Method of forming a void-free interlayer dielectric (ILD0) for 0.18-μm flash memory technology and semiconductor device thereby formed

The present invention relates to flash memory semiconductor devices. More particularly, the present invention relates to 0.18-μm flash memory semiconductor devices. Even more particularly, the present invention relates to eliminating voids in the interlayer dielectric material of 0.18-μm flash memory semiconductor devices.

Currently, the semiconductor industry is experiencing shorting problems associated with the silicon (Si) of a CS59 0.18-mm flash memory technology device coming in contact with a tungsten plug due to void formation within the interlayer dielectric (ILD 0 ) boron phosphorous tetraethylorthosilicate (BPTEOS) layer. Void formation has been found to be especially prevalent between drain contacts in related art devices. FIG. 1 is a scanning electron micrograph (SEM) of such a device, in cross-section, demonstrating such void 10 formation along a “word line” direction between the drain contacts 11 , in accordance with the related art. FIG. 2 is another SEM illustrating, at higher magnification, a device cross-section in which a barrier metal deposition (BMD)/tungsten material 12 from a plug has extended into the voids 10 formed in the ILD, thereby shorting the neighboring drain contacts 11 , as experienced in the related art devices. Although boron-phosphorous-silica (BP—SiO 2 ) films, having a relatively high density, have been deposited using a lower deposition rate, a method for forming BPTEOS films using a lower deposition rate has not been known to the Applicants before their invention. Therefore, a need exists for providing a method of eliminating voids in the interlayer dielectric material of 0.18-μm flash memory semiconductor devices and a device thereby formed.

Accordingly, the present invention provides a method of eliminating voids in the interlayer dielectric material of 0.18-μm flash memory semiconductor devices and a voidless device thereby formed. More specifically, the present invention provides a method for eliminating voids in the interlayer dielectric material of a 0.18-μm flash memory semiconductor device by providing a first BPTEOS layer being formed by using a very low deposition rate and having a thickness in a range of approximately 3 kÅ; and providing a second BPTEOS layer being formed by using a standard deposition rate and having a thickness in a range of approximately 13 kÅ, wherein both layers have an atomic dopant concentration of approximately 4.5% boron (B) from triethylborate (TEB: C 6 H 15 O 3 B) and approximately 5% phosphorous (P) from triethylphosphate (TEPO: C 6 H 15 O 4 P).

This two-step deposition process completely eliminates voids in the ILD layer for a 0.5-μm distance (gate-to-gate) as well as 0.38-μm distance (gate-to-gate) which is the future flash technology. A low deposition rate such as 8±2 Å/sec is driven by a combination of low flow rates of the precursor materials of B and P dopants and tetraethyl orthosilicate (TEOS; i.e., Si(OC 2 H 5 ) 4 ). Particularly, a low dopant/TEOS flow (e.g., TEB at 60 g/min±30% TEPO at 30 g/min±30%, TEOS at 200 g/min±30%) performed at a higher pressure (e.g., 450±250 Torr) during the deposition of the first layer provides an excellent gap-filling capability which eliminates voiding. The second BPTEOS layer may be deposited at a higher deposition rate such as 100±10 Å/sec. Further, the present invention has the advantage of in-situ deposition of the void-free ILD0 layer of the 0.18-μm flash memory semiconductor device having a sound dopant concentration by preventing crystallization of boron phosphate (BPO 4 ) and maintaining the “C1” etch process using existing tools such as a heat lamp.

For a better understanding of the present invention, reference is made to the below-referenced accompanying Drawing. Reference numbers refer to the same or equivalent parts of the present invention throughout the several figures of the Drawing.

(1) FIG. 1 is a schematic of a scanning electron micrograph (SEM) of a device, in cross-section, demonstrating such void formation along a “word line” direction between the drain contacts, in accordance with the related art.

(2) FIG. 2 is another schematic of a SEM illustrating, at higher magnification, a device of FIG. 1 in cross-section where a BMD/tungsten material has extended into the voids, thereby shorting the neighboring contacts, in accordance with the related art.

(3) FIG. 3 is a schematic of a scanning electron micrograph (SEM) of a device, in cross-section, demonstrating no void formation, in accordance with the present invention.

(4) FIG. 4 is a flowchart of a method for fabricating a semiconductor device having a virtually void-free interlayer dielectric layer, in accordance with the present invention.

FIG. 3 illustrates, in a schematic of a scanning electron micrograph (SEM), a device cross-section, having no void formation in its unique BPTEOS interlayer dielectric (ILD), comprising a first BPTEOS layer 31 being deposited on a silicon substrate 33 ; and a second BPTEOS layer 32 being deposited on the first BPTEOS layer 31 , in accordance with the present invention.

FIG. 4 flowcharts a method M for fabricating a semiconductor device having a virtually void-free interlayer dielectric layer, in accordance with the present invention. The method M of fabricating a 0.18-μm flash memory semiconductor device, having a virtually void-free interlayer dielectric, comprises the steps of: (A) depositing a first boronphosphorous-tetraethyl-orthosilicate (BPTEOS) layer on a silicon substrate, the first and the second boron-phosphorous-tetraethyl-orthosilicate (BPTEOS) layer being formed from a group of reagents comprising a boron dopant, a phosphorous dopant, and TEOS, and the depositing step (A) comprises a first boron dopant flow rate, a first phosphorous dopant flow rate, and a first TEOS flow rate, as indicated by block 100 ; (B) depositing a second boron-phosphorous-tetraethyl-orthosilicate (BPTEOS) layer on the first BPTEOS layer, the second boronphosphorous-tetraethyl-orthosilicate (BPTEOS) layer being formed from a group of reagents comprising a boron dopant, a phosphorous dopant, and TEOS, and the depositing step (B) comprises a second boron dopant flow rate, a second phosphorous dopant flow rate, and a second TEOS flow rate, thereby forming the virtually void-free interlayer dielectric, as indicated by block 200 ; and (C) completing formation of the semiconductor device, thereby forming the 0.18-μm flash memory semiconductor device, having a virtually void-free interlayer dielectric, as indicted by block 300 .

Information as herein shown and described in detail is fully capable of attaining the above-described object of the invention, the presently preferred embodiment of the invention, and is, thus, representative of the subject matter which is broadly contemplated by the present invention. The scope of the present invention fully encompasses other embodiments which may become obvious to those skilled in the art, and is to be limited, accordingly, by nothing other than the appended claims, wherein reference to an element in the singular is not intended to mean “one and only one” unless explicitly so stated, but rather “one or more.” All structural and functional equivalents to the elements of the above-described preferred embodiment and additional embodiments that are known to those of ordinary skill in the art are hereby expressly incorporated by reference and are intended to be encompassed by the present claims.

Moreover, no requirement exists for a device or method to address each and every problem sought to be resolved by the present invention, for such to be encompassed by the present claims. Furthermore, no element, component, or method step in the present disclosure is intended to be dedicated to the public regardless of whether the element, component, or method step is explicitly recited in the claims. However, it should be readily apparent to those of ordinary skill in the art that various changes and modifications in form, semiconductor material, and fabrication material detail may be made without departing from the spirit and scope of the inventions as set forth in the appended claims. No claim herein is to be construed under the provisions of 35 U.S.C. §112, sixth paragraph, unless the element is expressly recited using the phrase “means for.”