JPH11168140A - Semiconductor device and manufacture thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To manufacture a semiconductor device having a low-resistance contact resistance by a method, wherein the same material as that for a first metal wiring is embedded in the shaved (recess) region of a lower metal layer. SOLUTION: An ashing treatment consists of of two steps: in the first step a resist is removed with O2 single gas in the first step, and in the record step fluorine gas is made to be added to O2 in the second step to perform an ashing treatment and the removal of the remaining resist and an oxide film formed on a metal wiring, which is opened, is conducted. Moreover, a conductive material 31, which is embedded in a contact hole, is formed into the same material as a metal wiring material of a lower layer. Owing to this, even if a film 32 for forming a contact wiring is not fed into the contact hole and to the side edges of a shaved part of a lower metal layer, the contact wiring can be easily formed as the material 31, which is embedded in the contact hole, and the metal wiring material of the lower layer are the same, so that a problem in which the material 31 being separated from the contact hole is eliminated, and the rise in the contact resistance of a semiconductor device due to the separation can be also modified.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor device and a method of manufacturing the same, and more particularly, to an Ashing process for a resist process when processing a contact wiring and a contact hole formed on a metal wiring. It is.

[0002]

2. Description of the Related Art In a conventional process around a contact on a lower metal wiring (for example, a tungsten layer, hereinafter simply referred to as W), a step of removing a resist and a Depo material after RIE (reactive ion etching) (Asher).
There is. The gas for this Asher treatment is oxygen (O2)
Is used. In order to sufficiently remove the resist and the Depo material after RIE, it is necessary to lengthen the Ashing time.

[0003]

As shown in FIG. 12, A
O2 used for the sher process is a contact hole 11
O reacts with W111 existing at the bottom of the oxide film 11 of W.
2 is formed. Long time A including O2
The shing promotes the growth of WOx112. After that, the conductive material 113 is embedded in the contact hole. FIG. 13 shows the contact resistance value (Ω) with respect to the Asher (O2 single gas) processing time (s). As can be understood from FIG. 13, the contact resistance increases as the Ashing time increases.
That is, this Ashing step increases the contact resistance between W111 and conductive material 113 embedded in the contact hole. Therefore, this WOx1
In order to remove 12, it is necessary to perform a strongly alkaline chemical solution treatment step (wet treatment) for gradually exfoliating by corrosion for a long time. As shown in FIG. 14, the longer the Wet processing time, the lower the contact resistance, and the longer the Wet processing time, the smaller the in-plane variation (degree of removal). In the conventional process, if it is considered that the lowering of the contact resistance is prioritized, it is necessary to lengthen the Wet processing time, but in this case, there is a problem that the amount of the chemical used increases. Therefore, it is necessary to shorten the processing time as much as possible. An object of the present invention is to provide a semiconductor device having a low-resistance contact resistance without performing the above-described wet processing step, and a method for manufacturing the same.

[0004]

In a semiconductor device according to the present invention, a lower metal layer formed by removing an oxide film on a surface of a first metal wiring layer in a lower region of a contact hole formed at the time of removing a resist. By embedding the same material as the first metal wiring in the shaved (dented) region of the layer, the oxide film on the surface of the lower first metal wiring layer can be positively removed, and the contact resistance can be reduced. Can be provided.

In the manufacturing method, a resist used for forming a contact hole and an oxide film formed on a lower first metal wiring grown on the bottom surface of the contact hole are formed by an Ashing process in two steps. Can be effectively removed.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to the drawings. The same parts in the respective embodiments will be described with the same reference numerals. (1) First Embodiment FIGS. 1A to 1D and FIG.
This will be described with reference to FIGS. A first metal wiring layer 2 which is a lower wiring and is made of a metal such as tungsten or aluminum is formed on the insulating film 1 (see FIG. 1A). Hereinafter, the first metal wiring layer 2 will be described in detail using tungsten (hereinafter, simply referred to as W). On this W2, an interlayer insulating film 3, for example, a TEOS film is deposited at 5500 angstroms (see FIG. 1B), and a resist 4 is further evaporated thereon (see FIG. 1C). The resist 4 is patterned by an exposure process, and thereafter, a contact hole 5 is formed by RIE (see FIG. 1D). Next, the Ash based on the present invention
The er process is performed. This Asher step is performed by using an Ashi process.
WOx8 grown by O2 included in the ng process is converted to a fluorine-based gas containing at least fluorine, for example, CF6, C2
By adding F6, C3F8, C4F8, NF3, and the like, the removal of the resist and the removal of WOx are performed. At this time, scraping 22 occurs due to the fluorine-based gas.

It is to be noted that the Ashing process of simply adding a fluorine-based gas to O2 is known (Japanese Patent Application No. Hei.
In the case of the present invention, the processing sequence for performing the Ashing processing is different, and as a result, the operation and effect are completely different. That is, Ashin in the prior art
When performing the g treatment, it is intended to remove the resist, particularly the altered resist, by performing a treatment for 100 (s) by mixing O2 with a fluorine-based gas in one step. However, the Ashing process according to the present invention includes an Ashing process including two steps, a first step (Main process: about 43 steps).
(S)), the resist is removed with O2 single gas (FIG. 2A).
In the second step, a fluorine-based gas was added to O2, and a mixture ratio of O2: fluorine-based gas = 24: 1 was used for Ma.
Ashing processing is performed for a processing time of 30% of the in processing time, and the remaining resist and the oxide film 21 formed on the opened metal wiring 2 are removed. In addition, the conductive material 31 filling the contact hole
Is made of the same material as the lower metal wiring material (see FIG. 3).

Here, there is a problem that must be taken into consideration when simultaneous processing is performed by adding a fluorine-based gas to O2 in one step. 1) In the case of only one step, if the Ashing process is performed with a mixed gas to which a fluorine-based gas is added, the Ashing process time required for removing the resist is required. Therefore, the processing time with the fluorine-based gas is 2nd.
Since the processing time is naturally longer than the processing time in the step, the amount of digging (shaving) of W at the bottom of the contact region increases. In order to facilitate the formation of a metal wiring to be embedded in the inside of the contact hole in the next step, TiN is deposited. However, when the amount of digging (shaving) of W increases, the content of TiN in the first metal layer wiring increases. Therefore, there is a concern about an increase in wiring resistance. However, shortening the Ashing processing time results in a decrease in the peelability of the resist. 2) When the amount of digging (shaving) of W generated by the first step increases, the side edge 9 is shaved deeply. Since TiN hardly adheres to the side edge portion 9, there is a possibility that the conductive material may be peeled off when a conductive material different from the first metal wiring is embedded in the contact hole. In addition, when peeling occurs, the contact resistance increases.

[0009] Due to the above-mentioned concerns, it is possible to remove WOx from the contact portion without deteriorating the resist and to remove WOx by performing the two steps as in the present invention. The amount of digging (cutting) on the surface of the bottom first metal wiring layer is also minimized. Also, in a conductive material filling the contact hole,
Since the same metal material as that of the lower metal wiring layer W is used,
Even if the film 32 (barrier metal) for forming the contact wiring (improving the coverage) cannot be supplied to the contact hole or the side edge of the shaved portion, the buried conductive material and the lower metal wiring may not be supplied. Since they are the same, it is possible to easily form a film, eliminate the problem of peeling of the conductive material, and improve the increase in contact resistance due to peeling. (See FIG. 3) When the process of the embodiment process of the present invention is compared with the process of the conventional process, it can be confirmed that the W of the contact bottom is cut off in the process of the present invention.

[0010] That is, WOx formed when Ashing with O2 becomes W and CF of WOx by adding CF4.
The F of 4 reacts to form WF6, and the O of WOx reacts with the C of CF4 to form COx for etching. Therefore, the W surface at the bottom of the contact is shaved and WOx is removed. As a result, the adhesion of W at the bottom of the contact is improved, and the contact resistance value is reduced.

FIGS. 4 and 5 show the results of elemental composition analysis of the contact bottom surface. The analysis is a sample after opening the contact hole and processing the Ashing time by adding CF4 at 0 [s] and 10 [s], respectively, and is performed at three points of the metal wiring in the device cross section. Point 1 shows the result at the left end of the cross section, point 2 shows the result at the center of the cross section, and point 3 shows the result at the right end of the cross section. From FIG. 4, it can be confirmed that [O] (oxygen element) is contained on the contact bottom surface of the sample treated at 0 [s]. That is, it can be determined that the WOx film is growing at the bottom of the contact. However, from FIG. 5, 10 [s]
[0] (oxygen element) on the contact bottom surface could not be confirmed for the sample treated in
Has been removed. Based on this result, FIG. 6 shows that 0 [s], 10 [s], 20 [s], 30 [s] and 40 [s].
The resistance value at the bottom of the contact when the CF4 addition time is performed is smaller than the resistance value at the CF4 addition time of 10 [s], and shows about 1/20 of the resistance value at 0 [s]. Become. By adding CF4, considerable effectiveness can be confirmed in reducing the contact resistance.

In this embodiment, a film formed on W
Although it is limited to Ox, this is a film containing WOx as a main component, and is an etching gas such as C, F, etc.
An insulating film, a resist component and other elements may be included. Also, the addition time of CF4 is 1
The addition time is not limited to 0 [s], but may be changed depending on the size of the diameter of the bottom of the contact hole.

According to the results shown in FIG. 7, it is possible to reduce the contact resistance by adding CF4 to the Ashing process and to reduce the processing time in the post-process (Wet process). You can check. In other words, the open circles are obtained by performing Ashing processing for 100 (s) with O2 single gas, and the closed circles are obtained by adding 100 (s) to the Main processing and adding CF4 to the 2nd Step and performing the processing for 13 (s). Is shown. The contact resistance value obtained by shortening the Wet processing time to 40 [s] is the lowest result under the conditions of the experiment, and it can be understood that the effectiveness is sufficient.

(2) Second Embodiment A second embodiment will be described with reference to FIG. In the following description of the embodiment, the same reference numerals are used for the same parts as in the first embodiment. A first metal wiring 2 of tungsten (hereinafter, referred to as W) as a lower wiring on an insulating film 1
To form An oxide film 3 serving as an interlayer insulating film is deposited thereon, patterned by a resist 4 on the interlayer insulating film 3, and then a contact hole 5 is formed by RIE. Until the contact hole opening, the first
Is the same as that shown in the embodiment of FIG.
Ashing by O2 single gas in the sher process
The resist is removed by processing. In the next step, Ashin
WOx21 grown by the g treatment is chemically etched with a gas containing fluorine not containing O2.
Therefore, W scraping 22 occurs at the bottom of the contact. Also in the second embodiment, since WOx, which is a factor for increasing the contact resistance, can be removed, the resistance value can be reduced. That is, the same effect as that of the first embodiment can be obtained.

(3) Third Embodiment A third embodiment will be described with reference to FIG. Insulating film 1
A first wiring layer 2 of tungsten (hereinafter, referred to as W), which is a lower wiring, is formed thereon. An interlayer insulating film 3 is deposited thereon, patterned by a resist 4 on the interlayer insulating film 3, and then a contact hole 5 is formed by RIE. The post-opening process is the same as in the first or second embodiment (see FIGS. 9A and 9B). Next, a barrier metal 32 is formed on the inner surface of the contact hole and on the opened metal wiring, and a conductor, for example, the same material 31 as W, which is a lower wiring, is buried in the contact hole. After that, the interlayer insulating film 91 is deposited again (see FIG. 9C). Thereafter, a resist 92 is deposited on the interlayer insulating film 91, the resist 92 is patterned, and a contact hole is formed by RIE.
The processing after the opening is the same as in the above-described embodiment (see FIGS. 10D and 10E). In the process of forming multiple contact holes as described above, the resistance value can be reduced because the oxide film which is a factor of increasing the contact resistance can be removed. That is, the same effects as those of the first and second embodiments can be obtained.

(4) Fourth Embodiment A fourth embodiment will be described with reference to FIG. A first wiring layer 2 of a tungsten silicide layer (hereinafter, referred to as WSi) as a lower wiring is formed on an insulating film 1. An interlayer insulating film 3 is deposited thereon, patterned by a resist on the interlayer insulating film, and then a contact hole 5 is formed by RIE. The Ashing process after the opening is the same as in the first or second embodiment, and the oxide film is removed by dilute hydrofluoric acid (DHS) before the barrier metal is sputtered in the contact hole.
Next, Ti3 is used as a barrier metal in the contact hole.
Then, a conductor, for example, W101, which is the same material as W as the lower wiring, is buried in the contact hole. The embedded W101 is planarized by CMP.
On this, the contact hole described in the first embodiment is formed, and Al101 wiring is processed. The above-described structure is a memory word line structure, that is, the present invention can be applied to a structure including a lower metal wire 2 serving as a gate of a select transistor and an upper word line 102 for lowering the resistance of a word line. Conceivable. Since WOx, which is a factor for increasing the contact resistance, can be removed, the resistance value can be reduced.

In the Ashing process of each embodiment of the present invention, if WOx is removed to a desired resistance (2 ohms at the main portion), the Wet process is unnecessary, but the contact bottom boundary is not required. In the case where [O] (oxygen element) is contained in the metal film surface and exceeds 2 ohms in the main part, the resistance can be effectively reduced by performing the Wet treatment for a short time.
It goes without saying that the amount is smaller than that of the conventional Wet treatment liquid.

Although the metal wiring layer itself using tungsten has been described, for example, when aluminum is used for the lower metal wiring, Ti / TiN may be used as a barrier metal in the upper layer of the metal wiring layer. Also in this case, the barrier metal Ti / TiN exposed at the time of opening the contact hole reacts with O2 to grow an oxide film (TiOx). Also in this case, the present invention is applicable as long as the amount of digging (abrasion) of the barrier metal on Al can be controlled and an optimum barrier metal can be left, and a low-resistance contact wiring can be realized. .

[0019]

According to the present invention, after the contact hole is formed, the surface of the first metal wiring at the bottom of the contact is chemically formed under a gas condition containing at least fluorine under a gas condition containing at least fluorine under a gas condition containing at least fluorine. The contact resistance can be reduced by removing the oxide film that grows on the substrate.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a method for manufacturing a semiconductor device according to a first embodiment of the present invention.

FIG. 2 is a sectional view showing the method of manufacturing the semiconductor device according to the first embodiment of the present invention.

FIG. 3 is a sectional view showing the semiconductor device according to the first embodiment of the present invention;

FIG. 4 is a graph showing a result of analysis of elements contained in a conventional contact bottom surface.

FIG. 5 is a graph showing the results of elemental analysis of the contact bottom surface according to the present invention.

FIG. 6 is a graph showing a contact resistance value with respect to a CF4 addition time.

FIG. 7 is a graph showing a relationship between a Wet process and a contact resistance value.

FIG. 8 is a sectional view showing a semiconductor device and a method for manufacturing the same according to a second embodiment of the present invention.

FIG. 9 is a sectional view showing a semiconductor device and a method for manufacturing the same according to a third embodiment of the present invention.

FIG. 10 is a sectional view showing a semiconductor device and a method for manufacturing the same according to a third embodiment of the present invention.

FIG. 11 is a sectional view showing a semiconductor device according to a fourth embodiment of the present invention.

FIG. 12 shows a semiconductor device according to a conventional technique.

FIG. 13 is a graph showing a relationship between a conventional Ashier processing time and a contact resistance value.

FIG. 14 is a graph showing the relationship between the Wet processing time after the Asher processing and the contact resistance according to the related art.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 insulating film 2 first metal wiring layer 3 interlayer insulating film 4 resist 5 contact hole 9 side edge portion 21 oxide film 22 shaved area 31 contact layer 32 barrier metal 91 interlayer insulating film 92 resist 93 contact hole 101 tungsten 102 aluminum 110 contact Hole 111 first metal wiring layer 112 oxide film 113 contact layer

Claims (4)

[Claims] A first metal wiring layer; an interlayer insulating film formed on the first metal wiring layer; a second metal wiring layer formed on the interlayer insulating film; A contact hole for connecting the second metal wiring layer and the second metal wiring layer; and a contact hole formed on the surface of the first metal wiring layer below the contact hole, and having a diameter of a bottom portion of the contact hole. A large depression region, a side wall of the contact hole and a barrier metal formed on a part of the depression region, and a contact layer having the barrier metal and a contact layer embedded in the depression region. A semiconductor device made of the same material as the first metal wiring. 2. A method of manufacturing a semiconductor device having a multi-layer wiring layer, comprising: forming a first metal wiring layer; forming an interlayer insulating film on the first metal wiring layer; Patterning a resist on the film and forming a contact hole using the resist;
(2) A first Ashing step of removing the resist in a plasma atmosphere with a single gas, and after the first Ashing step, the remaining resist and the bottom of the contact hole are removed in a plasma atmosphere in which a fluorine-based gas is added to O2. The second step of removing the oxide film on the first metal wiring formed
And a method of manufacturing a semiconductor device, wherein the Ashing step comprises two steps. 3. A method of manufacturing a semiconductor device having a multilayer wiring layer, comprising: forming a first metal wiring layer; forming an interlayer insulating film on the first metal wiring layer; Patterning a resist on the film and forming a contact hole using the resist;
(2) a first Ashing step of removing the resist in a plasma atmosphere using a single gas; and a first Ashin step.
after the step g, a second Ashing step of chemically removing the oxide film on the first metal wiring formed on the bottom surface of the contact hole with a fluorine-based gas;
A method for manufacturing a semiconductor device, wherein the ing step comprises two steps. 4. After removing an oxide film on the first metal wiring grown on the bottom surface of the resist and the contact hole, a contact layer is formed in the contact hole with the same material as the first metal wiring layer. 4. The method for manufacturing a semiconductor device according to claim 2, further comprising the step of: