JPH01225350A - Manufacture of semiconductor integrated circuit device - Google Patents

Abstract

PURPOSE:To form a trench capacitor whose leakage current is little by a method wherein a crystal defect layer is formed on a groove inner wall where a groove for the trench capacitor has been formed, a heavy metal in a semiconductor substrate is gettered by using the crystal defect layer and, after that, the crystal defect layer is removed. CONSTITUTION:A groove 3 is formed in a silicon substrate 1 by an etching operation by RIE by making use of a photoresist 2 as a mask; argon ions 5 are implanted into its inner wall; an argon-implanted layer 6 is formed. The photoresist is removed; after that, this assembly is heat-treated in an nitrogen atmosphere; a crystal defect layer 7 is formed by using the argon ions of the argon-implanted layer as a nucleus; in addition, heavy metal ions 4 in the substrate are gettered to the crystal defect layer 7 by an identical treatment. Then, the surface of the substrate 1 is oxidized; a silicon dioxide film 8 is formed; this film is removed; after that, a capacitance insulating film 9 is formed. Furthermore, a phosphorus-doped polycrystalline silicon film 10 to be used as an electrode is formed; the groove 3 is filled. This is removed selectively by using a photoetching method; thereby a trench capacitor A is formed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for manufacturing a semiconductor integrated circuit device, and more particularly to a method for manufacturing a trench capacitor from which heavy metal ions are removed and leakage current is small.

[Conventional technology]

Conventionally, in the manufacturing method of this type of semiconductor integrated circuit device, a crystal defect layer is previously formed on the back surface of a silicon substrate by sandblasting, excimer laser irradiation, or the like. Next, a pattern for trench etching is formed on the silicon substrate using photoresist, followed by RIE (Reactive I).
The silicon substrate is etched to form a groove.

Next, after removing the photoresist, a SiO□ film is formed on the surface of the silicon substrate and the inner wall of the trench in a high temperature oxygen atmosphere. Next, a phosphorus-doped polycrystalline silicon film is formed so that the trench is filled over the entire surface of the silicon substrate and the surface is flat.

Next, using a photoresist as a mask, the phosphorus-doped polycrystalline silicon film other than the capacitor forming portion is selectively etched away. A trench capacitor is formed through the above steps, and then heat treatment is performed to getter the heavy metal ions that entered the silicon substrate from the inner wall of the trench during trench etching in the crystal defect layer on the back surface of the silicon substrate. Ta.

[Problem to be solved by the invention]

However, in the conventional method for manufacturing semiconductor integrated circuit devices described above, a crystal defect layer that getters heavy metal ions is formed at the earliest stage of the manufacturing process of semiconductor integrated circuit devices by mechanical strain using sandblasting and excimer laser irradiation. Therefore, crystal defects are recovered during the heat treatment for forming the N-well or field oxide film before the step of forming the trench capacitor, and the gettering effect is lost when forming the trench capacitor. Furthermore, since the crystal defect layer is formed on the back surface of the silicon substrate, there is also the drawback that a sufficient gettering effect cannot be obtained far from the formation region of the trench capacitor. Therefore, the charge accumulated in the capacitor leaks due to the residual heavy metal ions that could not be gettered near the trench capacitor, and the MOS dynamic RAM
There was a problem in that the hold time of the device worsened.

[Differences between the invention and the prior art] In contrast to the above-described conventional method of manufacturing a semiconductor integrated circuit device, the present invention forms a crystal defect layer on the inner wall of the trench immediately after forming the groove of a trench capacitor, and the crystal defect layer The difference is that a trench capacitor with low leakage current can be formed by removing the crystal defect layer after gettering heavy metals in the semiconductor substrate.

[Means to solve the problem]

The method for manufacturing a semiconductor integrated circuit device of the present invention includes the steps of forming a groove in a semiconductor substrate from the surface toward the inside, implanting ions of an inert element into the inner wall of the groove, and implanting the inert element into the semiconductor substrate on the inner wall of the groove. a step of heat-treating the semiconductor substrate to form a crystal defect layer in the semiconductor substrate using the implanted inert element as a core, and a step of completely oxidizing the crystal defect layer on the inner wall of the groove. configured.

〔Example〕

Next, the present invention will be explained with reference to the drawings.

First, as shown in Figure 1, the P type resistivity is 4~5Ω/<1
A trench 3 having a depth of 2 to 3 μm is formed by masking and selectively etching a photoresist 2 from the surface to the inside of a silicon substrate 1 having a crystal orientation of 00>. Groove etching is done using RIE (React 1veIon Etch).
Next, as shown in FIG. 2, argon ions 5 are implanted into the inner wall of the groove 3 using the photoresist 2 as a mask to form an argon implantation layer 6 on the silicon substrate 1. do.

At this time, the argon ions 5 are implanted using an oblique rotational ion implantation method, with an energy of 10 to 30 KeV, at an angle of 5 to 30 degrees with respect to the silicon substrate 1, and the amount of implantation is IX 10"' to I
It is preferable to inject at 1014an''2. Also, the photoresist masking the argon ions 5 is the first one.
After removing the photoresist as shown in Figure 3, we reused the material used for etching the grooves explained in Figure
A heat treatment is applied for 10 to 30 minutes in a nitrogen atmosphere at 50 to 1100° C. to form a crystal defect layer 7 using argon ions in the argon injection layer 6 as nuclei. Further, by applying heat treatment for 1 to 3 hours in a nitrogen atmosphere at 800 to 900° C., heavy metal ions 4 in the silicon substrate are gettered to the crystal defect layer 7. Next, as shown in FIG. 4, the surface of the silicon substrate 1 including the inner wall of the groove 3 is oxidized to form a silicon dioxide film 8 of 300 to 500 layers. At this time, the silicon dioxide film takes in the heavy metal ions gettered into the crystal defect layer, and the thickness of this silicon dioxide film must be set so as to completely oxidize the crystal defect layer 7 shown in FIG. 3. Next, as shown in FIG. 5, after removing the dioxide film 8,
As shown in FIG. 6, a capacitive insulating film 9 made of silicon dioxide or silicon dioxide and silicon nitride is formed to a thickness of 100 to 150 nm on the surface of the silicon substrate 1 including the inner wall of the groove 3. Further, a phosphorus-doped polycrystalline silicon film 10, which will become an electrode of a trench capacitor, is formed to fill the trench 3.

Next, the phosphorus-doped polycrystalline silicon film IO is selectively removed using a conventional photoetching method to form a trench capacitor A (FIG. 7).

〔Effect of the invention〕

As explained above, the present invention effectively removes heavy metals remaining on the silicon substrate in the trench capacitor formation region by forming a crystal defect layer on the inner wall of the trench during formation of the trench capacitor and removing it after gettering the heavy metal. It can be removed. Furthermore, the damaged layer caused by plasma during trench etching can also be removed, making it possible to form a trench capacitor with a small league current.

[Brief explanation of the drawing]

1 to 7 are cross-sectional views showing an embodiment of the present invention in the order of steps. 1...Silicon substrate, 2...Photoresist, 3...Groove, 4...Heavy metal ion, 5...Argon ion, 6... ... Argon injection layer, 7 ... Crystal defect layer, 8 ...
・Silicon dioxide film, 9...Capacitive insulating film, 10
...Phosphorus-doped polycrystalline silicon film, A...
...Trench capacitor. Agent Patent Attorney Uchihara Oto￥f2 diagram

Claims (1)

[Claims] a step of forming a groove in the semiconductor substrate from the surface toward the inside; a step of ion-implanting an inert element into the inner wall of the groove to form an inert element implantation layer in the semiconductor substrate on the inner wall of the groove; and heat treating the semiconductor substrate. A semiconductor integrated circuit device comprising the steps of forming a crystal defect layer in a semiconductor substrate using the inert element of the inert element injection layer as a core, and completely oxidizing the crystal defect layer on the inner wall of the groove. manufacturing method.