JPS63110728A - Manufacture of etching mask - Google Patents

Abstract

PURPOSE:To enable high-precision formation of an opening sufficiently small in diameter or width when the opening is bored in an insulating layer, by forming the first mask layer and sticking the second mask layer on the first mask layer inclusive of the inside of the first mask layer's opening and forming an opening, which is smaller than the first mask's opening, in the second mask layer by the use of anisotropic etching. CONSTITUTION:After the first mask layer 3 of a photoresist film or the like is formed on a surface of a matter to be etched 2, an opening 3a of a required pattern is formed in the first mask layer 3 by photolithography or the like, and the second mask layer 4 capable of serving as an etching mask is formed/ stuck on the first mask layer part inclusive of the inside of the opening 3a. A part of thickness (d) smaller than total thickness D of the first and second mask layers 3 and 4 is formed over the required diameter and width in the central part of the opening 3a of the first mask layer 3. Next, when only the part of thickness (d) is etched all over the surface by the use of anisotropic etching, an opening 4a smaller in diameter or width than the opening 3a is formed in the second mask layer 4 existing inside the opening 3a.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to, for example, forming an electrode window in an insulating layer formed on the surface of a semiconductor substrate in the manufacturing process of a semiconductor integrated circuit device, and, for example, forming an interlayer insulating layer between a plurality of wiring layers. Contact window openings for interlayer insulating layers for interconnecting upper and lower layer wiring in a multilayer wiring structure laminated via a multilayer wiring structure are related to a method of forming an etching mask applied to, for example.

[Summary of the invention]

In the present invention, a first mask layer having a required pattern opening is formed, a second mask layer is deposited including the inside of the opening, and an opening smaller than the opening in the first mask layer is formed by anisotropic etching. By forming this in the second mask layer, it is possible to form an etching mask pattern using an opening having a smaller diameter or width than the limitations of the opening diameter or width in photolithography, for example.

[Conventional technology]

With the development and spread of ultra-large integrated circuits, so-called ultra-LSIs,
In recent years, there has been a demand for denser patterns, which has led to an increase in the density of wiring patterns, which has led to a demand for denser multilayer wiring structures in which multiple wiring layers are laminated via interlayer insulating layers. In line with this, for example, there is a need to reduce the diameter of openings for wiring or electrodes in an insulating layer formed on a semiconductor substrate, or openings for contact windows for connection between laminated wiring layers in an insulating layer between the eyebrows.

Normally, this type of window opening is performed using photolithography using a photoresist etching mask, but in this case, the actual line and space (L/S) resolution and the actual opening Since the resolution differs due to the nature of light, it is difficult to form an etching mask itself using a sufficiently fine photoresist.

For example, in the glabella insulating layer in the multilayer wiring structure disclosed in Japanese Patent Application Laid-Open No. 61-20352, the contact window is selectively formed in the first insulating layer, and the contact window is selectively formed in the first insulating layer. A second insulating layer is formed on the contact window of the insulating layer, and RIE (Reactive I) is performed.
A method of forming a contact window in the second insulating layer by on etching (reactive ion etching), which has a diameter smaller than that of the contact window in the first insulating layer;
A structure is disclosed in which a second insulating layer is deposited on the inner periphery of the contact window of the insulating layer. In this case, a smaller contact window is ultimately formed compared to opening a window in the first insulating layer by photolithography. Since the second insulating layer needs to be deposited reliably, the thickness of the first insulating layer needs to be relatively thick. Therefore, when this insulating layer is used, for example, as an insulating layer between the eyebrows or an insulating layer formed on the surface of a semiconductor substrate, problems arise such as the presence of the contact window makes the surface uneven, since the insulating layer is relatively thick.

Further, if a defect exists at the interface between the first and second insulating layers, the function as an insulating layer or a protective film is impaired, causing a problem in reliability.

[Problem that the invention seeks to solve]

The present invention solves problems such as restrictions on the thickness or the above-mentioned decrease in reliability when forming a contact window, that is, an opening in an insulating layer, and a sufficiently small diameter or width. Provided is a method for forming an etching mask that can form an opening with high precision.

[Means for solving problems]

The present invention includes a step of forming a first mask layer having a desired pattern of openings on an object to be etched, such as an opening such as a contact window, and an inner circumferential surface of the opening of the first mask layer. and a step of performing anisotropic etching such as RIE on the entire surface of the second mask layer. For example, only the part in the center of the opening where the substantial thickness of the second mask layer is smaller than the other parts is etched, leaving the part where the thickness is large in the etching direction of the anisotropic etching using the second mask layer. The etching is removed depending on the time setting, and an opening with a small diameter or width is bored here.

In this way, an etching mask is formed by the cooperation of these first and second mask layers, and this etching mask is used to open a contact window for an object to be etched, such as an insulating layer, below it. According to the method of the invention, although a relatively large opening is formed in the first insulating layer by, for example, photolithography, the second mask layer is formed by utilizing the characteristics of anisotropic etching. By leaving a substantial thick part in the etching direction of the anisotropic etching around the opening in the first insulating layer, and forming the opening only in the thin part at the center, the opening can be formed with a small diameter or narrow width that is less than the restriction of the opening diameter of photolithography. It is possible to form an opening with Therefore, by selectively etching an object to be etched, such as an insulating layer, using an etching mask having openings with a small diameter or width, openings with a sufficiently small diameter and therefore high resolution can be formed.

〔Example〕

The present invention will be described in detail with reference to FIGS. 1 to 3. In this example, a substrate (1), for example a semiconductor substrate (1
) is formed on the object to be etched (
In 2), a window is opened for this, that is, an etching mask for performing selective etching is formed. In this case, first, a first mask layer (3) made of a photoresist film or the like is formed on the surface of the object to be etched (2). Then, openings (3a) of a desired pattern are formed in this first mask layer (3) by, for example, photolithography.
form.

Next, as shown in FIG. 2A, B, or C, an etching mask, such as a photoresist or other organic material that does not require photosensitivity, is formed by etching the area within the opening (3a) of the first mask layer. The second mask layer obtained (4)
Form the adhesion. If this second mask layer (4) is made of a material with a relatively high viscosity, as shown in FIG. 2A,
The coating is applied onto the first mask layer (3) so as to substantially follow the inner peripheral surface within the opening (3a). If the viscosity is relatively low, the first mask layer (3) is formed so as to fill the opening (3a) to some extent as shown in FIG. 2B; A recess (4c) is formed at the center. That is, on the first mask layer (3), the opening (3a
) so that it occurs in the center of the area. Further, as the second mask layer (4), for example, a CVD method (Chemical V
When using apor deposition), as shown in FIG. 2C, an opening (
3a) is formed to have a substantially uniform thickness along the inner peripheral surface. However, in any of the cases shown in FIGS. 2A to 2C, a portion extending over a required diameter or width is formed at the center of the opening (3a) in the first mask layer (3).

Next, anisotropic etching such as 02 RIE and CHF
A strip (3a) in which only the portion having the required thickness, that is, the small thickness d explained in FIG.
A small diameter or narrow opening (
Form 4a).

The opening (4a) thus formed has a smaller diameter or width than the opening (3a) of the first mask layer (3). Moreover, the diameter or width of this opening (4a) is the second
As is clear from the explanation in Figures A to C, the second
Depending on the viscosity of the material used to form the mask layer (4) or the forming method, the diameter or width can be selected to be sufficiently smaller than the opening (3a). In this way the first and second
The desired etching mask (5) is formed by the cooperation of the masks N (3) and (4). Therefore, by selectively etching, for example, an insulating layer of the object to be etched (2) using this etching mask (5) as a mask, it is possible to form an opening with a small diameter or narrow width, such as a contact window, corresponding to the opening (4a). can.

〔Effect of the invention〕

As described above, according to the method of the present invention, by combining the formation of the first and second mask layers and anisotropic etching,
For example, since it is possible to form an etching mask having an opening with a diameter sufficiently smaller than the opening (3a) in the first mask layer formed by photolithography, it is possible to perform etching of a small pattern below the limit of photolithography technology. .

Furthermore, when using the method of the present invention, as explained at the beginning,
For example, when using a method in which the insulating layer itself is formed by two layers of first and second insulating layers, there are problems with the film thickness, and reliability problems such as a decrease in insulation properties due to defects at the interface between the first and second insulating layers. It has great practical benefits, such as being able to avoid a decline in sexual performance.

[Brief explanation of the drawing]

1 to 3 are enlarged cross-sectional views showing each step of an example of the method for forming an etching mask according to the present invention. (3) is the first mask layer, (4) is the second mask layer, (
3a) and (4a) are openings.

Claims (1)

[Claims] A step of forming a first mask layer having openings in a desired pattern; and a step of forming a second mask layer including the inner peripheral surface of the openings of the first mask layer. performing anisotropic etching from above the second mask layer, and by the anisotropic etching, an opening is formed in the opening by the second mask layer having a smaller diameter or width than the opening. A method for forming an etching mask, characterized in that an etching mask is formed by the cooperation of the first and second mask layers.