JP3226251B2 - Method for manufacturing semiconductor device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a semiconductor device, and more particularly to a method for stabilizing the quality of an interlayer insulating film formed using an organic source gas.

[0002]

2. Description of the Related Art With the increase in the degree of integration of semiconductor devices, multilayering of fine devices has become an inevitable trend, but many problems must be solved in order to proceed. One of them is to improve the film quality of the interlayer insulating film, and the PSG (Phosph
o-Silicate Glass) Film or BPSG (PSG with boron)
This is to remove organic substances mixed in the film.

[0003] In the current mainstream of the film forming method, the CVD method using an organic gas as a source gas,
This is because a part of the organic substance in the organic gas was charged into the film being formed without being decomposed, and was mixed into the film being formed. For this reason, when a voltage is applied to the finally formed semiconductor device, the organic substance functions as a carrier, and the electrical characteristics are reduced. Therefore, conventionally, (1) N ₂ atmosphere or (2) O
Heat treatment was performed in _two atmospheres to remove organic substances in the film.

[0004]

As described above, BPSG
In removing organic substances in the film or PSG film, (1) In the conventional method of performing heat treatment in an N ₂ atmosphere, in order to remove organic substances in the film, a high temperature of about 900 ° C. for about 30 minutes,
Although a long heat treatment is required, when applied to a semiconductor device having a layer into which an impurity is introduced, there is a problem that diffusion of the impurity progresses and desired electrical characteristics cannot be obtained.
Particularly in a semiconductor device having a Shallow Junction structure,
This is a serious problem that causes leakage current.

(2) In the method of performing heat treatment in an O ₂ atmosphere (or an oxidizing atmosphere), in order to remove organic substances in a film,
A heat treatment of about 800 ° C. for about 20 minutes is required, but when applied to a semiconductor device having a wiring layer below the film, the wiring layer is oxidized, so that the wiring becomes thin and the resistance becomes high. .

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to solve the above problems and to remove organic substances in a BPSG film or a PSG film without adversely affecting the electrical characteristics of a finally formed semiconductor device. .

[0007]

In order to achieve the above object, a method of manufacturing a semiconductor device according to the present invention comprises the steps of: depositing an insulating film on a semiconductor substrate using an organic source gas;
Performing a heat treatment under an oxygen partial pressure of 200 to 400 Torr after depositing the insulating film.

[0008] It is characterized in that the heat treatment is performed at 400 ° C or higher. Note that the atmosphere during the heat treatment is an oxidizing atmosphere diluted with an inert gas.

The organic source gas is tetraethoxysilane (TEOS; Si (C ₂ H ₅ O) ₄ ), trimethyl borate (TMB; B (CH ₃ ) ₃ ), trimethyl phosphate
(TMP; PO (CH ₃ O) ₃ ). Note that an element isolation region or a wiring is present below the insulating film in contact with the insulating film.

[0010]

After forming an insulating film using an organic source gas,
Heat treatment is performed at an oxygen partial pressure of less than 760 Torr. It is considered that by performing this heat treatment, oxygen molecules penetrate into the insulating film, convert organic substances in the film into volatile substances such as carbon dioxide and water, and remove organic substances in the insulating film.

Further, the atmosphere to which the insulating film is exposed is:
The number of oxygen molecules is small, and the number of oxygen molecules that enter the insulating film by heat treatment is the minimum number of molecules necessary for removing organic substances. Therefore, organic substances in the insulating film can be efficiently removed without binding to constituent molecules in the insulating film or other layers covered by the insulating film.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A method of manufacturing a semiconductor device according to the present invention will be described below with reference to the drawings, taking a DRAM as an example. After forming an element isolation region by a LOCOS process on a P-type Si substrate 1, a gate oxide film 2 is formed at a predetermined position by a thermal oxidation method, impurities are implanted into a capacitor portion, and an N-type layer 3 is formed on the surface of the Si substrate. create.

Next, a first polycrystalline Si layer 4a is formed on the entire surface, P is introduced by POCl3 diffusion to make it N-type, and then patterned to form a gate electrode. Where the first polycrystalline
Since the portion of the gate oxide film 2 from which the Si layer 4a has been removed is damaged during the etching of the first polycrystalline Si layer 4a, the gate oxide film 2 is removed and the surface of the Si layer is exposed.

Next, a gate oxide film 2 for a select transistor is grown on the exposed portion of the surface of the Si layer. Then, the steps up to this point are repeated (after ion implantation into necessary portions, the second polycrystalline Si layer 4b is deposited, POCl3 diffused, and then patterned to form a gate electrode). Subsequently, the BPSG film 5 was applied as an interlayer insulating film to TEOS ((C ₂ H ₅ O) ₄ S
i), phosphine (PH ₃ ), TMB (B (CH ₃ ) ₃ ), and O
₂ is formed to a thickness of about 400 nm by the LP-CVD method. At this time, the concentration of the dopant is [P] = 7 wt% and [B] = 4 wt%.

Next, in an atmosphere of O ₂ partial pressure of 300 Torr, about 80
A heat treatment is performed at 0 ° C. for 20 minutes (see FIG. 1). In FIG.
When the above-described semiconductor device is subjected to a heat treatment at 800 ° C. for 20 minutes in an oxidizing atmosphere, its O ₂ partial pressure, the amount of carbon remaining in the BPSG film 5, and the polycrystalline Si under the BPSG film 5 The relationship with the oxide film thickness formed on the layer electrode was shown.

According to previous studies, in order to obtain desired device characteristics, the amount of charged organic substances in the insulating film must be 10 ²¹
It is known that it is necessary to reduce to about atoms / cm ³ . Looking at Figure 3 from this point, the O ₂ partial pressure is 200 Tor
r or more is preferable. Further, it can be seen that even if the O2 partial pressure is increased to 200 Torr or more, the amount of carbon in the insulating film does not change significantly, that is, the efficiency of carbon removal does not change.

Next, looking at the oxidation amount in the polycrystalline Si electrode layer, the oxidation amount increases as the O ₂ partial pressure increases, and the O ₂ partial pressure increases.
It can be seen that at a partial pressure of 200 Torr or less, the change in the amount of oxidation in the polycrystalline Si electrode layer is reduced.

From these two points, it can be seen that the optimum value of the O ₂ partial pressure is 200 to 400 Torr, preferably 400 Torr.
Therefore, the heat treatment in the O ₂ partial pressure 300 Torr atmosphere as described above minimizes the oxidation amount of the electrode under the BPSG film 5,
In addition, carbon in the insulating film is removed, and the reliability of device characteristics in the DRAM can be improved.

After opening the contact hole 6 for the bit line, a third polycrystalline Si layer 4c and a metal silicide layer 7 are formed in this order, and a heat treatment is performed. Next, the third polycrystalline Si layer 4c and the metal silicide layer 7 are patterned to form bit line wiring. Further, a BPSG film 5 is formed on the entire surface as an interlayer insulating film in the same manner as described above, and an O ₂ partial pressure of 300 T
Heat treatment at about 800 ° C for 20 minutes in orr atmosphere.

As a result, the same effects as those described above can be obtained, and a decrease in device characteristics can be prevented.
Subsequently, a predetermined portion is opened, an Al layer 8 is deposited, and then patterned to form an Al wiring.
An N film 9 is formed, and a pad is opened to manufacture a DRAM (FIG. 2) .

FIG. 4 shows two elements separated by an element isolation region.
A BPSG film formed using an organic source gas on a semiconductor substrate having an N-type diffusion layer,
FIG. 6 is a diagram showing a relationship between applied voltages when an inversion layer is formed under a field oxide film with a BPSG film. For comparison, a film was formed with silane, diborane, oxygen, and phosphine.
The relationship between the BPSG film and the applied voltage is also shown.

According to this, it is understood that the same breakdown voltage can be obtained by performing the heat treatment as in the case where the film is formed without using the organic source. Therefore, the DR manufactured in this way
In AM, the amount of charged organic substances in the interlayer insulating film is reduced, so that when a voltage is applied to the interlayer insulating film formed in contact with the element isolation region, carriers (organic substances transfer charges) in the interlayer insulating film. (Which is caused by being carried) can be prevented from deteriorating device characteristics such as conduction of an element which has been separated at a low voltage. In particular, the effect of the present invention is great in a flash memory in which a condition in which a voltage value for conducting between element isolation regions is high is desirable.

Although the BPSG film 5 is hygroscopic, the heat treatment reduces the hygroscopicity, so that the film quality of the BPSG film 5 can be maintained in the same manner as when the film was formed. Further, the effect can be expected in terms of flattening the interlayer insulating film.

Further, if a heat treatment is performed in the same device after forming the interlayer insulating film, the film is not exposed to the outside air.
The processing time can be shortened without lowering the film quality.

The present invention is not limited to the above embodiment,
For example, it may be changed as shown below. The type of the interlayer insulating film, the method of forming the same, and the thickness of the formed film are not limited to those in the above embodiment.

Further, the material for forming the interlayer insulating film is not limited to the above-described embodiment, but may be trimethyl phosphate (PO (CH ₃
O) It is sufficient if organic substances such as ₃ are included. The atmosphere at the time of the heat treatment for removing organic substances from the insulating film is not limited to the above embodiment, and may be an oxidizing atmosphere or a steam atmosphere diluted with an inert gas under reduced pressure. However, the partial pressure of oxygen contained in the atmosphere is less than 760 Torr, preferably 20
It may be 0 to 400 Torr. Although the present invention has been described by taking a DRAM as an example, the present invention can be applied to a semiconductor device having a multi-layer device structure, and the effect can be improved.

[0027]

Since the present invention is configured as described above, it is possible to prevent a decrease in device characteristics of a semiconductor device having a multilayer device structure.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing a step in a method for manufacturing a semiconductor device according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view illustrating a step in a method for manufacturing a semiconductor device according to an embodiment of the present invention.

FIG. 3 shows a result of a heat treatment performed after depositing a BPSG film on the wiring of the polycrystalline Si layer in the embodiment of the present invention.
Diagram showing the relationship of the amount of organic matter contained in the oxidation amount and the BPSG film in the wiring of the polycrystalline Si layer in the case of changing the ₂ partial pressure.

FIG. 4 shows a relationship between applied voltages when an inversion layer is formed under a field oxide film in a BPSG film having different conditions at the time of film formation on a semiconductor substrate having two N-type diffusion layers separated by an element isolation region. FIG.

[Explanation of symbols]

 1 P-type Si substrate 2 Thermal oxide film 3 N-type diffusion layer 4a First polycrystalline Si layer 4b Second polycrystalline Si layer 4c Third polycrystalline Si layer 5 BPSG film 6 Contact hole 7 Tungsten silicide layer 8 Al Wiring 9 Plasma SiN layer

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H01L 21/312-21/318 H01L 21/31

Claims (5)

(57) [Claims] A step of depositing an insulating film on a semiconductor substrate using an organic source gas; and
Performing a heat treatment under an oxygen partial pressure of 200 to 400 Torr. 2. The method according to claim 1, wherein said heat treatment is performed at 400 ° C. or higher. 3. The method according to claim 1, wherein the atmosphere during the heat treatment is an oxidizing atmosphere diluted with an inert gas. 4. The organic source gas includes tetraethoxysilane (TEOS; Si (C ₂ H ₅ O) ₄ ), trimethyl borate (TMB; B (CH ₃ ) ₃ ), and trimethyl phosphate (T
2. The method for manufacturing a semiconductor device according to claim 1, wherein the method is any one of MP; PO (CH ₃ O) ₃ ). 5. The method according to claim 1, wherein an element isolation region or a wiring exists under the insulating film.