CN101777495A - Method for improving rounding of active area corner - Google Patents

Abstract

The invention discloses a method for improving rounding of an active area (AA) corner. After the procedures of AA etch and pre-pullback, the method comprises the steps of carrying out ion bombarding on the exposed AA corner to convert the structure of the single crystal silicon at the corner into amorphous structure; and oxidizing the single crystal silicon exposed on the side wall of AA and at the bottom of the groove and the AA corner which is subjected to ion bombarding to obtain the oxide films of the silicon. In the method, by changing the existing treatment flow, oxidation is not immediately carried out after pre-pullback but the silicon at the AA corner is subjected to one-step ion bombarding to convert the single crystal structure of the silicon at the AA corner into amorphous structure, and then oxidation is carried out; and oxidation of the silicon of amorphous structure is faster than oxidation of the single crystal silicon, so that the silicon oxide generated at the AA corner becomes thicker, thus improving the rounding of the AA corner.

Description

Improve the method for rounding of active area corner

Technical field

The present invention relates to integrated circuit processing and manufacturing technology, be specifically related to improve active region (ActiveArea, AA) method of corner circularity.

Background technology

In integrated circuit processing and manufacturing process, the processing technology of wafer (wafer) is in core and crucial status the most, and the quality of wafer processing technology has decisive influence for the service behaviour of the gate circuit that finally obtains.

After to the silicon chip process oxide layer growth and nitride deposition processing that obtain at first, the cross-section structure of wafer as shown in Figure 1 at this moment, the AA that the zone constitutes for monocrystalline silicon shown in the orlop cross spider, the zone is the thermal oxide of silicon shown in the right oblique line in intermediate layer, and the zone then (is generally Si for the nitride of silicon shown in the superiors' left side oblique line ₃N ₄).Then wafer shown in Figure 1 is carried out AA etching (Etch), can obtain groove structure as shown in Figure 2.

Next the preliminary treatment (Pre Pullback) of retreating, the pretreated method of described retreatment is to use phosphoric acid and hydrofluoric acid wet etching that the thermal oxide and the nitride of both sides, groove opening place are reacted away a part, make coming out that the AA corner at groove opening place can be complete, as shown in Figure 3, the distance that " retreats " of the sidewall border of described thermal oxide and nitride is generally 75 ± 25 dusts (1 dust is 10 ^-10Rice, i.e. 0.1 nanometer), and then described groove structure carried out oxidation processes---promptly, to the AA sidewall that comes out owing to AA Etch and the monocrystalline silicon of channel bottom, and the monocrystalline silicon of the corner surfaces that is come out via the retreatment preliminary treatment carries out oxidation processes simultaneously, generate the layer of silicon dioxide film, as shown in Figure 4.

Usually will be called AA Corner through the groove corner location after the oxidation processes (as the A among Fig. 4, the position shown in the B), in integrated circuit processing and manufacturing field, the figure of the resulting wafer section of per step operation has significant effects for the service behaviour of the gate circuit that finally obtains, and it substantially all is because the profile graphics that manufacturing procedure can't obtain design causes that the service behaviour of gate circuit can't meet design requirement.For AA Etch and retreatment pretreatment process, the circularity of described AA corner (rounding) is exactly the major criterion of weighing described working procedure processing quality, and the processing effect of the described operation of the big more expression of circularity is good more.Described circularity promptly is meant the radius of a circle at radian place of AA corner corner shape or the size of diameter, understands easily, and the corner shape of the big more AA corner of circularity is gentle more slow, and the corner shape of the more little then AA of circularity corner is sharp-pointed more.

Described circularity is mainly reflected in the following aspects for the influence of the gate circuit service behaviour that finally obtains:

At first, because the electric field line in the electric field is intensive more in the sharp-pointed more position of profile, therefore the corner shape of AA corner is gentle more slow, its parasitic transistor effect (Parasitic Transistor Effect) is just more not remarkable, and parasitic transistor effect is more little, and the service behaviour of the gate circuit that finally obtains is just good more;

Secondly, when behind described retreatment pretreatment process, carrying out oxidation processes, the monocrystalline silicon at the AA corner place that the corner shape is sharp-pointed more, its oxidation effectiveness when oxidation processes is just poor more than the monocrystalline silicon of AA side-walls---, corner circularity is more little, the thickness of oxide layer that AA corner place generates is thin more, and its thickness is than the difference also obvious more (common this defective is also referred to as Corner Oxide Thinning Issue) of the thickness of oxide layer of AA sidewall formation, as shown in Figure 4, among Fig. 4 the oxidated layer thickness at corner location place less than the oxidated layer thickness at AA sidewall locations place; And the monocrystalline silicon at the gentle more slow AAcorner place of corner shape is abundant more and even with contacting of oxygen, thereby the thickness of oxide layer that forms is just thick more even more.And through evidence, the oxide layer at corner location place is thick more, and described parasitic transistor effect equally also can be got over not remarkable;

At last, the effective width of AA is big more, and the drive circuit of the gate associated transistor that then finally obtains is just big more.And according to the definition of AA effective width: the oxidated layer thickness at AA corner place is even more, and correspondingly effective width is just big more.Therefore draw easily, the AA corner that circularity is big more, the effective width of its AA is big more, thus the gate circuit service behaviour that finally obtains is good more.

As seen, for described AA Etch and retreatment pretreatment process, the circularity of the AA corner that obtains is big more, the service behaviour of the gate circuit that then finally obtains is just outstanding more, therefore, the circularity that how further to improve AA corner just becomes the problem of each integrated circuit processing and manufacturing commercial city in active research.

Summary of the invention

The invention provides the method that improves AA corner circularity, can improve the corner circularity of AA.

For achieving the above object, technical scheme of the present invention specifically is achieved in that

A kind of method that improves rounding of active area corner, after active region etching and retreatment pretreatment process, this method comprises:

Ion bombardment is carried out in the active region corner of coming out, make the monocrystal silicon structure of described edge change non crystalline structure into;

Carry out oxidation processes to the monocrystalline silicon of active region sidewall and channel bottom exposure with through the active region corner that ion bombardment is handled, obtain the oxide film of silicon.

The described incidence angle that the ion bombardment in the vertical direction is carried out in the active region corner of coming out is: with crystal column surface vertical direction angle be the directions of 0 degree, 7 degree or 30 degree.

Groove structure with two kinds of directions of crystal column surface is directions X and Y direction respectively, describedly ion bombardment is carried out in the active region corner of coming out comprises: along the positive and negative twocouese of X and Y, carry out the bombardment of 4 secondary ions altogether.

Describedly ion bombardment carried out in the active region corner of coming out comprise:

Selecting energy for use is that 30Kev, concentration are 10 ¹⁵Germanium ion beam, in the vertical direction along with the crystal column surface vertical direction be 30 the degree angles incidence angle, the positive and negative twocouese of upper edge X and Y bombards described active region corner in the horizontal direction.

As seen from the above technical solutions, the method of raising AA provided by the invention corner circularity, by changing existing handling process, after the retreatment preliminary treatment, do not carry out oxidation processes immediately, but elder generation carries out the processing of a step ion bombardment to the silicon at AA corner place, the silicon at described AA corner place is become non crystalline structure by crystal structure, carry out oxidation processes afterwards again; Because the oxidation rate of non crystalline structure silicon is faster than crystalline silicon, the silicon oxide thickness that makes AA corner place generate becomes big, thereby has improved the circularity of AAcorner.

Description of drawings

Fig. 1 is the wafer cross-sectional view before the AA Etch in the prior art.

Fig. 2 is the wafer cross-sectional view after the AA Etch in the prior art.

Fig. 3 is the wafer cross-sectional view after the retreatment preliminary treatment in the prior art.

Fig. 4 is the wafer cross-sectional view after the oxidation processes in the prior art.

Fig. 5 improves the schematic flow sheet of the method for AA corner circularity for the embodiment of the invention.

The schematic diagram of bombardment direction when Fig. 6 carries out ion bombardment for the embodiment of the invention to the groove structure on wafer surface.

Embodiment

For making purpose of the present invention, technical scheme and advantage clearer, below with reference to the accompanying drawing embodiment that develops simultaneously, the present invention is described in more detail.

The invention provides the method that improves AA corner circularity, this method flow specifically comprises as shown in Figure 5:

Step 501: after AA Etch and retreatment pretreatment process, the AA corner that comes out is carried out ion bombardment, make the silicon at described AA corner place change non crystalline structure into by mono-crystalline structures;

Step 502: the monocrystalline silicon of the AA sidewall that comes out and channel bottom and the AA corner that handles through ion bombardment are carried out oxidation processes, obtain oxide film.

Wherein, step 501 couple AA corner carries out ion bombardment, make the silicon crystalline structure at AA corner place change, engagement keys stress between described AA corner place silicon atom is weakened or destruction owing to the bump that is subjected to described ion, thereby described silicon atom becomes more unsettled non crystalline structure by more stable mono-crystalline structures.Therefore, the silicon of the described non crystalline structure that obtains after the process ion bombardment, than not carrying out the crystalline silicon that ion bombardment is handled, its oxidation rate is obviously accelerated.

In this case, when the AA corner that the silicon crystal of step 502 pair AA sidewall that comes out and channel bottom and process ion bombardment are handled carries out oxidation processes, the thickness of the silica that AA corner place generates will be thicker than the thickness of the silica that generates under the prior art, understand easily, the circularity nature of the AA corner that obtain this moment is bigger than the circularity of the AA corner under the prior art.

Need to prove, the energy size of the described ionic species that carries out ion bombardment, ion beam and doping content and ion beam incidence angle all have numerous embodiments, and those skilled in the art can carry out necessary adjustment according to actual application environment satisfying under the situation of following constraints:

1) ionic species;

With regard to the effect of ion bombardment, the big more then bombardment effect of the atomic weight of the ion beam of selecting for use is good more;

2) doping content of ion beam energy size and ion;

The energy of ion beam can not be too high or too low, cross low possibly and can't change the original atomic bond of monocrystalline silicon and play the effect that crystalline silicon is changed into amorphous silicon, thereby the too high then original atomic bond of monocrystalline silicon might the destruction of energy be caused lattice damage;

The doping content of ion beam can not be too high or too low, crossing the low structural transformation that may can't play equally monocrystalline silicon is the effect of non crystalline structure, the too high characteristic of semiconductor that then may too much change original AA owing to the ion that mixes causes the electric property of AA to change;

3) the ion beam bombardment direction is at the angle of inclination of vertical direction;

Spatial arrangements characteristic according to the monocrystalline silicon lattice structure changes monocrystal silicon structure into non crystalline structure if want to reach, then the incident angle of described ion bombardment be merely able to be 0 the degree, 7 the degree or 30 the degree;

4) ion beam bombardment direction selection in the horizontal direction;

In the horizontal direction, owing to exist simultaneously on the wafer along the groove structure of directions X distribution and the groove structure that distributes along the Y direction, and can both have higher circularity for the left and right sides that guarantees groove structure, need simultaneously ion bombardment all to be carried out in the both sides of groove structure, therefore, need to carry out the bombardment of 4 secondary ions altogether, be respectively positive and negative twocouese along X and Y.

Be the implication of further clear and definite above-mentioned constraints, the invention provides a kind of embodiment through checking, at this moment:

The method of described in the step 501 the AA corner that comes out being carried out ion bombardment specifically comprises: select for use energy be 30Kev (kiloelectron-volt), concentration is 10 ¹⁵Germanium ion beam, bombard (angle that is incident direction and the vertical direction of ion beam be 30 spend) with the vertical incidence angles of 30 degree; At last, described ion bombardment is carried out in horizontal plane 4 times, the each anglec of rotation 90 degree (can be that the ion beam emitter changes direction, certainly easier method is to drive the wafer rotation by the wafer pallet), can describe by wafer vertical view shown in Figure 6, as shown in Figure 6, owing to comprise the groove structure of x direction and y direction simultaneously on the wafer surface, therefore, for guaranteeing that all AA corner have better circularity in x, the y direction groove structure, need all carry out ion bombardment to the AA corner of all directions groove structure.Therefore in the wafer plane, need to carry out 4 secondary ions bombardments (being respectively the positive negative direction of X and the positive negative direction of Y) altogether, and revolve at every turn and turn 90 degrees.

Through actual verification and measurement, adopt prior art to process, the circularity data of the gate structure several commonly used that obtains are as follows respectively:

PMOS under CMOS structure pipe, the circularity of its AA corner is 130A, and NMOS to manage the circularity of its AA corner be 123A;

And the pipe of the NMOS in the SDRAM structure, the circularity of its AA corner is 96A;

Adopt after the method for raising AA provided by the invention corner circularity, same gate structure, its circularity data then are:

PMOS pipe under the CMOS structure, the circularity of its AA corner is 141A, its circularity has improved 8% compared to existing technology; The circularity that NMOS manages its AA corner is 153A, and its circularity has improved 24% compared to existing technology;

And the pipe of the NMOS in the SDRAM structure, the circularity of its AA corner is 152A, its circularity has improved 58% compared to existing technology.

Obviously, use the circularity that method provided by the invention has significantly improved AA corner.

By as seen above-mentioned, the present invention is by changing existing handling process, after the retreatment preliminary treatment, do not carry out oxidation processes immediately, but elder generation carries out the processing of a step ion bombardment to the silicon at AA corner place, the silicon at described AA corner place is become non crystalline structure by mono-crystalline structures, carry out oxidation processes afterwards again; Because the oxidation rate of non crystalline structure silicon is faster than monocrystalline silicon, the silicon oxide thickness that makes AA corner place generate becomes big, has therefore improved the circularity of AA corner, thereby can improve the service behaviour of the gate circuit that finally obtains.

Claims (4)

1. a method that improves rounding of active area corner is used after active region etching and the retreatment pretreatment process, it is characterized in that this method comprises:

Ion bombardment is carried out in the active region corner of coming out, make the monocrystal silicon structure of described edge change non crystalline structure into;

Carry out oxidation processes to the monocrystalline silicon of active region sidewall and channel bottom exposure with through the active region corner that ion bombardment is handled, obtain the oxide film of silicon.

2. method according to claim 1 is characterized in that, the described incidence angle that the ion bombardment in the vertical direction is carried out in the active region corner of coming out is: with crystal column surface vertical direction angle be the directions of 0 degree, 7 degree or 30 degree.

3. method according to claim 1 and 2, it is characterized in that, groove structure with two kinds of directions of crystal column surface is directions X and Y direction respectively, describedly ion bombardment is carried out in the active region corner of coming out comprises: along the positive and negative twocouese of X and Y, carry out the bombardment of 4 secondary ions altogether.

4. method according to claim 3 is characterized in that, describedly ion bombardment is carried out in the active region corner of coming out comprises:

Selecting energy for use is that 30Kev, concentration are 10 ¹⁵Germanium ion beam, in the vertical direction along with the crystal column surface vertical direction be 30 the degree angles incidence angle, the positive and negative twocouese of upper edge X and Y bombards described active region corner in the horizontal direction.

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