阅读说明：本技术 半导体装置 (Semiconductor device with a plurality of semiconductor chips ) 是由 渡边健一 于 2019-06-05 设计创作，主要内容包括：一种半导体装置,包括：在半导体基板上形成包含Al的欧姆电极的工序；形成将欧姆电极覆盖的SiN膜的工序；在SiN膜上形成具有与欧姆电极重叠的开口图案的第一光致抗蚀剂的工序；对第一光致抗蚀剂进行紫外线固化的工序；在从开口图案露出的SiN膜形成开口,使欧姆电极的表面露出的工序；在第一光致抗蚀剂上及从开口露出的欧姆电极上形成阻挡金属层的工序；在开口图案内形成第二光致抗蚀剂的工序；对第二光致抗蚀剂进行热处理,利用第二光致抗蚀剂将与开口重叠的阻挡金属层覆盖的工序；及使用第二光致抗蚀剂对阻挡金属层进行蚀刻的工序。(A semiconductor device, comprising: forming an ohmic electrode containing Al on a semiconductor substrate; forming a SiN film covering the ohmic electrode; forming a first photoresist having an opening pattern overlapping the ohmic electrode on the SiN film; a step of curing the first photoresist by ultraviolet rays; forming an opening in the SiN film exposed from the opening pattern to expose a surface of the ohmic electrode; forming a barrier metal layer on the first photoresist and the ohmic electrode exposed from the opening; forming a second photoresist in the opening pattern; a step of performing heat treatment on the second photoresist to cover the barrier metal layer overlapping the opening with the second photoresist; and a step of etching the barrier metal layer using the second photoresist.)

1. A semiconductor device, comprising:

a semiconductor substrate;

a semiconductor laminate on the semiconductor substrate;

an ohmic electrode comprising Al on the semiconductor laminate;

a SiN film covering the ohmic electrode;

an opening in the SiN film;

a barrier metal layer formed inside the opening; and

a gap between an edge of the opening and an end of the barrier metal layer,

wherein the width of the gap is less than the thickness of the barrier metal layer.

2. The semiconductor device according to claim 1, wherein the first and second electrodes are formed on a substrate,

the barrier metal layer comprises a Ti layer, a TiWN layer and a TiW layer which are sequentially stacked.

3. The semiconductor device according to claim 1, wherein the first and second electrodes are formed on a substrate,

wherein a thickness of the SiN film is in a range of 30nm to 50 nm.

4. The semiconductor device according to claim 1, wherein the first and second electrodes are formed on a substrate,

wherein the width of the gap is 100nm or less.

Technical Field

The present invention relates to a method for manufacturing a semiconductor device.

Background

From the viewpoint of conductivity and the like, Al (aluminum) is sometimes used for the wiring and the ohmic electrode of the semiconductor device. For example, japanese patent application laid-open No. 4-162531 discloses that a first layer made of an Al film or an alloy film containing Al as a main component is provided on the surface of a diffusion layer in a semiconductor substrate.

In the wiring and the ohmic electrode including Al, hillocks tend to be generated in the manufacture of the semiconductor device. For example, when a gap is formed between a barrier metal film on an ohmic electrode containing Al and an insulating film covering the wiring, the hillock is generated in the gap. Such generation of hillocks is not preferable because it can cause short-circuiting of the wiring or the electrode.

Disclosure of Invention

A method for manufacturing a semiconductor device according to an aspect of the present invention includes: forming an ohmic electrode containing Al on a semiconductor substrate; forming a SiN film covering the ohmic electrode; forming a first photoresist having an opening pattern overlapping the ohmic electrode on the SiN film; a step of curing the first photoresist by ultraviolet rays; forming an opening in the SiN film exposed from the opening pattern, and exposing a surface of the ohmic electrode in the opening; forming a barrier metal layer on the first photoresist and the ohmic electrode exposed from the opening; forming a second photoresist in the opening pattern; a step of performing heat treatment on the second photoresist and covering the barrier metal layer overlapping the opening with the second photoresist; and a step of etching the barrier metal layer using the second photoresist.

Drawings

Fig. 1 is a cross-sectional view showing an example of a semiconductor device manufactured by the manufacturing method of the embodiment.

Fig. 2 (a) to 2 (c) are views for explaining a method of manufacturing a part of the semiconductor device according to the embodiment.

Fig. 3 (a) to 3 (c) are views for explaining a method of manufacturing a part of the semiconductor device according to the embodiment.

Fig. 4 (a) and 4 (b) are diagrams illustrating a method for manufacturing a part of the semiconductor device according to the embodiment.

Fig. 5 (a) to 5 (c) are views for explaining a method of manufacturing a part of the semiconductor device according to the embodiment.

Detailed Description

[ description of embodiments of the present disclosure ]

First, the contents of the embodiments of the present disclosure will be described.

One embodiment of the present disclosure relates to a method for manufacturing a semiconductor device, including: forming an ohmic electrode containing Al on a semiconductor substrate; forming a SiN film covering the ohmic electrode; forming a first photoresist having an opening pattern overlapping the ohmic electrode on the SiN film; a step of curing the first photoresist by ultraviolet rays; forming an opening in the SiN film exposed from the opening pattern, and exposing a surface of the ohmic electrode in the opening; forming a barrier metal layer on the first photoresist and the ohmic electrode exposed from the opening; forming a second photoresist in the opening pattern; a step of performing heat treatment on the second photoresist and covering the barrier metal layer overlapping the opening with the second photoresist; and a step of etching the barrier metal layer using the second photoresist.

The above manufacturing method may further include a step of heat-treating the first photoresist before the first photoresist is cured by ultraviolet light.

The barrier metal layer may have a Ti layer, a TiWN layer, and a TiW layer stacked on each other.

The SiN film may have a thickness of 30nm to 50 nm.

The second photoresist may be an ultraviolet resist, and the heat treatment of the second photoresist may be performed at 140 ℃.

[ details of embodiments of the present disclosure ]

A specific example of the method for manufacturing a semiconductor device according to the embodiment of the present invention will be described below with reference to the drawings. The present invention is not limited to these examples, and is disclosed by the claims, and all changes that come within the meaning and range of equivalency of the claims are intended to be embraced therein. In the following description, the same elements in the description of the drawings are denoted by the same reference numerals, and redundant description thereof is omitted.

Fig. 1 is a cross-sectional view showing a semiconductor device manufactured by the manufacturing method of the present embodiment. As shown in fig. 1, the semiconductor device 1 is, for example, a field effect transistor provided on a substrate 2. The substrate 2 is a substrate for crystal growth. Examples of the substrate 2 include a semiconductor substrate such as a SiC substrate and a GaN substrate, and sapphire (Al)₂O₃) A substrate. In the present embodiment, the substrate 2 is a semiconductor substrate.

The semiconductor device 1 includes a semiconductor multilayer body 11, insulating films 12 and 21, a source electrode 13, a drain electrode 14, a gate electrode 15, and barrier conductive layers 16 and 17.

The semiconductor laminate 11 is a laminate of semiconductor layers epitaxially grown on the substrate 2. The semiconductor multilayer body 11 includes, for example, a buffer layer, a trench layer, and a barrier layer in this order from the surface of the substrate 2. The semiconductor device 1 of the present embodiment is a High Electron Mobility Transistor (HEMT), and forms a trench region in a trench layer by generating a Two-Dimensional Electron Gas (2 DEG: Two Dimensional Electron Gas) on the trench layer side of an interface between the trench layer and a barrier layer. The buffer layer is, for example, an AlN layer, the trench layer is, for example, a GaN layer, and the barrier layer is, for example, an AlGaN layer. The semiconductor stack 11 may also have a gap layer on the barrier layer. The gap layer is, for example, a GaN layer.

The insulating film 21 is a passivation film that protects the surface of the semiconductor laminate 11, and is provided on the semiconductor laminate 11. The insulating film 12 is a protective film that protects the source electrode 13, the drain electrode 14, and the gate electrode 15. The insulating film 12 is provided with openings 12a and 12 b. The opening 12a exposes a part of the source electrode 13, and the opening 12b exposes a part of the drain electrode 14. An opening 21a is provided in the insulating film 21 at a portion corresponding to the gate electrode 15. The gate electrode 15 is in contact with the semiconductor stacked body 11 through the opening 21 a. The insulating film 21 is a silicon nitride (SiN) film formed by a reduced pressure CVD method, and the insulating film 12 is a SiN film formed by a plasma CVD method.

The source electrode 13 and the drain electrode 14 are in contact with the barrier layer of the semiconductor multilayer body 11. The source electrode 13 and the drain electrode 14 are ohmic electrodes containing aluminum (Al). The source electrode 13 and the drain electrode 14 have a structure in which, for example, a stacked structure of a tantalum (Ta) layer, an Al layer, and a Ta layer is alloyed at a temperature of, for example, 500 to 800 ℃. Instead of the Ta layer, a titanium (Ti) layer may be used. Further, a gold (Au) layer may be formed on the laminated structure. The surfaces of the source electrode 13 and the drain electrode 14 are partially covered with the insulating film 12.

The gate electrode 15 is disposed between the source electrode 13 and the drain electrode 14. The gate electrode 15 is made of, for example, a metal that makes a Schottky-contact (Schottky-contact) with the gap layer of the semiconductor stacked body 11, and has, for example, a stacked structure of a nickel (Ni) layer and a gold (Au) layer. In this case, the Ni layer makes schottky contact with the gap layer.

The barrier conductive layer 16 is a conductive layer that protects the source electrode 13 and is provided in the opening 12 a. The barrier conductive layer 16 has, for example, a Ti layer, a TiWN layer, and a TiW layer stacked on each other. The barrier conductive layer 17 is a conductive layer for protecting the drain electrode 14, and is provided in the opening 12 b. The structures of the barrier conductive layers 16, 17 are identical to each other.

Next, a part of the method for manufacturing a semiconductor device according to the present embodiment will be described with reference to fig. 2 to 5. Fig. 2 (a) to 2 (c), 3 (a) to 3 (c), 4 (a), 4 (b), and 5 (a) to 5 (c) are diagrams illustrating a method for manufacturing a part of the semiconductor device 1 according to the present embodiment. Hereinafter, a method for manufacturing the source electrode 13 as an ohmic electrode included in the semiconductor device 1 and the barrier conductive layer 16 provided on the source electrode 13 will be described in detail.

First, as shown in fig. 2 (a), an insulating film 21 is formed on a substrate 2. First, a semiconductor laminate 11 is grown on a substrate 2 by Metal Organic Chemical Vapor Deposition (MOCVD). Next, the insulating film 21 is formed on the semiconductor laminated body 11. The insulating film 21 is, for example, a SiN film formed by a Low Pressure Chemical Vapor Deposition (LPCVD) method. The LPCVD method is a method of forming a dense film by lowering the film formation pressure and raising the film formation temperature. The thickness of the insulating film 21 is, for example, 10nm or more and 30nm or less. The film formation temperature of the insulating film 21 is, for example, 800 ℃ to 900 ℃ inclusive, and the film formation pressure is, for example, 10Pa to 100Pa inclusive.

Next, as shown in fig. 2 (b), the source electrode 13, which is an ohmic electrode containing Al, is formed on the substrate 2. First, an opening 21b is formed in the insulating film 21. Next, a source metal having a Ta layer, an Al layer, and a Ta layer stacked in this order is deposited in the opening 21 b. The lower Ta layer has a thickness of, for example, 5nm to 10nm, the Al layer has a thickness of, for example, 200nm to 400nm, and the upper Ta layer has a thickness of, for example, 5nm to 10 nm. Next, the source electrode 13 is formed by heating the source metal at 500 to 800 ℃. Although not shown, the drain electrode 14 is also formed when the source electrode 13 is formed (see fig. 1). The source metal is formed by, for example, vapor deposition and lift-off using a resist pattern (not shown). The resist pattern may also be used for the formation of the opening 21 b.

Next, as shown in fig. 2 (c), an insulating film 12 covering the insulating film 21 and the source electrode 13 is formed. In this embodiment, the insulating film 12 is a SiN film formed by a plasma CVD method. The film formation temperature of the insulating film 12 is, for example, 300 ℃ to 320 ℃. The thickness of the insulating film 12 is, for example, 30nm or more and 50nm or less.

Next, as shown in fig. 3 (a), a first photoresist 31 having an opening pattern 31a overlapping the source electrode 13 is formed on the insulating film 12. First, a first photoresist 31 is coated on the insulating film 12. Next, photolithography is performed on the first photoresist 31, thereby forming an opening pattern 31a in the first photoresist 31. The opening pattern 31a is provided in the first photoresist 31 at a position overlapping the source electrode 13. A part of the insulating film 12 is exposed in the opening pattern 31 a. The first photoresist 31 is, for example, an ultraviolet resist. The thickness of the first photoresist 31 is, for example, 1 μm or more and 2 μm or less.

Next, the first photoresist 31 is subjected to heat treatment. The first photoresist 31 is heated (baked) at 120 ℃ or higher, for example. The fluidity of the first photoresist 31 is increased by this baking. Thereby, as shown in fig. 3 (b), the end of the first photoresist 31 forming the opening pattern 31a is blunted. The flow of the first photoresist 31 onto the source electrode 13 is hindered by the surface tension of the first photoresist 31. Next, the first photoresist 31 is subjected to ultraviolet curing. In this step, the first photoresist 31 is irradiated with ultraviolet rays U. This cures the first photoresist 31, and therefore, swelling and the like are less likely to occur in the first photoresist 31. Further, the shape of the opening pattern 31a is less likely to change. The ultraviolet light U is ultraviolet light obtained from a mercury lamp having a wavelength of, for example, about 365 nm.

Next, the first photoresist 3 is coated on the insulating film 12 by using a fluorine-containing gas1 is dry etched. Thereby, as shown in fig. 3 (c), a part of the surface of the source electrode 13 is exposed in the opening 12 a. Specifically, a portion of the top surface 13a of the source electrode 13 overlapping the opening 12a is exposed. The dry Etching is, for example, Reactive Ion Etching (RIE). As the fluorine-containing gas, for example, from SF₆、CF₄、CHF₃、C₃F₆And C₂F₆At least 1 selected from the group. The RIE apparatus may be an Inductively Coupled Plasma (ICP) apparatus.

Next, as shown in fig. 4 (a), a barrier metal layer 41 is formed on the first photoresist 31 and on the source electrode 13 exposed from the opening 12a of the insulating film 12. The barrier metal layer 41 having a Ti layer, a TiWN layer, and a TiW layer stacked on each other is formed by, for example, a sputtering method. A part of the barrier metal layer 41 is in contact with the source electrode 13 within the opening 12 a. The thickness of the Ti layer is, for example, 5nm, the thickness of the TiWN layer is, for example, 300nm, and the thickness of the TiW layer is, for example, 6 nm. The thickness of the barrier metal layer 41 deposited on the plane is about the sum of the thicknesses of the above layers. However, in the barrier metal layer 41, for example, the thickness of a portion deposited on the sidewall of the first photoresist 31 or the sidewall of the opening 12a of the insulating film 12 is thinner than the above thickness. In this embodiment, the thickness of the portion of the barrier metal layer 41 located on the sidewall of the first photoresist 31 is 100nm or less.

Next, as shown in fig. 4 (b), a second photoresist 51 is formed within the opening pattern 31a of the first photoresist 31. A second photoresist 51 is formed on the portion 41a of the barrier metal layer 41 overlapping the opening 12 a. As shown in fig. 4 (b), a part of the portion 41a of the barrier metal layer 41 that exists above the source electrode 13 may be exposed from the second photoresist 51. The second photoresist 51 is, for example, an ultraviolet resist as in the first photoresist 31. The thickness of the second photoresist 51 is, for example, 1 μm or more and 2 μm or less.

Next, as shown in fig. 5 (a), the second photoresist 51 is subjected to a heat treatment, and the barrier metal layer 41 overlapping the opening 12a of the insulating film 12 is covered with the second photoresist 51. The second photoresist 51 is heated (baked) at 140 deg.c or higher, for example. The baking temperature may be higher than that of the first photoresist 31 from the viewpoint of covering the portion 41a of the barrier metal layer 41 overlapping the source electrode 13 with the second photoresist 51. Thereby, the second photoresist 51 flows, and the portion 41a of the barrier metal layer 41 is covered with the second photoresist 51. On the other hand, the flow of the first photoresist 31 does not occur or does not substantially occur. Further, swelling and the like of the first photoresist 31 do not occur, or do not substantially occur. This is because the first photoresist 31 has been baked and cured with the ultraviolet rays U.

Next, as shown in fig. 5 (b), the barrier metal layer 41 is etched using the second photoresist 51. The portion of the barrier metal layer 41 exposed from the second photoresist 51 is dry etched using a fluorine-based gas. Thereby, the barrier conductive layer 16 is formed so as to cover the top surface 13a of the source electrode 13 and the source electrode 13 exposed from the opening 12a of the insulating film 12. At this time, the surface of the source electrode 13 is exposed between the end of the second photoresist 51 and the edge of the opening 12a of the insulating film 12 in the portion 41a on the source electrode 13 of the barrier metal layer 41. The exposed surface has a width corresponding to the thickness of the barrier metal layer 41. Since the thickness of the barrier metal layer 41 on the sidewall of the first photoresist 31 is 100nm or less, the width of the gap where the source electrode 13 is exposed is suppressed to 100nm or less.

Next, as shown in fig. 5 (c), the first photoresist 31 and the second photoresist 51 are removed. When a part of the barrier metal layer 41 remains on the first photoresist 31, the part can be removed together with the first photoresist 31 by lifting off the part. By performing the steps described above, the source electrode 13 and the barrier conductive layer 16 are formed.

Through the above steps, the semiconductor device 1 of the present embodiment is formed. After the semiconductor device 1 is formed, an interlayer insulating film covering the semiconductor device 1 may be formed, a through hole penetrating the interlayer insulating film to expose the barrier conductive layer may be formed, and an Au wiring layer buried in the through hole may be formed.

According to the method for manufacturing the semiconductor device 1 of the present embodiment described above, the second photoresist 51 flowing through the above steps can cover the portion 41a of the barrier metal layer 41 that overlaps the opening 12 a. By removing the barrier metal layer 41 exposed from the second photoresist 51, the top surface 13a of the source electrode 13, which is an ohmic electrode containing Al, can be covered, and the gap between the insulating film 12 and the barrier conductive layer 16 can be suppressed to a very small width. Thus, even when heat treatment is performed later in the process of manufacturing the semiconductor device 1, or even when stress is applied to the source electrode 13 due to the formation of the interlayer insulating film covering the semiconductor device 1, hillocks due to Al contained in the source electrode 13 can be prevented from being generated.

Generally, when baking is performed on a photoresist covered with a metal layer, the photoresist expands to pierce through the metal layer. However, in this embodiment, the first photoresist 31 is baked once and cured by the ultraviolet rays U before the second photoresist 51 is baked again. Therefore, in the re-baking, the swelling of the first photoresist 31 does not occur or does not substantially occur. This corresponds to the case where the second baking temperature is higher than the first baking temperature.

The method of manufacturing the semiconductor device 1 of the present embodiment includes a step of heat-treating the first photoresist 31 before curing the first photoresist 31 with ultraviolet rays. In this case, since the corners of the first photoresist 31 are rounded, the side surfaces of the first photoresist 31 and the insulating film 12 can be reliably covered when the barrier metal layer 41 is formed as shown in fig. 4 (a). When the barrier metal layer 41 shown in fig. 5 (a) is etched in a state where the side surface is not covered, the width of the gap exposed on the surface of the source electrode 13 is increased.

In this embodiment, the barrier metal layer 41 includes a Ti layer, a TiWN layer, and a TiW layer stacked on each other. In this case, the barrier properties of the barrier conductive layers 16, 17 are well exhibited.

The method for manufacturing a semiconductor device of the present invention is not limited to the above-described embodiments, and various modifications can be made thereto. For example, in the above-described embodiment, the example in which the present invention is applied to the HEMT has been described, but the manufacturing method of the present invention can be applied to various field effect transistors other than the HEMT.