Methods of forming DRAM assemblies, transistor devices, and openings in substrates

• US 6,500,744 B2
• Filed: 09/02/1999
• Issued: 12/31/2002
• Est. Priority Date: 09/02/1999
• Status: Expired due to Term

• Current Assignee: Micron Technology, Inc.
• Original Assignee: Micron Technology, Inc.
• Inventors: Ping, Er-Xuan, Gonzalez, Fernando
• Primary Examiner(s): TRINH, MICHAEL MANH
• Application Number:
  US09/389,670
• Publication Number:
  US 20020072208A1
• Time in Patent Office: 1,216 Days
• Field of Search: 438/595, 438/589, 438/424, 438/430, 438/700, 438/243, 438/270, 438/386
• US Class Current: 438/595
• CPC Class Codes: H01L 21/3086 characterised by the process involved to create the mask, e.g. lift-off masks, sidewalls, or to modify the mask, e.g. pre-treatment, post-treatment
• CPC Class Codes: H01L 21/3088 Process specially adapted to improve the resolution of the mask
• CPC Class Codes: H01L 21/76224 using trench refilling with dielectric materials trench filling with polycristalline silicon H01L21/763; together with vertical isolation, e.g. trench refilling in a SOI substrate H01L21/76264
• CPC Class Codes: H01L 21/763 Polycrystalline semiconductor regions H01L21/76264 takes precedence
• CPC Class Codes: H10B 12/053 the transistor being at least partially in a trench in the substrate vertical transistor in combination with a capacitor formed in a substrate trench H10B12/0383

Abstract

The invention encompasses a method of forming an opening in a substrate. A first expanse of a first material is formed over the substrate, and such expanse comprises a sidewall edge. A second material is formed along the sidewall edge, and subsequently a second expanse of the first material is formed over the substrate and separated from the first expanse by the second material. The first and second expanses together define a mask. The second material is removed with an etch selective for the second material relative to the first material to form an opening extending through the mask. The substrate is etched through the opening in the mask to extend the opening into the substrate. In a particular embodiment of the invention, the opening is filled with insulative material to form a trenched isolation region. In another embodiment of the invention, the opening is filled with a conductive material to form a transistor gate.

Claims

1. A method of forming an opening in a substrate, comprising:

forming at least two blocks of a first material over a substrate, a pair of the at least two blocks being separated by a gap and comprising sidewall edges;

forming spacers of a second material along the sidewall edges, the spacers only partially filling the gap and leaving a remaining portion of the gap unfilled;

forming a layer of the first material within the unfilled remaining portion of the gap, the first material of the blocks and the first material within the gap together defining a mask;

removing the second material spacers with an etch selective for the second material relative to the first material to form openings extending through the mask;

etching the substrate through the openings in the mask to form an opening into the substrate, the method further comprising;

before forming the first material blocks, forming a layer of second material over the substrate;

forming the first material blocks and the second material spacers over the layer of second material; and

etching the layer of second material through the openings in the mask.

2. A method of forming an opening in a substrate, comprising:

forming at least two blocks of a first material over a substrate, a pair of the at least two blocks being separated by a gap and comprising sidewall edges;

forming spacers of a second material along the sidewall edges, the spacers only partially filling the gap and leaving a remaining portion of the gap unfilled;

forming a layer of the first material within the unfilled remaining portion of the gap, the first material of the blocks and the first material within the gap together defining a mask;

removing the second material spacers with an etch selective for the second material relative to the first material to form openings extending through the mask;

etching the substrate through the openings in the mask to form an opening into the substrate, the method further comprising;

before forming the second material spacers, forming a layer of the second material over the substrate and forming a layer of a third material over the layer of second material;

forming the second material spacers over the layer of the third material; and

removing portions of the layer of third material and portions of the layer of second material through the openings in the mask.

3. The method of claim 2 wherein the substrate comprises monocrystalline silicon, the first material comprises silicon dioxide, the second material comprises silicon nitride, and the third material comprises silicon, and wherein the silicon of the third material is oxidized to form the silicon dioxide first material within the gap.

4. The method of claim 3 wherein the silicon of the third material is in the form of polycrystalline silicon.

5. A method of forming a trench in a semiconductive material substrate, comprising:

providing a semiconductive material substrate;

forming a silicon nitride layer over the substrate;

forming at least two blocks over the silicon nitride layer, the at least two blocks comprising silicon dioxide, a pair of the at least two blocks being separated by a gap and comprising sidewall edges;

forming a non-oxidized silicon layer over the silicon nitride layer and proximate the at least two blocks;

forming silicon nitride spacers along the sidewall edges and over a portion of the non-oxidized silicon layer, the spacers only partially filling the gap to leave a narrowed gap between the pair of blocks, the narrowed gap having an other portion of the non-oxidized silicon layer exposed therein;

oxidizing said other portion of the non-oxidized silicon layer to convert the exposed non-oxidized silicon to silicon dioxide;

removing the silicon nitride spacers with an etch selective for silicon nitride relative to the silicon dioxide;

the removing of the silicon nitride spacers leaving a silicon dioxide mask over the semiconductive material substrate, the silicon dioxide mask comprising the pair of blocks and the silicon dioxide formed within the gap by oxidizing the exposed non-oxidized silicon, the silicon dioxide mask having openings extending therethrough corresponding to the locations from which the silicon nitride spacers were removed;

removing portions of the non-oxidized silicon layer and silicon nitride layer exposed through the openings in the silicon dioxide mask; and

removing portions of the substrate exposed through the openings in the silicon dioxide mask to form at least one trench extending into the substrate.

6. The method of claim 5 wherein the non-oxidized silicon comprises polysilicon.

7. The method of claim 5 further comprising filling the trench in the substrate with an insulative material to form a trenched isolation region.

8. The method of claim 5 further comprising:

filling the trench in the substrate with silicon dioxide; and

utilizing the silicon nitride layer over the substrate as an etch stop during a polishing process to form a planarized upper surface over the substrate.

9. The method of claim 8 wherein the silicon dioxide is formed in the trench by high density plasma silicon dioxide deposition.

10. The method of claim 8 wherein the substrate comprises silicon and the filling the trench with silicon dioxide comprises:

thermally growing a thin layer of oxide over walls of the silicon-comprising substrate within the trench to partially fill the trench; and

deposition of high density plasma silicon dioxide to fill a remainder of the partially filled trench.

11. A method of forming a transistor device supported by a semiconductive material substrate, comprising:

providing a semiconductive material substrate;

forming at least two blocks over the substrate, the at least two blocks comprising silicon dioxide, a pair of the at least two blocks being separated by a gap and comprising sidewall edges;

forming a silicon layer over the substrate and proximate the at least two blocks;

forming silicon nitride spacers along the sidewall edges and over a portion of the silicon layer, the spacers only partially filling the gap to leave a narrowed gap between the pair of blocks, the narrowed gap having an other portion of the silicon layer exposed therein;

oxidizing said other portion of the silicon layer to convert the exposed silicon to a silicon dioxide segment;

removing the silicon nitride spacers with an etch selective for silicon nitride relative to silicon dioxide;

the removing of the silicon nitride spacers leaving a silicon dioxide mask over the semiconductive material substrate, the silicon dioxide mask comprising the pair of blocks and the silicon dioxide segment formed within the gap by oxidizing the exposed silicon, the silicon dioxide mask having openings extending therethrough corresponding to the locations from which the silicon nitride spacers were removed;

removing portions of the silicon layer and silicon nitride layer exposed through the openings in the silicon dioxide mask;

removing portions of the substrate exposed through the openings in the silicon dioxide mask to form at least one trench extending into the substrate, the trench having walls;

forming an insulative material over the trench walls to partially fill the trench and leaving a narrowed opening within the trench;

filling the narrowed opening with a conductive material; and

forming source/drain regions extending into the substrate and separated from the conductive material by the insulative material over the trench walls;

the conductive material and source/drain regions together comprising a transistor device.

12. The method of claim 11 wherein the silicon layer comprises polysilicon.

13. The method of claim 11 wherein the substrate comprises silicon, and wherein the forming the insulative material over the trench walls comprises oxidizing the silicon of the trench walls to form silicon dioxide.

14. The method of claim 11 wherein the filling the narrowed trench with conductive material comprises filling the narrowed trench with conductively doped polysilicon.

15. The method of claim 11 wherein the forming the source/drain regions comprises:

removing the silicon dioxide blocks and silicon dioxide segment from over the substrate; and

implanting a conductivity-enhancing dopant into the substrate to form source/drain regions proximate the conductive material.

16. The method of claim 11 wherein the conductive material formed within the trench comprises conductively doped polysilicon, and the method further comprising forming a diffusion region beneath the conductively doped polysilicon.

17. The method of claim 11 wherein the conductive material formed within the trench comprises conductively doped polysilicon, and wherein one of the source/drain regions extends to beneath the conductively doped polysilicon.