阅读说明：本技术 蚀刻方法 (Etching method ) 是由 福世知行 于 2018-06-01 设计创作，主要内容包括：提供一种能够将硅氮化物层的蚀刻速度和硅氧化物层的蚀刻速度控制为相同程度的蚀刻方法。将具备具有层叠了的硅氧化物层(2)和硅氮化物层(3)的层叠膜(5)的被处理体,通过含有由碳、溴和氟构成的卤化碳化合物的蚀刻气体进行处理。硅氧化物层(2)和硅氮化物层(3)以相同程度的蚀刻速度被蚀刻。(Provided is an etching method capable of controlling the etching rate of a silicon nitride layer and the etching rate of a silicon oxide layer to the same degree. An object to be processed having a laminated film (5) having a silicon oxide layer (2) and a silicon nitride layer (3) laminated thereon is processed by an etching gas containing a halogenated carbon compound composed of carbon, bromine, and fluorine. The silicon oxide layer (2) and the silicon nitride layer (3) are etched at the same etching rate.)

1. An etching method comprises an etching step,

In the etching step, a target object having a laminated film including a silicon oxide layer and a silicon nitride layer laminated thereon is treated with an etching gas containing a halogenated carbon compound including carbon, bromine, and fluorine, and both the silicon oxide layer and the silicon nitride layer are etched.

2. The etching method according to claim 1, wherein the etching step is carried out,

The halogenated carbon compound is at least one of dibromodifluoromethane and bromopentafluoroethane.

3. The etching method according to claim 1 or 2,

The etching gas also contains an inert gas.

4. The etching method according to any one of claims 1 to 3,

In the etching step, etching is performed using a plasma gas obtained by plasmatizing the etching gas.

Technical Field

The present invention relates to an etching method.

Background

The semiconductor manufacturing process includes a step of etching a laminated film including a silicon oxide layer and a silicon nitride layer laminated with each other with an etching gas using a resist, an organic film, and a carbon film as a mask. For example, patent document 1 discloses a method for etching the laminated film using an etching gas composed of 1,3,3, 3-tetrafluoropropene, an additive gas, and an inert gas. However, since Si-N bonds are weaker than Si-O bonds, the etching rate of the silicon nitride layer is about 1.2 times faster than that of the silicon oxide layer.

Therefore, when the laminated film is subjected to deep etching for forming a through hole having a high aspect ratio such as an aspect ratio of more than 20, the silicon nitride layer is etched at a higher rate in the plane direction perpendicular to the thickness direction than the silicon oxide layer is etched in the thickness direction, and therefore the silicon nitride layer is excessively etched in the plane direction, and there is a possibility that an abnormality in the etched shape occurs.

Prior art documents

patent document 1: japanese laid-open patent publication No. 114402 2012

Disclosure of Invention

The invention provides an etching method capable of controlling the etching rate of a silicon nitride layer and the etching rate of a silicon oxide layer to be the same.

To solve the above problems, one aspect of the present invention is as described in the following [1] to [4 ].

[1] An etching method includes an etching step of etching both a silicon oxide layer and a silicon nitride layer by treating a target object having a laminated film including the laminated silicon oxide layer and the laminated silicon nitride layer with an etching gas containing a halogenated carbon compound including carbon, bromine, and fluorine.

[2] The etching method according to [1], wherein the halogenated carbon compound is at least one of dibromodifluoromethane and bromopentafluoroethane.

[3] The etching method according to [1] or [2], wherein the etching gas further contains an inert gas.

[4] The etching method according to any one of [1] to [3], wherein etching is performed using a plasma gas obtained by plasmatizing the etching gas in the etching step.

According to the etching method of the present invention, the object to be processed having the laminated film including the silicon oxide layer and the silicon nitride layer laminated thereon is etched, and the etching rate of the silicon nitride layer and the etching rate of the silicon oxide layer can be controlled to be the same.

Drawings

Fig. 1 is a sectional view of an object to be processed for explaining an etching method according to an embodiment of the present invention.

Fig. 2 is a graph showing a relationship between ICP power and etching rate.

Detailed Description

Hereinafter, an embodiment of the present invention will be described. The present embodiment is an example of the present invention, and the present invention is not limited to the present embodiment. Various modifications and improvements may be added to the present embodiment, and embodiments to which modifications and improvements are added are also included in the present invention.

the etching method of the present embodiment includes an etching step of etching both the silicon oxide layer and the silicon nitride layer by treating a target object having a laminated film including a silicon oxide layer (SiOx layer) and a silicon nitride layer laminated with each other with an etching gas containing a halocarbon compound including carbon, bromine, and fluorine.

By the etching method of the present embodiment, a target object having a laminated film including a silicon oxide layer and a silicon nitride layer laminated can be etched, and the ratio of the etching rate of the silicon nitride layer to the etching rate of the silicon oxide layer ([ etching rate of silicon nitride layer ]/[ etching rate of silicon oxide layer ]) can be arbitrarily controlled to be 0.8 or more and less than 1.5 depending on the etching conditions and the like. Thus, according to the etching method of the present embodiment, the etching rate of the silicon nitride layer and the etching rate of the silicon oxide layer can be controlled to the same extent, and the ratio of the etching rate of the silicon nitride layer to the etching rate of the silicon oxide layer is preferably 0.9 or more and less than 1.2.

The kind of the halogenated carbon compound composed of carbon, bromine, and fluorine is not particularly limited, and at least one of dibromodifluoromethane (CBr2F2) and bromopentafluoroethane (C2BrF5) can be used.

The etching gas may contain a halogenated carbon compound and an inert gas. By performing etching in a state where an inert gas is coexistent, the silicon oxide layer and the silicon nitride layer can be etched selectively to the mask and at a high etching rate. The type of inert gas is not particularly limited, and examples thereof include helium (He), argon (Ar), neon (Ne), krypton (Kr), xenon (Xe), and nitrogen (N2). These inert gases may be used alone or in combination of two or more.

The etching method used in the etching step is not particularly limited, and a plasma etching method in which etching is performed using a plasma gas obtained by converting an etching gas into a plasma can be used.

Examples of the Plasma used for etching include Capacitively Coupled Plasma (CCP), Electron Cyclotron resonance Plasma (ECP), Helicon Wave excited Plasma (HWP), Inductively Coupled Plasma (ICP), and microwave Surface Wave excited Plasma (SWP).

The etching method of the present embodiment can be used, for example, in a step of forming a through hole extending in the thickness direction in a laminated film in which a plurality of silicon nitride layers and silicon oxide layers are alternately laminated on a substrate, as one step in the manufacturing process of a three-dimensional NAND-type flash memory.

An example of a method for etching a target object having a laminated film including a silicon oxide layer and a silicon nitride layer laminated thereon and forming a through hole in the laminated film by the etching method according to the present embodiment will be described with reference to fig. 1.

Fig. 1 is a cross-sectional view of an object to be processed in which a through-hole 9 is formed in a laminated film 5, and the object to be processed is configured by providing the laminated film 5, in which a plurality of silicon nitride layers 3 and silicon oxide layers 2 (3 layers in the example of fig. 1) are alternately laminated, on a semiconductor substrate 1. Further, a silicon oxide layer 2 of a laminate film 5 is laminated immediately above the semiconductor substrate 1.

A patterned mask 7 is coated on the uppermost silicon nitride layer 3 of the laminated film 5, and etching is performed by the etching method of the present embodiment, so that the laminated film 5 exposed from the mask 7 is etched to form a through hole 9.

In the etching method of the present embodiment, since the etching rate of the silicon nitride layer 3 and the etching rate of the silicon oxide layer 2 can be controlled to be the same, when the through-hole 9 is formed in the laminated film 5, the silicon nitride layer 3 exposed to the inner surface of the through-hole 9 can be prevented from being excessively etched in the surface direction (the direction orthogonal to the thickness direction). Thus, even when the laminated film 5 is subjected to deep etching for forming the through hole 9 having a high aspect ratio of more than 20, as shown in fig. 1, the through hole 9 can be formed without causing collapse of the laminated structure of the laminated film 5 or abnormal etching shape.

The present invention will be described in more detail below by showing various test examples.

[ test example 1]

And forming a silicon nitride layer on the Si substrate by adopting a plasma chemical vapor deposition method to obtain the test piece. The film thickness of the silicon nitride layer was 500 nm. The test piece was subjected to inductively coupled plasma etching (ICP etching) to etch the silicon nitride layer. The etching conditions are as follows.

An etching device: ICP etching device RIE-200iP manufactured by samco Ltd

Etching time: 120 seconds

ICP power: 200W, 500W or 800W

Bias power: 200W

Pressure: 2Pa

Etching gas: mixed gas of 1 part by volume of dibromodifluoromethane and 9 parts by volume of argon

flow rate of etching gas: 100SCCM

When the etching was completed, the film thickness of the silicon nitride layer was measured using an ellipsometer M-550 manufactured by Japan Spectroscopy Co., Ltd. Then, the etching rate of the silicon nitride layer was calculated by dividing the difference in film thickness between before and after etching by the etching time.

[ test example 2]

The etching rate of the silicon oxide layer was calculated in the same manner as in test example 1, except that a test piece was obtained by forming a silicon oxide layer having a film thickness of 2000nm on an Si substrate instead of the silicon nitride layer.

[ test example 3]

The etching rate of the silicon nitride layer was calculated in the same manner as in test example 1, except that the kind of the halogenated carbon compound in the etching gas was changed from dibromodifluoromethane to carbon tetrafluoride (CF 4).

[ test example 4]

The etching rate of the silicon oxide layer was calculated in the same manner as in test example 2, except that the kind of the halogenated carbon compound in the etching gas was changed from dibromodifluoromethane to carbon tetrafluoride (CF 4).

[ test example 5 ]

The etching rate of the silicon nitride layer was calculated in the same manner as in test example 3, except that the etching gas was replaced with a mixed gas of 1 part by volume of carbon tetrafluoride, 8 parts by volume of argon gas, and 1 part by volume of oxygen gas.

[ test example 6 ]

The etching rate of the silicon oxide layer was calculated in the same manner as in test example 4, except that the etching gas was replaced with a mixed gas of 1 part by volume of carbon tetrafluoride, 8 parts by volume of argon, and 1 part by volume of oxygen.

TABLE 1

The results of the respective test examples are shown in tables 1 and 2. The "ratio" in table 1 refers to the ratio of the etching rate of the silicon nitride layer to the etching rate of the silicon oxide layer ([ etching rate of silicon nitride layer ]/[ etching rate of silicon oxide layer ]). As can be seen from the graphs of table 1 and fig. 2, in the case where the kind of the halogenated carbon compound in the etching gas is carbon tetrafluoride, the etching rate of the silicon nitride layer is faster than that of the silicon oxide layer. In contrast, when the kind of the halogenated carbon compound in the etching gas is dibromodifluoromethane, the etching rate of the silicon oxide layer and the etching rate of the silicon nitride layer are substantially the same (see the column "ratio" in table 1).

By using a mixed gas of carbon tetrafluoride, argon, and oxygen as an etching gas, the etching rate of the silicon nitride layer can be reduced. However, there is a problem that the etching rate of the entire laminated film including the laminated silicon oxide layer and the laminated silicon nitride layer is greatly reduced. In addition, if oxygen is mixed, a mask such as a photoresist is easily etched in etching of a pattern substrate.

When dibromodifluoromethane is used, the etching rate of the silicon oxide layer and the etching rate of the silicon nitride layer can be controlled to be substantially the same level without lowering the etching rate of the entire laminated film.

Description of the reference numerals

1 semiconductor substrate

2 silicon oxide layer

3 silicon nitride layer

5 laminated film

7 mask

9 through hole