JP2000049294A - Manufacture of semiconductor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent a barrier metal from being undercut, and to make the step coverage satisfactory. SOLUTION: A photoresist 23 is deposited on an Al film 5, including the interior of opening 5c, portions of the photoresist 23 deposited in the openings 5c are removed to form smaller openings 23a than the openings 5c. A barrier metal 4 is removed by etching through openings 23a. Thus the barrier metal 4 can be etched from a position further interior than the opening ends of the Al film 5 by etching through the openings 23a, so that undercuts of the barrier metal 4 underlying the Al film 5 can be prevented. As a result, the step coverage can be made satisfactory.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for manufacturing a thin film resistor in a semiconductor device.

[0002]

2. Description of the Related Art As a method of manufacturing a semiconductor device having a metal thin film resistor, there is a method disclosed in, for example, US Pat. The manufacturing process of this semiconductor device will be described with reference to FIG. As shown in FIG. 6A, after an insulating film 102 is formed on a silicon substrate 101 by thermal oxidation, a metal thin film resistor 103 made of CrSi is deposited by a sputtering method, and a barrier metal 104 made of TiW is further formed. To adhere.

[0006] Next, as shown in FIG. 6 (b), the barrier metal 104 and the metal thin film resistor 103 are patterned by dry etching using a gas such as CF ₄ using the photoresist 105 as a mask. Subsequently, FIG.
As shown in FIG. 6C, after removing the photoresist 105, an Al film 106 is entirely deposited, and furthermore, FIG.
As shown in (d), dry etching is performed using CCl ₄ or the like with the photoresist 107 as a mask, and the Al film 106 is patterned to form an electrode portion of the metal thin film resistor 103.

[0004] Then, as shown in FIG. 6 (e), H ₂ O
Wet etching is performed using an etching solution mainly composed of ₂ to remove the barrier metal 104 and expose the metal thin film resistor 103. Thereafter, a semiconductor device having the metal thin film resistor 103 is completed by forming a protective film or the like.

[0005]

FIG. 7 is an enlarged view of the vicinity of the barrier metal 104 when a semiconductor device is formed by the above-described conventional manufacturing method. As shown in this figure, when wet etching is performed from the opening 106a formed in the Al film 106, the barrier metal 104 becomes under the inner side of the opening end of the opening 106a formed in the Al film 106. Be cut. If the amount of undercut is large, when the protective film is formed in a later step, as shown in FIG.
There is a problem that the step coverage is hardly formed at the lower portion of the semiconductor device 6 and the step coverage is deteriorated.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a method of manufacturing a thin film resistor which prevents a barrier metal from being undercut, has good step coverage of a protective film, and has high reliability. And

[0007]

In order to achieve the above object, the following technical means are employed. Claim 1 or 2
In the invention described in (1), the mask opening width for exposing the barrier metal material when etching the barrier metal material (4) is smaller than the mask opening width for exposing the electrode material when patterning the electrode material (5). It is characterized by doing.

As described above, by making the mask opening width of the mask used at the time of etching the barrier metal material smaller than the mask opening width of the mask used at the time of patterning the electrode material, the mask opening width of the electrode material mask is made smaller than the single opening. Since the barrier metal material can be etched from below, the undercut of the barrier metal material located below the electrode material can be prevented. This makes it possible to provide a thin film resistor with good step coverage of the protective film and high reliability.

According to the third aspect of the present invention, in the step of etching the barrier metal material (4), the surface is partially dry-etched and then wet-etched, so that the thin-film resistor other than the electrode take-out position is obtained. The method is characterized in that the barrier metal material deposited on the top is removed. Thus, by performing dry etching with a small amount of side etching and then performing wet etching, the amount of wet etching can be reduced,
Accordingly, the amount of side etching in wet etching can be reduced. Thus, the variation in the amount of side etching during wet etching can be reduced, and the variation in the contact width between the barrier metal material (4) and the thin film resistance material (2) can be reduced.

According to the present invention, the barrier metal (4) is removed by performing dry etching, and then the barrier metal (4) is removed by performing wet etching. The method is characterized in that the metal thin film constituting (2) is exposed. in this way,
By performing wet etching after performing dry etching with a small amount of side etching, the amount of wet etching can be reduced, and accordingly, the amount of side etching in wet etching can be reduced.
Thereby, the variation in the amount of side etching during wet etching can be reduced, and the barrier metal (4)
Of the contact width between the thin film resistor and the thin film resistor (2) can be reduced.

Specifically, in dry etching, an etching gas containing CF ₄ can be used in dry etching. Further, as described in claim 9, in wet etching, an etching solution containing H ₂ O ₂ can be used. In the invention described in claim 5, after the step of forming the first opening (5c) in the conductive film (5), a photoresist (23) is deposited and the photoresist (23) is formed. The first opening (5
c) removing the portion deposited in the first opening (5);
forming a second opening (23a) smaller than c), wherein the dry etching step and the wet etching step are performed through the second opening (23c).

According to the present invention, the thickness of the barrier metal (4) is reduced to 20 by dry etching.
% Or more is removed. in this way,
If the barrier metal (4) is removed by dry etching by 20% or more, the influence of wet etching can be reduced, and the shape obtained by dry etching can be successfully inherited.

According to a seventh aspect of the present invention, the dry etching is performed so that the thickness of the barrier metal (4) remains at least 100 °. The etching gas of the dry etching may increase the sheet resistance of the thin film resistor (2). Therefore, the barrier metal (4) has a thickness of 100 ° in consideration of the variation in the etching amount.
It is preferable that the etching gas for dry etching does not come into contact with the thin film resistor (2) so as to remain as described above.

In order to prevent mutual diffusion from the conductive film (5) and the thin film resistor (2), the barrier metal (4) is formed to a thickness of 500 ° or more. It is preferable to form a film. According to the eleventh aspect, a photoresist (23) is deposited on the conductive film (5) including the inside of the first opening (5c), and the first of the photoresist (23) is formed. The portion deposited in the opening (5c) is removed to form a second opening (23a) smaller than the first opening (5c), and etching is performed from the second opening (23a). Done, barrier metal (4)
It is characterized by removing.

As described above, by performing etching through the second opening (23a) inside the first opening (5c), the barrier metal (from the inside of the opening end of the conductive film (5)) is formed. Since 4) can be etched, the undercut of the barrier metal (4) located below the conductive film (5) can be prevented. Thereby, it is possible to prevent the step coverage from deteriorating.

Note that the reference numerals in the parentheses indicate the correspondence with the specific means described in the embodiment described later.

[0017]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing a first embodiment of the present invention. FIG. 1 shows a cross-sectional view of a semiconductor device provided with a metal thin-film resistor manufactured by applying one embodiment of the present invention. As shown in FIG. 1, the semiconductor device has P
A circuit portion including an N-junction element (for example, a diode or a transistor) is provided, and a metal thin film resistor 2 made of CrSi is formed on a semiconductor substrate 1 provided with the circuit portion.

A specific structure of the semiconductor device will be described. As shown in FIG. 1, an n-type diffusion layer 10 is provided on a surface portion of a semiconductor substrate 1 made of silicon on a circuit portion side.
And a PN junction composed of a p-type diffusion layer 11 and
These constitute a PN junction element. An insulating film 3 made of a BPSG film or the like containing boron (B) or phosphorus (P) is deposited on a semiconductor substrate 1, and a metal thin film resistor 2 is formed on the insulating film 3.

An Al electrode 5a is formed at both ends of the metal thin film resistor 2 via a barrier metal 4 made of TiW or the like. Further, a contact hole 3a is formed in the insulating film 3 above the PN junction, and the Al wiring 5b is electrically connected to the PN junction via the contact hole 3a. The metal thin film resistor 2, barrier metal 4, Al electrode 5a and Al wiring 5b are TE
The semiconductor device is covered with a protective film 6 made of an OS oxide film or the like.

Next, a method of manufacturing the semiconductor device formed in FIG. 1 will be described. FIG. 2 shows a manufacturing process of the semiconductor device, which will be described with reference to FIG. On the semiconductor substrate 1 made of [FIGS. 2 (a) to indicate Step] n ⁺ -type diffusion layer 10 and made of p ⁺ -type diffusion layer 11 PN junction device is formed of silicon, a plasma CVD, normal temperature CV
D, The insulating film 3 is formed by thermal oxidation or the like. Next, Cr
A metal thin-film resistor 2 made of Si or CrSiN or the like is deposited by sputtering to a thickness of about 200 °, and a barrier metal 4 made of TiW is deposited to a thickness of about 2000 °.

[Step shown in FIG. 2B] Using the photoresist 21 as a mask, the barrier metal 4 and the metal thin film resistor 2 are patterned by dry etching using a gas such as CF ₄ . [Step shown in FIG. 2 (c)] Through a photolithography step, a contact hole 3a for making an electrical connection with a PN junction in the circuit portion is formed in the insulating film 3.

Subsequently, an Al film 5 made of Al, AlSi or the like is deposited on the entire surface to a thickness of about 1.0 μm. [Step shown in FIG. 2D] Using the photoresist 22 as a mask, dry etching using CCl ₄ or the like is performed.
The Al film 5 is patterned to simultaneously form an Al electrode 5a for connection to the metal thin film resistor 2 and an Al wiring 5b in the circuit section. At this time, A on the metal thin film resistor 2
The l film 5 is removed, and an opening 5c is formed in the Al film 5.

[Step shown in FIG. 2E] First, a photoresist 23 is deposited, and the photoresist 23 on the barrier metal 4 is removed to form an opening 23a. At this time, the opening 5c formed in the Al film 5 is opened from the opening end of the opening 23a provided in the photoresist 23.
The thickness of the photoresist 23 formed in the opening 5c formed in the Al film 5 is 2 μm.
m.

Then, the barrier metal 4 is removed using the photoresist 23 as a mask. Thus, the Al film 5
When the barrier metal 4 is removed by using the photoresist 23 formed in the opening 5c of FIG.
Since it is removed from the inside of the opening end of the l film, even if wet etching is performed, the barrier metal 4 located below the Al film 5 can be substantially not removed.

As described above, through the second photolithography step, the opening 5 formed in the Al film 5 is formed.
The barrier metal 4 is not undercut inside the opening end of c, that is, to the lower part of the Al film 5, and it is not necessary to form the protective film 6 to be formed in a later step by entering the lower part of the Al film 5. Therefore, the step coverage of the protective film 6 can be improved, and the reliability of the semiconductor device can be maintained.

Here, it is conceivable that the removal of the barrier metal 4 is performed only by wet etching as in the conventional case. However, when the barrier metal 4 is removed by wet etching, as shown in FIG. 3, the side etching amount S varies greatly and is difficult to control, so that the length of contact between the barrier metal 4 and the metal thin film resistor 2 is long. It has been found that there is a problem that the actual resistance length as the metal thin-film resistor 2 is largely varied.

For this reason, in the step shown in FIG. 2E, first, using the photoresist 23 as a mask, dry etching is performed from the opening 23a using a gas such as CF ₄ to a thickness of about 1000 °. The barrier metal 4 is removed to make it thinner. At this time, since the barrier metal 4 is etched by dry etching, the amount of side etching can be reduced. It should be noted that the barrier metal 4
Has a thickness of about 1000 mm.

At this time, a part of the insulating film 3 around the metal thin film resistor 2 is removed by dry etching to leave its shape. [Step shown in FIG. 2 (f)] Next, using the photoresist 23 as a mask, wet etching is performed using an etchant mainly composed of H ₂ O ₂ to remove the remaining part of the barrier metal 4 and remove the metal thin film resistor. The body 2 is exposed. FIG. 4 shows a partially enlarged view of the vicinity of the barrier metal 4 at this time.

As described above, when the barrier metal 4 is removed by wet etching, the barrier metal 4 is removed in the lateral direction by side etching.
In the present embodiment, wet etching is performed after a part of the barrier metal 4 is dry-etched, and the shape obtained by the dry etching is inherited, and the etching is performed in a stepped shape.

At this time, since the dry etching has been performed first, the remaining portion may be removed by wet etching. Therefore, the amount of side etching that increases the amount of side etching can be reduced, and the overall amount of side etching can be reduced as compared with the conventional case where the barrier metal is removed only by wet etching.

As described above, by performing dry etching with a small amount of side etching first, the amount of wet etching can be reduced, and accordingly, the amount of side etching can be reduced. Therefore, the amount of side etching of the barrier metal 4 can be defined with good controllability, and the variation in the contact length between the barrier metal 4 and the metal thin-film resistor 2 can be reduced. Thereby, the substantial resistance length of the metal thin film resistor 2 can be defined with good controllability.

The barrier metal 4 and the metal thin film resistor 2
If to reduce the variation in contact length between, without performing wet etching, it is conceivable that all may be performed dry etching, a gas such as CF ₄ for use in dry etching, the metal thin film resistor 2 This is not preferable because it causes damage to the sheet metal and extremely increases the sheet resistance of the metal thin film resistor 2. Therefore, the barrier metal 4 on the outermost surface of the metal thin film resistor 2 needs to be removed by wet etching.

Thereafter, after forming an insulating film 3 and a protective film, a heat treatment is performed at 450 ° C. for 20 minutes in a nitrogen atmosphere to complete a semiconductor device provided with the metal thin film resistor 2.
As described above, by performing dry etching after partially etching the barrier metal 4, variation in the amount of side etching during wet etching can be reduced, and the contact length between the barrier metal 4 and the metal thin film resistor 2 can be reduced. Variation can be reduced.

In this embodiment, as shown in FIG. 2E, a photoresist 23 having a predetermined thickness is applied to the inner wall side of the opening 5c formed in the Al film 5. An opening 2 having a smaller diameter than the opening 5c is formed in the photoresist 23.
3a is formed. And resist 23
As a result, the barrier metal 4 is etched from a region inside the opening 5c of the Al film 5, so that the barrier metal 4 can be prevented from being largely under-etched under the Al film 5. Further, at the time of the wet etching, the Al film 5 is covered with the resist 23, so that the Al film 5 and the barrier metal 4 can be prevented from being simultaneously exposed to the etching solution of the wet etching.

For this reason, the Al film 5 which does not cover the Al film at the time of wet etching and has a different ionization tendency as in the prior art is used.
Undesired etching (elution of Al) due to the battery effect that occurs when the barrier metal 4 and the metal thin-film resistor 2 are simultaneously made into an etchant can be suppressed. (Other Embodiments) In the above embodiment, the thickness of the barrier metal 4 is set to about 2000 °, but is not limited to this, and may be a desired thickness. However, the barrier metal 4 is A
Since it is for preventing interdiffusion between the l film 5 and the metal thin film resistor 2, a thickness of about 500 ° is required.

In the above embodiment, the barrier metal 4
Although the film thickness is about 2000 °, the etching amount by dry etching is set to about 1000 °, which prevents the effect of wet etching from appearing greatly and preventing the effect of dry etching from being lost. Therefore, the above etching amount is used. If the amount of dry etching is small, the influence of wet etching appears significantly, the shape obtained by dry etching cannot be inherited well, and the above effect cannot be obtained much, that is, the side etching amount S can be precisely defined. May disappear. When a specific experiment was performed, the results shown in FIG. 5 were obtained. This figure shows the side etching amount with respect to the dry etching amount / (dry etching amount + wet etching amount (= total etching amount)). If it is required that the variation of the side etching amount is, for example, 2 μm or less, What is necessary is just to remove about 20% or more of the thickness of the barrier metal 4 by dry etching. Therefore, the above etching amount is selected.

In order to reduce the influence of wet etching, the amount of dry etching may be increased. However, as described above, the dry etching increases the sheet resistance of the metal thin-film resistor 2. For this reason, it is preferable that the barrier metal 4 remain at least 100 ° in consideration of the variation in the etching amount.

In the above-described embodiment, the opening 23a is formed in the resist 23, and the dry etching and the wet etching are performed. After the partial etching of the barrier metal 4 is performed by dry etching using the opening 5c of the resist 22 as a mask, the resist 23 having a small opening window is formed to finish etch the barrier metal 4 by wet etching. May be performed.

In the above embodiment, the Al electrode 5a and the Al wiring 5b are both formed by using the Al film 5, but they may be formed by separate Al films.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a semiconductor device manufactured by applying one embodiment of the present invention.

FIG. 2 is a view illustrating a manufacturing process of the semiconductor device shown in FIG. 1;

FIG. 3 is a partially enlarged view showing the vicinity of a barrier metal 4 when wet etching is performed.

FIG. 4 is a partially enlarged view showing the vicinity of a barrier metal 4 when dry etching and wet etching are performed.

FIG. 5 is a diagram showing a relationship between a dry etching amount and a side etching amount.

FIG. 6 is a view for explaining a conventional manufacturing process of a semiconductor device.

FIG. 7 is a diagram for explaining undercut of a barrier metal by conventional wet etching.

FIG. 8 is a diagram for explaining step coverage of the semiconductor device;

[Explanation of symbols]

REFERENCE SIGNS LIST 1 semiconductor substrate 2 metal thin film resistor 3 insulating film 4
... Barrier metal, 5 ... Al film, 5a ... Al electrode, 5b ...
Al wiring, 5c opening, 6 protective film, 21-23 photoresist, 23a opening.

 ──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Akihito Fukui 1-1-1, Showa-cho, Kariya-shi, Aichi Prefecture Inside Denso Corporation (72) Takashi Sugisaka 1-1-1, Showa-cho, Kariya-shi, Aichi Stock Company F term in DENSO Corporation (reference) 5F033 AA04 AA13 BA12 CA07 DA05 DA16 DA26 EA05 5F038 AR07 AR08 AR16 EZ14 EZ15 EZ20

Claims (11)

[Claims] 1. A thin-film resistance material (2), a barrier metal material (4) and an electrode material (5) are sequentially arranged on a substrate (1),
The barrier metal material (4) is etched based on the patterned electrode material (5) to determine a thin-film resistor made of the thin-film resistor material (2), and a barrier metal is provided at an electrode extraction position of the thin-film resistor. In the method for manufacturing a thin film resistor, the barrier metal material (4) is etched when the barrier metal material (4) is etched, based on a mask opening width exposing the electrode material (5) when patterning the electrode material (5). A method for manufacturing a thin film resistor, characterized in that a mask opening width for exposing a metal material (4) is made smaller. 2. The step of etching the barrier metal material (4) includes, after partially dry-etching the surface, wet-etching the wet-etched metal to cover the thin-film resistor other than the electrode take-out position. 2. The method according to claim 1, further comprising the step of removing the barrier metal material. 3. A thin film resistance material (2), a barrier metal material (4), and an electrode material (5) are sequentially arranged on a substrate (1),
The barrier metal material (4) is etched based on the patterned electrode material (5) to determine a thin-film resistor made of the thin-film resistance material (5), and a barrier metal is provided at an electrode extraction position of the thin-film resistor. Wherein the step of etching the barrier metal material (4) comprises:
The thin film characterized in that the barrier metal material (4) deposited on the thin film resistor other than the electrode take-out position is removed by partially wet-etching the surface after dry etching. Manufacturing method of resistor. 4. A method for manufacturing a thin film resistor for forming a thin film resistor (2) on a substrate (1), comprising: forming a metal thin film constituting the thin film resistor (2) on the substrate (1). Forming a barrier metal (4) on the metal thin film, forming a conductive film (5) on the barrier metal (4), and forming the conductive film on the barrier metal (4). Membrane (5)
Is removed, and a first opening (5c) is formed in the conductive film (5).
A step of performing dry etching based on the first opening (5c) to remove a part of the barrier metal (4); and a step of performing dry etching based on the first opening (5c). Performing a wet etching to remove the barrier metal (4) to expose the metal thin film. 5. A first opening (5) in said conductive film (5).
After the step of forming c), a photoresist (23) is deposited, and a portion of the photoresist (23) deposited in the first opening (5c) is removed to remove the first photoresist (23). The second opening (23) smaller than the opening (5c)
The method according to claim 4, further comprising the step of forming (a), wherein the dry etching step and the wet etching step are performed through the second opening (23c). 6. The method according to claim 4, wherein the dry etching removes at least 20% of the film thickness of the barrier metal (4). 7. The method according to claim 4, wherein the dry etching is performed so that the film thickness of the barrier metal remains at least 100 °. . 8. In the dry etching, CF _{4 is used.}
The method for manufacturing a thin film resistor according to claim 4, wherein an etching gas containing: is used. 9. The method according to claim 9, wherein the wet etching is performed by using H _2.
9. The method according to claim 4, wherein an etching solution containing O ₂ is used. 10. The method of manufacturing a thin film resistor according to claim 4, wherein the barrier metal is formed to a thickness of 500 ° or more. 11. A method for manufacturing a thin-film resistor comprising a thin-film resistor (2) disposed on a substrate (1), wherein the thin-film resistor (2) is formed on the substrate (1). Forming a barrier metal (4) on the thin-film resistor (3); forming a conductive film (5) on the barrier metal (4); and forming the conductive film (5) on the barrier metal (4). Conductive film (5)
Is removed, and a first opening (5c) is formed in the conductive film (5).
Forming the conductive film, and the conductive film (5) including the inside of the first opening (5c).
A photoresist (23) is deposited thereon, and a portion of the photoresist (23) deposited in the first opening (5c) is removed to remove the first opening (5c).
Forming a smaller second opening (23a); and etching the second opening (23a) to remove the barrier metal (4). A method for manufacturing a thin film resistor.