JPH03154346A - Gettering - Google Patents

Abstract

PURPOSE:To prevent contaminants of a heavy metal from accumulating to the field of a distortion at the periphery of LOCOS by forming an element isolation region on a semiconductor substrate by means of selective oxidation and allowing impurities of the heavy metal to be absorbed into the internal imperfect layer of the semiconductor substrate by performing heat treatment. CONSTITUTION:Intrinsic gettering(IG) heat treatment is performed for a silicon wafer 1 and an internal imperfect layer 2 is formed. Then, a prescribed position is thermally oxidized so as to form a device region and a field oxide film 3 is formed. While heat treatment (annealing with N2) is performed in an atmosphere of nitrogen (N2), annealing with N2 makes N2 4 accumulate to an interface of SiO2/Si, i.e., the periphery of local oxidation of silicon (LOCOS). This prevents a heavy metal to be mixed in a device process afterwards from accumulating to the periphery of LOCOS and its metal is absorbed into an IG layer 2. This approach prevents contaminants of the heavy metal in a semiconductor device process from accumulating to the field of a distortion at the periphery of LOCOS.

Description

[Detailed Description of the Invention] [Summary] It relates to a gettering method, particularly in the production of semiconductor devices, in which heavy metal impurities are removed by LOGO5 (Local 0xi).
Regarding a gettering method that prevents heavy metal contamination during semiconductor device processing from accumulating in the strain field around the LOCO3 and absorbing it into the internal defect layer of the semiconductor wafer. A step of forming an element isolation region on a semiconductor substrate by selective oxidation with the aim of absorbing the heavy metal impurities into the internal defect layer of the semiconductor substrate while suppressing their accumulation in the periphery;
The composition shall include the following.

[Industrial application field]

The present invention relates to a gettering method, and particularly to a gettering method for removing heavy metal impurities from LOGO3 (Lo-ca) in the manufacture of semiconductor devices.
The present invention relates to a gettering method for preventing oxidation of 5 ilicon from accumulating around the oxidation of 5 ilicon.

[Conventional technology]

In gettering technology, which is a type of cleaning technology within silicon substrates in the manufacture of semiconductor devices, especially Fe
Intrinsic gettering (IG), which creates a gettering center inside a semiconductor wafer, has traditionally been used to deal with heavy metal contamination such as Cu, Ni, and Cr.
c Getlering) is effective. However, as semiconductor devices become more expensive, for example, between the field oxide film formed by thermal oxidation on the semiconductor substrate (silicon etc.) and the device active region (formation region) (around LOCOS).
It is beginning to be pointed out that the place where distortion occurs (strain field) becomes a gettering site, where the heavy metals mentioned above accumulate.

Therefore, the present inventor used LOCOS to isolate elements.
TEG (Test El
ment Group) and DLTS (Dee
pLevel Transient 5pectros
Copy) measurement was carried out, and Fe
The concentration dependence was investigated.

As a result, it was found that there was a correlation between the peripheral length of the LOCOS pattern and the Fe concentration (see Figure 2).

The fact that the Fe concentration is proportional to the peripheral length/area (L/S) of the LOCOS pattern suggests that Fe is attracted to the strain field around the LOGOS pattern.

Furthermore, looking at the DLTS spectrum, it can be seen that Fe exists in a Fe-B bare state.

In this way, it has become clear that heavy metals accumulate around LOGDS.

[Problem to be solved by the invention]

However, the heavy metals accumulated in the strain field are normal I
G alone cannot remove it. Therefore, it has a bad influence on device characteristics. Basically, problems include an increase in leakage current in pn junctions and deterioration of carrier lifetime, and leakage or short circuits in bipolar LSIs.

The present invention aims to prevent heavy metal contamination during semiconductor device processing from accumulating in the strain field around the LOCOS and absorbing it into internal defect layers of the semiconductor wafer.

[Means to solve the problem]

According to the present invention, heavy metal impurities mixed into the semiconductor substrate are removed from the semiconductor substrate by forming an element isolation region on the semiconductor substrate by selective oxidation, and by heat-treating the semiconductor substrate in a nitrogen or hydrogen atmosphere. The problem is solved by a gettering method characterized by including the step of absorbing the heavy metal impurities into an internal defect layer of the semiconductor substrate while suppressing their accumulation around the isolation region.

[For production]

In the present invention, heat treatment in a nitrogen atmosphere (
This method utilizes known phenomena such as nitrogen in the silicon wafer gathering at the oxide film interface when nitrogen annealing is performed, or hydrogen annealing reducing the interface states between the oxide film and the silicon crystal. In other words, by performing this nitrogen annealing or hydrogen annealing, nitrogen or hydrogen is accumulated in the strain field around the LOCO5, which can be used during the semiconductor device process, especially during the high temperature (approximately 1200°C) heat treatment process for ion implantation, resist, and well formation. Also, the heavy metal impurities are prevented from accumulating around LOGO3. Nitrogen or hydrogen accumulated around LOCO3, so-called device active region, does not have any adverse effect on device characteristics.

〔Example〕

Embodiments of the present invention will be described below based on the drawings.

FIGS. 1(a) to 1(d) are process sectional views showing one embodiment of the present invention.

As shown in FIG. 1(a), for example, a silicon wafer 1
Then, an internal defect layer 2 is formed by performing an IG (intrinsic gettering) heat treatment, for example, a three-step IG heat treatment of a high temperature of 1000° C. for 30 minutes, a low temperature of 700° C. for 6 hours, and a high temperature of 1000° C. for 1 hour.

Next, as shown in FIG. 1(b), a field oxide film 3 (L
OCO3 formation).

Next, as shown in Figure 1 (C),
Heat treatment (N
2 annealing) was performed. With this N2 annealing, 5i
At the n2/Si interface (around LOCO3), nitrogen in Si is accumulated at 2xlQ17~3x10''/ctl (4 in the figure).
shows the accumulated N2. With this N2 annealing, the LOC
N2 accumulates around O3, and heavy metals that are mixed in during the subsequent device process are prevented from accumulating around the LDC port S, and can be absorbed into the IG layer 2 as shown in FIG. 1(d). Ta.

In the above example, hydrogen gas was used instead of nitrogen.
A similar effect was obtained even when heat treatment (hydrogen annealing) was performed at 50°C for 1 hour in an H2 atmosphere.

〔Effect of the invention〕

As explained above, according to the present invention, heavy metals such as Fe and Ni are prevented from accumulating in the strain field at the interface between the oxide film and the substrate obtained in the LOCO 9 step in the semiconductor device process, thereby improving device characteristics, yield, etc. This will lead to improvements in

[Brief explanation of the drawing]

FIGS. 1(a) to (d) are process cross-sectional views for explaining one embodiment of the present invention, and FIG. 2 shows the peripheral length/area (L/S) of the LOCOS pattern.
1 is a diagram showing DLTS measurement results showing that the Fe concentration is proportional to . 1... Silicon wafer, 2... Internal defect layer, 3... Field oxide film, 4... Integrated N2゜

Claims (1)

[Claims] 1. A step of forming an element isolation region on a semiconductor substrate by selective oxidation, by heat-treating the semiconductor substrate in a nitrogen or hydrogen atmosphere, heavy metal impurities mixed into the semiconductor substrate are removed from the elements. absorbing the heavy metal impurities into the internal defect layer of the semiconductor substrate while suppressing their accumulation around the isolation region;
A gettering method comprising: