPOSE:To improve the contact by using alkaline system etching liquid as etching liquid when the damage layer on the semiconductor surface after a contact hole has been formed. CONSTITUTION:After an N<+> type region 12 has been formed on the surface of a P-type surface of a semiconductor substrate 10 made by silicon, an insulative film 14 of silicon oxcide, etc. is formed on the surface of the substrate, and a photo-resist layer 16 having a hole corresponding to the desired contact hole is formed on the surface of the insulative film 14. Then, a part of the insulative film 14 is selectively removed with reactive ion etching to form a contact hole 14A, and to expose a part of the N<+> type region 12. After the photo-resist film 16 has been removed, the exposed surface of the N<+> region 12 is etch-removed with alkaline system etching liquid. Patterning is done by coating the surface of the substrate with electrode metal of Al or Al alloy to form an electrode layer 18 ohmically contacting with the N<+> type region 12 through the contact hole 14A, thereby providing highly reliable contact with low resistance.

Description

[Detailed description of the invention] [Industrial application field].

The present invention relates to an improved contact forming method suitable for forming semi-dedicated tp# fine electrodes in LSIs and the like.

[Summary of the invention]

Hit this shot 1. After a contact hole is formed by reactive ion etching, a damaged layer generated by ion bombardment on the semiconductor surface within the contact hole is etched away using an alkaline etchant, thereby reducing contact resistance. 150, [Conventional technology] ・
・ ・It has been known to form man-tact holes by using a driver or a punch when forming fine electrodes such as L@■. Reactive ion etching is the mainstream dry etching used in such cases. This is because reactive ion etching has both radical (chemical) and oxidative (physical) factors, making it possible to perform directional etching with excellent material selectivity. This is because it is passing through.

However, reactive ion etching also has the following problems.

, (1) Ion bombardment causes %Dan crystal defects on the surface of semiconductors such as 8i.

(3) Reactive gas and chamber materials 1. As a result of the reaction between the electrode and the resist, impurities such as C, F, and O are generated and contaminate the semiconductor surface.

(4) Irradiation damage occurs due to the ultraviolet rays generated by the gas plasma.

These defects, contamination, damage, etc. affect the electrical characteristics of the device, and cause, for example, an increase in contact resistance in the electrode interconnection, an increase in leakage current in the PNQ connection, and the like.

As a countermeasure for this, after forming a contact hole by reactive ion etching, the damaged layer on the semiconductor surface inside the contact hole is etched by low-damage plasma etching (for example, isotropic radical etching using CP4+02-based or C12-based gas). A method of etching is known.

[Problems to be Solved by the Invention] According to the method of plasma etching the damaged layer on the semiconductor surface as described above, the time-depression setting is critical due to the short processing time, and the reproducibility is not good.

``Especially in the case of shallow PN junctions of 0.3' [μm] or less, contact resistance and junction leakage current may increase due to excessive etching, making etching control difficult.

Another method is to remove the damaged layer on the semiconductor surface using an HF-HNO3-based etchant, but with this method, the reaction is rapid and a stain film may be formed on the semiconductor surface after etching. .

[Means for solving problems]

This invention was made to solve the above-mentioned problems, and is characterized by using an alkaline etchant as an etchant when removing the damaged layer on the semiconductor surface after contact hole formation. It is something to do.

[Effect]

According to the method of the present invention, since an alkaline etchant '1 is used, the reaction is slow, the etching can be easily controlled, and a stain film is not formed.

Therefore, if the damaged layer is removed by etching and the electrode layer or wiring layer is brought into electrical contact with the electrode layer, a good coherence tact can be obtained. Here is a wiring forming process according to an embodiment of the present invention! 11) to (3) corresponding to each figure number.
) 7 yen: Explanation will be made in sequence ゛ -'・(1) For example, N+
After forming the mold region 12, the upper surface of the substrate is coated with, for example, CvD (
An insulating film 14 made of silicon dioxide or the like is formed by a chemical deposition method. After forming a photoresist film 16 having a large number of holes corresponding to desired contact holes on the surface of the insulating film 14 by a well-known method,
A contact hole 14A is formed by selectively removing a portion of the insulating film 14 by performing reactive ion etching using the photoresist film 16' and a mask, and exposing a portion of the N+ type region 12. -'(2) Next, after removing the photoresist film 16 by an appropriate method, an alkaline etchant such as choline (HOCH2CH2N (cI(3)a)+o)(
Using a 1% to 2% aqueous solution of - and using the insulating film 14 as a mask, the exposed surface of the N
Etches to the depths of a person. As a result, the damaged layer caused by the aforementioned reactive ion etching is completely removed at tl. It should be noted that in this alkaline wet etching, there is almost no reduction in the film of the insulation gi (14).

(3) After heating, an electrode metal such as Al or A1 alloy is deposited on the top surface of the substrate by any method such as vapor deposition or sputtering, and nose turning is performed using photolithography.
Through the contact hole 14A'%-N+ type region 1
An electrode layer 18 making 2-ohm contact is formed.

In the above embodiments, the present invention has been described with respect to the formation of electrodes on the surface of a substrate, but the present invention can also be applied to the case where, for example, in a multilayer wiring structure, another wiring layer is brought into electrical contact with a polysilicon layer through a contact hole. It is applicable. □
.

[Effects of the Invention]' As described above, according to the present invention, the damaged layer caused by reactive ion etching is removed by etching with an alkaline etchant, so the following excellent effects can be obtained. .

(1) Plasma etching causes some damage, but alkaline wet etching causes no damage at all.

(2) Etching control is easier and reproducibility is better than plasma etching or HF-HNO3 wet etching.

Unlike f31HF4NOB wet etching, no stain film is formed on the semiconductor surface after etching. This, together with the removal of the damaged layer, makes it possible to obtain a low resistance and highly reliable contact.

[Brief explanation of drawings]

1 to 3 are cross-sectional views of a substrate showing an electrode forming process according to an embodiment of the present invention. 10... Semiconductor substrate, 12... N+ type region 14.
...Insulating film, 16... Photoresist film, 18... Electrode layer. Figure 1 (Anti J Sosetio〉Ezuchi) Figure 2
(Aru Hosu Itoku/Toezuchi) ・Figure 3 (/1. Polar figure)

Claims (1)

[Claims] (a) forming a contact hole by selectively removing a part of the insulating film covering the semiconductor surface by reactive ion etching; (b) removing a portion of the semiconductor surface within the contact hole; (c) electrically contacting the conductive layer with the semiconductor surface portion from which the damaged layer has been removed through the contact hole; A contact forming method including a step of