Semiconductor device manufacturing: process – Coating with electrically or thermally conductive material – To form ohmic contact to semiconductive material
Reexamination Certificate
2002-05-21
2003-12-02
Ghyka, Alexander (Department: 2812)
Semiconductor device manufacturing: process
Coating with electrically or thermally conductive material
To form ohmic contact to semiconductive material
C438S758000, C427S255180, C427S255270, C427S585000, C118S715000, C118S725000
Reexamination Certificate
active
06656838
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a process and an apparatus for producing a semiconductor, and more particularly to a process and an apparatus for producing a semiconductor, which can form a CVD film with a good step coverage at a high film-forming rate.
BACKGROUND ART
Production of semiconductor integrated circuits is now making much use of a process for forming a film, i.e. forming a thin film on a wafer by subatmospheric thermal CVD, where it is required to deposit a thin film of uniform thickness with uniform characteristics on a wafer. To fill step gaps around holes, vias, trench, etc. of a high aspect ratio (depth/opening diameter), a high step coverage is required. Voids, when formed in the deposition film on the step gaps due to a low step coverage, will give rise to lowering of reliability or failure of semiconductor integrated circuits.
Heretofore, a batch type CVD apparatus capable of treating a few tens to a hundred and a few tens wafers in one batch has been much used in the subatmospheric thermal CVD process. The batch type CVD apparatus itself has a high throughput and thus improvement of film thickness uniformity and higher step coverage is attained by forming films even at a somewhat low film-forming rate (a few nm/min. or so) under relatively low pressure, e.g. a few tens to a few hundred Pa.
On the other hand, shifting to a single wafer processing type CVD apparatus, which treats wafers one by one, is now gradually taking place. With the recent trend toward larger wafer diameter and more strict requirements for film thickness uniformity, the batch type CVD apparatus is confronting difficulties in keeping the film thickness uniformity not only within the in-place region of wafer, but also throughout wafers. The batch type requires a long treating time for one run and thus is not suitable for more flexible, short TAT (Turn Around Time) production. This is accelerating the shifting tendency.
A well known single wafer processing type CVD apparatus is a lamp heating type apparatus using a halogen lamp as a heat source and its structure is disclosed is JP-A-6-326078, JP-A-10-144619, JP-A-6-293595, etc. The lamp heating type apparatus requires cooling of the lamp by air injection to prevent the lamp durability from lowering due to excessive temperature elevation and thus the lamp cannot be provided in the subatmospheric treating chamber. Instead, the lamp is provided outside the treating chamber to irradiate a wafer or a susceptor (on which a wafer is mounted) with a lamp light through a light-transmissible window provided on one side of the treating chamber.
Another well known single wafer processing type CVD apparatus is an apparatus for heating a wafer mounted on a heater-incorporated stage, and its structure is disclosed in JP-A-9-45624. The stage is in such a structure that a plate type heater divided into a plurality of zones is fixed to the backside of a susceptor having a thickness of a few centimeters, composed of a material of high heat conductivity, and a pair of insulated electrodes are provided on the wafer-mounting side and an insulating film is further provided thereon to constitute an electrostatic chuck. Gas injection nozzles are provided in a circular region around the center of a shower plate, the circular region having a substantially the same diameter as that of the susceptor and a film is formed by injecting a gas through the nozzles, while securing the wafer onto the susceptor by electrostatic force. It is disclosed that the film thickness uniformity within the in-plane region of the wafer can be improved by balancing an injection gas rate against a gas consumption rate.
To make the throughput of the single wafer processing type CVD apparatus equal to that of the batch type, the film-forming rate must be increased to a few tens-a hundred and a few tens nm/min, and thus the film must be formed at a higher film-forming temperature under higher pressure than those of the batch type. The single wafer processing CVD apparatus has had such an inevitable problem as poor step coverage. JP-A-10-74703 discloses a method of improving the step coverage by using a high total pressure (20−300 Torr=2666−39990 Pa), a high silicon-containing gas partial pressure (4−40 Torr=533.2−5332 Pa) and a low temperature (550°-620° C.).
DISCLOSURE OF THE INVENTION
An object of the present invention is to solve the following problems of the prior art.
In the lamp heating type apparatus as disclosed in JP-A-6-326078, JP-A-10-144619, JP-A-6-293595, etc., the lamp cannot be provided too nearer to the wafer or susceptor as a heating target, so that it is difficult to appropriately control distribution of heating rate to the wafer or susceptor. For example, there is such a problem that even if the heating rate is increased only in the peripheral region of high heat radiation, its influence will be propagated even to the central region, resulting in difficulty in making the wafer temperature uniform.
In the heater-heating type apparatus as disclosed in JP-A-9-45624, it is necessary to increase the heat transfer rate to the wafer by elevating the temperature of susceptor (which is referred to as “mounting base” in the reference) in the peripheral region of high heat radiation to make the wafer temperature uniform, as mentioned in the reference. However, it is difficult to elevate the temperature only of susceptor having a high heat conductivity and a thickness as large as a few centimeters, and the temperature of the central region is also elevated to a higher level by heat transfer through the susceptor than as required. Furthermore, the heat capacity of the susceptor is so large that the susceptor surface temperature cannot be elevated rapidly even by increasing the heat generation rate of heater, and it is difficult to change a heat transfer rate to the wafer with a good responsibility. Therefore, it is difficult to make the wafer mounted on the susceptor reach a desired temperature for a short time and there is such a problem that the susceptor temperature is gradually changed during the continuous treatment of wafers. Still furthermore, no consideration has been paid to the fact that a film is deposition also on the susceptor surface acting to secure the wafer by electrostatic force. Particularly in case that a conductive film such as a phosphorus-doped silicon film is deposited on the upper side of a susceptor so as to cover electrodes having different polarities of a dipole type electrostatic chuck, charges migrate through the deposited film, resulting in such a problem failure to secure the wafer by electrostatic force.
As a result of numerical simulation studies based on information disclosed in JP-A-10-74703, the present inventors have found that only control of film-forming conditions within said range has a limit to improvement of step coverage, and no desired step coverage can be obtained at such film-forming rates as required by the present inventors.
FIG. 23
shows results of simulation of relations between film-forming rates and step coverage (film thickness at hole inside/film thickness in flat part×100%) when a silicon film is formed by introduction of monosilane (SiH
4
), phosphine (pH
3
) and hydrogen (H
2
), where hole aspect ratio is set to 2. Continuous line shows a case that total pressure is 13320 Pa and monosilane partial pressure is 600 Pa, dotted line shows a case that total pressure is 21310 Pa and monosilane partial pressure 1000 Pa, and alternate long and short dash line shows a case that total pressure is 42620 Pa and monosilane partial pressure is 2000 Pa. Mark “◯” shows film formation at the wafer temperature of 580° C., “&Dgr;” shows film formation at the wafer temperature of 600° C. and “□” shows film formation at the wafer temperature of 620° C. Comparison at the same film-forming rate reveals that the step coverage can be improved by increasing a monosilane partial pressure from 600 Pa to 1,000 Pa and further to 2,000 Pa and by decreasing a wafer temperature from 620°
Kagatsume Akiko
Watanabe Tomoji
Yoshida Tadanori
Antonelli Terry Stout & Kraus LLP
Ghyka Alexander
Hitachi , Ltd.
LandOfFree
Process for producing semiconductor and apparatus for... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Process for producing semiconductor and apparatus for..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Process for producing semiconductor and apparatus for... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3101839