JPH04324629A - Working method of silicate glass film - Google Patents

Abstract

PURPOSE:To facilitate the control of a working shape when a contact hole is formed in a silicate glass film, or a silicate glass film is heat-treated to be fluidized. CONSTITUTION:A BPSG(boron phosphorus silicate glass) film 16 is formed on the substrate 10 via an insulating film 14 and the like. Said BPSG film 16 is formed by using CVD method, ion implantation method, etc., in the manner in which the concentration of admixture like boron and phosphorus become high in the upper part. When a contact hole CH is formed by selective etching, the aperture size of the contact hole CH is increased, because the etching rate is high in the upper part of the BPSG film 16. After that, when heat treatment is performed to fluidize the BPSG film 16, the vicinity of the aperture end edge E of the contact hole CH is rounded, and the corresponding part S with a step-difference is smoothed.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention relates to boron phosphosilicate glass (Boro-
Regarding silicate glass film processing methods such as Phospho-Silicate-Glass (hereinafter abbreviated as BPSG), silicic acid is By adding additives such as boron and phosphorus into the glass film in advance so that the concentration becomes higher toward the top, the processed shape can be easily controlled.

0002

[Prior Art] Conventionally, when forming wiring for LSI etc.,
BPS as an insulating film between wiring layers or a base insulating film for wiring layers
It is known to use a G film. It is also known to heat-treat the BPSG film in order to fluidize it in order to alleviate or smooth the steps caused by the insulating film, wiring, etc. formed on the semiconductor substrate (for example, in the Monthly Semiconductor
or World, September 1987 issue, No. 150-1
(See page 64).

As an interlayer insulating film, phosphosilicate glass (
It has also been proposed to use a Phospho-Silicate-Glass (hereinafter abbreviated as PSG) film. However, the PSG film has a softening temperature of 95°C, which causes viscous flow.
Since the temperature is as high as 0° C. or more, conductivity type determining impurities are likely to redistribute within the substrate during heat treatment, which may lead to fluctuations or deterioration of device characteristics. On the other hand, BPSG film has a low softening temperature of 900°C or less, so there is less risk of characteristic fluctuations.
For example, it has come to be used in LSIs having fine elements of 1 μm or less.

0004

[Problem to be Solved by the Invention] When using a BPSG film as an interlayer insulating film or a base insulating film, the film quality and softening temperature vary greatly depending on the concentration of boron and phosphorus in the film, so it is difficult to control the processing shape. There is a point. Such problems will be explained with reference to FIGS. 9 to 15.

In the step shown in FIG. 9, an insulating film 14 made of SiO2 or the like is formed on the surface of the semiconductor substrate 10 to cover a step formation 12 such as an insulating film or a stack of an insulating film and a wiring layer. After forming the BPSG film 16 covering the insulating film 14, the film 1 is selectively etched using the resist layer RS as a mask.
Contact holes CH are formed in 6 and 14.

Next, in the process shown in FIG.
Heat treatment is performed to fluidize the material. As a result, the portion near the opening edge E of the contact hole CH is rounded, and the step corresponding portion S is smoothed. However, if the concentration of boron or phosphorus in the BPSG film 16 is too high or the heat treatment temperature is too high, the BPSG film 16 as a whole becomes excessively fluid. Therefore, as shown in FIG. 10, for example, a portion near the opening edge E of the contact hole CH largely protrudes into the hole CH, resulting in an overhang state.

After this, in the process shown in FIG. 11, a wiring layer 18 of Al alloy or the like is formed. However, when the vicinity of the opening edge E of the contact hole CH is in an overhang state as described above, the coverage of the wiring material is not good due to the step of the contact hole, resulting in disconnection of the wiring layer 18 and reliability. There is an inconvenience that leads to a decline in sexuality.

On the other hand, if the concentration of boron or phosphorus in the BPSG film 16 is too low or the heat treatment temperature is too low, the BPS
The flow of the G film 16 becomes insufficient. For this reason, as shown in FIG. 12, for example, although the portion near the opening edge E of the contact hole CH does not overhang into the hole CH, sufficient roundness cannot be obtained near the opening edge E, and there is a step. In the corresponding portion S, sufficient smoothness cannot be obtained. Therefore, there is an inconvenience that the coverage of the wiring layer 18 deteriorates at the contact hole step and the step corresponding portion S.

The process shown in FIG. 10 also has the problem that self-doping and self-CVD (chemical vapor deposition) occur. Self-doping is
As shown in FIG. 13, this is a phenomenon in which boron B and phosphorus P in the BPSG film 16 diffuse outward during heat treatment, and some of them are doped into the semiconductor surface at the bottom of the contact hole CH. Deterioration of electrical characteristics, such as an increase in

Further, in self-CVD, as shown in FIG. 14, boron B and phosphorus P diffused outward from the BPSG film 16 are deposited on the inner wall of the contact hole CH, resulting in a rock sugar-like deposit D.
This is a phenomenon that causes P, which causes defects such as contact open.

One possible method for suppressing self-doping and self-CVD is to form the insulating film 14 thick and the BPSG film 16 thin, as shown in FIG. However, in this method, even if the BPSG film 16 is fluidized, sufficient roundness cannot be obtained in the vicinity of the opening edge E of the contact hole CH because the film 16 is thin, and sufficient smoothness cannot be obtained in the step corresponding portion S. I can't do it. Therefore, there is an inconvenience that the coverage of the wiring layer 18 deteriorates at the contact hole step and the step corresponding portion S.

[0012] An object of the present invention is to be able to easily control the processed shape and to avoid self-doping and self-CV.
An object of the present invention is to provide a novel silicate glass film processing method that can suppress D.

[0013]

[Means for Solving the Problems] The first method of processing a silicate glass film according to the present invention includes the steps of preparing a substrate having a contact portion on one main surface, and increasing the concentration of an etching accelerating additive toward the upper part. A step of forming a silicate glass film containing a high concentration on the one main surface to cover the contacted portion, and selectively etching the glass film to form a contact hole corresponding to the contacted portion in the glass. The method includes a step of forming the film into a film.

[0014] In such a processing method, an additive having heat fluidization promoting properties may be used as the additive, and the glass film may be heat-treated to fluidize the glass film after the contact hole is formed.

Further, the second silicate glass film processing method according to the present invention includes a step of preparing a substrate having a stepped portion on one main surface, and containing an additive having a heating fluidity promoting property at a higher concentration toward the upper part. The method includes a step of forming a silicate glass film on the one main surface to cover the stepped portion, and a step of heat-treating the glass film to fluidize it.

In the present invention, as the additive, one or more elements selected from groups IIIa, IVa, and Va in the periodic table, such as boron, phosphorus, arsenic, lead, and germanium, are used. be able to. Further, the contacted portion may be a part of the semiconductor surface when the substrate is made of a semiconductor, or may be a part of the wiring when wiring is formed on the substrate. Furthermore, the silicate glass film may be either a single-layer film or a multi-layer film; in the case of a single-layer film, the concentration of the additive is higher toward the upper surface, and in the case of a multi-layer film, the concentration of the additive is higher toward the upper layer. can do.

[0017]

[Operation] According to the first silicate glass film processing method described above, the etch rate is high in the upper part of the silicate glass film due to the high concentration of additives, so the opening size of the contact hole is increased outward. It will gradually increase towards Therefore, coverage of the contact hole step with the wiring material is improved.

[0018] Furthermore, after forming the contact hole, heat treatment is performed to fluidize the silicate glass film, so that the opening edge of the contact hole becomes smooth and rounded, further improving coverage at the step of the contact hole. be done. In this case, since the concentration of the additive is higher in the upper part of the silicate glass film than in the lower part, the entire film is not fluidized even if the heat treatment temperature is high, and overhang is less likely to occur. In addition, fluidization does not progress much below the middle part of the membrane, so
The initial processed shape can be maintained at the lower part of the contact hole. Moreover, since the concentration of additives is lower at the bottom of the silicate glass film, the amount of additives that diffuse out from the bottom of the film into the contact hole during heat treatment is small, preventing self-doping and self-CVD. suppressed.

According to the second silicate glass film processing method described above, the silicate glass film is smoothed by flowing. In this case, the concentration of additives is higher in the upper part of the silicate glass film than in the lower part, so even if the heat treatment temperature is low, fluidization progresses in the upper part of the silicate glass film, especially in areas corresponding to steps. Achieves excellent smoothness.

[0020]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIGS. 1 to 5 show an embodiment in which the present invention is applied to a wiring forming process, and steps (1) to (5) corresponding to each figure will be explained in sequence.

(1) An insulating film 14 made of non-doped (or lightly doped) SiO2 or the like is formed on the upper surface of a semiconductor substrate 10 made of silicon or the like by a CVD method or the like, covering the step formation 12.
form. The step formation 12 is, for example, a MOS type LSI.
In this case, it may be a field insulating film or a stack of a gate insulating film and a gate electrode layer. The insulating film 14 is for preventing additives such as boron and phosphorus from diffusing into the lower layer, and is preferably thinner. Insulating film 1
By making 4 thinner, the thickness of the BPSG film, which will be described later, can be increased, and the inconvenience described with reference to FIG. 15 can be eliminated.

After forming the insulating film 14, an insulating film 16A made of PSG, BSG (borosilicate glass) or non-doped SiO2 is formed covering the insulating film 14 by CVD or the like.

(2) Next, the insulating film 16A is converted into the BPSG film 16 by implanting impurity ions such as B+, BF2+, P+, etc. into the entire insulating film 16A. In this case, the concentration of boron and/or phosphorus in the BPSG film 16 is set to gradually increase as it approaches the surface by adjusting the accelerating voltage. For example, when the insulating film 16A is made of non-doped SiO2, both boron ions and phosphorus ions are implanted, but the concentration gradient may be limited to only one of the ions. Further, when the insulating film 16A is made of PSG, only boron ions may be implanted and phosphorus ions may be implanted without implantation. Furthermore, when the insulating film 16A is made of BSG, only phosphorus ions may be implanted and boron ions may be omitted. B.P.
Near the top surface of the SG film 16, the boron concentration is about 1 to
6 wt%, the phosphorus concentration can be about 3-10 wt%. Note that arsenic ions can also be implanted.

(3) Next, after forming a resist layer RS having an opening corresponding to a contact area such as a part of the substrate surface on the BPSG film 16, a dry etching process is performed using this resist layer RS as a mask. selectively etches the BPSG film 16 and the insulating film 14 thereunder to form a contact hole CH.
form. At this time, since the BPSG film 16 has a higher dopant concentration near the surface and therefore a higher etch rate, the contact hole CH is formed so that the opening size gradually increases outward. After this, the resist layer RS is removed.

(4) Next, heat treatment is performed to fluidize the BPSG film 16. As a result, the portion near the opening edge E of the contact hole CH is rounded, and the step corresponding portion S is smoothed.

During the heat treatment, the lower part of the BPSG film 16 tends to have insufficient flow due to the low additive concentration, so as shown in FIG.
Overhang as shown by 0 is less likely to occur, and moreover, the initial processed shape shown in FIG. 3 is maintained near the bottom of the contact hole CH. In addition, the amount of additives that diffuse out from the lower part of the BPSG film 16 into the contact hole during heat treatment is small, and the additives that diffuse out from the upper part of the BPSG film 16 are carried away by the gas flow, resulting in self-doping. and self-CVD will be suppressed.

(5) Next, a wiring layer 18 is formed by depositing a wiring material such as Al or Al alloy on the upper surface of the substrate and patterning it. In this case, as shown in FIG. 4, the contact hole CH gradually increases in size outward and becomes rounded near the opening edge E, and the BPSG film 16 is adapted to accommodate the step. Since the portion S is sufficiently smoothed, the wiring layer 18 exhibits good coverage in both the contact hole step and the step corresponding portion S.

FIGS. 6 to 8 show another embodiment of the present invention, and this embodiment is characterized in that the BPSG film is formed as a multilayer film.

In the process shown in FIG. 6, N2 (50 slm), O2 (7 slm), SiH4 (6 slm), and
The insulating film 14 made of PSG was formed by introducing PH3 (2.5 sccm) and PH3 (2.5 sccm). Membrane 1
The thickness of No. 4 was made thin enough to prevent self-doping.

Subsequently, B2H6 was introduced into the reaction chamber to form the first BPSG layer 16a. BPSG
The gas component state just before the completion of the formation of the layer 16a is SiH4 (
53.75sccm), PH3 (5.0sccm), B
2H6 (3.75sccm), O2 (7slm), N2
(50slm). In addition, the introduction conditions were such that the ratio of O2 to hydride remained unchanged.
H4+PH3+B2H6=constant, and O2 and N2 were always constant. As a result, the BPSG layer 16a
The boron concentration therein was about 2 wt%, and the phosphorus concentration was about 4 wt%.

Thereafter, in the same reaction chamber, the second BPSG layer 16 is formed by continuing film formation while increasing the flow rates of PH3 and B2H6 and decreasing the flow rate of SiH4.
b was formed. The gas component state just before the completion of the formation of the BPSG layer 16b is SiH4 (46.25 sccm), PH3
(8.75sccm), B2H6 (7.5sccm),
O2 (7slm), N2 (50slm). As a result, a BPSG layer 16b was obtained in which the boron and phosphorus concentrations increased closer to the surface, and the boron concentration and phosphorus concentration near the surface were approximately 4 wt% and 6 wt%, respectively. Note that arsenic doping is also possible by using AsH3 or the like.

Next, in the step of FIG. 7, the BPSG layer 16a
FIG.
A contact hole CH was formed in the same manner as described above. As a result, a contact hole CH whose opening size increases toward the outside as shown in FIG. 7 was obtained.

Thereafter, in the step shown in FIG. 8, the BPSG film 16 was heat-treated in the same manner as described in FIG. 4 to fluidize it. As a result, the opening edge E of the contact hole CH was rounded, and the step corresponding portion S was smoothed. Then, a wiring layer 18 was formed on the BPSG film 16 on the upper surface of the substrate in FIG. 8 in the same manner as described with reference to FIG. 5, and good coverage was obtained.

Therefore, the embodiments shown in FIGS.
The same effects as in Examples 1 to 5 can be obtained. In addition, Figure 6
In the process, the BPSG layer 16a is
If the additive concentration is higher than b, there may be no concentration gradient. Furthermore, it is also possible to form a third BPSG layer with a higher dopant concentration on the BPSG layer 16b, or to repeat the formation of the BPSG layer with increasing concentration. Furthermore, an ion implantation method may be used to form an additive concentration gradient each time the BPSG layer 16a or 16b is formed.

It should be noted that the present invention is not limited to the above embodiments, but can be implemented in various modified forms. For example, the film forming method is not limited to normal pressure CVD, but may also be low pressure CVD, plasma CVD, reactive sputtering, or the like. Further, the present invention is applicable not only to BPSG films but also to PSG films, BSG films, etc.

[0036]

As described above, according to the present invention, by setting the concentration of additives such as boron and phosphorus in the silicate glass film to be higher toward the upper part, the contact hole shape or fluidization shape can be improved. Since control is facilitated, highly reliable wiring can be formed with high yield in the wiring formation process of LSI.

[Brief explanation of the drawing]

[Figure 1] ~

FIG. 5 is a cross-sectional view of a substrate showing an embodiment in which the present invention is applied to a wiring formation process.

[Figure 6] ~

FIG. 8 is a sectional view of a substrate showing another embodiment of the invention.

[Figure 9] ~

FIG. 15 is a cross-sectional view of a substrate for explaining the problems of the prior art.

[Explanation of symbols]

10: semiconductor substrate, 12: step formation, 14: insulating film,
16: BPSG film, 18: wiring layer, CH: contact hole.

Claims (3)

[Claims] 1. (a) preparing a substrate having a contact portion on one main surface; and (b) applying a silicate glass film containing an etching-promoting additive at a higher concentration toward the upper part of the contact portion; and (c) forming a contact hole corresponding to the contact portion in the glass film by selectively etching the glass film. Acid glass membrane processing method. 2. The method for processing a silicate glass film according to claim 1, wherein an additive having heat fluidization promoting properties is used as the additive, and the glass film is heat-treated to fluidize the glass film after forming the contact hole. . 3. (a) preparing a substrate having a stepped portion on one main surface; and (b) applying a silicate glass film containing a heat-flow promoting additive at a higher concentration toward the upper portion of the stepped portion; (c) a step of heat-treating the glass film to fluidize the glass film.