JPS62183142A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To form a contact diffused layer without erasing a fine contact hole by melting (flowing) a BPAG film in steam before opening the hole to sufficiently flatten the surface of a substrate. CONSTITUTION:An LOCOS film 2 formed on a silicon substrate 1, a gate oxide film 3 and a polycrystalline silicon gate layer 4 are formed. A silicon nitride film 6 is deposited on the entire substrate surface of a sample formed with a diffused layer 5 in the substrate 1 at both sides of the layer 4. Then, a BPSG film 7 is deposited on the film 6. Subsequently, a heat treatment is executed in steam for the purpose of shrink-fitting and melting the film 7. Thereafter, with a photoresist as a mask a contact hole 9 is opened by etching. Then, a heat treatment is performed in an atmosphere including phosphine (PH3) to melt second the film 7 and to form the contact diffused layer.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a method for manufacturing a semiconductor device, and more particularly to a method for flattening a substrate surface having a step structure by coating with a boron phosphosilicate glass (hereinafter abbreviated as BPSG) film.

Conventional technology Flattening by melting (reflow) phosphosilicate glass (hereinafter abbreviated as PSG) has been conventionally performed, but PSG
Because the G glue flow temperature is as high as 1oQo°C or more, this process increases the depth of impurity diffusion in the source and drain diffusion layers of MO3 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, the PSG adhesive flow temperature can be lowered by increasing the phosphorus concentration of PSG, but increasing the phosphorus concentration has disadvantages such as lowering the reliability of the semiconductor device. In recent years, as a method to solve these problems, BPS, which melts even at low temperatures below 1000°C, has been introduced instead of PSG.
G is attracting attention.

The manufacturing process of a channel MO3 type semiconductor device employing a conventional BPSG flow will be described with reference to FIGS. First, as shown in FIG. 2(-), a selective oxidation (LOCO3) film 2. Gate oxide film 3. Polycrystalline silicon gate layer 4. A diffusion layer 5 is formed, and a silicon nitride film 6 is further deposited over the entire surface of the substrate.

Next, as shown in FIG. 2(b) K, a BPSG film 7 with, for example, a boron concentration of 3% by weight and a phosphorus concentration of 4% by weight is deposited.
In order to bake the G film, heat treatment (flow) is performed at 900° C. for 60 minutes in oxygen gas. Subsequently, as shown in FIG. 2(c), contact holes 9 are formed in the BPSG film 7 and the silicon nitride film 6. Next, as shown in Fig. 2(d)K, in oxygen gas containing phosphine (PH3), 10
Apply heat treatment for 1 minute. Through this heat treatment, the BPSG film 7 can be remelted (reflowed) and flattened, and at the same time, heavy metals, Na, etc. are removed as phosphorus, improving the reliability of the semiconductor device characteristics.In addition, the BPSG film 7 can be re-melted (reflowed) and flattened, and at the same time, the reliability of the semiconductor device characteristics is improved because heavy metals, Na, etc. are phosphorus-gettered. Because of thermal diffusion, if the diffusion is shallow, the occurrence of leakage current at the contact portion due to junction breakdown due to spikes caused by alloying of the aluminum electrode and silicon substrate during aluminum wiring is also suppressed.

Thereafter, as shown in FIG. 2(a), the oxide film formed on the exposed silicon surface is removed in a reflow process, and finally an aluminum wiring 8 is formed to complete an n-channel MO3 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.

Either it is possible to prevent the contact hole from disappearing by lowering the boron concentration or phosphorus concentration of the BPSG film and suppressing the degree of reflow, or the BPSG film cannot be sufficiently planarized in a single flow process. On the other hand, when lowering the heat treatment temperature or shortening the heat treatment time in step 70 in order to suppress the flow of the BPSG film, the problem arises that the ring getter effect of heavy metals etc. is reduced and the characteristics of the semiconductor element are deteriorated.

Means for Solving the Problems In order to solve the above problems, the present invention provides a step of depositing a silicon nitride film on a desired region of a semiconductor device, and a step of depositing a boron phosphosilicate glass film on the silicon nitride film. and a step of heat treating the boron phosphosilicate glass film with water vapor, a step of forming contact holes in the boron phosphosilicate glass film and the silicon nitride film, and a step of heat treating the boron phosphosilicate glass film in a gas atmosphere containing a phosphorus compound. A method for manufacturing a semiconductor device with features is provided.

Effect According to the above means, sufficient flattening is possible because the flow of the BPSG film is in a water vapor atmosphere, and during the heat treatment of the flow, boron (B) and phosphorus (P) (particularly B) are removed from the outside. As the diffusion progresses, B and P in BPSG (
In particular, B) the concentration decreases. Therefore, without changing the heat treatment conditions in step 70, the melting of the BPSG film is suppressed, the fine contact holes opened in the BPSG film do not disappear, and an appropriate flow shape can be obtained at the upper end of the contact hole. It will be done.

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 MO3 type transistor section.

First, as shown in Figure 1), a LOGO8 film 2. is formed on a silicon substrate 1. The gate oxide film 3 has a polycrystalline silicon gate layer 4, and further has a polycrystalline silicon gate layer 4.
For example, silicon nitride M6 having a thickness of 1000 Å is deposited over the entire substrate surface on a sample in which diffusion layers 6 are formed in the substrate 1 on both sides of the substrate. Next, as shown in Figure 1 (b), boron concentration 3
Weight%, phosphorus concentration 4% by weight, film thickness 8000A+7) BPS
A G film 7 is deposited on the silicon nitride film 6.

Following this, as shown in FIG. 1(C)K, the BPSG film 7 is
For the purpose of hardening and melting (flow), heat treatment is performed in steam at 900''C for 60 minutes.

Thereafter, as shown in FIG. 1(d), etching is performed using a photoresist as a mask to open a contact hole 9. Next, as shown in Figure 1 (6m) K, for the second melting (reflow) of the BPSG film 70 and the formation of a contact diffusion layer, it was heated at 960°C in an atmosphere containing phosphine (PH3).
Heat-treat for 10 minutes. During this heat treatment process, an oxide film is formed on the exposed silicon surface, so after removing the oxide film, the aluminum wiring 8 is formed. Above is n channel MO3
type transistor is completed.

In the above embodiment, since the BPSGi film is melted (flowed) in water vapor before forming the contact hole, even the BPSG film with low boron and phosphorus concentrations can be sufficiently flattened, and the water vapor heat treatment process In this case, the outward diffusion of boron progresses more than in the case of a dry oxygen gas atmosphere, so the B and P concentrations of the BPSG decrease after the flow ends. As a result, the melting of BPSG in one reflow process is moderately suppressed, so that fine contact holes do not disappear. BPSG
The present invention can resolve the contradictory conditions of film flattening, contact hole miniaturization, and contact diffusion layer formation.

Although the present invention has been explained by exemplifying the manufacture of MOS type integrated circuits, the present invention can be applied to all semiconductor devices requiring a BPSG film bonding flow.

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

[Brief explanation of drawings]

FIGS. 1(-) to 1(e) are process sectional views for explaining an embodiment of the present invention, and FIGS. 2(a) to 2(e) are process sectional views for explaining the prior art. 1...Silicon substrate, 2...LOCO
3 oxide film, 3... Gate oxide film, 4...
Polycrystalline silicon gate layer, 5...diffusion layer, 6...
...Silicon nitride film, 7...B P S
G film, 8... Aluminum wiring, 9...
・Contact hole. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
Figure 1 Figure 2 Figure 2

Claims (1)

[Claims] depositing a silicon nitride film on a desired region of a semiconductor device; depositing a boron phosphosilicate glass film on the silicon nitride film; heat-treating the boron phosphosilicate glass film in water vapor; A method for manufacturing a semiconductor device, comprising the steps of forming a contact hole in a glass film and the silicon nitride film, and performing heat treatment in a gas atmosphere containing a phosphorous compound.