JPS62235739A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To form a contact diffused layer without stopping up a fine contact hole while sufficiently flattening the surface of a substrate by a method wherein the first and the second boron phosphorus silicide glass films are deposited on an insulating film deposited on the surface of a semiconductor device to be flattened by heat-treatment and then the contact hole is made to be heat- heated. CONSTITUTION:An oxide film 2, a gate oxide film 3, a polycrystalline silicon gate layer 4 and diffused layers 5 are formed on a silicon substrate 1 and then a silicon nitride film 6 is deposited on the overall surface of silicon substrate 1. Next, the first BSG film 7 in 2 weight % of boron concentration, 3 weight W of phosphorus concentration and 300 Angstrom in thickness is deposited on the silicon nitride film 6. Successively, the second BSG film 8 in 3 weight % of boron concentration, 5 weight % of phosphorus concentration and 500 Angstrom in thickness is deposited on the first BSG film 7 to be heat-treated for baking shrinkage, and flowing. Then, a contact hole is made by etching process using a photoresist as a mask for heat-treatment. Finally, after removing another oxide film formed on the exposed silicon surface during the heat-treatment, aluminium interconnections 9 are formed.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a semiconductor device, and particularly to a method for manufacturing a semiconductor device having a boron phosphosilicate glass (hereinafter abbreviated as BPSG) film on its surface.

Conventional technology Melting of phosphosilicate glass (hereinafter abbreviated as PSG)
Flattening by reflow) has been done for a long time, but
Because the PSG glue flow temperature is as high as 1000°C or more, this processing step increases the depth of impurity diffusion in the source and drain diffusion layers of MO8 type devices, for example, and is difficult to use in ultra-LSI devices with channel lengths of 2 μm or less. It is difficult to achieve the necessary precision control of short channel lengths.

On the other hand, by increasing the phosphorus concentration of PSG, the PSG adhesive flow temperature can be lowered, but increasing the phosphorus concentration has disadvantages such as lowering the reliability of the semiconductor device.

As a method that can solve these problems, in recent years, BPSG, which melts (flows) even at low temperatures of 3''-/ below 1000° C., has been attracting attention in place of PSG.

The manufacturing process of an n-channel MO8 type semiconductor device using the conventional BPSG flow will be explained with reference to FIG. 2 a'-e.As shown in FIG. (LOCO8) Membrane 2. Gate oxide film 3. Polycrystalline silicon gate layer 4. A diffusion layer 6 is formed, and a silicon nitride film 6 is further deposited over the entire surface of the substrate.

Next, as shown in Figure 2, for example, a boron concentration of 3% by weight,
A BPSG film 7 with a quadruple phosphorus concentration layer is deposited, and heat treatment (flow) is performed at 900° C. for 60 minutes in oxygen gas to bake the BPSG film. 7 Osufin as continued (
Heat treatment is performed at 950° C. for 10 minutes in oxygen gas containing PH3). This heat treatment melts the BPSG film 7 again (
At the same time, since heavy metals and N4 are ring-gettered, the reliability of semiconductor device characteristics is improved.

Furthermore, since phosphorus is thermally diffused deeply into the silicon substrate within the contact hole, leakage current at the contact portion due to spikes caused by alloying the aluminum electrode and the silicon substrate is also suppressed.

Thereafter, as shown in FIG. 2e, the oxide film formed on the exposed silicon surface is removed in a reflow step, and finally an aluminum wiring 9 is formed to complete an n-channel MO8 type transistor.

Problems to be Solved by the Invention However, in this case, fine contact holes formed in the BPSG film often disappear due to melting of the BPSG during heat treatment in the reflow step. Although it is possible to prevent contact holes from disappearing by lowering the boron concentration and phosphorus concentration of the BPSG film and suppressing the degree of reflow, the BPSG film cannot be sufficiently planarized in the flow process. On the other hand, in order to suppress the BPSG film glue flow,
If the heat treatment temperature or heat treatment time in the 01 step is lowered, the ring getter effect of heavy metals etc. will be reduced, causing a problem that the characteristics of the semiconductor element will deteriorate.

Means for Solving the Problems 6.7 In order to solve the above problems, the present invention provides a step of depositing an insulating film on the surface of a desired semiconductor device formed on a semiconductor substrate, and a step of depositing the insulating film on the surface of a desired semiconductor device formed on a semiconductor substrate. a step of depositing a first boronphosphosilicate glass film on the boronphosphosilicate glass film; a step of depositing a second boronphosphosilicate glass film having a different composition ratio from the boronphosphosilicate glass on the first boronphosphosilicate glass film; flattening the first and second boron phosphosilicate glasses by heat treatment; forming a contact hole penetrating the first and second boron phosphosilicate glass films and the insulating film; Provided is a method for manufacturing a semiconductor device, comprising the step of heat-treating the semiconductor substrate in a gas atmosphere containing impurities of the substrate. According to the above means, since the boron/phosphorus concentration of the second BPSG film is high, the BPSG film can be made sufficiently flat in one flow process. In the first reflow process, even without changing the heat treatment conditions, the boron and phosphorous concentration of the first BPSG film is low, so melting of the BPSG film at the bottom of the contact hole is suppressed and the BPSG
Fine contact holes opened in the film do not disappear.

In addition, the second BPSG film at the upper end of the contact hole is easily melted during the flow process, and a suitable slope can be obtained on the side wall of the upper end of the contact hole.

EXAMPLE An example of the method for manufacturing an MO8 type semiconductor integrated circuit according to the present invention will be described below. For the sake of simplicity, the description will be made with reference to FIG. 1, which shows an enlarged view of one MO8 type transistor section.

A sample having a crystalline silicon gate layer 4 and a diffusion layer 6 formed within the substrate 1 is coated with a film thickness of, for example, 10 mm over the entire surface of the substrate.
A silicon nitride film 6 of 00A is deposited.

Next, as shown in Figure 1, the boron concentration is 2 weight. Subsequently, a second BPSG film 8 having a boron concentration of 3% by weight, a phosphorus concentration of 7%-5% by weight, and a thickness of 5000 is deposited on the first BPSG film.

After this, as shown in FIG. 1C, the first and second BPSG
Heat treatment is performed at 900'C for 60 minutes in oxygen gas for the purpose of baking and melting (flowing) the films 7 and 8. next,
As shown in FIG. 1d, etching is performed using a photoresist as a mask to form a contact hole. Then, as shown in FIG. 1e, in order to melt the first and second BPSG films 7 and 802 times and form a contact diffusion layer, 950'
Heat treatment at C for 10 minutes. During this heat treatment process, an oxide film is formed on the exposed silicon surface, so after removing this oxide film, aluminum wiring 9 is formed. With the above steps, an n-channel MO8 type transistor is completed.

In the embodiments described above, the second BPSG film is deposited with a higher concentration of boron and phosphorus than in the conventional example, so that even if the film thickness is reduced compared to the conventional example, it can be sufficiently flattened in one flow process.

On the other hand, since the first BPSG film has a low concentration of boron and phosphorus, melting can be suppressed in one flow process, but it is effective in preventing the disappearance of fine contact holes in one reflow process. Further, in the reflow step, the second BPSG is easily melted, and an appropriate slope can be obtained at the upper end side wall of the contact hole.

Although the present invention has been described by exemplifying the manufacture of an MO8 type integrated circuit, the present invention can be applied to all semiconductor devices requiring reflow of a BPSG film. In addition, although the example was explained using a BPSG film with a two-layer structure, it is also possible to use a BPS film with a three-layer structure or more.
A similar effect can be obtained by forming a distribution of boron or phosphorus concentration in the thickness direction of the G film or BPSG film.

Effects of the Invention According to the present invention, a BPSG film is used to make the substrate surface sufficiently flat, without eliminating even minute contact holes.
A contact diffusion layer can be formed. As described above, the present invention can eliminate inconveniences such as the disappearance of contact holes caused by conventional melting heat treatment of BPSG films, and greatly contributes to the production of highly integrated semiconductor devices.

Ichino to 9

[Brief explanation of drawings]

FIGS. 1A to 1E are cross-sectional views illustrating an embodiment of the present invention, and FIGS. 2A to 2E are cross-sectional views illustrating a conventional technique. 1...Silicon substrate, 2...LOCO8
Oxide film, 3...Gate oxide film, 4...
polycrystalline silicon gate layer, 6...diffusion layer, 6.
・・Silicon nitride film, 7゜8・・・・・・BPSG
Film, 9... Aluminum wiring. Name of agent: Patent attorney Toshio Nakao and 1 other person1-
--Sisocon 1-8η 2~LOCO5 drama (臘3---1-1- ・! 8--One side 2 ・ 1 Figure 9---Aluminum; Tsu Afl Otomi Otomi-βIδ prayer

Claims (2)

[Claims] (1) Depositing an insulating film on the surface of a desired semiconductor device formed on a semiconductor substrate; depositing a first boron phosphosilicate glass film on the insulating film;
depositing a second boronphosphosilicate glass film having a different composition ratio from the first boronphosphosilicate glass on the boronphosphosilicate glass film, and flattening the first and second boronphosphosilicate glasses by heat treatment. a step of opening a contact hole penetrating the first and second boron phosphosilicate glass films and the insulating film;
A method for manufacturing a semiconductor device, comprising the step of heat-treating the semiconductor substrate in a gas atmosphere containing impurities. (2) The method for manufacturing a semiconductor device according to claim 1, wherein the boron and phosphorus concentrations of the second boronphosphosilicate glass are higher than those of the first boronphosphosilicate glass.