JPS5968921A - Formation of thin film - Google Patents

Abstract

PURPOSE:To obtain a thin film with very low content of impurities by a method wherein a film forming chamber and pre-exhaust chamber are provided adiacent to each other and a door is provided between them and after a PSG film is formed on a lower surface of a quartz substrate placed in the film forming chamber by CVD method a semiconductor substrate placed in the pre-exhaust chamber is transferred into the film forming chamber and the PSG film is transferred onto the semiconductor substrate by plasma CVD method. CONSTITUTION:A plurality of semiconductor substrates 10 are put on a substrate holder 11 and placed in a pre-exhaust chamber 2 and a door 13 to an adjacent film forming chamber 1 is closed and the chamber 2 is exhausted by an exhaust pipe 12. On the other hand, a quartz substrate 3, the 1st substrate, is placed and a PSG film 14 is formed on a lower surface of the 1st substrate. Then the door 13 is opened and the holder 11 is transferred onto a parallel electrode 6 for plasma CVD placed below the substrate 3. Then Ar gas is introduced from an inlet 8 and a voltage is applied between a supporting electrode 4 in which a magnet is contained and a sputtering electrode 5 to drive Si, O and P atoms out by Ar ions and the PSG film 15 is formed on the substrate 10.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a method of forming a thin film in the manufacturing process of a semiconductor device.

Structures of conventional examples and their problems Semiconductor devices, for example, MO8LSI manufacturing Zl; thin films of insulators, semiconductors, or metals are formed several times in the process, and the method of forming them depends on the nature of the thin film. Or CVD method under reduced pressure (chemical vapor
(r deposition method), vacuum evaporation method, sputtering method, etc. are selected. For example, in the manufacturing process of MO8LSI (Si game), a 5102 film or a PSG (phosphosilicate glass) film is formed by CVD as an interlayer insulating film between the first layer wiring made of polycrystalline S1 and the second layer wiring made of A1. .

The SiO2 film and psG film formed by the CVD method have a low content of impurities such as heavy metals and alkali ions that adversely affect the characteristics of MO3LSI. This is because the CVD method uses highly purified reaction gases such as SiH+, 02, and PHs because gas purification is easy. On the other hand, since the GVD method forms a thin film at a normal temperature, for example, 450° C., this thin film has weak adhesion to the substrate and is insufficiently dense. Therefore, in order to strengthen the adhesion, make it dense, and have sufficient characteristics as an interlayer insulating film, it is necessary to perform heat treatment at a high temperature close to 1"OOO"C.

In order to form MOS transistors with fine dimensions as the density of LSIs continues to increase, it is necessary to reduce the junction depth of the source and drain. For example, M with a gate length of 1.5 μm
To form the OS) disk, it is necessary to make the junction depth of the source and drain region about 0.3 μm, and after adding B-i to the source and drain region by ion implantation, it is necessary to It is not possible to perform high-temperature heat treatment.

Therefore, a SiO2 film or a PSG film formed only by the C or VD method as an interlayer insulating film is insufficiently dense and is inferior in dielectric strength, impurity blocking ability, alkali ion capturing ability, etc. necessary for an interlayer insulating film.

The 5102 film and PSG film formed by the CVD method as an interlayer insulating film of a large scale LSI have poor stamp coverage on the lower wiring. For this reason, the thickness of the upper wiring formed on these 5102 films or PSG films may become smaller at the portions where they intersect with the lower wiring, the line width may become thinner during pattern formation using etching nog, or even breakage may occur. It also becomes more likely to occur. To solve this problem, we formed a PSG film containing a high concentration of phosphorus as an interlayer insulating film, and
A so-called reflow treatment was performed in which the material was heat-treated in an atmosphere containing . However, this 1000
Reflow processing, which is heat treatment at a high temperature of °C, cannot be performed to form shallow sources and drains/junctions as mentioned above, and therefore problems such as thinning or disconnection of upper wiring occur in high-density LSI manufacturing. It often occurs.

As described above, in the manufacturing process of high-density LSIs in which high-temperature heat treatment cannot be performed, interlayer insulating films formed by conventional CVD methods are a major cause of deterioration in manufacturing yield and reliability.

OBJECTS OF THE INVENTION An object of the present invention is to provide a method and a thin film forming apparatus for forming a thin film with a low content of impurities and sufficiently good characteristics without the need for heat treatment at high temperatures.

One of the methods for forming thin films constituting the invention is the spankling method. In this method, for example, Ar ions are accelerated in a high electric field and collided with a target to dissociate the atoms constituting the target and deposit them on, for example, a semiconductor substrate placed opposite the target, thereby forming a thin film.

The thin film forming method of the present invention includes forming a thin film on a first layer by the above-mentioned CVD method, and subsequently forming a thin film on a first layer on which this thin film is formed.
The method is characterized in that a thin film of a desired thickness is formed on the surface iA+ of a semiconductor substrate which is rotated around the substrate by a sputtering method using the substrate as a target.

As already mentioned, the l formed on the first substrate by the CVD method
The '4!7 membrane can sufficiently reduce the impurity content by supplying highly pure reaction gas once a month.

On the other hand, in the sputtering method, atoms dissociated from the target have commercial energy. This is because the high-energy Ar ions accelerated in a high electric field are ejected from the target surface, and the thin film formed by these high-energy atoms landing on the semiconductor substrate surface (semiconductor), (semiconductor) It has strong adhesion to the surface and is sufficiently dense even without high-temperature heat treatment.

Therefore, when forming a thin film with good LL characteristics by a sputtering method as described above, the present invention provides a first substrate on which a thin film with a low impurity content is formed by a CVD method, and furthermore, after this thin film is formed. It is used as a cugette facing a semiconductor substrate without being contaminated from the outside.

Description of examples An embodiment of the present invention will be described below.

A cross-sectional view of the thin film forming apparatus in this example is shown in FIG.

The thin film forming apparatus shown in FIG. 1 includes a film forming chamber 1 and a spare chamber. 11
- It has an air chamber 2. Inside the film forming chamber 1, there is a first substrate, for example, a quartz substrate 3, and a quartz substrate 3'f for holding and holding the same: a holder containing a heating device for heating and a magnet for accelerating electrons during sputtering. An electrode 4, a sputtering electrode 6, and a counter electrode 6 are provided, and furthermore, a reaction gas introduction pipe 7 for CVD, a mixed gas introduction pipe 8 for sputtering, and an exhaust pipe connected to an exhaust pump to exhaust the inside of the film forming chamber 1. A pipe 9 is connected.

The preliminary exhaust chamber 2 has a semiconductor substrate holder 11 on which a semiconductor substrate 10 is placed, and is connected to an exhaust pipe 12 leading to an exhaust pump. Further, a door 13 is provided on the partition wall of the film forming chamber 1 and the preliminary exhaust chamber 2, and when the door 13 is opened, the semiconductor substrate IC)'(1-1) is placed on the semiconductor substrate holder 11.
A conveyance device is also provided for conveying the gas from the preliminary exhaust gas 2 to the film forming chamber ivC or in the opposite direction.

Using this thin film forming apparatus, PS is applied to the surface of the semiconductor substrate 1o.
The case of forming a G film will be explained.

A plurality of semiconductor substrates 10 are mounted on a semiconductor substrate holder 11 and placed in the preliminary evacuation chamber 2. The door 13 is closed and the interior of the preliminary exhaust chamber 2 is exhausted by the exhaust pump connected to the exhaust pipe 12.

On the other hand, in the film forming chamber 1, a PSG film is formed on the surface of a quartz substrate 3, which is a first substrate, by the 4VD method.

1. The film forming chamber 1 is evacuated by an exhaust pump connected to an exhaust pipe 9 in a trench with a vacuum level of 1Q'1:orr, and during this time the quartz substrate 3 held by the holding electrode 4 is heated by the heating device of the holding electrode 4. It is heated to 5350'C. After that, from the reaction gas introduction pipe 7, the reaction gas SiH4,02,
PH5 is introduced and the degree of vacuum in the film forming chamber 1 is 10 Torr.
After stabilizing at r, high frequency power is applied between the counter electrode 6 and the holding type single pole 4. Reactive gas molecules are excited by high frequency power between the two electrodes, and reactions between the gases tend to occur. As a result, the quartz substrate 30 held by the holding electrode 4 and heated
5IH4 and 0 containing p-1 decomposed by PHs gas on the surface
A 5102 film, that is, a PSG film with a film thickness of 4 is formed by the reaction with 2. PSG film 1 film thickness 4 kink P
The flow rate of PH3 is controlled so that the amount of PH3 becomes, for example, 4 weight percent, and the reaction time, that is, the application time of high frequency power is controlled so that the film thickness becomes, for example, 1 μm (FIG. 1a).

At this time, the PSG film 1 formed on the surface of the quartz substrate 3 has a film thickness of 4
Because the temperature of the quartz substrate 3 during formation is as low as 360°C, the reaction gas 5IH4r 02 + is not dense but has a high density.
Since PHs is used and the temperature inside the film forming chamber 1 is as low as 350° C. or less, there is no contamination from the inner wall, the counter electrode 6, etc., and the content of impurities is sufficiently small.

When the residual gas is exhausted from the exhaust pipe 9 and the degree of vacuum in the film forming chamber 1 and the pre-evacuation chamber 2 become equal, the door 13 provided on the partition between these two spaces opens and the 10M4 substrate 1o is exposed to r+
The semiconductor substrate holder 11 placed in the z-position is transported from the pre-evacuation chamber 2 to the film formation chamber, and each semiconductor substrate 10 is placed so as to face each of the quartz substrates 3 below the holding electrode 4 .

Ar gas is introduced through the Ar gas inlet 8, and high frequency power is applied between the holding electrode 4, which has a built-in magnet, and the spacing mold 1-1j 50. At this time, substrate drilling is performed targeting the quartz substrate 3 on which the PSG film 1 film thickness 4 has been formed, and Si, O, which has formed the PSG film 1 film thickness 4
, P atoms are ejected by accelerated Ar ions,
The particles fly onto the surface of the semiconductor substrate 10 which faces the target, and the psG film 15 is again formed on the surface of the semiconductor substrate 1Q.

When the PSG film 15 with a desired film thickness of 0.5 μm, for example, is formed, high frequency power and Ar gas are emitted, and after the residual gas is exhausted from the exhaust port 9, the door 13 is opened and the semiconductor substrate 10 is placed. The semiconductor substrate holder 11 is transported from the film forming chamber 1 to the preliminary chamber 2Vc and taken out.

Using the method described above, the PSG film 1 is
6 is formed, the Si, O, and P atoms ejected from the quartz substrate 3, which is a cuget, have sufficiently high energy, so that the semiconductor substrate 1 on which the lower wiring is formed has a sufficiently high energy.
The PSG film 15 formed on the 00 surface has good coverage on the lower wiring and is dense enough to prevent moisture or impurities from entering from the outside. In addition, the concentration in one PSG film, which determines the gettering effect for alkali ions that degrade the characteristics of semiconductor devices, is CV.
By controlling the flow rate of PS (1, PH3) when forming the PS (1, film 14) on the surface of the quartz substrate 3 using the D method, it is possible to precisely control the temperature. When forming the PSG film 16 using a high-purity reaction gas, the temperature is low when forming the PSG film 16 using the CVD method or the spackling method, so impurities do not enter from the outside, and the PSG film 16 is The film 16 has a great feature of having a low content of impurities that adversely affect the characteristics of semiconductor devices.In this way, an interlayer insulating film with good characteristics can be formed without performing high-temperature heat treatment. In this embodiment, when forming the PSG film 15 on the surface of the quartz substrate 3 by the CVD method, the PSG film is also formed on the inner wall of the film forming chamber 1. Therefore, when a PSG film is later formed on the surface of the semiconductor substrate 1Q by a sputtering method, metal ions A and impurities can be prevented from coming out from the inner wall of the film forming chamber 1, so that the PSG film on which the semiconductor substrate 10 is formed is not contaminated. It also has the advantage of not causing any problems.

In the embodiment described above, the surface K of the quartz substrate 3 is
In order to form the PSG film 14, a plasma CVD method in which a reactive gas is excited with high frequency power is used, but a CVD method using a thermal decomposition reaction or an optical CVD method in which a reactive gas is excited with ultraviolet light is used. Also good. The spun thin film forming apparatus does not need to perform the CVD method and the spackling method in the same film forming chamber 1 as in the embodiment, and the quartz substrate 3 on which the PSG film 14 has been formed by the CVD method is transported to an adjacent chamber. There, ps is applied to the surface of the semiconductor substrate 10 using a spackle method.
A G film 16 may also be formed. Furthermore, if sufficient consideration is given to contamination from the outside, it is possible to form a PSG film on the surface of a quartz substrate by the CVN method, and then use this quartz substrate 3 as a target in another sputtering device to form a PSG film on the surface of the semiconductor substrate 11. 15 may be formed.

The above has described the method and apparatus for forming a PSG film used as an interlayer insulating film of a semiconductor device, but the manufacturing method of the present invention also has great effects when forming a high melting point metal thin film to form a gate electrode. have High-melting point metals such as MO have electrical resistance two orders of magnitude lower than polycrystalline Si, which is conventionally used as gate electrodes, and are therefore expected to be used as gate electrode materials for high-density, high-speed LSIs. However, when a thin film is formed by the spackling method, it is difficult to obtain a highly pure target, which makes it difficult to form a high melting point metal thin film with a low content of impurities such as alkali ions. This is a major obstacle to using high melting point metals as gate electrodes. Therefore, by using the thin film forming method of the present invention, a target having 9 films of high melting point metal with low impurity content can be easily obtained, and a high melting point metal thin film with low impurity content can be formed by the spackling method. high density,
A high-speed and highly reliable LSI can be manufactured with a high yield.

Effects of the invention: The content of impurities that adversely affect semiconductor devices is small;
Moreover, a dense thin film with sufficiently good properties can be formed without heat treatment at high temperatures.

[Brief explanation of the drawing]

1 and 2 are schematic cross-sectional views of a thin film forming apparatus for explaining the thin film forming method of the present invention. 3...Quartz substrate, 4...Holding type electrode when forming a thin film by CVD method or spackling method, 5... Electrode for spackling method , 6...
...Counter electrode when performing plasma G V D method, 10
Punching...Half ij:, L-body substrate, 14...Thin film formed on the surface of a quartz substrate by CVD method5.16...C11 film formed by sputtering method. @Figure 1 Figure 2

Claims (1)

[Claims] After forming a thin film on the surface of the substrate by vapor phase chemical deposition,
A method for forming a thin film, comprising forming a V'1J film of a predetermined thickness on a semiconductor substrate by a sputtering method using the substrate as a target.