JPH0691082B2 - Method for manufacturing semiconductor device - Google Patents

Description

The present invention relates to a method for manufacturing a semiconductor device, and more particularly to a technique for forming an inorganic insulating film layer used for an interlayer insulating film of a multilayer wiring. Is.

(Prior Art) A conventional example of a method for forming an interlayer insulating film layer of a plasma silicon oxide film in a two-layer wiring will be briefly described with reference to FIG.
As shown in FIG. 5A, the first-layer wiring 12 made of Al-Si-Cu having a predetermined pattern and having a predetermined pattern, which is provided on the semiconductor substrate 11 on which the thermal silicon oxide film is formed. A plasma silicon oxide film (hereinafter referred to as a P-SiO film) 13 is deposited to a thickness of 1.5 μm by a plasma CVD method, and a thickness of 2.0 μm
After applying m-thick positive photoresist 14, the P-SiO
Under the RIE condition that the film 13 and the positive photoresist 14 have the same etching rate, the P-SiO film 13 on the wiring 12 of the first layer
Etch back to 0.2 μm.

After cleaning the surface, as shown in Fig. 5 (b), 1.0 μm thick P
-The SiO film 15 is redeposited to form a flat interlayer insulating film layer, and then the through hole 17 is formed at a predetermined position by the usual photolithography method and RIE method. After that, the second-layer wiring 18 made of Al—Si—Cu having a predetermined pattern and having a thickness of 1.0 μm is formed by the usual sputtering method, photolithography method, and RIE method.

Next, as shown in FIG. 5C, as the top passivation film 19, a P-SiO film having a thickness of 1.0 μm is deposited by the above-mentioned plasma CVD method, and then by a normal photolithography method and an RIE method. A predetermined bonding pad opening is formed to complete the two-layer wiring structure.

(Problems to be Solved by the Invention) Generally, in order to improve the reliability of a semiconductor device, an inorganic insulating film such as a P-SiO film is used as an interlayer insulating film or a top passivation film of a multilayer wiring. However, the conventional inorganic insulating film layer forming technique has the following problems.

Plasma CVD method shown in the conventional example (film forming conditions: SiH ₄ / N ₂ O
= 200 / 2400SCCM-1.5KW-0.4Torr-300 ℃)
It can be seen from Auger electron analysis shown in FIG. 6 that the silicon excess layer 16 exists in the P-SiO film up to a depth of about 0.2 μm from the film surface. Although an example is shown in FIG. 7, the thickness of the silicon excess layer 16 varies depending on the film forming conditions, the forming method (plasma CVD, low pressure CVD, atmospheric pressure CVD, sputtering method or ECR plasma CVD method) and equipment. It has been found that, in most cases, it is in the range of 5 to 35% of the formed film thickness. Furthermore, it was also confirmed that in the case of a silicon nitride film or a silicon carbide film other than the silicon oxide film, the silicon excess layer is formed in the same range of thickness.

It is considered that the silicon excess layer 16 is formed by atoms with a light mass (eg, oxygen atoms in the case of P-SiO) escaping from the film surface when the formation reaction is suddenly stopped for film thickness control,
There are many incomplete or weak bonds in the bonds between atoms in the silicon excess layer 16. For this reason, the electrical characteristics become extremely unstable, and the conventional example has the following problems.

The leakage level between wirings on the insulating film is extremely high. For example, as shown in FIG. 3, the leakage between the wirings of the second layer on the P-SiO interlayer insulating film is 1.5 μm between the wirings and the electric field is 0.5 MV / c.
It is about 203 pA / cm in m, which is about 390 times the wiring leak (0.52 pA / cm) when formed on the thermal silicon oxide film.

The interface charge density Nss due to the MIS structure as shown in FIG.
The level of variation ΔNss in the interface charge density due to BT treatment is high. For example, in the case of the conventional P-SiO film, Nss = 2.0 × 10 ¹¹ c
High as m ^-2 , the fluctuation amount ΔNss after BT treatment (1MV / cm-300 ° C-20 minutes) is ΔNss ≒ + 1.2 × 1 when the gate electrode is anode (+ BT)
It shows normal behavior with positive ion movable type of 0 ¹¹ cm ^-2 , but ΔNss ≒ +7.5 × 10 ¹⁰ cm ^-2 at gate electrode (-BT), which is different from the positive ion movable type. Nss fluctuations and Vth stability and reliability are reduced. In FIG. 4, a gate oxide film 62, a P-SiO film 63, and a gate electrode (1.0 μm Al) 64 are sequentially laminated on an n-type silicon substrate 61.

The present invention has been made in view of the above circumstances.
After forming an inorganic insulating film by a conventional method such as the CVD method, light constituent atoms such as a silicon excess layer formed from the surface of the inorganic insulating film to a thickness of about 5 to 35% of the formed film diffuses outwardly. However, by supplementing the surface layer portion where the heavy constituent atoms are excessive with the light constituent atoms that have been diffused outward by plasma oxidation, etc., the film quality of the surface layer portion is improved, and electrically stable and highly reliable inorganic insulation An object of the present invention is to provide a method for manufacturing a semiconductor device capable of forming a film.

[Structure of the Invention] (Means and Actions for Solving the Problems) The present invention is directed to plasma formation when an inorganic insulating film is formed as an interlayer insulating film or a passivation film on a semiconductor substrate having a predetermined structure and pattern. After forming the inorganic insulating film by the CVD method or the like, at the end of the inorganic insulating film forming reaction, at least a part of the light constituent atoms are out-diffused, and the heavy constituent atoms are excessive. For the purpose, plasma in an atmosphere containing at least one kind of lighter atom, such as oxygen, nitrogen, or carbon, which reacts with the heavy constituent atoms and is necessary for forming a stable insulating film having a film quality equivalent to that of the inorganic insulating film. This is an inorganic insulating film forming technique characterized by performing a treatment, by supplementing light constituent atoms lost by the plasma treatment and modifying an excess layer of the heavy constituent atoms to obtain electrical characteristics, etc. Stable, can be easily realized in the formation of more reliable inorganic insulating film.

Embodiments Embodiments of the present invention will be described in detail below with reference to the drawings.

1 (a), (b), (c) and (d) show one embodiment of the present invention. That is, as shown in FIG. 1A, a 1.0 μm thick Al—Si—Cu film is deposited on a semiconductor substrate 71 on which a thermal silicon oxide film is formed by a normal sputtering method, and then a normal photo film is formed. The wiring 72 of the first layer having a predetermined pattern was formed by the lithography method and the RIE method. Plasma CVD method (S
iH ₄ / N ₂ O = 200 / 2400SCCM-0.4Torr-1.5KW-300 ℃)
P-SiO film 73 with a thickness of 1.5 μm is deposited, and a positive photoresist is used.
After applying 74 to 2.0 μm thick, RIE method (CHF ₃ / C ₂ F ₆ / O ₂ / He
= 10/35/20 / 35SCCM-3.0Torr-550W) with the same etching rate for the P-SiO film 73 and the positive photoresist 74,
Etching back was performed until the film thickness of the P-SiO film 73 on the wiring 72 of the first layer became 0.2 μm.

After surface cleaning by O ₂ plasma ashing method and washing with running water, as shown in FIG. 1 (b), P-SiO film 75 with a thickness of 1.0 μm
Was deposited in the same plasma CVD conditions as described above, pull up the ultimate vacuum of the plasma CVD apparatus was conducted continuously N ₂ O by plasma treatment _{(N 2 O = 2800SCCM-0.4Torr} -1.2KW-300 ℃). By the plasma treatment, a silicon excess layer 76 (confirmed by Auger electron analysis as shown in FIG. 2) existing in a surface layer of the P-SiO film 75 after deposition with a thickness of 0.20 μm corresponding to 20% of the deposited film thickness is formed. It was modified to a P-SiO film. 76 'is the part with improved film quality.

Next, as shown in FIG. 1 (c), after forming through holes 77 at predetermined positions by the ordinary photolithography method and the RIE method, the ordinary sputtering method and the photolithography method are used.
1.0μm thick Al-Si- having a predetermined pattern by RIE method
A second wiring layer 78 made of Cu was formed.

Next, as shown in FIG. 1D, as the top passivation film 79, 1.0 μm under the plasma CVD conditions described above is used.
After depositing a thick P-SiO film and performing the plasma treatment,
A predetermined bonding pad opening portion was formed by the usual photolithography method and RIE method to complete the two-layer wiring structure according to the present invention.

In the above-mentioned embodiment, the interlayer insulating film of the multi-layer wiring is taken as an example, but it may be applied at any stage as long as it is an inorganic insulating film formed on the semiconductor substrate such as a passivation film.

Further, in the above embodiment, the P-SiO film formed by the plasma CVD method was used as the inorganic insulating film, but the forming method is a low pressure CVD method other than the plasma CVD method, a chemical vapor phase method such as the atmospheric pressure CVD method or the ECR plasma CVD method. Any physical growth such as a growth method or a sputtering method may be used, and an inorganic insulating film made of a silicon compound such as a silicon oxide film, a silicon nitride film, or a silicon carbide film, or an inorganic material other than a silicon compound that can be applied to a semiconductor device It goes without saying that any insulating film may be used.

Further, in the silicon compound such as the P-SiO film used in the above example, a silicon excess layer is formed in the film surface layer portion,
Needless to say, other than silicon compounds, an excess layer of heavy constituent atoms is formed by the outdiffusion of light constituent atoms as described above.

In addition, in the present embodiment, N ₂ O plasma treatment is performed to modify the silicon excess layer formed on the surface layer of the P-SiO film, and the silicon excess layer is a normal P-SiO film. The plasma treatment aimed at improving the excess layer of heavy constituent atoms by the outdiffusion of the constituent atoms into a stable insulating film is performed by reacting with the heavy constituent atoms to form a stable insulating film. A gas atmosphere containing at least one lighter atom of the same kind as the light element,
It suffices that the film quality obtained by modifying the excess layer of heavy constituent atoms is a stable insulating film and is equivalent to the film quality formed under the excess layer of heavy atoms. That is, in order to improve the film quality of the silicon-rich layer on the surface layer, O that reacts with Si atoms such as O ₂ , N ₂ , NO, NO ₂ , CO, CO ₂ , CH ₄ , C ₂ H ₈ other than N ₂ O, , Plasma treatment with at least one gas supplying N, C atoms,
The modified film quality may be P-SiN other than P-SiO, P-SiC, or a stable intermediate insulating material of these.

Further, the condition of the plasma treatment for improving the film quality of the excessive layer of heavy atoms is only required to form the insulating film in a stable manner, and it is not always necessary to continuously perform the formation of the inorganic insulating film.

The meanings of “heavy” and “light” indicate relative differences in atomic weight.

[Effects of the Invention] As described above, according to the present invention, light constituent atoms existing in the surface layer of an inorganic insulating film formed by a chemical vapor deposition method such as plasma CVD method or a physical growth method such as sputtering method are diffused out. Of the unstable layer containing excess heavy constituent atoms is reacted with the heavy constituent atoms, and plasma treatment is performed in a gas atmosphere containing at least one kind of relatively light atom necessary for forming a stable insulating film. The present invention is characterized by supplementing excess heavy atoms with relatively light atoms of the same kind as the lost light atoms to form a stable insulating film layer, and has the following effects.

The leak level on the surface of the inorganic insulating film is extremely low. The leakage between the wirings of the second layer on the P-SiO interlayer insulating film in the example is 0.8 to 1.0 pA / cm under the same measurement condition as the conventional one (wiring interval 1.5 μm, applied electric field 0.5 MV / cm), and the conventional example. About 1/203 ~ 1 /
It is at a very low level of 254 (see Fig. 3).

Interface charge density Nss = 1.1 × 1 according to the MIS structure shown in FIG.
0 ¹¹ cm ^-2 , which is about half that of the conventional example, and BT treatment (1MV / cm-300 ° C
After -20 minutes, the fluctuation amount ΔNss is the gate electrode anode (+ BT)
ΔNss ≒ + 6.5 × 10 ¹⁰ cm ^-2 , gate electrode cathode (-BT)
ΔNss = + 0.52 × 10 ¹⁰ cm ^-2 (almost no increase) and normal positive ion movable type behavior, and both Nss and ΔNss levels are low, indicating improved stability and reliability. .

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a forming process of one embodiment of the present invention, FIG. 2 is a characteristic diagram showing an example of the result of Auger electron analysis showing the effect of improving the quality of a silicon excess layer film according to the present invention, and FIG. FIG. 4 is a characteristic view showing an example of leak measurement results between wirings on an inorganic insulating film according to the invention and the prior art, FIG. 4 is a sectional view showing an example of a MIS structure semiconductor device, and FIG. 5 is a sectional view showing a conventional inorganic insulating film forming process. 6 and 6 are characteristic diagrams showing the results of Auger electron analysis showing the existence of a silicon excess layer on the surface layer of a conventional P-SiO film, and FIG. 7 shows an example of the plasma CVD condition dependency of the conventional silicon excess layer. It is a characteristic diagram. 71 …… Semiconductor substrate, 72 …… First layer wiring, 73 …… P-Si
O film, 74 …… Positive photoresist, 75 …… P-SiO film, 76
…… Silicon excess layer, 77 …… Through hole, 78 …… Second
Wiring of the first layer, 79 ... Top passivation film.

Continuation of front page (56) Reference JP 54-2070 (JP, A) JP 55-113335 (JP, A) JP 60-54469 (JP, A)

Claims (4)

[Claims] 1. A method of manufacturing a semiconductor device in which an inorganic insulating film is formed on a semiconductor substrate, the step of forming the inorganic insulating film on the semiconductor substrate, and the relatively heavy structure of the inorganic insulating film formed by this step. And a step of performing plasma treatment in a gas atmosphere containing at least one kind of relatively light constituent element necessary for forming a stable insulating film having a film quality equivalent to that of the inorganic insulating film. A method for manufacturing a semiconductor device, comprising: 2. The method of manufacturing a semiconductor device according to claim 1, wherein the step of forming the inorganic insulating film and the step of performing the plasma treatment are continuously performed without exposing the semiconductor substrate to the atmosphere. 3. The method of manufacturing a semiconductor device according to claim 1, wherein at least Si is contained as a heavy constituent element. 4. The method of manufacturing a semiconductor device according to claim 1, wherein at least one of O, N, and C is contained as a relatively light constituent element.