Methods of forming capacitors

Details Methods of forming capacitors Methods of forming capacitors

2001-09-18

2004-11-30

Thompson, Craig A. (Department: 2813)

Semiconductor device manufacturing: process

Making passive device

Stacked capacitor

C438S255000

Reexamination Certificate

active

06825095

ABSTRACT:

TECHNICAL FIELD
The invention pertains to semiconductor capacitor constructions and to methods of forming semiconductor capacitor constructions. The invention is thought to have particular significance in application to methods of forming dynamic random access memory (DRAM) cell structures, to DRAM cell structures, and to integrated circuitry incorporating DRAM cell structures.
BACKGROUND OF THE INVENTION
A commonly used semiconductor memory device is a DRAM cell. A DRAM cell generally consists of a capacitor coupled through a transistor to a
1
a bitline. A semiconductor wafer fragment
10
is illustrated in
FIG. 1
showing a prior art DRAM array
83
. Wafer fragment
10
comprises a semiconductive material
12
, field oxide regions
14
, and wordlines
24
and
26
. Wordlines
24
and
26
comprise a gate oxide layer
16
, a polysilicon layer
18
, a silicide layer
20
and a silicon oxide layer
22
. Silicide layer
20
comprises a refractory metal silicide, such as tungsten silicide, and polysilicon layer
18
typically comprises polysilicon doped with a conductivity enhancing dopant. Nitride spacers
30
are laterally adjacent wordlines
24
and
26
.
Electrical node locations
25
,
27
and
29
are between wordlines
24
and
26
and are electrically connected by transistor gates comprised by wordlines
24
and
26
. Node locations
25
,
27
and
29
are diffusion regions formed within semiconductive material
12
.
A borophosphosilicate glass (BPSG) layer
34
is over semiconductive material
12
and wordlines
24
and
26
. An oxide layer
32
is provided between BPSG layer
34
and material
12
. Oxide layer
32
inhibits diffusion of phosphorus from BPSG layer
34
into underlying materials.
Conductive pedestals
54
,
55
and
56
extend through BPSG layer
34
to node locations
25
,
27
and
29
, respectively. Capacitor constructions
62
and
64
contact upper surfaces of pedestals
54
and
56
, respectively. Capacitor constructions
62
and
64
comprise a storage node layer
66
, a dielectric layer
68
, and a cell plate layer
70
. Dielectric layer
68
comprises an electrically insulative layer, such as silicon nitride. Cell plate layer
70
comprises conductively doped polysilicon, and may alternatively be referred to as a cell layer
70
. Storage node layer
66
comprises conductively doped hemispherical grain (HSG) polysilicon.
A conductive bitline plug
75
contacts an upper surface of pedestal
55
. Bitline plug
75
may comprise, for example, tungsten. Together, bitline plug
75
and pedestal
55
comprise a bitline contact
77
.
A bitline
76
extends over capacitors
62
and
64
and in electrical connection with bitline contact
77
. Bitline
76
may comprise, for example, aluminum.
The capacitors
62
and
64
are electrically connected to bitline contact
77
through transistor gates comprised by wordlines
26
. A first DRAM cell
79
comprises capacitor
62
electrically connected to bitline
76
through a wordline
26
and bitline contact
77
. A second DRAM cell
81
comprises capacitor
64
electrically connected to bitline
76
through wordline a
26
and bitline contact
77
. DRAM array
83
comprises first and second DRAM cells
79
and
81
.
If capacitors
62
and
64
are inadvertently shorted together, a so-called “double bit failure” will occur. Such double bit failures can occur if a stray piece of polysilicon, or HSG polysilicon, breaks off during formation of DRAM array
83
and disadvantageously electrically connects capacitors
62
and
64
. Prior art capacitor fabrication methods employ chemical-mechanical polishing (CMP) of HSG polysilicon. HSG polysilicon pieces can break off during such CMP processes and cause double bit failures. It would be desirable to develop alternative DRAM constructions which could be formed by methods avoiding double bit failures.
SUMMARY OF THE INVENTION
The invention includes a number of methods and structures pertaining to semiconductor circuit technology, including: methods of forming DRAM memory cell constructions; methods of forming capacitor constructions; DRAM memory cell constructions; capacitor constructions; and integrated circuitry For instance, the invention encompasses a method of forming a capacitor wherein a mass of silicon material is formed over a node location, and wherein the mass comprises exposed doped silicon and exposed undoped silicon. The method can further include substantially selectively forming rugged polysilicon from the exposed undoped silicon and not from the exposed doped silicon. Also, the method can include forming a capacitor dielectric layer and a complementary capacitor plate proximate the rugged polysilicon and doped silicon.
As another example, the invention encompasses a capacitor having a capacitor dielectric layer intermediate a first capacitor plate and a second capacitor plate, wherein at least one of the first and second capacitor plates has a surface against the capacitor dielectric layer, and wherein said surface comprises both doped rugged polysilicon and doped non-rugged polysilicon.


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